United States

Department of

Agriculture

Forest Service

Rocky Mountain

Forest and Range

Experiment Station

Southwestern

Region

General Technical Report

RM-GTR-295

An Assessment of

Forest Ecosystem Health

in the Southwest

Illustrations: Mary Beath

This file was created by scanning the printed publication.

Errors identified by the software have been corrected;

however, some errors may remain.
Dahms, Cathy W.; Geils, Brian W., tech. eds. 1997. An assessment of forest 

ecosystem health in the Southwest. General Technical Report RM-GTR-295. 

Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Forest and Range Experiment Station. 97 p. 

This report documents an ecological assessment of forest ecosystem health 

in the Southwest. The assessment focuses at the regional level and mostly 

pertains to lands administered by the National Forest System. Information is 

presented for use by forest and district resource managers as well as collaborative partners in the stewardship of Southwestern forests. The report 

establishes a scientific basis for conducting forest health projects, provides a 

context for planning ecosystem restoration, and contributes to the understanding of the physical, biological, and human dimensions of these ecosystems. Chapters describe Southwestern forest ecosystems of the past, changes 

since the Colonial Period, and the implications of those changes for the 

health of current and future forests. Opportunities, tools, and research needs 

for improving long-term sustainability of these forest ecosystems are also 

identified. 

Keywords: ecosystem health, forest health, disturbance, ecosystem management, ecological processes. 

Publisher's note: Most of this report underwent editorial review by Southwestern Region staff. The Station composed pages directly from copy supplied by 

Cathy W. Dahms and Brian W. Geils. 

Cover art by Mary Beath 

July 1997 
USDA Forest Service 

General Technical Report RM-GTR-295 

An Assessment of Forest Ecosystem Health 

in the Southwest 

Cathy W. Dahms and Brian W. Geils 

Technical Editors 

July 1997 

CONTENTS 

Preface ......................................................................................................... 

Chapter 1 

Introduction ................................................................................................. 

Purpose .................................................................................................... 

What is Forest Health? ............................................................................. 

Ecosystem Management .......................................................................... 

Adaptive Management .............................................................................. 

Rise of the Forest Ecosystem Health Issue in the Southwest .................. 

Chapter 2 

Assessment Approach ............................................................................... 

Ecosystem Scale. Hierarchy. and Classification ....................................... 

Forested Provinces of the Southwest ....................................................... 

Arizona-New Mexico Mountains Semi-Desert - Open Woodland . 

Coniferous Forest . Alpine Meadow Province ..................................... 

Colorado Plateau Semi-Desert Province ............................................. 

Southern Rocky Mountain Steppe . Open Woodland . 

Coniferous Forest . Alpine Meadow Province ..................................... 

Great Plains . Palouse Dry Steppe Province ...................................... 

Life Zones of the Southwest ..................................................................... 

Evergreen oak and coniferous woodlands ........................................... 

Ponderosa pine ..................................................................................... 

Mixed conifer ........................................................................................ 

Spruce-fir .............................................................................................. 

Aspen ................................................................................................... 

Riparian wetlands ................................................................................. 

Chapter 3 

The Human Dimension of the Land .......................................................... 

Reading Myths .......................................................................................... 

Some Popular American Land Myths ....................................................... 

There was no land management in America before 

Europeans arrived ................................................................................ 

American wildlands are "pristine" and "untrammeled" .......................... 

Public lands were created to preserve America's wildlands ................ 

Myth in Forest Management ..................................................................... 

The Situation Today .................................................................................. 

Conclusion ................................................................................................ 

Chapter 4 

Historic Conditions ..................................................................................... 

Climate ...................................................................................................... 

Fire ............................................................................................................ 

Demographics and Land Use ................................................................... 

Timber and Fuelwood Resources ............................................................. 

Forest Insects and Pathogens .................................................................. 

Bark beetles ......................................................................................... 

Defoliating insects ................................................................................ 

Page 

i 
Root Decay Fungi ................................................................................. 

Dwarf Mistletoes ................................................................................... 

Historic Condition by Forest Community .................................................. 

Woodlands ............................................................................................ 

Ponderosa pine ..................................................................................... 

Mixed conifer ........................................................................................ 

Spruce-fir .............................................................................................. 

Aspen ................................................................................................... 

Riparian wetlands ................................................................................. 

Wildlife ...................................................................................................... 

