United States

Department of

Agriculture

Fire and

Forest Service the Environment:

Ecological and

Southeastern Forest

Experiment Station Cultural Perspectives

General Technical

Report SE-69

United States

Department of

Interior

Park Service

Proceedings of an

fnternational Symposium

Knoxville, Tennessee

March 20-24, 1990
Nodvin, Stephen C.; Waldrop, Thomas A., eds.

1991. Fire and the environment: ecological and cultural perspectives: Proceedings of an international

symposium; 1990 March 20-24; Knoxville, TN. Gen. Tech. Rep. SE-69. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southeastern Forest Experiment Station. 429 pp.

Forty-one papers based on oral presentations are included under four categories: Fire Ecology; Fire

Management; Cultural; and Fire History. In addition, three papers are presented from a special session

on the 1988 tires in the Greater Yellowstone Area and fourteen papers are presented from a poster

session.
Fire and the Environment:

Ecological and Cultural Perspectives

Proceedings of an International Symposium

Editors

Stephen C. Nodvin and Thomas A. Waldrop

Knoxyille, Tennessee

March 20-24, 1990

Sponsored by:

The University of Tennessee, Knoxville:

Department of Geography

Department of Forestry, Wildlife, and Fisheries

Graduate Program in Ecology

Science Alliance

College of Liberal Arts

Office of Research Administration

Clemson University

Department of Forest Resources

Tennessee Division of Forestry

National Park Service:

Cooperative Park Studies Unit-University of Tennessee

Great Smoky Mountains National Park

USDA Forest Service:

Southern Forest Experiment Station

Southeastern Forest Experiment Station

Region 8, National Forest System

Society of American Foresters

Tall Timbers Research Station

Association of American Geographers

Published by: Southeastern Forest Experiment Station

P.O. Box 2680, Asheville, NC 28802

August 199 1

PREFACE

Fire and the Environment: Ecological and Cultural Perspectives was an international symposium held on

March 20-24, 1990, in Knoxville, TN. The meeting was attended by over 150 researchers, land

managers, and wildlife managers. Forty-one papers based on oral presentations are included under four

categories: Fire Ecology; Fire Management; Cultural; and Fire History. In addition, three papers are

presented from a special session on the 1988 tires in the Greater Yellowstone Area and fourteen papers

are presented from a poster session.

Papers and posters were selected by the program committee based on title summaries submitted prior to

the meeting. The major objective of the editorial committee was to compile a proceedings covering a

broad range of topics with papers representing new results, ongoing research, overviews of past research,

and new ideas or hypotheses. Preference was given to papers covering cultural aspects of fire; such as

public perception of tire, fue policy, wildland/urban interface, historical and prehistoric roles, fire and

climate, use of fi toward management objectives, and effects of fue exclusion; and ecological effects of

f.re on climate, air quality, water quality, nutrient cycling, wildlife, fisheries, vegetation, and soils.

After the meeting, papers were submitted to the editorial board for review. Each paper was given a

blind review by two peers and one grammatical editor. Reviewer comments were incorporated by

authors and submitted to the editorial board for approval. Some papers required additional revision but

all papers were accepted. These proceedings have been prepared electronically from copy supplied by

the authors. Authors are responsible for the content and accuracy of their papers as well as any stated

opinions or conclusions.

The steering committee gratefully appreciates the efforts of authors and reviewers who contributed to a

successful and informative program. Our appreciation is given to Brian Ostby and John Mullins, who

arranged the poster session, and to Janet Paces, Ellen Williams, and Julie Smith, who served as assistants

to the Program Chairman and proceedings editors. A special note of thanks is given to the moderators

who provided additional insight to each topic and kept each Session on schedule. Moderators included

William Boyer, Southern Forest Experiment Station; Bob James, USDA Forest Service, Region 8; Gary

Schneider, The University of Tennessee; Eugene McGee, The University of Tennessee; Joe Abrell,

USDI Park Service; Frank Woods, The University of Tennessee; Joe Clayton III, Tennessee Division of

Forestry; Dale Wade, Southeastern Forest Experiment Station; David Van Lear, Clemson University;

Larry Landers, Tall Timbers Research Station; Thomas Waldrop, Southeastern Forest Experiment

Station; and Stephen Nodvin, USDI Park Service.
STEERING COMMITTEE

Edward Buckner, Conference Chainnan

The University of Tennessee

Charles Hardin,

Society of American Foresters

Stephen Nodvin, Prop-am Co~irtPe Chairman

and Proceedings Editor

National Park Service

Thomas Waldrop, ProceedingsEd$or

Southeastern Forest Experiment Station

Frank Woods, Publicity Committeechainnon

The University of Tennessee

George Weaver, Editotil Committee Chairman

The University of Tennessee

Joe Abrell

National Park Service

William Boyer

Southern Forest Experiment Station

Dewey Bunting

The University of Tennessee

Joe Clayton III

Tennessee Division of Forestry

Bob James

USDA Forest Service, Region 8

Sid Jumper

The University of Tennessee

Larry Landers

Tall Timbers Research Station

David Van Lear

Clemson University

Dale Wade

Southeastern Forest Experiment Station
CONTENTS

Keynote Address

Variable Fire Regimes on Complex Landscapes:

Ecological Consequences, Policy Implications, and

Management Strategies

N.L. Christensen, Jr.

FIREECOLOGY

Effects of Fire Exclusion on Tallgrass Prairie and

Gallery Forest Communities in Eastern Kansas

M.D. Abrams and D.J. Gibson

Fire Management for Maximum Biodiversity of

California Chaparral

J. E. Keeley

Fire and Oak Regeneration in the Southern Appalachians

D.H. Van Lear

Response Types to Prescribed Fire in Oak Forest

Understory

H.R. DeSebn and E. E. C. Clebsch

Implications for Long-Term Prairie Management from

Seasonal Burning of Loess Hill and Tallgrass Prairies

T.B. Bragg

Forty Years of Prescribed Burning on the Santee Fire

Plots: Effects on Overstory and Midstory Vegetation

TX Wakirop and F.T. Lhyd

Forty Years of Prescribed Burning on the Santee Fire

Plots: Effects on Understory Vegetation

D.L. White, T.A. Wakirop, and S.M. Jones

Forest Development Following Disturbances by Fire and

by Timber Cutting for Charcoal Production

W. K. CIatterbuck

Natural Revegetation of Burned and Unburned Clearcuts

in Western Larch Forests of Northwest Montana

R. C. Shearer and P. F. Sticky

Changes in Woody Vegetation in Florida Dry Prairie and

Wetlands During a Period of Fire Exclusion, and After

Dry-Growing-Season Fire

J.M. Hu@nan and S. W. Blanchard

Page

ix

3

1 1

15

22

34

45

51

60

66

75

Page

Livestock Grazing Alters Succession After Fire in a

Colorado Subalpine Forest

W.L. Baker

84

Climatic Change and the Modeling of Fire Effects in

Coastal Sage Scrub and Chaparral

G. P. Malanson and W. E. Westman

91

Wildland Fire Management and Landscape Diversity in

the Boreal Forest of Northwestern Ontario During an Era

of Climatic Warming

R. Sufling

97

Hazel Pistol Erosion Plot Study on the Siskiyou National

Forest in Southwest Oregon

W.F. Hansen

The Significance of Fire in an Oligotrophic Forest

Ecosystem

F. S. Gilliam

The Effect of a High Intensity Fire on the Patch

Dynamics of VA Mycorrhizae in Piiyon-Juniper

Woodlands

CC. Klopatek, C. Friese, M.F. Allen, L.F. DeBano,

and J.M. Klopatek

Forest Soil Characteristics Following Wildfue in the

Shenandoah National Park, Virginia

D.A. Groeschl, J. E. Johnson, and D. Wm. Smith

The Interaction of Prescribed Fire, Monoterpenes, and

Soil N-Cycling Processes in a Stand of Ponderosa Pine

(pinus ponderosa)

C.S. White

Loss, Retention, and Replacement of Nitrogen

Associated with Site Preparation Burning in Southern

Pie-Hardwood Forests

L.R. Boring, J.J. Hendricks, and M. B. Edwards

Fire Effects on Nutrient Pools of Woodland Floor

Materials and Soils in a Piiyon-Juniper Ecosystem

J.M. Klopatek, C.C. Klopatek, and L.F. DeBano

Effects of Fell-and-Bum Site Preparation on Wildlife

Habitat and Small Mammals in the Upper Southeastern

Piedmont

TL. Evans, D.C. Guynn, Jr., and T.A. Waldrop

Effects of Fire and Timber Harvest on Vegetation and

Cervid Use on Oak-Pie Sites in Oklahoma Ouachita

Mountains

R. E. Masters

107

113

123

129

138

145

154

160

168
Page Page

FIREMANAGEMENT FIREHISTORY

Cost-Effective Wilderness Fire Management: A Case

Study in Southern California

c.A. Chi&rs and D.D. Piirto

179

Fire History and Effects on Vegetation in Three

Biogeoclimatic Zones of British Columbia

J. Panninter

263

Adaptive Fire Policy

J.M. Saveland

187 Anthropogenic Fire and Tropical Deforestation: A

Literature Perspective

M. R. Wetzel and P. N. Omi

213

Prescribed Fire and Visual Resources in Sequoia

National Park 192

K. J. Dawson and S. E. Greco

GIS Applications to the Indirect Effects of Forest Fires

in Mountainous Terrain

D. R. Butler, S. J. Walsh, and G. P. Malanson

202

Wildfire in the Paleozoic: Preliminary Results of a Case

Study on the Fire Ecology of a Pennsylvanian Floodplain

Forest, Joggins, Nova Scotia, Canada 219

N. C. Arens

G]S Applications in Fire Management and Research

J. W. van Wagtendonk

212

Fire History and Fire Ecology in the Costa Rican

Paramos

S. P. Horn

289

FIREMAP 215

G.L. Ball and D. P. Guertin

A Survey of Aboriginal Fire Patterns in the Western

Desert of Australia

N.D. Burrows and P. ES. Christensen

291

The Art of Long-Range Fire Weather Forecasting

F. M. Fujioka

219 Indian Use of Fire and Land Clearance in the Southern

Appalachians

M. S. DeVivo

306

CULTURAL

Private, Non-Industrial Forest Owner’s Perceptions of

Controlled Burning Influencing Forest Management

D. W. McConnell II and S. B. Baldwin

221

SPECLAL SESSION:

THEYELLOWSTONE FIRES

Social Impact of Computers in Urban Fire Fighting

S.M. Davi

234

Bark Beetle-Fire Associations in the Greater

Yellowstone Area

G. D. Amman

313

Fire’s Importance in South Central U.S. Forests:

Distribution of Fire Evidence d

V. A. Rudis and T. V. Skinner

240

Yellowstone Media Myths: Print and Television

Coverage of the 1988 Fires

C. Smith

321

A Site-Specific Approach for Assessing the Fire Risk to

Structures at the WildlandKJrban Interface

J.D. Cohen

252

251

The Evolution of National Park Service Fire Policy

J. W. van Wagtendonk

328

Perception of Fire Danger and Wildland/Urban Policies

AAer Wildfire

R.C. Abt. M. Kuvoers. and J.B. Whitson
Page

POSTER SESSION

The 1985 Butte Fire in Central Idaho: A Canadian

Perspective on the Associated Burning Conditions

M. E. Alexander

334

Climate, Fire, and Late Quaternary Vegetation Change

in the Central Sierra Nevada

E.G. Edlund and R. Byrne

Behavior of Headfines and Backfires on Tallgrass Prairie 344 Fire-Herbicide Systems for Manipulating Juniper

T.G. Bidwell and D.M. EngJe D.M. EngIe and j.F. Siritzke

Fire and Agricultural Origins: Preliminary investigations 351

M. A. 

Elasticities Assist Targeting of Arson Prevention

Programs

R.A. Klueader and L. C.Thompson

Floristic and Historical Evidence of Fire-Maintained,

Grassy Pine-Oak Barrens Before Settlement in

Southeastern Kentucky

J.J. h? Campbell, 13. D. Taylor, M.E. Medley, and

A. C. Risk

359

Long-Term Impacts of Fire on Coastal Plain Pine Soils

W.X. M&Tee, Jr.

Lodgepole Pine Arthropod Litter Community Structure

One Year After the 1988 Yellowstone Fires 316

T.A. Christiansen, R.J. Lao&e, and /.A. Lockwood

Fires, Forests, and Tribes in the Northern Philippines:

Cultural and Ecological Perspectives

5. Codamon-Quitron

Some Thoughts on Prescribed Natural Fires

JD. Cohn

381

Smoke Management: Are Rights Included With the

Responsibility to Use Fire in Managing Public Lands?

D.A. Skinn

Use of the 1990 Census to Define Wildland Urban

Interface Problems

J.B. Davis

384

Spatial Dynamic Fire Behavior Simulation as an Aid to

Forest Planning and Management

M. J. Vaxoncekw and J.M. C. Pereira

LIST OF AUTHORS

390

397

402

405

414

418

421

429

vii

Key note Address

VAFUABLE FIRE REGIMES ON COMPLEX LANDSCAPES:

ECOLOGICAL CONSEQUENCES, POLICY IMPLICATIONS,

AND MANAGEMENT STRATEGIES

Norman L. Christensen, Jr.’

XN’I’RODUCTION

Half a century ago, fiie policy in most public and private

agencies charged with the management of wilderness was

neatly summarized in the so-called 10 A.M. Rule: If a fire

starts, it should be extinguished by 10 the next morning. Our

attitudes toward fire and other natural disturbances in

wilderness landscapes have changed during recent decades.

We now recognize that disturbances caused by lire, wind,

insects, and pathogens play key roles in a variety of

ecosystems processes. The folly of excluding or trying to

exclude agents of disturbance from landscapes is now obvious

to most wilderness managers.

Despite this knowledge, articulation of operational policies

and management strategies for wilderness preserves has

proven to be a daunting task. What arc the proper fire

regimes for our diverse wilderness ecosystems? How and

why have the frequency and behavior of tire changed through

time? How have human activities such as a century of tire

exclusion, landscape fragmentation, and alteration of ignition

patterns affected fire regimes? How can we reintroduce hre

into landscapes so altered? How can wilderness fire managers

accommodate nonwilderness values such as recreation, timber

and watershed resources, and air quality? Finally, how do we

know when we are managing fire correctly?

In this paper, I shall argue that questions such as these can

only be answered in the context of a clear understanding of

wilderness processes and overall wilderness management

objectives. I shall assert that wilderness management should

be based on the answers to three questions, and since we have

generally answered two of these questions incorrectly presents

us with our most difficult management challenges.

NATURAL DISTUFGMNCE AND

MANAGEMENT POLICY

Wilderness management can be reduced to answering

correctly three questions: 1. What should be preserved?

2. How should preserves bc configured? 3. How should

management be executed (Christensen 1988)?

‘Professor and Dean, School of the Environment, Duke University,

Durham, NC 27706.

What should we preserve?

The actual foci of preservation in particular wilderness

ecosystems are often identified in nebulous, nonoperational

terms or are not stated at all. The question must be answered

in both philosophical and practical terms. We must first

agree on the categories of items that will be the objects of

preservation (i.e., genotypes, species, ecosystems, landscapes,

etc.). Having made this decision, we must then determine

which items within a category are worthy of preservation; that

is, we must produce “shopping lists”--lists of rare and

endangered species, or inventories of various ecosystem

types, for example. The formulation of such lists is often the

occasion for battles over the dedication of land to wilderness

or nonwildemess management. In many regions, our

ignorance of ecosystem variability prevents us from making

such lists.

How should preserves be configured?

Patterns of natural disturbance have rarely, if ever, been a

major consideration in the spatial configuration of wilderness

preserves. However, if a wilderness preserve is to include

the full range of patterns generated by natural disturbance, the

frequency, area1 extent, and behavior of such disturbances

must be considered. Ideally, a preserve should be sufficiently

large to include not only the variety of post-disturbance age

classes typical of a pristine wilderness landscape, but also the

range of variation in disturbance severity. When disturbances

occur on small spatial scales and at high frequency, small

preserves will suffice. However, in environments in which

large-scale tires are the norm (e.g., western coniferous forests

and shrublands), few existing preserves are large enough. In

addition, those who determine preserve boundaries should

understand the effects of landscape features on the behavior of

disturbances.

How should management be executed?

The details of procedures for managing natural disturbances

depend on a variety of considerations. For unpredictable and

uncontrollable disturbances such as the Mt. St. Helens

eruption, management will focus on post disturbance

intervention and will likely involve compromises between the

wish to allow the affected area to recover as it would have in

our absence and the potential consequences of the lack of

intervention for areas outside the preserve (e.g., flooding,

siltation, etc.). In the case of fire, where management

intervention may alter the course of the disturbance,

additional issues must be addressed. The manager must

ix
decide the extent of disturbance that is acceptable within the

constraints of the design of the preserve. For example,

assuming suppression is a real option, should a naturally

ignited fire be allowed to become so large that containment is

impossible or allowed to consume a major portion of the

preserve? We know very little about the ecological

consequences of artiticially limiting the size of such

disturbances. Are there wilderness processes that depend on

the occurrence of fues of large spatial extent?

FIRE REGIMES AND ECOSYSTEM

RElSPONSE

Many of our views about the role of natural disturbance in

general, and of wilderness fire in particular, reflect the

evolution of ecological theories pertaining to succession, the

recovery of ecosystems from disturbance. Clements’ (1916)

theory of succession portrayed wilderness as the touchstone of

stability and order. Natural disturbances such as tire not only

alter the structure of ecosystems, but render the landscape less

habitable. Pioneer species that colonize such disturbed areas

are usually organisms with high dispersal ability and

considerable tolerance of harsh conditions; such organisms are

rarely effective competitors under favorable growing

conditions. Clements posited that these vagrant species

become established and alter the environment of a disturbed

site by stabilizing and enriching soil and by creating a

microclimate that favors establishment of other species.

Similarly, these new invaders alter their environment so as to

favor yet another wave of immigrants. This succession of

species continues until a community of organisms is

established that maintains its environment in such a way as to

perpetuate itself. This so-called climax ecosystem was

considered to be the most stable assemblage of organisms that

could exist on a given site within the constraints of regional

Thus, ecosystems develop much like individual organisms

from simple beginnings toward increasing complexity and

stability. Ecologists of Clements’ era recognized that individual organisms would necessarily die, but asserted that the

regeneration of climax community species was associated with

small-scale disturbances such as the deaths of individual trees.

Over spatial scales of interest to wilderness managers, the

composition and structure of climax ecosystems was thought

to remain constant over long periods of time. In Clements’

(1935) words, “Under primitive conditions, the great climaxes

of the globe must have remained essentially intact, since fires

from natural causes were undoubtedly infrequent and

localized.” The quantity of data supporting this theory was

quite small However, we generally require little data to

support theories that portray the world as we wish it to be. It

was indeed appealing to view wilderness as inevitably

converging on stability. The vision of a climax ecosystem as

a “super organism” composed of species performing specific

functions as if they were roles much like the organs and

tissues of an individual organism was proof of the “balance of

nature.”

This model of ecosystem change provided clear guidelines for

management of wilderness. The object of management (Whf

should be climax ecosystems. The supposed

structure of attributed to climax communities was often based

on romantic accounts by early explorers and naturalists. The

view that species comprising natural communities were

regenerated by small disturbances implied that questions about

preserve configuration could be answered by reference to

economic and political factors. If the dominant species can

reproduce in openings created by the demise of individual

trees, then relatively small areas should be sufficient to

perpetuate the entire community. Consequently, the

boundaries of our major wilderness parks have very little in

common with natural ecological barriers or divides. Finally,

it was clear that the key to preserving wilderness areas

(management e.recution.f’)thus defined was the prevention of

catastrophic disturbances. Only in this way could we nurture

wilderness to its climax state.

Research over the past three decades has taught us that

Clements’ theory was at best too simple and at worst flat

wrong. Long-term studies demonstrate that the process of

ecosystem change is not nearly so predictable or simple as

Clements imagined (See Christensen 1991 for a review).

Perhaps the most startling discovery was that many

ecosystems become increasingly unatuble during succession,

particularly in areas where fire is an important factor. Early

in the development of most forests there is an abundance of

green, moist, and relatively non-flammable plant tissue.

However, as communities develop, dead woody debris

accumulates increasing the ability of such communities to

carry a fire. Exclusion of tire from such systems may result

in additional fuel accumulation, increased flammability, and

higher fire intensity when fires eventually occur. We have

learned that fire is an essential and inevitable agent of

biomass decomposition in many forest ecosystems.

If succession following disturbance is not a linear, predictable

process that terminates with the establishment of a stable

climax community, perhaps we can view it as a deterministic

and stable cycle, driven by internal feedbacks such as fuel

accumulation and inevitable fires. In this view, ecosystems

are dynamically stable, like a pendulum with a period

determined by return times between disturbances.

Alas, wilderness landscapes are not so easily modeled.

Disturbances are indeed regulated in part by internal

feedbacks, but actual periods or return times are quite

variable and heavily dependent on extrinsic factors such as

variations in regional climate. Furthermore, variations in

disturbance intensity result in highly variable trajectories of

X
postdisturbance change. Thus, the pendulum may swing in a

highly chaotic random fashion. Wilderness landscapes are

best viewed as an ever-changing “patch mosaics,” and the

frequency distribution of patch types may vary as a

consequence of short- and long-term changes in climate and

other chance factors (See Pickett and White 1985).

The pattern of successional change from less to more

habitable conditions proposed by Clements is often reversed

in the case of postfire ecosystem succession. As forests

develop following fire, mineral nutrients such as nitrogen and

phosphorus become less available in the soil as they are taken

up and stored in plant tissues. Thus, low fertility, organic

debris in the forest floor, and shade cast by mature trees may

severely limit opportunities for seedling establishment and

growth of the young plants in late succession ecosystems.

The ash raining onto burned soils is an effective fertilizer, and

postfue microclimate often favors successful plant

reproduction.

This pattern of environmental change in relation to tire has

resulted in evolution of plant adaptations that concentrate

reproductive effort in the period immediately following the

tire. Such adaptations include underground buds that are

protected from heat, production of seeds that germinate only

when heated, cones or fruits that open only when heated, and

production of flowers only following fire. The evolution of

such adaptations has not simply made some ecosystems

tolerant of fire; it has made them dependent on it. Burned

areas quickly lose their bleak aspect and, by the end of a

single growing season, are carpeted with new growth.

Describing the evolution of knowledge in another area,

Samuel Clements quipped that “the researches of many

commentators have shed considerable darkness on this

subject, and should they continue we shall soon know nothing

about it.” What once appeared to be a tidy linear process

leading inevitably to stability on relatively small spatial scales

is now seen as a dynamic, chaotic, and complex pattern of

change in which the word “stable” may have little if any

meaning.

POLICY, MANAGEMENT, AND RESEA RCH

IMPLICATIONS

Policy Considerations

Given the variability in tire history, tire behavior, fire effects,

and fire responses, it is clear that fire policies must vary from

preserve to preserve. Nevertheless, I suggest that successful

policies will have three common characteristics: (1) clearly

stated operational goals, (2) identification of potential

constraints, and (3) recognition of the variability and

complexity of the successional process.

It is not enough to acknowledge that tire is an important

natural process in an ecosystem and then simply reintroduce

tire to the ecosystem. We must formulate specific operational

goals for fire management programs. We do not set aside

wilderness preserves in order to bum them. Rather we

should withhold, apply, regulate, and respond to tire in order

to accomplish specific management goals. The specification

of these goals is made more difficult by the complexity of

change on many landscapes.

The difliculty of setting operational goals is illustrated by the

problems that the National Fire Management Policy Review

Team (Philpot 1988) encountered when it attempted to define

the specific goals of the Fire Manager Programs in federal

wilderness areas. The overall goal was relatively simple--i.e.,

“to restore fue to a more natural role.” But this formula begs

the question “What is natural?” The Review Team defined

natural as “those dynamic processes in components which

would likely exist today and go on functioning, if

technological humankind had not altered them.” Putting aside

the implication that Native Americans lacked technology, this

statement seems to suggest that if natural processes are simply

allowed to operate, ecosystems will converge to some

preferred state. Although the details are far from clear, we

are beginning to appreciate that landscape change is more

chaotic than convergent.

Specification of objectives requires a clear understanding of

the specific elements for which a preserve was dedicated.

These may include historical features, species preservation, or

preservation of entire wilderness areas. With regard to

specific objects or species populations, policy objectives will

likely be clear. However, a great deal of confusion exists

regarding what constitutes wilderness. Wilderness is usually

detined in contrast to human-altered landscapes, where

wilderness represents the lack of human intervention. Given

this definition, the phrase “wilderness management” should be

considered an oxymoron. However, the pervasiveness of

human influence ranging from the dissection and

fragmentation of landscapes to global climate change may

create conditions in which the most potent form of human

intervention may be restraint.

We cannot simply set aside a piece of real estate and expect

that, in the absence of human intervention, “those dynamic

processes and components” will go on functioning as if

“technological humankind had not altered them.” We have

created a world that we are obliged to manage. Given this

situation, we are obliged to formulate policy based on

operational definitions of wilderness. In particular we need to

be explicit about such goals as preservation of ecosystem

processes, biodiversity, and heterogeneity.

It is essential that policymakers understand the potential

constraints on management in wilderness preserves. Within

the realm of the “natural,” a wide variety of landscape

configurations is possible. However, within the constraints of

preserve design, not all these configurations are equally

xi
desirable. Million-acre fires may be natural phenomena on

the Yellowstone Plateau, but the desirability of such fires in

the context of the altered landscape can be determined only by

evaluating the costs and benefits of events on this scale.

In many cases, policymakers arc faced with competing or

conflicting preserve objectives. For example, the Organic

Act of 1916 that established the National Park Service extols

managers to “conserve the scenery in natural and historic

objects and the wildlife therein and to provide for the

enjoyment of the same in such a manner and by such means

as will leave them unimpaired for the enjoyment of future

generations . * It does not take a lawyer to detect the

multitude of ambiguities and possible interpretations in this

statement. For that matter, the 1963 Leopold Committee’s

assertion that the proper goal of national park conservation is

the preservation of a “vignette of primitive America” is open

to various interpretations. Some would view it as a mandate

for the so-called “living museum” approach to park

management, where the goal is to preserve “snapshots” of the

past. Alternatively, the term vignette can be defined as a

“moving picture” so as to include the process orientation of

current Park Service policy.

The constraints on tire management posed by liability to other

public and private resources are considerable. This is

particularly true in wilderness preserves where goals include

recreation or watershed management, and in situations where

arbitrary borders separate wilderness from land dedicated to

nonwildemess functions. The constraints on conservation of

wilderness in an increasingly urbanized context are

exemplified by issues such as air quality and smoke

management. For example, burning in Sequoia National Park

contributes to air quality problems in California’s Central

Valley. It may bc natural that wilderness fires inject

particulates into the atmosphere, but the emission of these

particulates may be deomed unacceptable by air quality

authorities who must consider that the atmosphere is already

polluted with a host of anthropogcnic emissions.

Fire policies must recognize the constraints set by preserve

design. We have chosen to preserve relatively little of once

vast expanses of wilderness, and the borders of most

preserves bear precious little relation to the natural processes

necessary for their preservation. The acceptability of fire

events of particular intensities or spatial extent cannot be

based solely on the naturalness of such events. Given the

constraints of preserve design, many natural events may be

deemed unacceptable or at least undesirable. This is

particularly true where we can preserve only small fragments

of formerly large landscapes. In these situations it is

important to understand the ecological costs of not allowing

large scale or high intensity events to occur.

Perhaps the most significant constraint on policy development

is ignorance. Stewards of wilderness cannot claim, nor does

the public have a right to expect, perfect knowledge. The

only fair expectation is good faith. Policy makers and the

public must understand the limits of our understanding.

When I was in my late teens, my grandmother took me to

task for some transgression, the specifics of which now

escape me. My excuse was that I was just trying to do what I

thought was right. Grandma’s reply? “Norman, you should

not do what you think is right, you should do what is right!”

I thought for a moment and said “Grandma, that’s the

dumbest thing i have ever hard. ”

The public’s expectations are much like my grandma’s,

Managers must be ever cognizant of what I shall call

Grandma’s Law: “All we can ever do is what we think is

right.’ However, what managers consider right has changed

markedly as our understanding has developed over the past

several decades. Thus, I propose a corollary to Grandma’s

Law: “Just because you think you are right does not

guarantee that you are.

Fire policies must allow for the variability and complexity of

the process and its context. We are learning that variability is

an essential component of fire regimes and that policies

should not necessarily seek to replicate mean values of

intensity, return time, etc. Furthermore, policy options and

goals will vary considerably across the spectrum of fire

regimes. Because we can prescribe low intensity tires like

those that occur in grasslands with high scientific precision,

we expect similar precision in the application of tire in heavy

forest fuels. However, our management options in these

latter situations may be more akin to those for large scale

disturbances such as hurricanes and volcanic eruptions.

Finally, policies must be developed against a backdrop of

constant change. In his classic paper on succession, Henry

Chandler Cowles (1901) characterized succession as “a

variable converging on a variable.” Given the pervasiveness

of human-caused environmental change, the notion of

“natural” may be moot at best.

Management Considerations

Management involves the development of interventions to

achieve specific policy objectives. Recognizing our

considerable uncertainty and ignorance about the processes WC

must manage, management should be thought of as a direct

application of the scientific method. Its success depends not

only on a clear understanding of available options

(hypotheses), but also on a monitoring system that provides

direct feedback to managers regarding management

consequences (experiments and tests).

xii
Fire management options include complete suppression,

planned-ignition prescriptions, natural emission prescriptions,

“let bum” strategies, and a range of fire surrogates. Where

complete fire suppression is necessary, guidelines for

managing the effects of suppression are critical. Such effects

include those of employing tire retardants, plow lines, and

heavy equipment. Where fires cannot be allowed to burn,

managers may need to consider surrogates for burning such as

mechanical field manipulation and artificial cutting.

Planned emission prescriptions must differentiate between the

means and the ends. Historically, most prescribed burning

protocols have been developed in the context of siivicultural

management in which the end goals are field reduction and

discouragement of competitors (i.e., reduced diversity).

Management goals in wilderness areas will likely be quite

different and require different burning protocols. In

developing bum plans it is important to distinguish between

fires set to restore fuel conditions to some “natural” state and

fires set to simulate a “natural” process.

Prescribed natural ignition programs allow fires ignited by

natural causes to bum so long as they are within prescribed

guidelines. In a sense, such fire management programs

substitute knowledge for intervention. They assume that

threshold levels of fire behavior can be established beyond

which tires can and should be suppressed. These is serious

question whether such fire programs are realistic and natural.

For example, such plans may call for the suppression of

ecologically important but intense fire events. Furthermore,

given the extent of landscape fragmentation and alteration, it

is unlikely that fire regimes developed in this manner will

simulate the full range of natural processes.

Only in the largest wilderness areas will an unmodified “let

bum” fne management plan be a viable alternative.

Nevertheless, wildfires will occur and fire management plans

must provide clear guidelines for specific postdisturbance

interventions. These guidelines must include appropriate

measures for erosion mitigation, reforestation, and wildlife

management interventions. Those who formulate guidelines

for postfire interventions should consider the benefits of the

intervention and their environmental and monetary costs, and

should consider the likelihood of their success.

Any reasonable management system must have a built-in

program for evaluating management’s success in

accomplishing policy goals. Such a monitoring program

should be viewed as a set of research hypotheses especially

designed to test whether management is providing the desired

effects on specific dependent variables such as fire diversity,

decomposition and nutrient cycling, and landscape

heterogeneity. Monitoring programs not only provide

information that can be used to adjust to management

protocols, but also serve to inform basic scientific research

programs.

Research Needs

it is clear that there is much that we do not know regarding

the role of fire in wilderness ecosystems. I feel three areas

deserve special attention. (1) There is much to learn about

the causes and consequences of variability in fire regimes.

For example, the Yellowstone lires taught us that models of

fire behavior are not easily transferred among ecosystems.

Even within a landscape, interactions between climate and

fuels may result in multiple patterns of fire behavior. The

consequences of variation in fire behavior are also little

known. Fire often results in a pulse of resource availability

which, although cphcmcral, may greatly influence patterns of

species establishment. The variability in such pulses may

have much to do with the biodiversity of landscapes

throughout the fire cycle. (2) Although we know that

variation in the spatial and temporal scale of fire events can

greatly affect patterns of species response, the specifics of

such patterns and their mechanisms are poorly understood.

Implicit in much of wilderness fire management is the notion

that many small events can be substituted for a single large

event, but in most cases this assertion has not been tested.

(3) Given the constraints on fire management programs, it is

important to understand the ecological consequences of

departures from “normal” fire regimes. Am them ecological

costs associated with the exclusion of high intensity fires from

certain parts of the landscape?

LITERATURE CITED

Christensen, N.W. 1988. Succession and natural disturbance:

paradigms, problems, and preservation of natural

ecosystems. In :Agee, J.K.; Johnson, D.R. eds..

Ecosystem management for parks and wilderness. Seattle:

University of Washington Press. 62-86.

Christensen, N.L. 1991. Wilderness and high intensity fire:

how much is enough? Proceedings, Tall Timbers Fire

Ecology Conference 17:9-24.

Clements, F.E. 1916 Plant succession: an analysis of the

development of vcgctation. Carnegie Institute Publication

242. Washington, DC: Carnegie Institute.

Clements, F.E. 1935. Ecology in the public service.

Ecology 16: 342-363.

Cowles, H. C. 1901. The physiographic ecology of Chicago

and vicinity: a study of the origin, development, and

classification of plant societies. The Botanical Gazette 31:

73-108, 145-182.

Pickett, S.T.A.;White, P.S., eds. 1985. The ecology

of natural disturbance and patch dynamics. New YorK:

Academic Press.

Xl11

FIRE ECOLOGY

EFFECTS OF FIRE EXCLUSION ON TALLGRASS PRAIRIE

AND GALLERY FOREST COMMUNITIES IN EASTERN KANSAS

Marc D. Abrams and David J. Gibson’

Abstract-The purpose of this review is 1 0 synthesize a long-term body of research dealing with fire

exclusion effects on tallgrass prairie and gallery forest communities on Konzn Prairie in eastern Kansas.

Upland and lowland prairie communities burned in spring at intervals ranging from 1-k 1 years were

consistently dominated (70-N percent cover) by .Andropogon&. Witit this increasing interval

between fires other dominant warn-season grasses, A. scouarius and SorEhastrum nutans, had decreased

cover, whereas fo&? and woody species had increased cover. Aboveground biomass was higher on an

annually bumed versus unburned lowland prairie, due to stimulated graminoid production. Sites unburned

for 10 or more years were converting to woodlands dominated by Juniperus, Ulmus. Gleditsil\pnd m.

Older gallery forests occurred in stream channels and ravines and were comprised of overstory Quercus and

ccllis and understory ~etiseE&s&andf~lery forests on Konvl Prairie dramatically

increased from the time of European settlement (18.50) to present; this has been attributed to decreased tire

frequency and intensity in the region. With continued fire exclusion this century forther succession in these

forests has caused oak replacement by more shade tolerant species.

IiWRODUCTION

Eastern Kansas receives approximately 33 inches (83.5

centimeters) of precipitation annually, which is enough to

sustain forest vegetation on all but the most xeric sites.

Historically, however, the region has been dominated by

Andropogon Sornhastrum Ykkxm t&grass prairie. n

forest vegetation does occur it is usually restricted to thin

bands along ravines and stream channels, called gallery

forests. It is well recognized that frequent fire in the region

limits woody vegetation expansion and helps to maintain

tallgrass prairie (Abrams 1988~). Moreover, the composition,

structure and productivity of tallgrass communities can vary

dramatically with relatively small changes in life frequency

(Abrams and Hulbert 1987, Gibson 1988). Following

European settlement in the mid-1800s, the number, extent and

intensity of fire most likely decreased in eastern Kansas,

resulting in changes in the ecological characteristics of prairie

and gallery forests in the region (Bragg and Hulbert 1976;

Abrams 1986). Similar changes in woody and prairie

vegetation occurred in eastern Oklahoma after decades of fire

suppression (Collins and Adams 1983).

Since the late 1970s the effects of fire and fire exclusion in

tallgrass prairie and gallery forest communities have been

studied on Konza Prairie in northeast Kansas. Studies

conducted in one or both community types include fire effects

on plant species composition, structure and productivity. The

purpose of this review is to synthesize these studies with

special reference to the effects of fire exclusion the grassland

and forest communities on Konza Prairie.

‘Assistant Professor of Forest Ecology/Physiology, School of Forest

Resources, The Pennsylvania State University; Assistant Professor of

Plant Ecology, Department of Biology, University of West Florida.

EONZA PRAIRIE

Konza Prairie Research Natural Area is 3,487 hectares of

tallgrass prairie habitat in Riley and Geary counties in the

Flint Hills of northeast Kansas. The Flint Hills are along the

western border of the tallgrass prairie province and because of

the steep and rocky topography include the only extensive

area of unplowed tallgrass prairie in North America. Gallery

forests in the region are dominated by Quercus spp. (oak) and

@& occidentalis (hackberry) and range from about 10 to

300 meters wide in protected portions in the prairie interior.

Specific methods for prairie and gallery forest data collection

and analysis can be found in papers by the authors cited

hereinafter. Prairie composition and productivity studies were

concentrated on 10-100 hectare water&& units, burned in

mid- to late April at various intervals since 1972. Each

watershed contains relatively broad, level upland (Florence

cherty silt loam or cherty silty clay loam soils) and lower

slope (Tully silty clay loam soils) sites. Florence soils are

relatively thin, well-drained and have numerous ch&

fragments in the top soil, whereas Tully soils are deep, gently

sloping and were formed from thick colluvial and alluvial

deposits, with few rocks (Jantz and others 1975). Because the

upland Florence soils store less water than Tully soils, plants

present become water-stressed sooner during dry periods than

plants on deep Tully soils (Abrams and others 1986).

The climate of the study area is continental, characterized by

hot summers, cold winters, moderately strong surface winds

and relatively low humidities (Brown and Bark 1971). The

average length of the frost-free season is 180 days. Mean

annual temperature was 12.8” C (range = -2.7 to 26.6” C)

and mean annual precipitation was 83.5 centimeters based on

a 30 year record (1951-1980). Precipitation ranges from 2.1

to 13.4 centimeters per month with May and June being the

wettest and December- February being the driest months.
Annual precipitation varies greatly and droughts occur

frequently. In northeast Kansas, drought occurred during 38

percent of the months between 193 1 and 1968 and of these 11

percent were rated severe or extreme (Brown and Bark 197 1).

COMPOSITION OF PRAIRIE

Presettlement Conditions

Although accurate presettlement conditions are not known, it

is generally accepted that the tallgrass prairie developed and

spread in an environment that included tire at frequent

intervals in the range of once every year to once every ten

years (Kucera 1981; Axelrod 1985; Hulbert 1973). In the

Kansas Flint Hills, frequently burned tallgrass prairie is

dominated by big blues&m (Andropogon gerardii) and other

tall warm-season grasses (e.g., Andropogon scoparius,

Sorghastrum w, and ‘Parhcumsvi~atum).p e c i e s

along with a number of forbs, e.g. Solidaeo missouriensis and

Yemonia baldwinii, occupy the majority of space in the

community and are referred to as matrix species (Collins and

Gibson 1990), whereas a large number of rarer interstitial

species occupy the spaces, e.g. Ambrosia psilostachva,

~tismiciana.

Effect of Fire Exclusion on Species Composition

On Konza Prairie, studies of permanent plots carried out since

1981 (Abrams and Hulbert 1987, Gibson and Hulbert 1987;

Gibson 1988) indicate that in the absence of grazing species

richness increases with time since fire until approximately 8

years, after which richness declines again (Gibson and

Hulbert 1987; Collins and Gibson 1990). This effect was

only observed in the context of the long-term study and was

not necessarily discernible on a yearly basis (table 1). Fire

exclusion from the tallgrass prairie allows the build up of a

soil seed bank (Abrams 1988a), which along with the more

suitable microsite conditions and heterogeneous community

structure (Collins and Gibson 1990) results in a more specie+

rich community.

Andropoxonperardii is the dominant species (cover = 70-90

percent) on Konza Prairie irrespective of fire treatment or

topography (table 1). Nevertheless, the cover of A.

scooarius, S. nutans and other warm-season species decrease

significantly with time since burning (table 1) (Abrams and

Hulbert 1987; Gibson and Hulbet-t 1987). In contrast,

Panicum virpatum showed no response to fire but had higher

cover on the deeper, moister soil of lowland sites. Cover of

Table 1. CMnwrity and plant species cover data (x- percent + standard

error) for three unborned and two emual~y burned upland (Florence cherty

Silt Loam) and louleod (Tul(y silt ciay Loam) SOitS 011 Koaza Prairie in

northeastern Kaosas in 1984. Valoes for each COmunit

species followed by the same Letter are not l

parameter or

* * values < 0.05 percent.

sigoificao ly different:

(After Abras and llulbert 1987)

Cmnity data

Buroed

treatsest Lowiand Upland

Total species cover burned

anberned

Sped es ri cbness borned

anburned

species/treatment burned

onbarned

Species data

Andropogon gerardii burned

unburned

A. scomrios burned

uobomed

Sorqhastrun nutans bmmed

aobmroed

Panicun virgatuq burned

unborned

Poa -pratensis burned

uoburned

-Forbs and woody plantsAster ericoides burned

unburned

Salvia azurea burned

unburned

&mbrosia silostacha barned

unburned

Artemi si a 1 tldovi ci ana burned

unbureed

Ammha cane$Cefj$ burned

unburned

176.5 + 3.2a

164.0 + 6.4a

g.33,’ (),o::

. .

46.0 + 2.8a

57.0 + 2.ab

83.5 + 5.la

04.5 + 2.2a

43.3 t 4.4a

5.4 + 1.4c

21.5 + 3.08

4.4 + l.Oc

12.5 + 6.h

5.6 + 2.4ab

0.0 I

21.9 + C.Ob

1.3 + 06a 0.5 + 0.3a

a.7 + 2.Ob 7.8 + 1.7b

*a 14.1 + 5.0b

*a 1.1 + 0.3c

2.8 + I.18 2.5 + l.la

lo.2 + 2.3b 8.2 + 1.56

0.1 + *a 0.1 + *a

12.6 + 2.9b a.0 + 1.7b

4.4 t 1.9a 1.1 + 0.4b

0.3 + O.lb 1.6 + 0.56

179.0 + 4.90

171.4 + 7.la

20.1 + O.Bb

21.2 + 0.76

54.0 + 0.7a

60.3 + 2.4b

80.6 + 2.2a

79.6 + 2.5a

24.0 + 4.9b

8.7 + 1.3c

33.4 + 4.bb

3.8 + 0.9c

5.6 + 2.lbc

1.9 + 0.9c

24.9 :a4.8b
the dominant cool-season grass Poa matens%, :vas not

affected by topography but was greatly reduced by annual

burning (table 1). The sensitivity to burning of this and other

cool season species is due to the loss of terminal growth from

spring burning (Abrams and Hulbert 1987). Warm-season

species are still dormant during spring burning and do not

show such sensitivity.

Cover of most forb and woody species increased with fire

exclusion. Salvia azurea (= 2. pitcherii) and Amotuha

canescens are exceptions to this, with cover being

significantly higher on annually burned upland and lowland

soils, respectively (table 1). Artemisia ludoviciana, Ambrosia

psilostachva and Aster ericoides are the dominant forbs on

fire excluded sites. Overall, woody species and forb species

cover increase with time since burning (Abrams and Hulbert

1987; Gibson and Hulbert 1987).

Multivariate analyses of species cover (Gibson and Hulbert

1987; Gibson 1988) have indicated that the species show an

individualistic response to fire frequency and topographic

position (fig. 1). This indicates that although it is clear that

fire exclusion from the tallgrass prairie leads to an increase in

the cover of many species, especially forbs (table l), the rate

of increase varies between species in a manner typical of

secondary successions (e.g., Pickett 1982). In contrast to

such typical models however, different species do not

successively attain and then lose predominance. Rather, A.

IX%-ardii remhins the dominant species throughout. S

likely a reflection of the fact that given continued fire

exclusion, grass dominated prairie is not the end-point of the

successional pathway. indeed, studies in Oklahoma indicate

an eventual dominance of tallgrass prairie by woody

vegetation after 32 years without fue (Collins and Adams

1983).

Sites that are burned every four years show cyclic fluctuations

in community composition, although soil effects and landscape

heterogeneity show a stronger relationship to the plant

community (Gibson 1988). Ungrazed prairie maintained

under such a frequent burning regime on Konza Prairie is

considered to be perhaps as comparable to presettlement

conditions as is possible under present day constraints.

Exclusion of fire for three year periods under this regime is,

however, sufficient time to allow for an invasion of woody

species (Briggs and Gibson, unpublished data).

0 .E

8 0.4

a ?

g

d ”

0.2

0.0

POPR ,/

/

1 2 3 4 5 6 7 8 9 10 11

Years since burning

Fig. 1. Fitted 1st and 2nd degree polynomial regression lines of species distribution along a tire interval gradient identified

by ordination analysis (Detrended Correspondence Analysis) (Afier Gibson and Hulbert 1987). ANGE = Androoonon

gerardii; ANSC = & scouarius: SONU = Sorghastrum_-, nutans. PAVI = Pan&urn-virgatumlPOPR = & pm&&+

SAA2 = &Jvia azurea; AMPS = Ambrosia osilostachva; ARLU = A&n&$&ludoviciana: AMCA = Amomha rln~v

ASER = Aster ericoides..
Prairie Productivity

Substantial differences in the seasonal (1984) production of

aboveground biomass by graminoids and forbs were evident

between an annually spring- burned and unburned watershed

on lower slopes (fig. 2). Peak standing crop of aboveground

production was significantly greater in the burned (430 + 26

grams per square meter) than unburned (368 + 31 grams per

square meter) watershed. This difference between burned and

unburned lowland prairie is consistent with the results of

long-term studies of productivity on Konza Prairie (Abrams

and others 1986; Briggs and others 1989). Peak live

graminoid biomass was also greater in the burned (285 + 20

grams per square meter) than unburned (205 + 22 grams per

square meter) site, whereas forb and woody plant biomass

was typically two-three times greater in the unburned

(maximum 94 + 15 grams per square meter) than the’burned

watershed (maximum 45 + 13 grams per square meter).

Woody plants, the smallest component of the total,

contributed little to total production. Both aboveground

production and the live graminoid component showed a

mid-season peak in late July-early August. In contrast, the

biomass of forbs and woody plants showed little seasonal

variation.

Invasion of Tree Species into Open Prairie

Woody species will rapidly invade open prairie in the absence

of fire and grazing, given a sufficient time and local seed

source (Gleason 1913; Weaver 1960; Grimm 1983; Bragg and

Hulbert 1976). On Konza Prairie, the invasion of trees has

been documented since 1971 by direct stem counts on over

500 hectares of open prairie. The principal tree species are

triacanthos, Populus deltoides, Salix spp., Ulmus americana,

and Celtis occidentalis (table 2). In frequently burned prairie,

, -

h

unturned

- annually turned ,+x, -----

I

I /

I Graminoids -\

Forts h Woody PhtsT

,-c--I.

-~---s---L-

-LT *I I , I 1 I , , I

June

lay 13

July July Aw Sept Sept act

2 4 3 2 3 12 I 2 1 I 1

1984

Fig. 2. The seasonal pattern of several components of

aboveground biomass on a burned and unburned lowland soil

during 1984 on Konza Prairie . Total aboveground

production includes live graminoids, forbs, and woody

plants, and current year’s dead biomass. Vertical bar

represents + standard error of the mean. (After Abrams and

others 1986).

densities of 2-3 trees per hectare have been recorded, while in

areas where tire has been excluded for 10 or more years

densities range from 12 to ‘77 trees per hectare. Over a five

year period, recruitment of all species into long-term

unburned areas is 6-7 individuals per hectare (Briggs and

Table 2. Stem density, species number, diversity and dominant species (> 15

percent of total stem density) of tree species in the open prairie on annually

burned and unburned (> IO years) watersheds on Konra Prairie in 1986.

Watersheds N4D and NIB contain large areas of gallery forest along the stream

channels.

Site and Tree Density Number of Diversity Dominant Species

Burn (number per Spec i es (Density per

Treatment hectare) (H’) hectare)

Annually Burned

1A

I D 2;

Unburned (IO years)

6 1.23 Gleditsia triacanthos (1.5)

4 0.94 Poputus deltoides (0.5)

UB 12.0 a 1.68

U C 29.6 9 1.28

N4D 54.7 1 8 1.50

NIB 76.9 1 3 1.20

Salix sp. (4.1)

ulmus americana (2.8)

G. triacanthos (0.7)

G. triacanthos (12.6)

P. deltoidas (12.6)

U. americana (28.5)

G. triacanthos (8.8)

U. americana (48.0)

Celtis occidentalis (12.1)
Gibson, unpublished data). In areas of open prairie adjacent

to stream channel gallery forests, U&americana and C&is

occidentalis are the dominant invasive species. This is a

reflection of their importance in the gallery forests (Abrams

1986). Other gallery forest dominants such as Quercus

muehlenbergii, Q. macrocama and Cercis candensis are only

occasionally found in open prairie. The ability of these forest

species to invade open prairie is related to their physiological

ability to withstand the relatively more xeric open prairie

habitat (Abrams 1988b). In areas further removed from the

gallery forests, ftre exclusion leads to an increase in the

density of species that normally persist in frequently burned

prairie albeit at low densities along the stream margins, i.e.

Cleditsia triacanthos. Ponulus deltoides, and %&,spp. (table

2). These are short-lived, early successional species common

in river floodplains and stream courses (BeUah and Hutbert

1974).

The spatial pattern of species invading open prairie from

which fire has been excluded is a function of species dispersal

vectors. Species such as Junioems virginiana, which are bird

dispersed, show a random pattern of distribution. In contrast,

wind dispersed species such as Ulmus americana show an

aggregated pattern. Juveniles of all species are clustered

around adults, but at a greater distance for the bird dispersed

species. At the landscape scale, invading tree species are

(except 2. virginiana) assoeialed with the stream channels.

[Group/ [Group2j

I 3 4

Upstream of mature gallery forest, attenuated gallery forest,

as seen on watersheds N4D and NIB (table 2) represents the

first stages of gallery forest development in open prairie in

the absence of tire.

GALLE:RY FOREST

Stand Classification and Ordination

Eighteen stands were method divided into four ecological

groups along the polar ordination axis according to

importance values of the three dominant species (fig. 3).

Group 1 (stands 1,2,6,18) included Celtis occidentalis -

Quercus macrocama dominated stands, with Q. muehlenbergii

and Ulmus as subdominants. Group 2 stands were dominated

by Q. macrocama (stands 3,9, IO) or Q. macrocama and Q.

muehlenbergii (stands 4,7) with lesser amounts of C&is and

0&rtms muehlenbergii and Q. macroeama G the

dominants and Ulmus and Cercis canadensis the subdominants

in group 3 (stands 5,8,11,12,14,16). Ouercus muehlenbergii

dominated stands in group 4 (stands 13,15,17), with Q.

macroca~~~ud..lJlmus as subdominants. Stand

positions along the polarordination axis were highly

correlated with increasing slope and decreasing silt, which

may be interpreted as a moisture gradient from me&e (group

1) to xeric (group 4) (Abrams 1986).

lGroup/ (Group/

I 8 12 14 1 7

:, 20 4'0 60 80 I 100 ?

250

.Bur Oak

m Chin uapin Oak

A Hat berry 9,

Laroup 4

3nn Group 2

1

I I I I I I

-

I +

1 0 20 30 40 50 60 70 80 90

Group Mean PO Score

Pig. 3. Polar ordination analysis and the mean importance values for the dominant spe&s in 18 gallery forest stands on

Konza Prairie. The four stand types are identified.
12.5

Stand 1

0

Fig. 4.

Age-diameter data

for gallery forest stand 1

on Konza Prairie.

(After Abrams 1986).

75-

%

a

so25-

A

o Quercus macrocarpa

8 Quercus muehlenbergii

A Celtis occidentalis

(I Ulmus son.

1 5 30

Age-diameter Data

Species age-diameter data from two representative gallery

forest stands are shown in figures 4 and 5. Stand 1 (fig 4) is

a Celtis - Q. macrocarua oak stand in which Q. macrocama

stems were the largest and oldest present; most Q.

macrocarna were over 40 centimeters diameter and 70 years

old and formed an even-aged canopy. The size and age of Q.

macrocarna was distinct from that of @& which generally

ranged from IO-40 centimeters diameter and 23-53 years old.

In stand 8, a Q. muehlenbergji - Q. macrocarpa stand, oak

species dominated the larger and older diameter and age

classes, whereaa,CeZeJUmus and, to a lesser extent, Celtis

dominated the smaller and younger classes (fig 5). A -

predominant age gap of 25-35 years separated these species

groups.

HISTORICAL DEVELOPMENT OF

GALLERY FORESTS ON KONZA PRAIRIE

Using data from the 1858 Original Land Office Survey of

Konza Prairie and aerial photographs taken in 1939 and 1978,

it was possible to determine changes in the extent of gallery

forests during that LX&year period (fig. 6). In 1858 only two

areas of continuous forest comprising about 5 hectares were

Fig. 5.

Age-diameter data

for gallery forest stand 8

on Konza Prairie.

(After Abrams 1986).

125

Stand 8

45 60 75

Diameter (cm)

90

noted. Occasionally, a few trees or scrubby timber and

shrubs were recorded in other areas of Konu Prairie,

especially along the stream channels and ravine bottoms, but

in general this area was described as rolling prairie devoid of

woody vegetation. The aerial photographs of Konza Prairie

taken in 1939 and 1978 were in marked contrast to that

described in 1858. During those periods a large expansion of

the gallery forests to approximately 111 and 206 hectares

occurred, respectively, with widespread invasion of

shrublands and forests onto the prairie and development of

shrublands into forests.

The distribution and overall ecology of the gallery forests on

Konza Prairie has been greatly affected by anthropogenic

factors. The limited extent of the gallery forests in 1858 was

probably due to higher tire intensity and frequency prior to

European settlement, which started about 1840 (cf. Penfound

1962). Following settlement, the number, extent and intensity

of fire most likely decreased in the Flint Hills due to road

construction, expansion of towns, agriculture, continuous

cattle grazing, suppression of wildfire and recommendations

against burning during the mid-1900s (Bragg and Hulbert

1976; Abrams 1985). Therefore, after settlement forests

8

0

l l

l Quercus macrocarpa

n Quercus muehlenbergii

). Celtis occidentalis

l Ulmus spp.

0 Cercis canadensis

1

I

I I I I

I

1 5 30 45 60 75 90

Diameter (cm)
1858

increased rapidly, which suggest that tire, rather than low

precipitation, limited growth of woody vegetation in northeast

Kansas (c.f Abrams 1988~).

It appears that a succession from shade intolerant Quercus

species to the more tolerant Celtis and Cercis is taking place,

despite these forests burning at intervals of about 1 I-20 years

since the mid-l 800s (Abrams 1985; Abrams 1986). Quercusmacrocama and/or Q. muehlcnbergii, which represented the

largest and oldest species in each stand, showed very little

recruitment into the tree size class for over half a century. In

contrast, numerous Cehis. Ulmus and Cercis trees younger

than 50 years old were present in these stands. On the mesic

sites Celtis may be the future sole dominant. Already in

group 1 stands (1,2,6,18) Celtis is the dominant despite it

being younger and smaller than 9. macrocama. On the

steeper, drier sites on Konza Prairie, where Celtis is rare,

Cercis may replace p. muehlcnberzii. The s~tature of

Cercis does not rule it out as a potential replacement species

here because the size of Q. muehlcnbergii is limited on these

harsh sites. Even though Ulmus is a dominant reproducer in

nearly ail stands, its potential as an overstory dominant is

probably limited by the Dutch Elm Disease. This blight was

discovered in Kansas in 1957 and has depleted many area

forests of mature elms (Thompson and others 1978). The less

advanced successional status of the xeric versus mesic forests

on Konza Prairie suggests that the rate of succession in xeric

forests is constrained by harsher environmental conditions

and/or higher fire frequency.

CONCLUSIONS

Subtle and gross changes in tire frequency dramatically alter

landscape patterns on Konza Prairie in the absence of grazing

Annual burning treatment resulted in the greatest dominance

for warn-season tallgrass species. Less frequently burned

areas develop progressively less cover of several dominant

grasses. However, cover of Androoogon, gerardii, the

dominant prairie grass, remained relatively unchanged in

upland and lowland prairie burned at I- to 1 l-year intervals.

With increasing intervals between fire, total cover of fort) and

woody species increased. Lowland sites, espectay along -

stream channels, unburned for 10 or more years show definite

signs of conversion to forest dominated by Juniperus,

OlddiGs. tlhnusnand M. e s t a b I i s h e d

woodlands along stream channels and ravines had overstories

dominated by ,,nJJcirfllE-anrt~t~~“With Celtis Cercis and

f0lmhs imthe &r&&ed&stribution o t h e s e

gallery forests since 1850 and successional changes resulting

in oak replacement by more shade tolerant species are

attributed to reduced fire frequency. Thus, our work on

Konza Prairie provides further evidence that fire is a primary

factor controlling community composition, productivity,

structure and successional processes in tallgrass ecosystems,

and that a frequent fire interval and possibly grazing and

periodic drought are necessary maintain tallgrass prairie in a

“‘pristine” condition.

R7E RBE 32 T 10 S

,I'

,,P -'

.,.

1 1 6

white Pasture '.'

' ...s.:I? 33

. ..+-<. 1113

. .._

Sham Creek

)- .<=-.5 4

24 19 20

p 7 E

I

1

J

c

1939

1978

R7E R6E

I

321 T 10s

!4 1 9 2 0

Fig. 6. Area] extent of gallery forests and shrublands

(shaded) in 1858, 1939 and 1978 on Konza Prairie.

9
LITERATURE CITED

Abrams, M. D. 1985. Fire history of oak gallery forests in

a northeast Kansas tallgrass prairie. Am. Midl. Nat.

114: 188-191.

Abrams, M. D. 1986. Historical development of gallery

forests in northeast Kansas. Vegetatio 65:29-37.

Abrams, M. D. 1988a. Effects of burning regime on buried

seed and canopy coverage in a Kansas tallgrass prairie.

Southwest. Nat. 33:65-70.

Abrams, M. D. 1988b. Genetic variation in leaf morphology

and plant and tissue water relations during drought in

Cercis canadensis L. Forest Sci. 34:200-207.

Abrams, M. S. 1988c. Effects of prescribed fire on woody

vegetation in a gallery forest understory in northeastern

Kansas. Trans. Kansas Acad. Sci. 9:63-70.

Abrams, M.D., A.K. Knapp and L.C. Hulbert. 1986. A

ten-year record of above ground biomass in a Kansas

tallgrass prairie: Effects of tire and topographic position.

Amer. J. Bot. 73:1X%1515.

Abrams, M.D. and L.C. Hulbert. 1987. Effect of

topographic position and tire on species composition in

tallgrass prairie in northeast Kansas. Am. Mid]. Nat.

117442-445.

Axelrod, D.I. 1985. Rise of the grassland biome, central

North America. Bot. Rev. 51:163-201.

Bellah, R.G. and L.C. Hulbert. 1974. Forest succession on

the Republican River floodplain in Clay County, Kansas.

The Southwestern Naturalist 19: 155-166.

Briggs, J.M., T.R. Seas& and D.J. Gibson. 1989.

Comparative analysis of temporal and spatial variability in

above-ground production in a deciduous forest and prairie.

Holartic Ecology 12:130-136.

Bragg, T.B. and L.C. Hulbert. 1976. Woody plant invasion

of unburned Kansas bluestem prairie. J. Range Manage.

29:19-24.

Brown, M.J. and L.D. Bark. 1971. Drought in Kansas

Kans. Agric. Exp. Stn. Bull. 547. 12~.

Collins, S.E. and D.E. Adams. 1983. Succession in

grasslands: Thirty-two years of change in a central

Oklahoma tallgrass prairie. Vegetatio 51:181-190.

Collins, S.L. and D.J. Gibson. 1990. Effects of fire on

community structure in tall and mixed-grass prairie. pp.

81-98. In: Effects of Fire in Tallgrass Prairie Ecosystems

(S. L. Collins and L.L. Wallace, Eds.) Univ. Okla. Press,

Norman.

Gibson, D.J. 1988. Regeneration and fluctuation of tallgrass

prairie vegetation in response to burning frequency. Bull.

Torrey Bot. Club 115:1-12.

Gibson, D.J. and L.L. Hulbert. 1987. Effects of fire,

topography and year-to-year climatic variation on species

composition in tallgrass prairie. Vegetatio 72:175-185.

Gleason, H.A. 1913. The relation of forest distribution and

prairie tires in the middle west. Toreya 13:173-181.

Great Plains Flora Association. 1986. Flora of the Great

Plains. Univ. Press of Kansas, Lawrence. 1392 p.

Grimm, E.C. 1983. Chronology and dynamics of vegetation

change in the prairie-woodland region of southern

Minnesota, U.S.A. New Phytol. 93:311- 350.

Hulbert, L.C. 1973. Management of Konza prairie to

approximate pre-whiteman tire influences, pp. 14-19. In

L. C. H&bet-t (ed.), 3rd Midwest Prairie Conf. Proc.,

Kansas State University, Manhattan.

Jantz, D. R., R. F. Hamer, H. T. Rowland and D. A. Gier.

1975. Soil survey of Riley county and part of Geary

county, Kansas, U. S. Dep. Agric. Soil Conserv. Serv.

71 p.

Kucera, C.L. 1981. Grasslands and fire, pp. 90-l 11. In H.

A. Mooney, T. M. Bonnicksen, N. L. Christensen, J. E.

Lotan and W. A. Reiners (eds.), Fire regimes and

ecosystem properties, USDA For. Serv. Gen. Tech. Rep.

WO- 26.

Penfound, W.T. 1962. The savanna concept in Oklahoma.

Ecology 43:774- 775. ,

Pickett, S.T.A. 1982. Population patterns through twenty

years of old field succession. Vegetatio 49:45-59.

Thompson, H.E., W.G. Willis and R.A. Keen. 1978.

Controlling Dutch Elm Disease. Kansas State Univ.

Agric. Exp. Sta. Bull. 626, 16 p.

Weaver, J.E. 1960. Flood plain vegetation of the central

Missouri Valley and contacts of woodland with prairie.

Ecol. Monogr. 30:37&k

1 0
FIRE MANAGEMENT FOR MAXIMUM BIODIVERSITY

OF CALIFORNIA CHAPARRAL

Jon E. Keeley’

Abshact-Two reproductive modes present in chaparral shrubs are affected very differentiy by fire. Some

species, called “tire-recruiters,” are dependent upon fire for seedling establishment. These species have

contributed to the notion that the chaparral community is dependent upon tire for rejuvenation. In the

absence of fire, chaparral is often described in pejorative terms which imply that long unburned conditions

represent an unhealthy state. However, many shrub species, called “fire-persisters,” do not establish

seedlings after fire, rather they require long fire-free periods in order to establish seedlings. These species

arc vigorous resprouteq not only after fire, but throughout their lifespan. Older stands of chapanal are

continually rejuvenated by recruitment of new resprouts and seedlings of these fire-resister species. It is

suggested that the long-term stability and diversity of chap-1 requires a mosaic of tire frequencies.

INTRODUCTION

California chaparral is considered a “fire-type” vegetation

based on the fact that all species are resilient to the modem

fire regime of tires every few decades (Keeley and Keeley

1988). Resilience of the vegetation is reflected in the

relatively minor changes in community composition resulting

from fire. Species present before fire return rapidly

afterwards, either regenerating aboveground parts from basal

resprouts or by seedling establishment.

In addition to being considered a fire-type vegetation,

chaparral is also often described as a fire-dependent

vegetation. This is based on both population and community

level phenomenon. Certain species, Adenostoma

fasciculatum (Rosaceae), Arctostaphvlos spp. (Ericaccae) and

Ceanothus spp. (Rhamnaceae) for instance, require tire for

seedling establishment. Seeds are dispersed in a dormant state

and accumulate in the soil until germination is triggered by

fire, either from heat or a chemical leaching from charred

wood (Keeley 1987). These species have specialized their

reproductive biology to the extent that they are dependent

upon fire for completion of their life cycle and may be

referred to as “fire-recruiters”. At the community level,

fire-dependence is implied by the frequent suggestion that

stands require fire for rejuvenation. Chaparral unburned for

60 years or more is often referred to as decadent, senescent,

senile and trashy (Hanes 1977).

This fire-dependent paradigm of chaparral has guided fire

management strategy in southern California, although it is

perhaps generous to call the modem fire regime “a strategy,”

since most acreage in southern California bums by

catastrophic wildfires. Nonetheless, federal, state and county

agencies have prescribe bum programs for chaparral sites

under their fire jurisdiction. Some areas that escape wildfires

are burned under prescription at return intervals of

‘Professor of Biology, Department of Biology, Occidental College,

Los Angeles.

approximately 15-25 years. Such a prescription follows

logically from the commonly accepted dogma about the

tire-dependence of chaparral. This, however, is not the

whole story.

FIRE RESIIJENCE VS. FIRE DEPENDENCE

While it is true that the chaparral community is highly

resilient to fire, all species within the community are not

fire-dependent. In fact, a large component of chaparral,

while persisting in the face of recut-rent fire, may actually

decline after repeated tires. Included here are species such as

Ouercus dumosa (Fagaceae), Heteromeles arbutifolia

Rosaceae), -us ilicifolia (Rosaceae), Cercocarnus

betuloides (Rosaceae) and Rhamnus spp. (Rhamnaceae).

These shrubs are resilient to tire by virtue of the fact that they

are vigorous resprouters, yet they do not establish seedlings

after fire. These species are “fire-persisters” but not

“fire-recruiters.” A management plan oriented towards

long-term stability and maintenance of biodiversity needs to

consider the conditions necessary for reproduction of these

taxa.

The conditions under which these species recruit seedlings

have not been well worked out. It is clear that these species

do not establish seedlings after fire, and there are aspects of

their seed germination physiology which account for this

(Keeley 1987). On the other hand, studies of mature

chaparral have consistently pointed out the lack of seedling

reproduction under the closed canopy of this dense shrub

vegetation (Sampson 1944; Horton and Kraebel 1955; Hanes

1971; Christensen and Muller 1975).

One clue to this mystery is an observation made in an early

paper by Patric and Wanes (1964). These authors studied a

stand of chaparral unburned for more than 60 years and noted

seedlings of OuercushrLlmnsa Prunus .%&Xa, and Rhamnus - -

m. Spurred in part by these early findings I have been

investigating the fate of chaparral in the long absence of fire.

II
My focus has been on the demographic structure of stands

free of tire for 100 years or more in some cases. This study

has revealed large se&hng populations in older stands of

chaparral; from 1,000 to 40,000 seedlings per hectare for taxa

such as Guercus,,Rha,au~ .P,otuu.~ Cercocamus and

Heteromeles (Keclcy unpublished data). It is apparent that

long fire-free conditions are required for seedling

establishment by these tire-persister shrub species.

In summary, chaparral is dominated by shrubs that are

resilient to tire. Some are fire-dependent taxa that recruit

seedlings only in the first season after fire, and these are

called fire-recruiters. Other shrubs, however, are not

fire-dependent. They persist after tire but these fire-persisters

require long fire-free conditions for seedling establishment

(figure 1).

What is the best strategy for management of these systems. It

appears that fire intervals on the order of every 20 years

would potentially benefit fire-recruiters. Fire-persisters,

while not obviously damaged .by this fue return interval, over

long periods of time wiil be threatened by the lack of

opportunities for seedling establishment. I suggest the

coexistence of these modes reflecs the natural stochastic fire

regime. Under natural conditions, the eventuality of tire on

any given site would have been nearly certain, however, the

return interval over time would have been variable. Short

return intervals would have provided opportunities for

population expansion of fire-recruiters and long return

intervals would have provided opportunities for population

expansion of tire-persisters.

RESILIENCE TO LONG FIREFREE

INTERVALS

Community stability is dependent on both fire-recruiters and

tire-persisters being resilient to both short and long fire return

intervals. The current fire. regime of relatively short intervals

of 20 years between fires does not pose an immediate threat

to either group. I suggest that all chaparral shrubs are also

resilient to long tire-free periods, although few chaparral sites

remain unburned for more than a few decades.

Relative

Shrub

Cover

Relative

Shrub

Seedling

Establishment

1Fire-Recruiter

*Syndrome

Fire -Persister

5

1 1

FIRE

I O

Log Years

Figure l.- Schematic illustration of the timing of seedling

recruitment for chaparral shrubs described as fire-recruiters

and as fire-persisters and longterm changes in relative shrub

cover for tire-recruiters (dashed line) and tire persisters (solid

line).

This notion would seem to be contrary to much of the dogma

about the decadence, senescence and senility of chaparral

stands older than 60 years. These terms, however, are seldom

defined; a former student once suggested that a senile

chaparral shrub was one which forgot to close its stomates,

and this definition is about as good as any proposed in the

literature. Most certainly these terms derive from

observations that, due to natural thinning of shrubs (e.g.,

Schlesinger and Gill 1978), dead wood accumulates.

However, something that is seldom appreciated is that dead

stems are continually replaced by basal sprouting in all

sprouting shrubs (figure 2). Consequently, the age structure

of sprouting shrub populations are not even-aged and exhibit

continuous recruitment and turnover of stems (figure 3). In

other words, resprouting, in addition to functioning to

rejuvenate shrubs after fire, functions to rejuvenate the

canopy throughout the life of the stand.

Age (Years)

Figure 2.- Number of stems of different ages on a single resprouting shrub of Adenostoma fasciculatum

in a stand of chaparral last burned 89 years ago (Keeley unpublished data).
How then did old stands of chaparral come to be described as

senescent and unproductive? This idea is apparently derived

from early studies which investigated browse production by

different aged stands of chaparral (Biswell and others 1952;

Hiehle 1964; Gibbens and Schultz 1963). These studies

concluded that chaparral became very unproductive within

several decades following tire. However, these studies were

only concerned with production available of wildlife.

Consequently they did not present valid measures of

productivity, because production above 1.5 meters, which is

unavailable for deer, was not included. Since most new

growth in older stands occurs above 2 meters, it is not

surprising that one would conclude that frequent fires were a

necessity for maintaining productive chaparral communities.

Since the concept of stand senescent seemed logically

consistent with the tire-dependent nature of many chaparral

species, this myth of low productivity in older stands of

chaparral was not questioned by many chaparral ecologists

and foresters. Modem studies, however, reveal that live

biomass increases with age in chaparm (figure 4), and the

terms decadence, senescence, and senility, while possibly true

of some species, should not be used to describe chaparral

communities.

Figure 3.- predicted population age structure

of Quercus dumosa stems sprouted from

root crowns of mature shrubs in a stand of

chaparral last burned 76 years ago (solid bars

are living stems, vertical lines arc dead stems).

Stem diameters wcrc measured in 36 4x4 m

plots randomly placed in the stand. Age was

predicted from the indicated regression line

based on 32 stems aged by ring counts.

$

In addition to the correlation coeflicicnt, 2

the estimate of relative error was calculated E

as the standard error divided by the mean ??

value of y. E

In conclusion, chaparral is resilient to short and long

tire-free intervals, and different tire-return intervals, favor

different components of the vegetation. Longterm stability

and biodiversity of chaparral communities may require a

mosaic of fire regimes.

80.000

s,

1 60,000

a

z 50,000 -

5 10 15 20 25 30 36 40 45 7 (>60)

Stand Age (years)

Figure 4.- Standing living biomass in chaparral stands as a

function of age since last fire (from Keeley and Keeley 1988,

with permission of Cambridge University Press, data from

studies by Specht 1969, Conrad and DeBano 1974,

Schlesinger & Gill 1980, Rundel and Parsons 1979, Stohlgren

and others 1984, as cited in Keeiey and KceIcy 1988.)

2500 -

2

2000

1

1800

1600

I 3nn 1

600

ill SAN ICiNAGI

PREDICTED AGE (YEARS)

1 3
LITERATURE CITED

Biswell, H. H., R.D. Taber, D.W. Hcdrick, and A.M.

Schultz. 1952. Management of chamise brushlands for

game in the north coast range of California. California

Fish and Game 38:453-484.

Christensen, N. L. and C. H. Muller. 1975. Relative

importance of factors controlling germination and seedling

survival in Adcnostoma chaparral. American Midland

Naturalist 93:71-78.

Gibbens, R. P. and A.M. Schuhz. 1963. Brush

manipulation on a deer winter range. California Fish and

Game 49:95-l 18.

Hanes, T.L. 1971. Succession after tire in the chaparral of

southern California. Ecological Monographs 41:27-52.

Hanes, T. L. 1977. California chaparral, pp. 417-170. In:

Barbour, M. G. and J. Major, eds. Terrestrial vegetation

of California. John Wiley, New York.

Hiehie, J.L. 1964. Measurement of browse growth and

utilization. California Fish and Game 50:148-151.

Horton, J.S. and C.J. Kraebel. 1955. Development of

vegetation after fire in the chamise chaparral of southern

California. Ecology 36:244-262.

Keeiey, J. E. 1987. Role of fire in seed germination of

woody taxa in California chaparral. Ecology 68:434-443.

Keeley, J. E. and S.C. Keelcy. 1988. Chaparral, pp.

165-207. In: Barbour M.G. and W. D. Billings, eds.

North American terrestrial vegetation. Cambridge

University Press, New York.

pat&, J. H. and T. L. Hanes. 1964. Chaparral succession

in a San Gabriel Mountain area of California. Ecology

45:353-360.

Sampson, A. W. 1944. Plant succession and burned

chaparral lands in northern California. Agricuhural

Experiment Station, University of California, Berkeley,

Bulletin 685.

Schlesinger, W.H. and D.S. Gill. 1978. Demographic

studies of the chaparral shrub, Ceanothus megacarpus, in

the Santa Ynez Mountains, California. Ecology

59:1256-1263.
FIRE AND OAK FtEGENERATION

IN THE SOUTHERN APPALACHIANS

David H. Van Leaf

Abstract-Oak forests throughout the southern Appalachians have been historically maintained in a regime

of frequent tire. Frequent fire over an indefinite time period favors oak establishment by reducing

understory and midstory competition 6om tire-intolerant species and by creating preferred conditions for

acorn caching by squirrels and bluejays. Fire also reduces populations of insects which prey on acorns and

young oak seedlings. Once established in the understory, oaks have a tenacious ability to resprout when

tops have been killed repeatedly by tire. The ability to continually resprout when numbers of other

sprouting hardwoods have been reduced by tire allows oak to accumulate in the advance regeneration pool

and dominate the next stand when suitable conditions prevail. Intense fires in logging debris also favor

establishment and development of high quality oak-dominated stands. Tentative guidelines for the

silvicultural .US of fire to regenerate oak are discussed.

INTRODUCTION

The abundance of oak in the southern Appalachians and

throughout eastern North America is related to past land use

and extensive disturbance (Crowe 1988). Most of the river

basins throughout the southern mountains were cut over and

subsequently bumed repeatedly around the turn of the century

(Secretary of Agriculture’s Report to Congress 1902). This

type of disturbance regime evidently favored oak regeneration

because oaks presently dominate mature mixed hardwood

stands on mesic to x&c sites throughout the region.

Today oaks arc often replaced by other species when mature

stands are harvested, especially on better quality sites (Sander

and others 1983). Failure to consistently regenerate oaks

following harvest is widely recognized as a major problem in

hardwood silviculture. Even though researchers generally

agree that lire played a role in the establishment of oakdominated stands at the turn of the century (Sander and others

1983; Crow 1988), no silvicultural guidelines exist for using

fire to regenerate oak (Rouse 1986). The purpose of this

paper will be to 1) describe the ecology of oak regeneration in

regard to fire, and 2) present tentative guidelines for the

silvicultural use of fire to regenerate oak.

It must be emphasized that these arc tentative guidelines and

must be tested prior to implementation as management

recommendations.

THE ECOLOGY OF OAK REGENERATION

Large seed crops are produced by oaks at 2- to lo-year

intervals, although there is great variation among species

(Sander and others 1983). In the southern Appalachians,

acorn yields of greater than 1000 pounds per acre (fresh

weight) occasionally occur which allow oak seedlings to

become established. Deer and turkeys are major consumers

‘Professor, Department of Forest Resources, Clemson

University, Clemson, SC.

of acorns, although Sciurids, especially chipmunks and flying

squirrels, may consume more than half of the oak mast

available to wildlife in the southern Appalachians (Johnson

and others 1989).

In addition to wildlife predation of acorns, insects also

consume large quantities of acorns. Annually about 50

percent of the acorn crop in Ohio is destroyed by the larvae

of Curculio weevils, acorn moths, and gall wasps. Other

insects attack germinating acorns and oak seedlings.

However, recent studies indicate that prescribed burning may

reduce populations of oak insect pests (Galford and others

1988). A reduction in insect predation would allow more

acorns to be scattered and buried by jays and squirrels, thus

enhancing the probability of successfbl germination, and also

encourage subsequent seedling establishment.

Areas of thin litter are preferred by squin& and blue jays for

acorn burial, suggesting that recently burned areas provide

conditions conducive to oak establishment (Gal&J and others

1988). An interesting and important ecological finding is that

jays collect and disperse only sound nuts (Dartey-Hill and

Johnson 1981), which implies that if these acorns escape

predation they will result in well-established first-year

seedlings. Seedlings from freshly germinated acorns are

unable to emerge through a heavy litter cover (Sander and

others 1983). Germination and first-year survival are best

when acorns are buried about i-inch deep in the mineral soil

(Sander and others 1983).

Species in the oak-pine complex adapted during their

evolutionary history to regimes of occasional and frequent fire

by developing survival mechanisms which enabled them to

withstand intense heat or to regenerate successfully following

tire. Martin (1989) suggests that bark thickness may be the

single attribute that best characterizes a species’s adaptation to

tire. While bark thickness is undoubtedly of great importance

to the survival of mature trees in regimes of frequent fire, it
is the ability to continually resprout following top-kill that

enables most hardwood species, and especially oak, to

regenerate under such conditions.

Although all hardwood species sprout in a regime of annual

winter fire, sprouts remain relatively small and inconspicuous

because of repeated top-kill by tire (Thor and Nichols 1974;

Langdon 198 1; Waldrop and others 1987). Annual summer

tires eventually eliminate all hardwood sprouts. Biennial

summer tires also gradually eliminate hardwood sprouts, but

oak succumbs more slowly than other species (fig. 1). Oaks,

in the absence of prolific root sprouters such as sweetgum,

would gradually dominate the advance regeneration pool

because of the tenacity of their sprouting (Carve1 1 and Tryon

1961; Waldrop and others 1987).

At the turn of the century, summer tires were quite common

as farmers burned the land to facilitate grazing. They had

learned from early settlers, who in turn had learned from

their Indian predecessors, that growing season fires best

maintained an open forest with a rich herbaceous layer

(Komarek 1974). However, not all areas would bum every

year, so hardwood sprouts would have survived in areas

where tire occurred at irregular intervals. It is reasonable to

assume that, because of their tenacious sprouting ability, oaks

would have dominated the advance regeneration pool.

100 -

90-

3 60-

E

u 70-

k

,n 60-

Periodic winter and summer bums at intervals of about 4-7

years allow a vigorous hardwood understory to develop

(Langdon 1981; Waldrop and others 1987). However, stems

generally remain small enough (< 2 in) to be top-killed by

the next fire. Hardwood sprouting is more vigorous

following periodic winter bums because of greater

carbohydrate reserves (Hodgkins 1958). Thor and Nichols

(1974) noted that even with periodic and annual winter

burning, oak stems tend to increase at the expense of

competing hardwoods. After two periodic winter bums and

eight annual winter bums, oak stems comprised 61 and

67 percent of the total stems, compared to 51 percent oak

stems on the unburned plots. Swan (1970) has similarly

shown that surface tires increase the proportion of oak in a

stand even if no seedling establishment occurs, i.e., by

persistent sprouting.

A regime of frequent burning over long periods of time would

create an open stand, whether burning occurs in pine or

hardwood stands. In hardwood stands, long-term burning

would tend to eliminate small understory stems outright and

would gradually reduce the mid- and overstory canopy

through mortality resulting from tire wounds. Increased light

reaching the forest floor in these open stands would maintain

the vigor of oak advance regeneration. Loftis (1990)

demonstrated that elimination of the subcanopy by herbicides

0 4 a 12 16 20 24

Years

Figure 1. Cumulative mortality of hardwood roots over 26

years of biennial prescribed burning (From Langdon 198 1).
encouraged development of advance regeneration of red oak

in mature mixed hardwood stands in the southern

Appalachians. Long-term burning would have created stands

similar to those created by injecting understory hardwoods

with herbicides.

Studies of effects of single fires on composition of mixed

stands have produced varied results. McGee (1979) found

that single spring and fall bums in small sapling-sized mixed

hardwood stands in northern Alabama had little effect on

species composition other than to increase relative dominance

of red maple. However, a single intense wildfire in a young

mixed hardwood stand in West Virginia shifted species

composition to a predominately oak stand (Carve11 and Maxey

1969).

Broadcast burning of logging slash in the mountains of South

Carolina and Georgia increased the number of oak sprouts

and, more importantly, the number of top-killed oak stems

(up to 6-in ground diameter) with basal sprouts (Augspurger

and others 1987). Severe fires xcrify forest sites by

consuming much of the forest floor and perhaps even organic

matter in the mineral soil, as well as by exposing the site to

greater solar radiation through canopy reduction. Conversion

of mesic sites to x&c conditions by intense fires or by a long

regime of low intensity fires, along with their tenacious

ability to resprout, could explain in large part the ability of

oaks to dominate sites where more mesic species normally

occur.

The absence of fire for long periods of time has allowed the

composition and structure of the southern Appalachian forest

to change to a condition where oak species can no longer

dominate on better sites. Species that arc intolerant of fire

have become established and grown to a size where they,

because of thicker bark associated with age, can resist fire

damage. Such species as mockemut and pignut hickories,

scarlet oak, red maple, and blackgum arc examples of such

species that arc oficn found on sites where fire has been long

absent (Harmon 1984; Martin 1989). Suppression of fire has

allowed mesic species, both trees and shrubs, to occupy drier

sites where fire was once more frequent and oak more

dominant. In particular, yellow poplar stands now often

reach ridge tops and rhododendron has dramatically increased

its area1 extent (Van Lear and Waldrop 1989; Martin 1989).

Impenetrable thickets of ericaceous species such as mountain

laurel and rhododendron now often dominate midstorics and

understories of hardwood stands in the Southern Appalachians

and prevent desirable hardwood regeneration from becoming

established (Beck 1988).

SILVICULTURAL USE OF FIRE IN OAK

REGENERATION

There is no dispute among silviculturists that oak advance

regeneration is ncccssary before a new oak-dominated stand

can be regenerated (Clark and Watt 1971; Sander and others

1983; Loftis 1988; Lorimer 1989). However, while many

acknowledge the role that fire may have played in creating the

present mature oak stands, no silvicultural guidelines have

been developed for using fire to regenerate oak stands.

Based on the history of fire in the southern Appalachians and

on documented ecological responses of oaks and associated

species to fire discussed earlier, the following scenarios are

presented as tentative guidelines for using fire in oak

management. Further research will be necessary to test and

line tune these suggestions before they can be recommended

as silvicultural practices.

To Promote Advance Regeneration

Little (1974) suggested, as did Van Lear and Waldrop (lpgp),

that an extended period of repeated burns prior to harvest

may be necessary to improve the status of oak in the advance

regeneration pool, especially on better sites. The famous

Santee Fire Plot study, although conducted in another

physiographic region, showed that annual summer bums for 5

years in a pine stand in the Coastal Plain killed about 40

percent of oak root stocks compared to 55 to PO percent of

other woody competitors (Waldrop and others 1987).

Biennial summer burning killed hardwood root stocks more

slowly but the rate, of mortality for other woody species was

still significantly greater than that of oak species. Annual

winter burning, while not as effective as summer burning in

altering species composition, still tends to xerify the site by

consuming litter and reducing shading of top-killed understory

species.

Thus, a regime of frequent understory bums, including both

summer and winter bums, during a period of 5 to 20 years

prior to harvest should promote oak seedling establishment

and allow oak seedling-sprouts to dominate the advance

regeneration pool (fig. 2). A relatively open stand with few

midstory and understory trees would provide sufficient light

for the oak advance regeneration to develop into stems of

sufficient size to outgrow other species after the overstory is

removed. Without frequent fire, all advance regeneration

species would respond to the favorable light conditions in an

open stand.

Preharvest burning reduces the forest floor, thereby

encouraging burial of acorns by squirrels and bluejays.

Burning theoretically reduces insect predation of acorns and

young oak seedlings. The proposed burning regime should be

a mix of summer and winter fires adjusted to maintain the

vigor of the oak advance regeneration. There is no research

1 7
Frequent bums

I” mature oakdcmkiated stard

Suppress fire through pole

and snail sawlimber stage

Remove o”erslory and a0.v cdc advanz

regeneration to dominate new stand

Mid- and under?.tory

competftwn reduced

>.

Squirrels and jq-s preler to bury

aOm!S CC m?aS Of thin litter

.Stcq burning to dkhv cak advaras

regeneration to dewki9

Burning favors successlul germmahon

and &y eslablishmenl d C&

as Well as amer spec,es

r)

Figure 2. Tentative scenario of using prescribed fire to encourage advance regeneration of oak.

18
that currently documents what this mix of bums should be.

Once an adequate number of oak seedling-sprouts are present

and numbers of competing species have been sufftciently

reduced, fire should be withheld to allow the oak advance

regeneration to attain sufficient size to outgrow other species

which germinate or sprout after the mature stand is cut.

Sander and others (1983) recommends that 435 advance

regeneration oak stems per acre over 4.5 f t tall be present

before the ovcrstory is removed.

Fire has been suppressed for so long in the southern

Appalachians that it may be necessary to use herbicides to

remove midstory trees that have grown too large to be killed

by low-intensity fires. Lofiis (1988, 1990) has convincingly

shown that growth of advance regeneration of northern red

oak can be enhanced by herbicidal removal of mid- and

understory competitors. A combination of herbicide treatment

and frequent fire may be required to secure oak regeneration

and allow it to maintain its vigor in mixed hardwood forests

which have not been burned for decades. Frequent

understory burning will be necessary because singe bums

benefit oak regeneration only slightly (Tcuke and Van Lear

1982).

Foresters have long recognized that wildfire during the

growing season is a major cause of butt rot in hardwoods, but

relatively little information is available concerning the

relationship between prescribed fires of lower intensity and

stem damage. Wendel and Smith (1986) found that a striphead fire in the spring in an oak-hickory stand in West

Virginia caused a decline in overstory vigor and resulted in

death of many trees during the 5 years after burning.

However, a low-intensity winter fire in a mixed hardwood

stand in the southern Appalachians resulted in little or no

cambium damage to large crop trees (Sanders and others

1987). Smaller trees did suffer stem damage, but in evenaged management these trees would be used for products not

requiring stems of high quality. If not removed, these

damaged trees would eventually succumb to disease and be

lost from the stand. More research is needed to determine if

and when low-intensity fires can be used without excessive

damage to stems of large valuable crop trees in mature

hardwood stands.

To Increase Quality and Numbers of Oak Stems

after Clearcuttlng

The fell-and-bum technique for regenerating mixed pinehardwood stands has been used successfully in the southern

Appalachians and is fully described in Waldrop and others

(1989). Basically, the technique involves felling residual trees

left after commercial clearcutting when their crowns arc

almost fully leafed out. After curing for l-3 months, the

logging debris is broadcast burned with a high intensity tire

conducted under conditions that produce little or no soil

damage. Planting pine seedlings at low densities among the

hardwood coppice produces a mixed pine-hardwood stand.

Broadcast burning following clearcutting of hardwood or

mixed pine-hardwood stands promotes better quality oak

sprouts by forcing them to develop from the groundline.

Over 97 percent of all oak sprouts developing after broadcast

burning of logging slash in the southern Appalachians were

basal sprouts, versus 71 percent for unburned areas

(Augspurger and others 1987). Suppressed buds higher on

the stump are apparently destroyed by the intense heat of the

fire. Sprouts from the base of the stump will not develop rot

as readily as those from higher on the stump and can be

grown on longer rotations for more valuable products.

Broadcast burning increases the number of oak sprouts, as

well as the number of small oak stumps with at least one

basal sprout. Small oak (< 6 in) stems in the understory of

mature stands often arc poorly formed and,, unless killed back

by fire or some other agent, will not develop into quality

stems. However, when top-killed by the intense heat of

broadcast bums, sprouts from these fire-killed stems are more

likely to develop into sound timber trees than other types of

oak regeneration (Roth and Hepting 1943).

Intense tires can sometimes result in the introduction of oak in

the succeeding stand. Nowacki (1988) documented cases in

northern Wisconsin where clearcutting of old-growth maplehemlock stands and slash burning resulted in even-aged stands

dominated by northern red oak. Lorimer (1989) suggested

that these oak stands probably developed from acorns brought

into the bumed area by birds and animals. The author has

made similar observations following an intense wildfire in the

mountains of South Carolina.

SUMMARY AND CONCLUSIONS

There is no doubt that oaks in the southern Appalachians are

being replaced by other species on better sites where oaks

were once dominant. Oaks are definitely favored by some

type of disturbance regime. Based on the history of this

region and literature concerning responses of oak to fire, it

appears that oak replacement is largely the result of a

different fire regime from that which existed in the region in

previous millennia. In the past, frequent fires allowed oak

regeneration to accumulate and develop in the understory of

open mature stands at the expense of shade-tolerant, fireintolerant species. When the overstory of these stands was

either completely or partially removed by various agents

(wind, insects, wildfire, Indian clearing, harvesting, etc.),

conditions were created which allowed advance-regeneration

dominated by oak to develop into mature stands.

If oaks are to bc maintained as a dominant overstory species

on medium to good quality sites in the southern Appalachians,

it seems that foresters will have to either restore tire to some

semblance of its historical role as a major environmental

factor or develop artificial methods that simulate the effects of

tire. If research does not soon discover the secrets of

maintaining oaks on these sites, foresters through their tire

suppression efforts will have encouraged the demise of oak on

these sites, much to the detriment of numerous ecosystem

values.

19
LITERATURE CITED

Augspurger, M. K., D. H. Van Lear, S. K. Cox, and D. R.

Phillips. 1987. Regeneration of hardwood coppice with

and without prescribed fire. p. 82-92. In: Phillips, D. R.

(ed.). Proceedings Fourth Biennial Silvicultural Research

Conference, Nov. 4-6, 1986, Atlanta, GA. U.S.

Department of Agriculture, Forest Service Gen. Tech.

Rep. SE-42. Ashebille, NC.

Beck, Donald E. 1989. Regenerating cove hardwood stands.

p. 156-166. In: Smith, H. Clay; Perkey, Arlyn W.; and

Kidd, William E. (cds.). Guidelines for Regenerating

Appalachian Hardwoods. May 24-26, 1988.

Morgantown, WV. SAF Publications 88-03. West

Virginia University Books, Office of Publications,

Morgantown, WV.

CarveIl, K. L. and W. R. Maxey. 1969. Wildfire adversely

affects composition of cove hardwood stands. West

Virginia Agricultural Experiment Station Bulletin

2(2):4-S.

CarveIl, K. L. and E. H. Tryon. 1961. The effect of

environmental factors on the abundance of oak

regeneration beneath mature oak stands. Forest Science

7:98-105.

Clark, F. Bryan and Richard Watt. 1971. Silvicultural

methods for regenerating oaks. Oak Symposium

Proceedings. August 16-20, Morgantown, WV. U.S.

Department of Agriculture, Forest Service. Northeastern

Forest Experiment Station, Upper Darby, PA.

Crowe, T. R. 1988. Reproductive mode and mechanisms for

self-replacement of northern red oak (Quercu.s rubra)--a

review. Forest Science 34: 19-40.

Darley-Hill and Johnson. 1981. Acorn disposa1 by the bIue

jay (C’yanociltu Oecologia 50:231-2X?.

Galford, Jimmy R., John W. Peacock, and Susan L. Wright.

1988. Insects and other pests affecting oak regeneration.

In: Smith, H. Clay; Perkey, Arlyn W.; Kidd, William E.

(eds.). Cuidelincs for Regenerating Appalachian

Hardwood Stands. May 24-26, 1989. Morgantown, WV.

SAF Publication 88-03. West Virginia University Books,

Office of Publications, Morgantown, WV.

Harmon, Mark E. 1984. Survival of trees after low-intensity

surface fires in Great Smokey Mountains National Park.

Ecology 65(3):796-802.

Hodgkins, E. J. 1958. Effects of fire on undergrowth

vegetation in upland southern pine forests. Ecology

39:36-46.

Johnson, A. Sydney, James M. Wentworth, and Philip E.

Hale. 1989. Cumulative mast needs of forest wildlife.

p. 18-23. In: McGee, C. E. (4.). Southern Appalachian

Mast Management Workshop Proceedings, August 14-16,

1989, Knoxville, TN.

Komarek, E. V. 1974. Appalachian mountains, mesophytic

forest, and grasslands. p, 269-272. In: Kozlowski, T. T.

and Ah&en, C. E. (cds.). Fire and Ecosystems.

Academic Press, New York.

Lang&n, 0. G. 1981. Some effects of prescribed fire on

understory vegetation in loblo@ pine stands. In: Wood,

G. W. (ed.). Prescribed fire and wildlife in Southern

forests: proceedings of a symposium, April 6-8, 198 1.

Myrtle Beach, SC. Clemson Univ., Belle W. Baruch

For. Sci. Inst., Georgetown, SC. p. 143-153.

Little, Silas. 1974. Effects of tire on temperate forests:

Northeastern United States. In: Kozlowski, T. T. and

Ahlgren, C. E. (eds.). Fire and Ecosystems. Academic

Press, New York.

Loftis, David L. 1988. Regenerating oaks on high sites, an

update. In: Smith, H. Clay; Pcrkey, Arlyn W.; and

Kidd, William E., Jr. (eds.). Guidelines for Regenerating

Appalachian Hardwood Stands. May 24-26, 1988,

Morgantown, WV. SAF Publication 88-03. West

Virginia University Books, Office of Publications, West

Virginia. p. 199-209.

Loftis, L. David. 1990. A shelterwood method for

regenerating red oak in the Southern Appalachians.

Forest Science 36:917-929.

Lorimer, Craig G. 1989. The oak regeneration problem:

New evidence on causes and possible solutions.

University of Wisconsin, Dept. of Forestry, Forest

Resource Analyses #8. 3 1 pp.

McGee, C. E. 1979. Fire and other factors related to oak

rcgcneration. In: Holt, H. A. and Fischer, B. C. (eds.)

Regenerating oaks in upland hardwood forests. John S.

Wright Forestry Conference, Purdue University.

Lafayette, IN. p. 75-81.

Martin, William H. 1989. The role and history of fze in the

Daniel Boone National Forest. U.S. Forest Service,

Daniel Boone National Forest, Winchester, KY.

Nowacki, G. J. 1988. Community and historical analysis of

northern red oak along a moisture gradient in northcentral Wisconsin. M.S. Thesis, University of Wisconsin

- Stevens Point.

2 0
Roth, E. R. and G. H. Hepting. 1943. Origin and

dcvclopmcnt of oak stump sprouts as affecting their

likelihood to decay. Jour. For. 41:27-36.

Rouse, C. 1986. Fire effects in northeastern forests: oak.

United States Department of Agriculture, Forest Service

General Technical Report NC-10.5. 7 p.

Sander, Ivan L., Charles E. McGee, Kenneth G. Day, and

Ralph E. Willard. 1983. Oak-Hickory. In: Bums,

Russell M. (camp.). Silvicultural systems for the major

forest types of the United States. U.S. Department of

Agriculture, Forest Service Agriculture Handbook No.

445. Washington, D.C. p. 116-120.

Sanders, D. L., D. H. Van Lear, and D. C. Guynn. 1987.

Prescribed burning in mature pine-hardwood stands--

effects on hardwoods and small mammals. In: Phillips,

Douglas R. (amp.). Proceedings of the 4th biennial

silvicultural research conference; 1986 Nov. 4-6; Atlanta,

GA. Gen. Tech. Rep. SE-42. Asheville, NC: US.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station, p. 93-96.

Secretary of Agriculture’s Report to Congress. 1902.

Forests, rivers, and mountains of the Southern

Appalachian region. Government Printing Office.

Washington, D.C.

Swan, F. R. 1970. Posttire response of four plant

communities in southcentral New York stale. Ecology

51:1074-1082.

Teuke, M. J. and D. H. Van Lear. 1982. Prescribed

burning and oak advance regeneration in the Southern

Appalachians. Georgia For. Corn. Res. Pap. 30. 11 pp

Thor, E. and G. M. Nichols. 1974. Some effects of fire on

litter, soil, and hardwood regeneration. Proc. Tall

Timbers Fire Ecology Conf. 13:317-329.

Van Lear, David H. and Thomas A. Waldrop. 1989.

History, uses, and effects of fire in the Appalachians.

U.S. Department of Agriculture, Forest Service Gen.

Tech. Rep. SE-54. 20 p.

Waldrop, Thomas A., David H. Van Lear, F. Thomas Lloyd,

and William R. Harms. 1987. Long-term studies of

prescribed burning in loblolly pine forests of the

Southeastern Coastal Plain. U.S. Department of

Agriculture, Forest Service Gen. Tech. Rep. SE-45

23 p.

Waldrop, Thomas A., F. Thomas Lloyd, and James A.

Abercrombie, Jr. 1989. Fell and bum to regenerate

mixed pine-hardwood stands: an overview of research on

stand development. In: Waldrop, Thomas A. (ed.).

Proceedings Pine-Hardwood Mixtures: A Symposium on

Management and Ecology of the Type. April 18-19,

1989, Atlanta, GA. US. Department of Agriculture,

Forest Service Gen. Tech. Rep. SE-58. p. 75-82.

Wendel, G. W. and H. Clay Smith. 1986. Effects of a

prescribed fire in a Central Appalachian oak-hickory

stand. U.S. Department of Agriculture, Forest Service

Northeastern Forest Experiment Station NE-RP-594. 8 p.

2 1
RESPONSE TYPES TO PRESCRIBED FIRE

IN OAK FOREST UNDERSTORY

H.R. DeSehn and E.E.C. Clebsch’

Abstract-We examined data collected on the understory of , g prescribe-burned upland oak forest at the

University of Tennessee Highland Rim Forestry Station from 1965 through 1989. Trcatmcnts were annual

and periodic (once in live years) burns and no bum. Each was replicated three times.

Species number declined dramatically under the no-bum regime. Tree seedling establishment was inhibited

and sprout size decreased in the annual and periodic burns-here the understory aspect is quite open. Tree

sprout cover in the periodic bums followed the incidence of tire, it has lowest in &c Seplember following

each winter burn. Graminoid cover, chiefly little bluestem Schizachyrium-scopa&Ldecreascd to zero in

the no-bum treatment. It was variable in other treatments but decreased inqularly from 1973-I 975 to

1988. In 1989 it established 8 new high. Composite, legume and other fort, cover declined to zero under

the no-bum treatment. Composite cover in annual plots peaked in 19734 but decreased irregularly since;

legume cover increased irregularly; other forb cover decreased irregularly in annual bum plots. Composite

cover in periodic plots oscillated around fire years when cover was generally highest; legume cover peaked

in four of the five fire years; other forb cover generally increased in tha year following a fire. Twenty-two

response-types occurred.

INTRODUCTION

Studies of the effects of fire on natural or man-fostered

systems in central and southeastern United States are chiefly

those in the grassland whcrc these communities were long

maintained as grazing land (Risser and others 1981) and in

southeastern pineland which were also maintained as grazing

and timberland (and for naval stores in the past) (Wahlcnberg

and others 1939). Summaries of the effects of fire on

grasslands can be found in Risser and others (198 ]),

Daubenmire (1968a), Wright and Bailey (1982), Vogl (1974),

and Collins and Wallace (1990). Summaries of the effects of

fire on conifer forests especially southeastern forests are in

chapters in Kozlowski and Ahlgrcn (1974), USDA Forest

Service (1971), Wright and Bailey (1982), and Wood (1981).

Older literature is summat-izcd in Garren (1943), and Ahlgrcn

and Ah&en (1960). USC of tire in the central Deciduous

Forest has been on the decline since abandonment of open

range practices and intensification and specialization in land

use (Vog] 1974, Chandler and others 1983). Fire use

continues in hardwood and mixed forests as a wildlife

management tool (Wood 1981), and to modify understory

composition or size class structure (Wade and others 1989,

Faulkner and others 1989). Studies on hardwood understory

include Paulsell (1957) and DeSelm and others (1973, in

press).

This paper is concerned with the consequences of 25 years of

annual and periodic prescribed fires on the undcrstory species

in oak-dominated vegetation at Highland Rim Forest

‘Department of Botany and Graduate Program in Ecology,

The University of Tennessee, Knoxville.

2 2

Expcrimcnt Station, Franklin County, Tennessee. The study

contributes to an understanding of the maintenance of

graminoid-forb undcrstory and openings in the upland oak

forests of this region and adds to our knowledge of response

behavior of these species to fire.

For the period 1965-1970 the understory of the bum and

control plots was examined (DeSelm and others 1973). In the

six treatment years number of species sampled were 13, 23

and 35 taxa in control, periodic and annual bum plots,

respectively. With increased burning, tree frequency and tree

sprout cover decreased, grass and forb cover increased, and

herbaceous vine and shrub cover became elevated on the

periodic burns. Eighty-four percent of the species responded

positively (by increased cover) to fire treatment by 1970.

Tree, litter and soil changes were examined by Nichols (1971)

and Thor and Nichols (1973).

THE STUDY AREA

The study area is at 360 30’N : 8&W at the eastern edge of

the Interior Low Plateau Province (the southeastern Highland

Rim) in Middle Tennessee. The land surface here undulates

and it has loess-derived soils in which a water-movementinhibiting pan has developed in several series (Fenneman

1938, Fox and others 1958, Love and others 1959). Forest

vegetation is of the upland oak swamp, post oak-blackjack,

and southern red oak-scarlet oak types (DeSelm and others

1973). Conversion of this vegetation to agricultural land and

to loblolly pine plantations is still occurring (Thor and

Huffman 1969, USDA Soil Conservation Service 1971,

Buckner and others 1986).
Early surveyors report a few places with no forest, and such

modem sites as the May Prairie have a physiognomic and

flor&ic resemblance to midwestem prairie (D&elm and

others 1973). The origin and maintenance of grass vegetation

and grass understory has in part stimulated this study.

American Indian use was f&wed by agriculture and

livestock grazing between the late 1700s and early 1940s.

Army maneuvers during World War II have been part of this

site’s history. The local farmers commonly burned off the

woods in winter and a railroad line on the edge of the station

also storied fires annually (Faulkner 1968, Haywood 1823,

D&elm and others 1973).

METHODS

Data were collected on nine I.8 acre experimental bum pIots,

19651989 inclusive. Plots were split among annual, periodic

(usually 5 years) and control. A 50-foot tape was stretched

three feet above the ground between permanent stakes in each

plot. At each one-foot mark a 0.19 inch diameter metal pin

was lowered vertically to the ground and each “hit” on each

vascular plant was recorded; those plants below three feet in

height are herein called understory. Annual burns began in

1963; periodic bums were made in 1964, 1969, 1974, 1979,

1983 and 1988. Late winter bums were used to simulate the

action of local land owners. Plant nomenclature follows

Fcmald (I 950).

Data reported here are cover (sum of hits per species x 2)

along each SO-foot line. Cover values are averages of the

three replications. No frequency or relativized data are

reported. Years have been segregated into early 1965-1972,

middle 1973-1981, and late 1982-1989 groups. Some taxa

occur widely (the wides) across the series of years with

somewhat variable-to-steady cover. In other taxa, the cover

increases (the increasers), or the cover decreases (the

decreasers), and in a few the cover increases (bulges) or

decreases (sags) in the middle years. Taxa not present in the

‘early years that appear later are termed “invaders.” Taxa

present in early or early and middle years but which are not

present in late years are termed “retreaters.” Sporadics,

which occur in early, middle, and late years, totaling 22 taxa,

were not considered. Some terminology is from Vogl (1974).

RESULTS AND DISCUSSION

General

Taxa seen along the strips over the years totaled 141 spccics:

13 tree, 15 shrub, 2 woody vine, 2 1 graminoid, 22 legumes,

40 composite and 22 other forb taxa (counts excluded

unknowns ofivarious categoties). This represented 52 percent

of the 270 known vascular flora of the Station. Of these, 119

are included in this study. TWO taxa occutxd only in control

plots: Gcntiana villosa and Lisuidambar stvracillua (but in

0.01 acre plots, Liquidambar has been found in the periodic

bum). Thus, all but one taxa was at least mildly fire tolerant.

Although several State rare taxa occurred on the Forest

(D&elm 1990) only one occurred on the bum plots;

$ymnopogon brevifolius is listed as a species of special

concern (Somers and others 1989).

Forty-five taxa occurred in all three treatments, 39 taxa

occurred in both bum treatments, 31 occurred in the annual

bum only, and 12 occurred in the periodic bum only.

Total cover (sum of woody plant-graminoid-forb) in annual

plots peaked in 1973--but by 1987 it decreased 43 percent

after which it rose again. In the periodic plots total cover fell

46 percent between 1980 and 1987 after which it rose

sharply. These 43 and 46 percent decreases in cover

represented temporary increases in bare ground. Total cover

in check plots decreased gradually until 1976 (the last year of

herb cover), remained more or less steady through 1988, then

increased in 1989 (Table 1).

Woody Plants

Cover by woody plants was irregular but more or less

constant in annual plots over the year series. In periodic

plots, woody plant cover increased irregularly. In check plots

woody plant cover decreased through 1988; in 1989 it

increased to the level approximating 1975 (Table 1).

Tr@!3

Sum of cover of tree taxa on control plots apparently

decreased until about I979 afier which it became variable.

Some tree stems grew upward beyond the sampling line and

were no longer recorded. Some young trees died under the

developing canopy but others have spread onto the sampling

line. Nyssa sylvatica, Qucrcus coccinea, Q. falcata, Q.

velutina and Vaccinium arborcum were recorded most to all

years (Nyssa and Q. coccinea were decrcasers). Qucrcus

stellata. Q. marilandica and Carya tomentosa occurred in

early or middle years. Lisuidambar and Cornus

occurred in late or middle and late years. Acer rubrum

appeared in 1969 and 1989, this apparently represent&

disappearance by height growth followed by recent sprouting

A summary of response types appears in Tables 2 and 3.

In annual bum plot strips, six taxa occurred widely (~arya,

w, Q. qoccinea,Q. stellata, Q. velutina and Sassafras

albidum). coccinea and Q velutina were decreasers,

Q. stellata and Sassafras we, increasers. &zJ~&% R&da, Q,

m and Vaccinium arboreum occurred in early and/or

middIe years. Qucrcus lvmta was recorded in five middle

and late years through 1983. The last several species, except

perhaps Q. lyrata, were fire sensitive.

23
In periodic plots sum of cover of tree species and cover of

several individual tree species was lower in fire years than

between tires--they were burned back by the tires. Taxa with

decreased cover on two to five fires were Carya. Nvssa,Q.

coccinea, Q. falcata. Q. marilandica. Q. stellata. Q. velutina,

and Vaccinium %#xszt~ (nresent six years) and

Q. jyr& (present two years) barely survived these fires.

kercrubrum was seen only recently (1982- 1988).

velutina and Vaccinium were increasers, Q. coccinea was a

dccreaser, and Q. falcata and Q. stellata increased in middle

years (bulge species).

Shrubs

In the control plot strips, shrubs persisted various numbers of

years under the developing canopy: Rhus alabra to 1965,

Rubus (erect) to 1972, Ceanothus americana and &

copallina to 1974, Rubus (dcwbcrry) to 1979, and Salix tristis

to 1980. Vaccinium vacillans occurred each year, v.

staminium appeared 1989. V. vacillans occurred in control

oak-pine plots in southern New Jersey where its cover was

reduced by 1950s drought (Stephenson 1965).

Certain shrubs in the annual burn plot strips occurred widely

across the years (mostly many years): Ceanothus,

Rhododendron nudiflorum,R~~onallina, j& toxicodendron,

~ubus (dewberry and erect), Salix tristis and Vaccinium

vacillans. Increase in ,Btmverhas been seen in central

Wisconsin with fire (Reich and others 1990). Vaccimum

vaci]la and m copallina increased in cover. In southern

New Jersey y. vacillans’s cover increased with burning

frequency (Rue11 and Cantlon 1953). Rhododendron was a

sag species. Ascvrum ~~.~~--L straoalum Pyrus mela,nocarpa, Rhus

& and Salix humilispersisted only one to three years

(1965- 1967). Ascvrum hvpericoides and Vaccinium

stamineum have been recorded since 1985 and 1988,

respectively.

Shrub cover on periodic plot strips included the widely

occurring Ceanothus. Rhus copallina, Rubus (dewberry and

erect), Salix and Vaccinium t h e s e r&iilarun g ,

Ceanothzecreased in cover while Rubus erect$aiix-tristih.

and Vaccinium vacillans increased in cover. Ascvrum

hvpericoides and A. stmrralum appeared in plot strips in 1983

and 1988 respectively. Rhus copallina cover peaked in fire

years and dropped 50 percent or more in each of the

following three to four years. Rosa Carolina and Rhus

toxicodendron disappeared after 1967 and 1972, rcspectivcly.

Rhus alabra behaved like Acer rubrum-in the control plots, it

occurred in both early and recent years, ehus in 1965, 1983

and 1984.

Woody Vines

Woody vines were mainly Smilax glauca-only a few hits

were made on l&is ulstivahso n t r o 1 p 1 o t s , Vitis

occurred 19651968 only. In these plots Smilax was a

dxreaser, early year covers averaged 5.8, later year covers

averaged 1.5 percent. Canopy closure and deer browse

affected coverage.

In the annual bum plot strips, Smilax cover decreased

slightly. In the periodic bum plot strips cover varied from

2.0 to 20.6 per year. Compared to the previous year, cover

increased one tire year, remained constant one tire year and

decreased three fire years. In the year following fire,

compared to the fire year, cover increased after one fim, and

decreased after four fires.

Graminoids

Total graminoid cover in annual plots peaked in 1973, 1978

and 1989. In periodic plots it peaked in 1975, 1980 and 1989

(the year following a fire in each case). Graminoid cover

decreased steadily in control plots (Table 1).

Little Bluestem-Schizwhvrium scooarium

Control plot strips showed the disappearance of blucstem by

1977. Shade and tree litter are believed to be causes.

Cover of bluestem on annual bum plot strips increased

irregularly to 1973, fell, peaked again in 1978, fell irregularly

until 1988 and peaked again in 1989. Biomass of

Schizachvrium also experienced multiple high and low value

years in the 61 year record in Kansas (Gene Towne, personal

communication). Although Androooeon d cover

increased with annual burning in Missouri, cover of

@tiza&yrium, increased with alternate year fires (Kucera and

Koclling 1964).

Periodic plot strip cover increased irregularly to 1975,

dccreascd, increased again to 1980, decreased to 1988, then

increased again in 1989. These variations do not match burn

years. On two fire years, 1969 and 1988, cover decreased

slightly From the year before, and it rose in 1974, 1979, 1983

from the year before. The positive effects of this treatment

on the cover of this grass were certainly not dramatic. The

high peaks of this grass in both treatments classed this taxon

as a midphasc bulge species. The 1989 peak may be part of a

new trend.
Table 1. Total cover of graaiwids, forbs, and twmdy plants by treatmeuts and year.

1865

1966

1967

1968

196s

1870

1871

1972

1973

1974

1975

1976

1877

1878

197s

1960

1981

1862

1863

1964

196.5

1966

1867

1996

32.6

46.0

64.2

63.9

58. 7

56.4

63.2

73.6

99.6

77.8

69.6

67.7

51.3

64.4

70.3

57.5

63.1

49.1

51.7

48.0

45.0

44.9

57.0

46.8

54.6

59.2

43.7

60.3

43.4

54.8

48.6

56.9

66.5

64.6

53.2

55.6

36.7

42.8

45.2

34.6

43.6

33.7

40.2

31.4

39.5

31.4

26.6

46.2

23.2 44.7

21.0 32.6

34.6 36.6

23.2 33.6

26.2 34.0

16.0 38.3

22.1 45.6

24.3 52.0

28.1 63.2

32.5 65.0

37.0 66.6

16.4 26.8

20.6 51.6

23.3 60.7

18.6 64.0

24.3 62.4

17.5 50.7

27.1 64.7

24.7 53.6

27.0 44.6

26.7 36.3

19.3 30.6

26.0 26.5

Periodic CbeclI

Gram. Forbs W=h’ Gram. Forbs Nbody

24.6 35.3 27.5 37.6 57.4 16.6

18.1

2.6

20.6

37.9

33.4

16.2

23.7

16.2

41.4

40.6

31.8

25.2

20.3

70.6

26.1

28.2

21.7

37.0

27.7

20.1

16.5

15.6

25. 4

23.4

27.5

26. 1

29.2

41.4

47.6

42.1

43.3

63.6

66.6

61.3

61.0

43.8

69.2

66.1

61.4

62.0

61.8

53.6

55.8

52.2

75.6

57.6

37.4

34.0

14.0

6.0

6.6

3.4

3.4

1.4

0.0

0.6

15.6

9.6

12.6

6.4

6.0

8.4

4.0

4.0

1.4

0.6

56.0

43.6

46.6

43.0

42.2

26.6

50.2

31.2

30.0

26.0

26.4

21.6

15.6

14.4

IO.6

7.4

13.4

13.6

9.2

12.4

10.6

14.6

15.2

8.6

12.0

196s 94.7 42.6 24.0 164.3 39.9 89.7 20.6

Other Grmiinoids (Gramineae [Poaceae],

Cyperaceae)

In control plots, other graminoids were represented by low

cover of only seven taxa--no more than five present any one

year. They persisted only through 197 1.

Twenty-four other graminoids occurred in annual burn plots.

Taxa present almost every year arc Andronorron gerardii and

Sorphastrum nutan~ with 6-10 percent cover per year. A few

other graminoids occurred more or less widely: Acdropogoq

gyrans, Carex sp., Eleocharis m, and Panicum

&h&mum tid 111. ltumtinoaum. a b o v e taxa,

Andropogon gerardii and Sorghastrum were increasers, and

the two Panicum species were decreasers. Aristida dichotoma

disappeared after 1966, 4. purourea after 1972, Gvmnouonon.

brevifolius after 1981, Panicum ~nUY&stifoliom after 1978, H.

raveneliii after 1975 ,SFA?auciflora alter 1972, and

wge+ataaller 1968. globularis

occurred only in the middle years of the series. A few taxa

appeared late in the series, Amostis perennansjn 1980,

Dieitaria iscmand Microstegium vimineum in 1989,

Muhlenbekai ____. in 1984, Panicum laxiflorumin 1977

and p.w in 1986. The Dieitaria and

Microstqiuqare widespread weeds.

Concurrent peaks and valleys of cover in the annual burns

occurred in a few taxa some years, but the correspondence in

peaks was not impressive and did not argue strongly for

response to weather. Peaks and valleys were best expressed

in the high cover species JndropoRon perardii and

Sorghastrum. These taxa also experienced rises and falls in

biomass values on Kansas prairie (Gene Towne, persona1

communication). The sum of all other graminoid cover

peaked in 1972, 1973, 1979, 1986, 1987, and 1989.

Sorghaslrurn. contributed greatly to all of these peaks.

Andropogon gerardii contributed in 1979, 1987, and 1989.

25
Other graminoids in periodic bum plot strips numbered 19

species A few hxa occurred 1 I or more years, Andropoyon

gerardii. Panicum commutatum. P. dichotomum. P;.

laxiflorum, p. microcarpon,and Sorghashum nutans. A.

gerardii was a bulge species, Sorghastmm was an increaser.

Two bxa were seen in the early or early and middle part of

the series, Agrostis hycmalis though 1976 and .uuhlenbergia.

tcnuifolia in 1965. A few taxa were seen only later, Aristida

curtisii only in 1974, Panicum laxiflorum since 1976, p.

sphaerocamon in 1979, p. villosissimum since 1981, and

Rhvnchosoora e1qbtjari.s in 1980.

The effects of the periodic fire on the total cover of all taxa in

fire years was variable, some years cover increased, some

years it decreases. However, the year following a fire, an

increase in cover was achieved, the increase in cover was 1.1

to 9.7 times the cover the year before. Taxa with increased

cover were the “fire follower” class of Lemon (1949). The

effect is temporary; the second year afler a tire, other

graminoid cover total decreased.

Forbs

In 1965 and 1966 annual plot total forb cover exceeded

woody plant and graminoid cover but after 1966 it decreased

to a level intermediate between them. This suggested an

early-in-the-treatment (early successional) forb dominant stage

as was seen early in some southeastern seKs (Quarterman

1957, Oosting 1942). Annual bum forb cover peaked in 1973

but decreased irregularly to 1987--a 60 percent loss of cover.

In periodic fire plots total forb cover peaked in 1969, 1974-5,

1979, 1983 and 1988 (each fire year). There was a decrease

in total forb cover 1979-1987 of 79 percent of the 1979 value.

Forb cover in control plots decreased irregularly through

1975 (Table I).

Composites (Compositae, Asteracee)

Sixteen composite taxa, including unknown categories,

occurred in the control burn plots. Occurrences ranged from

one to 10 taxa per year. All were eliminated by 1975.

Annual bum composites, expressed as total hits on all taxa,

increased to a peak in 1973 and 1974 and decreased

irregularly thereafter (but increased slightly in 1989). This

decrease in cover was apparent to us and was a cause. of

comment. Recent plot photographs showed few composites in

most late years compared to earlier years. Numbers of taxa

in early years averaged 19.3, in late years 10.0. Taxa

showing the above trend with peaks in 1973 or 1974,

sometimes with additional peaks, were: Aster &.IJw~~, A.

hemisphericus, A. patens, A. undulatis, Coreopsis tripteris

and SolidaPo odora. All but A. hcmisphericus were bulge

species.

Several taxa occurred only in the early years: Antennaria

plantaginifolia through 1968, Hieracium grpnovii- through

1971, Sericocarpus linifolius in 1968. A few taxa persisted

through the middle years: Helianthus aneustifolius through

1978, E. silphioides through 1977, Solidago bicolor through

1977, S. erecta through 1981, and S. speciosa through 1974.

Two taxa only occurred in the middle years: Helianthus

strumosus and Scnecio anonvmus. Several bxa appeared only

in late or middle and late years; these were Ambrosia

artimisiifolia seen first in 1987, Erectites hiem seen

first in 1982, Eupatorium album seen first in 1975, E.

aromaticum seen first in 1973, Jj. semiserratum seenin 1985,

and &lidago canadcnsis seen first in 1973. The Ambrosia,

Erectitis,~aahum~densis were

weedy taxa locally.

Helianthus hirsutus and Coreopsis & were dccreasers--in

the late years these taxa were present live of 16 possible

times. H. mollis appeared to be on a two- to four-year low to

high cover cycle. The reasons for this was unknown but its

negative response to insect attack and wet weather were

noted.

Total hits on composites increased and decreased with bums

and between bums in the periodic plot strips. Composite

cover generally peaked in fire years and decreased thereaRer

(although this did not happen during the wet year of 1989

after the 1988 tire).

A few taxa occurred only early in the total year sequence:

Aster natens, Antennaria plantaginifolia, Gnaphalium

obtusifolium. Soli_dago nemoralia and Vemonia flaccidifolia.

A few other taxa occurred in early and middle or middle

years: & hemisphericus, Eupatorium sessilifolium,

Hieracium gronovii, Senecio anonymus and &l$agoW

speciosa. Some taxa occurred only in the middle and late or

late years of the series: Aster simplex, Chrysopsis.m,

Eriaeron canadensis, Soli&eo canadensis, and Solidapro

w. The Erigeron-and S. canadcnsis were weeds locally.

Chrvsopsis spp. invaded burned longleaf pine stands

(Heywood and Bumette 1934).

Sixteen other taxa occurred sparingly to frequently across the

year-series. Solidaeo odora was a decreaser. A few ycarfrequent taxa peaked during fire years. They were

Euoatorium aromaticum (five fires), Solidaeo & (four

fires), Helianthus silphioidcs and Aster dumosus (two fires),

and Helianthus hirsutus, and Eupatorium rotundifolium (one

fire each). On the other hand, Coreopsis & cover

decreased in fire years (means were 0.52 percent cover in fire

years versus 1.7 percent cover during non-fire years).

Composite seedling rosettes (unknown &r, composite,

Eupatorium, Helianthus and Solidago) increased in cover the

year after the fire years (four of five fires).

26
Legumes (Lxguminosae, Fabaceae, Mimosae,

Caesalpinaceae)

Thirteen legume taxa occur in the control plots at the rate of

one to six taxa per year. All were eliminated by 1970.

Twenty one named species, one hybrid and three unknown

Iegurne taxa occurred in the annual bum plot strips. Taxa

which occurred only in the early years were Amphicarpabractcata. Dcsmodium virginianum and Psoralea usoralioides.

Species which occurred in middle or early and middle years

were Dcsmodium paniculatum, Lespedeza capitata and &.

virginica. The hybrid L. intermedia x capitata occurred

annually in the middle and late years.

Sixteen taxa occurred widely across the year-series; 10 taxa

13 or more years, six taxa occurred only 2- 12 years. Of

these wide taxa, Desmodium marilandicum. Lesuedeza

intermedia, L. reoens, Stvlosanthes biflora and Tephrosia

virginiana were increasers. These were part of a general

trend of increased legume cover with time; the cover

increased 40.8 percent from the early to late year groups.

Similar increases in legume importance were rcportcd by

Wahlenberg and others (1939). L. procumbens has a lowmiddle, and Schrankia microohvlla has a high middle year

cover.

Sum-of-legume cover and certain species cover suggested

cycles of 2-5 years intervals but dates of species peaks usually

did not correspond. Response of legumes to periodic bums

was various; a general response was that species drop out.

The mean number of taxa in early years was 9.8; the mean

number in the late years was 20 percent lower. Several

legume taxa occurred in 12 or more years across the series.

Included were three increasers --P.&a&.~ ..&!&T,Q~ Clitoria

mariana and Tcphrosia virginiana, Lespedeza repensa

decreaser, and L. intermcdia a bulge species. Taxa present in

early or early and middle years that disappeared later were:

Amphicarpum bracteatum in 1969, Desmodium ciliare 1977,

g. marilandicum 1976, D. viridiflorum 1967, Calactia

volubilis 1981, Lesnedeza & 1967, Psoralea usoralioides

1968. Apparently only one species invaded, Cassia

fasciculata; this has been present since 1975. Two taxa

occurred only in the middle years, Desmodium obtusum and

Q. paniculatum.

Among wide taxa, peaks usually occurred in the periodic bum

years. The two highest peaks (1979 and 1988) arc amplified

by high cover of Cassia nictitans. An increase in frequency - -

of S. nictitans with burning has been rcportcd (Cushwa and

others 1970). Four other taxa had high cover in three to four

fire years compared to non-tire years: f’.:lilnb --I .matina

Lespedeza repens L. procumbens and Schrankia micronhvlla. _- --L

The cover of these taxa decreased in the years after each fire.

Lespedeza intermedia peaked in two fire years only. Cover

of Lesnedeza vireinica and Tcnhrosia increased on three of

five hres the year after the fire.

In periodic tire years the cover of Stvlosanthes a, which

averaged 1.6, fell to zero--it was absent in tire years. it was

another species influenced negatively by fire.

Other Forhs

In the control plots, other forb cover averaged low and lasted

only until 1975.

In annual plot strips only Pvcnanthemum tenuifolium and

unknown forb were present widely across the years. Seven

taxa occurred only one year; eight taxa occurred 2-10 years.

Taxa occurring in the early or early and middle years in

annual plots were Aureolaria virgin& Galium circaezans,

pp*p-,=. Gerardia .terutitIo~ Lobelia inflata 1. puberula, Scutellaria

inteerifolia, and Viola saeittata. Three taxa occurred only in

middIe of the seqze: Gerardia pectinata, Hyp&cum

densiflorum, and Trichostema diw. Late occurring

taxa were Houstonia caerulea, Jpomq pandnrata, Leehea

m,and Rhexia mariana,

Over the annual bum year-series, the number of &xa dechned

slightly; the mean number of taxa in early versus late years

was 4.8 versus 2.8, respectively. Similarly, the sum of all

hits was 13.6 versus 5.0; this cover comparison was heavily

influenced by an early-in-the-series peak by unknown forb

cover in 1971, and peaks by Pvcnanthemum tenuifolium in

1965 and 1968.

Periodic other forb bum plot data, as in the annual strips,

contained few species and those that appeared did so for only

a few years. One species, Hvnericum dcnsiflorum,

disappeared--it was last seen in 1978. A few taxa occurred

only in the middle of the year series: Acalvpha virginica,

Convolvulus seuium. Diodia viruinica, Gerardia pectinata,

Houstonia raerulea, Lechea minor ahd Lobelia nuberula. e

Dj,dia and Lobelia have been seen two years, the others one

year. The only new hxon was -which

appeared in 1983. Mean cover in tire years was 3.0; mean

cover in non-tire years was 4.0, the difference suggested a

depressing effect of fire on forbs. The year following the tire

the mean cover was 5.8~the rise suggests a positive

fertilization or release-from-competition effect. These effects

can be seen in Potcntilla simplex in which percent cover in

fire years was low; in non-tire years it was intcrmediatc; the

year after a fire, cover was highest.

General Discussion

The methods used collected minimal annual data although

they were favored by nearly exact position replication

between years and places. The three-foot maximum height

measurement over-emphasized disappearance of understory

stems which grew taller than three feet. Early maturing

species may not be seen, and late maturing species may have

2 1
been over-represented in this constant-date sampling. The

wet year of 1989 increased cover of some species groups

markedly. Although time of year collection of data has

always been a bias in ecological studies, in this summerautumn flora bias is believed minimal. Animal activity may

influence data; some Smilax was browsed and one

Rhododendron was lost by burrowing. A peduncle-biting

insect inhibited fruit set in Helianthus molljs.

Results expressed as percentage cover simply measured the

degree of success achieved by the species in that environment

(Daubcnmire 1968b). A parallel expression is “number of

years seen, ” which represents the species response to

comparatively stable soil conditions but changing climatic

conditions and changing conditions of interspecific

competition. Variable responses (variable occurrence,

increase, decrease, invade, retreat) are typical behaviors of

populations under stress (Grime 1979).

The mechanisms of response to fire, for the woody plants,

were related to top death and subsequent growth of sprouts

from suppressed or adventitious buds (Barbour and others

1987). Most herbs were hemicryptophytes with terminal bud

which, if not injured by fire, provides post-bum growth

potential (Daubenmire 1968b). Annual herbs (therophytes)

comprise I 1.2 percent of the flora of these plots--their

occurrence is more or less equally divided between annual

and periodic bum plots. They make up nearly one-fourth

(23.5 percent) of invader occurrences in annual and periodic

plots--a proportion twice that in the plot flora. They often

invade burned gmssland (Vogl 1974).

Species can be rated on their response to fire treatment. Only

two bxa were exclusive to the control plots--this suggested

that other taxa were at least tolerant of the stress of fires of

this study and the long history of previous woods fires and

accidental railroad fires. Of low tolerance were taxa which

were early and early and middle retrcaters, decreaserretrcaters, and the late and middle and late invaders. Widely

occurring taxa make up the rest of the classes. Wide

decreasers. wide sag species, and wide taxa with low cover in

fire years were more tolerant than previous classes. The most

tolerant were wides with peaks in fire years, certain wides

with their own cycle of variable cover, those with middle year

bulges, and wide increasers. Least tolerant taxa were called

pyrophobes; most tolerant taxa here were called pyrophiles.

But these terms are absolutes and express only the extremes

of a group of classes of fire tolerance suggested above. In

fact, these classes may be part of a gradient of responses to a

large number of fire intensity/frequencies.

Burns

In both bum treatments, the canopy was open, and overstory

trees were few. The 0.5-5.0 inch DBH class was essentially

missing (D&elm and others in press). In late years annual

bum plots were grass-forb-woody plant dominated. In late

years, periodic plots were woody plant-grass-forb dominated.

Due to a flush of Cassia nictitans after the fire of 1988, the

order was woody plants-forb-grass. In the wet year of 1989

the order was grass-woody plant-forb. In 1989 periodic plots

had 44 percent more cover than annual bum plots. Total

species number on periodic plots always increased in fue

years and after four fires, and decreased thereafter (see also

Collins and Gibson 1990).

Individual species response to the two types of bum

treatments were seldom identical; only 20 taxa (14 percent)

had the same response to annual and periodic burning. The

variety of responses suggested that the sprouting habit of trees

and shrubs and the hemicryptophytic life form of most herbs

here was not strictly fire adaptations, but were a fire response

to adaptive mechanisms evolved under a complex of

disturbances including fire, grazing, browsing, and/or

drought.

The net response of legumes to fire was positive; there was an

increase in cover in both annual and periodic treatments. The

species number remained constant in annual burns (although it

decreases slightly in periodic bums). A few legume taxa

peaked dramatically in periodic fire years and two taxa

peaked the year after a periodic fire. The legumes, plus

Ceanothus (Bond, 1983), widely occurring in annual and

periodic plots, and free-living N-fixers, replace at least some

nitrogen volatilized in fires (Chandler and others 1983).

Nitrogen losses arc reported in soil in burned grassland

(Collins and Wallace 1990).

After 27 years of treatment, eight taxa, all woody, occurred

on the strips in control bum plots. This is similar to the 10

woody taxa after 20 years under loblolly pine in coastal South

Carolina (Lewis and Harshberger 1976). Eleven herb taxa

were present in the pine stand but there were none under oaks

here. A more open canopy or physical factors associated with

the litter or oak roots (McPherson and Thompson 1972) or

allclopathic substances (Rice 1984) may be responsible for the

contrasting numbers of taxon under these overstories.

Slightly more woody taxa occurred in the oak plots here with

fire (13 annual, 16 periodic taxa) than under pine (10 annual,

12 periodic taxa). Under oak 39 (annual) and 34 (periodic)

herb taxa occurred; under pine 26 (annual) and 18 (periodic)

herbs occurred. Although the species number is lower under

pine, the percentage distribution of grass, composite and

legume taxa is similar. The lower numbers of taxa in bum

plots under pine versus oak may represent differential preplot-establishment land use history (as grazing intensity) or

some factor as fertility or moisture holding capacity.

The plots described by Paulsell (1957) are floristically and

physiognomically similar to our study plots. But his specific

results, reported as species frequencies after seven years of

treatment bear little similarity to ours.

2 8
Species Equilibrium

In the control plots, 42 taxa have retreated (including 10

woody taxa) and only three woody taxa have invaded for a

net loss of 39 taxa. The overall loss rate was 1.1 taxa per

year. Herbs persisted on control plots only until 1978--they

disappeared at a rate of 1.6 taxa per year.

In the periodic burn plots there were 12 invader and 21

retreater taxa over the years for a net loss of nine species. In

the annual bum plots there were 18 invaders and 33 r&caters

for a net loss of 15 species. Eliminating species cooccurrence between annual and periodic plots there were 48

retreaters (nearly two per year) and 26 invading taxa for a net

loss of 22 taxa (nearly one per year). These losses include

three tree retreaters and one tree invader for a net loss of two

tree taxa--hardly suggestive of succession toward forest

stability. In all taxa, maximum disturbance (annual bum) has

induced maximum species movements but with littlc

likelihood of establishment of equilibrium vegetation (Grime

1979, Risscr and others 1981).

In the periodic bums, five of 12 invaders appeared for the

first time the year of one of the live periodic fires. That one

species invading per (periodic) fire compares to the annual

bums with 0.72 species per fire invading (18 invaders/25

fk).

Life Form/History

Much has been made of life history/life form as control of

response to lire. In this flora very little is known of the

details of life history response to stress. The form/family

species classification used previously indicated a surge of

Hemicryptophyte cover with increased lire as was expected

(DeSelm and others 1973). Kccley (1981) has shown how life

form/history dcterrnines response to fire. In this study many

response types have been discussed. Only occasionally do

they match with life form/family classes (Tables 2 and 3).

The tree form, for example, occurred in 13 response types,

shrubs occurred in 10, gmminoids occurred in 12, legumes

occurred in 15 and composites occurred in 13.

Equally, bum plot trees had 11 responses. Rhizome

spreading shrubs had seven responses, other shrub six.

Among herbs, annuals had nine responses and occurred only

in bum plots. Chamaephytes (two species) had two responses

in bum plots. Geophytes (five species) had three responses in

bums and did not occur in check plots. Stolmferons herbs

(three species) had live responses in hre plots. Climbing

herbs (live species) had six responses in bum plots.

Graminoids had 11 responses in tire plots, other forbs had 17

responses. Clearly much more needs to be known about the

life history of these taxa to explain this level of variable

response to fire. Such knowledge would aid those who seek

to manage extensive wildland pastures of the southeastern

United States (U.S.D.A. Forest Service 1981).

Table 2. -PO= types. tx-eataent -, nsbers of taxa -P---ted

per type and life foxmdfanilies of taxa in burn and check plots.‘,’

bpaaw? Treatment 3 No. of Taxa in Life FoIm, Families

Type me All Treab~ts bmg Taxa

ux A, P, C 2 5 T, Sk, Cr. C, le

w A, P, C 1 3 T, Sk, W, Cr, C, Ot

lm A, P, C 1 6 T, Sk, WV. Cr. C. Le. Ot

WA P 6 T, C, Le. Ot

wu) P 2 T

lu4N P 2

U P P 6 Sh. c, Le

El3

A, p 5 cr. lE

A 5 C

GN

A c. Le

P i Le

WA) P I le

U C A Le

RR A, p, C 5 9 T, Sk. IW, Gr, C, Ie, Ot

E m A, P, C 29 T, sb, Cr. C, la, Ot

EMOR C 3 Sk, cllzm C 5 Gr

Y A, P2 2 T, Cr. C. Le, Ot

ML1 A, J’, C 10 T, G; C, Le

LI An p, c 2 3 T, Sk, Cr. C, Ot

lwi A, P 3 2 T, Sk, Cr. C, Le, Ot

EL A, P, C 5 T, Sk. WV, la

‘See text for species in mspmse types.

‘See table 3 for key to abbreviations.

3A ’ Almoal, P - periodic, C - ckack plots.

2 9
Table 3. Key to response type abbreviations

A . Low in fire years of periodic burns

I3 - Bulge, curved year-trend, cover high in middle years

C + Composite

D . Decreaser, cover v6lUeS decrease with years

E . Early years (1965-1972)

G * Sag, cover decreases in middle years

Gr - Graminoid

I l invaders, taxa found on plots

after initial inventory of 1965

K 0 Constant, cover varies ( i tt (a between years, no trends

L . Late year* (1962-1989)

Le * Legume

M * Middle years (1973-1981)

N - Increaser, cover values increase with years

0 - Own cycle, cover with apparent high-low periodicity

ot - Other forb

P l Peak, cover peaks in periodic burn fire years

S * Scattered, taXa wide but only T/3 - 213

of years represented

S h - Shrub

T * Tree

W = Wide, occurs in two thirds of years

scattered in early, middle, and late years

WV - Woody vine

CONCLUSIONS

General

Species in the same genus or family or life form group

behaved both similarly in some cases and dissimilarly in other

cases with respect to their long-term response to tire. It is

impossible to generalize with any accuracy about any group.

For example, in the genus Rhus in periodic plots, &. alabra

appeared in early and late years, &. toxicodendron

disappeared aher 1972 and the cover of I~.LQ&I& which

was present throughout, peaked in fire years but was

depressed between fires. la annual bums, B. glabra occurred

only in early years, II. toxicodendron and &. conallina both

occurred widely but the latter was an increaser. Other

species in the same family or life form exhibit equally

variable responses.

Cover of species on contro1 plots changed as it did in

treatment plots. The causes of change were not known in

either case. Differences extant between bum (annual and

periodic) and control plots were not necessarily due only to

treatment effects on burned plots; there may have been

equally large chronological developmental changes on control

plots induced by or paralleled by canopy closure and litter

accumulation.

In addition to widely occurring species--all species which

exhibited little cover change, or which were increasers or

dccreascrs--there were also other classes. Retreaters were

present in early or early and middle years and disappeared

thereafter. Invaders appeared in middle or middle and late

years but were not present in early years. Sporadic& which

occurred in early, middle and late years totaled 10 or fewer,

have not been considered in this paper. Of the 22 response

types seen among the 141 taxa, 10 types occurred in all three

treatments, but a few others were specific to treatment or lifeform-family categories. A gradient of response occurred

among the species present. Those that responded most

positively were called pyrophiles--those that responded least

positively (but have been there long enough to see once) were

termed pyrophobes. Most taxa occurred between these

extremes.

Annual Burns

Some taxa seem to have oscillating cover even in the uniform

treatment of annual bums. These wides may have responded

to some internal growth cycle (as trees that fmit cyclically)

(Fowells 196.5). They may also have responded to annual

weather changes (Fritts 1976). For example Towne and

Owensby (1989) found annual Kansas prairie biomass

correlated with precipitation. Or they may have responded to

changes in competition from neighbors whose cover

responded as above. Weather regimes seemed to be a likely

source of year to year variation in species behavior. Its

effects will be considered in a later paper.

A few taxa (as Schizachvrium) peaked in middle years, cover

before and after these peaks was generally lower. They were,

in early years increasers, in later years decreasers. These

may have been the oscilating cover type with their own cycle

but with a very long time between peaks.

Taxa which occurred only in middle years may have been a

low average cover example of the middle-years-peak species

noted above. Or perhaps they should be considered invaderretreaters. They occurred in four form-family groups in all

three treatments. With more extensive sampling, these might

prove to be middle years peak species noted above. Wide,

middle-year-sag species occurred as did those that occur only

in early and late years.

Periodic Burns

Composite seedlings established in the year of periodic fires

on those plots. Comparable cohorts of grass and legume

seedlings were not seen. New taxa were also most likely to

invade the periodic plots during bum years.

30
Six kinds of response types occurred in periodic burns only.

Three of these had low cover in tire years, and high cover

between tires; there were those with more or less constant

cover between peaks and between valleys, those with a middle

year-group bulge, and those which were increasers, Three

other types have peak cover during fire years. There were

those with constant or uniform peaks and valleys across the

year-series, those which were increasers, and those which

were decreasers.

ACKNOWLEDGMENTS

These experimental plots are in Compartment 1 at Highland

Rim Forestry Experiment Station, a facility of the University

of Tennessee Agricultural Experiment Station, and the

Department of Forestry, Fisheries and Wildlife. This work

could not have been done without their long support.

The writers acknowledge the help of Mr. J. Huffman, Mr. T.

Seay who have managed the plots, and the Tennessee Division

of Forestry, Franklin County, who, with Huffman or Seay,

made the burns. We acknowledge the personnel of the

University of Tennessee Herbarium who assisted in

identifying plants. The Department of Botany, and the

Graduate Program in Ecology have also materially aided the

study. Two anonymous reviewers suggested additions and

clarifications.

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33
IMPLICATIONS FOR LONG-TERM PRAIRIE MANAGEMENT

FROM SEASONAL BURNING OF LOESS HILL

AND TALLGRASS PRAIRIES

Thomas B. Bragg’

Abstract-Data From prescribed bums of no&western Iowa loess hills and eastern Nebraska tallgrass

prairies were used to assess the e&k of season of burning and implications for long-term management of

grassland ecosjstems. Overall forb cover declined most without burning (-22%). Compared to unburned

areas, species number on both sites was higher (i-5) wirh fall burning with the response most pronounced

at the loess hills site. The response of species such as false. sunflower @eliopsis heliantboides) suggest that

summer and fall burning may do most to encourage seedling germination and establishment. Other species,

such as white aster (Aster eticoides) on the taligrass site and gray goldenrod (Solidapo nemoralisj at the

loess hills site, increased in cover with summer or fall burning. Some species showed significant changes

irrespective of treatment; in he tallgrass area, porcupine-grass (Stipa spartea). decrease d and flowering

spurge (Euphorbia codlate) increased.

The vegetative responses recorded suggest the likely importance of applying some summer and fail burning,

in conjunction with the usual spring burning, to the long-term maintenance of diversity in the tallgrass,

loess hills, and perhaps other, grassland ecosystems

INTRODUCTION

The effects of fire in prairie ecosystems of the North

America have been extensively studied (for example, see

Vogel 1974; Risser and others 1981; Wright and Bailey

1982 j. Generally, studies have determined that fire is a

natural component of these grassland ecosystems and that

continued fire management i s important, whether the objective

is to maintain the vitality and diversity of the natural

ecosystem or to manage for other, agmeconomic, pmposes.

More recently, research has begun to reline the understanding

of fire’s role in grassland ecosystems with an increased focus

on fite frequency (the number of years between bums) and

fire season (the season during which fire is applied).

Grassland fua occurred naturally at various times of the

year, including summets (Moore 1972; Bragg 1982), thus the

seasonal aspect of fire is important to understanding its rule in

the long-term management of this ecosystem. Studies

comparing differences in efffxk of season of bum, however,

have largely focused on the northerly, mixed-grass prairies of

North and South Dakota. Few community-level studies on

this specific aspect of fire ecology have been published for the

tallgrass prairie.

Response of Grasses and Grass-Like Species

Many comparative studies on the effect of iire season on

prairie vegetation have focused on either Spring or Fall, these

being times most often appropriate for the management

objective of cattle grazing. Burning during these seasons,

particularly in the Spring, has also been carried over into

ecoIogical management of grasslands. Studies on the effects

of fire often focus on grasses since they are the predominant

‘Professor of Biology, University of Nebraska at Omaha, Omaha, NJ.?.

vegetation type and since they have the greatest effect on

forage production. When considered ecosystem-wide, the

results of such studies have been found to be similar only in

that they all differ considerably depending on season of

burning, latitudinal location, and local climatic conditions.

These differences on grass and grass-like species are reflected

in two general areas of fire effects: productivity and species

composition. For the sake of comparison of effects of season

of burning, results are discussed separately for northern

prairies (e.g. North and South Dakota) and for central (more

southerly) prairies (e.g. Nebraska, Kansas, and Oklahoma).

Effect on Productivity

Native grass or grass-lie species, for which studies on

productivity have been conducted both under various burning

regimes and at different locations, include the warm-season

(C,) species blue grams [Bouteloua & (H.B.K.) Lag. ex

Criffths) and cool-season (C,) species such as western

wheatgrass (Arrronvron smithii Rydb.), needle-and-thread

(Stina comata Trin. & Rupr.), and Kentucky bluegrass (Pea

pratensis L.). Also included is threadleaf sedge (Carex

tilifolia Nutt.) although the carbon-fixation status of this

species does not appear to have been determined.

As with most species, the effect of burning on blue grama

differ by location and’with climatic conditions. In studies in

South Dakota, for example, spring (April) burning was found

to reduce the productivity of blue grama whereas the response

to fall burning was variable, increasing production when

precipitation was adequate and decreasing it when

precipitation was low. In the mixed prairie of North Dakota,

however, both spring (May) and fall (October) fires increased

blue grama production with spring burning resulting in the

3 4
greater increase (Whisenant and Uresk 1989). For western

wheatgrass in South Dakota, productivity increased with Fall

burning but either increased or decreased in response to

spring burning, again depending on precipitation. The

response of this species to fire in the more northern North

Dakota prairies, however, was an increase in production with

both spring and fall burning (Whisenant and Uresk 1989). As

with blue grama, spring burning resulted in the greater

response.

Needle-and-thread is one native grass species for which

productivity is generally reduced by fire throughout much of

its range. In the mixed-grass prairies of both North and

South Dakota, productivity of this cool-season grass declined

with both spring and fall bums (Dix 1960; Wright and

Klemmedson 1965; Engle and Bultsma 1984; Whisenant and

Uresk 1989). Gartner 9 & (1986), however, did report a

greater productivity of this species with both spring and fall

bums. In the central, more southerly, Nebraska tallgrass

prairie, however, summer mowing (approximating summer

burning) resulted in a higher canopy cover of the congeneric

porcupine-grass (Stipa spar-tea Trin.) than in areas burned in

the spring (Hover and Bragg 1982).

Threadleaf sedge, a species common in the mixed-grass

prairies of the Dakotas is particularly informative. It has

been reported to be unaffected by spring or fall burning

(Schripsema 1977; Whisenant and Uresk 1989) although it is

reduced by fall burning in North Dakota @ix 1960; White

and Currie 1983). The general response of this species to

burning is similar to that of needle-and-thread, a C, species,

but unlike that of western wheatgrass, another C, species. If

this observation is extrapolated to other species, it suggests

either that the response to burning may occurs independent of

carbon-fixation pathway or that the tire conditions under

which the previous studies were conducted are not fully

known.

A summary of the effects of fire on grass productivity, then,

suggests that the complexity of fire effect studies. Only two

common denominators are suggested, first, fires in dry years

reduce productivity, and second, not all C, and C, species can

be expected to respond similarly to burning.

Effect on Composition.

Another aspect of the effect of season of bum is the response

of the community as a whole, which is the principal focus of

this study. Despite individual species responses, community

level studies in the northern mixed-grass prairie have

indicated that season of fire occurrence is not a sufficient

factor to substantially alter community composition @ix

1960) or to alter the q/C, ratio of the northern mixed-grass

prairie (Steutcr 1987).

The C, grasses of the northern mix&prairie appear to be a

fire-adapted guild (Steuter 1987). The tendency for coolseason grass species to increase or to bc unaffected in the

northern Great Plains, however, is opposite to the response in

more southerly tallgrass prairies of Kansas and Oklahoma. In

these tallgrass prairies, dominated by warm-season, C,

species, spring bums more consistently decrease cool-season,

C, species, including porcupine-grass, Kentucky bluegrass,

Canada wild rye (Elvmus canadensis L.), and Scribner

dichanthelium [Dichanthelium olieosanthes (Schult.) Gould

var. scribnerianum (Nash) Gould] (IIensel 1923; Ehrenreich

1959; Hadley and Kieckhefer 1963; Robocker and Miller

1955; Old 1969; Anderson and others 1983). The effect of

fire at other seasons, however, has not been widely studied

although it has been found that little bluestem (Androooeon

scopor~ur Michx.), is most adversely affected by summer

(July) bums (Adams g& 1982)

Response of Forbs

General results on fue effects indicate that forbs are

increasingly adversely affected as burning occurs at

increasingly later spring dates. For example, late spring

burning in the tallgrass prairies of Kansas reduced all forbs

(McMurphy and Anderson 1965; Towne and Owcnsby 1984;

Hulbert 1988) compared to earlier dates. However, while

these studies reflect a reduction in cover (suggesting also a

reduction in productivity), the actual composition of forbs is

little effected (Anderson 1965). Similar effects related to

season of bum are reflected in the shortgrass prairies of

western Kansas. There, forbs are less effected by dormant

season (fall/winter) bums than by spring bums which occur

after they have initiated growth (Hopkins and others 1948).

One principal study on the response of individual forb species

to seasonal effects of burning was conducted by Biondini and

others (1989) in northern mixed prairie. In this study, the

density of nine forbs was significantly effected by tire season.

Species responses relevant to the present study include

western ragweed (Ambrosia psilostachva DC.) and white aster

(Aster ericoides L.), which were most positively affected by

fail bums, blue lettuce (Lactuca oblonnifolia Nutt.) most

effected by summer burns, and stiff sunflower velianthus

~+idus~ (Cass.) Desf.] and wavy-leaf thistle [Cirsium

undulatum (Nutt.) Spreng.] most effected by spring burns.

Only pasque flower (Anemone patcns L.) had the highest

density without burning. In another study in the northern

prairie region, Schripsema (1977) recorded increases in

species such as silver-leaf scurf-pea (Psoralea argophyk

Pursh) with late spring (late May) burning whereas a winter

(March) bum had the opposite effect.

In more southerly tallgrass prairies, fall burning increased

rigid sunflower (Solidigo rigida L.) (Schwegman and McClain

1985) and leadplant (Amomha canescens Pursh) (Towne and

Owensby 1984) although the greatest increase was among the

annual species such as grooved flax (Linus sulcatum Ridd.)

and white sweet clover (Melilotus alba Medic. (Schwegman

and McClain 1985). Whorlcd milkwort (Polvgala verticilata

L.) and grooved flax were best established in spring burned

plots (Schwegman and McClain 1985) but late spring

35
(mid-May) burns adversely affected species such as prairie

violet (Viola pedatifida G. Don), white-eyed grass

(Sisvrinchium campestre Bickn.) and downy gentian (Gentiana

pubenrlenta Pringle); gay-feather (I .iatris a~~~.ra Michx.) and

smooth blue aster (&ter laevis L.), however, ad

significantly more leaves with late than with early spring

bums (Love1 1 and others 1983).

The results of previous studies on effects burning suggest that

the basic characteristics (e.g. productivity and species

composition) of grasslands of different latitudes should

respond differently to fire and that the response will be

further modified by season of burning and climatic conditions.

The objective of this paper is to identify such differences by

comparing the results from two grasslands that are similar

physiognomically but that differ in both latitude and dominant

species. Specifically, the study will compare a Loess Hills

prairie of northwestern Iowa and a tallgrass prairie of eastern

Nebraska in order to assess similarities in plant responses to

fire. Further, the study is designed to assess the possible role

of different seasons of burning and their implications for

global application in long--term management of grassland

ecosystems.

METHODS AND MATERIAL

The study involves unreplicated sites and unreplicated

locations within each site. This design was necessitated by a

combination of the travel distance, the absence of additional

sites to which access could be controlled, and the time

required for both fire treatment and field evaluation.

Therefore, extrapolation of results to other sites of the same

vegetation type can only be used in a speculative manner and

then only with caution. However, in those instances where

similar responses to burning are noted at each site, the

response could be considered to be replicated (e.g. two prairie

sites were evaluated) and thus it is more likely to be

representative of general trends. In addition to limiting how

broadly the results can be inferred, the lack of adequate

replication limited the kind of statistical evaluations that could

be appropriately applied.

An additional caution to extrapolation of results is necessary

due to the absence of any tire treatment at either site for

many years, probably decades, prior to the study. The plant

communities that were burned, therefore, may not be the

same as those that dominated historically when fires

reoccurred with some regularity. Studies at these sites are

continuing at least through the 1990’s in order to assess this

possibility.

Study Site

The LO&Q Hills study site was located on Five Ridge Prairie

(within Sections 20, 21 and 29, Township 9IN, Range 48:W)

located in northwest Iowa approximately 20 kilometers north

of Sioux City. The prairie is managed by the Plymouth

County Conservation Board in cooperation with the Iowa

Chapter of The Nature Conservancy. Treatment plots were

located in the northwest quarter of Section 29 along a

southwest facing, 20-26% slope on which native prairie

vegetation prevailed. The site was dominated by grass

species, particularly little blue-stem and plains muhly

[Muhlenberzia cusuidata (Torr.) Rydb.]. The soil of the site

is a Hamburg silt loam (Typic Udorthent soil subgroup,

Entisol soil order). The Hamburg series consists of

excessively drained, calcareous, silty soils formed on loess

(Worster and Harvey 1976). Climate of the region is

continental with normal daily highs of 30 C in July and a low

of minus -14 C in January. Normal annual precipitation

(based on 1951 to 1980 data) averages 64 centimeters with

74% occurring during the growing season (April through

September). Climatic data are from National Oceanic and

Atmospheric Association (1989a).

The tallgrass study site was located on Stolley Prairie,

approximately 20 kilometers west of Omaha, Nebraska in

Douglas County (NW 114 Section 15, Township 15N Range11 E) Stolley prairie is privately o\uned, jointly leased for

wildlife habitat by the Audubon Society of Omaha and the

Papio-Missouri River Natural Resources District, and

managed by the Biology Department, University of Nebraska

at Omaha. The prairie had been mowed for more than 20

years until haying ceased in 1980 with leasing of the site.

Treatment plots were located on a north-facing, 7-l 1% slope,

tallgrass prairie dominated by big bluestem and porcupincgrass. The soil is a Marshall silty clay loam (Typic Hapludoll

Subgroup, Mollisol Soil Order), a deep, well-drained soil

formed in loess (Bartlett 1975). Climate of the region is

continental with normal mean highs of 30 C in July and

normal mean lows of minus 12 C in January. Normal annual

precipitation (based on 195 1 to 1980 data) averages 76

centimeters with 74% occurring during the growing season

(April through September). Climatic data are from National

Oceanic and Atmospheric Association (1989b).

Treafment

At each study site, treatment plots, approximately 20 by 20

meters in size, were established in a strati&d, complete block

design with plots situated at either upper-slope or mid-slope

locations. A single, lo-meter (Tallgrass) or 20-meter (Loess

Hills) transect was centrally located within each treatment plot

and permanently established with two metal rods at each end.

Differences in transect length were due to size of the area

available for the study; the loess hills prairie was smaller in

size due to woody plant invasion from lowland valleys.

Along each transect, ten microplots were systematically

placed. I was able to evaluate the same microplots each year

of the study by extending a meter tape between the rods and

using established intervals at each evaluation.

Neither of the study sites had been burned within recent

memory. After preliminary data collection in 1981, randomly

selected treatment plots at the Tallgrass site were burned in

3 6
early May, early July, and mid-Scptembcr 1983. With the

cxccption of Fall treatments, all plots were resampled in the

Fall of i983, 1984, and 1986. Fall bum treatment plots were

not sampled in 1983 since treatment had not yet been applied:

evaluations for 1981 were used to represent pm-bum

conditions for this treatment.

At the Loess Hills site, plots were burned in mid-October

1986 (after pretreatment data collection) and in late April and

early July 1987; the fan burn was conducted in 1986 (rather

than 1987) so that all fire treatment plots would be effected

by the same (1987) growing season. Treatment plots were

resampied the Fail of 1987, 1988, and 1989. At this site,

spring evaluations were also conducted in each sampling year

in order to record any species that were not visible in the

Fall.

Data Collection

Because of different, site-specific characteristics of the plant

canopy cover, microplot size varied for each site. Microplot

size was 30 x 50 centimeters For the Tallgrass site and 50 x

100 centimeters for the LOCSS Hills site. The larger size used

in the Loess Hills was needed due to lower total plant canopy

cover and more widely spaced plants. The number of

microplots to be evaluated was determined From preliminary

sampling of each community type from which it was

determined that ten microplots incorporated 90% of all

species situated along each transect in each site. Microplots

were systematically placed along each transect to facilitate

relocation in subsequent years.

Within each microplot, canopy cover of each species was

recorded as were the general cover categories of “bare soil”

(soil devoid of surface litter; litter is dead plant matter that is

no longer connected to a living plant) and “forb”. Coverage

was estimated based on procedures modified from

Daubcnmire (1959). Cover categories were 0%, l-5%,

S-25%, 25SO%, SO-75%, 75-95%, 95-B%, and >99%.

Because of lack of adequate replicates and for the purpose of

this broad scope paper, descriptive statistics (Mean t

Standard Error) were calculated for all species and used to

compare effects of treatment.

RESULTS AND DISCUSSION

Site Differences

Site differences are characterized by data collected prior to

the year of fie treatment. In addition to species differences,

noteworthy pretreatment differences included significant

differences (based on Standard Error) in bare soil (soil not

covered with litter) (7% on the loess hills site compared to

1% on the tallgrass site) and in forb cover (38% loess hills;

45% tallgrass) (tables I and 2). In addition, 49 native species

were recorded in loess hills, pretreatment microplots

compared to 44 species for the tallgrass microplots. ARer

adjusting for species observed at each site, but not necessarily

present within microplots, 16 species were identified to be

unique to the loess hills with 7 unique to the tallgrass site.

This supports a qualitative observation made during field

evaluations that the loess hills had higher plant species

diversity than the tallgrass site and that this difference may bc

due to more niches afforded by the greater surface

heterogeneity as reflected in bare soil. The tallgrass site,

however, did have an active pocket gopher (Gwmvs

butsarius) population that has the potential to profoundly

affect the ecosystem (Huntly and Inouye 1988) and is likely to

afford some, continuous bare soil niches. Pocket gopher

activity was not observed at the loess hills site

Community-Level Responses

Some treatment effects were found to be similar at both sites

of which the effect on forb cover and Species Richness (the

total number of species) are most noteworthy. The fall

following spring and summer treatment, forb cover declined

from pre-treatment conditions in all microplots at both sites

regardless of whether burned or unburned. The cause for this

response is unclear except that precipitation does not appear

to be the principal factor; both treatment years were followed

by hear average or above-average precipitation (fig. I).

While the decline in forb cover occurred at both study sites, it

was greatest in unburned plots (-15%) at the tallgrass prairie

and second greatest in the unburned plots (-33%) at the loess

hills prairie where it was second only to summer burning

(- 35%). Three growing seasons following fire treatment (4

seasons for the tallgrass prairie), the unburned plots continued

to show the greatest loss of forb cover based on pre-treatment

values (-18% for tallgrass; -21% for loess hills) (tables 1 and

2). It should be noted, however, that the decline in forb

cover in the absence of fire, reflects only a change in the

amount of a species and not necessarily changes in population

size.

120

1

l h tills Prairii

100 (3 Tallgrass Prairie

IS85 1088 1081 1988 1088

Year

Fig. I.-Precipitation for Sioux City, Iowa Loess Hills (=

LWP) Prairie site] and North Omaha, Nebraska ~allgrass

(TGP) Prairie site] weather stations for the years 1981

through 1989. Horizontal lines represent normal precipitation

(National Oceanic and Atmospheric Administration 1989a,

1989b). “b” = bum treatment year (For LHP, 1986 = Fall

treatment and 1987 = Spring and Surmrrer treatments)

3 7
Tabte 1. csnopy cover (Mean + Stendard Error) of tallmxs prairie site

species with frequency va~*s-greater rbsn 50 perceaf, in either this Or

the loess hilts prairie site. v810e~ represent 20 microplots from tua

transects per trestmenf. scientific and camm mams we frm the Crest

Plains Flora Association (1986). *-II I w data; tr : qO.5 percent cover. Table 1. (contimwd)

Season of Prescribed Burn season of Prescribed Sun

SpeCieS Evaluation Species Ev8kation

Year SPMj Sunwr Fal I Unburned Year spring Sumw FelI UnkR-Zd

CEKERAL CATEWSIES

Nmber of species

Forb Cover

Bare Soit

Achilles mii'efolim

(yarrw)

canestens

(leadplant)

Andropoqon &mrardfl

(big bluestal

hdrcimgon scovarius

Wttle bluestem)

mcvlindrica

(candle amnone)

Aster ericoides

(abi te ester)

Boutel wtiwmb

(sideoats gram)

Q$,g.& S'TQ.

(sedge)

ceanothusls

(Neu Jugey tee)

.

YZotlS I s

(boawe- mi)

Dichantheliun

o!agossnthes var.

P

dichanthcl'm)

1901 2 9

1983 34

1984 3 2

1986 2 7

1981

1983

1984

1986

1981

1963

1984

1986

6912.5

2Tl.O

2z1.9

1981

1983

1964

1%. 1

1991

1983

1984

1986

1901

IOIl3

1984

191

IS01

1983

1984

198S

1961

1983

lS84

19%

I981

1983

1984

1986

1911

lw13

:9%

19al

1983

'984

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1911

1883

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1984

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1984

Kuhnia

-i-m

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Tarsxacint-

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38
Hmtw of species

Forb Cover

Bare Soil

Andropog~n qerardii

(big bluestem)

Aster sericeus

(sitkv aster)

sourdare curtiwodula

(SldecdS 9rw)

,

Carex SFQ.

(sedge)

Dalea WP. (plrie clover)

Dichantheliun

oliaosanthes var.

(Uilcox

dichsnthetiun)

1986

1967

19e.e

1989

1986

1987

1988

1989

1980

IS87

1988

1980

1986

lSS7

2:

19%

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1sSS

1989

1986

1987

1988

190

19%

1987

1988

1989

1986

1987

198a

1989

1986

1987

19811

1989

1986

1981

Et

1986

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1Sa.l

1%

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3 8

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Echinaces an ustifolie

--%r---- (plrplc CDoe ower)

Gnua rioi&n var.

EmDaCtM

(stiffstun fler)

Psoralea teouiflora

(uitd alfalfa)

Sisvrinchiun canoestre

(nblte-eyed grass)

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(ri@d @&.Wd)

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(hoary vervain)

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1987 k2.2 2Tl.2

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39
One consideration in the changes in species richness and forb

cover with treatment is climate of which precipitation is an

important component. Precipitation during all post-bum years

at the loess hills site and during the second post-bum year at

the tallgrass site averaged less than normal (fig. 1). The

different responses of species diversity, both positive and

negative, to season of burning, suggest that, while a drought

year may be a poor time to bum prairies during some season

of a year, some other season of the same year may be a

reasonable time to bum. These results, if verified by further

study, are particularly relevant to prairie management.

Woody plant invasion threatens both loess hills (Heineman,

1982) and tallgrass (Bragg and Hulbert 1976) prairie areas.

This study suggests that tire, a management tool that controls

woody plant invasion, can be applied during appropriate

seasons, even those of a drought year, without adversely

affecting long-term species diversity. Further, results of this

study that show increased diversity with different seasons of

bum, suggest that any season of burning is better for

maintaining grassland diversity than is fire exclusion. In the

present study, this effect appears to be particularly true for

the loess hills prairie ecosystem.

While one common effect between sites was a decline in forb

cover without burning, another common effect was a shortterm decrease in Species Richness with summer burning (-8%

for tallgrass species; -7% for loess hills species); sufficient

data were not available, however, to test for the statistical

significance of this difference. This overall reduction in

number with summer burning, however, did not persist

beyond the second post-bum growing season (tables 1 and 2).

For example, three growing seasons after burning in the loess

hills, Summer treatment plots had recovered to pm-bum

numbers. By this time, it was the Spring burned microplots

that reflected the greatest loss of species (-5); unburned

microplots averaged four less and fall burned plots averaged

two less species. For the tallgrass prairie site, four growing

seasons after treatment, species richness of all but the Spring

treatment (-2 species) was at pre-bum numbers. Thus, for

both the loess hills and tke tallgrass prairie ecosystcn~e~ spring

treatments, which represent the most widely applied time of

fire management, showed the greatest long-term (f-4 year)

loss of species;

Individual Species’ Responses

The response of individual species provides further insight

into the seasonal effect of burning on specific prairie types

and on grassland ecosystems in general. Of the several

species common to both sites, only big bluestem (Andropogon

gerarda Vitala@, g r a s:s [Sorghastrum nutans (L.) Nash],

sideoats grama mouteloua_ curtipendula (Michx.) Torr.) , and

sedge /Carex spp.) were sufficiently abundant to make

comparisons between the tallgrass and loess kills sites. Tke

responses of all but sideoats grama were similar between sites

(tables I and 2). Sideoats grama, however, declined an

average of 11 percent with all treatments at the tallgrass site

but was maintained at or above prebum amounts both without

burning and with all bum treatments except spring burning

(fig. 2). The most likely explanation for this difference in

40 1 Loeas Hills Prairie

LIB B3Sp B3Su B3Fa

Treatment

3 0 1

Tallgrass Prairie

q 1986

881 1967

lBBl 1988

Eg 1989

Bi 1981

q 1983

19 1984

ta 1986

U B B3Sp BBSU l33Fa

Treatment

Fig. 2.-Sideoats grama cover for loess kills and tallgrass

prairie sites contrasting the site-specific response of this

species to burning, Vertical lines represent one Standard

Error. B3 = three-year bum schedule, Sp = Spring, Su =

Summer, Fa = Fall, UB = Unburned. Tallgrass site bum

year = 1983; loess hills burn years = 1986 for Fall treatment

and 1987 for Spring and Summer treatments; “-I’ for Tallgrass

Prairie in 1983 indicates “no data”.

40
response between sites is the long history of mowing

management prior to the initiation of this study. Such

m?nagement would have maintained a low canopy thus

enabling sideoats grama, a mid-height grass, to persist in an

ecosystem otherwise dominated by tall-statured species. With

the cessation of mowing at the tallgrass prairie in 1980,

canopy cover of the tall-statured component of the ecosystem

increased as evidenced, for example, by the 15 percent

increase in big bluestem and the 20 percent increase in

indiangrass cover in unburned plots (table 1). The decline in

mid-height and increase in tall-statured species were amplified

by fire’s tendency to favor tallgrass species (Ehrenreich 1959;

Hadley 1970). At the loess hills site, however, tallgrass

species were only a minor component of the ecosystem thus,

fue’s favoring of tallgrass species did not substantially affect

the mid-height grasses such as sideoats grama and little

bluestem (table 2). The effect of fire on a species (e.g.

sideoats grama), therefore, may not operate directly on that

species but rather may operate indirectly by favoring an

intermediate species (e.g. indiangrass) that outcompetes the

shorter grasses for some limited resource such as light.

Other species, either found only at one site or found in

sufficient numbers only at one site, provide yet further insight

on long-term management implications for prairies in general.

One such insight of particular importance would be any

evidence that fire encourages seedling establishment in a

prairie ecosystem. Recruitment is one of the most critical

facets of long-term prairie management since it ensures a

replacement of a spies’ population, thereby maintaining

ecosystem diversity over decades. No studies have been

conducted on fire-affected seedling germination and

establishment in the loess hills prairie but those in the

tallgrass prairie generally show variable results. For

example, Glenn-Lewin s & (1990) found that, in years with

adequate precipitation, burning resulted in higher seedling

establishment than occurred without burning; one species that

showed this effect was Scribncr dichanthelium. In dry years,

however, they found that burning reduced seedling

establishment. Also noteworthy WES that, with adequate

precipitation, germination of some species (e.g. Kentucky

bluegrass and prairie violet) was particularly high in either the

unburned area or in areas burned the previous year.

While the present study did not focus on identification and

establishment of seedlings, one might hypothesize that

significant increases in canopy cover would be a logical

consequence of such fire-initiated establishment. Initially

being absent or having low cover (e.g. with seedlings) growth

of new plants would be reflected in a significant increases in

canopy cover over a few years. Evidence for such an effect

of fire was found in the tallgrass prairie with summer burning

of false sunflower WeIiopsis helianthoides (L.) Sweet var.

& (Dun.) Fem.] (fig. 3), summer and fall burning of

white aster, and fall burning of leadplant (table 1). In the

loess hills, such a response was found for prairie clover

(Dalea spp.) with summer and fall burning (fig. 3). Note that

all of these seedling-initiation signatures occurred only with

summer and fall burning, which are not the normal times for

prairie management burning in the tallgrass or loess hills

prairie regions. Rohn and Bragg (1989), for example, found

that germinability of false sunflower and white prairie clover

(Dalea candida Michx. a Willd) declined with spring

burning. These results suggest that, for the long-term

maintenance of a diverse community, occasional bums of

some portions of an area at times of the year other than

spring may be important to ensuring the continuation of a full

complement of species.

1 8

1

Loess Hills Prairie

1 6 T

E 14

g 1 2

g 1 0 n 1986

8

q 1987

a D 1988

z 6 • d 1989

(3” 4

2

0

U S 03sp 83%~

Treatment

B3Fa

30

1

Tallgrass Prairie

l 1981

E 1963

0 1984

0 1986

u 0 t33sp B3su B3Fa

Treatment

Fig. 3.-Canopy cover of Dalea spp. (prairie clover; loess hills

prairie) and false sunflower (tallgrass prairie) showing the

type of increase in cover hypothesized to reflect an increase in

number of individuals in response to summer burning.

Vertical lines represent one Standard Error. B3 = three-year

bum schedule, Sp = Spring, Su = Summer, Fa = Fall, UB

= Unburned; “-* for Tallgrass Prairie in 1983 indicates “no

data”. Tallgrass site bum year = 1983; loess hills bum years

= 1986 for Fall treatment and 1987 for Spring and Summer

treatments.

41
In addition to possibly encouraging seedling success, fires at

different times of the year both in the loess hills and in the

tailgrass prairie sites increased the cover of some species.

Among the species that showed this response at the tallgrass

prairie were white aster, stiffstem flax &,inum rigidum var.

compactum (A. Nels.) Rogers] (fig. 4), and black-eyed Susan

(Rudbeckia m L.), all of which increased with summer and

fall burning; Stiffstem flax and black-eyed Susan declined in

cover without burning. At the loess hills site, other species

showed a similar response pattern including gray goldenrod

(Solidago nemoralis Ait.) with fall burning (fig. 4) and, as at

the tallgrass site, stiffstem flax with summer and fall burning.

Gray goldenrod, for example, declined during the four years

of the study with all treatments except fall burning. Again,

note the apparent importance of summer and fall burning to

maximizing the canopy cover these species.

Significant declines with all seasons of burning were dctccted

for sideoats grama and rough dropseed [Snorobolus B

(Michx.) Kunth] in the tallgrass prairie and silky aster (Aster

Little sericeus Vent.) in the loess hills prairie. bluestem

declined with summer burning in the loess hills prairie. As

has been pointed out above, note the particular role of

summer and fall burning in affecting species’ responses.

Only candle anemone (Anemone cvlindrica A. Gray) in the

tallgrass prairie site increased significantly without some fire

treatment.

Some species showed significant changes irrespective of

treatment. For these, it appears that some factor other than

fue is important in explaining their response. Species that

decreased without regard to treatment included Scribner

dichanthelium and porcupine-grass in the tallgrass prairie and

white-eyed grass in the loess hills (tables 1 and 2). The one

species that increased significantly was flowering spurge

(Eunhorbia corollata L.).

CONCLUSIONS

When taken in combination, the vegetative responses to fire

reported at the tallgrass and loess hills study sites, suggest

several considerations. First, the same species may respond

differently in different ecosystems. This is a logical

conclusion but one that needs to be carefully considered

particularly when developing management plans for grasslands

even withii the same general geographic area. Second, in

order to maintain long-term (many decades long) diversity of

a grassland ecosystem under relatively static climatic

conditions, this study suggests that serious consideration be

given to some application of fue management at various times

of the year. While further research is clearly needed, data

from both the tallgrass and the loess hills grasslands suggest

that successful seedling establishment, for example, might

re+re different seasons of burning. Summer and fall

burning seem to be times that are most likely to encourage

such seedling success for several species. Higher biomass

produced by some species with summer and fall bums further

suggests the need for a consideration of occasional non-spring

bums.