Chapter 5 

Changes in Ecological Processes and Forest Conditions ...................... 32 

Grazing and Browsing .............................................................................. 32 

Fire ............................................................................................................ 34 

Demographics and Land Use ................................................................... 35 

Recreation ................................................................................................. 36 

Developed site recreation ..................................................................... 36 

Wilderness ............................................................................................ 37 

Heritage sites ........................................................................................ 37 

River use ............................................................................................... 37 

Hunters. anglers. and wildlife viewers .................................................. 37 

Outfitter guide services ......................................................................... 38 

Winter use ............................................................................................ 38 

Recreation impacts ............................................................................... 38 

Watershed Processes ............................................................................... 38 

Introduction of Exotic Plants ..................................................................... 39 

Forest Insects and Pathogens .................................................................. 39 

Bark beetles ......................................................................................... 40 

Western spruce budworm ..................................................................... 41 

Root decay fungi ................................................................................... 41 

White pine blister rust ......................................................................... 42 

Dwarf mistletoes ................................................................................... 42 

Timber Harvest ......................................................................................... 42 

Succession ................................................................................................ 43 

Definitions and theories ........................................................................ 43 

Factors affecting succession and resulting patterns ............................. 44 

Succession and ecosystem trends ....................................................... 45 

Succession in the Southwest ............................................................... 46 

Resultant Changes in Forest Conditions .................................................. 46 

Forest overstory/understory relationships ............................................. 46 

Oak woodland ....................................................................................... 48 

Coniferous woodland ........................................................................... 48 

Ponderosa pine ................................................................................ 49 

Mixed conifer ....................................................................................... 51 

Spruce-fir .............................................................................................. 51 

Aspen ................................................................................................... 51 

Riparian wetlands ................................................................................. 52 

Wildlife Population Dynamics .................................................................... 52 

AirQuality ................................................................................................. 54 

Chapter 6 

A Summary of Current Ecosystem Conditions ........................................ 56 

Woodlands ................................................................................................ 56 

Biological diversity .............................................................................. 56 
lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Ponderosa Pine ........................................................................................ 

Biological diversity ................................................................................ 

lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Mixed Conifer ............................................................................................ 

Biological diversity ................................................................................ 

lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Spruce-Fir ................................................................................................. 

Biological diversity, integrity, and resilience .......................................... 

Human needs and uses ....................................................................... 

Aspen ........................................................................................................ 

Biological diversity ................................................................................ 

lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Montane Riparian ..................................................................................... 

Biological diversity ................................................................................ 

lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Floodplain-Plains Riparian Wetlands ....................................................... 

Biological diversity ................................................................................ 

lntegrity and resilience ......................................................................... 

Human needs and uses ....................................................................... 

Conclusion ................................................................................................ 

Is adequate provision being made for the conservation of 

biological diversity? .............................................................................. 

Is ecosystem integrity and resilience being maintained 

in the long-term? .................................................................................. 

Are human needs for ecosystem resource use and landscape 

occupancy being adequately accommodated? .................................... 

Chapter 7 

Opportunities ............................................................................................... 62 

Chapter 8 

Tools to Achieve Desired Results ............................................................. 

Density Management ................................................................................ 

Even-aged vs Uneven-aged Management ............................................... 

Combination Silvicultural Methods ............................................................ 

Slash. Woody Debris. and Snags ............................................................. 

Salvage ..................................................................................................... 

Prescribed Fire ......................................................................................... 

Smoke Management ................................................................................. 

Insect and Pathogen Considerations ........................................................ 

Treatment Priorities ................................................................................... 

Aspen ..................... ; .................................................................................. 

Riparian Areas .......................................................................................... 

Channel Stabilization ................................................................................ 

Recreation Tools ....................................................................................... 

Exotic Plants ............................................................................................. 

Soil Amendment Techniques .................................................................... 
Chapter 9 

Research Needs .......................................................................................... 75 

Understanding Historic Variability ............................................................. 75 

Understanding Forest Ecosystem Health .............................................. 76 

Understanding Insect and Pathogen Interactions .................................... 76 

Understanding Wildlife Habitat Requirements .......................................... 76 

Developing Techniques to Restore and Maintain Ecosystems ................. 76 

Cultural and Social Assessments ........................................................... 77 

Literature Cited ............................................................................................ 78 

Glossary ....................................................................................................... 91 

Common and Scientific Names .............................................................. 95 
PREFACE 

This report was prepared by the Southwestern Forest Ecosystem Health Team. 

When first established, the team included representatives from the Rocky Mountain Forest Range and Experiment Station and each resource staff in the Southwestern Region. Participants either served as members of a core team or assisted with 

writing. An initial draft was completed in 1995 and reviewed. At the suggestion of 

various reviewers, we have significantly re-written and re-structured the original 

draft. 