Thus, to maintain vegetative diversity both by seedling

establishment and by maximizing species productivity, some

areas or portions of areas within a preserve should be burned

some time during the growing season. The size of such

growing-season bums, however, should not be so extensive as

to adversely affect the resident invertebrate population of the

area. Such small scale summer bums are probably

representative of the natural ecosystem in which sufficient

fuel is present to support a fire (Bragg 1982) but where the

amount of green matter in the fuel bed would not have

supported a high intensity, widespread fire.

14

7

L0e.S.s Hills Prairie

f 12

1 10

‘Ii: 8 n 1966

5 q 1967

: 6

4 n • d 1966 1969

z

6 2

0

UB B3Sp B3Su B3Fa

Tallgraas prdrie

n 1981

q 1983

n 1964

q 1986

ii

55

0

UB m6P B3Su ENFS

Treatment

Fig. 4.-Canopy cover of grey goldenrod (loess hills prairie)

and stiffstem flax (tallgrass prairie) indicating that their

persistence may be dependent on summer or fall bums.

Vertical lines represent one Standard Error. B3 I= three-year

bum schedule, Sp = Spring, Su = Summer, Fa = Fall, UB

= Unburned; “-” for Tallgrass Prairie in 1983 indicates “no

data”. Tallgrass site bum year = 1983; loeas hills bum years

= 1986 for Fall treatment and 1987 for Spring and Summer

treatments.

4 2
ACKNOWLEDGEMENTS

This study was completed with funding support from the-Iowa

Chapter of The Nature Conservancy and the University

Committee on Research, University of Nebraska at Omaha.

Fire management assistance was provided by The Nature

Conservancy and the Plymouth County Conservation

Commission. Assistance in field collections, species

identification, and computer graphics were provided by Dr.

David M. Sutherland.

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43
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FORTY YEARS OF PRESCRIBED BURNING

ON THE SANTEE FIRE PLOTS:

EFFECTS ON OVERSTORY AND MIDSTORY VEGETATION

Thomas A. Waldrop and F. Thomas Lloyd’

Abstract-Several combinations of season and frequency of burning were applied in Coastal Plain loblolly

pine (Pinus taeda L.) stands over a 40-year period. Pine growth was unaffected by treatment. Aboveground portions of small hardwoods (less than 12.5 cm d.b.h.) were killed and replaced by numerous

sprouts. With annual summer burning, sprouts were replaced by grasses and forbs. Study results

emphasize the resilience of southern forests to low-intensity burning and that frequent burning over a long

period is needed to produce significanl changes to forest StNCNIX and species composition.

INTRODUCTION

It is well established in the literature and in other papers at

this symposium that frte has been a major ecological force in

the evolution of southern forests. Ecological and

meteorological evidence suggest that lightning-caused fires

were a major force in creating open pine forests in the

Southeast (Komarek 1974). Archeological evidence has

established the presence of Paleo-Indians in the region as

early as 12,000 years ago (Chapman 1985). The movement

of Indian tribes for game and cropland crested variable

patterns of fue frequency across the landscape, thus

producing a mosaic of vegetation types and stand ages

(Buckner 1989). Southeastern forests described by the fust

white settlers of the 1600’s and 1700’s were often open pine

and hardwood stands with grasses underneath. Early writers

suggested these open forests owed their existence to frequent

burning (Bartram 1791; Harper 1962; Van Lear and Waldrop

1989). Frequent burning continued through the early 1900’s,

when fue protection policies of the U.S. Department of

Agriculture, Forest Service, and cooperating State Forestry

agencies attempted to prevent the use of fue. Prescribed

burning for fuel reduction gained acceptance in the 1940’s and

1950’s, but only after a series of wildfues showed the

disastrous consequences of fm exclusion (Pyne 1982). As a

result, contemporary forests developed with a dense

understory and a larger hardwood component.

It can be difficult to appreciate the important role of fire in

shaping the species composition and structure of Southeastern

forests. The changes fire causes in plant communities can be

slow and depend on fire intensity, the season and frequency of

burning, and the number of successive fires used.

Opportunities to observe changes in vegetative characteristics

over long periods are limited. A long-term study by the

Southeastern Forest Experiment Station may give an

indication of the ecological role fire once played. The

experiment, known as the Santee Fire Plot Study, was

established in 1946. Various combinations of season and

‘Research Forester and Project Leader, Southeastern Forest

Experiment Station, USDA Forest Service, Clemson, SC.

frequency of burning were maintained for over 40 years.

Previous papers have compared the effects of these various

fire regimes on pine growth, understory vegetation, and soil

properties at specific years during the study. This paper

discusses changes to the structure and species composition of

the overstory and midstory as they occurred over time and

relates those changes to presettlement fire frequency and

effects. Changes to understory vegetation after 43 years of

burning are presented in another paper in these proceedings

(White and others 1991).

DESCRWI’ION OF THE STUDY

Study plots are on the Santee Experimental Forest in Berkeley

County, SC, and on the Westvaco Woodlands in neighboring

Georgetown County. Both areas are on a Pleistocene terrace

on the Lower Coastal Plain at 7.5 to 9.0 m above sea level.

Soils include a variety of series but are generally described as

poorly drained Ultisols of medium to heavy texture (McKee

1982). Soils are considered productive with a site index of 27

to 30 m for loblolly pine at age 50. In 1946, the overstory of

both study sites consisted of unmanaged, but well-stocked

even-aged stands of loblolly pine. Common midstory species

were dogwood (Comus florida L.), hickory (Carva SD.),

southern red oak (Ouercus falcata Michx.), post oak (Q.

stellata Wangenh.), water oak (Q. & L.), and willow oak

(Q. Dhelios L.). The Santee stand was 42 years old when the

study was initiated, while the Westvaco stand was 36 years

old. Both stands resulted from natural regeneration after

logging. No evidence of previous burning was observed.

Six treatment plots, 0.1 ha in size, were established in each of

five replications. Three replications are on the Santee

Experimental Forest and two are on the Westvaco woodlands.

Treatments include: (1) periodic winter burning, (2) periodic

summer burning, (3) biennial summer burning, (4) annual

winter burning, (5) annual summer burning, and (6) an

unburned control. All winter burning was done on December

1 or as soon afterward as weather permitted. Summer

burning was done on or soon after June 1. Periodic bums

were conducted when 25 percent of the understory hardwood

stems reached 2.5 cm in diameter at breast height (d.b.h.).

45
This prescription resulted in variable burning intervals

ranging from 3 to 7 years. Annual burning has not been

interrupted since 1946. Biennial summer burning was added

to the study in 1951.

To protect the study, burning techniques were selected to

ensure low fire intensity. Selection was made at the time of

burning based on prevalent fuel and weather conditions. In

general, backing fues were used on periodically burned plots

that had thick underbrush or when hot and dry weather

increased the risk of high-intensity fires. Headfues or strip

headfires were used on annually burned plots that had little

underbrush or when fuels were too moist to support a backing

fire.

OVERSTORY PINES

Loblolly pine remained the dominant overstory species in all

study plots from 1946 to the present. However, growth rates

may have been affected. The Santee Fire Plots were designed

to study effects on understory vegetation with little

consideration to tree growth. Detailed records of the number

and size of trees were not kept throughout the history of the

study. Therefore, comparisons of treatment effects on

diameter and height growth were conducted through

increment core analysis and stem analysis procedures,

respectively. A more detailed description of these methods

was given by Waldrop and others (1987).

Basal area per hectare for each burning treatment throughout

the study is shown in figure 1. Since records of tree

mortality were not kept, figure 1 represents the basal area of

only those trees that survived until the time of sampling

(1984). Differences in the levels of these curves represent

differences in numbers and sizes of trees in treatment plots in

1984, rather than treatment effects. If burning treatments

alter tree growth rates, the effect would be shown as

Poflodlc wlntor

Annual Wlntof

c - Annual Summw

. . . Pwbdlt Summrr

Years Slncc Study Establishment

Figure 1 .-Cumulative basal area of trees surviving from 1946

through 1984 by burning treatment.

differences in the slopes of these curves rather than

differences in the relative heights. All curves in tigure 1 are

generally parallel, indicating that burning did not affect

diameter growth. Basal area increment during each of four

IO-year periods was subjected to analysis of covariance, using

measured stand basal area to adjust growth rates for stocking

effects. These tests indicated that differences between the

slopes of lines were not significant for any period

(alpha=O.OS).

Mean tree height for each treatment throughout the lives of

these stands is shown in figure 2. Curves are very close

together, indicating that trees in various treatment plots had

similar height growth patterns. During the last 30 years,

trees in plots burned annually in winter or summer appear to

have slightly reduced height growth. These differences were

not significant, however, when compared by analysis of

variance (alpha=O.OS).

*IS ’ 4 , I I I t I

0 10 20 Jo 40 60 (10 70 a0

Yoerr Since Stand Eatablirhment

Figure ‘L.-Mean height of sampled trees by burning treatment

from 1905 through 1984.

The lack of differences in diameter and height growth was

unexpected. We expected that these low-intensity fires would

not cause enough crown damage to reduce growth, and that

vegetation control and increased soil fertility resulting from

prescribed burning would improve growth. However,

overstory pines averaged 40 years old at the beginning of the

study and were probably too old to respond by the time these

site changes reached meaningful levels. Even though McKee

(1982) showed increases in phosphorus and calcium

availability, no fertilization studies in the Coastal Plain have

shown positive responses to these elements in trees of this

age. In addition, soil moisture is rarely limiting to pine

growth on these poorly drained Coastal Plain sites, even when

competing vegetation is not controlhA.

4 6
MIDSTORY

Diameter Distribution

Species composition of midstory vegetation changed little

since study establishment. Dogwood, hickory, and oaks have

remained common on alJ treatment plots since 1946.

However, repeated measurements of the midstory show that

diameter distribution of these hardwoods has been changed by

the various combinations of season and frequency of burning.

The d.b.h. of alJ hardwoods in all plots was measured at

study establishment (1946), at year 20 (1966), and at year 30

(1976). Later descriptions are unavailable due to severe

damage from Hurricane Hugo in September 1989. Stem

numbers in each of five diameter classes (< 2.5 cm, 2.6-7.5

cm, 7.6-12.5 cm, 12.6-17.5 cm, and 17.5+ cm) were used as

dependent variables in a split-plot design of an analysis of

variance to compare treatment differences over time. Wholeplot effects were those created by burning treatments while

the years since study establishment were sub-plot effects.

Mean separation was by linear contrast (alpha = 0.05).

At the beginning of the study, unburned control plots

appeared to be undisturbed. Every size class of hardwoods

from less than 2.5 cm to over 17.5 cm d.b.h. was present

(fig. 3A). Diameter distribution followed a reverse-J pattern

with numerous stems in small size classes and few stems in

larger classes. The number of stems in each size class varied

somewhat over time as individual trees grew into larger

classes. However, the reverse-J pattern remained.

Hardwood diameter distributions were altered by periodic

winter bums and periodic summer bums. For both

treatments, the number of stems in the smallest size class

(O-2.5 cm) increased significantly between year 0 and year 20

and between year 20 and year 30 (figs. 3B and 3C).

Hardwood numbers in the next two classes (2.6-7.5 cm and

7.6-12.5 cm) decreased significantly over the same periods.

With periodic summer burning, the smallest size class

increased from approximately 11,000 to over 19,000 stems

per hectare by year 30. The 2.6- to 7.5-cm size class was

most affected, decreasing from over 1,100 to approximately

100 stems per hectare in both periodic treatments. Most

changes occurred during the first 20 years, but the changes

continued at a reduced rate through year 30.

Hardwoods greater than 12.5 cm d.b.h. were generally

unaffected by periodic winter and summer burning (figs. 3B

and 3C). At the beginning of the study, these trees were old

enough to be protected by thick bark and tall enough that

their buds were protected. Most stems less than 12.5 cm

d.b.h. were too small to survive burning. However, root

systems of these smaller trees survived and produced multiple

sprouts, causing the increase in stem numbers in the smallest

size class. Bums were frequent enough to prevent the growth

of sprouts into a larger size class. Fewer than 10 percent of

the trees in the 2.6- to 7.5-cm d.b.h. class survived until year

30. Trees of this intermediate size class are susceptible to

top-kill from occasional flareups or hot spots. Since hot spots

occur more often during the summer, fewer trees of this size

class survived periodic summer bums than periodic winter

bums.

Annual winter burning caused changes in the hardwood d.b.h.

distribution similar to periodic winter and summer burning.

Most stems in the 2.6 to 7.5-cm d.b.h. class were top-killed

or girdled during the first few years. Stem numbers in this

size class were significantly reduced (from approximately

1,200 per hectare to less than 100) by year 20, with no

additional reduction through year 30 (fig. 3D). The number

of stems per hectare in the smallest d.b.h. class (O-2.5 cm)

increased dramatically over the 30-year period. By year 20,

this size class had increased significantly from 16,000 to

21,000 stems per hectare. Between years 20 and 30, that

number increased to over 47,000 per hectare. Most of these

stems were sprouts less than 1 m talJ. Since annual winter

bums allow sprouts a full growing season to recover from

fme, many root systems survived and produced larger

numbers of sprouts after each fire. In year 44, White and

others (1991) found a slight decrease in the number of stems

per hectare in annual winter bum plots and a substantial

decrease in cover by woody plants. Even though sprouts are

still numerous, these decreases may indicate declining sprout

vigor.

Annual summer burning has nearly eliminated woody

vegetation in the 0- to 2.5-cm d.b.h. class (fig. 3E). Root

systems were probably weakened by burning during the

growing season when carbohydrate reserves were low.

Burning was frequent enough to kill root systems of all

hardwoods less than 7.5 cm d.b.h. during the first 20 years.

A few hardwood seedlings appeared each spring but did not

survive the next fue. As with other treatments, the number

of stems between 2.6 and 12.5 cm d.b.h. was significantly

reduced by annual summer burning and the majority of the

change occurred during the fust 20 years. Stem numbers of

hardwoods over 12.5 cm d.b.h. were unaffected by annual

summer burning.

Root Mortality

Patterns of hardwood rootstock mortality observed during the

first few years on the Santee Fii Plots prompted investigators

to expand the study. In 1951, biennial summer burning was

added to provide a comparison with annual summer burning

to study root system survival for four hardwood species

(Langdon 1981). Individual trees were observed repeatedly to

47
Year0 YW20 Y0W30

A Unburned Controls

100,000 lOQDb0

10,mo lb,@30

2 1,060 2

k k

1,Dbo

g loo 61m

tj G

10 1 0

0 0

Year 0 Year20 Year 30 Year0 Y0W20 Year 30

8. Periodic Winter Burns C. Periodic Summer Burns

im,ooo

I

1

im,mo

10,ooo

glDm 2

k

f,@xJ

ii im

iii i

3rn

23

1 0 10

0 0

Year0 Year20 Y-30 Year0 Year 20 Year 30

D. Annual Winter Burns E. Annual Summer Burns

Figure 3.--Diameter distribution of all hardwoods at selected years for (a) unburned control plots, @) period winter bum

plots, (c) periodic summer bum plots, (d) annual winter bum plots, and (e) annual summer bum plots.
determine Ihe number of bums required to kill their root

systems. With annual summer burning (fig. 4A), mortality

was rapid for sweetgum (Lictuidambar stvraciflua L.) and

waxmyrtle (Mvrica cerifera L.), nearing 100 percent within 8

years. Oaks and blackgum msvlvatica Marsh.) were

more difficult to kili, requiring approximately 20 years to

reach I00 percent mortality. Biennial summer burning (fig.

4B) was less effective in killing root systems of all species

tested. After 26 years (13 bums), mortality among the oak

species remained less than 50 percent. With biennial burning,

root systems have an entire growing season to recover.

Apparently, that time is sufficient for carbohydrate reserves to

accumulate enough to allow some resistance to fire.

-..- Swrrtgum

. . *. . Dlackgum

-O*kD

---W4xmyftlr

0

0 6 10 1 6 a0 as

Y8W8

A. Annual Summer Burn

-es- Bwr*lpm

a. - -. Bkckpum

-O&C

- - - Waxmyfllm

4 (I 10 16 10 26

YDDW

8. Blannlrl Summer Burn

Figure 4.-Cumulative mortality of hardwood roots over 26

years of (a) annual summer burning and (b) biennial summer

burning (Langdon 1981).

Species Composition

Survival of hardwoods over 12.5 cm d.b.h. was unaffected by

burning treatments and, therefore, changes in species

composition among larger trees were not observed. The

major effect of burning treatments was to kill the

aboveground portion of stems smaller than 12.5 cm d.b.h.

With most burning treatments, however, root systems

survived and sprouted. If burning was stopped or delayed,

sprouts would eventually grow into the midstory producing a

stand with species similar to unburned controls. Variations

among species in plants’ abilities to regenerate after fue

created changes in the species composition of regeneration

(fig. 5). In year 44, control plots were covered mostly by

shrubs with some grasses and hardwoods (White and others

1991). Total coverage was increased by periodic winter and

summer bums due to increased sprouting of hardwoods and

shrubs. Total coverage after annual winter bums was greater

than in control plots, but species composition had changed.

Burning greatly reduced the shrub component, which was

replaced by grasses and forbs. However, numerous hardwood

sprouts remained. Annual summer burning was the only

treatment which eliminated regeneration of hardwoods. In

these plots, the shrubs and hardwoods that were dominant in

1946 were replaced entirely by grasses’and forbs.

Summrr

Byrnlng Treatment

Figure 5.-Percent crown coverage of all understory planta

after 44 years of prescribed burning (White and others 1991).

DISCUSSION AND CONCLUSIONS

All tree species on the Santee Fi Plots were well adapted to

frequent low-intensity burning. Thick bark and high crowns

protected the pines from damage and no growth loss was

detected. Hardwoods over 12.5 cm d.b.h. were protected by

thick bark and most survived. During the first few years of

the study, most hardwoods below 12.5 cm d.b.h. were either

top killed or girdled, particularly by summer burning.

However, root systems survived and produced multiple

sprouts Annual summer burning over a 20-year period was

the only treatment that eliminated hardwood sprouts.

The response of tree species to these long-term prescribed

burning treatments was considered minimal. Only one major

trend was observed. Small hardwoods were replaced by Large

numbers of sprouts during the early years of the study.

Later, those sprouts were replaced by grasses and forbs. The

49
gradual change from small hardwoods to grasses and forbs

was completed by only the most intensive treatment, annual

summer burning. White and others (1991) provide evidence

that sprout vigor is decreased by annual winter burning,

suggesting that these sprouts may eventually be eliminated.

However, a large regeneration Pool of hardwoods stiU exists

after 44 years of treatment. Periodic bums did little to reduce

numbers or vigor of hardwood sprouts.

Hardwood sprout survival was affected by the season and

frequency of burning (Langdon 1981). Hot summer fires

conducted each year when carbohydrate reserves are low

produced relatively rapid (20 years) mortality of hardwood

rootstocks. Periodic winter, Periodic summer, and annual

winter burning allow at least one growing season for sprouts

to store carbohydrate reserves in root systems and, therefore,

resist mortality. Without annual summer fues, it is

questionable whether hardwood sprouts can be eliminated by

fue.

This study emphasizes that frequent fires over long periods

are needed to create and maintain the open character of pine

forests described by early explorers in the Southeast.

Periodic burning over 40 years did little to eliminate

hardwoods and supported a dense understory shrub layer.

Annual winter bums maintain an open understory with

vegetation generally leas than 1 m tall. However, that

understory includes numerous woody sprouts and a dense

hardwood midstory would return if burning was delayed a few

years. Of all treatments tested, only annual summer bums

produced an open understory with no hardwood regeneration.

However, presettlement forests did not support the midstory

hardwoods present in study plots. In addition to frequent

low-intensity fires, an occasional high-intensity fue or other

disturbance would elimiiate large hardwoods.

Although the Santee Fii Plot Study provides information on

the frequency and number of fires ~+ired to create and

maintain open pine forests, differences exist between its

controfled experimental conditions and the environment of

presettlement fires. Annual fires set by Indians were

controlled only by weather and geographic barriers.

Therefore, fue intensity was probably higher than in the

Santee study. Also, large herds of deer (Odocoileus

virpinianus) browsed the open forests and grasslands. Hotter

fires and intense browsing would cause higher mortality rates

of hardwood sprouts. The Santee Fire Plots were dominated

by loblolly pine, which was much less common than longleaf

pine (Pinus Since oalustris Mill.) prior to the 26th century.

loblolly pine seedlings are susceptible to fire, pine

regeneration is unlikely to escape the frequent fires on study

plots. Seedlings of longleaf pine are resistant to fire during

the grass stage. Prior to the 20th century, longleaf pine

seedlings probably escaped to form the overstory during short

gaps in fire frequency or in localized areas where fire

intensity was low.

LITERATURE CITED

Bartram, William. 1791. Travel through North and South

Carolina, Georgia, East and West Florida. New York:

Dover Publications, Inc. 414 pp.

Buckner, Edward. 1989. Evolution of forest types in the

Southeast. In: Waldrop, Thomas A., ed. Proceedings of

pine-hardwood mixtures: a symposium on management

and ecology of the type; 1989 April 18-19; Atlanta, GA.

Gen. Tech. Rep. SE-58. Asheville, NC: U.S. Department

of Agriculture, Forest Service, Southeastern Forest

Experiment Station: 27-33.

Chapman, Jefferson. 1985. Telico archeology: 12,000 years

of Native American history. Knoxville: Tennessee Valley

Authority.

Harper, Roland M. 1962. Historical notes on the relation of

fires to forests. In: Proceedings, Tall Timbers fue

ecology conference 1: 1 l-29.

Komarek, E.V., Sr. 1974. Effects of fire on tempetate

forests and related ecosystems: Southeastern United

States. pp. 251-277. In: Kozlowslci, T.T.; Ahlgren, C.E.,

eds. Fire and Ecosystems. New York: Academic Press.

Langdon, 0. Gordon. 1981. Some effects of prescribed fire

on understory vegetation in loblolly pine stands. pp.

143-153. In: Wood, Gene W.. ed. Prescribed fue and

wildlife in southern forests: Proceedings of a symposium.

Georgetown, SC: The Belle W. Baruch Institute of

Clemson University.

McKee, William H., Jr. 1982. Changes in soil fertility

following prescribed burning on Coastal Plain pine sites.

Res. Pap. SE-234. Asheville, NC: U. S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 23 pp.

Pyne, Stephen J. 1982. Fire in America. Princeton, NJ:

Princeton University Press. 654 pp.

Van Lear, David J-I.; Waldrop, Thomas A. 1989. History,

use, and effects of fire in the Appalachians. Gen. Tech.

Rep. SE-54. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 20 pp.

Waldrop, Thomas A.; Van Lear, David H.; Lloyd, F.

Thomas; Harms, William R. 1987. Long-term studies of

prescribed burning in loblolly pine forests of the

Southeastern Coastal Plain. Gen. Tech. Rep. SE&.

Asheville, NC: U.S. Department of Agriculture, Forest

Service, Southeastern Forest Experiment Station. 23 pp.

White, David L.; Waldrop, Thomas A.; Jones, Steven M.

1991. Forty years of prescribed burning on the Santee

Fii Plots: effects on understory vegetation. mese

proceedings .] .

50
FORTY YEARS OF PRESCRIBED BURNING ON

THE SANTEE FIRE PLOTS:

EFFECTS ON UNDERSTORY VEGETATION

David L. White, Thomas A. Waldrop, and Steven M. Jones’

Abstract-The effects of 43 years of repeated prescribed burning on crown cover, species composition,

species richness, and diversity in the lower understory strata of the Santee Fire Plots were examined. Five

study treatments, installed in 1946, include an unburned control, periodic winter and summer bums, and

annual winter and summer bums. Understory cover has not changed in the past 20 years except in the

annual winter bum plots where cover of trees (I.5 m in height declined and grass cover increased.

Detrended correspondence analysis indentilied four distinct understory plant communitites corresponding to

season and frequency of bum. Distribution of understory species across a fire disturbance gradient is

discussed in terms of varying plant adaptations to fire. Species richness, when separated into herbaceous

and woody species groups, and Shannon’s diversity index varied significantly across treatments.

INTRODUCTION

The Santee Fire Plot (SFP) study in the Francis Marion

National Forest provides a unique opportunity to examine the

response of understory vegetation to long-term use of several

combinations of season and frequency of burning. Several

studies have examined the effects of single or repeated

prescribed fires on understory vegetation (Abrahamson 1984;

Conde and others 1983; Cushwa and others 1966, 1969;

DeSelm and others 1974; Fox and Fox 1986; Gilliam and

Christensen 1986; Grano 1970; Grelen 1975; Hodgkins 1958;

Lemon 1949, 1967), but none of these studies was conducted

over a period as long as the period of the SFP study.

Prescribed burning in lobloily pine stands on the SFP was

initiated in 1946 and continued without interruption until

1989, when the overstory pines were destroyed by Hurricane

Hugo.

Previous SFP studies focused on the effect of prescribed fire

on understory vegetation (Langdon 1971, 1981; Lewis and

Harshbarger 1976; Lotti 1955, 1956; Lotti and others 1960),

benefits to wildtife (Lewis and Harshbarger 1976) and soil

chemical changes (Wells 1971; McKee 1982). Waldrop and

others (1987) summarized the effects of the various treatments

on the growth of overstory pines after 40 years. Lewis and

Harshbarger (1976) reported the effects of prescribed fire on

shrub and herbaceous vegetation in the plots after 20 years.

On the basis of information developed by Lewis and

Harshbarger (1976), Langdon (1981), Waldrop and others

(1987), and Waldrop and Lloyd (1991), the following

generalizations can be made regarding the effects of long-term

use of prescribed fue on understory vegetation in the SFP: (1)

the unburned control plots were dominated by several size

classes of shrub and hardwood species and contained only

‘Ecologist, Southeastern Forest Experiment Station, Clemson, SC;

Research Forester, Southeastern Forest Experiment Station, Clemson,

SC; and Assistant Professor, Department of Forcsr Resources,

Clemson University, Clemson, SC.

small numbers of grasses and virtually no forbs; (2) plots that

were burned periodically contained two distinct size classes of

understory hardwoods (> 15 cm and <5 cm d.b.h.) and

herbaceous species, most of which were grasses; (3) annual

winter and biennial summer bums resulted in large numbers

of woody stems < 1 m taU and many grasses and forbs; and

(4) annual summer burning virtually eliminated understory

woody vegetation, and produced an understory dominated by

grasses and forbs.

This paper describes differences among plant communities in

the Santee Fire Plots after 43 years of prescribed burning.

More specifically, we compare the understory plant

communities in the context of plant species composition,

species richness, and diversity. We also sought to determine

whether there have been any changes in understory species

composition since year 20 (1967).

METHODS

Site Description

The SFP study was originally designed with three replications

on the Santee Experimental Forest in Berkeley County, SC,

and two replications on the Westvaco Woodlands in

Georgetown, SC. The Westvaco plots were regenerated in

1984 so the present study is confined to the three Santee

replications. Study plots are located on the upper terrace of

the coastal flatwoods region of the Flatwoods Coastal Plain

Province, at an elevation of 9.0 m above sea level (Meyers

and others 1986). They contain a variety of soil series, which

are generally described as poorly drained Ultisols of medium

to heavy texture.

Study Design

The SFP study was initiated in 1946 in 42-year-old naturally

regenerated loblolly pine with a we&developed understory of

hardwoods @ost oak, blackjack oak, southern red oak,

51
dogwood, American holly, miscellaneous hickories,

sweetgum, and blackgum) and shrubs (bayberry, pepperbush,

and gallberry). Initially, five treatments were installed: (1) nobum control, (2) periodic winter bum, (3) periodic summer

bum, (4) annual winter bum and (5) annual summer bum. An

additional treatment, biennial summer bum, was installed in

195 1. Because of recent insect-related mortality in some plots

of the biennial summer bum, it was not included in this

study.

Winter burning was conducted as soon as possible after

December 1 of each year when the temperature was 16 “C

(60 “F) or higher. Summer burning was conducted after June

1 when the temperature was 32 “C (90 “F) or higher. Burning

was conducted only when relative humidity was less than 50

Percent, wind speed was 1 to 7 mi/h and fuel moisture was <

10 percent. Backing fires were used initially; later, head fires

(strip and flanking) were used in the annual bum plots.

Periodic bums were conducted when 25 percent of the

understory stems reached 2.5 cm dbh. The average bum

interval for periodic bums was 5 years. More detailed site

descriptions can be found in Lotti (1960) and Waldrop and

others (1987).

For sampling understory vegetation, a 25- by 25-m sample

plot was established within each of the 32- by 32-m treatment

plots. TWO 25-m line transects were randomly located in each

sample plot to determine percent crown cover for the

following species groups: grasses, legumes, other herbs,

woody vines, shrubs, and trees. The vegetation sampled in

this study was the lower understory, which was defined as

plants 5 1.5 m tall or plants having a majority of their crown

at or below a height of 1.5 m. Cover was determined along a

25-m line transect by measuring the portion of a crown

intersected by the 25-m Line. Where two or more crowns

overlapped, the overlapping sections of the lower crown(s)

were not included.

Two 05 by 2-m subplots were randomly located along each

25-m transect (four subplots per piot) to measure stem density

or abundance. AIJ plants were identified to species or genus

and the number of plants per species or genus was recorded.

In measuring abundance of plants that sprout from roots or

rhizomes, no attempt was made to determine whether a clump

of stems was associated with just one individual or many.

Species not encountered in the four subplots were tallied in

two l- by 25-m subplots, each of which was located adjacent

to a 25-m transect. The larger subplots (I- by 25-m) were

used primarily to sample relatively uncommon species.

Species not encountered in subplots of either size but

occurring in a 25 by 25-m sample plot were listed as present

but not tallied. The species and density data were used to

determine species diversity and richness.

Data Analysis

Analysis of variance was used to test for significant treatment

and block effects on species richness and diversity. Mean

separation was by Fisher’s unprotected LSD test (Statistical

Analysis System (SAS) 1987). Species richness is the total

number of species in a given area. The Shannon-Weaver

index was used as a measure of species diversity and was

calculated as:

ti = -~@JnpJ

where p,=proportion of individuals of species i to the total

number of individuals of all species (base e logarithms are

used here).

Detrended Correspondence Analysis (Gauche 1982; Hill 1979;

Hill and Gauche 1980) was used to interpret the variation in

vegetation composition among treatments. The technique

groups plots or communities based on similarity of species

composition and relative abundance. The degree of difference

between plots is indicated by standard deviation (S.D.) units.

A separation of communities by four S.D. units generally

indicates that the two communities have no species in

common, while one S.D. unit indicates approximately a SOpercent difference in species composition (Hill 1979; Hill and

Gauche 1980).

R33SULTS ANJJ DISCUSSION

Changes in Understory Cover Between 1967

and 1989

Lewis and Harshbarger (1976) reported on the status of

herbacwus and shrub vegetation after 20 years of prescribed

burning on the SFP. We chose to compare percent cover by

species group at year 43 with their data to determine whether

vegetation changes had occwred since their 1967 study. Only

the no-bum, periodic summer, and annual winter treatments

were compared, because the interval between burning and

sampling was not always the same in both studies.

In the no-bum treatments (fig. la), both shrub and tree cover

declined over the 23-year period. Some trees and shrubs

formerly in the understory grew into the midstory. Also,

midstory hardwoods that were present in 1967 continued to

grow, further reducing the amount of light reaching the forest

floor.

In the periodic summer bum plots (fig. lb), there were few

changes between years 20 and 43. At both times, the

understory was dominated by shrubs and trees. A slight

increase in total cover (all species) may have been caused by

increased sprouting of trees and shrubs (Langdon 1981).

Greater changes were observed in the annual winter bum

plots (fig. lc). From year 20 to year 43, tree cover declined

and grass cover increased. Little change was observed for the

other species groups. Although tree cover declined, the

number of hardwood stems (44,700 stems ha-‘) was similar to

52
6 C

5 c

4 c

3c

2c

K c

W

> 6c

0 5 0

0 40

2 30

8 20

c1L lo

k O

60

( a:

1967 1989

Kl 17751 TREES OTHER

~ SHRUBS m LEGUMES

f-l VINES GRASSES

the number reported by Langdon (1981) at year 30 (47,000

stems ha-‘). This pattern suggests that hardwood sprouts are

smaller than before and that frequent winter burning may

reduce sprout vigor over time. The increased importance of

grasses in these plots may be a response to the decline in tree

cover or it may have contributed to that decline. While the

majority of vegetation changes in annual winter bum plots

occurred early in the SFP study, our results indicate that the

frequent but relatively mild disturbance associated with this

treatment continues to cause changes in vegetation over

extended periods of time.

Plant Community Differences

Community Analysis

Detrended correspondence analysis identified four distinct

vegetative communities that were associated with season and

frequency of burning (fig. 2). AnnuaI summer bums, annual

winter bums, Periodic bums, and no-bum controls produced

distinctive communities. Differences between treatments were

less distinct for the periodically burned plots and the control

plots, where woody vegetation predominated. The understory

communities produced by periodic winter and summer

burning were very similar. The distribution of plots along the

X axis leads us to interpret this axis as a tire-mediated

disturbance gradient. The relatively large magnitude of

difference across treatments (3.5 S.D. units) indicates that

beta diversity, or between-community diversity, is high and is

affected by season and frequency of burning. Separations

along the Y axis are less easily understood, but are

interpreted as representing a natural variability gradient.

Variability in species composition within a community type

decreases as the level of burning increases.

The distribution of species along a fire disturbance gradient

reflects the species fire tolerance and competitive vigor. Table

1 is a species synthesis table, as described by MuellerDombois and Ellenburg (1974), showing the relative

abundance of each species in each treatment plot. This list has

been edited to contain only differential species, or those

species that demonstrate clear associations for a given

treatment or treatments. The 32 species in this table were

placed in 5 groups based on their affinity for a given

treatment or treatments. Detrended correspondence analysis

indicated that the periodic winter and summer burn plots were

vegetatively similar and since our sampling of the vegetation

took place during the growing season following the burning of

the periodic winter plots, only the periodic summer bum

treatment is shown in table 1.

Figure I-Understory cover by treatment, 1967 and 1989.

Treatments: (a) no-bum control, (b) Periodic summer bum,

(c) annual winter bum. 1967 data are from Lewis and

Harshbarger (1976).

53
DETRENDED

CORRESPONDENCE ANALYSIS

AS=ANNUAL SUMMER

AW=ANNUAL WINTER

PW==PERIODlC WINTER

PS=PERIODIC SUMMER

N=NO BURN

N

PW

1.0 2.0 3.0 4.0

AXIS 1

(Standard Deviation units)

Figure 2-Results of detrended correspondence analysis of all understory plants in alI treatment plots. Treatments indicated

by the following codes: AS=annual summer bum, AW=annual winter bum, PS=periodic summer bum, PW=periodic

winter burn, N=no-bum control. Lines are drawn to show separation between dissimilar groups of plots. See text for

explanation of axes.

With few exceptions, groups 1, 2, and 3 are herbaceous

plants that have been described as “fire followers” (Lemon

1949, 1967). Many of these plants are also associated with

early successional plant communities following non-fire

disturbance. Other species, such as the legumes, are known to

benefit directly from the effects of fire (Cushwa and others

1969; Martin and Cushwa 1966; Martin and others 1975).

The species in group 1 are found almost entirely in the annual

summer bum plots. These are generally opportunistic species

that lack the competitive vigor to become established in other

burned plots, where more vigorous grasses and woody plants

predominate. Species in group 2 are most common in the

annual winter bum plots, but some of the legume species are

also common in the periodic summer or annual summer bum

plots. Generally, group 2 species are less tolerant of annual

summer burning and do not compete well with the hardier

woody vegetation characteristic of the periodically burned

plots. The relatively low abundance of legumes in plots that

have been burned every summer may result from the lack of

full growing seasons in which to partition photosynthate into

perennial rootstocks. Plants in group 3 were common in all

burned plots but absent in the no-bum control plots, indicating

a dependence on frequent disturbance. Four composite

species, two grasses (Panicum species and Androoogon

virainicus), and three woody plants (Hvoericum species,

J&&s species, and Rhus coooaliia) comprised this group.

Most species in group 3 disperse their seed broadly and

compete vigorously for resources and this enables them to

become established quickly after fue.

Groups 4 and 5 (table 1) contain all woody plants with the

exception of one grass (Uniola laxa) and one perennial

(Mitchella renens). Most of the species in this group

reproduce vegetatively - but with varying degrees of vigor, as

is indicated by the absence of some species from either the

annually or periodically burned plots. Group 4 species are

relatively abundant in all but the annual summer plots,

maintaining their abundance primarily through vegetative

reproduction. About half of these species occurred rarely or

infrequently in the annual summer plots; however, their

occurence in the annual summer plots is probably due to

germination from seed that was transported to the plot by

54
Table l--Species synthesis table showing relative abundance” of each species

across treatments (three plots per treatment)

Treatment

Speciesb Group

Unburned

control

Periodic

suner

Annua 1

uinter

Annua 1

Sumner

R

Paspalun species 1 9 R

Polvgala lutea 9 R 5

Hvpoxis micrantha R 1 9 7

Rhexia species 9 R

Coreopsis major 2 +;; +

Cassia nictitans 5 5 9

Stvlosanthes biftora

-

418 4 9

Galactia nurre~ -.,. ..,l 9 1

Desmodim -species 2 + 9 + R

Tephl-., =n=ra hispidula R R R 9 1

Cent rosema I viroinianun R R 9 9

Lesoedeza SFn.r:rr id ++o

Lobe1 ia nut’

Aster SCM?&

XClCJ

..rellii

-

3 + 9 Ii + 6 4

~, 3es 1 1 9 2 1 + +

Solidaso species + R 9 + 4

Eupatoriun species Elaphantopus + + R 8 9 7 : : species

; ; ix3

1 1 :

Pani cun species + 6 2 3

Andropogon vi rginicus + + 6 9 5 9 3

Hypericun species

Rubus species 1 4’

8 + 2 1

5 5 +k + R

Rhus coma1 ina + R 2 R 1 1 R R

Pinus taede 4 + 1 ; + + R + + 7 9 6

Gavlussacia species + + + + 3 1 +14 R +

Vaccinium species 1 + 1 1 6 +39 + +

Uniola lexa + + + 3 + + 9 3 5 +

Myrica cerifera 1 + + 9 2 1 +

Liauidambar stvraciflua

; t r

5 1 +

1 ‘:

9

Smilax species 2 + R 1 +

Vitisspec i es + 1 + ll+ + + R

Puercus species + + + 643 + 9 +

Gelsemiun swervirens + * + 7 9 1 + +

Cornus florida 5 3 2 7 8 9 R

Mitchella repens

Persea borbonia

Lvonia lucida

2 + 3 9 2

9 + + R

+ 9

* Relative abundance indicated as deciles :1~+11=1-10 percent of the maximum

abundance value for a given species,~*li~=ll-20 percent; etc. “R” indicates

that a species uas rare in the vegetation plot (i.e., uas present only).

’ Nomenclature follows Radford and others (1968).

wind or animals. Species in group 5 were relatively intolerant

of frequent burning. Comus florida (dogwood) and Mitchella

w (partridge berry) were absent from annual bum plots,

while Persea borbonia (redbay) and Lvonia lucida (fetterbush) - -

were absent from both periodic and annual plots. Fetterbush

has been previously mentioned as one of several shrubs on the

SFP that sprout prolifically after fm (Langdon 1981). Data

from other studies (Cypert 1973; Abrahamson 1984) also

suggest that this species is tolerant of fire. The absence of this

species in year 43 may indicate that the species is intolerant

of long-term frequent burning, at least on sites similar to

those in the SFP study area.

Species Abundance

Understory species abundance (number of plants 0.1 ha-‘) for

woody plants is shown in figure 3. Abundance of hardwoods,

shrubs, and vines was dramatically reduced by annual summer

burning. In the periodic bum plots and the annual winter bum

plots, understory hardwood abundance was slightly greater

than in unburned controls. Only the annual summer bum plots

had lower shrub abundance than the control plots. The large

values for shrubs are attributable primarily to the rhizomatous

shrubs, Gavlusaccia spp. (Huckleberry) and Vaccinium spp.

@&berry), which sprout prolifically after tire. The greater

abundance of all three woody plant groups in periodic winter

bum plots was due to the fact that these plots had been

burned the winter prior to sampling, which illustrates the

immediate response to fire by this predominantly woody

understory.

Abundance of grasses, legumes, and other forbs is shown in

figure 4. Herbaceous plant abundance increased with

increasing fue frequency, and abundance of all three groups

was greatest in the annual winter bum plots. The annual

winter treatment yielded a substantially higher number of

legume stems than all the other treatments. Legume

abundance in the annual winter bum plots was higher than

values reported from other studies in the South (Buckner and

Landers 1979; Cushwa and Jones 1969; Cushwa and others

1970, 1971; Hendricks 1989; Speake and others 1975).

Legume abundance in the periodic and the annual summer

bum plots was in the range found in the studies cited above,

most of which were conducted after single or periodic bums.

5 5
UNDERSTORY SPECIES ABUNDANCE

WOODY SPECIES

r

80000- ggEpl HNZDWODDS3

6aooo- ~SHRuas -

a Y m - VMS /

LL - 15000

O9

&--

Cn~loooO

il

3

5000

I

0

NO TURN pkxiootc PERIODIC ANFiUAL

wlNrER SUMMER WINTER SUMMER

Figure 3--Mean number of stems 0.1 ha-’ for understory

woody plant groups across all treatments. Note axis scale

change.

Species Richness and Diversity

Understory species richness was not significantly affected by

treatment. When species richness was separated into woody

and herbaceous categories, treatment effects were significant

(fig. 5). Woody species richness was signiticantly higher for

the no-bum and periodic bum treatments than for either of the

annual bum treatments. In contrast, herbaceous species

richness increased with increasing burning frequency and was

significantly higher for the annual winter bum treatment than

for the periodic winter and the no-bum treatments.

Shannon diversity, calculated using all understory species,

was significantly affected by treatment (table 2). Understory

species diversity was significantly higher for the annual winter

UNDERSTORY SPECIES ABUNDANCE

HERBACEOUS SPECIES

f

1OQOOO m GRASS5

QJ olHEF4 FoRBE

2

L soooo

;a 40000

#=I07 30000

=z - 20000

$ 1ooDo 0

NO &RN PERIODIC PtRiODlC ANILL

WINTER SUMMDi WINTER SUMMER

Figure 4--Mean number of stems per 0.1 ha-’ for understory

herbaceous plant groups across all treatments. Note axis scale

change.

bum treatment than for the annual summer and periodic

winter bum treatment but not higher than for the periodic

summer and no-bum treatments. It is significant that

differences in richness and diversity among treatments were

not more distinct. As burning frequency increased,

herbaceous species importance increased and there was an

associated decline of woody species. This species replacement

resulted in relatively small differences in diversity and

richness between most treatments. Annual winter burning

resulted in higher richness and diversity values because

woody biomass was reduced to a level sufficient to allow

establishment of herbaceous plants, many of which responded

positively to the conditions created by fire.

UNDERSTORY SPECIES RICHNESS

WOODY AND HERBACEOUS SPECIES

30

m WOODY SPECIES

25 $jj$$J HERBACEOUS SPECIES I

NO BURN PERiODlC PERiODlC ANNUAL ANNUAL

WINTER SUMMER WINTER SUMMER

(Error Bars represent 2 standard errors)

Figure 5--Understory species richness. Error bars represent two standard errors.

56
Table Z--Shannon diversity indices for

understory plant commmities from each

treatment

Diversity

Treatment Index”

Annual uinter burn 2.40 a

Periodic smaer burn 2.28 ab

NO burn control 2.07 abc

Annual smmer burn 1.88 bc

Periodic winter burn 1.70 c

’ Means uith different letters are

significantly different at the 0.05 level.

CONCLUSIONS

While all plants in this southern pine ecosystem are well

adapted to fire, it is the fire regime--incorporating intensity,

frequency, and season--rather than fire itself, to which plant

species are adapted (GilJ 1975). Observed differences in

species composition of understory plant communities along a

fire disturbance gradient were explained by reference to

differences in fire tolerance and competitive vigor.

Differences in frequency and season of fire produced four

distinct plant communities which, when viewed as

communities distributed over the landscape, resulted in

relatively high beta diversity.

Land managers are faced with increasingly complex problems

as the concept of multiple resource management expands to

include compositional, structural, and functional biodiversity.

Our increased understanding of the “natural” or historical role

of fire in shaping forested ecosystems should enable us to

better incorporate the use of fue in the management of whole

landscapes to accomplish multiple resource objectives.

ACKNOWLEDGMENTS

We thank John Haney and Darla Miller of the USDA Forest

Service for assistance in field sampling and Dr. Steven R.

Hill, curator of the Clemson University herbarium for

assistance with species identification. We also appreciate

assistance from Dr. Wiiam R. Harms and other personnel at

the Santee Experimental Forest.

LITERATURE CITED

Abrahamson, Warren G. 1984. Post fire recovery of Florida

Lake Wales Ridge vegetation. American Journal of

Botany 71(1):9-21.

Buckner, lames L.; Landers, J. Larry. 1979. Fire and disking

effects on herbaceous food plants and seed supplies.

Journal of Wildlife Management 43(3):807-811.

Conde, Louis F.; Swindel, Benee F.; Smith, Joel E. 1983.

Plant species cover, frequency and biomass: early

responses to clearcutting, burning, windrowing, discing

and bedding in Pinus elliottii flatwoods. Forest Ecology

and Management 6:3 19-33 1.

Cushwa, Charles T.; Brender, Ernst V.; Cooper, Robert W.

1966. The response of herbacwus vegetation to prescribed

burning. Res. Note SE-53. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station. 2 pp.

Cushwa, Charles T.; Czuhai, Eugene; Cooper, Robert W.;

Julian, William H. 1969. Burning clearcut openings in

loblolly pine to improve wildlife habitat. Res. Pap. 61,

Georgia Forestry Research Council. 5 pp.

Cushwa, Charles T.; Jones, MB.; 1969. Wildlife food plants

on chopped areas in the Piedmont of South Carolina. Res.

Note SE-119. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 4 pp.

Cushwa, Charles T.; Hopkins, Melvin; M’Ginnes, Burd S.

1970. Response of legumes to prescibed bums in loblolly

pine stands of the South Carolina Piedmont. Res. Note

SE-140. Asheville, NC: U.S. Department of Agriculture,

Forest Service, Southeastern Forest Experiment Station.

6 PP.

Cushwa, Charles T.; Martin, Robert E.; Hopkins, Melvin.

1971. Management of bobwhite quail habitat in pine

forests of the Atlantic Piedmont. Res. Pap. 65. Georgia

Forestry Research Council. 5 pp.

Cypert, Eugene. 1973. Plant succession on burned areas of

the Okefenokee Swamp following the fires of 1954 and

1955. In: Proceedings, Tall Timbers tire ecology

conference 12; 1972 June 8-P; Lubbock, TX. Tallahassee,

FL :TaU Timbers Research Station: 199-217.

57
DeSelm, H.R.; Clebsh, E.E.C.; Nichols, G.M.; Thor, E.

1974. Response of herbs, shrubs and tree sprouts in

prescibed burned hardwoods in Tennessee. In:

Proceedings, Tall Timbers fire ecology conference 13;

Tallahassee, FL: Tall Timbers Research Station: 331-344.

FOX, Marilyn D.; Fox, Barry J. 1986. The effect of fire

frequency on the structure and floristic composition of a

woodland understorey. Australian Journal of Ecology

11:77-85.

Gauch, Hugh G., Jr.; 1982. Multivariate analysis in

community ecology. Beck, E.; Birks, H.J.B.; Connor,

E.F., eds. New York: Cambridge University Press.

298 pp.

Gill, A.M. 1975. Fire and the Australian flora: a review.

Australian Forestry 38:4-25.

Gil&am, Frank S.; Christensen, Norman L. 1986. Herb layer

response to burning in pine-flatwoods of the lower Coastal

Plain of South Carolina. Bulletin of the Torrey Botanical

Club 113(1):42-45.

Grano, Charles X. 1970. Eradicating understory hardwoods

by repeated prescribed burning. Res. Pap. SO-56. New

Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station. 11 pp.

Grelen, Harold E. 1975. Vegetative response to 12 years of

seasonal burning on a Louisiana longleaf pine site. Res.

Note SO-192. New Orleans, LA: U.S. Department of

Agriculture, Forest Service, Southern Forest Experiment

Station. 4 pp.

Hendricks, J.J. 1989. Nitrogen fvtation and litter quality of

understory legumes in a burned pine forest of the Georgia

Piedmont. Athens: University of Georgia. 90 pp. Thesis.

Hill, M.O. 1979. DECORANA-A FORTRAN program for

detrended correspondence analysis and reciprocal

averaging. Ithaca, NY: Cornell University. 52 pp.

Hill, M.O.; Gauch, H.G., Jr. 1980. Detrended

correspondence analysis: an improved ordination

technique. Vegetatio 42:47-58.

Hodgkins, Earl J. 1958. Effects of fue on undergrowth

vegetation in upland southern pine forests. Ecology

39(1):36-46.

Langdon, 0. Gordon. 1971. Effects of prescribed burning on

timber species in the southeastern Coastal Plain. In:

Proceedings, Prescribed burning symposium; 1971 April

14-16; Charleston, SC. Asheville, NC: U.S. Department

of Agriculture, Forest Service, Southeastern Forest

Experiment Station: 34-44.

Langdon, 0. Gordon. 1981. Some effects of prescribed fue

on understory vegetation in loblolly pine stands. In:

Wood, Gene W., ed. Prescribed fire and wildlife in

southern forests: Proceedings of a symposium; 1981 April

6-8; Myrtle Beach, SC. Georgetown, SC: Clemson

University, Belle W. Baruch Institute: 143-153.

Lemon, Paul C. 1949. Successional responses of herbs in

longleaf-slash pine forest after fire. Ecology 30:135-145.

Lemon, Paul C. 1967. Effects of fire on herbs of the

southeastern United States and central Africa. In:

Proceedings, Tall Timbers fue ecology conference 6;

Tallahassee, FL: Tall Timbers Research Station: 113-127.

Lewis, Clifford E.; Harshbarger, Thomas J. 1976. Shrub and

herbaceous vegetation after 20 years of prescribed burning

in the South Carolina Coastal Plain. Journal of Range

Management 29(1):13-18.

Lotti, Thomas. 1955. Summer fues kill understory

hardwoods. Res. Paper SE-71. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station. 2 pp.

. Lotti, Thomas. 1956. Eliminating understory hardwoods with

summer prescribed fires in Coastal Plain loblolly pine

stands. Journal of Forestry 54:191-192.

Lotti, Thomas.; Klawitter, Ralph A.; LeGrande, W.P. 1960.

Prescribed burning for understory control in loblolly pine

stands of the Coastal Plain. Res. Paper SE-l 16. Asheville,

NC: U.S. Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station. 19 pp.

Martin, Robert E.; Cushwa, Charles T. 1966. Effects of heat

and moisture on leguminous seed. In: Proceedings, Tall

Timbers fue ecology conference 5; Tallahassee, FL: Tall

Timbers Research Station: 159-175.

Martin, Robert E.; Miller, Robert L.; Cushwa, Charles T.

1975. Germination response of legume seeds subjected to

moist and dry heat. Ecology 56:1441-1445.

McKee, William H., Jr. 1982. Changes in soil fertility

following prescribed burning on Coastal Plain pine sites.

Res. Paper SE-234. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 23 pp.

58
Mueller-Dombois, Dieter; Ellenberg, Heinz. 1974. Aims and

Methods of Vegetation Ecology. New York: John Wiley

and Sons. 547 pp.

Myers, Richard K.; Zahner, Robert; Jones, Steven M. 1986.

Forest habitat regions of South Carolina. Res. Ser. 42.

Clemson, SC: Clemson University Department of

Forestry. 31 pp. Map supplement, scale 1:1,000,000.

Radford, Albert E.; Ahles, Harry E.; Bell, C. Ritchie. 1968.

Manual of the vascular flora of the Carolinas. Chapel

Hill, NC: The University of North Carolina Press. 1183

PP.

Statistical Analysis System (SAS) 1987. SASISTAT guide for

personal computers. SAS Institute Inc., Cat-y, NC.

1028 pp.

Speake, D.W.; Hill, E.P.; Carter, V.E. 1975. Aspects of

land management with regard to production of wood and

wildlife in the southeastern United States. In: Forest soils

and forest land management, Proceedings of the fourth

North American forest soils conference; 1973 August;

Quebec, Canada: Lava1 University: 333-349.

Waldrop, Thomas A.; Van Lear, David H.; Lloyd, F,

Thomas; Harms, William R. 198’7. Long-term studies of

prescribed burning in loblolly pine forests of the

Southeastern Coastal Plain. Gen. Tech. Rep. SE-45.

Asheville, NC: U.S. Department of Agriculture, Forest

Service, Southeastern Forest Experiment Station. 23 pp.

Waldrop, Thomas A.; Lloyd, F. Thomas. 1991. Forty years

of prescribed burning on the Santee fire plots: effects on

overstory and midstory vegetation. mese Proceedings].

Wells, Carol G. 1971. Effects of prescribed burning on soil

chemical properties and nutrient availability. pp. 86-97.

In: Proceedings, Prescribed Burning Symposium; 1971

April 14-16; Charleston, SC. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station. 160 pp.

59
FOREST DEVELOPMENT FOLLOWING DISTURBANCES BY FIRE

AND BY TIMBER CUTTING FOR CHARCOAL PRODUCTION

Wayne K. Clatterbuck’

Abstract-Stand reconstruction techniques and historical documentation were used to analyze present

species composition, stand sUucture, and successional trends on forest lands on the Western Highland Rim

of Tennessee. These lands were affected by fire and tuning practices during Ihe late 1800’s, when local

wood was burned to make charcoal fuel for use at a nearby iron forge. The present two-aged stand

structure indicates that there was a discriminatory cutting pattern in which white oak (9uercus alba L.) and

hickories lCarya spp.) were selectively harvested for charcoal. Trees of other species, whatever their size

and location, were often left to form the residual stand. Iron forgers apparently favored the hotter burning

charcoal of white oak and hickories for producing wrought iron. These results anyin contrast to those from

other areas, where all tree species were cuf and burned to provide charcoal fuel wood for the production of

crude pig iron in imn firI’fUCeS.

INTRODUCTION

The iron industry flourished on the Western Highland Rim in

middle Tennessee during the 19th century. Historical

documentation of this industry has focused on the iron-making

process, community and social development, and biographies

of leading men associated with the indhstry. Little

information is available about the production of charcoal,

which was the fuel used to smelt the iron ore and forge

wrought iron. Vast timber reserves were necessary to

produce sufficient quantities of charcoal as one ton of

charcoal was required for each ton of iron produced (Baker

1985). Luther (1977) states that

“an early chronicler of the industry estimated

that to keep a furnace with a 12-ton-per-day

iron production going for a year required the

cutting of 500 acres of forest, and that to keep

one going permanently . . . would require about

16,000 acres (25 square miles) per furnace,

allowing 30 years for timber to grow back

before the next cutting. In the year 1873 there

were 11 furnaces in blast on the Rim,

producing iron at the rate of about 50,000 tons

per year. In order for all of these furnaces to

operate on a ‘permanent’ basis, then, something

on the order of 375 square miles of timber

would have been necessary to support them. ”

Thus, large units of forest land were affected by the charcoal

activity. This paper reports on the present species

composition, stand structure, and successional trends on forest

lands that were affected by (1) cutting during the 1800’s for

the production of charcoal, (2) fire and grazing during and

after the charcoal activities until 1938, and (3) stable State

ownership, management, and protection from 1938 to present.

‘Staff Forester, Forest Resource Planning, Tennessee Division of

Forestry, Nashville, TN.

60

STUDY AREA

The study was conducted on the 19,887-acre Cheatham

Wildlife Management Area (CWMA), which is located 25

miles west of Nashville, TN (36” 12’N, 87” SW), on the

Western Highland Rim Physiographic Region (Fenneman

1938).

Braun (1950) describes the Western Highland Rim as part of

the Western Mesophytic Forest, a transition area between the

Mixed Mesophytic Forest Region of the mountains to the east

and the Oak-Hickory Forest Region to the west. CWMA is

located on the strongly dissected, mature plateau of the

Western Highland Rim and consists of narrow to broad

ridges, steep dissected side slopes, and V-shaped upland

stream valleys (Smalley 1980). Elevations range from 480 to

820 feet. The climate is classified as humid mesothermal

(Thomthwaite 1948). Mean annual precipitation is 50 inches

and is fairly well distributed throughout the year with slight

deficits in late summer and early falI and surpluses during the

winter months. Average daily temperature is 15” C with

mean temperatures of 2” C in January and 26” C in July

(SmalIey 1980).

The CWMA was logged and burned in the 19th century

during the production of charcoal for a nearby iron forge.

Trees were harvested on the ridges and ridge margins where

timber was abundant and where the charcoal could easiIy be

transported by wagon downhill to the forge. Most of the land

in the broader valleys had been cleared previously for

agriculture. Many of the “charcoal hearths” or “fire circles”

where the charcoal was produced are still evident on the study

area. For more details on charcoal making and iron

production processes, see Smith and others (1988) and Ash

(1986).

During and after the decline of the iron industry in the

1880’s, these cutover areas were periodically, if not annually,

burned to promote production of forage for livestock and to

retard the advance of woody undergrowth. Fires were also
used locally to control snakes and ticks and to expose mast

for grazing livestock. Open-range laws were also in effect at

that time. Scattered logging for firewood, local building

materials, railroad ties, and to clear forest land for agriculture

continued, primarily near homesites. The loss of American

chestnut (Castanea dentata (Marsh.) Borkh.) to chestnut blight

(Endothia parasitica (Mm-r.) P.J. & H.W. And.) also shaped

the composition and structure of the present forest.

In 1938, the State of Tennessee acquired the land for a

wildlife management area. The area supports a heavy deer

(Odocoileus virginianus L.) population which is intensively

managed through controlled hunts. CWMA has been

protected from fire and livestock grazing since 1940. Apart

from hunting and occasional scattered timber harvesting

(mainly in the last 10 years), there has been little disturbance

by man. Currently, dieback and mortality associated with

“oak decline” are present in varying degrees.

Vegetation on two adjacent narrow ridges (A and B) was

studied. Ridge A and Ridge B contained 6 and 5 charcoal

hearths, respectively. The hearths were located about 200

yards apart along the ridges. The ridges were two miles from

the Narrows of the Harpeth River, a historical landmark and

the site of the iron forge.

Soils on these ridges and ridge margins are either of the

Bodine or Mountview series (North 1981). Both soils are

Typic Paleudults and are deep, well-drained, and fine

textured. Mountview soils developed in 2 to 3 feet of loess

over limestone residuum, while Bodine soils developed in

limestone residuum without the loess. Chert fragments are

frequent on the surface and throughout the soil mass. Site

index (base age 50) for upland oaks is 65 to 70 feet (Schnur

1937). The primary tree species on these ridges are white

oak, black oak (9. velutina Lam.), hickories, flowering

dogwood (Comus florida L.), sourwood (Oxvdendrum

arboreum L. DC.), and sassafras (Sassafras albidum (Nutt.)

Nees.). Other associated species are northern red oak (Q.

a L.), yellow-poplar (Liriodendron tulipifera L.), white

ash (Fraxinus americana L.), scarlet oak (Q. coccinea

Muenchh.), and blackgum (Nvssa svlvatica Marsh.).

PROCEDURES

In 1986, a total of 12 one-fifth-acre circular plots were used

to sample existing vegetation. Six plots were established on

each ridge. Three plots on each ridge had their outer

boundary adjacent to a charcoal hearth, while the other three

were located in relatively undisturbed areas not affected by

charcoal cutting. On each plot, the following data were

recorded for each tree with diameters at breast height (4.5

feet) of 5.5 inches and greater: species, azimuth and distance

,from plot center, I-inch diameter class, and crown class

(dominant, codominant, intermediate, or suppressed). Trees

with diameters from 1.6 to 5.4 inches were tallied by l-inch

diameter class and species. Total heights were measured, and

increment cores at DBH were taken from at least three

overstory trees on each plot for site productivity assessments,

diameter growth profiles, and to determine total age. Point

basal area was estimated from plot center with a lo-factor

prism. Data from each of the two ridges were pooled by

disturbance class (cut for charcoal or not) because the ridges

were similar in disturbance history and site quality.

Stem analysis to reconstruct height and diameter growth

patterns, to reference fire scars, and to determine age

structure was conducted on 12 trees from two plots, one plot

from each ridge. Each tree was sectioned at 0.5 feet above

the ground and at 4-foot intervals along the bole to the tallest

centrally located growing tip. The number of annual rings in

each section was subtracted from the tree’s total age to

determine how old the tree was when its terminal leader was

at or near the height of each section. Heights were plotted

over corresponding ages to illustrate the height growth pattern

of each tree. Diameter growth at 4.5 feet was determined by

measuring the annual increment along four Perpendicular

radii. Height and diameter data were analyzed using accepted

stand reconstruction and graphical procedures (Oliver 1982,

Clatterbuck and Hodges 1988). Only height and diameter

relationships of individual trees are presented in this paper

because the small sample size prevents making statistically

testable generalizations.

Historical documentation was used as much as possible to

reference forest development. Local newspapers, magazines,

and books were searched for relevant information about early

iron and charcoal production as were county survey records.

The earliest aerial photographs of the study area, which were

taken in 1938, were obtained. Local residents were

interviewed concerning their recollections of land use events.

RESULTS AND DISCUSSION

Plot Data

Data from the study plots indicated that areas cut for charcoal

and the uncut areas had different age structures (table 1). The

dominant and codominant trees in the uncut areas were

even-aged and averaged 125 years old. White oak, black

oak, hickories, and occasional yellow-poplar and blackgum

composed the overstory, while dogwood and sounvood made

up the midstory. These areas were in the understory

reinitiation stage (Oliver 1981): the dominant overstory trees

were beginning to decline, allowing a more favorable

understory environment for herbaceous and woody vegetation,

especially advanced reproduction of tree species.

61
Table I.- Stand parameters, based on trees greater than 5.5 inches in

diameter, from six sample plots in areas cut for charcoal and from six

sample plots in uncut areas.

DBH Age Density

(inches) (years) (stems/acre)

mean range mean range mean range

BLack oak

White oak

Hickories

Other species"

Black oak

White oak

Hickories

Other species"

AREAS CUT FOR CHARCOAL

2 2 12-29 130 106-139 2 4 14-32

1 2 6-16 6 0 48-75 4 2 30-60

9 6-14 58 52-68 1 0 4-19

1 0 6-21 7 5 40-135 11 6-24

UNCUT AREAS

2 0 a-27 130 110-136 ia a-32

1; 6-31 6-22 127 91 115-132 63-125 26 a 17-50 3-16

1 0 6-24 115 55-130 11 6-17

"Includes yellow-poplar, blackgum, scarlet oak, northern red oak, white

ash, flowering doguood, and sourwood.

In contrast, the areas cut for charcoal were two-aged, with

60- and 130-year age classes (table 1). More surprising was

the species segregation in these stands. One might

hypothesize that any tree species that was easy to cut and

transport would have been used to make charcoal. However,

the charcoal producers were discriminating enough to cut only

white oak and hickories, presumably because they judged that

these species made the best and hottest burning charcoal for

forging iron. Black oak and other species were not cut.

Black oaks adjacent to the charcoal hearths have diameters of

20 to 28 inches and many possess fire scars caused by the

charcoal activities and subsequent burning for grazing. Many

suppressed black oaks were released by the charcoal cutting

contributing to their poor, open-grown form. White oak and

hickories near the charcoal hearths are 60 to 70 years old.

They originated from sprouts or seeds after cutting and

burning ceased, and are in the large pole to small sawtimber

size classes. Although two-aged, the cut areas were also in

the understory reinitiation stage.

The charcoal hearths, with their circular shape, black soil,

and absence of overstory vegetation, were conspicuous on the

landscape. The soils in these hearths had lost their structure

and were nearly sterile as a result of the intense heat

associated with charcoal production. The only tree species to

colonize these areas were sassafras and dogwood. These trees

averaged 32 feet in height, 3 inches in diameter, and 55 years

of age.

Stem Analysis

Cumulative height and diameter growth patterns were

reconstructed using stem analysis information. Data from

trees on the uncut areas are not presented here because these

areas exhibited structure and growth patterns typically

associated with even-aged stands (Smith 1962). Figure 1

shows the height and diameter growth for the following

representative trees on a plot in an area where trees were cut

for charcoal: (1) a 132-year-old black oak located 20 feet

from the edge of the charcoal hearth, (2) a 132-year-old white

oak located 75 feet from the hearth, (3) a 55year-old

sassafras present in the hearth, and (4) a .54-year-old white

oak located 30 feet from the hearth. The 132-year-old oaks

are residuals left from the charcoal cutting. The older white

oak probably was not cut for charcoal because of its distance

from the hearth. The younger white oak and sassafras

regenerated once the burning and grazing ceased in the

1930’s.

Stem analysis supplemented and corroborated the plot data for

the area that was cut for charcoal. In 1885, the present

132-year-old oaks were 31 years old, 3 to 4 inches in

diameter, and 32 to 40 feet tall (fig. la). By most accounts,

charcoal production had stopped by that time (Smith and

others 1988). These stems grew slowly and were probably

suppressed resulting in spindly form and flat-topped crowns.

These trees were probably released when the overstory was

cut for charcoal. However, little increase in height occurred

between 1885 and 1935 for two possible reasons: (1) the

annual burning of the area to enhance grazing and (2) the

time necessary for suppressed trees to respond to release.

The combination of these two factors is hypothesized to have

hindered trees from increasing their crown volumes and

altering their crown shapes enough to allow substantial

increase in height over this 50-year period.

However, with a slow buildup in crown volume, substantial

increases in total height began to occur in the 1930’s (fig. la)

when these stands were protected from fire and open-range

grazing was prohibited. Total height increased 35 percent for

each of the older oaks for the 50 years from 1935 to 1985.

For the previous SO-year period (1885 to 1935) when fue and

grazing was common, total height only increased 18 to 20

percent for both trees.

6 2
90

8 0

I-

/ -

7 0

60

s

z

50

s

z

40

P

30

20

1 0

0

Cl BLO-132 l a + WHO-132 0

0

0 WHO-54

0

L( SAS-55 0 0

0 0

n 0 + +

0 a -

0 -+3

0 + 0

0

+ 0

0 + 0

0 0

0 +

0

Of 0 x Las

0

0 x

o + 0 x

0

0 x

O f 0 ;?I

0

0 x

q + 0 x

I3 OX

1850 1885 1920 1955 1990

YEARS

2 1

20 - 0 BLO-132 l b

19 _ + WHO-132

18 - o WHO-54

17 _ X SAS-55

0

16 -

15 -

0

14 -

+ 13 -

0

12 -

t

11 -

10 - 0 -4-

ii- +

0

0

7 -

6 - 9 5! +

5- rfi 0

4 - cf 3 - + x X 2 - 0 0 x

l- i!i 0 x

x

- 1 q

0

+

+

0

0

Ys x

0 ’

1850 1885 1920 1955 1990

YEARS

Figure 1 .-Cumulative height (la) and diameter (lb) growth patterns of a 332-year-old white oak (WHO-132), a 132-year-old

black oak, a 54-yc+xr-old white oak (X%0-54), and a %-year-old sassafras (SAS-55) from an area that

was cut for charcoal.

63
Height growth of the 54-year-old white oak was almost linear,

increasing in height at an average of 1.3 feet per year. This

oak regenerated in a cutover open area that had been burned

and grazed for many years. Older trees were not close

enough to affect its growth, form, and development. The

sassafras was 33 feet tall at age 55; its slow growth is

indicative of low soil productivity in the charcoal hearth.

The diameter growth patterns of these stem-analyzed trees are

similar to the height growth patterns (fig. lb). Both the older

white oak and black oak had diameters of 4 inches in the

1880’s when they were released from overstory vegetation, 8

and 10 inches, respectively in 1940 following the grazing and

burning, and presently are 16 and 21 inches, respectively.

The 54-year-old white oak with its uninhibited growth had a

steady diameter growth rate of 2.1 inches per decade. The

sassafras in the charcoal hearth was only 3.5 inches in

diameter at 55 years of age.

Fire scars were numerous in the basal cross-sections of the

older oaks. For both trees, the most severe scarring occurred

in 1872, 1894, and 1922. These major fire occurrences

probably were localized because they were not referenced in

the local literature. However, the abundance of fue scars on

these older oaks suggests that burning the forest was common

practice in this area prior to 1940.

Historical Documentation

The 1938 aerial photographs of the study area showed a series

of patchliie I- to 3-acre openings along the ridges. Although

the charcoal hearths could not be distinguished on the black

and white photographs, the centers of the openings were

devoid of trees. Isolated individual trees were scattered in

these openings; the majority of these were black oaks that

.were not cut for charcoal and that survived the numerous

ground fires.

Long-time local residents verified that fire had been used on a

annual basis to “green-up” the hexbaceous vegetation for

grazing and to control encroachment of woody vegetation into

open areas. Both cattle and hogs roamed freely and grazed in

the forest until fence laws were passed and enforced. It has

been verified that cattle were transported by rail from Texas

to the study area during the Dust Bowl years of the 1930’s.

American chestnut was a component of these forests and was

valued not only for local uses such as ftrewood, building

materials, and mast, but also as a cash product. A

manufacturing plant near Nashville, TN purchased chestnut

wood in quantity and extracted tannin from it. The tannin

was then used to fix coloring in dyes, wine, and beer and to

produce an astringent drug. Chestnut logs, whether green,

affected with blight, or dead and lying on the forest floor,

were used by this industry. The decayed remains of

American chestnut logs that are evident in other areas of

Tennessee are not present on or in the immediate vicinity of

CWMA. The frequent use of fire, chestnut blight, and this

specialized industrial use of chestnut logs all influenced stand

development in the study area before 1940. American

chestnut may have also been used to produce charcoal, but

that could not be determined from this study.

Implications

Forest development following charcoal cutting in the study

area was unlike forest development in other places where

charcoal has been produced and used to fuel iron furnaces.

The iron forgers who operated at the Narrows of the Harpeth

River used only those species that they judged would produce

the best and hottest burning charcoal, primarily white oak and

hickories. Other species were intentionally left, and this

cutting pattern eventually created a two-aged forest. This

unique two-aged species segregation does not occur in areas

where all trees, regardless of species, were cut and burned to

produce charcoal for iron furnaces. Where charcoal has been

produced for use in iron furnaces, larger areas of land,

approaching 100 acres, have been cut. The same charcoal

hearths were generally used several times, and on many areas

the woody even-aged regrowth was cut two or three times

(Ash 1986; Smith et al. 1988; Martin 1989). On the study

area, the forest was cut once, the charcoal hearths were used

once, and a mosaic of l- to 3-acre cuts resulted.

Oak decline and associated mortality have been prevalent at

CWMA for the last decade. Mostly black oaks and scarlet

oaks have died, but so have other oak species and hickories.

Generally, mortality occurs on the poorer sites - the drier

upper side slopes, ridge margins, and ridge crests. Several

stress-related factors including senescence, insect defoliation,

disease pathogens, climatic fluctuations (particularly drought),

and above average stand densities have been proposed as

causes for oak decline and mortality. Although none of these

hypotheses has been adequately proven, it is probable that a

complex of factors contribute to the mortality (Starkey and

Oak 1989). On CWMA, the large, fire scarred, overmature

black oaks that survived the charcoal cutting and the

subsequent fires and grazing are the trees most susceptible to

decline and mortality. The younger, more vigorous oaks, for

the most part, have not been affected. Thus, current oak

decline and mortality may be attributed at least in part to the

older age classes and the species segregation initiated by the

charcoal cutting.

Data from this study reflect the ability of oaks and hickories

to persist in areas that are grazed and burned repeatedly

following timber harvesting. Although burning and grazing

usually precludes the establishment of woody vegetation, the

rootstocks of oaks and hickories have the ability to resprout

repeatedly from suppressed buds at or below ground level.

64
Thus, periodic burning and associated grazing promotes

advanced regeneration and establishment of oaks and hickories

and gives them an ecological advantage over their associates

(Van Lear and Waldrop 1989). Even though research has not

determined the precise combination of season, frequency, and

number of bums needed to promote oaks through silvicultural

practices, it is evident that the land use events on CWMA

have favored the development of an oak-hickory forest.

ACKNOWLEDGMENTS

This study was sponsored under a cooperative agreement

between the USDA-Forest Service, Southern Forest

Experiment Station and the Tennessee Wildlife Resources

Agency. Field work was completed while the author was

Research Forester, Sewanee Silviculture Laboratory, formerly

maintained at Sewanee, TN by the Southern Forest

Experiment Station, USDA-Forest Service, in cooperation

with the University of the South.

LITERATURE CITED

Ash, Stephen V. 1986. Tennessee’s iron industry revisited:

the Stewart County story. Land Between the Lakes

Association and Tennessee Valley Authority, Land

Between the Lakes Cultural Resource Program, Golden

Pond, KY. 41 p.

Baker, A.J. 1985. Charcoal industry in the U.S.A. In:

Symposium on Forest Products Research

International-Achievements and the Future; Vol. 5. 1985

April 22-26; Pretoria, Republic of South Africa. South

African Council for Scientific and Industrial Research,

National Timber Research Institute. 15 p.

Braun, E.L. 1950. Deciduous forests of eastern North

America. The Blakiston Co., Philadelphia. 596 p.

Clatterbuck, W.K.; Hodges, John D. 1988. Development of

chenybark oak and sweetgum in mixed, even-aged

bottomland stands in central Mississippi, U.S.A. Canadian

Journal of Forest Research 18(1):12-18.

Fenneman, N.M. 1938. Physiography of eastern United

States. McGraw-Hill Co., New York. 714 p.

Luther, Edward T. 1977. Our restless earth. University of

Tennessee press, Knoxville. 94 p.

Martin, W.H. 1989. The role and history of fire in the Daniel

Boone National Forest. U.S. Department of Agriculture,

Forest Service, Daniel Boone National Forest,

Winchester, KY. 131 p.

North, Olii L. 1981. Soil survey of Davidson County,

Tennessee. U.S. Department of Agriculture, Soil

Conservation Service, Washington, DC. 116 p.

Oliver, Chadwick Dearing. 1981. Forest development in

North America following major disturbances. Forest

Ecology and Management 3:153-168.

Oliver, Chadwick Dearing. 1982. Stand development-its uses

and methods of study. p. 100-112. In: Means, Joseph E.,

ed. Forest succession and stand development research in

the Pacific Northwest; 1981 March 26; Corvallis, OR.

Corvalhs: Forest Research Laboratory, Oregon State

University.

Schnur, G.L. 1937. Yield, stand, and volume tables for

even-aged upland oak forests. Agric. Tech. Bull. 560.

Washington, DC: U.S. Department of Agriculture. 87 p.

Smalley, Giendon W. 1980. Classification and evaluation of

forest sites on the Western Highland Rim and Pennyroyal.

Gen. Tech. Rep. SO-30. New Orleans, LA: U.S.

Department of Agriculture, Forest Service, Southern

Forest Experiment Station. 120 p.

Smith, David Martyn. 1962. The practice of silviculture. John

Wiley & Sons, Inc., New York. 578 p.

Smith, Samuel D.; Stripling, Charles P.; Brannon, James M.

1988. A cultural resource survey of Tennessee’s Western

Highland Rim iron industry, 179Os-1930s. Research

Series No. 8. Nashville, TN: Tennessee Department of

Conservation, Division of Archaeology. 209 p.

Starkey, Dale A.; Oak, Steven W. 1989. Silvicultural

implications of factors associated with oak decline in

southern upland hardwoods. p. 579-586. In: MiJler, James

H., compiler. Proceedings of the Fifth Biennial Southern

Silvicultural Research Conference; 1988 November l-3;

Memphis, TN. Gen. Tech Rep. SO-74. New Orleans,

LA: U.S. Department of Agriculture, Forest Service,

Southern Forest Experiment Station.

Thomthwaite, C.W. 1948. An approach toward rational

classification of climate. Geographical Review 38:55-94.

Van Lear, David H.; Waldrop, Thomas A. 1989. History,

uses, and effects of fire in the Appalachians. Gen. Tech.

Rep. SE-54. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 20 p.

65
NATURAL REVEGETATION OF BURNED AND UNBURNED

CLEARCUTS IN WESTERN LARCH FORESTS

OF NORTHWEST MONTANA

Raymond C. Shearer and Peter F. Stickney’

Abstract-In 1967 and 1968, seven south- and east-facing units, averaging 4-ha each, in a western larch

forest of northwest Montana were (1) clearcut and burned by prescribed fire or wildfire, (2) clearcut and

unburned, or (3) uncut and burned by wildfire. More than 20 years of forest succession data from

permanent transects show that fire caused a marked change in composition of ail vegetation. Herb cover,

mostly tireweed, dominated burned sites through the fifth year. Shrub cover (such as from willow or shiny

leaf ceanothus) dominated burned sites from the 6th through the 20th years, but the herb cover changed

little during this period. Trees rapidly regenerated burned sites, and height of pioneer species, such as

western larch and lodgepole pine, exceeded that of shrubs about 7 years after treatment. But the percentage

of conifer cover increased slowly and usually required al least 20 years to equal shrub cover. Without tire,

the herb and shrub component remained relatively stable; trees were limited to the smaller, more

shade-tolerant uncut conifers. Trees established slowly on unburned sites, and most were shade-tolerant

subalpine fir and Engelmann spruce.

INTRODUCTION

Disturbance reinitiates the plant succession cycle. Fire has

been the agent of the most extensive disturbances in the

Northern Rocky Mountains. Land managers can predict

successional pathways on the basis of early responses to

prescribed burning. Postfire vegetation is composed of

“survivor” and “colonizer” species (Stickney 1982).

Survivors are established plants capable of regrowth after fire,

and colonizers are new plants that establish from seed on the

burned site. Seeds of residual colonizers are already on the

site and survive fire either in seedbanks in the ground (Baker

1989) or in tree crowns. Seeds of offsite colonizers disperse

onto burned areas, usually from nearby unburned sites.

Stickney (1986) attributes early stages of forest succession

after fire to differential development of species present in the

initial community. Prebum species composition and severity

of burning largely determine what survivor and residual

colonizer species will be present. Establishment of offsite

colonizers depends on the production and dispersal of seed,

mostly from nearby sources, and on favorable site conditions

for germination and establishment. Once the initial vegetation

is established, successional development usually is limited to

changes in species abundance.

Establishment of trees may begin immediately after

disturbance, but trees develop more slowly than do some

herbs and shrubs. Conifer regeneration in the Northern

Rockies continues, sometimes in large numbers, for at least

15 years after burning (Shearer 1989). The faster growing

herbs and shrubs dominate the conifers until the trees begin

sustained rapid height growth.

‘Principal Silviculturist and Associate Plant Ecologist, respectively,

U.S. Depanment of Agriculture, Forest Service, Intermountain

Research Station, Forestry Sciences Laboratory, Missoula, MT.

This paper describes differences in natural revegetation of

south- and east-facing burned and unburned clearcuts in a

western larch (Larix occidentalis) forest. Revegetation of a

wildfire-burned uncut stand is also compared.

STUDY AREA

The experimental work was conducted in the Miller Creek

Demonstration Forest (MC) in western Montana, at latitude

48” 31’ N., longitude 114” 43’ W. MC is a research and

demonstration area in the Flathead National Forest.

Elevations of the treated units are 1,424 to 1,654 m, and

slopes average 24 percent (12 to 37 percent). The local

climate is cool and moist; mean annual temperature is 5 “C,

and mean annual precipitation is 635 mm. The growing

season (May to August) has a high proportion of clear, hot

days and only 17 to 30 percent of the yearly precipitation falls

during this period (Schmidt and others 1976). Soils have

developed in glacial till composed of argillites and quartzites

of the Wallace (Belt) Formation and overlain with 13 to

140 mm of loess (DeByle 1981).

Forest cover is of the western larch type (Eyre 1980).

Percent conifer composition (based on volume of the uncut

forest) was: Engelmann spruce (picea ennelmannii) 31,

Douglas-fir (Pseudotsuea menziesii var. elauca) 31, western

larch 26, subalpine fii (Abies lasiocama) 6, and lodgepole

pine (Pinus contorta) 6 (Beaufait and others 1977). The

predominant potential climax vegetation is classified as the

&IasiocamalClintonia uniflora (ABLAKLUN) habitat

type (Pfister and others 1977). Three phases are represented:

Xerouhvllum tenax (XETE) on the drier south- and

west-facing slopes, Menziesia ferruainea (MEFE) on the

cooler middle and upper east- and north-facing terrain, and

Clintonia uniflora (CLUN) on west-, east-, and north-facing

slopes on the remaining sites.

66
Table 1.--Site and fire effects description of four units on south-facing slopes,

Miller Creek Demonstration Forest

Prescr. fire Prescr. fire Wildfire

Unburned May 18. 1968 Aus. 8 . 1967 Aug. 23. 1967

SITE

Elevation (m) 1456 1498 1479 1424

slope (%)

23:

2 2

1;:

2 4

Azimuth (deg.) 196 189

Dry slope (XI 100 8 8 9 1 9 4

Habitat type ABLA/CLUN,XETE ABLA/CLUN,XETE ABLA/CLUN,XETE ABLA/CLUN,XETE

FIRE EFFECTS

Fine fuel red. C%) N/A 82 74 ca 90

Duff red. (X1 N/A 1 6 8 4 100

Unburned duff (cm) WA 4.3 0.5 0

Soil exposure (XI N/A 1 4 8 4 100

METHODS

This paper reports on portions of two studies that describe

herb, shrub, and tree development on south- and east-facing

experimental burning units that were (1) clearcut and burned

by prescribed broadcast burning or wildfire, (2) clearcut

without burning, or (3) uncut but burned by wildfire. The

burning units averaged 4-ha in area.

Three south-facing units were clearcut in 1967; the fourth was

not cut (table 1). Two of the south-facing clearcuts were

prescribed burned (one in early August 1967, the other in

mid-May 1968), and the third was not burned. A wildfire

burned the uncut unit in late August 1967. The three

east-facing units were clearcut in 1967 (table 2). Two of

these units were prescribed burned in early October 1967 and

early August 1968; the third unit was not burned.

Successional Development

The postfire development of vegetation was measured

annually (most units) on permanent plots located within the

4-ha experimental burning units. The permanent plots within

a burning unit were referenced to two 25-m baselines, usually

arranged end to end (Stickney 1980). Each baseline served as

the base for live contiguous 5 x 5 m plots. Within each S-m

plot, three smaller plots were nested to accommodate the

sampling of lower/shorter woody plants and herbaceous

vegetation. Shrubs and trees were sampled according to

height as: (1) 2.5 m and taller on 5 x 5 m plots, (2) height

1.5 to 2.45 m on 3 x 3 m plots, and (3) height 0.5 to 1.45 m

on 1.5 x 1.5 m plots. Herbs (irrespective of height) and low

woody plants (including shrubs and trees <OS m high) were

sampled in two 0.5 x 0.5 m pIots nested in each 5 x 5 m plot

along the baseline. Cover (aerial crown) by plant species was

measured to quantify the successional development of shrubs

and trees and ocularly estimated for herbaceous and low

woody plants.

The total number of conifer seedlings and saplings and the

number of plots with at least one conifer seedling or sapling

were determined at S-year intervals on 31 to 74 temporary

0.0004-ha circular plots systematically installed throughout

each unit. Each of these circular plots was enlarged to

Table 2.-- Site and fire effects description of three units on east-facing

slopes, Miller Creek Demonstration Forest

Prescr. fire Prescr. fire

Unburned Auu. 7. 1968 Oct. 2. 1967

SITE

Elevation (m) 1585 1654 1448

Slope (%) 22

Azimuth (deg.) :; 4 63

Hoist slope (X) 9 2 7 8 80

Habitat type ABLA/CLUN,MEFE ABLA/CLUN,MEFE ABLA/CLUN,CLUN

FIRE EFFECTS

Fine fuel red. (X) N/A 9 2 44

Duff red. (XI N/A

Unburned duff (cm) N/A 2”;:

Soil exposure (X) N/A iI8

6 7
0.0013 ha to determine the number of (1) established (at least

30.5 cm tall for larch and lodgepole pine or 15 cm for other

species) and (2) plots with one tree present. Also, the height

of the tallest conifer of each species was recorded for each

plot.

The data presented in this paper were not analyzed

statistically.

Severity of Fire Treatment

Assessment of fire severity treatment to vegetation follows the

Ryan-Noste Fire Severity Index (Ryan and Noste 1985,

p. 232) as the standard. Severity, as defined by Ryan and

Noste, differs from “tire intensity” because it incorporates the

downward heat pulse to site in addition to the upward heat

pulse. Expressed as ground char depth, the downward heat

pulse is the critical one so far as understory vegetation is

concerned. The postfve manifestations of ground char class

are expressed in the depth reduction of the litter/duff

layer/mantle. On the experimental burning units being

reported here, ground char classes ranged from light for most

of the broadcast burned units to moderate for the wildfve and

summer burned units.

RESULTS

Fire caused changes in composition of all vegetation. The

degree of modification varied with severity of the tire

treatment as shown by changes on units receiving differing

fire treatments on south- and east-facing slopes.

Reforestation of South-Facing Slopes

Overstory trees common in 200- to 250-year-old virgin forests

on south-facing slopes at MC include Douglas-fu, western

larch, Engelmann spruce, subalpine fir, and less frequently

lodgepole pine. The more prominent understory plants

include the shrubs huckleberry (Vaccinium globulare),

mountain maple (Acer glabrum), and spirea (Suiraea

betulifolia); and the herbs amica (Amica latifolia), beargrass

(Xeronhvllum tenax), and prince’s pine (Chimanhilia

Clearcutting removes the overstory conifers and, umbellata).

when followed by slash burning, eliminates any onsite seed

source for trees.

Clearcut and a spring prescribed fwe.

Following clearcutting, a prescribed tire on May 18, 1968

(when the lower half of the duff was still wet from snowmelt

and rain) left a continuous, intact, duff mantle as a seedbed

and killed the aerial portions of understory herbs and shrubs.

Many topkilled herbs and shrubs quickly regrew from root

crowns and rootstocks. Forest succession began with the

regrowth of an abundant survivor component of amica and

beargrass and the establishment of the offsite colonizers

fireweed (Epilobium annustifolium) and bullthistle (Cirsium

vulgare). Herbaceous cover developed rapidly. Fireweed

quickly established; beargrass regrew less rapidly but more

persistently than did tireweed, and was a major component of

the herbaceous cover. The herb stage dominated the first 15

years of succession (fig. 1) because shrub development was

dependent on the slow recovery of huckleberry and sparse

colonization by Scouler’s willow (Salix scouleriana).

Conifers regenerated slowly because of unfavorable seedbed

and harsh site. Regeneration may also have been limited by

infrequent good seed crops and the distance from the seed

source.

Herbaceous cover and shrub cover were similar (45 to 50

percent) from the 15th through the 20th years. Tree cover

developed slowly; increasing to about 10 percent after 20

years (fig. 1). In 1984, 17 growing seasons after treatment,

at least one conifer seedling or sapling grew on 79 percent of

the plots. There were more than 1,900 total and established

trees/ha (fig. 2). Most of these were Douglas-frr, larch,

Engelmann spruce, and subalpine fir (table 3). Conifer

density was greatest close to the nearby uncut timber;

overstocking occurred in patches. There were few trees on a

drier slope in the interior of the clearcut. Many of the

conifers growing on that slope were exposed to direct

sunlight. Most conifers originated from the 1971 cone crop

that was rated good for all species.

COVER 1%)

PRE o 1 5 10 15 2 0

YEAR SINCE TREATMENT

Survivor :

XETE (HI 13 3 12 15 18 2 5

ARLA (HI 14 7 11 1 41 4

VAGL (S) 29 <l 3 8 16 11

Colonizer :

EPAN (H) 0 <1 17 22 12 8

SASC 6) 0 0 5 4 5 2

Figure 1. - Early successional development (cover) of major

life form groups and prominent species from 1968 through

1988 on a south-facing clearcut, prescribed burned May 18,

1968, Miller Creek Demonstration Forest; ARLA = amica,

EPAN = fireweed, SASC = willow, VAGL = huckleberry,

XETE = beargrass; H = herb, S = shrub.
SOUTH-FACING UNITS

PRESCRIEED BURN WILDFIRE

TREES/HA NOT BURNED MAY. 1060 AUG., 1967 AUG.. 1967

-I---- TREES ALL c] q ESTABLISHED

-_mw

7 1217 17 81116 1 6 71217 17 71217 17

YEAR SINCE TREATMENT

Figure 2. - Average number of all conifer seedlings and

saplings per hectare (open bars) by years since treatment and

number of established conifers (larch and pine at least

30.5 cm tall, others at least 15 cm) at the most recent

measurement (crosshatched bar) on four south-facing units,

Miller Creek Demonstration Forest, 1984.

Because all of the important nonconiferous species present in

1988 are traceable to the plant community established in the

first postfire year, it may be several decades before seeds

from other shrubs or tree species influence succession on this

site.

Clearcut and a summer prescribed fire.

In contrast to the spring burning, a prescribed fire on August

8, 1967, when duff moisture was low, consumed most of the

duff and as a consequence, killed many plants by burning

their aerial portions and lethally heating their roots within the

surface 3 cm of soil. A wildfire rebuming the area on

August 23 consumed the remaining duff, thereby increasing

plant mortality. Consequently, the postfire community

resulting from this double-bum treatment contained few

survivor plants and revegetation was largely in the form of

colonization by pioneer plants. Predominant colonizers were

shinylcaf ceanothus (Ccanothus velutinus) originating from

seed in a ground-stored seedbank emplaced well prior to the

fue and fireweed whose seed dispersed onto the bum in the

fall following the fire. A few seeds of conifers dispersed long

distances from outside the bum.

Forest succession began with the germination of these seeds

and the regrowth of spirea, beargrass, and huckleberry.

Early dominance by herbaceous plants, mainly fireweed, was

of short duration. Shrub seedlings of ceanothus, germinating

profusely from the seedbanks, dominated the site after about

7 years of postfire development. Once the herb and shrub

layer provided shade on this south-facing site, more conifer

seedlings became established, especially from the good cone

crop of 1971 4 years after the fire. Cover estimates are not

available for this unit, but shrubs still dominate after 20 years

although scattered conifers have overtopped the shrubs. In

1984, most of the 1,500 total and the 970 established trees/ha

were Douglas-fir and larch (fig. 2, table 3). Conifers grew

on nearly half of the plots.

In spite of an ash seedbed, tree density on most of the

clearcut has remained low because there is no onsite seed

source. A few trees on a ridge above the unit survived the

wildfve and provided some seed for regeneration. High

temperature at the soil-air interface and low moisture in the

surface 10 cm limited earIy conifer seedling survival. Lack

of moisture and competition with shrubs limited recent

survival. The number of established shade-intolerant larch

Table 3.--Percent composition of established conifer regeneration’ on southand east-facing slopes by treatmen?‘, Mitter Creek Demonstration Forest, 1984

Treatment

Tree cotsposition

w pi& yEJ m pIc0

SOUTH-FACING UNITS

CC, N B P B May 1968 0 4: 220 130 3 0

CC, P B Aug. 1967 32: 4s 9 10

UC, WF Aug. 1967 1 0 2 1 1 fi

EAST-FACING CLEARCUTS

CC, N B 67 33 0

CC, P B Aug. 1968

:

12 57

2:

1

CC, P B Oct. 1967 28 29 2 1 22 0

‘Based on data from 0.0013-ha circular plots that recorded et1 subsequent

natural regeneration 230.5 cm tall for western larch end lodgepole pine and

~15.0 cm tall for all other species. ABLA = subalpine fir, LAOC = uestern

larch, PICO = todgepole pine, PIEN = Engelmann spruce, PSHE = Douglas-fir.

kc = clearcut, UC = Uncut;

PB = prescribed burned, UF = wildfire, NB = not burned

69
and lodgepole pine decreased by 40 percent from 1979

through 1984, while numbers of shade-tolerant Douglas-fir

increased 192 percent.

Clearcut without fire.

A third clearcut was slashed but received no fire treatment.

Logging and slashing removed all overstory trees but did not

remove the small-diameter understory trees, most of which

were subalpine fir. The initial post treatment community was

composed almost exclusively of species that were present in

the prelogged forest (fireweed was the exception). Alder and

menziesia were important shrubs, both before and after

logging and site treatment. During the 20 years since

disturbance, only a few subalpine fir and Engelmann spruce

have regenerated (fig. 2, table 3).

Uncut, summer wildfire.

On August 23, 1967, a wildfire burned a virgin stand of

larch, DougIas-fir, and lodgepole pine that was designated for

logging later in the summer. The fire killed the overstory

trees (except two larch), burned the aerial portion of all other

vegetation, and ashed the litter/duff layer to the soil surface.

High mortality of huckleberry and beargrass, the major shrub

and herb species, resulted from this fire. Because few plants

survived the fire, the site was available for colonization by

pioneer species. Colonizers in the fist postfire year were

fireweed (herb), ceanothus (shrub), and lodgepole pine and

larch (tree). Seed sources for these initial colonizers were

onsite seedbanks for ceanothus (ground-stored) and lodgepole

‘pine and larch (tree crowns) and offsite for fiieweed. Forest

succession began with the germination and establishment of

these tree species coupled with regrowth of surviving spirea,

beargrass, and huckleberry. The fast initial growth of herb

cover was due mostly to the rapid development of fireweed.

Herb cover peaked at 4 years and shrub cover dominated after

only 7 years, mainly because spirea and ceanothus grew

rapidly (fig. 3). Although most conifers established in the

first year at the same time as fueweed and ceanothus, their

height did not begin to exceed that of the shrubs until the

ninth year. After 20 years, shrub cover still was twice as

great as that of conifers (fig. 3). It is expected that increased

shading resulting from height growth and crown development

of conifers will cause reductions in ceanothus cover. During

the winter of 1986-87, low temperature coupled with

lower-than-average snow cover killed a large proportion of

ceanothus crowns. Some recovery was noted in 1989.

In 1984 (succession year 17), more than 6,400 total and 5,600

established trees/ha, mostly lodgepole pine and western larch,

covered the area (fig. 3, table 3). Trees occurred in

97 percent of the plots-the result of seedfall from fire-killed

onsite trees.

COVER (%I

150 I-

,’

100 - 8’

* ’

S”R”SS,.”

..**

*.*..

: .* .*

. . . ...***

:

,’

.’ /?REES

, .*

PRE 0 1 5 10 15 2 0

YEAR SINCE TREATMENT

Survivor:

XETE (H) 2 3 2 5 10 10 8

swiE 6) a 2 1 1 16 23 2 6

VAGL (S) 5 4 0 1 4 5 8

Colonizer:

EPAN (HI 0 0 16 0 5 3

CEVE @I 0 ~1 <l 55 100 7 5

PICO (T) 0 2 22 58 82

Figure 3. - Early succession development (cover) of major

life form groups and prominent species from 1967 through

1987 of a south-facing uncut forest burned by wildfire on

August 23, 1967, Miller Creek Demonstration Forest; CEVE

= ceanothus, EPAN = fireweed, PICO = lodgepole pine,

SPBE = spirea, VAGL = huckleberry, XETE = beargrass;

H = herb, S = shrub, T = tree.

Reforestation of East-Facing Slopes

Tree species found on the south-facing slopes at MC are also

characteristic of virgin forests on more mesic east-facing

slopes. The understory shrub and herb species found on the

east-facing slopes are typical of moister sites. Prominent

shrubs include yew (Taxus brevifolia), menziesia (Menziesia

ferruainea), and alder (Alnus sinuata), in addition to

huckleberry; important herbs were amica and oak fern

(Gvmnocamium drvouteris). As on south aspects,

clearcutting and burning eliminated onsite sources for

coniferous seed. Burning decreased or eliminated potential

sources for seed in the slash. Where slash is not burned,

advance coniferous regeneration survived on the site.

Clearcut and a fall prescribed fue.

After a record-dry summer, a prescribed fire on October 2,

1967 (during the first major storm since late June) burned half

of the freshly moistened 5.8 cm duff layer. The fire

eliminated western yew, the major understory species, and

greatly reduced the cover percentages of the other principal

70
understory species, huckleberry and amica (fig. 4). The

reduced duff layer and poor survival of understory shrubs and

herbs combined to provide a conducive site for colonization.

Five offsite colonizers attained prominence in early

succession: fireweed, Scouler’s willow, western larch,

Douglas-fir, and subalpine fir. As on the south-facing slopes,

fireweed showed the most rapid development and attained

47 percent canopy cover by the second year after fire. It

remained the most abundant cover species for the duration of

the herb stage. Recovery of huckleberry survivors and

development of initial colonizer Scouler’s willow were

primarily responsible for succession to the shrub stage in the

13th year. Shrubs remained the most abundant life form

through 1989. Some conifer seeds germinated the first year

after the fire but most of them originated as secondary offsite

colonizers from the seed crop of 1971, 4 years after burning.

Because two edges of the unit bordered uncut forest,

thousands of conifer seedlings per hectare germinated in

1972. More than 12,600 seedlings/ha, mostly larch and

COVER (96)

15t

100

50

0

Survivor

ARLA (H)

VAGL (S)

ALSI (S)

TAER (S)

PRE 0 , 5 10 15 20

YEAR SINCE TREATMENT

12 2 1 2 6 9

26 1 2 9 21 38

7 0 0 0 3 1 2

63 0 0 0 0 0

Colonizer :

EPAN (HI o 41 30 17 9 1 2

SASC 6) 0 0 cl 7 14 1 5

LAOC (1) 0 (1 <l 6 2 0 44

Figure 4. - Early successional development (cover) of major

life form groups and prominent species from 1967 through

1987 of an east-facing clearcut, prescribed burned October 2,

1967, Miller Creek Demonstration Forest; ALSI = alder,

ARLA = amica, EPAN = fireweed, LAOC = western

larch, SASC = willow, TABR = yew, VAGL =

huckleberry; H = herb, S = shrub, T = tree.

Douglas-fir, survived in 1974 (fig. 5, table 3). Regeneration

more than doubled over the next 10 years because of large

increases in Douglas-fir, Engelmann spruce, and subalpine

fir. During this period the number of shade-intolerant

western larch decreased about 22 percent. More than 22,000

conifer seedlings and saplings/ha were counted in 1984, and

more than 21,000 of these were considered established. In

the 20th year of succession, percentages of cover of trees and

of shrubs were high and almost equal, while percentages of

herb cover were much less (fig. 4).

EAST-FACING UNITS

PRESCRIBEO BURN

- NOT BURNED

--I

AUG., 1966 OCT.. 1067

TREES

ALL c]q ESTABLISHED

71217 17 0 1’ 16 71217 17

YEAR SINCE TREATMENT

Figure 5. - Average number of all conifer seedlings and

saplings per hectare by years (open bars) since treatment and

number of established conifers (larch and pine at least 30.5

cm tall, others at least 15 cm) at the most recent measurement

(crosshatched bar) on three east-facing units, Miller Creek

Demonstration Forest, 1984.

7 1
Clearcut and a summer prescribed fire.

AAer the onsite conifer seed source was removed by

clearcutting and slashing, the August 7, 1968, prescribed fire

burned the aerial portions of the understory vegetation and

removed the upper 60 percent of the duff layer. The fire

substantially reduced cover of most of the shade-tolerant

understory species, especially huckleberry, alder, and

menziesia. Herbs responded quickly, covering 68 percent of

the freshly burned site by the second year of succession.

Amica, a rhizomatous herb, attained 19 percent by

regrowth; fireweed, which grew from seed from offsite

sources, attained 47 percent coverage. The few survivor

shrubs regrew slowly in early succession, and cover of herbs

was live times as great as cover of shrubs by the sixth year,

the last year for which data are available.

Conifers regenerated quickly from seed of offsite trees

bordering two sides of the clearcut. Most seedlings resulted

from the abundant 1971 seedfall. The moderate or good cone

crops of 1974, 1976, and 1980 provided seed for additional

seedling establishment. In 1974, 6 years after the fue, there

were 6,300 seedlings/ha (fig. 5). This increased to more than

18,100 in 1984 and 21,800 in 1989. About two-thirds of the

tree seedlings counted in 1984 were considered

established-there were seven times more established seedlings

in 1984 as there were in 1979. Of the established conifers,

57 percent were Engelmann spruce, 22 percent suablpine fir,

12 percent Douglas-fir, 8 percent larch, and 1 percent

lodgepole pine (table 3). Only the Engelmann spruce were as

tall here as they were on the other clearcuts. The few

established lodgepole pine were much shorter than elsewhere,

but they were 0.6 m taller than the other species. In contrast,

height growth of Engelmann spruce was greater than on other

burned clearcuts at Miller.

Cleat-cut and no fire.

An cast-facing unit bordering the clearcut prescribed burned

on August 7, 1968, provided an unburned contrast. The

unmerchantable trees were cut but not removed after

clearcutting, but many small subalpine fir and a few other

shade-tolerant conifers were. not cut. With no further

disturbance, the understory alder, menziesia, amica, and

small conifers constituted the initial community with species

composition little changed from the prelogging forest (fig. 6).

The major exception, fireweed, colonized sites where removal

of overstory trees revealed gaps in the shrub layer. Because

shrubs constituted the most important cover group both before

and after logging, forest succession began with an initial

shrub stage that has continued for 20 years. Possibly some

secondary colonization of aider and menziesia from onsite

seed sources occurred during the middle of the first decade.

Alder and menziesia have become codominant for the shrub

stage. Twenty years after logging, fueweed represents a

minor component overall but maintains higher coverage in the

openings of the shrub stand. Although adjacent uncut stands

supplied much seed, competition for light and moisture is

intense and few conifers became established. The current tree

component is sparse and consists of subalpine fu that were

established before the stand was clearcut and were too small

for slashing in 1967 and about 62 Douglas-fir and Engelmann

spruce/ha (table 3, fig. 5). A few western larch and

lodgepole pine are present, probably growing on small areas

disturbed during timber harvest.

PRE 0 5 10 15 19

YEAR SINCE TREATMENT

Survivor :

ARLA (H) 5 1 9 8

VAGL(S) 2 5 1 8 20

MEFE (S) 2 8 2 3 so

ALSI (S) 2 6 3 4 90

Colonizer :

EPAN (Ii) 0 3 4 8

Figure 6. - Early successional development (cover) of major

life form groups and prominent survivor and colonizer species

from 1968 through 1987 on an east-facing clearcut that was

not burned, Miller Creek Demonstration Forest; ALSI =

alder, ARLA = amica, EPAN = tireweed; MEFE =

menziesia, VAGL = huckleberry; H = herb, S = shrub.

DISCUSSION

Maturing forests are inhospitable to the establishment and

growth of many native species. Fire renews and rejuvenates

aging ecosystems following years of successional changes and

the accumulation of duff and litter. The potential for fire to

alter succession depends mainly on the composition of the

forest community, the onsite seed source, and the severity of

the fire. Low-severity fires leave a high survivor component

and do little to change species composition, leaving sites in a

later stage of succession. As fire severity increases, the

burned area becomes more favorable to colonizers. Severe

fires kill more of the existing vegetation and have the

potential to greatly change the course of subsequent

succession, that is, set succession back to an earlier stage.

Fire similarly affects succession after clearcutting. Without

fire or other site modification after timber harvest, conifer

regeneration is slow and often excludes shade-intolerant

species. The MC study showed response of vegetation to a

72
wide range of fire characteristics. On south aspects conifer

regeneration was successful on an uncut unit burned during

the August I967 wildfire, less so on prescribed burned

clearcuts, and unsuccessful on an unburned clearcut. On the

east-facing slopes conifer regeneration was successful on

prescribed burned clearcuts but was also unsuccessful on an

unburned clearcut. Ryan and Noste (1985) show that when

plenty of conifer seed is present, regeneration on clearcuts

following fire depends on the severity of burning treatment.

Clearcutting followed by prescribed burning can deplete the

surface of most of the woody residues. Although conifer

regeneration following clearcutting was usually most

successful when the duff layer was removed by fire, research

has shown that most conifers successfully regenerate through

1.3 cm of duff in the western larch forest type (DeByle

1981). Retention of a shallow duff layer and other organic

matter, especially the woody component, protects the soil

from intense summer rainfall for the first few years (DeByle

1981) and helps maintain the productivity of the site (Harvey

and others 1987).

Many trees that burned during the wildfire on the south-facing

uncut unit bore mature cones. Some cones burned and their

seeds were lost while other cones were singed and their

undamaged seeds dispersed on the ash covered surface a few

days after the fire. Seeds with unburned wings could disperse

farther than seeds with partly burned wings. Overhead shade

from dead and surviving trees promoted seedling survival

through decreased surface soil temperatures and reduced

evapotranspiration. Prompt conifer seedfall permitted

establishment before shrub and herb competition for moisture

and light became extreme. Following less severe wildfire,

more overstory trees survive and serve as a continuing onsite

seed source. The availability of onsite seed to affect

regeneration depends on the regularity and amount of seed

crops and the duration of a receptive seedbed after burning.

Burned seedbed had greater conifer germination and seedling

establishment than on unburned sites. Regeneration usually

increased where the duff layer was reduced most. Sparse

conifer establishment on the two presecribed burned clearcuts

on south aspects resulted from the harsh site conditions.

Without shading, the soil surface dried quickly and

temperatures as high as 79 “C were measured in June and July

(Shearer 1976). The combination of lethal temperature and

rapid drying of surface soil soon after germination often

causes high mortality of new seedlings (Shearer 1976). The

May prescribed fire left a 4-cm-deep residual duff layer that

was unfavorable for seedling survival. Cracks developed in

the duff as it warmed and dried during the sunny, dry season

following site treatment. In subsequent years, seedlings

survived much better in the enlarging cracks than on the

surface of duff. The August prescribed fire nearly eliminated

all of the duff layer on the other clearcut and left it exposed

to extremes in light and temperature. Seedfall was deficient

because few trees grew nearby.

The east-facing clearcuts were less influenced by long periods

of intense radiation. Each of the clearcuts had one or two

sides bordering uncut timber that provided abundant seed for

natural regeneration. Both prescribed burned clearcuts

regenerated readily and conifers now account for a substantial

percentage of the plant cover. Subsequent regeneration failed

on the unburned clearcut where no exposed mineral seedbed

was left after logging.

Lodgepole pine have serotinous cones, but the other conifers

present depend on the current cone crop to provide seeds after

late summer or early fall burning. A fair or good cone crop

usually provides sufficient seed to regenerate the site the

spring after the fire. But for stands that are burned when few

or no onsite cones are available, regeneration is dependent on

offsite seed sources. The number of new seedlings decreases

as distance to the trees increases.

If clearcutting occurs near the time of cone maturity, the

cones will open and disperse their seeds. Severe slash fires

bum much of the duff layer and destroy all or most of the

seed, preparing a substrate free of heavy duff and favorable

for seed germination. If seeds are present in nearby stands

and disseminate into the units, as they did on the east-facing

clearcuts that were burned by the summer and fall prescribed

fires, prompt regeneration occurs. If seed is unavailable, as

in the south-facing clearcut prescribed burned in August 1967,

regeneration is delayed. Cutting without slash burning

maintains the viable seed, but does not prepare a seedbed

conducive to seedling establishment (examples are east- and

south-facing clearcuts where fire was excluded).

Exposed charred duff apparently decomposed rapidly. Within

a few years, the depth of this layer decreased sufficiently so

that significant numbers of conifer seedlings became

established. After some early seedling establishment, the

abundant seed crop of 1971 dispersed onto the 5-year-old

nearly duff-free ground surface and a substantial pulse of new

conifer seedlings established.

If these new forests were to bum with a tree-killing fire, the

initial postfire community would be composed mostly of

survivor species. Principal shrubs would be ceanothus,

spirea, and huckleberry; principal herbs would be fueweed

and beargrass. Tree species probably would be excluded

from the site for lack of an onsite seed source. This

condition would be equivalent to the double bum situation in

the Northern Rocky Mountains that created large shrubfields

as noted by foresters at the turn of the century (Lieberg

1897).

73
LITERATURE CITED

Baker, Herbert G. 1989. Some aspects of the natural history

of seed banks. In: Leek, Mary Allessio; Parker, V.

Thomas; Simpson, Robert L. eds. Ecology of soil seed

banks. Academic Press, Inc. San Diego, CA: 9-21.

Beaufait, William R.; Hardy, Charles E.; Fischer, William C.

1977. Broadcast burning in larch-fu clearcuts: The Miller

Creek - Newman Ridge Study. Research Paper INT-175.

Ogden, UT: U.S. Department of Agriculture, Forest

Service, Intermountain Forest and Range Experiment

Station. 53 p.

DeByle, Norbert V. 1981. Clearcutting and fire in the

larch/Douglas-fir forests of western Montana--a

multifaceted research summary. General Technical Report

INT-99. Ogden, UT: U.S. Department of Agriculture,

Forest Service, Intermountain Forest and Range

Experiment Station. 73 p.

Eyre, F. H., ed. 1980. Forest cover types of the United

States and Canada. Society of American Foresters. 148 p.

Harvey, Alan E.; Jurgensen, M.F.; Larsen, M.J.; Graham.

R.T. 1987. Decaying organic materials and soil quality in

the Inland Northwest: a management opportunity. General

Technical Report INT-225. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Intermountain Research

Station. 15 p.

Leiberg, John B. 1897. General report on a botanical survey

of the Coeur d’AIene Mountains in Idaho during the

summer of 1895. Contributions from the U.S. National

Herbarium. Washington, DC: U.S. Department of

Agriculture, Division of Botany. 5(l)%81.

Pfister, Robert D.; Kovalchik, Bernard L.; Amo, Stephen F.;

Presby, Richard C. 1977. Forest habitat types of

Montana. General Technical Report INT-34. Ogden, UT:

US. Department of Agriculture, Forest Service,

Intermountain Forest and Range Experiment Station.

174 p.

Ryan, Kevin C.; Noste, Nonan V. 1985. Evaluating

prescribed fires. In: Lotan, James E.; Kilgore, Bruce M.;

Fischer, William C.; Mutch, Robert W. tech. coords.

Proceedings-Symposium and workshop on wilderness

fue; 1983 November 15-18; Missoula, MT. General

Technical Report INT-182. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station: 230-238.

Schmidt, Wyman C.; Shearer, Raymond C.; Roe, Arthur L.

1976. Ecology and silviculture of western larch forests.

Technical Bulletin 1520. Washington, DC: U.S.

Department of Agriculture. 96 p .

Shearer, Raymond C. 1976. Early establishment of conifers

following prescribed broadcast burning in western

larch/Douglas-fir forests. Proceedings, Tall Timbers Fire

Ecology Conference; 4:481-500.

Shearer, Raymond C. 1989. Fire effects on natural conifer

regeneration in Montana. In: Baumgartner, David M.;

Breuer, David W.; Zamom, Benjamin A.;

Neuenschwander, Leon F.; Wakimoto, Ronald H.

compilers and eds. Prescribed tire in the Intermountain

Region-forest site preparation and range improvement.

1986 March 3-5; Spokane, WA. Pullman, WA:

Washington State University, Cooperative Extension:

19-33.

Stickney, Peter F. 1980. Data base for post-fire succession,

first 6 to 9 years, in Montana larch-frr forests. General

Technical Report INT-62. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Inter-mountain Forest and

Range Experiment Station. 133 p.

Stickney, Peter F. 1982. Vegetation response to clearcutting

and broadcast burning on north and south slopes at

Newman Ridge. In: Site preparation and fuels

management on steep terrain: Proceedings of symposium;

1982 February 15-17; Spokane, WA. Pullman, WA:

Washington State University, Inland Empire Reforestation

Council: 119-124.

Stickney, Peter F. 1986. First decade plant succession

following the Sundance Fire, northern Idaho. General

Technical Report INT-197. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station. 26 p.

74
CHANGES IN WOODY VEGETATION IN FLORIDA DRY PRAIRIE

AND WETLANDS DURING A PERIOD OF FIRE EXCLUSION,

AND AFTER DRY-GROWING-SEASON FIRE

Jean M. Huffman and S.W. Blanchard’

Abstract-South Florida dry prairie and herbaceous wetlands are recognized as tire maintained

communities. Aerial photography was used to show how the woody vegetation in Myakka River State Park

(Sarasota County, Florida) changed over approximately thirty years of fire exclusion (1939-1968). Rapid

increases occurred in Quercus virginiana and Serenoa renens uplands and in forested and shrubby wetland

associations. Corresponding decreases occurred in dry prairies and herbaceous wetlands. Present

management goals are to maintain and restore tire-dependant plant communities. Drought-condition bums

early in the growing season appear to be mote effective in reducing woody species cover than traditional

dormant-season bums or wet growing-season bums.

INTRODUCTION

Increases in woody vegetation are known to occur in many

southeastern Coastal Plain plant communities following fire

excusion or when fire frequency is reduced (Heyward 1939;

Alexander 1973; Platt and Schwartz 1990; Wade and others

1980).

We mapped vegetation change over a thirty-year period of

fue exclusion in two areas within Myakka River State Park, a

11,686 ha. preserve of dry prairie, pine flatwoods, marshes

and oak-palm @uercus vireiniana, 0. laurifolia and Sabal

palmetto) hammock located in Sarasota and Manatee Counties

in Southwest Florida (Fig.1).

Vegetation changes that have occurred following fire

exclusion in Florida dry prairies and imbedded wetlands were

documented. We also mapped changes resulting from attempts

at restoration using the reintroduction of different types of

prescribed tires. Restoration efforts over the past several

decades suggest that not just fire, but fire at a specific time of

year and under specific moisture conditions is critical for

restoration of dry prairie habitats invaded by woody species

during periods of tire suppression.

Fig. I.- Myakka River State Park and location of study sites.

The inset map of Florida shows Sarasota and Manatee

Counties, the counties within which the park is located.

‘Park Biologist, Myakka River State Park, Florida Department of

Natural Resources, Division of Recreation and Parks, Sarasota,

Florida; and Research Assistant, Myakka River State Park, Sarasota

Florida.

75
STUDY AREA

Climate

The climate of Southwest Florida is characterized by an

annual cycle that includes a dry season from October through

May and a wet season from June through September (Chen

and Gerber 1990). At Myakka River State Park, 61 percent

of the average total annual rainfall (144 cm) occurs during the

wet season (Fitzgerald 1990). The wet season does not

correspond exactly to the growing season, which typically

occurs from April through October. Therefore, at the time

that growth of plants is initiated in the spring, the dry season

has not yet ended.

Fire History

Myakka River State Park lies within an area that has a long

history of lightning-ignited fves and fires set by cattlemen.

The thunderstorm (lightning) season typically occurs from

May through September in south Florida, and approximately

95 percent of total annual thunderstorm days occur during this

period (Robbins and Meyers 1989). Fire records from

southwest Florida indicate that naturally-ignited tires bum the

largest areas at the end of the dry season in early spring

(Miller and others 1983). Presumably this was the historic

pattern of burning in this region before European settlement.

For the last 100 years or more cattlemen and ranchers have

burned primarily in the winter, in the beginning and middle of

the dry season. These bums usually occur after the passage

of a cold front brings rain, when fuel moistures, and often

water tables, are high and seasonal wetlands have standing

water.

The State Park was established in 1934, a period of strong

anti-fire sentiment in the Southeastern United States. During

the late 1930’s and early 1940’s the Civilian Conservation

Corps made the fighting of fires at Myakka a high priority.

Hundreds of miles of firebreaks were cut throughout the park

and fves were extinguished whenever possible. Although

many lightning fires were ignited, they were suppressed as

quickly as possible. The result was not total fire exclusion

but a much reduced fire frequency in most areas. This tiresuppression policy continued in effect through the late 1960’s

when prescribed burning was accepted as a management tool.

Prescribed fire was not regularly used within the park until

the late 1970’s, when winter-burning was initiated. Spring and

summer growing season bums were initiated in the early

1980’s (Robert Dye pen. comm.).

Plant Communities

Early accounts of the Myakka region suggest an almost

treeless landscape of dry and wet prairies, and scattered pine

flatwoods in which closed canopy hardwood forest occurred

only as scattered, small “islands” and narrow borders along

the river and lake systems. (Townshend 1875; Reid 1843).

These are still the major habitat types present in Myakka

River State Park today.

A large Portion of the park (6,0000-7,000 ha.) consists of dry

prairie, which contains a highly diverse mix of grasses (e.g.

-Axistida -9stricta Schizachvrium scoDarium, and Sorghastrum

secundum) forbs (e.g. Rhvnchospora olumosa, Lachnocaulon

anceps, Pityousis nraminifolia, and Caroheohorous

odoritissima) low shrubs ( e.g. Ouercus geminata, Vaccinium

darrowii Ilex -)-&, and Lvonia fruticosa ), and saw

palmetto (Serenoa reoens). Florida dry prairie is a fire

maintained plant community that occurs only in south central

and southwest Florida (Davis 1967, Harper 1927). This

community has been globally ranked (GZ) as threatened by

The Nature Conservancy (Florida Natural Areas Inventory

1990). Dry prairie is the native habitat for several species of

listed animals including Crested Caracara, Florida

Grasshopper Sparrow and Florida Burrowing Owl, all species

or subspecies which were common in the 1940’s (Van Duyn

1941) but do not regularly occur in Myakka River State Park

today.

Hundreds of small wetlands are scattered within dry prairie

and flatwoods areas. These wetlands have seasonally

fluctuating water levels, typically drying near the end of the

dry season. Dominant species include Hvoericum

fasciculatum, Panicum hemitomon, and Pontederia cordata

-.

Hammocks are closed canopy forests that are dominated by

Quercus vireiniana and Sabal palmetto. They occur along the

Myakka River and lakes, and, in smaller patches adjacent to

other wetlands. Groundcover is generally lacking or

consisting of a sparse cover of herbs.

METHODS

We used Soil Conservation Service and Florida Department of

Transportation aerial photos from the 1940’s and 1980’s to

map vegetation in two selected areas within the park. We

selected sites that currently have large amounts of dry prairiehammock edge. The Wilderness Preserve site covers

approximately 850 acres and the Mossy Island Hammock site

covers approximately 1,500 acres. Site locations are shown in

figure 1. In the earlier photographs, boundaries between areas

with and those without canopy cover were quite distinct, as

most canopied areas had 90 percent or greater tree cover.

Boundaries between forested and nonforested communities

were very sharp. In photos from the later series, these

boundaries were not as clear. Ground-truthing was used for

the 1990 series.

Wilderness Preserve areas with greater than 75 percent

canopy cover in March 1948 and March 1985 were

delineated. The majority of cover consisted of live oaks

(Quercus virainiana), laurel oaks (0. laurifolia), sabal palms

(Sabal palmetto), and smaller numbers of South Florida slash

pines (Pinus elliottii var. densa). Wetlands with woody cover

76
of red maple (Acer rubrum), buttonbush (Cenhalanthus

occidentalis), willow (Saiix caroliniana), or popash (Fraxinus

caroliniana) were also included in the canopy-covered

category. Wherever oaks (especially laurel oaks in wetter

areas) invaded wetlands, the area was then classified as

forested upland.

Mossy Island aerials taken in April 1940 and January 1986

were used both to delineate canopy-covered areas and to

distinguish between forested and open wetlands. Species

comprising upland and wetland woody cover in Mossy Island

were the same as those comprising Wilderness Preserve

upland and wetland cover.

Fires that occur during the growing season, after an extended

dry period are hereafter referred to as dry growing-season

burns. Reductions in the cover of woody vegetation after one

dry growing-season bum in the Wilderness Preserve study

area, and after two, or in some sections three, dry-growingseason burns in the Mossy lsland Hammock area, are shown

using the same mapping methods on aerial photography from

November 1990.

Community boundaries were mapped and digitized into a PC

ARC/lNPO Geographic information System computer

database. The digital maps were transformed into state plane

coordinates, and areas occupied by the vegetation types were

calculated. The aerial photographs were not rectified; because

landmarks had changed during the course of 40 yesrs, it was

sometimes difficult to locate registration points precisely.

Transforming maps lo state plane coordinates helped minimize

errors resulting from the use of unrectified aerials. We also

used percentage of area covered rather than total acreage to

compensate for unrectified aerials.

Field observations were used for descriptions of vegetation

composition and change in the mapped areas. Fire and

weather records kept at Myakka River State Park were

consulted for information on fire conditions.

RESULTS

Before Fire Suppression (1940’s Maps)

In the 1940’s vegetation cover of the two study areas was

predominantly open, with non-woody vegetation the dominant

cover type. Open prairie reached to the lake shore in both

series (see Figs. 2 and 3). Most wetlands were open, with

very few forested or woody wetlands. Hardwood hammocks

occurred in smail areas closely associated with wetlands.

1948 1985 1990

WILDERNESS PRESERVE

q CANOPY COVER

ABSENT CANOPY COVER

Fig. 2.- Wilderness Preserve canopy cover in 1948 before fire exclusion,. in 1985, after fire exclusion; and in 1990, after

one dry-growing season bum. Shaded areas indicate canopy cover. The north, east and southern edges are bounded by

roads. The west side is bordered by the marshes of the Lower Lake Myakka.

7 7
MOSSY ISLAND HAMMOCK

n OPEN UPLAND

FORESTED UPLAND

OPEN WETLAND

FORESTED WETLAND

BORROW PIT q UPPER LAKE MYAKKA

(NOT INTERPRETED)

After Fire Suppression (1980’s)

Uplands - In both sites woody canopy coverage (mostly

Ouercus virpiniana and 9. laurifolia) increased dramatically

from 1948 to 1986.

Where oaks were adjacent to dry prairie or pine flatwoods

they expanded into these habitats (Figs. 2,3). In the

Wilderness Preserve Series (fig. 2) open areas decreased from

66 percent to 26 percent of the total area (fig. 4). In the

Mossy Island series (fig. 5) dry prairie decreased from 58 to

39 percent of the total mapped area. Nearly all of this

decrease is traceable to the large increases oak stands. It is

important to note that oak canopy stands that have expanded

into dry prairie since the 1940’s are very different from the

original oak hammocks. Oak stands that have developed

during fi exclusion have a dense palmetto understory (Fig.

6). In contrast, the older, pre-fue-exclusion hammock has an

open understory or a sabal palm understory (Fig. 7), with

palmettos only along hammock fringes. It is this border fringe

of oaks and palmettos that have expanded tremendously

during the period of fire suppression.

Wetlands - Nearly half of open wetlands were lost between

the 1940’s and 1986 (Figs. 2 and 3). In the Mossy Island

series in 1940 most wetlands were open and grassy, and

wetlands of this type constituted 14 percent of the total area.

In 1986 many wetlands were dominated by trees or shrubs

and open wetlands constituted only 8 percent of the total area.

Areas of forested wetlands increased from 1 to 4 percent of

the total area. This change accounts for 37.5 percent of open

wetland loss. Fifty-one percent of open wetland reduction

Fig. 3.- Mossy Island Hammock study site vegetation in 1940

before fue exclusion; in 1986 after fure exclusion; and in

1990, after two dry-growing season bums.

78
represents shifts to the forested upland category. Construction

of a shallow drainage ditch (combined with fire exclusion)

contributed to the extensive change from wetland to oak cover

m the northeast section of the map. The remaining open

wetland reduction is represented by the open wetland area that

was converted to shallow borrow pits.

All woody species were mapped as a group, however there

were several patterns apparent in woody species increase in

wetlands. Open wetlands that are surrounded by hammock

are less likely to bum as often as wetlands surrounded by dry

prairie. These wetlands were the most hkely to change from

open herbaceous to woody cover during the period of fue

exclusion. This change was especially rapid in floodplain

wetlands along the river and lake, and in other wetlands that

contained areas of hardwoods in 1940 (compare 1940 and

1986 maps in Fig. 3).

Woody species, including Mvrica cerifera (wax myrtle),

Fraxinus caroliniana (popash), && caroliniana (willow), and

Cephalanthus occidentalis (buttonbush), expanded their

coverage of formerly grassy wetlands. The most common

woody colonizer of small floodplain marshes was popash.

This species was not observed, however, to colonize isolated,

prairie wetlands. Laurel oaks often moved into the outer

zones of wetlands bordered by hammocks. Very little oak

cover increase occurred in wetlands that did not have adjacent

hammock.

Cover type

Open uplands

and uettands

Percentage of cover

1948 j9&

66 26

Closed canopy uplands

and wettands

34 7 4

Fig. 4.-Vegetation cover Wilderness Preserve, Myakka River

State Park.

Cover type Percentage of cover

gwJ 1986

Open upland 58 39

Forested upland 1 8 39

Open wetland 1 4 8

Forested uettand 1 4

Borrou pits 0 1

Upper take 9 9

Fig. 5.- Vegetation cover of Mossy Island Hammock, Myakka

River State Park.

Fig. 6.- Live oaks with dense saw palmetto understory typical of areas where oak has expanded into dry prairie since the 1940%.

79
In both floodplain hammock and prairie-bordered ponds wax

myrtle sometimes established in the outer zones. Willow,

buttonbush or more rarely, maple, colonized or expanded

coverage in the deeper, more central wetland zones.

After Reintroduction of Fire (1990 maps)

Prescribed burning was initiated at Myakka River State Park

in the late 1960’s. Burning in the sixties and seventies halted

the expansion of young oaks but resulted in little or no

reduction of existing canopy cover. Because fires were

conducted in the traditional manner during the dormant-season

(winter), at times when fuel moisture and water table levels

were. relatively high, fires did not move into the oak-palmetto

areas. Pie also did not move into wetlands with increased

woody vegetation. Growing-season prescribed bums were

initiated in the park in 1983, but it was not until 1986 that a

bum moved into oak-palmetto and woody wetland areas.

Mossy Island Hammock. Three bums have occurred in the

Mossy Island Hammock area between 1986 and 1990. On

May 31, 1986, at the end of a long dry season a fire,

resulting from a natural ignition, occurred in the Mossy Island

Hammock area. Prior to this fire, the area was last partially

burned by a lightning-ignited fire which occurred on August

21, 1985. This fire occurred late in the afternoon and was

accompanied by high humidities and rain. Typical of earlier

bums it did not result in any significant reduction in oak or

woody wetland species cover (Robert Dye pers. comm.). The

effects of the May, 1986 bum were quite different from those

of previous bums. Many oaks that had invaded dry prairie

since 1940 were damaged severely. Some individuals with

d.b.h. over 12 inches were killed outright; epicormic and

basal resprouting occurred on others. This fire was the first to

cause substantial reductions in oak canopy cover.

A second growing-season headfve burned into the same area

on June 30, 1988. This fire took place under only moderately

dry conditions but also killed many oaks that presumably had

already been weakened by the first fue. These bums

demonstrated that fre can cause mortality of large oaks when

a palmetto understory is present. Slash pine also survived the

fire (Figure 8). No oaks in the older hammock areas without

palmetto understory were kiIled. Areas in which oak cover

burned corresponded to areas that were dry prairie in 1948

(see figs. 4 and 5).

The Mossy Island Hammock series also shows changes in

woody-wetland vegetation, Wetland water levels at the time

of these fires were low, especially during the 1988 bum. This

allowed fue to sweep across wetlands, reducing woody

species cover.

The western portion of the Mossy Island Hammock study area

burned once more, on May 11, 1990, with an intense bum.

The remainder of the area burned on May 24 and 31, 1990

with a milder bum. The 1990 map of the Mossy Island

Hammock series (fig. 3) shows the extent of woody species

cover reduction following the 3 bums of June 1986, June

1988 and May 1990.

Wilderness Preserve. The Wilderness Preserve area was

burned in May 1983 under high humidities without any

significant reduction of oak cover (Robert Dye, park

manager, pers. comm.). The first growing-season fue under

dry conditions occurred in this area on June 1, 1989. This

fire occurred during a period of very low wetland water levels

and low humidities and reduced oak canopy coverage in oakpalmetto areas that had established during the period of fire

exciusion. The 1990 Wilderness Preserve series map in Iigure

2 shows the extent of hardwood canopy reduction in 1990

after the dry growing-season fur: of June 1, 1989.

This fire occurred 90 days after the last l/2 inch rain when

nearly all wetlands were without standing water. The fire

burned into wax myrtle, wilIow, popash and buttonbush in

areas that had increased in cover since 1948. The fire

reduced woody cover in wetlands and resulted in a return of

characteristic herbaceous species such as Panicum hemitomom

(maidencane) and Polveonum nunctatum (smartweed). No

previous prescribed bum had touched these areas.

DISCUSSION

Fire suppression and vegetation change

When fire suppression occurs the boundaries between habitat

types change (Myers 1985; Platt and Schwartz 1990). Our

data suggests an expansion of a habitat type with elements of

dry prairie and hammock but which is actually neither. This

oak-savanna, fringing habitat tyPe only, not the original

hammock, increased during the thirty-year period of fire

exclusion. The dense cover of palmetto still present in the

understory of this new habitat type burned under drycondition prescribed fves and contributed the fuel that

resulted in oak mortality. These processes cause this boundary

type habitat between dry prairie and oak-palm hammock to be

very dynamic, expanding and contracting with varying fire

regimes, while true hammock areas remained more stable.

While aerial photography can be used to illustrate oak canopy

cover increases and decreases, the changes within dry prairies

are more difficult to document. In the absence of fire shrubs

and palmetto are known to increase, both in cover and height

(Givens and others 1982; Hilmon 1969). These increases may

occur at the expense of the herbaceous element of the dry

prairie flora. The increase in palmetto and woody shrubs

alters fire intensity and behavior, causing less frequent, more

80
__-.--..-- _-

Fig. 7.- Original hammock with live oaks and sabal palms, note absence of saw palmetto understory.

Fig. 8.- Fire kill and stress of live oaks in Mossy Island Hammock area, 1991. South Florida slash pines survived fires that

killed large oaks.

8 1
intense fires, which may contribute to oak mortality. However

the reintroduction of fue, even during the dry growingseason, does not appear to be sufficient to control increased

amounts of saw palmetto occurring as a result of altered fire

regimes (‘pers. obs.).

Fire and Hardwood Mortality

Only dry growing-season fves were observed to move into

shrub-dominated wetlands. Although other fves occasionally ’

impacted the edge of the oak palmetto zone only dry growingseason fires were observed to move far into this zone and

cause mortality in large oaks. These results are similar to

those found by (Platt and others 1991), who found that spring

fires caused the highest mortality rates for oaks in sandhill

habitats in north Florida. They found that fue temperature

was not a significant factor in their study of oak mortality but

suggested that the phenological state of the vegetation was the

most critical factor. We suggest that dry conditions appear to

cause added stress to oaks making them even more vulnerable

to fire during the growing season.

Management Considerations

Fiie management plans often are implemented in areas that

have previously had a history of fur: suppression. When

managing a natural area it is important to consider the

vegetation changes that occurred during these fire suppression

periods.

When reversal of fue exclusion changes is a management goal

growing season bums are very useful for obtaining hardwood

control. The growing season is recognized as the “natural”

fue season in Florida. Growing season bums are known to

stimulate flowering of some species and kill invading oaks

(Platt and others 1991). Our present study demonstrates the

success of dry growing season fires in restoring herbaceous

wetlands and reducing oak-palmetto fringe habitat. Many

recognize the probable significance of spring drought fves

(Robbins and Meyers 1989; Wade and others 1980), however,

few managers of natural areas use prescribed fue under

spring drought conditions.

Fires occurring under very dry conditions are more difficult

to control and more likely to spot for long distances. These

considerations must be taken into account but experienced fire

managers can conduct successful bums in very dry conditions.

A dry growing-season bum should not be implemented in

areas with large fuel accumulations. A fuel reduction bum

may be required in these cases and it may be necessary to

take special precautions such as removing fuel that has

accumulated around the bases of pines before attempting a dry

growing-season fire. General sensitivity of pines should be

considered. It is important to think about any other possible

sensitive elements before conducting bums under very dry

conditions.

CONCLUSIONS

In the absence of frequent fire, oaks colonize dry prairie and

wetland edges, and hardwood wetland species increase

dramatically within wetlands. Where plant communities

depend on frequent fire for maintenance, even a few decades

of fue exclusion can cause major changes in dominant woody

vegetation. The maintenance of open, grassy, dry prairie and

wetlands in South Florida is dependent on frequent burning.

The reintroduction of fire after an extended period of fire

exclusion, however, does not always reverse the abundance of

woody species that have increased as a result of altered fire

regimes. Prescribed fire usually does not move into long

excluded areas that have oak canopy cover. Even when fire

does occur in these areas usually very low or no mortality of

well-established hardwoods occurs.

Observations of dry growing-season bums at Myakka indicate

that such bums, which usually occur in South Florida at the

end of the dry season and the beginning of the lightning

season (April and May) may be an important element of

habitat management. Conducting all bums under conditions

when fuel moisture and water levels are high may be causing

significant shifts to occur in vegetation, especially in

wetlands. Growing season bums under dry conditions at the

end of the dry season, were almost certainly ‘part of the

presettlement fire regime. At least a periodic bums of this

type may be necessary for the long-term maintenance of

wetland plant communities.

Dry growing-season bums have also been observed to kill

well-established hardwoods - large oaks in dry prairie and

various woody species in wetlands. In areas where hardwood

cover has increased as a result of long-term fire exclusion or

long intervals between fines, dry growing-season fire therefore

is an important component of a fire management plan where.

restoration and reversal of fse-exclusion effects is a

management goal.

ACKNOWLEDGEMENTS

We thank Dr. William J. Platt for his many insightful

suggestions which greatly improved this paper; Robert Dye,

District 8 Manager, Florida D.N.R., Division of Recreation

and Parks, for his dedication to natural areas management and

research, and his support of this project; and Nina Arlet who

provided the photographs.

82
LITERATURE CITED

Alexander, T.R., and A.G. Crook. 1973. Recent and longterm vegetation changes and patterns in south Florida.

Final Rep. Part 1. USDI Natl. Park Serv. NTIS No. PB

231939.

Chen E. and J.F. Gerber. 1990. In (R. Myers and J. Ewel,

eds., Ecosystems of Florida. University of Central

Florida Press, Orlando, Florida.

Davis, J. H., Jr. 1967. General map of the natural vegetation

of Florida. Circ. S-178, Inst. Food Agric. Sci., Agric.

Exp. Stn., University of Florida, Gainesville.

Fitzgerald, S.M. 1990. Small mammal, bird and plant

responses to the rehabilitation of a dry prairie grassland

association using fire and roller chopping applied in two

seasons. Unpublished thesis, Univ. of Florida.

Gainesville.

Florida Natural Areas Inventory and FL. D.N.R. 1990. Guide

to the natural communities of Florida. Tallahassee,

Florida.

Givens, K. T., J. N. Layne, W. G. Abrahamson and S. C.

White-Schuller. 1982. “Structural changes and

successional relationships of five Florida Lake Wales

Ridge plant communities”. Bulletin of the Torrey

Botanical Club. 111:8-18.

Harper, R. M. 1927. Natural resources of Southern Florida.

18th Annual Report of the Florida State Geological

Survey.

Heyward, F. 1939. The relation of fire to stand composition

of longleaf pine forests. Ecology 20:287-304.

H&non, J. B. 1969. Autecology of saw palmetto (Serenoa

repens (Bartram) Small). Phd. Dissertation. Duke

University.

Miller, J., J. Huffman and J. Morris. 1983. The changing

landscape of North Pott, Florida. Unpublished Report,

Environmental Studies Program, New College of the

Univ. of S. Florida. Sarasota, Florida.

Platt, W.J. and M.W. Schwartz. 1990. Temperate hardwood

forests. In (R. Myers and J. Ewe], eds.), Ecosystems of

Florida. University of Central Florida Press, Orlando.

Platt, W.J., J.S. Glitzenstein and D.R. Streng. 1991.

Evaluating pyrogenicity and its effects on vegetation in

longleaf pine savannas. In Proceedings of the Annual Tall

Timbers Fire Ecology Conference 1989. Tallahassee,

Florida.

Reid, S. 1843. U.S. survey notes and plats for Township 37

South Range 20 East and Township 36 South Range 20

East. Florida Department of Natural Resources,

Tallahassee.

Robbins, L.E. and R.L. Myers. 1989. Seasonal effects of

prescribed burning in florida: a review. Nongame

Wildlife Report. Florida Game and Freshwater Fish

Commission Nongame Wildlife Program. Tallahassee,

Florida.

Townshend, F.T. 1875. Wildlife in Florida. Hurst and

Blackett London, England.

Van Duyn, G. 1941. Biological reconnaissance, Myakka

River State Park, Florida, with preliminary check Lists of

vertebrate fauna. Unpublished Report Florida Park

Service.

Wade, D., J. Ewe1 and R. Hofstetter. 1980. Fire in South

Florida eosystems. U.S.D.A. Forest Service General

Technical Report SE-17. Southeastern Forest Experiment

Station Asheville, North Carolina.

Myers, R.L. 1985. Fire and the dynamic relationship between

Florida sandhill and sand pine scrub vegetation. Bull. of

the Torrey Bot. Club 112:241-252.

83
LIVESTOCK GRAZING ALTERS SUCCESSION AFTER FIRE

IN A COLORADO SUBALPINE FOREST

William L. Bake8

Abstract-Plant succession after fires is often considered a relatively predictable process, yet the possibility

of alternative outcomes, or multiple stable states, has not been thoroughly studied. The present study

makes use of field data collected along a livestock exclosure fence on a site near Pikes Peak, CO, at an

elevation of about 3350 m. These data suggest that the west-facing part of the site was once occupied by a

subalpine forest dominated by Picea enaelmannii and that this forest was burned in about A.D. 1867.

Livestock grazing discouraged tree regeneration until a major decrease in use in the mid-1940’s. On the

grazed side of the fence, the forest became dominated by Pinus aristata, a tree commonly found on drier,

rockier sites like that produced on this moister site by heavy grazing. On the ungrazed side of the fence

Picea eneelmannii appears lo be regaining its dominance. This is an example of extrinsically produced

alternative outcomes, a successional result that warrants further study.

INTRODUCTION

Plant succession after fires and other natural disturbances has

traditionally been viewed as a relatively predictable process

ending in reestablishment of the predisturbance climatic

climax vegetation. This traditional postfire succession model,

which derives from the ideas of Clements (1916), has formed

the basis for much research on posttire succession (e.g.

Fischer and Bradley 1987). The possibility of relatively

permanent alternative outcomes, or multiple stable states

(Helling 1973), has been raised (Jameson 1987) but has not

been demonstrated with empirical data.

The multiple stable states model was developed to account for

the observation that some ecological systems can be moved

into alternative states by insect outbreaks, overgrazing,

overfishing, pollution, and other disturbances. The essential

characteristics of a system with multiple stable states is that

the original state is not regained once the disturbance is

discontinued (Holling 1973). The existence of multiple stable

states can be demonstrated theoretically (e.g. May 1977), but

the empirical evidence for their existence has been challenged

(Connell and Sousa 1983). Connell and Sousa suggest that all

purported examples fail for one or more of three reasons: (1)

the physical environment is different in the different alternate

states; (2) the alternate states persist only when disturbances

are maintained; or (3) the evidence is simply inadequate.

Succession after fires in southern Rocky Mountain subalpine

forests is often slow and variable (Stahelin 1943; Veblen and

Lorenz 1986). There is some evidence of failure to restore

pre-fire tree composition (Veblen and Lorenz 1986), but no

clear evidence of multiple stable states. The evidence

presented here suggests that livestock grazing following a fire

can alter the course of succession, and that the result may be

a potentially stable alternative forest.

‘Assistant Professor of Geography and Recreation, University of

Wyoming, Laramie, WY 82071.

84

STUDY SITE

The study site consists of two hillsides in a subalpine forest

about 7 km south-southeast of the summit of Pies Peak,

Colorado (figs. 1 and 2). The forest is now dominated by

bristlecone pine (Pinus aristata), Engelmann spruce (picea

engelmannii), and quaking aspen (Po~ulus tremuloides).

Smaller numbers of limber pine (Pinus flexilis) are present.

Elevation of the sloping study area ranges from 3,290 to

3,400 m. Treeline is at about 3,650 m.

The study is focused on vegetation on two sides of a fence

that prevents livestock that graze on a U.S.D.A. Forest

Service allotment south of the fence from entering a protected

watershed owned by the City of Colorado Springs (fig. 1).

The fence was installed between 1890 and 1902, and the

watershed on the north side has not been grazed by livestock

since that time (Personal communication, Bennie Baucom,

Superintendent, Water System Operations, City of Colorado

Springs). The Forest Service lands south of the fence are part

of the Deer Park Unit of the Beaver C&H Allotment, which

has been a designated cattle allotment since the early 1900’s

(U.S.D.A. Forest Service, Pikes Peak Ranger District

records). Forest Service records of grazing levels in this

allotment are spotty, but by the 1950’s grazing had been

reduced to less than 20 percent of the 1930 level (fig. 3a).

Evidence of excessive use was apparent by the 1930’s. In

1934, Forest Ranger William Cochran commented in a memo

to the Forest Supervisor that “...a very heavy reduction of the

present use must be made” (Working Plans, Pies Peak

District Office, Colorado Springs). The site was burned by a

large forest fire, which is discussed below. The fire burned

both sides of the fence and much of the area in figure 2.

METHODS

Six 20- by 50-m (0.1 ha) plots were sampled. Plots 1, 3, and

5 were on the south (grazed) side of the fence, and plots 2, 4,

and 6 were on the north (ungrazed) side of the fence.
Figure I.-Looking east along the fenceline at the west-facing part of the site. The ungrazed side, with abundant Picea

eneelmannii and m, is on the left, and the grazed side, with abundant Pinus aristata, is on the right. The fire burned

across the entire hillside.

LEGEND

----- Fence

0 Sampling Plot t

-b Location for Figure 1 N

Photograph

I

DENVER. .5 Km.

1

.

.5Mi.

1 COLORADO 1

100’ Contour interval

Source: U.S.G.S. Pikes Peak 1:24,000, 1951(Pr 1984).

Figure Z.-Study area map.

85
% 2000 3 (4

!

t; 1500

4

a

2 1000

2

r

,E 500

3

i

.

zc 0 , t 1 I 1 I I 5 , I I t I I I t I I 1 8 I a I 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

PIAR (n = 34)

gg

$2

z 0

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

5

2; 4 (d

PIEN (n = 9)

5; 0 .-, I I I I z L,vT 7 I”1”I 11 VI $1 l ’ ’

1867 1885 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

YEAR

Figure 3.-(a) History of cattle use on the Deer Park Unit of the Beaver C&H Allotment. Data are from U.S. Forest

Service-Pies Peak Ranger District records. (b) Dates of establishment of largest Pinus aristata. Solid bars are dates from

cores that contained the actual center of the tree. Shaded bars are dates estimated from cores that were close to containing

the center (three or fewer years added to estimate the date). Unshaded bars are dates from cores that were an estimated 4-8

years from containing the center. (c) Dates of establishment of largest picea engelmannii. The shading is as in (b).

Elevation, aspect, and slope were identical in adjoining plots

(table 1). In each plot I tallied all trees, including seedlings

and saplings, by size class. Seedlings are defined as stems

< 5 cm diameter and < 1 m tall. Saplings are < 5 cm

diameter and > 1 m tall. The remaining size classes,

beginning at 5.0 cm diameter, are all 5 cm wide (e.g. 5 to

9.99 cm).

Table 1. --Environmental data for the

six fenceline plots.

Envi romental variabies

Plot

Elevation Aspect Slope

To determine the composition and structure of the prefire Meters -----Degrees-----

forest, we tallied by size classes the standing dead and

downed trees killed by the tire in plots 5 and 6. Standing 1 3,307 100 22

dead trees were not sufficiently abundant in the other plots.

Nearly all the trees killed in the fue could be identiIied to

2 3,307 100 22

species, and most stems remained intact, although smaller

trees probably were consumed by the fire. 3 3,307 285 20

4 3,307 285 20

To determine the approximate date when trees became

established following the fire, we removed increment cores 5 3,377 270 19

from the bases of 34 of the largest P. aristata and 9 of the

largest p. engelmannii. The cores were sanded, and each 6 3,377 270 19

core’s rings were counted under a stereomicroscope. When

the core did not extend to the center of a stem, the number of

additional rings needed to reach the center was estimated.

86
First the radius of the circle that contained the first ring on

the core was estimated. Then the number of rings that might

occur within that radius was estimated by multiplying the

radius in cm by the average density of rings over the length

of the core (rings/cm of core).

The date of the forest fire was determined by cross

correlating tree-ring width variations in 14 standing dead

burned trees with ring-width variations in the Almagre

Mountain master chronology developed by the University of

Arizona’s Laboratory of Tree-Ring Research (Drew 1974).

This chronology is from a site approximately 2 km east of the

study area. Tree-ring widths were measured with a

stereomicroscope and a computer-assisted Henson incremental

measuring machine. Ring-width time series were corrected

for growth trends by fitting a negative exponential or straight

line to each series. The series were then standardized.

INDEX, a program produced by the University of Arizona’s

Laboratory of Tree-Ring Research (Graybill 1979), was used

to perform these computations. Each series, including the

Almagre Mountain series, was then pre-whitened by fitting

standard autoregressive-moving average (ARMA) time series

models. This is necessary to avoid spurious results from

cross-correlation (Yamaguchi 1986). The last year of growth

present on each burned tree was then determined by floating

each time series against the Almagre Mountain chronology

and locating the highest cross-correlation coefficient.

RESULTS

The tire probably occurred in A.D. 1867. Many of the last

years of growth present on the burned trees, based on the

ring-width cross correlations, are near that date. Last years

of growth for 14 burned trees were: 1867, 1867, 1866, 1866,

1861, 1861, 1860, 1858, 1856, 1851, 1847, 1840, 1828, and

1815. The last year of growth is not necessarily the fire year,

as the tire might have burned into the stem, removing the

outer part of the core. Thus the evidence from the burned

trees only suggests that the fire occurred in or after 1867.

The abundance of dates in the 1860’s suggests that the fire

occurred within a few years of 1867. The oldest living tree

Cp. engelmannii) contained 121 rings and an estimated one

additional ring to the center, for a pith date of A.D. 1867,

suggesting that 1867 was the actual fire year.

The prefire forest on the west-facing part of the site was

dominated by g. engelmannii. Stems in diameter classes from

about 15 to 25 cm were most numerous, and only a few _P.

aristata were present (fig. 4). The null hypothesis that the

prefire size class distribution for _P. engelmannii in plot 5 does

not differ from the preiire distribution in plot 6 (across the

fence) cannot be rejected at the 0.05 level of significance (chisquare=8.70 and d.f.=6).

While prefire size class distributions in adjoining plots on

opposite sides of the fence had not differed significantly, there

were significant differences between posttire size class

distributions (fig. 4). In general, P. aristata was much more

abundant on the grazed side of the fence, particularly in the

west-facing plots (3-6). The nuU hypothesis, that P. aristata

age class distributions were the same on both sides of the

fence, was rejected at the 0.05 level of significance (chisquare=51.86 and d.f.=6), for paired plots 1 and 2, but

could not be tested for the remaining plots (too many zero

entries). Nonetheless, these distributions are completely

different (fig. 4). P. aristata is much more common on the

grazed side of the fence, and p. eneelmannii was generally

much more abundant on the ungrazed side of the fence (fig.

4). The null hypothesis, that p. engelmannii distributions

were the same on both sides of the fence, was rejected at the

0.05 level of significance for paired plots 3 and 4 (chisquare= 16.41 and d.f. =5) and paired plots 5 and 6 (chisquare=53.59 and d.f.=6), but could not be tested for paired

plots 1 and 2. Po~1~1us tremuloides was also more abundant

on the ungrazed side of the fence, but was absent from both

plots 3 and 4 (fig. 4). The null hypothesis, that fl.

tremuloides distributions were the same on both sides of the

fence, was rejected at the 0.05 level of significance for paired

plots 1 and 2 (chi-square=22.36 and d.f. =3).

DISCUSSION

These data suggest that a wildfire in A.D. 1867 burned a

west-facing hillside subalpine forest that was dominated by _P.

enrrelmannii. p. engelmannii began reestablishing on the

burned hillside immediately after the tire, but had not fully

reoccupied the site when livestock grazing began. Grazing

probably occurred on both sides of the fence until the fence

was installed sometime between 1890 and 1902. g.

eneelmannii continued to reestablish on both sides of the

fence, but at a slower rate on the south side due to livestock

use. When the intensity of livestock use was decreased to 20

percent of its former level, in the 1940’s, the environment

had been modified by the effects of grazing on the vegetation.

As a consequence, the site probably had lower cover of Sa&

and other subalpine plants (as is apparent now-fig. I), and

thus greater insolation received at ground level, resulting in

an effectively drier site. ,P. aristata is typically found on

drier, more southerly-facing, rockier sites, often in close

proximity to moister, more northerly-facing, less rocky _P.

engelmannii sites (Baker, unpublished data). The grazing

may thus have shifted the environment on this site toward one

favoring 11. aristata establishment. Until grazing was

decreased, establishment was not possible. Pearson (1934)

has described a similar pattern in which Pinus ponderosa

establishment was favored when heavy grazing, which

decreased competition from grass, was followed by lighter

grazing, that allowed tree seedlings to survive.

Five of eight posttire p. eneelmannii became established

between 1886 and 1921, whereas most of the largest _P.

aristata originated between 1934 and 1952 (Fig. 3c, 3b).

87
Pinus aristata

s 50

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Picea engelmanii

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Populus tremuloides

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ki/0 15 25 35 45 55 zz5

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Figure 4.-Size class distributions for all live trees present in the six fenceline plots and for dead and downed trees in plots 5

and 6. Size classes are: SE=Seedlings (< 1 m tall and <5 cm diameter), SA=Saplings (> 1 m tall and < 5 cm diameter).

Other size classes are 5.0 cm wide, with the label indicating the lower limit of the size class.
It is not known whether the II. aristata and p. tremuloides

postfire forest on the east-facing part of the site (plots 1 and

2) represents reestablishment of the pretire forest. The

prefire composition is unknown. P. aristata is common in the

postlire forest on both the grazed and ungrazed sides of the

fence, suggesting that on this part of the site grazing is not

the primary reason for p. aristata abundance. This part of the

site is probably drier, however, because its aspect is

somewhat more southerly than that in plots 3 to 6. This drier

environment may have favored _P. aristata postfire

establishment even without grazing.

The pattern of succession on the ungrazed part of the westfacing burned hillside has been as expected. _P. eneelmannii

has returned and has reestablished dominance. In the grazed

area on this hillside, however, p. engelmannii has not

reestablished dominance. P. aristata has achieved dominance

and will likely retain it for some time. The traditional

successional model is not appropriate in this case.

1s this, then, an example of multiple stable states? The case

described here fails to fulfill Connell and Sousa’s (1983) first

criterion, as the environment & different on opposite sides of

the fence and the difference is the result of an extrinsic

influence--overgrazing. The environment is different because

Sa& is nearly absent from the grazed side of the fence (Fig.

1). This results in a different microenvironment on the two

sides of the fence at ground level. The case described here

does, however, meet the second criterion of Connell and

Sousa, as the alternative state would persist if the disturbance

were excluded. Excluding livestock from the south side of

the fence could conceivably reverse most of the abiotic effects

of grazing and even some of the biotic changes, but the p.

aristata population is firmly established and is not likely to die

if livestock are removed. Moreover, the coincidence of peak

p. aristata invasion with a decline in grazing intensity (fig. 3),

suggests that the alternative state of 52. aristata dominance is

now favored by removal of the disturbance source.

ConnelJ and Sousa also argue that the persistence of the

alternative state must be demonstrated through at least one

turnover of the population. f2. aristata has a maximum

lifespan of over 1,500 years (Krebs 1972), and forests

containing trees that are 400 or more years old are common

(Baker, unpublished data). Connell and Sousa’s requirement

for persistence is theoretically sound, but neither persistence

nor the lack of it can be demonstrated in the near future. The

alternative state of _P. aristata dominance has already persisted

for about 50 years, however, a duration that is significant in

terms of forest management. I suggest that a true alternative

state should persist following removal of the disturbance

agent, but that a variety of inferential evidence of this

persistence should be acceptable.

The multiple stable states described by Connell and Sousa

(1983), where the alternate state must be maintained

intrinsically (by the biota), have yet to be clearly

demonstrated to occur in nature. The rigorous criterion of

intrinsic maintenance these authors use may be justified from

a theoretical standpoint, but it is important not to discourage

further study of extrinsically produced and maintained

multiple stable states.

Environmental changes accompany most kinds of natural

disturbances and human land uses. The possibility of

unexpected outcomes folIowing these disturbances and land

uses is thus of considerable interest. This possibility has

previously been raised in connection with various human

influences on vegetation, including effects of tire suppression

(Vale 1982), overgrazing (Anderson and Holte 1981; Walker

and others 1981; Westoby and others 1989), and clearcut

logging (Vale 1988). The failure of trees to regenerate

following fires (e.g. Payette and Gagnon 1985) due to

climatic change may also produce alternative states. Other

potential examples of extrinsic multiple stable states have been

reviewed by HolIing (1973), Vale (1982), and Connell and

Sousa (1983).

In an increasingly managed world in which environmental

changes accompany many ordinary human land uses, it is

critical to understand how and why persisting alternative

states may arise. Livestock grazing following fires may

produce unexpected and persistent alternative outcomes.

ACKNOWLEDGMENTS

This investigation was supported by University of Kansas

General Research allocation #3954-X0-0038. Deborah

Paulson assisted with the fieldwork. John Dunham and Marla

Kerr assisted with the tree-ring analysis. Bennie Baucom of

the City of Colorado Springs kindly permitted access to the

watershed.

89
LITERATURE CITED

Anderson, J. E. and Holte, K. E. 1981. Vegetation

development over 25 years without grazing on sagebrushdominated rangeland in southeastern Idaho. Journal of

Range Management 3425-29.

Clements, F. E. 1916. Plant succession: an analysis of the

development of vegetation. Carnegie Institute of

Washington Publication 242, Washington, D.C.

Connell, J. H. and Sousa, W. P. 1983. On the evidence

needed to judge ecological stability or persistence. The

American Naturalist 121:789-824.

Drew, L. G., ed 1974. Tree-ring chronologies of western

America. N. Colorado, Utah, Nebraska and South

Dakota. Chronology Series 1, Laboratory of Tree-Ring

Research, University of Arizona, Tucson, AZ. 41 pp.

Fischer, W. C. and Bradley, A. F. 1987. Fire ecology of

western Montana forest habitat types. U.S. Department of

Agriculture, Forest Service, General Technical Report

INT-223, Intermountain Research Station, Ogden, UT. 95

PP.

Graybill, D. A. 1979. Revised computer programs for treering research. Tree-Ring Bulletin 39:77-82.

Helling, C. S. 1973. Resilience and stability of ecological

systems. Annual Review of Ecology and Systematics 4:1-

23.

Jameson, D. A. 1987. Climax or alternative steady states in

woodland ecology. p. 9-13 In: Everett, R. L., compiler.

Proceedings-pinyon-juniper conference peno, NV-Jan.

13-16, 19861. U.S. Department of Agriculture, Forest

Service, Genera1 Technical Report INT-215,

lntermountain Research Station, Ogden, UT. 581 pp.

May, R. M. 1977. Thresholds and breakpoints in ecosystems

with a multiplicity of stable states. Nature 269:471-477.

Payette, S. and Gagnon, R. 1985. Late Holocene

deforestation and tree regeneration in the forest-tundra of

Quebec. Nature 313570-572.

Pearson, G. A. 1934. Grass, pine seedlings, and grazing.

Journal of Forestry 32545555.

Stahelin, R. 1943. Factors influencing the natural restocking

of high altitude bums by coniferous trees in the central

Rocky Mountains. Ecology 24: 19-30.

Vale, T. R. 1982. Plants and people: vegetation change in

North America. Resource Publications in Geography,

Association of American Geographers, Washington, D.C.

88 PP.

Vale, T. R. 1988. Clearcut logging, vegetation dynamics, and

human wisdom. Geographical Review 78:375-386.

Veblen, T. T. and Lorenz, D. C. 1986. Anthropogenic

disturbance and recovery patterns in montane forests,

Colorado Front Range. Physical Geography 7:1-24.

Walker, B. H., Ludwig, D., Holling, C. S., and Peterman,

R. M. 1981. Stability of semi-arid savanna grazing

systems. Journal of Ecology 69:473-498.

Westoby, M., Walker, B., and Noy-Meir, I. 1989.

Opportunistic management for rangelands not at

equilibrium. Journal of Range Management 42(4):266-

274.

Yamaguchi, D. K. 1986. Interpretation of cross correlation

between tree-ring series. Tree-Ring Bulletin 46~47-54.

Krebs, P. V. H. 1972. Dendrochronology and the distribution

of bristlecone pine (Pinus aristata Engelm.) in Colorado.

PhD. Dissertation, University of Colorado, Boulder, CO.

211 pp.

90
CLIMATIC CHANGE AND THE MODELING OF FIRE EFFECTS IN

COASTAL SAGE SCRUB AND CHAPARRAL

George P. Malanson and Walter E. W&man’

Abstract-Human-inducedclimatic change will affect Ihe processes and rates of species growth and thus the

rates of accumulation and the composition of fuel loads. The combination of altered furl loads and altered

weather patterns will result in altered fire regimes. Altered tire regimes will in turn affect species growth

and community composition. This feedback can be incorporated in computer simulation models of the

response of vegetation to a changing climate, but the ways species will grow in climates in which they do

not now exist and the way this growth can be translated into fuel loads are not well understood for

California shrublands, in which the continual production of basal sprouts allows shrubs to continue life

while some branches die, we propose that the apportionment of biomass into live and dead fuel classes is

the critical issue in modeling this feedback.

INTRODUCTION

It is becoming increasingly clear that minimizing the risk of

wildfires and maximizing natural processes in wildlands are

often incompatible goals for land managers (cf. Malanson

1985a). This realization has come with increasing

understanding of the history and processes both of wildfire

and of ecosystems. If land managers are to resolve these

conflicts, it is necessary that the relationship between

wildfires and biotic elements of wild ecosystems bc

understood. In this paper we discuss how human-induced

climatic changes may affect w&&e-vegetation interactions

and how some aspects of the wildfire-vegetation relationship

might be addressed in future research. We examine computer

simulation models of population dynamics in California

shrublands in which fire intensity is important, and we

consider the way in which ecosystem processes must be

translated into fuel dynamics.

The relationship between ecological processes and quantitative

estimalcs of life intensity has been addressed in a number of

ecological studies. We used a calculation of fire intensity to

assess the impacts of fire regime on Californian costal sage

scrub (Westman and others 1981; Malanson and O’Leary

1982). chaparral (Malanson and O’Leary 1983, and French

ganigue (Malanson and Trabaud 1987). WC have also

altcmpted to determine what ecological processes produce fuel

loads different enough to result in different fire intensities and

rates of spread (Malanson and Butler 1984; Malanson and

Trabaud 1988). The incorporation of fire behavior into an

iterative computer simulation model of sp&s dynamics is,

however, elementary. WC mod&d the dynamics of

Californian coastal sage scrub OVCf periods of 200 years

under a variety of lire regimes, and WC included the effects of

altcrcd fit-c intensity at diffcrcnt fire inlcrvals in this model

‘Associate Professor of Geography, University of Iowa, Iowa City,

IA, and Staff Scientist, Applied Science Division, Lawrence Berkeley

Lahoralory, Be&&y, CA (Wait Weslman died 112191).

(Malanson 1983, 1985b). These studies and others like them,

have shown that the dynamics of species populations and

individual growth affect fuel loads, and that these fuel loads

affect fire behavior which in turn affects species dynamics.

CLIMATIC CHANGE

Projected Changes and Responses

If the global climate changes, our present understanding of the

feedbacks between ecological processes and fue behavior

maybe inadequate for the purposes of managing fire regimes.

Projections of general circulation models (GCM’s) indicate

that the global climate may warm from 1 to 5 “C in the next

century due to emissions of radiatively-active trace gases

(Schneider 1991). Species responses to a change in climate

are not easily predicted. The rate of change in climate at the

Pleistocene-Holocene boundary was not as rapid as that

projected for the next century, and so analogs !?om the fossil

record may not bc applicable. We know that species can live

in less stressful (warmer and moister?) conditions than those

occurring in their natural range (Darwin 1859, MacArthur

1972, Woodward 1991); yet we do not know how well

species will grow in their present locations if and when the

climate changes. The inertia of biogeographic response,

which results from the advantage to species already occupying

sites, is likely to be important (cf. Cole 1985; Hanson and

others 1989). But eventually climatic change will alter relative

abundances in given locales and also the production of fuel

(e.g., SuMing, this volume). The changes wilt also alter the

frequency of the conditions under which fires are ignited and

spread (Beer and others 1988). These changes in frequency

will not be directly analogous to those that occurred during

the Holocene (cf. Clark 1985). Current conceptions of the

problems of suppression and prescribed burning are based on

the pattern of fuel development and fire weather from the

recent past. These concepts may not lit the patterns of the

filture (cf. van wagcncr 1987).

91
First-Generation Model for Coastal Sage Scrub

Research on the effects of climatic change on Californian

coastal sage scrub suggests that altered fire regimes may

result in greater changes in species composition than the

direct effects of climatic change (Malanson and Westman

1991; Westman and Malanson 1991). We used a computer

simulation model that was designed to examine the effects of

different fire regimes under a constant climate and altered the

fire intensities and ecological functions to include the effects

of climatic change. In this model, however, we simulated

conditions at a new equilibrium climate, and we did not

include a feedback connecting plant growth, fuel, fire, and

regeneration. We had previously made observations and

estimated fuel loads in Californian coastal sage scrub

(Westman and others 1981; Malanson 1985); we altered these

estimates as we judged appropriate to reflect climatic changes

projected by two different GCM’s. These GCM’s, the GISS

(Hansen and others 1981) and GFDL (Manabe and Wetherald

1980), project warmer temperatures and increased

precipitation in southern California. To analyze the effects of

altered temperature (Temperature runs), we changed the fuel

loads by the same proportion as the change in total foliar

cover projected for the species in question in a direct gradient

analysis: fuel load was reduced by 13%. To analyze the

effects of increased winter precipitation (Composite Moisture

Index, CM1 runs), we increased the dead fuel linearly from

zero at the time of fire up to double that currently found on

40-year-old sites. Albini’s FIREMODS program (1976a),

which makes use of Rothermel’s fire model (1972), was used

to calculate new fire intensities on the basis of the new total

fuel loads. As an index of fire intensity we used the total

heat release (Joules per square meter) calculated by the

program (fig. 1). Albini (1976b) recommended total heat

release as the best indicator of the effects of tire on

vegetation. Because of the complexity of fire behavior and

the lack of functions describing the flux of heat from the fire

to the regeneration organs of the plants, this index of intensity

is best considered to be a surrogate measure of fire effect.

These fire intensities were used to alter the rates of

resprouting of the component species for the new climates

through previously described response functions based on

field observations (Malanson and Westman 1991). Under

these fire regimes thee are changes in the relative abundances

of the five species involved. However, overall cover changes

only when a IO-year fire interval, i.e., a short interval, is

assumed; in this case, cover declines throughout the 200-year

period simulated. This result indicates that the increases in

dead me1 may be the most realistic assumption for most

conditions. But this assumption does not address the issue of

declining fuel loads under the lo-year-interval fire regime,

which indicates that increasing fire intensities are not the only

impact. Neither does it address the fuel load changes that

would occur if spcxies with different physiognomies were

considered. If the area were occupied by increasing cover of

grasses or chaparral shrubs, the fuel loads would have to be

9 2

6

TOTAL

HEAT

RELEASE

2

CMI run

Standard run

run

, 1

10 20 30 40

FIRE INTERVAL (yr)

Figure 1. Fire intensities projected for coastal sage scrub

under assumptions of altered climate (doubled carbon dioxide

levels, GISS model). The Standard run is produced for

current observed fuel loads; the Temperature run indicates the

results of a decrease in me1 load assumed for an increase in

temperature; the CMI (Composite Moisture Index) run

indicates the results of an increase in fuel load assumed for an

increase in precipitation.

altered in a different ay than to simply assume change in the

growth of the coastal sage scrub species. Therefore, it is

necessary to include the feedback between species

composition and growth in the iterative process of modeling

fire in the simulation (e.g., fig 2).

FUELRESPONSES

The concept that the growth of plants in a simulation should

determine the tie1 load at the next tire seems straightforward.

The fuel load, however, is more complex than a direct

measure of foliar cover or of biomass would indicate. First,

the distribution of wood in different branch sizes, with

different surface to volume ratios and thus different rates of

combustion, is known for present shrub species, but both the

species and their growth forms may be altered under a

different climate. Second, the heat content of the fuel,

especially in Mediterranean-type ecosystems where the

content of volatile oils is high, may change in anew climate.

Third, the spatial distribution of fuels in three dimensions

(e.g., grass-shrub proximity or fuel packing) could change

with changing grass/shrub biomass ratio. These three factors

could result in changes in both fire behavior and intensity,

and thus in potential effects on vegetation. For the present,

however, WC will discuss one change in the fuel load: the

ratio of live to dead biomass.
STORE0 INTERACl IVt

Species tral ts Populations

FIR Intensity CONDITIONS Fsre regtme

fuel types

t

flORTALlTY

FUEL b

COVER

Figure 2. Vegetative response to fire and climate with a

f&back to fire intensity through fuel load.

Importance of Dead Fuel

Calculations of fire intensity show that the livedead ratio is

of great importance. Using the fuel loads reported by

countryman (1964) for light, medium, and heavy chaparral,

we divided these fuels into six categories of live to dead fuel

ratios, and entered them into FIREMODS. The results

indicate that especially at high fuel loads, when larger stems

that are live contribute less to combustion, the proportion of

dead fuel greatly affects the estimation of fire intensity (fig.

3). These results are not always consistent with our

simulations of tire intensity (total heat release) in coastal sage

scrub in an altered climate: our estimates of fire intensity

under conditions of increased moisture availability

(approximately 6 x lo61 rn? may be too high (fig. I), while

our calculations based on Countryman’s estimates of fuel load

for light chaparral (approximately 2.4 x 106J rn-*) may be too

low (fig. 3).

Dead Fuel in Coastal Sage Scrub and Chaparral

Both chaparral and coastal sage scrub can produce

considerable amounts of dead fuel during long fire-free

periods. Chaparral has been noted for this feature, which is

often referred to as sencsccnce. In coastal sage scrub, we

observed that individual shrubs continually produce new basal

branches during the fire-free period (Malanson and Westman

1985). Kecley and Keelcy (1988) ohset-ved the same

characteristic in certain chaparral species. A plant with this

trait can replace its dead branches with live ones, and thus

can produce new growth without expanding its area. This

ability is critical for the continued production of dead standing

fuel. In the Mcditerrancan climate, standing dead fuel does

not decompose rapidly, although fuel falling to the ground

does not seem to accumulate, since litter loads arc not heavy.

This trait of coastal sage and chaparral shrubs, while

indicating the importance of recording the change in fuel

characteristics through time, may also indicate a pathway for

assessing the potential effects of climatic change on standing

dead fuel.

Standing dead fuel becomes common in these shrublands after

the canopy has closed. This indicates that as the site becomes

crowded, and perhaps as nutrient and moisture reserves

become more finely divided among individual shrubs and

even among the branches of a single shrub, the ratio of

production to respiration (Ps/Pr) in and individual branch

becomes critical and that branch may then die. Under a

7

t

6 /

t

TOTAL

HEAT 5-

RELEASE

6 - 2

x IOJm

4-

3 -

2 - Light, Medium, & Heavy

Chaparral Fuel Loads

I -

(after Countryman 1964)

1

0 IS 35 SO 65 8 5

X DEAD FUEL

Figure 3. Fire intensities projected for three fuel loads

apportioned into six classes of live-todead fuel ratio.

93
closed canopy, light levels for subcanopy leaves may be

insufficient to support a net positive Ps/Pr ratio. This

reasoning allows us o link the production of dead fuel to the

overall crowding, or foliar cover, and a site--the abundance

variable most easily assessed.

Proposed Modeling of Fuel Loads

In our current modeling work for both coastal sage scrub and

chaparral, we are incorporating the dynamics of dad fuel. In

our previous model of coastal sage scrub (Malanson 1984;

Malanson and Westman 1991), and in other models of shrub

and forest dynamics (e.g., Botkin and others 1972; van

Tongeren and Prentice 1986) growth is limited by crowding.

In our previous model, when foliar cover reaches 90 percent,

no further growth occurs in any iteration until enough

mortality has occurred to reduce cover below this threshold.

In other models, and in our own current work, growth is

limited much as population growth is limited in the logistic,

i.e., exponential growth is increasingly reduced as an upper

limit, in our case of total foliar cover, is approached. In

order to apportion this growth between live and dead fuels, it

is necessary to assume that a proportion of the growth

produced during an iteration is in replacement of a branch

that has died. We propose to set the upper limit of total

foliar cover at 150 percent on a site. When cover exceeds

100 percent, however, an increasing proportion of the

decreasing amount of growth is considered to be replacement

only (fig. 4). The increase in fuel will proceed as follows:

following fire, live growth will begin to Ii11 a site; as the site

fills, the rate of growth will slow; once the canopy closes, the

rate of growth continues to slow and much of the growth will

be recorded as an accumulation of dead fuei; no upper limit

for dead fuel is specified a priori. In this function, climate

has no direct effect on the quantity of dead fuel, but affects it

only indirectly by influencing growth.

150 ----“---111- r

Total I /

Foliar

Cover

----------

lndlvidual

Growth

Time

Figure 4. Apportionment of growth into live and dead fuel as

overall growth is limited by crowding.

Them is another route to modeling dead fuel, however. In

earlier models, individuals or proportions of cohorts die: in

the forest dynamic models, individual trees die if their rate of

growth drops below a threshold; in our earlier simulation,

mortality was a function of age. We propose to use the

threshold approach in new models of California shrublands.

If growth is reduced below a threshold as climate changes, a

proportion of the cohort, which is the unit of record in our

model, will die and that proportion of the biomass will be

added to the dead fuel category. Thus if climates become

more harsh, mortality will increase and add to dead fuel,

while simultaneously releasing extant shrubs from competition

and allowing continued growth.

In our present mode, fuel loads, both in terms of the biomass

and the live-to-dead ratio, can then be calculated in a

simulation as the growth of species responds to climatic

change. Fire behavior simulations that make use of models

like FIREMODS require a great deal of computation; it will

therefore be best to calculate a matrix of fire intensities for

fuel mixtures that vary in live-to-dead ratio, biomass, and the

content of chaparral, coastal sage, and grass species (the

different physiognomic types vary in their fuel packing and

surface to volume ratios). When a hypothetical fire is to

occur in hypothetical vegetation, the fire intensity that is

appropriate for the projected vegetation can be selected from

the matrix. In this way the feedback between fuel and

regeneration can be completed.