This assessment is a team effort by the following individuals: 

Cathy Dahms, Southwestern Region, Ecosystem Analysis and Planning, 

Albuquerque, New Mexico 

Brian Geils, Rocky Mountain Forest and Range Experiment Station, 

Flagstaff, Arizona 

James Beard, Coconino National Forest 

Dale Brockway, Rocky Mountain Forest and Range Experiment Station 

Dayle Bennett, New Mexico Zone, Entomology and Pathology (formerly) 

David Conklin, New Mexico Zone, Entomology and Pathology 

Lorene Guffey, Cibola National Forest 

Marlin Johnson, Forestry Management 

George Martinez, Range Management 

Edwin (Gus) McCutchen, Range Management (formerly) 

Ron Moody, Aviation and Fire Management 

Rodney Replogle, Public Affairs Office 

Bryce Rickel, Wildlife Management 

John Shafer, Forestry Management 

Douglas Shaw, Watershed and Air Management (formerly) 

Charles Shaw, Rocky Mountain Forest and Range Experiment Station (formerly) 

Jill Wilson, Arizona Zone, Entomology and Pathology 

In addition, the following individuals contributed sections of the report: 

John Conner, Lincoln National Forest 

Reggie Fletcher, Ecosystem Analysis and Planning 

Wally Haussamen, New Mexico Department of Game and Fish 

Janet Johnson, Tonto National Forest 

Raymond Lee, Arizona Game and Fish Department 

John Peterson, Santa Fe National Forest 

Deborah Potter, Watershed and Air Management 

Judith Propper, Recreation Management 

George Robertson, Coconino National Forest 

Jay Stephan, Recreation Management 

Thomas Subirge, Apache-Sitgreaves National Forest 

Frank Wozniak, Recreation Management 

We acknowledge Lane Eskew (Rocky Mountain Forest and Range Experiment 

Station) and Mary Zabinski (Southwestern Region) for their roles as managing 

editors. Joyce Patterson assisted with preparation of figures. The team also recognizes the valuable comments and useful critiques provided by the following individuals: William Block, Brent Botts, Arthur Briggs, Sally Campbell, James Cooper, 

W. Wallace Covington, James Crawford, John Dale, Leon Fisher, Alan Harvey, Roy 

Jemison, Charles Lennahan, Gus McPherson, Keith Menasco, Will Moir, Richard 

Reitz, Mert Richards, John Schmid, Lamar Smith, Peter Stewart, Walter Stewart, 

Dan Winner, Michael Wagner, as well as several anonymous reviewers. 
Support for this project was provided by the Southwestern Region and Rocky 

Mountain Forest and Range Experiment Station (Ecology, Recovery, and Sustainability of Grassland and Riparian Ecosystems in the Southwest and Impact of Natural Ecological Disturbances on Western Conifers). 

Although this report may be used as input in processes initiated under the 

National Environmental Policy Act (NEPA), National Forest Management Act 

(NFMA), and other applicable laws, it is not a decision document, does not allocate resources on public lands, anddoes not make recommendations to that effect. 

The information in this report is general in nature, rather than site-specific. The 

opinions expressed by the authors do not necessarily represent the policy or position of the U.S. Department of Agriculture and the Forest Service. 
CHAPTER 1 : INTRODUCTION 

"The most important characteristic of an organism is that capacity for self-renewal 

known as health. There are two organisms whose processes of self-renewal have 

been subjected to human interference and control. One of these is man himself. 

The other is land." Aldo Leopold (1 949) 

PURPOSE 

This report documents an ecological assessment1 of 

forest ecosystem health in the Southwest (Arizona and 

New Mexico). The assessment focuses at the regional 

level and mostly pertains to lands administered by the 

National Forest System in the Southwestern Region. 

Information is presented for use by forest and district 

resource managers as well as collaborative partners in 

the stewardship of these lands and resources. The 

report establishes a scientific basis for conducting forest health projects, provides a context for planning 

ecosystem restoration, and contributes to the understanding of the physical, biological, and human 

dimensions of these forests. Chapters describe Southwestern forest ecosystems of the past, changes since 

the Colonial Period, and consequences to biodiversity, 

resilience, biotic integrity, and human use. Opportunities, tools, and research needs for improving ecosystem sustainability are also identified. 

WHAT IS FOREST HEALTH? 

The definition of forest health is controversial. The 

concept of health is well understood as applied to 

humans but may not be appropriate for ecosystems. 