CONCLUSIONS

These models of species growth and fuel load cannot predict

with certainty the abundances of species in climates that do

not now exist. They can indicate the general direction and

magnitude of changes we might expect. They certainly will

help to pinpoint areas in which additional empirical work is

needed. While uncertainties do exist, it is probable that the

rates at which ecological processes operate in fire

environments and the current patterns of fire regime and of

species distributions will change with climatic change (cf.

Clark 1988). Investments in the planning and implementation

of wildland and fire management programs can be more

efficient if models of the system in altered climatic conditions

are incorporated in the planning process.

ACKNOWLEDGMENTS

This research is funded by a grant from the Environmental

Protection Agency through Interagency Agreement DN89933219-01-o with the Department of Energy. Any views

or opinions expressed here are those of the authors, and do

not necessarily reflect those of the sponsoring agencies.

94
LITERATURE CITED

Albini, F.A. 1976a. Computer-Based Models of Wildland

Fire Behavior: A User’s Manual. Ogden, UT: U.S. Forest

Service.

Albini, F.A. 1976b. Estimating wildfire behavior and effects.

U.S. Forest Service General Technical Report INT-30.

Beer, T., Gill, A.M. and Moore, P.H.R. 1988. Australian

bushfire danger under changing climatic regimes. In

Pearman, C.I., ed. Greenhouse, Planning for Climate

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regeneration strategies of Californian coastal sage shrubs

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9.5
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change on Mediterranean-type ecosystems in California

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Biological Diversity. New Haven: Yale University Press,

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postfire growth of Californian coastal sage scrub. In

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96
WILDLAND FIRE MANAGEMENT AND LANDSCAPE DIVERSITY IN

THE BOREAL FOREST OF NORTHWESTERN ONTARIO DURING AN

ERA OF CLIMATIC WARMING

Roger Suffling’

Abstract-A climatic gradient across Northwestern Ontario induces a spatial gradienl in tire incidence, with

few fires in the Northeastern part and many in the Southwestern part The resultant landscape mosaics

exhibit maximum landscape (beta) diversity with intermediate distnrbance frequency, as predicted by a

theoretical model. This implies that the results of tire suppression on landscape-scale habitat diversity differ

qualitatively, depending on previous fire occurrence. Diversity is promoted by fire in tire-free areas, and

suppressed by fire where fim occnrs frequently. Fire occurrence has fluctuated wildly, however, over

periods shorter and longer than the life span of forest trees and, with anticipated anthropogcnic global

climate warming, fire occurrence may depart from the norms of living memory. Thus the fntnre lightningfire regime cannot necessarily be regarded as an unmodified feature of the natural environment. Because

temporal variation in fire frequency makes estimation of a “natural” tire frequency almost meaningless,

wildland fire management policies should not be aimed at maintaining vegsuttion in B stale that is

represcntativc of a particular historical time. Policy objeclives can be set, however, to retain a minimum

area of each ecosystem type, with the minimum defined by reference to historical variation.

INTRODUCTION

Fire management by Europeans in North American forests has

proceeded through a number of philosophical phases: from no

management, to complcle 6~ suppression, to a mixed model

with fire suppression in some area8 under some circumstances

and fire tolerance or fire sclting under others (e.g. Dub6

1977; Elrring 1989; Van Wagner 1990). Change in attitude

has been most dramatic in some designated wilderness areas

in fire-prone regions where fire is no longer seen as

destructive and tends to be viewed as an integral component

of the natural environment (e.g. Woods and Day 1977;

Houston 1973; Van Wagner and Mcthvcn 1980; Rommc and

Knight 1983; Hcmstrom and Franklin 1983; Lopoukhinc

1991). In such areas, lircs arc okn categorized as of natural

origin and therefore to be lefi to bum if possible, or of hnman

origin and thus to be supprcsscd (e.g. Anon 1975; Elfring

1989; Sc.hullery 1989). Not everyone endorses this approach,

however, as the aftcnnath of the 1988 Yellowstone fires has

demonslratcd (Bonnickscn 1989; Buck 1989). In overtly

modified landscapes, fire is usually suppressed, but is also

used as a tool for deliberate modification of the landscape

(c.g. Rcgo and others 1988; Amo and Grucll 1986), or for

reduction of nnnatnral fuel accumulation (e.g. Wade and

others 1980; Pchl and others 1986; Birk and Bridges 1989).

There is a widespread belief that fire promotes what is

variously described as landscape diversity or heterogeneity in

both wilderness and overtly modified landscapes (e.g. Wright

1974; Romme and Knight 1982; White 1987; Hannson 1979;

Forman and Godron 1986; Lou&s 1970 ; Agce and others

1990). The Jirst part of this paper calls into question the

‘Associate Professor, School of Urban and Regional Planning,

University of Walcrloo, Waterloo, On., Canada.

universality of this notion. It is hypothesized that fire,

whether natural or otherwise, can promote landscape

diversity, but can also suppress it in definable circumstances.

These ideas arc of more compelling concern in view of

anticipated global climate change. Atmospheric carbon

dioxide concentration will probably reach double the preindustrial revolution level in the next 50 to 100 years (Bolin

1986), thus trapping more heat in the lower atmosphere.

Various general circulation models suggest that a doubled CO,

concentration will increase global mean equilibrium surface

temperature by 1.5 to 5.X in this period (Botin and others

1986; Flavin 1989; Anon 1990).

Stud& by Van Wagner (1988) and Suffling (1990) confirm

the general belief the area of forest burnt in Northern

Hemisphcrc regions is greater during warm summers. Thus

climate warming is of direct concern to fire managers, as the

fire climate will probably deviate from that of living memory.

The second part of the paper addresses possible fire

management responses to climate warming and landscape

diversity questions in wildland areas.

A MODEL OF LANDSCAPE DIVERSITY

Many landscapes, including continental boreal forests, can be

thought of as disturbance mosaics or, in more abstract terms,

as populations of ecosystems. Heinselman (1973) introduced

this notion when hc r&fined fire as normal but infrequent in

temperate forest landscapes. This led to the attractive notion

of Temperate Zone wildland forested landscapes in which

“Fire rotation controls the distribution of age classes of stands

and the succession within stands. The resulting diversity may

represent long range stability, as implied by the

9 7
517901

c

AGE CLASS

516662

AGE CLASS

Figure I --Stand age-class distributions for Northwest Ontario for four areas ranging from most fre prone (la) to least fireprone (Id). The data for the 4 graphs are stand ages of main stands since disturbance recorded on 1: 15840 Ontario Forestry

Resource Inventory maps at the 8 locations shown on figure 2. Map titles indicate longitude and latitude (e.g. 516882 =

51.6”N 88.2”W). A negative exponential curve (Van Wagner 1978) is fitted for figure la (?=O.Sl), but omitting the

“barren and scattered” category which is an amalgam of recently regenerated stands and sparsely treed areas such as rock

barrens.

98
palaeoccological record” (Wright 1974). This theory was

given quantitative form by Van Wagner (1978) who showed,

for the same Minnesota Great Lakes mixed forest landscape,

that the distribution of stand ages followed a negative

exponential curve (see figure la for an example of this

distribution). The model applies if the chance of disturbance

of any stand is equal throughout its life and if the amount of

disturbance remains substantially unaltered in the long term.

Some subsequent investigations confirmed the model (Jaric

1979; Harmon 1984), but other studies and data did not

support it, or applied inconsistently (e.g. Hemstrom and

Franklin 1982; S&fling 1983; Tande 1979; Antonovski and

Ter-Mikhaelian 1987). This is leading to increasing support

for a shifting-state concept of forest landscape. These latter

results tend to demonstrate what palaeoecologists have long

claimed, that the area1 amount of disturbance fluctuates

widely over time, not only in the short term, but also over

periods as long as or longer than the life span of individual

trees (e.g. MacDonald and others 1991; Romme and Knight

1982; Romme and Despain 1989). Figure 1 shows a typical

range of age-class distributions encountered in Northwest

Ontario, Canada, where change in fire occurrence over time

disrupts the negative exponential pattern, especially where the

overall fire return period is long, as in figure Id.

The disturbance mosaic can be used to calculate the landscape

diversity, or beta diversity associated with differences

between stands in the mosaic (Suffling 1983). This diversity

has a richness component (essentially the number of kinds of

stand), and an evenness component expressing the relative

amount of different kinds of forest (Suffling and others 1988).

The two measures are commonly combined in the Shannon

equation (Shannon 1948).

Landscape diversity is a function of inherent differences

between sites based, for instance, on aspect or drainage. It

also depends on the forest age class distribution that has been

created by disturbance. Simulation models of stand-age

distributions over time predict that landscapes with

intermediate frequency of disturbance should have higher

landscape diversity than those with very frequent disturbance

and those that have almost no disturbance (Suffling and others

1988). This is the case whether fire occurs equally in a)1 age

classes or is concentrated on older ones.

The continental boreal forest of Northwest Ontario (fig. 2)

was used to test the model (Suffling and others 1988). This

huge, more-or-less flat glacial peneplain, exhibits spatial

climatic variation that is little affcctcd by altitude, and its

95’ 85’

I

\

HUDSON BAY

Figure ~--TIE location of the study area in Northwest Ontario

99
geology is sufficiently uniform that climate variation begins to

show consistently across the landscape. The area ad.jaccnt to

the Hudson Bay Lowland is cooler and more humid than that

against the Manitoba border. The amount of fire reflects this

climatic variation, grading from a high of over 1 percent of

land area burnt per year in the Southwest to almost no fire at

all in the Northeast (Fig. 3). Most fires arc stand-replacing

crown fires, and the size of the disturbance patch created can

vary from less than 1 to over 100,000 ha. There has, thus far,

been very little logging in this area.

The fire gradient induces a clinc in vcgctation. Forests in the

southwest arc generally young and are dominated by fireadapted jack pine (Pinrrs hkrimm Lamb.) and aspen

(Popuh lrelnrJoides Michx.). Those in the northwest arc

generally much older and balsam fir (Abies balsarneo (L.)

Mill.) and white spruce (Piceo glurtco (Mocnch) Voss) are

much commoner there (figs. 1 and 4). In the center of the

region, a mixture of these forest types prevails (Suffling

1988). Measurements of landscape diversity (fig. 5) confirm

the theoretical predictions that diversity will be highest in the

center of the area, where frequency of disturbance is

intermediate (Suffling and others 1988).

EFFECTS OF PRESCRJRED FJRE AN-D FIRE

SUPPRESSION ON LANDSCAPE DIVERSITY

Predictions that the model generates, and the empirical

confirmation of its applicability, justify several generalizations

concerning fire management. In a landscape with little

previous disturbance, prescribed burning will increase

landscape diversity by creating patches of immature habitat in

the primarily mature mosaic. Conversely, application of more

fire in an already frequently burnt landscape will reduce the

diversity of the landscape. In a landscape previously

experiencing intermediate disturbance that has produced

maximal landscape diversity, either tire suppression or

increased prescribed or natural fire will reduce the

landscape’s diversity.

Land managers are thus faced with a problem: Promoting

maximal landscape diversity is not necessarily synonymous

with keeping an area pristine. By managing for some primeval

wilderness condition with a different tire occurrence from the

present one, a manager might actually reduce landscape

diversity. In reality, howcvcr, many wildland areas have for

many years been managed under tire exclusion policies that

have climinnted or reduced both lightning tires and aboriginal

burning patterns (Barrett and Amo 1982; Lewis 1977). and

have tended to result in a bell-shaped distribution of stand

age classes (Van Wagner and Methvcn 1980).

1.00

ale

2 ’

- 0.5

am

w-0

n

5 0.25 -1

ROCK BARRENS

,ESKERS AND LAKE AGASSIZ SHORE

EDGE OF HUDSON

BAY LOWLAND

0.20

0.15

0.10

0.05

Figure 3--The gradient in fire occurrence across the study area in Northwest Ontario. (Aher Suffling and others 1988)

100
COMMUNITIES AS Z TOTAL FORESTED AREA

Total Barren and Scattered

!!?I Minor communities

B

Poplar/Jock pine

Es3 Jack pine/Black spruce

Black spruce/Jack Pine

Slack spruca/‘Poplar/White birch

DEGREES WEST

Figure 4--The change in community composition of forested upland sites

across the study arca in Northwest Ontario.(Akr Suffling 1988).

Y * -2.16 -2.16 Inx- 0.34(lnx)*

PC 0.025

r*- 0.83

PROPORTION Of ‘AND AREA BURNT PER 2Oyr PERIOD

0.025 0.05 0.075 0.1 0.25 0.5 0.75 1.0 2.5

% LAND AREA BURNT PER YEAR

Fig. S--The relationship of landscape diversity (Shannon’s H statistic) in the Northwest Ontario

study area, to disturbance by forest fires (A&r Suflling and others 1988).

101
FIRE MANAGEMENT IN AN ERA OF

CLIMATE CHANGE

The policy of allowing natural fires to bum while suppressing

human-caused tires (if they can be recognized as suchl) rettcs

on Q prcmisc that the cIimate that starts fires or encourages

them to spread is an unmodified component of the natural

system. Now, however, there are predictions that climate will

be anthropogenically warmed. The amount of change is

dcbatcd and the “control” situation without greenhouse

warming is not clearly definable for several reasons: First,

natural climatic fluctuation will certainly occur anyway.

Second, we presently have much less reliable information

about anthropogcnic change in precipitation than we do about

temperature. Third, regional forecasts from the present

generation of general circulation models (GCM’s) are not

thought to be very accurate, and good regional analogues of

GCM’s will be 3 to 5 years in the making. Fourth, there is

the possibility of deliberately ameliorating anthropogenic

climate change, but it is generally agreed that some warming

is now inevitable. The “predictions” are thus scenarios. Those

who make them are under no illusion that they represent

anything other than options or a range of possible futures.

Given these complications, one can only be reasonably sure

that there will be more fire in many forest regions than is

natural, so that a “let bum” policy will no longer promote a

natural tire regime. There will be changes in the relative

amounts of different habitats, in landscape diversity, in the

kinds and amounts of fire ecotone, and in the spatial

relationships and patch sizes of different habitats (Suffling and

others 1988; Turner 1989; Turner and others 1989).

The wildland tire manager’s first reaction might be to attempt

to control fires to an extent that approximates the historical

pristine condition (e.g. Hawkes 1980), so as to preserve a

“vignette of primitive America” (Leopold and others 1963).

The development of landscape-based fire ecology models (e.g.

Hcinselman 1973; Wright 1974; Van Wagner 1978; Johnson

and Van Wagner 1985; Parks and Alig 1988) gave much

theoretical support to this philosophy. However, considerable

research aimed at defining a pristine condition (either today’s,

or an earlier era’s), has ofien demonstrated that there has

been considerable variation in fire occurrence even the last

hundred years (e.g. Romme and Despain 1982; Suf%ling

1988). Thus, the objective of recreating the pristine has been

reinterpreted as not... Yrying to hold nature steady but rather

maintaining natural dynamics and discouraging anthropogenic

deterioration” (Ness 1987). Where one is able, however, to

assemble a history that predates the end of the little ice age

(1820- 1835 in many areas of North America), the variation

between present and the fire past regimes is sufficiently

enormous to render unworkable even NOSS’ interpretation of

Leopold’s concept.

Fire records from Northwest Ontario demonstrate this clearly,

Government records provide a history of tire only since 1926

(fig. 6) and demonstrate a steady diminution of fire until the

1940’s. Except in 1961, a disastrous fire year, very little

forest was burnt until 1974. Fire areas increased dramatically

thereafter in response to some of the warmest and driest

summers of this century.

Because of the fierce, stand-replacing nature of fires in this

region, it is difficult to establish a reliable quantitative history

from fire scar information. Our attempts to establish a

regional fire history from charcoal in lake sediments have

proved fruitless because varves are not formed in the area’s

oligotrophic lakes. Fortunately, however, historical

information from Hudson’s Bay Company fur trade journals

for Osnaburgh House spans the period from 1786 to 19 11,

and demonstrates a massive outbreak of forest fires in the

1820’s, a relatively quiescent period from 1830 to 1860, and

then a steadily increasing tire incidence until the turn of the

century. While much of this variation was climatically driven,

we know that a large proportion of the recorded tires were

started by people (SuMing and others in press), and that this

activity was intimately bound up with economic, social, and

attitudinal changes associated with the fur trade. This

information on the temporal distribution of fires tallies well

with the stand-age distributions for this area (fig. 1) that show

many present-day stands dating from between 1860 and about

1900. (The data for figure 1 largely predate the post-1974 fire

outbreak, so this latter outbreak does not show on these

figures).

If one wished to manage the fire regime of this Northwest

Ontario area, what information base should be used to identify

the “natural” condition? The present high fire activity is

anomalous if considered in the context of the period of

government statistics from 1927 to the present, and would

thus require suppression, but the current increase in fires is

driven by climatic variation rather than by some change in

human-set fires. (We do not yet have the advantage of

hindsight, however, and cannot say whether the recent fire

outbreak is lust a major fluctuation, or represents the

beginning of anthropogenic climate warming). Conversely, if

one used the stand age distribution to establish a “natural”

baseline, one would conclude that fire was virtually absent

from the 1920’s but was common before that. If one used the

Hudson’s Bay Company record (which does not allow a

quantitative determination of fire frequency), one could use

the low fire period at the end of the little ice age or the high

fire period of the 1820’s (though there is a strong suspicion

that numerous large fires of the 1820’s resulted from both

climatic influence and human activity). Alternatively, one

could pick any of the subsequent high or low fire eras.

102
% 601 a

5 0

F

I 4 0

R

E 3 0

umerous unrecorded fires in 1820’s

D 2 0

A

Y 1 0

S

0

1800 1820 1840 1860 1880 1900

T

1930 1940 1950 1960 1970 1980

b

i

Fig. 6- Historical variation in fire occurrence in Northwest Ontario. a: Fire occurrence as reprcscnted by “fire days”

(Suffling 1988) at Osnaburgh House. b: Ontario government statistics for area burnt in the Kenora District, 1927-1989

(Ontario Ministry of Natural Resources 1928-1990).

It is possible that the outbreaks of fire in Northwest Ontario

follow about a SO-year cycle, with high fire eras in the

1820’s, 1870's, and 1980’s. There is little information for the

early 1920’s but oral tradition suggests that fires were

frequent at that time. Data from other regions support the

possibility that cyclical fire occurrence is commonplace at a

landscape scale. Charcoal fragment counts in varvcd lake

sediments in the boreal forest of Wood Buffalo National Park

in Canada’s Northwest Tcrritorics (MacDonald 1990 pcrs.

comm.) imply a 100 to 300 year cyclr: of fire in the landscape

over a 2OOJl year period. Similarly, the conifer forests of the

Yellowstone Plateau in Wyoming have experienced long

quiescent periods punctuated by major cyclic fire outbreaks

about every 300 to 400 years, as in 1988 (Romme and Knight

1982; Rommc and Despain 1989). Current research on the

effects of spatial landscape patterns is beginning to explain

these temporal variations (Antonovski and Ter-Mikhaclian

1987; Turner 1989).

In none of the cases noted above is there any indication that

the major fire oulbrcaks arc merely extremely large events in

a stochastic series. In each Case, fire occurrence appears to

have “flipped” bctwecn high nod low states without the

appearance of 211 intermediate condition. Thus, adoption of an

average lirc return period would be arbih;uy, and would not

mimic nature. Likcwisc, any attempt to “fix” the la&cape

adopting a particular fire frequency from a high or low fire

period will be unnatural.

103
How can the fire manager resolve this dilemma? One

approach is to identify acceptable limits of variation in the

disturbance mosaic over time -an ecosystem supply strategy.

For instance, if one decides that it is desirable to retain some

mature stands of jack pine over 100 years old, tire

management policy can be tailored to protect such stands if

their total area falls below a defined limit represented by a

certain percentage of potential jack pine site area. Conversely,

one might set prescribed bums in potential jack pine areas if

the total area of jack pine under 20 years old were to fall

below a defined limit. Acceptable limits could be set on the

basis of the historical representation of ecosystem types in the

landscape, on aesthetic or other cultural values, or on the

need to preserve certain ecosystem types for their valued flora

or fauna.

CONCLUSION

Fire managers should not assume, a that forest fires

(or, for that matter, any other patch disturbance) will

increase landscape diversity, or that they will reduce it. The

effect of fire on landscape diversity depends on the current

status of the landscape mosaic and, thus, on previous

disturbance. Because global climate warming will increase

forest fire occurrence in the boreal and other biomes,

wildland fire managers should no longer assume that the

lightning fire regime as non-anthropogenic. The timing and

extent of increase in fire, as well as the “control” fire regime

that might occur without global climate warming arc currently

unknown. One might wish to maintain the status quo in

wildland areas in terms of proportions of different ecosystem

types. However, these proportions shift constantly over time,

even at the landscape scale, in response to natural climate

variation and the spatial pattern in the landscape (Antonovski

and Ter-Mikhaelian 1987; Turner 1989), which links to

endogenous fuel processes. Thus, one must decide what fire is

to create and what to protect from tire. This can mean

determining what minimum area of each ecosystem type

should exist in the landscape. Such definitions can be based

on the status quo, on historical variation, or on culturally

defined values. Sadly, in an era of climate warming the ethic

of leaving nature to continue without human interference

becomes illusory.

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history of Desolation Peak, Washington. Canadian Journal

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modelling of long-term fire dynamics. IIASA Working

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Amo, S.F.; Gruel], G.E. 1986. Douglas fir encroachment

into mountain grasslands in southwestern Montana.

Journal of Range Management 39:272-276.

Barrett, SW.; Amo, S.F. 1982. Indian Fires as an ecological

influence in the Northern Rockies. Journal of Forestry

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Birk, E.M.; Bridges, R.G. 1989. Recurrent fires and fuel

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Bonnicksen, T.M. 1989. Nature vs. Man(agement): “Fire” is

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Buck, B. 1989. A Yellowstone critique: Something did go

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Hawkcs, B.C. 1980. Fire history of Kananaskis Provincial

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106
HAZEL PISTOL EROSION PLOT STUDY

ON THE SISKIYOU NATIONAL FOREST IN SOUTHWEST OREGON

William F. Hansen’

Abstract-In November 1977, small erosion plots were installed on 30, 50 and 70 percent slopes following

forest management activities in southwest Oregon. Activities included clearcutting using a skyline yarding

system, followed by burning to reduce logging debris and hardwood competition in 1976. Little of the soil

was exposed prior to burning because one end of the logs was suspended during the yarding operation. The

burning intensity was severe due to the high amounts of logging debris and the relatively dry conditions

with low fuel moistures. AAer burning, mineral soils were exposed on over 75 percent of the area.

Rainfall measured 111 and 150 inches after 3 months and 12 months, respectively. Surface runoff and

erosion leaving the plots were collected and measured. Some data loss occurred due to pipes plugging or

container overflow. During the first 3 months, surface runoff measured from the burned area varied from

27.6 to 33.4 inches on 30 percent plots, 35.0 to 51.6 inches on SO percent plots and 43.9 to 44.3 inches on

70 percent plots. The unburned 70 percent plots had water movement of 22.4 to 34.2 inches. Soil loss

(<2mm) was 2.02 to 3.57 tons/acre on 30 percent plots, 2.18 to 5.89 tons/acre on SO percent plots and

4.04 to 18.68 tons/acre on 70 percent slopes. Plots on 70 percent slopes within the clearcut area that were

not burned had erosion ranging from 1.26 to 3.09 tons/acre. Surface tunoff and erosion figures after one

year are also presented. The magnitude of erosion was partly due to wind-driven rains near the Pacific

Ocean and the highly erosive siltstone soils of the Dothan Formation. This study was heipfbl in changing

attitudes about the effects of burning and requiring burning prescriptions that protect soils (e.g., by burning

under conditions with greater fuel and soil moistures or requiring more fuel removed during the yarding

operation), Visual indicators of surface erosion and methods for minimizing or mitigating the effects of

prescribed burning are also discussed.

INTRODUCTION

Relatively little information was available on surface erosion

quantities following forest practices in southwest OrCgOfl

when this study was conducted on the Siskiyou National

Forest (SNF) in 1977 and 1978. During that time, the SNF

was a leader in developing and implementing technology to

reduce environmental impacts from forest practices.

Resource values and constraints were extremely high with

steep slopes covered with old growth Douglas-fir

(Pseudotsuga menziesii) and beautiful streams with some of

the most valuable salmon and steelhead habitat in the nation.

Prior to the study, the Siskiyou National Forest had identified

many sensitive environmental issues. In response to the

critical issues, forest practices were being carefnlly

scmtinized to reduce environmental impacts. Road

construction was a primary concern because of its potential

effects to the soil, water and fishery resources. Access roads

were typically kept near ridges to avoid stream crossings and

reduce surface and mass soil movement into streams. Side

casting of soils during road construction was minimized or

even hauled away in very steep terrain. An aggressive

program to provide road surFace drainage and to revcgctate

the bare soils adjacent to roads was also being implemented.

Skyline yarding systems, which partially or totally suspend

‘Forest Hydrologist, National Forests in South Carolina and Georgia,

Forest Service, U.S. Department of Agriculture, Columbia, S.C.

(formerly Forest Hydrologist on the Siskiyou National Forest in

Grants Pass, Oregon).

logs on steep slopes or in streamside areas, were being

successfully used to reduce the logging impacts associated

with conventional ground-based skidders on steep slopes.

Fire management practices were addressed after the major

contributors to erosion and stream sedimentation had been

identified and were being reduced. The effects of

post-logging bums became a concern of watershed specialists

during monitoring trips on the SNF. Observations causing

concern included loss of surface organic layer, exposure of

mineral soil, soil pedestals, fresh silt in streams, and turbid

water during storm events. Burning practices and attitudes

about burning would be difficult to change without some

evidence to back up observations. The challenge to “prove

it” or at least “measure it” was a necessary and reasonable

request by the unconvinced majority.

The concerns about erosion following Prescribed burns would

have been reduced if erosion was not measured under severe

conditions. The SNF was an ideal testing ground to measure

erosion in the late 1970’s, and severe conditions following

prescribed bums were not hard to find. The usual objectives

of burning were to reduce heavy fuel loading from logging

debris and to reduce competing vegetation with the next

generation of Douglas-fir seedlings. These objectives were

usually accomplished with hot burns, in the summer or early

fall. Soil litter and the organic layer were often consumed

107
To the untrained eye, overland flow and erosion were not

problems because the streams usually carry little sediment.

Soil erosion and water quality changes occur rapidly in

response to rainfall intensity and duration. These procasrer

are not easy to measure. Small plots were chosen to collect

surface runoff and erosion realizing potential problems with

variability within an area and impact from the plot edge.

Advantages included the low cost, ability to collect and

measure all the soil and water leaving each plot and ease with

which photos could be used to show plot and sampling details.

D‘ESCRI IVON OF THE STUDY

Location

The study was conducted on the Chetco Ranger District of the

SNF in southwest Oregon, (specifically the north side of unit

2 of the Hazel-Pistol timber sale, Township 38S, Range 13W,

section 28, NE 114 of the SW 114, Willamctte Meridian).

The study area is about 8 miles from the Pacific Ocean in the

Pistol River basin between Brookings and Gold Beach,

Oregon. The aspect was generally southwest to southeast.

Background Information

Following clear-cutting using skyline yarding with one-end log

suspension, the unit was burned in the fall of 1976 to reduce

fuel residue and vegetation competition. Although not

measured, over 7.5 percent of the mineral soils were exposed.

Unusually dry conditions persisted until the fall of 1977 when

the plots were installed.

The coastal landscape is typically deeply dissected by streams

with boulders, bedrock or debris, which prevent further

channel degradation (downcutting). Adjacent slopes often

have high potential for erosion or instability due to soil

materials, high rainfall, steep slopes and loss of support from

channel erosion. The soils are also extremely complex due to

numerous geologic changes. Average annual rainfall is over

100 inches (2.5 m) for much of the National Forest. Dry, hot

summers with periodic lightning storms and burning by early

natives and settlers have caused many past wildfires. In many

cases, the litter layer and organic surface soils are shallow to

non-existent. High decomposition rates and erosion are

contributing factors. Such harsh site conditions present

rcvcgetation and regeneration problems, especially on the

south-facing, skeletal (gravelly) soils. The study area selected

has some of the most severe conditions on the SNF and in

Oregon.

Geology and Soils

The bedrock of the study area consists of bedded layers of

moderately hard s&stone, massive to slightly fractured

mudstone and sandstone rocks of the Dothan formation. The

soils were derived from colluvial and residual material. Soils

of the area are primarily thin gravelly loams on slopes over

40 percent and thick silt and clay loams on slopes under 40

percent. Slopes in the unit are locally highly dissected and

range from 20 to 90 percent, The soils arc moderately

unstable and highly erosive.

Climate

The temperature extremes of cold winters and hot summers in

southwest Oregon are moderated somewhat due to the close

proximity to the Pacific Ocean. Warm, moist air masses are

cooled as they are pushed upward by the coastal mountains.

At an elevation of 2600 feet and only 8 miles from the coast,

the study area is subject to high wind speeds and

precipitation. Winds typically blow from the west to

southwest with speeds occasionally exceeding 50 miles per

hour. The average annual precipitation for the study area is

estimated at over 125 inches and occurs primarily between

November and May. Rainfall events are usually long

duration with low to moderate intensity. Temperature

differences from the coast may be present when the coast is

fogged in and the study area is clear. Winter freeze-thaw

cycles occur with few snow events.

METHODS

Experimental Design

The sampling methods were designed to test the effectiveness

of grass seeding in reducing water movement and surface

erosion on an area clearcut and broadcast burned. The

experimental design was a 3 X 2 factorial analysis with one

replication, or 12 plots total. The factors varied were slope

and grass seed. Slopes used were 30, 50 and 70 percent and

grass seeding was either 0 or 7 pounds per acre.

Plot Design

The plot boundaries consisted of 2 X 4 lumber with a 2 X 8

for the upper boundary. Each plot was designed to be 112500

of an acre (17.4 square feet) and the plot dimensions varied

according to the slope. Each plot was drained into 6 inch

fascia gutter scraps along the lower boundary. The gutter

with end caps was nailed to the wooden boundary with the

gutter lip bent down about 112 inch. The wooden boundary

with gutter was eased into the correct position on the plot and

staked to the ground at several locations outside the plot. The

bent gutter lip was pressed into the soii. On the outside of

the wooden boundary, a small ditch about 4 inches deep was

constructed and filled with concrete to provide a good seal to

prevent surface water from entering or leaving. Concrete was

also placed by hand above the bent gutter inside the plot to

prevent water from bypassing the gutter. A small trench

above each plot diverted other runoff away from the plot.

Soil and Water Measurements

Surface water from the plot drained into a 55 gallon drum

using 3/4 inch black plastic tubing. However, after

continuous clogging problems, 1 l/2 inch black plastic tubing

was installed. Plastic tubing fittings were used to go from the

gutter into the 55 gallon drum lid, A 500 ml plastic bottle

was placed over the tubing outlet to collect the heavier

sediment. The lighter sediment was collected in the drum

with the water from the plot. The water in the drum was

measured, mixed and sampled. The concentration in the

108
sample multiplied by the volume in the drum gave the amount

of sediment in the drum. Larger or heavier materials oRen

settled out in the gutter. This material was collcctcd, ovendried, sieved into soil ( < 2mm) or large. particles ( > Zmm),

weighed separately and added to the estimated sediment from

the drum. Large particles included rocks or pebbles,

Douglas-fir cones, needles, leaves and other debris. The

collection gutters were cleaned out in February 1978 and

November 1978, respectively, approximately 3 months and 12

months afier installation. Rainfall mcasurcmcnts were made

using a Belfort recording raingage. Under $5,000 was spent

to collect this information.

RESULTS AND DISCUSSION

Some adjustments in the data analysis had to be made due to

unforeseen problems. The grass failed to germinate properly

within the plots and only scattered depressions had any

success. Two plots were accidently located on an unburned

portion of the burned unit. Another plot flooded with water

and filled with sediment from an ephemeral microchannel

which had not been diverted away from the plot. Lost data

from plugged tubing and drum overflows from large storm

events posed additional problems. The statistical efticicncy of

the factorial plot design was lost with these problems, but the

information collected provided valuable insight to surface

erosion and water movement atter typical forest practices of

the time.

Information was intensively collected on the study plots from

November 11, 1977 to February 22, 1978 (104 days).

Fourteen separate rainfall events were identified during this

period, ranging from 1.1 to 18.4 inches. Rainfall totaled 11 1

inches (2.8m) Average storm intensities were less than 0.25

inches per hour, while peak Z&hour intensity reached 0.82

inches per hour. During the first year, over 143 inches of

rainfall was measured and about 7 inches was estimated, for a

total of 150 inches (3.8m).

Figure 1 presents data to compare rainfall and runoff by plot

slope and treatment for only those dates when collectors did

not plug or overtlow. There were a few discrepancies when

runoff exceeded rainfall (the raingage opening was level while

the plot openings were not) during individual storms.

Whether the raingage caught less of the windblown rain, or

the plots caught more, is not known. The amount of overland

flow from the plots was alarming and provided strong

evidence that surface erosion mechanisms existed. The

following table presents the measured rainfall and runoff

summarized at two points in time over a year. Since the

collectors occasionally plugged or overflowed, estimates of

runoff are low by approximately 10 percent for all treatments,

except the 70B treatment data are 30 percent low.

Time Period Time Rainfall Average Plot Runoff (in) by Treatment

(months) (in) 308 SOB 709 7ou

11/77-2178 3 4 111 30.7 41.8 44.1 28.3

11177-1 1178 12 IS0 57.8 71.5 63.8 48.8

(30, 50, 70=% slopes, B=Bumcd, U=Unhumed, 1 in=2.54 cm)

Figure 2 presents the measured erosion by treatment for the

one year. Due to collection problems, some data was

probably lost. The amount lost is believed to be much less

than the amount of runoff lost because the gutters were

effe&e sediment traps when pipes clogged. The following

table summarizes soil and total erosion after 3 months and one

year.

Time Period Time Rainfall Total Erosion (tons/at) by Treatment

(months) (in) 308 SOB 70B 7ou

1 l/17-2118 3.4 III IS(2.7) 4.6(5.8) 11.4(20.0) 2.20.8)

11177-l 1178 12 150 3.8(4.3) 6.1,(9.1) 12.8Q2.2) 2.7(6.0)

(same symbols as previous table, 1 ton/acre = 2240 kg/ha)

Poor record keeping after November 1978 made the data

collcctcd atier one year questionable. However, visual

indications of continued surface water and erosion occurred

because vegetative cover was slow to develop. In 1983,

seven years after the bum, signs of accelerated erosion of

litter, mineral soil and rock fragments on the 70 percent

unburned plots were disturbing.

Several types of erosion processes were observed on the area,

including raindrop, sheet, and fill erosion. These were

detected or inferred by close observations during intense

rainfall pe&ds or inspection during the study period on the

erosion plots.

Raindrop erosion occurred when large amounts of kinetic

energy were expended on the soil surface by falling

raindrops. In an undisturbed forest, vegetation and litter

absorb this energy. Soil particles exposed during

management activities are susceptible to detachment by the

raindrop impact. The wind driven rain supplies additional

velocity and energy. Raindrop erosion may clog surface

pores thereby reducing infiltration. Soil pedestals formed

under the protection of pebbles or wood were another

indicator of soil remaining in place when shielded from

raindrop impact.

Sheet erosion occurred as thin layers of surface materials

were gradually removed. This was noticed as a fine root

network was eventually exposed on the 30 percent plots.

Larger roots and gravel were also exposed on the steeper sites

as tines were removed. Soil delivery to the collection device

was diffuse and defined water movement was difficult to

observe.

Rill erosion was apparent during one heavy rainfall event on

plot 6 (70 percent bum slope). Microchannels no more than

an inch in cross section developed. Soil was being removed

by running water of sufficient volume and velocity to generate

109
I Figure 1

CUMULAT1[VE RAINFALL AND RUNOFF

BY TREATMENT FOR SELECTED DATES

46 i

6

' 0 - w *I I I

0 8 74 81 101 116 1SS 144 167 ml 188 186

SELECTED OBSERVATION DATES (DAY)

LEGEND

RAINFALL B n BURNED

RUNOFF 3oB u - UNBURNED

- RUNOFF SOB 30, 60, 70 - PERCENT

SLOPE

a m - - - RUNOFF 7oB

- 4- RUNOFF ‘7OU

110
lI(

4t

4C

88

8 C

su

*a

1 6

10

6

0

Figure 2

SOIL EROSION BY SLOPE

AND TREATMENT 11177 TO 11/78

8OB 6OB ‘?oB TOO

SLOPE Cperoent)

LEGEND

[--‘-I COARSE >8mm B - BURNED

@Z@B SOIL 4mm U = UN BURNED

130, 60, 70 - PERCENT SLOPE

.I-
cutting power. As the soil particles eroded away, pebbles and

small rocks could be seen and heard tumbling down the slope

as they were moved by water and gravity.

Other visual observations of erosion were made outside of the

erosion plots, within the harvest unit. Examples of exposed

roots could be found on all slope classes. Fine roots were

often exposed on 30 percent slopes and larger roots were

sometimes exposed on steeper areas. These roots were not

tire scarred and were apparently buried at the time of the

prescribed bum. Fire scars on trees were occasionally above

the soil surface, indicating measurable soil erosion. An

increase in surface rock content was noticeable on slopes

exceeding 50 percent or more. Soil deposition occurred in

surface depressions, above woody debris and in pool areas

within the stream channels. Soil protected from the bum

under large woody debris or rocks had about l/2 to 1 inch of

litter and organic soil. Small rocks were suspended on soil

pedestals. Streams would rapidly change in turbidity and

sediment loads in response to rainfall intensity.

Part of the results include management’s reaction to

information collected on the study area. This study was an

eye opener to forest managers, who previously perceived that

surface erosion and overland flow effects were negligible

following prescribed burning. After some initial deliberations

and reactions to change, adjustments were made to strengthen

the prescribed burning program.

Prescribed burning plans were adjusted to protect the surface

soil and organic layer, including its ability to take up and

store water. Burning is accomplished when the duff layer is

moist (usually a few days after a soaking rain in the spring).

Directional falling of the old growth trees on steep slopes

reduced breakage of logs, prevented high debris loads in

streams and increased the tree utilization. Required yarding

of unutilized material (YUM), is another method to reduce the

logging waste and fire intensity.

Burning specialists began to receive additional training in

measuring weather, fuel moisture, fuel load, and flame height

values to reduce tire impacts to soil resources. Strategies

such as helicopter lighting also reduced fire intensity.

Monitoring post-burning conditions also help evaluate the

bum. When areas are accidently burned too hot, grass

seeding with fertilization helped mitigate burning effects. The

grass species mixture can help provide

immediate cover needs with soil improvement and wildlife

benefits.

CONCLUSIONS

This study was undertaken to document the presence or

absence of surface runoff and erosion following typical

&.arcut and prescribed burning practices in southwest Oregon

during the late 1970s. Severe conditions were chosen to lest

whether surface runoff and erosion were valid concerns. The

effects of using grass seeding as possible mitigation was not

possible because much of the grass was apparently lost due to

erosion. During the intensive l&&day study of the burned

area, Ill inches of precipitation occurred, producing surface

runoff in excess of 30 to 50 inches and soil erosion from 2 to

over 18 tons/acre. In contrast, the steep unburned areas

produced substantially less runoff (20 to 30 inches) and soil

erosion (1 to 3 tons/acre).

The results of this study convinced forest managers that some

adjustments in prescribed burning practices were needed to

protect soil, water and tishery resources. Resetting burning

objectives to protect these resources was the first step.

Methods designed at minimizing potential impacts to both

onsite resources, such as soil productivity, and offsite

resources such as downstream water quality, fishery habitat

and air quality, were included in prescribed burning plans.

Practices were implemented to reduce me1 loading through

greater utilization and adjust burning intensity to protect soil

resources.

Burning is a useful and necessary tool in forest management,

but it can cause unacceptable adverse impacts if not properly

applied. With adequate planning, timber harvest and burning

practices can be adjusted to achieve soil and water resource

objectives, with good success at residue abatement and

temporary vegetation control. Soil, slope, climatic and

historic land use factors should be assessed to help evaluate

the erosion potential of an area prior to burning. When

burning under conditions with severe erosion potential cannot

be avoided, aggressive efforts to revegetate exposed mineral

soils are needed.

Despite the limited application of small plot studies, they are

helpful in this case to identify and measure site specific

processes that arc difficult to measure on a large scale.

However, several factors should be considered before

applying the results of this study to other conditions. The

presence of abundant wind-blown rain, highly crodiblc soils,

steep slopes and exposed mineral soil from a combination of

forest logging and burning practices were all important

contributing factors in the severity of the study results.

ACKNOWLEDGEMENTS

Foremost, I recognize and thank Malcolm Drake, Hydrologic

Technician, for his valuable assistance and hard work in the

installation and service of the plots. Other USDA-Forest

Service employees that I want to recognize include John

Millet (retired), encouraged and supported this study; Harvey

Timeus, Joe Waller, and Ed Gross, Chetco Ranger District,

helped service the erosion plots; Roy Meyer and Mike

Amaranthus, described the soils; Bob Ettner, encouraged

reporting of these findings; Luis Mundo helped with the

computer graphics and Lynda Hansen helped with typing and

editing.

112
THE SIGNIFICANCE OF FIRE IN AN

OLIGOTROPHIC FOREST ECOSYSTEM

Frank S. Gilliam’

Abstract-Past and prcsenl climate conditions have interacted with soil development to result in distinctly

oligotrophic (nutrient-poor) conditions in many southeastern U. S. Coastal Plain ecosystems. Fire

historically has been an important ahiotic component in these systems favoring the dominance of plant

species which require fin: for successful regeneration and growth. This study examined the role of periodic

fire in several components of an oligotrophic lower Coastal Plain pine flatwoods ecosystem. Except for

some loss of nitrogen (N) from the forest floor, experimental bums had slight effects on nutrient loss from

the system. Fires volalilizcd an average of 24 kilograms N per hectare. Much of this loss is halanscd by

annual net (precipitation input minus stream flow output) ecosystem increases in N. Fire increased nutrient

availability in the soil, an increase which coincided with increases in the biomass and species diversity of

the hcrhaccous layer. Thus, fire is important in maintaining nutrient availability in these nutrient-poor

soils. Evidence presented in this study support the idea that pine flatwoods arc especially Iimited by

phosphorus (P) and potassium gc) availability and that iire signiiicanlly increases available lcvcls of P and

K in the soil. Fire is considered here a characteristic property of the ecosystem, one which integrates all

hierarchical lcvcls of organization of the system.

INTRODUCTION

General hypotheses concerning the importance or role of lire

in ecosystems appear difficult to make, given the great variety

of ecosystem types wherein lirc occurs at a sufficient

frequency to bc considered a component of lhe system. It is a

reasonable hypothesis, howcvcr, that a predominant role of

fire, regardless of ecosystem type, is lo increase or maintain

the availability of an essential (usually growth-limiting)

resource, either energy (sunlight), nutrients, or water. The

specific role of fire would be dctcrmincd by which I’CSOUI’CC,

or combination of rcsourccs, is limiting in a particular

ccosystcm. For example, in tallgrass prairie, which has

nutrient-rich soils, but experiences substantial build-up of

plant detritus which intercepts both light and water, fire

appears to be important in maintaining availability of energy

and water. but not nutrients.

The Coastal Plain of the southeastern United States has long

been a region of great interest to fire ecologists, as cvidcnced

by earlier reviews by Wells (1943) and Garrcn (1943), and

more rcccntly by Christensen (1981). This is a region

whcr& past and present climatic factors have influenced soil

dcvclopmcnt in a way that resulted in oligotrophic (nutrientpoor) conditions (Gilliam 1990). Such conditions have, in

turn, favored the dominance of plant species, such as pines,

which require fire for successful reproduction and growth.

These species, adapted to low soil fertility, product acidic,

low-nutrient detritus, thus maintaining oligotrophic conditions,

a scheme that represents co-development of biotic and abiotic

components of the ccosystcm (Jenny 1980).

‘Assistant Professor of Biological Sciences, Marshall Univcrsi~y,

Huntington, WV

The main ohjcctivc of this study was to examine the effects of

tire on several components of a pine flatwoods ecosystem of

the lower Coastal Plain of South Carolina. These results

were used to address the hypothesis that tire, as an integral

part of the system, serves a significant function in increasing

nutrient availability. A second objective of this study is to

look at the specific role of tire at each hierarchical level of

organization of the system (ecosystem, community, and

population) to address the contention that fire is

“incorporated” (sensu O’Ncill and others 1986) at the level of

rhc ecosystem.

In addition to the presentation of previously unpublished data,

this paper provides a brief synthesis of several aspects of the

Santee Watershed Study. These include studies on the effects

of fire on water quality (Richter and others 1982, 1984),

precipitation chemistry (Richter and others 1983). soil

n&en& (Gilliam and Richter 1985, 1988; Gilliam 1990), and

effects of fire on hcrbaceous layer vegetation (Gilliam and

Christensen 1986; Gilliam 1988).

MATERIALS AND METHODS

Study Site

The study was carried out on Watershed 77 (WS77) of the

Santee Experimental Forest. This forest is within the Francis

Marion National Forest in South Carolina, approximately 50

kj]omctcrs north-northwest of Charleston (33”N, 80%‘).

WS77 is 165 hectares in area and is typical of lower Coastal

Plain pine flatwoods ecosystems. Topographic relief of this

and other first-order watersheds of the region varies by 5.5

meters. Prior to the start of the study, WS77 had not been

burned for 40 years.

II3
WS77 soils are clayey, mixed, thermic, v&c Aquults of the

Bayboro, Bcthera, Carolina, and Wahee series. Although

these soils are of mixed mineralogies they arc gcncdy

derived from old and highly-weathered secondary sediments

of an alluvial origin and from montmorillonitic deposits of a

marine origin. The soils tend to be extremely acidic,

infertile, and low in weatherable minerals (Gilliam 1990).

Each of the four series are described as very strongly acidic

in reaction to at least 130 centimeters (Hatchcll and

Henderson 1976).

Vegetation of WS77 is characteristic of Coastal Plain pine

flatwoods. The dominant ovcrstory species were pines,

loblolly pine (Pinus taeda L.--75 percent of the overstory

basal area) and longleaf’ pine (P. palustris Miller--l7 percent).

Other canopy species were sweetgum (Liauidambar stvraciflua

L.--4 percent), black gum (Nvssa Svlvatica Marshall--3

percent), and shortleaf pine (P. echinata Miller--Z percent).

Dominant shrub spies included nearly equal mixtures of

wax myrtle (Myrica cerifera L.), gallbeny (Ilex alabra 6.)

Gray), and lowbush blueberry (Vaccinum tenellum Aiton.).

The herb layer was dominated by broom sedge (Andropononvirginicux L.), with switch cane (Arundinaria gigantea.

(Walter) Muhl.) abundant along seeps and stream channels.

The climate for this region is classified as humid mesothermal

(Trewartha 1954), with mild winters and warm, moist

summers. Mean monthly minimum temperatures for January

and July (extreme months) are 4 and 2O”C, respectively,

whereas mean monthly maximum temperatures are 12 and

32°C. Seasonal patterns of precipitation, stream flow, and

cvapotranspiration for WS77 are shown in fig. 1.

Precipitation averaged 135 centimeters annually, while stream

flow averaged 35 centimeters annually. Precipitation typically

exceeded evapotranspiration throughout the year (fig. 1).

Sampling

Precipitation and Stream Flow

Nutrient inputs were estimated from weekly precipitation

sampling and chemical analysis. Precipitation was sampled

with a network of nine bulk collectors and volume was

determined directly using a method described in Thicssen

(1911).

Similarly, nutrient outputs were estimated from chemical

analysis of weekly stream flow grab samples t&en behind the

calibrated weir at WS77. Weekly flow volume was calculated

from continuous stream height monitoring. Daily flow

volume was calculated from these readings by U. S. D. A.

Forest Service Computations. All sampling (precipitation and

stream flow) was carried out for 6 years.

---cl-- Ppt

S F

. . . . *... EvTs

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Figure 1 .-Mean monthly fluxes of precipitation (Ppt), stream flow (SF), and evapotranspiration (EvTs) for WS77

114
Fire Effects

WS77 was divided into 20 compartments of approximately 8

hectares. Fires were administered as summer or winter

prescribed fires, largely as backing tires. A total of nine fires

administered during this study. See Gilliam and Christensen

(I 986) for a complete description of compartments and fire

treatments. Briefly, nine compartments receiving either

winter-only fires, winter and summer fires, or no fire

(control) were chosen randomly from the 20 compartments of

the watershed.

Effects of tire were estimated from sampling (usually both

before and after the fire) within 10 IO-meter x lo-meter plots

in each compartment. Forest floor and mineral soil were

sampled both before and after the bum. Forest floor was

sampled with a 14.7-centimeter diameter litter cutter; mineral

soil was sampled with a 2.0-centimeter diameter soil corer to

a depth of 20 centimeters and cores were divided into O-5

centimeters, 5-10 centimeters, and lo-20 centimeters depths.

Five subsamples taken randomly within each plot were

compositcd for each sample type.

Overstory and shrub layer vegetation were sampled once prior

to burning. All stems > 0.6 centimeters diameter (at 1.5

meter in height) within each plot were identified and

measured, either for diameter (trees) or canopy cover

(shrubs).

The hcrbaceous layer, defined as all vascular plants (1 meter

in height, was sampled in five of the 10 plots in each

compartment to determine 1) herb layer cover and biomass,

2) species richness and diversity, and 3) nutrient content.

Herb layer cover was estimated non-destructively in two 0.5

meter x lo-meter transects in each of the live sample plots.

The transects were subdivided to yield 10 I-square meter

subplots. Per cent cover was estimated visually for each

species in all subplots. Biomass was estimated by harvesting

three separate SO-meter x 0.5meter transects. These

transects were subdivided into 7.5 O.Smeter x 2-meter

subplots.

A separate design was used to determine nutrient

concentrations of herb layer vegetation in burned and

unburned areas. Ten pairs of sample plots were established in

the topographic extremes of WS77, five in upslope areas and

live in lowland areas. One plot of each pair was burned and

the other was let? unburned. Herb layer vegetation was

sampled by harvesting all above-ground parts within the two

transects as described previously. All herb sampling (cover

estimates, biomass harvests, and nutrient analysis harvests)

was car&l out in the summer.

Analyses

Precipitation and Stream Flow

Precipitation and stream flow were analyzed for pH with a

glass electrode. Metal cations (Na’, KC, Ca++, Mg’ ‘) were

determined with atomic absorption spectrophotomctry (Isaac

and Kerber 1971). Ammonium (NH4’) was determined by

isocyanurate colorimctry (Reardon and others 1966), NOr. by

Cd reduction and azo-dye calorimetry (APHA 1976). PO,’ by

molybdenum blue calorimetry (Mehlich 1953), and SO,’ by

turbidimetry (Schlesinger and others 1982).

Mineral Soil

Samples of mineral soil were air-dried and ground in a

hammer mill to pass a 2-millimeter screen. Measured

samples of about 10 grams each were extracted with a dilute

double-acid solution at a 1:5 soil/solution ratio according to

Mchlich (1953), a method established for acid, clay soils.

Extractable elements were determined as described above.

Ilerb Layer Vegetation

Harvested herb layer material was oven-dried and ground in a

Wiley mill. Plant tissue was digested using a H$O,-HaO,

method (Lowther 1980) and analyzed for Ca, Mg, K, N, and

P as described above.

Data Analysis

Fire effects on soil were tested using t-tests to compare prebum soil pH and nutrient cation concentrations and those of

post-bum soils. T-tests were also used to test the effects of

fire on plant tissue nutrient concentrations by comparing

burned and unburned means. In each case the level of

significance was p c 0.05. Linear regression analysis was

used to generate a model relating herb layer cover to biomass

The level of signiticance was p <O.Ol (Zar 1974).

RESULTS AND DISCUSSION

Ecosystem-Level Effects of Fire

Although nutrient budgets arc somewhat incomplete in this

study, the components studied provide reasonable estimates of

total nutrient flux. For example, soil surveys suggest minimal

deep seepage loss because of poorly drained throughout WS77

(U.S.D.A. 1980). Denitrification should also be minimal,

due to low NO; production in these extremely acidic soils.

Finally, N fixation is probably low because of the low

frequency of legumes in the forest (Gilliam and Christensen

1986) and because non-symbiotic N fixers are generally rare

in acidic forest soils (Alexander 1977). Thus, input/output

data may be strongly indicative of the nutrient status of the

115
Table 1. Inpltmwtplt buagets for cations in precipitation and stream flow for WS77. Data

represent averages from 1976- 1982.

Input-Output H’ Na’ K' Ca" NJ' '4 NO3 so,= Cl PO,"

----------------*--------------*--------~e~,ha,yr---------------------------------

Precipitation 0.54 0.27 0.03 0.26 0.13 0.06 0.12 0.50 0.45 0.01

stream Flow 0.05 0.49 0.03 0.37 0.22 0.01 0.00 0.51 0.61 0.01

Net (1-O) +.49 -.22 0 -.ll - .09 +.05 +.12 -.01 -.I6 0

ecosystem. Table 1 shows precipitation and stream flow others 1982). The main loss of nutrients due to fire was an

nutrient budgets for the entire b-year pe$d of the study. average volatilization of 24 kilograms N per hectare from the

Hydrogen ion was greatly conserved by the system, with forest floor (Richter, and others 1984). Assuming a tire cycle

precipitation H+ inputs exceeding stream flow outputs by an of 5 to 7 years (Christensen 1981), however, this loss is

order of magnitude. Also conserved were NH4+ and NO;. balanced by annual accumulations of inorganic N (2.4

Although such patterns are not conclusive, these data suggest kilograms per hectare per year--calculated from table 1) and

that N, commonly limiting in forest ecosystems, may be a organic N (approximately 2 kilograms per he&m per year--

limiting nutrient in this forest. Richter 1980) from precipitation.

There were net annual outputs of Nat, Ca” +, Mg’ ‘, SO4=,

and Cl- over the study period (table 1). Although many of the

soils of this region were derived from highly-weathered

sediments of an alluvial origin, net outputs of these ions

indicates that, for WS77, further weathering is taking place

and that these parent material sediments were largely of a

marine origin.

None of the nine fires in the six years of the study had any

significant effect on stream flow nutrient output (Richter and

Nutrient budgets were balanced for K and P (table l),

suggesting strongly that K and P (in addition to N) may be

grow&limiting in these soils. As discussed in Gilliam

(1988), this contention is supported further by comparisons of

nutrient concentrations in herb layer vegetation from similar

and contrasting ecosystems (table 2). Among these sites,

including hardwood forests and other conifer forests, K, N,

and P concentrations were typically lowest for herb layer

vegetation from WS77 (table 2).

Table 2. lIrsbaceous Layer Jlutrient. calcentrati- for various sites.

si tcdstlldy K C a M9 N P

-----------------------------%-----------------------------

Eastern Illinois bardwwds/

Pet-m and Rolfe WSi!)

3.79 1.17 0.42 2.32 0.36

Northern barmvood forest/ 3.18 0.74 0.33 2.38 0.18

Siccama. and Others (1970)

Northeast Mi-ta/

Grigal and Ohmann (1980)

3.25 2.28 0.50 1.38 0.34

Central New York State/ 3.01 2.00 ---- 1.93 0.21

Bard (1949)

Boreal forest/

Gagnon, and others (18.58)

0.51 0.81 0.24 . ..vw 0.19

Lower coaSta PLain/ 0.60 0.85 0.16 0.18

cartes (1978)

Coastal Plain ftatwoods/ 0.84 0.77 0.20 1. 19 0.06

Gilliam (1988)

116
Nutrient Availability and Uptake

The effect of fire on extractable soil nutrients was minimal

and varied with season of bum (table 3). Summer burns

seemed to have little influence on soil nutrients, except for a

significant decrease in extractable NH4 ‘, For winter burns,

howcvcr, there were significant increases in pH and

extractable K’ , Ca’ *, and NH,+. Although data for

extractable P are not shown here, increases in extractable P in

these soils in response to Iire has been demonstrated (Gilliam

1983). Therefore, there is an indication that tire may

increase availability of limiting nutrients.

Gilliam and Christensen (1986) summarized the response of

herb layer cover and species richness of WS77 to fire. They

sampled nine randomly chosen compartments representing six

tire treatments, including winter- and summer-burned

compartments and unburned control compartments. They

found that only (but not all) winter fires had appreciable

effects on the herb layer. Thus, it should be stressed that,

depending on the ecosystem component being studied, fire

effects may be seasonal and highly variable. Furthermore,

such variability itself can have great significance on the level

of the ecosystem (Christensen 1981). For the purpose of

comparison, specific results ,for a particular winter fire will be.

presented in this paper.

Tissue nutrient concentrations for herb layer vegetation were

significantly (p < 0.05) higher in burned plots than unburned

plots for K, N, and P (fig. 2). There were no signiiicant

differences for Ca and Mg. This pattern suggests that tire

may increase the availability of K, N, and P.

The relationship of herb layer cover and harvested biomass

for each species in the three harvest transects is shown in fig.

3. This relationship yielded the equation

y = -0.03 t 1.81x (1)

where y is herb biomass in grams per square meter and x is

herb cover in per cent. The correlation coefficient was 0.94

and was significant at p <O.Ol. The relationship is based on

mean values for individual species. Thus, given the highly

significant correlation, equation (1) can be used to estimate

biomass for individual species in plots of the burned and

unburned compartments. Biomass was summed for all species

in each plot to yield total herb layer biomass per plot.

Average cover was significantly (p < 0.05) higher in the

winter bum plots compared to the control plots (37 percent

vs. 16 percent, respectively; table 4). Using equation (1) for

each individual species in these plots, this difference

translated to a greater than two-fold increase in herb layer

above-ground biomass (65 grams per square meter versus 28

grams per square meter).

Table 3. T-test cam~arisons of Pm- vs. Post-bum soils at different depths

and seasons of bllmi~.

Sumner burn

De@/Treafnmt PH

-I K C a ’ -ng+( N H

-------------------------lreq/g--------------------------4-

o-5 au/PN?-blml 4.38 0. 7 12.2 5.5 1.1

o-5 cm/Post-burn 4.35 0.7 11.0 5.4 o.l5*

5-5- 10 10 tzlulbst- cu/Pre-burnbum 4.48 4.46 0.3 6.64 4.1 4.0 E*

16-20 IO- 20 cm/Pre-burn cm/Post-bum 4.58 4.65 0.2 0.2 6. 5.6I 4.7 4.4 oO:t*

* indicates significant differeoce (pCO.05) betwear pm- and post-burn llpeans

Winter born

DepWTreatmmt PH K' c a " &I NH4

---------------------*----------------------------

b5 cm/Pre-burn 4.16 4 . 25 *

o-5 cm/Post- hum 4.2@

0 i.Y*

7.3* 3.0

ii.;* 0

5-5- 10 10 c&Post- --burn bum 44:E* 0.5 0.5 3.4 3.2 2.2 1.9 o":i*

16-20 cm/PR?-blun 4.48 0.4 3.6 2.8

10-20 cmIP@st-~ 4.58 0.3 2.6 2.3

* imllcates significant difference (p<O.O5) behreen Pm- 4 Wt-- IUCS+BS

117
Unburned '

0 Burned

Figure ‘L.-Nutrient concentrations of burned and unburned plot herb layer vcgctation. *Indicates significant diffctence

between burned and unburned treatments at p < 0.05.

8-

i7

E

?n

2 6-

i

iii

4-

2-

ff

0 I I I I I

0 1 2 3 4 5

Cover (56)

Figure 3.-R&tionship of herb cover and harvested herb biomass for WS77. Each point represents average biomass and

cover values for individual species. See text for equation.

118
Table 4. Herbaceous Layer cover, biomass, species richness, Shannon-Weiner diversity, and

nutrient content for burned and unburned plots of WS77. Error vatues are one standard

error of the mean.

Treatment Cover Biomass K C a li P Richness

(%I (g/d)

Mg Dlverslty ------------kg/ha----------- (spp./ptot)

Control 16 2+2 7 28 3 4 7 I.9 2.2 0.5 3.1 0.2 * - - a + . 1.95 0 + * 15 . + .

Winter bum 36.723.7 65.1k6.3 6.8 5.0 1.3 8.3 0.5 2.50+0.10 29.521.9

H&I layer nutrient content was approximated by applying the

appropriate nutrient concentration data from fig. 2 to

unburned and burned herb layer biomass means in table 4;

i.e., “burned” K, N, and P values from fig. 2 wcrc used with

“winter bum” biomass from table 4 and “unburned” values in

fig. 2 were used with “control” biomass. Since fire did not

significantly influence Ca and Mg concentrations, overall

mean values from fig. 2 for these nutrients were used with

mean biomass values from table 4.

Not surprisingly, using this method, increases in herb layer

nutrient content were especially pronounced for K, N, and P.

These increases were >3.5-fold, 2.7~fold, and >2.5-fold for

K, N, and P, respectiveIy (table 4).

It merits repeating that these degrees of differences, whether

for herb cover, biomass, or nutrient content, are not

indicative of aI1 fires in this ecosystem, since some fires

(especially summer tires) had no appreciable influence on the

herb layer. These data, thcrcfor, provide a meaningful

comparison representative of the potential effects of fire in

this system.

Community-Level Effects of Fire

Although the major emphasis of much of this work has been

on ecosystem-level effects of fire, the hcrbaceous layer is also

useful in assessing the effects of Iirc on the level of the plant

community, especially with respect to effects on species

diversity and composition. Herb layer species diversity was

measured for each plot in winter bum and control

compartments as the Shannon-Weiner Diversity Index (H),

using the equation

where pi is the decimal fraction of individuals of the ith

species and a is the total number of species.

Fire significantly increased species diversity of the herb layer

for this particular winter bum (table 4), a response typical for

other winter tires of WS77 (Cilliam and Christensen 1986).

The value of H reflects both numbers of species present as

well as their relative importance, measured here as relative

cover. Thus, much of the increase in the diversity index was

from a significant increase in species richness, from 17

species per plot in control compartments to 30 species per

plot in winter bum compartments (table 4).

In addition ‘to increasing the numbers of species in burned

plots, fire altered species composition as well (table 5). Grass

spccics in particular increased in importance in burned areas.

Indeed, for the species listed in table 5, tire did not so much

alter which species were important as it altcrcd species cover,

on both an absolute and a relative basis.

Table 5. Important species for the herbaceous layer in burned and

unburned plots of WS77. Nomenclature follows Radford, and others (1968).

Control Wmter burn

Species Relative Relative

Cover

Species

Cover

(Xl (%I

Lonicera ianonica 16.3 Andropogon vngmicus 21.4

Andropogon virginicus 15.2 Ltqutdambar styractttua

J iex etabra 12.1 Vaccinum tene r‘?;

Vaccinum sene I L m 8.8 Vitistundifolia 5:8

Mvricaerifera 7.6 Vaccinium elliottii

Liquidambarstyraciflua Rubus betulifottus 24

Em

2: ltex qlabra 4.0

Mvrica cerifera 3.2

Mitchella renens it.:

2:1

Festuca elatior

Vitis . .randI folly lonicerajaponica119
Population-Level Effects of Fire

Fire will affect populations of plant species differentially,

depending on the species’ life history characteristics and

resource requirements. Many species in southeastern Coastal

Plain ecosystem not only respond positively to relatively high

fire frequencies, but actually are dependent on fire for

successful reproduction and growth. A well-documented

example of such a fire-dependent species is longleaf pine.

There are excellent accounts of the relationship between fire

and lor&af pine, the most recent of which focuses on the

importance of fire in several aspects of its population

dynamics (Platt and others 1988).

Woody species data for WS77 provides an example of the

effects of long-term fire exclusion on lon&af pine, since

WS77 had not been burned for approximately 40 year prior to

the initiation of the study. Figure 4 is a size class frequency

distribution comparing longleaf pine to loblolly pine, which is

a much less tire-dependent species. The distribution pattern

for loblolly pine is typical of a successfully regenerating

species, with high frequencies of small stems and attenuating

numbers toward larger size classes. In contrast, the pattern

for longleaf pine (e.g., extremely low frequencies of small

stems) is indicative of greatly suppressed regeneration. Thus,

long-term fire exclusion and greatly reduced fire frequencies

cause sharp declines in lon&af pine populations.

Conclusions

This Coastal Plain pine flatwoods ecosystem is distinctly

oligotrophic and fire, as an integral part of the system, serves

a significant role in increasing nutrient availability. It is thus

notable that P and K typically increase in availability after

fire.

The importance of fire on the plant community level was

evident in its effects on the herbaceous layer. Although these

effects were variable (especially varying with season of bum),

fire can cause substantial increases in species diversity,

apparently by altering microenvironments and ultimately

increasing resource availability.

Fire also plays a vital role in the life history and population

dynamics of several plant species in pine flatwoods systems.

Data presented here demonstrate the importance of fire in

maintaining successful regeneration of the canopy codominant species, longleaf pine.

Thus, tire effects appear to be integrated across all

hierarchical levels of organization, from the population to the

community to the ecosystem. Fire serves significant functions

that are both required and unique at each level.

ACKNOWLEDGEMENTS

This research was supported by cooperative grants from the

Southeastern Forest Experiment Station, U. S. D. A. Forest

Service, and Duke University. The author thanks Forest

Service scientists at the Charleston, S.C., Forest Sciences Lab

and technicians at the Santce Experimental Forest for

cooperation and logistical support. The author also thanks the

numerous graduate students at Duke Univeristy who also

assisted in the project.

Size Class (cm)

Figure 4.-Size-class distributions for loblolly pine (P. taeda) and longleaf pine (P. palustris) for WS77.

120
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D.C.

Wells, B.W. 1942. Ecological problems of the southeastern

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Englewood Cliffs, N.J.

122
TI-$23 EFFECT OF A HIGH INTENSITY FHlE

ON THE PATCH DYNAMICS OF VA MYCORRHIZAE

IN PINYON-JUNIPER WOODLANDS

Carole Coe Klopatek, Carl Frieze, Michael F. Allen,

Leonard F. DeBsnn and Jeffrey M. Klopntek’

Abstract-overall effats of fire on forest ecosystems are complex, ranging from reduction of aboveground

biomass to impacts on soil microbial processes. This study reports on the short-term ecological effects of B

high intensity fire on the vesicular-arbuscular (VA) mycorrhizae dishibution, densily and diversity in

pinyon-juniper woodlands. In fall of 1989, I hectare of mature pinyon-juniper located near the Grand

Canyon, Arizona, was intentionally burned using drip torches. Soil cores were taken from interspaces and

beneath canopies of pinyon and juniper during the spring of 1989 and immediately prior to and 96 hours

after burning the following fall. In the spring, there were I M differences in VA mycorrhizaI species

richness under pinyon, juniper or interspaces. Glomus fasciculahun and C. aareg&m.were the two most

frequently observed species. Immediately before the bum, species richness was slightly lower than in

spring for each of the three cover types. Following burning, & fasciculahun, G. deserticola. and G.

macrocarpum were the only remaining species in each of the three cover types. Seasonal differences% soil

spore densities were found between spring and pre-burned conditions. Spore numbers were significantly

lower in interspaces than under canopies. Post-bum spore numbers were significantly reduced under tree

canopies (up to X8 percent loss) as compared with the interspaces (47 percent loss). Loss of mycorrhiie

was negatively correlated with soil temperature and heating duration, which varied with the amount of litter

and dufT burned (under tree canopies) and suhcanopy position.

INTRODUCTION

The importance of mycorrhizae in ecosystem function is well

documented (Allen 1988; Masse 1973; Menge and others

1978; Safir and others 1987). Without mycorrhizac many

plants show a decreased growth rate or fail to develop beyond

germination and Smith 1983; Masse 1973; Powell

and Bagyaraj 1984). Sludies have shown that this symbiosis

is fragile, and that mycorrhizal activity decreases with

increasing levels of disturbance (DaR and Nicholson 1974;

Habte 1989; Janos 1980; Jasper and others 1989; Klopatck

and others 1988; Warner 1983; Williams and Allen 1984).

For example, the frequency of vesicular-arbuscula (VA)

mycorrhizal propagules decreases from a moderate

disturbance such as livestock grazing (Bcthlcnfalvy and

Dakcssian 1984a; Rcece and Bonham 1978) to a severe

disturbance such as surface mining (Allen and Allen 1980;

Gould and Liberta 1981; Zac and Parkinson 1982).

Klopatck and others (1979) estimated that the pinyon-juniper

association is the third most expansive vegetation type in the

United States. It COVCI’S approximately 32.5 million hectares

‘Microbial Biologist, USDA Forasl Service, Rocky Mountain Forest

and Range Expcximcnt Station, Forestry Sciences Lab., Arizonia State

University Campus, Tempe, AZ and Department of Microbiology,

Arizona State University. Tempe, AZ; Research Assistant and

Professor, respectively, Systems Ecology Research Group, San Diego

State University, San Diego, CA; Supervisory Soil Scientist, USDA

Forest Service, Rocky Mountain Forest and Range Experiment

Station, Forestry Sciences Lab., Arizonia State University Campus,

Tempe, AZ; Associate Professor of Botany, Arizona State University,

Tempe, AZ.

in the western U.S. and 5.75 million hectares in Arizona

(Arnold and others 1964). Pinyon-juniper woodlands are

located between arid and semiarid mesic ecosystems. On the

xcric end of the scale, juniper trees and desert shrubs coexist,

while pinyon and ponderosa pine coexist on more me.& sites.

Intermediate between these limits both pinyon pine and

species of juniper exist together with interspace areas

occupied by shrubs, grasses and other herbaceous cover.

Why these trees exist in such diverse environments may be

due to their mycorrhizal association. For example, it is

known that many arid land shrub species are VA mycorrhizal,

as are juniper bees, while all pine species are

cctomycorrhizal.

Pinyon-juniper woodlands are managed for multiple use. As

a result, both grazing (over 100 years West 1984) and

prescribed burning (over 75 years USDA Forest Service) are

perturbations that have occurred simultaneously in these

woodlands for many years. Natural and prescribed fires

impact the spatial mosaic patchwork of both VA mycorrhizae

ti~pm> interspace grass and shrub) (Klopatck and others

1988) and ectomycorrhizac in forest ecosystems (pine, spruce,

and fir) (Mikola and others 1964; Schoenbcrger and Perry

1982). Until recently, little was known about the response of

VA mycorrhizal symbionts to fire. Klopatck and others

(1988) showed that atier a simulated fire, VA mycorrhizal

colonization was reduced when burning temperatures

exceeded 90” C. Soil water availability at the time of burning

also played an important role in VA mycorrhiil survival,

with dry soils being more of a detriment than wet soils

because of higher resultant temperatures. Gibson and Hctrick

123
(1988) found significant reductions of three VA mycorrhizal

species following a tire in the tall grass prairie of Kansas.

Dhillion and others (1988) stated that colonization levels of

VA mycorrhizal fungi in little bluestem roots were

significantly reduced on burned sites when compared to

unburned but, increased significantly afier one growing

season. Their results suggest that the response of VA

mycorrhizal fungi to fire may be attributed to changes in the

host plant rather than the direct effect of fire. Fire

temperatures did not reach a level high enough to kill all the

plants, thereby leaving a large residual VA mycorrhizal pool

in the soil and in plant roots. In fact, they showed that fire

actually stimulated plant ‘growth, unlike tires in pinyonjuniper woodlands.

In previous work, we determined that fire had a negative

impact on VA mycorrhizae by decreasing the number of

propagules. We wanted to determine if these results were

representative under field conditions. Thus, the objective of

this study was to determine how fire effects VA mycorrhizae

density, diversity and distribution under field conditions in the

pinyon-juniper ecosystem. Results on the effects of tire on

ectomycorrhizae arc forthcoming.

MATERIALS AND METHODS

Site Description

The study area is located on the Coconino Plateau of the

Colorado Plateau, adjacent to the Grand Canyon National

Park on the Kaibab National Forest. Site elevations range

from 1875 to 2075 meters. Soils are Lithic and Fluventic

Ustochrepts having a sandy loam texture and belong to the

Winona-Boysag association (Hendricks 1985). Kaibab

limestone, with intrusions of Moenkopi sandstone, are the

dominant parent materials; slope is minimal, ranging from O-2

percent. The seasonal regime of cold, wet winters and hot

summers with occasional thunderstorms in this region, results

in this being the evolutionary center for pinyon-juniper

development (Nielson 1987). Annual precipitation of 350

millimeters is bimodally distributed, approximately half

occurs as intense thunderstorms from July to September, with

the remainder coming as mild winter rains or snows from

December to April. Soil moisture deficits exist from March

through October. Temperatures are variable, ranging from -

27 to +38” C with an average of 150 days between last and

first frost. Permanent weather recording stations are located

in Tusayan, Arizona, less than 20 kilometers from the study

area.

The area is dominated by pinyon pine w edulis Engclm.)

and Utah juniper (Juniperus osteosperma (Torr.) Little).

Several species of grass [blue grama grass (Bouteloua gracilis

(H.B.K.) Lag. ex Steud.), squirrel tail (Sitanion Jlystrix

(Nutt.) J.G. Smith), s sp.] and shrub species [snakeweed

(Guttierrezia sarothrae (Pursh) Britt and Rusby), rabbitbrush

(Chrvthothamnus sp.), cliffrose (Cowania mcxicana var.

stansburiana (Torr.) Jepson)] dominate the interspaces.

Experimental Design

From the area described above, we chose approximately 1

hectare of mature pinyon-juniper (250 plus years old) as our

study site. The site was divided into quadrants (4 subplots) in

which the position and number of each pinyon, juniper, and

interspace was mapped. Every tree was marked with brass

tags bearing ID numbers. The site was fenced to exclude

livestock grazing. On September 11, 1989, we burned the

site using hand-held drip torches. All living, downed, and

dead fuels were ignited. Burning was conducted by the

Kaibab National Forest, Tusayan Ranger District with

assistance of the National Park Service, Grand Canyon.

Soil samples were evaluated for VA mycorrhizal spores in the

spring of 1989 and immediately before and 96 hours after the

September bum. Spring samples were taken to assess

seasonal variability. During each sampling period, soil cores

were taken from the same three randomly selected pinyon and

juniper and interspaces in each of the four quadrants. Soil

cores were t&en 96 hours a&r the burn (post-bum) because

trees were still burning and smoldering. Soil cores were

taken from the base of the tree, mid canopy and at the canopy

edge to a depth of 10 centimeters. This yielded 18 cores per

quadrant, totaling 72 tree cores (2 tree species X 3 trees per

quadrant X 3 samples per tree X 4 quadrants = 72). Four

additional soil cores were taken per quadrant from

interspaces, for a total of 16 interspace samples. Cores were

wrapped in polyurethane and refrigerated at 4” C until

processed.

In the laboratory, each sample was sieved (2 millimeters) to

remove rocks and allowed to air-dry. From this, 20-gram

samples were taken to estimate spore numbers using

differential centrifugation (lanson and Allen 1986). Spores

were placed in a petri dish with sterile distilled water and

examined under a dissecting microscope at 40X. Spores were

divided into live and dead. Viability was determined by

placing spores on a microscope slide, those which exuded

cytoplasm when crushed were considered viable. Species

identification were determined with a compound microscope

at 400-1000X. Spore numbers are reported as means with +

standard errors of the mean. Significant differences (p

< 0.05) in spore numbers were isolated using Tukcy’s honest

significant difference measure. Percent loss of mycorrhizae

was calculated by subtracting the difference between pre- and

post-bum spore numbers and dividing it by the pre-bum spore

number.

124
RESULTS ANDDISCUSSION

Species Richness

Eight species of VA mycorrhizal fungi were recovered from

the site (table 1). In spring (May 1989), there were no

differences in species richness under pinyon, juniper, or

interspaces (fig. I). m fasciculatum and G. aggrc~atum

were the two most frequently observed specics;ith c

macrocarpum being the least dominant. Pinyon pine,

although ectomycorrhizai, has been reported to have

numerous VA mycorrhizal propagules around its base

(Klopatek and Klopatek 1986). This is likely due to: 1)

aeolian deposition of spores, and 2) the intermixing of juniper

roots with those of pinyon. Wind deposits sand particles

under pinyon pine (Barth 1980; Klopatek 1987) and

presumably deposits these large spores along with the sand.

In addition, on a recent excavation, we found juniper roots

intertwined with pine roofs (Klopatek and Klopatek,

unpublished). Thus, pinyon is an important repository for

VA mycorrhizal propagules. This is in contrast to other pine

dominated forests where no VA mycorrhizal spores are found

(Kovacic and others 1984).

TabIe I.--List of species from soi Is taken from under

pin on

fy

and juniper canopies and interspaces. No

diferences in species were found in either of the three

cover types. Species are Listed in the order of relative

abundance.

Gtomus macrocarpum Tut & Tut

G. occuttum (Walker)

G. mosseae (Nicot & Gerd) Gerd. g Trap

B

e

Scutettospora calospora (Nicol. & Ger .) Ualker & Sanders

G. deserticuta Trappe, Bless & Menge

G. a gregatun Schenck & Smith

G. fgascicutatum (Taxter sensu Gerd.) Gerd. & Trappe

Acaulospora laevis Gerd. & Trappe

Species richness varied with season. Immcdiatcly before the

fall burn, species richness dropped in each of the three cover

types (fig. 1) compared with spring. Species richness was

greatest in interspaces covered with grass, followed by pine

and juniper soils, respectively. In post-burn samples, no

differences in richness were found among the three cover

types; but, species richness declined in all post-bum samples

(fig, 1). G. fasiculatum, 

-

& desetticula, and & macrocarpum

were the only species that survived the fire. These species

arc all thick walled as compared with the other five (table I).

In addition, they are commonly found in very arid, alkaline

soils (Bethlenfalvay and others 1984; El-Giahmi and others

1976; Pfeiffer and Bless 1980; Safir 1987) and, therefore,

may be more resistant to extreme temperatures.

P i nyon

I Pre-Burn El Post-Burn

--_.._

unlper Interspace

Figure 1 .--Change in the number of VA mycorrhizal species

in soils taken from beneath pinyon and juniper and interspaces

due to change in season and effect of lire

Spore Densities

Spore density varied under pinyon, juniper, and interspaces

during the spring and pre-bum samplings (fig. 2). Overall

spore counts under pinyon were not significantly higher in the

spring than in pre-bum samples. Significant differences

existed (p < 0.05) between spring and pre-bum samples in

juniper and interspace soils (fig. 2). This decrease between

spring and pre-bum samples may be attributed to a large

amount of germination and hyphal activity rather than spore

production following the summer rains. There were statistical

differences @ < 0.05) in spore numbers between juniper and

pinyon soils in the spring sampling, and most samples were

significantly greater 0, < 0.05) than interspaces (fig. 2). In

general, the pre-bum pattern of spore dispersal exhibited the

highest proportion at the base of the trees and decreased

outward.

Burning significantly (p = < 0.05) decrease the overall

number of VA mycorrhizal spores in soils beneath pinyon

and juniper canopies (up to 88 percent) and interspaces (up to

47 percent loss) (fig. 2). Following the burn, spore numbers

under canopies ranged from a high of sixteen to a low of four

per 20 grams of soil. There did not seem to be a pattern of

spore distribution and subcanopy position. The substantial

losses under canopies was probably due to the direct effects of

the soil temperatures. The highest soil temperatures were

reached under canopies (up to 315” C at 2 centimeter depth)

compared with interspaces (up to 68” C at 2 centimeter

depth). The large fuel load, including aboveground material,

litter, and duff, in addition to a more complete combustion of

these fuels, probably contributed to a more intense bum under

the canopies. Smoldering duff and tree stumps maintained

high temperatures for several days. Magnitude and duration

12.5
P i nyon

Cl Spring

I Pre-Burn

i3 Post-Burn

Base Mid

Lcnopy Pos i t on

Edge

Juniper

I

Mid

0 Spring

I Pre-Burn

El Post-Burn

I

L

Edge canopy Pos i t i on

Interspace

Cl Spring

1 Pre-Burn

H Post-Burn

arc the two principal factors causing heat injury to plants

(Hare 1961) and are also likely to be deleterious to VA

mycorrhizal fungi. Smoke resulting from burning of the trees

may also have contributed to the loss in mycorrhizae as it has

been shown to reduce other microbial activities (e.g., Li and

others 1988).

Interspaces had little aboveground vegetation and litter and no

duff, which resulted in an overall lower soil temperature.

Klopatek and others (1988) showed interspaces were the least

affected by a simulated bum compared with canopy

microcosms. We observed that tire either swept through the

interspaces or did not bum at all. Pruning of grasses does not

adversely affect mycorrhizal colonization, but temporarily

inhibits sporulation (Powell and Bagyaraj 1984). We

anticipate that the burning of grasses will produce the same

response. If grasses are killed, and roots are not severely

damaged by the fire, we theorize that root pieces will serve as

propagules. Tommerup and Abbot (1981) showed that

colonized root pieces can remain viable propagules for

extended periods in partially dried soils, but they lose

viability once moisture levels increase, (Gould and Liberta

198 1; Hall 1979) due to decomposition. Thus, the fire shifted

the distribution of spores from under the canopies to the

interspaces.

The time required for mycorrhizal populations to recover

following tire in pinyon-juniper woodlands is unknown.

Janos (1980), MacMahon (1987), and Allen and Allen (1988)

suggest that mycorrhizal fungi are essential in ecosystem

recovery, facilitating plant establishment by regulating

nutrient flow from the soil to the plant. Thus, in order to

understand and manage this ecosystem, it is necessary to

understand mycorrhizal response to tire and how it affects

patch dynamics that lead to a mosaic landscape pattern (i.e.,

from a canopy dominated mycorrhizal community to a

interspace dominated mycorrhizal community). This “patch”

pattern of disturbance is unlike a widespread disturbance,

such as stripmining (Klopatek and Klopatek 1984). Thus, the

natural mosaic configuration of canopy and interspace leads to

a significant shift in the “patchwork dynamics” of mycorrhizal

distribution following fire.

ACKNOWLEDGMENTS

The authors would like to give our sincerest appreciation to

the tire crews at the Tusayan Ranger district and the National

Park Service, and the entire staff of the Tusayan Ranger

District, for without their help this project could not have

been a success. We also thank Lenny Schwarz for his

invaluable field assistance. And lastly, to the Bambart Seed

Company for providing the seeds for this experiment.

Figure Z.--Number of VA mycorrhizal spores per 20-gram

soil sample taken from beneath pinyon and juniper canopies

and interspaces. Samples were taken at three locations under

tree canopies--base, mid and canopy edge and from grass

covered interspaces

126
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128
FOREST SOIL CHARACTERISTICS FOLLOWING WILDFIRE

IN THE SHENANDOAH NATIONAL PARK, VIRGINIA

David A. Groeschl’, James E. Johnson, and David Wm. Smith”

Abstract-Forest floor and mineral soil samples were collec!cd and analyzed to determine physical and

chemical differences among three bum levels (high, low, and unborncd) under a mixed pine forest one year

after a mid-July, 19X8 wildfire. Total forest floor thickness and weight were significantly different among

all three burn levels. Low intensity surface tires consumed the surface Oi-Oc layer of the forest floor

leaving the Oa layer relatively intact, whereas high intensity fires resulted in the complete destruction of Ihe

forest floor. Total carbon and nitrogen concentration and content were significantly higher in residual Oa

material of low bum areas compared to unburned Oa material. Active acidity @H) in the top 10 cm of

mineral soil in high and low bum areas measured 4.6 and was significantly higher than unburned areas with

a value of 4.3. Total carbon and nitrogen levels in the surface 10 cm of mineral soil were also higher in

low burn areas whereas high bum areas were lower than unburned sites. Mineral soil inorganic nitrogen

lcve]s were significantly higher in both high and low bum areas compared to unburned arc as, thcrehy

providing a pulse of available nitrogen for plant uptake

INTRODUCTION

Fire has and will continue to play an important role in

affecting biotic and edaphic components of forest ecosystems.

The Table Mountain pine (Pinus puwens Lamb.) pitch pine

(Pinus tieida Mill.) forest complex is typically considered a

fire-adapted community. In fact, several authors (Sanders and

Buckncr 1988; Bardcn and Woods 1976; Zobei 1969)

concluded that high intensity fires were necessary to ensure

successful regeneration and establishment of Table Mountain

pine by (1) opening serotinous cones (Table Mountain pine),

(2) inducing basal sprouting (pitch pine), (3) destroying

excessive litter and exposing the mineral soil, (4) eliminating

dense undcrstory vegetation, and (5) destroying allclopathic

substances. However, little is known about the role and

impact of variable intensity wildfire on forest floor and

mineral soil characteristics upon which these species occur.

High elevation sites supporting mixed pine forests arc

generally moisture-limiting and typified by shallow, acidic

rocky soils with minimal rooting volume and associated

infertile conditions. Low intensity tires (prescribed and

wildfire) may actually enhance soil fertility by increasing pH

(Gricr 1975; Mctz and others 1961; Wells and others 1979),

providing an influx of inorganic forma of nutrients and

increasing solubility of these nutrients (Alban 1977; Metz et

al 1961; Lewis 1974; Covington and Sacket 198(j), and

volatilizing compounds such as monoterpcnes which arc

known to have inhibiting effects on bacteria populations

responsible for ammonification and nitrification processes

‘Silviculture Forester, lTT Rayonict Inc., Forest Research Center,

P.O. Box 819, Yulee, FL 32097.

‘Associate Professor-Extension Specialist, and Professor of Forestry,

respectively, DePstirnent of Forestry, Chcatham Hall, Virginia

Polytechnic Institute and State University, Blacksburg, VA 24061.

(White 1986a). Conversely, high intensity fires may result in

a significant reduction of the total nutrient capital from the

site resulting in the further reduction of already poor site

quality conditions. However, these losses following high

intcnsiry fires may not bc altogether detrimental, since Table

Mountain pine is thought to have a low nutrient requirement

which may naturally select and promote fhe maintenance of

this species on xeric, poor quality sites.

Much work has been done on the effect of prescribed tires on

soil properties, but these fires arc generally of low intensity

and results are stated as contrasts between burned and

unburned. In contrast, variable intensity wildfires provide

comparisons among several intensity levels; however,

statistical analyses and inferences from results are limited due

to non-random placement and inability to replicate treatments.

Nonetheless, wildfires provide a unique study arena because

of Ihcir natural occurrence and exhibition of several intensity

levels. The objectives of our study are to determine forest

floor and mineral soil physical and chemical properties

following a variable intensity wildfire within a mixed pine

forest and to discuss the possible importance of these impacts

in relation to existing vegetation.

METHODS

Study Site

On July 11, 1988, the National Park Service (NPS) located a

lightning-caused wildfire on Dove1 Mountain in the

Shenandoah National Park and adjacent private lands. Dove1

Mountain is located approximately 6.5 km northcast of the

town of Shenandoah in Page county, Virginia. The mid-July

wildfire burned approximately 350 ha before being brought

under control and declared extinguished on August 8, 1988.

129
The study area is located in the Blue Ridge Physiographic

region and is underlain by the Erwin (Antictam) and Hampton

Geologic Formations (Allen 1967). Soils are derived from

granodioritc, arkosic sandstone, and grcenstone and have not

been classified into series but are typically shallow and

skeletal, with numerous rock outcroppings. Elevations in the

area range from 350 to 800 m and slope inclination ranges

from 40 to 65 percent. Mixed pine forests consist

prcdominatly of Table Mountain, pitch, and Virginia pine

(pinus viminiana Mill.).

Field Met hods

Areas were selected within the burned and adjacent unburned

forest so that conditions of uniform species composition, age,

and density; slope position, aspect, elevation, and steepness;

and soil character&tjcs were represented. Fire intensity or

bum levels were not actually measured, however, this

terminology is used to categorize and represent the level of

overstory mortality that resulted following fire occurrence.

High intensity bum levels represent greater than 75 percent

overstory mortality of basal area and crown cover, whereas

low intensity bum levels represent less than 25 percent

overstory mortality. A combination of crown and surface

fires resulted in high intensity bum sites whereas surface fires

represented low intensity burn areas. All sampling occurred

on backslope positions with southwest-facing slopes.

Forest floor and mineral soil sampling occurred

simultaneously during the first full growing season following

the fire. Three sites were located within each bum level for a

total of 9 sites. At each site, six sampling points were

randomly located for a total of I8 forest floor and composite

mineral soil samples within each burn level. The forest floor

was sampled with a lo(l-cm2 template. At each sampling

point, a knife was used to cut along the template border and

the Oi-Oe layer was removed and bagged. The Oa layer was

removed separately and also bagged. Mean depth of the

Oi-Oe and Oa layers were determined within each Iire

intensity level. At each sampling point, three mineral soil

samples were taken to a depth of 10 cm, and combined to

form one composite sample. Bulk density samples were also

taken to the lo-cm depth at each sampling point using the

excavation method (Blake and Hartge 1986).

Lab Methods

Forest floor samples wereoven-dried at 65°C for 48 hours,

and rocks and other non-plant material were removed to

determine weight of the Oi-Oe and Oa layers of the forest

floor per unit area. Forest floor samples were sieved to

remove the mineral soil fraction before being ground in a

2-mm Wiley mill. Ground samples were then remixed with

the mineral soil fraction using a sample splitter. Total carbon

was determined using a LecoN high-temperature induction

furnace (Nelson and Sommers 1982). Total nitrogen was

digested using the micro-Kjeldahl method of Bremner and

Mulvaney (1982), followed by analysis of the resultant

extracts using a TechniconlM autoanalyzer.

Composite mineral soil samples were air-dried and sieved to

separate coarse fragments. Active acidity, measured as pH,

was determined using a 21 distilled water to soil ratio. Total

nitrogen and carbon levels of the surface IO cm of mineral

soil were determined using the same procedures as those used

for forest floor samples. Inorganic nitrogen was determined

by extracting exchangeable NH,-N, NO,-N, and NO,-N, using

2M KC1 extractant, followed by analysis with a Technicon”

autoanalyzer.

Statistical Methods

Forest floor and mineral soil variables were subjected to

analysis of variance for a completely randomized design

followed by Tukey’s multiple comparison procedure to

determine significant differences at the 0.05 level among fire

intensity levels (high, low, and unburned).

RESULTS AND DISCUSSION

Forest Floor Parameters

In forest ecosystems, the major portion of macro-nutrients arc

tied up in the surface organic matter. These nutrients are

slowly released through the process of microbial-mediated

decomposition and mineralization. Under normal oxidation

conditions, organic matter provides a slow release, revolving

fund of nutrients for plant uptake. Conversely, fire tends to

rapidly release these nutrients either by volatilizing lower

molecular weight gases (H,O, and N) into the atmosphere or

concentrating many basic cations in the residual ash.

Wildfire consumes the forest floor in direct proportion to the

intensity of the fire. Mean depth of the Oi-Oe layer in

unburned areas was 1.4 cm; however, this layer was totally

absent in low bum areas the first year after the tire (fig. 1).

depth (cm)

n

3.5

Unburned LOW

Bum Level

High

Figure 1 . Forest floor depth one year after fire occurrence.

[Values in boxes represent comparisons among Oa layers

while values in parentheses represent totals (Oi-Oe + Oa).

Means followed by the same letter are not significantly

different at the 0.05 level.]

30
Although the Oi-Oc layer was consumed following low Several studies (Brender and Cooper 1968; Moehring and

intensity fires, the Oa layer was left relatively intact with a others 1966; Romancier 1960) have demonstrated that

mean depth of 1.6 cm. Mean depth of the Oa layer in prescribed burning does not result in a significant loss of

unburned areas was also 1.6 cm. Unlike low intensity surface forest floor material. In fact, a single prescribed bum may

fires, high intensity fires resulted in the complete destruction remove only a small percentage of the total forest floor depth

of the entire forest floor (Oi-Oe + Oa). Therefore, the and weight. Results from this and other related studies

remaining discussion of forest floor parameters will focus indicate that reductions in forest floor material arc directly

mainly on differences between low and unburned areas. related to tire intensity.

Similar to trends in depth, forest floor weight also changes in

direct proportion to the intensity of the fire. Mean weight of

the Oi-Oe layer for unburned sites averaged 24390 kg ha.’

while no weights were recorded for low bum areas due to the

consumption of this layer during pyrolysis (fig. 2). Unlike

the Oi-Oe layer, Oa layer weights were not different between

unburned and low bum areas.

Total C concentration (%) and content (kg hd’) were

significantly higher in the residual Oa material collected from

low bum areas compared to unburned Oa material. Total C

concentration of Oa material from low and unburned areas

were 61 .O and 52.7 percent, respectively (fig. 3). Since

post-tire Oa weights were similar for low and unburned areas,

increases in total C concentration also resulted in greater C

content (kg ha-‘) of the Oa layer on low bum sites. Overall,

however, total C content for the entire forest floor was 50

percent lower on low bum areas, compared to unburned

areas, due to the consumption of the overlying Oi-Oe layer.

Weight (kg/ha) (Thousands)

- -

5 0

40

30

2 0

1 0

0

(18.7b)

0

/’

Unburned low

Burn Level

High

0 Oa layer RiEl Oi-Oe layer 1

Figure 2 Forest floor weight (kg ha.‘) one year aflcr fire

occurrence. Means followed by the same letter are not

significantly different at the 0.05 level.

Total forest floor depth and weight, represented by combining

the Oi-Oe and Oa values, was significantly less on burned

areas due to the partial or complete destruction of forest floor

material (figs. 1, 2). Assuming that high, low, and unburned

areas had similar forest floor depths and weights prior to fire

occurrence, low bum values would then represent a 47

percent reduction in depth and a 57 percent reduction in

weight while high intensity bum areas represent a 100 percent

reduction in depth and weight compared to unburned sites.

Reductions in forest floor depth and weight following burning

have been well documented in the literature. Immediately

aficr a periodic winter bum in the south, total forest floor

weights were decreased from 26900 kg ha t to 19600 kg ha I .

ARer 20 years of annual summer bums, the forest floor was

reduced to 7800 kg ha ‘, whereas annual winter burns reduced

the forest floor to 14600 kg ha-’ (Brendcr and Cooper 1968).

TC (‘W TC (kg/ha) (Thousands)

7 0’

601

50

40

30

20

10

0

52.7a

6 1 .Ob

0 0

Unburned LOW

Burn Level

High

Figure 3 . Total carbon concentration (%) and content (kg

ha t) of the Oa layer one year after fire occurrence. Means

followed by the same letter are not significantly different at

the 0.05 level.

1 4

12

1 0

6

6

131
The major elemcnbl components of organic matter include N,

0, H, and C. During normal decay processes of organic

matter, some C is converted to CO,, some is incorporated

into microbial tissue while the remaining C is converted to

more stable humus forms which are higher in total C

concentration than the original organic matter (Stevenson

1986). Pyrolysis reactions tend to accelerate this process by

volatilizing lighter atomic elements (N,O,H) while converting

the original organic matter to more stable humus forms that

contain a higher percentage of reduced, elemental C.

Likewise, other basic cations (K,Ca,etc.) along with reduced,

elemental C, are concentrated in the residual ash following

fire. The reduction of C and the concentrating effect of

pyrolysis reactions would explain the increase of total C noted

in the Oa layer of low bum areas in this study. This reduced

form of C does not supply a readily mineralizable source for

microbial assimilation and may remain in the soil as fusain

for many years (Sopcr 1919; Hansen 1943). Since C is a

large chemical constituent of organic matter (approximately

58%), a loss of organic matter following fire will result in a

reduction in C content from the site. The more intense the

tires, the greater the consumption of the forest floor and

subsequent C pool. Organic matter also serves as an

important source of N, P, and S, which are also reduced

following consumption of the forest floor.

Similar to C trends, total N concentration (ppm) and content

(kg ha ‘) were also higher in the residual Oa material of low

bum areas compared to unburned Oa material (fig. 4). An

increase in total N following low intensity tires may be due,

in part, to an increase in inorganic N in the Oa layer.

Several authors (White and others 1973; Klemmedson and

others 1962; Kovacic and others 1986) have found similar

trends in inorganic N concentrations one year after prescribed

tires. This increase may be attributed to incomplete

combustion and volatilization of N with subsequent downward

translocation and reprecipitation of N gases in cooler forest

floor and mineral soil layers (Klemmcndson and others 1962;

Tangren and McMahon 1976; Wells 1971). Substantial

amounts of NHCN are also produced chemically by soil

heating and microbially after tire. Unlike N&-N, NO,-N is

not produced during soil heating, but is formed during

subsequent mineralization and nitrification processes.

Additionally, White (1986a) found that potential N

mineralization and nitrification increased in residual forest

floor material following prescribed fires. Jones and Richards

(1977) suggested that nitrification processes following fire

may not be due to Nitrosomonas or Nitrobacter bacteria but

to heterotrophic fungi. Increases in total N may also be

correlated with an increase in total C and/or to an increase in

NZ-fixation following fire. N3-fixation may contribute 10 to

100 kg ha 1 of N annually (Stevenson 1986).

TKN @pm) (Thousands)

i

i

2:

20

1 5

1 0

5

0

14.4a

Unburned Low

Burn Level

J-KN &e/ha)

0 0

High

I----- m TKN (ppm) m TKN (kg/ha)

Figure 4 Total nitrogen concentration (%) and content (kg

ha ‘) of the Oa layer one year after fire occurrence. Means

followed by the same letter are not significantly different at

the 0.05 level.

Assuming homogeneity on burned and unburned sites prior to

fire occurrence, combined forest floor (Oi-Oe + Oa) C and N

values for low burn areas would represent a 50 and 28

percent reduction, respectively, compared to unburned values

(figs. 5, 6). These reductions in total C and N content of the

residual forest floor in low bum areas is attributed to the

consumption of the overlying Oi-Oe layer during pyrolysis.

Generally, low intensity tires, as occurred on some areas in

this study, may remove only the Oi-Oe layer, leaving the Oa

layer relatively intact. This residual Oa layer serves to

protect the underlying mineral soil from erosion and provides

a more mineralizable source of nutrients (White 1986a).

Conversely, high intensity fires may remove the entire forest

floor, thereby exposing the mineral soil to the vagaries of

weather and possibly reducing infiltration, water holding

capacity, and other associated benefits attributable to the

surface organic matter.

500

400

300

200

100

3

132
Total Carbon (%) (Thousands)

4--- -;*sa

I

Unburned

11.4b

-I 0 _. -4.w - ---

Low

Burn Level

High

m ()a layer EB Oi-Oe layer

Figure 5 - Total carbon content (kg ha ‘) of the entire forest

floor (Oi-Oe + Oa values) one year after fire occurrence.

Means followed by the same letter are not significantly

different at the 0.05 level.

700

J

Total Nitrogen (kg/ha)

577a

/

Unburned Low

Burn Level

High

Figure 6 . Total nitrogen content (kg ha”) of the entire forest

floor (Oi-Oe + Oa values) one year aher tire occurrence.

Means followed by the same letter arc not significantly

different at the 0.05 level.

Mineral Soil Parameters

Fire generally results in a decrease in soil acidity. Soil

acidity in the surface 10 cm of mineral soil was 4.3 in

unburned areas and significantly higher than low and high

bum areas which measured 4.6. This rise in pH following

lirc is generally attributed to an influx of nutrient-rich ash and

a resultant increase in exchangeable cations in the surface

mineral soil. The magnitude of change in soil acidity is

dependent upon such factors as nutrient concentration of the

overlying litter, cation exchange capacity (CEC), buffering

capacity and original pH of the soil, and rainfall frequency

and amounts (Gricr 1975; Metz and others 1961). McKee

(1982) found that soil acidity decreased in the surface (O-8

cm) mineral soil following a combination of different

prescribed bum treatments on four coastal plain pine sites.

Changes in pH ranged from 0.1 to 0.4 units across the four

study areas. Greater changes in @-I may occur, however,

most studies indicate changes of less than one pH unit

following prescribed tires which return to prcbum levels

within a few years.

Total C and N levels in the surface 10 cm of mineral soil

were higher on low bum sites compared to unburned areas

(iigs. 7, 8). Conversely, high bum areas had lower total C

and N levels than unburned sites. An increase in total C

following low intensity fires may be associated with the

redistribution and movement of colloidal-sized charred

material, high in elemental carbon, downward from the

overlying residual ash into the mineral soil by gravity and

water (Mctz and others 1961), and/or by isoelectric

precipitation of alkali humatcs produced during burning (Viro

1969). A large portion of the mineral soil organic matter

(humus) is associated with the forest floor-mineral soil

interface and within the top 2-3 centimeters of the mineral

soil. Following the removal of the entire forest floor by high

intensity Iires, soil humus may also be destroyed where

temperatures exceed 250°C. These temperatures are easily

achieved during high intensity fires where temperatures have

been shown to exceed 700°C at the mineral soil surface

(Debano and Rice 1971). Another factor which may

contribute to a loss of total C from the mineral soil is the

physical removal of the surface mineral soil and associated C

due to erosion. Once the protective forest floor mantle is

removed from the site, such as by high intensity tires, erosion

may lead to a direct loss of C and other nutrients from the

site. In this study, erosion was not measured, but was

observed by the accumulation of mineral soil at downslope

positions below the high intensity bum areas. Low and

unburned sites did not show any observable signs of surface

erosion.

Total N followed similar trends to total C levels. Increases in

total N following fire are likely due to an increase in organic

and inorganic forms of N. Reasons for these increases in

total N following tire have already been discussed earlier in

relation to forest floor material.

133
Total Carbon (kg/ha) (Thousands)

20 -/’

Ii 16.2a

14.6a /

10 -i

5

0

!

Unbirned Low

Bum Level

High

Total Nitrogen (kg/ha)

/

401b

/

328a

314a

/

Unburned Low

Bum Level

High

/ m TC (kg/ha) I!%?i TKN (kg/ha)

Figure 7 . Total carbon content (kg ha ‘) within the top 10 cm Figure 8 - Total nitrogen content (kg ha”) within the top 10

of the mineral soil one year aher fire occurrcncc. Means cm of the mineral soil one year after fire occurrence. Means

followed by the same letter are not significantly different at followed by the same letter are not significantly different at

the 0.05 level. the 0.05 level.

KCI-ext. N (DDm)

Inorganic N levels were signiticantty higher on burned areas

compared to unburned areas (fig. 9). Similar results by other

authors (Bums 1952; Wells 1971; Alban 1977; White 1986a;

Covington and Sackct 1986) have also shown increases in

inorganic N following burning which is generally attributed to

an increase in mineralization rates (Likens and others 1970;

White 1986b; Lodhi and Killingbeck 1980) following a

disturbance such as fire or clearcutting. Mineralization

(ammonification t nitrihcation) is the process whereby

organic N is converted to plant available inorganic forms

through microbial-mediated biochemical transformations and

is influenced by factors which affect microbial populations

and activities such as pH, temperature, soil moisture, and the

presence of compounds such as polyphenolics, tannins, and

monotcrpenes. Following tire, increases in soil pH,

temperature, and moisture, and the removal of inhibiting

compounds favor increased rates of mineralization. An

increase in inorganic N may also be associated with the

downward translocation and rcprecipitation of N gases at

cooler mineral soil depths. Klemmendson and others (1962)

showed that burning accelerated N movement from the

overlying forest floor into the mineral soil. Although

mineralization rates vary over time with fluctuations of the

factors which influence this process, the results of our

point-in-time sampling of inorganic N reflects the conditions

found by other investigators.

10.0b

r-----r

7.5b

Unburned Low

Bum Level

High

Figure 9 - KCLextractable nitrogen concentration (ppm)

within lhe top 10 cm of the mineral. soil one year alter fire

occurrence. Means followed by the same letter are not

significantly different at the 0.05 level.

134
Most of the increase in inorganic N following low intensity

fires is due to NH,N, whereas most of the increase in

inorganic N following high intensity fires is due to an

increase in both NH,-N and NO,-N levels (fig. 9). A lack of

NO,-N in low and unburned areas suggests that nilrification

processes may be inhibited by some factor. Nitrification

processes are severely limited at pH values below 4.5,

insufficient soil moisture and cool temperatures, and in the

presence of inhibitory compounds such as phenols, tannins,

and monoterpenes (Stevenson 1986; White 1986b; Lodhi and

Killingbeck 1986). Given the fact that low and high intensity

areas had a pH of 4.6, the increase in NH,-N and the lack of

NO,-N following low intensity fires suggests that the process

of ammonification may be enhanced or less affected than

nitrilication in the presence of factors such as monotcrpenes,

phenols, and tannins in the residual forest floor material.

White (in press) suggested that monoterpenes may have a

greater inhibitory effect on Nitrosomonas and Nitrobacter

populations, responsible for nitrification, than on

microorganisms responsible for ammonification. Lodhi and

Killingbeck (1980) found that water extracts laden with

soluble polyphenolics, tannins, and monoterpenes reduced

numbers of Nitrosomonas by 93 percent. Other factors

possibly contributing to an increase in the NO,-N to NH,-N

ratio, following high intensity fires, is the fact that the

overstory canopy was left mainly intact following low

intensity fires, whereas complete ovcrstory mortality result&

following high intensity fires. This overstory removal

following high intensity fires results in more direct solar

radiation and a resultant increase in soil temperature.

Sub-surface soil moisture also increases due to removal of

transpiring vegetation. Increased soil temperatures and

moisture favor rapid nitrilication (Stevenson 1986).

Since N is the most limiting nutrient on most forest sites and

C sources contributing to the “Greenhouse Effect” are

important considerations, changes in these pools should be

considcrcd. Total C and N pools (forest floor + mineral soil)

in low bum arcas one year alter fire occurrence were 25 and

10 percent lower, rcspcctivcly, than unburned areas. Unlike

low intensity bum areas, total C and N pools in high intensity

burn areas were 68 and 65 percent lower, respectively, than

unburned areas. Low intensity lires resulted in a partial

redistribution of C and N from the forest floor into the

mineral soil with a slight overall reduction in the combined

nutrient capital. High intensity fires, however, resulted in no

redistribution of nutrients and a greater loss of combined C

and N capital from the site. Although reductions in these

pools may bc severe following high intensity fires, losses may

not be altogether detrimental when considering the synccology

of mixed pine forests on these poor sites. Periodic severe

fires may bc necessary to prevent stagnation and to promote

successful regeneration and establishment of these species

while inhibiting more nu(ricnt- and moisture-demanding

hardwood species.

The impacts of fire on soil are highly variable and depend on

such factors as tire intensity and duration, weather conditions,

and forest floor and mineral soil characteristics at the time of

burning. Overall, low intensity fires in this ecosystem seem

to have little deleterious effects on soil properties and may, in

fact, facilitate increased mineralization rates, thereby releasing

a pulse of nutrients to the site. Increases in pH, microbial

activity and nitrogen fixation may also occur. Conversely,

high intensity fires result in the removal of the protective

forest floor and a much greater loss of nutrients from the site.

However, a question must be raised in relation to the overall

impact of high intensity tires in relation to site quality and the

associated vegetation occupying a site. Is the loss of nutrients

more significant on better sites where there is a greater buffer

capacity and the total loss of nutrients in proportion to the

whole is small? Or is the loss more significant on poorer

sites where a smaI1 loss may represent a Iarge portion of the

nutrient capital for that site? Given adequate time without

disturbance, forest floor and mineral soil properties tend to

increase in both depth and fertility. On minimally developed

soils as in this study, where soil depth is shallow and inherent

fertility of parent material is low, much of the sites’ fertility

is derived from and dependent upon the turnover of forest

floor material and external inputs. Considering the five major

soil-forming factors, and in the absence of disturbance, depth

and fertility of the mineral soil should increase, thereby

allowing more nutrient-demanding species to invade and

compete for site resources.

Tree species occupying better, more productive sites generally

have higher nutrient requirements; thercforc, even a small

change in nutrient levels may result in a species shift.

Convcrscly, tree species occupying poorer sites may have

lower minimal nutrient requirements and may actually depend

on periodic fire to disrupt the progress towards site quality

improvcmcnt. In fact, one of the possible secondary

functions for the high content and slow turnover rate of

monoterpcnes in fresh litter of fire-adapted Pinus species, may

be to increase probability of fire occurrence. Terpenes and

resins have a heat of combustion of 7720 calories per gram,

which is twice that of cellulose (Rothermal 1976). These

extractivcs are outgassed early in the pyrolysis process and

may contribute three-fourths of the total flame height and

intensity of the flame zone (Philpot 1969).

It is possible that low intensity fires would not provide the

necessary conditions required by Tahle Mountain pine to

~ucccss~ully regenerate and compete, whereas high intensity

&res generally result in (1) opening of scrotinous cones; (2)

removal of the forest floor providing favorable seed bed

conditions; (3) removal of inhibitory compounds such as

monoterpcncs, tannins, and polyphenolics; and (4) ironically,

limiting site quality improvcmcnt by preventing nutrient

buildup to occur. Thus, a combination of ihcsc factors may

result in retarding the invasion of more nutrient-demanding

competitors and sustaining the endemic Table Mountain pine

on nutrient- and moisture-limiting sites.

135
SUMMARY

Total forest floor thickness and weight were significantly

reduced following low and high intensity tires. However, low

intensity tires consumed only the Oi-Oe layer, leaving the Oa

layer relatively intact, whereas high intensity fires resulted in

the complete removal and destruction of the entire forest

floor. Total C and N content of the Oa layer was higher on

low bum areas compared to unburned Oa material. However,

an overall reduction of forest floor total C and N resulted

following both low and high intensity tires due to the partial

or complete destruction of forest floor material.

Mineral soil pH was significantly higher in both low and high

intensity bum areas compared to unburned areas.

Additionally, total C and N content of the surface IO cm of

mineral soil was also higher on low bum areas compared to

unburned areas. However, high bum areas had lower total C

and N levels. Inorganic N levels were significantly higher in

both low and high intensity bum areas, thereby providing a

pulse of available N for plant uptake.

ACKNOWLEDGEMENTS

The authors would like to thank Sigma Xi for a grant-in-aid

of research and the National Park Service for funding this

project.

LITERATURE CITED

Alban, D.H. 1977. Influence on soil properties of prescribed

burning under mature red pine. USDA For. Serv. NC

For. Exp. Sta. Res. Pap. NC-139, 8p.

Allen, R.M. 1967. Geology and mineral resources of Page

County. Dept. of Conserv. and Economic Development.

Virg. Div. of Mineral Res. Bull. No. 81, 78~.

Bardcn, L.S., and F.W. Woods. 1976. Effects of fire on

pine and pine-hardwood forests in the Southem

Appalachians. For. Sci. 22:399-403.

Blake, G.R., and K.H. Hartge. 1986. Bulk density. In

Methods of Soil Analysis, Part I-Physical and

Mineralogical Methods (2nd ed.). Arnold Klute ted.).

Agron. Monogr. No. 9, Madison, WI. pp. 363-375.

Bremner, J.M., and C.S. Mulvaney. 1982. Total nitrogen.

In Methods of Soil Analysis, Part Ii-Chemical and

Microbiological Properties (2nd ed.). Page, A.L., R.H.

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periodic burning on soil nitrogen concentrations in

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Biol. Biochem. 9:383-392.

136
Klemmedson, J.o., A. M. Schultz, H. ~~~~~~ and H.H.

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litter on total soil nitrogen. Soil Sci. Sot. Am. PrOC.

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Kovacic, D.A., D.MSwift, J.E. Ellis, and T.E. Hakonson.

1986. Immediate effects of prescribed burning on mincrd

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inhibition of nilrificalion and nitrifying bacteria in a

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component in Table Mountain pine ecosystems?

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Ccol. Survey Bull. 16~.

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Pub., New York, N.Y. 380~.

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chemical properties and nutrient availability. In USDA

For. Serv. SE For. Expt. Sta. Proc. Prescribed Burning

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341’.

White, C.S. 1986a. EfTects of prescribed lire on rates of

decomposition and nitrogen mineralization in a pondcrosa

pine ccosystcm. Biol. and ht. of Soils 2:87-95.

white, C.S. 1986b. Volatile and water-soluble inhibitors of

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pine ccosystcm. Biol. and Fcrt. of Soils 2:97-104.

White, C.S. In press. The role of monoterpenes in soil

nitrogen cycling processes. Accepted by

BioEcochemistry.

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Heat effects on nutrient release from soils under

pan&rosa pint. .I Range Manage. 3_6:32-24.

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39:303-333.

137
THE INTERACTION OF PRESCRIBED FIRE, MONOTERPENES, AND

SOIL N-CYCLING PROCESSES IN A STAND OF

PONDEROSA PINE (Pinus ponderosa).

Carleton S. White’

Abstract-Monotcrpenes, principal components of turpentine, have been shown to be invcrscly cor&a[cd

with N mineralization and nitrification rates in ponderosa pine (Pinus pondcrosa Dougl. ex Laws.) soil. and

sre suspected to be allelopathic substances causing germination inhibition or growth regulation. Because

monoterpenes are highly flammable, prescribed fire may represent an efficient method of lowering

monoterpene concentrations in both organic and mineral soil horizons. Samples of the forest floor and the

0- to IO-cm soil horizon were collected from four separate plots within a pondcrosa pine stand immediately

bef0r.e and a&r fore treatment. The prescribed tire treahnents resulted in a greater proportionate loss of

monoterpenes than of forest-floor biomass: loss of 55 percent of the forest-floor mass corresponded to a 99

percent loss of monoterpenes. Forest-floor inorganic N content was doubled following treatment, with all

the increase as NH,‘-N; the mineral soil inorganic N content was unchanged. During incubation for

potential N mineralization, only the burned forest-floor samples produced nitrate. Thus, the prescribed lire

treatments resulied in potentially favorable changes in organic malter quantity and quality, levels of

inorganic N, and potential rales of N-cycling processes.

INTRODUCTION

Management of southwestern pondcrosa pine (Pinus

ponderosa Doug]. ex Laws.) olkn includes the USC of

prescribed burning to reduce accumulated fuels. Studies have

documented increases in the inorganic N content of forestfloor or mineral soil horizons immediately after burning

(White 1986a; Kovacic and othcrs1986) or within the first

growing season aRer burning (White 1986a; Ryan and

Covington 1986; Covington and Sackett 1984; Covington and

Sack&t 1986). The increase in inorganic N is accompanied

by a decrease in total N within the forest floor (White and

others 1973 ; Klemmcdson and others 1962; Kovacic and

others 1986) and by an increase in biomass and nutrient

content of understory vegetation (Harris and Covington 1983;

Vlamis and others 19.55).

White (1986a) conducted research on the effects of prescribed

burning on four plots within a ponderosa pine stand located in

the Jemcz Mountains of New Mexico. The bum treatments

resulted in an immediate increase in the amount of NH,+-N in

the forest floor. Potential N mineralization and nitrilication,

as determined by laboratory incubations, were increased in

samples of the forest floor collected within 12 hours of the

bum. Nitrogen mineralization and nitrification potentials of

the mineral soil were significantly increased in only 1 of 4

plots immediately after the bums; howcvcr, both processes

were significantly increased in the mineral soil from all plots

6 months after the bum and remained elevated 10 months

after the bum. White suggested that the immediate increase

in nitrilication in the forest floor and the subsequent increase

‘Research Assistant Professor, Department of Biology, University of

New Mexico, Albuquerque, NM.

138

in nitrification in the mineral soil could be explained by the

IOSS of volatile inhibitors from the forest floor.

The roles of volatile and water-soluble inhibitors of N

mineralization and nitrificatjon in the forest floor of the same

pondcrosa pine ecosystem were studied by White (1986b).

Water extracts of unburned forest floor inhibited nitrification

by 17 percent when applied to actively nitrifying mineral soil

from the same pondcrosa pine ecosystem after the bum

treatment. Placing vials containing unburned forest floor or

selected monoterpenes of ponderosa pine in sealed jars that

contained actively nitrifying soil inhibited nitrification by 87.4

percent and 100 percent, respectively, and inhibited N

mineralization by 73.3 percent and 67.7 percent, respectively.

White (1986b) suggested that organic compounds that are

water-soluble and volatile act as inhibitors of N mineralization

and nitrilication in this ponderosa pine ecosystem. Inhibition

of nitrification was also observed by Lodhi and Killingbeck

(1980), who found that water extracts of pondcrosa pine

needles applied to soil suspensions reduced numbers of

Nirrosomonas by 93 percent. They suspected that

polyphenolics and condensed tannins were the active

compounds inhibiting nitrification. It appears that a number

of secondary compounds produced by ponderosa pine could

act synergistically to inhibit nitrilication and N-mineralization

processes.

Laboratory bioassays (White, in press) showed that

monotcrpenes could interact with N-cycling processes through

four mechanisms: (a) by reducing net N mineralization; (II)

by inhibiting nitrification; (c) by enhancing assimilatory

uptake of NO;-N; and (d) by stimulating immobilization of

inorganic N. The net effect of monoterpene addition on soil
inorganic N content was to reduce the amount of NO,‘-N

relative to NH,+-N, leading to net immobilization of inorganic

N at high monoterpenc additions (fig. 1). While (n\r PRESS)

also showed that monoterpcnc concen&ations were highest in

the L horizon and declined by an order of magnitude with

each descending organic and mineral soil horizon (fig. 2).

Prescribed burning has the potential to reduce the total

monoterpene content of the soil profile drastically bccausc the

organic horizons rich in monoterpenes would be consumed

preferentially.

The goal of this stady was to identify the changes in

monoterpenc and inorganic N concentrations in the forest

floor and mineral soil immediately following (within hours)

prescribed burning of plots within a ponderosa pine stand, and

to identify the change in potential N mineralization and

nibilication characteristics of these horizons.

METHODS

The present study was conducted on the same site where

White (1986a, in press) had worked. The site is in northcentral New Mexico, within the Jemez National Forest, near

Bear Springs (elevation 2225 m). It is located on a small

knoll of volcanic ash and pumice, with very uniform A

horizon soils. Slope of each plot was less than 7”. The

overstory was composed entirely of pondcrosa pine.

Scattered seedlings and saplings of pinyon pine (Pinus edUliS)

and various species of junipers (Juniperus spp.) were present.

White originally chose the plots to avoid heavy fuel deposits

and to favor areas with approximately equal accumulations of

forest floor material and woody debris. Four of the 8 original

plots were treated with prescribed burning on 7 November

1983. The 4 remaining plots were used in this study

foilowing a study of seasonal dynamics in mOnOttYpCI%

content and potential N mineralization and nitrification

characteristics (White, in press).

‘*’n 0 Ammonium

\ \

q Nitrate

b

Relative Monoterpene Concentration

Fig. 1. Generalized response of soil inorganic-N levels to

increasing monoterpenc additions. Monoterpcnc additions arc

relative values, not actual concentrations (from White in

Pm%).

- FRESH 0 1 LI lTEA

OLD

LITTER

Oe F

0.3 H

O-1Ocm

A MINERAL

ScnL

MONOTERPENO(D LEVEL

lvg 1 81

.I loo IO’ d fl3 x)’

Fig. 2. Mean monoterpenc concentration (n = 8) within the

designated soil horizons of a ponderosa pine stand in New

Mexico. The fresh litter was collected in October 1987; other

horizons were collected in November 1987. Horizons are

drawn in approximate proportion to actual depth in the field

based upon the mineral soil horizon equal to IO cm.

The plots were burned by U.S.D.A. Forest SerViCe perSOrlnC!~

on 27 October 1988. A fire break was scraped around the

perimeter of each plot and the associated 5-m buffer zone.

The plots Were burned by igniting three ships about 5 m apart

parallel to the length of the plot. Rates of fire spread ranged

from 0.02 to 0.05 m s.‘, OII 3 of the 4 plots, postbum

samples were collected within one hour of burning. The

fourth plot, which had a southern aspect, burned the longest;

glowing combustion was observed about 2 hours after

ignition. Samples fium the fourth plot were taken

approximately 3 hours aRer ignition. The amount of forest

floor consumed by the burning was determined as the

diffcrcncc bchvccn ash-free mass of the prcbum and postbum

samples.

Collections were made from each plot on 27 October 1988

immediately before and after burning. Each plot measured

4m by 9m. A 5-m buffer zone around the perimeter of each

plot was also burned. One sample per plot was collected

before burning, and one sample along the same line transect

was collected aRcr burning. For each sample, all of the

forest-floor material (0 horizon) beneath a 0.25 m* template

was /jarvested. The template was placed on the forest floor, a

139
knife was used to make cuts around the template border, and

the surrounding forest floor was scraped away. Mineral soil

was collected to a lo-cm depth with a lo-cm-diameter corer.

The soil collection was made at the center of the area from

which the forest floor was harvested.

All samples were placed in resealable plastic bags and kept in

the dark on ice during transport to the laboratory. In the

laboratory, all samples were kept refrigerated at 4 “C. Roots

with diameter greater than about I mm were removed by

hand sorting. All material larger than 6.4 mm in diameter

was removed from all samples by sieving. Needles and other

materials too long to lit into the incubation cup were cut into

appropriate lengths (usually into halves or thirds). All

samples were corrected for ash content by determining weight

remaining after ignition at 500°C.

Nitrogen mineralization and nitritication potentials were

measured by aerobic incubation. After a portion of each

sample had been adjusted to 50 percent of determined waterholding capacity (WHC) by methods described in White and

McDonnell (1988), a total of 17 subsamples per horizon were

apportioned into I25-mI plastic cups. Each cup received

approximately IO g dry-weight (DW) of mineral soil or 3 g

DW of forest floor. One subsample of each horizon was

immediately extracted with 100 ml 2 E KC1 for NO,--N and

NH,+-N analyses, and another subsample was frozen (-5 “C)

prior to processing for monoterpene analysis. The remainder

of the cups were covered with plastic wrap, sealed with a

rubber band, and incubated in the dark at 20 “C. As reported

by Jones and Richards (1977), the plastic wrap minimized

water loss during incubation, yet exchange of CO, and 0, was

sufficient to keep the subsamples aerobic during incubation.

Moisture content was monitored by weight loss and

replenished as needed

At weekly intervals to 10 weeks, a subsample of each horizon

was removed for NO;-N and NH,+-N analyses. After

extraction with 100 ml 2N KC1 for 18-24 hours, the clarified

supcrnatant was analyzed for NH,‘-N and NOi-N +NO;-N

(NO;-N was never detected) on a Technicon AutoAnalyzer.

White (1986a) has described the procedures employed.

A&r incubation for 1, 2, 4, 7, and IO weeks, a subsample of

each horizon was frozen (-5 “C) prior to processing for

monoterpcnc analyses. Subsamplcs of mineral soil were

transferred to plastic scintillation vials and stored at -80 “C.

A mortar and pestle were used to gring the forest floor

subsamples separately under liquid nitrogen to break apart the

larger material. These subsamplcs were then transferred with

liquid nitrogen to a Tecatori centrifugal grinder fitted with a

LO-mm screen. After grinding, the forest-floor material was

transferred to plastic scintillation vials, sealed, and stored at U

80 “C until monoterpene analyses could be performed.

Subsamples (ranging in weight from 9 to 10 g for mineral soil

and 2 to 3 g for forest floor) were extracted with 10 ml of

ether, which contained a known amount of fenchyl acetate for

use as an internal standard, in a 50-ml Erlcnmeyer flask that

was covered with paraffin film and aluminum foil. Aher 1

hour extraction at room temperature, the ether was decanted

and centrifuged (mineral soils did not require centrifugation).

The clarified supematant was pipetted into a ground-glassstoppered culture tube, sealed with paraffin film, and

refrigerated at 4 “C. A 4-~1 portion of the refrigerated ether

extract was injected into a Shimadzu GC-9 fitted with a split

injector (split ratio was 50: I), a bonded methyl silicone

capillary column (25 m in length, 0.25 mm in inside

diameter, 0.25 micron in film thickness), and a flameionization detector. The injector temperature was 270 “C,

flow rate was 4 cc min.‘, and initial oven temperature was 60

“C. Oven temperature was increased by 4 “C min.’ to 109 “C,

then by 40 “C min.’ to 250 “C. Individual monotcrpene

standards (verified with CC-MS) were added to sample

extracts, and monoterpenes were identified by cochromatography. Peak area was converted to mass of

individual monoterpenes by means of calibration curves

generated with standards. An average calibration factor was

used to convert the peak area of each unknown to relative

mass.

The effects of the prescribed tire treatment were determined

for each analysis by comparing the 4 pretreatment samples to

the 4 post-treatment samples by analysis of variance (control

vs. treatment, n=4). Ash-free mass lost upon ignition was

used as a measure of burn intensity since rates of spread and

flame heights were approximately equal for each plot. All

concentration data were converted to mass per unit area for

seasonal comparisons. Net N mineralization was defined as

the increase in the amount of inorganic N (NH,‘-N f NO, -

N) over the entire IO-week incubation. Net immobilization

was defined as the decrease in the amount of inorganic N

over the entire IO-we& incubation. Relative nitrification was

defined as the percent of the total inorganic-N pool comprised

by NO<-N at the end of the incubation period. All statistical

analyses were performed with SAS-PC r (Statistical Analysis

System, SAS Institute Inc.) or with S&tViewr (Brainpower,

inc.). The a pnbn’probabihty level accepted to be significant

was <O. 10; however, the probability level for each statistical

analysis will be given below.

140
Total Monoterpene Concentration

RESULTS

The amount of forest floor remaining afier the prescribed

burning treatments was significantly less than before treatment

(P<O.O03), but varied from 38 to 80 percent (fig. 3). The

lowest amount of mass lost was approximately equal to the

mass of the L horizon alone as determined in previous

collections (White in press), while the greatest amount of

mass lost was approximately equal to the entire L horizon and

about half of the combined F and H horizons.

Forest Floor Mass

N

3ow

E

e p

1 2000 CA Pre Mass

m Post- Mass

zi IL 1000

f

(P 5 0.003)

a

0

I 2 3 4

PLOT

Fig. 3. Ash-free forest floor mass before (Pre-Mass) and

after (Post-Mass) prescribed burning. Probability level for

the comparison of prebum and postbum mass is shown

(n=4).

Total monoterpene concentration in the postbum forest floor

declined in 3 of the 4 plots and increased in the plot with the

smallest loss of mass (fig. 4). When expressed on an area

basis, the total amount of monoterpene declined in all plots

(P=O.O67, fig. 5). Monoterpene content of the postbum

forest floor was a frmction of the fraction of original forestfloor mass (2=0.993, P < 0.01; fig. 6). The bum

treatments reduced the content of some monoterpcnes to a

greater extent than others. Monoterpenes with a doublebonded carbon atom in a terminal position on the molecule

(including camphene, b-pincne, sabinene, Iimonene, myrcene,

and limoncne oxide; fig. 7) and monocyclic monoterpencs

(including p-cymene, a-phellandrene, limonene, and gterpinene; fig. 8) were reduced to very low or undetectable

levels, even in the plot that lost the least amount of forest

floor (plot 1).

The bum treatments significantly increased the amount of

inorganic N in the forest floor (P=O.O12; fig. P), with all the

increase due to higher NH,‘-N content and no change in NO,’

-N content. The amount of inorganic N in the mineral soil

was unchanged by the bum treatment (P=O.91; fig. 10).

Measurement of potential N mineralization and nitritication

for the prebumed forest floor showed net immobilization of

inorganic N and no net nitritication (net decline in inorganic

cn 100

2

75

i 50 0 Preburn

i Postburn

5

E

(P : 0.165)

25

z

0

I 2 3 4

PLOT

Fig. 4. Total monoterpenc concentration of the 0 horizon

before (Preburn) and aRer (Postbum) prescribed burning.

Probability level for the comparison of prebum and postbum

concentrations is shown (n=4).

Total Monoterpenes per Unit Area

M)O,

300

200

100

q Preburn

0 Postburn

P : 0.067)

0

I 2 3 4

PLOT

Fig. 5. Total monoterpene content of the combined organic

and 0- to IO-cm mineral soil horizons before (Pre-bum) and

after (Postbum) prescribed burning. Probability level for the

comparison of prebum and postbum content is shown (n=4).

Relationship Between Monoterpene

Content and Consumption of Forest Floor

ol , . , . , , 1

0.3 0.4 0.5 0.6 0.7 0.6

Fraction of Original Forest-floor Mass

Fig. 6 Relationship between monoterpene content of the

combined postbum organic and 0- to lo-cm mineral soil

horizons and the amount of consumption (expressed as the

remaining fraction of original forest-floor mass) by the

prescribed burning.

I41
Terminal C=C Bond Monoterpenes per Unit Area

Cl Preburn

m Poslburn

(P = 0.006)

2 3 4

PLOT

Fig. 7. Content of monoterpencs that contain terminal

unsaturated carbon-carbon bonds for the combined organic

and 0- to lo-cm mineral soil horizons before (Prebum) and

after (Postbum) prescribed burning. Probability level for the

comparison of prcbum and postbum content is shown (n=4).

Monocyclic Monoterpenes per Unit Area

2 0

N

7

E

E”

1 5

c 10 c] Prebum

it

n Postburn

2 5

z

(P : 0.045)

0

I 2 3 I

PLOT

Fig. 8. Content of monocyclic monoterpcnes for the

combined organic and 0- to IO-cm mineral soil horizons

before (Prcbum) and after (Posthum) prescribed burning.

Probability level for the comparison of prebum and postbum

content is shown (n =4).

Extractable Inorganic N per Unit Area

500 ,

n

‘E 400

k? 300

z

5 200

P 100 (P : 0.012)

I 2 3

PLOT

Fig. 9. Extractable inorganic N content of the 0 horizon

before (Prebum) and alter (Postbum) prescribed burning.

Probability level for the comparison of prebum and postbum

content is shown (n =4).

N, shown by comparison of prebum values in figures 9 and

11). Although the burned forest floor showed the same basic

pattern of net immobilization (difference in postburn values in

figures 9 and 1 l), the potential N mineralization and

nitrilication pattern for the burned forest floor substantially

deviated from the pattern shown by the pre-burned forest

floor in two ways. First, net inorganic N levels in the burned

forest floor began to increase rapidly over the final 3 weeks

of incubation (fig. 12), whereas the pre-burned forest floor

showed very little increase over the same period. Second,

forest floor samples from all of the burned plots produced

NO;-N during the IO-week incubation, whereas all of samples

from the pre-burned plots showed no detectable amount of

NO;-N after the IO-week incubation. When the amount of

NO;-N present at the end of incubation in the four burned

forest floor samples was compared with the amount in the

prcbumcd samples (none in all 4 prcbumed), the difference

was not statistically significant (P=O. 18). In part, the lack of

significance was due to the large variation in the amount of

NO;-N produced by the burned forest floors. The plot that

had the greatest reduction in forest-floor mass (plot 4)

produced the most NO,-N, but NOs-N production was not

significantly correlated (P > 0.10) either with forest floor

consumption or with the amount of NH,‘-N present in the

sample (representing substrate for nitrilication; fig. 13).

DISCUSSION

The plots burned in the present study were the control plots

for a previous study (White 1986a) on the effects of

prescribed burning in ponderosa pine. In the previous study,

there was a greater range in prebum biomass (from 1650 to

3590 g rn-’ ash-free weight) and in the amount of forest floor

consumed by the bum (from 150 to 2070 g m.2). The

prescribed burning treatments were conducted under similar

conditions (same prescription in both studies) and had similar

characteristics, and therefore had very similar effects on soil

inorganic N levels. In both studies, the increase in forestfloor inorganic N was proportional to the amount of forest

floor consumed, with all the increase as NH,‘-N. This

relationship was highly significant in the first bum (rr=0.97,

P<O.Ol; White 1986a), where the range in forest floor

consumption was greater, but was not as strong in the current

study ($=0.‘78). Burning did not significantly change

mineral soil inorganic N levels in either study, except in the

plot where consumption of forest floor was greatest (White

1986a). Potential N mineralization and nitrilication in the

mineral soil was unchanged in both studies.

Prescribed burning reduced weight of monoterpenes

proportionally more than it reduced forest-floor mass.

Removal of the upper organic horizon with the highest

monoterpene concentration could explain a large portion of

the decline, but monoterpene concentrations after burning

were even lower than those measured in pm-burned F-H

142
Total Extractable inorganic N

Mineral Soil

El Prebum

n Postburn

(P I 0.91)

1 2 3 4

PLOT

Fig. 10. Extractable inorganic N content of the 0- to IO-cm

mineral soil horizon before (Prebum) and after (Postbum)

prescribed burning. Probability level for the comparison of

prebum and postbum content is shown (n=4).

Extractable inorganic N after Incubation

q Ptebum

n Poslbum

(P : 0.056)

I 2 3 4

PLOT

Fig. 11. Extractable inorganic N content of the 0 horizon

before (Prebum) and aRer (Postbum) prescribed burning at

the end of IO-week aerobic incubation for potential N

mineralization. Probability level for the comparison of

prcbum and postbum content is shown (n=4).

Extractable Inorganic N During incubation

Forest Floor

N "1 Preburn

300

MO

100

0

i 4 6 6 *0

WEEKS

- Nitrate

--o--- SumN

Postburn

---+-- Nitrate

- SumN

Extractable Inorganic N after Incubation

q Nitrate

(P x 0.18)

n Ammonium

+ Nitrate

(P 5 0.056)

1 2 3 4

PLOT

Fig. 13. Extractable nitrate and ammonium + nitrate

content of the postbum 0 horizon at the end of IO-week

aerobic incubation for potential N mineralization. Probability

level for the comparison of prebum and postbum nitrate and

ammonium + nitrate content is shown (n=4).

horizons in 4 other collections before the bum (White IN

PRESS). The lower-than-expected concentrations suggest

that monoterpcnes were volatilized and probably cornbusted.

The relationship between monoterpene concentration and

residual forest-floor mass (fig. 6) suggests that reduction in

forest-floor fuels by 50 percent can reduce monoterpcnes by

over 90 percent. Removal of monotcrpenes would reduce the

probability of fire and enhance the potential for higher rates

of N mineralization and nitrilication. White (1986a) observed

increased rates of N mineralization in the forest floor and

mineral soil in bumed plots 10 months after treatment. If

burning that reduces forest-floor mass by 50 percent resuits in

increased soil moisture as in other studies in ponderosa pine

(Haase 1986, Ryan 1978), field conditions will become more

favorable for N mineralization. Thus, bums that consume

half of the forest floor could increase site fertility

significantly.

ACKNOWLEDGMENTS

I thank Co&en Wyss for her valuable assistance throughout

this project, but especially for the monoterpene analyses.

Two reviewers and a technical editor provided helpful

comments. Tony Tanuz and Ken Seonia of the Jemez Ranger

District performed the prescribed burning. Funds for this

project were provided by the National Science Foundation

(BSR-8717514).

Fig. 12. Mean values (n-4) of extractable nitrate and

ammonium + nitrate (Sum N) content of the 0 horizon

before (Prcbum) and aRcr (Postbum) prescribed burning at

w&ly intcrvajs during aerobic incubation at 20 “C.

143
LITERATURE CITED

Covington, W.W., and S.S. Sackett. 1984. The effect of a

prescribed bum in Southwestern ponderosa pine on

organic matter and nutrients in woody debris and forest

floor. Forest Science 30:183-192.

Covington, W.W., and S.S. Sackett. 1986. Effect of

periodic burning on soil itrogen concentrations in

ponderosa pine. Soil Science Society of America Journal

50:452-457.

Harris, G.R., and W.W. Covington. 1983. The effect of a

prescribed tire on nutrient concentration and standing crop

of understory vegetation in ponderosa pine. Canadian

Journal of Forest Research 13:501-507.

Haase, S.M. 1986. Effect of prescribed burning on soil

moisture and germination of Southwestern ponderosa pine

seed on basaltic soils. U.S.D.A. Forest Service Research

Note RM-462, 6 p.

Jones, J.M., and B.N. Richards. 1977. Effect of

reforestation on turnover of “N-labelled nitrate and

ammonium in relation to changes in soil microflora. Soil

Biology & Biochemistry 9:383-392.

Klemmedson, J.O., A.M. Schultz, H. Jenny, and H.H.

Biswell. 1962. Effect of prescribed burning of forest

litter on total soil nitrogen. Soil Science Society of

America Proceedings 26:2(X)-202.

Kovacic, D.A., D.M. Swift, J.E. Ellis, and T.E. Hakonson.

1986. Immediate effects of prescribed burning on mineral

soil nitrogen in ponderosa pine of New Mexico. Soil

Science 141(1):71-76.

Ryan, M.G. 1978. The effect of prescribed burning in

ponderosa pine on the inorganic nitrogen content of the

soil. M.S. thesis, 64 p. Northern Arizona University,

Flagstaff, AZ.

Ryan, M.G., and W.W. Covington. 1986. Effect of a

prescribed bum in ponderosa pine on inorganic nitrogen

concentrations of mineral soil. U.S.D.A. Forest Service

Research Note RM-464, 5 p.

Vlamis, J., H.H. Biswell, and A.M. Schultz. 1955. Effects

of prescribed burning on soil fertility in second growth

ponderosa pine. Journal of Forestry 53:905-909.

White, C.S. 1986a. Effects of prescribed fire on rates of

decomposition and nitrogen mineralization in a ponderosa

pine ecosystem. Biology and Fertility of Soils 2:87-95.

White, C.S. 1986b. Volatile and water-soluble inhibitors of

nitrogen mineralization and nitrification in a ponderosa

pine ecosystem. Biology and Fertility of Soils 2:97-104.

White, C.S. 1991. The role of monoterpenes in soil nitrogen

cycling processes. Biogeochemistry IN PRESS.

White, C.S., and M.J. McDonnell. 1988. Nitrogen cycling

processes and soil characteristics in an urban versus rural

forest. Biogeochemistry 5:243-262.

white, E.M., W.W. Thompson, and F.R. Gartner. 1973.

Heat effects on nutrient release from soils under

ponderosa pine. Journal of Range Management 16(1):22-

24.

Lodhi, M.A.K., and Keith T. Killingbeck. 1980.

Allelopathic inhibition of nitritication and nitrifying

bacteria in a ponderosa pine (Pinus ponderosa Dougl.)

community. American Journal of Botany 67(10):1423-

1429.

144
LOSS, RETENTION, AND REPLACEMENT OF NITROGEN

ASSOCIATED WITH SITE PREPARATION BURNING

IN SOUTHERN PINE-HARDWOOD FORESTS

Lindsay R. Boring, Joseph J. Hendricks, and M. Boyd Edwards’

Abstract-High-intensity site preparation burning is a common forest regeneration practice on harvested

pine and mixed pine-hardwood sites in the southeastern USA. This practice could result in excessive losses

of forest floor organic matter and nitrogen, and could subsequently decrease long-term productivity. In

general, intensive burning may result in large losses of forest floor nitrogen, primarily by combustion and

convection of N gases. However, past studies may have overestimated combustion losses due to inadequate

knowledge of potential gaseous N retention mechanisms. Long-term inputs of N from biological tixation

and atmospheric deposition may replace large amounts of N lost from tire, but more information on &-

fixation processes is needed over time and space. Also, additionai studies are needed to determine practical

N,-fixation management applications, such as retention of coarse woody debris and enhancement of I$-

fixing plant populations.

INTRODUCTION

kfigh-intensity site preparation burning is a common and

cost-effective regeneration tool on harvested pine and mixed

pine-hardwood forest sites in the southeastern United States

(Abercrombie and Sims 1986). Few studies have

comprehensively examined the immediate and potential

long-term impacts of this practice upon site productivity (Van

Lear and Johnson 1983; Van Lear and Waldrop 1986). Site

preparation effects are a central concern of many forest

managers since the technique may alter forest floor organic

malter and nutrient reserves that provide long-term site

productivity for future stand rotations (Van Lear and others

1983).

Although low-intensity prescribed burning has been shown to

have no deleterious effects upon the productivity of loblolly

pine forests in the southeastern Coastal Plain (McKee 1982),

high intensity site-preparation burning could result in

cxccssivc losses of forest floor organic matter and nitrogen.

Several studies have provided gross mass-balance estimates of

organic nitrogen loss in logging residues up to several

hundred kg ha-’ from site-preparation burning (Van Lear and

Ka@uck 1989). However, few detailed, process-level

studies have been conducted to examine forest floor nitrogen

losses and the mechanisms of nitrogen loss and retention

during and following burning (fig. 1; Jorgensen and Wells

1986; Little and Ohmann 1988; Van Lear and others 1983).

In addition, long-term replacement of nitrogen through

biological fixation and other inputs has not been adequately

examined to assess the potential contributions to the nitrogen

balance of intensively-burned sites (Boring and others 1988,

Hendricks 1989).

‘Associate Professor of Forest Ecology, School of Forest Resources,

University of Georgia, Athens, GA; Research Technician, School of

Forest Resources, University of Georgia, Athens, GA; Plant

Ecologist, Southeastern Forest Experiment Station, Forest Service,

U.S. Department of Agriculture, Dry Branch, GA.

In this paper, we summarize the state of knowledge

concerning key processes regulating N losses, retention, and

replacement associated with intense fire in southeastern pine

and mixed pine-hardwood forests, as well as in other related

ecosystems. We synthesize the research results and

perspectives from our work, as well as those from other

investigators, and identify key areas for further research.

NITROGEN LOSSES AND RETENTION

There are several mechanisms by which N may be lost during

and following intensive burning, including combustion and

convection of N gases and particulates, leaching of NO,‘ in

the soil solution, denitrification of residual inorganic N, and

erosion of organic matter by water and wind (fig. 1).

Although each of these mechanisms may pfay a role in the

loss of N reserves, past studies suggest that the combustion

losses may exceed the others in importance (Christensen

1987; Raison and others 1985; Van Lear and Waldrop 1989).

Intensive burning results in large losses of N by volatilization

and the removal of gases and particulates in wind currents

(Jorgensen and Wells 1986). The amount of N lost varies and

depends primarily on the fire severity, which in turn is

d&hind by the amount and flammability of organic matter,

moisture conditions, and the residence time of the peak

thermal pulse. Mass balance estimates based upon loss of

woody debris and other forest floor fuels have indicated losses

may range as high as 300 kg ha“ for severe site-preparation

fires in the southeastern Piedmont region (Van Lear and

Kapcluck 1989; Wells and others 1979), and up to 1000 kg

ha” for intense fires in western Douglas-fir forests (Binkley

1986; Little and Ohmann 1988).

Although a considerable amount of the lost N may have

originated from the smaller-sized fuels of residual logging

slash and young colonizing vegetation, the potential losses

from the original forest floor and soil organic matter may

have the greatest impact upon N balance and long-term site

145
N CYCLING PROCESSES

r---GASEOUS N/-NK -

Figure 1. Nitrogen cycling processes and their relationships to losses, retention, and replacement

productivity (Van Lear and Kapeluck 1989). Losses of N

from forest floor mass have been estimated to range from 130

to 170 kg ha“ (Van Lear and Kapeluck 1989), depending

primarily upon the severity of the bum, with hotter and

slower tires causing greater losses (Knight 1966).

Most N loss from tires is associated with gaseous loss rather

than particulates (Raison and others 1985). Using controlled

ignitions in a muffle furnace, volatile loss of N was shown to

begin at approximately 300°C and increase to 60 percent at

700°C. Such controlled experiments formerly assumed that

most of the N was lost as N,, and that it was convected offsite

following oxidation (DeBelI and Ralston 1970; Knight 1966).

However, other workers have shown that ammonia gases may

be liberated at temperatures as low as lOO”C, and subsequent

information has revealed more complex processes regulating

these losses (Raison 1979).

Combustion studies with southern pine litter-soil systems have

shown a complex scenario of N loss, which includes

significant volatilization of NH, and NO, at relatively low

temperatures (Lewis 1975). Although we now appreciate the

complexity of N volatilization, we still have few detailed case

studies that accurately document N losses from southern pine

and pine-hardwood forests. We also suggest that there may

be retention mechanisms in southern pine forests which have

not been examined by early studies (Lewis 1975; Raison

1979).

146

Some researchers have reported surprisingly variable and low

losses of N from burned forest floors of different types, and

some of the increases in inorganic N availability have been

attributed to rapid increases in nonsymbiotic N fixation or to

the occurrence of legumes on the sites (Jorgensen and Hodges

1970, Mroz and others 1980). Although replacement of N

from these sources is known to occur, some of these rapid

increases in inorganic N availability are not explainable by

decomposition and nitrogen fixation since the increases appear

immediately (hours to a day) following burning (Raison

1979).

Instead, it is likely that ‘thermal mineralization of organic

matter occurs, where inorganic N is released and retained in

significant amounts in subsurface layers of the mineral soil.

Studies in some soil-plant systems have documented elevated

inorganic N immediately following burning as N&-N, NO,-

N, and possibly as labile organic compounds. This may

happen by ammonia hydrolysis and vertical translocation as

gases are volatilized by the initial thermal pulse of the tire

and are subsequently condensed by cooler temperatures in

lower soil mineral horizons (DeBano and others 1976, 1979;

Kitur and Frye 1983). Although this process has been

examined in North American chaparral and in Australian

eucalyptus forests, the mechanism has not been documented in

southern pine or pine-hardwood forests.
Biological transformations related to decomposition and

nitrification become more important with time after burning,

and play dominant roles in the welldocumented but

short-term (weeks to months after burning) increases of

inorganic N availability in southern pine forests (Christensen

1987; Raison 1979; Schoch and Binkley 1986). The

magnitude and duration of such effects may be highly specific

to individual forest floor types and bum characteristics,

especially as related to initial litter quality and N contents.

Mroz and others (1980) found widely variable

ammonification, nitrification and immobilization responses

among different forest floor types, and concluded that it was

difficult to make universal generalizations about microbial

processes following burning. Although stimulation of

nitrification may be a key burning response in southern forest

ecosystems, elevation or reduction of microbial

immobilization and gaseous N,O flux also play significant

roles in regulating the availability of NO,-N (Christensen

1987). Nitrification and gaseous nitrogen transformations

require further research and it is not clear to what degree N

retention after burning may be quantitatively affected by

either NO,-N leaching or gaseous losses. Further, these

processes likely interact with the recovery rates of microbial

and plant nitrogen uptake which may minimize N losses

through biomass immobilization.

NITROGEN REPLACEMENT

Although site-preparation burning may cause large losses of

forest floor nitrogen reserves, natural sources of replacement

may help maintain or improve the productivity and quality of

these forest ecosystems. Two major pathways of nitrogen

replacement are atmospheric deposition and biological

nitrogen fiation (Boring and others 1988) (fig. 1).

Atmospheric deposition includes the input of a variety of

nitrogen-containing compounds by both dry and wet modes.

Atmospheric N, may be biologically fixed (and converted to

organic N) by symbiotic and nonsymbiotic organisms. A

thorough understanding of the magnitudes of these nitrogen

inputs and their impacts on nutrient cycling is incomplete for

any single ecosystem. Furthermore, knowledge of these

fundamental processes is essential to accurately assess the

impact of site-preparation burning on the nitrogen balance and

long-term productivity of forest ecosystems.

Atmospheric Deposition

A variety of nitrogen forms may be deposited in terrestrial

ecosystems from the atmosphere (Boring and others 1988).

Some of these, such as dissolved NH,+ and NO<, can be

rapidly incorporated into terrestrial nitrogen cycles following

wet or dry deposition. Other constituents, such as those in

aerosol and gaseous forms, may be transferred directly to

vegetation surfaces (Okano and Machida 1989). Many factors

that may affect the spatial and temporal patterns of these

deposition inputs. One is the proximity to nitrogen sources

such as industrial emissions. Also, factors that regulate the

transport and transformation of atmospheric nitrogen forms,

such as precipitation patterns and meteorological conditions,

are important considerations.

Measurements of alJ of the potential forms of nitrogen

deposition are unavailable for any terrestrial ecosystem.

However, although conservatively estimated, nitrogen inputs

measured in bulk precipitation provide some measure of the

relative importance of atmospheric deposition to forests.

Estimates of wet deposition inputs to southeastern forest

ecosystems may range from 5.1 to 12.4 kg ha-’ yr” (Kelly and

Meagher 1986; Richter and others 1983; Riekerk 1983;

Swank and Waide 1987; Van Lear and others 1983; Wells

and Jorgensen 1975). The upper value of this range was

recorded at Walker Branch in eastern Tennessee which is in

close proximity to coal-fired power plants (Kelly and Meagher

1986).

Dry deposition may also contribute significant amounts of

nitrogen to forest ecosystems. The dryfall contribution to the

total NH,+ and NO; deposited in open collectors exceeds 20

percent at Coweeta (Swank and Waide 1987) and exceeds 50

percent at the Walker Branch site (Kelly and Meagher 1986).

These figures primarily represent large particulate inputs and

are not representative of all nitrogen in aerosols and gases

which may originate from combustion processes. Combining

both wet and dry N inputs, general estimates for southeastern

forest ecosystems may range from 6 to 14 kg ha-’ yi’

excluding aerosol and gas fractions which may also be high

(fig. 2).

Nitrogen Fixation

In southeastern forest ecosystems, detectable nitrogen-fixation

activity may occur in the forest floor and surface mineral soil

horizons, coarse woody debris (CWD) on the forest floor, and

the, nodules of symbiotic nitrogen-fling plants. In general,

the fixation rates of symbiotic organisms are greatest during

the early successional stages of forest development (Boring

and Swank 1984; Boring and others 1988). The harvesting of

merchantable timber, followed by the felling of residual stems

and intense site-preparation burning creates an early

successional environment and may therefore promote

detectable, if not significant, nitrogen-fixation activity among

a variety of organisms.

Forest Floor and Soil

Clearcutting may increase nonsymbiotic nitrogen-fixation in

the forest floor (excluding CWD) and soil through the transfer

of large carbon pools in the form of dead roots and small

fractions of logging debris (Boring and others 1988). At the

Coweeta Hydrologic Laboratory, maximum fixation rates of

4-6 kg ha-’ yi’ were measured three to tive years following

clearcutting (Waide and others 1987). These high rates are

likely to be short-lived, however, due to the sensitivity of

nitrogen-futing bacterial populations to substrate quality,

moisture, temperature, and pH (Jorgensen and Wells 1986;

147
NITROGEN INPUTS

-i- 20

e

- ATMOSPHERIC DEPOSITION

--- SYMBIOTIC N2-FIXATION

-i -- FREE-LIVING Nt-FIXATION

;:

c

2

kz

5

?I

&

2:

PRE- t CROWN THINNING AND UNDERSORY

FIRE FIRE CLOSURE BURNING

LEVELS

TIME (YEARS)

Figure 2. Range of temporal dynamics of nitrogen replacement in relation to forest succession;

based upon studies of sites with at least moderate N-fixing plant populations.

Vance and others 1983). Most estimates of nonsymbiotic

futation in southeastern temperate coniferous and deciduous

forest are much smaller and range from 0.1 to 3.7 kg ha-’ yri

(Di Stefano and Gholz 1989; Gholz and others 1985; Grant

and Binkley 1987; Jorgensen and Wells 1986; Van Lear and

others 1983).

There appears to be a paucity of information concerning the

effect of intense site-preparation burning on nonsymbiotic

forest floor and soil nitrogen fixation. However, research on

the effects of less intense understory burning on this form of

fixation have been contradictory. Maggs and Hewett (1986)

reported a three-fold increase in nitrogen-fixation activity

following understory burning, whereas Vance and others

(1983) and DiStefano and Gholz (1989) reported little or no

response to burning. Even given these conflicting results, it

is generally assumed that such low nonsymbiotic fiation

activity in the forest floor and soil will not make a significant

contribution to the replacement of nitrogen following intense

site-preparation burning.

Coarse Woody Debris

Silvicultural clearcutting of southeastern forests may deposit

from 15 to 50 tons ha-’ of non-harvestable coarse woody

debris (CWD) to a site (Sanders and Van Lear 1988). The

majority of this CWD remains on the site following burning

since even the most intense fires generally consume stems

only up to 10 centimeters in diameter. This CWD may play a

significant nitrogen replacement role by serving as a carbon

substrate for a highly diverse group of nonsymbiotic nitrogenfeting organisms, as well as for wood-eating insects that form

symbiotic relationships with nitrogen-fling gut bacteria

(Dawson 1983; Roskoski 1980; Silvester and others 1982).

Research conducted in old-growth Douglas-fu stands of the

Pacific Northwest has revealed that nonsymbiotic furation

rates in large masses of well-decomposed wood by such

organisms as bacteria, fungi, blue-green algae, and lichens

may reach 1.4 kg ha-’ yi’ (Silvester and others 1982). In a

northern hardwood forest at the Hubbard Brook Experimental

Forest, comparable annual nitrogen fixation rates in decaying

wood ranged from 0 to 2 kg ha-’ yi’, with the rates being

directly correlated to the standing crop of decaying wood

(Roskoski 1980, 1981). Although the nitrogen replacement

role of CWD in southeastern forest ecosystems is less well

understood, Todd and others (1975, 1978) reported values of

1.22 to 1.66 kg ha-’ yr-i for an oak hickory forest at Coweeta

and DiStefano and Gholz (1989) measured high specific rates

in low masses of decomposing wood of slash pine plantations

in North Florida.

It is important to note that these area estimates of nonsymbiotic nitrogen futation are a function of CWD biomass as

well as actual rates of fixation activity. Also, Silvester and

others (1982) suggested that fixation rates generally increase

as the CWD, which may remain on the site for several years,

becomes more highly decomposed. Therefore, nonsymbiotic

fixers (even with low specilic activity) in the abundant CWD

of southeastern clearcut sites may Potentially contribute

significant amounts of nitrogen during the decomposition

process of the debris.

As stated earlier, CWD serves as a substrate for wood-eating

fauna such as termites, bark beetles, and cockroaches, which

may contain nitrogen-f&g bacteria in their gut (Dawson

1983; French and others 1976; Potrikus and Breznak 1977).

Among these organisms, the process of nitrogen fmation has

been best established for temperate and Siopical termites

148
(Bentlcy 1984; Prestwich and others 1980). Due to numerous

difliculties preventing accurate measurements, nitrogen

fixation values for termites have not been related to nitrogenbalance estimates, although their contribution could be

signiiicanl on some forest sites.

lligher Plants

Symbiotic nitrogen-fixing plants commonly occur on sites

where nitrogen is limiting, early successional areas, or sites

subject to substantial N loss, such as from intense and/or

frequent fires (Boring and others 1988). In southeastern

forest ecosystems, fire-adapted native herbaceous legumes

generally thrive during the first few years following

clearcutting and intense site-preparation burning (Cushwa and

others 1969; Czuhai and Cushwa 1968).

Legume populations are typically largest during early stages

of stand development for a number of reasons. The seed of

several legumes have their highest germination rates following

scarification with moist heat at temperatures approaching 80”

C (Cushwa and others 1968, 1970). Also, it is believed that

these seeds remain viable in the litter layer and soil for

prolonged periods of time. Finally, these fire-adapted, early

successional species thrive under the high light environment

of pine stands prior to crown closure (Brunswig and Johnson

1972; Cushwa and others 1971).

Nitrogen furation rates of these herbaceous legumes are

predicted to be highest during this early stage of stand

development (fig. 2). The absence of a developed overstory

and the reduced competition from non-fire adapted species

should result in larger quantities of photosynthate available for

the energetically expensive nitrogen fixation process.

Hendricks (1989) assessed the nitrogen fiiation activity of

three dominant legume species (Desmodium viridiflorum,

Lemedeza hirta, and L. procumbens) in a cleared and burned

area of a Georgia Piedmont pine forest. In the early to

middle part of the growing season, Q. viridiflorum and L.

procumbens exhibited specific acetylene reduction activity per

nodule biomass comparable to those of black locust, Robinia

pseudoacacia (Boring and Swank 1984), and greater than

those of many actinorhizal nitrogen-fixing species, although

total nodule biomass was considerably lower (Binkley 1981;

McNabb and Geist 1979; Tripp and others 1979). This

nodule activity, however, declined substantially during the

remainder of the hot and dry growing season, and the third

species L. hirta was rarely observed to nodulate.

The total amount of nitrogen fixed by herbaceous legumes on

these Georgia Piedmont sites was roughly estimated to range

from <OS kg N ha” yi’ for areas with small legume

populations (500 - 700 individuals ha”) to 7 - 9 kg N ha-’ yi’

for areas with relatively large populations (20,000 - 30,000

individuals ha-‘; Hendricks 1989). These values represent

broad ranges of estimates and illustrate the potential

importance that factors controlling the spatial and temporal

variation of legume populations may have on forest floor and

soil nitrogen reserves. Sites with larger legume populations

than ours may have substantially more nitrogen fixation.

The spatial variation of herbaceous legumes depends upon

many factors including the fire-history of the site. Table 1

gives the results of a legume population survey for two

similar Georgia Piedmont sites that were cleared and burned

following southern pine beetle infestation. These sites, which

were sampled two years following the intensive bum, differed

primarily in their fire history as one had no previous burning

and the other had received periodic winter understory bums

since 1962. The site that had been managed under a burning

regime had a substantially higher diversity and density of

Table 1. Density (#/ha) of native and naturalized

herbaceoup tegune species on cleared ar@ burned sites

in the Georgia Piedmont. Site 1 had no previous

burning history, uhereas site 2 has been managed under

a 4 year burning regime since 1962

SPECIES

DENSITY (#/ha)

SITE 1 SITE 2

Cassia nictitans

Centrosema virginianun

Crotelaria sagittalis

Desrnodiun

ci 1 i-are

Laevigatun ..,.

prilandicun

f+uttallii

rotundifoliun “. ..-.

$enuifoliun

yiridiflorun

Other spp.

Lespedeza

bicolor’

cuneata’

hirta

nuttallii

procunbens

virginica

Other spp.

spicata Tephrosia

TOTAL

1 2

1 2

32

74

28

3

42

380

6

731

3,429

381

143

238

1,048

2,333

1,238

381

333

3,952

334

619

667

3,333

1,048

6,905

2,333

476

667

29,858

149
legumes due primarily to increases in species of Destnodium

and Lesoedeza (table 1). Although these data only represent

two sites, other reports also underscore the importance of

regular burning to generate a cycle of high seed germination

and plant establishment rates (Cushwa and others 1966, 1969,

1970; Czuhai and Cushwa 1968; Devet and Hopkins 1967;

Speake 1966).

Brunswig and Johnson (1972) studied the temporal variation

of legume populations in southeastern pine plantations during

the first seven years following intense site-preparation. The

results indicated that annuals, primarily C. nictitans, were the

predominant legumes in one-year old plantations. By the

third year, perennial legumes (primarily species of

Desmodium and Lesoedeza) were more abundant than

annuals. In older stands, the annuals were essentially

eliminated and the perennials decreased substantially due to

crown closure. However, in latter stages of stand

development when light gaps appear and understory burning

is commonly initiated, legumes may still influence nitrogen

availability via the temporal dispersal of a viable seed bank.

Approximately 300 native legumes occur in the southeastern

United States (Wilbur 1963). A majority of these are

herbaceous legumes that are tolerant of acidic soils, shading,

and litter accumulation on the forest floor, and commonly

occur in pine and mixed pine-hardwood forest ecosystems.

Although the value of these legumes to wildlife has long been

recognized, their nitrogen accretion role as well as their

contribution to functional biodiversity are just beginning to be

recognized in southeastern forest ecosystems.

SUMMARY AND RESEARCH NEEDS

Our present knowledge of the impacts of intensive fire upon

ecosystem nitrogen cycling processes and long-term

productivity in southern forests is incomplete, and many key

questions require additional research. We generally know

that large amounts of forest floor nitrogen are lost with severe

bums, and that long-term replacement sources may be

potentially significant but variable. However, in the past we

may have overestimated N volatilization on some sites by not

examining potential retention processes in humus and mineral

soil horizons below the litter. Simultaneously we have not

examined the potential for additional and smaller short-term

gaseous losses via NsO flux from residual inorganic N

following burning, or examined the interactions of

immobilization by microbial or plant biomass with

nitritication and gaseous N flux (Matson and Vitousek 1987).

Our interpretation of intensive fire effects upon long-term N

balance is uncertain until we better understand how

adequately nitrogen fixation processes replace N losses over

time and space. We need to better understand how to more

effectively manage nitrogen fixation inputs. More effective

management may require retention of coarse woody debris,

increased populations of nitrogen-fixing plants, and

modification of environmental factors that control their

futation rates (e.g. P fertilization). A more complete

understanding of these processes and their potential

management need to be integrated into a whole-ecosystem

perspective, possibly with the use of simulation models, to

better interpret their impacts upon long-term N balance and

forest productivity over several stand rotations.

150
LITERATURE CITED

Abercrombie, J.A.; Sims, D.A. 1986. Fell and bum for

low-cost site preparation. Forest Farmer 46(1):14-17.

Bentley, B.L. 1984. Nitrogen futation in termites: fate of

newly futed nitrogen. Journal of Insect Physiology

30:653-655.

Binkley, D. 1981. Nodule biomass and acetylene reduction

rates of red alder and Sitka alder on Vancouver Island,

B.C. Canadian Journal of Forest Research 11:281-286.

Binkley, D. 1986. Forest nutrition management. John Wiley

and Sons, Inc., New York.

Boring, L.R.; Swank, W.T. 1984. Symbiotic nitrogen fixation

in regenerating black locust stands. Forest Science

30(2):528-537.

Boring, L.R.; Swank W.T.; Waide J.B.; Henderson G.S.

1988. Sources fates, and impacts of nitrogen inputs to

terrestrial ecosystems: a review and synthesis.

Biogeochemistry 6:119-159.

Brunswig, N.L.; Johnson, A.S. 1972. Bobwhite quail foods

and quail populations on pine plantations in the Georgia

Piedmont during the first seven years following site

preparation. Proceedings of the Southeastern Association

of Game and Fish Commissioners 26:96-107.

Christensen, N.L. 1987. The biogeochemical consequences of

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153
FIRE EFFECTS ON NUTRIENT POOLS OF WOODLAND FLOOR

MATERIALS AND SOILS IN A PINYON-JUNIPER ECOSYSTEM

Jeffrey M. Klopatek, Carole Coe Klopatek,

and Leonard F. DeBano’

Abstract-The total pools of carbon and nitrogen in the liner, duff, and soil compartments were quantified

in a mature pinyon-juniper woodland. One hectare of the woodland was burned in a fire similar to a severe

wildfire, where almost all aboveground vegetation was killed. Soil temperatures reached as high as 325” C

a1 5 cm below the soil surface. The total nutrient pools were again quantitied after fire indicating

significant losses of both C and N from forest floor material. The litter loss of C was as high as 92 percent

and N loss was as high as 88 percent. Loss of C from the duff layer was estimated from 78-80 percent,

while nitrogen loss was 75 percent. Soil N displayed a slight, significant increase under canopy, but not in

the interspaces. The greatest initial effect was the reduction of the C/N ratios favoring mineralization. The

total amount of C and N lost from the woodland was 12.6 Mg ha” C and 167 kg ha-’ N.

INTRODUCTION

Pinyon-juniper woodlands occupy a significant expanse of the

semiarid United States (Klopatek and others 1979). They are

characterized by extreme variability in climate, soil, and

topography that produces units of canopy-covered and noncanopy covered (interspace) patches. Therefore, a seemingly

uniform disturbance, such as fire, to this patchy mosaic

ecosystem type may result in complex, non-uniform

responses. Despite the expansiveness of the pinyon-juniper

woodlands and their susceptibility to fire, studies of fire

effects in pinyon-juniper woodlands have only been recent and

limited (DeBano and others 1987; DeBano and Klopatek

1988; Gifford 1981; Klopatek and others 1988).

Studies on the effects of fire upon soil nutrients, and

specifically soil N, have produced conflicting results. Some

investigators have reported no significant changes in total soil

N contents (Covington and Sackett 1986; Jurgensen and

others 1981; Kovacic and others 1986; White 1986).

Waldrop and others (1987) found no changes in either soil

organic matter or total N after 30 years of various prescribed

burning treatments in loblolly pine.

Stock and Lewis (1986) reported significant increases in N

that were due to leaching of ash material in fynbos (chaparral)

ecosystems, whereas DeBano and others (1979) reported a

significant loss of total N from laboratory burnings of

chaparral soils. Fuller and others (1955) described that loss

of soil N was proportional to the fire intensity in ponderosa

pine forests with a concomitant decrease in C/N ratios. Grier

(1975) noted significant nutrient losses from an intense fire on

the eastern slope of the Cascade Mountains of Washington

and estimated a loss of 855 kg ha-’ of N. Covington and

Sackett (1986) found a 37% reduction in forest floor material

‘Associate Professor of Botany, Deparlment of Botany, Arizona State

University, Tempe, AZ; and Microbial Ecologist and Project Leader,

respectively, USDA Forest Service, Forestry Sciences Laboratory,

Arizona Stale University, Tempe, AZ.

154

following a low-intensity prescribed fire in ponderosa pine

forest with an additional 20% reduction 7 months after

burning, but no significant soil N loss.

In a comprehensive study of the effects of prescribed burning,

Wells (1971) noted that while periodic bums had caused

significant losses of forest floor material immediately after the

bum, there seemed to be a tendency for the system to regain

its organic matter (both C and N) over time and approach the

control condition. Additionally, he found a small increase in

available P, but the increase may be short lived in calcareous

soils (DeBano and Klopatek 1988).

Christensen (1973) found greater NH, availability and

nit&cation rates following burning in chaparral, and

Jurgensen and others (1981) found that broadcast burning

caused a minor net loss of N (approximately 100 kg ha”), but

resulted in greatly enhanced soil N, nitrification, and base

cation availability from a clearcut site in Montana. They

concluded that no significant long-term losses of N occurred.

Schoch and Binkley (1986) found that prescribed burning

increased decomposition rates and N availability (as indexed

by incubation) in loblolly pine stands in North Carolina.

Similar results of increased levels of NH, and NO, have been

reported in ponderosa pine (Covington and Sackett 1986;

Kovacic and others 1986; White 1986) and Douglas-fu

ecosystems (Jurgensen and others 1981). Increases in NH4

are presumably the result of physicochemical reactions caused

by the elevated temperature (Kovacic and others 1986).

Subsequent, post-fire increases in NO, are attributed to

increased nitrification rates, that are possibly enhanced by the

reduction of allelochemical compounds (White 1986).

In summary, the results of fire on C and N losses from

shrubland and coniferous forest ecosystems are mixed, but

appear related to fire intensity. With this as a background,

we attempted to document changes in the total pools of C and

N in a pinyon-juniper woodland resulting from fire. The

objective of the study was to determine if the patchy nature of
this ecosystem was reflected in the fire effects on its nutrient

pools. Initially, we conducted our experiment using

microcosms and determined that there might be a substantial

loss of nutrients from the ecosystem (Klopatek and others

1990). Here, we report on the effects of the subsequent field

study. While a complete inventory of the pools of both C and

N was undertaken in this ecosystem, only the effects of fire

on the forest floor and soil components are reported on in this

paper.

METHODS

In September, 1989 a bum was conducted of a l-ha section of

mature pinyon-juniper woodland in the Kaibab National

Forest in northcentral Arizona. The meteorological

conditions at the beginning of the bum were: a wind speed of

6.0 m sec.‘, temperature of 27” C, and a relative humidity of

18 percent. Moisture content of the large downed fuel and

litter was 9 and 6 percent, respectively. Fire temperatures

were monitored at the litter surface and the 0, 2, 5, and 10

cm depth of soil by a series of chrome]-alumel thermocouples

connected to a data logger. Burning was conducted by U.S.

Forest Service personnel from the Tusayan Ranger District

and Grand Canyon National Park staff. The bum and a

nearby control site were fenced with barbed wire to prevent

disturbance from local Livestock. Prior to the bum, an

inventory was conducted of the biomass of all trees, shrubs

and herbaceous species on the site using previously developed

allometric relationships. The site contained 340 pinyons and

167 juniper ha” (ail of which were marked with permanent

brass id tags) with a tree cover of 4286 m* ha-‘.

Aboveground tree biomass totaled 135.2 mt ha”. Tree-ring

analysis revealed that many of the trees were > 350 years old

without any fire scars and, combined with replacement

patterns, indicated a substantial time since intense burning.

Soils were primarily sandy loams with Ph values ranging

from 7.3 to 8.1. The site was part of the Dillman mature site

described elsewhere in this volume (C.C. Klopatek and others

1990).

The site was divided into four relatively equal-sized

quadrants. Samples were taken of litter and duff

accumulations from under the mid-canopy of four randomly

selected trees of each species in each quadrant using 2.5 cm x

2.5 cm quadrats. Five quadrats were sampled for litter in the

interspaces of each quadrant. There was no duff in the

interspaces. These measurements were combined with

identical measurements taken from the nearby control site to

yield a statistical population (n = 32) used to calculate

regression coeflicients of total C and N relative to the crosssectional area of the bole and canopy cover.

Subsamples of litter and duff were taken back to the

laboratory for analysis of organic C and total N.

Additionally, soil samples were taken from the O-10 and lo20 cm depth along with the litter and duff samples, yielding

16 soil samples from each depth and in each cover type.

Sampling was repeated from 24 to 48 hrs post-bum when the

canopy sites had cooled down. Although a qualitative

separation of litter and duff ash were possible for estimation

of loss by ignition, samples were combined for nutrient

analysis.

Litter, duff, and ash samples were analyzed for C content by

ashing in a muffle furnace at 550” C for 8 hrs with the

oxidized portion multiplied by 0.58 to yield organic C; soil

organic C was analyzed by the Walkley-Black Method (Page

and others 1982). All material was analyzed for N by

digesting the material following methods of Raveh and

Avnimelech (1979) and measuring the digest with a Wescan

ammonia analyzer. Statistical analyses were conducted using

simple linear regressions for calculating duff and litter

biomass per tree and AOV procedures for measurements of

before and after burning differences (SAS 1985).

RESULTS

To understand the effects of fire on the nutrient pools in the

landscape it was necessary to quantify the partitioning of

nutrients relative to the patch mosaic of the woodland. We

multiplied the total amount of pre-bum C and N in the litter,

duff and soil (0 - 20 cm depth) per unit area by the area

occupied by each cover type to obtain the total woodland

floor and soil nutrient pools. Figures la,b show that, despite

the fact that the interspace and its associated vegetation

covered 57.1 percent of the area compared to 42.9 percent by

the trees (28.4 pinyon, 14.5 juniper), the trees partitioned the

majority of the resources under their canopies, accumulating

nearly 68 percent of the total C and 70 percent of the total N.

There existed significant differences between the pre-bum

organic C concentrations of litter, duff, and soil material of

all three cover types (table 1). Total N concentrations of

pinyon, juniper, and interspace litter were not different. The

C:N ratios of pinyon and juniper litter (83 and 77,

respectively) were similar but differed with that of the

interspace litter (120). Higher C:N ratios for the interspace

litter compared to under the canopies is typical of mature

pinyon-juniper ecosystems in Arizona and may represent

greater competition for available N in the interspaces

(Klopatek 1987). Total N of litter and duff were not

statistically different under pinyon but were under juniper;

both differed from their respective underlying soil.

Peak fire temperatures experienced under the canopy were as

high as 374, 305 and 260” C at the 2, 5, and 10 cm soil

depths and 68” C at the 2 cm depth of the interspaces. The

effect of fire was most noticeable on the litter and duff pools

of the tree patches. Figures 2 and 3 represent the amount of

C and N per unit area by cover type. Organic C was reduced

an average of 92 and 80 percent in pinyon litter and duff, and

91 and 78 percent of the juniper litter and duff, respectively

(fig. 2a,b). The resulting post-fire concentrations of organic

C did not differ between types (table 1).

155
Portitioninq of C in Woodland Floor Carbon Storage - Pre-Burn

25,

II Litter

cl Duff

So i I coP i nyon Juniper Interspace P i nyon Jun i per Interspace

Partitioning of N in Woodland Floor

2 80C

\ 700

:600

E?

L 500 4

2 400

J&o0

200

100

I Litter

0

P i nyon Juniper In terspoce

Figure l.-Total organic carbon (a) and nitrogen (b) in a

pinyon-juniper woodland floor located in northern Arizona.

Nitrogen exhibited similar results (fig. 3a,b), but the relative

concentration of total N did not decrease as much as C (table

1). If corrections are made for weight loss due to

combustion, loss of N from the pinyon litter and duff

compartments was 87 and 75 percent, and 88 and 75 percent

of the juniper litter and duff, respectively. The loss of C and

N closely parallel the results reported by Raison and others

(1985). An important result of the fue is the change in the

C:N ratios of the ash as compared to the litter and duff (table

l), being significantly reduced for both pinyon and juniper.

I Litter

Carbon Storage - Post-Burn

101

I Litter

N a

E

7

\

C6

B

ii5

C-3

In4

Y

3

P i nyon Jun i per In te rspoce

Figure 2.--Carbon storage pre- (a) and post- (b) bum in the

woodland floor of a pinyon-juniper ecosystem in northern

Arizona.

The effect of burning on total N and organic C were less

pronounced in the underlying soil compared to the overlaying

duff and litter. Both pinyon and juniper soils at the O-10 cm

depth displayed significant increases in concentrations of total

N (table 1) although no significant differences in organic C.

Decreases in the soils at the lo-20 cm depth were not

significant. The interspace soils followed a similar pattern,

but differences were not significant. Increases in both C and

N in underlying soils are consistent with reports that organic

materials are translocated downward in the soil during

burning and are wicked up from lower depths (DeBano and

others 1976). Soil C:N ratios exhibited no significance before

and after differences.

156
0.E

0.1

N

E

\

Go.:

F

502

z

y"

0.1

0.0

0.5

0.4

N

E

\

CO.3

FL

,o

20.2

y"

0. I

0.0

N i t rogen Storage - Pre-Burn

0

I Litter

P i nyon Juniper Interspace

Ni troaen Storaae - Post-Burn

b

I ii tter

P i nyon Juniper In tefspace

Figure 3.--Nitrogen storage pre- (a) and post- (b) bum in the

woodland floor of a pinyon-juniper ecosystem in northern

Arizona.

DISCUSSION

The effect of burning a pinyon-juniper woodland had

surprisingly similar results to our microcosm experiment in

which simulated bums conducted over both pinyon and

juniper soils led to a large loss of C and N [as well as 50

percent of the P] (DeBano and Klopatek 1988; Klopatek and

others 1990). Loss of N agreed with that reported by Raison

and others (1985) in that nitrogenous compounds are usually

lost proportionally to the amount of C oxidized.

The effect of burning on soil N has presented an interesting

paradox that has been vigorously debated in the literature for

years (e.g., Knight 1966; McKee 1982). As stated

previously, some authors have reported insignificant total N

increases, while others reported significant increases in soil N

that were caused by the leaching of the above ash material.

WC found significant losses of N from the woodland floor.

When the loss of C and N are applied to the spatial

distribution of pinyon-juniper-interspace mosaic, the losses

total nearly 12.6 Mg ha” of C and 167 kg ha” N. Although

large amounts of C and N were lost from the litter and duff in

this study, the changes in total N of the combined soil depths

were minimal. However, the soils at the surrounding field

sites that had been previously (lo-90 years) burned all had

significantly less soil N than the unburned (Klopatek 1987).

Our findings do not indicate why the loss of N occurs,

although we hypothesize it may be due to the loss of C. This

is a result of a combination of reduced C/N ratios of the ash

(compared to the litter and duff) and the increase in

decomposable substrates in dead root material. It should be

mentioned that our reported organic C concentrations include

the reduced charcoal that probably is not available for

microbial utilization. The newly available root material will

lead to a initial immobilization of soil N, but a release after

decomposition has occurred. Our preliminary findings

indicate an increase in CO, release from the forest floor of

the bum site when compared to the nearby control site,

indicating increased decomposition similar to that reported by

Shoch and Binkley (1986).

Pinyon-juniper woodlands in Arizona are ohen situated

between fire adapted ecosystems: chaparral and grasslands on

the xeric end and ponderosa pine on the more mesic end.

Clearly, pinyon-juniper is not a fire adapted system as many

of its trees have low-lying branches that act as ladder fuels

resulting in the trees “torching” or crown fires. This torching

adds considerable heat to the system, effectively consumes all

litter and duff, and may sterilize the upper soil layers. The

result is an initial greater loss of nutrients and provides a

positive feedback mechanism to accelerate subsequent losses.

157
Table l.--Organic carbon, total nitrogen and carbon:nitrogen ratios of pinyon, juniper,

and interspace Litter and duff material before and after burning

Carbon g kg” Nitrogen g kg.’ C/N

Pre-burn Post-burn Pre-burn Post-burn Pre-burn Post-burn

nyon P i

Litter (ash) 432a,w 41b,x’ 5.2a,x 2.lb,x’ 83.la,x 19.5b,x

Duff (ash) 231a,x 41b,x 4.6a,x Z.lb,x

Soil O-10 cm 40a,y 43a,x

50.2a,y

1.9b,y

19.5b,x

IO-20 cm 27a,z

Z.la,x

WY

21.la,z

1.6a,y

20.5a,x

1 .Sa,y 16.9a,z 18,7a,x

Juniper

Litter (ash) 352a,x 47b,x 4.6a,x

Duff (ash) 169a,y

1.8b,x

47b,x

76.5a,y 26.lb,y

3.2a,x

Soil O-10 cm 39a,z

1.8b,x

40a,x

52.8a,y

1.8b,y

26. Lb,y

2.3a,x

lo-20 cm 33a,z

21.7a,z

31a,y

17.4a,y

1.7a,y 1 .Sa,x 19.4a,z 20.7a,y

Interspace

titter (ash) 445a,x 34b, x

Soil O-10 cm 13a,y

3.7a,x O.Pb,x

14a,y

120.2a,x

1 .Oa,y

37.2b,x

lo-20 cm 16a,y

l.Oa,x

16a,y

13,4a,y

1.3a,y

14.la,y

1.3a,x 12.3a,y 13.3a,y

‘Post-burn litter and duff ash values represent composites due to the difficulty in

separating ash material for chemical analysis.

Coamon letters (a,b) following values indicate no significant differences (p -z 0.05)

between pre- and post-burn for the same element, while coaraon letters (x,y,z) indicate

no significant differences within columns for the same cover type.

LITERATURE CITED

Christensen, N.L. 1973. Fire and nitrogen cycle in California

chaparral. Science 181:66-68.

Covington, W.W; Sackett, S.S. 1986. Effect of burning on

soil nitrogen concentrations in ponderosa pine. Soil

Science Society of America Journal 50:453-457.

DeBano, L.F.; KIopatek, J.M. 1988. Phosphorus dynamics of

pinyon-juniper soils following simulated burning. Soil

Science Society of America Journal 52:271-277.

DeBano, L.F.; Eberlein, G.E.; Dunn, P.H. 1979. Effects of

burning-on chaparral soils: I. Soil nitrogen. Soil Science

Society of America Journal 43:504-509.

DeBano L.F.; Perry, H.M.; Overby, S. 1987. The effect of

fuelwood harvesting and slash burning on biomass and

nutrient relationships in a juniper (Juniperus osteosperma)

stand in central Arizona. In: Proc. Pinyon-Juniper Conf.

peno, NV; 13-16 Jan. 19861. Gen Tech Rep INT-215,

Ogden, UT: U.S. Department of Agriculture, Forest

Service, Intermountain Forest and Range Experiment

Station. pp. 382-386.

DeBano L.F.; Savage, S.M.; Hamilton, D.A. 1976. The

transfer of heat and hydrophobic substances during

burning. Soil Science Society Journal 40:779-782.

Fuller, W.H.; Shannon, S.; Burgess, P.S. 1955. Effect of

burning on certain forest soils of northern Arizona. Forest

Science 1:44-50.

Gifford, G.F. 1981. Impact of burning pinyon-juniper debris

on select soil properties. Journal of Range Management

34:357-359.

Grier, CC. 1975. Wildfire effects on nutrient distribution and

leaching in a coniferous forest ecosystem. Canadian

Journal of Forest Research 5:599-607.

Jurgensen, M.F.; Harvey, A.E.; Larsen, M.J. 1981. Effects

of prescribed fire on soil nitrogen levels in a cutover

Douglas-fir/western larch forest. Res. Pap. INT-27.5.

Ogden, UT: U.S. Department of Agriculture, Forest

Service, Intermountain Forest and Range Experiment

Station. 6 p.

Klopatek, C. Coe; Friese, C.; Allen, M.F.; DeBano, L.F.;

Klopatek, J.M. The effects of an intense fire on the patch

dynamics of vesicular-arbuscular mycorrhixae in a pinyonjuniper woodland. flhese proceedings.].

Klopatek, CC.; DeBano, L.F.; Klopatek, J.M. 1988. Effects

of simulated fue on vesicular-arbuscular mycorrhizae in

pinyon-juniper woodland soils. Plant and Soil 109:245-

249.

158
Klopatek, J.M. 1987. Nutrient patterns and succession in

pinyon-juniper ecosystems of northern Arizona. In: Proc.

Pinyon-juniper conf peno, NV; 13-16 Jan. 19861. Gen.

Tech. Rep. INT-215. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station. pp. 391-396.

Klopatek, J.M.; Klopatek, C.C.; DeBano, L.F. 1990.

Potential variation of nitrogen transformations in pinyonjuniper ecosystems resulting from burning. Biology and

Fertility of Soils 10:35-44.

Klopatek, J.M.; Olson, R.J.; Emerson, C.J.; Jones, J.L.

1979. Land-use conflicts with natural vegetation in the

United States. Environmental Conservation 6:191-199.

Knight, H. 1966. Loss of nitrogen from the forest floor

following burning. Forestry Chronicle 42:149-152.

Kovacic, D.A.; Swift, D.M.; Ellis, J.E.; Hakonson,T.E.

1986. Immediate effects of prescribed burning on mineral

soil nitrogen in ponderosa pine of New Mexico. Soil

Science 141:71-76.

McKee, W.H., Jr. 1982. Changes in soil fertility following

prescribed burning on coastal plain sites. Res. Pap. SE234. Asheville, NC: U.S. Department of Agriculture,

Forest Service, Southeast Forest Experiment Station.

23 PP.

Page, A.L.; Miller, R.H.; Keeney, D.R. (eds.). 1982.

Methods of soil analysis, part 2. Chemical and

microbiological properties (2nd ed.). American Society

of Agronomy, Madison, WI, Agronomy Serial 9.

Raveh, A.; Avnimelech, Y.A. 1979. Total nitrogen analysis

in water, soil and plant material with persulfate oxidation.

Water Resources 13:911-912.

SAS Institute, Inc. 1985. SAS users’ guide: Statistics. Version

5. SAS Institute, Inc. Car-y, NC.

Schoch, P.; Binkley, D. 1986. Prescribed burning increased

nitrogen availability in a mature loblolly pine stand.

Forest Ecology and Management 14:13-22.

Stock, W.D.; Lewis, O.A.M. 1986. Soil nitrogen and the

role of fire as a mineralizing agent in a South African

coastal fynbos ecosystem. Journal of Ecology 74:317-328.

Waldrop, T.A.; Van Lear, D.H.; Lloyd, F.T.; Harms, W.R.

1987. Long-term studies of prescribed burning in loblolly

pine forests of the Southeastern Coastal Plain. Gen.

Tech. Rep. SE-45. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station. 23 p.

Wells, C.G. 1971. Effects of prescribed burning on soil

chemical properties and nutrient availability. In:

Prescribed burning symposium proceedings. Asheville,

NC: U.S. Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station. pp. 86-97.

White, C.S. 1986. Effects of prescribed fire on rates of

decomposition and nitrogen mineralization in a ponderosa

pine ecosystem. Biology and Fertility of Soils 2:87-95.

Raison, R.J.; Khanna, P.K.; Woods, P.V. 1985. Mechanisms

of element transfer to the atmosphere during vegetation

fires. Canadian Journal of Forest Research 151132-140.

159
EFFECTS OF FELL-AND-BURN SITE PREPARATION ON

WILDLIFE HABITAT AND SMALL MAMMALS IN TIXE

UPPER SOUTHEASTERN PIEDMONT

Timothy L. Evans, David C. Guynn, Jr.‘, and Thomas A. Waldrop’

Abstract-The fell-and-bum site preparation technique is an effective means of regenerating low-quality

hardwood stands in the Southern Appalachian Mountains to more productive pine-hardwood mixtures. This

technique offers a number of advantages over conversion to pine monoculture. These in&de: lower cost,

increased vegetation diversity within the stand, improved aesthetics, and continued mast production.

However, the technique has not been fully tested in the Piedmont and other regions. This study reports the

early successional effects of several variations of the fell-and-bum technique on small mammal communities

and wildlife habitat in the Upper Southeastern Piedmont. Burning was increased forage production and

species richness of vegetation. Winter felling of residual stems was more effective than spring felling in

stimulating forage production and increasing species richness of vegetation.

INTRODUCTION

The fell-and-bum site preparation technique has proven

successful as an inexpensive means to regenerate low-quality

stands to more productive pine-hardwood mixtures in the

Southern Appalachian Mountains (Phillips and Abercrombie

1987). Complete descriptions of the technique are given by

Abercrombie and Sims (1986), Phillips and Abercrombie

(1987), and Van Lear and Waldrop (1988). Briefly, the

technique involves a commercial clearcut followed by a spring

felling of residual stems (> 2 m in height) and a summer

broadcast bum, after which pines are planted on a 3 m by 3

m (10 by 10 feet) or wider spacing. It is anticipated that the

technique will produce results in the Upper Southeastern

Piedmont similar to those observed in the mountains.

However, differences in climate, soils, topography, and

rainfall may make refinements to the technique necessary

(Waldrop and others 1989). This method could become an

attractive alternative to pine monoculture management for

nonindustrial private forest landowners, who control

approximately 80 percent of the commercial forested land in

the Piedmont.

Benefits to wildlife have not been documented. However, it

has been supposed that use of fell-and-bum methods would

benefit certain game species, but their has been little

consideration of effects on small mammals, insects, and

herpetofauna in treated stands. For these reasons it is

important to determine the effects of the technique on a!1

components of the natural community before promoting its

use in the Piedmont.

‘Graduate Research Assistant and Professor Department of Forest

Resources, Clemson University, Clemson, SC.

‘Research Forester, USDA Forest Service, Soutbeastem Forest

Experiment Station, Clemson, SC.

METHODS

Study Area

Study areas were located in the Upper Piedmont Plateau

region of western South Carolina, on the Clemson University

Experimental Forest in Pickens and Oconee Counties. Soils

were sandy loams of the Cecil and Pacolet series. Annual

temperature and precipitation average 15.5” C and 148 cm,

respectively. During 1989, mean annual temperature was

0.8” C below normal, and mean annual precipitation was 23

cm above normal (NOAA 1989).

Prior to harvest, stand ages ranged from 4.5 to 55 years. Site

indexes for shortleaf pine (Pinus echinata Mill.) at base age

50 years averaged 18 m (range 15 to 20 m). Stands consisted

primarily of low-quality hardwoods dominated by upland oaks

(Quercus spp.) and small numbers of shortleaf pine, loblolly

pine (P. taeda L.), and Virginia pine (P. Virginia Mill.).

Basal area averaged 8.6 m*/ha. Aspects ranged from 180 to

230 degrees, and slope. averaged 13 -5 percent (range 10.0 to

20.0 percent).

Treatments

Each of three replications was divided into five 0.8 ha

treatment areas. Each treatment area contained 5 to 7 sample

plots, 0.1 ha in size. Treatments included clearcutting

followed by winter-felling with and without summer burning;

spring-felling with and without summer burning; and an

unharvested control.

Habitat Analysis

Procedures for habitat analysis were modified from United

States Fish and Wildlife Service Habitat Suitability Index

(HSI) models (Mengak 1987, Mengak and others 1989, and

Sanders 1985). Prior to the harvest, 10 to 20 0.04 ha

vegetation plots were established along a transect within each

treatment area. Plots were spaced at varying distances along

the transect to best utilize the available area, avoid overlap,

and maintain a southerly aspect. Perminent small-mammal

160
trapping stations were also established at each plot center.

Sampling was conducted during three sampling periods in

1989. Periods were chosen to evaluate the habitat at the

lowest level of vegetation production (Jan. 1 to Mar. 31), the

peak of production (May 1 to July 31), and the end of the

growing season (Sept. 1 to Nov. 31). Ground cover estimates

(by species) were obtained using a 35 mm ocular tube (James

and Shugart 1970). Estimates were made at l-m intervals

along two 10-m transects within each sample plot, Transects

were centered on the trap station.

Aboveground forage biomass was determined by clipping the

current year’s growth of all plants in a 1 m by 1 m plot

randomly located within each 0.04-ha plot to a height of 1.5

m; forage was weighed in the field. Clipped material was

separated into three categories: woody, forbs, and grasses.

Moisture content of forage biomass was determined in the

laboratory after drying in a forced-air oven at 60 degrees C”

for 72 hours.

Trapping

Trapping took place during the three periods when vegetation

was sampled. Traplines were prebaited with peanut butter for

5 nights with the traps closed and then sampling was

conducted for 5 consecutive nights during each trapping

period. Four trap types were used in each treatment area:

Victor rat traps, Victor mouse traps, Museum special traps,

and pitfalls with drift fences. All traps were rebaited each

day during the prebaiting and trapping periods. Trapping

design was identical for all periods.

One snap trap of each type was placed within 2 m of each

randomly located trap station. Trapping stations were marked

with l-m sections of rebar in order to establish permanent

trap locations. Pitfalls were randomly located on each site by

overlaying a grid on the site map and using a random number

table to determine their coordinates. A modification of the

trap design described by Williams and Braun (1983) was

used. Each drift fence consisted of three 5 m by 51 cm legs

of aluminum flashing that met at a common point centered on

the pitfall, with 120 degrees between each pair of legs.

Flashing was set in a ditch 8 to 10 cm deep. These ditches

were then packed with soil and the fences supported with

wooden stakes. At the center of the fences, a 19-1 plastic

bucket was buried flush with the ground. Buckets were kept

one-third to one-half full of water to drown captured animals,

and were covered with a lid when not in use. All traps were

checked daily during trapping periods.

Vegetation and trapping data were used to calculate Shannon

diversity (H ‘), evenness (J), and species richness (S) for each

trapping period. Shannon diversity was calculated as H ’ =-

CP, (In P, ) where (Pi ) is the proportion of the ith species in

the population (Shannon and Weaver 1949). This function

measures the uncertainty in predicting the identity of any

randomly selected individual based on the total number of

species in the sample (S) and the number of individuals (N),

or the proportion of that species to the whole sample (P, ) for

each species represented in the sample. (J) is a measure of

the evenness of the distribution of individuals within the

species present, and is calculated as J =H ‘/(lnS) (Pielou,

1977).

Insects were collected in ten randomly located 600-ml pitfalls

on each site. Traps were used for biomass collection, since

terrestrial insects are more susceptible to capture in pitfalls,

their numbers would be overestimated if individuals were

singled out for identification (Southwood 1978). Traps were

kept one-third to one-half full of equal parts of water and

ethylene glycol, to keep the insects flexible. Traps were

emptied daily during the 5-day period when small mammal

trapping took place. AI1 insects were identified to family and

weighed for biomass.

All habitat and trapping data were summarized for each site

and treatment type. Analysis of variance was used to test for

differences between treatments, blocks, and collection

periods. Differences were tested for significance at the 0.05

level.

RESULTS AND DISCUSSION

Vegetation

Biomass. Total forage biomass was greatest on winter-felled

sites and on burned sites (Fig. 1). All treatments that

included felling produced more forage biomass than the

unharvested control plots. Total woody biomass, which was

highly variable, did not differ significantly among treatments.

Woody biomass production varied within the treatments

depending on the species of woody vegetation present on the

site. This variation within treatments masked any betweentreatment differences that might have been developing. Forb

production was greatest on burned sites, particularly with

winter felling. This fort, response resulted from removal of

the litter layer which improved seed germination conditions.

Grass production was significantly higher on the winter-felled

no-bum sites than all other treatments as a result of sprouting

from pre-existing rootstocks beneath the little layer. The

controls had significantly lower grass production than all

other treatments as a result of the heavy litter layer and

almost complete shading of the forest floor. Increases in

grass and fort, coverage at the expense of woody vegetation

are common after burning and have been documented by

(Langdon 1981, Waldrop and others 1987, Van Lear and

Waldrop 1989).

161
3600 1

n-L

Wlnter Felled Wlnter Felled Sprlng Felled Sprlng Felled Control

Burn No Burn Burn No Burn

Figure 1. Forage biomass production by species group and treatment on fell-and-bum site-prepared areas in the Upper

Southeastern Piedmont.

During the first sampling period after the bum, considerable

browsing occurred on blackgum (Nvssa svlvatica Marsh.),

American holly (llex opaca Ait.), sassafras (Sassafras albidum

(Nutt.) Ness.), and smilax (Smilax SRQ.) seedlings and

sprouts. During the second sampling period, utilization of the

same species continued. Pokeweed (Phvtolacca americana L.)

however emerged as the most heavily browsed species.

Pokeweed was often browsed to the point of being stunted.

During the final sampling period, utilization of woody browse

seemed to decline, probably due to the lignification of the

woody tissue. While utilization of pokeweed and smilax

remained steady. Because summer rainfall was higher than

normal forbs on these sites remained succulent into October

and November, when they would normally have hardened and

been abandoned as preferred browse species.

Diversity, Richness, and Evenness. Diversity of vegetation

(H ‘) increased slightly as a result of winter felling, but there

were no significant differences in H ’ between treatments.

Species differences did occur among treatments as a result of

burning, but these differences did not significantly affect H ‘.

Burning favored grasses and forbs while unburned areas were

dominated by sprouts of trees and shrubs.

Species richness of vegetation (S) was significantly higher on

burned areas than in unburned areas and unharvested controls

(fig. 2). Among the burning treatments, winter felling

produced significantly greater species richness values’. Due

to the absence of leaves on the slash, winter-felled sites

typically did not bum as evenly or completely as spring-felled

sites (Geisinger and others 1989). Therefore a mosaic of

burned and unburned microsites was created, with each one

capable of supporting a different complement of species.

‘See Evans (1990, unpublished thesis) for a full species listing.

162

Vegetative evenness (J) did not differ significantly among

treatments. However, J was slightly higher on winter-felled

no-bum sites due to increased grass production on those sites.

Small Mammals

Diversity, Richness, and Evenness. Diversity of small

mammals (H’) showed no significant differences among

treatments until the third sampling period (Sept. 1 to Nov. 31)

(table 1). At th? time, small mammal abundance on all siteprepared areas declined with the winter decline of vegetative

browse and ground cover. This pattern agrees with the

finding of Briese and Smith (1974) that small mammals shift

the centers of their ranges throughout the year to take

advantage of the distributional change in food and cover. H ’

was greater on the unharvested controls than on the treated

sites during the third period as a result of the fall mast crop

and the greater cover afforded by the undisturbed little layer.

Species richness (S) values were low in the lirst sampling

period and there were no significant differences in S among

treatments (table 2). In the second sampling period, winterfelled, burned sites had significantly higher S values than

other sites. However, in the third sampling period, species

richness was significantly lower on winter-felled burned sites

as a result of the early senescence of the fort, species that

dominated those sites. Both food and cover declined much

earlier on winter-felled burned sites than on those where

grasses or woody vegetation were more dominant. Evenness

(J) values did not differ significantly among treatments in any

period.
50

40

30

20

10

0

b

Vhnter Felled Winter Felled Sprlng Felled Sprlng Felled

Burn No Burn Burn No Burn

Control

Figure 2. Plant species richness on fell-and-bum site-prepared areas in the Upper Southeastern Piedmont (columns with the

same letter were not significantly different at the 0.05 level using Duncan’s Multiple Range Test).

Table 1. Small-mama1 diversity (H') on felled-and-burned study sites in the

Upper Southeastern Piedmont, 1989.

Treatment Period

Jan. T-Mar. 31 May I-July 31 Sept. l-Nov. 31

Uinter-Fell, Burn O.Oe 0.261a 0 092a

Winter-Fell, No-burn O.la 0.173a 0:360ab

Spring-Fell, Burn O.Oa 0.235a 0.409ab

Spring-Fell, No burn O.Oa 0.19la 0.192a

Control O.Oa O.OOOa 0.519b

-Values folloued by the same letter uithin a column uere not significantly

different at the 0.05 level using Duncan's Multiple Range Test.

Table 2. Species richness (S) of small mam~ls on felled-and-burned study

sites in the Upper Southeastern Piedmont 1989.

Treatment Period

Jan. t-Mar. 31 May I-July 31 Sept. l-Nov. 31

Uinter-Fell, Burn 0.333a 2.667a 1.333a

Winter-Fell, No-burn 1.333a 1.667ab 2.667ab

Spring-Fell, Burn 0.667a 2.000ab 3.333b

Spring-Fell, No burn l.OOOa 2.000ab 2.000ab

Control 0.667a 0.333b 3.333b

-Values folloued by the same letter uithin a column uere not significantly

different at the 0.05 level using Duncan's Multiple Range Test.

163
6

a

ab

b

Wlnter Felled Wlnter Felled Sprlng Felled Sprlng Felled

Burn No Burn Burn No Burn

Control

Number of individual small mammals on fell-and-bum site-prepared areas in the Upper Southeastern Piedmont

(columns with the same letter were not significantly different at the 0.05 level).

Number of individuals. Both winter-felling and burning

resulted in higher numbers of small mammals (N) utilizing an

area (fig. 3). This increase is probably a response to the

increase in available forage (vegetation biomass) that resulted

from this treatment combination. Not all small mammal

species increased in numbers in response to disturbance.

Species that were trapped most often, such as white-footed

mice (Peromvscus leuconus), were those that are best adapted

to an early successional environment (table 3). This finding

agrees with a number of other studies that show an increase in

Peromvscus spp. following fire (Ahlgren 1966; KreRig and

Ahlgren 1974; Hingtgen and Clark 1984). The increase in

Peromvscus spp. was most pronounced during the first two

sampling periods and was no longer evident by the third

sampling period. By that time the habitat was sufficiently

developed to support a larger number of species with more

varied food habits and cover requirements.

Table 3. Relative ekndance etxi total number of individual aninrals (Y)

captured, by species, on alt fell-and-burn study sites in the Upper

southeastern Piechwnt 1989.

“AWAL

white-footed mouse (Peromyscus Leucopus) 97 63.0

golden mouse (Ochrotays wftsllii) 1 3 8.5

hwse mcuse (UUS m.E.culus) 1 0 6.6

ea*tem cottontail rabbit (Sylvilsgus floridanus) 7

cotton Cat (Signodw, hispidus) 6 :4

cotton mouse (P. gossypinus) 2 1:2

eastern chipmnk (Tmnias striatus) 1 0.7

tcest shreu (Cryptotis parve) 1 0.7

southeastern shrew (Sorex Longirostris) 0.7

bteck rat (Rattus rattus)

1

0.7

BIRDS

mourning dove,

HERPETOFAUNA

American toed

Uocdhouse's toad

-?estem tax turtle,

(Zenaide macrwra) 1 0.7

TOTAL= 1 0.7

(Bufo emricsnus) 2.0

(5. uoodhwsei) : 1.2

(Terapme carolina) 2 1.2

southern leopard frog fR.ww sphcncocephete) 1 0.7

eastern narrow-mouthed toad (Gestrophyrne cerolinensis) 1

ring-necked snake (Diadophus pnctstus) 1 i::

OTHER

brown grand-daddy LongLegs, (Phalangiun opiLio) 1 0.7

Carolina Locust, (Dissostiers cerolina) 1 0.7

TOTAL= 2 1.4

GRAND TOTAL=

I-irdicetes an incidental capture in B snap trap

152 100.0

164
II,’ ., Period 3

.:,. ......

cl .:,;....: period 2

q Period 1

”

Wlnter Felled Winter Felled Sprlng Felled Sprlng Felled Control

Burn No Burn Burn No Burn

Figure 4. Insect biomass production on fell-and-bum site-prepared areas in the Upper Southeastern Piedmont, 1989.

Insects

Biomass. Total insect biomass was decreased temporarily by

all site preparation treatments (fig. 4). Control sites averaged

4.7 kg/ha, while treated sites averaged 2.8 kg/ha. Insect

biomass did not decrease as dramatically on winter-felled sites

as on other sites, probably because fire intensities were lower

on the winter-felled sites. Insect biomass was significantly

higher on control sites than on other sites during the first

sampling period. Both winter-felled and control sites were

significantly higher than other sites during the second

sampling period. Recovery of insect biomass production was

rapid and there were no longer significant differences by the

third sampling period.

SUMMARY AND CONCLUSIONS

Vegetation biomass production was greater for all site

preparation treatments than for the control. Burned plots

supported richer, more productive plant communities and

higher numbers of small mammals than did unburned plots.

Winter-felling and burning yielded richer, more productive

plant communities and higher numbers of small mammals

than spring felling and burning. As vegetation biomass

production declined in the fall, small-mammal numbers

became highly variable within treatments. Insect biomass

production was reduced by all site preparation treatments due

to disturbance of the litter layer. However, this decrease in

production lasted less than 1 year.

This study indicates that the fell-and-bum site preparation

technique, as it is practiced in the Southern Appalachian

Mountains, can be used in the Upper Piedmont without

adversely affecting forage production for wildlife habitat. If

felling of residual stems is conducted in the spring, as is

recommended in the Southern Appalachian Mountains, site

preparation bums can significantly reduce fuel loads and

provide uniform Planting conditions (Sanders and Van Lear

1987; Geisinger and others 1989). Bums conducted after

winter felling are less uniform (Geisinger and others 1989)

and leave more of the slash and logs that provide cover and

foraging sites for small mammals. More complete bums also

result in a more homogenous habitat than the mosaic of

burned and unburned microsites found on winter-felled areas.

The fell-and-bum technique is a relatively inexpensive method

to regenerate pine-hardwood mixtures but its application in

the Piedmont requires additional study. Effects on wildlife,

water quality, and soil as well as on stand regeneration and

development are currently being studied. As Van Lear and

Kapeluck (1989) have shown, burning prescriptions on

Piedmont sites must be modified if erosion is to be controlled.

Species composition and soil characteristics of Piedmont sites

are different from those of mountain sites, and it may be

necessary to modify fell-and-bum techniques because of those

differences. Finally, this study addressed only the early

successional habitat changes that resulted from this technique.

The impact of this type of site preparation on wildlife as the

stands continue to develop is yet to be determined.

165
LITERATURE CITED

Abercrombie, James A., Jr.; Sims, Daniel H. 1986. Fell

and bum for low-cost site preparation. Forest Farmer

46(1):14-17.

Ahlgren, Clifford E. 1966. Small mammals and

reforestation following prescribed burning. Journal of

Forestry 64(9):614-618.

Briese, Linda A.; Smith, Michael H. 1974. Seasonal

abundance and movements of nine species of small

mammals. Journal of Mammalogy 55:615-629.

Evans, Timothy L. 1990. Effects of fell-and-bum site

preparation on wildlife habitat and small mammals in the

Upper Piedmont of Georgia and South Carolina. MS.

Thesis, Clemson University, Clemson, SC.

Geisinger, Donn R.; Waldrop, Thomas A.; Haymond,

Jacqueline L.; Van Lear, David H. 1989. Sprout growth

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167
EFFECTS OF FIRE AND TIMBER HARVEST ON VEGETATION

AND CERVID USE ON OAK-PINE SITES IN

OKLAHOMA OUACHITA MOUNTAINS

Ronald E. Masters’

Abstract-This study compared vegetation response and cervid browse use within the Ouachita Mountains

following an array of timber harvest and fire regimes. Nine treatments were replicated l-3 times in a

completely randomized design on 23 (1.2-I .6 ha) units. The treatments were a no treatment control, a

winter rough reduction bum treatment, a clearcut, mechanical site preparation and summer bum treatment,

a harvest pine (Pinus echinata) only and annual bum treatment, and 5 harvest pine and thin hardwood

treatments with no bum, 4, 3, 2, and 1 year winter-bum intervals. Pine timber was harvested in June and

July of 1984 and hardwoods selectively thinned to a basal area of 9 d/ha in appropriate treatments.

Clearcut treatments were sheared, raked, and windrowed in spring 1985 followed by a summer site

preparation bum, and then contour ripped prior to planting in early April 1986. Winter bums were strip

headfires applied in mid- to late winter in 1985 through 1988. Little bluestem (Schizachvrium scooarium)

and big bluestem [Andropoaon perardi) dominated harvested and winter burned (retrogressed) treatments.

Plant frequency and percent ground cover of these 2 species incressed on sites burned more frequently.

The clearcut and summer burned sites were initially dominated by forbs and panicums (Dicanthelium spp.

and Panicum spp.). Then as forbs declined, little bluestem increased in frequency and percent ground

cover. Plant species richness was significantly @ < 0.05) increased by timber harvest and fire. Among

harvested sites, frequency of burning had no significant effect on plant species diversity or plant species

evenness. Longer bum intervals or no burning on retrogressed sites allowed woody browse species used by

white-tailed deer (Odocoileus virginianus) and possibly elk (Cervus Frequency of elaphus) to increase.

browse use by cervids in 1988 was greatest on the harvest, thin, 3-year bum interval; harvest, thin, nobum; harvest, thin, 2-year bum interval; and clearcut treatments. The harvest, thin, no-bum and clearcut

treatments also provided screening and bedding cover for cervids, in contrast to other treatments. Winter

prescribed fire at I- or ‘L-year intervals favored legumes and created habitat conditions favorable for

bobwhite quail (Colinus virrrinianus). Timber management strategies that create a mosaic of retrogressed

burned and unburned sites, and regeneration clearcuts with adequate provisions for hard mast production

should provide management flexibility to meet habitat needs of most game species.

INTRODUCTION

The oak (Ouercus spp.)-shortleaf pine forest is the most

extensive forest type in the eastern United States (Lotan and

others 1978), and is widely considered to be a fire subclimax

association (Oosting 1956). In spite of the type’s prevalence

and importance, there has been insufficient research on forest

management and fire ecology in the oak-shortleaf pine type

and specifically in the Ouachita Highlands (Lotan and others

1978).

Segelquist and Pennington (1968) documented the lack of an

adequate understory forage base for deer in the Ouachita

Mountains of Oklahoma. Winter mortality of deer has been

related to mast failure and may be compounded by the lack of

an evergreen winter browse (Segelquist and Pennington 1968;

Segelquist and others 1969, 1972). Forage production in late

summer and early fall may be of critical importance in the

advent of mast shortfall (Fenwood and others 1984).

In 1977, the Oklahoma Department of Wildlife Conservation

began using timber harvest and prescribed fire to improve

habitat conditions for deer and elk on the Pushmataha Wildlife

Management Area. Harvested settings were maintained in

early stages of secondary succession with prescribed fire (site

retrogression). Although the effects of forest management

and fire on wildlife have often been studied, little research

has dealt with manipulation of forested ecosystems for the

purpose of benefiting wildlife (Ripley 1980).

My objective was to compare site retrogression through

timber harvest and periodic prescribed fire, with regeneration

clearcutting and understory rough reduction bums. Changes

in plant species richness, diversity, evenness, composition,

percent ground cover and browse utilization by cervids were

used as measures of treatment effects.

STUDY AREA

The 29.1-ha study area was located within the Forest Habitat

Research Area (FHRA) on the 7,395 ha Pushmataha Wildlife

Management Area near Clayton, Oklahoma. The Pushmataha

Wildlife Management Area lies along the western edge of the

Ouachita Highland Province. Study area soils belong to the

Camasaw-Pirum-Clebit association with areas of rock

‘Forest Wildlife Biologist, Oklahoma Department of Wildlife

Conservation, 1801 N. Lincoln, Oklahoma City, OK.

168
outcrop. The soils developed from chetty shales and resistant

sandstones and were thin and drought prone. The climate was

semihumid to humid with hot summers and mild winters (Bain

and Watterson 1979).

Prior to acquisition from 1946 to 1954, Pushmataha Wildlife

Management Area was grazed, selectively harvested, and

frequently burned (Oklahoma Department of Wildlife

Conservation 1972). The FHRA was protected from further

logging, grazing and fire from acquisition until 1984 (R.

Robinson, Area Biologist, Oklahoma Department of Wildlife

Conservation, personal communication). From 1983 to 1988

the Pushmataha Wildlife Management Area supported an

average deer population of 540 -+ 40 (SE) and 9 + 1 (SE) elk

(Masters 1991).

Post oak (Q. stellata), shortleaf pine, and to a lesser extent,

blackjack oak (Q. marilandica), and mockemut hickory

(Carva tomentosa) dominated the overstory. Common woody

understory species included tree sparkleberry (Vaccinium

arboreum), Virginia creeper (Parthenocissus quinouefolia),

greenbriar (Smilax Common spp.), and grape (Q& spp.).

herbaceous plants included little bluestem, panicums, and

sedges (Carex spp.) (Masters 1991).

METHODS

Cultural Treatments

Beginning in summer 1984, 9 treatments were applied to 23,

I .2-l .6 ha contiguous, rectangular units on the FHRA in a

completely randomized experimental design (Chambers and

Brown 1983). Treatments, burning sequence, treatment code,

and number of replications (n) were:

(1) no treatment (control) (n = 3);

(2) rough-reduction winter prescribed bum at &year

interval, 1985 (RRB) (n=3);

(3) clearcut and summer site prep bum, 1985 (CCSP)

(n=3);

(4) harvest pine timber only, winter prescribed bum,

l-year interval, 1985 to 1988 (H-NT-l) (n=3);

(5) harvest pine timber, thin hardwoods, no bum (H-T)

@=I);

(6) harvest pine timber, thin hardwoods, winter prescribed

bum at 4-year interval, 1985 (H-T-4) (n=3);

(7) harvest pine timber, thin hardwoods, winter prescribed

bum at 3-year interval, 1985, 1988 (H-T-3) (n=2);

(8) harvest pine timber, thin hardwoods, winter prescribed

bum at Z-year interval, 1985, 1987 (H-T-Z) (n=3);

and

(9) harvest pine timber, thin hardwoods, winter prescribed

bum at l-year interval, 1985 to 1988 (H-T-l)

(n=2).

In appropriate treatments merchantable pine timber was

harvested and hardwoods selectively thinned by single stem

injection using 2-4 D, to a basal area of 9 m*/ha (includes

stems > 5 cm diameter at 1.4 m height), in summer 1984.

Prescribed bums using strip headlires were conducted in

winter 1985 and in succeeding years at appropriate intervals.

Several replications were dropped because they were either

burned out of sequence by spotovers or not burned because of

rain. The clearcut site-prep treatment included shearing,

raking and windrowing of logging debris with a site-prep bum

conducted during summer 1985. After contour ripping,

genetically improved loblolly pine (12. w was planted on a

2.1 m by 2.4 m spacing, in early April, 1986.

Vegetation Sampling

Understory, midstory and overstory vegetation was sampled

using nested quadrats (1 m by 1 m and 4 m by 4 m) (Oosting

1956:47-50, 62). On each treatment unit, 10 permanent plots

were established at 19.8 m intervals on two randomly located

lines perpendicular to the contour. In order to avoid bias

caused by influences from adjacent treatment units, I did not

sample within 19.8 m of any edge (Oosting 1956; MueIIerDombois and Ellenberg 1974). Data collected included plant

species density, frequency, percent ground cover, and

utilization.

Utilization was categorized based on proportion of current

annual growth (CAG) browsed. The categories were none,

trace--less than 25 percent, moderate--25 to 50 percent, and

heavy--greater than 50 percent utilization.

Overstory and midstory vegetation were categorized by

vertical strata and crown position relative to stand canopy

structure. Strata designations were 0 to 1 m, 1 to 3 m, and

greater than 3 m. Strata greater than 3 m were categorized

by position relative to stand canopy structure and were

suppressed, intermediate, codominant, and dominant canopy

position (Smith 1962). On harvested treatments strata

designation of residual trees was based on prior stand

structure. No tree or shrub regrowth was greater than 3 m.

Overstory vegetation was further quantified using the variable

radius plot method (Avery 1964). Basal areas were taken

using a 10 basal area factor prism with plot center at the

center of each 4 m by 4 m plot. Vegetation sampling and

browse use determinations were conducted in September and

October of each year because this was a critical period of the

year for deer (Fenwood and others 1984). A baseline survey

was conducted in 1983.

Data Analysis

Species diversity, evenness, richness, density, and frequency

were calculated from vegetation samples (Ludwig and

Reynolds 1988). A modification of Krueger’s (1972)

preference index (RPI) combined across years and treatments

was used to rank plant species used by deer and elk. Analysis

I69
Table 1 .--Average percent cover for major species groups 1983-88. Timber harvest

was applied in smr 1984 and prescribed burns were conducted in 1985 and fo1lowing.l'

TREATMENT"

VEGETATIVE

GROUP CONT RRB H-NT-1 H-T H-T-4 H-l-3 H-l-2 H-l-l CCSP

____--______--_-____-------.

GRASSES 3 6

FORBS 2 2

LEGUMES

1

1

VINES <l

SHRUB 0-1M 6 1 3

SHRUB l-3M 1 3

TREE MIDR' 14a 10a

__________---_--____--------

GRASSES 9 1 0

FORBS

LEGUMES : s

VINES SHRUB 0-1M 1 01 2 2

SHRUB l-3W 3 5

TREE MID 23a 24a

-_-

_--

.

.

YEAR=83 ---_--_--__---__-----------------------

71 1 2; t r8 4 . 2 . 37

1 1 2 . 1

<l <l 1: <l

06 1 0 7 :

ql

4 b 2: l b

<l

4b :

i

4 b

YEAR=84 ---_-_-------------____________________

1 4 1 4 8 5 . 7

7 1

<l 1 1 : : :

<l <l Tl

1 6 11 ii :, : 7

1 2 <l 1

9ab lb 7 b ib : 9ab

____________---_____--------------- YEA,+85 __--_________-______----.--------------

GRASSES 7 b 6b . 23a 22a 2Oa 14ab . 5 b

FORBS 2 2 . 25a 17b llb 14b . 3

LEGUMES 1 1 . 2 4 3 6 . 1

VINES : <l

SHRUB 0-1M 9 :

0 <l

2 0 1 3

1: 1;

:

ql

4

SHRUB l-3M !ia 3ab . l b <lb

TREE MI0 24a 17a fb

------.----.-.-----------------~---- YEAR=&

2 b zt: 5: :

clb

<lb

_--_______-_-____----------------------

GRASSES 7 b 8b 30a 20ab 29a 27a 20ab 28a 17ab

FORBS 3 c 5bc 13bc 16bc 18b 17b 19b 18b 37a

LEGUMES : 2 4 4 5 6 7 9 3

VINES cl

SHRUB 0-1M 9 ;2, ;lt ;: 2: 1 2 1; 12 9

SHRUB l-3H 6a lbc 3bc

E 4bc

2bc

:P oc

4ab <lIX o c

TREE MID 22a lob lc o c o c

__-__-_---------------------------- YEAR=87 ---------------_-----------------------

GRASSES 4 c 7 c 34a 19b 2Sab 21b 21b 3Sa 2Sab

FORBS

:b

2 llabc 1obc 9bc 7c 17ab 13abc 20a

LEGUMES l b 6ab 8a 4ab 3ab Pa Sab 4ab

VINES 1 <l <l <l 3 a 1 1 Cl

SHRUB 0-1M 6c 14abc 1obc 29a 2;abc 24ab 22abc 8bc 13abc

SHRUB l-311 4 2 1 2 6 5 3 2 3

TREE MID 22a l:b 4 c 2 c 4c 2c lc o c o c

___________________________________ YEAR== _______________________________________

GRASSES 3 d

E

31ab llcd 2Sab 32ab 2Ocb 37a 28ab

FORES l b 7ab 4b 7ab 8ab 6ab 13a

LEGUMES l c lc sabc 2bc ::bc Sabc 9a 8ab Sabc

VINES

:C

<l <l el 1 1 <l

SHRUB 0-1M 1Sabc 1obc 29a 26ab 28a ;:ab l&c 17abc

SHRUB 1-3M 4b 2b

f:: 2c

24a lib 2 b 9 b l b 12b

TREE MID 16a 12ab lc o c <lc o c o c

' Row means with the same Letter are not significantly different (p < 0.05).

' CONT = control, no treatment; RR8 = rough reduction burn in winter, at 4 year

intervals; H-NT-l = harvest pine tinber, no thinning of hardwoods, winter

prescribed burn at 1 year intervals; H-T = harvest pine timber, thin hardwoods;

H-T-4 = harvest pine timber, thin hardwoods, winter prescribed burn at 4 year

intervals; H-T-3 = harvest pine timber, thin hardwoods, winter prescribed burn at

3 year intervals; H-T-2 = harvest pine timber, thin hardwoods, winter prescribed

burn at 2 year intervals; H-T-l = harvest pine timber, thin hardwoods, winter

prescribed burn at 1 year intervals; CCSP = clearcut, windrow logging slash, summer

site prep burn, rip.

3 TREE MI0 = Suppressed trees > 3 m height in the midstory, but not extending into

the upper canopy layer.

170
was performed using PC-SAS @AS Institute 1985, 1987) and

SPDIVERS.BAS (Ludwig and Reynolds 1988). Statistical

analysis of treatments was by one-way analysis of variance

(ANOVA) for unequal sample size. To determine treatment

prcfcrence by cervids, browse utilization frequency for all

sample plots was summed by unit (replication), ranked and

analyzed by ANOVA, the equivalent of the Kruskal-Wallis

nonparametric procedure (SAS Institute 1985). Mean ranks

were separated by Duncan’s Multiple Range Test (Steele and

Torrie 1980).

RESULTS

Vegetation Response

Pretreatment vegetation sampling in 1983 indicated higher Cp

< 0.05) percent cover of midstory trees in control and RRB

replicates than on other treatment units (table 1). Values for

utilization and other descriptors of vegetation did not differ

among units prior to application of treatments. The only

significant differences found bexween control and RRB

treatments in succeeding years were in percent cover of

suppressed trees. Rough reduction burning reduced Cp <

0.05) percent cover in that stratum by 1986-88 (table 1).

Understory response varied after initial timber harvest and

thinning of residual hardwoods. In 1984, species diversity

increased, and evenness declined @ < 0.05) on aU harvested

and thinned treatments compared to the control and RRB

treatments. Species evenness provided an adequate measure

of shrub response only in 1984. Species richness of herbs

and shrubs immediately after timber harvest was unchanged

(figs. 1 and 2).

In 1985 and 1986 after all burning and timber harvest

treatments had been applied species richness of herbaceous

and shrub vegetation on treated areas were significantly Q <

0.05) higher (figs. 1 and 2). Grass cover on treated areas

was dominated by little bluestem, big biuestem and panicums.

The predominant forbs were horseweed (Convza canadensis),

white snakeroot (EuDatorium rueosum), and fireweed

(Erechtities hieracifolia). Shrub response on harvested and

burned treatments was composed of primarily winged sumac

(Rhus cooallina), dewberry (Rubus spp.), and post oak

sprouts. Only legume and vine categories showed no

difference in cover among treatments (table 1).

In 1986, values of most vegetational characteristics of CCSP

areas did not differ significantly from comesponding values

for areas that were harvested and burned (table 1). However

species composition and shrub species richness differed by

treatment (Jj < 0.05) (fig. 2). Panicums and little bluestem

were respective grass dominants on CCSP and all the

harvested, thinned and burned treatments. Crabgrass

40 ,

0 =BlJRNED A H-NT-11

CONTROL

5 : CYT / TB / “r” ,

1983 1984 1985 1966 1987 1988

YEAR

Figure l.-Mean species richness of herbaceous plants 1983-

88. For clarity of presentation some burned treatmenu were

not depicted. Those not depicted were intermediate in

response.

1 8

t

CUT SPB RIP -0

8 --3---l- I f I I

1983 1984 1985 1986 1987 1988

YEAR

Figure 2.-Mean species richness of shrubs 1983-88. For

clarity of presentation some burned treatments were not

depicted. Those not depicted were intermediate in response.

171
(Digitaria violescens) was a significant component of the grass

response of the CCSP treatment and occurred infrequently on

other treatments. Broomsedge bluestem (Andropoppn

virginianus) also occurred more frequently on CCSP

treatments than on other treatments. Forb response was

greatest during 1986 on the CCSP treated areas and was

significantly higher for this treatment than for others @ <

0.05) (table 1).

By 1988, percent cover of all plant groups, except vines,

differed among treatments (table 1). For herbaceous plants,

species richness and evenness differed significantly among

treatments. Species richness and diversity differed

significantly among treatments for shrubs (fig. 2). Timber

harvest and prescribed fire decreased herbaceous species

evenness but increased shrub and herb richness and shrub

diversity (figs. 1 and 2). Bluestems and panicums were

dominant grasses on harvested and burned treatments. In the

CCSP treatment areas, the grasses were mainly comprised of

panicurns and to a lesser extent little bluestem. Broomsedge

bluestem occurred more frequently on this treatment than

others.

Dominant shrub species on harvested and burned sites

included winged sumac, dewberry, post oak sprouts, tree

sparkleberry, and winged elm (Ulmus On the H-T alat@.

treatment, sumac was not prevalent, but the above species and

shortleaf pine seedlings and saplings were prominent.

Dewberry, post oak, coralberry (Svmohoricaruos orbiculatus)

and loblolly pine were primary shrub constituents on CCSP

treatments.

Abundance of preferred forbs increased c < 0.05) (fig. 3)

after timber harvest and prescribed fire then declined as grass

cover increased (table 1). Preferred browse increased @ <

0.05) in alI except RRB, control and annual burned treatments

(tig. 4). Percent cover of preferred browse in the annual

burned treatments were not different from percent cover of

preferred browse on the control or RRB sites. By 1988

legumes, preferred forbs and preferred browse responded

differentially by treatment (figs. 3-5). More frequent burning

intervals favored legumes and preferred forbs while less

frequent intervals favored shrubs (figs. 4 and 5).

Utilization

Cervids utilized 74 species of plants and 17 plant groups

identified to genera. Forbs of 31 species, and additional

plants identified only as members of 7 genera were used.

Thirteen species of legumes and additional legumes identified

to 1 genus (Desmodium spp.) were used. Utilization occurred

on 29 species and an additional 7 genera of woody browse.

Grass-likes utilized included panicums, sedges, and little

bluestem. Rankings of relative preference revealed that

woody browse was used more than forbs (table 2).

YEAR

Figure 3.-Percent cover of preferred forbs 1983-88. For

clarity of presentation some burned treatments were not

depicted. Those not depicted were intermediate in response.

YEAR

Figure 4.--Percent cover of preferred browse 1983-88. For

clarity of presentation some burned treatments were not

depicted. Those not depicted were intermediate in response.

-3

3lFtN

TREATNENT

Figure S.--Percent cover of preferred forbs, other forbs, and

legumes after all bum intervals had been completed in 1988.

172
Table Z.--Rankings of preferred cervid food plants based on a

surmed preference index for all years and treatments.

Browse Index Forbs index

Smilax spp. 808 Lespedeza spp. 322

Ulmus alata 745 Aster patens 311

mnanch arborea 448 Solidago ulmifolia 201

Vitis spp. 422 135

Vacciniun spp.

Honarda fistulosa

201 Phytolacca americana 128

Hvpericun spp. 195 Conyza canadensis 120

Rhus glabra 167 Solanun carolinense 116

Rhus cocallina 159 Aster spp. 106

103

Cervid Use

Mean ranks of cervid frequency of utilization on replicates

was significantly different Cp < 0.001) among treatments

(table 3). Annual bum and RRB treatments had significantly

lower frequency of utilization than other treatments.

DISCUSSION

Vegetation response varied by species. Some plant species

increased on retrogressed sites and others decreased from

pretreatment levels. Species evenness was highest on the

control and pretreatment, which indicated that herbaceous

species were equally abundant. Site perturbation, caused

some plant species, particularly tallgrasses, to become more

abundant relative to other species.

Community progression on harvested and burned sites was

similar to that reported by Hebb (1971) for clearcutting.

Successional stages alter harvest were; (1) disturbed site with

pretreatment understory ground cover; (2) profusion of

grasses and annual forbs; (3) increase in perennial forbs and

grasses, decrease in annuals and increase in shrubs; and (4)

in the absence of periodic prescribed fire, increases in shrubs

and grasses and declines in forbs.

Chronosequences of vegetation on retrogressed sites subjected

to fire at varying frequencies was similar to response of

burned mesic tallgrass prairie (Anderson and Brown 1986).

Longer fue intervals allowed woody species to increase

(Bragg and Hulbert 1976; Petranka and McPherson 1979).

Summer site-prep bums and ripping associated with the CCSP

treatment caused a lag in pIant community progression.

Species composition was different under this treatment regime

with forbs dominating the year following the summer site

prep bum. As grasses increased, panicums were the primary

dominant followed by little bluestem. The broomsedge

bluestem component was higher on the CCSP treatment than

others. The summer site prep burn apparently set back

bluestems and allowed cool season grasses (panicums) and

sedges to increase. Shrub species richness and percent cover

were slower to increase on CCSP than retrogressed and

winter burned sites (table 1 and fig. 2).

Rough-reduction bums caused smaller increases in herbaceous

cover and species richness than they have in other cases

(Oosting 1944, Lewis and Harshbarger 1976). However, oakpine forest in the Ouachita Mountains do not have well

Table 3. --Mean ranks of 1988 cervid utilization frequency by

treatment on the Pushmataha Forest Habitat Research Area.l’

TREATMENT”

H-T-3 H-T H-l-2 CCSP CON1 H-T-4 H-T-l H-NT-1 RRB

19.8 18.5 17.2 17.2 13.2 9.8 8.5 7.3 2.3

’ Means underscored with the same line are not significantly

different (p < 0.05).

’ H-l-3 = harvest pine timber, thin harduocds, uinter prescribed

burn at 3 year intervals; H-T = harvest pine timber, thin

harduoods; H-T-2 = harvest pine tin&r, thin hardwoods, winter

prescribed burn at 2 year intervats; CCSP = clearcut, windrow

logging slash, sunnet- site prep burn, rip; CONT = control, no

treatment; H-T-4 = harvest pine timber, thin hardwoods, uinter

prescribed burn at 4 year intervats; H-T-1 = harvest pine

timber, thin hardwoods, winter prescribed burn at 1 year

intervals; H-NT-1 = harvest pine timber only, winter prescribed

burn at 1 year intervals; RRB = rough reduction burn in uinter,

at 4 year intervals.

173
developed midstories. Herbaceous species will increase as

repeated fire eliminates smaller diameter overstory hardwoods

and as pines assume dominance (Lewis and Harshbarger

1976).

Browse use on a treated area was probably related to percent

cover of preferred browse and shrub species richness (table 3

and figs. 2 and 4). Woody browse is the major component of

deer diets in all months except May (Jenks and others 1990).

However when hard mast is available in fall and winter it

comprises the major portion of deer diets (Fenwood and

others 1985). Presence of preferred forbs, panicums, and

sedges on a treatment probably affected use because of the

selective foraging nature of deer (Vangilder and others 1982).

Screening, bedding, or escape cover may be important

because deer were flushed frequently out of beds only in the

H-T and CCSP treatments. The shrub component on H-T and

CCSP treatments in the O-l m and l-3 m categories was

primarily pine saplings. Pines probably provided a more

dense horizontal cover but this parameter was not measured in

this study. The presence of cover on HT and CCSP

treatments may have increased use on these areas. Deer use

increases on recent clearcuts but is limited to 100 m from

cover on large clearcuts (Tomm and others 1981). As pine

stands develop in height on regeneration areas, deer use of the

central portion of the stand will increase. All portions of

large (128-276 ha) 4-S year old pine stands were used in a

southeast Oklahoma study (Melchoirs and others 1985).

CONCLUSIONS

The primary values associated with controlled burning and

overstory removal were increased species richness and

availability of preferred food items for deer, elk and possibly

bobwhite quail. By varying frequency of fire, managers can

shift plant communities to benefit target game species.

Winter prescribed fue at l- or 2-year intervals favored

legumes and created habitat conditions favorable for bobwhite

quail. Less frequent burning or no burning allowed woody

browse species prefered by deer to increase on retrogressed

sites (Landers 1987). A prescribed burning rotation at 2- or 3

year intervals on retrogressed sites will allow growth of

important deer and quail foods. Clearcutting and site

preparation provide benefits in terms of food and cover for

deer. However benefits from regenerated clearcuts last only

until canopy closure. Site retrogression without burning

provides an important cover component to deer.

Timber management strategies that create a mosaic of

retrogressed burned and unburned sites, and regeneration

clearcuts with adequate provisions for hard mast production

should provide management flexibility to meet habitat needs

of most game species. The effects of growing season bums

on maintaining retrogressed sites for forage production should

be evaluated in a similar manner. The long-term effects of

prescribed fue on vegetation response and site quality in

mountainous terrain should also be evaluated.

ACKNOWLEDGEMENTS

This project was funded by Oklahoma Federal Aid to Wildlife

Restoration Project W-80-R, Study 4, Job 2. The author

received assistance in setting up this study from R. Robinson

and J. S. Harrison, and valuable field assistance and technical

suggestions from R. E. Thackston, R. W. Umber, and M.

Thompson.

174
LITERATURE CITED

Avery, T. E. 1964. Forest measurements. McGraw-Hill

Co., New York. 290 p.

Anderson, R. C., and L. E. Brown. 1986. Stability and

instability in plant communities following tire. American

Journal of Botany 73:364-368.

Bain, W. R., and A. Watterson. J979. Soil survey of

Pushmataha County, Oklahoma. U.S. Department of

Agriculture, Soil Conservation Service. 77 p.

Bragg, T. B., and L. C. Hulbert. 1976. Woody plant

invasion of unburned Kansas bluestem prairie. Journal of

Range Management 29:19-24.

Chambers, J. C., and R. W. Brown. 1983. Methods for

vegetation sampling and analysis on revegetated mined

lands. U.S. Department of Agriculture, Forest Service.

General Technical Report INT-151. lntermountain Forest

and Range Experiment Station. Ogden, UT. 57 p.

Fenwood, J. D., D. F. Urbston, and R. F. Harlow. 1984.

Determining deer habitat capability in Ouachita National

Forest pine stands. Proceedings of the Annual Conference

of the Southeast Association of Fish and Wildlife

Agencies 38:13-22.

Fenwood, J. D., D. A. Saugey, and C. A. Racchini. 1985.

Fall deer food selection in the Ouachita National Forest.

Arkansas Academy of Science Proceedings 39: 123.

Hebb, E. A. 1971. Site preparation decreases game food

plants in Florida sandhills. Journal of Wildlife

Management 35:155-162.

Jenks, J. A., D. M. Leslie, Jr., and R. L. Lochmiller. 1990.

Food habits and nutritional condition of white-tailed deer

and cattle. Final Report, P&man-Robertson Project W142-R. Game Division, Oklahoma Department of Wildlife

Conservation, Oklahoma City. 91 p.

Krueger, W. C. 1972. Evaluating animal forage

preference. Journal of Range Management 25:471-475.

Landers, J. L. 1987. Prescribed burning for managing

wildlife in southeastern pine forests. In: D. D. Wade,

compiler. Prescribed fue and smoke management in the

south: Conference Proceedings. pp. 19-27. U.S.

Department of Agriculture, Forest Service. Southern

Forest Experiment Station, Asheville, NC.

Lewis, C. E., and T. J. Harshbarger. 1976. Shrub and

herbaceous vegetation after 20 years of prescribed burning

in the South Carolina Coastal Plain. Journal of Range

Management 29:13-18.

Lotan, J. E., M. E. Alexander, S. F. Amo, R. E. French,

0. G. Langdon, R. M. Loomis, R. A. Norum, R. C.

Rothermel, W. C. Schmidt, and J. V. Wagtendonk. 1978.

Effects of fire on flora -A state-of-knowledge review.

U.S. Department of Agriculture, Forest Service. General

Technical Report WO-16. Denver, CO. 71 p.

Ludwig, J. A., and J. F. Reynolds. 1988. Statistical

ecology. John Wiley and Sons, Inc., New York. 337 p,

Masters, R. E. 1991. Effects of timber harvest and

prescribed fire on wildlife habitat and use in the Ouachita

Mountains of eastern Oklahoma. Ph.D. Thesis, Oklahoma

State University, Stillwater. 330 p.

Melchoirs, M. A., T. H. Silker, and J. E. Reeb. 1985. Deer

use of young pine plantations in southeastern Oklahoma.

Journal of Wildlife Management 49:958-962.

Mueller-Dombois, D., and H. Ellenberg. 1974. Aims and

methods of vegetational ecology. John Wiley and Sons,

Inc., New York 547 p.

Oklahoma Department of Wildlife Conservation. 1972. Big

game report 1972. Federal Aid in Wildlife Restoration

Report. Game Division, Oklahoma City. 22 p.

Oosting, H. 1. 1944. The comparative effect of surface and

crown fire on the composition of a loblolly pine

community. Ecology 25:61-69.

Oosting, H. J. 1956. The study of plant communities. W.

H. Freeman and Co., San Francisco. 440 p.

Petranka, J. W., and J. K. McPherson. 1979. The role of

.m conallina in the dynamics of the forest-prairie

Feotone in north-central Oklahoma. Ecology 60:956-965.

Ripley, T; H. 1980. Planning wildlife management

inveatigatio,ns and projects. In: S. D. Schemnitz, ed.,

Wildlife mamigement techniques manual. pp l-6. The

Wildlife Society, ,Washington, DC.

SAS institute Inc. 1987. SAS procedures guide for

Personal computers, version 6.03 edition. SAS Institute

Inc., Cat-y, SC. 373 p.

SAS Institute Inc. 1985. SAS user’s guide: statistics,

version 5 edition. SAS Institute Inc., Cat-y, SC. 956 p.

175
Segelquist, C. A. and R. E. Pennington. 1968. Deer

browse in the Ouachita National Forest in Oklahoma.

Journal of Wildlife Management 323623626.

Segelquist, C. A., M. Rogers, F. D. Ward, and R. G.

Leonard. 1972. Forest habitat and deer populations in an

Arkansas Ozark enclosure. Proceedings of the Annual

Conference of the Southeast Association of Game and

Fish Commissioners 26: 15-35.

Segelquist, C. A., F. D. Ward, and R. G. Leonard. 1969.

Habitat-deer relations in two Ozark enclosures. Journal of

Wildlife Management 3351 l-520.

Smith, D. M. 1962. The practice of silviculture, seventh

ed. John Wiley and Sons, Inc., New York. 578 p.

Steele, R. G. D., and J. H. Torrie. 1980. Principles and

procedures of statistics, a biometrical approach. 2nd ed.

McGraw-Hi& Inc., New York. 633 p.

Tomm, H. O., J. A. Beck, Jr., and P. J. Hudson 1981.

Response of wild ungulates to logging practices in

Alberta. Canadian Journal of Forest Research 11606-614.

Vangilder, L. D., 0. Togerson, and W. R. Porath. 1982.

Factors influencing diet selection by white-tailed deer.

Journal of Wildlife Management 46:711-718.

176
FIRE MANAGEMENT

COST-EFFECTIVE WILDERNESS FIRE MANAGEMENT:

A CASE STUDY IN SOUTHERN CALIFORNIA

Christian A. Childers and Douglas D. F’iirto’

Abstract-Federal wilderness fire management policies have been scrutinizedsince the catastrophic fires in

the Greater Yellowstone Area in 1988. While wilderness tire management objectives are still aimed at

recreating natural fire regimes, all USDA Forest Service fire management programs must be cost-effective.

Since current Forest Service economic analyses do not fully represeni the value of fire IO wilderness, a

cost-effectiveness analysis was developed to compare wilderness fire management options. The analytical

procedure is briefly reviewed, illustrated through a soulhem California case study and case study results arc

discussed. These results suggest that containment of some tires may be more cost-efkctive than current

control-oriented practices.

Federal wilderness fire management policies have been

scrutinized since the catastrophic tires in the Greater

Yellowstone Area in 1988. Catastrophic,in this context, is a

tire of any size that results in excessive resource damage,

excessive suppression costs, excessive damage to private

inholdings, or loss of life (Savcland 1986). No lives were

lost in Yellowstonc and many have argued the bcnctits, rather

than damages, of these fires to the Yellowstone ecosystems,

but private lands were damaged and suppression costs were

excessive (US Senate 1988). While wilderness fire

management objectives are still aimed at recreating natural

tire regimes, all Forest Service fire management programs

must be cost-effective. If these objectives were difficult to

implement in Yellowstone, they will be even more so in

southern California, where chaparral covered wilderness areas

are often surrounded by high valued private property and

improvements. The Forest Service’s range of options to meet

these objectives include the use of appropriate suppression

responses and prescribed tire.

Prescribed tires can take two forms: prescribed natural fires

and management ignited prescribed fires (USDA Forest

Service 1989). AIf prescribed fires are monitored and

managed through the use of detailed bum plans (USDA Forest

Service 1989). Theoretically, the only difference between the

two forms of prescribed tire is the source of the ignition, but

the timing of the fires is also often different. Prescribed

natural fires are naturally occurring unplanned ignitions

usually caused by infrequent summer or fall lightning storms.

Management ignited prescribed fires are ignited by Forest

Service personnel on their own time schedule when burning

conditions and resource availabilities are optimal (usually late

fall, winter, or spring in southern California).

‘Graduate Research Assistant and Professor, respectively, Natural

Resources Management Department, Cal Poly, San Luis Obispo, CA.

Any fire not classified as a prescribed tire is a wildfire and

must receive an appropriate suppression response. These

responses range from intensive suppression efforts aimed at

keeping the tire as small as possible (a control response) to

containment or confinement responses. Containment means

surrounding a fire with minimal control lines and utilizing

natural barriers to stop its spread. Continement means

limiting a fire’s spread to a predetermined area principally

using natural barriers, preconstructed barriers, or

environmental conditions (USDA Forest Service 1989). ~

A cost-effectiveness analysis has been developed to compare

these options for wilderness fire management programs

(Childers and Piirto 1989). In this analysis, approximating

the average annual burned area of the natural fire regime is

defined as the objective, fire gaming is used to develop

representative fire costs and sizes, and decision trees are used

to develop expected annual cost and burned area values for a

range of fire management alternatives. This paper briefly

reviews the analytical procedure, illustrates the procedure

through a southern California case study (two contiguous

wilderness areas on Los Padres National Forest, Santa

Barbara, CA.), and discusses the case study results.

THE STUDY AREA

Our case study area comprises 23 1,500 acres of the Dick

Smith and San Rafael Wilderness Areas on Los Padres

National Forest (fig. 1). The vegetation of this area is

predominantly chaparral brush species, including chamise

(Adenostoma fasciculatum), assorted ceanothus and manzanita

species (Ceanothus spp. and Arctostauhvlos spp.), two types

of scrub oak (Ouercus dumosa and 0. turbinella) and several

other pyrophytic shrubs. The chaparral intergrades

with coast live oak [Ouercus aerifolia) in some riparian areas,

big cone Douglas fir (Psuedotsuea macrocama) and digger

pine (Pinus sabiniana) on some north slopes, and a variety of

other pines at higher elevations. Fire is a natural component

of a11 of these ecosystems.

179
J

Figure l--Los Padres National Forest, with the Dick Smith and San Rafael Wilderness Areas highlighted

COST-EFFECTIVENESS ANALYSIS

Most Forest Service economic analyses use cost-benefit

models. For example, economic analysis of forest level fire

management programs is based on the Cost Plus Net Value

Change (C + NVC) model (USDA Forest Service 1987). C

+ NVC computes the sum of program costs and the

quantifiable (in monetary terms) effects of fire on resource

values. To be efficient, these cost-benelit analyses must

include the effects of tire on all relevant resources. C +

NVC models currently include tire effect values for many

primary forest resources such as timber, minerals, and forage,

and many wilderness outputs such as water, fish and wildlife

(measured in numbers of visits by hunters and fishermen),

and recreational use (USDA Forest Service 1987). Fire’s

effects on these resources can be and usually is much different

than its effects on a wilderness ecosystem. Since the primary

economic value of wilderness remains undefined, fire’s effects

on wilderness also remain undefined. A cost-benefit analysis

which does not include all of the relevant costs and benefits

will be incomplete, and often misleading (Williams 1973).

Therefore, analyses based solely on C + NVC models are

inadequate for wilderness fire management planning.

Saveland (1986) avoided this C + NVC problem in a

cost-effectiveness comparison of tire management options for

the Frank Church-River of No Return Wilderness Area. In

his Analysis, the costs of each alternative were the expected

annual suppression costs. “Effectiveness” was the

approximation of the average “natural” annual burned ares

based on what fire history studies revealed. Saveland (1986)

justified this well: Plant communities require a certain amount

of fire, just as they require a certain amount of

precipitation. ..Altering the average annual burned area would

be like altering the average annual rainfall. Though

Saveland’s analysis involved a different fire regime and

setting, his definitions and much of his methodology are

appropriate for southern California’s chaparral.

Cost-effectiveness analysis (CEA), in its truest form,

compares the costs of different alternatives, where each

alternative will meet the desired objectives, or have the same

effects. A CEA has five key elements: the objective; the

alternatives; the costs; the model; and a criterion for ranking

the alternatives (Quade 1967).

180
The Objective

The most important, and often the most difficult, step in CEA

is a clear definition of the goals or the objectives. Public

policy usually includes several goals or objectives and these

are often conflicting (Quade 1982). Forest Service Policy is

no exception. The Forest Service Manual (USDA Forest

Service 1986) defines two objectives for wilderness fire

management:

1. (to) permit lightning caused fires to play, as nearly as

possible, their natural ecological role in wilderness;

2. (to) reduce to an acceptable level, the risks and

consequences of wildfire within wilderness or escaping from

wilderness.

The value of fire playing its natural ecological role is

currently unquantifiable in monetary terms; thus, it is not

included in Forest Service economic evaluations. The

consequences of fire are more straight forward. They include

resource and property damage and suppression costs. Risk,

while also difficult to quantify monetarily, is the probability

of a fire resulting in excessive resource damages or

suppression costs. Current Los Padres National Forest tire

management plans stress the second objective (reducing the

risks and consequences); proposed wildfire responses are

suppression intensive (control and contain strategies) and no

wilderness prescribed fires have been planned. The Forest’s

current wilderness fire management objective might be to

respond to and suppress each ignition at minimal cost,

regardless of annual burned area. If we are interested in

allowing lightning fire to play its natural role, this must be

included in the analysis. Our redefined objective might then

be to recreate the natural fire regime at minimal cost.

To further define this objective, we need to look at the natural

fire return interval. By defining the maximum time interval

between fires, we can determine the minimal average annual

burned area required to recreate the natural fire regime.

Research suggests that the area’s chaparral historically burned

every 30 years (Byrne 1979, Minnich 1983). Los Padres

National Forest fire records (1911-1987) suggest that the

chaparral bums every 45 years (USDA Forest Service 1988).

Forty-five years probably represents the maximum fire return

interval since these records were taken while all fires were

being actively suppressed. Using the 45year return interval,

an average of over 5,000 acres of the 23 1,500-acre study area

would have to bum annually. It is important to note that this

SOOO-acre average is a long-term objective, not an annual

goal. In some years, 20,000-30,000 acres might bum while

in other years no prescribed fires will be implemented (just as

lightning strikes frequently in some years, while no lightning

activity occurs in other years).

The Alternatives

Four alternatives were chosen for the Los Padres CEA.

1. Alternative 1 is the Forest Service’s past policy: Control

all wildfires regardless of cause, and attempt to meet annual

burned area objectives through prescribed burning.

2. Alternative 2 is the fire management strategy proposed in

the Los Padres’ Land Management Plan: Contain all fires

which occur under low intensity and control all moderate to

high intensity tires, while pursuing an active prescribed

burning program.

3. Alternative 3 (the Confinement Alternative): Contine all

low intensity starts, contain moderate to high intensity starts,

and control only the starts which occur under extreme tire

weather conditions (augmented by prescribed burning as

needed).

4. Alternative 4 (the Prescribed Natural Fire Alternative):

The same as Alternative 3, with the addition of an approved

plan for prescribed natural fire management.

The Costs

Only the relevant variable costs should be included in a CEA

(Quade 1982).

Fixed costs--those that remain the same for each

alternative-=should not be included. For this analysis, fied

costs include tire suppression equipment, suppression manning

levels, and fire management Personnel,, because these

forestwide resource level requirements.are baseh on over 100

fires a year and an average of less than two ignitions occur

annually in the ease study area. The variable costs that must

be considered are annual suppression costs, prescribed .f@

costs, and NVCs for fires originating in the study area.

The ‘Model

A model is a simplified representation of the real world which

includes all of the relevant features (Quade 1967). Decision

trees can be used to evaluate alternative fire management

programs in the face of uncertainties about future fire

occurrences, weather, behavior, and sizes (Hirsch and others

1981). Decision trees are used to develop expected values.

Expected values are probability weighted averages of all

possible outcomes. Expected values are not predictions of

actual future costs due to the many variables involved in

wildland tires; they provide relative values for comparison.

For our analysis, decision tree probabilities were derived

from fire history records. The range of cost and burned area

values were developed through fire gaming since no .historic

or comparable fire history records were available for

containment, confinement, or prescribed natural fire responses

(Childers and Piirto 1989).

181
Alt8HLative4

Gamed

WeStbCZ aaIDed ValW Gamed Vahle Fire Value

calm Pattsla Strategy Gut cc& s i Sk.?. NVG NVG

A(.441) q.75) a095 $117 4.0 a 2 $44 f2

I Rx(.w

B(.118) CF(.A)

Iighiog I Rr(w

a385 C&147) ci

D(.294) C A

RL2

a25

RL3

a364

tif#ltlliIl~

a933

s46

$66

S23

S867

EL387

4.0

45ao

450.0

265.0

39ao

ai

4.5

ls

4.4

13.1

33,095 $56 40 a l

s4530 s?38 45ao 164

sat30 s/s83 265.0 9.6

s4/41M S3,769 390.0 35.5

S&887 s2n 3.0 a 2

547.814 Sl.230 740.0 19.0

5163,384 S3,373 /%O.O 48.3

Slaz254 Sk254 p65.0 l3.s

$93335 S3,200 780.0 267

3527,336 S4.416 4,200.o 35.2

S2887 Es 3.0 a0

s163384 S547 /%O.O 65

SW35 s3l3 788.0 26

S!z?,336 $36,162 4,ux).o 2880

sm.5

W=l

S401

SllOs46

s17.@7

SW639

s914362

S285

$181

S12

s/113

S670

slJ.2

SW83

0.1

0.1

0.1

833.0

40.0

835.0

2a0

a0

a0

a0

84

ls

la5

261-O

s/525

$401

s17*8@7

#lQ362

$6

sz

$19273

a l

a l

4&O

2600.0

a0

a0

a 2

29.3

S3.475

Sam

$167,088

$183,371

SW%

5973,519

Llti

$484

s/346

s492

El.318

*%046

5.0

748.0

/955.0

L970.0

gi:

Q2

7.4

15.7

5.3

ia

74.9

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*E

El

$72

$203

$621

Wl)

(S533)

w08)

(S174)

0

El4522

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a018

Figure Z-The decision tree for Alternative 4

E.xpc&d vahla: h94,O83 9425 Elw97

E?apded Anoual valua: s34lm l&S&8 s329@7
A decision tree must be completed for each alternative, using

the same probabilities but with different suppression responses

and thus different cost and burned area values. The

probabilities for each branch of the trees were calculated from

the 25-year (I 963-87) fire history of the San Rafael and Dick

Smith Wilderness Areas (Childers and Piirto 1989). The

decision tree for Alternative 4 of the Los Padres study (fig. 2)

illustrates the values and probabilities which were developed

for our CEA. Alternative 4’s decision tree is presented since

it is the most complex decision tree (this is the only

altemativc in which strategy is not solely based on weather

pattern).

Fire gaming is the prediction of representative fire sizes by

fire management professionals. Predictions are based on the

interactions of estimated tire behavior conditions and given

suppression force responses (Harrod and Smith 1983). Our

garners included the fire management personnel from the

Forest Supervisor’s Office and from each of the three ranger

districts responsible for the case study area. The “games”

consisted of first mapping an overlay of the free-burning fire

spread (without any suppression efforts) for a series of time

periods. Four weather patterns were mapped at each location

and these “fires” were then controlled, contained, confined

and managed as prescribed natural tires to develop the cost

and burned area values needed to fill in each decision tree.

Net Resource Value Changes (NVCs) were calculated using

the Forest’s 1988 NVC values based on acreage burned by

intensity level in each watershed (Childcrs 1991).

Management ignited prescribed fire costs were subjectively

estimated at $50 per acre by the garners and by the Santa

Barbara Ranger District’s Fuels Management Staff. This is

more expensive than most recent prescribed fires adjacent to

the case study wilderness areas, but initial wilderness

prescribed tires will probably be expensive due to the age and

continuity of the fuelbeds, remoteness of the fires, and

limitations on control lines and the use of mechanized

equipment in wildcmess.

A Criterion

The criterion for ranking alternatives depends on the agency’s

goals and objectives. Many different rankings are possible.

For this analysis, we defined our objective as the recreation

of the natural fire regime at minimal cost. Given current

budgetary constraints, minimizing costs regardless of burned

area might be the agency’s actual objective. The sources of

proposed expenditures (i.e., forest fire fighting funds vs.

program or budgeted dollars) might be important

considerations. Risk is also a concern. Finally, the ignition

source and timing of the tires might be important to

prescribed tire planners. Therefore, all of this information

must be provided.

RESULTS

Four weather patterns were gamed at each of four fire

locations: the first set at representative fire location (RL) 1,

the second at RL 2, the third at RL 3, and the fourth set

under double ignition conditions (two tires occurring

simultaneously) using RLs 2 and 4 (Childers 1991). The

results of these games are presented in table 1. These values

Table 1--Finat size and cost figures for gamed fires.

CONTROL CONTAIN

Size cost Size cost

CONFINE

Size cost

Rx Natural Fire

Size cost

(acres) (8) (acres) ($1 (acres) ($) (acres) ($1

Representative Fire Game 1

Ueather Pattern A 0.5 7,693 0.5 5,113 4.0 3,095 4.0 3,689

Weather Pattern B 2.0 7,900 2.0 4,722 450.0 6,530 450.0 6,941

Weather Pattern C 120.0 84,592 265.0 51,730 (not gamed) (not gamed)

Ueather Pattern D 40.0 36,989 390.0 41,403 (not gamed) (not gamed)

Representative Fire Game 2

Weather Pattern A 0.3 3,129 0.3 2,756 3.0 2,887 740.0 47,814

Weather Pattern 6 70.0 40,498 780.0 47,792 1,950.O 163,384 1,965.0 182,254

Ueather Pattern C 145.0 86,604 780.0 93,335 (not gamed) (not gamed)

Weather Pattern D 1,090.o 366,894 4,200.O 527,336 (not gamed) (not gamed)

Representative Fire Game 3

Ueather Pattern A 0.1 8,415 0.1

Weather Pattern B 0.1 7,541 0.1

Weather Pattern C 18,249 10.0

Weather Pattern D 50::: 370,193 2,600.O

Representative fire Game 4

Weather Pattern A 7K 3,275 0.5

Weather Pattern 6 44,518 785.0

Ueather Pattern C 31o:o 136,861 800.0

Weather Pattern D 2.260.0 851,674 2.800.0

4,427 2 2,525

4,896 401

9,029 40.0 17,807

910,362 (not gamed)

2,903 5.0 3,475

61,549 1,955.0 167,088

98,496 (not gamed)

973.519 (not gamed)

0.1 4,821

833.0 110,546

835.0 88,639

(not gamed)

740.0 48,227

1,970.o 183,371

(not gamed)

(not gamed)

183
were then run through the appropriate alternatives’ decision

trees (as per Childers and Piirto 1989) and expected values

for average annual suppression costs, burned area, and NVCs

were calculated for each decision tree. These results are

presented in table 2.

Table 3 includes a breakdown of annual suppression costs and

acreage into prescribed fire and forest fire fighting (FFF)

costs. Table 3 also illustrates the prescribed bum acreage and

costs that would be required to meet our S,OOO-acre average

annual burned area objective under each alternative. All cost

values are presented in 1988 dollars.

DISCUSSION

One of the most obvious observations from the decision tree

results (table 2) and the total cost of implementing each

alternative (table 3) is that alternatives 1 and 2 are very

similar, as are alternatives 3 and 4. This can be attributed to

the similarity of the containment and control responses and

the confinement and prescribed natural fire responses as they

were used on many of the gamed ftres. One gamer concluded

that they were still “fighting” the fires, even under the

prescribed natural tire responses. For example, the actual

dispatch cards of initial attack resources were used to

determine who would respond to each fire under both

containment and control; thus, many of the same resources

were used on both of these strategies. The run cards were

heavily modified for confinement and prescribed natural fire

responses, but the objectives of these two were often similar.

Once these strategies have been implemented, familiarity with

appropriate suppression responses and pre-approved

prescribed fire bum plans should lead to greater differences in

their results. Despite the similarities, these results do provide

some valuable information for the decisionmaker.

Table 2--Average annual wiLdfire and prescribed natural fire cost, cost and

San Rafael Wilderness Areas highlighted per acre managed, average annual

burned area, and average annual cost per area burned for four alternative

fire management programs for the Dick Figure 2--The decision tree for

Alternative 4 Smith and San Rafael Uilderness Areas

Historical

Alternative 1

ALternative 2

Alternative 3

ALternative 4

Average Average

annual annual

Average Cost per burned cost per

annual acre area burned

cost managed (acres) acre

5000+

9197,611 $0.85 394.8 $500.53

9195,474 SO.84 447.2 $437.11

8334,773 $1.45 1,580.O $211.88

8341,586 $1.48 1,658.8 $205.92

Table 3--Breakdoun of total average annual suppression/management costs

and burned areas by source

ALTERNATIVE

1 2 3 4

Uildfire Acreage: 394.8 447.2 1,580.O 1,543.2

Rx Natural Fire Acreage: 0.0 0.0 0.0 115.6

Mgt Ign Rx Fire Acreage: 4,605.2 4,552.8 3,420.O 3,341.2

F.F.F. costs: $197,611 $195,474 $334,773 $331,140

Rx Natural Fire Costs: 0 0 0 $10,446

Mgt Ign Rx Fire Costs: $230,260 $227,640 $171,000 $167,060

Total Annual Costs: $427,871 $423,114 $505,773 $508,646

184
If the agency’s goal was simply to respond to and suppress or

manage each ignition at minimal cost, regardless of annual

burned area, alternative 2 would be the most cost-effective.

This result is due to the cost-saving advantages of containment

over control on most lower intensity tires and the expensive

outcomes that can result from trying to confine or manage

fires in the decadent fuelbeds.

If, however, the goal is to recreate the natural fire regime

(i.e., to meet the 5,OOO-acre average annual burned area), the

decision might be a little more involved. Alternative 2 would

still be the least expensive, but alternatives 3 and 4 would

require much less program or budgeted dollars to accomplish

the objective and result in much more of the acreage burning

under natural conditions (natural ignition sources and during

the natural fire season).

Containment or confinement strategies can only be used when

they are less expensive than controlling a given fire (USDA

Forest Service 1989). Table 1 shows that containment cost

less than control 56 percent of the times it was used and that

confinement cost less or about the same as control 78 percent

of the times it was used. This suggests that containment and

confinement are both feasible and cost-effective for our case

study ares.

Risk is incorporated into the analysis through the probability

of a fire resulting in excessive resource damages or

suppression costs (e.g., fire 4D, which cost over $850,000 to

suppress regardless of the strategy used). However, none of

the confinement or prescribed natural fire responses resulted

in a catastrophic fire, and it could be argued that $953,000

(the most expensive gamed fire) is not really catastrophic

when compared to historic fires like the 1966 Wellman Fire.

The Wellman Fire burned 93,600 acres of the case study area

and cost over $6.2 million (in 1988 dollars) to suppress. But,

since the Wellman Fire occurred under extreme site-specific

weather conditions, it would receive a control response under

any alternative; and, since it became catastrophic despite

control efforts (the only possible response in 1966) it could

happen again under any alternative. The risk of another

catastrophic fire might seem greater under alternatives 3 and

4, since fires are allowed to get larger, but this is only the

short term risk factor. These alternatives would allow more

acres to bum under natural conditions, resulting in cleaner

bums than management ignited off-season fires and larger

breaks in the decadent fuelbeds, which should help to limit

the size of future fires.

SUMMARY

Developing cost-effective wilderness tire management

programs is a dilemma faced by many Forest Service land

managers. Wilderness fire management is a requirement, but

the value of fire in wilderness remains undefinable in

monetary terms so it is excluded from most Forest Service

economic analyses. Therefore, cost-effectiveness analysis,

using the recreation of the natural fire regime as the

objective, can provide important economic information.

Decision trees help us predict future fire occurrence

potentials, and intensive gaming efforts help us estimate fire

sizes and costs associated with the implementation of

appropriate suppression responses and prescribed natural

fires. Case study results suggest that appropriate suppression

responses could provide cost-effective alternatives to current

control-oriented practices. Through this extensive and

thorough cost-effectiveness analysis we can, hopefully, avoid

some of the costly mistakes of past experiences in wilderness

fire management.

ACKNOWLjEDGMENTS

The authors thank the following USDA Forest Service

personnel: Chet Cash, Santa Lucia Ranger District Fire

Management Officer (FMO); Tom Goldenbee, Santa Barbara

R.D. FM0 (recently retired); Jim Smith, Mount Pinos R.D.

Assistant FMO; Dennis Ensign, Forest Fire Prevention

Officer (recently retired); Harold “Fritz” Cahill, Forest Fuels

Management Officer; and Lonnie Briggs, Forest Assistant

FM0 for their extensive time commitments to fire games,

And, Armando Gonzalez-Caban, Economist, Forest Fire

Laboratory, Riverside, CA., and Jane Childers, Los Padres

Forest Business Management Staff, respectively, for technical

and editorial review. This project was funded by a McIntire

Stennis grant from the Natural Resources Management

Department, California Polytechnic State University, San Luis

Obispo, CA.

185
LITERATURE CITED

Byrne, Roger. 1979. Fossil charcoal from varved sediments

in the Santa Barbara Channel: an index of wildfire

frequencies in the Los Padres National Forest.

Unpublished report, Res. Agreement PSW-47. Berkeley,

CA: Pacific Southwest Forest and Range Experiment

Station, Forest Service, U.S. Department of Agriculture;

96 p.

Childers, Christian A. 1991. Wilderness tire economics: a

cost-effectiveness analysis and case study. Masters Thesis,

Natural Resources Management Department, Cal Poly,

San Luis Obispo, CA. (in press).

Childers, Chris A., and Piirto, Douglas D. 1989.

Cost-effective wilderness fire management for southern

California’s chaparral wilderness: an analytical

procedure. In: Berg, Neil H., technical coordinator.

Proceedings of the symposium on fire and watershed

management. October 26-28, 1988. Sacramento, CA.

Gen. Tech. Report PSW-109. Berkeley, CA. Pacific

Southwest Forest and Range Experiment Station, Forest

Service, U.S. Department of Agriculture; 30-37.

Harrod, Mike; Smith, Eric. 1983. Fire gaming for low

resolution planning--a low resolution planning--a review

of concepts and procedures. Unpublished report by the

Fire Management Planning and Economics Unit;

Riverside, CA: Forest Fire Laboratory, Pacific Southwest

Forest and Range Experiment Station, Forest Service,

U.S. Department of Agriculture; 38 p.

Hirsch, Stanley N.; Radloff, David L.; Schopfer, and others.

1981. The activity fuel appraisal process: instructions and

examples. Gen. Tech. Rep. RM-83. Fort Collins, CO:

Rocky Mountain Forest and Range Experiment Station,

Forest Service, U.S. Department of Agriculture. 46 p.

Minnich, Richard A. 1983. Fire mosaics in southern

California and northern Baja California. Science

219(4590):1287-1294.

Quade, Edward S. 1967. Introduction and Overview. pp.

1-16. In: Goldman, Thomas A., Ed. Cost-effectiveness

analysis: new approaches in decision making. New York:

Frederick Praeger, Inc.

Quade, Edward S. 1982. Analysis for public decisions. New

York: Elsevier Science Publishing Co., Inc.; Second

edition by The Rand Corporation; 381 p.

Saveland, James M. 1986. Wilderness fire economics: the

Frank Church-River of No Return Wilderness. In: Lucas,

Robert C. Proceedings of the National Wilderness

Research Conference: current research. 1985. July 23-25;

Gen. Tech. Rep. INT-212. Ogden, UT: Intermountain

Forest and Range Experiment Station, Forest Service,

U.S. Department of Agriculture; 39-48.

U.S. Department of Agriculture, Forest Service. 1986. Forest

Service Manual, Chapter 2320. Wilderness Management.

Washington, D.C.

U.S. Department of Agriculture, Forest Service. 1987. Forest

Service Handbook 5109.19, Fire management analysis and

planning handbook. Washington, DC.

U.S. Department of Agriculture, Forest Service. 1988. Los

Padres National Forest land and resource management

plan. Goleta, CA.

U.S. Department of Agriculture, Forest Service. 1989. Forest

Service Manual, Title 5100. Fire management.

Washington, D.C.

U.S. Senate. 1988. Second session on current fire

management policies. Notes from the joint hearing before

the subcommittee on Public Lands, National Parks and

Forests of the committee on Energy and Natural

Resources and the subcommittee on Conservation and

Forestry of the committee on Agriculture, Nutrition, and

Forestry, United States Senate, One Hundredth Congress;

158 p.

Williams, Alan. 1973. Cost-benefit analysis: bastard science?

and/or insidious poison in the body politick. In: Wolfe,

J.N. Cost benefit and cost effectiveness. New York:

George Allen and Unwin, Ltd.; 236 p.

186
ADAITIVE FIRE POLICY

James M. Saveland’

Abstract-Adaptive resource management is a coniinuous learning process in which current knowledge

always leads to further experimentation and discovery. Adaptive management evolves by learning from

mistakes. Designing adaptive management strategies involves four tasks. First, the problem must be

defined and bounded. There is growing recognition of the need to define and bound problems at the

landscape level. Second, existing knowledge must be readily accessible so that errors can be detected and

used as a basis for funber learning. The current information structure supporting fire management was

designed to support the 10 a.m. policy and is inadequate I O support current policy. Expert systems and

other recent developments in artificial intelligence can provide the necessary means to develop an accessible

repository of current knowledge. Third, the inherent unceflainty and risk surrounding possible future

outcomes must be displayed.- Bayesian decision analysis can be used IO deal wi& uncetiinty and risk.

Fou&, balanced policies must be designed. These must provide forresource production and protection

while creating opporrunities to develop better understinding. Signal detection theory and receiver operating

characteristic curve analysis provide 1001s to help design balanced policy. These concepts are illustrated by

applying them to Lhe problems surrounding wilderness fire management and the need for long-range tire

danger information.

INTRODUCTION - SEEKING A BALANCE

The need to balance competing and often conflicting

objectives is a problem whcncver policy is being made. In

resource management, there is oRcn the riced to balance

utilization with preservation. The disputes about wilderness

designation and forestry activities in spotted owl and redcockaded woodpecker habitats are controversies in search of a

balance point. Several aspects of fire management require a

balance. In wilderness fire management, the role of fire in

perpetuating disturbance regimes in near-natural landscapes

must be balanced with the necessity of protecting resources

that would be damaged by lire. In smoke management the

use of prescribed fire must be balanced with minimizing the

nuisance of smoke. During periods of high fire danger,

shutting down the woods to protect them must be balanced

with the need to keep the woods open for people who earn

their livelihood there. At the interface between wildland and

urban areas, it is necessary to balance the threat of wildfire

and the costs of risk-reduction measures. How should

government regulatory agencies go about determining the

balance point? And how can they describe their search for

balance and its results to affected parties?

ADAPTIVE RESOURCE MANAGEMENT

Adnptivc resource management (Clark 1989, Holling 1978,

Saveland 1989, Thomas and others 1990, Walters 1986)

recognizes the fact that the knowledge we base our decisions

on is forever incomplete and almost always shrouded in

uncertainty. Management is a continual learning process that

evolves by learning from mistakes. Several authors have

expressed the importance of learning from failure. “You have

‘Research Forester, Southeastern Forest Experiment Station, Forest

Service, U.S. Department of Agriculture, Dry Branch, GA.

to accclcrate the failure rate to accelerate the success rate“

(Peters 1987). “Intelligent needs to be tolerated.

Multitudes of bad ideas need to be floated and freely

discussed, in order to harvest a single good one” (Toffler

1990). “The willingness to risk failure is an essential

component of most successful initiatives. The unwillingness

to face the risks of failure--or an excessive zeal to avoid all

risks--is, in the end, an acceptance of mediocrity and an

abdication of leadership” (Shapiro 1990).

Designing adaptive policy involves four tasks. First, the

management problems must be defined and bounded, often in

terms of objectives and constraints. There is an increasing

awareness of the need to define resource problems from a

landscape perspective (Forman and Godron 1986, Naveh and

Lieberman 1984). With the proliferation of geographic

information systems, the importance of defining and bounding

problems at the landscape level will become even more

apparent.

Second, existing knowledge must be readily accessible so that

errors can be detected and used as a basis for further

learning. Walters (1986) used models to represent existing

knowledge. The field of artificial intelligence, especially

knowledge-based systems, provide additiona capability to

capture knowledge (Saveland 1990).

Current fire information systems are inadequate. Most, if not

all, fire information systems were designed to support the 10

a.m. policy and do not adequately deal with the complexities

of modem fire management. Fire occurrence reports track

the efficiency of the suppression effort. When policy was

changed to allow prescribed natural fires, only half of the fire

occurrence report form for the Forest Service had to be filled

187
out for these fires. These reports provide almost no useful

historical information for managing wilderness and park tire

management programs. In addition, adequate cost data is

severely lacking, preventing useful economic analysis.

Structure and site characteristics in the wildland urban

interface are not recorded, preventing analysis of structure

losses. The national weather data library is known for its

missing and questionable data. Currently, there are no links

between national fire occurrence databases and fire weather

databases. Entrepreneurial fire managers have been able to

download the data into relational databases to conduct

analysis. In addition, there are plans to convert the national

databases into a relational form. Forest Service fire

occurrence data resides in Fort Collins while Park Service

data resides in Boise in different formats, further complicating

the sharing of data and historical analysis. Prescribed bum

plans exist in paper copy or as a word processing document

on a computer, the vast historical information largely

inaccessible, tucked away in personal file cabinets. The

collapse of wilderness and park fire management during the

summer of 1988 was not so much a failure of policy as a

reflection of an outdated information system’s inadequacy to

support fire management decisions in today’s complex world.

Information needs analysis have been conducted recently and

the situation is rapidly changing for the better. In addition

the coming explosion of GIS technology, with the shortage of

spatial data, will improve the situation dramatically.

Third, uncertainty and its propagation through time in relation

to management actions must be addressed. Fire managers all

too often live in a fairytale world of deterministic models that

ignore uncertainty. Bayesian decision analysis offers one

means of coming to terms with the inherent uncertainty and

risk.

Fourth, balanced policies must be designed. These must

provide for continuing resource production and protection

while simultaneously probing for more knowledge and

untested opportunity. Signal detection theory provides one

mechanism to help design balanced policies.

WILDERNESS FIRE MANAGEMENT - AN

EXAMPLE

Signal detection theory (Egan 1975, Saveland and

Neuenschwander 1990, Swets and Pickett 1982, Wilson 1987)

divides a decision problem into three parts: state of nature,

response, and outcome (fig. 1). State of nature refers to

presence or absence of a signal at the time a person makes a

response. The signal is either present or absent. Responses

are alternative actions decision makers must choose between.

Decision makers can control their response, but have no

control over the state of nature. They can respond by saying

that they detect signals or that they do not. The point where

a person switches between responding yes and responding no

is the threshold of evidence. If the signal strength is greater

than the threshold of evidence, the response is yes. If signal

strength does not reach the threshold of evidence, decision

makers will not detect the signal and the response will be no.

The threshold of evidence can be varied. As the threshold of

evidence is increased, a person is more likely to say no, thus

reducing the number of false alarms, but increasing the

number of misses. As the threshold of evidence is decreased,

a person is more likely to say yes, thus reducing the number

of misses and increasing the number of false alarms. This

inherent trade-off between misses and false alarms provides

the opportunity to find a balance point. A response combined

with a state of nature results in an outcome for which the

decision maker has some level of utility. One of the strengths

of decision theory is that it separates the decision from the

outcome.

Response State of Nature

Signal Present Noise

S n

Yes

Y

No

N

HIT FALSE ALARM

Wld P(Yln>

MISS

PWlsl

CORRECT REJECTION

P(Nln)

Figure 1 .-The signal detection paradigm.

188
Response State of Nature

Undesirable Desirable

Fire Fire

Initial HIT FALSE ALARM

Attack (????)

Do not

Initial

Attack

MISS

(Yellowstone ‘88) CORRECT REJECTION

Figure 2.--Signal detection for wilderness fire.

The wilderness fire decision can be divided into two responses

that combine with two states of nature to produce four

possible outcomes (tig. 2). The decision maker could choose

to suppress a tire that, had it been allowed to bum, would

have eventually exceeded acceptable conditions (i.e. become a

wildfire). This hit is a desirable outcome because money has

been saved by putting the fire out when it was small.

Second, the decision maker could choose to let such a fire

bum, in which case it would have to be put out later. This

miss is an undesirable outcome because the costs of putting

out a fire increase exponentially as the fire’s size increases.

Third, the decision maker could choose to put out a fire that,

had it been allowed to bum, would not have exceeded

acceptable conditions (i.e. would have stayed within

prescription). This false alarm is an undesirable outcome

because an opportunity to allow fire to play its natural role

has been missed. Fuel management benefits are not realized,

firefighters are exposed to unnecessary risk of injury, and

unnecessary costs associated with the suppression effort are

incurred. Perhaps most important, nothing is learned. There

is no increase in knowledge. Although this block and the hit

block can be discussed conceptually, they are counterfactuals,

and there is no way to determine these blocks in reality.

Finally, the decision maker might choose to let a fire bum,

and this fire would stay within prescription. This correct

rejection is another desirable outcome. Fire is allowed to

play its natural role in maintaining various ecosystems,

benefits associated with fuel management are realized, and the

costs of fire suppression are saved.

Thus, the strategy for wilderness fire management is to allow

as many non-problem-causing fires to bum as possible. For

fires that are expected to cause problems, quick suppression

while the fire is small is necessary to minimize costs and

damages.

Long-range assessments of fire danger are key factors when

managers have to decide whether to suppress specific

wilderness fires. The fire danger prediction task can also be

put into a signal detection framework (fig. 3). When

Response State of Nature

High

Danger

Low

Danger

Predict HIT FALSE ALARM

High

l

Predict

Low

MISS CORRECT REJECTION

Figure 3.--Signal detection for long-range forecasting.

189
lightning ignites fires early in the season, there must be an

assessment of what fire danger conditions are likely to evolve

later in the season.

An analytical procedure called the receiver operating

characteristic (ROC) curve is an inherent part of signal

detection theory. The ROC curve is a plot of the percentage

of hits on the Y axis against the percentage of false alarms on

the X axis (fig. 4). An ROC curve summarizes the set of 2 x

2 matrices (fig. 3) that result when the threshold of evidence

is varied continuously, from its largest possible value down to

its smallest possible value. The upper left-hand comer, where

the percentage of hits equals one and the percentage of false

alarms equals zero, represents perfect performance. The

positive diagonal, where the percentage of hits equals the

percentage of false alarms, is what would be expected based

on pure chance.

HITS

1

0.8

0.6

0.4

0.2

0

- ROC Curve 1

---. ROC Curve 2

.“.“. d’

- Chance Line

0 0.2 0.4 0.6 0.8

FALSE ALARMS

Figure 4.--Receiver operating characteristic (ROC) curves.

Various strategies can be used to select an appropriate

threshold of evidence. One such strategy, minimax, attempts

to minimize false alarms while maximizing hits.

The ROC curve has four important properties which

correspond to the four tasks required to implement adaptive

resource management. First, ROC analysis requires that the

problem be defined explicitly. In this case, it is necessary to

say just what constitutes high fire danger and what does not.

In the example to follow, fire danger is defined in terms of

the energy release component (ERC) of the national fire

danger rating system. If the ERC at a certain date early in

the fire season exceeds a threshold (predict high fue danger)

and the ERC exceeds a critical value later in the fire season

(late-season fire danger is high), the result is a hit. If the

ERC early in the fire season exceeds a threshold but the ERC

does not exceed the critical value later on, the result is a false

alarm. Miss and correct rejection can be defined in a similar

manner. The threshold varies to display the possible tradeoffs. The critical value is site specific. The manager can

select a critical value based on past experience. For example,

noting that tires start to spread rapidly on north slopes,

develop into crown tires, and become uncontrollable at a

certain value, would be a suitable critical value. An explicit

definition of fire danger and fire severity will enhance

communication between fire staff and line officer decision

makers, and between the line officer and the public. Second,

the ROC curve displays skill prediction, or how much

confidence to place in the prediction. A point near the chance

line does not warrant much confidence, while a point close to

the upper left-hand comer is reliable. The area under the

curve is a measure of skill prediction and can be compared to

chance. Skill prediction can also be considered a measure of

our current state of knowledge. As more knowledge is

obtained prediction systems should improve, and this

improvement should result in new ROC curves that get

progressively closer to the upper left-hand comer, which

represents perfect prediction. Third, the ROC curve

expresses the inherent uncertainty of the predictions in terms

of Bayesian probability. Each point on the curve corresponds

to percentages of hits, false alarms, misses, and correct

rejections on a scale of zero to one. Foutih, the ROC curve

displays the possible trade-offs between misses and false

alarms as the threshold of evidence varies. A high percentage

of hits is often possible only when there is a high percentage

of false alarms. To reduce the number of false alarms often

implies an increase in the number of misses. Selecting an

operating point on the ROC curve is selecting a balance point.

Figure 5 is an ROC curve developed for the Westfork Ranger

District weather station. The Westfork weather station

collects data used by those who make decisions about

prescribed natural fires in a portion of the Selway-Bitterroot

Wilderness. Fire danger prediction is explicitly defined by a

threshold ERC early in the tire season and a critical ERC

later on in the season. A critical ERC value of 52 was

chosen. During the period from 1973 to 1987, the ERC

reached 52 in four of the fifteen years,(1973, 1977, 1978, and

1979). Thus in 73 percent of the years, the ERC does not

exceed 52 (low danger years), while 27 percent of the years,

the ERC exceeds 52 (high danger years). The ROC curve

displays percentages of hits and false alarms for threshold

ERC values from 20 to 43. The probability that the ERC

exceeds 29 on July 10 given that the ERC exceeds the critical

190
1j 1 :::“::;:e

0

I I I I 1 I I I

0 0.2 0.4 0.6 0.8 1

FALSE ALARMS

1988 ERC 41

Critical ERC = 52

Data: 1973-1987

Figure 5.--Long-range ERC forecast for Westfork R.D. on

July 10.

value of52 later on in the fire season (hit) is 1.0. The

probability that the ERC exceeds 29 on July 10 given that the

ERC does not exceed the critical value of 52 later on in the

tire season (false alarm) is 0.18. it follows that the

probability of a miss at that point on the ROC curve is 0 and

the probability of a correct rejection .82. Skill prediction is

high. The area under the ROC curve is 0.91. If it were

important to minimize the number of false alarms, the

threshold of evidence could be increased to 43. This would

reduce the number of false alarms by 18 percent, but would

increase the number of misses by 50 percent. Saveland (1989)

presents a similar analysis for Yellowstone National Park.

CONCLUSIONS

Most resource management controversies require seeking a

balance between competing, conflicting objectives. Finding a

balance is an integral part of adaptive resource management.

Implementing adaptive policy involves four steps: defming

and bounding the problem, representing current knowledge,

representing the uncertainty surrounding our predictions of the

future, and designing balanced policies that provide for

resource production and protection while permitting

experimentation aimed at increasing knowledge. Receiver

operating characteristic curve analysis can assist adaptive

resource management. ROC forces explicit definitions,

represents current knowledge through skill prediction and

readily displays uncertainty and possible tradeoffs.

Adaptive resource management points out the limits of our

current knowledge and the importance of increasing our

knowledge of the structure and function of natural resources.

In fact, knowledge can be considered a resource. Surely our

policies should promote the acquisition of new knowledge.

LITERATURE CITED

Clark, W. C. 1989. Managing planet earth. Scientific

American 261(3):47-54.

Egan, J. P. 197.5. Signal detection theory and ROC analysis.

New York: Academic Press.

Forman, R. T. T.; Godron, M. 1986. Landscapeecology.

New York: John Wiley and Sons, Inc.

Holling, C. S., ed. 1978. Adaptive environmental assessment

and management. New York: John Wiley and Sons.

Naveh, 2.; Lieberman, A. S. 1984. Landscape ecology

theory and application. New York: Springer-Verlag.

Peters, T. 1987. Thriving on chaos. New York: Alfred A.

Knopf. 561 pp.

Saveland, J. M. 1989. Knowledge-based systems approach to

wilderness tire management. Ph.D. Dissertation. Moscow,

ID: University of Idaho.

Saveland, J. M. 1990. Artificial intelligence and GIS: tools to

implement adaptive resource management. In: C.

Goodbrand, ed. Proceedings of GIS ‘90. Vancouver, BC:

Reid, Collins and Associates: pp. 507-512.

Saveland, J. M.; Neuenschwander, L. F. 1990. A signal

detection framework to evaluate models of tree mortality

following fire damage. Forest Science 3666-76.

Shapiro, H. 1990. The willingness to risk failure. Science

250:609.

Swets, 1. A.; Picket, R. M. 1982. Evaluation of diagnostic:

methods from signal detection theory. New York:

Academic Press,

Thomas, J. W.; Forsman, E. D.; Lint, J. B.; Meslow, E. C.;

Noon, B. R.; Vemer, J. 1990. A conservation strategy

for the Northern Spotted Owl. Report of the Interagency

Scientific Committee to Address the Conservation of the

Northern Spotted Owl. Portland, OR: U.S. Department of

Agriculture and U.S. Department of Interior.

Toffler, A. 1990. Powershift: knowledge, wealth, and

violence at the edge of the 21st century. New York:

Bantam Books. 585 pp.

Walters, C. 1986. Adaptive management of renewable

resources. New York: MacMillan Publishing Co.

Wilson, R. A., Jr. 1987. A theoretical basis for modeling

probability distributions of fire behavior. Forest Service

Res. Pap. INT-382. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station, 11 pp.

191
PRESCRIBED FIFW AND VISUAL RESOURCES

IN SEQUOIA NATIONAL PARK

Kerry J. Dawson and Steven E. Greco’

Abstract-The management goals 81 Sequoia National Park are to restore the tire climax ecosystems of the

giant sequoia-mixed conifer forests to more natural conditions through the reintroduction of tire after many

years of tire suppression. Objectives of prescribed tire must address the need for mitigation in “special

management areas” (SMAs) that are under heavy impact from human use. The sensitive treatment of scenic

resources in these SMAs can augment natural diversity if the structure of “naturalness” is given priority

over uniformity of fuel load reduction. Management actions should seek to: (1) mimic natural fire patterns

whenever possible; (2) avoid aniticial infrastructure as bum unit determinants; and (3) conserve and

enhance scenic resources in areas threatened by intensive human use. Visual resources were inventoried

and management objectives recommended.

INTRODUCTION

Prescription fire began in the Giant Forest of Sequoia

National Park in 1979. Since then several bums have been

conducted. The management objectives of these bums have

been primarily to reduce hazardous fuel accumulations and to

restore the forest to a more natural ecosystem while sustaining

populations of giant sequoias (Sequoiadedron giganteum)

(NPS 1987a). The overall bum pattern on the forested

landscape was originally designed to prevent or minimize the

potential risk of a catastrophic fire sweeping over the Giant

Forest plateau. In an effort to accomplish these objectives,

park resource managers were charged with a variety of

sometimes conflicting objectives An independent review was

commissioned by then Director of the National Parks Service

Western Region, Mr. Chapman in 1986.

The independent review of the giant sequoia-mixed conifer

prescribed burning program of Sequoia and Kings Canyon

National Parks by the Christensen Panel resulted in a report

(Christensen and others 1987). Among many

recommendations were instructions to explicitly address

aesthetic concerns within the park’s “Showcase” areas. The

Sequoia Natural Resources Management Division has since

changed the term “Showcase” to Special Management Areas.

The Panel Report specifically recommended consultation with

landscape architects in the development of bum plans with

special emphasis on the SMAs.

Special Management Areas are located in the most heavily

visited portions of the park. The three primary sources of

visual impact within these areas that must be mitigated are the

reintroduction of fire, visitor overuse, and overgrown thickets

of non-fire climax species. The Sequoia and Kings Canyon

Vegetation Management Plan (NPS 1987b) notes that SMAs

‘Kerry J. Dawson is a Professor in the Graduate Group in Ecology

and Head of the Landscape Architecture Program at the University of

California, Davis. Steven E. Greco is a Postgraduate Researcher in

the Landscape Architecture Program and a graduate student in the

Graduate Group in Ecology at the University of California, Davis.

192

are designated “where maintenance of natural processes is

guided more by scenic concerns.”

High visitation via roads and trails are a significant

anthropogenic impact within an ecosystem that has

management goals for ‘naturalness’. The challenge of

maintaining a natural aesthetic for this type of visitation is

made compelling by the fact that roads and trails concentrate

human impacts and have human facilities associated with them

(food vendors, parking lots, restrooms, etc.). Current

management goals of ‘naturalness’ are further complicated by

historic cultural values that have developed over the past one

hundred years since the establishment of the park. The

named trees and logs have become ‘cultural objects’ along

trails and roads, such as the General Sherman Tree and other

named trees, groves, logs, and stumps in the Giant Forest.

These areas of heavy visitation and subsequent substantial

human impact must be managed more intensively and thus are

termed SMAs.

As stated in the Panel Report (Christensen and others 1987),

SMAs should not be seen as “static museums,” created

through “scene” management, but rather as a part of dynamic

ecosystems, sensitively managed to preserve scenic and

ecological resources. The Prescribed Fire Management

Program (1987a) notes that the intention of management in

these areas is not to apply a method of “greenscreening”,

whereby dramatically different appearing landscapes exist

behind SMAs. Instead, these areas should be burned as more

sensitive units with special attention given to specific goals

and objectives for visual quality, environmental enhancement,

and interpretation, as complemented by associated resource

objectives.

The National Park Service Act of 1916 declared that “the

fundamental purpose of [a National Park] is to conserve the

scenery and, the natural and historic objects and the wildlife

therein and to provide for enjoyment of the same in such a

manner and by such a means as will leave them unimpaired

for the enjoyment of future generations.” Interpretation of

this mandate has clearly demanded a sophisticated level of
management since the release of the Leopold Panel Report

(Leopold and others 1963). The relationship between

aesthetics, scenery, and natural process is a complex natural

and cultural issue that continues to evolve and will do so

through ongoing multidisciplinary research. Visual resources

are a prime asset in our National Parks and they must be

conserved and managed sensitively.

Preservation and restoration of natural ecosystems and their

processes is important to maintain the dynamic character

which ultimately formed the giant sequoia-mixed conifer

forests prior to intensive human occupaion (Parsons and

Nichols 1985). In the Giant Forest, aesthetic and ecological

goals need not conflict, but should seek to complement each

other as much as possible. It can be achieved by utilizing the

recommendations from recent aesthetic research in Sequoia

National Park (Dawson and Creco 1987). Most importantly,

management should seek to mitigate the effects of past fire

suppression and mimic natural tire patterns while educating

park visitors about tire ecology.

Historically, the giant sequoia-mixed conifer ecosystem

experienced frequent, low intensity fires (Kilgore 1987)

which structured the forest prior to human interference. The

effects of past management actions in suppressing all natural

lightning fires, for some seventy-five years,(possibly

representing many natural cycles), has resulted in an altered

forest structure and high ground fuel accumulation in many

areas. The forest structure has been changed to favor shade

tolerant fir and incense cedar (Harvey 1985; Kilgore 1985;

Bonnicksen and Stone 1982; Bonnicksen 1975) while

unnaturally high fuel accumulation risks increased mortality of

giant sequoias and understory species during a fire. Past

prescribed fires have resulted in what many environmental

groups see as unnatural due to inadequate mitigative measures

and procedures. Prescription tires are now designed to

mitigate these effects through “cool bums” meant to restore

natural conditions. The overall concern in SMAs is to have

the forest “look” like a low intensity natural bum has moved

through the forest even though the fuel load may have the

potential for a high intensity fire; and environmental

degredation through intensive use may not have the potential

for recovery without active mitigation.

RESEARCH PROCEDURES AND

METHODOLOGY

The procedures applied in this research were determined by

the specific needs of management and recommendations from

the Panel Report (Christensen and others 1987). They are (I)

to delineate the viewshed boundaries of the SMAs, (2) to

inventory and conduct an analysis on the visual resources

within the SMAs, (3) to recommend ecologically acceptable

visual resource management goals and objectives, and (4) to

recommend management treatments to fulfill the visual quality

goals and objectives.

The research consisted of an inventory of visual resource

elements, formulation of goals and objectives, and

development of a set of guidelines for the treatment of fire

effects on the character of the landscape and on the character

of individual giant sequoia features. The methodology

developed for assessing the visual resources at Sequoia

National Park can be applied to all roadways and trails within

the park. The process model (iig. 1) graphically depicts the

recommended methodology for SMA visual resource

planning.

RESEARCH METHODOLOGY PROCESS MODEL

2.

Figure 1 .--Visual resource research methodology and planning

approach.

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SMA BOUNDARY DELINEATION

The study areas within the SMAs are defined in terms of their

respective viewshed boundaries. A viewshed, or visual

corridor, is a routed (by road or trail), physically bounded

area of landscape that is visible to an observer (Litton 1979).

A viewshed delineates the dimensions of the “seen”

environment in terms of visual penetration. The viewshed

boundary is formed from the dynamic composition of viewing

points on a continuum (i.e. a road or trail). The viewing

points are representative of a number of observer positions

accounting for several viewing orientations (Litton 1973,

1968).

VISUAL RESOURCES INVENTORY AND

ANALYSIS

An inventory of visual resources is a descriptive field survey

that identifies the seen areas, and physically locates visual and

perceptual elements within the selected SMA study areas. It

consists of several parts including viewshed delineation, areas

of viewshed overlap, visual unit delineation, identification of

special features and visual element subunits, determination of

giant sequoia visibility through a visual prominence rating,

and the location of impacted views due to fire suppression.

An inventory was surveyed and compiled for each study area

SMA.

The goal of the feature analysis is to provide park managers

with a tool to assess the relative difficulty of achieving the

visual quality objectives. The Management Scale provides an

indexed classification for each visual unit to indicate pre-bum

planning intensity and (bum) labor requirements that will be

necessary for any given bum unit. For example, in an area

with many visual features (i.e., giant sequoias, logs, etc.) the

Management Scale value could be rated as class “1” and an

area with few visual features could rate as a class “4” value.

Hence, if a bum unit contains several class “1” values, then

more labor will be required to mitigate excessive fire effects.

Formulation of the Visual Unit Management Scale consisted

of five steps: a tabulation of features per visual unit; a

feature aggregation index calculation; determination of visual

unit acreage; a feature density value calculation; and an

indexed classification of those values into the Visual Unit

Management Scale values.

SMA VISUAL MANAGEMENT GOALS AND

VISUAL QUALITY OBJECTIVES

Fire management planning in SMAs requires the development

of clear goals and specific objectives as a critical step in the

prescribed fire planning process (Fischer 1985; Bancroft and

others 1983). Clear exposition of goals and objectives is

necessary to evaluate the effectiveness of management actions.

Management goals should be broad in scope and attainable

through specific objectives that address issues within each

goal. The three central issues for visual quality goals and

objectives are (1) fire effects on the character of the

landscape, (2) fire effects on individual giant sequoias, and

(3) enhancement of currently affected visual resources.

Fire Effects on Landscape Character

The giant sequoia-mixed conifer forests have evolved in

context of frequent fire return intervals and low fire

intensities (Kilgore 1987; Van Wagtendonk 1985). Less

frequent, more extensive and intense events, though, have

also played an important role in this ecosystem. Kilgore and

Taylor (1979) found through tree ring analysis that historical

fires near the Giant Forest area were frequently small in size

and generally confined to a single slope or drainage. They

also report that fues ranged in size between 0.001 ha to 16

ha. In the same study area, Harvey and others (1980)

confirm the small nature of these bums, suggesting they were

about 10 ha.

In the Redwood Mountain area, the Kilgore and Taylor study

(1979) also found tire return intervals on west-facing slopes to

be about every 9 years, and on east-facing slopes to be about

every 16 years. They also report mean fire-free intervals of 5

years on dry ridges of ponderosa pine and 15-18 years in

moist sites of white fir. The average maximum fire-free

interval was found to be 14-28 years. Their data also reveals

that some clusters of giant sequoias have escaped fire for up

to 39 years. Some areas may have escaped tire for a hundred

or more years.

Restorative SMA prescription fires should be planned within

an appropriate temporal and spatial framework. The

juxtaposition of prescribed bums can greatly enhance or

detract from the visual and ecological diversity of the forest.

The goal should not be to create bums that result in large

scale areas of an early successional stage. Rather,

management bums should concentrate on maintaining, or

creating, successional diversity throughout the forest (Harvey

and others 1980). Fire should be introduced on a gradual

spatial and temporal basis to restore the forest to a more

natural state. Although reducing fuel accumulations is

important, it is not necessary that this be the immediate

objective of an SMA bum. Small-scale bums should be

designed to maintain ecological and visual diversity over

appropriate time scales. Planning should incorporate

available site-specific fue history research.

To preserve successional and visual diversity, management

plans should include small-scale bums, random juxtaposition

of bums (a variety of bum contrasts), selected retention of

understory vegetation, and limiting the number of bum units

treated each year. Planned variation in future bum unit

boundaries will also help maintain an ecologically and visually

diverse park environment. To increase visual diversity and

maintain a sense of ecological continuity along travel

194
corridors, bum unit boundaries should cross roads and trails

in some areas and remain adjacent to them in others. If roads

and trails are always used as boundaries, one side will always

appear different than the other. Human infrastructure should

be avoided or limited as bum unit determinants. Because it

could lead to a confused perception of the forest to some

visitors and contribute to a less naturalistic aesthetic.

Extended long-range plans, or areas in need of a second

prescribed bum, should include variation in the boundaries of

the first prescribed bum, or possibly the relocation of trails

during this planning process. It is not recommended that the

same boundaries be used for future bums. The return of fire

should also be variable, both spatially and temporally.

Variation is another very important aspect of visual and

ecological diversity, as pointed out in the Christensen Report

(1987).

Treatments of designated SMA bum units should be “cooler”

prescriptions as noted in the Grant Tree SMA plan (NPS

1980a). Taylor and Daniel (1985) confirm that fire intensity

correlates with scenic quality and recreational acceptability in

ponderosa pine forests. They found that in comparison to

unbumcd areas, low intensity fires produced improved scenic

quality ratings after 3-5 years, but that high intensity tires

“seriously declined” in scenic quality ratings after the same

time period.

Efforts to provide a high value interpretive program are

essential to educate the public about tire ecology and the

aesthetic implications of tire ecology in the Giant Forest

SMAs. The program is important because visitors are

barraged with fire danger signs as they approach the park.

McCool and Stankey (1986) found that visitors who were

confused and uncertain about the effects of prescribed tire

were afraid that it could be “detrimental” and negatively

impact the park, but that visitor center exhibits and guided

tours help engender an understanding and appreciation of the

dynamic processes of forest succession and tire ecology.

Roadside and trailside interpretive dispiays in appropriate

locations, with descriptive graphics facilitate this objective.

The Hazelwood Nature Trail is an excellent example.

Hammit (1979) indicated that the value of interpretive

displays located in visually preferred areas can be more

rewarding and more likely remembered. Proper placement of

displays in the environment appears to aid in the memory

process of park visitors.

Fire Effects on Individual Giant Sequoia Trees, Logs

and Stumps

Visual features in the Giant Forest are highlighted by the

grandeur and presence of a high density of giant sequoias. As

a result of this density and the park’s design, visitor

appreciation of the giant sequoias has rendered many of them

as unique natural/cultural objects in the landscape. Hammit

(1979) reports that the most remembered scenes by visitors

are characterized by visually distinct features. It appears

there is a strong correlation between familiarity and

preference of scenery. Familiarity is highest in both most

preferred and least preferred scenes, indicating that visitors

are affected by both positive and negative features observed

in landscape experiences.

Since the giant sequoias are a primary visual resource in the

Giant Forest, the most visually prominent trees should receive

the greatest scenic mitigative measures to retain a natural

visual character following restoration bums. Maintaining

high scenic and recreational values in the Giant Forest

requires sensitive visual resource planning of fire effects and

a strong interpretive program to effectively communicate fire

ecology to the public. It was recommended that a

management goal for the visual quality of distinct foreground

features receive judicious burning around the bases of the

SMA giant sequoias. The foreground trees have the dual

distinction of being most impacted by intense human use and

are also visually vulnerable.

Protecting all visible trees from intensive fire effects is not

desirable. For visitors to gain a sense of appreciation for a

wide range of tire effects, some of the less visibly prominent

trees could provide an opportunity for such diversity. It is

not intended that foreground trees should be protected at the

expense of background giant sequoias. Rather, foreground

sequoias should receive more sensitive treatment due to their

proximity to high human use pressures and park

infrastructure. Intense human use proximate to these trees

has resulted in decreased duff cover, soil compaction,

increased erosion, and lack of understory regeneration. Many

of these trees are under unnatural stress. Background trees

receive wilderness standards for giant sequoia management.

To gain better insight and understanding of visitor sensitivity

to singeing and charring on highly visible giant sequoias, a

special study would have to be conducted. A study has been

completed (Quinn 1989) of visitor perceptions of recent

prescribed fire management in Sequoia National Park and

generally, visitors were not adverse toward fire scars.

However, no research was conducted on reaction to singeing

versus charring in recent bum units within the park.

The last issue regarding protection of individual giant

sequoias is the maintenance of ecological and visual/cultural

values associated with horizontal features in the forest

landscape experience. The preservation of a select number of

highly visible sequoia logs (in addition to named logs) along

trails and roadways has been strongly recommended by some

groups (Fontaine 1985). The interpretive value of these logs

stems from the direct “involvement” the public has with these

elements. The tactile experience of touching and passing

under these logs can engender a strong appreciation for the

grandeur of the giant sequoias. They also demonstrate the

dynamic nature of succession in the giant sequoia-mixed

conifer ecosystem. Hammit (1979) suggests that prolonged

195
contact with such features increases familiarity. It was

recommended that a balanced number of strategically located

logs be protected from intense prescribed bums.

Currently Affected Visual Resources

Scenic resources are currently impacted by (1) intensive

recreational use, and (2) the structural changes of vegetation

in the giant sequoia-mixed conifer forest. The first is due to

the effects of visitor overuse and the lack of facilities to

accommodate the use volume. The second impact results

from tire suppression which promotes the growth of shade

tolerant conifer thickets (non-fire climax species) that limit the

visibility of numerous giant sequoias within the viewshed.

Management goals to alleviate both of these impacts would

enhance the overall experience of the park.

Many high visitation areas such as the Congress Trail,

General Sherman Tree, and Hazelwood Nature Trail suffer

from severe overuse. Strategic signage in these areas is

essential to better guide foot traffic (trampling) in these areas

which has caused the disintegration of duff and subsequent

erosion of surface soil. As a result, dusty or muddy visitor

environments have inadvertently created biological and visual

resource problems. Problems include erosion around the

bases of sequoias exposing fibrous roots, erosion and decay of

asphalted edges in parking areas and on trails, and a lack of

understory vegetative cover due to trampling and soil

compaction. Means to reduce these effects focus primarily on

redirecting foot traffic in and around facilities and reducing

trampling around the trees.

The second issue concerning enhancement of affected visual

resources is the extensive growth of shade tolerant conifer

thickets (non-tire climax species) resulting from tire

suppression and disturbances due to road, trail, and facility

construction (NPS 1980b; Bonnicksen 1985). In the absence

of regular fire disturbance cycles, these thickets have grown

unchecked by natural process, thus hindering the ability of the

giant sequoia to reproduce successfully and also blocking both

historic views and potentially valuable views of the giant

sequoias in the Giant Forest SMAs. In addition to these

problems, the thickets also represent future fuel load and fuel

ladder problems. The visual resource goal should be to

conserve scenery which enhances visitor experience within the

SMAs through active management of the thickets. The means

to achieve this goal is the limited strategic removal of these

“overrepresented aggregation types” (Bonnicksen 1985;

Cotton and McBride 1987).

VISUAL RESOURCE TREATMENTS

The recommended treatments consists of a Landscape

Management Plan and a set of guidelines for visuat resource

management in the SMAs. Visual resource treatments are

management actions designed to fulfti management goals and

visual quality objectives. A photographic monitoring

program is also recommended.

196

Landscape Management Plan

The SMA Landscape Management Plan identifies proposed

bum units, planning units, past prescribed bums, bum

exclusion areas and thicket problem areas. The bum units

have been designed in accordance with the visual quality

objectives to maintain a diverse visual character within the

SMA study areas. Sections requiring additional research

studies are classified as “planning units” and “SMA planning

units” on the plan. Small areas of cultural value that are

recommended for exclusion from prescribed fire are also

indicated on the plan. Additionally, thickets that block views

of giant sequoias, and thickets that present future visual

resource problems are identified for treatment. Finally,

measures to protect visually prominent giant sequoias are

based upon the visual prominence ratings are shown on the

Visual Resource Inventory maps.

Protection of visual elements is also meant to preserve

pockets of mature understory vegetation in addition to giant

sequoia protection. These pockets are ecologically important

because intensive human use interferes with regeneration and

colonization sources which are needed to avoid further

damage and are needed as vegetative use buffers. These, too,

are identified on the Visual Resource Inventory Maps. The

analysis of visual features within the visual units provides a

guide for resource managers to evaluate planning for labor

requirements when planning bum units. A feature “density”

value was generated for each visual unit and broken down

into management intensity classes.

Bum Unit Design and Schedule

Bum units were designed based on the Fire Effects Guidelines

for SMA Landscape Character. Natural boundaries for the

SMA bum units are preferred to man-made boundaries in the

design. It is recognized that it is essential to use roads and

hiking trails in many cases due to economic constraints.

However, alternatives to their use should be used where

Possible, such as streams, drainages, ridges, old fire lines,

meadows, rock outcrops, and new fire limes.

The bum units in a maintenance fire regime should be varied

from previous prescribed bums. It is not recommended that

the same bum unit boundaries be used more than once if they

are unnatural boundaries (trails or roads). Using the same

boundaries runs an ecological and visual risk of creating an

unnatural mosaic of forest succession. The maintenance bum

regime units should concentrate on natural fire breaks that

travel across trails instead of being bound by them.

Timing of the bum units is a very important aspect of

planning. The bum units have been designed to restore the

Congress Trail and the SMA section of the Generals Highway

to more natural conditions. Following the restoration bum

regime, a long-term maintenance fire regime should be

formulated for the Giant Forest. It is recommended that this

regime be based on area-specific fire history research.
A computer geographic information system (GIS) would

greatly enhance the analysis and planning of the bum units in

the Giant Forest because it is a very useful tool for evaluating

large spatial data sets and many variables.

Guidelines for Thicket Problem Areas

The visual quality objectives regarding enhancement are

designed to increase the visibility of giant sequoias affected by

extensive thicket growth throughout SMA viewsheds. These

thickets are blocking numerous potentially valuable views of

giant sequoias (fig. 2). Management for a natural aesthetic

and increased visual penetration into the forest within the

SMAs warrants judicious mechanical thinning of some of

these thickets (Bonnicksen and Stone 1982; Christensen 1987;

Cotton and McBride 1987).

Figure 2.--Thickets of mixed conifers are encroaching on the

views of giant sequoias due to the disturbance of road

construction.

The thickets were mapped on the SMA Landscape

Management Plan in two ways. Existing “blocked” views

were mapped, and visually “encroaching” thickets are also

shown. The encroaching thickets did not present a visual

problem at the time the field work was conducted, but will

cause visual penetration problems in the near future. They

should be monitored photographically and evaluated for

mechanical thinning. It was recommended that this be

incorporated into the park’s Vegetation Management Plan for

the development zone (NPS 1987b).

Guidelines for Giant Sequoia Fire Effects Mitigation

As discussed in the visual quality objectives, it is the visually

prominent trees which are impacted most by human use

pressures. Park infrastructure, such as trails, roads, signs,

restrooms, etc., are proximate to the visually prominent trees.

The most valuable scenic resources are also the most visually

prominent trees. Mitigative measures to protect these trees

are critical in terms of ecological, scenic, and park

infrastructure resources The objective is not to leave these

trees unburned, but to mitigate fire effects. Trees impacted

by intensive human use are under stress and unsuppressed fire

risks unnatural mortality. The four categories of giant

sequoia protection (mitigation measures) are illustrated in

tigure 3 and include: (1) scorch exclusion, (2) minimal

scorch, (3) limited scorch, and (4) unsuppressed scorch

(within standard management tree protection guidelines).

These relate directly to visual proximity as well as distance

from human impact (Dawson and Greco 1987).

Fire Effects Guidelines for Individual Giant Seauoias

1. Scorch Exclusion

2. Minimal Scorch

3. Limited Scorch

4. Unsuppressed Scorch

Figure 3.--SMA mitigation measures for giant sequoias

197
To understand properly the descriptions of the four categories

of giant sequoia protection, definitions of scorching, singeing

and charring are necessary. In this study, “scorching” is the

singeing or charring of sequoia bark. “Singeing” is bark

ignition to a depth under one half an inch (< l/2”).

“Charring” is defined as bark ignition to a depth over one half

an inch (> 112”). The question of singeing is not an intense

aesthetic issue because park visitors seem to accept some fire

damage to sequoias (Quinn 1989). However, reaction to

varying levels of charring is undetermined and can impair the

scenic quality of giant sequoias for longer time periods if the

trees are under stress. Therefore, it was recommended that

scorch and char guidelines be established in addition to

current tree preparation standards (pre-fire) and firing

techniques. It should be remembered that the guidelines

apply only during the restoration prescribed fire phase.

Guidelines for Understory Protection

Planned retention of understory vegetation pockets is

recommended in the SMA bum units. They offer

opportunities to maintain visual and ecological diversity while

increasing the probability of regeneration by providing

colonization sources. Often, these pockets grow among rock

outcrops and probably have escaped fire for longer periods

under more natural ecosystem conditions. Historically,

natural bums have undoubtedly missed many areas creating a

mosaic of vegetation characteristic of the sequoia-mixed

conifer ecosystem. The most obvious pockets for retention

would be growing among rocks that could be supplemented

with fire lines to lengthen their presence.

For aesthetics, these groups of plants provide a visual focus,

diversity of elements, and demonstrate the scale between

visitors and the large-scale giant sequoias and older conifers.

Some good examples in Giant Forest are the native dogwoods

(Cornus nuttallii) and Sierra chinquapin (Castanopsis

sempervirens), and greenleaf manzanita (Arctostaphylos

patulu). Although some are adapted to fire and resprout after

a fire, their rate of growth is slow. Their visual qualities and

interpretive qualities could be diminished for many years.

DISCUSSION

There has been concern on the part of National Park Service

scientists about some of the research recommendations on

visual resources (Dawson and Greco 1987). An

interdisciplinary group of staff from Sequoia National Park

representing science, administrative management, visitor

interpretation, fire management, and resource management

met and forwarded comments. The following discussion

presents these views as well as further discussion on the

visual resource research.

NPS and Understory Issues

The NPS group does not favor “the deliberate retention of

mature groups of understory plants, since prescribed fire

tends to leave mosaics of burned and unburned areas, and the

recovery of the understory plants in post-tire succession is an

important part of the story of the forest” (NPS 1988).

At several prescribed bums in the Giant Forest, the visual

resource research team observed that fire was applied

homogeneously within the bum units. Fire management staff

frequently bum areas completely and uniformly, and if fue

bypassed any fuel loads, the fire technicians returned

moments later to fire that area. This does not mimic natural

tire patterns and as a result, pockets of understory plants

rarely survive. The practice of multiple-spot firing after the

fue has moved through should be modified to rely on this

technique only in situations where absolutely necessary

(greater than lOOO-hour class fuels). Kilgore (1985)

supported this concept by pointing out that increased

uniformity and lessened mosaic pattern is unnatural.

Litton (1988) has written to Sequoia National Park that “In

addition to modifying fuel concentrations, both down material

and standing live trees, related to dominant specimens, I

further urge protective measure for certain visually significant

understory - ground floor components. Several obvious

examples of these subordinate features are snags, fallen big

trees and mature, tree-form dogwoods; these and others

contribute significantly to experiencing a rich landscape, are

signs of time and succession, and represent considerably more

than fuel needing to be burned. n

Litton further added, “Brewer, King, and Muir confirm and

give emphasis to other contemporary accounts that the Sierra

Nevada forest were [sic] impressive for their [sic] openness

and for the large scale of mature trees. At the same time,

these three early observers note the diversity of what they saw

in the various forest and woodland species, their associations,

regeneration and some of the ground plane and understory

characteristics. Brewer notes species or type distribution in

space and elevation, the combinations of the mixed conifers -

some with Big Trees, the array of ages and sizes in Big

Trees, [and] the significance of fallen Big Trees in

appreciating their size and age. King emphasizes the impact

of contrasts found in the association of Big Trees and Sugar

Pine and White Fir as well as the experience of the spatial

quality found in the open forest. Muir comments on

openness, on spatial distribution, on the smooth floor, but also

points to the contrast of underbrush with Big Tree bark and

speaks in considerable detail about Big Tree regeneration.

Diversity, then, appears to be an historic clue about the

historic forest in addition to the frequently stated perception

of openness.”

198
NRS and Visibility ISSRS

The NPS group -was unanimously opposed to allowing

changes in appearance due to fire only in the medium and low

visibility trees, while retaining foreground trees in their

present unburned state... in general, all trees regardless of

[visibility] rating will be prepared and burned according to

current standards...” (NPS 1988).

In the visual resource recommendations, scorch exclusion

does not mean “unburned”. More importantly, it will be very

dif!icult to treat focal point trees, such as the General

Sherman Tree, with prescribed fire. These trees are

surrounded by trails, fences, facilities, and/or roads and are

also subject to intensive visitor use and abuse. Most

foreground trees in special management areas are stressed by

pavement, soil compaction and altered topography. As one

moves farther from view corridors, this type of impact (direct

human disturbance) is lessened. It is evident that there is an

ecological relationship between aesthetics and the built

environment and treating giant sequoias in the foreground

more sensitively than those further away actually recognizes

the impact of these conditions.

NPS and Downed Log Issues

The NPS Group agreed “that logs identified by inlerpretation

as having cultural or interpretive value will be protected from

Iire. However, no effort should be made to preserve logs as

horizontal elements, since these logs are important sources for

seedbeds, which are an important part of the forest story. In

addition, the SMA bum units are small, and it is not likely

the loss of logs will produce an impact on the visual resources

of the area as a whole” (NPS 1988).

The Yellowstone fires document that horizontal elements

(logs) are increased by fire, not decreased, regardless of fire

intensity (Ekey 1989; Guth 1989; Simpson 1989). Although

it is difficult to compare Yellowstone and Sequoia, logs are

universally important ecologically and visually for the

maintenance of habitat diversity. It is important to avoid the

homogeneous bum coverage typical of hot fires in unnatural

fuel accumulations. While totally burnt logs can play a role

in sequoia regeneration, fling techniques which attempt to

bum all logs does not recognize that some logs also play an

important rote in the nutrient cycling of the forest by acting as

nutrient reservoirs and reducing soil erosion following a fire.

If the fire bums a log as it moves through, this seems

acceptable. The problem is when fire crews return to

spot-bum a log that the fire has by-passed.

In discussing visual resources, the thickets are diminishing the

scenic value of the park from roads and trails. Many of these

thickets are less than fifty years old and exist as a result of

managed fire exclusion and site disturbance, such as road

construction. This abundant growth impacts scenic resources

and ecological processes. Kilgore (1987) states that

“removing fuel from the intermediate layer between between

surface and crown fuels greatly reduces the potential for high

intensity surface fires that could lead to crown fires.” Under

a more natural fire cycle, crown fires are a relatively rare

event in the giant sequoia-mixed conifer ecosystem and would

be an unnatural and unfortunate consequence of the fuel load

build-up due to past fire suppression.

The Christensen Report (1987) indicates approval of

‘judicious pre-bum cutting of understory trees...where

ignition of such trees might have a negative effect on stand

appearance and/or when their removal would enhance the

visual effect of adjacent specimen trees.”

CONCLUSION

Past human interference with the ecosystem of the giant

sequoia-mixed conifer forests has impacted the visual and

ecological resources in Sequoia National Park. These impacts

have been augmented by concentrated visitor pressure in the

areas of the park with roads, trails, and built facilities.

Special management areas have been established to address

these complex management problems of balancing cultural

and natural ecosystem interests.

The detailed visual resource database and mitigation

guidelines developed for the Prescribed Fire Management

Program were designed to provide park resource managers

with new tools to achieve more natural fire effects for the

landscape and giant sequoia visual resources. There were

forty-four separate treatments recommended with roughly half

of the recommendations known to be implemented (Dawson

and Greco 1987). It is pleasing and appreciated that support

was so forthcoming from the National Park Service for over

half of the treatments. This paper has attempted to explore

the complexities of the remainder. However, creating

favorable conditions for the perpetuation of the giant sequoia

is supported and current management policies using

prescribed fire management are improving continuously. The

visual resource research has strived to present ecologically

acceptable solutions to problems of culture in the context of a

naturat environment and the role of fue in the giant

sequoia-mixed conifer ecosystem which support this continued

improvement.

NF’S and Thinning Issues

The NPS group “agreed that existing vistas of the Sherman,

Grant, and McKinley trees should be preserved. The group

was opposed to pre-bum thinning of trees which obstruct

sequoias as weIl as to the suggestion that trees killed by the

fue should be cut out” (NPS 1988).

199
LITERATURE CITED

Bancroft, W.L., H.T. Nichols, D.J. Parsons, D.G. Graber,

Q.B. Evison, and J. Van Wagtendonk. 1983. Presented at

the Wilderness Fire Symposium, Missoula, MT, USDA,

Forest Service Intermountain Forest and Range

Experiment Station, Ogden, UT, General Technical

Report INT-182, pp. 26-29.

Bonnicksen, T.M. 1985’. Ecological Information Base for

Park and Wilderness Fire Management Planning.

Presented at the Wilderness Fire Symposium, Missoula,

MT, USDA, Forest Service Intermountain Forest and

Range Experiment Station, Ogden, UT, General Technical

Report INT-182, pp. 168-173.

Bonnicksen, T.M. 1975. Spatial Pattern and Succession

Within a Mixed Conifer-Giant Sequoia Forest Ecosystem.

University of California, Berkeley, CA, dissertation.

Bonnicksen, T.M. and E.C. Stone. 1982. Reconstruction of a

Presettlement Giant Sequoia-Mixed Conifer Forest

Community Using the Aggregation Approach. Ecology

63(4):1134-1148.

Christensen, N. L., L. Cotton, T. Harvey, R. Martin, J.

McBride, P. Rundel, and R. Wakimoto. 1987. Final

Report--Review of Fire Management Program for

Sequoia-Mixed Conifer Forests of Yosemite, Sequoia and

Kings Canyon National Parks. National Park Service

Western Regional Office, San Francisco, CA, 37 pp..

Cotton, L. and J.R. McBride. 1987. Visual Impacts of

Prescribed Burning on Mixed conifer and Giant Sequoia

Forests. Wildfue 2000. USFS General Technical Report

PSW-101, Berkeley, CA, pp. 32-37.

Dawson, K.J. and S.E. Greco. 1987. Special Management

Area Visual Resources Management Study for the Sequoia

National Park Prescribed Fire Management Program.

Center for Design Research, University of California,

Davis, CA, 96 pp.

Ekey, R. 1989. Yellowstone on Fire. Billings Gazette.

Billings, Montana, 128 pp.

Fischer, W.C. 1985. Elements of Widemess Fire

Management Planning. Presented at the Wilderness Fire

Symposium, Missoula, MT, USDA, Forest Service

Intermountain Forest and Range Experiment Station,

Ogden, UT, General Technical Report INT-182, pp.

138-144.

Fontaine, 1. 1985. Recommendations from the Sierra Club for

Managing Giant Sequoia. Proceedings from the Workshop

on Management of Giant Sequoia, U.S. Forest Service,

Pacific SW Forest and Range Experiment Station, General

Technical Report PSW-95, Reedley, CA, pp. 24-26.

Guth, A.R. and S.B. Cohen. 1989. Red Skies of ‘88. Pictoral

Histories Publishing Co., Missoula, Montana, 124 pp.

Hammitt, W.E. 1979. Measuring Familiarity for Natural

Environments Through Visual Images. Presented at the

National Conference on Applied Techniques for Analysis

and Management of the Visual Resource, Incline Village,

Nevada, April, 1979. This paper is taken from National

Forest Landscape Management, vol. 2,. U.S.D.A.,

Handbook No. 559, pp. 217-226.

Harvey, H.T. 1985. Evolution and History of Giant Sequoia.

Proceedings from the Workshop on Management of Giant

Sequoia, U.S. Forest Service, Pacific SW Forest and

Range Experiment Station, General Technical Report

PSW-95, Reedley, CA, pp. 1-4.

Harvey, H.T., H.S. Shellhammer, and R.E. Stecker. 1980.

Giant Sequoia Ecology, Fire and Reproduction. Scientific

monograph series - U.S. National Park Service; no. 12,

182 pp.

Kilgore, B.M. 1987. The Role of Fire in Wilderness: A

State-of-the-Knowledge Review. National Wilderness

Research Conference Proceedings, USDA Forest Service,

General Technical Report, INT-220, pp. 70-103.

Kilgore, B.M. 1985. What is “Natural” in Wilderness Fire

Management? Presented at the Wilderness Fire

Symposium, Missoula, MT, USDA Forest Service

Intermountain Forest and Range Experiment Station,

Ogden, UT, General Technical Report INT-182, pp.

57-66.

Kilgore, B.M., and Dan Taylor. 1979. Fire History of a

Sequoia-Mixed Conifer Forest. Ecology, 60:129-142.

Leopold, A.S., S.A. Cam, C.M. Cottam, J.N. Gabrielson,

and T.L. Kimball 1963. Wildlife Management in the

National Parks. American Forests, 69:32-35, 61-63.

Litton, R.B. Jr. 1988. The Forest Landscape and Fire

Management: A Report to Sequoia National Park. USDA

Forest Service, Pacific Southwest Experiment Station,

Berkeley, CA, 36 pp.
Litton, R.B. Jr. 1979. Descriptive Approaches to Landscape

Analysis. Presented at the National Conference on

Applied Techniques for Analysis and Management of the

Visual Resource, Incline Village, Nevada, April, 19’79.

This paper is .&ken from National Forest Landscape

Management, vol. 2, U.S.D.A., Handbook No. 559, pp.

77-87.

Litton, R.B. Jr. 1973. Landscape Control Points: a

procedure for predicting and monitoring visual impacts.

U.S.D.A. Forest Service Research Paper PSW-91.

Pacific Southwest Forest and Range Experiment Station,

Berkeley, CA, 22 pp.

Litton, R.B. Jr. 1968. Forest Landscape Description and

Inventories- -a basis for land planning and design.

U.S.D.A. Forest Service Research Paper PSW-49.

Pacific Southwest Forest and Range Experiment Station,

Berkeley, CA, 64 pp.

McCool, S.F. and G.H Stankey. 1986. Visitor Attitudes

Toward Wilderness Fire Management Policy from

1971-84. USFS Research Paper INT-357. Ogden Utah, 7

PP.

NPS (Sequoia and Kings Canyon National Parks). 1988.

Unpublished letter Y1421. Three Rivers, CA, 4 pp.

NPS (Sequoia and Kings Canyon National Parks). 1987a.

Prescribed Fire Management Program. Sequoia and

Kings Canyon National Parks, Three Rivers, CA. 26 pp.

NPS (Sequoia and Kings Canyon National Parks). 1987b.

Vegetation Management Plan (For the Development

Zone). National Parks Service, Western Regional Office,

San Francisco, CA. 140 pp.

NPS (Sequoia and Kings Canyon National Parks). 1980a. The

Effect of Past Management Actions on the Composition

and Structure of Vegetation in the Grant Tree Portion of

Grant Grove, Kings Canyon National Park, California.

Ash Mountain, Three Rivers, CA. 174 pp.

NPS (Sequoia and Kings Canyon National Parks). 1980b.

Development Concept Plan, Giant Forest/Lodgepole Ares

of Sequoia and Kings Canyon National Parks. U.S.D.I.,

Washington, D.C., 46 pp.

Parsons, D.J. and H.T. Nichols. 1985. Management of Giant

Sequoia in the National Parks of the Sierra Nevada,

California. Proceedings from the Workshop on

Management of Giant Sequoia, U.S. Forest Service,

Pacific SW Forest and Range Experiment Station, General

Technical Report PSW-95, Reedley, CA, pp. 26-30.

Quinn, J. 1989. Visitor Perception of NPS Fire Management

in Sequoia and Kings Canyon National Parks: Results of a

Survey conducted Summer 1987. Technical Report

Number 36, University of California, Davis, 108 pp.

Simpson, R. 1989. The Fires of ‘88. American Geographic

Publishing, Helena, Montana, 80 pp.

Taylor, J.G. and T.C. Daniel. 1985. Perceived Scenic and

Recreational Quality of Forest Bum Areas. Presented at

the Wilderness Fire Symposium, Missoula, MT, USDA

Forest Service Intermountain Forest and Range

Experiment Station, Ogden, UT, General Technical

Report INT-182, pp. 398-406.

Van Wagtendonk, J.W. 1985. Fire Suppression Effects on

Fuels and Succession in Short-Fire-interval Wilderness

Ecosystems. Presented at the Wilderness Fire Symposium,

Missoula, MT, USDA Forest Service Intermountain

Forest and Range Experiment Station, Ogden, UT,

General Technical Report INT-182, pp. 119-126.

201
GIS APPLICATIONS TO THE INDIFUXT EFFECTS OF

FOREST FIRIES IN MOUNTAINOUS TERFtAIN

David R. Butler, Stephen J. Walsh, and George P. Maianson’

Abstract-Snow-avalanche paths and landslides are common geomorphic features in Glacier National Park

(GNP), Montana, and represent hazards to human occupancy and utilization of the park. Forest fires have

been spatially extensive there, and it is well documented that areas subjected to forest fires become

increasingly susceptible to avalanching and landsliding.

The locations of all snow avalanche paths and landslides in east- central GNP have been mapped on

topographic maps and verified. The avalanche paths have been digitized and entered into a geographic

information system (GIS) using ARC/INFO. Digital elevation models and Landsat Thematic Mapper digital

data were processed to create elevation, slope angle and aspect, and landcover GIS overlays. Merging of

overlays illustrates areas of maximum erosion potential by snow avalanching and by landsliding in the event

of a forest fire. Post-fire vegetational succession can be accommodated into the GIS to illustrate areas of

high, medium, and low hazard from avalanching and landsliding.

INTRODUCTION

The western cordillera of North America experiences

hundreds of thousands of snow avalanches and numerous

landslides annually. Most snow avalanches follow well

defined topographic indentations on the mountainous slopes

(Butler, 1989). These snow-avalanche paths (fig. 1) are

easily mapped at a variety of scales, so that hazard zones

resulting from snow avalanching may be easily delineated

(Butler 1979, 1986b, 1989; Butler and Malanson 1985; Walsh

and others 1989). Mass movements of earth and rock

material, or landslides for the sake of convenience, are also

common in the cordillera. Steep terrain, seismic triggers, and

unusual precipitation and snowmelt events produce widespread

landsliding in the area (Butler and others 1986).

It has been well documented that forest fires geomorphically

destabilize a burned area, making it more susceptible to

erosion by both snow avalanching (Beals 1910; Munger 1911;

Winterbottom 1974; Harris 1986) and landsliding (Swanson

1981; Morris and Moses 1987; Parrett 1987). The removal

of forest cover particularly affects areas prone to snow

avalanching. Most starting zones for snow avalanches are on

fairly steep slopes of 30-45” (fig. 1). The forest cover in this

environment provides a significant stabilizing influence on the

snowpack, reducing the avalanche hazard. If a forest fire

removes this stabilizing influence (fig. 2). expansion of the

area of snow movement is likely to occur. This in turn can

provide more frequent and larger, and therefore more

dangerous, snow avalanches on the low- angle slopes near

valley bottoms where roads, railroads, tourist facilities, and

communities are likely to be concentrated (Munger 1911;

Winterbottom 1974).

‘Associate Professor of Geography, University of Georgia, Athens,

GA; Associate Professor of Geography, University of North Carolina,

Chapel Hill, NC; and Associate Professor of Geography, University

of Iowa, Iowa City, IA.

202

Figure 1. Typical snow avalanche path, southern Glacier

National Park, Montana. Arrow points to location of figure

2 . Note how lateral boundary of avalanche path exceeds the

protective capacity of the snowshed, a result of destabilizing

forest fires during 1910-1919. Photo by D.R. Butler.
Figure 2. Burr&-over starting zone of the Shed Seven avalanche path shown in figure 1. Dead snags are especially visible

along the skyline. Photo by D.R. Butler.

Areas already susceptible to landsliding are also likely, in the

event of forest fire, to experience reactivation of previously

stabilized landslide deposits (Swanson 1981), and accelerated

erosion on the surface of these deposits by running water will

also occur (Morris and Moses 1987). Burned areas will also

generate landslides whereas adjacent unburned areas do not

(Parrett 1987). It is, therefore, of paramount importance in

mountainous areas where tourism and multiple-use forestry

form the economic base, to know where expansion of snowavalanche paths, reactivation of landslides, and accelerated

erosion is likely to occur in a post-bum scenario.

This study describes how a Geographic Information System

(GIS) may be used to map and study snow-avalanche paths

and landslides, and in turn how information on areas and year

of burning by forest fires and the level of plant revegetation

can be incorporated into the GIS. This allows the delineation

of areas of potential expansion of snow avalanching and

landsliding, as well as areas affected by less hazardous but

geomorphically and environmentally significant accelerated

surface erosion. This information can be used by forest and

park management personnel who need to critically examine

areas of sensitive habitat, or who may be in charge of hazard

analysis in areas of heavy transportation and tourism. In

addition, such information can be used to evaluate sediment

movement and concentrations within hydrologic systems as a

consequence of forest fires and snow avalanching or

landsliding and their spatial/temporal distributions.

THE STUDY AREA

Snow avalanching and landsliding are common geomorphic

occurrences in the Rocky Mountains of northwestern

Montana. Forest fires of varying intensity and extent have

burned broad areas susceptible to both avalanches and

landslides. One area particularly susceptible to both

avalanching and landsliding, a result of a set of unique

topographic and geologic conditions, is Glacier National Park,

Montana (Butler 1979; Butler and others 1986). This park,

created by act of Congress in 1910, preserves approximately

one million acres of wilderness which has never been logged.

Glacier National Park contains a mosaic of vegetational types

dependent on such factors as elevation, slope aspect, position

west or east of the Continental Divide which bisects the park,

and fire history. Many historical tires have burned portions

of the park before and since 1910 (see, for example, BeaIs

1910; McLaughlin 1978; Holterman 1985; Finklin 1986;

Larson 1987). Until recently, it has been the policy of

Glacier Park management to vigorously suppress al1 forest

tires, whether natural or human- caused (Wakimoto 1984).

The 1980s saw a shift in policy, with movement toward a

management plan that would allow natural fire to play a role

in the park ecosystem in designated areas.

Along the southern boundary of Glacier Park, several

widespread forest fves occurred during the period 1910-1919

(Payne 1919). There, numerous snow-avalanche paths

impinge onto the tracks of the Burlington Northern Railroad,

203
L

1Figure 3. Specific study area for snow-avalanche terrain modeling. Dot pattern shows area

of 1936 Swiftcurrent Valley tire which came from across the Continental Divide; stipled pattern shows

the Napi Point fire of 1984 (fig. 5)

which form the park boundary. Snowsheds were built in

1910-1914 to protect the rail line from burial by avalanching;

however, the burning of large areas of forest in and near

avalanche starting zones (fig. 2) expanded the geographic

extent of unstable snow so that avalanches cover broader

swaths of railroad track than were originally covered with

protective sheds (Butler and Malanson 1985).

For this study, we chose to examine a section of Glacier

National Park east of the Continental Divide, which contains

over 100 snow- avalanche paths and dozens of landslide

deposits, and has been subjected to forest fires in 1936 and

1984 (fig. 3). The area chosen is one of the most heavily

visited portions of the park, and has several roads and

backcountry trails which allow access to field sites.

METHODS

Landslide locations (fig. 4), particularly with reference to

landslides occurring in burned parts of the study area (fig. 5a,

b), were mapped on the basis of aerial photointerpretation and

fieldwork (Oelfke and Butler 1985). Landslide type and slope

aspect have also been categorized for these deposits. No

other data have yet been calculated for the landslide deposits

in the study area. Preliminary examination of this mapping

and categorization reveals that generally north-facing, and

therefore moister, landslide deposits of the slumplearthflow

variety would be most likely to be reactivated in case of

forest fire. However, because this portion of the research is

still continuing, we devote the remainder of the paper to the

analysis of snow- avalanche path location.

Because avalanches tend to occur in spatially-distinct

locations, we used a GIS to delineate path location and

analyze the spatial characteristics of sites subject to

avalanching. We wished to determine why snow-avalanche

paths are located where they are in the study area, so that we

could then develop a cartographic model which illustrates

areas of highest probability for areas of new snow

avalanching in the event of a forest fire removing the

vegetational cover. It was therefore necessary to map the

locations of all avalanche paths within the study area shown in

figure 3.

Aerial photointerpretation and field reconnaissance confumed

the location of 121 snow-avalanche paths within the study

area. Field work in 1987 and 1988 revealed that Little change

had occurred in the outer boundaries, or numbers, of

avalanche paths since 1966 when aerial photography was

acquired. Minor extension of the longitudinal boundaries of

some paths occurred as the result of a major high-magnitude

avalanche episode in February, 1979 (Butler and Malanson

1985; Butler 1986a).

204
CANADA

U.S.A. I

FAULT TRACE

NATIONAL

L Rockfall / Rockslide

l Slump / Eorthflow

o Undifferentiated Moss Movement Deposit

Figure 4. Landshde types and locations in eastern Glacier

National Park. Compare to inset map, figure 3, for location

of specific study area.

Figure 5. a. Napi Point (arrow), with rockfall avalanche and

landslide deposits draping its north-facing base. Photo by

D.R. Butler. b. Napi Point (arrow) fire of August, 1984,

where forest fire burned and destabilized a broad area of

landslide deposits. Photo by Brian Kennedy, Hungry Horse

News, Columbia Falls, MT.
The location and area1 extent of each snow-avalanche path

were plotted on 1:24,000-scale topographic maps.

Morphometric data were collected for each path from the

topographic maps, aerial photographs, and field observations.

The morphometric variables were entered into an INFO table

within the ARC/INFO GIS for defining the character of each

path from a geographic and geomorphic perspective. A GIS

thematic overlay of path location was produced and merged

with overlays developed for hydrography, geologic structure,

lithology, topographic orientation, and land- cover type.

Details of the development of these overlays may be found in

Walsh and others (1990).

Most of the GIS overlays were compiled by direct digitization

and transformation of mapped information for precise coregistration with other thematic overlays. Land-cover type

and structural lineaments, however, were characterized

through the digital analysis of Landsat Thematic Mapper

(TM) data (fig. 6). Terrain orientation was characterized by

a U.S. Geological Survey digital elevation model of the study

area (fig. 7).

The land-cover GIS overlay was produced through an

unsupervised classification of a 6 August 1988 TM scene (see

Walsh and others, 1989, for details). Ground control

information for approximately one-half of the avalanche paths

was acquired during the summers of 1987 and 1988 to aid in

cluster-labeling of the land-cover classification. Field data

from other avalanche paths within the park (Malanson and

Butler 1984a, 1984b, 1986; Butler 1985) revealed broadly

similar vegetational types with similar spectral signatures.

Cover-type classes used for this study were water, snow and

ice, bare rock, lodgepole pine (Pinus contorta) forest,

spruce/fir forest (primarily picea engelmannii and &

lasiocaroa), mixed herbaceous, and mixed shrubs.

Figure 6. Landsat TM principal components image of study area, with darker shades representing coniferous forest, lakes

are black, alpine tundra is grey, and light tones representing fire successional lodgepole pine in Swiftcurrent Valley, and

herbaceous plants and shrubs on avalanche paths and landslide deposits.
ELEVATION

CONTOUR INTERVAL SOURCE:

50m USGS 1:25O,OOfl DEM

Figure 7. Digital elevation model of the study area.

UNC-CH DEPT. OF GEOG.

SPATIAL ANALYSIS LABS.

207
FACTOR WEIGHTINGS

Landcover

I

Lithology

I

Slope Angle

I

I

Elevation

DISTANCE BUFFERS

Spatial proximity to geologic structural elements and

hydrologic features (also controlled largely by structural

elements) on the landscape was an important influence on the

geographic distribution of snow-avalanche paths within the

study area (Butler and Walsh 1990). Measurement of the

distance of paths from sills, dikes, faults and lineaments, and

rivers and streams was carried out within the ARC/INFO

environment through the generation of buffers. Buffers are

spatial zones of user-defied diameter that indicate distance

from a specified target phenomenon. Distance measures of

each path to the selected landscape feature were calculated

and added to the path morphometric database. A separate

thematic overlay of buffers surrounding sills, dikes, faults and

lineaments, and rivers and streams was added to the GIS for

integration with the other coverages (fig. 8).

Utilizing the morphometric measures of each path contained

within the INFO tables, frequency counts of avalanche paths

by factors of elevation, slope angle, slope aspect, lithology,

and land cover were determined. The frequency data for each

overlay were then normalized by weighted area measures

(details of the weighting procedure may be found in Walsh

and others 1990). Normalized frequency weightings also

were derived for the proximal measures associated with

spatial buffering. Buffers were weighted by the percent of all

snow-avalanche paths occurring within the various buffer

distances from the target feature.

Figure 8. Schematic diagram of the units of the geographic

information system used to model the spatial probability of

snow avalanche paths in the study area.
RESULTS AND DJSCUSSION

The end result of the GIS analysis, shown in figure 8, was a

spatial probability map illustrating where, based on the factors

and buffers analyzed, snow avalanches are most likely to

develop in the event of removal of forest vegetation by a

forest fire (fig. 9). When a forest fue occurs within the

study area, the boundaries of the fire can be rapidly digitized

and entered into the GIS, and merged with the spatial

probability data displayed in figure 9. Forest fire extent and

plant regeneration can be assessed through high spatial,

spectral, and temporal resolution satellites, such as Landsat

and SPOT. Walsh and others (1981) reported on the role of

Landsat satellite data for delineating and assessing forest

disturbances and levels of forest regeneration. Remotely

sensed measures of plant productivity with time can be

assessed through use of vegetation indices and merged into

the GIS as distinct multi-temporal landcover coverages.

Assessment of the information in the GIS follows. Did the

fire bum an area that is likeIy to become more prone to snow

avalanching? If the burned area coincides with terrain

categorized as high probability, the answer is yes. Park

managers can almost certainly expect currently-existing path

margins to expand, as occurred in the southern portion of the

park during the 1910-1919 period described earlier, and new

paths will probably also develop in those areas marked on

figure 9 as high probability areas. If the burned area

coincides with the area of medium avalanche probability,

expansion of areas of pre-existing avalanching may be likely,

but it is questionable if new avalanche-prone areas will

become established. Little concern for expansion of

avalanching need be given if the iire occurred in the regions

of low avalanche probability.

Temporal data could also be added into the GIS in order to

examine the effects of time passed since a fire. For example,

the portion of the study area burned in 1936 currently

supports a successional lodgepole pine forest assemblage.

This provides stability and anchorage for snow on the slopes,

but during the lirst several years after the fire more unstable

snow would have existed. High, medium, and low hazard

likelihood categories could be added to the GIS based on time

since fire: high hazard/spatial probability during the first

year after fire; medium hazard/spatial probability during the

early successional stages prior to conifer establishment (S-10

years in Glacier Park); and low hazard/spatial probability

once the forest has reestablished itself and stabilizes the

snowpack. However, once some areas are opened to snow

avalanching, it is likely that avalanching will continue there

and that succession to coniferous forest will be indefinitely

retarded; the still-bare upper reaches of the burned and

expanded avalanche paths along the southern margins of the

park are mute testament to the disruptive longevity of fire in

avalanche-prone terrain.

SPATIAL PROBABILITY

OF PATH LOCATION

- HIGH

MEDIUM

LOW

meters

o- 2000 4000

UNC.CH DEPT. OF CEOC.

SPATIAL ANALYSIS LABS.

Figure 9. Composite probability of where new avalanche

paths should develop in the event of removal of forest

vegetation by a forest fire.

209
ACKNOWLEDGMENTS

The authors acknowledge the fmancial support of NASA

(Grant Number NAGW-926), and the computing facilities and

financial support provided through their respective

departments and universities. Logistical support during Iield

work was provided by the friendly personnel. of Freda’s, West

Glacier.

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National Park, Montana: meteorologic and climatologic

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snow avalanche hazard, Glacier National Park, Montana,

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subalpine snow-avalanche slopes. The Canadian

Geographer 33(3), 269-273.

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Development 5(2), 175-182.

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rockfall avalanches, northeastern Glacier National Park,

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6(3), 261-271.

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locations, eastern Glacier National Park, Montana.

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80(3), 362-378.

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fuel breaks: implications for fire management. Journal

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173, 12pp. Washington, D.C.: Government Printing

Office.

Oelfke, J.G., and D.R. Butler, 1985. Landslides along the

Lewis Overthrust Fault, Glacier National Park, Montana,

The Geographical Bulletin 27( 1), 7-15.

Payne, W.W., 1919. Glacier National Park.

Superintendent’s Report, in: Report of the Director of the

National Park Service to the Secretary of the Interior for

the Fiscal Year Ended June 30, 1919. Washington, D.C.:

Government Printing Office, pp. 230- 236.

Parrett, C., 1987. Fire-related debris flows in the Beaver

Creek drainage, Lewis and Clark County, Montana. U.S.

Geological Survey Water-Supply Paper 2330, pp. 57-67.

210
Swanson, F.J., 1981. Fire and geomorphic processes. In:

Fire Regimes and Ecosystem Properties, U.S.D.A. Forest

Set-vice General Technical Report WO-26. Washington,

D.C.: Government Printing Ofice, 401-41-O.

Wakimoto, R.H., 1984. Current lire management research in

Glacier National Park. Western Wildlands lO(3). 20-25.

Walsh, S.J., L. Bian, D.G. Brown, D.R. Butler, and G.P.

Malanson. 1989. Image enhancement of Landsat

Thematic Mapper higital data for terrain evaloarion,

Glacier National Park, Montana, U.S.A. GuxarlO

International 4(3), S-58.

Walsh, S.J., J.D. Vitck, and M.S. Gregory. 1981. Landsat

digital analysis of forest clearcuts and reforcs~tjon. In:

Remote Sensing for Resource Management (c.J.

Johannsen and J.L. Sanders, eds.); (Soil Conservation

Society of America) Ankcny, Iowa, pp. 159-171.

Wintcrbottom, K.M., 1974. The Effects of Slope Angie,

Aspect and Fire on Snow Avalanching in the Field, Lake

Louise, and Marble Canyon Region of the Canadian

Rocky Mountains. Unpublished Master’s Thesis,

Department of Geography, University of Calgary,

Calgary, Alberta.

Walsh, S.J., D.R. Butler, D.G. Brown, and L. Bian. 1990.

Cartographic modeling of snow avalanche path location

within Glacier National Park, Montana. Photogrammetric

Engineering and Remote Sensing 56(5). 615-621.

211
GIS APPLICATIONS IN FIRE MANAGEMENT AND RESEARCH

Jan W. van Wagtendonk’

&Stract-ln 1985, Yosemite began using a geographic information system as a for tire management and

research. The system has been used to compare historic fire incidence over a range of topography and

vegetation types. Parkwide fuel inventories and prescribed bum units have also been depicted to predict

fire behavior and effects. Research applications have included a lightning strike incidence analysis and a

fire regime analysis hascd on climate, vegetation, fueh, and topography. Current projects include

developing a l-hour-timclag tieI moisture theme by coupling the GIS with the BEHAVE fire behavior

system to predict the behavior and spread of large fires.

When Yosemite National Park was established in 1890, the

enabling legislation spwificd that all “timber, mineral

deposits, natural curios&s or wonders in the area be

presctvcd from injury and retained in their natural condition.”

Since then, the natural resources of the park have changed.

Some of this change has reswltcd from past Iirc suppression

policies which were intended lo prcscrvc the timber from

injury, but which have significantly altered vegclalion

composition and have allowed fuels to accumulalc.

In 1970, a program of prcscribd burning was initiated to

mitigate these conditions; and in 1972, lightning iires were

allowed to burn in much of the park under a specific set of

prescriptions (van Wagtcndonk 1978). These programs WCK

initiated based on the results of numerous research studies and

cxtcnsivc analyses of field data. To aid in theses analyses, a

geographic information system (CIS) was installed in 1985

(van Wagtendonk and Grabcr 199 1).

In the past, resource information was scattered in files and

publications, and on maps of varying scale and accuracy.

The advent of relatively inexpensive microprocessors, highresolution graphics, and large mass-storage devices has made

lhc USC of computers for entering, storing, rctricving, and

analyzing resource information a practical tcchnotogy. Such a

system is being used to help Park Service personnel make

informed fire management decisions, monitor tong-term fire

effects, and research complex fire relationships.

Data used to &v&p the various data themes were obtained

from several sources. Digital data for elevation, slope, and

aspect were obtained from the U.S.G.S. Mapped data from

the park were used for fire management zones, vegetation

type, fuel model, and past fire occurrence. Lightning strike

data were obtained from the Automated Lightning Detection

System operated by the Bureau of Land Management al the

Boise Interagency Fire Center. Digital satellite imagery was

usd to reline the vcgctation data.

The park’s vcgctation and fuels data are being surveyed in the

field. The systematic surveys now being conducted mark the

‘Research Scientist, National Park Service, Yosemite National Park,

El Portal, CA.

212

beginning of long-term monitoring of park resources. They

will provide baseline data that will be used to verify

classifications of remotely sensed imagery.

The sofiware currently in use is the Geographical Resources

Analysis Support System (GRASS) developed and supported

by the U.S. Army Corps of Engineers (Westervett 1988). 11

is a raster-based system with vector and image analysis

capability and employs the UNIX operating system. GRASS

was selected because it is in the public domain and runs on a

computer with an open architecture.

FIRE MANAGEMENT APPLICATIONS

The first use of the GIS was to evaluate the rote fire has

played in Yosemite’s ecosystems (van Wagtendonk 1986).

Fire has been an important factor in these systems for

thousands of years and is of considerable scientific and

political interest.

Fire records dating back to 1930 were reviewed and the point

of ignition and area1 extent of each lightning fire were

digitized. These were than compared to information from the

other themes. This analysis showed that fire occurrence and

size varied significantly with vegetation type, elevation zone,

topographic position, and drainage basin. Table 1 shows the

distribution of lightning tires by vegetation type. Wcstfacing slopes received 67 percent of the fires greater than 50

acres in size. In addition, fires were significantly smaller

during the 12-year period before the prescribed natural fire

management program was implemented in 1972 than during

the following 12 years.

The GIS was also used to develop a fuel model map for the

park. Fuel models are generalizations of actual fuel

parameters and are used to predict fire behavior (Albini

1976). The vegetation and slope themes were combined with

field sutveys to assign a fuel model to each area of burnable

vegetation.

The GIS depicts fire management zones which divide the park

into units where different fire strategies are employed. These

units include the routine suppression zone where all fires are

put out regardless of origin, the conditional zone where
Table I. Distribution of Lightning fires by vegetation type, Yosemite

National Park, 1930- 1983. The n&r of fires per milt ion a- per year

is sbmn in the Last column.

Vegetation Type

Chaparral UoodLand

Imer Mixed Conifer

upper Mixed conifer

I&d Fir

Area of Park Liabteniae Fires

Acres % hiodwr % #/D/Y

31,975 3.1 3 8 1.9 22.0

146,935 7.6 563 27.7 70.5

108,669 15.3 513 25.4 87.3

63.951 24.3 327 16.2 S4.7

Indgqmle Pine 232,202 21.5 467 23.1 37.2

Subalpine 59,383 8.6 3 6 I. 8 Il.2

Alphf! 110,391 9.5 3 8 3.6 12.2

Hiscellaoeous 7,613 10.2 4 1 .3 14.6

Total 761.319 loo. 0 2.023 100.0 49.1

lightning fires are allowed to bum before and gficr the fire

season based under specific conditions, and the prescribed

natural fhe zone where lightning fires are allowed to bum at

any time based on prescribed conditions. Thcsc zones were

revise following the Greater Ycllowstone Area tires in 1988:

bu&s were established between adjacent lands managed for

different objectives. The GIS made this easy.