Defining health in terms of homeostasis, whereby any 

change in condition represents a decline in health, fits 

humans well but not ecosystems. A human is an 

organism with a highly integrated physiology; survival requires precise regulation of internal temperature. An ecosystem, however, is a dynamic 

community of competing and evolving populations 

bound by common energy pathways and nutrient 

' Selected terms with technical meaning or special usage are 

initially presented in bold type and defined in the Glossary 

cycles. Although ecosystems display stability, they 

are not homeostatic organisms. Similarly human 

health can be defined by the absence of disease from 

parasites, bacteria, and viral infections. But in ecosystems, herbivorous insects, parasitic plants, and decay 

fungi are essential members of the biotic community 

with important roles determining ecosystem structure 

and function. It is only when their numbers increase 

beyond a range of historic variability, persist at 

chronic high levels, or when exotic species are introduced into the ecosystem that these disturbance 

agents might be considered indicators of unhealthy 

forests. The difficulties of defining an optimal condition for ecosystem health, coupled with the lack of 

universally accepted indicators to measure ecosystem 

health, have led some scientists to conclude that the 

concept of ecosystem health is ecologically inappropriate (Wicklum and Davies 1995). 

Although the analogy of forest health with human 

health is invalid, there are general concepts applicable to all complex dynamic systems that can be used 

to describe and assess their condition. Sustainability-a comprehensive, multiscale, measure of system 

organization, resilience, function, and productivityis proposed as a more useful concept than stability or 

absence of disturbance (Costanza et al. 1992). This 

property accounts for the dynamic nature of ecosystems and their adaptability to disturbance. Expressed 

in terms of biodiversity, resilience, biotic integrity, 

and human use, sustainability can be described at 

different scales of an ecological hierarchy and for 

biotic communities of any species composition. 

Although there are no simple and inexpensive methods for assessing ecosystem health, progress has 

been achieved over the last decade in development 

of data collection methods, identification of appropriate indicators and indices, and construction of 
diagnostic models. Defining and assessing the health 

of complex ecosystems is not easy, but it is not 

impossible. 

For practical reasons, it may be unimportant to 

define forest health in other than "fuzzy" terms (More 

1996). One of the strengths of the forest health 

metaphor is that people can relate to it (Rapport 

1995). A consensus on the need for forest health is sufficient to bring together resource managers, lawmakers, and the public. Most people have an intuitive 

idea of what constitutes a healthy ecosystem; at least, 

they believe they can recognize an unhealthy one 

when they see it. Perhaps more than any other event, 

the Yellowstone Fire of 1988 drew attention to the 

health of America's forests. Images of other devastating wildfires were kindled by media exposure of the 

destructive Dude Fire in 1990 and the fatal Storm 

King Fire in 1994. After decades of successful fire suppression, did these catastrophx fires indicate something was seriously wrong? In 1994, the Forest Service 

contracted with Kaset International for an independent poll of U.S. residents to learn what the public 

valued from its forests and what were their concerns 

over resource management. Even though no definition of forest health was provided, respondents overwhelmingly identified healthy forests as important 

and their protection as a high priority. 

Although a general concept of forest health may be 

enough to bring people together over specific issues, 

resource managers also need the ability to assess 

overall ecosystem health. Attempts to translate general concepts of ecosystem health into operational standards have resulted in definitions that either focus on 

ecosystem structures and functions or on the capability to provide for human needs. Kolb et al. (1994) 

reviews a number of definitions and categorizes these 

perspectives as ecosystem or utilitarian. Kolb et al. 

(1994) proposes that healthy forests are distinguished 

by four qualitative attributes: 

1. the physical environment, biotic resources, 

and trophic networks to support productive 

forests during at least some seral stages, 

2. resistance to catastrophic change and/or the 

ability to recover from catastrophic change at 

the landscape level, 

3. a functional equilibrium between supply and 

demand of essential resources (water, nutrients, light, growing space) for major portions 

of the vegetation, and 

4. a diversity of seral stages and stand structures 

that provide habitat for many native species 

and all essential ecosystem processes. 

Within the Forest Service, the definition of ecosystem health and its integration into goals and activities 

has evolved since 1988 from three different sourcesforest pest management, global change (fire and 

atmosphere), and ecosystem management. As a consequence of various national strategic plans and programs, the Forest Service mission, and regional 

assessments (Wickman 1992, Quigley 1992, O'Laughlin et al. 1993, Everett et al. 1994, Campbell and Liege1 

1996, Clark and Sampson 1995), a consensus is emerging on how to combine the utilitarian and ecosystem 

perspectives and what standards to use for judging 

biodiversity, biotic integrity resilience, and human 

use. 