There are prescribed bum units within the suppression and

conditional zones. Park personnel set fires in thcsc units to

meet specific management objectives. Maps of thcsc

prescribed bum units are ais0 on the systen and arc linked to

data bases that include information on previous burns and

bum schedules. Prior to burning, GIS maps of each unit arc

prcparcd to show topography, fuel models, and ITSOUrCCS of

special concern such as archwlogical sites or cndangercd

species habitat. These maps am used to plan burns and to

predict fire behavior and effects.

FIRE RESEARCH APPLICATIONS

A fire regime analysis based on climate, vegetation, fuels,

and topography is underway. Climatic data have been

collected at a network of weather stations, and climate themes

am being created by extrapolating these data to the rest of the

park by means of topographic variables, temperalure lapse

rates, and solar radiation equations. These themes, in

conjunction with fire incidence, are being used to develop

relationships with fire regime parameters such as fire

frequency, intensity, and size.

Data on lightning strikes have been analyzed to dotcct spatial

patterns and predict fire occurrence. Lightning strikes Were

significantly correlated with elevation but not by slope and

aspect. Since vegetation is strongly related with elevation,

vegetation also showed a significant effect on lightning strike

occrm‘ence (table 2). Although the vegetation types in Table

2 am slightly different than those in Table 1, a comparison

Table 2. Percent of -ad number of Ligbtnlng strih by

vegetation type, Yasemite National Park, l!Bs- 1989.

vegetation % 1985 lS66 1981 1988 1989 Total

Chaparral 3.1 2 7 12 2 1 2 7 3 2 III

7.6 7 3 25 49 6 7 7 7 291

Mite Fir 15.3 193 5 8 114 130 168 663

Red Fir 24.3 378 9 8 151 259 333 1219

Ldgepole 21.5 301 135 130 292 380 1238

mitebark 8.6 123 5 9 71 115 183 551

Alpine 9.5 115 8.5 5 3 161 266 614

10.1 116 5 8 66 117 182 539

Total 100.0 1326 530 655 1166 1555 5234

213
shows that the greater number of strikes in the lodgcpole

pine, subalpine, and alpine types did not result in a

propo&naly larger number of fires. In those types burning

and fuel conditions are not condusive to fire ignition and

spread.

The locational accuracy of the strike detection system is

reported to be approximately one mile (Krider and others

1980). Additional analyses will be performed in which the

data will be adjusted to compensate for this error. The GIS

will draw a circle with a l-mile radius around each slrikc and

then select a random point within the circle.

The GIS’ most important application in fire management and

resmrch will be the prediction of growth of large fires.

Initial steps have been taken to develop a map of fuel

moisture based on a given set of weather conditions along

with topographic, vegetation, and fuel variables (Andrews

1986). Elevation is used to adjust temperature, while slope

and aspect adjust for diffcrcnccs in solar radiation. Fuel

model and vegetation type determine how much shading

occurs. The GIS combined these five themes into over

14,000 unique catcgorics. When these were linked to the

SITE module in BEHAVE (Andrews 1986), a fuel moisture

value for each category was calculated.

Once fuel moisture is determined, fire behavior predictions

can be made by linking the GIS directly to a large fire growth

simulator. Bcvins and Andrcws (1989) are currently working

on such a simulator; it operates in GRASS and combines the

effects of moisture, wind, and topography on fire behavior.

Outputs from the simulator will be residence time, flame

length, and rate of spread. These could be displayed as

maps, as could the area burned by time increments.

Predictions of tire growth will be invaluable to the manager

who has to make a decision about a fire today based on the

fire’s expe.xt& location a month from now. These decisions

will be easier to make if information about predicted future

fire behavior and effects is available. For instance, a decision

to suppress a fire because of smoke problems could be

avoided if information about fire spread, fuel accumulation,

and smoke dispersal were available. This may bc available

when all of the various predictive models are fully developed

and linked with a GIS that contains current rcsouree

information.

CONCLUSION

The GIS in Yosemite has already proven to be a useful tool in

fire management and research. Fire operations have become

more efIicicnt, and the role tire plays in park ecosystems is

better understood. Future applications in rca-time situations

will increase the utility of this system. Such applications will

include tire planning, suppression operations, and post-fire

rehabilitation efforts. GIS technology promises to make

increasingly accurate information more accessible to decision

makers and researchers; thus make possible more effc&e

protection of our park’s valuable resources.

LITERATURE CITED

Albini, Frank A. Estimating wildfire behavior and effects.

General Technical Report INT-30. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Intermountain

Forest and Range Experiment Station; 1976. 92 p.

Andrews, Patricia L. BEHAVE; fire behavior prediction and

fuel modeling system-bum subsystem, part 1. General

Technical Report INT-194. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station; 1986. 130 p.

Bcvins, Collin D.; Andrews, Patricia L. Fire Growth

Simulation Model. Final Report INT-89417RJVA.

Missoula, MT: Systems for Environmental Management;

1989. 5 p.

Krider, E. P., R. C. Noogle, A. E. Pifer, and D. L. Vance.

Lightning direction-finding systems for forest tire

detection. Boston, MA: Bulletin American Meteorological

Society; 61(9): 980-986; 1980.

van Wagtendonk, J.W. 1978. Wilderness fire management in

Yosemite National Park. In: Schofield, Edmund A.,

editor. EARTHCARE: global protection of natural areas,

proceedings of the 14th biennial wilderness conference;

1975 June 5-8; New York. Boulder, CO: W&view Press;

1978: 324-335.

van Wagtendonk, Jan W. The role of fire in the Yosemite

Wilderness. In: Lucas, Robert C., compiler. Proceedingsnational wilderness research conference: current research;

1985 July 23-26; Fort Collins, CO. General Technical

Report INT-212. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station; 1986: 2-9.

van Wagtendonk, Jan W.; Graber, David M. Developing a

geographic information system for the Sierra Nevada

national parks. In: editor. Proceedings of the Conference

on Science in the National Parks; 1986 July 13-l 8; Fort

Collins, CO. Washington, DC: The George Wright

Society; 1991: vol. 7 (in press).

Westervelt, James. An introduction to GRASS: geographical

resources analysis support system. Champaign, IL: U.S.

Army, Corps of Engineers, Construction Engineering

Research Laboratory; 1988. 10 p.

214
FIREMAP

George L. Ball and D. Phillip Guertin’

Abstract-FIREMAP is a model Tar simulating surfxc fire spread through helcrogcncous lucls and over

non-uniform terrain. The nl&] was sonstrucrcd using PROMAP, a language which allows dynamic spatial

models m be cons~~c~zd using raslcr GIS data bases. The GIS syslcn> is used to construct the necessary

input data Of fuel lypcs, moislurcs, Slope, wind speed and wind direction. Ths model has been tested

against a set of conditions under which specified fire perimcler shapes should h I: cxpeclcd. The results of

the tests indicate that the fire shapes developed using data representing actual field conditions arc

reasonable. A model such as FIREMAP has application for prescribed hums. evaluating lirc cffcc~s, and

fire in the wildland/urban interface.

INTRODUCTION

Predicting the spread of fire is qually important for the use

of fix as a managcmcnt tool as it is in fire suppression. The

difficulty of predicting the direction and speed with which a

fire will move is cornpoundcd when the iirc is burning in a

rugged terrain of mixed fuel lypcs. The dcvelopmcnt of a

usable model that could gcncratc and display ihe possible path

of a fire using data from an actual silt in a simple and

straight forward manner would be cxtrcmcly beneficial.

The BEHAVE system (Andrcws 1986) gave fire pcrsonnci a

tooI which could bc used to calculate various fire

characteristics based on the Rothcrmcl qualions (Rothcrmcl

1973). BEHAVE allowed lhc fire behavior analyst to use a

set of measured conditions pertaining to lhc fire arca and

predict the rate of spread of the fire as well as scvcral other

factors. The rate of spread is calculated for the maximum

direction of spread which is usually dclcrmincd by the slope

of the (crrain and the wind direction. Additionally,

adjustments arc available to give the rates of spread for the

flanking and backing fires. It is impractical to try to calculate

all possible directions and try to chart the iirc over any

distance for extcndcd periods of time. As the iire pcrimctcr

becomes larger, changes in the variables start to incrcasc so

quickly in complex tcrrajtl that it bccomcs no longer possible

to try to predict the entire lirc pcrimclcr.

Attempts to model fire spread using computers has been an

ongoing project in many locations. In Australia, GKXX

(1983) and Green and others (1983) have developed a model

of Gre spread for bush fires (grassland and shrub vc@.ation

types). Although the model seems to provide a reasonable

fire shape it has certain disadvantages. First, the use of an

ignition template predetermines what fire shape will bc

gencratcd (in this case an ellipse). Second, is the assumption

that fire spread is by the shortest path thm the ignition point.

‘Research Specialist, Advanced Resource Technology Program,

University of Arizona, Tucson, AZ; Assistant Professor Watershed

Management, IJnivLtrsity of Arizona, Tucson, AZ.

This ignores the fact that as the fire grows the influcncc of

the ignition source diminishes to Zero.

A computer program written by Ecnigenburg (1987) provides

a method for calculating the lirc dir&on and ralc of spread.

It is only applicable on small plots and rquircs the use of

pre-marked locations to gather data about the fire. This

makes it impractical for use in most situations.

Cohen and others (1989) have crcatcd a computer based

simulation of fire that is used to test the stralegics of fire

manapcmcnt by deploying simulated ljrc fighting equipment.

Although they indicate that the environment they are using is

derived from Ycllowstonc National Park, there is no

indication as to how the fire charactcris(ics arc calculated and

what algorithms are used lo spread the fire. The use of this

program is not to predict the spread of fire but the

managcmcnt of fire. Again, this program is not practical for

use in fire spread prediction.

A model called FIREMAP was conccivcd as a method of

prcdicling the spread of a surface lire through hctcrogcncous

l’ucls and over non-uniform terrain by linking to a CIS data

base (Vasconcclos 1988; Vasconcclos and others 1990).

Vasconcclos used the Map Analysis Package (Tomlin, 1986)

which is a GIS available on IBM PCs and clones. The

FIREMAP model was applied to data collcctcd during a fire

in Ivins Canyon, located in the Spotted Mountains in

east-central Arizona. The correspondence bctwccn the actual

Grc and the model was encouraging enough to pursue the

timber development of the model.

Although the model produced results that mimicked the actual

fire, there was concern about the accuracy of the model due

to the underlying algorithms employed by the MAP program.

The basic premise of the Spread operator in the MAP GIS is

to move uphill. Although this is a reasonable assumption for

fix, it ignores the fact that lire spread is a result of local

changes in the neighborhood of the flame front. What was

needed was an algorithm that would display the same

characteristics as an actual fire and still maintain the

215
integration with the GIS data base. If such a model could be

constructed it would have to be vcrihcd against some known

fire shapes.

Three important papers concerning fire shape proved to be

relevant to the FIREMAP problem. The papers by Pect

(1967), Van Wagner (1969) and Anderson (1983) present a

comparison of fire shapes under wind driven conditions. The

wind speed ranged from low (2-4 miles per hour) up to

modcrate (12-15 miles per hour). The corresponding shapes

range from ovoid to elongated ellipse. These shapes arc the

result of fitting mathematical shapes to approximate the actual

observed fire shapes. A test of the FIREMAP model would

be to run it using a set of conditions under which the shape of

the fire would be predictable. The remainder of this paper

will discuss the development of the second version of

FIREMAP and give examples of the results of the tests

against predicted fire shape.

PROMAP

The original FIREMAP mode! was hampcrcd by the

deficiencies of the GIS program that was used to implement

it. An analysis of what would be required to use GlS data

bases to model processes such as fire led Ball (1990a, 1990b)

to author PROMAP. PROMAP is a simulation language

based on raster GIS. It overcomes the limitations of

traditional GIS programs by using real numbers and the

algorithms used in the operators arc designed for iterative

operations. These are essential components in dynamic

simulation. The basic premise of PROMAP is the principle

of cellular automata (Wolfram 1984; Couclelis 1985, 1987;

Gimblctt 1989, Casli 1989; Ball 199Oc).

Cellular automata theory is based on the premise that

processes can be described by the influences of neighbors. In

this case the neighbors are adjacent cells in the data base.

PROMAP make use of this idea in the action of many of its

operators. This allows the development of models that

respond to neighborhood influences. The spread of fire is

dependent on what it encounters in the environment as it

moves across the landscape. By utilizing cellular automata

theory, the spread of fire can be related to the progression of

the flame front from one cell to the next. Therefore, what is

required is an algorithm which incorporates the transitions

from one cell to another into neighborhood effects.

The implementation of FIREMAP in the second version

operates from what would normally be considered the

ncighbot-ing cell. In this manner the algorithm can scan the

surrounding area and determine if there is more than one

potential direction from which fire might spread into the cell.

Every cell is considered to be homogeneous as to fuel type,

slope and other variables. Consequently, the fire

characteristics of each cell can be validly computed using

Rothcrmel’s approach (Rothermel, 1972; Andrcws, 1986).

Each cell, however, can have its own characteristics. The

direction of maximum spread in one neighboring cell may be

away from the ccl I the algorithm is currently occupying.

216

Another neighbor may have a direction of maximum spread

directly toward the current cell. In this case the fire would

spread from the second cell because the fire will spread faster

from it then from the first cell. In this manner the modei

accounts for the diffcrcnces in neighborhoods as the fire

progresses across the landscape.

Testing the Model

To test the function of FIREMAP we established a set of

criteria which would allow us to predict the shape of a fire.

This set of criteria describes what WC call the Zero State

Conditions. Under zero state, we assume that the area of the

fire is uniform as to li.rel, zero percent slope, zero wind, and

all other factors held constant. Under these conditions a fire

started as a point source would bum in a circular pattern as in

ligure 1.

If we relax the condition of zero wind and allow the fire to be

wind driven, then the shape of the fire should begin to

approximate the shapes predicted by Peet, Van Wagner, and

Anderson. With a 4 mile per hour wind the shape of the fire

created by the model is seen in figure 2. The shape is not as

elliptical as the mathematical formulation because of the

square grid cell on which the model is running. The overall

shape, however does show the expected heading fire with

reasonable flanking and backing fires. Figure 3 shows the

result of a wind shift during the simulation.

In figure 4 the right half of the simulation has been made

using random fuel moistures in the range of O-20%. The

overall shape of the simulation compared to the uniform

moisture simulation shows a more realistic tire pattern.

The ability of the FIREMAP simulation to produce shapes

corresponding to the expected mathematical shapes is

encouraging. The next step will be to compare the simulation

to actual fire shapes using controlled burns.

FUTURE IMPLICATIONS

The capabilities found in FIREMAP show the potential for the

development of a complete fire management tool. Two areas

can be used as examples of how spatial dynamic models of

this type could be used for fire management.

Fire Effects

The capability of FZREMAP to produce a realistic simulation

of surface fire spread can be extended to post-fire effects.

Since the intermediate calculations of the fire equations

provide information concerning fire characteristics, such as

fire intensity, the spread map can be altered to depict a map

of those characteristics. For example, using the map of lire

intensity, a model can be generated that would show what

percentage of certain type of vegetation wouid be killed

(Kunzmann and others 1990). Once this type of information

is available, the next step is to consider what vegetation

changes will occur over time.
Figure l--Fire spread simulation with zero wind speed.

Unless otherwise noted, all simulations used a fuel model 9,

2% fuel moisture, 100% live woody moisture, ZCfO slope, and

wind direction of zero degrees. Duration of the bum is 400

minutes with cell sizes of 50 feet.

Figure 3--Fit-C spread simulation with a wind speed of 4 milts

per hour. After 400 minutes the wind was shifkd to 45

dcgrws for an additional 100 minutes. All other conditions

arc the same as in figure 1.

Figure ?--Fire spread simulation with a wind speed of 4 miles

per hour. AlI other conditions arc the game as in figure 1.

Figure 4--Fire spread simulation with 4 mile per hour wind

for 480 minutes. The conditions for part a are the same as in

figure 3. In part b the fuircl rnois~ures arc randomly

distributed across the area with values from 0% to 3-070. All

other conditions are the same as in part a.

117
Risk Management

Even at the level of the current capabilities of FIREMAP, the

application of this type of model to risk management is

cvidcnt. The ability of the fire analyst to anticipate flame

lengths, intensity and direction of spread of a fire would

provide better utilization of effort and reduce the possible loss

of life and property when managing fires.

In areas of the urban/rural interface, the use of FIREMAp

could provide information on potential property loss of forest

areas managed for fuel reduction versus areas that are not

managed. This could have a significant effect on insurance

rates and on gaining acceptance by the public for prescribed

bum policies.

CONCLUSION

The ability of the FIREMAp model to simulate the spread of

surface fire under specific conditions indicates that the use of

this technology can provide better management tools. Further

work will need to be done on improving the mathematical

descriptions of tire for use in spatial dynamic models. As the

mod& become more sophisticated and are verified by field

tests, their application for fire management, fire ecology and

related areas is readily apparent

LITERATURE CITED

Anderson, Hal E. 1983. Predicting wind-driven wild land fire

size and shape. U.S. Forest Service, Research Paper

INT-305.

Andrews, Patricia L. 1986. BEHAVE: Fire behavior

prediction and fuel modeling system . BURN subsystem,

Part 1. U.S. Forest Service, General Technical Report

INT-194. 13Opp.

Ball George L. 1990a. A Spatial Dynamic Approach to

Ecological Modeling: Simulating Fire Spread. Ph.D..

Dissertation, University of Arizona, May 1990. 99pp.

Bail George L. 199Ob. PROMAp: Spatial Modeling with

Geographic Information Systems Data Bases. International

Journal of Geographic Information Systems. (Submitted).

Bail George L. 1990~. PROMAP: Cellular Automaton in a

GIS framework. Annual Meeting of the Association of

American Geographers in Toronto, Canada, April 1990

(Abstract).

Casti, J.L. 1989. Alternate Realities, Mathematical Models of

Nature and Man. John Wiley and Sons, New York.

Cohen, Paul R., Michael L. Greenburg, David M. Hart, and

Adele E. Howe. 1989. Trial by Fire: Understanding the

Design Requirements for Agents in Complex

Environments. AI Magazine 10(3), Fall 1989. pp 34-48.

218

Couclelis, H. 1985. Cellular Worlds: A Framework for

Modeling Micro-Macro Dynamics. Environment and

Planning A, Vol 17, pp. 585-596.

Couclelis, H.1987. Cellular Dynamics: How Individual

Decisions Lead to Global Urban Change. European

Journal of Operational Research. Vol. 30, pp. 344-346.

Eenigcnburg, James E. 1987. Computer Program for

Calculating and Plotting Fire Direction and Rate of

Spread. U.S. Forest Service General Technical Report

NC-l 17.

Gimblctt, H.R. 1989. Dynamic Modeling in GIS: A Cellular

Automaton Approach to Modeling the Growth Behavior of

Urban and Rural Development. In: Proceedings of the

GIS National Conference ‘89. Ottawa, Ontario, Canada.

Green, David G. 1983. Shapes of Simulated Fires in Discrete

Fuels. Ecological Modclling, 20. pp 21-32.

Green, D. G., A.M. Gill, I.R. Noble. 1983. Fire Shapes and

the Adequacy of Fire-Spread Models. Ecological

Modelling, 20. pp 33-45.

Kunzmann, Michael R., Peter S. Bennet, and George L. Ball.

1990. The use of Geographic Information Systems for

Ecological Modeling: The prediction of LD50 Tree

Mortality from fire intensity. Proceedings of the Resource

Technology 90 Symposium, Washington, D.C.,

November 1990.

Peel, G.B. 1967. The shape of mild fires in Jarrah forest.

Australian Forestry 31(z): 121-127.

Rothermel, Richard C. 1972. A mathematical model for

predicting tire spread in wildland fuels. U.S. Forest

Service Research Paper INT-I 15.

Tomlin, C.D. 1986. The IBM Personal Computer Version of

the Map Analysis Package. Cambridge: Harvard Graduate

School of Design, Laboratory for Computer Graphics and

Spatial Analysis.

Wolfram, S. 1984. Cellular Automata: A Model of

Complexity. Nature, 31:4. pp. 419-424.

Van Wagner, C.E. 1969. A Simple Fire-Growth Model. The

Forestry Chronicle, 45(2).

Vasconcclos, Maria Jose. 1988. Simulation of Fire Behavior

with a Geographic Information System. Unpublished

Masters Thesis, University of Arizona.

Vasconcclos, M., P. Gucrtin, and M. Zwolinski. 1990.

“FIREMAP: Simulation of Fire Behavior v A GIS

Supported System.” Symposium Proceedings: Effects of

Fire Management of Southwestern Natural Resources.

Tucson, AZ. November 14-17, 1988. GTR RM-191.

Fort Collins, CO. USDA, Forest Service, Rocky Mt.

Forest and Range Expcrimcnt Station. pp 2 17-221.
I’HE ART OF LONG-RANGE FIRE WEATHER FORECASTING

Francis M. Fu*jioka’

Abstract-On the heels of the Yeilowsionc fires of 1988, a Cabinet-level tire management review [cam

recommended research “to improve the ability to predict severe tire behavior, conduct long-term weather

forecasting, and identify past abnormal events.” In a 1989 report, a Forest Sewice task force idenlified a

high priority need for long-range weather forecasting, in support of prescribed fire managemenl.

Research on long-range fire weather forecasting started in 1986 is described, particularly a newly devclopcd

system for forecasting fire weather elements in a monthly timeframe. Some fundamental diftkcnccs

hctween current and fuurure foracasls arc envisioned, not only in terms of content, but also in preparation

and review. Both forccasrcr and user must come to grips with the quality of forecast information, which

has implications for both long-range forecasting and long-range planning.

INTRODUCTION

The Yell~~st~nc fires of 1988 have iefi scorch marks, not

only among the Park’s surviving trees, but also in the annals

of United States fire managcrncnl policy. The fire event was

scrutinized at the highest level of fcdcral govcmmcnt, when

the Sccrctarics of Agriculture and Interior convened a fire

managcmcnt team to rcvicw national fire managcmcnt policies

and practices. Among the rccommcndations in the team’s

report’ was the need for research “to improve the ability to

predict scvcrc fire behavior, conduct long-term wcathcr

forecasting, and identify past abnormal events.”

On a separate but rclatcd issue, a Forest Service task force

cstahlishcd to review prescribed fire managemcnl policy

rccornrncndcd in 1989 that high priority be given to research

on long-range weather forecasting, to support prescribed

natural fire management. Fire planners need to detcrminc, as

far ahead as reasonably possible, the buildup, duration, and

lcrmirlaljon of weather-inciuccd fire potential. The assignment

is hardly trivial; even in our most common experiences, each

of us can probably recall an errant forecast, at that not cvcn a

long-range forecast.

Some rcflcction is warranted on cxpcctations for long-range

fire wealhcr forecasts. This paper describes the goals,

progress, and prospects of a program for long-range fit-c

weather forecasting research, currently being conducted at the

Pacific Southwest Research Station @SW), in Riverside,

California. The first section outlines the objectives of the

rcscarch program, including a paradigm for the application of

weather forecast information, irrespective of the forecast

horizon (i.e., seasonal, extended-, medium-, or short-range).

Rcscarch results obtained to date arc then dcscribcd. Finally,

some conjectures arc made on the nature of fire weather

forecasts of the future.

‘Pacific Southwest Rescarch Station, Forest Service, U.S. Departmcm

of Agriculture, Riverside, CA.

‘Report on Fire Management Policy, USDAIUSDI, December 14,

198X. Unpuhlishcd report available at the USDA Forest Serv., Fire

and Aviation Mgmt., Washington, D.C. 20090.

FIRE WEATHER RESEARCH OBJECmS

The research on long-range fire weather forecasting at PSW

was inspired by the information needs articulated by fire

managers and fire scientists in 1985 (Rios, 1989). The group

recognized that fire management planning required weather

forecast information at lead times that varied from hours to

months (Table 1). In this paper, seasonal refers to a go-day

forecast, extended-range to a 30-day forecast, medium to the

3-14 day range, and short-range to forecasts of less than 3

days. Strategic planning, therefore, requires seasonal and

cxtcndcd-range forecasts, preparedness planning requires

medium-range forecasts, and implementation planning utilizes

short-range forecasts. Particular effort was focused on the

concept of a 30-day fire potential forecast for national level

planning within the Boise Interagency Fire Center.

Eventually, the Intelligence Section at BIFC developed a

process for creating 30-day categorical forecasts of fire

potential for the contiguous United States.

The purpose of the fire weather forecasting research at PSW

is to develop lire weather forecast products identified (Table

I), but not generally available. In 1987, research was

initiated to develop models for a monthly forecast of mean

aficrnoon dry-bulb temperature, dewpoint temperature,

windspccd, and precipitation frequency for the U.S.

(precipitation frequency is &find as the number of days in ,

the month that precipitation exceeds 0.1 inch). In 1988,

research began on medium-range forecasts of the daily

variations in these variables, over a period of (nominally) 10

days. In 1989, work commenced on the feasibility of

forecasting seasonal fire climate, particularly in relation to El

Nino and La Nina events (see Philander, 1989, for a good

description of these events).

An equally important goal of the research program is to

evaluate uncertainties in the forecasts. It is well-known that,

by extending the forecast further into the future, the quality of

the forecast can be seriously degraded. If the probabilistic

character of the forecast uncertainties is described, the user

can assess the risk inherent in using the forecast information

in the decision process.

219
Table l--The lead times for weather forecast information vary, depending on

the mmagemnt decision under consideration.

strategic Prem Immlementation

Decision Seasonal. 30-15 days 14-6 days 5-3 days 3-l days < 1 day

4x/yr 2x/ma Zx/wk Daily Zx/day Zx/dav

staffing and

support (BIFC X X

SeYeti ty

fimd requests X X

Nati onal

-e sq?8t

iaentify

1 ocate X X

Alert

SteKing

Ievel I

X

X

X X

faa%

Level n X

Deployment X X

Using Forecast Uncertainty Information

In its report, the Forest Service Task Force on Prescribed

Fire Managcmcnt Criteria recommended a risk assessment

procedure comparable to decision analysi?. Decision

analysis provides a means of evaluating the merits of decision

alternatives, weighted by information uncertainty (e.g.,

wcalher forecasts), and the values at risk (fig. 1). An

example by Seaver and others (1983) shows how uncertainty

information is used.

$26,243

$6,496,121

Figure l--Decision tree from Seaver and others (1983)

illustrates how decision analysis integrates information on the

uncertainties and the values of decisions and their outcomes.

‘Report of the Task Force on Prescribed Fire Management Criteria,

Forest Service, 1989. Unpublished report available at the USDA

Forest Serv., Fire and Aviation Mgmt., Washington, D.C. 20090.

In an escaped tire situation analysis, a tire manager considers

whether to suppress a tire at (A) 7 hectares, or at (B) 40

hectares. The loss is much less at 7 hectares, but the

probability of successfully implementing A is also small. The

losses and probabilities can be depicted on a decision Ime

Suppose we decide, as a rule, to pursue that course of action

which results in the smallest expected loss. The information

in the decision tree can be used to calculate the expected loss

for each decision:

Expected loss for A = probability of success of A * loss with

success of A

+ probability of failure of A * loss

with failure of A

= 0.146*$26,243 +0.854*$6,496,121

= %.5,551,519

Expcctcd loss for B = probability of success of B * loss with

success of B

+ probability of failure of B * loss

with failure of B

=0.610*$130,397+0.390*$13,444,313

= $5,322,824

The above analysis suggests that the alternative to suppress at

40 hectares is optimal. Although a smaller loss would be

incurred by implementing A successfully, the probabilities

indicate that, in the long run, choosing A over B is more

costly. Recently, Brown and Murphy (1988) demonstrated

how decision analysis can be used to assess the economic

vat= of weather forecasts in wildfire management. Their

decision tree was more complicated than the one in the

previous example, but the principle behind the analysis

remains the same: consider the consequences of the

decisions, and the probabilities of their outcomes, before

deciding on an appropriate response.

220
Effect of Uncertainties in the Probabilities

The preceding example assumed that the probabilities were

known; the expected losses calculated in that context are [rut

expected values. In reality, the probabilities can only be

estimated, which introduces another level of uncertainty in the

decision process. Suppose, therefore, that the probabilities

arc random variables, and that the values used in the

computations are estimates. The resultant expected losses

therefore are also random variables, subject to uncertainty.

Where the calculated expectations in the preceding example

were represented by points on the real line, the expected loss

values calculated with the probability estimates are themselves

only estimates. If the random variable representing the

probability estimates can be described by a probability model,

the calculated expected losses may be viewed in the context of

confidence intervals. Hence, where the decision previously

considered only which of the expected values was the larger,

now the overlap, if any, of the confidence intervals might also

bc considered. In other words, the loss of certainty in the

probability information clouds the expected loss calculations.

If the smeared results (intervals) are still distinct from one

another, the decision rule can be applied unambiguously. If,

on the other hand, the intervals overlap, then the decision rule

is compromised. The degree of overlap may be used as a

basis for evaluating the acceptability of forecast uncertainties.

Presently, fire weather forecasts are not expressed in

probabilities. Nor do they usually extend beyond a j-day

period. The research at PSW is aimed at providing the means

to do both. The next generation of fire weather forecasts will

extend the forecast horizon to 30 days.

EXTENDED-RANGE FIRE WEATHER

FORECAST

The 30-day tire weather forecast was developed primarily in

response to the national level strategic planning needs at the

Boise Interagency Fire Center. The fire weather forecast will

be integrated with information on crop moisture, the Palmer

Drought Severity Index, and various fire danger and fire

behavior indicators, to produce a forecast of 30-day fire

potential for the continental U.S. The system that presently

produces the fire potential map uses 30day and 90-day

predictions of temperature and precipitation from the National

Weather Scrvicc (fig. 2).

The newly developed 30-day forecast models were tailored to

fire weather needs (Klein and Whistler, 1989). They focus on

mean afternoon conditions, when the tire weather threat is

usually the grcatcst, and, they add the elements of relative

humidity and windspeed. Specifically, the models predict the

departures from the monthly afternoon (approximately 1300

Local Standard Time) means of the following variables:

. Dry-bulb temperature

. Dcwpoint tcmpcrature

l Windspced

-290 rZa70- 90 czl30-70 czl(30

Figure ‘J--An extcndcd-range forecast of the 30-day mean tcmpcraturc percentiles for the contiguous U.S. The pcrccntilcs

rcllrcscnt the proportion of the climatological database that the forecast value cxcecds.

221
A model was also developed to predict the number of days in

a month that precipitation would exceed 0.10 inch. This is

complemented by existing National Weather Scrvicc models

for monthly precipitation amount.

The models arc driven by the forecast monthly mean

pressure-h&&s at the 700 millibar level (nominally 10,000

I?), which is prepared by the National Weather Service twice

monthly. The assumption underlying the models is that

excursions of a variable from its monthly mean, as observed

at a given location, arc associated with large-scale

atmospheric pressure patterns over the earth’s surface;

moreover, the excursions can be predicted statistically from

information about the expected pressure-heights at a few

points, and current conditions at the location of interest. In

fact, the models are derived from regression analysis:

(x,1+1) = a,&,t) + $ a#,

i-l

in which d-&,r + 1) is the forecast surface weather anomaly

for location x and month f+l, ~I’xJ) is the observed surface

weather anomaly for month f at location x, and (@,,I are

forecast 700 mb height anomalies at designated gridpoints for

month I+ I. The {a, 1 are regression constants. The constant

a, may bc 0, which then implies that current weather

conditions at the location are not strongly correlated with next

month’s weather. Regression models have been developed for

127 stations across the contiguous U.S.

The forecasts are interpolated to an orthogonal grid, and

contoured. The forecast at each station is also compared to

the empirical distribution of the variable, and expressed as a

percentage of the observed monthly means in the station

record that the forecast value equals or cxcecds. This

transformation converts the forecast from its original units to

a dimensionless number ranging from 0 to 100.

Consequently, diffcrcnt variables may be forecast in different

regions of the country, transformed to a percentage value by

the process described above, and represented concurrently

with other forecasts on a map. McCutchan and Main (1989)

found that no single variable is best correlated with fire

activity in the U.S., and that the forecast of different

variables in diffcrcnt parts of the country might in fact be

preferable.

LONG-RANGE FORECAST TOOLS OF THE

FUTURE

Medium-range Fire Weather Forecasts

Research is presently focused on the development of

medium-range tire weather forecasts, which implement

computer models of global weather processes. Currently, the

National Meteorological Center gcncratcs a daily

medium-range forecast of weather conditions out to 10 days,

but the distribution of this product is limited (Petersen and

Stackpole, 1989). The forecast can describe daily variations

of weather, which is the minimum temporal resolution

required for National Fire-Danger Rating System (NFDRS)

calculations.

Spatial resolution, however, is limiting, for local fire weather

applications. The minimum grid interval is approximately 85

km, but the terrain model used to define the surface boundary

removes terrain features of less than 5 degrees; the maximum

height depicted in the Rocky Mountains is 2600 m. Therefore,

the model cannot be expected to describe terrain-induced

windflows that complicate fire behavior. Moreover, sea and

lake breezes are not forecast accurately, thus reducing the

ability to predict moisture variations in areas influenced by

large water bodies. A typical way of enhancing the spatial

resolution is through statistical mod&. For example, weather

variations at Ere weather stations can be modeled as a

function of corresponding medium-range model output.

Presently, however, the database for such studies are

somewhat limited, particularly for the current version of the

medium-range forecast model. An objective of the current

PSW research effort is to develop forecasts of the daily

variations in fire weather over a IO-day period.

Seasonal Fire Weather Forecasts

The objective of the seasonal Iire weather forecast is to

estimate the weather-induced tire potential in a 90-day

timeframe. This forecast will be a prediction of the mean

weather conditions over the 90-day time period that begins

approximately from the day that the forecast is issued. Like

the JO-day forecast, the seasonal forecast will key on

variations in large-scale, slowly changing weather patterns.

The experience of the National Weather Service shows that

90-day forecasts of temperature are moderately skillful in

winter and summer, but precipitation forecasts do not fare

well (Wagner, 1989). The forccastibility of anomalous

precipitation may be enhanced during periods that global

circulation systems exhibit strong anomalies, e.g. the El Nino

and Southern Oscillation events, which are characterized by

unusually low sea-surface temperatures in the Pacific Ocean,

and unusually strong negative pressure gradient between

Tahiti and Darwin, Australia (Chu, 1989). But the question

of forccastibility cannot be answered without considering the

intended use of the forecast.

A study of the correlation between El Nino and fire activity

(Simard and others, 1985) showed that fire activity tended to

decrease in the Southeast during El Nino years, but no

relationship was apparent in most of the other states in the

contiguous U.S. The correlation in the southeastern states

was attributed to anomalously high precipitation experienced

by those states in El Nino years, which generally decreased

fire potential.

222
SUMhlARY

The not-too-distant future will see the addition of long-range

fire weather forecast guidance to the tools of the Jim

manager. These will include a forecast of daily variations of

fire weather out to 10 days (nominally), a forecast of the

30-&y means of fire weather variables, and a seasonal

forecast of the 90-day means of temperature and precipitation

effects. Statistics of forecast reliability will also be provided,

so that the manager can assess the credibility of the forecast

information, which can vary over time, space, and with

particular climatic conditions. Equally important to the

decision process arc the values at risk, which can be

integrated with the forecast information in a decision analytic

model. At hcst, the models can provide guidance; decisions

must still bc made by decisionmakers. The forecasting

system visualized here will provide the user with the tools,

the process, and the information necessary to deal with

long-range fire weather forecasts and their uncertaintics.

LITERATURE CITED

Brown, B.G. and Murphy, A.H., 1988: On the economic

value of weather forecasts in wildfire suppression

mobilization decisions. Can. J. Forest Res.

18:1641-1649.

Chu, P.S., 1989: Hawaiian drought and the Southern

Oscillation. Intl. J. Climatol., 9:619-631.

Klein, W.H. and Whistler, B.T., 1989: Specifying monthly

man anomalies of tire weather elements in the U.S.

Proc., 14th Annual Climate Diagnostics Workshop, La

Jolla, CA, Oct. 16-20, 1989, NOAA. 403-409.

McCutchan, M.H. and Main, W.A., 1989: The relationship

bctwccn mean monthly fire potential indices and monthly

tire scvcrity. proc. 10th Conf. on Fire and Forest

Mcteorol., Ottawa, Ontario, Apr. 17-21, 1989. 430-435.

Petersen, R.A. and Stackpole, J.D., 1989: Overview of

NMC production suite. Wea. and Forecasting, 4:3 13-322.

Rios, T.J., 1989: Predicting fire potential. Fire Mgmt

Notes, 50:38-41.

Philander, G., 1989: El Nina and La Nina. Am. Sci

77:451-459.

Scavcr, D.A., Roussopoulos, P.J., and Frccling, A.N.S.,

1983: The escaped fire situation: a decision analysis

approach. Res. Pap. RM-244, Forest Serv., Ft. Collins,

12 p.

Simard, A.J., Haines, D.A., and Main, W.A., 1985: EI

Nino and wildland fire: an exploratory study. Proc. 8th

Conf. on Fire and Forest Mcteorol., Detroit, MI,

Apr. 29-May 2, 1985. 88-95.

Wagner, A.J., 1989: Medium- and long-range forecasting.

Wca. and Forecasting, 4:413-426.

223

CULTURAL

PRIVATE, NON-INDUSTRIAL FOREST OWNER’S PERCEPTIONS OF

CONTROLLED BURNING INFLUENCING FOREST MANAGEMENT

D.W. McConnell II and S.B. Baldwin’

Abstract-Perceptions of controlled burning’ by private, non- industrial forest (PNIF) owners provide

insight into their forest management behavior. Detailed personal interviews of randomly selected forest

owners in the Wiregrass region of Alabama were conducted to determine relationships between these

perceptions, ownership objectives, and forest management activities. Over two-thirds of those interviewed

felt controlled burning was a useful forest management practice on their land although only 25.3 Percent

were presently using controlled burning. Both positive and negative perceptions of conMIed burning are

presented. Emphasis is made on the relationship of these perceptions to forest management behavior by

PNIF owners and the subsequent importance to professional foresters who work with this public.

INTRODUCTION

There are nutnerot.ts and conflicting perceptions of lire in the

context of forest management. While professional foresters

pcrccivc tire as a useful tool in manipulating forest

conditions, fire use by private, non-industrial forest (PN I F)

owners likwise has an cnvironmcrttal and historic logic.

Trained fire management pcrsonncl may at times criticize or

question reasons given by these owners for burning; however,

the act itself is a planned, dclibcrate application of knowledge

to meet a determined goal. Forester’s perceptions of PNIF

owners may not encompass this knowledge and may therefore

limit communication bctwccn the hvo groups. In order to

improve communication and coopctativc managcmcnt efforts

between foresters and PMF owners, it is important to

discover the perceptions that these individuals have of forest

management activities -- in this case, the use of controlled

burning.

What are PNIF owner’s altitudes regarding lit-c as a for&

management activity? How do they become aware of its

utility? Where do they look for information and assistance in

its application? What arc their reasons for using controlled

burning on their lands? And can WC dctcrminc whether those

Owner8 with positive perceptions of controlled burning arc

more active managers (that is, using more activilies) than

owners with negative perceptions of controlled burning?

With the advent of the professional forester and the growth of

industrial forestry in the South, the practice of burning was

‘Visiting Assistant Professor, Department of Forestry, University of

Florida, Gainesville, FL; and PhD Candidate, Dcpartmcnt of Forest

Resources, Clemson University, Clemson, SC.

‘The term “controlled burning” is used in this paper as it reflects

PMF owner’s perceptions of what fire in the woods should bc, and

was the term used by participants in this study. No diffcrcnce is

implied hy the author between the terms “prescribed burning” and

“controlled burning”; rather, the terms tend to illustrate the

differences in paradigms of professional forcstcrs and PMF owners,

respectively.

seen as a major obstruction to implementing scientific forest

management (,‘j&if[ 1962, Riebold 1971). Frequent burning

by livestock owners, turpenliners, and other woods residents

prevented foresters from applying their knowledge in forest

managemenl (Pyne 1981). To the contrary, forcslcrs found

they spent the majority of their time working to control woods

fires. It is doubtful that foresters of the early 1900s in the

South felt fire was a useful tool in forest management,

primarily because of their lack of control over its application.

John Shea undertook a “psycho-social” investigation of

woods- burners in and around Bankhead National Forest in

Alabama in the late 193Os, and generalized his findings to the

conditions and behaviors of other tire users across the

southcast (Shea 1940). Shea presented the typical southern

woodsburner as backward, wearing, and irresponsible.

Perhaps the most significant conclusion drawn from his

research was that: .m:l “Southern ‘woods burning’ is a

human problem and should be tackled in a scientific and

human way.” (Shea 1940) The significance lies in the

recognition of human behavior as the problem source and in

the proposition that systematic investigation was nccdcd to

dctcrminc the nature of that behavior and to identify possible

means to modify that behavior.

Historically, PNIF’s have been considered under-managed

resources, producing much less than their capacity of

ecological, economic, and social benefits (Burger and Teer

1981, Dutrow 1986, Rogers and others 1988). A perceived

lack of PNIF owner awareness and undcrslanding of forest

management technology concerns professional foresters (Sedjo

and Ostcm&r 1978) as a cause of under-management (Black

1983). These problems have justified research on forest

management technology transfer based upon communication

behveen professional forcstcrs and PNIF owners. A better

understanding of communication elements, patterns, and needs

between professional foresters and PNlF owners could

contribute to the effectiveness of forest management efforts by

both groups.
Research on agricultural technology transfer has typically

employed diffusion and adoption models, which provide

theoretical generalizations about how technology information

is communicated to landowners and how they decide to use

new technologies (Rogers 1983). M uth and Hendee (1980)

demonstrated that such models could also be useful in

explaining the adoption of forest management technologies.

Key elements in a diffusion model are an innovation, its

adoption by individuals, and its diffusion through a social

system over time as a result of communication. An innovation

is an idea or object that is perceived as new; its adoption is

affected by a variety of characteristics. An adoption decision

is a five-step learning process. First, an individual becomes

aware of the innovation; if his interest is aroused, the

individual will then se& additional information about the

innovation. As his knowledge accumulates, the individual

evaluates the merits of the innovation relative to current or

alternative conditions. In the fourth s&p, the individual

conducts a trial or experiment with the innovation, from

which he eventually decides to either adopt, reject, or

conlinue to gather information concerning the innovation.

Information about technoiogica] innovations is often

disseminated by technical practitioners, change agents,

professionals, and educators (M&au1 1972, Vickcrs 1974,

Grunig 1980, Rogers 1983, Rogers and others 1988). The

practicing professional forester who assists PNIF owners has

a dual communication role: that of helping owners become

aware of new forest management technologies as well as

providing detailed information in later stages of the adoption

process. A major goal of extension forestry programs is to

provide information and education opportunities for the

improvement of PNIF management (Gould 1975).

Adoption models suggest that practitioners who cultivate an

understanding of their client audience, including that

audicncc’s technical knowledge and decision patterns, arc

more effective in educating landowners and changing their

behavior (Rogers 1983). This is consistent with interpersonal

communication models described in communication texts

(Fazio and Gilbert 1981). The goal of this study was to help

foreslers understand PNIF oWner!j and their use of controlled

burning; more specific objectives are presented b&W.

STUDY OBJECTIVES

The problem addressed by this study was to identify how

private, non-industrial forest owners bccomc aware, gather

information, and conduct evaluations and trials in determining

whether to adopt a particular forest management activity.

Specifically, the study was devclopcd to: (I) assess the

background experiences of Alabama PNIF owners with

controlled burning; (2) identify patterns by which Alabama

PNIF owners make decisions about undertaking controlled

burning; (3) identify PNIF owner characteristics useful in

delineating adopter categories as described by Rogers (1983);

(4) identify the use and influence of information and

assistance sources in stages of adoption and diftision

behavior.

STUDYAREA

This study was conducted in the eight southeastern counties of

Alabama that comprise the majority of the Wiregrass region

of the state. These counties cover approximately 3.72 million

acres, of which 2.34 million acres are forested. In these eight

counties there are approximately 20,310 PNIF owners of

between 5 and 500 acres who control 44.5 percent of the

area’s forestland.

METHODOLOGY

A standardized interview instrument was designed and pretested to obtain: (1) information on PNIF ownership

objectives; (2) information on PNIF forest management

practices; (3) indications of owners’ opinions on these

practices; (4) indications of information sources used by

owners; and (5) information on controlled burning use by

PNIF owners.

The sampling procedure us4 was a stratified random sample

of PNIF owners in the eight counties who owned more than 5

acres but less than 500 acres of forest land. The sample size

for the study was calculated from the total population

following Blalock (1982), resulting in a sample of 145

individuals. The sample was stratified across the region by the

ratio of the number of owners in each county to the total for

the study area, giving the number of interviews n&cd for

each county. The number of interviews planned for each

county was increased by an expansion factor of 1.86. This

buffer eliminated the need for additional selection of names

from county records in order to rcptace names of persons who

were deceased, no longer owned land, &&cd interviews, or

otherwise could not be contacted to schedule an interview. A

random sample of names was drawn from county land records

in the tax assessor’s office of the respective county

courthouses. Each name drawn was checked against the

criteria of ownership (PNIF versus public or industrial) and

size (greater fhan 5 but less than 500 acres). For the latter

criterion, Alabama Forestry Commission records were used to

determine that individuals did not own more than 500 acres of

land in the county. In addition, individuals living outside the

state of Alabama or at a distance greater than 60 miles from

the boundary of the study area within the state were rejected

from the sample. Appointments for interviews were made

either through telephone contact or by locating individuals

using rural post office routes. All interviews were conducld

in person by the principle investigator. Interviews were

primarily conducted in individuals’ homes, although a number

of interviews were arranged at businesses, restaurants, or in

farm fields to accommodate participants’ schedules.

A bound copy of the interview instrument was offered to each

respondent so they might better follow the questions of the

interviewer. The interviewer recorded all answers given by

participants on his copy of the instrument. These answers

included comments in open-ended questions as well as

remarks made throughout any portion of the interview
session. Completion of the surfcy instrument required an

average of 23 minutes. Responses from the completed

interview questionnaires Were coded for analysis using the

Statistical Package for the Social Sciences (SPSSX) (Nit and

others 1983). Chi-square tests Were usd to detcrminc whcthcr

statistically significant associations existed between groups

within the sample. The lambda statistic was also used to

determine whether independent variables associated with

PNIF owners were of any use in predicting particular

dependent variables of PNIF OWIltXS and their actions.

Open-ended question responses were organi& and coded

using content analysis. A measure of PNIF owner attitudes

toward forest management activities was dctcrmincd through a

Likert scale. The Likert method is based on the assumption

that a scoring of the responses to items describing a particular

variable provides a reasonably good measure of the

respondent’s attitude towards the variable (Babbie 1983). The

use of the scale also prevents purposive response bias or

manipulation in that the respondent does not know what

variable is being measured. Factor analyses were perforKEd

on Likert scale statements to identify attitudinal themes of

participants. Cronbach’s alpha was used to dctcmtinc the

correlation and homogeneity of participant responses in order

develop attitudinal rankings.

RESULTS

The private, non-industrial forest owners of bctwccn 5 and

500 acres of forestland in the Wiregrass Region of Alabama

WcTe predominantly male, rcsidcnt owners of approximatciy

75 acres of forestland. Most of the non-residcnl owners (64.9

percent) lived within ten miles of their forestland. The

majority of individuals lived on farms or in NC& non-farm

locations. While the average age of these PNIF owners was

between 55 and 60, the ages ranged from 29 to 99 years.

One- third of the individuals had less than a high school

education, another third had completed high school, and tile

remainder had junior college to graduate dcgrces. The

occupations of study participants tanged from tcachcrs,

construction workers, and ministers to government

employees, housewives, and barbers. Among those PNIP

owners who were retired (35.9 pcrccnt), the majority had

been businessmen or farmers.

Within the study area, 71.7 percent of PNIF owners felt

controlled burning was a useful forest managcmcnt activity on

their land. These owners commented that controlled burning

helped clear understory brush and trash trees, helped fireproof their land and kept the pines growing free. These

individuals had ownerships that ranged from 25 to 500 acres

and displayed a broad range of occupations and educational

backgrounds. The primary ownership objectives of those

individuals who perceived controlled burning as useful

ranged from the production of income from the sale of timber

or providing a homesite to their land providing a heritage for

fkture generations or shelter for wildlife (Table 1). The

rcmain&r of the PNIF owners cited the following primary

ownership objectives: land as a future invcstmenl (9.6

percent); family recreation area (6.7 percent); hunting aICa

(5.8 percent); firewood production area (3.8 percent); to

preserve natural beauty (I .9 percent); and other reasons (4.8

percent).

Table 1. Primary forest ownership objectives of PNlf OWWS

in the Uiregrass Region of Alabama uho perceive controlled

burning as a useful forest management activity on their

forestland (N=lOL).

Primary Objective Frequency Percentage

Income from sale of timber 22 21.2

Homesite 2 2 21.2

Heritage for future generations

Shelter for wildlife ::

14.4

10.6

Future investment 10 9.6

Family recreation I 6. I

Hunting 6 5.8

F i reuood production

Natural beauty t

3.8

1.9

Other reasons 5 4.8

Total 104 100.0

The primary reasons given by the 38.3 percent of PNIF

owners who felt that controlled burning was not a useful

forest managcmcnt activity on their forestland were that

burning “Destroys small trees.” or “Damages timber.” (31.7

percent); “1 It] runs-off wildlife, especially songbirds.” (15.1

percent); and “Mine is hardwood forest, so it doesn’t tit.”

(12.2 percent). Demographic characteristics indicated that

these PNIF owners tended to have smaller individual

ownerships, somewhat lower education levels, and were more

often non-resident owners. However, none of these

demographic characteristics were significantly different at the

0.10 level from those of persons who felt controlled burning

was a useful forest managcmcnt activity. Further, the lambda

statistic indicates that these individual characteristics arc of

little value in predicting the controlled burning utility

perception of PNIF owners in the Wiregmss region.

The primary ownership objectives of 41 PNIF owners who

fc]I controlled burning was not a useful forest management

activity on their land ranged from their land providing a

homesite or a heritage for future generations to providing

shelter for wildlife or an area for family recreation (Table 2).

Other primary ownership objectives cited by this group were:

land as a tbture investment (9.8 percent); to have an area to

cut firewood (4.9 percent); to preserve natural beauty (2.4

percent); and other reasons (4.9 percent). No one in this

group identified having an area to hunt as their primary

ownership objective.

129
Table 2. Primary forest onnersbip objectives of PNIF ounefs in

the Uiregmss Region of Alabama uha do not perceive controlled

burning as a useful forest snamgmmt activity on their

forestkaod (N=41).

Primary Objective F=l-=Y Percentage

lncoi6e from sale of tiuber 5 12.2

Heritage for future generations 1 11.1

Homesite a 19.5

Shelter for uildlife 6 14.6

Fotore investment 4 9.8

Family recreation 6 14.6

Hunting 0 0.0

F i r euood prohrctioo 8 4.9

Natural beauty I 2.4 other reasons- 2 4.9

Total 4 loo. 0

Of the 104 individuals interviewed who pcrceivcd controlled

burning as a useful forest management activity on their land,

35 percent cited “personal cxpcrience or observation” as their

initial source of awareness of controlled burning utility. These

persons described having firs1 observed controlled burning in

some fortuitous manner, such as noticing smoke. following it

to its source, and then observing the actions of the fire and

the individuals tending it. A number of these owners recalled

returning to the burn area at some later date, ranging from a

few days or weeks to two or more years, and making personal

assessments of the impacts of the bums. Almost twice as

many study participants who stated that controlled burning

was useful cited personal experience or observation as their

initial awareness source compared to the number who cited

either mass media (ncwspapcr or magazine articles, primarily)

or Alabama Forestry Commission personnel as their initial

awareness source (Table 3).

Table 3. Sources of initial awareness of controlled burning

ut i 1 ity cited by PNIF owners uho perceived cootmlled boming

useful on their forestiand in the Uiregrass Region of Alabama

(N=119)'.

Source ~resuency Pel-Cell;age

Pewsowl experience or observation 3.5 29.4

Mass media 20 16.8

AL&ma Forestry Conmission 19 16.0

Mead or neighbor 1 2 10.1

Indostrv forester I I 9.2

Others -(five -es)

Total

18.5

12 100.0

'N is m-eater than the 104 individuals ubo perceived controlled

bumi& usefut because some ouners could not confidently

identify a single sauce of initial wareness of controlted

burning utility.

Responses to Likert statements on controlled burning grouped

study participants as having positive, neutral, or negative

attitude scores concerning controlled burning. These attitude

scores were developed independent of the questions regarding

the perceived utility of controlled burning. Study participants

with positive attitude scores toward controlled burning as a

forest management activity tended to cite Alabama Forestry

Commission foresters as their initial awareness source twice

as often as owners with neutral to negative controlled burning

attitude scores. Individuals with neutral attitude scores

concerning controlled burning as a forest management

practice tended to cite mass media or personal experience or

observation as their initial awareness sources.

Private, non-industrial forest owners were asked whether they

knew of any neighbor’s or aquaintance’s use of controlled

burning in the management of their forrestland. This line of

questioning was intended to investigate possible vicarious

experiences with controlled burning through others’ use of the

practice. Almost half (47.5 percent) of all individuals

interviewed stated that they were aware of controlled burning

use by neighbors or aquaintanccs. Over 82 percent of this

group of owners also perceived controlled burning as a useful

forest management activity on their forestland. A

generalization from this could be that owners using or

predisposed toward a particular forest management practice,

such as controlled burning, arc more likely to be attuned to

other’s use of the same or similar activities.

Approximately two-thirds (65.8 percent) of those persons who

were aware of controlled burning use by neighbors or

aquaintanccs felt positively influenced by the controlled

burning cxpcricnces of others (Table 4). This number was

equivalent to 3 1 .O percent of the total number of individuals

interviewed. These persons commented that they saw burning

as an effective means for “clearing understory brush”,

“eliminating trash trees”, promoting “better food for deer and

turkey”, and “helping pine trees grow better”

Of those individuals aware of others’ use of controlled

burning, 26.3 percent felt negatively influenced by neighbors’

or aquaintances’ experiences with controlled burning. Eighty

percent of these persons stated that they felt the iirc was too

hot or damaging, or said that the fire had escaped, burning

unintended areas or someone else’s land.

Table 4. Private, non-industrial forest ouner's stated

direction of influence fmm neighbor’s or aquaintaoce’s use

of controlled burning (N=69).

Influence Frwluency

Positive 45

Neutral 6

Percentage

65.8

Negative 18

Total 69

All study participants were asked to whom they would most

likely go for information if they had specific questions about

the use of controlled burning on their forestland. This

question was asked regardless of the individual’s perception of

the utility of controlled burning. Alabama Forestry

Commission foresters were cited significantly more often than

any other controlled burning information source regardless of

230
Table 5. Controlled burning information sources identified by PNIF owners of the

Alabama Uiregrass Region by attitudes of owners toward controlled burning (N=145).

Sources Attitudes

Negative Neutral Positive

AFC forester 3 0 2 9 2 0 7 9

62.5 47.5 55.6 54.5

industry forester 5 5 3 1 3

10.4 6.2 a.3 9.0

Other’ 13 2 7 1 3 5 3

27.1 44.3 36.1 36.5

48 6 1 3 6 $45

100.0 100.0 100.0 100.0

Chi-square: 3.451, d.f. = 4 Significant a t alpha = 0.10

‘Other: ASCS PrsonneI , Cooperative Extension Agents, friends or fellow Landowners,

and forestry consultants.

owner’s attitudes of controlled burning (Table 5). Those PNIF

owners with negative attitudes of controlled burning cxprcsscd

a distrust of industry foresters as in~omlation SOIJKCS for

controlled burning and Cited county COOpWh’C Extension

Service agents lhrce times as often as their preferred

information source.

When landownels WlX asked to whom they would most

likely go for information if they had a specific question on

forest management, there was a slightly greater range of

sources given (Table 6). Again, Alabama FOXSIr)’

Commission foresters WIXC the most kcqucntly cited

information source. There WLX no significant differences in

the proportions of forest management information SOUKCS

cited when compared with owner’s attitudes of controlled

burning

Private, non-industrial forest owners in the Wircgrass Region

of Alabama who perceived controlled burning as a useful

forest management activity on their forestland condwted or

contracted a variety of forest management activities (Table 7).

The crosstabulation indicates that PMF owners were more

likely to conduct the following forest management activities

when they considered controlled burning usefid than those

who did not perceive it useful: planting trees, establishing

wildlife food plots, selling timber, using herbicides, preparing

a l”oresl inventory, using a written contract to sell timber, and

constructing a road on their forestland Individual PN[F

owner.3 who perceived controlled burning useful undertook 35

percent more forest management activities than those owners

who did not feel controlled burning was a useful forest

management activity. While the Chi-square statistic indicates

a significant relationship at the 0.10 level between perceived

utility of controlled burning and the number forest

management activities undertaken by PN[F owners, the

number of crosstabulation cells with fewer than five C~SCS is

too large to accept Chi-square as a valid test. However, the

lambda statistic indicates that knowledge of PNIF owner’s

perceptions of controlled burning is a significant factor in

predicting their use of other forest management aclivitics.

Table 6. Forest management information sources identified by PNI F owners of the Alabama

Uiregrass Region by attitudes of owners toward controlled burning (N=145).

Sources Attitudes

Negative Neutral Positive

AFC forester 2 1 2 1 1 0 5 2

43.6 34.4 27.6 35.9

Industry forester G.7 5 3 1 6

6.2 6.3 11.0

Other’ 1 9 3 5 2 3 7 7

39.5 57.4 63.9 53.1

48 61 3 6 145

100.0 100.0 100.0 100.0

Chi-square: 6.255, d.f. = 4 Significant at alpha = 0.10

‘Other: ASCS personnel, Cooperative Extension Agents, friends or fellow landowners, and

forestry consultants.

231
Table 7. Forest management activities conducted by PNIF Owners in tbe

Alabama Uimgrass region by perception of contmiled burning as a useful

forest management activity on their forestland (N=226).

Activity

PI asting trees

Wildlife plots

Sel L ing timber

Useful.

3 3

18.3

3 8

21.1

aa. 3

Not Useful

3 9

1: 17.2

30.4 5 2

23.0

36.4 ::.*

Herbicide applications 14 4 I8

7.8 8.7 8.0

Forest inventory 14 2 16

7.8 4.4 7.1

sales contract 2 6 4 3 0

14.5 8.7 13.3

Road construction 13 2 1 5

7. 2 4.4 6.6

Total 180 4 6 226

100.0 109.0 160.9

chi-square: 4.7479’, d.f. = 6 Significant at alpha = 0.10 Lambda: 0.2860

‘The number of celk in the cmsstabalation with expected frequencies of

less than five is greater than 20 percent. This condition does not allow

statistically valid Cbi-sqaare tests.

SUMMARY CONCLUSIONS

While studies of fire impacts began in the early 19OOs, there

appears to have been a hesitancy to study man’s behavior in

using fire. This investigation indicates that a significant

proportion of PNlF owners in the Wiregrass Region of

Alabama see controlled burning as a useful forest managcmcnt

activity in meeting a variety of ownership objectives. Further,

nearly one-third of the PNIF owners first become aware of

controlled burning utility through some personal experknce

rather than any media lrgUS&I~ message. Regardless of

PNIF owner’s attitudes and perceptions of controlled burning,

the Alabama Forestry Commission is the most frquent]y cited

formal information SOUTCC of conlrokd burning. Those

owners who perceive controlled bunting as a USefUl foresI

management tool tend to be more active forest managers

relative to those owners who do not feel controlled burning is

usefui.

Controlled burning is a very visible forcsl management

activity whose impacts can be observed in a short time period

relative to many other activities. It is also suited to use on a

variety of size scales, which is important when considering

the range of ownership sizes or individual stand sizes found

on PNIF lands. State forestry agencies can utilize their

standing as controlled burning information sources as an

opening to promote other forest managcmcnt activities by

PNIF owners who use controlled burning. Neighboring forest

owners could similarly be encouraged to undertake more

forest management activities through observation of other’s

activities. Controlled burning can therefore serve professional

foresters as a communication tool by promoting increased

contacts with PNIF owners. Through a better Understanding

of adoption and diffusion behaviors of private, non-industrial

forest owners, professional foresters can become more

proactive in their forest management information and

assistance efforts with this public. Controlled burning users

can be developed as informal change agents and secondaty

information sources by state forestry agencies, thus utilizing

interpersonal networks within PNIF owner publics. This

diffusion network approach by professional foresters would

increase the effective targetting of information desired by

PNIF owners for their specific management objectives. A

consequence of this would be that PNIF lands would produce

more of their potential ecological, economic, and social

benefits.
LITERATURE CITED

Babbie, E. 1983. The practice of social research (third

edition). Wadsworth Publishing Company, Belmont, CA

Black, C.D. 1983. Coordinating efforts: the view from

extension. pp. 383-384. In Nonindustrial Private Forests:

A Review of Economic and Policy Studies. J.P. ROyer

and CD. Risbrudt, editors. School of Forestry and

Environmental Studies, Duke Universily , Durham, North

Carolina.

Blalock, Jr., H.MI987,. Conceptualization a n d measuremcnl

in the social sciences. Sage Publications, Bcvcrly Hills,

CA.

Burger, G.V. and Teer, J.G. 1981. Economic and socioeconomic issues influencing wildlife. pp. 73 87. In

Proceedings of Symposium on Wildiifc Mana&ement on

Private Lands, Milwaukee, WI.

Dutrow, G. 1986. Effects of below-cost timber s&s on

private foreshy investments and future timber supplies.

pp. 121-126. In Proceedings on Below-Cost Timber Saks:

A Conference on the Economics of National Forest

Timber Sales. Sponsored by: The Wilderness Society, the

College of Forestry, Wildlife, and Range Sciences of the

University of Idaho, and the Depadmcnt of Forcslry and

Range Management of Washington State University.

Fazjo, J.R. and Gilbert, D.L. 1981. Public relations and

communicalions for natural resource managers.

Kendall/Hunt Publishing Company, Dubuque, Iowa.

Gould, E.M. 1975. The search for parity. Journal of Forestry

73(4): pp. 217-X1.

Grunig, J.E. 1980. Communication of scienliiic information

to non-scientists. pp. 167-214. In Progress in

Communication Scicnccs, Vol. 2. B. Dervin and M.J.

Voght, editors. Ablex Publishing Company, NOIWOO~,

New Jersey.

McNaul, J.P. 1972. Relations between rescarchcrs and

practitioners. pp. 269-288. In The Social Contexts of

Research. S.Z. Nagi and R.G. Cowin, cdiiors. Wiley

intcrscience, New York.

Muth, R.M. and Hendce, J.C. 1980. Technology transfer and

human behavior. Journal of Forestry 78(3): pp. 141-144.

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wildland and rural fires. Princeton University Press,

Princeton, New Jersey.

Riebold, R.J. 1971. The early history of w&fires and

prescribed burning. In Prescribed burning symposium

proceedings. USDA Forest Service Southeastern Fdrcst

Experiment Station, Asheville, North Carolina. Rogers,

D.L., Bartlett, E.T., Dyer, A.A., and Hughes, J .M.

1988. Research and education systems for renewable

resources: a study of public and private-sector research

and education for private forcsfland management. Wood

Utilization and Rangcland Management, Vol. 5, Executive

Summary. Department of Sociology, Colorado State

University, Ft. Collins.

Rogers, E.M. 1983. Diffusion of innovations (third edition)

The Frt~ Press, New York.

Schiff, A.L. 1962. Fire and water: scientific heresy in lhc

Forest Service. Harvard University Press, Cambridge,

MA. Scdjo, R.A. and Oslcrmeier, D.M. 1977. Policy

alternatives for nonindustrial private forests. The Society

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American Behavioral Scientist 18: 164-189. .M:l

233
SOCIAL IMPACT OF COMPUTERS IN URBAN FIRE FIGHTING

Steven RI. Davi’

Abstract-Computers are rapidly expanding into the urban fire safety area. This paper presents some

social implica:ions caused by the use of computers for lirc safely databases, arson prsdiction programs, and

fire simulation programs. In regards IO the new technological advances this paper raises questions

concerning the pros and cons of how computers are being used, who is responsible for the technology, who

decides how the technology is used, how does the new technology affect insurance rates, how does it affect

the builders and owners, and who is liable for personal damage indirectly caused by the new tschnology.

INTRODUCTION

With rapid advances in computers and software, new

technology is being employed in the area of fire safety. This

paper discusses the social impact of this new technology,

addressing social issues such as how computers are being

used, who is responsible for the technology, who dccidcs how

the technology is used, how does the new technology affcc.1

insurance rates, how does it affect the builders and owners,

and who is liable for personal damage in&r&y caused by the

new technology.

Current Technology

The USC of computee in the fight against urban fires has

included diverse areas such as resource allocation, planning,

dispatching, training, inventory managcmcnt, C[C. This paper

concentrates on the implications of compt.ttcr usage in three

main areas; computer databases, models to predict arson, and

models to predict fire movcmcnt contained in structures.

Computer databases are being designed to provide the lire

fighters with more information about the area in which the

fire is contained; the models to predict arson arc being

dcvelopcd to stop the loss of property and lives which occurs

each year due to deliberate fires; the models to predict fire

movement are being designed to help risk managers dctcrminc

the safety level of their structures.

Cwiputer Databases

Probably the widest application of computers to the lirc safely

fic[d has been in the area of databases. The National Fire

Information Retrieval System (NFIRS) has a database for

hazardous materials (HAZMAT) which contains information

like the chemical name, its flashpoint, upper and lower

explosive points, water miscibility, etc. Another database

maintained by Ihe Insurance Services Office (ISO) contains

details on commercial and public buildings throughout the

country. The National institute of Standards and Technology

(NIST) Center for Fire Research (CFR) has developed a

computerized card catalog (FIREDOC) containing localized

information about buildings and materials which can he

rctricvcd by local fire departments (Watts 1987).

‘Graduate Student, Northeastern University, Roslon, MA.

234

In Lcominster, Massachusetts, the fire department uses

sofiware entitled CAMEO to store information about the

location and nature of hazardous materials in the industrial

areas of the city. The database contains information such as

the propertics of the hazardous material, health hazards, first

aid measures, protective clothing, etc. mile approaching the

scene, fire fighters can be informed about the material by the

dispatcher (Bisol 1989).

In Phoenix. Arizona, the fire department has gone one step

further. They work with a sophisticated Computer Aided

Dispatch (CAD) and Mobile Digital Terminal (MDT) syslem

to incrase their ability to more efficiently respond to the

needs of the public. The system supports over 1.4 million

people in Phoenix. Glendale, and Temi’c. Each emergency

vehicle is quipped with a computer system which can

communicate to the main computers at the fire station. MDT

enables them to display emergency data on their screen as

they rush to the Scene of the incident, sometimes even helping

them to find the exact location of the emergency (Sawyer

1984). The Phoenix Occupancy Activity Reporting System

contains information from building inspections, providing

them with information such as the owner, number of

occupants (calling out elderly or handicapped persons), fire

code violations, hazardous materials, floor plans, etc. which

enables the arriving fire chief to better position the fire

apparatus to contain the fire (Sawyer 1984).

With CAD and MDT, communications have improved

tremendously; messages go more quickly. For example,

when a lire box alarm was triggered, the dispatcher

previously searched the fire box catalog manually to

determine the street address and nearest fire station. With

CAD, the computer system handles this operation at a much

higher speed. Furthermore, in a major fire up to sixteen

pieces of equipment need to be dispatched. Using radio

communications this would take ninety-six messages to

dispatch the equipment and put it back on line. With the new

system, all communication is done by computer (Sawyer

1984). Dispatch operators can now keep up with the calls

during peak periods. Equipment is being put to more

efficient use. Record keeping and data collection for
management reports has been automated freeing the

individuals lo focus on OthCr areas. The safety of the public

and fire personnel has been improved due to increased

knowlcdgc of the structure and its contents (people and

material). The overall success of lhc system is attrihutcd to

the fact that the dcVClOpmCtlt team members worked Wry

closely with the fire fighlcrs. The fire lighters’ cxpcricncc

enabled the developers to better understand what was required

of the system to help the fire fighter; continuous fadback has

helped to constantly improve Ihc system. Using the computer

has become common place for the new generation of fife

fi@lcrs in Phoenix (Sawyer 1984).

Arson Prediction It’rograrns

Each year arson causes thousands of deaths and injuries

nationwide as well as property loss in the billions of dollars

(Cook 1985). Arson-prevention workers, backed by

insurance agencies, city officials, and community

organizations, have applied computer technology to the fight

against arson and have found that they can reduce the losses.

The idea behind the effort is that certain economic, structural,

and demographic characteristics of a building and its

neighborhood could he connected to arson rates. Generally,

owners who have a building occupied by low income minority

individuals, with long term leases, at very little rent, have a

higher incidence rate of using arson as a means of clearing

the building for renovation.

Arson prediction models were constructed so arson-prevention

workers could use the results of the model to target specific

buildings which arc at high risk for arson. By knowing

where arson is most likely to occur, the arson-prevenlion

workers can focus their efforts (Iire marshal monitoring to

tenant organizing) more cflicienlly on prcvcnting arson in that

arca. The computer has enabled arson-prevention workers to

do what they could not do before; “store and analyze the

large data scls necessary to pinpoint the buildings most likely

to bc torch& (Cook 1985). Using databases from various

agcncics, which arc available to the general public, Ihe arson

prcventjon workers are able to combine information about a

particular building; this information is then \tsed to dcterminc

the possibility this building will be victim to arson. Some

problems were cxpcricnccd due to the dissimilar manner in

which the various organizations stored data in their database.

For example, the PIrc department idcntificd fires by addresses

which were not always accurate; Ihc housing departments

used block and lot numbers.

In 1979, the Boston-based Urban Educational Systcnl Inc.

developed a computer program to identify buildings that arc

prone to arson. The variables used by the program include

lirc history, code violations, and tenant complaints. The

program enabled the Atlorncy Gcncral at that time, Francis

X. Bcllotii, to prosecute arson-for-profil opcralions with

unprcccdcntcd success. The program has hclpcd the

prosecution through bcttcr data collection of prior fire history,

code violations, etc. (Anon 1979).

Using the work performed in Boston as a starting point,

workers in arson prediction in New York City created a

program called lhe Arson Risk Prediction Index (ARPI).

APRl is mainly a formula which takes into account Vafiablcs,

and weights associated with those variables, to produce a

probability that the building will bc victim to arson in the next

year. Variables include building type, building location,

vacancy rate, lire history, serious code violations, number 0 1

apartments, owner history, clc. (Dillenbeck 1985). The

computer program was not only cmploycd to predict which

buildings were at high risk to arson but the arson-prevention

workers were also able to discover patterns among owners

and problem buildings. This capability enables arsonprevention workers to discover building owners who make a

practice of burning their buildings for profit.

The experience gained by the New York City arsonprcvenlion workers has shown that although the program can

help narrow the scope of building which are prone to arson,

Ihc model is not perfect. Many of the buildings which the

program put at high risk did not bum. In fact, when the

formula was applied city-wide only 40 percent of the

buildings selected were burned. However, when the formula

was modified for specific neighborhoods, it was accurate 80

percent of the time. Such results indicate that this

information might bc best used to identify the buildings where

minimal prevention methods, such as sending warning notices

to the occupants, should be employed (Cook 1985).

Fire Simulation Programs

Bcforc the use of computers, engineers approached fire safety

risks by looking at the codes. Codes arc standards of practice

dcvelopcd by consensus among engineers and other tire

cxpcrts. The codes were based on very little actual

calculation of fire hazard; therefore, COIIS~IUC~~O~ based on

these codes could not be accurately evaluated as far as risk

during a fire. Most observations of fire movcmcnt were done

by investigating accidental Iire or from experiments conducted

by various organizations. Fire safety engineers in lhcsc

organizations ignited a lot of materials and watched how lhcy

burned. This was costly and time consuming especially when

trying different configurations of material. In 1971 a group

of scientists, observing that fire is rigidly bound by physical

laws, concluded that fire is a rational physical phenomena

which follows a logical system (Fitzgerald 1983). Based .,.

this premise, lirc safely engineers started to develop models

to predict the spread of fire through a building.

Thcrc are three aspccls to analyze during a fit-c; fire

movement, smoke movcmcnl, and people movcmcnt. The

goal of a computer simulation is lo analyze these movements

to identify the acceptable time interval between when am

occupant is aware of a tire and when the exits arc blocked

because of fire or smoke, thus, providing a tool to

“understand, evaluate, and dcscribc the expccled performance

and reliability of the fire safety systems” (Fitzgerald 1987).

23.5
Fire simulations can be modelled either as zones or networks.

Zone models work by dividing the structure into several

zones, defined by room boundaries. “Advantages of ZOflC

mod& arc that they provide fast, reasonably accurate,

modular code that rum on a personal compuler (PC), they arc

fairly simple to update and extend, and can bc used by nonexperts. The disadvantages arc that the model is twodimensional, only works with simple room geometries, and

uscs empirical knowledge, which introduces further limits on

its applications” (Anon 1989).

Thcrc are two major advantages to providing fire simulation

programs which run on PCs. First, most organizations can

afford a PC; thcreforc, they will be more inclined to use the

so&ware. Second, PCs arc portable and can go whcrcvcr the

user needs to take it. For example, ftre engineers could carry

the computer around as they examine the structure and input

information immcdiatcly. The PCs could be installed on fire

trucks and tied into the main system so the fire chief can

obtain information on the structure and run analyses of the

spread of the lire.

A disadvantage to zone models is the USC of empirical

knowlcdgc throughout the simulation. Input data to the

program is generally provided by a fire engineer who has

inspcctcd the structure. These values arc the only data used

by the fire simulation program to produce the results. The

assignment of these values arc purely cxpcrt guesses based on

common training given the fire engineers. A current problem

is lhe inconsistency of 11~ numbers produced by the fire

safety engineers; unique buildings require unique judgemcnt

which varies from one person to another. The credibility of

the numbers can be increased by providing the analysts with a

“&c&ion support system” or “engineering support system”

which will help them produce the more consistent numbers

for the input data. The challenge to creating tbcsc expert

systems is programming the “judgcmcnt” of the cnginecrs.

Fire safety engineers analyze fire movement by looking at the

various input data; for example, room coBlent and barrier

strengths, to determine when these factors come into play and

how much they influence the outcome. A graphical, or

neural, network of inputs (contents) and outcomes (fire

propagation) could be produced. The next generation neural

network-based fire simulation program will be able to learn

how fire spreads by observing constructed fires and learning

the properties of fire movement much like an experienced fire

safely cnginccr.

SOCIAL IMPACT

Some scientists bclicve that true answers to scientific

problems lit in an analytical equation; numeric answers am

only approximations. Today computer simulations arc dealing

with problems with so many variables that [jlc “true

visualization requires a numerical solution; the analytical

equation is only an approximation” (Koshland, 1985). The

lire simulation programs take into account so many variables

1136

(i.e. room fuel, barrier strength, etc.), and there are many it

does not take into account (i.e. explosions, wind directions,

etc.) that the model may bc entirely different from the actual

outcome. The arson prediction program has shown that arson

patterns cannot be truly summarized in a mathematical

formula.

“When decisions are based on the results of computer models,

it is extremely important that we can trust the model’s

hardware, software, arid input data” (Perrolie 1987). All

three technologies are negatively affected by bad input data.

In the fire simulation program, all the values for the input

data arc provided by the ftre engineers. Therefore,

interpretation may be different among various fire engineers

resulting in the same structure producing different results

based on the input data. Additionally, these results may all

bc different from what actually happens when the structure is

on tire due to the absence of a critical factor in the program.

For example, the fire simulation model relies on the fire

suppression systems (e.g. sprinklers) working perfKl]y;

however, in reality, complex systems have a tendency to

malfunction and break down. If the fire suppression systems

fail in an actual fire, the results of the model arc incorrect.

In the arsotr prediction program, diverse databases resulted in

information not being matched with the correct structure;

therefore, the predictions for arson in that structure were

incorrect. In the computer databases, mistakes can happen at

many stages. The data collected may contain errors; the data

may be entered incorrectly; the joining of &verse databases

may be done incorrectly. All these factors cart contribute to

an et-ronmB8 database which could result in mishaps at the

scene of the fire. Another factor impacting portable

computers, such as those used by lire fighters in Phoenix, is

the failure of the hardware. On site, equipment Will be

exposed to excessive heat, smoke, waler, and chemicals.

Equipment failure in these harsh conditions must bc

prevented. Back at the station, down-time on the mainframe

should be minimized since it would impact the flow of

information to the on-site fire fighters.

All these factors contribute to the possibility that the programs

can be very inaccurate or the systems can fail at critical

times. When the new technology does not perform as

expected the public, builders, occupants, fire fighters,

insurance agencies, etc. are all affected The following

sections describe effects that computer technology has had on

thcsc groups of individuals.

The Public

As society’s structures &come larger and more complex the

fear of an extensive fire where massive human lives are lost

causes the public to &v&l> what Pet-row called dread risk.

“Dread risk is associated with

* lack of control over the activity,

0 fatal consequences if there were a mishap of

some sort,
l sanctions of dread,

l inequitable distribution of risks and

benefits, and

0 the belief that risks are increasing and not easily

reducible” (PCrr~w 1984).

PCoplC perish in buildings year af\cr year bCC:1llSC Of

CombuS(ihlC materials used in construction and furnishings.

Incidents occur weekly which show that the current codes arc

inadequate. The public, SyurrCd on by such incidents as the

MGM Grand Hotel fire on 71 November 1980 which killed

84 pcoplc and injured 679, wants to b c belter protcctcd tirn

accidental and dctiberatc fires, cspccially in high-rise

buildings, nursing homes, and hospihls.

The public’s COnCCrn have caused the introduction of stricter

fire codes as well as the desire to lost building dcsigrls for Jirc

safety before construction starts. Now, the currenl problem

has shiflcd into the other direction; the public trusts that the

new technology will solve the problems Caused by other

modern convcnicnccs, such as high-rises, condominiums, etc.

The public has come to dcpcnd on technology to provide a

comfortable standard of living, yet the public does not

consider the health, safety, and environmental Conscqucnccs

that accompany this new technology. Additionally, along

with more accurate iechniques for measuring risk COmCS

incrcascd public expectations for safety. The public Cx~ecls

that builders will implcmcnt all safety measures outlined by

the CnginCcrS using the computer technology (Zuckcrman

1989).

The lirc prediction programs and other USCS of comyutcrs in

fire safety have increased the levd of protcclion that the

gcncral public has in fires but has not yet climinatcd 1hC

possibility of major fires and accidents.

Software Engineers

“Public awarenesi of the risks of modem technology spawned

vast amounts of nCW rcgulalions and laws helping to Creak a

litigious Society, a Society in which juries arc inclined to

award large SCUlcmcnlS to an individual no matlcr who is at

fault” (Zuckcrman 1989). A current issue b&g dcbatcd in

[IlC courts is “If ‘the simulation is wrong, and because of this

deaths and injuries occur, who is at fault; the dcvelopcrs, the

lxoplc who supplied the input, the users?” Pcrroilc points out

that “If computer Sofiware is considered ‘goods’ under the

law, soRwarc suppliers cOvla be held liable for damages

CauScd by program errors’* (Pcrrolle 1987).

If the company that produces or uses fire technology gets sued

they will most likely discontinue development and USC of thcsc

products. Many companies decide not to pursue ideas

because of the threat of liability partly due to the lawyers who

promote the idea that whenever there is an accident SOITlCOIle

must pay. The technological advances in the fire lighting

arca have been, and will conlinuc to bc, slowed by the courts

Another issue ConCcrnS how much the company that produces

thcsc prediction programs should charge for lhc technology.

In an i&al society cvcryonc would have equal access to ,the

programs, not just those who can afford them. Volunteer [ire

departments, which arc funded entirely by local citizens,

would not be able to afford the hardware and software costs

to install these systems. However, if they were made

available to the genCra/ public at a low cost, there is no

means to prevent the malicious misuse of the technology.

Fire Safety Engineers

The intent of the fire safely cnginccrs is to better protect the

public caught in a firC and the fire lighters combatting the

inferno. Armed with bcflcr analytical icchniques, ftre

CngineerS can tell archilccts and designers how to Crcatc

Struclurcs that will contain fires. If fire safety cngincers a~:

constantly coming up with new methods to contain fires and

using the prediction programs to prove that building codes

should bc stricter, old buildings can never meet current code

rcqtiircnlents. Additionally, the time required to Change. fire

codes exceeds the rate at which new standards arc being

dcvclopcd so fire codes cannot be kept up to date. Thcrcforc,

when a case appears before a judge, he must decide what

Co& standards the case will be based on.

Additionally, the prediction programs arc having a negative

effect on the fire safety profession. Previously, the codes

were scl by consensus among the lire safety engineers. Now,

by running the fire simulation program against structures

which have recently burned, lire safety engineers can

determine where better codes could have reduced the damage

done by the fire. Therefore, the cocks arc being set by the

results of the fire simulation program and not by the fire

safety engineers. This may result in fire safely engineers

viewing the simulation programs and expert systems as

&Creasing their status because this new technology is taking

away their judgcment.

The attitude of the fire safety cnginccrs towards the new

technology may severely impact the work being done in the

expert system area. The new technology ncc& to be

introduced into their profession as a Set of tools to enhance

their job not replace them. Even if Ihe fire safety engineers

accept the technology and assist in successfully completing the

expert system work, the next generation of fire safety

cnginecrs must be careful to scrutinize the computer programs

to catch mistakes; the fire Safety engineers still riced to be

instructed in the older methods so they can make judgement

calls in situations where the expert system cannot make a

decision. A future problem facing fire safety engineers is the

work load resulting from pressure to examine more and more

structures. As more pressure is put on the fire engineers to

examine more buildings, the chance that they overlook an

237
important factor increases. However, the “decision or

engineering support systetns” will help to reduce the number

of mistakes made during inspections.

Fire Fighters

Today, tire lighters are seeing the slow cmcrgence of

computers into their field. In Phoenix, the success of the new

computer system can be directly Elated to the input supplied

by the fit-e lighters during the design s[a~e of the system. In

a profession which is in dire needs of new recruits, members

are hoping that the glamour of the computer technology and

the promise of increased safety as a benefit of the technology

will entice younger people to consider the profession.

However, the new technology presents the fire fighters with

other issues. The next generation fire fighter must not only

understand the older methods but must also be computer

j&et-ate causing problems finding qualified individuals. The

younger fire lighters, dependent on the new computer system,

need to still be taught the old system in case of system

failure. The old techniques cannot he totally abandoned since

lives may be threatened when the computer system is

unavailable.

New issues concerning responsibility are being presented to

the next generation of fire fighters. For instance, let’s

assume the building owner moves something into the building

after the data for that structure was collected or the simulation

program erroneously predicts the path of fire propagation.

Both of these errors may cause the fire fighters to combat the

fire differently which could result in fire burning out of

control in a situation when it would normally be contained

quickly. In incidents such as these, who is responsible for

loss of life and property, the person who developed the

computer system, the person who coliected the input data, the

person who entered the data, the fire chief who bclicvcd the

output? Prior history has shown that the fire chief would

most likely be blamed; in fact, the computer simulations

might cause incidents of second guessing the fire chiefs

decisions by proving that if mother slcp had been taken the

fire would have been controlled. The fire fighters riced to be

aware that the technology is not flawless and they should not

r&y on it as their sole source of decision-making criteria.

They need to find a balance between what their experience

tells them and what the cornpuler tells them to combat the

fiR?S.

Builders and Owners

Arson prediction models, and the databases used by them, arc

considcrcd “an invasion of privacy” to most building owners.

On the other hand, the occupants are glad to see measures

taken to protect their homes. Since most owners arc the OXS

who burn their buildings for profit, they feel their privacy is

being invaded by this technology which enables insurance

agencies, who do not want owners to collect money by

burning their buildings, to track their prior history. Knowing

they are being tracked may deter them from burning their

OWl buildings.

Fire simulation models are beneficial in assessing d&Ens and

dcvcloping more flcxiblc and cost effective fire safety

practices. The United Kingdom’s Safety and Reliability

Directorate (SRD) uses the model routinely in sal”cly

assessments; the U.S. Coast Guard uses fire simulation

models to improve ship designs in an effect to bcttcr protect

(heir crews. Although, the program can be used to dctcct a

serious problem at the design stage instead of the building

stage, where it may be too late to make any changes, the

strength lies in analyzing current buildings and making

improvemenls to those buildings. By examining structures at

the design stage, the fire simulation program enables one

design to be compared to another to point out the weaknesses

in the performance of some fire prcvcntion systems.

However, the program dots not force the buil&r to

implement the appropriate design. Most building owners,

armed with the programs, can make decisions to determine

whether they should risk lives (currently valued at

$‘LSOK/pcrson) during a fire or spend extra money at

construction time to install better fire dclcction and

suppression systems.

If the builders and owners decide to put in a better fire

detection and suppression system, any additional money spent

on these systems can, and probably will be, passed on to the

public in higher costs, fees, and taxes. The builders and

owners need to determine just how much the public is willing

to spend to be better protected in buildings such as hospitals,

schools, nursing homes, high-rises, etc.

Corporate Risk Managers

A corporate risk manager’s job is to dccidc whether to buy

insurance or protect the corporate risk through SOme other

means. The corporation views the purchase of insum~~ as

risk. Most companies don’t have risk management; they ’

handle it by buying 100 percent insurance. With the

introduction of new technology, many companies wishing to

decrease money spent on insurance will create new positions

for the risk manager or make existing positions more

prevalent.

By using decision trees, expert systems, databases, and

prediction programs, the modem high-tech risk manager has

the ability to determine how much is at risk in the corporation

due to a fire. They can dctcrminc what they feel is

acceptable risk and modify their existing buildings

appropriately or purchase more insurance.

Insurance Agencies

Most insurance companies do not have technological

engineers; they rely on history to provide them with the

information necessary to determine rates. Faced with major

losses due to structural fires, insurance agencies will bring

computer technology into their office to help protect their

interests. They arc being forced to hire engineers on SW to

insp& buildings being insured and set up computer systems

238
which allow them to tap into the same information and

databases used by the arson prediction program &.?vc~o~c~s

Insurance agcncics are faced with some tough ethical issues.

The insurance agency is a business which must be profitable;

therefox, most insurance companies will not insure a building

which the programs state arc either likely targets for arson or

will have massive damage if started on fire. The insurance

companies would probably even review older policies to

determine if any should bc cancelled for these same reasons.

Furthermore, the technology will be used to justify higher

insurance rates. The insurance company can simply point to

the output of the program lo “prove” the building is at high

risk.

Armed with this new information and the compute power to

process it, the insurance agencies can build a “Bad Building

and Ownez’ database. This database could bc used as basis to

refuse insurance to the individuals who own buildings. If a

building/owner is incorrectly placed on this list, lTlCaSUI’CS

need to bc put in place to notify PCOP~C when information

about [hems&es or their building is in the database and how

they can get incorrect information corrected.

CONCLUSION

This paper has focused on the social impact of the new

technology being applied to fire safety engineering. At times

the new technology seems to have more of a negative impact

on society; however, there are cases wcx the new technology

has saved iivcs. In Phoenix, the new computer system was

reccivcd positively by all who used it and Ihe rcsu][ was more

efficient response to the needs of the public. In New York

City, the arson prediction program helped to decrease the

amount of arson which took place in the Flatbush and Crown

Heights communities. The U.S. Coast Guard has increased

the safety of their crew by using fire simulation programs to

improve the fire safety level of their ships.

The intentions of the devclolxrs of this new technology are

rooted in helping the general public to be better protccled

from fires. As new technology appears, the developers and

sellers must be careful to ensure that the systems arc not

blindly trusted or put to the USC for which they were not

intcndcd.

Additionally, the public needs to made aware that technolo&y

is neutral; it’s how technology is managed that cause

problems. Thcrcfore, it’s not so much the information and

output of the new technology but what is done with this

information that is Ihc potential problem.

LITERATURE: =D

Anon. 1979. How Computers Fight Fires. Boston Globe,

Deccml)cr 28:21.

Anon. 1987. Expert System Aids Firciighters. Design News

July 6:51.

Anon. 1989. Computer Modclling Yields Practical Benefits

Nuclear Engineering International. February:2 I-23.

Bisol, Anna L. 1989. The Front Line. Montachusett Review.

November 15:6-7.

Cook, Roycr. 198.5. Predicting Arson. Byte. October:739-

145.

Dillcnbeck, Bruce. 1985. Fighting Fire With Technology

Byte. October:249-15 1.

Fitzgerald, Robert W. and Wilson, Rcxford. 1983. Building

Firesafety Evaluation.

Fitzgerald, Robert w., Richards, Robert C., and Bcylcr Craig

L. 1987. Firesafety Analysis of the Polar Iccbrcakcr

Replacement Design.

Fitzgerald, Robert W. 1989. Worcester Polytechnic h&tute,

Worcester, MA. Intcrvicw, November 8.

Koshland, Daniel E. 1985. The Computer Issue. Science,

April 1,6:401.

Pcrrollc, Judith A. 1987. Computers and Social Change.

Wadsworth Publishing Company. Belmont, California

Pcrrollc, Judith A. 1988. Risk and Responsibility in a

Computerized Environment.

Pcrrollc, Judith A. 1989. White Collar Computers

Pcrrow, Charles. 1984. Normal Accidents: Living with High

Risk Technology. Basic Books. New York.

Sawyer, Thomas F. 1984. Phoenix is first with MDTs. FIRE

SERVICE Today. August: 1 1-12.

Watts, John M. 1987. Databases. Fire Journal.

July/August: II.

Zuckerman, Amy. 1989. A World Out of Balance. WPI

Journal. Summer:&10.

The author thanks Professor Robert Fitzgerald, Professor

Judith A. perro]]c, and the Northcastcrn students in lhc Fall

1989 Computers and Society class for contributing

information.

239
FIRE’S IMPORTANCE IN SOUTH CENTRAL U.S. FORESTS:

DISTRIBUTION OF FIRE EVIDENCE

Victor A. Rudis and Thomas V. Skinner’

Abstract-Evidence of past fire occurrence is estimated to occur on 22.4 million acres, or 26 percent, of

the 87.2 million acres of forests in Alabama, Arkansas, southeast Louisiana, Mississippi, east Oklahoma,

Tennessee, and east Texas. Data are drawn from a systematic survey of fire evidence conducted in

conjunction with recent inventories of private and public forested areas in the South Central United States.

Some 8.9 million acres that are estimated to contain evidence of fire are nonstocked or consist of sapling or

seedling stands; X.2 million acres consist of awlimbcr stands, and 5.3 million acres consist of polelimber

stands. Fire evidence commonly occurs in forests of the Gulf Coastal Plain and the Ouachita Highlands--in

areas dominated by pine and oak-pine forest types and by National Forest and forest industry ownership.

Fire evidence is relatively rare in the Mississippi Alluvial Plain, the Boston Mountains of Arkansas, and

most of Tennessee--areas dominated by bollonlland or upland hardwood forest types and hy a mix of

ownerships. Seventy-five percent of the acreag e showing evidence of having burned during the past 10

years is associated with wood, livestock, or wildlife production, or with vegetation management; 3 pcrcen1

is associated with 8 natural disturbance. No causal agent has been identified with fires occurring on 22

percent of the acreage.

Comparison with other estimates of annual average fire frequency by State and by potential causal agent

suggests that tire frequency estimates based on evidence observations from forest surveys arc credit)le.

Given be widespread extent and distribution of fire evidence presented in this report, one implication is that

any changes in lire regulations will have important consequences for forestry in this region. Bccauss survey

estimates 8~ linked with location, forest stand, and tree characteristics, forest survey fire data should prove

usefitl for exploring the relationship of past tire occurrence to regional air quality and wildfire danger. With

the addition of measurements fium a subsanlpl~ of plots, forest survey fire data could be used to assess

fire’s impact on the production of water, livestock forage, wildlife habitat, and timber for multi-county and

larger areas.

INTRODUCTION

Rccurrcnt fire is essential to many pine forest ecosystems in

the southern United States, but there have been few surveys

of fire OCCUKCnCC over broad geographic areas. State and

federal iirc control agencies use information about fire

occurrcncc to estimate regional smoke hazard and to establish

priorities for fire protection in forested areas. Forest resource

analysts and others USC such information to assess timber

resource conditions and fix-USC practices in sclectcd areas.

Fire also plays a role in livestock forage production, wildlife

browse production, carbon storage, leaf litter biomass

accumulation, and maintenance of water quality. Models of

these multiple values therefore should include fire as a

variable that influences the current and projected status of

forest resources.

In lix South, fire occurrence--whether planned or

unplanned-is not uniformly documcnlcd. Wildfires occurring

on Southern U.S. National Forest land arc recorded by

number, causal agent, and total acres affected (USDA Forest

Service 198%). For private and other public land under the

proteclion of state forest fire control agcncics, similar wildfire

statistics are noted in a separate report (USDA Forest Service

‘Rcscarch Forester and Foreslcr, respectively, U.S. Department 0 1

Agriculture, Forcsr Service, Southern Forest Experiment Station, 201

Lincoln Green. Starkville, MS 39759-0906.

1988b). State forest lirc control agency wildfire records have

been compiled Southwide by county for the periods

1956-1965 (Doolittlc 1969) and 1966-1975 (Doolittlc 1977).

Wildfire records for areas not protect& by fire control

agencies arc not available. Neither are there more recent

compilations or more detailed Wildfire statistics.

Information on the occurrence of prescribed (i.e. planned)

fires across the South is scant. The use of tire as a vegetation

managcmcnt tool in southern pine stands has increased during

the last 50 years (Williams 1985). Fire is used to prepare a

site for stand regcncration, to dispose of logging slash, to

reduce hardwood competition, and to limit wildfire hazards.

For National Forest land, prescribed fire statistics are i&d

by total acres and management objective (USDA Forest

Service 1988a). Comparable estimates for other public

landholdings and private land arcas arc not available.

In some fire districts, local fire control personnel know only

incidentally of owners with large landholdings where

prescribed fire is used, as permission to bum is not required

in all States. Many State agencies must rely on “ballpark”

estimates gatl]ered from these district personnel, From allied

natural resource agencies, from coopcmting forest industries,

and from self-administered questionnaires completed by

persons in districts that require bum permits. Annual

340
slat&de prcscribcd fire acreage estimates are compiled from

thcsc data sources (e.g. Ashley 1985, Miles 1985, Moody

1985). However, reliability of these eslimalcs is uncertain

(Wade 1985).

Since available lirc occurrcncc data am incomplctc at bcs( and

anecdotal at worst, they are difficult to compare at

multi-county and mljlti-&lc lcvcls of resolution. Regional

distribution paLtcms and detailed fire OccLlrrCncc data by

stand-size class, rorcst type, and acres afl”cclcd on

nonindustrial private ownership arc not reported and rarely

arc collcctcd.

In this report, data about fire cvidcncc and about related

measures are presented and discussed. These data WC~C

collected during a systematic survey of fire evidence in South

Central U.S. forests. Arcas included in this survey were:

Alabama, Arkansas, southeast Louisiana, Mississippi, cast

Oklahoma, Tennessee, and cast Texas. Data on evidcncc of

fire occurmncc in the past decade are presented together with

data on cvidcnce of other activities in the past dccadc so that

polcntial sources of fire, or causal agents, can be at lcast

tcntativcly idcntilicd. These data, and the conclusions drawn

from lhcm, ate examined for consistency with average annual

fire occurrcncc information obtained from other sou~ccs.

METHODS

The Southern Forest Expcrimcnt Station’s Forest Inventory

and Analysis (FIA) Unit conducts an inventory sampling

program that assesses the current status of and trends in

private and public forest rcsourccs. Permanent l-acre plots

are located at the intersections of perpendicular grid lines

spaced at 3-m&z intervals throughout the South Central States.

Detailed field &ct-va;ions arc &hincd in some 17,000 plots

on land classified as forest (i.e., at least l-acre in size, 110

reel in width, and capable of producing crops of industrial

wood). When combined with ground-truth of

plio&ointc~~rctation for additional areas, observations from

plot samples are expanded statistically to estimate all forest

rcso~rccs in a county, state, or region. Field observations are

updated about every 8 to 10 years. Periodic analytical

assessments and tabular summaries report the current status

and trends in species, number of trees, forested area, and

timber productivity. Data arc reported by forest type,

stand-size class, ownership class, and other characteristics.

Further details, including definitions and criteria for

classifying forest characteristics, are available in State

Resource Bulletins (e.g., McWilliams and Lord 1988, Rudis

1988).

Evidence of past fire occunence is recorded as present or

absent, and consists of physical evidence of bum scars on

trees and other objects, reduced litter depth, and other

vegetational indicators. Fire cvidencc also is recorded by age

class of the most recent occurrence. For the 1981 survey of

Alabama, age class was defined as: recent (1 or 2 years),

within 3 years, or 3 years or older. In subsequent surveys,

catcgorics have been line-tuned to limit overlapping ages and

establish an open-ended highest age category. The updated

categories are recent (I or 2 years), 3 years to previous

survey, and older than previous survey.

Fire cvidcncc observations have been recorded only once for

the most recent surveys of each region: Alabama (AL) 1982,

southcast Louisiana (LA) 1984*, east Texas (TX) 1986, east

Oklahoma (OK) 1986, Mississippi (MS) 1987, Arkansas (AR)

1988, and Tcnncssec (TN) 1989. Statistical inferences

regarding diffcrcnces in fire occurrence by forest

characteristics are based on chi-square analysis of category

kcqucncics, with significance of chi-square values established

a priori at the 5-perccnl probability level.

Evidence of other activities originating since the previous

survey an: used to suggest whether fires wcrc planned or

unplanned. Timber production is recorded if evidence

suggests such activity occurred since the last survey. These

include timber management activities--site preparation and

timber stand improvement-and timber harvest

activities-clearcutting and partial cutting. Similarly, evidence

of livestock USC, game management, and nontimbcr cutting or

clearing, and miscellaneous artifacts associated with human

USC, are noted as well. (Since age categories used in the 1982

survey did not specify age beyond 3 years, some of the

cvidcncc coded ihcn may relate to fires that occurred prior to

the previous survey. To avoid confounding by time period,

dctailcd analysis of causal agents includes only data for

surveys conducted after 1982.)

For the purposes of this report, fires are classified as

‘prescribed” where fire evidence occurs in conjunction with

cvidencc of production (timber management or harvest

activities, livestock USC, game or nongame wildlife

management) or miscellaneous activities associated with

cutting or clearing (woody debris Tom noncommercial wood

harvest, maintenance of right-of-way). Fires are classified as

“wildfire” where fire evi&nce occurs together with evidence

of natural disturbance or salvage operations. “Other agents” is

applied to fires in plots with fire evidence and no evidence of

production, miscellaneous activities, or wildfire. Detailed

observation codes by category are available from the senior

author upon request. These and other category and

observation codes can be found in Forest Inventory and

Analysis (FIA) field manuals (Quick 1980, FIA 1989)

‘Budgetary constraints in 1983 limited the tally of fire evidence and

nontimhcr activities. A statewide tally is planned for 1991 in

Louisiana.

241
RESULTS

Fire evidence is cstimatcd lo occur on 22.4 million acres, or

26 pcrccnt of the 87.2 million acres of timberland surveyed.

Fir-c cvidcncc and survey year for each state arc as follows:

Alabama, 1982, 7.1 million acres (33 pcrccnt of the

timberland); Arkansas, 1988, 3.4 million acres (20 pcrccnt);

southcast Louisiana, 1984, 0.8 million acres (43 percent);

Mississippi, 1987, 4.8 million acres (28 pcrccnl); east

Oklahoma, 1986, 2.1 million acres (43 percent); Tenncssec,

1989, 1.7 million acres (13 pcrccnt); and cast Texas, 1986,

2.6 million acres (22 pcrccnt). For surveys conducted aRcr

1982, 73 percent of the evidence is associated with fires that

occurred since each State was surveyed (approximately 10

years previously).

Estimates of fire evidence in forested areas by county provide

regional summaries within and among States (fig. 1).

Counties with fire evidence in forests are concentrated chiefly

in the Gulf Coastal Plain (sputh Alabama, Mississippi, and

Texas) and the Ouachita Highlands (southcast Oklahoma and

west central Arkansas). Fire evidence in forests is relatively

rare in the Mississippi Alluvial Plain, the Boston Mountains

of Arkansas, and most of Tennessee.

Forest Characteristics

Unless otherwise noted, all differences in fire evidence

frequency by forest characteristics are significant, with

chi-square values at probabilities less than 0.001.

Area estimates by forest type and stand-size class arc

summarized in table 1. Forty percent of the 22.4 million acres

estimated to have fire evidence is composed of nonstockcd,

sapling, or seedling stands, 37 percent is composed of

sawtimber stands, and 24 percent is composed of polctimbcr

stands. Fire evidence occurs in all forest types. It occurs in

54 percent of pine plantations, 3.5 percent of natural pine

stands, 30 pcrccnt of oak-pint stands, 20 percent of upland

hardwood stands, and 6 pcrccnt of bottomland hardwood

stands. Within stand size classes fire evidence occurs in 3.5

pcrccnt of nonstockcd, sapling, or seedling stands, 22 percent

of poletimber stands, and 22 percent of sawtimbcr stands.

Percent of timberland area with fire evidence by forest type

and stand-size class is shown in figure 2.

In pine plantations, the proportion of timberland area with firr

evidcncc is 57 percent in nonstocked, sapling, or seedling

stands, and declines to 48 percent in sawtimbcr stands, a

relatively small but significant difference. In natural pine

stands, the proportion of area with tire cvidcnce, 35 percent,

is not statistically significant by stand-size class. The majority

of pine plantation area is in sapling-seedling stand-size class

and the majority of natural pine area is in sawtimber

stand-size class. Results suggest that fire occurrence remains

higher in pine plantations relative to other forest types

throughout the life of these stands.

Fire evidcncc occurs more frequently in plantations than in

natural pine stands, regardless of stand-size class. Fire

evidence is less common in upland hardwoods and bottomland

hardwoods than in pine stands. Fire evidence declines as

stands mature.

Fire evidence occurs on 41 percent of forest industry land, 28

pcrccnt of public land, 19 percent of farmer-owned land, and

21 percent of nonindustrial private land (table 2). Forest

acreage with fire evidence is concentrated in sapling-seedling

stand-size class and in forest industry and public ownership.

Public land with fire evidence is primarily in the sawtimber

Figure 1 .--Percent timberland area with fire evidence per land

area by county, South Central United States, 1982-1989.

Unshaded counties arc scheduled lo be surveyed in 1991.

242
Table l.--Tj&er[artcj acres with and without fire evidence by forest type and

stand-size class.”

Fire evidence ALL Planted Natural Oak- Upland Bottomland

and stand-size class types pine pine pine hardwood” hardwood

Mj[(ion acres”-------------------

ALL stand sizes

With fire evidence

No fire evidence

Total

Sapling-seedling”

With fire evidence

No fire evidence

Total

Polet imber

With fire evidence

No fire evidence

Total

Sawt imber

Uith fire evidence

No fire evidence

Total

22.43 3.51 6.00 4.83 7.25 0.75

64.19 2.99 10.94 11.08 28.95 IO.82

81.22 6.56 16.94 15.92 34.22 11.57

8.92 1.98 1.03 2.42 3.25 .21

16.45 1.49 2.00 3.27 8.14 1.58

25.37 3.48 3.02 5.69 Ii.40 1.78

5.30 1.06 1.27 .91 1.88 .I9

19.16 .91 2.38 3.22 0.09 2.59

24.48 1.96 3.64 4.13 1.96 2.78

8.20 .53 3.70 1.49 2.12 .36

29.16 .59 6.57 4.62 10.74 6.66

31.31 1.12 10.27 6.1 1 12.86 7.01

’ Rows and columns may not sum to totals due to rounding

b Includes 67,000 acres classified as nontyped.

’ Includes 341,000 acres classified as nonstocked.

stand-six class and in natural pine and oak-pine forest typCS.

Half of the forest industry land with fire cvidcnce is in

nonstockcd, sapling, or seedling stand-six class. Forest

industry land with fire cvidcnce is relalivcly evenly distributed

over planted pine, natural pine, oak-pine, and upland

hardwood forest types. Farmer-owned land with lire evidence

is evenly distributed by stand-six class; acres are primarily in

upland hardwood forest type. Nonindustrial private land with

fire cvidcnce is even/y distributed by stand-six class; acres

arc conccnlratcd in upland hardwoods, natural Pine, and

oak-pint stands.

Location

If one is to correctly interpret regional patterns of fire

occurrence in forested areas, one needs to consider the

arrangement of forests and adjacent nonforcst areas. The

forested urban-wildland interface, i.e., the forested land

adjacent to urban areas, is of considerable interest in fire

scicncc. Memphis, Houston, Little Rock, Mobile, and

Birmingham represent the major urban centers in the South

Central Slates survey area. Howcvcr, the Present sampling

schcmc is inadequate to categorize urban influences; few

sampled plots occur in this area.

FOREST TYPE

Figttrc 7-.--Percent timberland area with fire evidence by

forest ty}X and stand-size class.

343
Table 2.-- Forested acres with fire evidence by forest type, stand-size

class, and oSwwrship class”

Forest type and All Public

stand-size classb OttlIen land

Forest

industry,

it-xl. other

leaSed Farsler private

ALI forest types

Sapling-seedling

Poletihw

Sawti*

Total

Planted pine

Sapling-seedling

Poleti&er

Sawtimber

Total

Natural pine

Sapling-seedling

Poletiaber

Sawtimber

Total

Oak- pine

Sapling-seedling

Poletinher

Smtislber

Total

up1-d haNlawd”

Sapling-seedling

Poletimber

Sawtimber

Total

Bottomland lladamd

Sapling-seedling

hletiaber

sati*

Total

. . . . * . . f Million acres . . . . . . . , .

8.92 0.57 4.15 1.24 2.95

5.30 -49 1.74 .96 2. 11

6.20 1.51 2.66 1.56 3.19

22.43 2.57 7.66 3. 70 8.25

1.98

1.66

.53

3.57

-07

-03

1:s"

1.58 .08

.a2 .05

.21 .06

2.61 -19

1.03 -13 .32 -18 -40

1.27 -18 .47 .16 .45

3.70 .a6 1.69 .45 1.30

6.66 1.18 1.88 -79 2. 18

2.42

.91

1.49

4.63

.18

2:

.62

1.20 .25

.21 .I6

.36 -29

1.76 .71

3.25

1.88

2.12

7.25

-21

:::

-75

:148

.23

.54

.68

.53

.60

1.82

.Ol

.Ol

.03

-05

1.66

.21

.24

1.44

2:

.lO

.20

:!I:

.09

.20

.79

-42

.53

1.74

1.46

1.01

1.05

3.46

.lO

.07

a Rms snd columns may not sum to totals due to mending.

l J Nonstocked areas (~,999xx-es) are included in sapling-seedling

stand- size C1aS.S.

’ Includes 26,666 acres classified as nontyped.

244
Tl~c largest non-[orcskd arcas in the South Ccnlral Slates

include [hc Cx[CnsivC farmland acrcagc along floodplains oj

the Mississippi and Arkansas Rivers, the Blackbclt Prairie

crcsccnl that strctchcs from north ceniral Mississippi to

central Alabama, and the Central Basin of central Tcnncsscc

and north Alabama (fig. 3).

Areas dominated by southern pint forest types contain the

largest conccnlration of forcstcd plots with fire evidence.

Clusters of plots with fire evidcncc, particularly those of

rclativcly recent origin (triangles, fig. 3), indicate areas whcrc

fire has played an important regional ro!c in forest ecosystem

dynamics. Although dctailcd gcoslalistics arc needed to verify

the significance of spatial patterns, the density of forest

industry landholdings and pint-dominated public timberland

(Rosson and Dooli[tlc 1987) appears directly rclatcd to the

density of lirc cvidcnce.

Hots with cvidcnce that fire occurred since the previous

survey (trian@s, fig. 3) arc to be distinguished from plots

with evidence of older fires (circles, fig. 3). A visual

inspection of paltcrns suggests that, on avcraec. areas with

historical fire cvidcncc also contain more rcccnt fire cvidencc.

-7

A careful examination of patterns formCd by plots with older

JjrC cvidcncc can suggest additional hypothcscs. Gcostatistical

analysis, coupled with a geographic information systcni and

knowledge of historical lire occurrcnccs, should 1~ helpful in

further investigation of pattern differences.

Causal Agents

Approximately 314 of the XXX with evidoncc of /ire since Ihc

previous survey (cxcludcs the 1982 Alabama s~rvcy) also

contains cvidcncc of activities associated with production of

timber, wildlife, or livestock, or with miscellaneous forms of

vcgctation management. Known wildfires are noted on 3

pcrccnt of the acres. Fire cvidcncc not clearly associated with

a causal agent occurs on 22 pcrccnt of the acres (table 3).

Figure 4 shows pcrccntagc of acres with iire evidcncc by

causal agent and ownership class. Timber production

dominates on forest industry land (81 pcrccnt), and animal

production is highest on farmer-owned land (30 pcrccnt).

Timber production dominates in sapling-seedling stands, and

is high for both polctimbcr and sawtimber stand-size &SW

(fig. 5). It is notable that the perccnlagc of sapling-seedling

acres in the “other” causal agents category is significantly

smaller than the ~rcentages of polctimbcr or sawtimber acres

in that category.

Plot Locations With

x Fire Evidence

A Since Previous Survey

0

Older Than Previous Survey

t No Fire Evidence

Figure 3.--Timberland arca surveyed with and without fire evidcncc
Table 3. --Area with fire evidence by stand-size class, owwship class, and potential

causal agent. ’

Stand-size class and

potential caosal ageot

Forest

industry,

ALL Public incl. other

ormets land leased Farmer private

Tiaber production

Tin&r aad Livestock or

wildlife pmdoction

Livestock or wildlife pxvduction

Miscellaaeous cutting or Cl&Wing

otker

NdZlOi3l distorllaoces

Total

Sapling-seedlingb

Ti &er production

Tiaber and Livestock or

wildlife production

Livestock or wildlife production

Miscellaneous cutting or Clearing

Other

Nam distarbances

2.68

.91

.24

.07

.54

.I9

Total 4.93

Poletinber

Ti&er prodaction

Timber and Livestock or

wildlife prudactioa

Livestock or wildlife prodaction

Miscellaaeeus cutting or Clearing

other

Nfd3U-d dis-e

.93

.24

.17

.06

.74

.07

Total 2.20

sawrisber

Timber production

Ti&er and Livestock or

wildlife proauction

Livestock or wildlife production

bfiscellaaeow catting or clearing

other

Natural disturbance

1.63

.52

.27

Total

.I7

1.16

.14

4.69

0.83 2.95 0.46 1.50

.I4

-06

.06

.41

.05

.18 -37

.26 -22

.06 .09

.42 1.20

-09 .I7

1.56

.97

.13

.08

.41

.08

4.63 1.47 3.56

.21

-06

.Ol

.OZ

.06

.36

.09

1.66

.62

.05

.OZ

2

.21

.08

.09

.02

.12

.05

.66

.I5

.08

.Ol

.28

-10

2.76 .57 1.30

.43 .lO .31

:E

.02

2;

.80

:A:

.25

.54

.07

.04

.05

.22

.03

.95

.62

.22

.03

-04

:A37

1.10

.02

.07

.Ol

.lO

.Ol

.31

.15

.08

.ll

.03

.I9

.03

.59

-53

:Z

.06

258

1.46

’ Excludes Alabama (7.1 mllliw acres) and other -eyed states with fire evidence

older than the prior survey (4.1 millioa acres).

b Iacludes 53,666 acres classified as nonstocked.

246
PUBLIC FOREST INDUSTRY

TIMBER 53/--‘..-,

/ l

/ \

MISC. 4

TIMBER 64 /-\

/ \

8 ANIMAL 21

FARMER OTHER PRIVATE

.,....._.,......._.. ~

OTHER 29 OTHER 34

Figure 4.--Pcrccnt timberland area with fire evi&ncc since the previous survey

by ownership class and potcnrial causal agent (excludes Alabama),

SAPLING-SEEDLING POLETIMBER SAWTIMBER

TIMBER 42

ANIMAL 19 ANIMAL 5

Figure 5.--Pcrccnt timberland area with fire evidence since the previous survey

by stand-six class snd potdalCYIUSS) agcnl (cxcludcs Alabama).

TIMBER MANAGEMENT HARVEST

SAPLING-SEEDLING SAWTIMBER SAPLING-SEEDLING SAWTIMBER

CLEARCUT 6% h ,,

PARTIAL

TSI 24 PARTIAL

CUT 1 8

N O

HARVEST 48

Figure b.--Pcrccnt timberland area with fire evidence and limber production activity

by lypc of tilnbcr munagemcnt anJ harvest activity (excludes Alabama).
Figure 6 contrasts the occurrence of lire evidence in

sapling-seedling stands and in sawtimber stands with timber

production by management and harvest activities. Timber

management includes site preparation (SITE PREP) and

timber stand improvement (TSI); no management (NO

MGMT) rcfcrs to harvest with no management. Timber

harvest includes partial cut and clearcut; no harvest refers to

timber managcmcnt with no harvest activity. A majority of

the fire evidence occurring with evidence of timber

rnsnagemcnt is associated with site preparation in

sapling-seedling stands and with timber stand improvement in

sawtimber stands. In sapling-seedling stands, the majority of

hrc cvidcncc associated with timber harvest is associated with

clcarcut operations. In sawtimbcr stands, most fire cvidcnce

associated with timber harvest is associated with partial cut

operations.

Estimates of average annual tire occurrence by State, causal

agent, and data sour-cc arc presented in table 4. It is worth

noting that the causal agent estimates derived from forest

survey data arc generally consistent with the estimates based

on data from other sources. There is 95 percent confidence

that forest survey total acres are reliable within the intervals

noted.

DISCUSSION

Forest survey plots arc: categorized simply as having or not

having tire cvidcnce, and no interpretation is made regarding

fire source. While this limits analysis of the data, the

extensive and systematic sampling conducted during forest

surveys yield descriptive regional information of heuristic

importance. There also will be opportunities to assess trends

in frre evidcncc when the area under study is rcsurvcyed in

the near future.

Total acrcagc with fire evidence from forest surveys

rcprcscnts an estimate of the cumulative acreage burned. No

scparatc cstimatc is made for the acrcagc burned more than

once bctwccn surveys. The forest survey estimate is based on

a sample and has a corresponding error associated with the

sampling process. In general, sampling error increases as the

area considered decreases. Ninety-five percent confidence

intervals arc gcncrally within 5 percent of the acreage

cstimatcs for data aggrcgatcd over multi-county and larger

arcas.

Since most plots arc surveyed about every 10 years, we feel

confident that observations of fire scars, vegetative growth

since the last fire, management activities, and other

disturbances can be observed readily. Howcvcr, we feel that

analysis of fire cvidcnce by causal agent should be intcrprctcd

with caution. For cxamplc, fire is attributed to “other” agents

less often for forest industry-owned land and in

sapling-seedling stands than stands belonging to other

catcgorics (figs, 4 and 5). Survey results suggest at least two

hypothcscs: (1) Iirc evidence is associated with forest

managcmcnt activities in younger, sapling-seedling stands and

on forest-industry land, rather than in older stands or on land

in other ownerships; (2) fire evidence occurring in poletimbcr

and sawtimber stands and associated with “other” agents is

caused by low-intensity surface wildfires that do little damage

tu trees, whereas tire evidence observed in sapling-seedling

stands is associated with damage that is readily attributed to

wildfire. An extension of the second hypothesis is that

because forest industries employ prescribed fire to a greater

degree than other landowners, fires caused by “other” agents

may have less opportunity to occur.

Although we suggest that co-occurring evidence on sampled

plots provides clues to the origin of fire evidence, we

recognize the weakness of the assumption. Additional field

measurements are needed to test this assumption to quantify

fire impacts on forest ecosystems, and to estimate wildfire

potential. Development of models that relate the type,

intensity, and frequency of fires to fire evidence, e.g., litter

depth on plots with and without fire evidence, and the

addition of field measures to FIA plots that quantify potential

surface moisture and the amount of live and dead materials

would be useful in this regard.

Comparison With Other Estimates

We have already said that “ballpark” estimates of fire

occurrcncc can be inaccurate. Nevertheless, the only available

estimates of regional fire occurrence arc “ballpark’ ones. Are

forest survey estimates consistent with existing regional

estimates of annual fire occurrence?

Except in the cast: of Alabama, FIA estimates of acreage arc

from 13 to 43 percent higher than estimates from other

sources. There are many reasons why estimates from other

sources are lower. FIA estimates represent averages of

cumulative acreage with fire evidence, include prescribed fire

as well as wildfire, and represent estimates for public, forest

industry, and nonindustrial private lands. Estimates from

other sources often represent acreage burned in a single year

or averages over a few years; such figures also include

prcscribcd fire and wildfire estimates for diffcrcnt reporting

periods and landowner groups. Information from other

sources is not as likely to come from all forested areas,

particularly in the case of prescribed fires not associated with

timber production activities.

248
Table 4.--Average ammal fire DC currence by state, causa L agent, and 5sotllve of

data.

State aad

causal agent lkwest !survey” 0th~ sourcesb

Years Percent Tllousand lllowad Percent Years

Alabama '

acres ZUXVS

(+,- 2, S.E.)

1973- 82

FrYscribed fire

other agents-wildfire

Total

4 4

5 6

518.1

238.9

757.0

1979- 86

Rescribed fire

other agents-wildfire

Total

7 7

2 3

182.6

34.9

217.5

-t Louisiana 197.5- 84

Fl-escribed fire

other agents-wildfk?

TOtA

7 4

2 6

318.1 (15.4)

497.3 (17.5)

725.4 (23.3)

191.2 (7.1)

58.2 (3.9)

249.4 (8.1)

53.9 (5.4)

18.7 (3.2)

72.6 (6.3)

333.2 (14.0)

91.1 (7.3)

424.3 (15.8)

80.5 (8.5)

53.7 (6.9)

134.2 (Il. 0)

46.5 (4.6)

45.1 (4.6)

91.6 (6.5)

160.3 (8.0)

33.7 (3.7)

194.0 (8.8)

57.6

6.6

64.2

Mississippi 1978- 87

PN?scribed fire

other agents-wildfire

Total

Fast OMslloma 1977- 66

Prescribed fire

other agents-wildfire

Total

TermesSee 1981-89

l%l?scribed fire

other agents-titdfire

Total

Fast Texas 1977- 86

Flvscl-ibed fire

other agents-wildfire

Total

7 9

21

6 0

4 0

5 1

4 9

8 3

17

233.5

108.9

342.4

55.0

39.0

94.0

26.9

51.0

77.9

123.8

52.9

176.7

6 8 1975,84&

3 2 1988

84

16

1975,aae

1988

9 0

1 0

1975 ( 84’

1988”

68 1975,84”

3 2 1988

59

4 1

3 5

65

79

2 1

1977- 86’

1977-66’

1975,841

1988

1975 ) 84k

1989

’ E Lapsed time in years: AL=9.8, AR=9.5, LA=9.1, Ms=9.5, OK=9.8, TN=9.0, TX=lO.4.

b 1988 wildfire estimates are fmm USW-Es (1998b). For the entire. Soath, average

nmmal acces lntmed by wildfire has chaaged little in the past decade (un)b-FS

1968a). 1975 prescribed fire estimates are fmm Johansen and McNab (1982).

’ May include fix-e evidence older than previoas -ey.

d Awrage of 157,320 - (1975) aad 878,970 acres (1984) (Mmdy 1985).

’ Far 1988: 35,206 -National Forest (MM-FS 1988a), ad 15,000 acres by the

State Forestry of&x (6amer Bamam, pers. CHMI.). For 1975: oa private Land,

132.350 acres in 1975. More recent data oa prescribed fire we oa forest industry

land BI+~ not available Khmer &U--R, pers. COrml.)

Statewide average of 462,420 acres (1975) aad 450,090 acrea (1984) (Mi [es 1985)

adjusted for the portian Of fOxested area smwyed.

’ Statewide estimate adjusted for tine forested area surveyed.

’ Average of 167,050 - (1975) aad 300,000 - (1984) (Miles 1985).

m-year average, 1977-1986, based on state aad forest indastry records (ICart

Atkinson, Oklahom Forestry Division, pen. comn.).

Average of 31,700 - (1975) aad 22,100 - (1984) (Ashley 1985).

’ Average of 47,600 acres (1975) aad 200,090 - (1984) (Mikes 1985).
IMPLICATIONS AND CONCLUSIONS

What can we conclude from the data presented? Thcrc arc

three major conclusions: (1) fire evidence is pcrvasivc in the

South Central States, (2) fire evidence is concentrated in

pine--growing parts of the South Central States, (3)

observations of evidence of hre occurrcncc from forest

surveys can be used as a basis for credible estimates of past

fire occurrence.

Projections of forest acres in South Central States by forest

type suggest a continuing increase in pine plantation acrcagc

and a corresponding decrcasc in natural pin e acreage, a trend

that has continued since 1970 (Birdscy and McWilliams

1986). If cvidcnce of past fire occurrcncc is an indication of

future trends, a* increase in pine plantation acreage will be

associated with increased fire frequency. Any existing or

proposed policies for regulating fire to rcducc smoke hazard

or increase protection from wildfire will have widespread

consequences for forestry in this region.

Forest survey fire cvidcnce data can be used as a basis for

studying the potential for air quality degradation and tire

danger at the regional level. When combined with wildfire

and weather statistics, forest survey tire zvidence data can be

used to establish regional forest protection priorities. The data

prcscntcd can be used as a basis for assessing fire occurrence

in strrdics of water, livestock forage, wildlife habitat, and

timber production in multi-county and larger areas. That

forest industries and other ownership groups in selected

regions have considerable acrcagc with tire evidence suggests

that fire plays an important role in these areas. The regional

extent of this influence is documented in this report and

should be considered when discussing forest management

policy and the future condition of forest ecosystems in the

South Central States.

The extent and importance of fire’s effects on South Central

States’ forests cannont be fully elucidated from forest survey

data without additional information. Because there exists a

wide array of forest characteristics, including previous land

use and ownership data, testing inferences regarding

prescribed fire and wildfire origins on a subsample of plots

should prove fruitful. Linkage of forest survey fire evidence

data with a suitable geographic information system also can

provide regional modelers with supplementary data for use in

assessing other values (e.g., water quality and soil erosion)

affected by fires.

Continued monitoring of fire evidence on forest survey plots

can supply analysts with information about trends in past fire

occurrence. Additional measures needed to identify causal

agents could he developed for a carefully selected subsample

of plots and then modeled for all plots. Such a method would

be especially useful for monitoring trends in fire use as a

management tool and evaluating tire’s effectiveness in

increasing timber productivity and other multiple-value forest

resources,

LITERATURE CITED

Ashlcy, Roy. 1985. Status of prescribed fire and smoke

managcmcnt in Arkansas, Kentucky, Oklahoma, and

Tennessee. In: Wade, Dale D., compiler. Prcscribcd tire

and smoke managcmcnt in the South: conference

proceedings; 1984 Septcmhcr 12- 14; Atlanta, GA.

Asheville, NC: U.S. Dcpartmcnt of Agriculture, Forest

Service, Southeastern Forest Experiment Station: 23-28.

Birdscy, Richard A.; McWilliams, William H. 1986.

Midsouth forest area trends. Resource Bulletin SO-107.

New Orleans, LA: U.S. Dcpartmcnt of Agriculture,

Forest Service, Southcm Forest Experiment Station. 17 p.

Doolittle, M.L. 1969. Forest fire occurrence in the South,

1956-1965. Research Note SO-97. New Orleans, LA:

U.S. Dcpartmcnt of Agriculture, Forest Service, Southern

Forest Experiment Station. 16 p.

Doolittle, M.L. 1977. Forest fire occurrcncc in Southern

counties, 1966-1975. Research Note SO-227. New

Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station. 41 p.

Forest Inventory and Analysis Research Work Unit (FIA).

1989. Forest survey inventory work plan: Alabama

1989-90. Starkville, MS: U.S. Department of Agriculture,

Forest Service, Southern Forest Experiment Station. 60 p.

(Appendices 60 p.)

Johansen, Ragner W.; McNab, William H. 1982. Prescribed

burning on large landholdings in the South. Research Note

SE-316. Asheville, NC: U.S. Department of Agriculture,

Forest Service, Southeastern Forest Experiment Station.

4 PP.

McWilliams, William H.; Lord, Roger G. 1988. Forest

resources of east Texas. Resource Bulletin SO-136. New

Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station. 61 p.

Miles, Bruce R. 1985. Prescribed fire and smoke management

in Texas, Louisiana, and Mississippi. In: Wade, Dale D.,

compiler. Prescribed fire and smoke management in the

South; conference proceedings; 1984 September 12-14;

Atlanta, GA. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station: 9-l 1.

Moody, C.W. “Bill”. 1985. Overview of prescribed burning

and smoke management programs and problems in

Alabama, Florida, and Georgia. In: Wade, Dale D.,

compiler. Prescribed fire and smoke management in the

South: conference proceedings; 1984 September 12- 14;

Atlanta, GA. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southeastern Forest

Experiment Station: 13- 17.

250
Quick, T. Richard. 1980. Renewable resources inventory

work plan: Alabama. New Orleans, LA: U.S. Department

of Agriculture, Forest Service, Southern Forest

Experiment Station. (6): l-25.

Rosson, James F., Jr.; Doolittle, Larry. 1987. Profiles of

Midsouth nonindustrial private forests and owners. New

Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station. 39 p.

Rudis, Victor A. 1988. Nontimber values of cast Texas

timberland. Rcsourcc Bulletin SO-139. New Orleans, LA:

U.S. Department of Agriculture, Forest Service, Southern

Forest Expcrimcnt Station. 34 p.

U.S. Department of Agriculture, Forest Service (USDA-FS),

Southern Region. 1988a. National Forests, Southern

Region, 1988 Annual Fire Report. 25 p.

Wade, Dale D. 198.5. Fire science adaptations for the

southeastern U.S.--a research update 1980-1984. In:

Wade, Dale D., compiler. Prescribed fire and smoke

management in the South: conference proceedings; 1984

September 12-14; Atlanta, GA. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station: 10 l- 112.

Williams, Richard A. 198.5. Use of prescribed fire on

industrial lands in the Gulf Coastal Plain and Uplands. In:

Wade, Dale D., compiler. Prescribed fire and smoke

management in the South: conference proceedings; 1984

Scptcmhcr 12-14; Atlanta, GA. Asheville, NC: U.S.

Dcpartmcnt of Agriculture, Forest Service, Southeastern

Forest Expcrimcnt Station: 33-38.

U.S. Department of Agriculture, Forest Scrvicc (USDA-FS),

Southern Region. 1988b. 1988 Annual Fire Report,

Southern Region, State and Private. 17 p.

251
A SITE-SPECIFIC APPROACH FOR ASSESSING THE FIRE RISK TO

STRUCTURES AT THE WILDLANDXJRBAN INTERFACE

Jack D. Cohen’

Abstract-The essence of the wildlandiurban interface fire problem is the loss of homes. The problem is

not new, hut is becoming increasingly important as more homes with inadequate adherence to safely codes

are built at the wildlandiurban interface. Current regulatory codes are inflexible. .$,pexificalions for

building and site characteristics cannot be adjusted to accommodate homeowner values. USDA Forest

Service Fire Research is developing a wildlandiurban fire interface ignition assessment model as an

alternative to current tire safety codes. This model is based on an analytical (rather than statistical)

assessment of shuch~ral characteristics, site characteristics, and fire severity conditions. The m&l will be

capable of assessing ignition risk for individual structures, and thus will be capable of accommodating

homeowner preferences as they al%3 tire safety.

INTRODUCTION

More than 1,400 homes were damaged or destroyed during

wildland fires in Florida, North Carolina, California, and

other States during 1985 (Laughlin and Page 1987). This

created national interest in what has come to be called the

wildlandlurban interface fire problem. Interest in the problem

continues to grow as the number of people who live in or

adjacent to wildland areas increases (Davis 1990).

Although new emphasis has been placed on the problem of

structure loss and damage associated with wildland fires, the

problem is an old new. During the last 30 years. frequent

conflagrations in California have resulted in losses of

structures, primarily homes. ARer major California fires,

reports that identified the fire problem and provided guidance

for mitigation were generated (California Dcpartmcnt of

Conservation 1971; California Department of Forestry 1980;

County Supervisors Association of California 1965; Howard

and others 1973; Moore 1981; Radtke 1983). Generally,

thcsc reports were commissioned by State and local

government agencies. With some exceptions (Dell [n.d.];

Radtke 1982), the target audiences were public officials and

Iire professionals. Many of these wildlandiurban fire reports

were comprchcnsive, providing recommendations, including

technical specifications, for urban planning, fire suppression

capabilities, vegetation managcmcnt, and building

construction. However, dcspitc the production of these

rcpofts, the wildlandiurban interface fire problem has

continued with little abatement.

Little attention has been given lo the social aspects of the

wildlandiurban interface fire problem, and this may be one

reason why the problem persists. The technical aspects of

this lire problem such as building codes and suppression

improvements, have dominated discussions about the subject.

However, the social aspects of the wi\dland/urban fire

problem gained attention at wildlandiurban intcrfacc

‘Rcscarch Physical Scientist, Southeastern Forest Espcrimsnt Station,

Forest Scrvicc, U.S. Dcpanmcnt of Agriculture, Dry Branch, GA.

2.52

workshops conducted during 1986 and 1987 (Laughlin and

.Page 1987; USDA Forest Service 1987). The participants

concluded that a solution to the fire problem must recognize

and accommodate homeowner values and motivations.

The social aspects of the problem have not yet been addressed

in the practical arena. Current fire standards are generally

cmbodied in zoning and building codes (specification codes).

These specification codes regulate minimum allowable

building and site characteristics. Examples of specification

codes include requirements for street width, the number of

structures per area, vegetation clearance, roof material, and

screening of vent openings. Standards such as these

(California Department of Forestry 1980; County Supervisors

Association of California 1965; Moore 1981) recommend

minimum building and site characteristics for improving

structure survival. Where these recommendations are

implcmcntcd, structure survival is increased -- but they are

gcncrally not implemented at the wildlandlurban interface.

Specification codes cannot make allowances for the diversity

of social values. Generally, specification codes arc not

llexible in responding to homeowner values and motivations;

trade-offs cannot be made to achieve a fire-safe condition.

Specification codes arc implcmcntcd or they are not. As a

result, specification codes connote uncompromising

compliance with government imposed regulations. Because

many of the property owners who live in wildlandlurban

intcrfacc areas move there to escape urban regulation

(Bradshaw 1988), there is great resistance to fire safety

regulations that restrict building and site characteristics. This

suggests the need for a regulatory approach that can make

allowances for the diversity of social values while it idcntilies

mcasurcs for reducing the fire risk.

This afiic]c examines the wildlandiurban intcr[acc fire

problem in terms of structure ignition and survival. It also

dcscribcs a current USDA Forest Service effort to develop a

flexible method for assessing the relative risk of structure

ignition.
THE WILDLAND/URBAN INTERFACE FIRE

PROBLEM--STRUCTURE SURVIVAL

The csscnce of the wildlandiurban interface fire problem is

tllc damage to homes during wildland fires. Any attempt lo

analyze lhc probicm should recognize rhe various factors that

jnfluencc the survivability of homes during wildland fires.

Struclurc survivability is the probability that a building will

not suffer major structural damage during a fire. A

structure’s survivability dcpcnds on the structure’s rcsistancc

lo ignition and on the ability to suppress any ignitions that

might occur. Thus, theoretically, for a given likelihood of

structure survival, a variety of ignition resistance levels can

be balanced by conlpcnsating suppression capabilities. This

introduces the idea of trade-offs--in this case, ignition

rcsistancc for suppression capabihties, and vice versa.

Structure survival can bc examined in greater detail. The

ignition aspect of stmcture survival can be further defined in

terms of Ihe structural fire performance, the fire exposure,

and tbc fire scvcrity conditions. Similarly, the suppression

aspect can be &fined in terms of SUppreSSiOn availability, Sib.7

access lo lhe structure, and firs scvcrity conditions. It is

llclpful to consider each of 11~~ factors in greater detail.

fue performwce: During a wildlandiurban

interface iire, ignition sources, i.e., firebrands, impinging

flames, convective heating, and radiative heating, arc initially

external to the structure. Structural fire performance is the

susceptibility to ignition and the degree of subsequent fire

involvement Structural fire performance depends on the

physical characteristics of the structure. For example, a

concrete structure wifh no window openings would resist an

cxtcmal ignition rTlOrC than a shucture with large window

openings and an exlcrior covered with wooden shingles.

Also, if an ignition occurs, the rate of fire involvement would

very likely he greater for the wooden structure. The concrete

structUTe has a higher fire performance than does the wooden

structure. These simple examples represent the cxtrcmcs of a

broad spectrum of physical characteristics that dctcrminc

structural fire performance.

Fire exposure:The fire exposure of a structure is defined

here as the external sources (burning materials excluding

flaming brands) of radiative and convective heating, and the

site characteristics that influence the amount of heat

transfcrrcd to the structure. For example, burning trees,

shrubs, and wood piles at various distances from the structure

dctcrminc how much Ihc exterior is heated When there is

burning material downslopc from the structure, the potential

for convective heating is increased. In terms of fire

cxposurc, only those burning materials close enough to the

structure to influence an ignition arc considered as heat

sources. The area containing such materials can be termed

the fire exposure zone. In this way, the concept of &re

cxposurc can be used to distinguish wildland vegetative fuels

(outside the fire exposure zone) from vegetation adjacent lo a

structure. Because a fire exposure zone is defined by the

characteristics of the fire and the fire performance of the

struclurc, fire cxposurc is not limited by property lines.

Thus, the dclincation of a site-specific fire exposure zone aids

in identifying all of the flammable materials relevant to

structure survivability.

8”Yt’ SUppR’SSioll avaihbifity: Availability of protection during

a fire is an important aspect of struchire survival. Structure

ignitions, if cxtinguishcd, can occur withoul lhc loss of the

structure. The quantity of fire suppression staff and

cquipmcnt, together with training, cxpcricncc, and rcsponsc

times, dctcrmincs fire suppression availability. This factor is

generally considered [he domain of fire suppression

organizalions, but community residents arc also a part of the

lirc suppression availability factor. Residents arc often the

source of fire reports and augment organized suppression

lbrc~s by working to protect individual properties.

kCeSS.- Asscssibility is critical for the utilization of available

suppression resources, and thus to structure protection during

a iirc. ACCCSS is the ability of fire suppression forces,

including residents, to locate, reach, and safely remain at a

structure and continue suppression efforts.

Fire sever@ condiliotts: This refers to the conditions that

affect the flammability of fuels, flame tilt, spr& rates, and

aerially transported burning brands. Fire severity conditions

are determined primarily by on-site weather and topography.

Fire scvcrity conditions influence the degree of fire exposure

and the cffcctivcncss of structure protection.

Structure survivability is an expression of the interactions of

the above-&fined factors. Spccilication codes seldom take

thcsc factor interactions into account, and therefore present

rclalivcly rigid formulas for providing fire-safe environments.

Thr failure lo account for these factor intelactions prevents

the incorporation of social values into fire safety mcasurcs.

The alternative to specifying minimum characteristics

(specification codes) to produce a given level of structure

survival is to make USC of a model that incorporates factor

inlcractions.

The essence of structure survival, and thus of the

wildlandiurban fire interface problem, is ignition. If ignitions

do not occur, then structures survive. Although structure

survival involves the interaction of all five factors discussed,

just three of them-stmchual fire performance, fire exposure,

and iire severity conditions-determine the potential for

ignition. For a given level of fire severity, the ignition

potential dctcrmincs the level of fire suppression availability

253
and accessibility necessary to produce a given level of

structure survival. As structural fire performance decreases

and fire exposure increases (increasing the ignition potential),

the accessibility and suppression availability must increase if a

structure is to survive. The wildland/urban fire interface

problem would virtually disappear if structures did not ignite;

thercforc, the emphasis of a wi]d]and/urban interface fire risk

assessment should be on structure ignition.

IGNITION RTSK ASSESSMENT MODEL

A structure ignition risk assessment model is now being

developed by the USDA Forest Service. This cooperative

effort involves the Forest Products Laboratory, Madison, WI,

the Riverside Fire Laboratory, Riverside, CA, and the

Southern Forest Fire Laboratory, Macon, GA. The product

will be a broadly applicable method for assessing the relative

risk of individual homes to external ignitions from wildland

fires. The prototype modei is expected to bc complctcd in

1991.

This model approaches interface home losses in a new way.

Recent models by Abt and others (1987) in the United States

and Wilson (1988) in Australia have used statistically derived

relationships, based on specific fires, to describe

characteristics related to potential fire incjdencc and structure

survival. Our model uses analytical relationships to describe

characteristics related to the potential for structure ignitions.

This approach has the following advantages:

l An analytical approach is not limited by specific event

data and its interpretation,

@ An analytical approach, based on physical

relationships can easily incorporate future gains in

understanding to fill current gaps,

* An analytical approach can incorporate the

interactions of the various factors affecting the

w&j]and/&an interface fire problem,

* The modeling of interactions provides a means for

analyzing mixes of factors, and thus a means for

analyzing trade-offs in meeting tire safety

requirements.

Our wildland/urt)an fire interface model assesses the risk of

potential ignitions rather than potential structure survival. As

noted previously, structure survival depends on both the

ignition factors and the suppression factors. Thus, an

assessment of potential structure survival would require an

assessment of the suppression factors. However, many of

these factors (access, suppression availability, and tire

severity) are very hard to quantify. For example, the

resident’s presence at the home during the fire can be critical

to the home’s survival. But it may not be possible to reliably

assess the likelihood that a homeowner will be at home at an

unspecified time, especially in a situation complicated by

emergency access limitations and evacuation policies. (The

statistical models previously cited also do not account for the

suppression factors, although structure survival is ostensibly

the product of the Australian method.)

The Ignition Risk Rating System

The Ignition Risk Rating System borrows some of its

underlying philosophy from the National Fire Danger Rating

System (NFDRS) (Deeming and others 1978) The Risk

Rating System is based on physical principles so that new

understanding can be easily incorporated into it. Whcrc gaps

in knowledge exist, personal expertise estimates the effects of

the physical processes. As with the NFDRS, the ratings arc

not incident-specific, but rate the potential fire situation.

Therefore, a worst case approach is taken in acquiring data

and making computations. Because it is not possible to make

precise evaluations of ignition occurrences, the risk ratings

arc placed in ordinal categories.

Rating risks of potential structure ignitions requires that

structure characteristics, site characteristics, and fire severity

conditions be described and analyzed to produce assessments.

The Ignition Risk Rating System does this in three stages. In

their computational order, these stages are the fire source

module, the heat transfer module, and the structure ignition

module.

The fire source module describes the site and fuels around the

structure and transforms that information into descriptions of

the potential flaming sources affecting the structure. The fire

severity conditions are locally identified using National Fire

Danger Rating System (NFDRS) burning index cumulative

frequency percentiles. The percentiles are computed from

historical fire weather data. The flaming source descriptions

arc based on an on-site fuel inventory in conjunction with the

potential fire behavior identified by the NFDRS calculations.

The potential flaming sources are described by their flame

length, flame zone depth, flaming width, flaming duration,

and distance from the structure. A subjective assessment of

the structure’s relative firebrand exposure is made on the

basis of the fuel sources adjacent to the structure and on

nearby wildlands. For example, a structure is considered less

exposed to ignition by firebrands from grass fuels than by a

conifer stand with heavy understory fuels. These descriptions

are then used by the other modules.

The heat transfer module uses flame source and homesite

information from the flame source module to estimate the

radiative and convective heating of the building exterior. Due

to the impossibility of knowing the specific characteristics of

a future incident, the worst case configurations for the heat

transfer are used. For example, all fuels are considered to be

burning at the same time, the radiative distance is considered

to be the closest distance to the fuel, and the view angle

between the structure and the flames is assumed to be the

254
angle that produces the greatest heat transfer. Convective

heating occurs if the convection column intercepts the

structure, but potential cooling from the wind is not

considered.

The structure ignition module calculates the System’s ignition

risk rating. The module uses descriptions of the building’s

exterior structural characteristics along with the heat transfer

information and the assessed fircbrand exposure to compute

the ignition risk. Exterior materials arc generally described

by type (wood, stucco, glass, etc.) and exposed surface area.

The ignition risk assessment is largely based on data derived

from laboratory fire tests conducted on exterior building

materials (roof materials, siding, windows, etc.). The module

produces the ignition risk rating based on the relative

availability of energy for an ignition. Relative risk ratings

fall into four classes: low, moderate, high, and extreme. To

facilitate a consistent assessment of the ignition potential, the

classes are defined in such a way that a structure in the next

higher class has twice as much ignition potential as a structure

in the one below.

System Benefits

The System will provide property owners and suppression

organizations with a guide to assessing, and thereby reducing

if necessary, the potential ignition risks to homes. The

System will provide the following:

l A flexible means of integrating social values and

tire performance requirements--one that wil1

encourage grcatcr acceptance of actions necessary to

decrease the risk of structure ignition,

* A means for evaluating a mix of conditions of the

components that contribute to structure ignition, thus

allowing for site-specific and property-owner-specific

actions that meet minimum requirements for ignition

risk-making informed tradeoffs,

* A means for informing and educating

property-owners about the rclativc risk to their homes,

* A means for informing suppression agencies of the

rclativc fire risk to homes, leading to more informed

suppression planning.

SUMMARY

The wildlandlurban interface fire problem, i.e., the loss of

homes during wildland fires, is not new. The problem

persists, not because there are no fire safety guidelines, but

because guidelines are not fully implemented. Until recently,

homeowner values and motives were not recognized as

important in achieving fire safe home sites. The current

guidelines used for the wiidland/urban fire interface arc fixed,

discrete specifications that cannot incorporate variations in

homeowner values while maintaining a given level of fire

safety.

A USDA Forest Service cooperative research effort is

currently developing a wildlandlurban interface structure

ignition risk assessment model. This physically based

analytical model is being designed to account for the

interactions of the factors that contribute to structure

ignitions. Thus, the model may be used to identify a variety

of fire safety measures that result in required risk reductions

and also accommodate specific homeowner desires.

LITERATURE CITED

Abt, Robert; Kelly, David; Kuypcrs, Mike. 1987. The

Florida Palm Coast Fire: an analysis of fire incidence and

rcsidcncc characteristics. Fire Technology 23(3):230-252.

Bradshaw, William C. 1988. Fire protection in the

urban/wildland interface: who plays what role. Fire

Technology 7,4(3): 195-203.

California Department of Conservation. 1972.

Recommendations to solve California’s wildland fire

problem, State of California. On file: Sacramento, CA:

California Department of Forestry and Fire Protection,

63 PP.

California Department of Forestry. 1980. Fire safety guides

for residential development in California, State of

California. On file: Sacramento, CA: California

Department of Forestry and Fire Protection, 38 pp.

County Supervisors Association of California. 1965. Fire

safety guides for California watersheds, State of

California. On tile: Sacramento, CA: California

Department of Forestry and Fire Protection, 26 pp.

Davis, James B. 1990. The wildland-urban interface: paradise

or battleground? Journal of Forestry 88(1):26-31.

Deeming, John E.; Burgan, Robert E.; Cohen, Jack D. 1977.

The National Fire Danger Rating System, 1978. Gen.

Tech. Rep. INT-39. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station, 63 pp.

255
Dell, Owen E. [n.d.] Landscaping for fire protection, City of

Santa Barbara, CA. On file: Santa Barbara: City Fire

Department, 10 pp.

Howard, Ronald A.; North, D. Warner; Offensend, Fred L.;

Smart, Charles N. 1973. Decision analysis of tire

protection strategy for the Santa Monica Mountains: an

initial assessment. On file: Menlo Park, CA: Stanford

Research Institute, 159 pp.

Laughlin, Jerry; Page, Cynthia, editors. 1987. Wildfire

strikes home. Report of the national wildland/urban fire

protection conference, Denver, CO, September, 1986.

NFPA No. SPP-86. Quincy, MA: National Fire

Protection Association. 89 pp.

Moore, Howard E. 1981. Protecting residences from

wildhrcs: a guide for homeowners, lawmakers, and

planners. Gen. Tech. Rep. PSW50. Berkeley, CA: U.S.

Department of Agriculture, Forest Service, Pacific

Southwest Forest and Range Experiment Station, 44 pp.

Radtke, Klaus W.H. 1982. A homeowner’s guide to fire and

watershed management at the chaparral/urban interface,

County of Los Angeles. On file: Los Angeles, CA: Los

Angeles County Fire Department, 33 p.

Radtke, Klaus W.H. 1983. Living more safely in the

chaparral-urban interface. Gen. Tech. Rep. PSW-67.

Berkclcy, CA: U.S. Department of Agriculture, Forest

Service, Pacific Southwest Forest and Range Experiment

Station, 51 pp.

Gale, Robert D.; Cortner, Hanna J., editors. 1987. People

and fire at the wildlandlurban interface: a sourcebook.

Report of wildland/urban fire interface workshop for

social scientists, Asheville, NC, April 6-8, 1987.

[non-serial] Washington, DC: U.S. Department of

Agriculture, Forest Service, 71 pp.

Wilson, A.A.G. 1988. A simple device for calculating the

probability of a house surviving a hushfire. Australian

Forestry 51(2):119-123.

256
PERCEPTION OF FIRE DANGER AND WILDLANDKJRIMN

POLICIES AIiTER WILDFIRE

R.C. Abt, M. Kuypers, and J. B. Whitson’

Abstract-Quantitative analysis conducted after the May 1985 Palm Coast iir e in Florida identified several

residential characteristics that influenced vulnerability to wildtire. As a t”ollowup to that analysis,

homeowners were surveyed to determine their perception of fire danger and lo determine their views on

alternative mitigation measures they have undertaken as individuals and their view of alternative government

mitigation policies. The survey indicates that homeowners perceive wildfire as a serious threat to their

safety and property. Homeowners were receptive to a wide variety of govcrnmenl policy options, including

restrictive planning, zoning, and building requirements. Older homeowners were more likely to have taken

mitigation measures and were more receptive to government intervention.

INTRODUCTION

Palm Coast is a 42,000.acre planned unit development

situated in the coastal plain flatwoods along the east coast of

Florida, Prior to its development, the land was actively

managed for pine timber production. Timhcr management

included the periodic use of prcscrihcd fires to control fuel

buildup.

Typical of other large developments that started in Florida in

the 1960’s, Palm Coast was primarily a lot-sales vcnturc.

Individuals purchased land using a long-term payment plan

with the intention of building at some future date. All roads,

underground utilities, and drainage systems were installed

within the first 10 years of construction. Except for a densely

developed core, homes have been built sporadically

throughout the devclopmcnt. Prescribed fires were no longer

used after construction began.

In May 1985, a devastating wildfire burned through Palm

Coast, destroying 100 homes and damaging 200 others. Lack

of brush clearance, fire intensity (due to abundant fuels), type

of soffit vent, and type of construction were shown to have

been associated with increased fire losses (Abt and others

1987).

In 1988, the Federal Emcrgcncy Management Agency and the

United States Forest Service jointly funded a followup study

to determine homeowner perception of the wildfire threat and

attitudes toward various mitigation strategies. Additional

objectives were to determine how mitigation could be

incorporated into the land-use planning process and to

determine the vulnerability of recently built homes. The

purpose of this paper is to summarize the residents’

pcrccption of wildfire danger, the mitigation measures taken,

and attitudes toward various mitigation policies.

‘Associate Professor of Forest Economics, Department of Forestry,

North Carolina State University, Raleigh, NC; District Forester,

Florida Division of Forestry, Bunnell, FL; Cooperative Fire

Protection Manager, Florida Division of Forestry, Tallahassee, FL.

METHODOLOGY

The study was conducted jointly by the Florida Division of

Forestry (DOF) and the University of Florida. A mail survey

was designed to gather information about the residents and

their perceptions about wildfire. The survey included a cover

letter signed by the local district forester and fire chief Two

survey areas were selected. One was an area burned in the

1985 fire and the other was a nearby area of similar housing

density that was not damaged by the lire. All of the homes in

the two sections were surveyed. The suNcy was handdclivcrcd by DOF personnel and returned via business reply

mail. Three weeks aRer the surveys were distributed a

follow-up letter was mailed. Approximately 276

questionnaires were distributed. There were 124 usable

questionnaires returned for a 45percent response rate. A

followup survey of 40 nonrespondcnts (20 in each section)

rcvcaled that many of the houses were vacant. The few

followup surveys completed by nonrespondcnts did not reveal

any significant differences with respondents.

The survey questions reported here fit into four categories,

(1) demographic information, (2) perceived threat of wildfire,

(3) mitigation measures taken, and (4) attitude toward

mitigation options. Simple summary statistics arc reported

below. Chi-square statistics were used to test for association

between the demographic variables and resident acceptance of

mitigation measures. For many of the subjective opinion

questions a l-to-6 scaIe was used. The Iower (l-to-3) end of

the scale was used to represent lack of a threat or agreement

with the question (3.5 represents neutral).

RESULTS

Initial tests for differences between the two sections of the

development revealed that they differed only in the number of

respondents who had personally experienced wildfire. The

results reported here are the combined responses from both

sections.

257
Demographics

The section of Palm Coast surveyed is predominantly a

retirement community. Sixty percent of the homes have one

or more family members over 6.5. Only 25 percent of the

homes have children under the age of 18. The average age of

the respondents was 56. On average the respondent had lived

in the current home for 3.6 years, and 75 percent planned to

continue living in the community for at least 5 years. Most

respondents (55 percent) had no more than a high school

education, though 25 percent had at least a bachelor’s degree.

The median income was approximately $30,000, and the

average market value of the homes was $98,000. Though

these statistics give an overview of the community, their

primary value was as an explanatory variable in determining

attitudes toward mitigation. These analyses are described

below.

Perceived Threat of Wildfire

Two aspects of wildfire threat were surveyed. The first was

the perceived danger of a wildfire to the home and family if it

were to occur. The second was the perceived probability of a

wildfire occurring. The questions regarding the perceived

threat from wildfire were put into the context of other threats

facing the community.

The first table below shows how the respondents viewed

wildfire compared to a wide spectrum of common problems.

Wildfire was considered the most serious threat facing the

community, even 4 years after the major fire. This is

especially important given that 69 percent of the respondents

had been in their current home for less than 4 years (after the

wildfire). The perceived threat of wildfire to the home and

family was measured on a 1 to 6 (1 =no threat, 6=extreme

threat) scale. The perceived threat of hurricanes and

tornadoes was also collected. Wildfire was given an average

score of 4.8 as a threat to the home and a score of 4.5 as a

threat to the family. Wildfire was rated higher in both

categories than either hurricanes or tornadoes.

Perceived problems facing the Palm Coast community: M.itigation Measures Taken

Mean score

Economic problems (unemployment, inflation, etc.) 2.98

Drought ............................. 3.99

Crime rates ........................... 3.59

Illegal drugs .......................... 4.04

Damage or injury from hurricanes ............. 2.49

Damage or injury from tornadoes .............. 2.34

Damage or injury from wildfire ............... 5.09

Exposure to radon ....................... 2.18

Water supply .......................... 3.07

21 = no problem, 6 = most serious problem.

The above questions asked about the threat of a wildfire if it

were to occur. There are at least two other factors that will

determine whether a resident should take action to mitigate

the damage. The first is the perceived probability of wildfire

occurrence and the second is the perceived effectiveness of

mitigation.

Residents were asked to give their best estimate of the

chances of a serious wildfire in their community in the next

10 years. The average estimate was 57 percent, which was

higher than either tornado or hurricane. Residents were also

asked to rate on a 1 to 6 scale the control they had over

wildfire damage (1 =no control, 6=complete control). The

average response was 3.0 which was higher than either

tomados or hurricanes. Given the high probability and threat

associated with wildfire and the high percentage of new

homes, one might expect that vulnerability to wildfire would

be important in the choice of a home. When rated on a 1 to

6 scale (1 =not important, 6=extremely important), however,

vulnerability to wildfire only rated 2.5 in choice of current

home.

The perceived threat of wildfire to the home was associated

with education (.04 significance level), where residents with

education beyond an undergraduate degree felt less

threatened. Residents whose insurance would cover all or

most of the damage Tom a wildfire also felt less of a threat

(.08 significance level). The perceived threat of wildfire to

the community was related to age, personal wildfire

experience, and income. Residents over 65 and residents who

had experienced wildfire were far more likely to rate wildfire

an extreme threat (.03 and < .Ol significance levels

respectively). Middle income ($40K-$50K) residents rated

wildfire as less of a community threat than others (.02

significance level). New residents (< 4 years) were far more

likely to have considered wildfire vulnerability in their home

choice. Those who had experienced wildfire, however, felt

they had less control over wildfire damage.

Sixty-seven percent of the respondents reported that they had

taken some sort of precaution against wildfire. The

probability of having taken safety measure was positively

related to whether the resident or a close friend had

experienced wildfire (.O3 and .Ol significane levels

respectively). The older residents (> 45) were more likely to

have taken measures (.002 significance level). Residents

without children at home, which were probably the older

residents, were also more likely to have taken precautions

(.03 significance level) as were homeowners (versus renters)

and residents who planned to stay in the community for at

least five years (.003 and .04 significance levels).

258
Ninety-three percent of these safety measures were taken aiter

the 1985 wildfire. Most measures taken cost less than $100

(65 percent). The most common measure was tree or brush

removal (53 percent). Others removed mulch (14 percent) or

purchased fire safety equipment (25 percent, including water

hoses, pool pumps, sprinklers, extinguishers, etc.).

Attitudes Toward Mitigation Policies

Resident attitudes about various mitigation measures and

government policies were examined. A wide variety of

measures were examined from passive voluntary measures to

restrictive governmental intervention. As the tabulations

below show, the residents generally favored any and all

mitigation measures mentioned. Even controversial measures

such as mandatory brush clearance and community-wide

control burning were considered acceptable.

Attitude toward government mitigation policies:

Government agencies should: Mean score’

Provide financial assistance to victims 2.3

Prohibit building in hazardous areas . 2.2

Impose stricter building codes in hazardous areas 1.8

Provide information to homeowners in hazardous areas 1.5

Conduct research on ways to reduce damages 1.8

impose stricter zoning requirements in hazardous areas 1.9

Impose stricter planning requirements in hazardous areas 1.8

Provide non-financial assistance to victims . . 2.7

‘1 = no problem, 6 = most serious problem

Attitude toward mitigation measures:

Voluntary brush clearance

Mandatory brush clearance

Mandatory home site survey for fire hazard

Community-wide control burning

Stricter building codes

Stricter planning requirements for developers

Increased wildland firefighting resources

increased structural firefighting resources

‘1 = no problem, 6 = most serious problem

Mean Score’

2.0

2.3

2.4

1.9

2.0

1.8

1.7

1.9

Though there was general acceptance of government policies,

older and permanent residents tended to accept restrictive

policies, while highly educated residents tended to be less

open to government intervention. For example, residents who

planned to stay in the community for the next 5 years were

three times more likely to favor government prohibition of

building in hazardous areas (.005 significance level). Older

residents (> 45) were four times more likely to favor strict

planning (.034 significance level), Residents with education

beyond an undergraduate degree were far more likely to

oppose the imposition of codes, zoning, or planning

restrictions (.OO, .04, and .OO significance levels

respectively). Lower income families ( < $30K) were more

likely to oppose nonfinancial support (.03 significance level)

while those who had experienced wildfire were much more

likely to favor non-financial support (.05 significance level).

There were only two resident characteristics that were

significantly related to specific mitigation measures.

Residents who planned to live in the community for at least 5

more years found a mandatory home survey more acceptable

(.04 significance level), while homeowners were much more

open to stricter codes than were renters (.04 significance

level).

SUMMARY

Five years after the Palm Coast fire, residents consider

wildfire the major threat to their community. Many residents

have taken precautionary measures, though wildfire

vulnerability was not important in home choice. Residents

over 65 were more likely to consider wildfire an extreme

threat and were more likely to have implemented mitigation

measures. They were also supportive of all policies

considered. Residents with an education beyond a bachelors

degree, however, were less tolerant of possible government

intervention.

LITERATURE CITED

Abt, Robert, David Kelly and Mike Kuypers, “The Florida

Palm Coast fire: an analysis of fire incidence and

residence characteristics”, Fire Technology, Vol. 23,

No.3, August 1987, pp. 186-197.

259

FIRE HISTORY

FIRE HISTORY AND EFFECTS ON VEGETATION

IN THREE BIOGEOCLIMATIC ZONES OF BRITISH COLUMBIA

John Pa-minter’

Abstract-The different tire regimes present in the province of British Columbia are well-illustrated by he

Coastal Western Hemlock, Boreal White and Black Spruce, and Ponderosa Pine Biogeoclimatic Zones.

Fires are variable in type, intensity, severity, effects, size, and interval. In the tirst two biogeoclimatic

zones, stand replacement and/or partial stand replacement fires occur. Surface tires that maintain open

forests with grassy un&rato&s are the historic norm in the Ponderosa Pine Zone.

Fire histories and fire effects have been determined for all three zones. In the Coastal Western Hemlock

Zone the emphasis has been on iire history, stand establishment, and prescribed burning. Ecosystemspecific guides describing the type of tire suitable for siivicullural site preparation are widely available

Post-fire vegetation successional pathways have been developed for the Boreal White and Black Spruce

Zone and are used to predict probable fire outcomes.

In recent times, the adverse implications of fire exclusion have been recognized in ecosystems such as those

found in the Ponderosa Pine Zone. The reintroduction of life through prescribed burning serves to address

the problems and meet several resource management objectives.

INTRODUCTION

British Columbia is a large and ecologically diverse province.

It covers a total area of 94,900,OOO ha, of which 52,200,OOO

ha arc forested (Farley 1979). The vegetation has been

classified into fourteen biogeoclimatic zones which range

from, but are not limited to, coastal rainforests, southern

grasslands, northern boreal forests, and alpine tundra (Pojar

1983; Pojar and others 1987).

The fire history and tire ecology of these biogeoclimatic

zones have been studied to varying degrees, depending on

location, the management agency, and context.

0BJEcms

The objective of this paper is to describe the tire history, and

general fire ecology, of three biogeoclimatic zones. For

several of the fourteen zones little information exists and in

others the focus has often been on just one subject area, such

as prescribed fire effects. By choosing three zones to

examine, a range of conditions within the province can bc

illustrated.

An historical perspective is provided since much of the older,

as well as some of the more recent, fire history work done in

the province has received little exposure to date.

COASTAL W'ESTERNHEMLOCKZONE

This zone occupies low to middle elevations, mostly west of

the coastal mountains, along the entire B.C. coast, on

Vancouver Island and the Queen Charlotte Islands (fig. 1). It

‘Fire Ecologist, Protection Branch, Ministry of Forests, Victoria,

British Columbia, Canada V8W 3E7

is the wettest zone and has cool summers and mild winters.

Mean annual precipitation is from 1,500 to 4,400 mm (Pojar

and Klinka 1983).

The major tree species present are western hemlock (T&go

and western redcedar (Thuja plicora). Douglasfir (Pseudouuga menziesii) is present in the drier subzones;

amabilis fir (A&es nmobifis) and yellow-cedar

(Chonzaecyparis noorkotenris) are common only in the wetter

subzones. Present, but restricted to certain habitats, are

grand fir (Abies grandis), western white pine (f%w.s

~lonticola), Sitka spruce (Piceo sifchenrti), bigleaf maple

(Acer macrophyllum), red alder (Alnus rubru), black

cottonwood (Populus balsamifera sap. lrichocarpa), and shore

pine (Pinus conforta Var. contorta).

Fire History

Evidence of fire primarily takes the form of charcoal layers in

the soil, fire-scarred trees (primarily Douglas-fir), charred

bark, and even-aged stands of shade-intolerant species. The

fire regime consists of long interval severe crown and surface

fires which result in total stand replacement. Lower severity

surface and crown tires with partial stand replacement are

also common, often within the larger more severe bums.

Historically, large areas burned when lightning-caused fires

occurred during extended regional summer droughts.

Physiography plays a role in tire history as well, with

differing fire incidence being a function of elevation,

topography, and aspect (Schmidt 1960).

The fire history of the Coastal Western Hemlock Zone in

British Columbia was first studied in the early part of this

263
FOREST SUCCESSION ON VANCOUVER ISLAND

Large trees

century. The situation is complicated by more than 1.50 years Perwnt stand oompoaltlon

of human disturbance. Removal of the original forests and

their replacement by second-growth plantations, in

combination with wildfires and prescribed bums, has made

the determination of historical tire frequencies difficult or

impossible in many localities.

Rigg and Richardson (1938) noted the presence of charred

remains in many bogs in northwest Washington and

southwestern British Columbia but did not indicate how long

tire had been a factor in the regional landscape. In lake

sediments from the adjacent western hemlock zone of

Washington state, Cwynar (1987) dated Douglas-fir and

western hemlock pollen mixed with charcoal fragments to

11,000 years before present. Climatic change has occurred

since then, and with it the tire regime and relative abundance

of the two conifer species.

Fire intervals likely range from 150 (Martin and others 1976)

to 3.50 years or more but may not be truly cyclic (Agw

1981). Fahnestock and Agce (1983) estimated the tire cycle

for western hemlock forests of western Washington to be 598

years. The value for western redccdar forests was 3,116

years but the authors considered that figure to be

unexpectedly long. Agce (1990) calculated a fire cycle of 400

years for the cedar/spruce/hemlock type in Oregon.

Dendrochronology has revealed fires as early as 670 A.D. in

Douglas-fir forests on northern Vancouver Island (Schmidt

1970). The even-aged character of these stands, coupled with

charcoal in the soil and charred bark on veteran trees,

denoted a tire disturbance history. A second disturbance by

tire may result in a stand with two major age classes.

Significant fire years on the British Columbia coast are

indicated for approximately 1100, 1210, 1410, 1560, 1610,

1660, 1740, and 1820 (Schmidt 1970).

Howe (1915) found that Douglas-fir forests in this zone

generally originate after fire. Stand establishment dates

suggest fires occurred in 1454, 1489, 1558, 1814, and 1844.

Scars on large old trees recorded tires in 1598, 1684, and

1844.

Eis (1962) also considered the oldest tree layer to be

indicative of a tire year, with younger and lower layers

recording subsequent and less severe disturbances. Based on

stand ages, tires are indicated for the lower mainland coast

around 1540, 1550, 1660, 1690, 1770, 1790, 1840, 1860, and

1890.

Correlations of tire dates within and between the data for

different localities in Schmidt (1970), Howe (191 S), and Eis

(1962) indicate more prominent lire years for the lower

British Columbia coast as 1489, 15.58, 1660, 1684, 1690,

1820, and 1890. Mathcwes (1973) found a charcoal-rich lake

scdimcnt layer which might very well coincide with a

100 300 400 600 800 1100-1200

Number 01 years 6hYOO b major firi?

lntermedlate trees

Percent stand oomw6l~ion

1001

76n

6fl%

25%

300 400 600 800 1100.1200

Number of year6rime li major fin

Advance regeneration

Psrosnt stand owvosltlon

300 400 600 BOO 1100-1200

Number of years 6inoe a major fire

Figure 1. Location of biogeoclimatic zones.

264
significant (800,000 ha) regional fire event in the mid-1600’s

described by Schmidt (1957) and/or a local fire dated to

around 1660 by Eis (1962).

On the north coast, other disturbance agents such as wind and

landslides may be more important than tire. Harris and Fan:

(1974) noted that while there arc significant areas of evenaged stands on the Alaska panhandle which apparently owe

their origin to fire, the bulk of the forests there are unevenaged. Age class structure suggests that extensive fires burned

in 1664, 1734, and between 1804 and 1824. Since 1900 few

fires have burned more than 40 ha.

Fire Effects and Succession

At a large scale, Schmidt (1960) felt the lower incidence of

forest fires on the north coast was responsible for limiting the

range of Douglas-fir. Western redcedar continues north for

480 km beyond the range of Douglas-fir, and western

hemlock for 1,100 km. Douglas-fir is capable of growing

outside its range but this has been prevented as, without fire,

the species cannot colonize new habitat.

On a site basis, post-tire vegetation succession in the Coastal

Western Hemlock Zone has been of interest for quite some

time. A pioneering study concluded that repeated burning

was destroying the seed trees and young growth (Howe 1915).

On one-half of the land examined, which had been logged and

burned over between 1884 and 1914, the reproduction of new

forests was considered inadequate. This was attributed to an

increase in the frequency of widespread fires from every 86

years for the period from 15’54 to 1814, to 27 years for the

period from 1814 to 1894, to 5 years between 1894 and 1914

(Howe 1915).

Howe (1915) observed that most young Douglas-fir forests

were establishing on areas which had been burned or logged

and burned. He found Douglas-fir established best on

moderately-burned areas and likely required fire to clear away

the slash and lesser vegetation. Western hemlock

reproduction was encouraged by light surface fires beneath

Douglas-fir stands as the moss layer, which usually develops

after tire, conserves moisture and is an ideal medium for

seedling germination (Howe 19 15).

When established together, western hemlock seedlings may

initially outnumber those of Douglas-fir, but the latter species

is more robust and has the advantage on exposed post-tire

sites with thin duff layers (Agee 1990). Understory

vegetation primarily consists of species which sprout from

underground rhizomes or from the bud collar (Agee 1981).

By 20 years post-fire most of the snags have fallen and

succession has led to a highly diverse shrub stage which

supports much wildlife (Agee 1981 and 1990). Shrub and

herb cover later decline as the tree canopy develops and

closes. Small openings in the canopy resulting from

windthrow, snowbreak, insect kill, or disease will be occupied

by the more shade-tolerant conifer species, with Douglas-fir

limited to the dominant trees which established soon after the

tire. If western hemlock did not become established with

Douglas-fir during the initial post-tire succession phase, and

form part of the main canopy, it may appear after 50 or 100

years have passed (Franklin and Dymess 1973).

After several centuries Douglas-fir density continues to

decrease, while the lower crown classes become occupied by

western hemlock, western redcedar, and amabilis fi (Agee

1981; Munger 1940; Schmidt 1970; Spies and Franklin 1988).

Understory regeneration of western hemlock and amabilis fir

may be limited by a dense western hemlock canopy until it

starts to break up after 300 to 400 years (Stewart 1986).

Decline of the Douglas-fir component may begin at 500 years,

or be delayed until after 1,000 (Franklin and Spies 1984).

Munger (1940) and Schmidt (1957) described the later stages

of development of these stands when Douglas-fir gives way to

the shade-tolerant species. Schmidt’s data from 142 plots on

Vancouver Island showed initial post-fire recolonization by

Douglas-fir, western hemlock, and western redcedar (fig. 2).

Amabilis fir is less capable of invading the burned site and

depends upon the offspring of its initial colonists to extend

itself. As time since fire increases, the species composition

shifis away from Douglas-fir and western redcedar to western

hemlock and amabilis fir. The long-term absence of fire

results in the loss of Douglas-fir.

It has been known for some time that most of the Douglas-Iir

forests in the Coastal Western Hemlock Zone are seral to the

climax western hemlock and western redcedar (Benedict 1915;

Eis 1962; Franklin and others 1981; Howe 1915; Judd 1915;

Munger 1940; Wright and Bailey 1982) and long believed that

post-fire Douglas-fir forests arc generally even-aged (Franklin

and Waring 1979; Judd 1915; Munger 1940).

Indeed, Munger’s data showed the Douglas-firs on a 65 ha

plot to be nearly all within 25 years of 590 years of age. The

western hemlocks of that stand, by contrast, ranged in age

from 130 to 525 years. Recent work has found that the range

in age of the dominant old-growth Douglas-fir trees may

surpass 200 years, indicating a lengthy site reoccupation

period (Franklin and Waring 1979; Franklin and others 1979).

This may be due to a lack of seed source (necessitating

gradual recolonization), vegetative competition (delaying tree

establishment), or multiple disturbances (partial rcbums

removing portions of the first stand) (Franklin and Waring

1979).

Resource Management Implications

Prescribed burning to remove logging slash and produce

conditions amenable to the establishment of Douglas-fir, the

preferred species, was considered a necessity (Howe 1915)

and has been carried out since the early part of this century.

265
Figure 2. Forest succession on Vancouver Island

(data from Schmidt 19.57).

: :.:a . .:. 1.. :-

., : . . . : . . . . . . . . . -0..

%f bk

3

?I v

-- . .+-. < .- . 4 *. *. . : 1. . . *: . . : . . .:.

. .**:*.:

. .

Although compulsory slash disposal was not imposed on

logging operators when the Forest Branch was created in

1911, such actions were encouraged. Without prescribed

burning aRer harvesting, it was expected that western

hemlock woutd predominate (Benedict 1915). In northern

parts of the zone, where soil conditions were different, slash

disposal by burning was not r-commended.

Fire effects in the Coastal Western Hemlock Zone have

generally been studied in the context of using prescribed fire

for site preparation. Considerable research has been carried

out and continues by provincial and federal government

agencies, local universities, and forest companies (Beese

1986; Cm-ran 1988; Peterson 1989).

Ecosystem-specific guides describe the proper use of

prescribed tire (Haeussler and others 1984; Klinka and others

1984). Recommendations arc made as to whether prescribed

fire should be applied to a site and if so, what particular fire

effects are suitable.

Concern is growing over the need to preserve islands of old

growth timber generally comprised of western hemlock,

western redcedar, Douglas-fir and sometimes Sitka spruce

(Spies and Franklin 1988). With long interval fires which can

grow to significant size, careful planning will be required to

preserve these old-growth islands. The need to consider the

role of natural tire in their life cycle is obvious.

BOREXL WHITE AND BLACK SPRUCE

ZONE

The Boreal White and Black Spruce Zone occupies the low to

middle elevations of the northern portion of the province,

primarily in the northeast comer (Annas 1983). It has a

northern continental climate with long, very cold winters and

therefore a short growing season. Discontinuous permafrost

exists in some locales.

The Boreal White and Black Spruce Zone is floristically very

diverse. Major tree species include white spruce W~U

gfauca), black spruce lodgepole pine (Pinn.r

contorta var. lafifolia), trembling aspen (Populus

rremuloides), paper birch (Betula papyr@ra), Alaska paper

birch (Bet&~ neoaluskunn), tamarack (Larir laricino), and

subalpine fir (A&s lasiocarpa). Balsam poplar (Popular;

balsamifera spp. balramijha) and white spruce occupy

alluvial floodplains.

Fire History

Physical evidence of fire in the boreal forest is found in the

form of charcoal deposits in the soil profile; fire-scarred trees

and charred snags; as well as in the mosaic character of the

forest stands, their age structure, and the morphological and

reproductive characteristics of the plant species present (Rowe

and Scatter 1973). The forest mosaic may take on the

appearance of a patchwork quilt, with each patch being

sharply differentiated by abrupt changes in tree species

266
composition and crown heights. Within each component the

stand structure and composition may be remarkably uniform

(Dix and Swan 1971).

The fire regime consists of short to long interval crown fires

and severe surface fires in combination. Stand replacement

tires are the norm and surface fires alone are rare, occurring

along the edges of crown fires where fire behavior was

moderated. Ground fires can be persistent in deep organic

soils.

Hazardous tire weather conditions are encouraged by lengthy

summer days which result in long diurnal drying periods as

well as by extended periods of low precipitation and

humidity. In northern British Columbia very large lightningcaused fires have occurred decadally and reached 180,000 ha.

Man-caused tires have sometimes surpassed this size during

the past 50 years.

Heinselman (1981) summarized flue regimes for the boreal

forest. Presettlement fue cycles ranged from 50 to 200 years

for types shared by the Boreal White and Black Spruce Zone

of northern British Columbia. Fire cycles there differ

between forest types, but likely average 140 years.

Since most of the landscape in this zone is subject to fire,

stand age class distribution data have been used to model fire

cycles and the effects of fire suppression. For northwestern

and northeastern British Columbia, fire cycles were 125 and

202 years respectively (Smith 1981). However, a regional

tire cycle is a composite, with the components having their

own shorter or longer cycles as a function of site type (Rowe

1983).

Although much evidence exists for aboriginal burning and an

increased fue frequency due to the presence of European man

in the boreal forest (Lutz 1959), specific references to

northern British Columbia are rare. House (1909) told of a

hunting expedition in northwestern British Columbia during

which his native guide set several grass fues in order to

approach a herd of caribou under the cover of smoke.

Lewis’s (1982) native informants in northern Alberta

described the use of prescribed tire for creating and

maintaining meadows, manipulating riparian vegetation,

clearing campsites and trails, removing windfalls, and

creating firewood. It is likely that such practices were carried

out in the boreal forest of neighboring British Columbia,

influencing the fire regime there as well.

Lutz (1959) documented fires in the boreal forest caused by

European man’s escaped campfires as well as his deliberate

firing of the forest in order to create supplies of dry

fuelwood, signal other parties, drive moose, and promote the

growth of forage for domestic stock. Fire was also used to

remove local forest cover, thus thawing the permafrost and

permitting excavation for minerals (Dawson 1888).

Fire Effects and Succession

The natural role of fire in the boreal forest of North America

has been described in detail (Foote 1983; Kayll 1968; Kelsall

and others 1977; Lutz 1955; Rowe 1983; Rowe and Scatter

1973; Viereck and Schandelmeier 1980). With standreplacing crown fires and tree species which are fire sensitive

and usually killed by fire, forest regeneration depends on “onsite” or “off-site” adaptations.

On-site adaptations to fue include cone serotiny (lodgepole

pine), semi-serotiny (black spruce), root suckering (trembling

aspen), and root collar sprouting (paper birches). Species

such as white spruce, tamarack, and subalpine fir require live

survivors off-site but near enough to provide seed to the

burned area. The hardwoods produce prolific amounts of

light seed which, if carried by the wind to the burned site,

may result in a post-fire hardwood component as well.

Lesser vegetation also possess post-fire reproductive

strategies, such as sprouting from roots, rhizomes, and stems,

or the production of many light wind-disseminated seeds

(Rowe 1983). Some, such as high bush cranberry (Viburnum

edule) and pink corydalis (Corydalis sempervirens) have seeds

that germinate following stimulation by Iire (Viereck and

Schandelmeier 1980).

Natural regeneration of tree species after fires in the Boreal

White and Black Spruce Zone is quite prompt; many forest

stands show an age range of only 10 to 15 years, sometimes

up to 20. A wave of tree establishment often takes place in

the first 5 to 7 years. However, where initial restocking

levels are low and seed source, seedbed, and vegetative

competition conditions continue to be favorable, recruitment

may continue for several decades (Parminter 1983).

Post-fire changes in floristic composition may be minor, with

succession becoming an exercise in changing structure and

species dominance. For instance, black spruce - sphagnum

moss and black spruce - lodgepole pine types generally

exhibit little change in composition as time since fire

increases. Even though identifiable stages exist (Foote 1983),

vegetation cycling by fue rather than orderly replacement of

species through succession is common (Methven and others

1975; Viereck 1983).

In other situations, the proportion of the post-fire stand made

up by early successional species, such as trembling aspen, the

paper birches, and lodgepole pine, may increase over the prefire values for those species. Indeed, they may not have been

present at alI. Other species, such as white spruce, black

spruce, and subalpine fir, will be less represented on a

proportional basis until later in the life of the stand.

Although trembling aspen and lodgepole pine overtop white

spruce during most of the stand’s lifetime, the latter species

survives and eventually replaces the former in the absence of

267
fire. In most cases all three species become established

simultaneously post-fire (Parminter 1983). A similar situation

holds for lodgepole pine and black spruce, and lodgepole pine

and subalpine frr mixes. Notably, if fire returns before the

more shade-tolerant species (the spruces and subalpine fir) are

sexually mature, the more tire-adapted early successional

species (trembling aspen, paper birches, and lodgepole pine)

will have the upper hand and dominate the post-fire site.

Resource Management Implications

Fire suppression costs in the Boreal White and Black Spruce

Zone can be high, the annual area burned large, and the

economic value of much of the timber resource relatively low.

Therefore, fire effects and post-fire vegetation response are

important when making decisions on appropriate wildfire

suppression response (as well as in planning for prescribed

burning).

Post-fire vegetation development depends on many factors

such as the type of pre-tire vegetation present and its state of

development; the season of fire occurrence; fire behavior and

intensity; the depth of bum; fire size; the nature of the off-site

vegetation; physical site characteristics; and post-fire

environmental conditions. In spite of all of these variables,

the most likely course of post-fire succession can be

anticipated.

Post-fire vegetation succession models act as predictive tools

to aid in resource management decision-making. After 17

cover types in the Boreal White and Black Spruce Zone were

delineated following the approach of Hansen and others

(1973), a modification of Kessell and Fischer’s (1981)

methodology was used to show the multiple pathways of postfire succession. The possible post-tire outcomes, and the

further development of the cover types with and without tire,

have been detailed (Pat-minter 1983).

Considerable prescribed burning is carried out to enhance

domestic range and wildlife habitat (primarily for large

ungulates). Conversion of coniferous to mixedwood stands or

of mixedwood to shrub- and herb-dominated types occurs as

prescribed burning shortens the fire frequency.

PONDEROSA PINE ZONE

This zone is found at lower elevations in some of the main

valleys of the southern third of the central interior. It extends

south into the Pacific Northwest states.

Climatically it is the driest, and in summer the warmest,

biogeoclimatic zone in the province (Mitchell and Erickson

1983). It is classed as semi-arid continental. The summers

are warm and the mean annual precipitation ranges from 200

to 300 mm. Moisture deficits occur during the growing

season.

Ponderosa pine (Pinus is the predominant tree

species, and often forms open park-like stands with an

understory of bluebunch wheatgrass (Agropyron spicorum).

Douglas-fir and trembling aspen occur on moister sites, an

western larch (Larir occidends) is rarer. Grasslands are

mixed with the forest cover throughout the zone.

Fire History

Evidence of fire is found as charcoal layers in the soil,

charred bark, and fire-scarred trees (primarily ponderosa pine

and Douglas-fir). The fire regime most often consists of

frequent light surface fires and, rarely, long interval crown

fires. The role of fire is to maintain the stand, keeping the

understory relatively open and the ground free of excessive

woody fuel buildup (Agee 1990). The rarer crown fires in

this type open up gaps within the stand which then fill in with

a new age class of ponderosa pines.

Charcoal deposited in lake sediments from local and regional

grassland and forest fires indicated a fire history going back

300 years or more in the southern part of the Ponderosa Pine

Zone (Cawker 1983). Many fires have been lightning-caused

A proportion can be attributed to aboriginal prescribed

burning, which Barrett and Amo (1982) and Gruel1 (1985)

found to have increased fire frequency in ponderosa pine

habitats of the interior western states.

Fire history studies in North America have revealed Iire

frequencies of about 6 to 15 years for the types of ponderosa

pine stands found in British Columbia (Wright 1978; Wright

and Bailey 1982). One of the earliest local investigations was

that of Melrose (1923). In the southeastern portion of the

province he dated 13 fire events between 1729 and 1908, for

a fire frequency of 13.7 years.

Dorey (1979), working just above the Montana border,

constructed a fire chronology based on 14 Iire-scarred trees

which indicated a history of surface fires between 1813 and

1940. The fire frequency works out to 6.3 years overall.

Cartwright’s (1983) data show a fire frequency of 9 years for

a mixed ponderosa pine - Douglas-fir forest near Kamloops,

British Columbia. Low (1988) found values of 7.2 and 10.5

years for two areas in the same vicinity.

Fire Effects and Succession

Windfall, insect attacks, mortality, and frequent fire have

historically maintained open ponderosa pine and mixed

ponderosa pine - Douglas-fir stands (Wright 1978). Tree

seedlings established after fire begin the development of an

even-aged group. An uneven-aged forest results from this

pattern.

268
Under a natural regime most of the understory grasses, forbs,

and shrubs are maintained and enhanced by fire. Low

severity fires favor resprouting, while germination from seed

is favored after high severity tires (Saveland and Bunting

1988). However, mortality of fire-sensitive understory

species, as well as conifers, does take place.

Fuel removal by grazing of domestic stock and fire

suppression has significantly affected tire frequencies, either

lengthening them substantially or removing the influence of

tire altogether. Dorey (1979) found the fire frequency to

have been 5.9 years prior to, and 9.6 years after 1911. No

fires took place since 1940. Low (1988) found an area with a

tire frequency of 10.5 years between 1672 and 1900 which

had not experienced fire since 1901. Another with a fire

frequency of 7.2 years between 1774 and 1933 had not had a

fire since 1934.

Early accounts of the ponderosa pine forests described them

as being fairly open and interspersed with large areas of

grassland. Crown tires seldom occurred in these types

(Whitford and Craig 1918). With fire exclusion, such stands

become dense, many younger trees establish in the

understory, and tree growth stagnates (Amo 1988). Total

fuel loading becomes higher and the amount of ladder fuels

increases dramatically, increasing the possibility of crown

tires (Steele and others 1986). Douglas-fir often invades the

lower canopy and becomes predominant, where before it had

been absent or minor (Amo 1988; Dorey 1979). Understory

vegetation becomes depleted due to the denser tree canopy.

Resource Management Implications

Historical sentiment against underbuming these ponderosa

pine forests related to the death of young seedlings, loss of

timber production, scarring of trees, and depletion of soil

nutrients (Melrose 1923). The opinion of the Forest Branch

was that a continued role for surface tires in these stands

would be an economic misfortune (Forest Branch 1923).

The ecological consequences of the exclusion of fire from

these stands have been recognized in the past two decades.

Prescribed burning is now carried out in many pondcrosa pine

and mixed ponderosa pine * Douglas-fir forests to maintain

and enhance domestic range and wildlife habitat. Other

reasons include fuels reduction (especially in the

urbanlwildland interface zone) and visual resource

management. Prescribed tire may be combined with

mechanical treatments, such as spacing, thinning, pruning, or

selection logging.

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272
ANTHROPOGENIC FIRE AND TROPICAL DEFORESTATION:

A LITERATURE PERSPECTIVE

Michael R. Wetzel and Philip N. Omi’

Abstract-Anlhropogenic fire is an important agent of tropical destruction. Fire has been the primary tool

of rural and technologically primitive people for managing and manipulating their natural environment For

more than a century observers and researchers have recorded and documented the process of deforesration

by fire throughout the tropics. Using the cumulative written work of these investigators, we describe how

human-caused fire in the tropics has contributed to deforestation. Human use of lire cannot be eliminated,

nor is its elimination necessarily desireable; however, it must be managed. Education of fire users must

form fhe core of any fire management program. Until an effective fire management policy can be

implemented, anthropogenic fire will continue to contribute to tropical deforestation.

INTRODUCTION

Fire in nature is an awesome force. In human hands it has

become our most powerful tool for altering the face of the

earth (Sauer 19.58). Today, as it has been since mankind first

learned to use it, fire is the primary tool of rural and

technologically primitive people for manipulating and

managing their natural environment (Stewart 1956).

Unfortunately, fire has become one of the most important

agents in the worldwide dcs[ruction of tropical forests, and 98

percent of tropical fires arc anthropogenic, started by some

intentional or unintentional human action (Batchelder 1967).

Anthropogenic fire has been identified as the most serious

threat to Venezuela’s forests (Budowski 19.5 1;

Camero-Zamorra 1952). In India human-caused fire has been

responsible for the loss of much of the subcontinent’s forests

(Troup 1926). On the Indonesian island of Java periodic,

long-continued human firing of vegetation has been the

greatest menace to its forests (Shuitcmaker 1950 in Bartlett

19.55). Through repeated burning the tropical forests around

the world have been rcduccd in area and oflen replaced by

savannas and grasslands (dc la Rue 1958; Batchelder and Hirt

1966; Walter 1971).

For more than a century observers and researchers have

recorded and documented tropical man’s often careless and

ncgligcnt use of Loire. Using the cumulative written work of

many of these scientists, we have put together a general

scenario, based upon a myriad of specific cases, about how

lire has contributed to forest destruction in the tropics.

Batchcldcr and Hirt (1966) wrote:

because the number of intcrrclationships among

fire, man, and [the] environment are nearly infinite;

no one condition or set of conditions can be

assumed to be dominant for all parts of the tropics.

‘Consulting Forester, Michael R. Wctzel & Co., Denmark, SC and

Professor of Forcsl Fire Science, Colorado State University, Fort

Collins, CO.

We understand and heartily endorse this observation. As a

result of the pantropical view we have taken, our

generalizations are not necessarily appropriate to all tropical

ecosystems, macrosites, and microsites. The information we

arc providing, while valid in general, must be checked against

site specific conditions. Undoubtedly, tropical forest land

managers and policy makers have a great and present need for

cxtcnsive and intensive research about fire behavior and fire

effects in their forests.

TROPICAL FOREST LOCATION

Tropical forests are located in lowland elevations -- generally

below 1300 meters -- of the large, global belt around the

equator, primarily between the Tropics of Cancer and

Capricorn. Where tropical climatic conditions extend beyond

the north and south tropical latitudes, so do the tropical

forests. The forests are concentrated in Africa and the

Americas with more than half of the closed forests located in

South and Central America. The forests of the Amazon River

drainage account for the bulk of the New World’s closed

forest. In contrast the vast majority of open tropical forests

are located in Aliica (See table I).

TROPICAL DEFORESTATION

Estimates of tropical forest area range from 15 million to 19

million square kilometers -- approximately 42 percent of all

tropical land and 13 percent of the earth’s land surface.

Closed forests -- those with a continuous canopy -- account

for about 9 to 1 I million square kilometers (UNE?SCO 1978).

Deforestation rates for the closed forests arc largely

hypothetical and vary with the estimator and the definition of

deforestation used. St&d loss rate figures run from IOO,OOO

to 245,000 square kilometers per year (Myers 1981).

Geographically, the losses are pantropical. The pressure on

the forests is greatest at the forest edge where they are most

accessible. This edge can be a broad ecotonal belt or an

abrupt boundary.

273
Table I. Global. location of tropical forests by percent of total tropical

forest area (U.S. Interagency Task Force 1980).

Type of Forest (p )

A[[ Tropical Fore::s (1.9 billion hectares)

Location

42 percent South and Central America

31 percent Africa

21 percent Asia/Australia/Oceania

Closed Tropicat Forests (1.1 billion hectares)

SO percent South and Central America

30 percent Africa

20 percent Asia/Australia/Oceania

Open Tropical Forests (0.8 billion hectares)

64 percent Africa, Asia, Australia,

Central and South America

Primary dcforcstation activities are industrial logging,

fuclwood gathering, and agricultural clearing. Of these [hrcc,

destruction associated with the forest fanner is the most

important; and the forest farmer’s primary tool is firc(Nichols

1901; Budowski 1956; Dcnevan 1978). Some overlap in

dclorestalion activities does exist. For example forest farmers

often move into log@ areas to establish their farm plots.

In using the term forest fanner we mean the traditional

shifting agriculturalist as well as the modem “pioneer’

farmer-scllkr. Development, grcatCr rural population

densities, and the demands of a market economy have in

many places changed subsistence shilling agriculture so much

that ecologically it is not much diffclrcnt than fhe farming

practices of the pioneer setllers.

FLAMMABILITY OF TROPICAL FOREST

TYPES

In the tropics the climatic regulators of vegetation type are the

amount of rainfall during the wet season and the duration and

intensity of the dry season (Walter 1971). Three general

forc$t types are relevant to our look at anthropogcnic fire and

dcforcstation. In order of most rainfall and shortest dry

season they arc: the tropical rain forest, the semi-deciduous

forest, and the deciduous forest (Mueller-Dombois 1981).

Deciduous forests can bc finther divided into moist and dry

forests (Walter 1973). The moist deciduous forests receive

more rainfall than the dry deciduous forests and grow on soils

with greater water-holding capacity. Rain, semi-deciduous,

and moist deciduous forests are closed forest types. Dry

deciduous forests are open types.

The three closed forest types arc fire independent ecosystems

(Vogl 1977). Successfui natural ignitions are rarely

sustained. Low light levels on the floor of the closed forest

during the growing periods prevent growth of significant

amounts of hcrbaccous vegetation. High temperatures and

moisture levels promote rapid decay of litterfall.

Furthcrmorc, low fuel loading and large fuel size, hiyh

moisture content, and wide fuel spacings, combined with the

high ignition temperature typical of most tropical forest fuels,

mitigate against prolonged, continuous combustion in the

undisturbed closed forest (Batchelder and Hirt 1966; Trollope

1980). Open forests do have herbaceous and shrub

understories because light penetrates to the forest floor.

Once the undisturbed closed forest is cleared, though, xeric

undcrstory and overstory species become established on the

site and at the forest edge. This secondary vegetation is more

likely to sustain combustion if ignited. Aflcr fire has invaded

the forest once, the forest remains in constant danger from

human sc[ fires (Spurway 1937; Aubrevi]]e 1947; Budowski

1966).

Flammability of Tropical Rain Forests

The tropical rain forest is evergreen or mostly evergreen.

Though there is no true dry season, there can be a relatively

dry period in this forest type. Even in such a “dry” period

precipitation CiVCragCS at least 100 millimeters per month.

Mean annual temperature hovers around 24 degrees Celsius.

Decomposition rates are rapid, so there is only a thin litter

layer on \hc forest floor at any given time. primarily due to

its high moisture level, the undisturbed tropical rain forest is

almost fireproof. Once the forest is opened, though, it

becomes susceptible to burning. Dead and live vegetation in

the opening and at the forest edge quickly dry upon exposure

to the intense tropical sun, thus becoming more flammable.

Under these circumstances the tropical rain forest will burn.

Flammability of Semi-deciduous and Deciduous

Forests

The semi-deciduous and deciduous forests are seasonal forests

because they exist in the alternating climates of wet summers

and dry winters. The number of dry months varies from

roughly three to six in the semi-deciduous forest, six to eight

in the moist deciduous forest, and eight to ten in the dry

deciduous forest (Walter 1971). Mean temperatures range

ixhvccn 10 and 28 degrees Celsius.

The alternating wet and dry seasons is conducive to fire

occurrence. During the wet season there is substantial plant

growth which cures in the dry season. The deciduous plants

not only dry out, but also shed their leaves. Nevertheless,

like the rain forest, the semi-deciduous forest ordinarily does

not bum easily. If this forest is opened to the sun’s

insolation, however, its vegetation dries, becomes more

flammable, and, therefore, more likely to bum if exposed to

an ignition source.

214
The deciduous is more susceptible to burning in its

unaltcrcd state (Walter 1971, 1973). As the dry period grows

longer and more scvcrc, greater numbers of deciduous tree

spccics and fewer evergreen spccics occupy the forest while

total tree density decrcascs. The deciduous forest, especially

the open forest, has greater fuel accumulations due to

abundant littcrfall and the curing of grasses and other low

understory vcgctation during the dry season. Exposed to the

tropical heat, thcsc fuels quickly &&ate. Under these

circumstances there arc sufficient fuels of small size, low

moisture contern, and CIOSC spatial arrangement to carry a

surface fire when fire enters the forest. AS the dry period

grows longer and more intense, the potential fuels become

more flammable and the fire danger is magnified.

The fuel complex and fire potential of tropical forests arc

altered by human activity that removes the vcgctation, thus

creating openings in the forests. After the initial clearing fuel

loading increases in all size classes, scattered evenly over the

site. AlIcr a variable period of exposure to solar heating

thcsc fuels dry sufficiently to burn. In the following years

grasses and other hcrbaccous vegetation, as welt as woody

spccics, occupy the site as pioneers in secondary succession.

This vcgctation, adapted to drier, open environments, grows

more or less evenly over the site and dries rapidly in the

absence of precipitation. These early successional conditions

provide a fuel complex that will bum without cutting and

cxtcnded drying (Vogl 1969; Walter 1971). If disturbed

forest sites are rcpcatcdly burned, highly flammable, quickly

rcgcncrating grasses such as Imperata species rapidly

dominate the site; creating an easily burned, self-replacing

fuel complex.

THE PROCESS OF DEFORESTATION BY

FIRE

Anthropogcnic fire is concentrated in the open and ecotonal

areas of the tropics where humans live and work. Annually,

sometimes more often, and usually at the end of the dry

season, residents set their fires. Generally, these are surface

tires which are carried by ground litter and herbaceous and

shrub vegetation. Fire intensities are usualIy low due to low

available fuel loadings, high me1 moisture and relative

humidity, and discontinuous fuel spacing. Fire fronts are

typically shallow and narrow. Areas burned arc normally

small and patchy (Batchelder and Hit-t 1966).

The second problem is a result of the first. Too many fires

escape the intcndcd burning arca. Cook (1909) observed that

tires were usually allowed to spread wherever fuels would

carry them. As the population density of forest farmers

increases, abandoned and productive agricultural plots remain

in close proximity (Dcncvan 1978). Abandoned plots arc

frequently composed of xcric secondary vegetation that

readily bums during the dry season. Fires intentionally set in

the productive plots accidentally bum into the nearby

abandoned plots. These escaped, uncontrolled, human set

wildfires eventually spread into the adjoining forest. This

scenario accounted for nearly 100,000 hectares of wildfires

in Mexico’s eastern Yucatan Peninsula during the summer of

1989 (National Fire Protection Association 1989; Garrett

19891.

The actual process of deforestation by iire has been dcscrihcd

by several authors from Cook in 1931 to Mueller-Dombois in

1981. Fire originating in adjacent open areas burns to the

forest border. Depending on the intensity of the fire, density

of the vcgctntion at the forest edge, fuel loading, and forest

moisture conditions, fire may or may not penetrate the forest.

Under normal circumstances fire will not enter a rain forest,

but fires can burn from several meters to 1 or 2 kilometers

into the scm-deciduous and deciduous forests. Once at or

within the forest cdgc, fire intensity lessens as available fuel

dccrcascs and relative humidity increases. Fire damage is

usually minimal. Hcrbaccous growth, coppice stumps, low

bushes, suckers, and seedlings are killed and varying amounts

of duff and litter arc removed by the fire. Saplings and some

fire sensitive species may be killed. Also, larger trees may

be scorched or scarred around the butt.

The killing of undergrowth and trees in the burned forest area

opens more of the forest to direct sunlight. Grasses quickly

establish and rapidly grow in the sunlit areas. In forests

which adjoin annually burned savannas or which surround

annually burned openings, the invading undcrstory vcgctation

provides the fuel that will allow the next season’s fires to

spread farther into the forest. Furthermore, opening of the

forest edge to greater sunlight alters the edge microclimate to

a drier type which also may contribute to increased intensity

of the next fire.

These tires pose two major problems important to

deforestation. Foremost, with some exceptions, few people

make any attempt to control their fires. They simply rely on

the low flammability of surrounding green vegetation to

contain the fires. This lack of concern about fire control is

all too common throughout the tropics.

215
LONG-TERM EFFECTS OF

UNCONTROLLED FIRE USE

Tile forcs[ vegetation shields the soil and the site from the

drying effects of the sun and wind. Repeated fires open

forests and expose the forest soils by removing living

vegetation and jitter. Soil surface tcmperaturos rise and

relative humidity &creases in response to direct solar

exposure. Addition of new organic matter is reduced. Given

these conditions, the closed nutrient cycling system of the

tropical forest is damaged. Movement of essential nutrients

to the forest vegetation is interrupted (Richards 1951). Wind

and solar insolation dcssicate the cxposcd soil and contrihutc

to increased evapotranspiration which further reduces soil

moisture. Microorganism populations shrink as organic

matter content causes reduced nitrogen fixation and nutrient

mineralization. Soil impoverishment is the result

(Camcro-Zamorra 19.51).

The combined cffcct of repeated firing, insolation, and

lorrcntial rains is a breakdown in soil structure. Under these

forces the soil disaggrcgates and compacts (Pilticr 1939; Jha

and others 1980). Soil density increases and porosity

dccrcascs leading to rcduccd soil moisture holding capacity.

In the oxisols, ultisols, inceptisols, and the red earths typical

of the humid and seasonal tropics a hardpan may develop if

cxposcd to fcI>caIcd wetting and drying (de la Rue 1958;

Donahue and others 1977). Once cxposcd to the elcm(XlIS,

erosion of the fragile topsoil becomes a serious problem.

With progressive opening of the forest microclimate warms

and dries, soil mojsturc and fertility decline, and less

demanding woody and hcrbaccous plants adapted to drier

conditions become established (Budowski 1956). Forest

vegetation that survives the rcpcatcd fires or degraded site

conditions lingers on singly or as relict groves and gallery

forests (Batcheldcr and Hirt 1966). Forest rcgcncration that

OvCrComcs the poorer site conditions is c&her killed during

regular burning or supprcsscd by the invading vcgctation

which is more fireresistant (inncs 1971; Vogl 1977):

Eventually, even the most fire-resistant woody species are

clirninatud. At this point the forest site is totally degraded

and &rorcstalion is complctc. Continual firing will prevent

the rclurn of forest growth to formerly forcstcd sites.

MANAGEMENT OF ANTHROPOGENlC

FIRE

The challenge is to halt haphazard fire USC without prohibiting

rational use of fire for legitimate agricultural and

non-agricultural land management. However, since fire is the

primary land clearing tool of most agriculturalists,

implementation of a rational fire management program will

bc a difficult and sensitive task. Human use of fire can never

bc successfUlly eliminated, nor is its prohibition necessarily

dcsirablc. A fire management program, while serving to

preserve and protect tropical forests and human welfare, must

respect the basic rural cult& foundations on which burning

rests. It must also allow for inevitable and unavoidable

economic use of forests and grasslands.

Govcrnmcnts of countries with tropical forests have become

more aware of the forest fire problems they face and of the.

need to protect their forest resources. We suggest that the

iirst task in dealing with the fire problem should be the

formulation of a national fire policy to provide a framework

for filfihcr actions. Every nation has a unique lire situation,

and each nation’s fire policy should reflect that uniqueness.

In every case, though, the all-important human dimensions of

fire must be addressed. Human-caused fires are preventable,

but Iire policy that threatens traditional land uses will

ultimately fail.

To bring anthropogenic lirc under control the affected people

must understand and support management programs.

Education is essential to impart understanding and to change

the attitudes of fire users toward fire and the environment.

Hand in hand with an educational effort, an agricultural or

forestry extension program could be established to instruct

user8 about the correct application of fire and its positive and

negative cffccts on the land and its vegetation. The negligent

and indifferent fire habits so common in the tropics must be

rcformcd for a program of managed fire to be successful.

Education is a long-term solution to a pressing problem;

ncvcrthclcss, the best of intentions, the finest po1iey

statcmcnt, and the most modern science and technology will

avail us little if the attitudes of fire users remain unaltered.

Mr. Helmut Haufc, FAO Regional Forestry Officer in Latin

America, sta.tcd ihat anthropogenic wildfires in too many

casts arc “due to the lack of a proper information and

instruction system” (pcrs. comm. 1981). Mr. Haufc’s

statcmcnt is a significant endorsement for an extensive and

vigorous fire education program.

Other actions that may help manage the anthropogenic fire

problem are more appropriately considered under the headings

of agricultural and rural development, but bear mentioning

216
here. These actions include providing alternatives to

traditional agricultural practices and incentives to take up the

alternatives. The already mentioned extension programs

could help develop and promote alternative methods and

technologies. Land use, tax, rural development, and internal

colonization policies can also he adjusted to reduce the

motives for negligent and abusive fire use.

CONCLUSION

In 1967 Batchelder wrote that the “use of fire in the tropical

world is no longer in a stage of ‘ecological climax’ wherein a

stable, harmonious relationship to the environment exists.” In

fact over the past hundred, if not several hundred years, the

careless and repeated use of tire has resulted in ecological

disturbances which have steadily forced the retreat of tropical

forests worldwide. Natural succession, which normally heals

ecological wounds and returns ecosystems to their

prcdisturbance states, has been halted by the frequent and

often devastating nature of anthropogenic tire. Insofar as

tropical forest regeneration is concerned, continuous

anthropogenic Iire disturbances are unnatural and, therefore,

beyond the adaptive and recuperative powers of forest

ecosystems. Repeated burning leads to repIacement of the

original vegetation by a series of seral communities more

easily burned until a tire disclimax community is finally

cstablishcd.

In a paper delivered to the West Indian Agricultural

Confcrcnce in 1901 Nichols called for an immediate end to

uncontrolled burning in the tropics. Ninety years later a great

variety of voices still echo his call. Since 1901 efforts to

reduce the frequency and effects of anthropogenic fire in the

tropics have failed. The burning continues. Effective tire

management policies, that are strong on education must be

developed and implemented. Without them increasing

population, development, and colonization pressures within

the tropical forest regions will assure the unabated cultural

use of hre in its present destructive form.

LITERATURE CITED

Aubreville, A. M. 1947. The disappearance of the tropical

forests of Africa. Unasylva 1:5-l 1.

Bartlett, H.H. 1955. Fire in relation to primitive agriculture

and grazing in the tropics: annotated bibliography.

Volume I. University of Michigan Botanical Gardens,

Ann Arbor.

Batchelder, R.B. 1967. Spatial and temporal patterns of frre

in the tropical world. In: Proceedings of the Tall Timbers

Fire Ecology Conference 6: 17 1- 190.

Batchclder, R. B. and Hirt, H. F. 1966. Fire in tropical

forests and grasslands. United States Army Natick

Laboratory Technical Report 67-47-ES.

Budowski, G. 1951. Los incendios forcstales en Venezuela.

Agricultor Venezolano 16( 152): 24-28.

Budowski, G. 1956. Tropical savanna: a sequence of forest

felling and repeated burnings. Turrialba 6:23-33.

Budowski, G. 1966. Fire in tropical American lowland areas.

In: Proceedings of the Tall Timbers Fire Ecology

Conference 5~5-22.

Camero-Zamorra, J. 1952. Quemas e incendios forestales.

Agricultor Venzolano 17( 158): 39-43.

Cook, 0. F. 1909. Vegetation affected by agriculture in

Central America. United States Department of Agriculture

Bureau of Plant Industry, Number 145.

Cook, 0. F. 1921. Milpa agriculture, a primitive tropical

system. In: Annual report of the Smithsonian Institution,

pp. 307-326.

Dcncvan, W. W. 1978. The causes and consequences of

shifting cultivation in relation to tropical forest survival.

In: Brown, S., Lugo, A. E. and Liel, B. eds., The role of

tropical forests on the world carbon cycle, pp. 140-156.

United States Department of Energy.

Donahue, R. L., Shickline, J. C. and Robertson, L. S. 1977.

Soils: an introduction to soils and plant growth.

Prcnticc-Hall, Englewood Cliffs, New Jersey.

Garrett, W. E. 1989. La ruta maya. National Geographic

176:424-479.

271
Jha, M. N. Bad&, K. C., and Pan&z, P. 1980. Soil changes

due to podt~ cultivation in the state of Orrissa. In:

Proceedings of the 2nd forestry conference, pp.?--7. Forest

Ruscarc/l institute and Collcgcs, Dchra Dun.

lnncs, R. R. 197 1, Fire in West African vcgclalion. In:

Proceedings of the Tall Timbers Fire Ecology Confcrcncc

11:147-174.

Mucllor-Durnbois, D. 1981. Fire in tropical ecosystems. In:

Proceedings of Ihe conference--fix regimes and

ccosyslcm propcrt’ics, pp. 137-l 76. United States

Dcpartmcnt of Agriculture Forest Service Gcncral

Technical Report WO-26.

Myers, N. 1981. Conversion rates in tropical moist rorcsls

In: Mcrgcn, F., cd., Tropical ft>rcsts * utilization and

conservation, pp. 48-66. Yale University, Schoot of

Forestry and Environmental Studies, New Haven,

Connecticut.

National Fire Protection Association 1989. Fires bum in

Yucatan jungle. Wildland Fire Managemcrlt Briclings

7(4):71.

Nichols, 11.A.A. 1901. The harmfulness of bush f&s in the

West Indies. Indian Forester 27:384-390.

Piltier, H. 1939. Considcracioncs acerca de la destrucc.ion de

10s bosqucs c incendio dc las sabanas. Boletin de la

Socicdsd Vcnezolano de Cicncias Naturales 3::91-307.

Richards, P. W. 1952. The tropical rain forest. Cambridge

University Press, Cambridge.

de la Rue, E. D. 19.58. Man’s influence on tropical

vegetation. In: Proceedings of the Ninth Paciiic S&XICC

Congress 20: 8 l-93.

Ssucr, C. 0. 1958. Man in the ecology of tropical America

III: Proceedings of [he Ninth Pacific Science Congress

20:104-110.

Spur-way, B. J. 1937. Shilling cultivation in Sarawak

Malayan Forcstcr 6: 124-138.

Stewart, 0. C. 1956. Fire as the lirst great force employed by

man. In: Thomas, W. L., ed., Man’s role in changing the

[ace of Ihc earth, pp. 115-133. University of Chicago

Press.

Trollope, W. S. W. 1980. Fire in savanna. In: De V.

Booyscn, P., cd., Ecological effects of fire in South

Africa. CSIR, Pretoria.

TI’OU~, R. S. 1926. Problems of forest ecology in India. In:

Tnnslcy, A. G. and Chipp, T. F., cd., Aims and methods

in the study of vegetation, pp. 283-3 13. White Friars

Press, London.

UNESCO 1978. Tropical forest ecosystems: a state-ofknowlcdgc report. Paris.

U. S. Interagency Task Force on Tropical Forests 1980. The

world’s tropical forests: a policy, strategy, and program

for the United States. Department of State Publication

9117.

Vogl, R. J. 1969. The role of fire in khc evolution of the

Hawaiian flora and vegetation. In: Proceedings of the Tall

Timbers Fire Ecology Confcrcnce 9:50-60.

Vogl, R. J. 1977. Fire: a destructive menace or a natural

process? In: Cairns, J. and Dickson, K., eds., Recovery

and management of damaged ecosystems, pp. 262-339.

University of Virginia Press, Charlottesville.

Walter, H. 1971. Ecology of tropical and subtropical

vegetation. Mueller-Dombois, D., trans., Burnett, J. H.,

cd. Van Nostrand Reinhold Company, New York.

Walter, H. 1973. Vegetation of the Earth in relation to

climate and ccophysiological conditions.Wise, J., trans

Springer-Vcrlag, New York.

278
WILDFIRE IN THE PALEOZOIC: PRELIMINARY RESULTS OF A

CASE STUDY ON THE FIRE ECOLOGY OF A PENNSYLVANIAN

FLOODPLAIN FOREST, JOGGINS, NOVA SCOTIA, CANADA

Nan Crystal Are&

Abstract-Sediments of the Joggins Section, Cumherland Basin, western Nova Scotia accumulared in

lowland forests approximately 300 million years ago. The 4,000.meter-thick sedimenrary sequence includes

channel and overbank sandstones interbedded v&b stacked immature paleosols developed in thick mudscone

horizons. Fusain (charcoal) is common in all sedimentary facies present at Joggins. Fusain occurs as

isolated macroscopic clasts and also as recognizable layers of clasts and particles within the

mudslone/paleosol facies. These layers are interpreted as tire-event horizons. In one example, an ancient

tree, rooted below B tire horizon, is preserved with its charred periderm intact. Palynological analysis

shows that there is an increase in taxonomic diversity immediately following this tire. Although

arborescent lycophytes remain dominant in the palynoflora, cordaitean and medulloan gymnosperms enter

the postfire community. These groups decline later as prefire vegetation is westablished. Numbers of fernspore species increased following fire, although ferns did not become more abundant. Studies of tirerelated floristic patterns preserved in Ihr fossil record can test ecological generalizations and theory dcrivcd

from present day ecosystems and may help ecologists understand the role of changing fire regimes in long

term vegetational change.

INTRODUCTION

The classic image of Carboniferous lowland ecosystems is a

static and steamy tropical wetland. Groves of arborcsccnt

lycophytcs with their understory of tree ferns and

ptcridosperms (seed-b+zring plants with fern-like foliage)

stand in ever-wet soils, while along the riverbanks clumps of

sphcnopsids flourish. Stutzcr and Not (1940) wrote: “It is

difficult to believe that such a thing [wildfire] happened in

view of the moist condition of the Carboniferous forests.

Judging fmm the plant associations that grew there, fires

could not have spread rapidly in a swamp forest.” Howcvcr,

Izlar (1984) reported that portions of the Okefcnokcc SwampMarsh Complex bum every 25 to 30 years, and that this fire

regime maintains the floral composition and hctcrogcneity

characteristic of the ecosystem. As our understanding of

wetland ecosystem ecology develops, we arc called to

rcevatuatc our view that ancient swamp and floodplain

ecosystems were static. We must reexamine the role of fire

in these systems.

For this reason, I have begun a study of community dynamics

and fire ecology in the Joggins Section (Middle

Pennsylvanian) of western Nova Scotia, Canada. This paper

reports on the initial study testing the feasibility of d&GM

ecological reconstruction of this ancient ecosystem. In this

paper, I will: (1) show that ecological-scale resolution of the

fossil record is possible in this stratigraphic section; (2)

establish that wildfire was a significant factor in this ancient

ecosystem; and (3) demonstrate that wildfire may have, in

part, controlled the distribution of some floodplain plants.

‘Botanical Museum of Harvard University, 26 Oxford St,,

Cambridge, MA 02138.

GEOLOGIC SETTING

The Joggins section is located in the Cum&&& depositional

basin of western Nova Scotia, Canada (fig. 1). Approximately

4,000 meters of sediment arc well exposed in a continuous

cliff outcrop along the eastern shore of Chignecto Bay. The

outcrop face is approximately perpendicular to strike; bedding

dips range from 15” to 20” south. Sediments are Middle

Pennsylvanian (approximately 305 m.y.b.p.), and have been

biostratigraphically dated as latest Wcstphalian A through

earliest Westphalian C using miospores (G. Dolby,

unpublished data). Joggins sediments are well correlated with

other terrestrial and marine deposits in the North American

midcontinent, the Appalachians, and Europe (Phillips and

others 1985).

The 4,000 meters of sediment exposed at Joggins record 2 to

5 million years of history (Harland and others 1989). The

inferred rapid sedimentation rate suggests that decade-scale or

liner stratigraphic resolution may be possible at Joggins.

Such line time-scale stratigraphic resolution is essential for

the study of community dynamics and responses to

disturbance in an ancient ecosystem. Without adequate timestratigraphic resolution the record of ecological-scale

processes will be obscured by the homogenizing effect of slow

sedimentation.

The Joggins stratigraphic sequence consists of channel, levee,

and overbank sandstones, floodplain mudstones, and thin

coals probably attributable to floodplain ponds. Fluvia] tics

were deposited in an anastomosing river system that drained

the Cobquid Highlands to the present-day southeast (Rust and

others 1984). Thin, organic-rich lacushine limestones also

occur in the lower portions of the section. I have observed

219
BRUNSWICK

Figure 1 .--Location of the Joggins Section area.

no cvidcncc of marine facies or marine influence on Icrrcslrial

facies at Joggins. Within the Joggins Section scdimcnts tend

to redden and sandstones to coarsen up-section. Rust and

others (1984) concluded that these trends indicated a

tectonically mediated steepening of the alluvial plain, which

lowered relative water table and increased the amount and

grain-size of transported sediment.

For this study, the elastic floodplain mudstone/palcosol facics

arc of particular interest. Mudstone horizons vary from 1 to

20 meters in thickness and are intcrbcdded with crevassesplay and channel sands. In lower portions of the section,

mudstones and paleosols constitute 70 to 80 pcrccnt of the

stratigraphic section. Color of mudstoncs varies from graygreen lo mottled to gray-red or red up section, corresponding

to the inferred water table gradient. Despite this gcncral

trend, there is substantial color variation on a finer

stratigraphic scale within the section. Mudstones are

commonly very poorly-bedded to structureless with moderate

to well-developed immature palcosols. Paleosols are

characterized by root traces and localized root casts, sidcritc

rhizoconcretions, and locally developed soil structures.

Recognizable soil horizons are commonly absent or poorly

developed; paleosols gcncmtly have uniform texture

vertically. Upright trees arc commonly prcscrved as partial

sandstone molds within mudstonc facies. These trunks may

be partially tilled or cast in mud, commonly with a rind of

vitrinous coal, which is the prcservcd remains of the

lycophytc lra’s thick peridcrm.

Together, these observations suggest that floodplain

mudstones were dcpositcd in frcqucnt (gcologicaily speaking)

flooding events that emplaced small amounts (ccntimctcrs) of

fine-graincd sediment, rather than in catastrophic events

depositing tens or hundreds of centimeters of sediment.

Under this depositional regime, elastic swamp trees would not

be substantially disrupted by sedimentation events, but,

continual redefinition of soil surface by sediment input would

cause successive readjustment of soil profile and lead to the

observed lack of well-developed horizons. This model fits

well with observations of modem tropical rivers such as the

Brahmaputra in India and Bangladesh (Coleman 1969) and the

Orinoco in Venezuela (Armando Torres, 1991, personal

communication).

During deposition of Joggins sediments, the Pennsylvanian

Maritimes Basin was near-equatorial and had a tropical to

subtropical climate (Rowley and others 1985, Galtier and

others 1986). Ziegler and others (1981) reconstructed this

region at about 1.5” north latitude and in a zone of Easterlies.

Peat-forming ecosystems at Joggins and in the Springhill coal

field to the east are interpreted as groundwater-influenced

(rhcotrophic), rather than raised, bog systems (Caldcr and

others in press). Groundwater-fed systems occur in the East

African i-3, where availability of moisture varies seasonahy

(Cecil and others 1988) If rhcotrophic bogs occurred in Nova

Scotia during the Pennsylvanian, it is possible that they, too,

formed under conditions of seasonally varying moisture

availability. However, Cecil and others intcrprctcd the

Westphalian B as equitably and adequately wet, based on the

relative abundance of ombotrophic versus rheotrophic bogs in

the central Appalachians. Conversely, Phillips and Peppers

(1984) interpret the Westphaiian B as drier and more seasonal

than the preceding and succeeding epochs based on swamps in

the North American midcontinent. Rowley and others (1985)

reconciled these interpretations by suggesting that an

increasingly monsoonal climate coupled with the orographic

effect of the developing Appalachian highlands to the

southwest of the Canadian Maritimes Basin created regionally

different rainfall patterns across the Euramerican coal

province. In the Maritimcs Cumbcrland Basin, higher

paleolatitude and the presence of highlands to the east could

further intensify such a regionally seasonal climate.

The Joggins fluvial sandstones provide direct scdimenlological

evidence for fluctuating discharge that suggests seasonal

rainfall. Multistoried sandstones, graded pebbly sandstones,

scour fills, conformable mud drapes, and fan sheetflow in

ovcrbank deposits all point to variability in stream discharge,

which is consistent with the monsoonal interpretation.

However, it is impossible to determine from scdimentological

evidence alone whether flood events occurred with seasonal or

decade-scale frequency. By either interpretation, though, the

ancient landscape at Joggins experienced periods when

evapotranspiralion exceeded prccipilalion, thus allowing fuels

to dry sufficiently to permit wildfire. In this respect, the

climate-induced fire regime may have been quite similar to

that in the Okefenokec swamp (Izlar 1984) or the Orinoco

floodplain.

280
EVIDENCE OF WILDFIRB 0 N THE

JOGGINS FLOODPLAIN

The presence of fire in the Joggins ecosystem is inferred from

the presence of fusain (charcoal) throughout Joggins

sediments. Fusain occurs at Joggins in several sedimentary

contexts. In coals, fusain occurs as discrete layers that are

laterally continuous for meters on the scale of the outcrop.

Within these horizons, fusain may occur as discrete,

macroscopic clasts or in a mechanically ground, powdery

form. Within the mudstone/paleosol facies, fusain also occurs

as clasts distributed in discrete, sharp-bounded horizons that

can be traced laterally for meters along the exposed outcrop.

Clasts occur in a matrix of fmely-ground charred material

with varying amounts of clay. Fusain clasts varying from a

few millimeters to 50 centimeters (fig. 2 a-c) are also

common in the sandstones and siltstones associated with

channel facies. The largest fusinized logs show a

perpendicular surface fracture pattern consistent with charring

by fire. In the reddest sandstone facies, charred logs arc

common in mud drapes of channel fill and in point-bar

deposits.

The origin of fusain and related materials described from coal

mace&s has been the subject of much debate between

workers who favor a pyrolitic origin for this material and

others who believe fusain is produced by some unknown slow

oxidization process. Scott (1989) reviewed the evidence and

arguments and concluded that most fusain found in the

Paleozoic and Tertiary rock record is the direct result of

surface burning of vegetation or other surficial organic

material. Ting (1982) agreed: “Fusinite and scmifusinitc arc

derived primarily from woody tissues charred or partially

charred during swamp fire. Once charred, the fusain

progenitor--charcoal--becomes extremely stable and inert to

any chemical and biochemical attack and is thus well

preserved. Some coal beds may contain 20-25 percent

fusinite, occurring in numerous fusain bands that suggest

frequent swamp fires during peat accumulation.” Cope and

Chaloner (1985) added that wildfire was an important

ecological factor since the evolution of a land flora in the

Silurian and Devonian. In accordance with these conclusions,

I adopt the charcoal interpretation of fusain and will refer to

fusain as fossil charcoal.

METHODS FOR POLLEN ANALYSIS

The samples analyzed were collected stratigraphically above

and below a horizon of fusain clasts, mechanically

disaggrcgated charcoal, and clay associated with the preserved

stump of an ancient tree (fig. 2 d-e). The stump, which is

located about 150 meters south of McCarren Creek (Rust and

others 1984), is preserved in mudstone/paleosol capped by an

ovcrbank sand body. The locality is in the lower portion of

the section measured by Rust and others (1984) but is not

noted in their published stratigraphic section, probably

because cliff-face erosion had not yet exposed the stump at

the time of their field work. When collections for this study

were made (August, 1989), the stump was badly eroded, but

periderm material preserved as fusain rather than vitrinite was

clearly visible and the outline of the enlarged base of the tree

was easily traceable to a well-defined and laterally continuous

horizon of fossil charcoal.

Based on the abundance of centimeter-sized fusain clasts

within the mudstone/paleosol facies, this horizon is interpreted

as a fire event horizon that records a single wildfire in an

ancient stand. This conclusion is based on analogy with

studies of Recent sediments, which show that even in lakes,

where in situ deposition is less likely than on the floodplain

environment, peaks in charcoal abundance can be correlated

with single fire events within the drainage basin and charcoal

clast size can be related to transport distance (Clark 1988,

1990).

A mudstone sample from below the charcoal horizon sampled

prefire vegetation. Stratigraphically successive samples were

taken at l-centimeter intervals above the fusain layer.

Samples were processed according to standard palynological

technique (e.g. Traverse 1988). Rock was degraded in

concentrated hydrofluoric acid, unwanted organic material

was oxidized with HCI and bleach, clay was removed by

heavy liquid separation with ZnCl. Strew slides were made

with glycerin jelly. Each slide was scanned systematically

and each palynomorph encountered was recorded by genus.

Species-level diagnosis was made only for the most abundant

spore genus, Lycospora, the spore of several arboresccnt

lycophytes. In each sample, 400 palynomorphs were counted

and taxa relative abundances were calculated. Following the

count, each slide was scanned for additional rare forms.

Relative abundance is plotted by stratigraphic position to yield

standard pollen diagrams (figs. 3 and 4).

When interpreting a palynological analysis, one must keep in

mind several caveats. First, differing quantities of pollen and

spores are produced by different taxa. Wind pollinated

plants, for example, produce prodigious amounts of pollen

and spores while partially or wholly entomophilous plants will

be relatively underrepresented in the dispersed pollen and

spore record. This caveat is traditionally reconciled by

admitting that palynomorph relative abundance cannot be

translated directly into quantitative stand measures such as

standing biomass or DBH. In the modem pollen record,

differential spore production can be a significant confounding

factor. However, entomophily was probably less important in

the Carbonifcrous than among modem angiosperms.

Consequently, one might expect pollen and spore relative

abundance to be a better proxy for individual plant relative

abundance in these ancient forests. It is also possible to

develop conversion factors that will allow pollen and spore

abundance to better approximate other measures of stand

composition. This approach has been successfully applied to

Pleistocene and Rcccnt stands (Davis and Goodlett 1960).

281
Figure Z.--Physical evidence for fire in Joggins Section rocks. (a-b) Compressions of fusinized iburncd) wood in finegrain& sandstone associated with a channel deposit, Spicer’s Cove. Note pcrpcndicular fracture pattern characteristic of

burned wood. (c) Charcoal fra&ments and impressions of unbumcd plant axes in channel sandstone. Arrows indicate

charcoal fragments. (d-c) Tree cast with bumcd peridenn. (d) Extensively eroded outline of tree stump showing outline of

tree base extending to dark, charcoal-tich horizon (at hammer shank). Palynoiogical samples tciken one meter to the lclt of

hammer position. (e) Close-up of burned trunk. Pen and arrow indicate fusinized material.
, o Monoletes

1

Lycospora pusilla

‘Ol

Lycospora pellucida

101

9

2

0’

1

0 20

per%nt 60 8 0

Floronites Calamospora

lo1 10

1

o0 20 40 60 80

percent

Figure 3.--Relative abundances of several palynomorph taxa. Arrows indicate stratigraphic position of fusain horizon.

283
Arborescent Lycophytes

10

1

0

0 20 40 60 A0

01

0 IO 20 30

percent percent

, o Gymnosperms

1

0'

0 5 IO 15

o0 IO 20 30

percent number of species

Ferns

10 1

10 %

Estimated Species Richness

Figure 4.--Relative abundances of major plant groups and cstimatcd spccics richness.

Arrows indicate stratigraphic position of fusain horizon.

However, such conversions are only now being dcvclopcd for

the Carbonifcrous (Willard 1986). Future interpretation of

these communities will incorporate this more quantitative

approach to stand composition; however, that is beyond the

scope of this preliminary study. Second, changes in pollen

and spore abundances do not ncccssarily mean a change in

stand composition. Some modern plants are stimulated to

reproduce by disturbance, thus enriching their representation

in the dispersed pollen and spore record. At this stage of the

study, this influence cannot be discounted, but at the scale of

stratigraphic resolution applied in this paper, pollen and

spores are regarded as good indicators of standing vegetation

(Davis and Goodlctt 1960). Clearly, one must tailor questions

asked of the pollen record to the time-stratigraphic,

taxonomic, and quantitative resolution appropriate to the data.

284
RESULTS

The spore species Lymora pusilla, produced by some

arborescent lycophytes, was most abundant (63 percent) in the

prcfire vegetation (fig. 3). The other arborcsccnt lycophyte

spore present (Lvcosoora ucllucida) represented only 10

percent of the palynoflora. Lycusporajs produced by a

number of species in the stem genus Lenidophloios. Other

palynomorphs including Calamosuora, the spore of the

sphenopsid Calamites, and a complex of ferns made up

approximately 10 and 15 percent of the palynoflora

respectively. The pollen of gymnosperm taxa including

Monoletes, the pollen of mcdullosan pteridospcrms, and

Florinites, pollen of the conifer relative Cordaitcs, were not

present in the pretire palynoflora. A simple count of

palynomorph taxa suggests that about 15 species were present.

This estimate of species richness (fig. 4) is tentative and

pending more complete taxonomic study of the palynoflora.

Note also that, in some cases, a single spore and pollen taxon

was produced by more than one mcgafossil taxon, thus

under-representing species richness.

The sample collected stratigraphically immediately above the

fire horizon shows several important changes in the

palynoflora. Abundance of Lvcospora pusilla declined

dramatically from 63 to 13 percent. Conversely, L. oellucida

increases from 1 I to 43 percent. The increased relative

abundance of Ldellucida-is not entirely a relic of decline in

abundance of L. pusilla; L. pellucida becomes absolutely

more common in an average microscope field on slides of

comparable palynomorph density. Fern spores and

Calamospora become more common above the charcoal

horizon. Medullosan and cordaitean gymnosperms also

appear to enter the community following tire. The

medullosan seed fern pollen, Monoletcs, reaches its greatest

abundance (6 percent) immediately above the tire horizon.

Estimated species richness also reaches maximum

(approximately 27 species) in the sample immediately above

the tire horizon. This maximum includes several added rare

or uncommon fern and hcrbaceous lycophytc taxa.

In stratigraphically successive samples above the fire horizon,

several trends emerge. First, L. nusilla increases in relative

abundance while L. pellucida declines until these taxa

returned to approximately prefire levels. However, L. ousilla

did not reclaim its prefire abundance within the sample

interval. Likewise, L. oellucida declined in abundance

throughout the sampling interval, but retained a higher

postfire abundance (25 to 30 percent) throughout the sampling

interval. In contrast with this gradual dominance exchange,

Monolctes declined rapidly to a background abundance of 2

or 3 percent immediately after its abundance peak. Florinitcs,

the pollen of cordaitean gymnospcrms, increased in abundance

more gradually to a maximum abundance in the second

centimeter above the fossil charcoal horizon. Following this

maximum, Florinites declined gradually to a background level

similar to that of mcdullosan pollen. Spccics richness

followed a similar trend of steady decline to the prefire level

in the fourth centimeter above the fire horizon. This decline

is driven mainly by the loss of the rare and uncommon fern

and herbaceous lycophyte taxa that appear immediately above

the fire horizon.

DlISCUSSION

Rapid and relatively continuous (perhaps seasonal)

sedimentation is a prerequisite for ecological-scale resolution

of the fossil record. The Joggins Section appears to provide

such conditions; however, absolute&imentation rates are

difficult or impossible to ascertain. Consequently, one must

look to the vegetation for confirmation of time scale. If the

Joggins strata can be interpreted at the ecological scale of

resolution, one should be able to detect vegetation change

stratigraphically above sedimentologically-inferred

disturbances such as tires. Similarly, ecological resolution

should show gradual reestablishment of plant abundances

similar to those seen before the disturbance. Clearly, these

predictions are realized in this case. Figure 4 shows that

arborescent lycophytes suffer a 20-percent decline in

abundance following fire. Note that arborescent lycophytes

with small, wind-dispersed microspores are likely to be overrepresented in the postfire palynoflora due to spores

transported from nearby, unburned stands into the gap. The

lycophyte decrease in postfie samples is largely

counterbalanced by an increase in gymnosperm+initially by

medullosan pteridosperms and subsequently by cordaiteans.

Medullosans were characterized by large fronds displayed on

an unbranched axis and minimal investment in low-density

wood. Both of these features (minimal branching and lowdensity wood) are characteristic of modem colonizer trees in

the tropics (Ashton 1978, Bazzzz and Pickett 1980, White

1983). Cordaiteans have a more substantial structural

investment in greater volumes of dense wood. These

structural observations support the conclusion that

medullosans, with their “inexpensive” construction, filled the

colonizer role in these ancient communities, with the more

structurally “expensive” cordaiteans following in a midsuccessional phase. Thus, the observed vegetation response,

particularly the increase in gymnospcrms, after fire

establishes that ecological-scale changes are being observed,

return to prefire abundances in stratigraphically subsequent

samples reinforces the conclusion. These biological

observations coupled with the inferred rapid sedimentation

rate support an ecological-scale interpretation of the Joggins

section. Thus, while I cannot conclude whether the sampled

interval records decades or centuries in absolute time, the

observed vegetation changes probably occurred within several

generations of the plants involved--clearly an ecological-scale

time frame.

If one accepts Scott’s (1989) conclusion that fusain in coals

and clastie sediments records wildfire, then it is clear from

the abundance of fusain in the Joggins sediments that fire was

not only present but common in the Joggins swamp

285
ccosystcm. The influence of periodic tire on vegetation then

becomes interesting. In a study of early Middle

Carboniferous peat-forming mires, Phillips and others (I 985)

reported a correlation between an increased abundance of

cordaitean gymnospcrms and higher fusain percentages. In

the upper “Pottsville” (Westphalian A/B correlativcs) coals of

northeastern Tcnncssce and eastern Kentucky, Cordai&

makes up 33 and 36.7 percent biovolume in coal balls with 9

and 7.4 percent fusain respectively. In the same region, two

correlative coals with lower cordaitean abundances (1.7 and

14.3 percent) contain lower proportions of fusain (0.8 and 2.6

percent respectively). A similar pattern was observed in the

Upper Foot Scam, Lancashire, England, the Bouxharmont

Scam in Belgium, and the Katharine Seam in the Ruhr, West

Germany. Phillips and others (1985) conclude that this

correlation reflects the cordaites’ preference for drier habitats,

which would be more prone to fire or other diagcnctic

oxidation.

The association of cordaitean gymnospcrms with fusain is also

observed in the Joggins fire horizon. In this case, howcvcr,

d&&d stratigraphic sampling shows that the cordaitcs were

not simply growing in drier, fire-prone areas; rather, they

were present in the community only afier ftre and could not

maintain a significant presence without further disturbance

This suggests that fire (or disturbance in general) was an

important factor in controlling the distribution of this taxon in

the floodplain community.

A clear fusainlabundance relationship for ptcridosperms is not

present in the data of Phillips and others (1985) from

]oca)jIies in the Euramerican Carbonifcrous. Medullosan

pollen, Monotetcs, is commonly not reported in standard

palynological analysis because the large grains (100 to 200

micrometers) are eliminated from preparations by standard

sieve techniques. Also, if the distribution of medullosan

pteridosperms is patchy and ephemeral as hypothesized in this

paper, its pollen might be easily missed in a grab-sampling

regime. Consequently, absence of Monoletes from these

reports (Phillips and others 1985) is not convincing evidence

that pteridosperms were absent at those localities. At Joggins,

however, the pollen of mcdullosan pteridospcrms, like that of

Cordaites, enters the community and has an abundance peak

immediately above the fire horizon. Again, these data

suggest that the distribution of Monoletcs-producing

pteridosperms was influenced by fire. Arens (manuscript in

preparation) notes that some of the medullosan pteridospcrms

show morphologic and distributional characteristics consistent

with their interpretation as colonizers of disturbed habitats,

while others appear to have been understory plants. While

colonizer and understory medutlosans cannot be distinguished

by their pollen, the restriction of medullosans to immediately

above the charcoal horizon at Joggins supports the conclusion

that some medullosans functioned as colonizing plants that

required disturbance (in this case, fire) and were unable to

maintain their presence (or at least to reproduce) on a site

without subsequent disturbance. This conclusion can easily bc

reconciled with Phillips and others (1985); mcdullosan

pteridosperms were an ecologically and taxonomically diverse

group, and summary data that include taxa from both

colonizer and understory medullosan guilds would obscure a

correlation between medullosan ccotypes and fusain.

Pollen analysis across the lirc horizon clearly shows that there

is a vegetative response to disturbance. Two important trends

emerge. First, the lycophytes--dominant taxa before the fire--

suffer a major decline after fire, but gradually recover prelire

dominance. Second, the lycophytcs were replaced in the

postfire community largely by gymnospcrms, primarily

ptcridospcrms and cordaiteans. However, these laxa

apparently could not replace themselves on the site and

eventually became locally extinct (Noble and Slatyer, 1980).

Thcrcfore, tycophytcs and gymnosperms may also be tilling

different ecological guilds in the floodplain communities. The

gymnosperms may represent key components of an early

successional community that colonized habitat opened by fire;

the lycophytes, then, constitute a later successional

community that established in the shade of the colonizers and

eventually succee&d to dominance in the area. Noble and

Slatyer’s (1980) modet predicts that if tire occurs again

during the gymnosperm stage of succession, mcdullosans and

cordaiteans will continue to exist on the site. However, in the

absence of fire (or some other disturbance), the gymnospcrms

will become locally extinct and lycophytcs will reassert

community dominance. This latter prediction was confirmed

in this sequence. The ephemeral distribution of early

successional gymnosperms, particularly pteridospcrms, is

supported by observations in many Pennsylvanian-age lowland

environments (Phillips 1981).

Species richness trends associated with disturbed ecosystems

are equivocal. In the tropical rain forests of Uganda

(Eggcling 1947) and old fields of Nigeria (Jones 1956) species

richness is low during the colonization stage, peaks in midsuccession, and declines in late succession. This is

inconsistent with the diversity peak observed immediately

alI.er disturbance in the Joggins sequence. One possible

interpretation is that the initial, low-diversity phase was too

brief to be resolved or was not re.cordd in this sequence.

However, in the Yellowstone National Park forest ecosystem

(Dale Taylor, 1990, personal communication), the Australian

grassland (Burrows, in preparation), and chaparral (Zedler

1977) species richness is greatest immediately following fire,

as in the Joggins floodplain community. In these cases,

species richness in enhanced by the presence of several

codominant species and a variety of less common species,

much as in the Joggins sequence. This pattern is promoted by

microenvironmental variation generated by heterogeneity in

the distribution of plant resources such as light, moisture, and

nutrients in the disturbed site (Bazz,az and Sipe, 1987).

Analyses of more Joggins fire horizons will undoubtedly

clarify the pattern of species richness following disturbance on

the ancient floodplain, and permit more definitive

interpretation.

286
FUTURE WORK AT JOGGINS

The research described here represents the first stage of a

larger study of the Joggins plant communities. Conclusions

prcscnted arc, therefore, more accurately described as

hypotheses to be tested. The Joggins record presents an

opportunity to use fine-scale palynologicaI analyses Lo

interpret the effects of disturbance on ancient plant

communities. With analysis of more stratigraphic sequences

spanning charcoal horizons, one may ask: (1) Is there a

gcneralizahle trajectory of vegetation replacement following

disturbance in the Middle Pennsylvanian moist floodplain

forests? (2) Does a similar pattern occur in contemporaneous

peat-forming ecosystems? (3) Does this observed pattern

change with sedimentologically-inferred differences in soil

moisture? (4) What trends in diversity are observed within

and between successional guilds in claslic floodplains and in

peat-forming mires? Such an approach, emphasizing dynamic

patterns within communities over time scales of several plant

generation, offers the opportunity to test ideas of community

stability and coherence suggested for the Carboniferous

(DiMichele and others 1985, Phillips and others 1985). It

also offers a new and different system to test similar ideas

derived from and argued about by ecologists studying modem

plant communities.

ACKNOWLEDGEMENTS

The author thanks Andrew H. Knoll, David R. Foster, Fakhri

A. Bazzaz, and Loren H. Smith, Harvard University; Tom L.

Phillips, University of Illinois; and William A. DiMichele,

Smithsonian Institution for critical and helpful readings of

various versions of this manuscript. Thanks to the reviewers

who provided comments that substantially improved this

paper. Field and laboratory research was supported, in part,

by the Department of Organismic and Evolutionary Biology,

Harvard University.

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Galticr, J., T.L. Phillips and F. Chalot-Prat. 1986.

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266.

288
F'IREHISTORYANDF'IREECOLOGY

INTHECOSTARICANPARAMOS

Sally P. Horn’

Abstract-The high peaks of the Cordillcra de Talamanca in southern Costa Rica extend above timberline

and support bamboo- and shrub-dominated pliramo vegetation. The charcoal stratigraphy of sediment cores

from glacial lakes reveals that fires set by people or lightning have occurred in the highlands for thousands

of years. Historical sources and field evidence document numerous pdramo fires since the mid-century.

During the past 40 years, fire recurrence intervals at specific sites have ranged from 6 to about 30 years.

Paltems of postfire vegetation development support the initial floristics model of succession. The dominant

bamboo (Chusquea [ =Swallenochloa\ subtessellata) resprouts vigorously following burning, as do

associated ericaceous shrubs. H.ypericum spp, suffer high mortality and recolonize by seed. Slow rates of

growth and colonization by both woody and herbaceous species result in the persistence of bare patches of

ground for a decade or more following burning.

INTFtODUCTION

In a recent review of tropical alpine plant ecology, Smith and

Young (1987) noted that fire is common on most tropical

mountaintops. But the authors found few references on fire

Frequencies or fire history in tropical highlands, or on the

impact of burning on vegetation, soil nutrients, and

hydrology.

Since 1984 I have been working to fill this gap for the high

mountains of southern Costa Rica. This paper summarizes

the results of my research -- and that of U.S. and Costa Rican

colleagues -- on fire history and fire ecology in the bambooand shrub-dominated priramos found above timberline in the

Cordillcra de Talamanca.

ENVIRONMENT AND VJZGETATION

The uplifted granitic batholith that forms the backbone of the

Cordillcra dc Talamanca is mantled by Tertiary volcanic and

scdimcntary rocks, which outcrop along with granodioritcs

and other intrusive rocks on the high peaks (wi?yl 1957).

About a dozen areas along the crest of the range reach above

timberline, and support small to extensive stands of

ncotropical priramo vegetation (fig. 1). Many of these areas

arc quite remote and remain poorly known botanically.

Ecological research has focused on the priramos surrounding

Ccrro Chinip6 (3819 m), the highest peak in Costa Rica, and

Ccrro Bucnavista (3491 m). Glaciers occupied the upper

valleys of the Chinip6 massif several times during the

Plcistoccne, leaving behind a picturesque ice-carved landscape

dotted by some thirty glacial lakes. The extensive ( > 5000

ha) Chirripb p;iramo is protected within ChirripG National

Park, which was cstablishcd in 1975. Access to this remote

‘Assistant Professor, Department of Geography, and Faculty member,

Graduate Program in Ecology, University of Tennessee, Knoxville, TN

area is provided by rough trails that lead out of settlements on

the lower foothills of the Cordillera de Talamanca.

The smaller (c. 1000 ha), unglaciated Buenavista piiramo

&addles the crest of the Cordillera de Talamanca along the

Inter-American Highway route. There are no settlements

within the piiramo, but Cerro Buenavista is festooned with

broadcasting towers, and jeep trails and electrical transmission

line corridors crisscross the piramo. This area was the main

route across the Cordillera de Talamanca even before the

construction of the Inter-American highway in the 194&j, and

the vegetation has long been affected by tree cutting, humanset fires, and grazing (Horn, 1989a). Janzen (19’73a, 1983)

believes that low forest, rather than plramo, covered the

Bucnavista peaks prior to extensive human disturbance.

In both physiognomy and floristics, the Taiamancan pAramos

resemble the more extensive priramos of the northern Andes

(W&r 1959). and most authorities consider them to mark the

northern limit of p&ram0 vegetation in the neotropics

(Cuatrecasas 1979; Lauer 1981). The dwarf bamboo

Chusauea. (=Swallenochloa) subtessellata (Janzen 1983;

Clark 1989; Horn 1989b) is a characteristic element within

the pciramos, forming monospecific stands in many areas (fig.

2). Woody dicots fhat grow intermixed with the bamboo

include species in the Ericaceae, Hypericaceac, and

Compositac families. A variety of herbaceous plants, many

of Andean affinity, occur beneath the shrub canopy and in

more open areas.

The oak Ouercus costaricensis dominates the montane forests

that arc found just below timberline in the Buenavista and

Chirri$ highlands. The upper limit of oak forest ranges in

elevation from about 3150 m to 3300 m. In some areas, oak

forest 20-30 m high gives way to l-3 m high bamboo- and

shrub-dominated pa’ramo along an abrupt boundary; elsewhere

289
cmrnpo

/ /

/ 9’30’ N. -

/

Ddrika

+

i

Figure 1. The pgramos of the Cordillera de Talamanca, Costa Rica. The extent of piram vcgctation is based on Glimcz

(1986) and the l:SO,OOO scale topographic maps published by the lnstituto Gcogdfico Nncional.

the two communities are separated by broad transitional zones

supporting large shrubs and small trees other than oak. Some

of the trees and shrubs within these transitional zone8 also

occur, in mote stunted form, within the paramos of the high

peaks.

Figure 2. Nearly monospecilic stand of the bamboo

Chusquea subtesseltata in the Valle de 10s Concjos in the

Chirrip6 ptkamo.

LOW annual temperatures and a highly seasonal precipitation

regime characterize the climate of the Costa Rican pkamos.

Meteorological data from the Cerro PBramo station (3475 m)

near Cerro Buenavista show a mean am& temperature

during the period 1971-79 of 7.6” C (IBStiiuto Costarricense

de Elcctricidad, unpub. data). The warmest months, April and

May, averaged only 1.4” C warmer than the coldest month,

January.

Average annual precipitation during the period 1971-1984 at

Ccrro Paramo was just over 25Of) mm. Typically only about

10% of the total precipitation falls during the dry StXSOil or

“vcrano” that lasts from mid-Deccmbcr to late April. Frost is

frcqucnt in the pdramos, and hail has been observed

(Dohrcnwcnd 1977,), but there ate no reliable reports of

snowfall (Coen 1983).

Clouds and mist frequently bathe the p&?ImOS, and must

contribute an appreciable (though as yet unmeasured) amount

of moisture. High atmospheric humidity moderates the dry

season, but for days or weeks during this period the

condensation belt lies below timberline, resulting in clear, dry
wcalhcr on the high peaks. Some perennial herbs die back at

this time, and vegetation and litter quickly dry out, providing

the fuel for fires.

Although burning is most widcsprcad during the driest first 4

months of lhc year, a secondary rainfall minimum (the

“vcranillo”) during mid-year may allow Some burning. Afier

a succession of several rainless days in July, 1981,

experimental fires started in the Bucnavista priramo ignited

readily and burned quickly to their fuel hrcaks (G.B.

Williamson, pers. comm. 1982).

RECENT FIRE HISTORY

All of the Costa Rican pitamos are protected within national

parks or reserves, hut there arc no written fire records for

these manngcmcnt areas. Documentary evidence of burning

consists of occasional refcrcnccs in the scientific and popular

literature, and old photographs that reveal evidence of

burning. Fires are often too small to bc readily apparent on

satellite imagery, and aerial photograph coverage of the

psiramos is limited.

However, the slow rate of organic matter decomposition in

the continuously cool pIram environment (Janzcn 1973b)

results in the long persistence of field evidence of past fires.

Fire-killed shrub stems are conspicuous throughout the

priramos, even at sites that burned more than two decades

carlicr. Some shrubs preserve evidence of multiple fires

(fig. 3), and annual growth rings in living and fire-killed

stems provide information on fire recurrence intervals (Horn

1986; Williamson and others 1986).

Field evidence indicates that all of the larger pciramos cast of

Cerro Utyum (Ddriia, Chirrip6, Urin, Cuerici, Buenavista,

Vu&as; fig. 1) have burned since the mid-cenhuy (Weston

1981). Human carelessness, arson, helicopter and plane

crashes, and escaped agricultural fires are among the ignition

sources for recent burns (Horn 1986). Although human

activity can explain all recent fires, lightning could also have

played a role. Costa Rica has one of the highest incidcnccs of

thunderstorms in the world (World Meteorological

Organization 1953, 1956), and lightning has been observed

striking both the forested slopes and treeless summit of Ccrro

Chirrip6 (Horn 198%). Such strikes might occasionally ignite

fires on the high Talamancan peaks, as they do on Mountain

Pine Ridge, Belize (Kcllman 1975).

Many areas within the Chirripci and Bucnavista piramos have

burned two or three times since 1950 (Horn 1986, I%%,

1989c, 199Oa). Fire recurrence intervals at specific sites have

ranged from 6 to about 30 years. Given the slow rate of

vegetation recovery within the pBramos (see below), 6 years

is probably close to the minimum fire rtiurrence interval

possible. At least this many years of postfire growth is likely

required to generate enough fuel to carry a second fire.

Figure 3. Resprouting shrub of Vaccinium consanguineum on

Cerro Zacat,&s in the Bucnavista pdramo showing stems

killed in two successive fires. The larger, central stem was

killed in tile penultimate fire at the site, after which the shrub

resprouted, producing the smaller dead stems that were killed

by the last tire at the site. Following the last fire the shrub

again rcsprouted. Older (twice-burned) stems can be

differentiated based on position, degree of charring, presence

or absence of bark, and extent of decay, and annual growth

rings in dead and living stems can be counted to estimate fire

recurrence intervals. The visible length of the tape measure

is 60 em.

Recent fires in the Chirripd piiramo have been much larger

than &es in [he Bucnavista ptiramo. PBramo fires along the

highway route have tended to bum out relatively quickly

because they encountered insufficient fuel, fuel that was too

moist, or a lire break created by a road or electrical

transmission line corridor. The larger Chirrip6 piiramo has

provided an extensive and continuous fuel bed not interrupted

by roads or other fire breaks, and fires, once started, have

tended to spread over hundreds or thousands of hectares.

291
The post-1950 fire record in the Buenavista and Chirtip6

highlands suggests a link between fire and drought. Figure 4

graphs monthly precipitation in the driest month and the two

consecutive driest months during the period 1%3,-1985 at

Ccrro Piram (1971 onwards) and at the nearby Villa Mills

station (3000 m) located just below timberline. 1 assume that

these data reflect trends that would also have been evident at

Cerro Ctlirt-ipcj, located 30 km to the east. The triangles

denote known fire years in the Bucnavista and Chirripci

highlands, and in the intervening Cuerici pdramo (fig. I),

with the size of the triang]cs indicating the total are8 above

3000 m clcvation estimated to have burned in that year.

Not surprisingly, the largest high-elevation fires have I&cd

to occur during the driest years. Between 1957, and 1985

there were 3 years in which the driest month (February or

March) rccordcd less than 0.5 mm rainfall, and in each of

11Iosc years a large (> 100 ha) lit-e occurred in the Chirripci

paramo and surrounding montane forests. If rainfall records

for 1951,-1985 are indicative of long-term trends, the data

suggest that exIrcmely dry years conducive to widespread

burning may bc cxpcctcd to occur about Once a decade in the

Chinipci and Buenavista pa’ramos.

LONG-TERM FIRE HISTORY

Charcoal rragrncnls in sediment cores from glacial lakes in

the Chirripd highlands provide evidence of ancient fires in the

Costa Rican piiramos. A short (I IO cm) scdimcnt core

rccovcrcd from Lago Chirripd (357_0 m) in the Valle de 10s

Lagos in 198.5 preserved two distinct layers of macroscopic

charcoal and an ahundnncc of microscopic charcoal fragments

(Horn 1989~). The charcoal pat%cJes appear to have been

dcrivcd primarily from fires within the watershed of the lake

and in adjacent areas of the Chirripci paramo. Charcoal

concentrations varied with depth in the sediments, suggesting

temporal variations in fire frequency (fig. 5). Although

absolute fire frequencies cannot be dctcrmincd from the

charcoal data, variations in charcoal abundance may provide

indications of rclativc the frcquencics. Howcvcr. the

rclalionship bctwccn fire history and sedimentary charcoal

concentrations is complicated (Clark 1983), and factors

unrclatcd to burning also may have affcctcd the charcoal

cttr~e (Horn, 1989~).

Charcoal fragments were prcscnt in all of the samples from

the Lago Chirripci scdimcnt core, indicating that fires have

&ii the lake basin and surrounding areas since the

scdimcB[s in the cofc began accumulating Some 4000 years

ago. A longer core raised from a glacial lake in an adjacent

valley in 1989 (Horn 199017, and in prep.) spans the last

10,000 years, and also contains charcoal, confirming and

cxtcnding the short core record. In the Chirrip6 pkamo Iire

is clearly not a disturbance factor introduced by modern

human society; burning due to human action or lighting has

occurred for thousands of years.

Area Burned

n

abavs 3wRlm

r10 km2

a l-10 km2 I

a'6

'61

~

‘6!

IIDriest Month ’

Year

Figure 4. Dry season precipitation in the Buenavista highlands

and the distribution of recent high clcvation fires. Rainfall

data arc from the Cerro Paramo (1971 onwards) and Villa

Mills stations (Institute Costarriccnse de Elcctricidad unpub.

data). The quo&n mark in 1977 reflects uncertainty as to

whcthcr a forest fire that burned near Ccrro Chirripd that

year cxtcndcd above 3000 m elevation.

THE IMPACT OF BURNING

Effects of Fire on Soils and Hydrology

Soils within the Costa Rican priramos arc usually we’lldrained, rich in organic matter, and acidic, with pH values aa

low as 4.0 (Harris 1971). Soil samples collected by LeAwich

(1973) within a recent burn area in the Buenavista pBramo

showed lower organic matter and C/N ratios, and higher

cxchangcablc calcium and magnesium, than did samples from

an ndjaccnt unburned arca. Field cvidcncc of erosion has

been noted On some bums, but soil loss following burning has

not been quantilicd. No information is available on the

hydrological impact of burning, though such 8tBdics would be

of interest given the important watershed function of the

$ramos and surrounding montane forests.

Effects of Fire on Phmo Vegetation

Postfire vegetation dynamics in the Buenavista and Chirripd

pBratnos have been examined by Janzen (1973b, 1983),

Chavcrri and others (1976, 1977, and in prep.), Williamson

and others (1986) and Horn (1986, 198%. 1990a). The slow

rate of decomposition in the Costa Rican pgratnos has been an

asset in these studies, as persistent fire killed stems can be

identified and measured to provide information on the species

composition and stature of the prebum woody vegetation.
DEPTH

STRATIGRAPHY (cm) CHARCOAL AREA

'4C

DATE:

1180

270 BF

2430

2100 BP

4110

+90 BP

6 0

8 0

100

110

maCrOSCOPlC 0 100 200 300

charcoal

TOTAL CHARCOAL AREA cm2/g

Figure 5. Diagram showing charcoal and sediment

stratigraphy of a 110 cm core from Lago Chirripd.

-7

Patterns of postfire vegetation recovery in the Costa Rican

pdramos support the initial floristics model of succession.

The first species to colonize burned ground are the shrubs and

herbs that comprise the mature vegetation. As appears to be

the case in other tropical montane ecosystems (Smith and

Young 1987), the Costa Rican piramos harbor no early

successional specialists, and no invasion of plant species from

outside communities takes place following disturbance.

Regeneration after and between tires is largely vegetative.

Following tire, most woody plants and many herbs resprout

vigorously, sometimes within just a few weeks of burning

(Chaverri and others 1977). The bamboo Chusquca

subtessellata and the ericaceous shrubs Vaccinium

consamxineum and Pemettia coriacea show resprout rates of

90-100 percent following crown consumption and the death of

aboveground stems (table 1). These vigorous sprouters

rareIy, if ever, establish seedlings, but may produce sprouts at

new locations along widely diverging root and rhizome

systems.

The common priramo shrub HvPericum irazuense supplements

vegetative reproduction with seedling establishment. The

species exhibited very low (4-14%) rates of basal resprouting

at my study sites (table l), but Janzen (1973b) noted abundant

suckering by H. irazuense (his & caracasanum) following a

fire on Cerro Asunci6n in the Buenavista paramo. Fire

intensity and antecedent soil moisture conditions may be

important controls of resprouting ability in this shrub.

For the narrow leaf congener Hvpericum strictum all tires

may be lethal; the species showed complete mortality at the

Tower 65 site (table 1) and may be an obligate seeder.

Postfire seedling recruitment by Hvoericum spp. and other

shrubs and herbs relies largely on the influx of seeds from

surrounding, unburned areas. The apparent lack of soil seed

reserves (Horn 1989b) results in a very slow rate of seedling

Table 1. Percent basal resprouting by bamboo and shrubs following crown

loss at paremo burn sites”.

Tower 65

BURN SITE

Conejos Zacatales Sabi La

Chusquea subtessettata

Vaccinium consansuineum

Pernettia coriacea

Escallonia poasana

pittieri Rapanea

Hyper i cum i razuense

Senecio firmipes

HVpericum strictum

100 9 6 100

ii

9 0

;: if

57

2 5 1 5

4 6 1 2 1 4

4

0

%nly data for species with sample sizes greater than twenty at individual

burn sites are included. For sample sizes and details on study sites and

methods, see Horn (198913).

293
Table 2. Postfire height and percent height recovery of resprouting shrubs and bamboo at

paramo burn sites”.

Touer 65

1 v

SITE AND YEARS SINCE LAST FIRE

Cone jos Zacatales S6bi la

9 yr 12 yr I 12 yr

Chusquea subtessettata 34 cm (18%) 103 cm (98%) 141 cm (113%) 191 cm (129%)

Vaccinium consanguineum 22 cm (26%) 76 cm (71%) 67 cm (87%) 103 cm (88%)

Pernettia coriacea 16 cm (24%) 46 cm (97%) 65 cm (79%)

Hyper icum i razuense 20 cm (15%) 91 cm (64%) 65 cm (71%) 111 cm (70%)

Escalionia poasana 14 cm (17%) 96 cm (116%) 148 cm (171%)

Rapanea pittieri 19 cm (14%) 117 cm (78%) 172 cm (126%)

“Only the six most comnon woody species are Listed. See Horn (1989b) for samples sizes and

standard deviations, and details on sites and field methods. Percentage height recovery

equals mean maximum postfire plant height divided by the mean maximum height of unbroken,

prefire (burned) stems. The prefire stature of plants partly reftects the time intervats

between the Last and penultimate fires at the sites, which was >I6 years at the Tower 65

site, 15 years at the Conejos site, ?: 12 years at the Zacatates site, and >29 years at the

Sgbita site.

colonization and may delay significant seedling recruitment

for several years following tire. Where potential seed sources

are distant (as near the centers of large burns), recolonization

by Hvpcricum irazuense and other fire-sensitive species may

not occur until the rare individuals that resprouted following

burning grow to maturity and begin seed production within

the burn area.

Growth rates of seedlings and suckers are extremely slow

(tables 2,3). The fastest growing woody species, the bamboo

Chusquea subtessellata, requires about 8-10 years to regain its

average prelire stature (Janzen 1983; table 2, this paper).

Coupled with the slow pace of seedling colonization, the slow

growth rates within the Costa Rican paramos result in the

long persistence of gaps created by burning. Bare patches of

ground from 0.1 mz to 0.5 m* or larger in size may persist

for a decade or more following fires, particularly on large

bums where seed influx is low.

The strong rcsprouting ability of most of the dominant woody

species in the Costa Rican paramos minimizes compositional

shifts following burning (Horn 1989b). If a site dominated by

bamboo and ericaceous shrubs bums, postfire cover the first

year, and for at least a decade afterwards, will be dominated

by bamboo and ericaceous shrubs. Major shifts in woody

species composition will be observed only at sites with a

substantial cover of lire-sensitive shrubs. Herbaceous species

may reach higher cover values on such bums, where greater

shrub mortality results initially in less competition for space

and other resources.

Based on observations at Cerro Zacatales in the Buenavista

paramo, Williamson and others (1986) described a “fire

cycle” in the Costa Rican paramos in which postbum cover is

initially dominated by grasses and sedges, but reverts

ultimately to shrub dominance if the site is kept free of fire

for a sufficient period (perhaps 20 years). For reasons

outlined above, such a cycle will be most evident where shrub

mortality is very high, and where flowering plants are present

nearby to reseed the bum site. When shrubs are closely

spaced and suffer low mortality from fire, grasses and sedges

may contribute little to postfire cover. Few graminoids or

other herbs were present 3 years aAer a fire on Cerro

Asuncidn (Janzen 1973b), a site characterized by high shrub

survival and vigorous suckering. Greater herbaceous cover

was observed 1 and 4 years after a fire at the nearby Tower

65 site, where 40% of the woody perennials (mostly

Hvnericum irazuense shrubs) died following crown loss. But

even at this site, shrubs and bamboo dominated the initial

postfire cover (Horn 1989b and unpub. data).

Graminoids, when abundant, will provide fine fuels that can

support frequent fires. Williamson and others (1986) have

suggested that when such fires occur at 5-10 year intervals

Table 3. Postfire stem diameters and percent diameter recovery for burned shrubs and

bamboo at paramo burn sites”.

Tower 65

1 v

SITE AND YEARS SINCE LAST FIRE

Cone jos Zacatales

9 yr 12 yr

S6bi ta

? 12 yr

Chusquea subtessettata 0.55 c m 0.73 c m 0.89 c m

Vaccinium consansuineum 0.29 cm (13%) 1.98 c m (66%) 1.50 c m (70%)

Pernettia coriacea 0.26 c m

Hypericum Ge

(26%) 0.68 c m (78%)

0.16 c m (13%) 1.19 cm (58%) 0.86 c m (55%)

Escatlonia poasana 3.07 c m (125%)

Rapanea pittieri 0.26 c m (15%)

1.20 c m

2.13 c m (64%)

1.03 c m (63%)

1.46 c m (60%)

3.52 c m (94%)

2.92 c m (103%)

‘Only the six most comaon woody species are tisted. Sample sizes and standard deviations

are Listed in Horn (1986). Percentage diameter recovery equals mean maximum postfire stem

diameter divided by the mean maximum prefire (burned) stem diameter. No data are

available on prefire stem diameters of Chusquea subtessellata.

294
they may impede shrub recovery and facilitate the ultimate

dcvcloprncnt of continuous grassland. Preliminary trials

indicated that some shrubs may release allelopathic chemicals

that inhibit the growth of grass and sedge seedlings and hence

reduce the risk of cre (Williamson and others 1986).

CONCLUSION

Fire plays an important rote in most of the world’s shrublands

(Christensen 1985), and the primmos of Costa Rica Seem to be

n o exception. The low annual temperatures, high annual

rainfall, and seasonal drought that characterize these tropical

alpine habitats provide the fuel for periodic tires.

Sedimentary charcoal evidence shows that fires have occurred

in the Chirrip6 pliramo for at /cast 10,000 years; fires dtle to

human activity or lightning may be of similar antiquity in

other pa’ramo areas.

Postfire rcgcnetalion follows initial floristics and is principally

vegetative for the major woody species, many of which

resprout vigorously abler fire. The ultimate origin of this

rcsprouting ability is uncertain, but selection in the face of

periodic fires may have reinforced the trait. Some shrubs

rely on seedling recruitment to repopulate burned areas, but

the lack of soil seed reserves gives the sprouters a strong

advantage in the first i&v pOStfiR? years. Low rates of seed

influx and slow growth following germination or sprouting

result in exceedingly slow recovery rates; 10 years after

burning, most shrubs will not have regained their prefire adult

stature and bare patches of ground may still be conspicuous.

ACKNOWLEDGMENTS

The research summarized here was supported by grants from

the National Geographic Society, the University of Tennessee,

the Institute of International Education, the Association of

American Geographers, and the Center for Latin American

Studies of the University of California, Berkeley. I thank

Roger Horn, Douglas Baird, Jr., Michael Mitchell, and Brian

Kermath for field assistance under adverse conditions, and the

Costa Rican National Park Service and the Department of

Geography at the University of Costa Rica for logistical

support. For comments on an earlier version of the

manuscript I thank Thomas Waldrop and two anonymous

revicwcrs.

LITERATURE CITED

Chavcni, A.; Vaughan, C.; Poveda, L.J. 1976. Infot-tne de

la gim cfcctuada al macizo de Chinip6 al raii! de1 fuego

ocurrido en Matzo de 1976. Rev&a de Costa Rica

11:1-43-7-79.

Chavcrri, A.; Vaughan, C.; Poveda, L.J. 1977. Datos

inicialcs sobre la lia@idad dc un p&ram0 fimte a 10s

efectos de fuego (abstract). In: Wolda, H., cd.

Rcsumencs recihido para cl IV simposio intcmacional de

ecoiogia tropical, 1977 March 7-l 1, Panama, pp. 26-28.

Christensen, N.L. 1985. Shrubland fire regimes and their

evolutionary consequencences. In: Pickett, S.T.A.;

White, P.S., cds. The ecology of natural disturbance and

patch dynamics, pp. 86-100. Orlando, FL: Academic

Press

Clark, R.L. 1983. Fire history from fossil charcoal in lake

and swamp sediments. Ph.D. dissertation, University of

Australia, Canberra. 189 p.

Clark, L.G. 1989. Systematics of Chusquea section

Swailenochloa. section Verticiik&~, section SerpentcS,

and section Longi folia (Poaceae: Bambusoideae).

Systematic Botany Monographs 2’7 : 1 - 127.

&en, E. 1983. Climate. In: Janzen, D.H., cd. Costa Rican

natural history, pp. 35-46. Chicago: University of

Chicago Press.

Custrccasas, J. 1979. Comparaci6n iitogeo&ica de

pgramos entre varias cordilleras. In: Salgado-Labouriau,

M.L., cd., El medio ambicnte pkamo, pp. 89-99.

MCrida, Venezuela: Edicioncs Centro de Estudios

Avanzados.

Dohrcnwcnd, R.E. 1972. The energetic role of the trade

wind inversion in a tropical subalpine ecosystem. Ph.D.

thesis, State University College of Forestry at Syracuse

University. 298 p.

Gbmez, L.D. 1986. Vegctacibn de Costa Rica. San JO&,

Costa Rica: Editorial Universidad Estatal a Distancia.

327 p.

Harris, S.A. 1971. Podsol development on volcanic ash

deposits in the Talamanca range, Costa Rica. In: Yaalon,

D.H., cd. Paleopedology: origin, nature, and dating of

paleosols, pp. 191-209. Jerusalem: International Society

of Soil Science and Israel University Press.

Horn, S.P. 1986. Fire and pgramo vegetation in the

Cordillera de Talamanca, Costa Rica. Ph.D. dissertation,

University of California, Berkeley. 146 p.

295
Horn, S.P. 1989a. The Inter-American highway and human

disturbance of piram vegetation in Costa Rica.

Yearbook of the Conference of Latin Americanist

Geographers IS: 13-22.

Horn, S.P. 1989b. Postfire vegetation dynamics in the Costa

tican piramos. Madroiio 36(7-):93-l 14.

Horn, S.P. 1989c. Prehistoric fires in the Chirripci highlands

of Costa Rica: sedimentary charcoal evidence. Revista de

Biologia Tropical 37(Z): 139-148.

Horn, S.P. 1990a. Vegetation recovery after the 1976 pgramo

fire in Chirripci National Park, Costa Rica. Rcvista de

Biologia Tropical (forthcoming).

Horn, S.P. 199%. Timing of deglaciation in the Cordillcra de

Talamanca. Costa Rica. Climate Research 1:8 l-83.

Janzen, D.H. 1973a. Sweep samples of tropical foliage

insccls: descriptions of study sites, with data on species

abundances and size distributions. Ecology 54(3):659-678.

Janzcn, D.H. 1973b. Rate of rcgencralion after a tropical

high elevation fire. Biotropica S(2): 117-l 22.

Janzcn, D.H. 1983. Swallcnochloa subtcssellata (chusquca,

batamba, matamba). In: Janzen, D.H., ed. Costa Rican

natural history, pp. 330-331. Chicago: University of

Chicago Press.

Kcllman, M. 1975. Evidence for Late Glacial age tire in a

tropical monlane savanna. Journal of Biogeography ‘?:57-

$ 63.

I

Laucr, W. 1981. Ecoclima[ological conditions of the piramo

belt in the tropical high mountains. Mountain Rcscarch

and Dcvciopmcnt 1(3-4):‘09-33-I.

Lcfiwich, V. 1973. Soil characteristics at the various field

sites in Costa Rica. In: Tropical biology: an ecological

approach, Organization for Tropical Studies coursebook

73.2, pp. 598-602. Durham, NC: Organization for

Tropical Studies.

Smith, A.P.; Young, T.P. 1987. Tropical alpine plant

ecology. Annual Rcvicw of Ecology and Systcmatics

18:137-158.

Wcbcr, H. 1959. Los piramos dc Costa Rica y sU

concatcnacidn fitogeogrrilico con 10s andcs suramcricanos.

San JosC, Costa Rica: Institute Geogra’fico National. 72 p.

Weston, A.S. 1981. PBramos. cicnwas, and subp,Gramo forest

in the castcrn part of the Cordillcra de Talamanca

Unpublished report prepared for the Tropical Scicncc

Center, San JosC, Costa Rica. 25 p.

Wcyl, R. 1957. Cont&uci6n a la geologia de la Cordillcra de

Talamanca de Costa Rica (Centro America). San lost,

Costa Rica: Instituto Geogr~tico National. 87 p.

Williamson, G.B.; Schatz, G.E.; Alavardo, A.; Redhead,

C.S.; Stam, A.C.; Sterner, R.W. 1986. Effect of

repeated fires on tropical pliramo vegetation. Tropical

Ecology 7,7&Y-69.

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of thunderstorm days. I. Tables. Geneva: World

Mctcorological Organization.

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of Ijlu&rslorm days. II. Tables of marine data and world

maps. Gcncva: World Mctcorological Organization.

296
A SURVEY OF ABORIGINAL FIRE PATTERNS

IN THE WESTERN DESERT OF AUSTRALIA

N.D. Burrows and P.E.S. Christensen’

Abstract.-Aborigines who occupied vast tracts of the Australian deserts used fire extensively for many

purposes. The recent departure of Aborigines from traditional burning practices has coincided with an

alarming decline in native mammal fauna. It has been postulated that the combined effects of a changed tire

regime, predation by feral animals, and competition from feral herbivores has contributed to mammal

decline in this otherwise pristine environment.

Black-and-white aerial photography, satellite imagery, and field observations have reve&d that the size,

distribution, frequency, and intensity of fires in a pan of the Western Desert have changed dramatically

over the last 36 years. In an area west of Lake Mackay the average fire size has increased from 34 hectares

in 1953 to over 32 COO hectares in 1986. The small-grainrd mosaic of burnt patches of varying ages that

existed during Ahoriginal occupation of the land has been obliterated by large, intense and infrequent

lightning-caused wildtires. Some evidence of a relationship between fire mosaic and the richness of Flora

and fauna was obtained during this survey.

INTRODUCTION

About One third of the Australian continent is classified as

desert. In the State of V&stern Australia, Ihc Grcal Victoria,

Gibson, and Great Sandy ~CScrtS occupy some 1.3 million

square kilomclrcs and collcctivcly are commonly known as

the Western Desert (Tonkinson 1978). Rainfall is low (annual

average ranges from 1.50 to 750 millirnctres), and

unprcdictablc, and long periods of drought are common.

Rainfall is mostly from cyclones and thunderstorms and

surface w&r is only abundant for short periods following

rain. Summers are hot and winters arc cool. The Wcstcrn

Desert is well vegetated and surprisingly rich in wildlife.

Highly flammable hummock grasslands, comprising species of

Triodia and Piccrrachne (spinifcx), dominate red sandy soils.

Aborigines first arrived on the Australian continent at least

50,000-60,000 years ago and occupied Ihc dcscrts of the

interior by at ICaSt 30,000 years ago (Mulvancy 197.5; Flood

1983). Aboriginal people showed remarkable rcsiiicnce and

rcsourccfulncss lo survive in a vast expanse of scattered food

and warcr resources (Tonkinson 1978). They were highly

mobile, WCI’C able lo exploit a variety of ~CSOUUXS in different

areas at different limes, and developed a dctailcd knowledge

of the environment. Fossil evidence suggests climatic and

cultural con(in&jcs lasting at Icast 10,000 years (Gould

1971), so thcrc has been a long period of Aboriginal influence

on the desert biota.

The Wcstcrn Australian Department of Conservation and

Land Managcmcnt (CALM) manages about Icn million

hcctarcs of dcscrt conservation rcscrvcs which range in arca

from two hundred thousand hcclarcs two million hectares.

‘Senior Research Scientist and Principal Senior Research Scientist,

Dcpanment of Conservation and Land Management, SO Hayman Rd,

Coma, Western Australia 61.53.

The management priority for these reserves is the

conservation of native flora and fauna. However, in spite of

the apparent pristine name of these reserves and the lack of

direct European impact, a sudden and alarming decline in

native mammals has been reported (Bolton and Latz 1978;

Burbidgc 198.5; Burbidgc and others 1988; Burbidge and

McKc& 1989). Burbidge and Jenkins (1984) reported that

about 33 pcrccnt of Western Australian desert mammmals are

extinct or endangered. They noted that this decline had

occurred Over the last 30 to SO years. Burbidgc and McKenzie

(1989) have shown that all declines and extinctions have been

restricted to native mammals with a mean adult body weight

in fhe range from 35 grams to 5,500 grams (critical weight

range). The desert conservation reserves arc relatively pristine

and have not been directly modified or disturbed by European

activities. Generally, recent extinctions of wildlife have been

associated with habitat destruction or modification by humans

(Burbidge 1985).

Ngaanyatjarra Aborigines from the Warburton area of

Western Australia believe that the “mitika”, or burrowing

bcttong (Beuongia les~rettr), had “gone to the sky because the

country had not been cleaned up” (de Graaff 1976). “Clean

up” is a term oficn used by Aborigines for burning the

vegetation (Jones 1980). Kimber (1983) reported that Pinlubi

Aborigines believed that perhaps a “big bushfire” caused the

disappearance of the golden handicoot (I.~oodon urrra~rcs).

Scjcntists have proposed three main hypotheses to explain the

decline and in some cases, extinction of desert mammals.

Burbidge and Johnson (1983) proposed that changes in fire

rcgimc, predation by feral animals, and competition from

feral herbivores as the main factors, acting either

indcpcndcntly or in combination, leading lo mammal decline

in the arid zone.

297
Rsccnt changes in IIK [ire rcgimc WC~C a direct conscqucncc

of the cxodos of Aboriginal pcoplc from the dcscrt to

sclllontnts in missions, outstations and other communities

(Could 1971; dc Graaf 1976; Latz and Griftin 1978; Kimbcr

1983; Saxon 1983). Latz and Griffin (1978) postulated that

A[)origj~lc:s crcatcd a stable ecosystem by “burning the country

in a mosaic pattern”. They claimed that mosaic burning

rcduccd ihc cxtcnt and continuity of heavy ftmhs, and

thcrcforc rcduccd the occurrence of intcnsc wildfires. They

also stated that a second cffcct of mosaic burning was to

crcttc 3 range of “sts[cs” in the vcgetalion, from early

l)ostiirc plant communilics to old mature paichcs. They were

of the opinion that such diversity of states would host a

gr~akf variety of plants and animals.

The cxtensivc use of firs by dcscrt Aborigines is ~~11

documcntcd by c3rJy cxplorcrs (Warburton 1875; Carncgic

1898) and more rcccntly by anthropologists and ccolo&s

(Finlayson 1943; Jones 1969; Cal&y 1971; Gould 1971; dc

Graaf 1976; Tonkinson 1978; Kimber 1983). Kimbcr (1983)

obscrvcd that the Pintuhi trscd fire in a skilful and conlrollcd

trtnnncr for many reasons, such as hunting, signalling. to

“clean up” the country, for ccrcmonics, and for fun. tic

provides a scncral description of when fires wcrc lit and the

rnnyc in fire sizes. Hc also made some rough calculations of

tlm proportion of country burnt and the a]>proximalc age since

fire, \)ascd on information in the diaries of Davidson, who

cxplorcd parts of the Tanami ~cscrt in 1900. Howcvcr, little

quantitative information about the fire regime during

traditional Aboriginal occupation of vast tracts of dcscrt land

i s available.

Quantitative data on past and prcscnt fire regimes arc of

considcrdble inter& lo the Wcstcm Australian Department of

Conservation and Land Managcmcnt, which is engaged in a

multidisciplinary study aimed at maintaining and improving

the conservation status of dcscrt ccosyslcms. As part of this

project. experimental reintroductions of selcctcd spccics of

rdrc and endsngcrcd mammals to the Gibson Desert Nature

Rcscrvc will bc aucmptcd. Prior to rcintroJuction, prcscrihcd

fires will be used to recrcatc the kind of fire mosaic which is

bclicvcd to have existed bcforc the departure of Aborigines.

Feral predators such as foxes and cats will also hc controlled

in the experiment.

The aim of this study is to define, as clearly as possible, the

fire regime during the occupation of the Western Dcscrt by

Aborigines prior to European contact and to compare this

with the prcscnt-day fire regime. In doing so, we could test

the hypothesis of a recent and dramatically changcd fire

regime as proposed by Latz and Griffin (1978) and others. A

knowlcdgc of past fire regime would also greatly assist with

the dcvclopmcnt of appropriate fire management strategies for

dcscrt conservation rcser~es.

We USC Gill’s (198 1) definition of lire @me, which is the

history of fire frcqucncy, lirc season (season in which ffrcs

burnt), fire intensity, and fire size.

iI4 ETHODS

The dcparturc of Aborigi’ncs from their dcseri hornzlands

started with first European contact at the end of the nineteenth

century. Amadio and Kimbcr (1988) present a summary of

European exploration and contact with Aborigines of the

northern portion of the Western Dcscrt and also dcscribc the

n]ovctncnLs of Aboriginal people away from their homelands

and into European SCttkmcntS. To reconstruct the fire

regime, it was desirable to study fire on land from which

Aboriginal people living a more-or-less traditional lifestyle,

had most reccntiy departed. WC learnt that a very remote tract

of land to the west of Lake Mackay. in Wcstcrn Australia was

probably the last homeland utilized in a traditional manner by

Pintubi people (Richard Kimbcr pcrs.comm.). The study site

of soml: 54,000 hectares is on the eastern edge of the Great

Sandy and Gibson Dcscrts and lies between longitudes

13875’E and 128”5O’E and latitudes 21%‘S and 2’18’S

(Figure I). The area is arid, with an average annual rainfall

STUDY SITE

@ ALICE PRINGS

\ WESTERN AUSTRAUA

SOUTH AUSTRAUA

Figure 1: Location of the study area in the Western Dcscrt

The approximate boundary of land classified as desert is

shown.

probably less than X5 mm (there arc no meteorological

stations nearby). Most of the rain falls in summer but both the

amount and the seasonal distribution arc highly variable. As a

rcsuit of the arid climate and sandy soils, the vegetalion

consists mainly of hummock grasses (spinifcx) and associated

small shrubs, lmrbaceous plants and scattered low trees. The

sand plain that covers most of the study area is crossed by

398
longitudinal, slablc dunes which trend east-west. There arc

numerous saltpans, salt lakes, and claypans scattcrcd

throughout the area. The largest salt lake is Lake Mackay,

which has a total area of about 3,500 sqttarc kilometres

(Blake 1977). The salt lakes, saltpans, and claypans arc dry

except after heavy rain.

The main exodus of Pintubi Aborigines from this area

commenced in the early 196Os, with the last people coming

into Kintore and Kiwirrikura communities in 1985 (Richard

Kimbcr, pm. comm.).

We have used early black-and-white aerial photographs to

help reconslruct the fire regime at the study site during

Aboriginal occupation. This technique was supplemented by

reviewing the literature and by talking with Pintubi and

Pitjantjatjarra Aborigines to obtain information about lhcir USC

of fire. The current Iirc rcgimc, particularly size and

distribution of burnt patches, was inferred from Landsat

satcllitc imagery and by visiting the study site and surveying

fire history. While in the field WC also surveyed vascular

plant and vcrtcbratc aniaal &UWLWHX within areas of

different age since the last fire.

Aerial Photographs and Landsat Imagery.

Details of aerial photography available for this alEi are

presented in table I. The earliest aerial photographic surveys

wcrc complctcd in 1953 by the Royal Australian Air Force as

part of the Blue Streak rocket project during an era of

cxtcnsivc rocket development and testing in Australia. Fire

scars showed clearly on both actial photographs and Landsat

imagery. Fire scars that appeared on the 1953 photography

were mapped onto a base map at a scale of 1:50,000.

Additional fire scars which appeared on successive

photographs were mapped onto separate sheets, but at the

same scale, to form a series of overlays. Landscape feahlres

such as salt lakes, claypans, saltpans, sand dunes, and major

creeks and streams were also mapped The area and perimeter

of each fire scar for each time series was calculated using a

computer-linked digitizing board. Initially, an attempt was

made to accurately age fire scars baaed on tonal intensities of

the scars indicated on the photographs. The different toning of

the fire scars represented different stages of revegetation, or

fire succession, with recently burnt areas showing up as very

bright patches. This proved to be difficult and fire scars could

only be rated as “very recent” (up to 5 years old), or “recent”

(5-10 years old), based on the extent of re-vegetation. While

o]dcr scars were barely discernible, no attempt was made to

map scars that did not have clearly visible boundaries.

Field Survey of Biological Indicators

The second technique used to obtain details about past and

present iire regimes and the fire environment of the study

area was ground survey of biological indicators. Some 50

kilomctrcs of line transect was surveyed by vehicle traverse in

1989 and visually discernible fire boundaries recorded. A fire

boundary was delincd as the boundary between two

recognizable fuel ages or between vegetation burnt at different

times. Within each fuel age encountered, the time since the

last tire was estimated by counting “annual” growth rings

from tree stem cross- sections. Because of the uncertainty of

the period between growth rings, accurate aging of fire scars

was not possible. Based on ring counts from areas of known

!ire history, stem analysis enabled the time since fire to bc

estimated to within +I 1 percent of actual time. Measures of

vegetation cover and height were also useful for estimating

the age of vegetation. In some instances, the aerial

photographs were used to estimate time since last fire.

Circular plots of IM) m&es radius were established in each

fud age and the number and abundance of plant species

rccordcd. A list of animals utilizing each fuel age was

compiled by searching for burrows, diggings, scats, and

tracks. The Pintubi and Pitjantjatjarra guides who

accompanied us, skillllly identified signs of animal activity

and provided us with the Aboriginal names for the animals.

RESULXS

Aerial Photographs

There has been a dramatic change in the mean and median

size of burnt patches in the period from 1953 to 1986. From

table 1, it can be seen that thk area recently burnt (up to 10

years prior to photography) haa increased from 23.6 percent

of the study area in 1953, to almost 60 percent by 1986.

Also, the mean size of fires has increased almost 1,000 fold

Table 1. Number, area, and perimeter statistics for burnt patches

clearly visible on black-and-white aerial photography and on

La&.at satellite imagery of a 53,483 ha study in the Western

Desert, Western Aa&ralia.

year Iflmh?r 6omt patch size (ha) Total Total

of burnt blmlt

patchas Maxianna Mean Mode Median (ha)

P=+$=

1

1953 372 1, 744 3 4 2 6 12,643 1,198

1973 2 7 13,534 645 5 197 22,600 412

1977 3 30,618 10,584 * * 31,752 203

1988 I 32,164 . 32,164 272

299
cwer the same period. Habitat boundary, which is the total

fire perimeter within the study site and is a measure of the

boundary between vegetation of different ages since fire, has

dccrcascd from 1,198 kilomctres in 1953 to 272 kilomctres in

1986. This indicates a substantial reduction in the diversity of

fire ages or states of pastfire succession within the landscape.

A visual inspection of the fire scars mapped for each time of

photography rcvcalcd a number of obvious patterns. In 19.53,

when groups of Pintuhi Aborigines were living on the land,

there were some 372 individual, recent fire scars visible on

the aerial photographs (see fig. 2). Many of these

concentrated around major salt lakes, claypans, and saltpans.

While it is not possible to determine the ignition source of all

fires, many scars showed the classic shape of having been lit

by a person dragging a firestick in a straight line. Many of

the fires burnt between the sparsely vegetated sand dune

crests. By 1973, some 11 years after Aborigines began to

icave the land, the small-graincd mosaic of burnt patches that

existed in 1953, had begun to be erased and to be replaced by

large tracts of rccent)y burnt country and large tracts long

unburnt. The ignition source of these fires may have been

lightning or the few Aboriginal people who remained in the

area. This temporal trend of increasing iire size and

increasing pyric homogeneity has continued until the present

day, and there now exists vast tracts of country burnt at the

same time by a single fire or multiple lightning strikes. There

arc also vast areas which have not been burnt for in excess of

30 years. This pattern is repeated across the Western and

Central Dcscrts (Griffin and Allan 1985).

Figure 2. The patchwork of fire scars is clearly evident on early (1953)

black-and-white aerial photographs. Most fires wet-c lit by Pintuhi Aborigines

Who occupied lhc dcscrt at the time of photography.

300
The frcqucncy distribution by size class of fire scars is shown

in figure 3 for 1953 and 1973 photography. By 1977 and

1986, most of the study area had been burnt by only a few

fires lit at about the same time.

A useful mca8~re of the size and distribution of burnt and

unburnt patches is the ratio of variance to mean patch size

(Pcilou 1977). A random distribution produces a ratio of EN

1. A uniform or over dispersed distribution results in a ratio

greater than 1 While a clumped or contiguous distribution

yields a value much less than 1. In 1953, the patchiness ratio

of both burnt and unburnt areas was 0.62 to 0.72, or close to

1, indicating a random distribution of patches (figure 4). The

mean length of continuous burnt vcgctation had increased

from 467 mctrcs in 1953 to 1,570 meters in 1986 and the

variance ratio had rdUce(j to 0.43, indicating a clumped

distribution of patch size and a significant increase in mosaic

grain size (Peiiou 1977). Line transects across photographs of

a portion of the study area to reveal a spectrum of recently

burnt (< 10 years) and long unburnt vegetation are also useful

for quantifying burn mosaics. This “substitute pattern” of

alternating black and white stripes is a representation of the

varying grain size of the two phase mosaic (Peilou, 1978).

These patterns are presented in figure 5 for the 1953

photography and 1986 salellitc imagery.

Field Survey of Biological Indicators

An example of the results of a vehicle traverse along a line

transect showing the ages of vegetation since the last fire and

the total number of animal species recorded from observations

of tracks, diggings, and scats is shown in figure 6. The

traverse was conducted in 1989. While most of the

vcgctation, was about 6 years old at the time of the traverse,

there were small patches of older vegetation which had

escaped the most recent Iire. Often, these patches were found

on the leeward side. of natural fire barriers such as sand dune

r From 1963 aerial photography

- Recently burnt

2 6

nt

-. 0 50 250 350 450 MO 650 750 850 95o.i

Sir* class midpoint (ho)

m 1973 photography m 1953 photography

Figure 3. Frcqucncy distribution of size classes of recent fire

scars evident on 1953 and 1973 black-and-white aerial

photographs of a part of the Western Deseti.

Patch frsquency

/I

20

IO

0

0 100 300 500 700 900 1100 1300 1500 1700

Patch wldlh class mldpolnt (m)

w Burnt patcher m Unburnt patches

Figure 4. Percentage frequency distribution by size classes of

the width of recently burnt (< 10 years) and long-unburnt

patches of desert vegetation measured along transects across

1953 black-and-white aerial photographs.

From 1986 lendaat imagery 1

6 IO 1 6

Diatance along traneecl (km)

20 2 6

Figure 5. Substitute patterns for two two-phase mosaics (recently burnt and long-unburnt vegetation) of the Western Dcscrt

study arc:1 from 1953 aerial photography and 1986 satellite imagery.

301
Time aInca life (years) Number of animal species 60 r-.- ._._ .-... -.--.-_ --.. - ..-...-----~__ -._ _ ..- _._..______ - _.., 26

i

- 4 20

0 6 10 1 6 2 0 26 3 0 36 4 0 46 60 66 a0

Distance along transect (km)

- The slnca fire -*- No. snlmal 8peciea

Figure 6 AgC of vcgctation (time since fire) along ; 1

[ranscct across dcscrt vcgctation in 1989. Also shown

3rC numbers of animal spccics cslimalcd from diggings,

scats, and tracks at points along the transect.

JU r 1

Ot-----

1

0 10

TimeYince firs &?oEi)

40 50

Figure 7. Numbers of plant sp~cics within a 100-meter-radius

plot with time since last fire in desert vegetation near Lake

Mackay, Wcstcrn Australia.

crests, salt lakes, and claypans. Generally , long unburnt

patches were small (200-400 m across). The oldest patch of

vegetation was 40 2 4 years. Animal species numbers, based

on the survey technique used here, were, highest in areas

where there was a mosaic of 6- and 1 S-year-old vegetation.

Where vegetation age was predominantly 6 years or less, or

in one case where it was 40 years old, species numbers were

1OW.

Plant species diversity decreased with increasing time since

fire (fig. 7). Older vegetation was dominated by large,

senescent rings of spinifcx (Trio& species), whereas recently

burnt patches contained a range of hC&aCaUS plants as well

as woody shrubs and spinifex. Many woody shrubs had

resprouted from lignotnbcr or regenerated from soil-stored

seed following fire.

DISCUSSION

Fire size

Thcrc has been a dramatic and sudden increase in the mean

and median size of burnt patches in the study area, coinciding

with the dcparturc of Pintubi Aborigines. The average size of

a burnt patch has increased from 34 hectares in 1953 to

32,184 he&rCS in 1986 (table 1). During Aboriginal

occupation of this land, there existed a fine- grained mosaic

of burnt patches across the landscape as a result of Aboriginal

burning and natural lightning fires. The Pint&i and

Pitjantjatjarra men who guided us around the study area,

found old, long-unburnt spinifcx aS aesthetically displeasing

and continually fired the spinifcx as we travellcd across the

dcscrt.

Kimbcr (1983) suggests that Aborigines had a good &a] of

control OVCr Tire. using wind, humidity and natural fire

barriers such as claypans and sand dunes to control the size

and inlcnsily of fires. Our observations of the concentration of

fire scars around resource-rich arCaS such as rockholes,

crc&S, claypans, and salt lakes is consistent with obSen&onS

made by Kimbcr (1983). The fire regime around these

resource rich landscape units may not be typical of arcas less

utilized by Aborigines. Partitioning and utilization of (he

landscape by Aborigines requires further investigation.

The abundance of small fire scars (< 10 hectares) visible on

the 1953 aerial photography suggests either fires wcrc lit

under mild conditions and burnt at a low intensity or

cxtCnSivc tracts of heavy fuel Sufficient to sustain large and

inlcnsc fires did not exist. Many generations of Aborigines

frcqucntly burning off Ihe land would result in a situation of

discontinuous, patchy fuels, ranging from recently burnt to

long-unburnt patches. However, when the human ignition

SOUfCC was removed from the desk the fuels gradually

accumulated over large, continuous tracts of land. Lightning

strikes in summer have resulted in the massive and intense

wildfires obscrvcd today. The grain size of the two-phase

mosaic (recently burnt and long-unburnt) has increased over

fhe last 36 years, as shown in figures 4 and 5.

Time of Yar of Fires

Kimbcr (1983) believes that most burning by AborigineS was

done in August to October and immediately prior to rains in

December to February. Occasionally, large fires caused either

by Aborigines or by lightning, burnt during the hot, dry,

windy summer months. In the area stidied here, it would not

have been possible for a fire to become very large in 1953, as

the fuels were discontinuous as a result of patch burning and

natural fire barriers. Kimber suggests that the time of year for

burning is not as important to Aboriginal people as the

opportunity to bum. de &daf (1976) observed that Aboriginal

fires in the dcscrt were lit all year round and not seasonally.

302
Both de Graaf (1976) and Kimber (1983) reported that certain

areas of the desert were not burnt by Aborigines because

Aborigines did not visit these places for religious reasons, or

fcarcd that fire would destroy sacred objects. The season of

burning was, howcvcr, very important in the monsoon forest

regions of the Northern Territory (Jones 1980; Haynes 1985)

and to Wad.juk Aborigines in the south-west of Wcstcm

Australia (Hallam 1975).

Today the main ignition source in the remote deserts is

lightning. Thunderstorms are common over the summer

months and large, lightning-caused wildfires have been

reported (Griffin and others 1983).

The bench& to Aborigines by way of increased food

resources as a result of tiring the spinifex were evident during

this study. Recently burnt country supported a diverse range

of herbs and animals, particularly reptiles, whereas longunburnt vegetation was generally less diverse in flora and

fauna. However, WC were unable to show any strong

correlations between time since fire (fuel age) and total

animal species numbers, although there was a trend between

the spatial diversity of fuel age and animal numbers (fig. 6).

Animal species numbers were based on visual observations of

tracks, diggings, and scats, thus limiting the extent to which

the data can bc interpreted. More detailed studies of animal

activity in relation to the temporal and spatial diversity of fuel

age are needed. Posttirc succession in spinifcx communities

has been described by Burbidge (1943) and Suijdendorp

(1981). All authors report an increased level of plant diversity

soon after fire. The range of tire-adaptive traits expressed by

desert vegetation has also been reported by these authors.

As noted, there has been a significant change in fire regimes

in recent times, and there is at least limited scientific

evidence to suggest that this has contributed to the decline in

mammal fauna. This change may have further predisposed

mammals to predation by introduced predators. It is

reasonable to accept the importance of temporal and spatial

diversity within a landscape on resource levels and habitat

opportunities (Latz and Griffin 1978, Pielou 1977). Saxon

(1984) stated that “when large areas of a single landscape type

are subjected to large uniform disturbances, they threaten the

survival of wildlife species which depend on irregular

boundaries of natural fire patterns to provide a fine grained

mosaic of resources”. Bolton and Latz (1978) have shown that

a range of post-fire successional stages is important habitat for

the western hare-wallaby (Largorchesfes hirsurrcs). Burbidge

and Pearson (1989) explain the lack of rufous hare-wallabies

(Largorchrsfes hirsurus) in the Great Sandy Deserts as being

due to the lack of frequency of small-scale bums and to high

fox numbers.

It is somewhat ironic that modem mammal extinctions in the

Australian deserts are in part due to the changed fire regime

that resulted from the departure of Aborigines and consequent

lack of Aboriginal burning. Tindale (1959), Merrilees (1968),

and Jones (1968) have all concluded that extensive burning by

Aborigines contributed to the extinction of the Pleistocene

mcga-fauna. Today, it is likely that the large, intense

wildfires which occur throughout the deserts are placing

extreme stress on some plant and animal communities (Griffin

1981). These intense fires arc damaging vast areas of liresensitive vegetation such as marble gum (Btca~:@r

gongliocarpa), desert oak (Alocasuarina decakneana), and

mulga (Acacia anuera) (Start 1986). There is sufficient

evidence of the disadvantages of the current wildfire regime

on the conservation status of desert reserves to warrant the

development and implementation of managed fire regimes that

mimic those in place during Aboriginal occupation of the

land.

Today, aircrati arc being used in parts of some Western

Australian desert conservation reserves to set patch bums

under carefully defined conditions to create a mosaic effect of

burnt and unburnt patches across the landscape (Burrows and

Thomson 1990). This study, together with detailed fire

ecology studies currently in progress, will provide a basis for

determining the frequency of fire and the size and distribution

of burnt patches.

When the habitat has been rehabilitated through the prescribed

use of fire and introduced predators controlled, then there will

be an opportunity for translocating rare and endangered

mammals to parts of their former range.

CONCLUSION

Black-and-white aerial photographs, Landsat imagery, and

field observations have revealed that the size and intensity of

fires in a part of the Western Desert west of Lake Mackay

have increased dramatically over the last 36 years or so. This

increase is attributed to the departure of Aboriginal people

from the area during the 1960s. Aborigines used fire

extensively for a multitude of reasons, resulting in a smallgrained mosaic of burnt patches of different ages across the

landscape. Such landscape diversity maximised resources

available to Aborigines and to desert animals. Today, in the

absence of frequent burning by Aborigines, fuels have

accumulated over vast areas and when these mels are ignited

by lightning under hot, dry, windy summer conditions, large

and intense wildfires sweep across the desert. This changed

fire regime appears to have resulted in a lower diversity of

animals and plants.

303
A CKNOWLEDGEMENTS

We thank the Central Lands Council, the Walunguru

Community Council and the Kiwirrikura Community Council

for their assistance with the project. We also thank Benny

Nolan Tjabinati and Warlimpirringa Tjapaltjarri for showing

us their country. We thank Graeme Liddclow, Phil Fuller and

Alex Robinson for their support in the field and Richard

Kimbcr and Andrew Burbidgc for advice on where to conduct

the study. We thank Department of Conservation and Land

Management staff at Kalgoorlie and Kununana for keeping

vigil on HF radio.

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management in relation to fire and to food. pp. 77-85. In:

Hetzel, B.S.; Frith, H.J. eds. The Nutrition of Aborigines

in Relation to the Ecosystem of Central Australia.

Melbourne: CSIRO.

Mcrrilecs, D. 1968. Man the destroyer; late Quatemary

changes in the Australian marsupial fauna. Journal of

Royal Society of Western Australia. 51(l): l-24.

Mulvancy, D.J. 1975. The Pre-History of Australia. Revised

edition. Baltimore: Penguin Books. 346 pp.

Pielou, E.C. 1977. Mathematical Ecology. New York: WileyInterscience Publishers. 268 pp.

Suijdcndorp, H. 1981. Responses of the hummock grasslands

of northwestern Australia to fire. pp. 417-424. In: Gill,

A.M.; Groves, R.H.; Noble, I.R. eds. Fire and the

Australian Biota. Canberra: Australian Academy of

Science Publishers.

Saxon, E.C. 1984. Introduction to patch-burning. pp. 5-6. In:

Saxon, E.C. cd. Anticipating the inevitable: A Patch-Bum

Strategy for Fire Management at Uluru (Ayers Rock . Mt.

Olga) National Park. Mclboume: CSIRO.

Start, A.N. 1986. Status and management of mulga in the

Pilbara region of Western Australia. pp. 136-139. In:

Sattler, P.J.S. ed. The Mulga Lands. The Royal Society,

Queensland.

Tindalc, N .B. 1959. Ecology of primitive Aboriginal man in

Australia. pp. 36-51. In: Keast, J.A.; Cracker, R.L.;

Christian, C.S. eds. Biogeography and Ecology In

Australia. Monographiae Biology. 8. The Hague: W.

Junk.

Tonkinson, R. 1978. The Mardudjara Aborigines: Living The

Dream In Australia’s Desert. New York: Holt, Rinehart

and Winston Publishers. 149 pp.

Warburton, P.E. 1875. Journey Across The Western Interior

of Australia. Perth: Fascimile edition 1981, Hespcrion

Press. 307 pp.

305
INDIAN USE OF FIRE AND LAND CLEARANCE

IN THE SOUTHERN APPALACHIANS

Michael S. DeVivo’

Abstract-The myth of an unbroken primeval forest, extending across eastern North America at the dawn

of European settlement, has been perpetuated in the writings of both laymen and scholars throughout the

present century. Accounts of sixteenth, seventeenth, and eighteenth century explorers, however, document

vast amounts of cleared land held by aboriginal inhabitants, who likely populated the continent in much

higher numbers than hate been traditionally accepted. Fire wes the principal tool used by the Indians to

clear vegetation. Despite frequent historical reference to the Indian use of fire and the documentation of

Indian old fields, the role of fire has been largely underplayed. Fire was implemented for forest

management, driving game, and preparing land for agriculture. This paper examines the impact of fire and

related a&ropogenic distuhancrs on the southern Appalachian landscape hcfore white settlement.

INTRODUCTION

Man’s role as an agent of landscape change has long been a

thcmc of rcscarch in historical geography (Newcomb 1969).

However, the influence of eastern North Am&a’s aboriginal

inhabitants on the physical environment before European

settlement has not been studied adequately. This paper offers

an overview of anthropogcnic disturbances in the southern

Appalachians during an era of aboriginal habitation, with

especial reference to population, fire, land use, and land

clearance.

ACCOUNTS BY EARLY EUROPEAN

EXPLOREXS

Permanent European scttlcmcnt of the eastern United States

did not occur until more than a century after the Columbus

landfall in 1491, despite explorers’ ventures along the coast,

and subsequently into the interior of the continent, in pursuit

of geographic knowledge during the sixteenth century (Brown

1948). Journals often contain comments as to the apparent

presence or absence of forest, but other landscape traits were

documented as well, such as aboriginal population and land

use. In any event, the early explorers have provided

documentation that refutes the popular notion of an unbroken

virgin forest extending across astcm North America. Of

particular significance were the travels of Giovanni Verrazano

in 1524, Jacques Cartier a decade later, and Samuel dc

Champlain in the early 1600s (Sauer 1971, 1980), but their

accounts depict extensive areas of cleared land prior to

European settlement only along the Atlantic coast and

adjacent navigable waterways. Very few reports documenting

conditions of the southeastern interior were provided by

explorers. Narratives of the expedition 14 by Hcmando de

Soto between the years 1538 and 1.543, however, offer

illustrations of extensive maize fields, canebrakes, and open

land on the southeastern coastal plain and in the southern

mountains (Boume 1904; Hakluyt 1611; Rostlund l9.57; U.S.

1939).

‘Assistant Professor of Geography and History, Oregon Institute of

Technology, Klamath Falls, OR.

306

ABORIGINAL, POPULATION AND

DEPOPULATION

Supplementing explorers’ accounts is a body of literature in

which students have sought to determine the prc-contact

aboriginal population of the Americas. These studies suggest

that the aboriginal population of the southern Appalachians

was much greater than heretofore accepted, and that it

declined rapidly, largely because of disease transmitted by the

Europeans following the Columbus landfall in 1492.

Furthermore, aboriginal inhabitants were numerous enough

and sufficiently advanced to significantly alter the region’s

vegetation.

Humans have occupied the southern AppaIachians for over

12,000 years (Dickens 1976; Frizzell 1987). It is widely

accepted that the Cherokees occupied the region at least since

the protohistoric period; their settlement core was restricted to

wcstcm North Carolina, cast Tennessee, north Georgia, and

northwestern South Carolina, but claimed lands extending

north to West Virginia and Kentucky (Dickens 1987; Frizzell

1987; Goodwin 1977). Mooney estimated the Cherokee

population at no more than 22,000, a figure accepted and

advanced by Kroeber (Dcncvan 1976; Goodwin 1977;

Kroeber 1939; Swanton 1946).

Denevan, however, has indicated that the “authority of

Kroeber has impeded serious consideration of North American

aboriginal populations” and that “it is time for a

reconsideration” (Denevan 1976). Unfomately, one of the

principal problems in estimating North American aboriginal

populations, especially in the southeastern interior, is the lack

of historical evidence. Historical documentation regarding

Indian populations is more widely available for Latin

American regions than for Anglo-America, largely because

the former have a longer history of direct European contact

and scttlemcnt. Because “estimates of aboriginal American

populations have yielded a picture of small scale preconquest

human population in the Western Hemisphere” (Dobyns 1966;

Denevan 1976), anthropologist Henry Dobyns has proposed

the use of depopulation ratios for calculating pre-Columbian
populations. His estimates contrast rather sharply with

Kroeber’s; for example, Krocber estimated a hemispheric

total of 8.40 million, whereas Dobyns estimates 90.04-I 12.55

million (Dcnevan 1976), and Geographer Michael Williams

has noted:

There is the strong possibility that in the late fifteenth

century the Western Hemisphere may have had a

greater total population than western Europe. The

implications of these figures for forest disturbance and

destruction arc enormous (Williams 1989).

Today, Krocber’s estimates arc considered much too low

(Denevan 1976), and Dobyns’ method offers an alternative,

probably more realistic estimate. Dobyns’ scheme employs a

depopulation ratio, that is “the ratio of degree of decline from

the time of contact to the population nadir” (Dencvan 1976).

Dobyns determined the depopulation ratios for aboriginal

tribes and regions for which relatively reliable information is

available and derived an average of 20: 1 (a population decline

of 95%). Borah further supports high figures; he estimated

pre-contact New World native population at about 100

million, which suggests a depopulation ratio of up to 25:1

(Borah 1964; Dencvan 1976; Dobyns 1966).

The apphcation of depopulation ratios is a viable means of

estimating the pre-contact aboriginal population of the

southern Appalachians. Archaeological evidence and travel

accounts indicate rapid population decline during the sixteenth

century, and the southeastern interior was not subject to

exploration, description and interpretation, and settlement by

Europeans u&I long after contact had been made on the East

and Gulf coasts, as well as in the Southwest (Denevan 1976).

Figures of 7,400.10,000 are assumed to be rather reliable

estimates for the Cherokees’ nadir population during the early

to mid-eighteenth century (Goodwin 1977), and application of

a 20: 1 or 25: 1 depopulation ratio indicates that the pre-contact

population would have been between 150,000 and 250,000.

The difference between these estimates and Kroeber’s

estimate of 22,000 is highly significant. A quarter of a

milhon inhabitants would have had a Iarger impact on the

region’s physical landscape than a comparatively scant

population of 22,000 peopIe. Obviously, the likelihood of

extensive forest clearance would have been much greater.

The aboriginal inhabitants had been important components in

the region’s ecosystem. When disease, a major perturbation,

decreased their numbers or eliminated them from some areas

entirely, a major ecological change took place. Geographer

Erhard Rostlund (1960) determined that buffalo (Bison bison)

had not entered the Southeast by A.D. 1500, but migrated

into the region after the middle of the sixteenth century,

extending their habitat to the Atlantic and Gulf coasts.

Historian Alfred Crosby suggests that the dramatic decrease in

numbers of Amerindians opened up an econiche for the

buffalo.

Something had kept these animals out of the expanses

of parklike clearings in the forest that periodic

Amerindian use of fire and hoe had created. That

something declined or disappeared after 1540. That

something was, in all likelihood, the Amerindians

themselves, who naturally would have killed the

buffalo for food and to protect their crops (Crosby

1986).

ABORIGINAL SETTLEMENT FEATURES

AND THE USE OF FZRE

Topography was probably the determining factor in the

distribution of Indian settlements (Dickens 1976). Virtuahy

all sites occurred along relatively extensive floodplains. A

nucleated village of two or three acres appears to have been

the predominant type of settlement, although sites could have

been as small as a quarter of an acre, or as Iarge as six acres

(Dickens 1976). Villages ranged in size from a few houses to

perhaps as many as fifty houses surrounded by log palisades.

Large areas of bottomland adjacent to the villages were

probably maintained for agricultural activity (Dickens 1976).

Fire was the principal tool used by Indians to clear

vegetation. Despite Frequent historical reference to fire, and

the documentation of “Indian old fields,” Indian use of fire in

North America has been greatly underestimated (Brown 1948;

Day 1953; Gersmehl 1970; Goodwin 1977; Johanncssen and

others 1971; Martin I973a, 1973b; Maxwell 1910; Thompson

and Smith 1970). Fire was useful in driving game and

opening the forest “to increase visibility, improve forage,

expose the mast, and help keep down the weeds” (Gersmehl

1970). In the Great Smoky Mountains, fues were set at

frequent intervals to encourage the growth of certain plant

species, such as blueberries (Vaccinium vacillans), which

were useful for human consumption as well as wildlife habitat

(Lindsay 1976).

The Cherokees, perhaps inadvertently, used fire for forest

management. Plants having relatively little value, such as

white pine, hemlock, birch, maple, and w&s were bum& in

order to encourage the growth of more valuable species. The

Indians also burned the areas surrounding their villages to

prevent catastrophic fires (Goodwin 1977).

Eastern Woodland Indians set fire periodically to bum

accumulated litter and undergrowth and to encourage

grassland (Thompson and Smith 1970). Periodic fire was

especially important for the maintenance of prairies and

canebrakes. Sondley has documented the existence of

expansive grassland communities in the Asheville Basin at the

dawn of white settlement.

Most of the lands on and near the French Broad River

. . were in prairies.... At the mouths of the smaller

streams in that region tributary to the French Broad

River were Iarge canebrakes extending for miles up

those tributaries (Sondley 1930).

307
Ralph Hughes determined that under continuous protection

from fire, cane stands “lose vigor, thin out and die” (1966).

Moreover, cancbrake deterioration can be prevented with

periodic fire. Thus, because cancbrakes were present in the

Asheville Basin at the onset of pioneer settlement and because

their maintenance requires frequent fire, it seems likely that

the Cherokees set fire to the Asheville Basin at regular

intervals in order to clear the land of brush and trees.

Following pioneer settlement, a combination of fire

suppression (or a decrease in burning), uncontrolled grazing,

and cultivation of floodplains was probably responsible for the

decline of the extensive canebrakes.

Perhaps the most widespread use of fire by the Indians was in

the preparation of land for agriculture. Afer undergrowth

was burned, larger trees were killed by girdling. Planting

began when sunlight passed through the dead branches;

maize, beans, and squash were usually planted in the same

field (Brown 1948). Maize {Zeo mays) was the most

important staple in the Indians’ diet, and may have been

cultivated as early as 100 B.C. It was planted extensively on

the floodplains of major streams and rivers. Corn was

harvested in the late summer and early fall and was oRen

processed into several different items. These most oRen

included various flours and cakes such as succotash, samp,

hominy, hoe&e, and ash-cake. Corn was also a principal

ingredient in soups and stews. Beans (J%~p&s), probably

introduced at a bout 800 A.D., were next in importance as a

cultivated crop, (Yarncli 1976) and were usually plant,A

alongside corn. In fact, cornstalks Were often used as

beanpoles. The USC of beans and corn in combination implied

“complementation” in the natives’ diet and as a result

provided high nutrition. Squashes (Cucurbikxae) including

pumpkins, gourds, and summer crookneck, Were also an

important staple. Certain squash varieties had been cultivated

as early as 2300 B.C. The Ckrokec8 planted squashes beside

beans and maize. The sunflower (He/ianfllus anmcs) was

probably domesticated during the. second or third mil/cnnium

B.C. (Yamell 1976) and had a multitude of uses. For

example, its seeds yielded an edible table oil and flour that

could be made into bread (Goodwin 1977).

Some wild edibles, such as spinach-like pigweed

(Amaranthus) and gooscfbot (Chenopodium album), grew

along wet ditches and streams. Blackberries (Rubtcc arguf~cr),

raspberries (Rubus odoraflu), and blueberries (Vaccinium

vucillans) were used. Nut-bearing trees provided ihe Indians

with acorns, chestnuts, and walnuts, and sap from some trees

provided sweetening agents such as maple syrup. Because

Indians were strongly dependent on food from “wild”

vegetation, some authorities believe that the Indians

rhemselves were responsible for the wide distribution of

certain trees, such a mockernut hickory (Carya cord~$xmti)

and black walnut (Jug/ans nigra) (Goodwin 1977; Maxwell

1910).

The Cherokees obtained a number of fruits through contact

with the Europeans in the sixteenth, seventeenth, and

eighteenth centuries. These introduced Fruits included

watermelon (Cirrullus vulgaris), peach (Prunus per&a), apple

(Malus pm&), and pear (Pyrur communir). Orchards were

generally confined to moist, sandy soils at elevations below

3,000 feet; however, isolated stands of apple trees are at

elevations up to 5,000 feet.

The Indians undoubtedly depended heavily on wild plants and

animals for food, and they nurtured some forestland as a

source of such fbods. They also cleared large areas of

settlements to provide fbelwood, and cleared extensive areas

for agriculture.

Accounts of travelers document the abundance of cultivated

liclds and expansive grasslands throughout the Cherokee

country. De Soto, in 1540, marched for a day through

cultivated fields in southwestern North Carolina; subsequent

explorers include De Luna in 1559-1561, Pardo in 15661568,

Batt in 1667, Lederer in 1670, Needham and Arthur in 1673,

Cuming ‘in 1730, and Timberlake in 1762 (Boume 1904;

Hudson and others 1985; Hudson 1987; Sondley 1977;

Williams 1927, 1928). Perhaps Bartram’s account of his

travels of 1775 are the most informative. The botanist

reported extensive open prairies and fields of corn along the

Little Tennessee River Valley (Harper 19.58).

Virtually all permanent native seltlements were limited to the

floodplains of major streams and rivers for good reason,

Their economy was based principally on agriculture, and it

was impractical, if not impossible, to farm on s&ply sloping

terrain or at high elevations where erosion and microclimatic

conditions were unfavorable. In southwestern North

Carolina, the 3,000.fwt contour follows the boundary

between lands that are relatively suitable for agriculture and

those that are not; the same is likely true for much of the

southern Appalachians. SIopes are typicatiy gentle below

3,000 feet and are typically much steeper at higher elevations.

Indians used fire to clear land for agriculture, and it is likely

that some fires burned larger areas than intended. On

shallow soils serotinous n&le]@f conifers tended to

dominate following a bum. On deep soils and open slopes

hardwoods persisted or invaded afier a fire. Deep-soiled,

sheltered mesic sites were probably less susceptible to

burning.

Rostlund suggested that in the prc-contact southeastern United

States, the aboriginal inhabitants’ burning of vegetation

resulted in maximum land clearance. Afier their depopulation

and the concomitant reduction in frequent burning, the area of

cleared land decreased and the propotion of forestland

increased (Rostlund 1957). Silvical characteristics of some

forested areas in the southern Appalachians seem to support

308
Rostlund’s hypothesis. For example, in the contemporary

Joyce Kilmer Memorial Forest in southwestern North

Carolina, a high proportion of old-growth yellow-poplar

dominates some mesic sites. Yellow-poplar is an aggressive

pioneer species on fertile sites following drastic disturbance

(McCracken 1978), and in examining the forest, Lorimer has

determined that “disturbances as far back as 1.550 are almost

certainly indicated by substantial numbers of the intolerant

tulip tree in corresponding age classes” (Lorimer 1980).

Possibly a fifteenth- to sixteenth-century Indian settlement that

was located at sites now dominated by yellow-poplar

(Liriodendron tulipfera) was a source of major disturbance.

Perhaps after the European introduction and the subsequent

diffusion of epidemic disease during the mid-fifteenth century,

the settlement was largely depopulated, and pioneer species,

such as yellow-poplar, invaded previously cleared areas.

CONCLUSION

The ability of aboriginal inhabitants to clear forest has often

been grossly underestimated. In fact, anthropogenic

perturbations over the last one or two millennia have

accounted for much of the Southeast’s forest composition,

which is dominated by disturbance-initiated species (Buckner

1989). In the southern Appalachians, the Indians’ livelihood

depended on the use of fire to clear land and on the

cultivation of crops along the floodplains of major rivers and

their tributaries. Before contact with Europeans, the

Cherokees and their ancestors probably cleared all bottomland

in the region at one time or another. Moreover, the

Cherokees’ pre-Columbian ancestors may at one time have

been numerous enough to clear all land below the 3,000-foot

contour.

LITERATURE CITED

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impact of European expansion upon the non-European

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Mexico: Actas y Memorias 3:379-387.

Boume, E.G., ed. 1904. Narratives of the Career of

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Brown, R.H. 1948. Historical Geography of the United

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Buckner, E.R. 1989. Evolution of forest types in the

Southeast. In Proceedings of Pine-Hardwood Mixtures: A

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T.A. Waldrop, pp. 27-33. Asheville, North Carolina:

U.S. Department of Agriculture, Forest Service,

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Crosby, A.W. 1986. Ecological Imperialism: The Biological

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Day, G.M. 1953. The Indian as an ecological factor in the

northeastern forest. Ecology 34:329-346.

Denevan, W.M. 1976. The Native Population of the

Americas in 1492. Madison: University of Wisconsin

Press.

Dickens, R.S. 1976. Cherokee Prehistory. Knoxville:

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Dobyns, H.F. 1966. Estimating aboriginal American

population, an appraisal of techniques with a new

hemispheric estimate, Current Anthropology 7:385-416.

Frizzell, G.E. 1987. The Native American experience. In

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33-66. Sylva, North Carolina: Jackson County Historical

Association.

Gersmehl, P.J. 1970. Factors leading to mountaintop

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Geographer 10(1):67-72.

Goodwin, G.C. 1977. Cherokees in Transition: A Study of

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Hakluyt, R., transl. 1611. The Discovery and Conquest of

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published by the Hakluyt Society, London, reprinted by

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Harper, F. 1958. The Travels of William Bartram:

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DePratter, C. 1985. Coosa: A chiefdom in the sixteenth.

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Hughes, R.H. 1966. Fire ecology of cancbrakes.

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Johanncssen, C.L.; Davenport, W.A.; Millet, A.; and

McWilliams, S. 1971. The vegetation of the Willamette

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265-273. New York: Academic Press.

310
SPECIAL SESSION: THE YELLOWSTONE FIRES

BARK BEETLE--FIRE ASSOCIATIONS

IN TFIIZ GREATER YELLOWSTONE AREA

Gene D. Amman’

Abstract--The large forest tires in and around Yellowstone National Park in 1988 bring up many

ecological questions, including the role of bark beetles. Bark beetles may contribute to fuel buildup over

the years preceding a fire, resulting in stand replacement fires. Fire is important to the survival of scral

tree species and bark beetles that reproduce in them. Without fire, seral species arc ultimately replaced hy

climax species. Following fire, bark- and wood-boring heclles respond to fire-injured trees. Because of

synchrony of the fires and life cycles of the beetles, beetle infestation in 1988 was not observed in

fire-injured trees. However, endemic populations of beetles, upon emergence in 1989, infested large

numbers of tire-injured trees. Of the trees examined in each species, 28 to 65 percent wee infested by

hark beetles: Pinus contorta (28 percent) by fps pini; Pscudotsuga mew&ii (32 percent) by Dcndrocronus

pseudotsueae; Picee en~elmannii (65 percent) by Dendroctonus mtipennis; and Ahies lasiocarpa (35

percent) hy Buprestidae and Cerambycidac. Most trees inf’estcd by hark beetles had SO percent or more of

their basal circumference killed by tire. Bark beetle populations probably will increase in the remaining

tire-injured trees.

INTRODUCTION

Insects and diseases arc important in modifying the age

structure and sp&cs composition of many forests. Their

activities contribute to accumulation of dead fuels that make

large-scale fires possible--resulting in new stands of the host

tree. The stands arc then temporarily free of attack (Kilgore

1986). The mosaics of different-aged stands created as the

result of fires assure survival of both trees and insects that

infest them. However, fire is more. important to the survival

of Some ecosystems than others. Following fires, injured

trees arc susceptible to infestation by bark beetles.

Subsequent buildup of bark beelk populations can result in

killing of uninjured trees.

In this paper I will discuss bark beetle ecology (I) as it may

contribute to fuel buildup and fire intensity and (2) as it

relates to fire-injured trees in the aftermath of forest fires.

Lodgcpole pine (Pinus contorta Douglas), the most prevalent

tree species in the Greater Ycllowstonc Area (GYA) and one

that we know the most about with ITSpCCt to bark beetle-tree

interactions, will be discussed more fully than other species.

BARK BEETLIES AS CONTRIBUTORS TO

FUEL BUILDUP

Pfistcr and Daubenmire (1975) recognized four basic

successional roles for lodgcpole pint: minor seral, dominant

scral, pcrsistcnt, and climax. Large areas of lodgepole pine

in the GYA have almost no spruce-fir component. Dcspain

(1983) concludes these arc essentially self-perpetuating climax

lodgcpole pine stands that oficn exceed 300 to 400 years of

age, with no cvidcncc of fire since establishment.

‘Principal Entomologist and Project Leader, Mountain Pine Beetle

Population Dynamics Research Work Unit, lntermounisin Research

Station, Forest Service, U.S. Department of Agriculture, Ogden, UT.

Mountain pine bectle (MPB) infestation characteristics differ

by lodgepole pine successionat roles. In stands where

lodgepole pine is seral and stands have been depleted by

beetle infestations, lodgepole will be replaced by the more

shade-tolerant species in the absence of fire. These

shade-tolerant species consist primarily of Douglas-fir

(Pseudo!spxa mcnzicsii [Mb-b.] France) at the lower

elevations and subalpine lir (& lasiocarpa [Hook.] Nutt.)

and Engclmann spruce (& $nRclmannii Parry) at the higher

elevations. Starting with the stand generated by fire,

lodgcpolc pine grows rapidly and occupies the dominant

position in the stand. Fir and spruce seedlings also become

established in the stand but grow more slowly than lodgepole

pine.

Once the lodgepole reach susceptible size, MPB infestations

kiil 30 to over 90 percent of trees 12.7 cm and larger

diameter at breast height (Cole and Amman 1980; McGregor

and others 1987). ARcr each infestation, both residual

lodgcpolc pint and the shade-tolerant species increase their

growth (Roe and Amman 1970). Infestations are repeated as

the residual lodgcpolc pines reach size and phlocm thickness

conducive to beetle infestation and survival (Amman 1977).

This cycle is repeated at 110- to a&year intervals, depending

upon growth of the trees (Roe and Amman 1970). Although

six0 and phlocm thickness arc: the variahlcs neuzary for

beetle cpidcmics to occur, some authors (e.g., Bcnyman

1978) bclicvc trees must be weakened before MPB can infest

[hem. Howcvcr, this has not beet-t demonstrated, and will

rcclt~irc detailed studies of beetle populations progressing from

low level into the early phases of an epidemic (Schmitz

1988). Fuel ~CVC~ and fire hazard continue to increase with

each bcctlc infestation (Brown 1975; Flint 1924; Gibson

1943; Roe and Amman 1970) until lodgcpolc pine is

313
eliminated from the stand, or until a fire occurs that kills most

trees (including thick-barked, fire-resistant species), and the

stand regcncrates to lodgepole pine.

Where lodgcpole pine is persistent or climax (Pfister and

Daubcnmire 1975), the association of lodgepole pine and

mountain pine beetle is somewhat different. In these cases,

the forest consists of lodgepole pine of different sizes and

ages, ranging from seedlings to a few overmature trees. In

these forests, MPB infests and kills many of the pines as trees

reach large size. Openings created in the stand, as a result of

the larger trees being killed, are seeded by lodgepole pine.

The cycle is then rcpcatcd as other lodgcpole pines reach

sizes and phloem thicknesses conducive to increases in beetle

populations (Amman 1977).

Amman (1977) hypothesized that periodic MPB infestations

continue the multi-aged nature of the stands. A mosaic of

small clumps of different ages and sizes may occur. The

overall effect is likely to be more chronic infestation by the

beetle because of the more constant source of food. Beetle

infestations in such forests may result in the death of fewer

trees per hectare during each infestation than would occur in

even-aged stands (caused by stand replacement fires) and in

those stands where lodgcpolc pine is seral. Fires in

uncvcn-aged persistent and climax lodgepole pine forests

should not be as hot as fires where widespread epidemics of

beetles have occurred because smaller, more continuous

deposits of fuel are added to the forest floor under chronic

beetle infestations. Thus, with lighter accumulations of fuel,

tires tend to eliminate or weaken some of the trees but do not

cause total elimination and complete regeneration of the stand.

An example is the situation described by Gara and others

(1985) in south-central Oregon, where lodgepolc pine forms

an cdaphic climax. Here, fires are slow moving, and the heat

of smoldering Iogs scorches roots and sides of trees. Later

these injured trees arc invaded by fungi that work their way

up the roots into the trunks. Subscqucntly, mountain pine

beetles arc attracted to and kill these trees. As the dead trees

rot and fall over, the stage is set for another fire.

Most tires that occur in lodgepole pine arc either slow and

smoldering or are rapidly moving, intense crown fires (Lotan

and others 1985). High-intensity tires tend to favor lodgepole

pine over such species as Douglas-fir (Kilgore 1986) and

would likely occur following epidemic beetle infestations.

Brown (1975) states that the major vegetation pattern found in

lodgcpolc pine today was caused by stand replacement fires,

although many uneven-aged lodgepolc pine stands result from

lower intensity surface fires.

In south-central Oregon, Stuart and others (1989) have related

lodgcpolc pine regeneration pulses to mountain pine beetle

and fire disturbances. They observed that (1) stands that

experienced periodic MPB epidemics accompanied by a fire

had an even-aged structure; (2) stands that had periodic MPB

314

epidemics and no fire had a storied, bimodal size structure;

and (3) stands that experienced mortality by low level MPB

populations, with or without low intensity fire, had multi-aged

structure.

Rommc and others (1986) examined the effects of beetle

outbreaks on primary productivity in forests dominated by

lodgepole pine in northwestern Wyoming. They concluded

that the mountain pine beetle does not regulate primary

productivity. Even though MPB has drastic effects upon

stands (considering the forest landscape comprises a mosaic of

stands in various stages of succession), annual productivity for

the landscape is relatively constant despite continual

fluctuations of individual stands. The sudden and massive

death of a large proportion of the biomass leads to only a

brief drop in primary productivity and to a more equitable

distribution of biomass and resources. Therefore, the primary

function of large MPB infestations and the death of large

numbers of IodgcpoIe pine appears to be survival of host and

beetle by creating large amounts of fuel for fire that, when

ignited, eliminate competing vegetation and regenerates

lodgcpolc pine (Amman 1977; Roe and Amman 1970;

Romme and others 1986).

The mosaic of stands of different ages created by the action of

MPB and fire is ideal for MPB survival. Because stands arc

coming into sizes conducive to continual MPB infestation and

survival, a continual supply of food is provided. However,

an ideal mosaic for MPB probably did not occur following the

1988 GYA fires because fire behavior was influenced more

by drought and wind than by fuels. Virtually all forest age

and fuel categories burned (Christensen and others 1989).

Romme and Despain (1989) state that the mosaic created by

the 1988 fires will be more homogeneous than the mosaic

created by fires in the early 1700’s, and few ecological

consequences will be incurred because succession is slow.

One consequence is likely to be a major MPB infestation in

80 to 120 years because at this age many lodgepole pine

stands sustain their first beetle outbreak, again creating a

large amount of dead fuel in a relatively short period, setting

the stage for another stand replacement fire (Roe and Amman

1970). The timing of MPB infestations, when lodgepole pine

arc mature in seral stands, not only assures large amounts of

fuel from the dead trees for a stand replacement fire but also

adequate seed to regenerate the stand (Pctcrman 1978).

Pctcrman suggests the ecological role of MPB could be to

decrease the probability of lodgepole stands, with a high

degree of serotiny, producing stagnant stands of offspring.

By preventing the stand from getting too old, much less seed

would be available. Such a mechanism could have

evolutionary significance to lodgepole pine because stagnant

stands do not reproduce well, and the stand following the

stagnant stand could be outcompeted by climax tree species.

Pcterman further points out that prevention of stagnant stands

would bc advantageous to MPB because the beetle does not

reproduce well in small, stagnant trees.
The contribution of dead fuel buildup, a result of the 391 000

ha infestation of MPB in Yellowstone National Park that was

still active in 1982 (Gibson and Oakcs 1987), to behavior of

the 1988 fires was masked by the extreme fire conditions

(Christcnscn and others 1989). Studies of small fires in

portions of Yellowstone not involved in the 1988 tires

probably would elucidate interactions of MPB infestations,

dead fuel buildup, and tires. A relationship similar to MPB,

lodgepole pine, and fire has been proposed for southern pine

bcetlc (SPB) (12, frontalis Zimmermann) and pines in the

Southern United States. There, pines arc replaced by

hardwood tree species in the absence of fire (Schowaltcr and

others 1981). Therefore, survival of SPB and its host in

natural stands is dependent upon frequent fires.

Bark beetles infesting climax tree species would not have the

same riced for a close relationship with forest fires as those

infesting seral species. The spruce beetle (SB) @. rufipennis

[Kirby]) and the Douglas-fir beetle (DFB) (Q. pseudotsugae)

usually kill small groups of trees. Howcvcr, occasionally

they also cause heavy mortality, favoring large trees over vast

areas, afier building up in windthrown trees. For example,

SB killed millions of Engclmann spruce in Colorado between

1939 and 1951 (Massey and Wygant 1954) and white spruce

e. glauca [Moench] Voss) in Alaska between 1960 and 1973

(Baker and Kemperman 1974). Schmid and Hinds (1974)

describe the scenario in spruce-fir stands in the central Rocky

Mountains following spruce beetle infestations. Following a

spruce-beetle outbreak, the percentage of subalpine fir in the

stand increases, with fir dominating the stand. As fir reach

125 to 175 years of age, they begin to die, with the bark

beetle &yocm1;9nfusus Swaine being one of the mortality

factors. Young spruce and fir increase their growth as

overstory fir die. The less shade-tolerant spruce is then

favored over I% as the original canopy fir are killed. Spruce

becomes dominant as it outlives fir and gains greater size.

Eventually, the cycle is repeated. Spruce beetle generally live

in moist forests where fires are less frequent and intense

because of moist, sparse fuels (Amo 1976). Small fires in the

spruce-fir type would expose mineral soil and probably favor

establishment of spruce.

The Douglas-fir beetle seldom creates widespread destruction

in the Rocky Mountains, generally killing groups of dense

mature Douglas-fir (Fumiss and Orr 1978). These groups are

usually widely separated, and the space created by death of

some overstory trees usually regenerates to Douglas-fir.

These observations suggest coadaptive or coevolutionary

relationships between bark beetles and their host trees, and

the importance of fire in maintaining these relationships for

seral tree spccics.

BARK BEETLE/FIRE-INJURED TREE

ASSOCIATIONS

Following the 1988 GYA fires, large numbers of trees girdled

or partially girdled by heat remained at the bum perimeter

and are providing infestation opportunity to bark beetles.

Beetles may increase to large numbers and infest uninjured

trees after most of the fire-injured trees are killed.

The bark beetle situation in the GYA at the time of the 1988

tires shows that the species were at low population levels,

except the DFB. The massive infestations of MPB that

covered over 391 000 ha in Yellowstone Park in 1982 had

&lined to only 135 ha by 1986 (Gibson and Oakes 1987)

and to no infested trees in 1987 (Gibson and Oakes 1988). In

1988, insect detection flights over the park were not made

because of tire fighting efforts and smoke (Gibson and Oakcs

1989). However, on the nearby Bridger-Teton National

Forest, MPB infestation had declined from 1,296 ha in 1987

to 364 ha in 1988 (Knapp and others 1988).

Although no survey estimates are available for other bark

beetle species in Yellowstone Park, surveys of adjacent areas

showed only the DFB was increasing, whereas spruce beetle

infestation was light (Knapp and others 1988) and pine

engraver (Ips pini Say) populations had declined (Gibson and

Oakes 1989).

The small populations of bark beetles in the GYA at the time

of the 1988 fires, coupled with timing of the tires in relation

to life cycles of bark and wood infesting beetles, resulted in

few fire-injured trees being infested in 1988. The SB, DFB,

and pine engraver all emerge to infest new material in the

spring, prior- to occurrence of the fires. The MPB emerges in

late July and early August, but few were in the GYA.

Studies were started in 1989 to determine bark beetle

infestation of fire-injured trees and potential buildup of beetle

populations. Observations were made in three areas: (1) near

the Madison River, approximately halfway between Madison

Junction and West Yellowstone (the North Fork tire); (2)

along the John D. Rockefelter, Jr., Memorial Parkway, south

of Yellowstone’s South Gate (the Huck fire); and (3) in the

Ditch Creek area of the Bridger-Teton National Forest

(Hunter fire). In each area, variable plots (10 basal area

factor) were established: area 1, three plots; area 2, nine

plots; and area 3, seven plots. All trees in the plots were

numbered so that survival of individual trees can be followed

for several years. Survival of scorched trees can be predicted

from volume of crown scorch (Ryan and others 1988).

Peterson and Arbaugh (1986) found crown scorch and basal

scorch were best predictors for lodgepole pine survival, and

crown scorch and insect attack were most important as

predictors of survival of Douglas-fir. However, the

researchers did not identify the insects. I used the percentage

of basal circumference in which the cambium was killed,

315
rather than relating infestation to crown scorch, because of

the high sensitivity of lodgcpolc and spruce to even light

ground tire. Some bark was removed from trees infested by

insects so that insects could be identified. Because our plots

were mostly at low elevations (2 050 to 2 400 m), trees

consisted mostly of lodgcpolc pine and Douglas-fir. The

limited nature of our observations preclude their use for

making predictions of bark beetle activity beyond our plots.

Greater coverage of the burned area is planned in 1990.

Lodgepole Pine

Lodgepole pine is the most abundant tree in the sampIes.

Overall, 28 percent of the trees were infested by the pine

engraver (QbsfniriH%y) o ~tr&leel$. n 1 i n f e s t e d , y

one had not been scorched by fire. All others had 50 percent

or more basal girdling (phloem killed by fire). Most

commonly, trees infested by the pine engraver had 100

percent basal girdling (table 2). Many of these trees showed

little evidence of scorch and looked healthy except for boring

frass made by the beetles. Upon closer inspection, however,

the trees were completely girdled at the base by a light

ground tire. Geiszler and others (1984) also found most

lodgepole pine infested by pine engraver were moderately to

heavily injured following a fire in Oregon.

It is not surprising that a large number of trees were infested

by pine engraver because they are able to reproduce in

wind-broken material (including large branches) and in

decadent trees near death (Sar+.vell and others 1971). There

always seems to be plenty of such material available.

Consequently, the engraver is almost always present in

substantial numbers, although not necessarily causing

noticeable tree mortality.

Only one tree containing MPB was observed (Hunter fire on

the Bridger-Teton National Forest) and it was not on a plot.

Observations over the years suggest that MPB is not strongly

attracted to tire-scorched trees, so few trees would be infested

even if a large population had been present in the GYA. The

MPB seldom breeds in trees injured or killed by tire in

numbers sufficient to cause an increase in the population.

Hopkins (1905) found no MPB in tire-injured ponderosa pine

in the Manitou Park area of Colorado. However, he did

observe several secondary species, including the red

turpentine beetle @. nraleas rSe@. b s e q u e n t _

publication concerning insect damage in the National Parks,

Hopkins (1912) stated that forest fires contribute, to a limited

extent, to the multiplication of certain species that breed in

fire-scorched trees, but as a rule forest fires kill more beetles

Table I.--Number of trees examined and the perceotage infested by bark- sod wood-boring

beetles for plots Located in three fires in the Greater Yellowtone Area, 1989

Fire

Tree species North Fork Huck Ibolter All fires

Lodgepole pine 0 0 67 2 4 5 9 3 3 125 2 8

oooglas-fir 3 4 IS 25 52 4 25 6 3 32

EOgd- SpllCe 0 0 2 15 6 7 1 7 65

subalpine fir 0 0 9

ii

8 3 8 3 5

AtI species 3 4 18 103 3 1 8 5 3 8 2:: 3 2

Table 2.--Number and percentage of trees infested by bark- and mod-boring beetles in

different fire-injury categories, Greater Yellowstone Arpia, 1989

Fex-ceotage of basal cimnference killed by fire

Tree species 0 l- 2 5 26- 5 0 51- 7 5 76- 100

%. pg &. !Q g. pcJ &. p& &. Pet

iicgzlr Pine 21 1 7 285 : 00 15 10 39 0 12 11 36 2 5 73 22 41 41 Engehnn space 0 0 1 0 0 0 0 0 16 6 9

subalpine fir 0 0 0 0 0 0 0 0 1 7 31

ALI species 3 8 16 8 0 25 1 2 23 3 6 128 4 3

316
than they protect (by protect, he probably meant provide

breeding habitat). Swaine (1918), referring to Canadian

conditions, wrote that ground tires that injure and kill large

numbers of trees may provide material for rapid development

of bark beetles. He thought this was particularly true if fires

occur year after year in neighboring localities. Apparently

the proximity of fires would allow beetles to continue to build

up their populations for several consecutive years. Blackman

(1931), working on the Kaibab National Forest in northern

Arizona, found MPB did not prefer fire-scorched trees. He

thought the scorched phlocm did not offer favorable

conditions for beetle offspring. The MPB has fairly limited

requirements of phloem thickness and moisture in order to

reproduce (Amman and Cole 1983).

In agreement with most observations in the Rocky Mountains

that MPB are not attracted to fire-scorched trees, Geiszler and

others (1984) observed MPB mostly in trees uninjured or

lightly injured by fire, in direct contrast to pine engraver in

moderate to heavily injured trees. Rust (1933) reported

fire-injured ponderosa pine were infested by MPB the first

year following a tire in northern Idaho; however, the

infestation declined the next year.

The wood borers, both Buprestidae and Ccrambycidae, were

found occasionally in fire-injured lodgepole.

Douglas-fir

Douglas-fir was the second most common tree found on the

plots. Of the trees examined, 32 percent were infested by

insects, mostly DFB and a few wood borer larvae of

Buprestidae and Cerambycidae (table 1). Most infested

Douglas-Iir had 50 percent or more girdling by fire (table 2).

Some Douglas-firs that had needles and limbs completely

burned were infested by DFB in the base where the bark was

thick enough to protect the phloem from complete incineration

or from drying so excessively that beetles would not construct

egg galleries in it. Phloem in such trees was completely

brown, and larvae probably will not complete development in

such trees.

Fumiss (1965) studied the susceptibility of fire-injured

Douglas-fir to bark beetle attack after a large fire in southern

Idaho. He found 70 percent of the trees were infested by

DFB 1 year after the fire. And even small or lightly burned

trees attracted the beetles. He found incidence of attack

increased with tree size and severity of crown and cambium

injury by fire. However, infestation decreased sharply with

outright tree killing by tire. Although beetles established

brood in 88 percent of the trees, offspring numbers were

small because of pitch invasion of the galleries and sour sap

condition.

Fumiss (1965) did not report on DFB infestation in

tire-scorched Douglas-fir beyond the first postfire year.

However, following the Tillamook tire of 1933 in the coastal

range of Oregon, DFB buildup in fire-injured Douglas-fir

occurred. Beetles then killed large numbers of uninjured

trees in 1935 and 1936, but the infestation soon subsided

(Fumiss 1941). Fumiss thought beetles were able to increase

because frequent tires in the Tillamook area provided large

numbers of injured trees in which the beetles could

reproduce.

Connaughton (1936) observed that delayed mortality of

fire-injured Douglas-fir was mostly caused by insects

(probably DFB) and fire damage to roots. He found

Douglas-fir had a thick layer of duff around the trunk that

burned slowly, heating the soil and badly injuring the roots.

The evidence for root injury did not show up until a year or

two after the fire in west-central Idaho.

Engelmann Spruce

Engelmann spruce constituted a small part of our tree sample,

with only 17 trees examined. Spruce beetle infested 65

percent of the trees (table l), and these were usually the

larger diameter trees. Of the spruce, only those with 7.5

percent or greater basal girdling were infested (table 2).

Some spruce burned similarly to Douglas-fir described by

Connaughton (1936). Duff around the base resulted in a slow

burning tire that often burned off the roots or so weakened

them that the trees were easily blown over by wind.

Windthrown trees with unscorched trunks created an ideal

habitat for the SB, which shows a strong preference for

windthrown trees (Massey and Wygant 1954; Schmid and

Hinds 1974). Large numbers of spruce beetle larvae occurred

in the spruce, as well as some larvae of Buprestidae and

Cerambycidae.

Subalpine fir

Wood borers (Buprestidae and Cerambycidae) infested 35

percent of the 17 subalpine fir in the sample (table 1). All of

the fir suffered 100 percent basal girdling. The bark was

badly burned and not conducive to bark beetle infestation

(table 2).

Whitebark Fine

Whitebark pine @. albacaulis Engelm.), which is generally

found at high elevations in GYA, did not occur in any of our

plots. MPB infestations during the past 20 years caused

considerable whitebark mortality (Bartos and Gibson 1990),

but the number of infested trees was low at the time of the

1988 fires. Although MPB is not strongly attracted to

fire-scorched lodgepole and pondcrosa pines in the Rocky

Mountains, Craighead and others (193 1) state that it prefers

weakened and tire-scorched western white pine (sz. monticola

Dougl.), one of the five-needle pines. Therefore, MPB may

be more attracted to fire-injured five-needle pines, whitebark

and limber (P. flexilis James), than to lodgepole pine.

3 II
CONCLUSIONS

Of the bark beetles in the GYA, MPB plays a significant role

in converting live fuels to dead fuels in a relatively short

period. This behavior probably promotes hot stand

replacement tires that assure survival of lodgepole pine and,

hence, survival of MPB. Fire is not as important in the

ecology of bark beetles infesting climax tree species.

Although a limited number of fire-injured trees were sampled

in the GYA, almost one-third were infested by bark beetles.

Therefore, numbers of infested trees in the sampled areas

likely will increase because of the remaining large numbers of

tire-injured trees.

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pine beetle outbreaks in the Rocky Mountains: regulators

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YELLOWSTONE MEDIA MYTHS:

PRINT AND TELEVISION COVERAGE OF THE 1988 FIRES

Conrad Smith’

Abstract-This paper draws o n COINIXXXS from 89 reporters who covered the fires, on comments from 146

of their news SOUKXS, and on evaluations of network television coverage by four groups of wildfire experts.

The research also incorporates a content analysis of stories about the fires that appeared in Yellowstone-area

and elite newspapers. The results suggest that repotters sometimes made serious factual errors, and ofien

did a poor job of reporting on ecological issues and fire management policy. There were substantial

differences in how the fires were covered by different news organizations.

INTRODUCTION

Molotch and Lester (1974, 1973, who examined hundreds of

newspaper stories about the 1969 Santa Barbara oil spill,

concluded that the contents of the news accounts were not

determined by objective characteristics of the spill, but rather

by a power struggle among various news sources who had

vested interests in differing interpretations of the event. Only

the local newspaper framed the story in the way it was

perceived by Santa Barbara residents.

In the present paper, coverage of the Yellowstone fires by six

newspapers and the three television networks is interpreted as

a power struggle among sources offering two competing

interpretations of the event: 1) Enlightened public land

managers attempted to maintain the ecological integrity of a

pristine national park by following a scientifically-based fire

suppression regime which treated wildfire as a natural and

necessary part of the biological process that shaped the

ecosystem, and 2) Inept government bureaucrats allowed a

national treasure to be destroyed because of their insensitivity

to the beauty of Yellowstone forests and a cavalier attitude

towards the fears of local residents and the right of local

merchants to realize a fair return from investments in

tourist-related business ventures.

BACKGROUND

On its surface, news can be viewed as an objective account of

reality, as an impartial reflection of what happened. This is

the newsgathering model offered by many journalists, and the

goal described by various professional codes of journalistic

ethics, which identify the search for truth as the most basic

goal of all journalistic endeavors. In the real world of

ncwsgathcring, however, reporters must make many

value-driven choices that shape the ensuing stories. Who to

interview? What questions to ask? Which facts to include at

the expense of others that arc left out? What angles should be

emphasized? What kinds of stories arc being written by

competing reporters? What instructions have been received

‘School of Journalism, The Ohio State University, 242 West 18th

Ave., Columbus, Ohio, 43210.

from an editor or producer? How much time is there before

deadline? What kind of story will advance my career?

The impression made by news accounts is also shaped by

editorial decisions that determine when the story is important

enough for a newspaper or network to assign a reporter rather

than relying on wire service accounts, the decision about who

to assign to the story, and the decision about where to place

the story and how much time or space to give it.

The Yellowstone fires were difficult to cover to the extent

that they occurred outside the normal news routine. National

reporters had to find their bearings in an unfamiliar place,

and to seek information and identify new sources from

scratch. Most of journalism has to do with routine stories

covered from fixed locations through repeated contact with

established sources. On the other hand, the urban fire is one

of the most basic stories in the journalist’s repertoire, and that

made coverage easier because the urban fire model could be

used as a model for covering wildfires. When reporters have

little expertise about an event, they arc more likely to rely on

their personal values to interpret it (Gans 1979), and more

likely to borrow information and story angles from other

reporters (Gitlin 1980). Research by Patterson (1989) and

Wilkins (1987) indicates that disaster coverage tends to focus

on immediate events rather than the context in which they

occur, and suggests that these stories are often told in terms

of cultural stereotypes and not as objective accounts of what

happened. A study of news stories about environmental

issues related to construction of the Tellico Dam (Glynn and

Timms 1982) indicated that the snail darter fish itself, rather

than the issues, dominated coverage.

Media scholar Gaye Tuchman (1978) says that journalists

create news stories by transforming real events into a socially

constructed “reality” that meets the organizational needs of

news work. Some sources and facts are discarded, she

observes, because of shared notions among journalists about

what constitutes news. This process, according to sociologist

David Altheide (1976), often distorts events by removing

them from the context in which they occurred. “Journalists,”

321
i---------------

writes Altbeide, “look for angles, interest, and entertainment

value. ” Some of the ways in which reporters frame news,

according to Gitlin (1980), “can be attributed to traditional

assumptions in news treatment: news concerns the event, not

the underlying condition; the person, not the group; conflict,

not consensus; the fact that advances the story, not the one

that explains it.”

Many of the reporters who covered the Yellowstone tires

were general assignment reporters rather than specialists in

regional or environmental subjects. Herbert Gans (1979)

observes that general assignment reporters “are like tourists,

albeit in their own culture; they seek out what is memorable

and perceive what clashes with the things they take for

granted.” Because of this, national news accounts of local

stories are almost always inaccurate and exaggerated.

METHOD

This study is based on examination of 814 news accounts

about the Yellowstone tires that appeared in 1988 in three

elite American newspapers (the New York Times,

Washington Post and Los AngeIes Times), three

Yellowstone-area newspapers (the Billings, MT Gazette, the

Bozeman, MT Daily Chronicle and the Casper, WY Star

Tribune), and in the evening newscasts of the three

commercial television networks. The three elite newspapers

are widely considered America’s best and most prominent,

while the three area newspapers circulate in Yellowstone and

adjacent communities.

Yellowstone-area newspaper stories were obtained from the

newspapers themselves, and newspaper employees judged

whether individual stories should be categorized as being

about the Yellowstone fires. Stories from the elite

newspapers were obtained from the VuText and Nexis

electronic databases, which allowed computer retrieval of all

stories that contained the words “Yellowstone” and “tire” or

“wildfire” (except for wire service stories in the Washington

Post, which are not included in either database). Television

stories were obtained from the Vanderbilt Television News

Archive in Nashville.

The New York Times, which is published in the nation’s

media capital, received special scrutiny. It is widely read by

journalists, and is o&en used by the networks and by

journalists not only as a source of news, but also as a guide to

the importance of stories and as a guide to how to cover

stories (Gitlin 1980).

This paper also draws on two earlier studies by the author.

One was about the Yellowstonc tires as seen by 68 print

journalists who covered them and by 146 news sources for

newspapers and news magazine stories (Smith 1989a). The

other was based on evaluations of all 1988 evening network

television stories about the fires by incident commanders,

forest ecologists, wildfire behavior experts, and fire

management policy experts (Smith 1989b).

RESULTS

Each of the six newspapers published its first account of the

Yellowstone fires between July 1 and July 8. ABC and NBC

television broadcast their first stories on July 25, after the

evacuation of Grant Village. The first CBS story was

broadcast on August 22, when soldiers joined the &refighting

effort.