An early definition of ecosystem health developed 

from the forest pest management perspective. Forest 

health is a condition where biotic and abiotic influences on the forest (i.e., insects, diseases, atmospheric 

deposition, silvicultural treatments, harvesting practices) do not threaten management objectives for a 

given forest now or in the future (McIntire 1988). The 

initial plan of providing forest health through silviculture and integrated pest management (McIntire 1988) 

was revised and given specific goals in a new strategic plan (USDA Forest Service 1993a). Although the 

initial definition of forest health was retained, greater 

weight was given in the revised plan to ecosystem 

management and maintaining functioning communities of plants and animals, including species formerly 

considered as "pests." Nonetheless, the goals of planning, prevention, suppression, protection, monitoring, 

restoration, and exclusion still mostly reflected an 

entomology and pathology perspective. In a 1994 

update (USDA Forest Service 1994~)~ three key indicators of forest health are identified as change in forest 

area, tree growth, and mortality. Forest health concerns focused on threatened tree species and damaging agents. 

Based on two workshops in 1987 and 1988, the 

USDA Forest Service (1988) proposed a research program for assessing forest health and productivity in a 

changing atmospheric environment. This program 

focused on issues at a global scale, incorporated 

atmospheric and other ecosystem processes into consideration of forest health, and identified the need for 

large scale monitoring and ecosystem models. Concerns over atmospheric pollution and climate change, 
as well as various forest declines and pest outbreaks, 

spurred participation by the Forest Service in a broad 

cooperative program (USDA Forest Service 1994a) 

called Forest Health Monitoring (FHM). The FHM 

program was designed to estimate the status, 

changes, and trends in selected indicators of forest 

ecosystem conditions on a regional basis (statewide 

and larger). In particular, this program was given 

responsibility for monitoring and reporting on 

ecosystem health, including air pollution effects on 

forests and insect, disease, and other stressor effects 

on forest ecosystems at the regional scale. Surveys 

conducted under this program emphasized change in 

forest area, tree growth, mortality, and crown appearance and tree damage caused by insects, pathogens, 

and abiotic agents (e.g., see Campbell and Liege1 

1996). 

Since 1994 the official mission and vision of the Forest Service is described in terms of ecosystem management (USDA Forest Service 199410, Thomas and Huke 

1996). In this context, ecosystem management refers to 

the integration of ecological, economic, and social factors to maintain and enhance the quality of the environment to best meet current and future needs. The 

focus priorities for the agency are protection, restoration, sustainability, and organizational effectiveness 

(USDA Forest Service 1994b, Thomas and Huke 1996). 

An integration of biophysical and human dimensions 

is described for each of these priorities. Protection 

through an understanding of the roles of various disturbance agents ensures the health and diversity of 

ecosystems while meeting people's needs. Ecological 

restoration using prescribed fire, thinning, and other 

management tools improves the likelihood that future 

options for resource use are maintained. In addition to 

providing multiple benefits for people withn the 

capabilities of ecosystems on National Forest System 

lands, the agency supports action that incorporates 

sustained economic, sociocultural, and community 

goals consistent with a shared vision of desired 

ecosystem condition (Interagency Ecosystem Management Task Force 1995). The fourth focus priority, organizational effectiveness, is achieved by using 

appropriate scientific information and involving 

diverse communities in making resource decisions. 

With these four priorities included in the meaning 

of ecosystem management, forest health (as a 

component of ecosystem management) gains an 

economic and social context. This context of the 

human dimension complements the ecological perspective provided by programs focused on vegetation 

condition and tree damage. 

Although the Forest Service has not yet adopted an 

official definition of forest health, there is an interim 

definition which reflects the evolving ideas described 

above. Twery and Gottschalk (1996) propose: 

forest health is a condition wherein a forest has the 

capacity across the landscape for renewal, for 

recovery from a wide range of disturbances, and for 

retention of its ecological resiliency, while meeting 

current and future needs of people for desired levels of values, uses, products, and services. 

This is the definition of forest ecosystem health 

accepted by the Southwest assessment team and used 

in this report. The philosophy of ecosystem management-looking at ecosystems as interacting systems 

rather than individual components, incorporating 

multiple spatial and temporal scales, and recognizing 

that ecosystem management incorporates the human 

dimension as well as the biophysical dimension-has 

profoundly affected the way the Forest Service 

addresses forest ecosystem health. 

ECOSYSTEM MANAGEMENT 

Ecosystem management is the overall concept 

which determines the Forest Service approach to 

restoring and maintaining forest health (Thomas and 

Huke 1996). The principles of ecosystem management 

emerge from both a philosophical land ethic and from 

various legislative acts. Although other organizations 

have embraced ecosystem management with their 

own meaning and context, the Forest Service uses the 

following definition (Thomas and Huke 1996): 

ecosystem management is a concept of natural 

resources management wherein national forest activities are considered wihn the context of economic, 

ecological, and social interactions widun a defined 

area or region over both short and long term. 

The land ethic behind ecosystem management traces 

back to Leopold (1949) and is call for a stewardshp 

that goes beyond treating the land as a commodity. 

Ecosystem management is a shift in focus from managing outputs of ecosystems to maintaining the structure 

and function of ecosystems through time and for the 

benefit of present and future generations. The applica- 
tion of ecosystem management in the Forest Service 

involves four principles-public involvement, an ecological approach, partnerships, and management 

based on sound science (Thomas and Huke 1996). 

The public is a partner in ecosystem management 

because people are an inseparable part of ecosystems 

and ecosystem management itself is a human endeavor (Carr 1995). Leopold's (1949) land ethic is based on 

the observation that people's beliefs and perceptions 

about the land influence how they treat it and what 

they expect from it. An understanding of the human 

dimension is as significant as the physical and biological dimensions for explaining how current ecosystem 

conditions (e.g., health) came to be. Forest health 

issues stem from human activity, are brought to light 

because of human concerns, and are addressed 

through human ingenuity (Carr 1995). Aspects of the 

human dimension include past and present land use, 

myths and beliefs, socio-economic structure and 

processes, demographics, lifestyles, and expectations. 

The ecological approach to management is based on 

the observation that ecosystems are organized and 

behave according to certain physical and biological 

principles. The biotic members of an ecosystem are 

connected and interdependent; this includes humans. 

Ecosys tems are dynamic; attempts to maintain them 

in a static condition can result in violent reaction (e.g., 

attempts to remove all fires from some ecosystems 

result in more serious fires). The boundaries of these 

interdependent and dynamic ecosystems are defined 

by geology, climate, and biotic history, not by administrative convention. Ecosystems are organized in 

herarchical patterns so that actions at one level can 

have consequences at another (e.g., global warming 

can induce local extinction of a species). To be successful, management must be adaptive, taking into 

account the productive capabilities of the ecosystem, 

its ability to change, and its response to manipulation. 

Because ecosystems are nested into larger and larger, interconnected units that cross many administrative boundaries, collaborative partnerships are 

necessary to make good decisions based on sound science. Stewardship requires the cooperation of multiple, public stakeholders and among managers and 

scientists of many agencies and disciplines. The elements of collaboration are-jointly develop shared 

vision and common goals; share responsibilities to 

obtain common goals where appropriate; and jointly 

work to achieve common goals using each collaboratofs experience (USDA Forest Service 1994d). 

Ecosystem management is based on sound science. 

This requires an understanding of how ecosystems 

function, how they support and tolerate human use, 

and how policy and management affects the environment (Thomas and Huke 1996). 

Ecosystem management is based on the legislative 

authority and responsibility of the Forest Service as 

provided in numerous public laws. Statutes include 

the Multiple Use-Sustained Yield Act (1960), the 

National Forest Management Act (1976), National 

Environmental Policy Act (NEPA, 1969), Endangered 

Species Act (ESA, 1973), and pollution control laws 

such as the Clean Water Act and Clean Air Act. Funding to implement ecosystem management is provided 

by annual appropriations, partial returns from timber 

sales as provided in the Knutson-Vandenberg Act 

(K-V, 1930), and numerous partnership programs. 

Ecosystem management is also embraced outside 

the Forest Service. In 1993, the Society of American 

Foresters appointed a task force to produce a report 

on sustaining long-term forest health and productivity. The report contained 26 recommendations within 

four broad areas-advocating ecosystem management, integrating ecosystem management into educational programs, promoting ecosystem management 

research, and coordination among landowners and 

with the public. Although the report represented an 

evolution of thinlung among some prominent Society 

members, it failed to adequately address differences 

in a number of regional issues. In 1996, a broader task 

force reported to the Society on these regional issues 

and the connection of forest health to landowner 

objectives. 

ADAPTIVE MANAGEMENT 

The proactive approach of the Forest Service to 

restore and maintain healthy forests is adaptive management. The theory and practice of adaptive management has evolved over the last two decades 

through the works of Walters (1986), Holling (19781, 

and Lee (1993). One of the fundamental tenets of 

adaptive management is that ecosystems and people 

are unpredictable as they evolve together. Ecosystems 

change as do the people that attempt to understand 

and manage them. In addition, the understanding of 

ecosystem behavior is imperfect, and managers will 

never be able to completely predict responses to management activities. Adaptive management encornpasses both deliberate experimentation to gain new 
knowledge (active adaptive management) as well as 

the ongoing process of using monitoring and inventory information to assess the effects of management 

actions on ecosystem health (passive adaptive management). Active adaptive management is a departure 

from traditional management in that it views management actions as experiments from which to learn. 

Implementing adaptive management experiments 

involves being explicit about expected outcomes, 

designing methods to measure responses, collecting 

and analyzing information to compare expectations to 

actual outcomes, learning from the comparisons, and 

changing actions and plans accordingly (USDA Forest 

Service 1995). Collaboration with research is essential 

to provide the expertise on designing adaptive management programs so that they can be monitored and 

evaluated. Passive adaptive management may seem a 

misnomer because it requires a very active program 

for monitoring and evaluation of project activities, as 

well as some aspects of management experiments. 