The Yellowstone tires were more newsworthy in the west

than in the east. They made the front page of the Los

Angeles Times 39 times, starting on July 18 with a news brief

about wildfires in the west; the front page of the Washington

Post three times, starting on September 8 after the fire’s visit

to the Old Faithful Geyser Complex; and the front page of the

New York Times three times, starting on September 11 when

the secretaries of Interior and Agriculture arrived in

Yellowstone for an inspection. Stories about the fires

appeared in the fist five pages of the Washington Post 17

times, but only three times (the front page stories) in the New

York Times.

The first Los Angeles Times story written by a full-time staff

reporter for the paper (Tamara Jones) was published on

August 24. The Los Angeles Times did not use freelance

stringers to cover the f&a. The Washington Post and New

York Times, however, relied partly on outsiders. Freelancer

Geoffrey O’Gara wrote seven stories for the Post. The first of

these appeared on July 17. The New York Times also made

use of material provided by stringers, starting with an August

10 article by Jim R&bins.

Although fire visited the Old Faithful geyser complex only on

September 7, the geyser was a recurrent theme in news

stories as a symbol of the park. Old Faithful is mentioned in

13 of 47 stories about the tires in the New York Times, in 13

of 41 stories about the tires in the Washington Post, and in 24

of 75 stories in the Los Angeles Times. The first stories on

ABC and NBC also mentioned Old Faithful, and pictures of

the geyser appeared in 18 network stories about the fires.

All of the Yellowstone tires were classified as wildfires on

July 21, and were subjected to full suppression (Christensen

1989). However, I was unable to find any mention of this

fact in any news report published or broadcast during July or

August. Several news organizations did quote Interior

Secretary Donald Hodel as saying on July 27 that all new

tires would be suppressed (emphasis added), but many

reporters retained the impression some fires were being

allowed to burn unchallenged, and perhaps unmonitored,

through all of August and into September.

322
Coverage in the New York Times

A free-lance story by Jim Robbins (1988a), published in the

New York Times on August 10, said the abandoned

natural-bum policy was still in effect, and was “the talk of the

campgrounds and restaurants” in the Yellowstone area. Four

days later, another story (Robbins 1988b) said that some tires

were being fought, but that a dozen were being allowed to

burn. On September I, yet another New York Times story

(Wilson 1988), said “Some of the fires arc allowed to bum

unchallenged as part of a philosophy that holds they arc a

natural process.” A September 10 article (Shabecoff 1988)

described criticism of Yellowstone’s natural-bum policy by

Wyoming senators Alan Simpson and Malcolm Wallop

without explaining that suppression of all fires began in July.

Seven weeks after all fires were in suppression mode, the

Nation’s most influential and prestigious newspaper thus

continued to support the myth that some of the tires were

being allowed to burn. A search through the Ncxis computer

database for all 1988 New York Times stories containing the

words “correction” and “Yellowstone” indicates that no

corrections of this mistake were ever published.

The language used to frame New York Times stories about

the tires sometimes encouraged the idea that they were being

managed ineptly and insensitively. On August 14: “m

seem strange to a generation that grew up with stem

admonitions from Smokey Bear, but the Park Service refuses

to use words like ‘damage’ or ‘destruction,’ and instead

describes how the tires will rejuvenate aging park forests and

benefit wildlife” (Robbins 1988b, emphasis added). This

clearly implies deviant behavior (“strangeness” and the

“refusal” to use “reasonable” language). On September 11, in

the Times’ first front-page story about the tires: “(0)fficials

could not keep up with reports of areas threatened by the

blazes.” “Evacuations were so numerous it was hard for park

officials to keep track of them.” (Robbins 1988d). The

language here implies a park administration in disarray. On

that same day, the major local paper, the Billings Gazette,

had no trouble keeping track of the same evacuations.

September 22: “(Elven at the height of the fires, bulldozers

were allowed into the park only on a case by case basis”

(Egan 1988, emphasis added). The qualifying phrase tends to

cast doubt on the management policy.

When Democratic Presidential candidate Michael Dukakis

visited Yellowstone on September 15, the Times was the only

elite newspaper to include an observation alluding to the

Bambi myth that animals cope poorly with wildfire. The

account describes Dukakis reading a letter from a firefighter

received from a little girl who wrote, “I wish you could help

the animals” (Toner 1988).

The kinds of factual errors described above continued in the

second New York Times front-page story, published on

September 22 (Egan 1988). This story said that the

government had a policy of allowing all naturally-caused fires

in parks and wilderness areas to bum themselves out, and also

that the Forest Service has a pohcy of fighting a[1 fires in

National Forests. The story said, incorrectly, that Interior

Secretary Hodel had ordered on July 21 that a11 fires be

fought.

A September 14 New York Times editorial supported the

National Park Service by stating that the fires were not a

disaster, as Interior Secretary Hodel had said they were, but

helped perpetuate the myth that natural ecosystems arc static

rather than dynamic, and supported the notion that it might

have been possible to preserve Yellowstone forever as it was

before the tires. “Yetlowstonc may take years,” the editorial

said, “to grow back exactlv as it was” (emphasis added).

The first New York Times story about scientific aspects of [he

1988 wildfires (Malcolm 1988) was thoughtful and thorough,

although it was not published until the end of September when

the tires were largely under control. It contained interviews

with Yellowstone research biologist Don Despain, with

Cornell soil biologist Susan Riha, with tire-behavior expert

Richard Rothermel, and with wildfire historian Stephen Pyne.

Coverage in the Washington Post

Stories in the Washington Post tended to be less judgmental

than those in the New York Times, and tended to contain

fewer factual errors. The first non-wire story (O’Gara 1988a)

described fire as a positive influence on the forest, although it

also helped establish the myth that Old Faithful was

threatened by a “natural bum” fire when it attributed the

human-ignited North Fork fire (the only one that ever

threatened the Old Faithful tourist complex) to lightrung. The

second non-wire story (O’Gara 1988b) contained a reasonably

good description of the natural-bum philosophy that later

became controversial. The Post interviewed tire experts Don

Despain and Richard Rothermel two months earlier than the

New York Times (O’Gara 1988c). Unlike the New York

Times and the three television networks, the Post specifically

pointed out that the North Fork fire, which made the

September 7 run on Old Faithful, and which caused all but

one of the major evacuations in the park, was never subject to

the natural-bum policy (Reid and Peterson 1988).

Coverage in the Los Angeles Times

The east-coast newspapers framed the fires as being more

controversial than the Los Angeles Times. Although the New

York Times mentioned controversy about Yellowstone’s

natural-bum policy on August 10, and the Washington Post

first ran a story describing the controversy on August 9, the

Los Angeles Times did not allude to any controversy about

Yellowstone’s natural-burn policy until September 1, and then

only in an editorial endorsing the wisdom of that policy.

323
“Most of the complaints,” the editorial said, “have come from

a handful of landowners who have felt threatened by the

raging fires and from business owners on the periphery of

Ycllowstone who have suffered economic losses because of

the fall-off of tourism.” This frames the hres quite

differently from the September 22 New York Times story that

said the fires had led to unspecified but “widespread”

criticism of lhe government’s natural-bum policy (Egan

1988).

The Los Angeles Times carried a second editorial on

September 13 that said the “unwarranted criticism of the Park

Service, the U.S. Forest Service and environmental experts

has reached a level of misinformed hysteria that is racing out

of control, as the fires have done.” This was followed by two

op-ed columns supporting the scientific validity of the

natural-bum policy, published on September 17 and

September 26. On September 22, the Times car+& an article

that suggested officials were overreacting when they canceled

a planned prescribed burn in the Santa Monica Mountains

because of negative publicity about the Yellowstone fires

(Fuentcs 1988).

Stories in the Los Angeles Times were presented in a way

that interpreted the Yellowstone fires as more natural and less

alarming than stories in the eastern elite newspapers.

Yellowstone-area residents described in the New York Times

and Washington Post tended to be critics of Yellowstone’s tire

management efforts. One of the very few local residents

described in the Los Angeles Times, a merchant whose

business was given a 2Qercent chance of surviving one of

the fires, was framed more positively. Ralph Glidden was

quoted as saying “I’m trusting the professionals involved in

this will do what they can do” (Los Angeles Times 1988).

The Television Networks

Like the New York Times, and perhaps following the

example set by the Times, the three television networks

continued to suggest that tires were being allowed to bum in

Yellowstone long after that policy had been abandoned. The

last such story on ABC was broadcast on August 25. NBC

implied on September 6 that fires were still being allowed to

burn, and CBS did so on September 7. The biggest

difference in how the three networks framed the story was the

differing ways in which they selected interviews with local

residents and tourists. CBS and NBC focused on tourists and

residents who were critics of Yellowstone’s fiie management

policy, but ABC did not carry a single critical comment on

park policy by a local resident or tourist.

NBC and CBS lent credibility to the Bambi myth of animals

fleeing from the tires; ABC did not. CBS, for example,

implied large-scale fire-induced migration in a September 7

story that said some Yellowstone animals had been spotted 50

miles from their normal range. NBC twice focused on

324

pictures of animals that appeared either to bc fleeing the

flames (September 8) or to be confused by the thick smoke

(August 25). ABC specifically said that moose didn’t seem to

notice the tires (August 25), and showed elk calmly grazing at

Mammoth Hot Springs on September 9 as evacuation loomed.

The Yellow&one-Area Newspapers

Of the three daily newspapers in the Yellowstone area, one

(the Casper, WY Star Tribune) circulates primarily outside

the direct economic influence of Yellowstone Park. The other

two (the Billings, MT Gazette and the Bozeman, MT Daily

Chronicle), circulate heavily within the area directly affect&

by the Yellowstone tourist trade. Perhaps for that reason, the

Casper Star Tribune carried virtually no stories about the

effects of the Yellowstone fires on area businesses, while the

Gazette and Chronicle carried many such articles.

The Star Tribune framed the tires as more natural and less

disruptive than either of the Montana newspapers, and carried

several stories and a column about the ecological benefits of

the fires. The Bozeman Daily Chronicle adopted a relatively

calm tone in describing the Iires, but virtually ignored the

scientific perspective about fire’s biological role. The Billings

Gazette carried far more stories about the fires than either of

the other papers, and published many thoughtful and

well-reported articles, especially those reported by Robert

Ekey. But the Gazette also published many letters containing

sharp attacks against the National Park Service and against

specific officials of Yellowstone National Park, and published

an editorial cartoon that ridiculed Yellowstone superintendent

Robert Barbee An August 29 Gazette editorial said “This

fiasco is riddled with questions, and it‘s not too late for

Congress to demand to know why Barbee blindly rode a dead

policy into hell.” A September 11 editorial called for the

tiring not only of Superintendent Barbee, but also of the

Director of the National Park Service and the Secretary of the

Interior.

Coverage of the Natural Burn Policy

Because virtually all of the controversy that made the

Yellowstone fires newsworthy centered around the policy that

initially allowed many lightning-ignited fires to bum

monitored but unsuppressed, it would have been reasonable to

expect detailed articles about that policy’s origins. Although

most news organizations paid lip service to explaining the

policy by explaining the role of fire in “cleansing” or

“renewing” the forest, I was unable to locate a single article

on the news pages of any of the newspapers published in

1988, or a single story in any of the evening network

newscasts broadcast in 1988, that specifically mentioned the

Leopold Report (Leopold 1963) that formed the philosophical

foundation for the prescribed natural-fire policy. The

Leopold Report was mentioned only once in all of the stories,

in a December 11 New York Times Magazine article by Peter

Matthiessen.
DISCUSSION

The New York Times and two of the three television

networks lent considerable credence to the interpretation of

the Yellowstone fires favored by local merchants and their

elected representatives (including senators Wallop and

Simpson of Wyoming and Baucus of Montana). This

interpretation suggested that the National Park Service

handled the fires ineptly. This reinforces findings by Molotch

and Lester (1974, 1975), who predicted that business interests

and federal officials would have more power to define the

context in which the news media interpreted the tires than

would environmentalists, scientists, or Yellowstone officials.

However, the Washington Post and ABC television news

framed the fires more neutrally, and the Los Angeles Times

interpreted them as natural and as a somewhat positive event.

Myths About the Fires

For the purposes of this paper, there are two kinds of myths

that help us define and explain features of the external world

about which we have insufficient or incorrect knowledge.

The first sort of myth is usually based on inadequate or

inaccurate information, such as the idea inspired by the

Disney film Bambi that animals flee in terror from forest

fires. The second form of myth rises out of our effort to

understand events that contradict cultural assumptions. For

example, often assumed is that modem technology can

extinguish forest tires. If the fires in Yellowstone are still

burning, the reasoning goes, there must be some kind of

conspiracy to mislead the public about tire suppression

efforts. This myth probably gained credibility because of the

initial policy not to suppress some of the naturally ignited

fires.

The news media helped foster several myths about the

Yellowstone tires. The most widely disseminated myth was

that many of the fires were allowed to bum unsuppressed

throughout August and into September. The New York

Times and the three television networks also helped spread

the myth that the most newsworthy of the tires, which was

apparently started by a woodcutter’s cigarette, spread because

of the park’s natural-bum policy. The North Fork tire was

fought with available resources from the day it started.

By quoting park critics and tourists who lamented the

fire-induced changes in Yellowstone (‘*it won’t be the same

for a hundred years”), many media accounts supported the

idea that Yellowstone is a static rather than dynamic

ecosystem, and that it could be managed like a city park in

which burned trees can be replaced by planting new ones, and

in which elk can escape mortality if only they are provided

with enough supplemental food. To a large degree, reporters

failed to understand (or at least to communicate) the dynamic

forces that shaped the way Yellowstone looked bcforc the

1988 tires.

Another myth, which has deep roots in the technological

orientation of our culture, persisted despite minimal support

from the media. This myth, that humans have the technology

to control all wildfires, was regularly debunked by news

accounts quoting firefighters and other officials who said only

a change in the weather would put the fires out. This myth

flourished in spite of the media.

The mythological way the media interpreted the fires is

apparent in the fact that Old Faithful geyser was featured in

about a quarter of all the stories in the elite press and on

national television newscasts, despite the fact that only a small

fraction of those stories dealt with the single day on which a

fire actually made a run on the geyser. Other prominent

Yellowstone features, such as Mammoth Hot Springs,

Yellowstone Lake, and Ycllowstone Falls, were seldom

mentioned. A person not familiar with the park could easily

have gotten the impression that Old Faithful Geyser was the

only real attraction in the park, and that virtually all of the

Yetlowstone firefighting efforts in 1988 were part of a

massive effort to save the geyser from destruction.

News as a Curriculum

Media scholar James W. Carey (1986) believes it is

“unforgivably self-righteous” to criticize daily news accounts

because they often fail to put news events into a perspective

that explains how they happened and what they mean. He

says news is a curriculum, and that it is unfair to expect the

initial reports of any event to provide complete information

about what happened. Considering the short deadlines under

which daily journalists must operate, this perspective has

some merit. But it does not explain why some interpretations

of events are more likely than others, and does not explain

why a major newspaper like the New York Times consistently

failed to report that all Yellowstone fire were being fought.

All of the media organizations studied here published or

broadcast thoughtful reports and analyses of the Yellowstone

fires after they were brought under control in 1988, and all of

the organizations continued to follow the story in 1989.

Although these analyses were less prominently displayed than

the initial dramatic stories about the tire’s various runs, the

persistent media consumer was eventually able to get a

balanced picture of the fires, especially if she or he

supplemented ordinary news sources with specialized

magazines such as Audubon and Smithsonian. Media

consumers without that kind of dedication, however, were

likely to be misled by the high visibility of the stories that

characterized the initial coverage. The panels of experts who

evaluated all of the 1988 evening television stories about the

Yellowstone fires rated the stories durjng the peak coverage

period, when the fires got top-of-the-show coverage, as

significantly less accurate than the stories that appeared earlier

or later (two-tail t-test, p (0.001).

325
The lesson here is that the initial news coverage of any

unanticipated natural event, such as the 1988 Yellowstone

fires, is likely to contain many flaws. It may be unrealistic

and even uncharitable to expect journalists to do a better job,

but as long as the public has confidence in the news media,

these shortcomings will continue to mislead newspaper

readers and television viewers. These misinformed media

consumers may support land-management decisions that are

based on interpretations of events provided by special interests

rather than on scientific research or long-term management

goals.

ACKNOWLEDGMENTS

Major support for this study was provided through a summer

research appointment from Ycllowstone National Park.

Additional support was provided by a Small Faculty Grant

from the Office of Research and Graduate Studies at The

Ohio State University.

LITERATURE CITED

Altheide, David L. 1976. Creating reality: how TV news

distorts events. Beverly Hills, CA: Sage. 220 pp.

Carey, James W. 1986. Why and how: the dark continent of

American journalism. In Manoff, Robert Karl; Schudson,

Michael Robert, eds. Reading the News. New York:

Pantheon. pp. 146-196.

Christensen, Norman L., Chairman, Greater Yellowstone

Postfire Ecological Workshop. 1989. Ecological

consequences of the 1988 fires in the greater Yellowstone

area. Final report, no place of publication. 58 pp.

Egan, Timothy. 1988. Ethic of protecting the land

fueled Yellowstone tires. New York Times (September

22): A.l.

Fuentes, Gabe. 1988. Jittery officials cancel 150~acre agora

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Evening News, NBC Nightly News, Newsweek and Time.

New York: Vintage Books. 393 pp.

Gitlin, Todd. 1980. The whole world is watching: mass

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Berkeley, CA: University of California Press. 327 pp

Leopold, Starker. 1963. A vignette of primitive America

Sierra Club Bulletin (March): 4-1 1.

Los Angeles Times. 1988. High winds feared: tires threaten

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Malcolm, Andrew H. 1988. In ashes of burned forests, a

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Molotch, Harvey; Lester, Marilyn. 1974. News as

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235-260.

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Lightning-sparked blaze backs away from Old Faithful.

Washington Post (July 27): A.3.

O’Gara, Geoffrey. 1988b. New fires to be fought at

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O’Gara, Geoffrey. 1988~. Firelighters’ fears realized as

Yellowstone blazes force evacuations. Washington Post

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326
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321
THE EVOLUTION OF NATIONAL PARK SERVICE FIRE POLICY

Jan W. van Wagtendonk’

Abstract-National Park Service policies concerning tire have changed over the years from no policy 8 1 all

in the early years, through years of absolute fire suppression, to a period of experimentation and relinemcnt

with a full spectrum of intcgratcd lire management strategies. During much of this time, the Service was

influcnccd by o~hcr agencies and organizations but is now emerging as a leader in the lire community.

Fire politics in tflc National Parks have evolved from no

managcmcnt at all, through the full suppression of all lircs, to

1hc sophisticated application of scientifically based lire

mattafcmcnt strategies. When Yoscmitc was set aside as a

Stale rcscrvc in 1864 and Ycllowstonc as a national Park in

1872, 1bcrc wax no efforts to control lircs. An era of full

fire suppression began when managcmcnt of Ycllowstone

pas~cci to lhc U.S. Army in 1886 and to the National Park

Scrvicc in 19 16. Expcrimcnhtl prcscribcd burning was first

conducted in Evcrgladcs N&n31 Park in 19.51. The Leopold

Ropofl (1963) influenced tbc Park Scrvicc to rccvaluatc its

fire politics. Revisions to the politics coml>lctcd in 1968

pcrmittcd the USC of lirc as a management tool and led to the

creation of the lirst wildcrncss lirc manngcmcnt Program, in

Sequoia and Kings Canyon National Parks. To data, more

LIltin 1_,000 lightning iircs have been allowed to bum under

carefully monitored conditions in 46 Parks, and more than

1,000 prcscrihcd bums have hscn set in 58 parks to meet

mtlna~smcnt objcctivcs. The Ycllowstonc lircs in 1988 led t0

an cxaminalion of Scrvicc fire policy which affirmed current

policy but rccommcndcd rcfincmcnts in imi~lcmcntation.

TIfE ERA OF FIRE SUPPRESSION

In 1863, Prcsi&ttI Lincoln set asi& Yoscmitc Valley and the

Msript>sa Grove of sequoias as a State reserve. This was the

first l&jcra] govcrnmcnt action specifically designating an area

for prcscrvalion and is cons&red by many to mark the

beginning of the national Park idea. Although the native

Americans who occupied the Yoscmitc region had at least

4,000 years (Riley 1987) used ftrc for many cuhutal

purposes, it is doubtful that they practiced any fire

sttpprcssion. Early Euro-American scttlcrs in the Yosemite

region used lirc to clear land and to improve grazing for

sl~cp and ca11l~‘. Their only fire suppression efforts were

dircctcd toward protecting structures. The State reserVe

cn~ploycd only one guardian, who had little lime to fight

lircs.

Ycllowstonc and Yoscmitc wcrc dcsigt1:itcd as national Parks

in 1873 and 1890.Howcvrr. no agency was assigned

responsibility for their administration and their new status did

not result in 1lle implcmcntation of fire management.

Although 1hcre no fire management policies or activilies

during those early years, tht: stage was set for the beginnings

of fire suppression.

‘Rcscarcb Scisntist, National Park Service, Yosemite National Park,

El Parlal, CA.

328

The Army Years

‘lhc United States Army was assigned the responsibility for

managing Ycllowstone in 1886 and Yosemite and Sequoia in

1891. The Policy of suppressing all fires began in

Ycllowstonc in 1886 (Agcc 1974) and was soon followed by

&n&r politics in the other two parks. The Army built

cx[cnsivc trail systems to facilitate patrolling the new parks

for sheep and timber trespass and for wildfires. As new

parks wcrc cstablishcd, the Army assumed control and

dispatched the troops to extinguish all tires. Although there

arc few records of the Army’s efforts, fire scats were formed

less frcqucrnly during this period (Kilgorc and Taylor 1979).

This could be jnterprctcd to mean cithcr that there were very

few lircs or that the Army was very successful in

extinguishing those that did occur.

The Years of Forest Service Influence

When the National Park Service was cstablishcd in the U. S.

Dcpartmcnt of the Interior in 1916, administration of the

Parks passed into civilian hands. Many of the personnel who

had previously scrvcd in the Army switched uniforms and

became the first park rangers. Although they carried with

them the lessons and experience of fire suppression, they had

little formal training. Professional guidance of the fire

program came from the Forc8I Service in the U. S.

Department of Agriculture (Pyne 1982). Established as a

separate agency in 1901, the Forest Service had developed

both a thcorctical basis for systematic fire protection and

considorablc cxpertisc in executing that theory. The

suppression of all lircs became the official policy of the new

National Park Service.

Since many of the Parks established during this period were

originally parts of national forests, the Park Service inherited

an infrastructure of lirc control facilities and equipment. Fire

stations, lookouts, and trails were already in place. In

addition, many of the new Park rangers came from the Forest

Service and had forestry and fire backgrounds (Pyne 1982).

The Forest Service and the Park Service joined together to

fotm the Forest Protection Board, which advised agencies on

rtrc policy and standards.

Although the Park Service developed a separate fire control

organization, it relied heavily on the Forest Service for

expertise, personnel, and equipment. Mutual-aid agreements

allowed the two agencies to respond to fire8 across boundaries
and to share training and dispatching facilities. In most casts,

however, the exchange was in the direction of the fledgling

Park Service.

The CCC Yea-s

Professional fire protection began in the Park Service with the

eslablishmcnt of the Civilian Conservation Corps in 1933. A

massive influx of personnel made it possible to expand

fircfighting facilities and deploy suppression forces throughout

lhc parks. During the first 10 years, the program went from

a single national fire officer, a special crew at Glacier

National Park, and a fire guard at Sequoia to an organization

of some 6.50 camps with OVCr 7,000 employees (Pync 1982).

The Park Service’s fire policy was still identical with that of

the Forest Service, which in 1935 adop(cd a policy of

extinguishing any fire during the first burning period or, if

that were not possible, by IO:00 a. m. the following day.

Strict adhcrcnce to this policy required quick response time

and numerous crews. Efforts were also dircctcd toward

developing better access to further rcducc rcsponsc times.

During this period, lhc Park Scrvicc greatly profcssionalizcd

its approach to fire protcclion. Vcjictation and mei hazard

maps were prcparcd from licld surveys and rcsponsc zones

wcrc dclincalcd. Complctc tire records were kept; each tire’s

cause and behavior wcrc dcscribcd, and the mcasurcs

ncccssary to control each fire Were detailed. These records

did &scribe occasional largc fires that might have cxcccdcd

the capabililics 0 f 11X sitpprcssion forces.

The War and Postwar Ye:m

World War II caused a dcclinc in lirc prolcction throughout

the llnlion. Sk&ton ucws were kept on to prolccl resources

ncccssary for the war c~fort. Park Scrvicc: crews wcrc

practically noncxislcnl, although LIE tine records show that

fires were still being supprcsscd strcccssftIlly.

Dcmobilizalion a& lhc war brought a new and diffcrcnt kind

01’ inllttx to the fire lighting agcnclcs. Although the Forest

Service bad used bulldozers and smokcjumpcrs bcforc the

war, aitplancs, hclicoptcrs, tanks, and parachutes wcrc

products that the war had rcftn&i that W~fc now available to

figIll the wat against lirc. Retardant drops, hcliattack crows,

bulldozers, and smokcjumpcrs bccamc the new tools of choice

(USDA Forest Scrvicc 1960). The Park Sctvicc relied

]lcavily on the Forest Scrvicc for this new technology, and

shnrcd support of aircraft and a smokcjutnpcr hasc at

Ycllowsto~~c (Pync 1981). The rcsttlling fire-fighting force

was very cffcclive in continuing 1111: policy of full ftre

suppression.

TIIE ERA OF FIRD MANAGE~IENT

The cffcclivcncss of lirc prolcction w:is psrlly responsible fat

the hcginnings of a shift in policy from lirc control to lirc

man:lgcmcnt. As had long l-teen rccognizcd in lhc South, lhc

absence of fire from an ecosystem that has evolved with fire

can lead to unexpected, and often undesirable, results.

Specifically, researchers found that periodic fires reduced

accumulations of woody and brushy fuels and thinned thick

undcrstorics of shade-tolerant species. Without tire, species

composition shificd and fuel accumulations increased.

The Years of Revelation

Although the National Park Scrvicc’s first experiments with

lhc USC of fire occurred in Bvcrglades National Park in 1951

(Robertson I%?), impetus for a change in policy came later

from outside rcscarchcts in California As early as 1959, Dr.

Harold H. Biswell. of the University of California at

Berkeley, advocated the use of prescribed fires to reduce the

accumulation of debris underneath pondcrosa pine stands in

the Sierra Nevada of California (B&well 1959). His work

was expanded upon by Dr. Richard Hartesvclt, from San Jose

State University, who concluded that the greatest threat to the

giant sequoia groves was not trampling by humans, but was

catastrophic fire burning through understory lhickcts and

unnaturally high accumulations of (Harlcsvcll 1962).

In IgQ, the Sccrctary of the lntcrior asked a committee to

look into wildlife manngcmcnt concerns in the national parks.

This commiltcc, named a&cr its chair, Dr. A. Starker

Leopold, did not confine its report to wildlife, but took a

broader ecological view that parks should be managed as

ecosystems (Leopold and others 1963). They recommended

that the biotic associations within a park be maintained or

rccrcatcd as nearly as possible in the condition that prevailed

when first visited by Euro-Americans. The report stated in an

oflcn quolcd passage:

When the forty-nincrs poured over lhc Sierra Nevada

into California, those that kept diaries spoke almost to

a man of the wide-spaced columns of mature lrccs that

grew on the lower wcstcrn sloRc in gigantic

magnificsncc. The ground was a grass parkland, in

springtime carp&cd with wildflowers. Deer and bears

were abundant. Today much of lhe w& sIope is a

dog-hair lhickct of young pines, white fir, incense

cedar, and mature brush a direct function of

ovcrprotcclion from natural ground fires. Within the

four national parks . Lasscn, Yoscmitc, Sequoia, and

Kings Canyon the thickets arc cvcn more

impcnctrable than elscwhcrc. Not only is this

accumulation of l&l dangerous to the giant sequoias

and other m:lturr: trees but Ihc animal lift is meager,

wildflowers are sparse, and to some at least the

vcgclation tangle is dcprcssing, not uplifting. Is it

possible that the primitive open forest could be

rcstorcd, at Icast on 3 local scale’? And if so, how?

(Leopold and others 1963)

It was not a coincidcncc that Dr. Lc~p~lcl’s office was just

across the street from Dr. Biswcll’s oflice. In fact, these

Ecnllctncn oflcn discussed the ccologicai ramifications of fire

exclusion over lunch and during seminars. Nor is it

329
surprising that their graduate students would pursue firerelated Ph.D. dissertation topics and become Park Service

scientists (Kilgore 1968; van Wagtcndonk 1972; Age 1973;

Graber 1981). The intellectual atmosphere at Berkeley

invited students to challenge conventional approaches and

practices.

The Turning Point

Only in 1968, aRer several false starts was the Leopold

Committee report incorporated into policy. First the

Secretary of the Interior had to find out whether or not the

report’s findings were acceptable to the public. A department

underling was sent to the m&ing where the report was being

presented and found it to be overwhelmingly supported The

Park Service was then directed to incorporate the report into

its management politics. The entire report was included as

an appendix and the section on fire management revised to

reflect the new thinking (USDI National Park Service 1968).

For the first time since 1916, the Park Scrvicc viewed fire as

a natural process rather than as a menace:

The prcscnce or absence of natural fire within a given

habitat is recognized as one of the ecological factors

contributing to the perpetuation of plants and animals

to that habitat.

Fires in vcgctation resulting from natural causes are

rcco@cd as natural phenomena and may be allowed

to run their course when such burning can be

contained within prcdctermined fire management units

and when such burning will contribute to the

accomplishment of approved vegetation and/or

wild/and managcmcnt objectives.

Prescribed burning to achieve approved vegetation

and/or wildland objcctivcs may be employed as a

substitute for natural fire (USDI National Park Service

1968).

The Years of Experimentation

As is oken the case with the National Park Service, a policy

change Icd to cxpcrimcntation. A prescribed natural fire

program was initiated in Sequoia and Kings Canyon National

Parks in 1968 (Kilgore and Brig@ 197?), as were concurrent

research studies of prescribed bums (Kilgorc 1971; Parsons

1976). At Yosemite National Park a similar prescribed

natural fire program was started in 1972 (van Wagtcndonk

1978), and research conccntratcd on relining tccbniyues for

prcscribcd burning (van Wagtcndonk 1974; van Wagtcndonk

and Botti 1983). Experimental bums were ignited in several

parks, and Ycllowstone and a few other parks established

prescribed natural fire zones (Romme and Dcspain 1989).

The Years of’ Policy Refinement

As cxpcricncc with both prcscribcd burning and prescribed

natural fire programs increased, inlcrim guidelines were

issued. Rcscarch also continued to contribute to the growing

body of knowlcdgc on both fire CCOlOgy and fire USC.

Contrary to Pyne’s (1982) assertion, the National Park

Service was a leader in the development of prescribed natural

fire techniques. Although National Park Service personnel

coopcrated with Forest Service managers and researchers in

the same field, they did not need to look to the Forest Service

for leadership.

The first revision of the 1968 fire policy came out in 1978

when all management policies for the National Park Service

were rewritten (USDI National Park Service 1978). The

policy staled:

Fire is a powerful phenomenon with the potential to

drastically alter the vegetative cover of any park.

The prcscnce or absence of natural fires within a

given ecosystem is recognized as a potent factor

stimulating, retarding or eliminating various

components of the ecosystem. Most natural &res am

lightningcaused and arc recognized as natural

phenomena which must be permitted to continue to

influence the ecosystem if truly natural systems am to

be pcyctuated.

Management fires, including both prescribed natural

fires and prescribed bums, arc those which contribute

to the attainment of the management objectives of the

park through execution of predetermined prescriptions

defined in detail in the Fire Management Plan, a

portion of the approved Natural Resources

Management Plan.

All fires not classed as management fires am

“wildfires” and will bc suPpressed. (USDI National

Park Set-vice 1978)

The policy further described the conditions under which fire

could be used and specified that any management fire would

be suppressed if it posed a threat to human life, cultural

resources, physical facilities, or thrcatcncd or endangered

species or if it thrcatencd lo escape f?om prcdctcrmincd

zones, or to exceed the prescription.

The Forest Service was also revising its fire policy to

embrace fire management rather than fire control (DeBruin

1974). In 1978 it abandoned the IO:00 a. m. policy in favor

of a new one that encouraged the USC of fire by prescription.

The Forcsl Scrvicc’s policy was also preccdcd by

expcrimcntation and research.

Thus, afier a period of 10 years, policies of both the National

Park Scrvicc and the Forest Scrvicc recognized the ecological

role of fire and provided for its use. Pyne (1982) states,

“Guided by the dazzling philosophy of the Leopold Report,

the Park Service had advanced a policy too far ahead of its

knowledge and technical skills; the Forest Service, with

expertise and information in abundance, lagged in policy.”

While not entirely cot-r&, his slatcment does point out the

distinctive and syncrgislic roles the two agcncics play.

330
in 1986, the Wildland Fire Management Guideline (NPS-18)

was issued. It outlined in &tail the procedures and standards

to be used to manage wildfires, prescribed natural fires, and

prcscrihcd burns (USDI National Park Setice 1986). With

regard to prescribed natural fires, the new guideline spccificd

that the condition limits under which naturally Ignited fires

would be permitted to bum must be clcariy stated. In

addition, the ultimate size and boundarics of the lires must be

preplanned and stated. Parks were also required to monitor

each fire and to assess each burning day whclher or not the

fire should he allowed to conlinuc to burn unimpeded.

Although there were no apparcnl problems with the Park

Service’s fire policies, they were revised again in March of

1988 as patI of a lo-year comprchcnsivc rcvicw of the

managcmcnt policies (USDI National Park Scrvicc 1988).

The new policy cmphasizcs rnanaycmcnt objectives and plans:

Fire is a powerful phcnorncnon with the potential to

drastically alter the vegctalivc cover of any park. Fire

may contribute to or hinder the achicvcmcnt of park

objectives. Park fire managcmcnt programs will be

dcsigncd around rcsourcc management ot?jcctivcs and

Ihc various managcmcnt zones of the park. Firerclatcd management objcctivcs will bc clearly stated in

a lirc managcmcnt plan, which is prcparcd for each

park with vegetation capable of burning, to guide a

fire managcmcnt program that is rcs~~onsivc to park

needs.

All fires in parks arc classifrcd as either prescribed

lircs or wildfires. Prescribed fires include fires

dclibcratcly set by managers (prcscribcd bums) or

tires of natural origins permitted to burn under

prcscrihcd conditions (prcscrihcd natural fires) to

achicvc predetermined resource managcmcnt

ohjcctivcs. To ensure that these ohjcctivcs are met,

each prescribed fire will he conducted according to a

written prcsctiplion. All lircs that do not meet the

criteria for prescribed fires arc wildfires and will he

suppressed. (USDI National Park Scrvicc 1988)

THE POST-YELLOWSTONE ERA

The f&s of the Greater Yellowstone Area during the summer

of 1988 brought fire policies of the National Park Service and

the Forest Service under CiOSe scrutiny. The Sccrctary of

Agriculture and the Secretary of the Interior appointed an

inlcragcncy fire management policy rcvicw team to investigate

the adequacy of national policies and their application for lire

managcmcnt actions in national parks and wilderness and to

recommend actions to address the problems cxpcricnccd

during the 1988 fire season. With regard to policy, the

review team rccommcnded that:

Prescribed fire policies be rcaflirmcd and

strcngthcned.

Fire management plans be reviewed to assure that

current policy rcquircments are met and expanded to

include interagency planning, stronger prescriptions,

and additional decision criteria. (USDA and USDI

19891

A moratorium was placed on all prescribed natural fire

programs until the agencies had complied with the

recommendations of the review team. Although the National

Park Service policies were dctcrmincd to be adequate,

implementation guidelines and fire management plans were

found to bc in need of revision.

A task force was convened to rcwt-ite NPS-18, the fire

management guideline. The guideline was completely

rcwrittcn and addressed all of the operational

recommendations of the rcvicw team report (USDI National

Park Service 1990). Specifically, it requires approved tire

management plans, established contingency plans, quantified

prescriptions, monitoring procedures, fire situation analyses,

and daily ceflificalion by the line manager that resources are

available to manage the fire within the prescription. In

addition, the prescription must include at least one indicator

of drought and at Icast one definition of the maximum

prcscribcd extent of the fire.

All the existing fire managcmcnt plans were reviewed by

teams of fire specialists from throughout the Park Service for

compliance with the rcvicw team report and for adequacy of

cnvironmcntaf documentation and public participation. Pians

were sent back to the parks for revision. To date, three fin:

managcmcnt plans have been approved Prescribed natural

fire programs will bc in effect in 1990 for Yosemite,

Voyagers, and Sequoia and Kings Canyon National Parks.

National Park Service fire policies have evolved in a pattern

of leaps forward followed by cxpcrimcntation and refincmcnt.

The dcccntralizcd nature of the agency allows it to take

advantage of new philosophical i&as and translate them into

policy. The experience and expertise within the Service

assures that it will co&UC to play that role.

LJTERATURE CITED

Agee, James K. Prescribed fire effects on physical and

hydrologic prOpehX of mixed conifer forest floor and

soil. Bcrkcley, CA: University of California; 1973. 57 p.

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Agcc, James IL Environmental impacts from fire management

alternatives. San Francisco, CA: U.S. Department of the

Interior, National Park Service, Western Regional Office;

1974. 92 p.

Biswcll, Harold H. Man and fire in ponderosa pine in the

Sierra Nevada of California. Sierra Club Bulletin. 44(7):

44-53: 19.59.

331
DcBruin, HC~JY W. From fire control to life management: a

major policy change in the Forest Service. In:

Proceedings 14th Tall Timbers fire ecology confcrcncc;

1974 [date unknown]; Missoula, MT. Tallahassee, FL:

Tall Timbers Research Station; 1974: I1 -17.

Graber, David M. Ecology and managcmcnt of black bears in

Yosemite National Park. Bcrkclcy, CA: University of

California; 1981. 206 p. Ph.D. dissertation.

Haficsvclt, Richard J. Effects of human impact upon ,$.?qUOi&

eigantca and its environment in the Mariposa Grove,

Yosemite National Park, California. Ann Arbor, MI:

University of Michigan; 1962. 310 p. Ph.D. dissertation.

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Kilgorc, Bruce M. The role of fix in managing red fir

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and natural ESOWCeS confcrcncc; 1971 May 7-10;

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Kilgorc, Bruce M.; Briggs, George S. Restoring iire to high

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mixed conifer forest. Ecology. 60(l): 129-142; 1979.

Leopold, A. Starker; Cain, Stanley A.; Coltam, Clarence M.;

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Parsons, David J. The role of tire in nahxal communities: an

example from the southern Sierra Nevada, California.

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Robertson, William B. Fire and vegetation in the Everglades.

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332

Rommc, William H.; Dcspain, Don C. The Yellowstone

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parks and national monuments of scientific significance.

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U.S. Department of the Interior, National Park Service

Wiidland fire managcmcnt guideline: NPS-18

Washington, DC: U.S. Department of the Interior,

National Park Service; 1986. 22 chap., 8 appcn.

U.S. Dcpartmcnt of the Interior, National Park Service.

Managcmcnt policies. Washington, DC: U.S. Department

of the Interior, National Park Service; 1988. 1 1 chap.

U.S. Department of the Interior, National Park Service.

Wildland fire management guideline: NPS-18

Washington, DC: U.S. Department of the Interior,

National Park Service; 1990. 22 chap., 8 appcn.

van Wagtendonk, Jan W. Fire and fuel relationships in

Yoscmitc National Park. Berkeley, CA: University of

California; 1972. 163 p. Ph.D. dissertation.

van Wagtcndonk, Jan W. Refined burning prescriptions for

Yosemite National Park. Occasional Paper 2. Washington,

DC: U.S. Department of the Interior, National Park

Service; 1974. 21 p.

van Wagtcndonk, Jan W. Wilderness Fire Management in

Yosemite National Park. In: Schofield, Edmund A.,

editor. EARTHCARE: Global protection of natural areas:

Proceedings of the 14th biennial wilderness conference;

1975 June 5-8; New York. Boulder, CO: Wcstview Press;

1978: 324-335.

van Wagtendonk, Jan W.; Botti, Stephen J. Modeling

behavior of prescribed fires in Yosemite National Park

Journal of Forestry. 82(8): 479-484; 1984.
POSTER SESSION
SHELTER AREAS

hermel & Mutch 1986)

I

Figure I.--Fire progress map for the Butte Fire, Salmon

National Forest, central Idaho, August 28-29, 1985 (after

Rothemel and Mutch 1986).

334
THE 1985 BUTTE FIRE IN CENTRAL IDAHO:

A CANADIAN PERSPECTIVE ON THE ASSOCIATED

BURNING CONDITIONS

Martin E. Alexander’

Abstract-During the aRemoon of August 29, 1985, the Butte Fire made a high-intensity crown tire run,

covering a distance of 2.22 km in one hour and 40 minutes, and forcing 73 tire fighters to deploy their

protective tire shelters. This paper presents a retrospective analysis of the fire behavior in terms of the two

major subsystems of the Canadian Forest Fire Danger Rating System. The fuel moisture codes (FFMC

94.6, DMC 172, DC 744) and tire behavior indexes (IS1 22.5, BUI 218, FWI 65) of the Canadian Forest

Fire Weather Index System were indicative of extreme fire behavior and ignition potential. The predictions

of headfire rate of spread (24.6 m/min or 1.48 km/h) and intensity (43,320 kW/m) based on the Canadian

Forest Fire Behavior Prediction System were remarkably close to the observed tire behavior characteristics.

INTRODUCTION

The Butte Fire occurred on the Salmon National Forest

toward the end of the 1985 fire St%SOn in central Idaho.

Seventy-three fire fighters were forced to deploy their

protective survival shelters in preestablished safety zones

when the fire made a major run during the afternoon of

August 39 (Mutch and Rothcrmel 1986). Fortunately, no one

was seriously injured. As a result of this incident, the Butte

Fire has attained a considerable degree of notoriety in the

United States. Several published accounts of the fire’s

behavior (Aronovitch 1989; Mulch and Rothennel 1986;

Rothcrmel 1991; Rothermel and Gorski 1987; Rothermel

and Mutch 1986; Wctih and Ochoa 1990) and the shelter

deployment (Jukkala and Putnam 1986; Turbak 1986) have

already appeared, and there is a 33-minute videotape featuring

interviews with those involved and photos taken during the

episode (National Wildfire Coordinating Group 1989). Since

a great deal of American information on wildland ljre

behavior finds its way into Canada, some means of relating it

to Canadian conditions is often desirable. Thus, this paper

offers a hindsight analysis of the Butte Fire in terms of the

two primary subsystems of the Canadian Forest Fire Danger

Rating System (CFFDRS) (Stocks and others 1989).

Emphasis is placed on the documentation of fuel moisture

codes and fire behavior indexes of the Canadian Forest Fire

Weather Index System and the quantitative prediction of

forward rate of spread and tiontal intensity based on the

Canadian Forest Fire Behavior Prediction System. Some

familiarity with the CFFDRS on the part of the reader is

presumed.

‘Fire Research Officer, Forestry Canada, Northwest Region, Northern

Forestry Centrc, 5320-122 Street, Edmonton, AB ‘I’6H 3S5; at the

time this paper was prepared the author was Visiting Fire Researcher,

National Bushfire Research Unit, CSIRO Division of Forestry and

Forest Products, and Ph.D. Scholar, Department of Forestry,

Australian National University, Canberra, ACT.

Table I.--Analysis of spread rates associated with

the major run of the Butte Fire on August 29, 1985

(after Rothermel and Mutch 1986).

Tim Elapsed Forward spread Headf ire

interval time distance Rate of Snread-.,

(hours MDT) (min) Cm) (m/min) Mm

1436- 1530 6 6 515 8.6 0.52

536- 1550 2 0 772 38.6 2.32

550-1555 5 467 93.4 5.66

I 555 1600 5 225 45.0 2.70

1660- 1610 10 241 24.1 1.45

--.-------...._-----*.-------.-..---------.-.-..-.-..-

1430-1610 100 2,220 22.2 1.33

OBSERVED FIRE: BE~WOR

The Butte Fire was started by lightning on July 20, 1985. By

the afternoon of August 29 approximately 10,500 ha had been

burned over and the northern perimeter of the fire was

uncontaincd (fig. 1). On August 29 the Butte Fire made a

forward advance of about 2,220 m between 1430 and 1610

hours Mountain Daylight Time (MDT) (table 1). This

hanslates into an average headfire rate of spread (ROS) of

22.2 m/min or 1.33 km/h for the lo&minute run. For short

time intervals, the main fire front travekd considerably

faster. The maximum observed headfire ROS was 93.4

m/min or 5.6 km/h. The convection column associated with

the major run (fig. 2a) was characterized by dense, black

smoke and eventually reached an estimated height of nearly

5,000 m above the ground surface. The behavior exhibited

by the Butte Fire on the afternoon of August 29 represents a

classical case of a high-intensity crown fire event. Flames

were observed to stand nearly vertical and greatly exceeded

the height of the forest in which the tire was spreading (figs.

2b and 2~). A photograph taken from one of the shelter sites

around 15.50 hours MDT, about 30 minutes before the arrival

335
a

of the active flame front, has been reproduced on the cover of

Fire Management Notes Volume 46, issue Number 4 in 1986,

and certainly attests to the severity of the tire behavior during

the major run.

THE FIRE ENVIRONMENT

The fire environment is defined as “the surrounding

conditions, influences, and modifying forces of topography,

fuel and fire weather that determines tire behavior” (Merrill

and Alexander 1987). The fire environment concept

(Countryman 1972) as applied to the Butte Fire is described

in the following sections.

b

Figure 2.-- (a) convection column development over the Butte

Fire at about 1520 hours MDT on August 29, 1985. (b & c)

views of flame front approaching shelter areas (latter photo

taken at about 1605 hours MDT). All photos reproduced

from 35 mm slides taken by L. Duncan, USDA Forest

Service.

Fuels

Forest cover types in the area of the major run consisted of

Engelmann spruce (Picea enaelmanii) - subalpine fir (Abies

lasiocarpa) associations in the drainage bottoms and lodgepole

pine (Pinus contorta) - subalpine lir stands at higher

elevations (Steele and others 1981). The average tree height

was considered to be about 18 m (Rothermel 1990) to 23 m

(Patten 1990). Surface fuel loads (i.e., downed dead woody

and forest floor materials) ranged from about 180 to 225 t/ha

in the lower canyon slopes to about 55 to 90 t/ha in the

midslope to upper slope areas (Rothermel and Mulch 1986).

These figures appear quite reasonable in comparison to other

areas in the Northern Rocky Mountains (Brown and Bevins

1986; Brown and See 1981; Fischer 1981). The forest floor

depth varied from 2.5 to 10 cm (Patten 1990). Most of the

tire area could be categorized by tire behavior fuel models 8

(closed timber litter) and 10 (timber-litter and understory) as

described by Anderson (1982).

Topography

The general aspect of the fire area was southerly (fig. 2a).

The tire swept up a well-defined north-south drainage that

became progressively steeper near the shelter sites.

Elevations from the start to the termination of the major run

of the fire varied from 2,146 m to 2,341 m above mean sea

level (MSL) (fig. 3). This vertical rise of 195 m coupled

with the horizontal distance represents an average terrain

slope of 9 percent (fig. 3). One unusual feature of the

topography in the tire area was the dome-like nature of the

upper slopes with continuous forest canopy cover.

Weather

In the spring of 1985, snow-free cover in the tire area

probably occurred in early May (Finklin 1988, 1989). The

area normally receives about 200 mm of precipitation between

early May and late August according to data presented in

Finklin (1988). A manually operated tire weather station at

the Indianola Guard Station (GS), located 21 km east of the

tire area at an elevation of 1,052 m MSL, reported 48.8 mm

of precipitation in May but only 8.0 mm in June. The Sk&I

Gulch remote automatic weather station (RAWS) (Warren and

336
- 2300

i!

E

------------ Position of Headfire Recorded at Various Time Intervals ---____---__

1430 6530 1550 1555 1600 1610 hours MM’

2100

k m

1~ Horizontal Distance: 2.22 km 21

Figure 3.--Topographic profile for the area traversed by the major run of the Butte Fire on August 29, 1985.

Note that the differences in the scales for the two axes (5,O:l) does accentuate the terrain relief.

Vance 1981), situated 14 km south of the fire area at 1,554 m

MSL, recorded just 2.4 mm and 16.6 mm in July and August,

whereas the lndianola GS measured 6.4 mm and 38.0 mm,

respectively. The last significant rain (i.e., > 0.6 mm)

received at the Skull Gulch RAWS prior to the major run of

the Butte Fire o~culrred on August 2 and 3 (14.8 mm total).

At Indianola GS, the last rainfall of any significance occurred

on August 19 (3.0 mm).

A U.S. National Weather Service mobile fire weather unit

was established at the base camp (2,256 m MSL),

approximately 9.1 km southwest of the area involved in the

fire run by the early afternoon of August 26. Weather

observations taken prior to and on the day of the major run

indicate relatively mild air temperatures with fairly low

relative humidities but only moderately strong winds (table 2).

Table 2. --Dally 1399 hours W dmervatioas and ext- recorded at the temporaly fire

xeather station at the hag Tao II Caeplex base caq (after 6orski 1999).

Calendar Dry-bulb Relative 10-m open wind. 24-h M a x i II u 81 Minimum relative

date temperatun? haoddity SkrDirection rain teQperatun? humidity

Cl=% ("C) (pefcent) (h/h) (from) (ml) ("Cl (P--N

Aagast 2 6 21.7 2 7 I 4 south 0.0 23.9 21

August 2 7 22.8 23 13(31) soutbaest 0.0 25.6 17

August 2 8 21.1 2 0 1 4 southuest 0.0 22.8 18

August 2 9 19.4 2 0 13(31) southwest 0.0 23.9 17

* l- miaate average. Reported gusts noted in parentheses.

337
Table 3.-- Hourly oixservatioos recorded at the teilporery

fire neather station at the Leo6 Tom II Coqlex base camp

on August 29, 1965 (after Corskl 1990).

Lncal Dry-boSb Relative 10-P open wind

time teloperatnre bmidity Sped IN recti on

0800

0630

1000

1045

1120

1290

1315

1400

1535

1630

1720

1830

12.2 4 9 3.7

15.0 4 0 9.3

16.1 3 8 5.6

17.2 3 6 5.6

18.9 3 2 0

21.1 2 9 13.0

21.1 2 0 13.0(31)

21.7 2 4 22.2(37)

21.7 2 0 18.5

22.2 19 23.1

23.9 17 14.8

23.3 19 15.7

21.1 I7 7.4

16.7 31 11.1

15.0 25 0

east

east

east

east

southeast

son-t

sontb

south

souti

south

sontb

nest

sontb

*1-mimlte average. Reported gusts noted in piuentbeses.

According to the observations made on August 29 (table 3),

the following weather conditions would have been

rcprcscntative of the period during the fire run:

Dry-bulb temperature: 22°C

Relative humidity: 19 percent

1 O-m open wind: 2okmih

Wind direction: south

Days since rain: 26

Relative humidities as low as 6 percent and air temperatures

of around 30°C were recorded at the Skull G&% RAWS site

during the major fire run (table 4); winds were generally

southwest and averaged about 17 km/h.

Table 4.--Hourly fire weather observations recorded at

tbe Skull Gulch RAW site oo August 29, 1985.

bcal Dry-bulb Relative 10-m open wind

time temperature hmidity -Speetf Direction

(b- nmr) (“Cl (P--e (-1 (from)

o800 11.2 37 3.0 8 0

0900 13.9 3 7 0.7 206

1000 16.3 2 9 6.3 163

1100 19.8 2 4 10.0 149

1200 22.6 22 9.3 184 '

1300 25.7 18 10.7 145

1460 28.1 10 15.9 -b

1509 30.0 8 12.6 257

1666 30.4 6 23.0 231

1700 30.0 6 17.0 256

1899 29.6 6 19.8 292

1990 28.1 6 26.7 292

2060 25.3 7 18.0 300

2166 24.1 7 13.9 285

2266 21.8 9 0.2 196

’ lo- minute average.

bNot available.

FIRE DANGER INDICES

The weather data used in calculations of CFFDRS haloes

were obtained from the U.S. National Fire Weather Data

Library (Furman and Brink 1975). These data were daily

measurements of dry-bulb temperature, relative humidity,

wind velocity, and 24-hour accumulated rainfall taken at 1300

hours MDT at Skull Gulch RAWS and Indianola GS during

the 1985 fire season. Emphasis was placed on using the Skull

Gulch readings since it was more representative of the fire

area. The Indianola GS weather record was used for missing

observations. Winds measured at the U.S. standard of 6.1 m

or 20 fi in the open were adjusted to the CFFDRS standard of

10 m by means of the factor suggested by Turner and Lawson

(1978). All weather data were converted to metric units.

The standard components of the Canadian Forest Fire

Weather Index (FWI) System (Van Wagner 1987) were

calculated by computer program (Van Wagner and Pickett

1985). Calculations were begun on May 1, using the standard

fuel moisture code starting values (Canadian Forestry Service

1984), and continued until August 25. Calculations for the

subsequent period were based on weather observations made

at the base camp immediately adjacent to the fire area.

338
Table 5 .--Fire danger indices calculated at 1300 hours MDT for the temporary fire weather

station at the Long Tom II Complex base camp.

Calendar Fine Fuel Duff Drought Initial Bui L dup Fire Ueather

date Moisture Code Moisture Code Code Spread Index Index i ndex

(1985) (FFMC)” (DMC)’ WY (ISI) (BUI 1 (FWI)

August 2 6 94.5 160 723 16.4 207 53

August 2 7 94.5 I&l 730 15.6 211 5 2

August 2 8 9 94.4 94.6 16872 73744 22.5 16.5 2185 i-:

“The FFMC, DMC, and DC at Skull Gulch RAWS on August 25, 1985, were 97, 157, and 716,

respectively.

The three fuel moisture codes and three fire behavior indexes

comprising the FWI System arc listed in table 5. Readers

should consult Canadian Forestry Service (1984) for

definitions of the six components. The moisture code values

are at] indicative of very low moisture contents for the types

of fuels they are designed to represent. For example, litter

and duff represented by the Fine Fuel Moisture Code (FFMC)

and Duff Moisture Code (DMC) would probably have been

6.1 and 25 percent (Van Wagner 1987). A Drought Code

(DC) value of 500 is generally considered to be a critical

threshold for deep-drying conditions in forest floor and

mineral soil layers (Muraro 197.5; Muraro and Lawson

1970). The Initial Spread Index (ISI), Buildup Index (BUI),

and the Fire Weather Index (FWI) component itself,

representing fire spread rate, fuel available for combustion,

and fire intensity are all suggestive of extreme suppression

difficulty (Alexander and De Groot 1988; British Columbia

Ministry of Forests 1983; Muraro 1975). In most regions of

Canada, an FWl value of greater than 30 would be rated as

an extreme fire danger class (Stocks and others 1989). The

fire danger ratings which prevailed on August 29 would also

be considered extreme according to the criteria used by the

British Columbia Ministry of Forests (1983).

PREDICTED m BEHAVIOR

In an earlier paper by the author (McAlpine and Alexander

1988), a hindsight prediction of the August 29 run of the

Butte Fire was made using the interim edition of the Canadian

Forest Fire Behavior Prediction (FBP) System (Alexander and

others 1984; Lawson and others 1985). This prediction was

based on the IS1 calculated for the Skull Gulch RAWS and the

terrain slope. A crown fire spreading at 24.1 m/min was

predicted. In the present paper, the basis for predicted tire

behavior is a draft version of the first complete edition of the

FBP System (Van Wagner 1989y. The following predictions

are based on the most representative FBP System fuel type

(C-3: mature jack or lodgepole pine), a g-percent slope, 10..

m open wind of 20 km/h, FFMC 94.6, and BUI 219 for a

line-source ignition spreading directly upslope with the

prevailing wind during the late afternoon over a period of one

hour and 40 minutes:

Headlire rate of spread:

Forward spread distance:

Fuel consumption:

Headlire intensity:

Type of fire:

24.6 mlmin or 1.48 km/h

2,460 m

58.7 t/ha (surface and

crown)

43,320 kW/m

continuous crowning ( > 99

percent crown fuel involvement)

In the above calculations, a foliar moisture content (FMC) of

105% (oven-dry weight basis) for lodgepole pine was used

based on an on-site sample taken two days after the fire run

by Rothermel(l990), and not the computational scheme for

determining FMC according to calendar date, geographical

location (i.e., latitude and longitude), and elevation. Fire

intensity was computed, assuming a low heat of combustion

value (reduced for fuel moisture) of 18,000 U/kg, on the

basis of the predicted rate of advance and amount of fuel

consumed (Alexander 1982).

DISCUSSION

The major runs of other well-documented wildfires in the

United States such as the 1967 Sundance Fire in northern

Idaho, the 1980 Mack Lake Fire in northern lower Michigan,

the 1980 Lily Lake Fire in northeastern Utah, the 1983 Rosie

Creek Fire in south-central Alaska, and the 1989 Black Tiger

Fire in north-central Colorado, all occurred like the Butte

‘To appear in linal published form, authored by the Forestry Canada

(ForCan) Fire Danger Group, as an Information Report issued by

ForCan headquarters entitled “Development and Structure of the

Canadian Forest Fire Behavior Prediction System” in 1991.

339
Table 6.--Canadian fire danger indices associated aith five otlaw major well-lmom U.S.

WildfIres.

NZOOC! Fine Fuel Daff Ikwrght Initial Baildop Fire M&&her

of Moisture Code Moisture code code Index Inde?c

Wildfire (FFMC)" (DHC)"

Spread Index

@Jo" (ISI) (BUI 1 (WI)

Sundance" 96.1 318 752 23.8 318 6 8

Mack Lakeb 94.6 3 5 5 9 43.2 35 5 0

Lily Lake” 95.0 6 6 107 562 66 77

ksie Creekd 92.7 114 299 18.0 114 4 9

Black Tiger” 95.2 111 299 24.5 111 5 9

’ Reference: Anderson (1968). 'Be FUI Syster coqoneats awe calculated on the basis of the

1606 hoam Pacific Daylight Time (PlYl’) fire aeatber ohservatiom for the Priest Iake

Experimental Fox-eat, ID (winds were coaverted to 10-m open standard according to T-r

and Lllvson 1978); data were kindly provided by A.I. Finklia, llesmmb MeteorologIst

(mtifed), USM Forest Service! Iatemoaa tain Fire Sciences laboratory, Hissou~a, MI.

h-y-bulb tesperattm aad relative hunidity mre adjusted based oa data presented in Fiaklia

(1983), by (-) 1 .b”C aad (+) 5.0 percent, respectively. in order to appmxlmte the 1300 PDf

valnes. ‘lke 1399 bows PDT fire aeatber observations on Septeaber 1, 1967, nem: dry-bulb

teaperature 30.8"C; relative bamidity 18x; 10-s open wind 17 km& and 25 days since ) 0.6 m

of rain.

’ Reference: Shard and others (1!%3). me Flw systes cooQonmts sex-e caladated oa tbe basis

of t&e 1300 hours Eastern lsyligbt Time (EUI') weather data &ven in Table 1 of Simard and otlws

(1983) for Mlo, MI (winds nere converted to 10-a open staadard accordlag to Tamer aad Laasoo

1978). Tlae 1306 hoora EDT fire aeatber ohservatioas on May 5, 1980, were: dry-bulb teqeratam

26.7"C; relative baaldity 24X; 10-a open wind 33 km& aad 6 days since > 0.6 m of rain.

“Reference: Rothermel (1883, 1991). lbe FWI Systm coapoaeats ware calculated oa tbe basis of

the 1300 bows Mm- firl? neather observations for the Bear River hard statloa, Btamtch- cache

National Forest, Ul’ (winds aem converted to 10-m opaa staadard accordlag to Tamer aad lawson

1978) ; these data am on file with the NatioaaI Fire Weather Data Library (F- and Brlak

1975) under station aohx 420703. The 1300 boars M9T fire weather ohsematiom oa Jaae 23,

1930, mere: dry-bulb teqeratom 20.6"C; relative lamidlty la 10-r open wind 37 km/h; aad a

atinlno of 12 daya since > 0.6 mn of rain.

dReference: Joday (1985). 'I&e FUI System colsponents mere calculated on tbe basis of the 1300

hoars Alaska lhylight Time (ADT) watbar data for the international airport at Fairbaaka, AK;

data -kindly provided by P. Perkius, formerly with the USDI Rweaa of Laad thaagmmt,

Alaska Fire Service, Fairbanks, AIL ‘l%e 1300 baam AD1 fire watbw observations on Joaa 2,

1983, Here: dry-bulb temperatam 23.5”C; relative bamidity 3% 10-m open wind 21 ka/h; and 4

daya since > 0.6 m of rain.

“Reference: National Fire Protection Association (1999). T&a FWl Systm colaponents wm

calculated on the basis of the 1300 boars MDT Heather data for tbe Betasso station operated

by thr? Sherrif's Departillent, Boulder Coaaty, Co (winds mere comerted to lo-s opea staadard

according to T- aad lawsoa 1978); these data are oa file with the National Fire weather

Data Library (Farman aad Brink 1975) ander station I’Wiber 056604. The 1300 boors MOF fire

meather observations on July 9, 1989, were: dry-balb temperatare 36.7"C; dative ianaMity

24X; 10-m open wind 20 km/h (based on an on-site estimate of add-flame wiad speed): sod 13

days since > 0.6 IIlll of rain.

Fire, under exceedingly severe burning conditions according

to the FWI component (Table 6)‘. Although extreme tire

behavior HBS absented in all tJ~ese cases, tbeFe -

differences in forward spread rates and frontal intensities.

This is to be fully expected given difference’s in wind

velocity, dead and live fuel mistwe levels, fuel types (e.g.,

closed vs. open conifer stands), and the topographic situation

(e. g. ,

level groand vs. steep aad complex mamtalaoas

terrain). The FWl System components offer a general

‘The major run of the 1971 Little Sioux Fire (Smdo and Haines 1972)

in northeastern Minnesota also occurred under an extreme fire danger

rating; the FM Systea coqmneatsaad 1200 hours local standard

the tire weather observations ache presented in Alexanderand Sand0

(1989).

indication of fire potential based largely on short- and longterm surface weather; presently there’s no provision made in

the FWl System to account for the influences of upper

atmospheric conditions on tire behavior such as instability or

low-level jet winds (Turner and Lawson 1978). It’s the role

of the FBP System, which depends in part on the FWI System

for input, to consider the differences in fuel characteristics

and topography on potential fire behavior.

The FBP System did, although admittedly in retrospect, a

remarkably good job of estimating the actual fire behavior

characteristics associated with the major run of the Butte Fire

on August 29. Head fire ROS and forward spread distance are

of course more easily verified in this particular case. A

predicted spread rate approaching the maximum observed

340
value would be possible if a 45 percent slope were used (Van

Wagner 1977b), as done by Rothcrmel and Mutch (1986), and

if winds momentarily exceeded the mean value (Crosby and

Chandler 1966). Patten (1990) has indicated that surface fuel

consumption was perhaps 7.5 to 100 percent complete, and so

the predicted value (47.3 t/ha) is quite reasonable given the

fuel moisture levels and prcbum fuel loads. The predicted

level of frontal fire intensity and type of tire are certainly

indicative of a fully-developed crown fire (Alexander 1988;

Alexander and Lanoville 1989; Anderson 1968; Simard and

others 1983; Stocks 1987; Van Wagner 1977a) and certainly

match the general impression obtained by viewing slides taken

during the fire run.

CLOSING REMARKS

The CFFDRS can be, if properly applied, a useful tool in

research and training for interpreting fire behavior

information emanating from wildfire case histories completed

in the United States. The present example has in fact been

used since 1987 in the annual advanced fire behavior course

held at the Forest Technology School in Hinton, Alberta. If

the required weather observations are available, then it is

possible to redescribe the burning conditions of previously

documented forest fires in terms of the weather-dependent

components of the F’WI System, thereby permitting

correlation with observed tire behavior and comparison with

predicted fire behavior using the FBP System.

ACKNOWLEDGMENTS

I wish to sincerely thank several members of the USDA

Forest Service for their assistance in the analysis of the Butte

Fire and in the preparation of this paper. These include T.

Patten (Salmon National Forest), R.C. Rothermel and A.I.

Finklin (Intermountain Research Station), B.J. Erickson and

L. Jakubowski (Boise Interagency Fire Center), and D.A.

Thomas (Lo10 National Forest). C.J. Gorski of the U.S.

National Weather Service at Boise, Idaho, was also very

helpfirl.

LITERATURE CITm

Alexander, M.E. 1982. Calculating and interpreting forest

fire intensities. Canadian Journal of Botany 60(4): 349-

351.

Alexander, M.E. 1988. Heip with making crown fire hazard

assessments. In: Fishcer, William C.; Amo, Stephen

F., camps. Protecting people and homes from wildfire in

the Interior West: Proceedings of the symposium and

workshop; 1987 October 6-8; Missoula, MT. Gen.

Tech. Rep. INT-251. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Research

Station. pp. 147-156.

Alexander, M.E.; De Groot, W.J. 1988. Fire behavior in

jack pine stands as related to the Canadian Forest Fire

Weather Index (FWI) System. Poster (with text).

Edmonton, AB: Canadian Forestry Service, Northern

Forestry Centre.

Alexander, M.E.; Lanoville, R.A. 1989. Predicting fire

behavior in the black spruce-lichen woodland fueltype of

western and northern Canada. Poster (with text).

Edmonton, AB and Fort Smith, NT: Forestry Canada,

Northern Forestry Centre, and Government of the

Northwest Territories, Department of Renewable

Resources, Territorial Forest Fire Centre.

Alexander, M .E.; Lawson, B.D.; Stocks, B.J.; Van Wagner,

C.E. 1984. User guide to the Canadian Forest Fire

Behavior Prediction System: rate of spread relationships.

Interim ed. Ottawa, ON: Environment Canada, Canadian

Forestry Service, Fire Danger Group. 73 p. +

supplements. [First printing July 1984; revision and

second printing September 1984.1

Alexander, M.E.; Sando, R.W. 1989. Fire behavior and

effects in aspen-northern hardwood stands. In: Maclver,

D.C., Auld, H., and Whitewood, R., eds. Proceedings

of the tenth conference on fire and forest meteorology;

1989 April 17-21; Ottawa, ON; Ottawa, ON: Forestry

Canada and Environment Canada. pp. 263-274.

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343
BEHAVIOR OF HEADF’IRES AND BACKFIRES

ON TALLGRASS PRAIRIE

Terrence G. Bidwell and David M. Engle’

Abstract-Byram’s lireline intensity model and time-temperature relationships at 0, 30, and 60 cm above

the soil surface were used to characterize the behavior of headtires and backfires on tallgrass prairie during

the spring. Weather and fuel parameters were used as independent variables in regression models of tire

behavior. Byram’s ftreline intensity was greater in headftrcs than backfires. Residence time for backfires

was not significantly different from residence time for headfires. Degree seconds for backfires was not

significantly different from degree seconds for hcadfires. Maximum temperature at 60 cm was greater in

headfires than backfires. Fire type (head fire or backfire) and variables related to fuel continuity, fuel

loading, and fuel moisture were related to time-temperature relationships. Variables related to fuel load and

weather were related to Byram’s tireline intensity for headftres and backfires and for rate of spread for

hcadfires.

INTRODUCTION

Data about the behavior of tire in the tallgrass prairie arc

needed in order to increase our understanding of the

interactions of fire behavior, fire environment, and iire

cffccts. Previous studies of fire behavior have been confined

primarily to wildfire in forests and shrublands and described

mainly in terms of fireline intensity (Byram 1959; Wright and

Bailey 1982). Because fire intensity is related to crown

scorch of conifers (Van Wagner 1973) and because fire&e

intensity is used for describing wildfire behavior (Albini

1976), lirelme intensity has been suggested for describing fire

behavior in grasslands (Rothermc] 1972; Albini 1976) and for

predicting scorch height on rangeland shrubs (Roberts and

others 1988). Although fireline intensity accounts for the heat

or energy released in the initial tire front, it does not account

for energy released over the entire depth of the combustion

Zone (Tangrcn 1976; Alexander 1982). Combinations of tire

temperatures and time-temperature relationships, rather than

fireline intensity, have been used to quantify fire behavior in

the residual combustion zone in tallgrass prairie fires (Engle

and others 1989) and to relate fire behavior to tire effttcts on

herbaccous vegetation (Stinson and Wright 1970; Wright

1971; Hobbs and Gimingham 1984; Ewing and Engle 1988;

Bidwcl] and others 1990).

Research has not established whether grassland backfires or

headfires produce higher maximum temperatures at the soil

surface (McKell and others 1962; Daubenmirc 1968; Bailey

and Anderson 1980). Because both fire types arc used in

prescribed spring bums in the tallgrass prairie, it would

enhance our knowledge of fire effects to e]ucidate their

behavior. The fuel, topography, and weather in which a fire

occurs dictates its behavior and may explain the

contradictions regarding the behavior of headfires and

backfires. Parameters of the fire environment that are easily

‘Assistant Professor and Professor of Range Science, Grazing Lands

Ecology and Management Group, Oklahoma State University,

Stillwater OK.

344

measured by rangeland fire managers may also bc useful for

predicting fire behavior in tallgrass prairie. Time-temperature

relationships may be useful in describing differences between

headfires and backfires by quantifying energy release in the

entire combustion zone in tallgrass prairie fires. The

objectives of our study were to compare the behavior of

headtires and backfires and to explore the relationship

between the behavior of tallgrass prairie tires and commonly

measured variables of the fire environment.

STUDY AREA

Our study area is located on the Agronomy Research Range

15 km west-southwest of Stillwater, Oklahoma. Mean annual

precipitation is 81 cm. The study area is a shallow prairie

range site in the Central Rolling Red Prairies Land Resource

Area (USDA Soil Conservation Service 1981). The soil is

Grainola clay loam with a clay B horizon and is a member of

the fine, mixed thermic family of Vertic Hap]usta]fs.

Dominant grasses on the site include big bluestem

(Andronogon gerardii Vitman), switchgrass (Panicum

virgatum- L.), indiangrass (Sorghastrum nutans (L.) Nash),

and little bluestem (Schizachyrium scoparium (Michx.) Nash).

The study area was grazed at a moderate to heavy stocking

rate (2.4 AUM ha”) from mid-July to mid-November in 1985

and 1986 before the treatments were applied in the spring of

1986 and the spring of 1987.

METHODS AND MATERIALS

We replicated treatments four times in a randomized complete

block design. The 10 m by 20 m plots were located on

nearly level terrain (< 2 percent slope), and oriented southeast

to northwest so the direction of their long axes would

correspond to the direction of the prevailing southeast spring

wind. Each replication consisted of a headfired plot and a

backfired plot. We used a drip torch to set the fires at plot

borders. Burning treatments began in March and ended in

April. Each replication was burned within a d-hour burning

period, and weather variables and fuel load were sampled
immediately before each bum. Weather variables included thermocouple data. A discrete summation algorithm was used

ambient air temperature, relative humidity, and wind speed 2 to arrive at an estimate of degree seconds, which is the area

m above the ground and were measured by means of a belt above ambient temperature and under the time-temperature

weather kit Fuel load was estimated by weighing clipped curve. The points of definite temperature rise and drop for

herbaceous material from five quadrats (0.5 m by 0.5 m) per computing residence time were determined numerically by

plot. Clipped herbage was separated into standing tine fuel sequential reverse progression through a IO-second interval of

and fallen tine fuel (litter and mulch) before weighing. Fuel the time-temperature curve to points of 2 “C or greater

moisture, expressed on a dry weight basis, was determined departure from the postbum ambient temperature (Engle and

after samples were oven dried at 70 “C for 72 hours. others 1989).

We measured tire temperatures at 2 second intervals by

means of high-temperature, chromel-alumel thermocouples at

three stations per plot and at three heights relative to the soil

surface (0 cm = soil surface; 30 cm = top of herbaceous

canopy; 60 cm = above the herbaceous canopy). The

thermocouple wire was 24 AWG with thermojunctions

approximately 6 mm long and 1 mm in diameter and with 5-

to 7-m leads overbraided with high temperature ceramic fiber

insulation. An electronic data logger (Campbell Scientific

model 21X with multiplexer) with tape data storage was used

to record time-temperature data. Traces of time-temperature

that were recorded for each thermocouple allowed estimates

of degree seconds above ambient temperature (Potter and

others 1983), maximum temperature, and residence time (the

time from initial temperature rise to time of definite

temperature drop) (Rothermel and Deeming 1980). A

program in Turbo Pascal for IBM compatible microcomputers

was used to generate each of these variables from the

Byram’s (1959) fir&e intensity model is expressed as

I=Hwr, where 1 is tireline intensity, H is the fuel’s low heat

of combustion (LHOC)(lcJ kg”), w is the weight of fuel

consumed per unit area (kg me2), and 1 is the rate of spread

(m s I). Low heat of combustion was determined by bomb

calorimetry for the total fuel sample (standing and fallen).

Fuel consumed was considered to be equal to fuel load

because of the completeness of the bums. Rate of spread was

reported in m min”. We measured rate of spread with a

stopwatch and photographically with a 35 mm camera

time-mode device in a manner similar to that employed by

Britton and others (1977).

Approximate T tests were performed on tire behavior data

(SAS, Inc. 1985). Differences between means of tire

behavior variables were considered significant at the 1 Opercent probability level. Stcpwise multiple regression

techniques were used to construct models of fire behavior

(Table I) from the mean values of the environmental variables

Tah[e 1. Fire behavior variables used in regression modets for relating fire

environment to fire behavior on tat tgrass prairie

Variable Code

Headfire(n-5);2)

Min Max Mean SE Min Max

SE

P>F

Fireline intensity (Ku m") BFI 7 5 2778 1167 445 31 146 9 7 16 0.02

Ratt? of spread Cm min.') 80s 1 3 5 1 2 6 .5 2 I .2 0.04

DI?gme seconds 0 cm ("C x s) KXl 2504 8260 5941 997 1035 31136 9508 4001 0.48

oegree seconds 30 CM (“C x s) DS30 993 10993 6096 1727 2863 21523 10244 2731 0.27

Degreeseconds6ocm ("CXS) lsal 551 6465 4962 1115 198 7767 4149 1249 0.65

Residence time 0 cm (S) KNI 111 705 250 114 74 589 255 75 0.97

Residence time 30 an (S) xl30 158 553 337 a 2 151 756 465 7 0 0.26

Residence tirw 60 cm (S) Rl-60 9 2 779 429 139 116 749 487 7 7 0.70

Maximom tesp. 0 an ("C) MT0 4 8 386 216 5 9 7 3 687 215 81 0.99

hfaximam ten+ 30 clll ("Cl Ml'30 6 7 537 307 a 3 10s 634 270 68 0.74

Maxilmm temp. 60 cm ("Cl Mlw 4 4 378 274 8 3 24 132 7 8 14 0.094

345
Table 2. Mean independent eaviromntal variables from beadfires

(n=S) aad backfires (n=7) used in multiple regression models

Variable Code &n Max Mean SE

Relative bddity (X)

Air temperature C”

wind speed (km hr.')

fuel load dry weigbt (kg ha")"

Foe1 load fresh might (kg ha’)

Foe1 moisture (standing) (%)

Fuel mistom (fallen) (%)

Foe1 moisture (total) (%I

Quadrat fresh weight STDb

Quadrat dry weight STD QFDS 11 5 0 3 2 3

Qua&at fresh wigbt min.” PFFMIN 1 5 122 69 8

Puadrat dry Height min. QFllMIN 12 100 5 4

Quadrat fresh w+ght cv (%)d CW 1 2 7 4 3 6

Puadrat dry Height cv (%) CVD 1 5 7 0 3 7

R R 1 8 5 1 3 4

TMP 1 5 2 6 2 1

WIND 3 24 10

FL0 2372 5584 3570

FLF 2720 6576 4707

Fm 5 5 9 28

FMF 1 3 149 4 6

FMT 12 6 0 3 1

QFFS 1 8 5 6 4 2

4

3

2 6

I7

1 5

a ,411 quadrat values (weight) in g 0.25m”

b !$I¶ = standard deviation

c MM- quadrat value witbin a plot

d CV = coefficient of variatioo

(Table 2) and tire type as a dummy variable (I for hcadlire

and 2 for backfire) (SAS, Inc. 1985). Measures of variation

associated with fuel load, standard deviation, and coefficient

of variation for a plot, were included as measures of fuel

continuity. Minimum qua&at sample values within a plot

were included to provide an estimate of minimum fuel loading

which, from observation, may affect fire spread over the fuel

bed. Variation and minimum values of fuel loading were

derived from five quadrats per plot. Five headlires and 7

backfires were used in the analysis because of wind shifts

away from the longitudinal axis of the plots.

REXJLTS

Byram’s fireline intensity (BFI) of headlires averaged 1167 +

445 kWm I, which was 12 times greater than fireline intensity

of backfires (97 + 16 Kw rn-‘) (P=O.O3). Rate of spread

(ROS), the main influence on BFI, was 10 times greater for

headfires (12.6 _t 6.0 m min.‘) than for backfires (1.0 t 0.2

m min ‘) (P=O.O9). Regression models explained more than

90 percent of the variation in BFI for both headlires and

backfires and in ROS for headfires (Table 3). Degree

Table 3. Regression models relating environmental variables to Byram’s

fireline intensity (BFI) and rate of spread (ROS) on tallgrass prairie

6eadfires

Jm=-

Variable b, b, Xl 4 X? R2 P>F

BP1 - 2274 0.39 FLF 2 4 FMF 0.94 0. oool

Rm 0.07 0.005 IWF -0.604 lo! 0.95 0. oool

Backfires

BP1 497 - 6 RB - 3 TMP 0.92 0. oool

Ros 0.04 -0.0006 FMS -O.oool QFDKIN 0.63 0. oool

346
seconds and residence time did not differ by fire type at any

height (P > 0.10) (Fig. la, lc). Head fires produced greater

maximum temperatures than backfires at 60 cm (P-0.004)

(Fig. lb).

Parameters related to mei load and fuel moisture were the

most important variables entering regression models of timetcmpcraturc relationships for all heights (Table 4). Fire type

occurred as a first-entered variable in four of nine models.

Environmental parameters and tire type explained at least 70

percent of the variation in each regression model (Table 4).

DISCUSSION

Behavior of Headfires and Backfires

Fireline intensity of headfires and backfires in our study were

similar to those observed in other grassland fire studies (En&

and others 1989; Roberts and others 1988). The greatest

fireline intensity we measured in a headfire, 2778 Kw m ‘ ,

was one-third as great as that observed in homogeneous grass

stands in West Texas (Roberts and others 1988), but was

comparable with the greatest fireline intensity in a summer

head fire in a moderately grazed tallgrass prairie (Englc and

others 1989). The magnitude of the difference between the

ROS of our headfires and the ROS of our backfires is

consistent with the rate of spread in two grassland

communities in west Texas (Roberts and others 1988). Rate

of spread and fuel consumption are the major variables in

Byram’s model of fireline intensity. Although fireline

intensity and rate of spread were greater in headfircs in our

study, several time-temperature parameters did not differ

between fire type because time-temperature profiles reflect

both the intensity (heat release rate) and heat transfer for the

entire combustion period. Headtires are considered more

intense than backfires because they consume fuel more rapidly

and spread more rapidly than backfires (Lindcnmuth and

Byram 1948; Trollope 1984). In contrast, the difference

between degree seconds for headfires and degree seconds for

backfires were much smaller. Degree seconds relate to the

heat released over the entire combustion period, whereas

fireline intensity represents only the rate of release of heat

energy from the flaming front. Thus, the rate of release of

heat energy is greater in headtires, but the two fire types

release similar total amounts of heat energy.

Both fire types have been reported to be hotter above the

herbaceous canopy (Fahnestock and Hare 1964; Bailey and

Anderson 1980; Troilope 1984). Although mean maximum

temperatures were not significantly different between

headfires and backfires, they were highest at 30 cm in both

backfires and headfires. Maximum temperature declined

more from 30 cm to 60 cm in backfires. Maximum

temperature above the herbaceous canopy is higher in

head fires because the rate of energy release and convection

are greater in h&fires. Thus, differences between above

Headfire

64

0

HEIGHT ABOVE TH;& SURFACE (CM)

@ I

(4

Headfire

----A

Backfire

w

- - l

0 30 -

6 0

HEIGHT ABOVE THE SOIL SURFACE (CM)

Backfire

Headfire

(4

OI- I -

0

HEIGHT ABOVE THE:O,L SURFACE (CM)

iiFigure 1. Time-temperature relationships in tallgrass prairie

headiires and backfires for degree seconds (a), maximum

tcmpcraturc (b), and residence time (c). Bars are plus or

minus one standard error.

347
Table 4. Regression models relating fire type and envimamental variables to time-temperature

mlatioasbips of spring fires on tallgrass prairie’

bo b,

Degree seconds at 0 CM

Xl b,

23027 - 462 FMT 1255

x2 b, X.3 RZ P>F

seconds at 30 CM

27647 4561 TYPE -2 cvo

Degme seconds at 60 CM

17183 I FL0 3 2 IMP

Residence time at 0 CM

18 -1 FMF

Residence time at 30 CM

2597 2.51 TYPE

Residence time at 60 CM

4048 212 Tn?R

Maxilapl temperatnm at 0 CM

1403 -0.19 Ful

4 8

Mm0 478

FL0 .250

FMF -212

WND 2674

RR -24

Rll -31

FMT 12

lw -8

R R 10

PFFS - 1049

RB 25466

RB -140

CVF .3251

TMP -1151

Tw - 1362

OFFS - 1798

RB .414

OFFS - 8

cvo

0.75 0.03

0.81 0.01

0.88 0.02

0.70 0.06

- 16 CVF 0.93 0.0004

-27 CVF

Maxima tempera~ at 30 CM

1016 -0.08 FLF

Maxinun tempemtam at 60 CM

605 -206 TYPE

-11

2

-9

cvo

cvll

Qm

0.89 0.002

0.79 0.02

0.73 0.04

0.87 o.OS3

‘See Table 2 for descriptors

canopy maximum temperatures for prairie headfires and (Trollope and Potgieter 1983). Our results were similar to

backfires reflect differences in rate of energy release much as those of other studies showing that fuel moisture affects

did differences in fireline intensity between headfires and ignition and combustion more than any other environmental

backfires. factor (Byram 1957; Brown and Davis 1973).

Disagreement exists in the literature as to which tire type

produces the hotter tire at the soil surface. McKell and

others( 1962) found that backfires produce higher temperatures

at the soil surface than head fires do, but Daubenmire (1968)

directly contradicts McKell and others Although maximum

temperature was highly variable in both tire types we did not

find that it differed significantly between fire types.

Fire temperature in the combustion zone is primarily

dependent upon the quantity of fine fuel consumed (Stinson

and Wright 1969; Engle and others 1989). Fine fuel load also

has a pronounced effect on residence time, which increases

proportionally to fuel load (Stinson and Wright 1969),

especially with accumulation of mulch on infrequently burned

tallgrass prairie (Engle and others 1989). The time required

for active combustion was very nearly the same in both tire

types in our study, and we would expect a difference in

residence time measured by thermocouples placed on the soil

surface only where there are differences in fuel loading or

fuel consumption.

Regression Models

Fuel load and fuel moisture variables rather than weather

variables were the tire environment parameters most strongly

related to tire behavior. Fuel load was an important variable

in our models. Fuel load accounted for 30 to 60% of the

variation in fireline intensity in grassland fires in Africa

Fuel continuity variables appeared in all but two models. Fuel

continuity is a primary factor in tire behavior but is less

important when heavy fuels arc available or wind speed is

high (Brown and Davis 1973). Wind speed is an important

influence on tire behavior including rate of spread (Rothermel

1972; Albini 1976), but fuel discontinuity may alter the

influence of wind so much that mathematical tire models

become poor approximations of tire behavior (Brown 1982).

Mathematical models assume uniform fuel (Brown 1982),

which seldom occurs in tallgrass prairie. Wind speed (< 24

km h”) was not an important variable in our tire behavior

models (Table 3).

CONCLUSIONS

Fireline intensity and rate of spread, measures of ‘fire

behavior that relate to behavior of the flaming fire front and

rate of energy release, indicate that headfires are at least ten

times more intense than backfires in grazed tallgrass prairie.

Time-temperature measures of fire behavior that account for

energy released across the entire combustion zone indicate

lesser differences between fire types. The behavior of

backtires is more variable than headfires in discontinuous

fuels.

In addition to tire type, fuel loading and fuel moisture were

important variables in regression models of fire behavior.

Fuel load largely determines the -t of energy available

348
for combustion. Fuel continuity measures were important

variables in regression models of fue behavior because they

reflect the subtle fuelbed and microclimate differences

associated with grazed fuel beds. Mosaics of discontinuous

fuels or disturbed patches oRen result from spot grazing by

large herbivores, soil disturbance by small mammals, soil

heterogeneity, or natural spatial heterogeneity of tallgrass

prairie vegetation (Loucks and others 1985). Our research

indicates that fuel parameters together with fire type are

major factors associated with variation in ftre behavior. This

should enable us to understand the role of fire as an

disturbance factor in the tallgrass prairie plant community.

LITERATURE CITED

Albini, F. A. 1976. Estimating wildfire behavior and

effects. USDA Forest Service General Technical Report

INT-30.

Alexander, M. E. 1982. Calculating and interpreting forest

fire intensities. Canadian Journal of Botany 60:349-357.

Bailey, A. W., and M. L. Anderson. 1980. Fire

temperatures in grass, shrub, and open forest communities

of Central Alberta. Journal of Range Management

33:37-40.

Bidwell, T. G., D. M. Engle, and P. L. Claypool. 1990.

Effects of spring headtires and backfires on tallgrass

prairie. Journal of Range Management 43(3):21 I-214.

Britton, C. M., B. L. Karr, and F. A. Sneva. 1977. A

technique for measuring rate of fire spread. Journal of

Range Management 30:395-397.

Brown, J. K. 1982. Fuel and tire behavior prediction in big

sagebrush. USDA Forest Service Research Paper

INT-290.

Brown, A. A., and K. P. Davis. 1973. Forest fire: control

and use. McGraw Hill, New York.

Byram, G. M. 1957. Some principles of combustion and

lheir significance in forest tires. Fire Control Notes

t8:47-57.

Byram, G. M. 1959. Combustion of forest fuels. pp.

61-89. In: K. M. Davis (cd.). Forest fire: control and

use. McGraw Hill, New York.

Daubenmire, R. 1968. Ecology of fire in grasslands.

Advanced Ecological Research 5:209-266.

Engle, D. M., T. G. Bidwell, A. L. Ewing, and J. R.

Williams. 1989. A technique for quantifying tire

behavior in grassland fire ecology studies. The

Southwestern Naturalist 34( 1):79-84.

Ewing, A. L., and D. M. Engle. 1988. Effects of late

summer tire on tallgrass prairie microclimate and

community composition. American Midland Naturalist

120:212-223.

Fahnestock, G. R., and R. C. Hare. 1964. Heating of tree

trunks in surface fires. Journal of Forestry 62:799-805.

Hobbs, R. J., and C. H. Gimingham. 1984. Studies on fire

on Scottish heathland communities. Journal of Ecology

72:223-240.

Lindenmuth, A. W., and G. M. Byram. 1948. Headfires are

cooler near the ground than backfires. Fire Control Notes

9:8-9.

Loucks, 0. L., M. L. Plumb-Mentjes, and D. Rogers. 1985.

Gap processes and large-scale disturbances in sand

prairies. pp.71-83. In: S. T. A. Pick&t and P. S. White

(eds.). The ecology of natural disturbance and patch

dynamics. Academic Press, New York.

McKell, C. M., A. M. Wilson, and B. L. Kay. 1962.

Effective burning of rangelands infested with medusahead.

Weeds 10:125-131.

Potter, R. L., D. N. Ueckert, and J. L. Peterson. 1983.

Internal temperature of pricklypcar cladophylls during

prescribed fire in West Texas. Texas Agricultural

Experiment Station. PR 4132.

Roberts, F. H., C. M. Britton, D. B. Wester, and R. G.

Clark. 1988. Fire effects on tobosagrass and weeping

lovegrass. Journal of Range Management 41:407-409.

Rothermel, R. C. 1972. A mathematical model for

predicting fire spread in wildland fuels. USDA Forest

Service Research Paper INT- 115.

Rothermel, R. C., and J. E. Deeming. 1980. Measuring and

interpreting fire behavior for correlation with fire effects.

USDA Forest Service General Technical Report INT-93.

SAS Institute Inc. 1985. SAS procedures guide for personal

computers. Version 6 edition. Cary, North Carolina.

373p.

Stinson, K. J., and H. A. Wright. 1969. Temperaturcof

headfires in the southern mixed prairie of Texas. Journal

of Range Management 24277-284.

349
Tangren, C. D. 1976. The trouble with fire intensity. Fire

Technology 12:261-265.

Trollope, W. S. W. 1984. Fire behavior. pp. 199-217. In:

P. de V. Booysen and N. M. Tainton (eds.). Ecological

effects of fire in South Africa ecosystems.

Springer-Verlag, New York.

Trollope, W. S. W., and A. I. F. Potgictcr. 1983.

Characteristics of fire behavior in the Kruger National

Park. Research Report, University of Fort Hare, Alice,

South Africa.

Van Wagner, C. E. 1973. Height of crown scorch in forest

tires. Canadian Journal of Forestry Research 3:373-378.

Wright, H. A. 1970. A method to determine heat-caused

mortality in bunchgrass. Ecology 51:582..587.

Wright, H. A. 1971. Why squirrel tail is more tolerant to

burning than needle-and-thread. Journal of Range

Management 24:277-284.

Wright, H. A., and A. W. Bailey. 1982. Fire ecology: U

nited States and southern Canada. John Wiley, New

York.

USDA Soil Conservation Service. 1981. Land resource

regions and major land resource areas of the United

States. Agricultural Handbook 296, U.S. Government

Printing Office, Washington, DC.

350
HRE AND AGRICULTURAL ORIGINS:

PRELIMINARY INVESTIGATIONS

Mark A. Blumler’

Abstract-testd the hypothesis that hunter-gathcrcrs used fire to manipulate wild cereal stands, in a process

leading lo agriculture. In Israel, wild cmmer (Triticwn dicoccoides), barlcy sponmnemt), and

oats (Avena sretilis) grow in mixed stands, so eflicienc harvest is difficult. Wild cereal grains are

diffcrenlially protected against fire by hull thickness and efficiency of self-burial. Wild oat diasporcs drill

deeper into soil than wild barley and emmcr, except next to rocks, where wild emmer drills best. Wild

barley has thin hulls that protect against charring less than the thick hulls of wild emmer and oats. I

predicted that wild barley is susceptible to tire, and wild oats more tolerant than wild emmer except around

rocks. Distribution and survival of wild cereal grains aAer arson fire supported these predictions. Wild

barley occurred almost exclusively in unburned spots. The percentage of charred wild oat grains was lower

than that of wild emmer in open soil, but not adjacent to rocks. The results suggest that people could have

set fires to reduce the importance of wild bat-Icy, and in rocky areas to favor wild emmer, but it is doubtful

whether they would have desired to do so.

The Agricultural Revolution was one of the major watersheds

in human history and cultural evolution, and led to

unprecedented, ongoing transformations of global ecosystems.

The causes of this change in human economy continue to be

debated (Adams 1983; Binford 1968; Blumlcr and Byrne

1991; Byme 1987; Cohen 1977; Flanncry 1965, 1969, 1973;

Harlan 1975, 1986; Henry 1989; Reed 1977; Rindos 1984;

Sauer 1952). Available cvidcncc suggests that environment

was at least as important as cultural/technological state: early

agricultural centers were characterized by semi-arid climates

with a long dry season, which favored the evolution of annual

grasses and legumes with unusaily large seeds, and gcophytcs

(Blumler 1984, 1987, 1991b; Byrne 1987); most if not all of

the first crop plants were derived from such species (Blumlcr

1987, 199lb; Byrne 1987). The Fertile Crescent is an area of

special interest since cultivation may have begun there first,

by 10,000 B.P. (Hillman and others 1989; Zohary and Hopf

1988), or perhaps several thousand years earlier (Kislcv and

Bar-Yosef 1988; Unger-Hamilton 1989). Some scholars have

suggested that the initiation of farming in this region was

connected to the USC of fire as a vegetation management tool

(Lewis 1977,; Navch 1974, 1984; &.tIjar 1977). They

proposed that fire was employed to increase and maintain the

abundance of wild cereal grasses, and may even have caused

the evolution of these unique monstrosities (fig. I) in the first

place.

Ethnographic and historical evidence demonstrates that

hunter-gatherers often manipulate vegetation with fire

(Burrows 1991; Day 1953; Hallam 197.5, 1989; Lewis 1973;

Reynolds 1959; Shipek 1989; Stewart 1956). Control of fire

certainly predates the Epipalcolithic, and may be of great age

in the Old World O\Javeh and Dan 1973; Sauer 1956).

Regular burning of vegetation is well-attested in early

historical times in Israel, Greece, and Rome (Liacos 1973;

Naveh 1974). Thus, it is reasonable to assume that Late

‘Graduate Student, Department of Geography, University of

California, Berkeley, CA.

Figure I.-D&pores (from left to right) of wild emmer

(Trih’cum dicoccoides), wild barley (Hordeum spontaneum),

and wild oats (Avena sferilk). (x 2/3).

351
Pleistocene peoples of the Near East would have set fires if

the availability of wild cereals or other resources could have

been enhanced by doing so. Noncthclcss, archaeologists and

paleoecologists have been suspicious of the fire/domestication

hypothesis, because archacological/paleobotanical evidence

offers no convincing support (Wright 1980). Furthermore,

the study of Near Eastern fire ecology is in its infancy, and

assertions about the response of wild cereals to tire have been

pure speculation. The proponents of the fire/domestication

hypothesis have generally assumed that the Fertile Crescent

was naturally covered by dense woody vegetation, and that

wild cereal stands could have formed only atIer the removal

of this cover by disturbances such as fire. However, it is

now well-established that steppic vegetation dominated the

region during the Late Pleistocene, except possibly along the

Levantine coast (Van Zeist 1969; Van Zeist and Bottema

1982), and that seedling establishment of woody species is

extremely difficult on the fertile basaltic and terra rossa soils

presently dominated by wild cereals (Berliner and others

1986; Blumler 1984, 1991b, c, d; Kaplan 1984; Litav and

others 1963; Rabinovich-Vin and Orshan 1974;

Rabinovitch-Vin 1983). Recent evidence also strongly

suggests that the wild cereals arc primarily adapted to

ungrazcd, undisturbed (i.e., unbumcd) conditions (Blumler

1984, 1991b, c; Litav 1965; Litav and others 1963; Naveh

and Whittaker 1979; Noy-Meir and others 1989; Zohary

1969). Thus, the tire/domestication hypothesis in its original

form can be dismissed although Naveh’s (1984; Kutiel and

Naveh 1987a, b) suggesfion that Natufians on Mt. Carmcl

used fire to open up maquis and allow establishment of wild

cereal stands is reasonable if unproven.

In any case, the possibility that fire may have been used to

favor wild cereals in certain specific circumstances, or to alter

the mix of cereal grasses on a given site, is worthy of

consideration. In Israel, for instance, wild emrner wheat,

wild barley, and wild oats commonly form dense, mixed

stands on good soils where grazing is light. The

archaeological record suggests that wild emmer and wild

barley were the first plants cultivated in the Near East

(Blumler and Byrne 1991; Harlan 1975; Van Zeist and

Bakker Heeres 1985).* Harvesting of wild oats seems to be

time-consuming (Ladizinsky 1975), and the oat (A. sofiva)

was not domesticated until much later; but wild oats tend to

dominate stands today, rendering efficient harvest difficult

(Ladizinsky 1975; Unger-Hamilton 1989). Since the three

wild cereal grasses mature at different times, they probably

were not harvested together. Any manipulation that would

have increased stand purity, especially of wild emmer or wild

barley, should have been of benefit to the pre-agricultural

peoples (Natufians) of the region.

‘Wild emmer is the progenitor of emmer (T. dicoccum~, durum (7:

&mm), and most other telraploid wheats, as well as bread wheat (T.

aestivcrm); wild barley is the progenitor of all domesticated barley6

(H. vu/gare).

While carrying out fieldwork in Israel during the 1987-8 rainy

season, I undertook preliminary investigations into the effects

of fire on the relative abundance of these three grasses. T o

this end, I considered diaspore characteristics that should

affect fire tolerance, and tested my conclusions by measuring

survival after fire. Ecological speculations arc rampant in the

literature on agricultural origins, but experimental testing of

ecological hypotheses is rare. This study was carried out in

part to provide an illustration of the sort of research

procedure that should prove fruitful in illuminating our

presently rather sketchy understanding of the circumstances

surrounding agricultural beginnings.

DIASPORE MORPHOLOGY AND FIRE

Several factors are likely to influence seed mortality during a

bum. Grass fires arc typically fast-moving and not very hot,

so seeds that are protected by a thick seed coat or other

investing structures may escape with only minimal charring.

During the passage of fire, a pronounced temperature gradient

exists between the surface and deeper soil layers, so buried

seeds should suffer much less mortality than those that lie on

the surface or are caught up in the litter.

Wild cereal diaspore morphology is an adaptation that allows

self-burial. I examined a number of sites early in the growing

season, and found that depth of burial depends on microsite

conditions and species (figs. 2 and 3).’ Wild oats have

hygroscopic awns, which cause burial, at approximately

identical depth, under a wide range of conditions. Where

there is no litter, wild emmer and barley tend to become

oriented horizontally, which precludes self-burial except when

diaspores are wedged up by rocks or soil cracks.

Immediately adjacent to rock outcrops, wild emmer typically

drills deeper than either wild barley or oats (in fact, it is

occasionally found 15 or more centimeters beneath the

surface).’ Where there is abundant litter, wild barley

diaspore rachis tips tend to weakly penetrate the soil surface,

leaving the grain almost completely exposed, while wild

emmer often remains suspended entirely above ground;

nonetheless, seedling establishment of both species is

excellent, presumably because litter shade reduces moisture

stress. It may be no coincidence that wild emmer is found

almost exclusively on hard limestone hills and basaltic

plateaus (Harlan and Zohary 1966; Zohary 1969, pers.

comm.), where rock cover is often so great that the seed rain

from plants growing adjacent to rocks is spread throughout

much of the open soil area, allowing rapid re-establishment

away from rocks under favorable (i.e., high litter) conditions.

‘Quantitative empirical data on drilling success in relation to microsite

will be presented elsewhere (Blumler n.d.). Variability is great, of

course; figures 2 and 3 are merely schematic diagrams illustrating the

most characterisitc final positions of wild cereal diaepores under

differing microsite conditions. Discussions of wild cereal self-burial

in the literature (Aaronsohn 1910; Cook 1913; Zohary 1960, 1969;

Zohary and Brick 1961) are generally in accord with my findings.

‘In such cases, seedling emergence may be problematic

352
Figure Z.-Characteristic final position of wild cereal diaspores in the absence of plant litter (i.e., as a

result of heavy grazing or other disturbance). Wild emmcr and wild barley tend to lie prone, which

prccludcs burial; when wedged upwards by rocks, however, wild emmcr, in particular, can drill very far

bcncath the soil surface (left). Wild oats buries itself well, even in open soil (n&t).

Figure 3,-Charactcristjc final position of wild cereal diasporcs where there has been an accumulation of litter

(under relatively undistukdconditions). Wild oats is about as SUCCCSS~U~ at self-burial as it is under no-litter

conditions; wild barlcy barely penetrates the soil surface with its rachis tip; while wild emmcr typically

remains suspended just above the soil surface.

353
Table 1. Characteristics presumably influencing resistance of wild cereal

diaspores to charring and heat caused by fire.

wild emner

wild barley

wild oats

Hull Self-Burial

Thickness Open Soi 1 By Rocks

thick very poor best

thin poor god

thick eood eood

Seed

Dormancy

less than 50 percent

almost none

50 aercent or more

Wild barley has relatively thin hulls, and no seed bank (table

1); hence, it is probably more vulnerable to fire than wild

emmer or wild oats, which enclose Lheir seeds in thick husks

and have a large pool of dormant seeds that tend to become

buried during the growing season, if not before.’ Hence, I

predicted that wild barley is susceptible to fire, and wild oats

more tolerant than wild emmer except around rocks.

MORTALITY DURING FIRE

Distribution and survival of wild cereal grains after arson fire

supported these predictions. The study site was a

Cenomanian limestone/dolomite plateau (Givat Ha-Kerem) in

Jerusalem, covered by terra rossa (Danin and others 1983).

Since 1948, grazing has been excluded almost completely

(there was no grazing at all by domestic animals during

1987-8), and as a result, the site is dominated by wild cereals

(as are many other outcrops of the same rock type around

Jerusalem). In recent years, fires have been set annually on

Givat Ha-Kerem by schoolchildren celebrating the end of

term; because of the extremely rocky terrain, however, fires

arc spotty, so that some patches remain unaffected. To

determine vulnerability of wild cereal diaspores to fire, I

roped off small (IO-27 dm’) plots in the burned parts of Givat

Ha-Kerem in March, 1988 (9 months after the fire, and long

after the completion of germination), and determined percent

mortality as the ratio of number of spikelets without seedlings

Table 2. Scorching of wild cereal diaspores

Jerusalem, 1987

to total number of spikelets. Random samples of spikelets

that failed to produce seedlings revealed that all grains were

discolored or charred, and probably inviable: germination of

spikelets in these species is normally on the order of 90

percent or more (Anikster and others 1988; Golcnberg 1986;

Blumler unpublished data). I sampled plots in open ground,

as well as adjacent areas by rocks. Because of the large size

and only partial burial of wild cereal diaspores in open areas,

all spikelets could be easily located. However, determination

of wild emmer mortality rates adjacent to rocks was more

problematic, because it often buries itself completely there.

Wild barley occurred almost exclusively in unburned spots,

such as ant nests and rockpiles; I was unable to locate it in

burned areas until anthesis, at which point it was too late to

sample the previous year’s diaspores. Hence, only the effects

of fire on wild emmer and wild oats could be studied and

compared. However, the strong preference of wild barley for

unburned spots suggests that it is intolerant of fire.

Unfortunately, I developed back problems arid was forced to

terminate the experiment after only a small number of plots

had been examined. Nonetheless, I obtained statistically

significant results.

The results are presented in table 2. In open areas, wild

emmcr spikelet mortality was high, on the order of 60

percent. Wild oat mortality was less than that of wild emmer

by an arson fire on Givat Ha-Kerem,

Plot”

Sl

s2

s 3

s 4

Uild Enter Wild Oats

Scorched Seed1 ings Pet Hortati tyb Scorched Seedlings Pet Mortal i tyb

164 9 8 62.6 1 2 4.5 21.1

3 9 4 2 48.1 4 7 140 25.1

112 17 86.8 I 0 100.0

6 1 63 49.2 4 II 26.1

s5 2 9 2 8 50.9

405 248 62.0

1 3 102 11.3

II 298 20.5

R I 1 6 1 5 51.6 I 66.7

R4 1 9 2 6 42.2 : 4 33.3

“Plots Sl-S5 were located in open soil; plots RI and R4 were located beside rocks,

adjacent to Sl and S4, respectively.

bPercent mortality was calculated assuming that one and only one seedling arose from

each viable diaspore. To the extent that seed predators may have removed diaspores,

total mortality rates are likely to have been higher than calculated here.

‘Wild emmer and wild oat d&spores typically contain a non-dormant

grain and one or more dormant ones; the roots of the plant derived

from the non-dormant grain tend to pull the d&pore down into the

soil to some extent, thus increasing burial of dormant grains (Zohary

pets. comm.).

354
at every open soil plot except S3, which contained only a

single wild oat diaspore. If this plot is excluded because of

the small wild oat sample size, wild emmer mortality was

significantly greater than that of wild oats (t-test, p < .Ol).

Most scorched diaspores lay on the surface or penetrated only

slightly beneath it. Many surviving grains, on the other hand,

wcrc almost completely buried. Wild oats were rare adjacent

to rocks, so comparison with wild emmcr in that microsite is

problematic. There was no clear indication that the two

species differed significantly in mortality around rocks. Wild

emmcr survival was greater in plots R] and R4 than in the

adjacent open soil plots, but tests of statistical significance

cannot be carried out on such limited data. Within RI and

R4, surviving wild emmcr diaspores wcrc often complctcly

buried, and immediately adjacent to a rock, whereas the

destroyed diasporcs tended to bc a few ccntimctcrs away from

the rocks, and not so well-buried.

DISCUSSION AND CONCLUSIONS

These preliminary results suggest that fire could have been

employed to selcctivcly reduce the importance of wild barley,

and perhaps also to favor wild emmer in rocky arcas, but that

wild oats would generally benefit most. At Givat Ha-Kcrcm

wild oats dominates most open soil areas, for instance, while

wild emmer shares dominance in open soil at Givat Ram, a

nearby unburned site. However, further multi-year studies

are needed to verify these conclusions, and other aspects of

wild cereal demography need to be studied, such as the

effects of fire on reproductive output and predation. Wild

emmcr seems to be a poor competitor (compared to wild

barley and wild oats), so reduction in seedling density might

allow it to establish larger, more productive individuals.

Harvester ants sernirufis) are the major seed

predators at many wild cereal sites, such as Givat Ha-Kcrem,

and they forage more efficiently where litter has been

removed. Observations indicate that ants take wild barley

relatively easily, perhaps because its single awn and elongate

shape increase its maneuverability; wild oats and emmcr, on

the other hand, have spreading awns that catch in litter, and

harvesting rates of these two species may increase

dramatically on a bare surface. In the absence of empirical

data, one cannot rule out the possibility that in open areas

wild emmer mortality from charring and heat might be

balanced by wild oat mortality from predation, although this

seems unlikely. Also, while the distribution of wild barley is

suggestive, other explanations for its rarity on the Givat

Ha-Kerem bum should be considered. It is possible, for

instance, that wild barlcy requires relatively fertile conditions,

such as are found on the harvester ant nests, which happen

also to be seldom burr&, However, data on species

composition before and after fire at other Israeli sites

(Olsvig-Whittaker and others n.d.; Blumler unpublished data;

Naveh and Whittaker unpublished data) indicate that wild

barley suffers dramatically during the first season aAer a

bum.

There is no archaeological record of use of wild oats, and

wild oats are less efficient to harvest than wild emmer or

barley (Ladizinsky 1975). Hence, it is by no means certain

that Epipaleolithic people would have found it worthwhile to

burn wild cereal stands. Nonethclcss, they may have burned

dense maquis on Mt. Carmel and other Levantine hills to

encourage wild cereal establishment, as proposed by Naveh

(1984; Kutiel and Navch 1987a, b).

Another possibility, which has not been considered in the

agricultural origins literature, is that fire may have been used

to favor wild legumes (specifically, the progenitors of lentils,

peas, and chickpeas). These plants are seldom abundant

today, and thus seem to be poor food resources (Blumlcr

1991a; Ladizinsky 1987; Zohaty and Hopf 1973). Yet they,

too, were cultivated at an early date-possibly as early as or

even earlier than the cereals (Kislev and Bar-Yosef 1988).*

Fire oRen seems to favor legumes (e.g., Barry 1971; Burrows

1991; Dc8elm and Clebsch 1991; Masters 1991; Parsons and

Stohlgrcn 1989). Future research should be directed towards

testing the hypothesis that burning could have markedly

increased the abundance of edible pulses, as well as to

refining our understanding of the effects of tire on wild cereal

grasses

ACKNOWLEDGEMENTS

I thank Avinoam Danin, Ron Cerson, Pua Kutiel, Zev Naveh,

Linda Olsvig-Whittaker, and Daniel Zohary for information

about my study site, and stimulating discussions concerning

the influence of fire on wild cereals.

%terpretation is problematic because of the diffuculty in

distinguishing wild from domesticated legumes in the archaeological

record.

35.5
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358
FLORISTIC AND HISTORICAL EVIDENCE OF FIRE-MAINTAINED,

GRASSY PINE-OAK BARRENS BEFORE SETTLEMENT IN

SOUTWEASTEFW KENTUCKY

J.J.N. Campbell’, D.D. Taylor”,

M.E. Medley-‘, and A.C. Risk’.

Abstract-Several rare plant species in Appalachian Kentucky have been found generally on sandy ridges of

lhe southern Cliff Section in native grassy roadside vegetation or young brushy pine-oak (P~~~s-@&)TI~s)

woods, and almost never in areas with less human disturbance. They include Agalinis &ce&&,Asrer

concolor, Casanea prtmila, Cirsium carolinianurn, Eryngium )wct~%lium, Gymnopogon ambigrcus,

Helianrhru awonrbens, tia~ris sqrrarrosa, Lilium philadelphicum, &n&era perennis, Parrhenirmr

inlegniJoiinm, Ph1o.r amoena, Polygala polygama, Rhynchosia lomeniosa, Robinia hispido var. rosea,

Sauicula n~ariian&ca (var. pefiofrrfala), Schwalbeo americana (a candidate for federal protection) and

Sporohohu c/andesrinus. Most are concentrated in the southeastern U.S.A., and sevcrai arc. typical of open

pine or oak woods with frequent fire. Either these species have invaded roadsides and other disturbed arcas

aRcr settlement, or they arc relicts from openings that Were maintained by fire, Indians and ]argi: hcrhivorcs

hcfore settlement. The latter hypothesis is supported by the virtual absence of tlxsc spccics in rcccnt

clearings, wggesling low reproductive rates; some species have disappeared since 19.50. Also, thcw are

historical indications that fire did maintain some Open pins-oak barrens, logclhcr with an associated

Federally Endangered animal-lhc red-cockaded woodpecker (Picoides borealis).

INTRODUCTION

During ongoing inventory of rare species in the Daniel Boone

National Forest (DBNF) and other areas of Appalachian

Kentucky (Palmer-Ball and others 1988, Campbcli and others

1989, 1990, 1991), it has become clear that several rare

plants are largely rcstrictcd to roadsides and other currently

disturbed upland areas in the southern “Cliff Section” (Braun

1950). The purpose of this paper is to summariT,,e the

distributions of these species, and to present the hypothesis

that most arc relicts from woodland openings maintained by

fire, which became supprcsscd with the establishment of

DBNF in 1930-40 (Martin 1990).

The Cliff Section is a highly disscctcd, largely forested region

with exposures of sandstone and, at low elevations, hmcstone

(fig. 1). To the west, it merges with the Highland Rim in the

south, or with the Knobs in the north. To the cast, there is a

transitional “Low Hills Belts”, then the “Rugged Eastern

Arca” of the Appalachian Plateau, then the Cumberland

Mountains (Bratm 19.50). The boundary of DBNF

approximates that of the Cliff Section, plus some extensions

‘The Nature Conservancy, 642 West Main Street, Lexington, KY

40508.

‘Dat$$[ Boone National FOTL’S~, &xca District, 18% Big Hill Road,

Berca, KY 40403

‘Department of Biology, University of Louisville, Louisville, KY

40292.

‘Department of Biology, Morshead State University, Morchcad. KY

42653.

into the southern Rugged Eastern Area. The Cliff Section has

a much greater density of globally and regionally rare plant

spccics than elsewhere in Appalachian Kentucky, except for

some parts of the Cumberland Mountains.

The rare species can be divided into groups based on their

typical habitats. These arc rocky banks of larger streams,

seeping streamheads on broader ridges, overhanging cliffs

with rockhouses, flatter rock outcrops on clifilops and ridges,

typical upland forest on moist to dry soil (with relatively few

examples), and upland roadsides or disturbed woods. There

is almost no overlap between these species groups, except for

about five of the roadside group that have also been found on

rocky riverbanks (see below). The “roadside” group mostly

occurs in the southern half of the Cliff Section, especially in

McCrcary, Pulaski, Whitley and Laurel Counties (fig. 1).

Most spccics are restricted to the southeastern U.S.A., and

several are typical of open pine or oak woods with frequent

fire. The term “barrens” is adopted in this paper for the

putative iire-maintained, prcsettlement vcgctation. This term

has similar meaning to “savanna”, which has been used more

widely in the southeastern Coastal Plain for particularly flat

and grassy woodland with greater seasonal changes in

hydrology. Species nomenclature generally follows Kartcsz

and Kartcsz (1980).

359
KENTUCKY

Figure 1. Map of Kentucky showing (a) major physiographic regions (dashed lines); (b) subsections (dotted lines) of the

Annalachian Plateau and Mountains--from west to east, Cliff Section, Low Hills Belt, Rugged Eastern Area and Cumhcrland 1 - r

Mountains; and (c) the study area referred to in text (hatched)

SOURCES OF INFORMATION

Most of the data summarized below is in the database on rare

species that the Kentucky State Nature Preserves Commission

(KSNPC) has compiled during the past 15 years from all

known publications on Kentucky plants, and from unpublished

data shared by cooperating rcscarchers. The rare species list

used by KSNPC is currently undergoing revision, and

relevant unpublished data of the authors should be

incorporated soon. Records from the Somerset and Steams

Districts of DBNF, with which this paper is largely

conccmcd, were increased 3-4 times during the 1987 and

1989 cooperative inventories (see Introduction). Most of the

earlier records were referred to by Rogers (1941) and Braun

(1943, plus her collection labels). The inventories included

searches along most public roads in the study areas, and much

exploration of remote forested areas. Although transects were

not quantitatively sampled, statements below that certain

species appear largely restricted to roadsides arc based on

intensive local exploration. At most open sites with rare

species, the adjacent forest was explored to see if these

species extended into the shade. For general information on

the effects of fire in recent history, D.D.T. interviewed

several older USFS personnel and other residents familiar

with the southern half of DBNF, especially Winnifer Freeman

(Somerset), Clcmon Garrison (Mount Victory), Joe Planck

(Somerset) and Ray Powell (McKee). The only other

summary of fire-history in DBNF is the recent study of

Martin (1990), which includes statistical details from USFS

files.

NOTES ON RARJI SPECIES OF ROADSIDES

AND THICKETS

The list below includes all native species that generally meet

two criteria.

(1) Within the Appalachian region of Kentucky, they are

largely restricted to well-drained non-calcareous uplands of

the Cliff Section (especially the southern half) and, in some

cases, the Cumbcrland Mountains.

(2) Within this region, there are generally fewer than 10

records of each species (excepting arrorubens,

Malus angustifolia and Phlox amoena),md most records are

from grassy roadsides, brushy areas or open woods disturbed

by man within the past IO-20 years.

In parentheses after each species: name is the number of

Kentucky counties where it is known, followed by the approximate total of known sites in the state. Unless stated, most

records are post-l 950.

AgaZin& decedoba(2/3). In Kentucky, this southeastern

(mostly Piedmont) species of dry open woods and edges is

known from only three collections. These were made in 1927

(oak-pine woods), 1934 and 1987 (grassy roadside), all on

dry, sandy ridges in the southern Cliff Section.

Asclepias ampt?&cauB (1 l/35). This widespread eastern

species of dry openings is scattered over southern Kentucky.

Almost all Appalachian records are from roadsides on ridges

in the southern half of the Cliff Section.

360
Aster correoior (4/12). In Kentucky, this southeastern species

of dry sandy barrens and open woods is known mostly from

the southern Cliff Section (plus two western sites). All post1970 records are from upland roadsides, with only l-20

plants, except for one site on Kentucky State Route (KSR)

751 with several hundred. Two of the four older (1940-50)

records are from “dry” or “open grassy pine” woods.

Aureoladapecfirrafa (7/10). In Kentucky, this southeastern

species of dry woods and openings is known From scattered

southern counties. There is one Appalachian collection, made

during 1939 in the southern Cliff Section on a “dry wooded

bank of Bridge Fork Pond” [an artificial pond]. The closely

related, or sometimes combined, northern species, A.

pedicularia is known from grassy openings on Pine Mountain

(Harlan Co.).

Curex grav& (13/3,0), This widespread mid-western species

of open ground is known from several scattcrcd areas of

Kentucky (except the Bluegrass Region), mostly as the more

southern var. lunelliana. In the Cliff Section, it is known

only from disturbed woods, edges and roadsides, on sandy

and calcareous soils.

 physorhytzca (2 14). This southeastern species of sandy

open woods was recently discovered in Kentucky, from a

barrens in the western Highland Rim (R. Cranfill, pers.

comm.), and from roadsides and adjacent young, open Pinus

virginiana woods in the southern Cliff Section.

Castanea pumila (7/10). In Kentucky, this southeastcm

species of dry, sandy thickets and disturbed woods is largely

restricted to the Cumberland Mountains, but there are a few,

mostly old, western records. There are only two verified

Cliff Section records, both southern, from 1935 and 1989 (a

suppressed individual on a small stream tcrracc). Johnson

(1989) noted “its ability to recover from fire and other

disturbances, through rapid suckering and sprouting from the

remaining stem at or below the ground level.” Near Jasper,

Georgia, M.E.M. observed abundant suckers afler

clearcutting, in association with Robinia hispi& varieties (see

below). In addition to fire-suppression, the chestnut blight

(Endofhia parczsitica) has probably reduced this species.

C$shm carolidanum (6115). This southeastern species,

generally of dry sandy open woods and edges, has been

recorded in scattered areas of Kentucky. Most sites are in the

Cliff Section with half these in a 50 km’ area along the

Cumberland River, generally on roadsides, except for one in

a more natural grassy pine-oak woods (table l), and another

at the edge of a small calcareous prairie. Only l-20 plants

have been found at each site.

&4wia &]a.rcens (414). This southern, pantropical species

of open pineland has been reported in scattcrcd noncalcareous regions of Kentucky. The two Appalachian

records are from dry sandy roadsides on Cliff Section ridges.

Whether it is truly native to open pine woods in this region

may be doubted given the weedy nature of this gnus.

Eryngium yuccifo&m ( > 201> 50). This southeastern and

mid-western species of prairies and barrens is frequent in

naturally open vegetation of westem Kentucky, but there is

only one Appalachian record, from the southern Cliff Section

on “a moist flat of pine-oak barrens” (Rogers 1941).

Gymnopogon ambiguus (7112). In Kentucky, this

southeastern species of dry, sandy openings and open pineland

(especially lire-maintained Pinus pa/rcc;fr& woods on the

Coastal Plain) is known from scattcrcd southern arms. There

are only three Appalachian records, from “sandy shores,

South Fork of Cumberland River” in 1935, and, in the 198Os,

from an open grassy roadside in the southern Cliff Section

and a seasonally wet field in the southern Rugged Eastern

Area.

H&tll/lus ntrorubetts (6/> 50). In Kentucky, this

southeastern and Appalachian species, generally of dry open

woods and edges, is known only from the southern Cliff

Section and the transition to the Low Hills Belt. The sites arc

mostly roadsides, and occasionally young open woods. It is

locally dominant, with patches of several hundred plants, but

only non-flowering plants occur in more shady areas.

Letiphyllum buwiJofium (Ill). This species of Appalachian

heath-balds, Coastal Plain sand-hills and pine-barrens, has

been collected once in Kentucky, during 1939: “[a single

individual] on top of dry [sandy] bank, Cumberland Falls,

within park on S side of road going west, about 10()-2(lo

yards from park entrance” (McInteer 1940). The area is

generally forested today, except for the roadsides. Another

Appalachian heath-bald spccics, Rhododendron minus, still

occurs in roadside woods near the park, but these may be

planted. There is one other report of R. minus from

Kentucky, on pine Mountain (E. Carr, pers. comm.).

361
Table 1. vascular plants fhmd on or near Rrassy roadsides with rare species

Nomenclature @nfmliy follows Hartes~ and wartesz (1980); selected symqym

are in parentheses. Family amaqeamt follow TImme (1961). + indicates

species present; * indicates species locally abomht.

A-H: areas of ID-150 m 2 armad patches of Aster uon l@R 751, fmm

1.5 km S of m 27 to 0.4 km N of railmad.~aski Co.

I: ca. 150 m 7 armmd pat&es of Aster concolor along dirt ruad, Bindsfield

RwF, 1.5 km SE of KSR 192, Pulaski Co.

J: ca. loo m’ around pat&es of PolyRaIa polyrcaera by Sand Hill Cbamb on KIR

700, 8.5 km S of IpiR 92, McCreary Co.

K: areas totaling ca. 50 m 2 around patches of Liliua pkiladelpkicam 011 KSR 192,

1.15-2 km E of Craig’s Creek Road, Laurel Co.

L: ea. 100 m 7 at “Bald Rock” on KSR 192, 1.7 km E of KSR 1193, Lame1 Co.

h k ca. 3000 m 7 along RSR 700 and adjacent utility right-of-may, 1.5-3 km SW of

sand Hill church, McClYary Co.

N: ca. 200 m2 arvund Poly&a pol.y~ama along dirt mad by Roaring Pamcb Creek,

0.8 stream-km N of KY-TN state-line, McCn?ary Co..

0: ca. 300 m2 arouad !%pombolos claodestims and phlox amoena.aloug I8R 791,

1.3 km W of RSR 92. hkCrexy Co.

p: ca. 2000 m 2 around outcrops at Dobbs Hill on RSR 1363, 0.8-1.1 km W of

pi-t Bill church, McCreary Co.

Q: ca. 5ooo m2 of pine-oak barrens. (traversed by old road bed), 0.8 km NW of

R~I-IWI Fork Cemetxy, I.6 km SSE of Flat Rock, Mcczwwy Co.

ABCDEFCHIJKLMNOPQ

PTERIDOPHYTES

Pteridiaa aq.ilimm var. latioscolam + + +

Pellaea atmpwpmw *

Aspleniom Platyneuroll + +

Rbodsla obtma t

polysticbUOl acrasticboides t t

GYMNOSPERMS

Pinus rigida + t

Pinus virginiana t++t tt t t t * *

Pinus echinat~+ +++ tt * t

virginiana

DIC%%!??b’JS

+ t * t

Magnoliaceae

Liz-i- tolipifera t t t t t

Annonaceae

Asimlae triloba

Lauraceae

sassafras albidoa t t ttt

Ranunculaceae

Aaesone virgiuiaoa t t

Aquifoliaceae

Ilex opaca

Clusiaceae

I&II&CISI (Ascyrum) kypericoides + t + t

w- geotianoides t +

Ericaceae

Dxydendrm arborem t t t

Caylussacia bmckycera t

Vacciniam stani- (and neglectwn) t t

vaccinium zlakmua ttt tt + t

VacCilliup vacillam + t + t

Ebenaceae

Dlospyms virginiana + A t t

Caryophyllaceae

E Cerastium glomeratum (viscosum) +

* serpyllifolia

F l$ZZ amerla

t

t

Silene virginica * +

E Silene aatirrhina +

Pottulacaceae

Talinum teretifoliom +

Ptiniulaceae

Lysimackia lanceolata +

Lysimachia qwuh-lfolia

Polygonaceae

E Romex acetosella

362
*

t t

+

t t

t

+

A

Table I. (contimml)

ABCDEFCHIJKLMNOPP

Geraniaceae

Gerauium carolinianum +

Oxalidaceae

E Oxa\is fontaM C”eUrOpaea”) +

Oxalis violacea t

Li aaceae

Lisum virginiaaum t +

Polygalaceae

Polygata poiygama + +

Polygata sfwga var. latifolia +

Polygala curtissii

Polygaia (verticillata var.1 dgua +

Celastraceae

Ce1astx-u~ scandens

lJ=onyous americaRIs

Violaceae

Viola pedata

;ik& hc;sutuia

. easu.ginata

Viola tripartita var. glaberrima

Viola rafinesquii

Brassicaceae

E Arabidqds thaliana

E-se birsuta

E Erophila venta (Draba v.) +

Iepidlum virgiuicum

Ulmaceae

Ulmus alata

Celtis tenuifolia

Cistaceae

Le&ca racemutosa

Rhamnaceae

Rbamus camliniam t

ceauutlaa? americaua

Euphorbiaceae

Fupborbia coroi tata

Anacardiaceae

Rhus (ToxJcod~) radicans

thus glabra

Rhus copallina

Juglandaceae

z gtxn;e;osa

Ace%aepJ’ i da

Acer rubrum var. II‘.

Fabaceae

Sclmmkla dcmphylla t

Cassia (Cbamecrista) nictitmw ++ +t

E Lotus corniculatus t

E Trlfolias a@-este (prOCumbenS) t

E Mel i (otus officinaiis t

ksmlitn nudiflorw .

Desrsodiua ciliare 0 8

~esaodim mari landicum t 0 t El

Desoodiua panicutah (sensu strict01 ax? + .

~esdtlol glabelLum* (nut bumifiwm) d 6 d +

b&tlip viridif lorum t 0

Desmediae laevipaha, + t t 0

Lespedeza repens +

Lespeaeza virginica t + t

Lespeaeza intermedia t t t t

Lespea~a istermdia x virginica +

L4!spedeza birta + t t tt t

E l.e.sw strlata + ?

E Iespedeza csne+a t t

Stylosanthes biflora + t

Tepbmsia virginiana var. v. ttt + t +

Clitoris mariana t t

t *

t

4

m *

+ m

t t t i

t * +

+

it++ t tt t t

+ t

t t

??+? t t

ttt++ttt tt *ttt

363
Table 1. (continued)

ABCDEFCHIJHLMNOPQ

Amphicarpa bra&e&a var. b.

Galactia volobilis

Hamamelidaceae

Liqoidambar styracifIoa

Fagaceae

Querms alba

Querms stellata

Qmemaa meataae ("prinus")

PO- falcata

Qae- marilaodica

z

velotiaa

cocci nea

Betulaceae

@-Ya virginiana

Rosaceae

Fl-agU-ia virginiaoa var. v.

Potentilla siqtlex var. s.

Poteotilla canadensis var. c.

Rubus Ftagellares (gmq~)

+

t tt t +

+

+ + + tt *

+ + + + *

+ t t t t t

+ t t +

ttt t+

+ t ttt t t t t

t t t+t t +

t

+ t *+

t t

+ + + ++ t

+t tt t t

+ +

Rubus allegbenieasis var. a.

Rubus Airgutae @-PI

Rosa Camlioo

Pnmos semtisa

Amelaocbler arlmrea var. a.

Crassulaceae

ESeduaaQp

Onagraceae

oenotbera bienois

E Oemthera laciniata

Rubiaceae

Bedyotis pupnrta (H0taonia Lanceolata)

Bedyotis caemlea (Houstonia C.)

Galiom pilosm var. p.

Apocynaceae

Alcmqmm camabiooa

Asclepias asplexicanlis

Asclepias exal atata

Asclepias variegata

Asclepias verticillata

Gentianaceae

Gentiana villosa

Scrophulariaceae

AgaIinis deceslo4a

PdiCOIiWiS craoadensis

Aebmsi a artemisifolia

E Achi I lea mlllefoliom

E -w$F(xi) (Le vu’gare) + i

Chrysopsis (Pityopsis) graahifolia +

Chysopsis marlana t t

Sol idago hispida

solidaao erecta +t*

Sot idago oemomlis +++

SoIidago arguta 5-m. a.

Solidago odora t t

Solidago qo~a

Solidago gigantea

Sol idago altissima t

Sol i&go (l?mt&mia) graminifolia

Aster mdolatw +

t

+

tt

+ +++

++ +++

ttttt + +

+ + ++ ++

++ t+ + *

t + t

t ttttt tt

t

?

t t

t

+ t t tt

t ++

+

t

t +

t

+

t

t

+

+

+

+

+

+

t

+

t

t

*

t

t

t

t

t

?

+

t

t

t

t

+*

*tt

?

t t

Aster

Aster

Aster

Aster

Aster

Aster

Aster

Aster

Aster

Aster

patens VW. patens

surmlOSOS

concolor

limriifoIius

inf i rmus

mhellatw

patemos

solidagineas

pilows var. pilaws

1aterifIorus

t tt ttt tt tt t

t t t t +*

ttttttttt

t tt tt

t

t

t

t t

tt t t t

t t

364
Table 1. (coatisaed)

ABCDEFGHIJWLMNOPQ

+++t +t

+

tt+

tt

tt

++ +tt+

1 ? ?

t tt

+ tt

ftt

t tt t tt

Aster damesus var. cm-i di fol i es

El-igeros -us

Frigema strigosus

cmadensis var.

zium

pasilla

obtusifoliam

Aatemeria plantaginifoiia

P.opatoriaa fistaiEupatoriaa alhua

F.qmt0l-i am r&uadifoliem

Eapatorium ammati cm

Eupatoriam Ngosom var. r.

Liatrls sqaamelosa

Lhtl-iS Si-ephdla

Cirsicm, mti am

Cirsiam camliniamm

Cirsima discolor

ELephantopus t-tasus

Plwlailtlle.s serpentaria

LaCtOCa canadeosis

Bieraciom venosam

lklgia virgiaica

MONOCOTYLEDONS

Liliaceae

Liliam pbiladelphiCua MT. p.

Ihwlaria perfol i ata

Aleris farimsa

Smilax glaE Verbascam tbapses

E Veroslca fUW?lLSiS

Plantaginaceae

Plantago rugelii

Plantago virginica

E Plantago laaceolata

Acanthaceae

Baellia camlinlensis

Lamiaceae

Pmaella vulgafis var. laaceolata

Salvia lyrata

E .%tmmja (Clinopodium) vul!W'iS

PY-- pycmatkmoides var. p.

E fbsla dianthera

Polemoniaceae

Phlox alsoena

Solanaceae

Solo CarolilliConvolvulaceae

Iposaea P-J-e

coavolvalus walystegw spi thameas

E Cowolvulus (Calystegla) sepia= var. s

Campanulaceae

Lobelia puberula var. simslam

L4helia inflata

Specolaria (Triodanis) pedoliata

Vitaceae

Vitis aestivalis

Vitis vulpina

Vitis rataadifolia

-iSSOS qaiaquefolia

Nyssaceae

Nyssa sylvatica var. s.

Cornaceae

Cornus florida

Apiaceae

Saaicala marilaadica var. petiolalata

Saoicala canadais

E Daucus cmta

Caprifoliaceae

E lmicera japonlca

+t

t

++ tt

t

ttt

+t

t

t

t

t

??t

t

+tt

tt

?+t

tt l 5%

+t+

+

t++

tt

t

t

t

**t

+

t

?

t t+

ttt

t

t

ttt

t

t

t *+

t t l

tt l

0

tt ttt

tt+

0

d

t

0

tt

365
Table 1. (coatiooed)

ABCDEFGHIJKLMNOPP

?+ t

+

t + + t

t t tt t t

tt ++ t t

t

t t

+ t

t *

tttttttttttt ++

t * t

Asteraceae

Heliaotkos atmwbem var. a.

Angeti ca venefwlsa

Beliastbss divaricatas

Bf?lialkhW aiCI-UCephal0.S

Beliantbos hirsotas

Verbesiaa (Actiaomxis) altemifolia

VerlRsisa occidentalis

Bmbeckia fulgida W I -. fulgida

bdbeckia triloba var. t.

con?opsis =t.inaJor

Partbeaiaa istegrifoliaa var. i.

SIEilaX bombarm

SailaX rotmdifolia

Dioscoreaceae

E Diascorea batatas

Juncaceae

Lamla ecbiaata

Cyperaceae

Ql=- owlaris

c- gravida

C- artitecta (and C. physorhynca)

Caret ambellata (tonsa)

c- sigm-maqisata

~arex hi-tells (ceqlaaata var. h. )

Cares camlisiasa

Carex masii

Poaceae

Stipa (Piptochaetiumf avenac~

Daathosia spicata

IhstJxmia sericea

~ristida dichotoma

Al-i&i& longespica

Aristida paqwascens var. drsata

E -jtiE ha collpressa

E Poa pratensis

E Festaca elatior (seasa [ato)

E Festuca (Vulpia) octoflora

E Holcus l~tns

E Dactylis glomerata

Elyms glabriflorus

igzzt

ambigow

spectabilis

SpmoboluS cleodestimls

F.riaothos alopecaruides

Antropogoo (Schizochyrium) =opari=

Anhopogon e=-dii

All- VirgiaiaLs var. v.

Alahpgm temarius

--i+=- outans

panicton flexile

Pasicam aaceps

Pasicoa (Dichaatbeliam) boscii

paninta (D.) comnutatum

panicam (D.) rawaelii

Panicon CD.1 polyaothes

paai- CD.1 Mahoicoa (D.) ladfIpanicam (0.) liadheimeri

P&CLUE CD.1 acuminatx~~ (sensu Lato)

hoiasa CD.1 miaocarpon<

t

t +

+

t t t

+

t

+

+ +

t t

t

t

t t

.

0

4 om *t*

*ml+ +*

t t

t

t

+

+

t

f

+

t t

t

*+***t+ t t

k t*

+ + + t

t t

* t*tt t

t

+*++ t

t t t

+

t +

t

hlicaa, (D.) dlcllotamla csensu sti-1cto1 t

pani- CD.1 depauperatmn

E? Setaria genicslata

+ +

t

t *

+

+* t*t

t t

t t

t

*+

t t*

t t

+ ?

t t

t

+t* t

t

t+t t

t * ? +

+

366
cap&a (or hybrids) ( > lOI> 20). In Kentucky,

this widespread eastern species of dry openings (oficn sandy

pincland) is scattered in western regions. Howcvcr, there arc

only three Appalachian records, all from the Cliff Section

during 1935-40 (Rogers 1941, Braun 1943). Braun’s plants

were idcntificJ as L. simulota, which has been interpreted as

a hybrid bctwecn L. capirara and L. virginica or L.

inrerrnedia. Also, it was found during 1989 in a wet

bottomland meadow half a mile south of the KY-TN stateline.

Lialrk squarrosa ( > 20/> SO). In Kentucky, this widcsprcad

sou[haslcrtl species of dry openings is frequent in southern

and western regions, but there are only two Appalachian

records. Both are from rclativcly undisscctcd ridges on the

eastern side of the soulhern Cliff Section, in 1937 (dry open

woods) and 1989 (dirt roadside). Liufrk spccics that are

more widcsprcad in the Cliff Section also occur on the

roadsides, cspccially L. sqrrarrulosa, less often L. spicala,

occasionally L.. aspera, and on rocky sites L. microcephalu.

LiLium ph&delph&m (g/1,1). In Kentucky, this species of

dry to damp, acid openings, thickets and pine barrens is

known only along the Cliff Section, as the largely

Appalachian var. philadelphicum. Most records are from

roadsides on ridges, but one is from the edge of a calcareous

prairie, and a 1940 record is from dry pine woods. It was

locally common (Rogers 1941) but several populations have

disappcarcd in the past lo-30 years. Currently, most sites

have only l-5 plants; none exceed 70. In addition to hrcsuppression, digging for ornament may have contributed to its

decline.

Malus angustifolia (61 >25). This southeastern species of

open woods and thickets is reported from scattered noncalcareous areas of southern Kentucky, mostly in the southern

Cliff Section. There may be some intermediates with the

more northern M. coronaria (cspccially var. lanclfdia). Most

sites have only 1-I 0 trees and are on dry ridges along roads

and in young woods of Pinus virginiana or pine-oak. One

population has at least 50 trees (with much Crulaegus spp.

and Prumts amen’cana). Less often, it has been found on

rocky riverbanks, or on bottomland thickets extending into the

Rugged Eastern Area.

Melampyrum lirteare (3/3). In Kentucky, this northern

species of dry to damp brushy grassland and open woods is

known from a few records in the Cumberland Mountains, as

var. lal~$/i/i~n, and in the Cliff Section, as var. americanurn.

The latter variety is currently known only along the 75 m

paved trail to Sky Bridge, with 400-500 plants at the edge of

dry woods dominated by Pinw rigida, Quercus spp.,

Gqlrtssacia baccara and Vacciniron vacillans. An annual

species, it oficn increases in woods afler fire or logging

(Swan 1970; Scheiner and Tecri 1981; Abrams and Dickmann

1984; Gibson and Good 1987).

Muh,Qrrbe@r torreyano (i/l). This southeastern species of

“pine-barrens and meadows” is a candidate for federal

protection. There is only one obscure Kentucky record

(Hitchcock and Chase 1950), presumably based on a

collection in the southern Cliff Section or the adjacent

Highland Rim. It was formerly known from the oak-barrens

region of Tennessee, in the transition from Highland Rim to

Applachian Plateau (Svenson 1941).

Uenothera perenntk (3/3). In Kentucky, this north-central

species of wet, or occasionally (in the south) dry, natural

openings is known from only three southern records. The

only Appalachian record, dated 1935, is from the southern

Cliff Section, in “dry soil, open woods” along a ridge road,

close to Schwalbeo atnericuna (Braun 1943 and collections).

The only post-1960 record in Tennessee is from a

physiographically similar roadside (Patrick and others 1983).

Orbexilum peduttculatum var. pedunculotum (Psorako

p.rorafioties var. p.) (4/l 0). In Kentucky, this southeastern

variety of dry openings has been found in a few southern

counties. The only Appalachian records are from the

southern Cliff Section, either on ridgetop roadsides, or on

open rocky riverbanks.

Panicum aciculare (415). In Kentucky, this southeastern

(generally Coastal Plain) spwies of sandy pine woods is

known from a few southwestern sites (as var. acicrtlare), and

from two sites in the southern Cliff Section (as var.

angustiJXum) on ridges in dry, open, grassy pine woods near

a road and a cliffIop. As “P. angu.stifolium”, this species was

reported to increase greatly with frequent prescribed burning

by De&lm and others (1973). Some other Punicran spp. may

have similar distributions and responses (e.g., p. ra~~enellir)

Partherrium irrtegrifolium ( > 201> 50). This mid-western

and east-central species of dry openings is not rare in western

Kentucky. Howcvcr, the only Appalachian records arc about

15 sites in the southernmost Cliff Section, mostly on ridgetop

roadsides with only l-10 plants. At least 20 non-flowering

plants were found in a more shady barrens (table 1).

Paspnlum setaceum var. lottgepedunculatum (414). In

Kentucky, this southeastern taxon of sandy openings with pine

is known from a few open ridgetop sites in the southern Cliff

Section, and as a railroad waif in Jefferson County.

367
Phlox amaena (7/> 2.5). In Kentucky, this southeastern

species of dry openings is known from the southern Cliff

Section and the adjacent Highland Rim. It is locally frequent

(with 100-1000 plants) along roads and adjacent forest edges,

generally on sandy soils and occasionally above limestone.

Only one site has frequent plants in more natural vegetation:

the rather open, grassy, stunted Pinus virginiana woods on

the sandstone outcrops ofDobbs Hill (table 1). j (

Polygala poijgama (116). In Kentucky, this northern and

Coastal Plain species of dry, sandy openings is known only

from the southernmost Cliff Section. Most sites are upland

roadsides (with lo-50 plants), but a 1935 record is from

“pine-oak” woods. It is a short-lived perennial that often

increases after fire (Abrams and Dickmann 1984; Niering and

Dreyer 1989).

Rhyrrchosia tomentosa (3/3). In Kentucky, this southeastern

species of dry, sandy openings is known from only three

records. The only Appalachian collection, dated 1949, is

from the “edge of cut-over woods, 4 miles east of

Cumberland Falls” (probably along KSR 92). Also, it was

found in 1989 about 2 km south of the KY-TN state-line, on

Big Island in the Big South Fork.

Robiniu hispi.da var. rosea [= R. boyntonic) (4/10). In

Kentucky, this Appalachian taxon is known only from the

Cumberland Mountains (with other varieties) and the southern

Cliff Section, mostly in a 10 km2 area around Day Ridge,

McCreary Co. All sites are on relatively narrow sandstone

ridges or knobs in dry pine or oak woods, especially young

stands, thickets and edges. It occurs at low density in patches

up to 30 m*, with flowering observed only in the open.

San&.& ntari.kndica (I/2). In Kentucky, this north-central

(to Rocky Mt.) species is known from only two localities,

each with less than 10 plants, in the southern Cliff Section.

They were found in edges and burned thickets along roads on

rather broad ridges between the Cumberland River and the

Big South Fork. The plants are var. periol~lafu, which

typically occurs in “dry sandy pineland” of the southern

Atlantic Coastal Plain (Fernald 1950).

Schwa&a americana (112). This species is a candidate for

federal protection that is known from sandy, acid, damp to

dry soil in open pine or oak barrens on the Atlantic Coastal

Plain, plus a few old collections from Tennessee (including

the “oak-barrens” of the Higland Rim-Cliff Section transition)

and Kentucky. The Kentucky collections were from “dry

sandy soil on knobs and sandstone plateau margins” in the

southern Cliff Section, “with Cl&es” at one site (Braun

I937b, 1943). This species appears restricted to tiremaintained vegetation (S. Orxll, pers. comm.). Musselman

and Mann (1977) noted: “particularly vigorous growth of

Schwalbea was evident aflcr early spring fire at the Horry

Co. [SC] site. In such years, seed production was abundant.”

It is parasitic on a wide range of woody plants.

Sporobolus ckrrldestks (7/8). In Kentucky, this widespread

eastern species of dry openings is known from scattered

southern regions. The only Appalachian records are from the

southern Cliff Section, on roadsides adjacent to sandstone

outcrops, and on some limestone clifftops. It is locally

dominant, with patches up to 300 m’.

Tephrosia spicalo (217). In Kentucky, this southeastern

species of sandy openings is known only from the southern

Cliff Section. Most records are from open rocky banks of the

Cumberland River. Two others are collections dated 1941

and 1980 from disturbed areas on rtdges near Barthell

(McCreary Co.).

Viola fdriatula /= V. sagitbta var. ovafix] (3/3). In

Kentucky, this north-central species of disturbed woods

(especially on mineral soil) is known from a few Cliff Section

records. The only post-1950 record is from McCreary Co.,

along an old eroded roadside, with at least 30 plants.

NOTES ON ASSOCIATED VEGETATION

Some of the roadsides with rare species have a relatively high

diversity of native species, and a low frequency of exotics.

Table 1 lists the ca. 300 vascular species found at good

examples of such vegetation and some nearby grassy woods.

The most abundant species include several warm-season (C4)

grasses, with Andropogon scopurius the most frequent

dominant. The only typical native cool-season (C3) grass is

Stipa ovenaceu, which is locally dominant in young pine

woods adjacent to the roads. Other frequent species include

composites, especially Coreopsis major, He1innthu.s spp.,

ChrysopsiE spp., Solidago spp., Aster spp. and Eupatorium

spp., and legumes, especially Lespedeza spp. and Desmodium

spp. About 10 percent of the species present are exotics, but

most of these were recorded only at the Dobbs Hill site,

which is the only site adjacent to houses. The only exotic

found at more than 2-3 sites is Chrysanthemum leucanthemum

(= t. v&are).

368
One of the most extensive native grassy areas, with several

rare species (especially Aster concolor), is along 3 km of KSR

751 between Bumside and Keno (Pulaski Co.). In addition to

the typical dominants--Andropogon scoparius, A. gerardii and

Sorghastrum nutans, frequent species here include Tephrosia

virginiana, Lobelia puberula, Helianthus hirsutus, Coreopsis

major, Senecio anonymus, Chrysopsis mariana, C.

graminfofolia, Solidago erecta, S. nemoralis, S. odora, Aster

patens, A. concolor, A. durnosus, Gnaphalirrm obtu.si$ofolium,

Eupatoriron rotundfolium, E. aromaticum, Panicum anceps

and Andropogon virginicus. Adjacent forest is dominated by

Pinus spp., Quercus spp. and Acer rubrum.

Typically the soils are hapludults with fine sandy or silty loam

texture, A horizon pH of 4.5-5, and a depth of SO-150 cm to

the sandstone or shale. On shallower hapludults or

dystrochrepts near sandstone outcrops, the vegetation

generally lacks taller species such as Andropogon gerardii,

Sorghastrum nutans, Helianthus atrorubens and Eupatorium

spp. An unusual variant with patches of Sporobolus

clandestinus was found on some rocky sites, especially Dobbs

Hill. In addition to abundant Pina virginiana at this site, the

trees included much Juniperus virginiana, which, together

with some of the other frequent species (especially Ulmus

alata, Celti.s tenuifolia, Rhamnus caroliniana, Phlox amoena,

Rudbeckia triloba, Pellaea atropurpurea and Woodsia

obtusa), may indicate more base-rich soils (following

Campbell 1987). S. clandestinus itself is also frequent on

some limestone sites.

Apart from these roadside remnants, there is little information

on the barrens or open forest that may have existed when

annual burning was a common practice before DBNF was

established. However, on drier ridges in the southern Cliff

Section, Braun (1950, p. 102) noted: “Instead of this

pint-heath or pine-oak-heath community, some of the

promontaries arc occupied by open pine woods (the three

species of pine) with a grassy layer of Andropogon scoparius

(little blucstcm), A. glomeratus (broom-sedge), and

Sorghastrum nutanr (Indian grass), in which arc a few scattercd forbs. Fires have modified most (perhaps all) of these

pine summits, although the abundance of large Cladonia

(lichen) mats is an indication that there has been no fire for

many years.”

Similar vegetation may have extended onto relatively moist

sites, where droughts still occurred oflen enough to spread

fires. The only direct information about such woods comes

from Rogers (1941). He noted the following plants in “a

moist flat of pine-oak barrens” along the road to Bauer: ,‘$a/&

hurnilis (vars. hurnilis and microphylla), &pericufn

punclawtn, Eryngium yuccifolium *, Liatris scariosa [probably

L. squarrulosa*] and L. spicata*; and he noted Helianthus

atrorubem* in “pine-oak barrens at the Tennessee State

Line.” Also near the Bauer Road, he noted several species

typical of openings or edges, all in “woods” unless note&

Andropogon gerardii (“common”), Robinia hbpjda*,

Lespedeza virginica, L. capitata*, Polygala verticillata,

Oxypolis rigidior, Angelica villosa, Cuscuta campestris,

Solidago caesia, Aster pafens (“var. phlogfolius”) and A.

solidagineus; Pycnanthemum pycnanthemoides, Helianthus

hirsutus and Coreopsis major var. stel[ata (all “dry woods”);

Anemone virginiana (“dry pine-oak woods”); Lobelia puberula

cwet woods”); Lilium philadelphicurn* (“common along

road”), Coreopsis tripterk var. deamii (“by the road”);

Hypericurnfrondosum [prolifcum?j (“low, moist, shafey soil

in open thicket”). In 1987, Andropogon gerardii is still

common along the road to Bauer, but of the rarer species

(shown by *), only Helianthus atrorubens was encountered.

Except for some of the roadsides, there are virtually no areas

where a diverse native barrens vegetation remains. A few

woodland-pastures today may bear some structural

resemblance to prcscttlement barrens, and such areas were

frequently burned by residents before the modem era of firesuppression. However, grazing has been intensive, and exotic

plants have often replaced the native flora in such pastures.

None of the rare plants listed above have been found in

actively pastured areas. A few dry, wooded areas near

cliffiops have an open grassy aspect, with occasional fires,

but these have generally become too shady for most of the

rare species noted here.

NOTES ON FIRE HISTORY

Archaeological evidence shows that, for at least 10,000 years

before 1650, Indians lived in many parts of Appalachian

Kentucky (e.g., Cowan 1985, Ison 1990). It is likely that

they used fires extensively for managing game animals and

clearing garden plots, especially on slopes near rockhouses.

Lightning fires are relatively infrequent in DBNF, with only

IO-15 per 1000 km’ each year (Martin 1990), and they are

probably not repeated often enough in the same locations to

create open grassy vegetation. However, the role of Indians

versus lightning in causing prescttlement fires must remain an

open question.

There was almost no landscape description in the pioneer

literature from the southern Appalachian Plateau in Kentucky

and the adjacent Highland Rim. A few accounts suggest areas

disturbed by fire, Indians or buffalo (Bison bison). Walker

(1749) dcscribcd an area in Jackson County where “The

woods have been burnt some years past, and are now very

thick, the only timber being almost all kill’d”, and an area in

Morgan County with “the only fresh burnt woods we have

369
seen.” He noted Indian trails and buffalo in several places.

Near Pincville, he initially named Clear Creek as “(Jovcr

Creek”, noting that “Clover and hop vines are plenty there”;

the clover was probably TriJoliutn stoloniferutn, which was

associated with buffalo in Kentucky (Campbell and others

1988). Walker (1824), recounting his travels in 1775, noted

“twenty miles, entirely covered with dead brush” in the

Rockcastle and Laurel County area. This statement suggests

the results of a large fire (see also McHarguc 1941). Amow

(1960) noted descriptions of pioneers in the Cumbcrland River

drainage that suggested “park-like” forests “with so little

undergrowth a traveler could see a deer for 1.50 paces. There

were, too, along the creeks and rivers, treeless glades and

valleys, sometimes lilled with cane...or only high grass...”

Edwards (1970) described Wayne County (mostly in the

eastern Highland Rim) during about 1775: “Three-fourths of

the county was covered with virgin forests; the lowlands

contained some cane, or tall grass as they preferred to call

it...Price’s Meadows [initially called the Big Meadow], near

the mouth of Meadow Creek, contained very high grass.

Corn could be planted without the forests being cleared.”

Interviews with older residents provide a general historical

view of the southern Cliff Section. Until DBNF was

established in 1930-40, intentional fires were widespread,

except perhaps for a few decades before 1910 when the

Kentucky Landsharers Association had control over much

land and restricted burning. Annual fires occurred in much of

the area during 1910- 1930. They were generally set in

February and March to promote grass and forb growth for

cattle. Also, hogs ran in the forest, with about 0.5-I per

km2, and many became feral. In some years, a second set of

fires were set in October or November “to keep the woods

open”. Fires were generally started along roadsides on ridges

and allowed to bum without control, unless property was

threatened. In general, ridgetop forests contained much

Quercus coccinea (ca. 50-60 cm dbh), Q. velutina and Pinus

echinata, with scattered Q. alba (to 100 cm dbh) and

Liriodendron. Most woody understory on ridges was

removed, except for scattered Quercus spp. and Liriodendron,

creating some savanna-like areas. The ground cover of

blueberries and other low ericaccous shrubs, grasses and forbs

was much thicker than today. Pink ladies’ slipper orchids

(Cypripediutn acaule) were more frequent, but yellow ones

(C. p&escem) were reduced by fire. Composites were more

frequent, though concentrated along roads. Birds were

generally more numerous, though wild turkey (Meleagrti

gallupavo), like deer (Odocoileus virginianus), had been much

reduced by hunting.

By some accounts, fire would generally stop near the top of

east and north slopes, but it would creep down west and south

slopes, creating a scrub forest with such species as Pinus

rigida, Quercus marilandica and Kabnia lutifolia. However,

by other accounts, the fire would often be blown onto cast

slopes by prevailing winds, and it would seldom move down

west and south slopes. Accounts agree that north slopes

seldom burned and oflen had thick understories of Acer

saccharum and A. rubrum below canopies of Liriodendron

and Quercus spp.

Acquisition of land in DBNF by USFS began about 1933,

bringing with it suppression of ftre. Burning for forage

generally stopped about 1945, though arson increased after

1970. All accounts agree that pine is more common today

than 40-60 years ago. Abandoned fields and open woods

grew back with much pine and Liriodendron. However, soils

on and near ridgetops were often so worn-out that only scrub

trees, mostly pines and oaks, grew back, and were called-

“barrens”. Fire was not generally set in this scrubby

vegetation, which did not bum well. Remaining barrens of

:his y,w ,kive ,rruub ,li~k4r,~~~.~~7\.~od31: “uggcQtin% fire

exclusion.

DISCUSSION

The restriction of several rare plants in southeastern Kentucky

to roadsides and similar disturbed sites might seem

paradoxical, because such artilicial habitats arc generally

considered to be dominated by common weeds and grasses.

Two general hypotheses may explain this phenomenon: (a)

these species have invaded the region along roads and other

disturbed ground after settlement and forest-clearance; or (b)

they arc relicts from natural openings that were maintained

largely by fire, with old stable roadsides and adjacent areas

offering them a continually open refuge.

The following two arguments favor the latter hypothesis (b),

involving fire.

(1) These species generally do not appear invasive or weedy

within this region, except perhaps a few of the more frequent

ones (also Digitaria violascens and Paspalum setaceum var.

longepeduncrtlatrtrn). Most have never been found in tree-fall

gaps, clear-cuts, cropland, pastures, old-fields, artificial

wildlife-openings or railroad rights-of-way. Moreover, some

of them appear to have declined or disappeared in recent

decades: Aureolaria pectinata, Castanea pumila, Eryngium

yuccfolium, Leiophyllum bu.$olium, Lespedeza capitata,

Lilium philade(phicum, Muhlenbergia torreyana, Oenothera

perennis, Rhynchosia tomentosa and Schwalbea americana. It

seems most unlikely that the rarest species, especially those

with disjunct records 100 miles or more further south

(Muhlenbergia torreyana, Schwalbea americana) dispersed

into Kentucky in the 200 years since settlement.

370
(2) As noted above, there is considerable evidence that fire

has played an important role in the upland forests of this

region within the past loo-200 years, before the modem era

of fire-suppression. It is possible that death of large trees due

to other factors in the prcsettlemenl forest crcakd temporary

gaps suitable for some of these spccics. However, rapid

dispersal into such gaps would still bc rcquircd, and, as

already noted, these species generally have not dispersed into

newly created openings.

Further support for the “fire hypothesis” comes from evidcncc

in other southcastcrn regions. Even in the Appalachians, fire,

mostly set by Indians, was probably a widespread factor

maintaining open vegcta{ion bcforc European 

(Dcvivo 1990), and early settlers continued frcqucnt burning

(pync 1982, Otto 1983). On the Coastal Plain, there is

evidcncc of widespread prehistoric, anthropogcnic fire (Myers

and Peroni 1983). and several of the rare spccics noted above

arc typical of fire-maintained vegetation in addition to rightsof-way (S. Or&l, Florida Natural Areas Inventory, pers.

comm.). Experimental USC of fire in the Southcast has

confirmed that barrens or savanna vegctalion can be rcstorcd

and maintained by decades of annual burning (Komarek 1974;

Kulhavy and Connor 1986; DcSclm and Clcbsch 1990).

One of the closest areas to southeastern Kcnkxky where

extensive fire-maintained arcas existed before settlement, and

where substantial pieces still survive, is the “oak-barrens”

region centered on Coffee County, Tennessee (Svcnson 1941;

Patrick 1979; D&elm 1989; DcSclm and Clebsch 1990). The

open grassy vegetation there is typically found in rclative[y

flat areas, locally with fragipan soils, on the Appalachian

Plateau and its residuum overlying the eastern Highland Rim.

Almost all the rare species noted above in soulhcastcm

Kentucky occur in that region, plus scvcral rat-c spcoics of

seasonal wetlands. Some species have no records in between,

but thcrc are a few well-known barrens sites with rare species

on the Appalachian Plateau in northeast Tcnncsscc (Patrick

1979; D&elm 1989, and unpublished).

Other circumstantial cvidcncc concerns the habitat of the

red-cockaded woodpecker (Picoides borealis), a Fcdcrally

Endangered Species. This species has dcclincd drastically in

Kentucky within the past 50-100 years, and only 10-l 5 birds

arc currently known (S. Phillips, pers. comm.). Optimal

habitat for this southeastern spccics appears to be dry, open

forest with large pine trees at least 75-100 years old. Given

the admixture of hardwoods in DBNF, it is estimated that 400

ha may bc required for a stable colony. In Kentucky, logging

of large pines has probably been the major cause of the

species’ decline, rather than understory encroachment, and the

birds may be more tolerant of closed forest than those on the

Coastal Plain (P. Kalisz, pers. comm.).

Much of the older pine today, including most trees used by

the woodpeckers, grew up during the period of frequent

burning for woodland-pastures. During the last century (from

County Court Deed Books; and Barton ]919), about 5-10

pcrccnt of the southern Cliff S&on forest was composed of

pine, mostly Pinw echinnta. This percentage is probably

much higher that which would exist without any fire.

Without fire, current patterns of succession suggest that pine

would be largely confined to the driest ridges and clifftops,

whcrc, despite extensive recent searches, signs of the redcockaded woodpecker remain extremely rare. Therefore,

before scttlcment, it seems likely that this species was largely

dcpendont on fires to rcgencratc extensive areas of pine,

especially the relatively fire-tolerant Pinrcs e&nolo (Martin

1990).

Although this paper focuses on the rare spccics of moderately

dry soils in open habitats, several other uncommon or rare

spccics in this region of Kentucky may have benefited from

fire. Some of these are restricted to thin soil around rock

outcrops with little or no woody cover, especially Arenaria

glabra, Crotonopsis elliptica, Oenothera IiniJolia and T&urn

tereti@liium. Fires may have increased the openness of such

places. Some more widespread species can persist in the

shade of relatively undisturbed pine-oak forests, but clearly do

belter in the open. Such species persist mostly along trails

and logging roads through the forest, but they are locally

frequent in small clearings and burned arms. They include

Cleistes divaricata (see also Komarek 1974; Gregg 1989),

Danthonia compressa (see also Lindsay and Bratton 1979),

Isotria verticillata (see also Baldwin and Wieboldt 1969) and

Porteranthus tri/oliatus. Such species are probably too

widespread, well-dispersed and persistent in shade to be good

indicators of prescttlement barrens, though they may well

have occurred in relatively moist or shady variants of such

vegetation.

The “fire hypothesis” may also be extended to some

uncommon or rare spccics of seasonally wet, flat ground in

thin-canopied forest, thickets, small natural openings or

adjacent old-fields. In Kentucky, some arc largely restricted

to strmmhcads in the southern Cliff Section: Curex joorii,

Calamagrostis cinnoides, Calopogon trtberosus, Grati&

pilosa, Lobelia nuttalii, Platanthera cristata, P. integrilabia

and Vernoniu noveboracenris. Others arc mostly in broader

valleys adjacent to, and in a few cases within, the Cliff

Section, mostly in fill-sun: Bartonia virginica, Drosera

brevi$olia, Eryngium prostratum, Gratiola viscidula,

Gytnnopogon brevifolius, Hypericum canadense, Hypericum

crux-andrewsii (Ascyrum stuns), Platanthera lacera, P.

ciliaris, Polygala cruciata, Sabatia catnpanulata, Stenanthium

gramineum var. micranthum, Trichostema setaceum and Xyris

torta. Although the wetness of these sites is probably

371
suflicicnt to maintain small openings, it is likely that fires

formerly increased the openness. Forest succession appears

to have eliminated some of these species from some sites, and

excessive mowing from others (Campbell and others 1989,

1990). They generally have southeastern ranges, especially

on the Coastal Plain (see also Braun 1937a,b), where several

occur typically in wet, open pine barrens or savanna, where

annuals fires promote unusually high diversity (Komarek

1974; Folsom 1979; Walker and Peet 1983).

In more rugged areas of Appalachian Kentucky cast of the

Cliff Section, the general lack of rare species suggesting a fire

history might be attributed to the general lack of extensive

broad, flat ridges where fire might have frequently spread

before settlement. However, the endemic Silphiu~n

wu.sioten.ris (similar to S. mohrii of the “oak-barrens” in

Tennessee and elsewhere) is restricted to young woods and

roadsides on lower slopes, often in areas that have burned

(Campbell and Medley 1990). Also, on Pine Mountain, there

are small grassy openings with a few rare species that may

have been mainhind by tire: Aureolariapedicularia (see also

A. pectinata above), Baptisia tinctoria (see also Niering and

Dreyer 1989, in relation to fire), Danthonia compressa and

Robinia hispida var. kekyi (see also var. rosea above).

In contrast, on more calcareous soils at or just beyond the

western margin of the Cliff Section (and in cases indicated by

* below, rarely on richer soils in the Rugged Eastern Area),

there are several uncommon or rare species of roadsides or

other openings that may indicate a tire-history. Some of these

species still occur in relatively natural glades, grassland or

brushy woods with occasional fire. They include Apocynum

medium (or A. androsaemifolium), Castilteja coccinea *,

Echinacea purpurea, Lathyrus venosus var. inton.ws*,

Gentiana alba, Orbexilum onobrychk* (Psoralea o.),

Phaseolus po/ystachios*, PO&ala senega var. senega, Salvia

urticifolia, Silene regia (Rogers 1941), Silphium

terebinthinaceum var. brauniae, Solidago ridiga, S. speciosa

var. speciosa* and Veronicastrum virginicum*. For

individual notes, see Campbell and others (1989, 1990;

Palmer-Ball and others 1988).

In conclusion, although no definitive statement can be made

based concerning the relationship of these rare species to tire

within Kentucky, it is likely that fire was a major factor

maintaining them on the presettlcment landscape. The exact

nature of their barrens habitat will perhaps never be known,

but it is likely that large areas were dominated by a relatively

open canopy of pines (especially Pinus echinata), with some

oaks, and much grass (especially Andropogoneae and Stipa

avenacea). Although the evidence is circumstantial,

biological interests, especially in the federally listed species,

warrant serious attention to the following suggestions.

(1) It should be recognized that most of these rare species are

probably relicts of a natural community that is virtually

extirpated within Kentucky.

(2) A search should be made for similar vegetation remaining

elsewhere, which might provide clues about ecological

factors.

(3) The roadsides and other rights-of-way where these species

survive should be managed to maintain their populations.

(4) Attempts should be made to reconstruct the original

pine-oak barrens using fire, starting in areas adjacent to the

roadsides with these species.

ACKNOWLEDGMENTS

This paper was stimulated by a conversation with Grady Clay,

of Louisville, KY. We thank The Nature Conservancy, U.S.

Forest Service and Kentucky State Nature Preserves

Commision for permitting us to use data from the cooperative

inventories of DBNF and other sources.

372
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375
LODGEPOLE PINE ARTHROPOD LITTER

COMMUNITY STRUCTURE ONE YEAR AFTER

THE 1988 YELLOWSTONE FIRES

Tim A. Christiansen, Robert J. Lavigne, and Jeffrey A. Lockwood’

Abstract-Litter arthropod data was collected every 10 days from nine intensively burned forest stands,

five lightly burned stands, and nine unburned forest stands. For burned forest stands (n=540 samples,

there were decreases in insect density (87 percent), noninsect density (67 Percent), noninsect taxa (63

percent), and noninsect diversity (20 percent).

Burned stands with greater densities of tree seedlings had significantly (P <O.OS) lower arthropod densities.

Those with greater densities of standing dead trees had si ni a I- tcanlty higher arthropod densities and lower

diversities. Those with greater densities of litter had significantly higher a&ropod densities and lower

diversities.

INTRODUCTION

Remarks by E.O. Wilson (1987) at the opening of the

invertebrate exhibit of the National Zoological Park in

Washington, DC, states the importance of invertebrates to

ecosystems. He remarked “if invertebrates were to disappear,

I doubt that the human species could last more than a few

months. Most of the fishes, amphibians, birds, and mammals

would crash to extinction about the same time. Next would

go the bulk of the flowering plants and with them the physical

structure of the majority of the forests and other terrestrial

habitats of the world. The earth would rot within a few

decades the world would return to the state of a billion years

ago, composed primarily of bacteria, algae, and a few other

very simple multicellular plants.” A researcher in forest

resources, K.J. Stoszek (1988), noted “insects are among

nature’s most prominent agents of influence. Almost every

process in forest ecosystems (for example, nutrient cycling),

each developmental phase of forest stands, and every life

stage of dominate and subordinate species of forest vegetation

are subject to direct or indirect influences of feeding by

insects. Without insects, current patterns of plant

reproduction, growth, and death would not exist.”

Arthropod communities located in unburned, lightly burned,

and intensively burned forest stands were studied 1 year after

the 1988 fires. The objectives of the study were (1) to

determine the effects of fire on habitat structure, (2) to

determine the effects of tire on litter arthropod diversity,

density, richness and species evenness, (3) to correlate habitat

factors (i.e., density of standing dead trees, herbaceous cover,

seedling and sapling density, number of fallen trees, and

litter biomass with arthropod ecological parameters, and (4)

discuss management procedures for conservation of arthropod

communities.

‘University of Wyoming, Department of Plant, Soil and Insect

Sciences, L.aramie, WY 82071.

METHODS AND MATEFUALS

Yellowstone National Park (YNP) occupies 8995 km’ in the

northwestern comer of Wyoming with small areas located in

neighboring Idaho and Montana. Elevations range from 1500

m to over 3400 m. Present climatic patterns produce

generally long, cold winters and short, cold summers.

Annual precipitation ranges from 75 mm to 200 mm

(Houston 1982).

Forested areas occupy 79 percent of YNP. Lodgepole pine

(Pinus contorta) comprises 81 percent of the forested areas at

elevations of 2300 m to 2600 m in which we have research

sites (Houston 1982).

Nine randomly chosen unburned forest stands of at least 5 ha

were paired with nine intensively burned forest sites and five

lightly burned forest stands. Lodgepole pine stands were

considered intensively burned if (1) all the trees la&cd

branches, (2) there was very little ground litter biomass, and

(3) fallen trees were burned to some degree. Lightly bumed

forest stands produced as halo fire stands around intense fires,

had a soil litter layer, fallen trees which were singed, and

trees with branches and needles burned and brown but still

intact.

Arthropods were collected during July to mid-September,

1989. Litter was collected from five 0.5 m2 quadrates every

20 m (the initial starting point was randomly chosen each

sampling period) along two of the three transects (the

transects were randomly chosen before each sampling period)

every 10 days in each forest site. Each litter sample collected

for arthropod extraction was stored in a zip-lock plastic bag

for not more than 12 hours before processing. These samples

were then placed in Berlese funnels for 24 hours. Arthropods

extracted from litter were stored in 70 percent ETOH.

Density of both live and standing dead trees, seedling density,

fallen trees, and percent herbaceous cover were determined

376
by making counts within a l-m swath along each transect on

each site. Litter samples, which were collected for biomass

weight, were placed into paper bags. Litter samples were

oven dried for 24 hours at 25 O C ZUIII weighed to the nearest

0.01 gram.

Ecological parameters were of arthropod and annelid density,

species richness, species evenness, and diversity. kmity

was based on the number of individuals per quadrate, species

richness was based on numbers of individual species

(Southwood 1978); evenness and diversity (Shannon-Weaver

using the natural log) were analyzed using a program

developed by Kotila (1986). Simple linear regression

(STATGRAF) was used to determine biotic correlations at the

P < 0.05 level of significance. %sdeot’ s t-tests was used to

identify statistical differences (P < 0.05) between ecological

parameters for unburned, lightly burned and intensively

burned stands.

RESULTS

Forest Arthropod Community

Undisturbed lodgepole pine forest stands (trees > 100 years)

contained higher biotic variables than fire disturbed lodgepole

pine stands (table 1). Litter biomass was decreased 19

percent in lightly burned stands and 62 percent in intensively

burned pine stands. Downed trees decreased 24 percent in

light bums and 30 percent in intensively burned pine stands.

The percentage of herbaceous cover decreased 96 percent in

light bums and 86 percent in intensively burned forest stands.

Litter mites were the dominate arthropod fauna in both

density and species richness (table 2). Insect richness

declined 63 percent in lightly burned mature lodgepole pine

stands and 67 percent in intensively burned stands of that type

(table 3). Insect community density was affected even more

than richness with a 92 percent loss in light bums and an 82

percent dcchne in intensively burned stands. Community

diversity declined more in light burns (66 percent) than in

more intensively burned sites (40 percent).

Noninscct richness declined in both lightly burned stands (71

percent) and intensively burned stands (66 percent) (table 3).

Community density declined 89 percent in light bums but

only 67 percent in intensive bums. Noninsect diversity

dcclmed most in light bums (65 percent) and less (32 percent)

in intensive bums.

Table 1. Biotic variables for tmhumed, lightly bumed, and

intensively burned lodgepole pine stands

Variable Fire distorbaace

Nose Light fire Intense fire

Litter bimmss

(g/lm2)

Trees with needtes

>1.82m ht. (no./100m2)

Tree seedlings

<15.24cm bt.

(no./100m2)

Trees with needles

>15.24cm ht.

and d.82m bt.

stanfling dead tzmes

needles

Zl > l.Om ht.

Logs

llerbacems cmef

(pe-4

153.20a’.’ 123.60a 57.801,

42.82a 45.20a O.oob

24.42s 7.80b 17.64a

40.50a 0. cm 0. oob

12.09a 14.20a 33.08b

38.11a 29.00a 26.73b

50.19a 1.9Ob 7.24b

'Meaos followed by different letters differ at the P<O.OS level

of significance according to Studeot’S t-test.

+27 transects.

Table 2. Major arthropod gnupings (percent) ia udsmed,

lightly burned, and intensively burned lodgepole pine stands

Fire disturbaoce

Ax-tbruood El-o00 None LiPht fire Inteusive fire

Mites

Oribatids 42’ 15 38

others 21 4 8 47

Insects

Collembola 24 31 s

0tbel-s 13 8 10

Species

Mites

oribatids

others

Insects

Collembola

16 2 3 17

38 23 37

25 31 3 0

2 3 23 16

In=540 samples.

377
Table 3. Ecological paranmeters (avg/n?) for litter

arthropodsin unburned, Lightly burned, and intensively

burned Lodgepole pine stands

Parameter

Fire disturbance

None Liaht fire intensive fire

Insects

Richness

Density

Evenness

Diversity

18.80a'pz ?.OOb 6.10b

154.70a 13.00b 19.40b

.82a .97b .87a

2.39a .82b 1.43c

Noninsects

Richness

Density

Evenness

Diversity

27.80a

222;;::

2.52a

a. OOb 9.40b

25.00b 74.1oc

.78a .75a

, 67b 1.70a

‘Means followed by a different Letter differ at the ptO.05

Levei of significance according to Student’s t-test.

‘n=540 samples.

Factors influencing litter arthropod ecological

parameters in unburned, lightly burned, and

intensively burned forest.

The following are biotic variables which have been correlated

(P < 0.05) with litter arthropod ecological variables.

Unburned forest stands.

Diversity was negatively correlated with tree

seedlings (f =0.91).

Diversity was positively correlated with trees over

1.84m in height (r*=O.66).

Diversity was negatively correlated with standing

dead trees (?=0.66).

Density was positively correlated with logs

(?=0.66).

Lightly and intensively burned forest stands.

Density was negatively correlated with tree

seedlings (?=0,66).

Discussion. Biodiversity conservation is currently an

important and intensively researched topic. Temperate

regions should not be given any less attention than tropical

regions. Temperate systems may not have the highly diverse

fauna as found in the tropics, but temperate systems are

important to world-wide biodivcrsity (Piclou 1979).

Management decisions which may affect temperate forest

arthropod communities cannot be based on research conducted

in the tropics.