Particularly for effectiveness and validation monitoring, the monitoring must be designed as statistically 

sound and scientifically credible. 

With adaptive management, specific treatment 

actions are determined using an ecological approach 

to implement land management plans on each national forest. Project-level analyses are done in the context 

of broader scale assessments that identified desired 

conditions for healthy, sustainable ecosystems. 

Desired conditions for sustainable forest management 

are identified using public participation and collaboration in consideration of local management objectives and local conditions. Desired conditions provide 

descriptions of the desired human dimensions and 

physical, biological characteristics to be achieved in 

an area over short and long time frames. 

RISE OF THE FOREST ECOSYSTEM HEALTH 

ISSUE IN THE SOUTHWEST 

In many respects, the Forest Service, Southwestern 

Region was a pioneer in adopting a broad perspective 

of forest ecosystem health. The emphasis on ecosystem health at the regional level began in 1992 with the 

adoption of a series of initiatives to address forest 

health in specific, threatened, biotic communities, 

namely pinyon-juniper, riparian, and aspen. In 1993, 

initiatives for these communities were combined with 

those for the remaining forest communities as the Forest Health Restoration Initiative (USDA Forest Service 

199313). The goal of this program was to increase public awareness in forest ecosystem health, gain agency 

and public support, and begin the work of ecosystem 

restoration. 

In 1994, the Southwestern Region developed a 

report on the human dimension of ecosystem management (USDA Forest Service 1994d). The report 

states that ecosystem management must include consideration of the physical, emotional, mental, spiritual, social, cultural, and economic well-being of people 

and communities within ecosystem capabilities. The 

report further observes that managerial decisions are 

in reality moral rather than technical judgements 

because they accommodate some people's values and 

not others. This underscores Carl's (1995) characterization of the complexity of these decisions and recognizes that there is rarely one correct solution for 

natural resource issues, only more or less useful solutions. The Southwestern Region and Rocky Mountain 

Forest and Range Experiment Station have several 

excellent collaborative projects. The Keystone Center 

(1996) highlights the Malpais Borderlands Group as a 

laboratory for demonstrating public involvement and 

collaborative techniques in the spirit of ecosystem 

management. The Yavapai Ecosystem Project received 

the Chiefs Ecosystem Management Award for their 

innovative private-public cooperative strategy to sustain ecological integrity while still allowing economically viable ranching operations. 

The Southwestern Region Leadership Team in partnership with the Rocky Mountain Station requested a 

detailed assessment of forest ecosystem health as an 

extension of the Forest Health Restoration Initiative. 

The Western Forest Health Initiative, announced in 

1994, recommended development of regional assessments to describe the existing health of all Western 

Forests. This document details ecosystem health in 

forests of the Southwest. 
CHAPTER 2: ASSESSMENT APPROACH 

"Under the concept of ecosystem management, planning is conducted using appropriate regional or area assessments of ecological, economic, and social effects and 

the interaction of these factors to enh,ance management ..." 

Jack Ward Thomas, 1995 

This assessment examines the condition of forested 

ecosystems in Arizona and New Mexico and describes 

their past, present, and future at a regional planning 

and analysis scale. A variety of hierarchies exist to 

delineate these ecosystems on different characteristics 

(e.g., climatic, terrestrial, aquatic, and social), and the 

assessment team had considerable discussion on 

which hierarchy to use. Although it would be 

appropriate to structure this assessment by either 

ecoregions (terrestrial), river basins (aquatic), or economic-political units (social), required ecological 

information on past conditions, current status, and 

potential trends is generally not available by these 

geographic designations. Data are, however, available 

for Southwestern ecosystems by life zone characterized by biotic community. The assessment is therefore 

based on taxonomic categories of dominant vegetation; and differences in condition and response for 

geographic provinces are noted within discussions 

organized by biotic community. 

The assessment uses guidelines in the draft 

National Framework for Integrated Ecological 

Assessments2 and includes the following elements 

for Southwestern forests as a whole and for each life 

zone in particular: 

A description of the current and historic composition, structure, and function. 

A description of the abiotic and biotic events, 

including human actions, that contributed to 

development of the current condition. 