What is the goal of biodiversity conservation? Why should

we study arthropod diversity and community structure? The

goal may be to maintain a system by prescribed bums or the

goal may be to allow system succession by naturally caused

fire. The goals are determined by forest and national park

resource managers. A number of studies indicate that natural

disturbances are critical in maintaining species diversity (Horn

1974; Levins 1968; Tilman 1982).

E.O. Wison’s address states the importance of understanding

arthropod communities. Arthropod community structure is

changed by habitat structure manipulation (Christiansen and

others 1989; Schowalter 1985).

Forest Arthropod Community Structure

Habitat structure.

Habitat structure is important for arthropod community

structure. One theory of preservation and conservation

practices is that natural systems should be left alone and not

cleaned except by natural phenomenon (Franklin 1988).

Prescribed fire is one approach that is used to modify forest

habitat structure. The degree of fire disturbance most

certainly affects various forest components. Comparsons of

unburned, lightly burned, and intensively burned lodgepole

pine stands in Yellowstone National Park lead to the

following conclusions.

If litter biomass and survival of older trees are important to

conservation practices for the Yellowstone region, than light

bums are a good strategy. However, intensively burned

stands contained more tree seedlings, standing dead trees, and

herbaceous cover than did lightly burned stands. Thus,

intensive burns provide more potential resources, at least in

the short term, for arthropod biodivcrsity than lightly burned

pine stands provide.

The greatest loss of litter arthropod diversity in lodgepolc

pine stands occurred in lightly burned stands. Lightly burned

pine stands also had lower arthropod community densities

than unburned or intensively burned stands had. These results

are interesting since the largest litter biomass loss occurred in

intensively burned stands. It is possible that light bums

disrupt trophic webs enough to eliminate many arthropod’s

food resources but do not disrupt niches enough to make

invader species competitive. lntensive bums drastically

&creased litter biomass, which may have disrupted niche and

food resources to such a degree that invader arthropod species

can compete. Disturbance may benefit species diversity by

opening habitats to fugitive species that ephemerally invade

disturbed habitats (Conncll 1978; Sprugal 1985).

Influence of habitat on arthropod ecological parameters.

Litter arthropod diversity in unburned and burned lodgepole

pine stands was lower in stands with higher tree seedling

densities. It may bc that stands with higher than average

seedling densities contained lower densities of mature trees.

Thus, habitats, in both unburned and burned stands might

378
have been more open than usual and might have had lower

litter arthropod diversity for that reason. Many arthropods,

such as Collcmbola (springtails) and many fitter mites, arc

sensitive to moisture differences which could be affected by

more open habitats. A study by Pontailler (1979) described

moisture fluctuation due to tree thinning and establishment of

forest gaps. A second possibility is that pine seedlings have

not yet produced enough litter to support litter fauna. Both of

these explanations are supported by the finding that higher

than average arthropod diversities occurred in dense stands of

mature lodgepole pines. These stands had closed canopies

and greater litter biomass than found in dense stands of tree

seedlings. Studies by Schowalter and others (1981) and

Seastedlt and Crossley (1981) showed that many arthropod

species became more abundant as debris increased, and that

numbers of insect species that inhabit leaf litter increased

enclosed-tree-canopy sites.

Lower arthropod diversity in unburned pine stands was

correlated with greater numbers of standing dead trees. The

occurrence of lower arthropod diversity in older stands may

be inconsistent with the view that old-growth forests support

high arthropod diversity (Franklin 1988). Older stands

contained more fallen trees than did younger stands. A

positive correlation existed bctwccn higher arthropod

community density and grcatcr numbers of logs. This

correlation indicates that old-growth pine stands support a few

high density litter arthropod species.

Litter arthropod community density correlated negatively with

pine seedlings. Higher pine seedling densities were found in

intensively burned stands, which also had lower litter

biomass. It is biologically significant that lower arthropod

density would be correlated with reduced litter biomass;

reduced litter biomass means reduced food and habitat

resources for litter-inhabiting arthropods. Increasing densities

of standing dead trees were corrclatcd with higher arthropod

densities but lower diversity.

Arthropod density and diversity were low on burned sites with

large numbers of logs. Lightly burned pine stands, which

contained more litter biomass than intensively burned stands,

contained higher arthropod community densities and lower

diversity. This implies either that a few species were able to

adapt and multiply in burned stands or that invader arthropod

species entered the stands from nearby unburned pine stands.

Conclusions About Arthropod Diversity

and Conservation

Habitat loss is one of the major factors in diversity reduction

(Pimm and Gilpin 1989). The present study showed that litter

arthropod diversity was lower in burned forest habitats than in

unburned stands. However, species evenness increased in

disturbed stands. Species evenness is an index describing the

distribution of species in a community. Thus, an increase in

species evenness suggests that competition is among more

species than just those which compose the majority of the

community. Chesson (1985) states that competing species

that cannot. coexist in a constant environment may coexist in

the presence of environmental variation.

If the immediate management goal of burning is to maintain

high litter arthropod diversity, either for biodiversity

conservation or ecosystem functions, then high intensive bums

are the suggested control method. Long-term management

may be a different matter for diversity. Mature unburned

lodgepole pine stands support greater diversity than found in

very young (i.e., seedlings) pine stands. However, litter

arthropod diversity in mature forests with high densities of

standing dead trees is not as great as litter arthropod diversity

in somewhat younger forest stands. These same older forests

support greater densities of fewer litter arthropod species,

however.

Results of our study indicate the complexity of conservation

and management of litter arthropods in lodgepole pine forests.

Our research has only provided preliminary data. There is

clearly a need for more habitat and arthropod community

structure interaction research on an ecosystem level if forest

management goals arc to be achieved.

ACKNOWLEDGMENTS

We wish to thank C. Legg for her help in the laboratory. W C

also thank the University of Wyoming’s National Park

Research Center for support.

LITERATURE CITE:D

Chcsson, Paul. 1985. Coexistence of competitors in spatially

and temporally varying environments: A look at the

combined effects of different sorts of variability.

Theoretical Population Biology. 28:263-287.

Christiansen, Tim .A.; Lockwood, Jeffrey A.; Powell, Jeff,

1989. Arthropod community dynamics in undisturbed and

intensively managed mountain brush habitats. Great

Basin Naturalist. 49570-586.

Conncll, J.H. 1978. Diversity in tropical rain forests and

coral reefs. Science. 199: 1302-13 10.

Franklin, Jerry F. 1988. Structural and functional diversity

in temperate forests. In: Wilson, E.O., ed. Biodiversity.

Washington, DC: National Academy Press: 166-176.

Horn, Henry S. 1974. The ecology of secondary succession.

Annual Review of Ecology and Systematics. 5:25-37,

Houston, Douglas B. 1982. The northern Yellowstone elk.

New York: Macmillian. 456 pp.

Kotila, Paul M. 1986. Ecological measures. [Software

package]. Canton, NY: St. Lawrence University.

Levins , Richard 1968. Evolution in changing environments.

Princeton, NJ: Princeton Press. 120 pp.

379
Pielou, E.C. 1979. Biogeography. New York: John Wiley

and Sons. 351 pp.

Pimm, Stuart T.; Gilpin Michael E. 1989. Theoretical

issues in conservation biology. In: Roughgarden,

Jonathan; May, Robert M.; Levin, Simon A., eds.

Princeton, NJ: Princeton University Press: 287-305.

Pontailler, J.Y. 1979. La regeneration du hetre en la foret

de Fontainbleau, ses relations avec les conditions

hydriques stationnelles. Paris: University of Paris.

361 pp.

Price, Peter W. 1984. Insect ecology. New York: John

Wiley and Sons. 607 pp.

Schowalter, Timothy D. 1985. Adaptations of insects to

disturbance. In: Picket& S.T.A.; White, P.S., eds. The

ecology of natural disturbance and patch dynamics.

Boston, MA: Academic Press: 235-252.

Schowalter, T.D.; Webb, T.; Crossley, D.A., Jr. 1981.

Community structure and nutrient content of canopy

arthropods in clearcut and uncut forest ecosystems.

Ecology. 62:1010-1019.

Seastedlt, T.R.; Crossley, D.A., Jr. 1981.

Microarthropod response following cable logging and

clear-cutting in the southern Appalachians. Ecology.

62:126-135.

Southwood, T.R.E. 1978. Ecological methods with

particular reference to the study of insect populations

New York: Chapman and Hall. 524 pp.

Sprugal, Douglas G. 1985. Natural disturbance and

ecosystem energetics. In: Pickett, S.T.A.; White, P.S.,

eds, The ecology of natural disturbance and patch

dynamics. New York: Academic Press: 335-352.

Stoszck, Karl J. 1988. Forests under stress and insect

outbreaks. The Northwest Environmental Journal. 4:247-

261.

Tilman, David. 1982. Resource competition and community

structure. Princeton, NJ: Princeton University Press.

352 pp.

Wilson, E.O. 1987. The little things that run the world (The

importance and conservation of invertebrates).

Conservation Biology. 1:344-346.

380
SOME THOUGHTS ON PRESCRIBED NATIJRAL FIRES

Jack D. Cohen*

Abstract-Wildland tire is a significant component of nearly all North American ecosystems. High

intensity, stand-replacement tires are normal in certain ecosystems, especially in the northern Rocky

Mountains. Wilderness fire managers are obligated to let tire operate as a natural influence to the extent

that this is possible. Where wilderness areas incorporate stand-replacement-type tire ecosystems,

ecologically significant prescribed natural fires must reach stand-replacement fire intensities. However,

because weather forecasting capabilities are limited, fire managers are unable to predict whether prescribed

natural tires will escape prescribed boundaries. Moreover, the effectiveness of suppression actions

decreases as wilderness tires increase in size. Thus, fire managers face the dilemma of managing for

natural tire influences on ecosystems, with the consequence of increasing the potential for escaped fue

situations.

Typically, thunderstorms develop over the northern Rocky

Mountains in late spring and early summer. The following

hypothetical situation begins on June 29, with lightning strikes

peppering a broad area of the Intermountain region of the

Northwestern United States.

A large wilderness area in the northern Rocky Mountains has

a prescribed natural fire plan under which a few fires are

allowed to bum within its boundaries. These fires are

prescribed so that natural fire will continue to be a significant

ecological influence in the wilderness area. Investigations

have determined that this ecosystem normally experiences

stand-replacement fires. Thus, to be ecologically significant,

the prescription permits some high intensity burning, i.e.,

crown tires.

The fire managers use criteria based on the National Fire

Danger Rating System’s Energy Release Component (ERC) to

decide whether or not to suppress lightning ignitions.

However, using the ERC has had its uncertainties. Last

season, the spring and early summer values were well above

normal. All fires were suppressed. But the July and August

weather had turned rainy and cool, and ERC’s were below

normal.

In the current season, the ERC’s have closely followed

normal values. The 30-day forecast predicts normal

temperatures and precipitation for July. On July 1, a reported

lightning fire is designated as a prescribed natural fire.

However, by July 11, there is a distinct trend toward hot,

dry, weather conditions. From the end of July to August 5,

the ERC’s are consistently and increasingly above normal.

The 30-day forecast for August calls for above-normal

tcmpcratures and below-normal precipitation. Although no

new natural Iires are allowed to bum, the July 1 lire

continues. Even with the hot, dry conditions, the burned area

‘Research Physical Scientist, Southeastern Forest Experiment Station,

Forest Service, U.S. Department of Agriculture, Dry Branch, GA

is less than 10 acres (4 ha) as of August 5, well within the

prescribed limits for size and proximity to boundaries. At

this point, the prescribed natural fire is not yet an ecologically

significant event.

On August 5, the National Weather Service forecasts the

possibility that a dry cold front will move through the area in

3 to 5 days. The forecast does not change the designation of

the prescribed natural fue. On August 8 and 11, two dry

cold fronts produce strong winds. As of August 13, after the

cold fronts pass, the fire perimeter contains over 8,000 acres

(3,200 ha). Numerous spot tires and crowning occur. Within

a period of 5 days, the fire has become ecologically

significant.

The fire managers in this scenario have executed the policy of

allowing fire to assume a more natural role in the wilderness

and have accomplished an ecologically significant fire. But

now they must deal with the uncertainty of the remainder of

the fire season and thus the possibility that their management

fire will escape predetermined boundaries. If undertaken at

this time, an effective suppression action must be capable of

containing an active 8,000-acre fire.

The Yellowstone Fires of 1988 represent one possible result

of the implementation of a Park Service (U.S. Department of

Interior) and Forest Service (U.S. Department of Agriculture)

pohcy that attempts to return historic fire occurrence to

designated areas. Research has established that fire is a

significant component of most North American ecosystems

(Amo and Brown 1989; Wright and Bailey 1982). The policy

that allowed some tires to bum in the Greater Yellowstone

area reflects management’s desire to maintain processes vital

to the ecosystem’s existence.

An effective natural fire policy provides for the occurrence of

ecologically significant fires. That is, the policy prescribes

the occurrence of periodic fires that achieve a range of

intensities over a large enough area so that tire will continue

to be a significant ecosystem process. Normal ranges of

crologically significant fire frequencies and intensities vary

381
among ecosystems. The spectrum ranges from ecosystems

with frequent tires of low intensity to those with infrequent

fires of high intensity (Bacon and Dell 1985). Much of the

Greater Yellowstone area as well as other wilderness areas in

North America have ecosystems where ecologically significant

fires are of the infrequent, high-intensity type that result in

the replacement of all surface vegetation in a portion of the

burned area (Brown 1989; Heinselman 1985).

A problem arises when a natural fire program that requires

high-intensity fires is implemented. Wilderness areas have

administrative boundaries that separate the wilderness

landscape from landscapes where uncontrolled high-intensity

tires are undesirable. Much of the concern during and after

the 1988 wilderness fires (the Yellowstone Complex and the

Canyon Creek Fire in the Scapegoat Wilderness) has related

to natural fires crossing wilderness boundaries and threatening

or destroying outside values. The wilderness fire manager’s

goal is to let tire operate as a natural process and at the same

time contain it within prescribed boundaries. But this goal

can create dilemmas. The following discussion examines, in

terms of scale characteristics, the various elements that

contribute to this potential fire management dilemma.

Although this discussion may relate to the initial

bum-or-suppress decision, it does not specifically address that

decision. Rather, this discussion focuses on the limitations of

managing an ongoing prescribed natural tire.

THE DILEMMA

A natural prescribed fire may bum for several months. Due

to the limits of weather predictability, a fire manager cannot

predict fire behavior on the basis of extended-range weather

forecasts. Thus, it is possible that any prescribed natural fire

will exceed its prescription. There are ecosystems in which

fires must be large and intense if they arc to be ecologically

significant -- and such tires have the potential to out-scale fire

suppression capabilities. By the time a fire manager realizes

a fire will exceed its prescribed limits, suppression efforts

may not be effective. Thus, managing for natural fire

processes in wilderness areas also enhances the potential for

escape.

ELEMENTS OF THE DILEMMA

The basis for the wilderness fire management dilemma can bc

found in the response of fire behavior to the weather,

limitations of weather predictability, and a limited fire

suppression capability.

Wildland Fire

The conditions associated with fast-spreading, high-intensity

tires (e.g., the 1988 Yellowstone Fires) are drought and high

winds. Drought conditions promote drying in vegetative

fuels, both dead and living, thus making the fuels more

flammable. High windspeeds increase spread rates, which

increases intensities and spot fire ignitions. Although drought

conditions are commonly referenced in discussions of severe

fire situations, drought alone is not sufficient to produce

large, high-intensity tires. High windspeeds are required to

drive fire to extreme behavior. Thus, given sufficient fuel

loadings, severe fire situations depend on two different

aspects of the weather.

Weather

Atmospheric phenomena can be generally characterized by

distinct time scales. Dutton (1976) describes the temporal

characteristics of several weather features as follows:

Atmosnheric Dhenomena Time scale

Planetary waves 1 yr- 1 mo

Synoptic systems 1 wk . 1 day

Mesoscale features 1 day . 1 hr

Trends in weather variables such as average monthly

temperature and precipitation are related to the planetary

scale, whereas, a specific day’s temperatures and precipitation

are related to synoptic and smaller scales. Drought conditions

arc associated with planetary waves, and high winds are

associated with synoptic systems and mesoscale features.

Thus, weather conditions operating on two different

atmospheric scales contribute to the conditions that produce

severe fires. In general, severe fire behavior potential

develops over a month or more as fuels become drier

(drought), but has an episodic time scale of one week to one

hour (high winds).

Weather Forecasting

The ability to forecast the weather depends on the atmosphere

having the characteristic of predictability (Lorenz 1968).

There arc indications that the atmosphere behaves in highly

nonlinear ways, and that this limits weather predictability

(Lorcnz 1963, 1969; Gleick 1987; Tennekcs 1988). In a

mathematical modeling context (which is largely how weather

forecasting is done), this non-linearity results in a loss of

connectivity over time. That is, the state of the atmosphere at

a given time (the initial conditions) loses its predictable

relation with the state of the atmosphere at some later time.

I think the general conclusion can be drawn that weather

conditions cannot be specifically predicted over time periods

longer than their associated atmospheric time scales. That is,

a forecast of weather variables associated with the mesoscale

to synoptic time scale (e.g., specific precipitation or wind

events) does not apply beyond about 3 days. Forecasts

covering several weeks to several months, which predict

general trends in weather variables (e.g., departures of mean

temperatures and precipitation amounts from normal) are

associated with planetary time scales. Extended-range

forecasts that provide likelihoods of shorter time scale

weather conditions are not an exception. in this case, the

statistical characteristics associated with a planetary scale

situation are described rather than a forecast of specific

deterministic information about a smaller time scale condition.

382
Effective Fire Suppression

To be effective, a fire suppression action must be scaled to

match a fire’s spread and intensity. A fire suppression action

must be capable of constructing a quantity of fire line

comparable to the spread rates and fire growth, and the fire

line must bc sufficiently wide to prevent crossing caused by

flames and firebrands. A fire suppression action can bc

ineffective because insufficient resources arc committed to it

or because the fire overpowers a maximum practical

suppression effort.

Managing for ecologically significant, high-intensity lircs

requires that these management fires reach large sizes relative

to fire sizes normally controlled as wildfires. To further

complicate matters, we&cr forecasting limitations prcvcnt

the long term prediction of a fire’s eventual size and intensity.

Thus, an effective suppression force must be capable of

constructing enough fire line to contain portions of or a11 of a

management fire that could be potentially of high-intensity

and extend over an area of several thousand acres. Howcvcr,

the larger a fire is, the less cffcctivc is a suppression action.

That is, the fire’s growth and/or intensity is more likely to

out-scale suppression efforts. Commonly, after wildfires

become large, suppression is not cffcctivc until a sufficient

weather or fuel change occurs, causing a fire to return to a

scale where suppression is effective. In the case of the 1988

Greater Yellowstone Fires and the Canyon Creek Fire, a

sufficient weather change (to cool and damp) did not occur

until mid-September.

CONCLUSION

Large, high-intensity fires are a natural occurrence in some

ecosystems. Where these ecosystems occur in wilderness

areas, fire managers arc obligated to maintain natural

processes for the existence of the ecosystem. Prescribed

natural fires are a reflection of this obligation.

Because a prescribed natural fire can bum for an extended

period, specific weather conditions cannot be selected. The

fire burns under whatever conditions occur. But, for an

ecologically significant fire, the weather must accommodate a

high-intensity fire for some period of time. If, however,

severe burning conditions are too persistent, the fire can

exceed prescribed limits.

The fire manager does not have extended-range forecast

information at the scale of specific fire weather conditions.

This is due to the lack of predictability of the atmosphere at

the scale responsible for high wind speeds. Thus, the

eventual state of the prescribed natural fire cannot be

predicted.

Fire suppression actions required to contain a prcscribcd

natural fire within designated boundaries may not succeed.

The achievement of an ecologically significant (large size,

high intensity) wilderness fire reduces the IikeIihood of

effective fire suppression, should suppression actions become

necessary. Thus, the maintenance of fire as a natural process

can lead to wilderness fires that escape prescribed boundaries

to become costly wildfires. This is the essence of the

prcscribcd natural fire dilemma.

LITERATURE CITED

Amo, Stephen F.; Brown, James K. 1989. Managing fire in

our forests: time for a new initiative. Journal of Forestry

87(12):44-46.

Bacon, Warren R.; Dell, John. 198.5. National Forest

landscape management: fire. Agric. Handb. 608.

Washington, DC: U.S. Deparhnent of Agriculture: vol. 2,

Chapter 6. 89 p.

Brown, James K. 1989. Could the 1988 fires in Yellowstone

have been avoided with a program of prescribed fire’?

Talk given before the American Association for the

Advancement of Science. San Francisco, CA, January 19.

Dutton, John A. 1976. The ceaseless wind. New York:

McGraw-Hill, Inc. 579 p.

Glcick, James. 1987. Chaos: making a new science. New

York: Penguin Books. 352 p.

Hcinselman, Miron L. 1985. Fire regimes and management

options in ecosystems with large high-intensity fires. In:

Lotan, J.E.; Kilgore, B.M.; Fischer, W.E.; Mutch,

R.W., camps. Proceedings of symposium and workshop

on wilderness fire; 1983 November 15-18; Missoula, MT.

Gen. Tech. Rep. INT-182. Ogden, UT: U.S. Department

of Agriculture, Forest Service, Intermountain Forest and

Range Experiment Station: p. 101-109.

Lorenz, Edward N. 1963. Deterministic nonperiodic flow.

Journal of Atmospheric Science 20: 130-41.

Lorenz, Edward N. 1968. Climatic determinism. In Mitchell,

J.M., Jr., ed. Boston, MA: American Meteorological

Society. Meteorological Monographs 8(30).

Lorenz, Edward N. 1969. The predictability of a flow which

possesses many scales of motion. Tellus 21:289-307.

Tennekes, Hendrick. 1988. The outlook: scaLtercd showers.

Bulletin American Meteorological Society 69(4):368-72.

Wright, Henry A.; Bailey, Arthur W. 1982. Fire ecology:

United States and Canada. New York: John Wiley &

Sons. 501 p.

383
USE OF THE 1990 CENSUS TO DEFINE

WILDLAND URBAN INTERFACE PROBLEMS

James B. Davis’

Abstract-Predicting the movement of people into rural wildlands previously has been limited to studies of

population and housing growth in counties or other large geographical areas. In these studies, the areas of

high tire danger that contain dispersed rural housing cannot be distinguished from the areas less vulnerable

to wildfire (small towns and adjacent urban areas) because the data and tie analysis procedures associated

with the 1980 m.w does did not give sufficient I&ma&n about mra/ and w&#& areas. Analysts

studying rural demographics supplement census data with information From such sources as local tax

assessors’ records or building permit files.

INTRODUCTION

If we are going to effectively manage the wildland urban

interface fire problem we need to know where people live,

work and play within the interface area. Wc also must know

something about their knowledge and attitudes toward the

environment and its mnnagcmcnt and protection (Davis 1990;

Irwin 1987, 1988). We need to know where people obtain

their knowledge and how they formulate their ideas and

attitudes--a rapidly developing field called psychographics. If

WC know what our customers want and what benefits &hey

perceive, we can kc more effcclive in communicating with

them.

We can help develop a firesafe community by influencing the

location of housing within fire-prone areas and help regulate

the design of homes and other structures in those locations

most likely to bum. The interrelationship between the factors

that result in a choice of a building site and the factors that

matter in fire spread and suppression, such as vegetation type,

slope class, and aspect, access and proximity to water and

roads riced to be understood. Reasonable estimates can be

made of housing to be built five or more years in the future

when these factors arc included in population projection

models (Bradshaw 1987). These estimates can be mapped and

overlaid on fire risk and hazard maps to allow a fire manager

to display to local policy and planning officials detailed

information on the areas likely to bc threatened by future

wildfires and the homes and population that will be at risk

unless mitigating measures a.re taken. The ability to display

this information will enable fire managers to be proactive

rather than reactive in their contacts with public leaders.

PROBLEMS

Rural Growth

Many foresters are surprised that they must cope with the

most rapidly changing and dynamic segment of our nation’s

population. Although the incrcsse in rural population has

slowed somewhat since the 1970’s when rural counties were

‘Research Forester, Fire Planning and Economics Research, Forest

Fire Laboratory, USDA Forest Service, Riverside, CA

384

growing three times as fast as the urban counties, population

growth in many of fhe Nation’s forest and range counties

continues to exceed urban population growth and will

probably continue to do so past the turn of the century (Long

1983; Rice 1987).

California, for example, has traditionally doubled its

population every 20 years since statehood. However, it will

not double its 1970 population again until at least 2020, a

period of 50 years. Yet, the population of I.5 of its

counties--all forested with the exception of one--is continuing

to double in 20 years or less--tEe areas that are increasing in

population most rapidly are those most prone to wildfires.

Problems Beyond Local Control

Another problem is that rural area population dynamics are

influenced by socioeconomic factors well beyond the borders

of the area involved. California has long appealed to

Americans who move for ona reason or another. By the late

1960’s, however, California gained migrants from fewer

states than previously, and it began to send migrants to

Oregon, Washington, and Nevada, as well as to Oklahoma

and Virginia (Hcrbcrs 1986). Between 1975 and 1980,

California had a net loss of 420,000 people in migration

exchanges with its ten western migration partners. But this

loss was offset by a net gain of 534,000 people from the rest

of the U.S., chiefly from the Northeast and Midwest because

of the decline of the iron and automobile industries and

because young professionals were being attracted to

California’s aerospace, computer and other high-tech

industries, resulting in a total gain of 114,000 to California’s

population.

In the late 1970’s Oregon residents sported bumper stickers

asking Californians to visit but not to stay. By the mid

1980’s such fears were allayed because Oregon began

exporting people to California due to the decline in the woods

products industry and rising unemployment in the Northwest

(Sweeney 1979).

This continually changing economic situation has made

population growth projections into fire prone areas difficult.
Figure l--Broad catcgorics of vcgctation found in Nevada County. The vegetation changes from mostly grass, chaparral,

and hardwoods at the lower elevations in the wcstem part of the county, to heavy stands of conifers in National Forests

covering the higher elevations in the cast. Major highways are indicated on the map as well.

Limitations on Population Growth Estimation

For forcstcrs, the 1980 census has not been helpful because of

the poor lcvcl of resolution in wildland arcas; the tracts are

very large areas in most instances and oRen include diverse

demographic characteristics within a tract. For example, the

twclvc tracts in Nevada County, California range from thinly

inhabited National Forest Land to urbanized rcsidcntial areas

(Fig. I).

Analysis Models Are Limited

While knowing “what is there now” is difficult, it is only part

of our battle. We need to know “what will be there in the

future.” The census information does the local planner little

good unIcss it can be intcrprctcd for his or her needs in both

a temporal and spatial manner. This is a particularly difficult

problem in the wildland urban interface because there have

been few predictive models. Although such models exist for

urban areas--the projections nccdcd for the construction of a

shopping center, for example--we know of no case in which

they have been used to predict the location and number of

households at risk from wildland fire. Population analysis in

rural areas has usually been concentrated on estimating the

movement of population to urban areas as farm and lumber

industries decline, or in predicting the broad overall change in

a county level population.

Extensive literature exists on the population change of

particular rural counties, and permits extrapolation of this

information to many potential rural growth situations

(California Department of Forestry and Fire protection 1988).

Howcvcr, virtually no micro-lcvcl studies have been done to

understand where people in rural arcas choose to live

(Lindhult and others 1988). Much of the rural demographic

rcscarch--if it has been done at all--has been in the

northeastern United States whcrc counties are generally small

and relatively homogeneous. Counties in the western United

States, on the other hand, arc large, heterogcnous, and

require a much more rigorous analysis.

Regional dcvelopmcnt models are similarly underdeveloped

outside of metropolitan arcas. Although they have been used

to establish the regional growth within urban areas, they are

less adequate for rural areas for which data and economic

conditions are less wcI1 understood (Befort and others 1988).

The intcrrclation bctwccn economic conditions and housing

dcvelopmcnt has been posited in the literature, and evidence

in rural arcas indicate that pcoplc often commute long

distances in order to take new jobs. Economic conditions go

hand in hand with changes in the housing supply, but little is

known about how economic growth affects the distribution of

housing in wildland interface arcas which often include a high

number of retired persons.

RESEARCH ON WILDLAND

DEMOGRAPHICS

The Riverside Forest Fire Laboratory, in cooperation with the

University of California’s Institute of Governmental Studies in

Bcrkclcy, is making an effort to solve the problem of

wildland urban interface demographics. Dr. Ted Bradshaw is

the principal investigator from the University for the project.

The cooperative effort is attacking the following three

questions and is using Nevada County, California, as a field

laboratory:

1. Can we identify reliable sources of demographic data

for the wildlands.

2. Can W C dcvclop models to define and belter understand

the movement and cvcntuai scttlcmcnt of pcoplc in our

wildland areas?

385
Figure 7,--Pa[tcrns of population from the 1980 census. These data demonstrate the capacity of GIS to translate data on total

population into density per acre. Current population densities

population growth of 6 percent since the census.

3. What must We do to take advantage of the much higher

resolution data that will be available from the 1990 census

and the commercially available data and analysis software

that will spin off from it?

Identification of Data Sources

The data we are using in our research come from various

sources with different geographical boundaries:

l The vegetation data are from a statewide species

mapping effort called “CAL VEG” based on land and

aerial data.

l Fire severity zones in Nevada County are based on a

scrics of maps prcparcd by the California Department of

Forestry and Fire protection and determined f?om

topographical, climaiological, and fuel considerations

(Phillips 1983).

@ Census data from the 1980 census arc given by

enumeration district (Fig. 2). In selected areas we are

examining the existing pattern of settlement by using

census data, current updates, and aerial photos, when

possible, and are seeking m&ho& to estimate the

accuracy of the statistical data. A major source of

information has been county tax assessor's records. We

have found that data on building permits arc a key factor

in determining patterns of growth since 1980.

* Property rolls contain information on the size, use, and

value of property in the county. Thcsc data arc shown for

geographical areas &lined by the county assessors’ books.

arc significantly higher due to an average annual county

Current research has enabled us to go from book to page

level--a degree of resolution that normally will include 50

or fewer households. Also obtained from the assessors’

records arc data on the per acre value of improvements.

The areas with the highest values usually arc associated

with residential construction and much of it is located in

areas of high fire hazard.

Using assessors’ data on average parcel size, trends in

dcvciopmcnt arc easy to identify. Further analysis will show

the characteristics of these parcels with regard to tire dangers,

roads, and physical amenities.

Our rcscarch is extending the field of investigation to include

groupings much smaller and more SpCCifiC than the usual

national or regional aggregates. We arc constrained by

neither political nor administrative boundaries such as cities,

villages, or natural regions, but our rcscarch is allowing us to

study lcv& of human catcgorics that arc not territorially well

delincd (for cxamplc wildland urban rcsidcnts).

Development of Models

While current population and attitudinal information should be

tlscfuj to foresters and fire managers, our long-range objective

is to dcvclop predictive models. WC arc conducting analyses

to estimate psramelcrs of various models that include growth

as well as attitude toward forest land and its management and

protection. The attitude and growth are related to factors

such as vegetation type, slope, aspect, attractive physical

features, proximity to urban selllemcnts, employment,

subdivisions, infrastructure, roads, etc. We will determine

whclhcr our models accurately estimate growth at reasonable

386
lcvcls of confidcncc by comparing our model dctcrminations

with patterns that have occurred over (11~ past 5-10 years and

with current building permit issuance and opinion surveys.

We will sclcct the most dcscriptivc modci and refine it as

nccdcd.

How do we take advantage of the 1990 Cemus?

Although we are m&in: h&way with non-census data, the

1990 CC~SUS data, when they become availahlc in 1992 or

1993, promise Lo crcatc a “dcsklop computer revolution.”

Along with hcnchmsrk demographic data, the censu.s includes

a survey of housing and housing units. For our purposes the

census of housing will hc very important ~CC~IJSC it describes

Iht2 localion and Jcrno~r:~~4~ic characl~rislics of the people

living in c:lch housing unit. It also &tails ownership,

condition. anJ va/uc of the property (Kirchner and Thomas

1989).

The 1990 ccllslls data will hc available on four census

compulcr “stlrnmary tape files” (STFs):

0 STF- I and STF-7, will contain data on household type,

race sex I > age, marital status, anJ J&&J information on

the residence ohtaincd [mm the “short” CCflSUS

questionnaire sent to cvcry home in the country. This

information for the first time will provide good resolution

in rural arcas and will bc traccahic to the equivalent of a

city block.

e STF-3 anJ STF-4 will conlain the same basic data as the

first two summary Ii&, plus the information from the

“long” census questionnaire. The long form will be

answered by a 17 percent sarl~plc of hOUSdlOk&. This

form will contain demographic information that fire

planners may need, including income, educational

background, migration, language, type and place of

cmploymcnt and housing information such as availability

of 3 tdcphunc.

In fact, this high lcvcl of resolution has created somewhat of

a problcnl to the Census Bureau in maintainig con&dentiality.

In rural areas it might bc possible to identifi the source of

~oine data--the income of a single ranch family for

exam@- -and lhc Burc;lu has had to incorporate methods to

screen out such information.

One objective of our analysis will be to determine whether the

Jctaitcd 17 pcrcenl survey will give us all of the demographic

inrormation we need in very s[)arsciy populated areas, or

whcthcr we will still have to dci~nd to some degree on other

sotlrccs such 3s building permits and assessors’ records.

Much of’ our rcscarch will bc aimed at correlating information

that we can obtain from census records with factors that cause

pcoplc to move into the interface area.

\licro Computers and Laser Discs

Although the 1990 census data will he available in several

forms from hard copy reports to computer tapes, the most

exciting improvement for computer-wise foresters will be that

the inform:i[ion will eventually bc available on laser read-only

memory compact discs known as CD-ROMS, reflecting a

decade of changing computer technology. By putting census

data on laser discs, the Census Bureau will make great

quantities of information available to the individual with a

good personal computer and the computer capability to use

the information. Compact discs have enormous potentiat

because each 4-S/8-inch disc can store as much information as

three computer tapes or 1,500 floppy disks. An expensive

mainframe computer is not required to process information

contained on a compact disc. However, one problem may be

“data overkill.” There is likely to be so much information

that determining what information to use and how to use it

e0icicntly will be dil’ficult.

With the addition of a klsor disc reader--available to almost

cvury forcslry or lire managcmcnt headquarters office for less

than $1000--a microcom)>utcr can become a desktop

information system capabic of printing STFs Otl demand.

Howcvcr, despite 111~ obvious advantages of COrllpaCt discs,

the Census Bureau is not releasing them as the basic medium

for distributing 1990 CCIISUS data because as yet, there is no

standardization in disc technology. Until there is

standardization as well as user-friendly Software, much

computer skill will bc nccJcd to use this ncW technology. To

http users gel started, the Census Bureau is making three

CD-ROMS--Test Discs 1 and 2, and the 198.5 American

Housing Survey--available IlOW. The discs sell for $125 each

and can be ordered from the Bureau’s Customer Service

Oflice.

TIGER Files

A recent innovation, that may prove very valuable for model

development and testing and for understanding wildland urban

interface population dynamics, is the automated mapping

system known as TIGER (Topologically Integrated

Geographic Encoding and Referencing). This system has

cnsbled I/X Census Bureau, working with the U.S. Geological

387
. .”

.

Figure 3--Scclion of preliminary map printed from the TIGER files. Map scale is

about 4 inches to the mile. For many locations TIGER is capable of generating the

most detailed and up-to-date maps available.

Survey, to develop computcrizcd maps covering the entire

IJnitcd States (U.S. Dcpartmcnt of Commerce 1985). TIGER

is essentially a digital street map of the country (Fig. 3). The

TIGER process uscs geographical information system (GIS)

technology that translates the intersection of boundaries of one

type of information--census rclatcd information, for

example--with information from another geographic feature.

The Bureau’s preliminary plans envision TIGER boundary

f11cs for counties, census tracts, block numbering areas, and

county subdivision. The road systems are so complete that

forestry agencies should bkc a good look at them From the

standpoint of updating their own transportation systems. The

TIGER files currently are available only on magnetic tape,

but the Bureau is looking at the possibility of rekxssing

TIGER on CD-ROM as well.

As of now, TIGER files contain only geographical

information--individual streets and other features digitally

coded by latitude and longitude. They will not contain any

1990 census data. Several &ware companies are planning

to combine the TIGER files with 1990 census data on

compact discs.

Geographical Information System Technology

Desktop demographic systems become even more powe&l

when linked to geocoding and mapping software--geographical

information systems (GIS). GIS technology and the proposed

census data systems are virtually made for each other.

Geographical information systems analysis can overlay many

[calufes about an area’s population and urban development

with data about the physical characteristics of the area

(Thompson 1989). A GIS also provides a set of tools

necessary to model and understand the flow of people,

resources and commodities into and through the

interface--essentially a depiction of the inliastructure.

CONCLUSION

The ability to assign a latitude and longitude to in-house

records will be a fast effective link between census

information and our wildland urban hazard reduction and fire

prevention efforts. GIS technology will allow land and fire

managers to superimpose population forecasts and trends, fire

behavior factors, and even past fire occurrence records,

enabling projections of fire problems years before they

actually occnr.

Although this paper has been oriented to the wildland urban

inte&ce fire problem, the potential for demographic research

is much grcatcr. The dynamics of populations and their

attitude toward wildlands and their management affect all

phases of forestry. We expect that many of the concepts and

models that we are developing will apply equally to other

forestry problems from wildlife management to watershed

management.

388
LITERATURE CITED

Bcfort, W.A., A.E. Luloff, and M. Morrone. 1988. Rural

land USC and demographic change in a rapidly urbanizing

cnvironmcnt. Landscape and Urban Planning, 16:

3453.56.

Bradshaw, T. K. 1987. The intrusion of human population

into forest and rangclan& of California. In: Proceedings

of the Symposium on Wildland Fire 2000. April 27-30,

1987, South Lake Tahoe, California. Gcn. Tech. Rep.

PSW-101. Bcrkclcy, CA: Pacific Southwest Forest and

Range Experiment Station, Forest Service, U.S.

Department of Agricullure; 15-21.

California Department of Forestry and Fire Protection. 1988.

California’s forest and range lands: growing conflict over

changing uses. Forest and Rangeland Resources

Assessment Program Rcpofl. Sacramento, CA. 347 p.

Davis, J. B. 1990. The wildland urban intcrfacc: paradise or

battleground. Jour. of Forestry, Jan. 1990

Herbcrs, J. 1986. The ncW heartland. Times Books. Random

House Inc., New York. 228 p.

Irwin, R. L. 1987. Local planning considerations for the

wildland-structural intermix in the year 2000. P. 38-46. in

Proc. Wildland Fire 2000. South Lake Tahoe, Calif.,

USDA For. Serv. Gcn. Tech. Rep. PSW-101.

Irwin, R. L. 1988. What arc WC waiting for? In: Fire Safe

California: Survival by Design. March 23,1988,

California State University, Pomona; Pomona, CA.

California Dcpartmcnt of Fores&y and Fit-c Protection,

Sacramcnlo, CA.

Kirchner, Russell J. and Richard K. Thomas. 1989. Desktop

decisions. American Demographics. 1 l(8): pp 34-37.

Lindhult, Mark S., Julius F&s, Pam Brown, and Nancy

Price. 1988. Using geographic information to assess

conflicts hctwecn agriculture and dcvelopmcnt. Landscape

and Urban Planning 16: 333-343.

Long, Michael C. 1983. Understanding CENSUS data. Western

Economics Rcscarch Co. Sherman Oaks, CA. 72 p.

Phillips, Clinton B. 1983. Instructions for zoning fire hazard

scvcrity in slate responsibility areas in California.

California Department of Forestry and Fire Protection.

Sacramento, CA. 85 p.

Rice, Carol L. 1987. What will the western wildlands be like

in the year ?OOO? future perfect or future imperfect. In:

Proceedings of the Symposium on Wildland Fire 2000.

April 27-30, 1987, South Lake Tahoe, California. Gen.

Tech. Rep. PSW-101. Bcrkclcy, CA: Pacific Southwest

Forest and Range Expcrimcnt Station, Forest Service,

U.S. Department of Agriculture; 26-31

Swcency, Joan. 1979. Sierra lure-urban dropouts bring urban

problems. Los Angclcs Times. March 2.5.

Thompson, Boyce. 1989. Maps with brains. Governing 3(3):

40-46.

U.S. Dcpsrtmcnt of Commerce, 1985. Tiger talcs. Bureau of

the Census. Washington DC. 48 p.

389
CLIMATE, FIRE, AND LATE QUATERNARY VEGETATION CHANGE

IN THE CENTRAL SIERRA NEVADA

Eric G. Edlund and Roger Byrne’

Abstract-Fossil charcoal provides a record of significant changes in the importance of fire in the Central

Sierra Nevada over the past 15,000 years. Changes in fire regime appear to be related to regional shifts in

climate. During the iate Pleistocene (ca. 12.5-10 ka), minimal sedimentary charcoal influx is correlated

with fossil pollen and macrofossil indicators of a moist climate, probably with deeper spring snowpack than

the present. In the early Holocene (IO-7 ka), macrofossils indicate a shiA from white and lodgepole pines

to more xeric ponderosa pine-dominated forest. Charcoal influx climbs rapidly to maximum values in this

zone, in conjunction with increases in fir, oak, and dwarf mistletoe pollen, along with bracken fcm spores.

Charcoal declines to modem values between about 7-3 ka, by which time the modem mixed conifer forest

became established.

Changes in the abundance of bracken, dwarf mistletoe, oak and ponderosa pine can be strongly correlated

with charcoal influx. The late-Pleistocene interval of minimum charcoal influx is a period in which dense

forest surrounded the lake, indicating that fire frequency was not directly a function of fuel availability.

Increasing summer drought in the early Holocene made tire an important factor in vegetation change. The

zone of rapid increase in charcoal ahundancc, beginning 10,000 years ago, is associated with abrupt

changes in vegetation, including the first appearance of pondwosa pines and tirs following dcglaciation.

INTRODUCTION

Concern over the potential impacts of climate change on

natural ecosystems has demonstrated a riced for long-term

studies of vegetation-climate-fire relationships. Recent

workers (Overpeck and others 1990; Clark 1988a) have

suggested that prolonged warm-dry climatic intervals may

lead to increases in fire frequency and intensity. The

relationship is not a linear one, however; a shift to a

warmer, drier climate could eventually reduce fire intensities

as a function of decreased biomass available for burning.

The composition of forests in the Sierra Nevada has been

strongly influenced by fire. Before twentieth-century fire

suppression, fire frequencies in mixed conifer forests

averaged about 7-10 years (Wagcncr 1961; Kilgorc 1973).

Studies of Sicrran ponderosa (Weaver 1968), red fir, and

sequoia-mixed conifer forests (Kilgore 1973) have

demonstrated the extent to which the dominant montane tree

species are adapted to periodic fire. The role of fire in higher

elevation forests, where mountain hemlock and lodgepole pine

dominate today, is less clearly understood (Rundel and others

1988). Before the twentieth century, natural fires in the

Sierra Nevada are believed to have been of generally mild

intensity and limited extent.

Computer modclling of forest responses to climate change

(Overpeck and others 1990) has indicated that an increase in

the rate of ecological disturbance accompanying potential

CO,-induced climatic changes would produce greater changes

in stand composition than would climate changes alone. Such

impacts are of concern in modern forest management,

‘Depanmcnt of Geography, University of California, Berkeley, CA

94720.

390

particularly since palcoccological work has tied rue to climate

changes on time scales of hundreds of years or less. Working

on lake sediments from northwestern Minnesota, Clark

(1988a) found high charcoal abundance from 1400-1600

A.D., a period of warm, dry climate in the area. Fire

frequency during this interval is estimated at 44 years,

compared to 85-90 years during the subsequent “Little Ice

Age” of the 17th-19th centuries.

The role of climate in determining fire regimes may have

been even more important during the major climatic shifts

which have occurred over thousands of years since the last

major ice age. Good evidence for a relationship between

climate and fire frequency has been uncovered in midwestem

North America. Early work by Waddington (1969)

documented an increase in charcoal influx at Rutz Lake,

Minnesota from S-4,000 years ago, corresponding to a shift

from oak to prairie vegetation. In southern Wisconsin,

Winklcr and others (1986) recorded increased charcoal

6,500-3,500 yr. B.P., at a time of lowered lake levels and a

shill from mixed mesophytic forest to oak savanna.

Paleoecological work in the Sierra Nevada provides a

chronology of postglacial climate change inferred from shifts

in vegetation (see fig. 1 for locations discussed below). Late

Plcistoccnc pollen and macrofossil records show evidence of

colder, drier conditions, with sagebrush (Ar!etni,.ria) and

juniper important components of the vegetation (Adam 1967;

Batchelder 1980; Cole 1983; Davis and others 1985; Davis

and Moratto 1988). At some sites, pine and fir forests

developed between 12,500-10,000 years ago, probably

responding to soil dcvclopmcnt and a wetter climate. In the
Figure 1. Base map of California showing Sierran

paleoccological sites and the present study site. OS =OS~OO~

Swamp (Adam 1967); SL=Swamp Lake (Batchelder 1980);

KC = Lower Kings Canyon (Cole 1983); BM = Balsam

Meadow (Davis and others 1985); GM =Gabbot Meadow

Lake (Mackey and Sullivan 1986); EM = Exchequer Meadow

(Davis and Moratto 1988); BL, SP, TP=Barrett Lake,

Starkweather Pond, Tioga Pass Pond (Anderson 1990);

LM = Lake Moran (Byrne and Edlund in preparation, and

present study).

early Holocene, warming and drying conditions arc reflcctcd

in increases in oak and other pollen types, beginning ca.

I&-9,000 yr. B.P., and lasting until at least 6,500-5,000 yr.

B.P. (Mackey and Sullivan 1986; Byrne 1988; Davis and

Moratto 1988; Anderson 1990). High elevation sites record

increased effective precipitation beginning about 6,000 yr.

B.P. (Anderson 1990). At some of the lower lake sites,

warn-climate indicators persist until ca. 4,OW--3,ooO yr.

B.P., when fir increased in response to the onset of

Neoglacial cooling (Adam 1967).

The early Holocene xerothcrmic interval has been widely

recognized in western North America. Mathcwes (1985)

summar&j work in British Columbia documenting

xerothermic conditions lo-7,000 yr. B.P., following an

interval of cool moist climate in the late Pleistocene (12-10

ka). He argued that douglas-lir, alder, and bracken fcm,

which reach maximum levels in pollen records over this

interval, are fire-adapted species which responded to

increased fire frequency along with climatic warming.

In the Sierra Nevada, the existing evidence for changes in the

role of tire during postglacial time is quite limited. At

Exchequer Meadow (Davis and Moratto 1988), sedimentary

charcoal reaches maximum abundance in deposits dated

approximately 8,I)oo-4,000 yr. B.P. At nearby Balsam

Meadow (Davis and others 1985), macroscopic charcoal

appears only after ca. 7,000 yr. B.P.

391
LAKE MORAN Cores 888 and 88C Pollen and Conifer Macrofossils

Ash: 6850 +/- 150 ’J

Pca1y il

c14: 11120+/-90

Transitional j

Sill &

Ash: 14750 +/- 500 E

5 10 15 20

-I-

: ok-l--&- (Radiocarbon yr B.P.) )w()cn (sawtooth) expressed as ‘K, of lotat non-aquatic pollen and spores; note scale change

rnncrofossils (bars) plotted as rslative abundance: I =present. 2=fairly common, 3=abundant

Figure 2. Selected pollen and macrofossils from Moran cores 88B and C. Sawtoothed pollen curves, labeled with genus or

family name, indicate abundance as a percentage of total non-aquatic pollen grains and spores counted. Macrofossil bars,

labeled by species, indicate relative abundance (see text). Zonation is by the authors. Radiocarbon dates were obtained

from Beta Analytic, and volcanic ash layers were identified by Andrei Sama-Wojciclci, U.S.G.S.

METHODS

The lake sediment samples analyzed for this project were

taken in October, 1988, using a standard Livingstone piston

corer with 2” diameter barrel. Two cores, 88B and C, were

taken within 2 meters of one another, and correlated by depth

and stratigraphy. Cores were transported intact to the U.C.

Berkeley Pollen Lab. Core B was used for macrofossil

analysis, while core C was subsampled at 10-2&m intervals

for pollen and microscopic charcoal analysis. 14C dates were

obtained on two ten-centimeter segments of core 88C. Two

volcanic ash layers present in the cores were identified by

Andrei Sama-Wojcicki at the United States Geological Survey

in Menlo Park.

Extraction and preparation of pollen samples followed

standard procedures as described by Faegri and Iversen

(1975). Each pollen and charcoal sample underwent the same

preparation, in order to eliminate differential effects of

chemical treatments on the samples (Clark 1984). Pollen

concentrations were calculated based on the ratios of

Lycopodiurn control grains counted at each level. The curves

of taxon abundance in Figure 2 are plotted as percentage of

total non-aquatic pollen and spores counted; a total of at least

300 grains was identified at each level in the core. The

diagrams were compiled using CALPALYN (Bauer and Grvis

1990).

Core 88B was sampled in measured segments of 5 or 10cm.

Macrofossil sampling was based on standard procedures

described by Birks (1980). Identification of pine needles was

accomplished by comparing external morphology and thin

sections with reference material and with Harlow’s (1947)

photographic key. For each sample, we calculated the total

Iength of needle remains of each taxon. For Figure 2, length

values were classified on a scale from 1, “present,” with only

one or two fragments per sample, to 3, “abundant,” with total

needle length exceeding 200mm per sample.

Microscopic charcoal was analyzed using 400x magnification

and an ocular grid with squares 19.8 pm on a side. All

charcoal fragments larger than one-half of a grid square were

assigned to the appropriate size class, and the total area of

charcoal was calculated. Calculated charcoal concentration

392
LAKE MORAN Core 88C Charcoal

( - 21 1

SC -

13

1OC 2 5 125

cf Iso

175*! I

200 -

225

3

250

(Radiocarbon yr B.P.)

---i-b

mmVcc (x100,ooo) mm21 mmVzm2/yr

grains/cc 10,000 grain.5

Figun: 3. Charcoal and pollen indices for Moran core 88C. Sample depths and zonation arc the same as in Figure 2

Calculated charcoal influx is divided into the share of fragments smaller (unshaded) and larger than 600~m2.

and influx to the lakebed arc based on the ratio of counted

charcoal to counted control spores (fig. 3).

Sedimentation is estimated at a linear rate between

radiocarbon and ash dates. Influx is not estimated for the

glacial flour sample below the lowest tephra date. To control

for variation in charcoal influx due to sedimentation

processes, the ratio of charcoal to pollen was calculated for

each sample (Cwynar 1978).

Charcoal Taphonomy

Questions of interpretation of sedimentary charcoal have been

discussed in detail by Patterson and others (1987) and Clark

(1988b). Charcoal in lake sediments ranges in size from fine

dust, < 2 micrometers in diamctcr, to macroscopic fragments

centimeters in length. Like dust, small particles may travel

long distances once entrained. Charcoal may reach high

altitudes in the convective plume which rises from a fire.

More intense tires produce higher plumes, resulting in

longer-distance transport of all size classes of charcoal. The

smallest sizes of charcoal may reflect a subcontinental source

(Clark 1988b). As a result, even lakes in areas of 20th

century fire suppression contain high levels of charcoal in

recent sediments (e.g., Lake of the Clouds, MN, Swain

1973). Conversely, local tires, recorded as fire scars on

trees, may go unrepresented in lake sediments if the plume

convects most charcoal beyond the lake basin (Patterson and

others 1987).

Lakes with small watersheds can accurately record local fires

(Anderson and others 1986). Lake Moran is a small lake

with no inlet stream, and a drainage basin of about 12

hectares. In this setting, it may be expected that larger

microscopic charcoal fragments in the lake sediments

originated from nearby fires, while the smallest fragments

record events within a larger region. Figure 3 breaks

microscopic charcoal influx into small fragments, <600~mz

in area, and larger pieces, which ranged up to > 14,50O/rm*.

WC assume that the fires which produced the larger charcoal

fragments probably occurred within S-10 km of the lake (cf.

Clark 1988b).

393
VEGETATION HISTORY AND THE

RECORD OF FIRES AT LAKE MORAN

The Mono Craters and Mazama ash layers and radiocarbon

dates provide a chronology for the Lake Moran sediments.

The lake was exposed by ice retreat some 15,000 years ago

This represents an early date for Tioga (late-Wisconsin)

dcglaciation in the Sierra Nevada, confirming Batchelder’s

(1980) report from nearby Swamp Lake.

The earliest pollen assemblages (zone 4 on figure 2) reveal an

open vegetation of sagebrush (,4rremkja), juniper, and pines.

This environment must have been effectively drier than the

present study area, perhaps similar in appearance to higher

subalpine environments today. No identifiable macrofossils

are present in these sediments. Sedimentation rates were slow

following the initial formation of the basin, and the calculated

annual charcoal influxes arc among the lowest in the ‘core.

Some large charcoal &agments (> 2.500 pm’ in area) are

present, but it is uncertain whether these fragments blew into

the lake fTom nearby fires, or were simply redeposited by the

melting of the nearby glacier.

In late-Pleistocene zone 3, spanning ca. 12,500--10,000 yr,

B.P., pine needles and high percentages of pine pollen

indicate the establishment of a closed-canopy forest

throughout much of the area (Figure 2). This forest signal is

accompanied by increases in taxa normally associated with

meadows, including members of the Umbelliferae, Liliaccac,

Onagraccae, Malvaceae, and Ranunculaccac. (These taxa are

grouped as “Umbellifcrae and others” in Figure 2). The

presence of mountain hemlock (zlrga merfensiona), white

pines (Pinu.~ monticolo and P. lumbertiana), and lodgepole

pine (P. contorta ssp. murrayana) indicate a moister climate

than that found in the Sierra Nevada today. The meadow taxa

may have become established on sites too wet for tree growth.

During this time, deep snowpacks may have persisted late into

the summer, damping the effects of California’s summer

drought season. Charcoal concentration is generally lower in

this interval than anywhere else in the core (Figure 3). The

ratio of charcoal to pollen is consistently low, and larger

charcoal fragments ( > 6OOpmq arc virtually absent. The

evidence suggests that fires rarely burned the dense forest

which surrounded the lake.

The Pleistocene/Holocene transition (subzone 2T) is marked

by rapid increases in all measures of charcoal abundance

(Figure 3). Charcoal concentration and influx reach

maximum values here, at levels 5-10 times greater than in

modern or late-Pleistocene scdimcnts. Lodgepole and white

pines Wcfe beginning to be replaced by yellow pints (P.

ponderosa and/or P. jegCrqi) (Figure 2). During this

transitional period, persisting less than 1000 years, fir8 (both

Abies magnifica and A. concolor) became important

constituents of the Moran forest.

The pollen record for zone 2 (Figure 2) shows a small

relative decrease in pines, with increases in oaks and bracken

fern (Pteridiron). The evidence reveals a more open forest,

with warmer summers allowing an increase in the relative

importance of oaks. Dwarf mistletoe (Arceuthobium) pollen

increases in this interval, perhaps indicating that conifers were

under increasing ecological stress. Charcoal influx remains

high until ca. 7,500 yr. B.P., dropping off to near-modem

levels just above the Mazama ash layer (Figure 3).

Interestingly, both the charcoaVpollen ratio curve and the oak

FrcenQe curve (fig. 2) show continued high values through

the middle Holocene (7,00&-3,~ yr. B.P.). Since there is

no evidence for changes in the lake’s sedimentation regime,

WC rely on the consistently low charcoal influx values to infer

a decrease in the intensity of fires during this interval,

compared to the early Holocene; however, the oak, bracken

and sagebrush suggest that the forest remained drier and more

open than it is today. By 3,000 yr. B.P., Neoglacial cooling

and/or increasing moisture allowed fir, lodgepole, and sugar

pine to reoccupy the lake margin. Fire has remained less

important than it was in the early Holocene, although modem

charcoal influx exceeds late-Pleistocene minimum values.

The important implication of the high charcoal values is that

the early Holocene was a period of more extensive and more

intense fires than either the late Pleistocene or the late

Holocene. Indeed, it seems likely that an increase in the

importance of fire was the mechanism by which the changing

postglacial climate produced dmmatic shiAs in vegetation.

The source of the early Holocene charcoal may well have

been the dense late-Pleistocene forest, which began to burn

under a more xcric climatic regime.

Temporal changes in several pollen and macrofossil types

show a strong correlation with the charcoal signal. Bracken

is highly correlated with total charcoal influx, as is fir to a

somewhat lesser extent. The latter relationship is puzzling

but important; fir is not normally considered a fire-adapted

species, particularly compared to its associates in the S&man

montane forest. Red fir (Abies magntjica), the first species to

appear in the macrofossil record, may have been able to

effectively colonize fire-cleared patches, or it may have

become established on soil fertilized by increased nutrient

cycling under more frequent fires. In zone 2, increases in

pondcrosa pine, oak and dwarf mistletoe lag behind charcoal

influx, but generally the CUIVCS for these taxa parallel the

changes in the charcoal/pollen ratio. Umbellifcrae and

Cupressaceae pollen arc negatively correlated with charcoal,

as are lodgepole (Pinus COntOrta) and white pines (P.

lambertiana and P. monticola).

394
CONCLUSIONS

Our results suggest that Sicmn fire regimes have changed as

a function of climate. In the Sierra Nevada, fire frequency

and intensity are controlled by California’s strongly seasonai

precipitation regime. Today, summer drought makes fires

increasingly likely in September and October, bcft>re the first

winter rains. The Lake Moran record shows that from

12,Ot)o to 10,000 years ago, summer drought was less

pronounced than today, probably as a result of late-spring

snowstorms and/or snowpack persisting into the summer. At

that time, warm summers coupled with more abundant

moisture led to the development of a dense mixed conifer

forest, comprising several specks which no longer grow

together in the Sierra Nevada. Fire was less important as an

ecological factor in this late-Pleistocene forest than in the

Holocene.

At 10,000 yr. B.P., in association with a rapid increase in

fossil charcoal influx, the local vcgctation changed abruptly.

Red fir and pondcrosa pine first appeared at this time.

Conversely, western white pine disappeared from the site, and

lodgepIe and sugar pine began a more gradual decline.

Bracken fern became much more important about 10,000

years ago, while oak and dwarf mistletoe pollen increased

more gradually, reaching maximum pollen percentages

between 9,ooO--3,ooO yr. B.P. We infer rapid environmental

changes beginning at the end of the Plcislocene. The Lake

Moran record demonstrates the importance of fire as a

determinant of vegetalion during this climatically significant

period.

LITERATURE CITED

Adam, D.P. (1967). Talc-Pleistocene and recent palynology

in the Sierra Nevsda, California. In Cushing, E.J. and

H.E.Wright, Jr., eds., Quaternary Paleowology, pp.

275-301. New Haven: Yale University Press.

Anderson, R.S. (1990). Holocene forest development and

palcoclimates within the central Sierra Nevada,

California. Journal of Ecology (in press).

Anderson, R.S., R.B.Davis, N.C.Miller, and R.Sbckenrath

(1986). History of late- and post-glacial vegetation and

disturbance around Upper South Branch Pond, northern

Maine. Canadian Journal of Botany 64: 1977-1986.

Bat&eldcr, G.L. (1980). A late Wisconsin and wrly

Holocene lacustrine stratigraphy and pollen record From

the west slope of the Sierra Nevada, California.

American Quaternary Association, 6th Biennial Meeting,

Program and Abstracts, p. 13.

Baucr, R.L. and K.H.Orvis (1989). CALPALYN Pollen

Diagram Program. University of California, Bcrkclcy

Pollen Lab.

Birks, H.H. (1980). Plant macrofossils in Quaternary lake

sediments. Archiv ftir Hydrobiologie BcihcRc:

Ergebnisse dcr Limnologie 15: I-60.

Byrne, R. (1988). Late-Quatcmary climate and vegetation

change in the central Sierra Nevada of California. 73rd

Annual Ecological Society of America Meting, Programs

and Abstracts, p. 89.

Clark, J.S. (1988a). Effect of climate change on ftre regimes

in northwestern Minnesota. Nature 334: 233-235.

Clark, J.S. (19881)). Pafiicle motion and the theory of

charcoal analysis: source area, transport, deposition, and

sampling. Quatcmary Research 30: 67-80.

Clark, R.L. (1984). Effects on Charcoal of Pollen

Preparation Procedures. Pollen et Spores 26: 559-576

Cole, K. (1983). La&Pleistocene vcgctation of Kings

Canyon, Sierra Nevada, California. Quatemary Research

19: 117-129.

Cwynar, L. (1978). Recent history of fire and vegctaliorl

from laminated sediment of Greenleaf Lake, Algonquin

Park, Ontario. Canadian Journal of Botany 56: 10-21.

Davis, O.K., R.S.Anderson, P.L.Fall, M.K.O’Rourke, and

R.S.Thompson (1985). Palynological evidence for early

Holocene aridity in the southern Sierra Nevada,

California. Quaternary Research 24: 322-332.

Davis, O.K. and M.J.Moratto (1988). Evidence for a warm

dry early Holocene in the western Sierra Nevada of

California. Madroiio 35: 132-149.

Facgri, K. and J.lversen (1975). Textbook of pollen analysis,

Third Edition. New York: Hafner Press.

Harlow, W.M(1947). The identification of the pines of the

United States, native and introduced, by needle structure.

New York State College of Forestry Technical Publication

32.

Kilgore, B.M. (1973). The ecological role of fire in Sicrran

conifer forests: its application to national park

management. Quaternary Research 3: 496-5 13.

Mackey, E.M. and D.G.Sullivan (1986). A 10,000 year

palynological and stratigraphic record from Gabbot Lake,

Alpine CO~ty, California. American Quaternary

Association, 9th Biennial Meeting, Programs and

Abstracts, p. 95.

395
Mathewes, R.W. (1985). Paleobotanical evidence for

climatic change in southern British Columbia during

late-glacial and Holocene time. Syllogeus 55: 397-422.

Ovcrpcck, J.T., D.Rind, and R.Goldberg (1990).

Climate-induced changes in forest disturbance and

vegetation. Nature 343: 5 l-53.

Patterson, W.A., K.J.Edwards, and D.J.Maguire (1987)

Microscopic charcoal as a fossil indicator of fire.

Quatemary Science Rcvicws 6: 3-23.

Rundcl, P.W., D.J.Parsons, and D.T.Gordon (1988).

Montane and subalpine vegetation of the Sierra Nevada

and Cascade Ranges. In Barbour, M.J. and J. Major,

cds., Terrestrial Vcgctation of California (2nd edition),

pp. 559-599. California Native Plant Society, Special

Publication 9.

Waddington, J.C.B. (1969). A stratigraphic record of the

pollen influx to a lake in the Big Woods of Minnesota

Geological Society of America Special Paper 123:

263-283.

Wagener, W.W. (1961). Past fire incidence in Sierra Nevada

forests. Journal of Forestry 59: 739-748.

Weaver, H. (1968). Fire and its relationship to pondcrosa

pine. Proceedings Tall Timbers Fire Ecology Conference

7: 127-149.

Winklcr, M.G., A.M.Swain. and J.E.Kutzbach (1986).

Middle Holocene dry period in the northern Midwestern

United States: lake levels and pollen stratigraphy.

Quatcmary Research 25: 235-250.

Swain, A.M. (1973). A history of fire and vegetation in

northeastern Minnesota as recorded in lake sediments

Quatemary Research 3: 383-396.

396
FIRE-IfIERBICIDE SYSTEMS FOR MANIPULATING JUNIPER

D.M. En@ and J.F. Stritzke’

Abstract-Fire exclusion results in extensive encroachment of fire-intolerant junipers, specifically eastern

redcedar (!~#ip$rus virginiana) and ashe juniper (J. ashei) into tallgrass prairies and other grasslands and

hardwood forests of the central US. Control of both juniper species is possible with fire because they do

not sprout from roots and so they are killed by intense tires that scorch the crown. However, low-intensity

fires on sites with dense stands of junipers do not scorch crowns of larger juniper trees. One objective of

our studies was to determine the effect of various paraquat treatments on juniper foliage water content, a

primary factor affecting flammability of juniper crowns. A second objective was to determine if paraqoat

pretreatment would increase crown scorch from broadcast tires in tallgrass prairie. We evaluated leaf water

content of eastern redcedar treated individually with two rates (0.3 or 1.I kg/ha) of paraquat, in two

carriers (water, oil-in-water emulsion), and at two volumes (47 or 188 I/ha) of carrier. The oil-in-water

emulsion carrier reduced leaf water content mom consistently than the other carriers, so we used the oil-inwater emulsion carrier in a study of paraquat applied aerially in early August. Rate ranged from 0.3 to 3.4

kg/ha and included two volumes (47 or 94 l/ha). All aerial applications of paraquat reduced juniper leaf

water content to 50 percent or less three weeks aher treatment compared to 100 percent water in untreated

junipers. Leaf water content in the late summer dry season will normally decline to about 80 percent, a

level too moist for ignition of juniper foliage. Combining paraquat with burning almost doubled the crown

scorch of large trees over either treatment alone and increased kill of large lrees to more than SO percent

compared to no lrees killed with the burning-only or paraquat-only treatments.

INTRODUCTION

Tallgrass prairie and other grasslands of North American arc

regarded as fire-tolerant systems which evolved with fire as a

part of the natural disturbance regime (Anderson 1982).

Protection from fire results in extensive encroachment of fireintolerant woody species, including eastern redcedar and ashe

juniper into tallgrass prairies as well as into other grasslands

and hardwood forests of the central U.S. (Arend 19.50; Bragg

and Hulbert 1976, Wright 1978). Juniper encroachment into

these ecosystems has increased exponentially in recent years,

modifying the Physiognomy of these ecosystems and reducing

their value as rangelands (Wright and Bailey 1980; Snook

1985).

Tallgrass Prairies that become dominated by juniper are

similar to other ecosystems that were previously grasslands or

savannahs but now have successional PrOCeSSCS driven by

woody vcgctation. Upon reaching a transitional threshold

Promoted by reduced fire frequency and intensity, new

successional PrOCCSSCS preVent reversion to grassland from

overstory dominance by woody species, and fire is no longer

an effective agent in reversing succession to grassland (Archer

1989; Bryant and others 1983; Walker and &hers 1981).

Drastic anthropogenic modification (i.e., herbicides or

mechanical manipulation) of the woody vegetation is

necessary to convert the plant community to dominance by

herbaccous Plants (Archer 1989; Engle 1987).

‘Professors of Range Science and Weed Science, respectively,

Oklahoma Stale University, Stillwater, OK.

Fire kills both species of juniper if fine heI loading is

sufYicient to produce an intense fire that completely scorches

the crown because neither species sprouts from roots or stems

after topkill (Owensby and others 1973; Wink and Wright

1973). However, tree mortality decreases as tree size

increases so fire intensity must in- to scorch the crown

of taller trees (E3vant and others 1983; Dalrymple 1969;

Engle and others 1988). Fire intensity and tree mortality are

reduced further in dense stands of large tmes because junipers

reduce the production of fine f&l so that fires in these stands

are of tow intensity or perhaps fires fail to carry at all (Bryant

and others 1983; Engle and others 1987).

Junipers arc o&n controlled mechanically or by herbicides,

but mechanical and herbicide methods of juniper control are

generally either too expensive or are ineffective on large trees

(Scifres 1980; Stritzke 198.5). Small trees can be controlled

individually with some soil-applied herbicides and paraquat

applied in hot weather can result in considcrabtc damage to

trees (En& and others 1988). Integration of several brush

control treatments into a single set of treatments, i.e.,

integrated brush management, is one way to deal effectively

with brush (Scifics 1980). Paraquat applied to individual

trees in the summer has increased juniper crown damage from

broadcast bums the following spring with light line fuel

loading (Engle and others 1988). A combination of broadcast

application of paraquat followed by a prescribed bum has

been suggested as an integrated method to control severe

inf&&ions of juniper (Engle and others 1988). We

397
conducted two studies, each with a separate objective: 1) to

determine the effect of various paraquat treatments on juniper

foliage water content, a primary factor affecting flammability

of juniper crowns (Bunting and others 1983), and 2) to

determine if aerial application of paraquat will reduce foliage

water content and increase crown scorch from broadcast fires

in tallgrass prairie.

METHODS

Study 1 was conducted on two sites approximately 15 km

southwest of Stillwater, OK on the Oklahoma Agricultural

Experiment Station’s Agronomy Research Range. Shallow

prairie was the primary range site of one location and red

clay prairie was the primary range site of the other location.

About 2800 kg/ha of fine fuel arc produced on both sites in a

normal year. Herbaceous understory was dominated by

tallgrasses and eastern redcedar canopy cover was less than 5

percent.

Paraquat was foliar applied to individual eastern redcedar

trees on August 17-18, 1988 with a compressed-air hand

sprayer using a T-3 conejet nozzle to simulate aerial

application. Treatments were in a factorial arrangement of

paraquat (0.3 or 1 .l kg/ha), carrier (water or oil-in-water

emulsion), and volume of carrier (47 or 188 l/ha). The

design was completely randomized with ten replications on

each of two sites located approximately 5 km apart. Eastcm

redcedar foliage was sampled at weekly intervals (August 24,

September I, and September 8) following treatment, weighed

in the field, and dried in a forced-air oven to determine

foliage water content, which is expressed on the basis of dry

weight.

Study 2 was conducted in Johnston County, OK,

approximately 30 km northeast of Ardmorc, OK. The study

area is located on a loamy prairie range site normally

producing about 3900 kg/ha of forage in the absence of

juniper interference. Ashe juniper, with canopy cover of

approximately 25 percent, was the overstory woody dominant

The under-story was a mixture of tallgrasses and midgrasses.

Paraquat was applied aerially in the oil-in-water emulsion

carrier to ashe juniper on August 9, 1989. Herbicide

treatments included no herbicide treatment and paraquat

applied at rates ranging from 0.3 to 3.4 kg/ha. Paraquat rate

treatments were nested within two volumes (47 or 94 l/ha) of

the carrier. Plots were 0.1 ha (30 X 30 m). The design was

a randomized complete block with four blocks. Foliage was

sampled three weeks after paraquat treatment, weighed in the

field, and dried in a forced-air oven to determine foliage

water content, which is expressed on the basis of dry weight.

Two blocks were burned with a headfire on September 1,

1989. At the time of the bum, air temperature was 38”C,

relative humidity was 40%, average wind velocity was 8

km/h, and fine fuel loading within the juniper stand was

visually estimated at 1500 kg/ha. Crown damage to trees and

tree kill were determined in all treatment plots two months

sher the bum. Visual estimates of crown damage and tree

kill were conducted on three size classes based on tree height:

small (0.8 to 1.5 m), medium (1.5 to 2.5 m), and large (2.5

to 5.0 m).

We subjected the data from both studies to analysis of

variance. Leaf water data from study 1 and study 2 were

analyzed as repeated measures in time (Winer 1971). Means

were separated by LSD subject to a protected F-test at the

95% probability level as suggested by Carmer and others

(1989).

RESULTS

Study 1

Study site interacted (P < 0.0001) with treatment and sampling

date so data from each study site were analyzed separately.

No treatment effects were significant one week after paraquat

application, but by two weeks after treatment, paraquat rate

interacted with both carrier and volume of carrier (P < 0.0224

and P < 0.0182, respectively) at Site 2 (fig. 1). Water

content of foliage with all treatments increased the second

week after treatment, which we attributed to a change in

available soil water in response to 20 millimeters of

precipitation on August 28 between the first and second week

aRer treatment. By the third week after treatment, leaf water

had dropped drastically in trees in all trcatmcnts, with some

below 50 percent leaf water. Paraquat treatment rate,

volume, and carrier interacted at study Site 1 and 2 on the

third week after treatment (PcO.0163 and P<O.O002,

respectively). Foliage water content was lower in trees

treated with the 1.1 kg/ha rate of paraquat and results were

more consistent with the oil-in-water carrier (fig. 1).

Study 2

Leaf water content did not differ (P > 0.1288) between the

two volumes of carrier on either sampling date so we

averaged the rate data over the two volumes. Leaf water

content was less in foliage of treated trees than in untreated

trees two weeks after paraquat treatment and declined to 50

percent or less by three weeks after treatment with all rates of

paraquat (PC 0.000l) (fig. 2). Although increasing rate of

paraquat was not additive, all rates of paraquat desiccated

ashe juniper foliage to the extent necessary to increase

flammability by three weeks after treatment (Bunting and

others 1983). Although juniper leaf water was higher in 1989

than in normal years (Engle and others 1988), leaf water

content in the late summer dry season will normally decline

only to about 80 percent, a level too moist for ignition of

juniper foliage.

398
99

Site 1

Trees Treated August 17

BC

I

g7c.b*..,

.‘.,. ‘..,

0 0.3

b

‘..,

0.3

n

I’

2 3

Weeks After

Site 2

Trees Treated August f8

Treatment _------ . . __. -_____I---- Low volume c

..;- High volume Oil-in-water

0

_-. -3

Figure l.- Leaf water (‘55) after paraquat application at Site 1

and Site 2. Paraquat rate (0.3 or 1.1) is in kg/ha. LOW

volume of carrier is 47 l/ha and high volume is 188 I/ha.

Values arc means of 10 trees, LSD,,,= 13 at Site 1 and

LSD,,,=23 at Site 2 on week 3. Foliage of untreated trees

was 80% water at both study sites on September 8.

2 Weeks After Treatment

100

00

00

M

- 2 0

,& 48

2

"0 120 0 1 100 3 Weeks After Treatment

J

80

60

40

2 0

0

Kate (kilograms/hectare)

Figure 2.- Leaf water (o/o) two weeks and three weeks after

paraquat was aerially applied on August 9, 1989. Valued art:

means of 8 trees, averaged over volume of car&x

O-Wm-- 10 on week 2 and LSD,a5= 11 on week 3).

399
n

SITAl Mcdwm Large

Tree size

0 Poroquot only Cl Bum only q Poroquot & burn

Figure 3.- Crown damage (%) two months after burning. Figure 4.- Tree kill (%) two months after burning. Values

Values for paraquat only treatments are averaged over rate for paraquat only treatments are averaged over rate.

Treatments were not different (P > 0.0604) for small and Treatments were not different (P > 0.303 1) for small trees, but

medium trees, but treatments were different (P <0.03 19) for treatments were different (P<O.O392) for medium and large

large trees (LSD,,,, =27). trees (LSD ,,Os =48 and 3 1, respectively).

The amount of crown damage to trees was not affected by

either carrier volume or paraquat rate within the paraquat plus

bum treatment for any size of tree (P>O. 1247). Howcvcr,

crown damage and tree kill of medium and large trees

differed (P < 0.0604) among the three treatments (paraquat

only, bum only, or paraquat plus bum) (fig. 3 and 4).

Crown damage to trees from fire alone and paraquat alone

was similar to the results of previous studies (Engle and

others 1987). The effects of paraquat and fire on large trees

were approximately additive in respect to crown damage

which exceeded 80 percent in the paraquat plus bum

treatment plots (fig. 3). Paraquat and burning appear to have

a synergistic effect in killing large trees in that almost no

trees were killed by the single treatment of either paraquat or

burning but half of large trees were killed by combining the

two treatments (fig. 4).

DISCUSSION

Paraquat applied in hot weather by hand to individual trees

(study 1) or applied aerially in a broadcast spray (study 2)

was effective in reducing juniper foliage water content to

below the critical point of 60 percent water (Bryant and others

1983; Bunting and others 1983; H.A. Wright, pers. comm.).

Desiccation of juniper foliage by paraquat applied aerially

almost doubled the crown scorch and increased the kill of

large trees from 0 to 50 percent. The results of this study arc

in agreement with previous work in which desiccation of

juniper foliage by treating individual trees with paraquat

compensated partially for light fine fuel loading in cool-season

fires the spring after summer paraquat application (Engle and

others 1988).

Small Medium

Tree size

We believe it is possible to use paraquat as a desiccant to

promote crown fires in closed-canopied stands of juniper.

Previous attempts to ignite crown fires have been unsuccessful

in dense stands of ashe juniper in Texas (Bryant and others

1983) and in pinyon (Pinus cdulis) and juniper woodlands in

Nevada (Bruner and Klebenow 1979) possibly because of high

foliage water content, gaps in the tree canopy, and cool fireweather conditions. Bryant and others (1983) evaluated

igniting windrows of recently dozed ashe juniper to produce

an intense fire with flames in contact with standing trees to

produce a crown fire in dense stands of ashe juniper, but no

sustained crown fire resulted. However, six standing trees

were killed for every dozed tree by the windrow fire thereby

reducing the overall cost of mechanical treatment of the

juniper stand. Bruner and Klebenow (1979) were unable to

obtain crown tires in closed stands (i.e., no understory) of

pinyon-juniper and concluded that crown fires are possible

only when burned under hazardous conditions.

Our research indicates an integrated approach using paraquat

and tire can be used to reduce overstories of large junipers

for restoring tallgrass prairie dominated by junipers. Further

research is needed to determine if crown fires can be ignited

from paraquat-desiccated strips in dense stands of junipers

using aerial ignition with a helitorch.

ACKNOWLEDGMENTS

The USDA-Soil Conservation Service funded a portion of this

study. We thank Mr. Sam Daube for allowing us to conduct

portions of this study on his ranch and Mr. Jim Altom of the

USDA-SCS for his support and assistance. This is journal

number J-5787 of the Oklahoma Agricultural Experiment

Station.

400
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Arend, J.L. 1950. Influence of fire and soil on distribution of

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48:129-130.

Archer, S. 1989. Have southern Texas savannahs been

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Bragg, T.B. and L.C. Hulbert. 1976. Woody plant invasion

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Management 29: 19-24.

Bryant, F.C., G.K. Launchbaugh, and B.H. Kocrth. 1983

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fires. Journal of Range Management 36: 165-168.

Bruner, A.D. and D.A. Klcbcnow. 1979. Predicting success

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U.S. Forest Service. Intermountain Forest and Range

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Bunting, S.C., H.A. Wright, and W.H. Wallace. 1983.

Seasonal variation in the ignition time of &berry juniper

in west Texas. Journal of Range Management 36: 169-171.

Canner, S.C., W.E. Nyquist, and W.M. Walker. 1989. Least

significant differences for combined analyses of

experiments with two- and three-factor treatment designs.

Agronomy Journal 8 1:665-672.

Dalrymple, R.L. 1969. Prescribed grass burning for ashe

juniper control. Progress Report from Noble Foundation,

Inc., Ardmore, OK.

Engle, D.M. 1987. The Cross Timbers Experimental Range--

tomorrow’s research today. In: Rollins, D., ed. Brush

Management in the Cross Timbers Proceedings.

Cooperative Extension Service. Oklahoma State

University. Stillwater. Circular E-862.

Engle, D.M., J.F. Stritzke, and P.L. Claypool. 1987. Effect

of paraquat plus prescribed burning on eastern redcedar

@Vn@ecuslvir&i~a$. h n o 1 o g y 2:172-174.

Engle, D.M., J.F. St&&e, and P.L. Claypool. 1988.

Herbage standing crop around eastern redcedar trees.

Journal of Range Management 40237-239.

Owensby, C.E., K.R. Blan, B.J. Easton, and O.G. Russ.

1973. Evaluation of eastern redcedar infestations in the

northern Flint Hills. Journal of Range Management

26:256-260.

Scifres, C.J. 1980. Brush management: Principles and

practices for Texas and the southwest. Texas A&M

University Press, College Station. 360 pp.

Snook, E.C. 1985. Distribution of eastern redcedar on

Oklahoma rangelands. p. 45-52 In: R.W. Wittwer and

D.M. Engle (eds.) Proceedings of the Eastern Redcedar in

Oklahoma Conference. Cooperative Extension Service,

Division of Agriculture. Oklahoma State University E849.

Stritzke, J.F. 1985. Chemical and mechanical control of

eastern redcedar. pp. 61-69. In: Wittwer, R.W. and

D.M. Engle, eds. Proceedings of the Eastern Rcdccdar in

Oklahoma Conference. Cooperative Extension Service,

Division of Agriculture. Oklahoma State University. E849.

Walker, B. H., D. Ludwig, C.S. Holling, and R.M.

Peterman. 1981. Stability of semi-arid savanna grazing

systems. Journal of Ecology 69:473-498.

Wirier, B.J. 1971. Statistical principles in experimental

design. McGraw-Hill. New York.

Wink, R.L. and H.A. Wright. 1973. Effects of lire on an

ashe juniper community. Journal of Range Management

26:326-329.

Wright, H.A. 1978. Use of fire to manage grasslands of the

Great Plains: Central and Southern Great Plains. pp. 694-

696. In: Hyder, D.N., ed. Proceeding of the First

International Rangelands Congress.

Wright, H.A. and A.W. Bailey. 1980. Fire ecology and

prescribed burning in the Great Plains--A research review.

U.S. Department of Agriculture. Forest Service.

Intermountain Forest and Range Experiment Station.

General Technical Report INT-77.

401
ELASTICITIES ASSIST TARGETING

OF ARSON PREVENTION PROGRAMS

R.A. Kluender arnd L.C. Thompson’

Abstract-Elasticities (percentage change in one factor divided by percentage change in another factor)

were calculated to demonstrate the effect that reducing the number of arson fires in Arkansas counties had

on area burned. Elasticities are employed by economists and managers to determine which factors yield the

greatest returns per unit of effort expended. Hypothetical reductions in area burned and average wildfire

size were determined by randomly decreasing arson wildfires. Results showed that as arson rates increased

above SO percent, disproportionately greater reductions in area burned accrued from reducing arson.

Accordingly, counties with high elasticities for area burned should he the first targets for arson reduction

campaigns. Elasticities for average fire size showed weak responsiveness to arson reductions. When the

primary objective of a prevention program is reducing area burned, elasticities for area burned can provide

another tool for wildfire prevention specialists to use in appraising where scarce resources can be best

utilized.

INTRODUCTION

Achieving effective wildfire prevention and suppression

programs requires proper analysis of available data and

correct interpretation of results, which supports the generation

and implementation of effective policy. Because of the

tremendous task of acquiring, entering and extracting meaning

from wildfire data, detailed analysis is commonly not

performed. Instead, management targets (typically calculated

statistics) or goals are used to gauge the yearly progression of

control programs. Generally, these management targets are

presented in a standardized form (as an example, on a “per

thousand protected hectares” basis) because they provide a

quick gauge across county and regional boundaries and can be

used across state boundaries to weigh the success of

innovative programs.

In Arkansas, state lands protected from wildfire by the

Arkansas Forestry Commission (AFC) include all privately

owned forest and pasture lands but not areas within

incorporated town and city borders, row-crop lands, federal

ownerships (such as national forest lands) and other public

ownerships. The Associate State Forester for Protection in

Arkansas has set four wildfire management targets for county

and state level programs. They are: 1) less than 1.5 hectares

per thousand protected hectares (TPH) burned per year; 2)

not more than 0.37 fires per TPH per year; 3) an average

fire size less than 4 hectares and; 4) less than 40 percent

arson fires. The most important of these goals is the first, to

keep burned area as low as possible. Counties below any

particular target are considered within compliance relative to

their wildfire prevention or suppression goals.

Factors such as weather, attitudes and prevention and

suppression efforts all play a part in determining the final

‘Associate Professor Forest Economics and Associate Professor Forest

Protection, Department of Forest Resources, Arkansas Agricultural

Experiment Station, Monticello, AR 71655.

402

yearly toll to wildfires. However, increasing rates of arson

(Arkansas Forestry Commission 1984-1989) have aroused

concern. These trends were first reported by Klucndcr et al.

(1988, 1989). Perhaps the most important findings of these

studies were that local residents caused 70 percent of the

arson tires and that arson fires had an average size twice that

of other causes (8.4 vs. 4.2 hectares). Additionally, these

studies indicated that while general state-wide trends were

important, they did not provide the detailed information

required to formulate county-level fue prevention and

suppression plans. Preferably, prevention and suppression

programs should be designed for local conditions to better

target problems and reduce wildfire losses. Kluender et al.

(1990) subsequently looked at county-level wildfire patterns

and found considerable variability among Arkansas’ 75

counties for arson rates and area burned. The data showed

that of the 35 counties that exceeded the AFC target of 40

percent arson rate, 27 counties also exceeded the target for

area burned; and, of the 39 counties that exceeded the target

for area burned, 28 counties also exceeded the target for

arson rate. Of the 48 counties that exceeded either target, 28

counties simultaneously exceeded both targets. So, the link

between higher arson rates and higher area burned is well

established among counties.

Wise management dictates that limited budget dollars be

disbursed in the most effective way. Frequently, in wildfire

prevention campaigns, managers may wonder whether money

is being spent in the right place or on the right program.

Numerous appraisal methods have been used by various

agencies from time to time. Benefit-cost ratios express some

measured benefit against the cost of obtaining it. Measures of

cost to protect a known “value at risk” adopt an actuarial

approach to the same problem. These measures, however,

are static, cross-sectional statements of expected benefit for

given expenditure. A more sophisticated concept is the use of

elasticities to identify the percentage change of a dependent

variable (like hectares burned) for a percentage change in an
independent variable (like arson rate); thus, elasticities

measure responsiveness to change. Elasticities are used by

economists and policy makers to show how much change in a

given factor to expect for a given change in a driving or

causal variable (Pindyck and Rubinfeld 1981). Generally,

those independent variables that produce the greatest changes

in the dependent variable (high& elasticities) are the best

choices for policy manipulation.

Two factors point to the need to reduce the total number of

arson tires in the South. First, arson is, in most southern

states, the greatest single cause of wildfires (USDA Forest

Service 1984). Second, arson tires tend to be larger than

those from other causes. This paper demonstrates the use of

elasticities as a measure of responsiveness to arson prevention

based on hypothetical reductions in total area burned and

average fire size. Our objective was to describe a tool that

wildfire managers might use to help them select targets for

arson prevention programs.

METHODS

We acquired the records of all reported wildfires on lands

protected by the Arkansas Forestry Commission (AFC) for

the period January 1983 through December 1988 (Arkansas

Forestry Commission unpublished data). These data included

records developed from Individual Fire Reports (AFC Form

24 10. I) tilled out by suppression personnel immediately after

a fire was investigated. Variables chosen for inclusion in this

study were year, county, cause (for example, arson or debris

burning) and hectares burned per fire. The data set included

reports of 16,047 tires. A second data set was obtained from

the AFC that contained total hectares and protected area per

county. The data sets were sorted by county and merged.

The number of fires per TPH, area burned per year per TPH,

average fire size, and percentage arson tires for each county

were calculated.

Because we (and the AFC) were interested in evaluating the

effects of reducing arson fires in counties with high arson

rates (by AFC definition, high includes those that exceeded

the AFC management target of 40 percent arson rate),

counties with an arson rate greater than 40 percent were

retained in the analysis. Thirty-five of Arkansas’ 75 counties

(47 percent) remained in the active data set.

To simulate an effective prevention program that reduced

arson rate to the AFC target, individual arson fires were

randomly eliminated from each county data set until arson

fires comprised 40 percent or less of the total fires. After

randomly reducing arson fires to 40 percent, average tire

size, area burned per TPH and number of fires per TPH were

recalculated for each county. Elasticities for area burned per

TPH (Ed, and average tire size (EAvazs) were calculated

for each county. For example, elasticity of area burned was

calculated by:

(AAREA I AREA)

EARFA =

(AARSON / ARSON)

Where:

AAREA = Change in area burned after reducing arson rate

AREA = Area burned before reducing arson rate

LARSON = Change in percentage arson tires

ARSON = Percentage arson fires before reducing arson rate.

Elasticity of average fire size was calculated in a similar

manner.

Three replicates of the random reductions in arson tires for

each county were created and the calculations for E,, and

E,,, performed for each county in each replicate. An

ANOVA was performed on the E,, and EAvsnE data sets to

determine if differences existed between replicates. To

establish relationships, EAREA and E,,, were regressed

against the percentage of arson tires in each county before the

reduction to 40 percent. Regression analysis was also used to

ascertain what contribution the pre-reduction arson rate and

average fire size of each county made to E,,.

A standard statistical package, SPSS (Norusis, 1988), was

used to p&or-m the initial data analysis and data sorting. The

Quattro Pro spreadsheet (Borland International 1989) was

used to calculate the elasticities, and SYSTAT (Wilkinson

1988) was used in the final comparison of pre- and postreduction conditions and in the regression analysis. Statistical

significance was accepted at the ( y = 0.05 level.

RESULTS ANDDISCUSSION

The ANOVA showed no differences among the replicates for

either E,, (F2,a = 0.085, p = 0.919) or E,,,, (Fzloz =

0.050, p = 0.951). Therefore, we used the mean value for

each county’s elasticities in all further analyses.

Elasticities for area burned per TPH (EAR& with respect to

arson rate were greater than 1 .O (unity elasticity) for 23 of 35

counties; these counties were considered responsive to

reductions in arson fires (Figure 1). When this elasticity was

regressed against arson rate the linear function was:

EARM = 0.388 + 0.013 x ARSON RATE

Both the constant and the slope were different from zero.

While considerable variation was present in the data, general

trends were obvious. The slope shows that the higher the

initial level of arson tires, the greater will be the response of

area burned to reductions in arson levels. Additionally, the

best-tit line (Rz = 0.435) rose above unitary elasticity at an

arson rate of 49 percent. Accordingly, we reason that area

burned per TPH would typically be responsive to changes

when the arson rate in a county exceeds 49 percent, or 50

percent in round numbers.

403
40 5 0 90

Figure 1. Elasticity for wildfire area burned compared with

arson rate for 36 of 75 counties in Arkansas that exceeded the

wildfire management target of 40 percent arson.

Elasticities for average fire size (EAvsn;E) with respect to arson

rate were ail below unity and, hence, considered

unresponsive. Although average fire size decreased when

arson fires were eliminated, the reduction was relatively small

when expressed as a percentage. Hence, I&,, was typically

low. When this elasticity was regressed against arson rate

neither the constant nor the slope were different from zero.

Finally, we regressed the elasticities of area burned as a

dependent variable against arson rate and average fire size

The response surface was a quadratic function:

E = 0.187 + 0.014 x ARSON RATE

+“o”Ib19 x AVERAGE FIRE SIZE +

0.001 x (ARSON RATE)(AVERAGE SIZE).

However, only arson rate was different from zero; this

surface had an R2 of 0.549. Therefore, we conclude that

arson rate alone, which had an R’ of 0.435, is the best

predictor for estimating BAREA.

This analysis establishes that when the primary objective of a

prevention program is reducing area burned, I good tool for

choosing targets for the prevention program is the elasticity

for area burned. For best results, ordinal ranking of counties

should logically proceed from those with the highest to lowest

elasticities. The best choice among counties with equal

elasticities shouId be made by selecting the county with the

largest average fire size.

We have shown that for Arkansas counties with high arson

rates, disproportionately greater reductions in area burned can

be expected when the number of arson fires is decreased.

This is important because keeping burned area as low as

possible is the most important goal of the AFC. Calculating

and using elasticities for area burned will aid the efficient

targeting of monies and other efforts for arson prevention

programs. In areas where arson is not the primary cause of

wildfires, perhaps other causes could be investigated in a

similar manner.

ACKNOWLEDGMENTS

Ms. Denise Steigerwald, Department of Forest Resources,

assisted with data analysis and Mr. Robert McFarland,

Associate State Forester for Protection with the Arkansas

Forestry Commission, provided insight and data. Drs. E.E.

Gbur, Agricultural Statistics Laboratory, T.B. Wigley and

J.M. Guldm, Department of Forest Resources, reviewed the

original draft. Published with the approval of the Director,

Arkansas Agricultural Experiment Station, Fayetteville.

LITERATURE CITElD

Arkansas Forestry Commission. 19841989. Annual fire

reports: size and cause statistics for the years 1983

through 1988. Department of Commerce, Little Rock,

AR (mimeo). 12 pp each.

Borland International. 1989. QUA?TRO PRO User’s Guide.

Borland International, Inc. Scotts Valley, CA. 709 pp.

Kluender, R. A., L. C. Thompson and G. W. Callahan.

1988. Analysis of wildfire occurrence in southeastern

Arkansas., 1984-1987. Proceedings Arkansas Academy of

Science. 42:41-44.

Kluender, R. A., L. C

D. M. Steigerwald.

record: 1983-1987.

Science. 43 :49-5 1.

Kluender, R. A., L. C.

D. M. Steigerwald.

Thompson, R. J. McFarland and

1989. Arkansas’ incendiary wildfire

Proceedings Arkansas Academy of

Thompson, R. J. McFarland and

1990. An analysis of Arkansas’

wildfire record by county, 1983-1988. Arkansas

Agricultural Experiment Station Bulletin 92.5. Fayetteville,

AR. I8 pp.

Nor&, M. J. 1988. SPSS/PC+, Statistical package for the

social sciences, IBM/PC version. SPSS, Inc. Chicago, IL.

1500 pp.

Pindyck, R. S. and D. L. Rubinfeld. 1981. Econometric

models and economic forecasts. McGraw-Hill. New

York, NY. 630 pp.

USDA Forest Service. 1984. 1982 Wildfire statistics. U S.

Department of Agriculture, Forest Service Publication

82-D-2. Washington, DC. 49 pp.

Wilkinson, L. 1988. SYSTAT: The system for

statistics. SYSTAT, Inc. Evanston, IL. 820 pp.

404
LONG-TERM IMPACTS OF FIRE ON COASTAL PLAIN PINE SOILS

William H. McKee, Jr.’

Abstract-Repeated burning of pine forests over long periods may have pronounced effects on the

maintenance of soil fertility and soil development. Analyses of soils from four long-term prescribed

burning studies in the Atlantic and Gulf Coastal Plain indicate that burning has had no effect on the total

carbon and nitrogen level in the surface mineral soil. Winter burning increased the retention of nitrogen in

the mineral soil over time. Changes in the carbon/nitrogen ratio in the forest floor with burning suggest

that at least part of the increase in nitrogen in the mineral soil was due to pyrolysis of the litter. Available

phosphorus was consistently increased in the surface 5 cm of soil by prescribed burning; however, the

effect is less apparent on total phosphorus reflecting the low mobility of the nutrient. Concentrations of

exchangeable bases in the surface soil increased with the frequency of burning. It is postulated that without

burning, immobilization of calcium in the forest floor can lead in time to a magnesium:cajcium imbalance

and alteration of the soil formation processes.

INTRODUCTION

A concern about repeated burning is that it may reduce the

“tilth” and productivity of soils it! the long-term. Studying

long-term effects of tire in the South is difI%ult, however,

because burning has been part of the ecology of most fire

sites there. Fire affects soil properties but measuring the

cumulative effects on soil development takes many years and

many fires. Data from some long-term burning studies in the

Southeastern Coastal Plain offer clues about how fire

influences soil forming processes.

Soil properties have been monitored in a number of Coastal

Plain prescribed burning studies (McKee 1982, Ralston and

others 1982, and McKee and Lewis 1983). In this paper I

have combined the findings and updated the measurements for

four major studies to develop indications of how ‘ounning may

alter soil chemical properties and influence soil development.

MATERIALS AND METHODS

Study Areas

The four prescribed burning studies represent a wide range of

soil textures, drainage classes, topographic positions, and

understory vegetation. Brief descriptions of the four areas arc

as follows:

Alabama. This study is near Brewton, Alabama, on the

upper Coastal Plain. Soils are classed as coarse loamy

siliceous thcrmic (Typic Paleudults), complexed with fine

loamy siliceous thermic (Typic Palcudults), loamy siliceous

thermic (Grossarenic Palcudults) and loamy skeletal siliceous

thermic (Typic Hapludults). Overstory vegetation consists of

60- to 70-year-old longleaf pine @$us oaltistris Mtil.). e

index (age 50) ranges from 19 to 24 m, and understory

vegetation consists of grasses, forbs. and small woody

sprouts.

‘Soil Scientist, USDA Forest Service, Southeastern Forest Experiment

Station, Charleston, SC.

Treatments are replicated eight times on 0.16ha plots.

Treatments examined here are an un-bum control and biennial

winter burning. The study was initiated in lslll and plots had

been burned five times when data reported here were

gathered. The last bum was applied about four months before

sampling.

Florida. This study is on the Coastal Plain flatwoods in

north central Florida. Soil on the study area is classed as

sandy siliceous thermic (Aeric Haplaquods) with an organic

pan between 46 and 61 cm deep. The overstory vegetation

contains mixed, naturally seeded longleaf and slash @.

eelliottii Engelm. var. efijottii)-pines i60 to 70 years old.

index (age 50) for the study area is 20 m, and average basal

area is approximately 15.3 rnz ha.

Treatments are replicated six times in a randomized block

design on 0.81-ha plots. Treatments consist of an un-bum

control, winter bum every four years, and annual winter

burning. The annual winter bum was not imposed until six

years after initiation of the study; at the time of sampling

there had been 14 annual burns.

Georgia. The study is on a nearly level Coastal Plain site in

south central Georgia. The site is poorly to somewhat poorly

drained. Soils are loamy siliceous thermic (Arenic

Paleaquults) covering about 2/3 of the site, loamy siliceous

thermic (Arenic Plinthoquic Paleudults), fine loamy siliceous

thermic (Plenthic Fraquidults), and loamy siliceous thermic

(Arenic Paleaquults). Overstory trees are longleaf and slash

pines ftom 25 to 30 years old.

Plots consist of pastures of about 19.7 ha on which grazing is

also observed. Treatments consist of no burning, triennial

winter burning, biennial winter burning, and annual winter

burning. Treatments have been in force for 40 years except

for a IO-year period 25 years previously when the stand was

regenerated.

406
South Carolina. This study is in eastern South Carolina on a

Pleistocene terrace of the lower Coastal Plain. The terrain is

nearly level and is poorly to somewhat poorly drained. Soils

are clayey mixed thermic (Umbric Paleaquults), clayey mixed

thermic (Typic Albaquults), clayey kaolinitic thermic (Typic

Paleaquults), clayey kaolinitic thermic (Aeric Paleaquult), fine

loamy siliceous thermic (Aquic Paleudults), tine loamy

siliceous thermic (Aeric Paleaquults). The overstory is

70-year-old 1obloIIy pine (P. tacda L.) and the site index (age

50) is 27 to 30 m. Burning treatments were begun 30 years

prior to the current sampling.

Plots are 0.10 ha in area. Treatments consist of an un-bum

control, periodic winter burning, periodic summer burning,

annual winter burning, and annual summer burning. Periodic

burning was done every seven years, or when hardwood

stems were approximately 2.5 cm d.b.h.

Sampling Methods

On each plot in the four studies, the forest floor and mineral

soil were sampled at 40 points. Samples collected at 10 points

were combined to make four composite samples per plot each

for the forest floor layer and the mineral soil. Forest floor

samples consisted of all material, including 01, 02, and 03 (L,

F, and H layers), collected from within a Is-cm square

frame. The forest floor was mor humus with little mineral

soil mixed in it. No attempt was made to separate the forest

floor by layers. Two 2.5-cm soil cores were collected from

within the square of each sample point. Depth of the cores

was 0 to 5 cm and 5 to 10 cm on the South Carolina site and

0 to 8 cm and 8 to 16 cm on the other sites. Only the surface

samples were used for soil reaction properties. Analysis of

both depths were used in computing total nutrients and

organic matter levels. The South Carolina and Georgia sites

were sampled in mid winter while the Florida and Alabama

sites were sampled in early summer.

Laboratory Methods

Forest floor samples were dried at 70” C for 24 h, weighed,

and ground to pass a 40-mesh screen. Nitrogen content was

determined by a modified micro-Kjeldahl procedure, and

ammonia was determined by the salicylate-cyanurate

procedure (Nelson and Sommcrs 1973). Other analyses were

made on material dry ashed for 2 h at 450” C and taken up in

0.03 M HNO,. Phosphorus was determined by the

molybdovanadate procedure (Jackson 1958); calcium and

magnesium were determined by atomic absorption. A

separate sample was dry ashed at 500’ C for 2 h to determine

mineral content, which was subtracted from the dry weight.

Thus, weights of forest floor material represent only the

component lost on ignition.

Soil samples were air dried and crushed to pass a 2-mm

sieve. Organic matter was assayed by wet oxidation (Jackson

1958). Exchangeable bases were determined by atomic

absorption on extracts made with 1M NH, OAC (Jackson

1958). Available phosphorus was determined by extracting

2.5 g of soil with 20 ml of Bray p2 solution (Bray and Kurt2

1945). Inorganic phosphorus was fractionated by the method

of Chang and Jackson (1957), and organic phosphorus was

determined by the procedure outlined by Olsen and Dean

(1965). Total soil nitrogen was extracted by micro-Kjeldahl

digestion, and ammonia was determined by the

salicylate-cyanurate method (Nelson and Sommcrs 1973).

Soil pH was measured with a glass electrode on a I:2

soihwater mixture.

Total levels of nutrients were computed using the

concentrations observed in laboratory analysis, the volume of

soil obseved, and bulk densities considered typical for the

series in the case of the South Carolina site measurements

were made of individual plots.

RFXJLTS AND DISCUSSION

Mineral Soil Properties

Burning effects tended to be consistent over the range of

Coastal Plain soils examined, with the degree of effect

reflecting soil properties of specific sites (Table 1).

pH. Soil pH increased slightly but significantly with intensity

of burning on the Florida and South Carolina sites. In the

South Carolina on the plots burned annually in summer soil

pH was significantly higher than on control plots on

periodically burned winter plots. The difference was about

0.4 pH unit. Periodic summer and annual winter burning

produced intermediate pH values, which did not differ

significantly from those of other treatments. On the Alabama

site, prescribed burning did not significantly alter pH values;

however, on burned areas, readings averaged 0.2 pH units

higher. Soil pH ranged from 3.5 to 4.4 among burning

treatments on the Georgia site. The effects were not

significant, but pH tended to increase with frequency of

burning.

For a wide range of soils and burning techniques, soil pH has

been shown to increase to some degree shortly after burning

(Wells and others 1979). As time passes, acidity increases

and soil pH returns to its prebuming value. Degree of pH

increase and time needed to return to the prcbuming level

depend on burning intensity, amount of forest floor

consumed, soil organic matter and clay contents, rainfall, and

internal soil drainage. Results of these studies indicate that

periodic burning raises pH values slightly. On heavy soils,

this effect is apparent for at least 7 years after burning. For

the sandy soil on the Florida site, the pH value for the

periodic burning treatment did not differ from that of the

unburned control. This result suggests that the pH increase

had a shorter duration on this site, which was last burned two

years before sampling.

406
TABJ..E 1. Soil reaction, exchangeable bases and cation ratios for foer sites

uitb different bluning tYreatux?nts.

Sample site ad

burn treatment

Soil

PH

Exchangeable bases

Ca f Hg

mot kg

Ratio

Hg/Ca

Alabam (o-8 cnl~

No Bum 5.2

Biennial uinter 5.4

1.278 0.20A 0.16

1.89A 0.148 0.07

norida (O-8 crnk

No Bum 4.lAB

Periodic winter 4.08.

Annuel uinter 4.2A

&o&a (O-S Cm2

NoBum 4.1

Triellldal winter 3.5

Biennial winter 4.4

Annua I winter 4.1

s0~tb h-~~li~+ (O-5 cm\

NoBum 4.18

Periodic minter 4.18

Periodic slnrner 4.2A6

Annual uinter 4.2AB

Amnal simmer 4.5A

0.256 0.22B 0.88

0.45A 0.35A 0.77

0.57A 0.38A 0.66

0.11 0.05 0.42

0.18 0.05 0.31

0.29 0.07 0.36

0.16 0.05 0.32

0.63 0.286 0.44

0.79 0.33AB 0.42

0.87 0.33AB 0.38

1.23 0.51A 0.41

1.08 0.38AE 0.35

Within col- and sites. vdues fo\ lowed by the same letter or no ktter do

not significantly differ at the 0.05 Level.

Samples collected after 10 years of burning on the South

Carolina site averaged within 0.1 to 0.2 pH unit of the values

alter 10 years of burning (Metz and others 1961). An

exception is the annual winter plots with a pH value of 4.2,

compared with 4.6 at 10 years.

Exchangeable bases. On the Alabama site, burning increased

exchangeable calcium in the surface 8 cm of soil by 0.62

mm01 kg 1 (Table 1). Similarly, on the Florida site the

burned plots had 0.30 to 0.32 mmol more exchangeable

calcium than did the control plots. On the Georgia site,

exchangeable calcium increased slightly but not significantly

with increased burning intensity. The difference was only .OS

to .018 mm01 kg’.

Burning treatments did not significantly alter exchangeable

calcium concentration on the South Carolina site, but calcium

tended to increase with increased burning in the O-5 cm soil

layer. Ten and 20 years of burning significantly increased

calcium on this site (Metz and others 1961; Wells 1971).

Values for exchangeable calcium 10 and 20 years after

initiating treatments were within the range of the 30-year

values. These data do not indicate any long-term change in

quantities of calcium in the mineral soil.

Generally, magnesium responses to burning were similar to

calcium. Exchangeable magnesium increased with burning by

0.06 mm01 kg-i in the O-8 cm soil layer on the Alabama site.

On the Florida site, magnesium content was 0.13 to 0.16

mm01 higher on burned plots than on control plots. Burning

treatments had no detectable effect on the exchangeable

magnesium levels on the Georgia site. The annual winter bum

had 82 percent more exchangeable magnesium than did the

control plot on the South Carolina site. Magnesium values

for other burning treatments did not differ from those for the

control or annual winter burning.

An indication of the degree of soil development or weathering

is the ratio of exchangeable magnesium to calcium (Buol et

al. 1973). As soils become more weathered, relative

magnesium levels increase and calcium levels decline. Within

the period of these studies, this effect is found only in the

surface Al horizon. Burning did not change the ratio of

exchangeable magnesium to calcium at lower depths. Over

an extended period, the effect of the accumulated forest floor

or presence of organic acids and leaching of cations from the

upper horizon--as observed by Herbauts (1980)--should appear

at lower depths, including the B horizon. In any case,

prescribed burning apparently slows the process of soil

formation and may help maintain soil productivity at a higher

level. A final proof of this hypothesis would require a

timespan approaching several hundred years.

A more immediate problem, as proposed by Lyle and Adams

(1971), is a nutrient imbalance caused by higher

concentrations of magnesium than of calcium. These authors

observed that because of “mass action effects,” magnesium in

excess of calcium results in reduced loblolly pine root growth.

According to this concept, the surface soil layer on unburned

control plots on the Florida site is nearing this condition while

that on burned plots is not. Such relationships also may bc

important to microbial processes found on pine sites.

Heyward (1937) observed that the elimination of burning on

Coastal Plain pine sites resulted.in abrupt changes in the

visual characteristics of a soil profile. His interpretation was

that exclusion of burning accelerates soil weathering or

407
development. With moisture conditions and parent materials

he was observing, the end results would probably be a

spodosol without fire and no spodic horizon with fire.

Specific reports of such effects of fire on soil formation have

not be published. It appears that the natural evolutionary

pattern of soil development caused by water-soluble carbon,

as observed by Herbauts (1980), can be moderated by

burning. This conclusion is based on lysimeter studies on

soils under forest cover where the degree of soil weathering

was found to relate to the amount of soluble carbon moving

through the profile. Nutrients moving from ash material after

burning are alkaline (Raison and McGarity 1978), at least

until the ash has dissolved and moved into the mineral soil.

To some degree, burning destroys the substrate and either

consumes or volatilizes organic acids produced in the forest

floor. Such a change is assumed to be roughly proportional

to the reduction of organic matter in the tire. The

water-soluble carbon may be in a humic and fluvic acid (De

Kimpe and Mattel 1976), in carbonic acid (McCall 1971), or

in other soluble organic acids. Observations of Binkley

(1986) on a site similar to that reported for on the South

Carolina site in this report found that burning may convey

resistance to soil acidifi\ation from atmospheric deposition or

other sources by reducing pools of acid in the forest soils.

Where sulfur dioxide from burning fossil fuels significantly

acidities precipitation, the resulting sulfuric acid is a much

larger factor than carbonic acid (Cronan and others 1978).

The acid radicals react with the soil to form salts with alkali,

alkali earth, and amorphic metals that move through the soil

horizons in the process of soil development.

Yaalon and Yaron (1966) indicate that any man-caused

activity such as adding fertilizer or changing the pH will

change the metapedogenetic processes that retard

podsolization; the rate of change depends upon the intensity of

treatments. Bidwell and Hole (1965) also discuss human

practices as dominant factors in altering soil formation by

controlling organic matter buildup. Thus, burning pine sites

on the Coastal Plain tends to maintain soils in a less

developed state and probably in a better tilth. Historically,

SUCK has been the case for much of the Coastal Plain, where

tire maintains the pine ecosystem.

Phosphorus fractions in the surface mineral soil.

Phosphorus was fractioned into various chemical forms in the

surface 5 to 8 cm to determine the effect of prescribed

burning on the disposition of phosphorus and its availability

for plant uptake.

The amount of available phosphorus in the soil was slightly

higher on burned than on control plots on all four study sites,

but the differences were significant only on the South

Carolina site (Table 2). On the Alabama site, phosphorus

levels were 0.1 to 0.2 mg kg.’ higher on burned plots.

TAELE 2. Mstrihotioa of soil pbospboms in available, dneral and organic ffor the surface sample Layer of soil on f&r sites.

!hmpled sites Flmsplnnvs Fractions

bam treatneot Available Milleral Qrganic Total

Alabama (o-8 cm,!

Nollam 2.3 11.6 20.18 31.70

8iemiol. winter 2.4 12.0 23.3A 35.3A

Florida (O-8 cat)

Nollam 7.1 15.4 18.0 33.48

PWiOdiC sister 9.5 19.0 21.6

Aaaasl tinter 10.5 19.3 21.2

Georgia (6.8 cm)

Noliom 2.4

wriodic winter 3.2

Feriodic $xJmer 3.3

Almaal winter 2.7

Sontb Carolina (O-5 cm1

NoBurn 25.9 52.1 78.0

Feriodic winter 4”:%8 27.5 45.8 73.3

Periodic summer 5.OAE 24.9 53.0 77.9

Almaal tinter 5.4A 29.9 56.4 86.3

Annual sumler 4. tAB 27.6 51.6 79.2

within COlLBmS sod sites, values for chemical frectiam followed by the -

letter do not differ significantly at the 0.05 Lewd. Available phsphorus

represents both organic mineral fractions and is not used in coqmtiag the total

em*

408
Annual and Periodic burns increased available phosphorus by

2.5 to 3.4 mg kg-’ in the O-8 cm depth on the Florida site.

Available phosphorus ranged from 2.4 to 3.3

mg g-i and increased with burning on the Georgia site.

Burning effect on individual mineral phosphorus fractions

were relatively small and in most cases did not alter

individual fractions, hence, the water sotuble, aluminum and

iron fractions are reported as mineral phosphorus. In general,

the mineral phosphorus levels tended to increase with intensity

of burning except on the South Carolina site where no trend

was apparent. Changes in the available form of phosphorus

or the magnitude of these changes do not appear to relate well

to the phosphorus present in the mineral or organic forms.

Organic phosphorus accounted for 50 to 69 percent of total

phosphorus in the surface 5 to 8 cm of soil on the three sites

where measurements were taken. On the Alabama site,

burning increased organic phosphorus by 16 percent or 3.2

mg kg’. On other sites, an apparent increase in organic

phosphorus of 3 to 5 mg kg’ was noted, but the increase was

not significant. The amount of organic phosphorus was

positively related to total phosphorus extracted from soils on

these sites, accounting for 86 to 94 percent of the variation in

total phosphorus.

Table 3.--Avenge weights of fomst

on four stsdy sites.

Burning significantly increased total phosphorus (sum of the

mineral and organic fractions extracted from sandy sites by 4

to 7 mg kg-‘. There is no apparent difference between the

annual and periodic burning on the Florida site. Burning also

tended to increase total phosphorus on the heavier soils of the

South Carolina site, hot the response was not significant. The

large proportion of the total phosphorus in the organic form in

soil indicates the n& to investigate this form of the nutrient

and to increase its availability to higher plants. Daughtrey and

others (1973) found the release of organic phosphorus from a

Coastal Plain soil was completely dependent on the activity of

soil micro-organisms in decomposing organic matter.

Nutrient release with burning would accelerate the breakdown

of organic matter and release of organic phosphorus to the

soit solution. Accumulation of organic matter and organic

phosphorus is partly the resuIt of small organic particles being

washed from the forest floor into the soil.

Forest Floor Properties

Organic content. Prescribed burning predictably lowered the

total weight and nutrient content of the forest floor on a11 four

sites (Table 3). Across the range of sites, the unbumd

control plots contained from 13 to 59 T ha“ of organic

matter. Annual and biennial burning reduced the weight of

organic matter in the forest floor by 39 to 44 percent on the

Site asd bsm or@;aniC

treatswYlt contest N P ca M9 C:N Ratio

k’

;d 1000 .*..,-..I kg he“ . . . . . . . . .

Site #I

Nobam

Biemllsl bum

Site#2

NoBum

PenlOdlC winter

Amlasl winter

Site #4

Nobnm

Periodic tinter

l%l-iodic suner

Ammal tinter

Annnsl s.Urmer

13&A

5.440

29.16A

9.52A

4.54c

59.5

12.4

7.48

17.18

26.27A

18.468

17.566

10.4ac

10.05c

2264 8.7A

276 3.18

131A 24.7A

378 8.78

75 3.06

494 16.5~

81 3.28

56 2.28

100 4.20

408A 17.4

3im 12.16

2778 10.68

156C 7.28

129c 7.18

67.2- 9.3A 3O:l

29.28 3.58 1OO:l

115.OA 21 .OA 111:l

40.08 ll.OB 12&l

19.08 6.06 324:l

83A

218

158

278

23.OA 6O:l

3.68 77:1

2.68 66:l

5.18 85:l

12.OA

91.08

77.08

52.oc

4a.oc

19.OA 32:l

19.OA 31:l

16.OAB 32:l

ll.OBC 33:l

6.OC 39:l

Within calms and sites, values followed bv the ssae letter do sot differ

sigsificant1y at tJB? 0.05 Level. Mere no” letters am. sbowt, so significant

differences are present.

409
Alabama site. Periodic burning on the Florida and South

Carolina sites reduced the weight of the forest floor by 33 and

70 percent respectively. The forest floor reduction was 71 to

87 percent with burning on the Georgia site. Season of

burning did not significantly affect the reduction total organic

content.

Organic content of the forest floor on control plots is

approximately the same for the South Carolina site as

reported 10 years earlier (Wells 1971). On these plots the

forest floor contained 18.57, 26.88, and 26.27 T ha” after 10,

20, and 30 years of measurements (Metz and others 1961;

Wells 1971). Thus, in terms of weight, the forest floor

reached an equilibrium between 10 and 20 years after

initiating the study, when the pine trees were about 45 years

old. At 30 years, the forest floor contained 18 to 39 percent

mineral material (determined by dry ashing the combined L,

F, and H layer samples).

Wells and Jorgensen (1975) found that forest floor biomass

reaches its peak in loblolly plantations at about age 30 in

Piedmont stands. The sites in this study had considerably

older trees, which produced less needles, but greater

production of litter by hardwoods and herbs probably

compensated for lower needle production.

Nitrogen. Nitrogen content in the forest floor decreased by

as much as 95 percent with annual tires and 72 percent with

biennial fires. Part of this nitrogen loss was from leaching

water-soluble components and tine particulates from the forest

floor into the soil. The forest floor of periodically burned

plots had nitrogen losses ranging from 26 to 32 percent on the

South Carohna site which had not been burned for live years

at sampling, to a 72 percent loss on the Florida site which had

been burned the previous year. Wells (1971) observed that

the periodic burning on the South Carolina site 10 years

earlier resulted in a nitrogen loss of about 112 kg ha” by

volatilization. The 408 kg ha-’ of nitrogen in the forest floor

on the control plots appear to represent an “equilibrium”

value for this nutrient under the conditions imposed by the

stand and the climate (Wells and Jorgensen 1975). Values on

control plots on the other sites probably also represent

near-equilibrium levels. Of interest are the nearly equal

amounts of organic matter on the control plots of the Florida

and South Carolina sites but about a four-fold greater amount

of nitrogen on the South Carolina site than on the Florida site.

The amounts of nitrogen in the forest floor probably reflect

species and site conditions specific to each location.

The C:N ratio is a major determinant of availability of

nitrogen and potential decomposition of the forest floor. The

ratio of carbon to nitrogen widened by l- to 3-fold on the

Alabama and Florida sites following ammal or biennial fires.

On the South Carolina site much smaller increases (5 to 20

percent) occurred after annual bums, and no increases

occurred after periodic bums. An exact C:N ratio is difficult

to obtain because much of the organic matter is charred after

burning. The magnitude of observed change, however,

reflects an apparent nitrogen mobilization that cannot be

explained by degree of carbon reduction. A number of rains

fell on all the burned plots between burning and sampling.

Comparison of forest floor values on the South Carolina site

after 20 years shows a similar trend.

Heyward and Bamette (1934) observed that the L layer had a

C:N ratio 2 to 3 times as wide as that of the F layer. Wells

and Jorgensen (1975) observed a similar relationship for

loblolly pine plantations in the Piedmont, where the C:N ratio

of litter narrowed over time. Because it is primarily the L

layer that is consumed by tire, it is surprising that burning

results in a wider C:N ratio. Apparently, low-intensity fires

have a “mobilizing effect” on nitrogen in the F layer, which

may in part account for the increased nitrogen concentration

in the upper 5 to 8 cm of mineral soil. Nitrogen relationships

are supported by findings of Klemmedson and others (1962),

who showed that burning accelerated nitrogen movement into

the mineral soil. Light burning in ponderosa pine @.

ponderosa Dougl. ex Laws.) stands caused movement of 12.4

kg ha.f nitrogen per year into the surface 2.5 cm of mineral

soil. Wells and others (1979) summarized a number of

investigations which indicate that appreciable mobilization of

nitrogen as well as volatilization of the forest floor occurs

after burning.

Phosphorus. Biennial or annual burning reduced the amount

of phosphorus in the forest floor by 42 to 88 percent on all

four sites. Periodic burning resulted in a 39 to 73 percent

decrease in phosphorus in the forest floor. The season of

periodic or annual burning did not affect phosphorus loss, and

there was no significant difference between annual and

periodic tires.

Cakium. Annual or biennial burning reduced calcium in the

forest floor by 50 to 92 percent. Periodic burning resulted in

a 28 to 39 percent reduction on the South Carolina site.

Season of burning had no effect on changes in calcium

content of this site. Thus, prescribed burning accelerated the

rate of calcium return to mineral soil. This movement

probably results from cations moving in the soil solution, but

ash conduction may also be a factor. Wells and Jorgensen

(1975) indicate that without burning, calcium loss from the

forest floor is slow compared to potassium or magnesium loss

and that after eight years appreciable quantities of the nutrient

remain in the forest floor from a given year’s deposition.

Quantitatively, 50 percent of the magnesium from a given

year’s accumulated litter is lost from the forest floor in less

than one year, while three years are required to obtain this

degree of calcium mineralization (Jorgensen and others 1980).

410
Magn&urn. Amounts of magnesium in the forest floor were

approximately 114 to l/IO those of calcium. The mobilization

of magnesium with burning appears to be similar to that of

calcium; and 43 to 71 percent magnesium was lost from the

forest floor with biennial or annual burning. Periodic burning

on the Florida site reduced magnesium by 52 percent. The

period between burns and the season of burning did not

significantly affect magnesium losses from the forest floor on

the South Carolina site. Based on values reported by Wells

and Jorgensen (1975) for loblolly pine in the Piedmont, the

forest floor on these sites contains about l/2 to l/3 as much

magnesium as in the tree biomass, and the nutrient would be

expected to move out of the floor faster than calcium.

Forest Floor Mineral Relatior&Gps

To understand the quantitative relationships of the forest floor

and increased nutrient concentration, the total contents are

presented together for the surface 10 to 16 cm of mineral soil

and forest floor.

Organic Matter. Burning reduced the organic matter content

of the forest floor but not of the mineral soil. In fact,

burning may have actually increased organic matter content of

the mineral soil for the Alabama and Florida site but the

increase was not statistically significant (Fig. 1). The result

was a rather small loss of total carbon from the system due to

burning part of the forest floor. The study sites in Florida

and South Carolina, which have poor drainage, appear to

have higher organic content in the mineral soil than those of

Alabama and Georgia.

,110

El100

e

x 90

a 00 I

‘;; 70

Y

5

60

I- 50

z

r 40

2 30

z

a 20

g 10

ALABAMA FLORIDA GEORGIA SOUlll

Figure 1. Organic matter content in the forest floor and soil

after prescribed burning of coastal plain pine stands.

Nitrogen. On the sandy Alabama, Florida, and Georgia sites,

burning caused a slight increase in nitrogen in the mineral soil

despite a marked loss of forest floor weight after 8 to 40

years (Fig. 2).

Soil at the South Carolina site had been sampled after 10

years (Metz and others 1961), 20 years (Wells 19’71), and 30

years (McKee 1982). Over 20 years between sample

collection, total nitrogen changed little on the unburned

control. After those treatments, there was a 20-year increase

of 34 to 42 kg/ha--a four percent change for the periodic

winter bum. The periodic summer bum (burned every seven

years) resulted in a 128&g nitrogen loss. The annual winter

bum increased total nitrogen by 137 kg/ha. The striking

effect was a 363&g loss due to annual summer bum. Since

both summer bums resulted in total nitrogen losses, summer

burning apparently has a detrimental effect on the amount of

nitrogen remaining in the surface mineral soil, while winter

burning increases nitrogen. The exact cause is difftcult-to

explain but may be related to a lack of nitrogen-fixing

legumes that invade these treatment sites after summer burns.

ALABAMA FLORIDA GEORGIA SOUTH CAROLINA

Figure 2. Nitrogen content in the forest floor and mineral

soil after prescribed burning of coastal plain pine stands.

Phosphorus. Without burning, appreciable quantities of

phosphorus were tied up in the forest floor on all four study

sites (4 to 24 kg/ha) (Fig. 3). The amount of phosphorus in

the mineral soil is difftcult to relate to that of the forest floor.

Available phosphorus was apparently increased by burning,

but the quantities found did not relate well to frequency of

burning. A standard chemical test suitable for all sites is

difficult to select because numerous chemical forms of

phosphorus are present. Available phosphorus levels appear

to be slightly more responsive to treatments and are

represented on all four sites.

411
ALABAMA FLORIDA GEORGIA SOUTH CAROLINA

Figure 3. Phosphorus content of the forest floor and available

phosphorus content in the mineral soil after prescribed

burning of coastal plain pine stands.

Calcium. All the effects of burning on calcium appear to

take place in the forest floor and the top 10 or 16 cm of

mineral soil (Fig. 4). Without burning, 16 to 61 percent of

the calcium present was in the forest floor. With burning,

only 4 to 16 percent of the calcium was in there. The

remainder was in the surface soil layers. These changes in

calcium distribution logically account for the pH increase in

the mineral soil associated with burning, and indicate a

long-term effect on soil acidity. The amount of calcium in

the forest floor decreased proportionally to the frequency of

the burning on the Florida and South Carolina site. Earlier

calcium observation on the South Carolina site, (Wells 1971)

showed similar results, indicating little change in the calcium

status of this site in the last 10 years.

12 r

&j FOREST FLOOR

n SOIL

FLORIDA GEORGIA SOUTH CAROLINA

CONCLUSIONS

The most striking result of this analysis is the similarity of

burning effects on soil properties despite obvious soil

differences and probable differences in burning techniques,

which were reported to be either low-tempcraturc flank fires,

or backfires.

Organic matter consistently builds up faster in mineral soil on

burned areas, and burning only reduces total nitrogen in the

forest floor. On unburned plots, 6 to 11 percent of the

nitrogen was in the forest floor. Over the range of study

sites, annual burning reduced total nitrogen in the forest floor

to 12 to 32 percent of the unburned levels, but burning did

not appear to reduce total nitrogen in the mineral soil after up

to 30 years of treatment. However, a balance sheet for the

studies requires nitrogen data for the vegetation which may be

causing an increase in soil nitrogen.

The consistent increase in available phosphorus in mineral soil

caused by prescribed burning, may be one of the most

beneficial effects of the treatment. No consistent pattern was

found for burning effects on phosphorus fractions. The nature

of compounds formed apparently represents specific pH

conditions and mineral components in the soil. However, in

all cases burning obviously accelerated mineralization.

The cation response was quite similar for all sites. The soil

depth used appeared to represent complete cycling of calcium.

Trends indicate that the unburned forest immobilizes a large

proportion of the calcium altering the nutrient balance of the

soil in some cases. Magnesium and calcium responded

similarly to burning treatments, but their ratios indicate that

magnesium recycles faster or at least accumulates in mineral

soil in the absence of burning.

It is apparent that burning alters soil formation and long-term

productivity over time. Evidence suggests that burning may

improve soil by retarding soil development and, probably,

formation of spodic layers in the profile. Proof of this

observation would probably require five to six pine rotations

to compare soil development with and without fire.

LITERATURE CI!l!ED

Bidwell, 0. W.; Hole, F. D. 1965. Man as a factor of soil

formation. Soil Science 99:65-72.

Binkley, D. 1986. Soil acidity in lobloily pine stands with

interval burning. Soil Science Society of America Journal

50:1590-1594.

Bray, R. H.; Kurtz, L. T. 1945. Determination of total

organic and available phosphorus in soils. Soil Science

59:39-45.

Figure 4. Calcium content in the forest floor and

exchangeable calcium content in the soil after prescribed

burning of coastal plain pine stands.

412
Buol, S. W.; Hole, F. D.; McCraken, R. J. 1973. Soil

genesis and classification. Ames, IA: Iowa State

University Press. 360 pp.

Chang, S. C.; Jackson, M. L. 1957. Fractionation of soil

phosphorus. Soil Science 84: 133-144.

Cronan, C. S.; Reynolds, R. C. Jr.; Lang, G. E. 1978.

Forest floor leaching contributions from mineral organic

and carbonic acids in New Hampshire subalpine forests.

Science 200:209-3 11.

Daughtrey, 2. W.; Gilliam, J. W.; Kamprath, E. J. 1973.

Phosphorus supply characteristics of acid organic soils as

measured by desorption and mineralization. Soil Science

115:18-24.

De Kimpe, C. R.; Mattel, Y. A. 1976. Effects of vegetation

on the distribution of carbon, iron and aluminum in the B

horizons of Northern Appalachian spodosols. Soil

Science Society of America Journal 40:77-80.

Herbauts, J. 1980. Direct evidence of water-soluble organic

matter leaching in brown earth and slightly podzolized

soil. Plant and Soils 54:317-321.

Heyward, F. 1937. The effect of frequent fires on profile

development of longleaf pine forest soils. Journal of

Forestry 35:23-27.

Heyward, F.; Bamett, R. M. 1934. Effect of frequent fires

on chemical composition of forest soils in the longlcaf

pine region. Bulletin 265. Gainesville, Fl: University of

Florida Agricultural Experiment Station. 39 pp.

Jackson, M. L. 1958. Soil chemical analysis. Englcwood

Cliffs, NJ: Prentice- Hall, Inc. 498 pp.

Jorgensen, J. R.; Well, C. G.; Metz, L. J 1980. Nutrient

changes in decomposing loblolly pine forest floor. Soil

Science Society of America Journal 44:1307-1314.

Klcmmedson, J. 0.; Schultz, A. M.; Jenny, H.; Biswell, H.

H. 1962. Effect of prescribed burning of forest litter on

total soil nitrogen. Soil Science Society of America

Proceedings 26:2(X&202.

Lyle, E. S.; Adams, F. 1971. Effect of available soil calcium

on taproot elongation of Ioblolly pine (Pinus taeda L.)

seedlings. Soil Science Society of America Proceedings

35:800-805.

McCall, J. G. 1972. Dynamics of ion transport during

moisture flow from a Douglas-fir forest floor. Soil

Science Society of America Proceedings 36:668-674.

McKee, W. H., Jr. 1982. Changes in soil fertility following

prescribed burning on Coastal Plain pine sites. U. S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station. Res. Pap. SE-234. 23 pp.

McKee, W. H., Jr.; Lewis, C. E. 1983. Influence of burning

and grazing on soil nutrient properties and tree growth on

a Georgia Coastal Plain site afier 40 years. Pages 79-86.

In: Proceedings of the Second Biennial Southern

Silvicultural Research Conference, Asheville, NC. U. S.

Department of Agriculture, Forest Service, Southeastern

Forest Experiment Station. Gen. Tech. Rep. SE-24.

Metz, L. J.; Lotti, T.; KIawitter, R. A. 1961. Some effects of

prescribed burning on Coastal Plain forest soil. Asheville

NC: U. S. Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station. Res. Pap.

SE-133. 10 pp.

Nelson. D. W.; Sommers, L. E. 1973. Determination of total

nitrogen in plant material. Agronomy Journal 65: 109-l 12.

Olsen, S. R.; Dean, L. A. 1965. Phosphorus. In: Black, C.

A., ed. Methods of soil analysis. Agronomy 9:1035-1049.

Raison, R. J.; McGarity, J. W. 1978. Effect of plant ash on

nitrogen fertilizer transformations and ammonia

volatilization. Soil Science of America Journal 42:

140-143.

Ralston, C. W.; McKee, W. H., Jr.; Langdon, 0. G.; and

Harms, W. R. 1982. Prescribed burning: uses and

effects. Pages 154-162. In: Proceedings of the

Symposium on The Loblolly Pine Ecosystem (East

Region). North Carolina School of Forestry, Raleigh, NC.

Wells, C. G. 1971. Effects of prescribed burning on soil

chemical properties and nub-& availability. Pages 86-99.

In: Prescribed burning symposium proceedings. Ashcvillc,

NC: U. S. Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station.

Wells, C. G. : Campbell, R. E.; DeBano, L. F.; et al. 1979.

Effects of fire on soil. Washington, DC: U. S.

Department of Agriculture, Forest Service. General

Technical Report WO-7.

Wells, C. G.; Jorgensen, J. R. 1975. Nutrient cycling in

loblolly pine plantations. Pages 137-158. In: Bemier, B.;

Winget, C. H., eds. Forest soils and forest land

management. Quebec, Canada: Les Prcsscs de

I’llniversite’ Lava].

Yaalon, D. H; Yaron, B. 1966. Framework for man-made

soil changes: an outline of mctapedogenesis. Soil Science

102:272-277.

413
FIRES, FORESTS, AND TRIBES IN THE NORTHERN PHILIPPINES:

CULTURAL AND ECOLOGICAL PERSPECTIVES

Sharon Codamon-Quitmnl

Abstract-The study was exploratory. The researcher utilized participant observation, case study, and

interview-discussion methods to gather data. Purposive stratified multi-stage sampling guided initial

selection of 103 respondents in 3 groups: kaingineros, school teachers, and government officials. The

study is an attempt to explain forest burning from the perspective of the tire-setter. It is the first of a series

of investigations that interpret forest burning as a lifeway of a people who inhibit a rugged environment and

who possess a unique s&o-cultural temperament. Specifically, research focused upon the forest fire-setting

behavior of the Itigao, an ethnic tribe in the Cordilleras, a mountain range in Northern Philippines. This

paper reports impacts of mio-cu]lurally sanctioned indigenous forest burning practices the local economy,

ecology, and society. Central to ihe issue of forest burning is the highly institutionalized Ifugao practice of

muyung, or inherited private ownership of forests. Muyung greatly complicates governmental efforts to

promote forest fire control, sound forest management, and sustainable forest development in Ifugao.

INTRODUCTION

Fire accounts for one-third of the damage done to the

Philippines’ critical watershed and forest lands. The problem

continues to be addressed largely as a technical one, and

forest management continues to he forestry-oriented following

inception of the Social Forestry Progmm in the DENR. (The

Philippine SFP, which was launched in 1982, is a radical

de- from traditional programs, which put the forest

before its occupants. Creation of the SFP is a mute

admission that the conventional methods used to conserve and

protect the forest have not succecdcd.) Ifugao, now legally

reco~zed as fhe Cordillera Autonomous Region, was chosen

for study because it had the highest rate of forest fires in the

Northern Philippines and because its supposedly civic-minded

and law-abiding people continue to bum forests despite the

region’s long history of Spanish and American religious

endeavor and continuing government administration.

The study was designed to:

* document relevant demographic, economic, and social

athibutes of selected kaingincro respondents involved in

forest burning practices in the area of study;

l determine level and type of knowledge (awareness),

assessment (perception), and predisposition (attitudes)

toward forests, forest fires, and forestry policies

(including the prcscncc and role of the local forcslry

agency in forest fire prevention and mana&mcnt),

l determine the existence and nature of beliefs relevant to

forests and forest burning activities among the natives in

fhe area.;

b dctcrminc the role of revenge as a factor in forest

burning;

‘Senior Science Research Specialist, Ecosystems Research and

Development Bureau, College, Laguna, Philippines.

b identify socio-cultural learning experiences that influence,

reinforce, and institutionalize the practice of forest

burning among the same; and

. review approaches adopted by the local forestry agency to

prevention of forest fires.

LITERATURE RJ3VIElW

Cruz (1985a, b) asserts that the fight against forest fire in the

country is hampered by certain institutional and external

problems compounded by public apathy toward forest

protection due to the misconception that tire is the sole

responsibility of the BFD. Misra (1983) described forest fire

types, causes, uses, and prevention but did not focus on the

personality of the fire-setter. Atabay (1978) and Binua (1978)

argued for forest fire research to support forest protection,

rcforcstation, and grassland management. Rabanal (1973)

believe8 that the problem reflects a lack of lolowledge on the

part of those who regularly burn forests, who use fire to

prepare land for planting and who do not fully understand the

consequences of burning. Researcher like Duldulao, and

others (n.d.) and Strasser (1970) stress the socio-economic

angle, arguing that forest conservation consciousness carmot

be instilled among those involved in the destructive activity

unless they are given an alternative way of earning their

living. Social and cultural characteristics of people living

near or within fire-prone forest areas, and attitudes of those

people regarding forest burning, local forestry agencies, and

their representatives, were identified by Bertrand and others

(196.5) as factors relevant to the potential success of fire

prevention programs. Forest fire has been attributed to plain

ignorance of fire prevention practices, irresponsibility,

carelessness, and grudges against forestry personnel.

METHODS

Place of Study

The study was conducted in the barangays of Bokiawan and

Hucab in the municipality of Kiangan (1975 population

414
15,985; area 443.3 km2), and in the barangays of Panopdopan

and Nayon in the municipality of Lamut (1975 population

9,516; area 104.5 km*). These sites were selected based on

greatest fire incidence, kaigin activity, concentration of

forested area, food or eating habits, sustainability and

availability of land, weather conditions and facilities affecting

agriculture as principal mean of livelihood.

Research Design

Upland farmers or kaingincro (shilling cultivators), who are

termed munhabals in the Imgao vernacular, served as the

primary source of data; teachers and government officials

served as secondary sources. The kaingincros were covered

by complete enumeration, which yielded 60 respondents. The

teachers and government officials group were criteria-selected

using purposive stratified and multi-stage sampling. The

Bureau of Public Schools (BPS) Form as of October 1978

and the Sangguniang Panlalawigan, Sangguniang Bayan,

Barangay Council, and local BFD personnel were the

sampling frames. Twenty respondents (10 from each

municipality) from each group made up the sample. There

were a total of 103 respondents (60 kaingineros, 20 teachers,

20 government officials, 2 municipal mayors and 1 BFD

district officer--the last 3 treated as special case studies).

Collection of Data

Interview Method. Semi-structured interviews, mostly

without the schedule on hand, were generally conducted

inside offices, school premises, business establishment, and

residential buildings in Bokiawan, Bolog, Ambabag,

Baynihan, Baguinge, Cawayan, and Poblacion for Kiangan

and in Panopdopan, Lawig, Nayon, Payawan, Mabatobato,

Piem, Bunog, Magullon, and Poblacion for Lamut. The term

“forest fire” was somttimes-used in place of “forest burning

behavior” to make it easier for the kringineros to grasp the

concept.

Interviews were sometimes recorded on tape, particularly

“huddled types” when one interviewee suddenly became

several as wives, children, and other members of the

household also sought attention. The recorder was introduced

as a radio set to prevent selfconsciousness. Inquiry was

directed primarily to the head of family, who was informed

beforehand of the object of research. For the secondary

sources, the average interview time took 1 hour and 40

minutes. Most of these were approached during their “break”

periods and were not briefed as to the purpose of the

interview.

Participant Observation or Case Study Method. “Live-in”

observations were made during waking hours and upon return

of the kaingineros from their kaingins in the evenings.

Interviews were conducted in the morning before the subjects

set out, when they invariably spend some time huddled

together outside their huts as if awaiting the sunrise. Some

return at noon in order to have an early start on the next

day’s work or because the kaingins are located some distance

from the dwellings. The interviewers also observed the baki

performed by the different households, and these occasions

also presented opportunities for casual and natural talks with

the natives. The babiis is an Ifugao native ceremony or rite

performed to invoke the favorable intervention of spirits of

dead ancestors and gods or deities on the occasion of sickness

in the family or in token of thanksgiving for favors received.

The last day was spent in the kaingins for a first-hand view of

the situation.

FINDINGS AND DISCUSSION

The case of the kaingineros is highlighted in this report.

Socio-Economic Attributes

Rokiawan. The study centered upon the activities of an all

native, almost SO-percent unconverted and non-formally

educated majority in the sitios of Bunog and Kayapa.

Farming is the main occupation, with almost 50 percent

professing ownership of payo (r&field), habal (kaingin),

muyung, and animals? Per-family income is not computed.

Most families are engaged in wood-carving business.

Elementary school children earn an average of P21 .OO per

week by carving pieces of spoon and fork figurines, while

older children earn an average of p87.50 per week. I n

Bunog, all heads of families depend on sales of coffee for

their monthly income. The average quantity brought by each

family to the town proper is to 5 gantas of coffee valued at

P40.00 at Pl .OO per chupa. Another source of money or cash

income is the littuco (rattan fruit) which is harvested during

September, October, and November and yields an average

income of P250.00 at p25 per container. If they were to sell

their palay, their income would be barely sufficient for daily

needs. The owners of ricefields plant the traditional variety

of palay and harvest only once a year. The yield is usually

reserved for family consumption or for emergency barter in

the adjacent or nearby barangays of Mungayang and

Bayninan. Camote (sweet potato) harvested from the kaingins

is the staple food. For those who own ricelields, rice is eaten

alternately with camote.

Iiucab. The study was centered in Hoba, where the kaingin

system is the chief occupation. ¬e is the main staple.

The respondents also own pigs, chickens, and ducks. Cash

income is derived from the sale of bananas and coffee grown

in backyard gardens or in small orchards leased from other

individuals (who arc not necessarily Ayangans). Unlike the

other native respondents, the residents of Hucab do not own

forests.

Nayon. The five primary subjects were predominately male,

married, educated, but unconverted kaingineros of

Binoblayan. All admit having a habal or patch of unirrigated

agricultural land, but not all possess a payo and a muyung.

The sale of bananas provides each family with an average

weekly income of P24.00. Three to 400 pieces of unripe

bananas are sold at an average of p&(J) per hundred.

Camote and corn arc sold for about P20.00 per kerosene can.

415
Rice is harvested only once a year. The cash value of the

palay harvested by a kainginero family averages P200.00 per

year.

Panopdopan. The respondents have their own hospital, an

elementary school building, and business establishments.

Their characteristics are not basically different from those of

residents of the other barangays studied. Those who were

first to settle in the area are better off economically than those

who came later. Panopdopan’s forests were originally a

public or communal forest site of the mother municipality of

Kiangan. The residents of Panopdopan established ownership

of these forests through the simple expediency of declaring

them for taxation purposes and by claim of continuous and

peaceful occupation. The privilege of developing these

forests into ricefields or banana or coffee plantations has been

exploited to the hilt. Residents leave their private forests well

enough alone.

Cognitive Attributes

The findings about the kaingineros are generally applicable to

all the groups studied. All kaingineros profess non-awareness

of any government-promulgated law regulating kaingin. They

believe that common law dictates that kaingins, are made in

“open areas” regarded as “public land,” and not on forests

owned by private individuals. They do not understand why

they should be prohibited from burning or utilizing fire as a

tool in their kaingin practice. Forests are viewed primarily as

private properties. The owner of a muyung is thought to be in

the best position to care for it properly and manage it as a

source of lumber, fuel, and the water that irrigates his

ricefield. All claim that no one from the FNB had ever

visited their areas. Non-observance of laws against burning

accordingly stems in part from non-enforcement by the

government. The local people arc scarcely aware of the

presence of a local forestry service, and find it very difficult

to conceive that the muyung could ever be placed under state

control. All agree that public lands should bc distributed to

the landless, who can develop these as sources of stable and

adequate income and livelihood. All endorse stricter

regulation and control of the activities of loggers and wood

carvers in Ifugao, who arc held responsible for the wanton

destruction of the public forests.

Beliefs Relevant to Forests and Forest Burning

Activities

Two pervasive beliefs are relevant. The first has to do with

forest ownership and seems to provide the key to the burning

behavior. The natives know that the government has legal

right over the forest, but they believe that the right belongs to

the people who own the forests. Some natives explained that

the government owned the public forests. The second belief

relates to fires in the muyung. The natives do not regard

these as forest fires but merely as a routine activity or tool for

preparing the kaingin portion of the forest land for planting.

The munhabal sets fire to what a non-native would consider

as forest when there is no known claimant to the area and

when customary law defines the area as public land primarily

for kaingin. Burning preparatory to planting is indispensably

customary.

Socio-Cultural Learning Experiences That Influence,

Reinforce and Institutionalize the Practice

The native who lives in a more remote area learns to eat

camote morning, noon, and evening, or, if he is luckier then

the other kids in the neighborhood, camote alternated with

rice. Camote is planted mainly in the family kaingin.

Cleaning of rice fields starts in January, and rice planting is

completed by March. The ricefields are then temporarily

abandoned while the natives prepare their kaingins, which are

usually located some distance away from the ricefields.

Cutting down of vegetation starts by April. The grasses and

trees are left to dry for at least a month, then the natives go

back to bum them. Burning commences by May. Mongo is

planted as soon as burning is completed, and camote is

planted August after the mongo is harvested. The camote

crop is harvested 5 months later. The habal is then left idle

until April, when the grasses are cut, dried, and burned

preparatory to planting activities. The process is repeated

year in and year out unless, the place is totally abandoned in

favor of another occupant. There is no room for idleness.

Those who do not own any habal or payo earn their livelihood

by helping clean and prepare rice fields for planting in

consideration of wages in money, or by cultivating and

planting someone else’s ricefield in return for half of the

harvest. The culture is highly animistic. The native believes

in a supreme being whom he calls Maknongan, in a hierarchy

of lesser deities, and in ancestral spirits (anito). When a baki

is performed for a particular purpose, sacrificial animals are

butchered and offered to the spirits. The number and kind of

animals sacrificed depend upon the financial capacity of the

family requesting the baki. The raising of animals is thus

required by religious customs, and kaingins must be cultivated

to provide food for the livestock.

Observing forest fires on mountainsides, especially during the

night, is pani-o (taboo). Those who observe such fires

accidentally are cautioned to keep the matter strictly to

themselves. This taboo enables a public forest fire-setter in

Ifugao to go about his way unchallenged.

Revenge as a Factor in Forest Burning

Envy, anger, or hatred were seen as motives for burning in

only a few cases. Respondents suggested that laborers

employed by the local BFD office in its nursery and

plantation set reforestation projects on fire to get even for

being laid off, for delayed payment of wages, or simply to

ensure their period of employment. There were insinuations

that the local forestry office was in cahoots with its laborers

in perpetuating tires, especially in the reforestation

plantations, to justify its continuing budgetary allocation for

forest fire protection.

416
Approaches Adopted by the Local Forestry Agency

to Prevention of Forest Fires

l Constant forest guard patrol in fire-prone areas before and

during the dry season.

* Intensification of forestry information drives

l Constant dialogue with local leaders on forest

conservation projects and programs.

Interestingly, the respondents interviewed in connection with

this study declared non-awareness of these activities allegedly

undertaken by the local BFD agency.

RECOMMENDATIONS

We recommend allocation of adequate funds for an intensive

and extensive census to determine the number of people

involved in kaingin-making throughout the country. The

census should determine (a) the circumstances and factors that

support kaingin-making, (b) the nature and extent of forest

destruction resulting from fire and other causes, (c) local

beliefs, customs, and practices pertaining to forests, their

ownership, purpose, use, etc. in relation to govemmentpromulgated forestry laws, rules, and regulations. The

findings of the should be used to guide the repeal or

amendment of existing forestry laws, which should be made

compatible with local beliefs, customs, and practices.

We recommend allocation under title in favor of landless

families solely dependent upon kaingin-making for survival of

all available forest lands claimed under current ownership by

reason of inheritance or succession or by actual, continuous,

and peaceful possession for a period of more than 15 years

provided that the recipients, their heirs, or their successorsin-interest shall not alienate their allocations or interests

therein within 30 years from the date of allocation of title

and, provided further, that no title of ownership shall be

granted except after the lapse of 5 years from the date of

allocation and upon proof of occupation, development, and

improvement of his allocation particularly in tree planting of

whatsoever kind suitable in the area. In the allocation of such

forest lands, first priority should be given to the natives and

second priority to local residents.

We recommend reorganization of the BFD, particularly on the

district level. Personnel should be dedicated, competent, and

active. Employment preference should be given to qualified

applicants who are natives or residents of the districts served.

We recommend that adequate funds be allocated so that FEB

offices throughout the country can regularly conduct

information drives, and so that special educational efforts can

be made in areas notorious for forest destruction.

The theoretical framework prcscntcd in this report should also

receive further consideration. Some hypotheses worth testing

are as follows:

There is no relationship between level of education and

level of information or knowledge about the destructive

nature of forest fues.

There is no relationship between level of information

about the destructive nature of fires and forest burning

behavior.

There is no relationship between perception of the local

forestry agency’s role and forest burning behavior.

There is no relationship between beliefs held about forest

ownership and forest burning behavior.

The indigenous institutions of the Ifugaos that may be

related to forest burning should receive further

consideration and study.

Camineros, or road maintainers employed by the

govemment, members of the local police force,

out-of-school youths, and others should be officially

consulted as respondents in studies of this nature; they can

be sources of pertinent and valuable information.

LITERATURE CITED

Atabay, Remilio C. 1978. Fire for grassland management.

Canopy 4(4).

Bertrand, A.L., Jones, A.R., Taylor, M.L. 1965. Some

human factors in woods burning: a study of change in

beliefs of the residents of a National Forest in Louisiana.

Bull. 601. Louisiana State University, Agricultural and

Mechanical College, Experiment Station.

Binua, Tomas M. 1978. Forest fire research to protect our

forest and save reforestation efforts Canopy 4(4).

Cruz, Marisa. 1985a. Will summer be forever a threat to

our forests? Bagong Sibol April.

Cruz, Marisa. 1985b. Forest protection Bagong Sibol April.

Duldulao, A.C. Depositario, W.C. Olivar, J.D. [n.d.] An

integrated project for kaingin control in the Philippines: a

new approach to forest conservation, [A research proposal

submitted to the Philippine Council for Agriculture and

Resources Research Development, College, Laguna].

Misra, C.M. 1973. Forest fire: kind, causes, control and

tool Canopy 9(7):5.

Rabanal, V.T. 1973. Forest destruction: a hindrance to

national progress. Conservation Circular 9(6).

Strasser, R.C. 1970. Solution to forest tires and kaingin--

making naval stores, Philippine Forests 12.

417
SMOKE MANAGEMENT: ARE RIGHTS INCLUDED WITH THE

RESPONSIBILITY TO USE FIRE IN MANAGING PUBLIC LANDS?

Dean A. Shinn’

In the southeastern United States, the native biota of many

natural ecosystems are adapted to periodic burning. It is

generally believed that in Florida at the time of European

intervention, thcsc ecosystems were sustained as fire climax

communities by relatively frequent fires, resulting both from

natural and from cultural causes.

The preservation and where necessary the restoration of the

aboriginal structure and function of biotic communities

occurring on State Parklands is central to the mission of the

Florida Park Service. In pursuit of this mission, park

managers throughout the State have been charged with the

responsibility of using fire and prescribed burning techniques

to manage Florida’s State Parks.

One might suppose that a public responsibility to use fire in

this way would be accompanied by certain rights to produce

and dispense smoke from the areas being burned. The

premise of this paper is that such rights should naturally

cmcrgc from that public charge. However, Florida Statutes

and the contingencies that they govern arc not yet viewed i n

such a way that the practical circumstances associated with

public land management can be administered form this point

of view. In fact, potential liabilities, rather than rights, are

among the most prominent aspects of the public responsibility

to USC fire as a tool in modern management of commonwealth

resources.

In Florida, many state parks are small and are defined by

bounda& that are uneven and oRen broken by parcels of

adjacent private land. Many parks contain private inholdings

wholly within their boundaries. Many arc also situated in

highly urbanized areas and are bordered, even surrounded, by

high-value commercial and residential development. Very

[ew of Florida’s slate parklands arc located away from major

roadways. In the Florida panhandle, large areas arc occupied

by military installations, and many other areas arc traversed

by military and commercial flight paths. In addition, a

relatively high proportion both of the seasonal and of the

year-round population is composed of elderly people, many of

whom have respiratory problems.

As a result, the heat, smoke, and ashes emitted from

prescribed lires are likely to affect people and property

beyond state park boundaries. Because develop4 areas

‘District Ecologist, Division of Recreation and Parks, Florida

Dcpartmcnt of Natural Resources.

418

potentially affected by prescribed fires are so close to

parklands, and in many places are a major component of a

park’s external environment, the weather conditions under

which tire can be safely used in parks are seriously

constrained. In many places, bum prescriptions can be

written to accommodate only winds of a very specific speed

and direction. Along the Panhandle Gulf Coast, many State

parklands can be burned under prescription only after a winter

cold front has passed. Under such circumstances, the wind

blows rather predictably from the north for a relatively

reliable period of time. This situation restricts the range of

options open to park managers in their use of fire to restore

and preserve Florida’s original natural ecosystems.

It must be emphasized here that land managers employed by

the Florida Park Service are well aware of the legitimate and

compelling hazards associated with the smoke emitted Erom

prescribed fires. They have been and will continue to be

diligent in planning fire management activities to avoid traffic

hazards along major transportation corridors and to protect

public health.

Certain other problems, such as ash falling into nearby

swimming pools, soot soiling laundry hung on clothes lines,

or simply the unusual smell of burning vegetation, are also

associated with the smoke and ash produced by prescribed

fires. These problems can be characterized as nuisances

rather than as genuine dangers or health hazards, however.

These problems should be addressed first by establishing

open, good-faith communications between park personnel and

local citizens. A conscientious public relations effort should

be an integral feature of each park’s fire management

program. The park’s neighbors need to be informed about

the benefits of responsible fire management procedures and

advised of the fire planning process prior to prescribed

burning activities being undertaken. Adoption of seriously

constrained prescribed fire management procedures as a

means of avoiding inconvcnicnce, rather than genuine hazard,

would be ill-advised and would likely not achieve anticipated

long-range ecological objectives. Thorough, good-faith public

relations efforts should be undertaken early in every

prescribed fire and smoke management program.

Of course, even the best efforts to inform the public and to

solicit the cooperation of all who might be affected may not

be entirely successful. Some among a park’s neighbors

simply may not be reached or may not be persuaded to

coopcrale. Litigation may result.
This being the case, the author sought to dctcrminc if a line

of legal reasoning could be set forth to advance the notion

that a set of legal rights to produce and dispense smoke

should be acknowledged as being implicit to the public

responsibility to USC tire as a resource management tool on

public lands. However, the existing case law in Florida dOCS

not specifically address this issue. Certain judicial decisions

and findings that can be grouped under legal classifications

such as “nuisanceS ,’ “ncgligcncc,” “environmental rights and

remedies .” and “explosion and fire” pertain to this subject

only in a very general sense. It is unlikely that a cogent legal

argument in support of “smoke rights” could be derived from

the existing case law. In&cd, the time invested in attempting

to do so might be ill-spent in the absence of a test case Well

suited to the development of such an argument. However, it

is not likely that the Florida Park Service would wish to

promote circumstances under which suitable legal reasoning

could be developed through litigation. Therefore, other

means of establishing “smoke rights” Were investigated -

means that would also serve to support the assertion of such

rights, should a judicial defense of this concept become

necessary.

Three options were examined: casements, land USC plans, and

original legislation.

Easements: Establishment of buffer zones around State

parklands through the institution of conservation easements or

other special land use agrccmcnts with owners of adjacent

private lands can be used to codify mutual acceptance of

specific fire and smoke management practices. This approach

is most practical and most likely to bc suCCt.%ftd if

undcfl&en while private lands surrounding parklands remain

open and undevclopcd. ARer residential or commercial

development occurs, ownership - and therefore dccisionmaking authority -- is likely to bc dissipated among many

separate private interests. To achieve agreement concerning

prescribed burning and smoke managcmcnt contingencies with

one, or with only a few, adjacent ranchers and limbermen can

be a rather straightforward matter. On the other hand,

reaching agreement among all potentially affeded parties in

an expanding area of mixed residential, commercial, and

industrial land uses would be a much more ambitious

undertaking. Therefore, conservation easements that

acknowledge specific fire and smoke management rights and

responsibilities should be established as early as possible in a

region’s development cycle. They should stipulate the

conditions under which such rights and responsibilities can be

exercised without risk of legal constraint and should attach in

perpetuity to the land, with provision for conveyance with the

deed to each succeeding OWllet.

Land Use Plans: In Florida. comprchcnsive growth

managcmcnt planning at the local level has been mandated by

stats law (Chapter 163, Part II, Florida Statutes), and a local

land USC planning process has been es&blishcd by

administrative rule (Chapter 9J-5, Florida Administrative

Code). In this way, each county and municipal government

in Florida has been charged with the responsibility to develop

and to implement a comprchcnsive land use and growth

management plan. This planning process can be used to

establish an explicit public acknowlcdgcmcnt of the need to

use prescribed fire as a land managcmcnt tool and of the

implicit consequence of dispersing smoke from the arcas

burned. Local planning documents arc Jilting legal

instruments in which to codify this public acknowlcdgcmcnt

of “smoke rights” in association with established fire

managcmcnt responsibilities.

However, the local planning process is a long and open-cndcd

procedure. Its results can vary widely from one county to

another and also among the municipalities within a single

county. Within certain general state-wide parameters

cstahlishcd by rule and within certain basic standards set by

each county, the specific provisions incorporated into any

particular plan can bc either favorable or very unfavorable

with respect to fire management on public lands. The quality

and strength of provisions addressing fire and smoke

management on parklands as finally adopted in a plan depend

largely on the commitment and tenacity of local park staff and

of sympathetic citizens. The propriety of fire as an

appropriate tool in modem land use management should be

inlroduccd early and should be re-enforced at ever stage of

the planning process. Because land ,use planning is a cyclic

and reverberative process. specific achievements can be rather

transitory. Involvement at the local level must be thorough

and continuing.

Leis&ion: The Florida legislature is now debating

enactment of the “Florida Prescribed Burning Act.” (Aflcr

this paper was presented, the Legislature cnactcd this

initiative as Chapter 590.026, Florida Statures.) This

document states that prescribed burning contributes to public

safety I) by reducing fuels and the risk of wildfires; 3) by

helping to maintain biotic diversity and the ecological

integrity of native communities; and 3) by facilitating the

rcvegctation, restoration, reforestation, and enhancement of

public and private lands. The bill also authorizes public

education and technical training programs, where appropriate,

in order to assure general acceptance and proper USC of Iixe. as

a land management tool. It then declares that prescribed

burning, when properly authorized, is in the public interest

and does not constitute a public or private nuisance. Most

important with respect to smoke management, the bill finds

that prescribed burning is a property right of the landowner

and that the owner or his agent, when conducting an

authorized bum, is not to be held liable for damage or injury

resulting from tire or smoke, unless negligence is proven.

419
This bill introduces into legal debate the prospect of

establishing certain smoke rights in association with an

acknowlcdgcmcnt of related prescribed burning and fire

managcmcnt rcsponsibilitics. Unfortunately, language in the

bill that is pertinent to the concept of “smoke rights” is rather

nebulous. It does not provide clear and precise guidance

concerning assertions of negligence, especially where drifting

or wind-driven smoke and ash arc concerned. Howcvcr, this

draR legislation establishes a useful context for continuing

public examination of the rights of land managers relative to

fire and smoke management.

SUMMARY

Are smoke rights included with the responsibility to use fire

in managing public lands? The premise of this paper is that

certain rights to produce and disperse of smoke from lands

subject to prescribed burning should be implicitly associated

with the public responsibility to use tire as a land

management tool.

The existing case law will not explicitly support such an

assertion through legal argumentation, while public agencies

are not inclined to promote litigation for the purpose of

establishing favorable case law.

However, three alternatives exist for establishing such rights,

or at least for developing legitimate public acknowledgement

of the concept of such rights. To be practical and reasonably

effective, casements specifying smoke rights should be

instituted early in a region’s development history. Local land

use planning processes can be used to develop explicit public

acknowledgement of contingencies associated with the USC of

tire as a land management tool, but involvement at the local

level must be both consistent and persistent. In Florida,

legislation specifically addressing fire and smoke management

as a property right has been drafted (and was enacted as of

October 1, 1990.) This latter alternative is a particularly

straightforward approach. In each case, however, clear and

direct communication with the public concerning the role of

prescribed burning and smoke managcmcnt in public land

management is ncccssary.

LITERATURE CITED

Chapter 163, Part II, Florida Statutes: Intergovernmental

Programs, County and Municipal Planning and Land

Dcvclopment Regulation.

Chapter 91-5, Florida Administrative Code: Local

Government Comprehensive Planning Regulations

Chapter 590.026, Florida Statutes: Florida Prescribed

Burning Act.

420
SPATIAL DYNAMIC FIRE BEHAVIOR SIMULATION AS AN AID TO

FOREST PLANNING AND MANAGEMENT

Maria J. Vasconcetos and Jose M. C. Pereira’

Abstract-Mediterranean shrub communities dominate fire-prone landscapes in many parts of Portugal. It is

feared that streamside anti-erosion buffers of natural shrub vegetation represent a fire hazard lo plantations

of eucalyptus and other trees. The F[REM,Q system, which can simulate fire behavior in spatially

nonuniform environments, was used to assess the extent to which fire buffers can become main vectors of

fue spread in Portnguese landscapes. FIREMAP predicted that tire will spread across landscapes consisting

of Eucalyptus sp. plantations and streamside borders of natural Mediterranean vegetation much more rapidly

than across landscapes consisting of Eucalyptus plantations and streamborders of planted Ouercus sp.

INTRODUCTION

About 70 percent of Portugal’s land area is unsuitable for

agricultum. It has been suggested that these areas should be

the subject of reafforestation programs (Grupo Coordcnador

do Proj&o Flores&l 1986). Forests cover only about 36

percent of the country, so there is much room for this kind of

initiatives, such as the ones recently akmpkd with support

from organizations such as the World Bank and the European

Economic Community.

Due to climatic and socio-economic factors, wildfires are a

major threat to Portuguese forests. An average area of 42 000

ha burned yearly from 1973 through 1985 and in 1989 about

54 COO ha of forests were destroyed by Wj]dfircS.

A recent trend in Portuguese forestry is the rapid expansion

of plantations of exotic species for short rotation biomass

production, for use by the paper and pulp induahies. The

environmental impacts of those plantations have been a topic

of he&d debate, and legislation was issued regulating soil

preparation and plantation and silvicullurai practices, with

special emphasis on minimizing soil erosion, hydrological

disturbances, and loss of biological diversity.

The legislation that regulates these plantations requires that

natural vegetation be ]efi along stream channels for erosion

protection. The widths required dcpcnd on particular

situations but are generally between 20 and 60 m.

Consequently, the majority of the projects generate a striped

landscape where buff&s of constant width indiscriminately

marginate stream channels.

In this paper WC investigate the possibility that Where natural

veg&&n consists of Mcditcrranean-type shrubs, this

landscape structure may contribute to improved fire

propagation by creating paths of faster spreading fire that

‘Forester, Centro N&&al de Infonna@o Geogrrifica, Rua

Braancamp, 82 I QD, 1200 LISBOA, Portugal; Assistant Professor,

Departamento de Engenharia Florestal, ISA, Universidade Te’enica de

Lisboa, Tapada da Ajuda 1399 LISBOA CODEX, Portugal.

make otherwise unavailable fuels more likely to bum. in fact,

these shrub communities bum intensely and contribute to

more effective preheating of the less easily ignited fuels in the

neighboring plantation forest, thus setting the stage for larger,

more intense fires.

The objective of this work was to USC a PC-based spatial

analysis system that simulates the spread of fire in a spatially

nonuniform landscape in discrete time steps (the FIREMAP

system) to assess the extent to which anti-erosion buffers

along streams can become the main vector of tire

propagation, or on the other hand, work as ban-&S to the

spreading fire.

We simulated structurally simple landscapes, not only to

facilitate interpretation of the results, but primarily because

this corresponds to the actual spatial structure of Eucalwtus

plantations.

FIREMAP

This fire spread simulation system, designed at the University

of Arizona (Vasconcelos 1988), estimates tire characteristics

in spatially nonuniform environments, and displays areas

burned on maps. FIREMAP consists of the integration of the

DIRECT module l%om the BEHAVE system (Andrcws 1986)

with a raster-based geographic information system, the Map

Analysis Package -MAP- (Tomlin 1986), and allows

distributed predictions of fire characteristics and

simulation of fire spread.

In this framework, nonuniform fuels, wcathcr, and

topography data arc encoded, stored, and manipulated on

thematic maps, where the field is represented as cells of a

grid corresponding to uniform parcels of land. Because the

homogeneity assumptions are met, Rothermel’s model can be

used within each unit.

The dynamic process of a spreading tire is simulated through

the use of the distance functions of MAP. Distance dictions

deal with the measurement of weighted distances, allowing

421
simulation of movement on a previously computed surface of

“frictions”. These are defined as the rate at which the fire

spreads from one cell to its neighbors given the direction of

the prevalent wind. The rates of spread overlay utilized

depends upon weather conditions, and a new rates of spread

overlay has to be utilized whenever there is a change in the

weather. This is done by stopping the simulation at the end of

a time step and proceeding with the spread process on a new

rates of spread overlay that was calculated according to the

new weather conditions.

Figure 1 illustrates how fire characteristics are computed for

each cell of the data base and set of constant meteorological

conditions, based on input overlays generated within MAP.

These input overlays are created from the topography,

vegetation, and weather data using the standard arithmetic and

reclassification capabilities of MAP and the tables presented

in Rothexmei (1983).

FUELS

SLCPE

WIND SPEED

WIND DIRECTION

MOISTURE

t

FIRE MODEL

EFFECTIVE WIN

HEAT/AREA

FLAME LENGTH

REACTION INTENSITY FIRELINE INTENSITY

APPLICATION

We ran four simulations to test fire sensitivity of four possible

forest landscapes corresponding to four management

alternatives for Eucalyptus sp. stands in a Mediterranean-type

region. The simulations are for a 1.5 hour bum, in three

30-minute time steps, with a likely early summer weather

scenario, which is summarized in table 1.

Table 1. --Weather conditions

Temperature Relative Wind

hunidity

W Uet Speed” Dlrectlon

* Degrees F * - Percent . * Nph m

First step 8 2 52 15 1 2 s

Second 8 04 5 1 1 2 1 2 s

third steps

) wind speed at mldf lame heght

Some comments may be appropriate regarding the temporal

and spatial scales we used. Under a normal weather scenario,

it seems reasonable to assume constancy of temperature and

relative humidity during 30 minute intervals. Windspeed and

wind direction probably vary significantly at a finer time

scale, and Fischer and Hardy (1972) indicate that the standard

time for averaging windspeed is 10 minutes. However,

Rothermel’s model was designed to predict fue behavior

under relatively uniform weather conditions (Rothermel,

1983), and although considerable weather changes in a

24-hour period should be expected, projection times of 2 to 4

hours, under constant meteorology are reasonable (Andrcws

1986). A more sophisticated treatment of the interactions

between wind, terrain, and fire behavior will probably require

expansion of the FIREMAP system to include a surface

windflow model such as KRISSY (Fosberg and Sestak 1986).

Spatial resolution of the database is considered appropriate

since it satisfies what we believe to be the two most important

considerations. On the one hand, cell size is small enough to

capture all essential landscape features and overall structure.

On the other hand, the cells are large enough in comparison

to average flame front depths to ensure that steady state

spread conditions are almost always present (Catchpole et al.

1989).

The Digital Data Base

The digital cartographic data base corresponds to a 2280 ha

area of undulating terrain. Altitudes range from 200 m to 600

m with aspect predominantly to the east, northeast, and

southwest on steeper slopes. The scale Is 1: 12,000 and there

are 7.5 rows by 76 columns with a cell size of approximately

0.4 ha (1 acre). The data base consists of the following

information layers: TOPOGRAPHY, STREAM CHANNELS,

an LANDSCAPE1 , 2, 3, and 4.

422
The landscape maps correspond to different management

alternatives for vegetation buffers along ephemeral streams in

Eucalvutus plantations. LANDSCAPE1 represents a landscape

of continuous Eucalvntus stands without any kind of stream

buffering. LANDSCAPE2 and LANDSCAPE3 represent soil

conservation alternatives favored by Portuguese environmental

legislation regarding fast-growing plantation forests. In

landscapes 2 and 3, natural vegetation is retained as stream

side buffer strips of predetermined minimum width. Different

stages of shrub development are considered in landscapes 2

and 3. Landscape 2 represents the case of having medium

height evergreen sclerophyllous shrubs along the streams and

landscape 3 the case of tall and dense stands of the same

shrub types. In the fourth vegetation alternative

(LANDSCAPE4) a more balanced and diverse landscape is

considered with wider strips of deciduous Quercus sp. planted

along stream banks. Figure 2 shows the stream channel

pattern.

Simulation

Four sets of input maps for the fire model were generated as

explained above. The FUELS overlays were created by

reclassifying the vegetation types to one of the 13 standard

fuel models (Anderson 1982) based on a correspondence

presented in Barreto (1985). Barreto classifies most of the

vegetation cover types found in Portuguese landscapes as the

models included in the mentioned set of 13 models.

The correspondence we used for this particular case is as

follows:

Eucalyptus sp, stands- fuel model 5

Medium evergreen sclerophyllous shrub staads- fuel model 6

Tall, dense evergreen sclerophyllous shrub standsfuel model 4

Deciduous oak stands- fuel model 9

FIREMAP generates maps with the expected fire

characteristics for the 4 Iandscape alternatives in the 3 time

steps and then simulates the spread of tire, with a given

source point, for the alternatives considered. Maps of the

expected flame lengths at each database cell are also

provided.

RESULTS

The maps displaying the predicted areas burned and respective

expected flame lengths are shown in figures 3 and 4. Table 2

shows the number of burned cells for each time step and

landscape and Table 3 the number of cells in each flame

length class for each of the 4 simulation scenarios.

u eucalyptus stands

natural vegetation

(stands of sclerophyllous

shrubs )

Figure 2.--The stream channels.

Table 2.--Cells burned

1st step 2d step 3rd step

. . . . . - &r ________

Sidation I

(2?4) ”

Sidatiom 2

(4.14)

Sidatim 3

$6)

Simulation 4

(22)

’ - bumed. in hectares

Table 3.--Expected flame leogtbs

0.4 4-a 8 * 11 >I1

feet feet feet feet

. . . , . . - Nmber of ceils - * - *

Sidation 1 4 153 38

Simulation 2 4 216 5 5

Simnlatios 3 6 218 87 84

Simlatioa 4 18 6 4 9

423
i’-J eucalyptus stands

Areas burned

0 to 30 wtin

m 30 to 60 tGn

m 60 to 90 nin

q eucalyptus stands

n sclsrophyl lous shrubs

fireas burned

0 to 30 bin

38 to 68 Min

m 60 to 90 nin

c] eucalyptus stands

mSC lerophy 1 lous shrubs

flreas burned

0 to 30 min

30 to 60 min

q 60 to 90 min

Figure 3.-Areas predicted to bum: (a) simulation 1, (b) simulation 2, (c) simulation 3, and (d) simulation 4.

c] eucalyptus stands

m deciduous oak stands

fireas burned

0 to 30 min

0 30 to 60 Min

m 60 to 90 Bin
N

0 eucalyptus

Flame length (

gfjl 0 to 4

4 to 8

u 8 to 11

stands

feet)

D

q eucalyptus stands

q sc lerophy 1 lous shrubs

Flame length (feet)

0 to 4

w 4 to 8

m 8 t o ii -

II ) 1 1

N

q eucalyptus stands

m sc lerophy 1 lous shrubs

Flame length (feet.1

pgj Q to 4

m 4 to 8

m 8 to 11

0 eucalyptus stands

m deciduous oak stands

FlaMe length <feet)

m 0 to 4

m 4 to 8

m 8 to 11

it? Figure 4.-Expected flame lengths: (a) simulation 1, (b) simulation 2, (c) simulation 3, and (d) simulation 4
DISCUSSION AND CONCLUSIONS

The results above indicate that under the simulation

conditions, natural vegetation left along stream banks may

actually contribute to increased fire problems. In fact, there

was an increase of 41 and 102 percent of predicted burned

area on the second and third alternatives (shrub stands along

stream banks) relative to the first alternative (Eucalvntus sp.

only)

The simulation outputs suggest that the striped patterns

generate preferential paths for fire, creating spreading

conditions that lead to higher perimeter-to-area ratios of the

burning area, thus improving propagation chances by

increasing the length of contact with unburned fuels. On the

other hand, the deciduous oak stands have lower rates of

spread and create zones of “higher friction” that retard

propagation of fire to the Eucalvntus stands. There was a

decrease of 46 percent of predicted burned area for this

alternative when compared with the first alternative. Given

the importance of convective heat transfer in deep fuelbeds

such as those represented by shrub formations, a worst case

scenario involving higher windspeeds would probably

emphasize even more the rapid spread of Iire along the stream

buffers.

Landscape planning in areas of intensively managed plantation

forests is a problem involving multiple, potentially conflicting

objectives. Conflicts arise not only between economic

production and environmental protection, but also between

different ecological concerns. In the present case study,

FIREMAP was used to emphasize one such conflict, between

erosion protection and tire hazard, in a way that provides

information about fire characteristics in a surrogate laboratory

mode. These quantitative data can be integrated with other

economic and environmental information to support costbenefit or multiobjective decision analyses of forest

management alternatives.

ACKNOWLEDGMENTS

The authors thank the Luso American Foundation for

Development.in Portugal for supporting most of the work that

led to the creation of FIREMAP and for supporting the

participation of the first author in this symposium.

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