These elements are incorporated into the assessment 

on the fundamental premise that human actions 

Unpublished document outlining a national strategy for integrated ecological assessments prepared by a bio-physical 

team (chaired by Eric Hyatt, EPA) and a human dimensions 

team (chaired by lsobel Sheifer; NOAA). 

change ecosystems. Past, present, and future perceptions and beliefs influence ecosystems, just as ecosystems influence the physical, spiritual, cultural, and 

economic well-being of people. Before managers can 

attempt to integrate goals, perceptions, beliefs, and 

values into ecosystem planning, they must be aware 

of the origin and evolution of these human wants and 

needs. This topic is addressed in Chapter 3. 

An hstorical perspective (element 1) establishes reference conditions for estimating how current ecosystems differ from ecosystems of the past. Historical 

characterizations also provide insights into possible 

future ecosystem development by identifying significant disturbance agents and regimes, vegetation patterns, environmental constraints, and the variability of 

biotic patterns and processes. Characterization of historic conditions in the Southwest during Native 

American and Spanish Colonial times is provided in 

Chapter 4. 

During the Territorial Period following the war of 

1848, came increasing levels of hunting, grazing, timber harvest, farming, irrigation, and building of 

towns, cities, and civil projects. The changes in forest 

ecosystems (element 2) that resulted from new 

resource demands and management regimes are 

described in Chapter 5. 

An summary of current ecosystem conditions is provided in Chapter 6. The indicators of forest health are: 

I) biological diversity, 2) biotic integrity and resilience, 

and 3) human needs and uses. The assessment team 

believes these three indicators accurately reflect the 

biological, physical, and human dimensions required 

for sustaining ecosystems. Biological diversity is a frequently used measure of ecosystem complexity; reduction of ecosystem complexity is generally considered 

detrimental to ecosystem health. Biotic integrity, as 

used in this report, refers to the ability of a community 
to recover and maintain system processes within his- such as plant re-establishment and succession after 

toric variability. Resilience to disturbance insures fire, or slow such as soil development. Some processmaintenance of biodiversity and biotic integrity. es, such as bark beetle outbreaks, are particularly releHuman needs and wants reflect not only the economic 

needs of society and communities, but also their cultural, spiritual, and aesthetic aspirations. 

Actions the assessment team believes could 

improve forest health are described in the remaining 

chapters. Management opportunities are discussed in 

Chapter 7; specific tools are covered in Chapter 8; and 

research needs are identified in Chapter 9. 

ECOSYSTEM SCALE, HIERARCHY, AND 

CLASSIFICATION 

One of the differences between ecosystem management and previous management approaches is the 

recognition of the importance of scale and hierarchy. 

Ecosystems are defined by their boundaries, and 

depending on one's perspective could be a pond, a 

small watershed, a major river basin, or even the 

whole biosphere. Ecosystems can be viewed both as a 

landscape of similarly scaled stands (like a patchwork 

quilt) and as an ordered nesting of patches within 

stands, stands within forests, and forests within 

regions (a hierarchical organization). The concept of 

scale applies not only to ecosystem structure but also 

to ecosystem processes (Figure 2.1). These processes 

act over distinct and characteristic spatial and temporal scales and determine ecosystem structure (Holling 

1992). These processes may be local such as tree fall, 

or landscape such as habitat fragmentation, or rapid 

Temporal 

Scale 

If Recruitment 

Spatial Scale 

Figure 2.1 Spatial and temporal scales of some common 

ecological processes. 

vant to ecosystem health because they occur at spatial 

and temporal scales which correspond to those with 

human interest and importance (Holling 1992). Identification of scale and hierarchy are necessary to provide the proper context for ecosystem description and 

analysis. 

The complexity of describing ecosystems over a 

range of scales and accounting for their hierarchical 

structure is handled through classification. Although 

classification is a challenging task, it produces very 

useful management tools. Ecological classifications 

range from relatively simple, using few characteristics 

such as species composition, to more comprehensive, 

integrating multiple environmental characteristics 

such as climate, topography, soil, and vegetation. 

Classification systems identify the relative degree of 

similarity among ecosystems and arrange these into 

groups ranked by spatial scale or hierarchy. One of 

the best uses of ecological classification is for stratifying the land base into units with similar productive 

capacities and responses to management. Classifications also help in the conduct of inventories for rare 

species (or other ecosystem elements) because these 

species are usually associated with a single or definable group of ecosystems. When classification is combined with a Geographic Information System (GIs), 

the pair becomes a powerful tool for analysis and display of spatial data. Ecological classification systems 

are developed from either a geographc or taxonomic 

approach. 

The geographical approach (Bailey 1996) is a topdown method whereby the classifier begins with a 

large land area and splits it into smaller units with 

similar vegetation, landform, or other attributes. This 

method, also called regionalization, is a simultaneous 

process of classification and mapping with the objective of identifying internally homogeneous map units. 

Because the method is used at a broad scale, map 

units often contain ecologically significant inclusions 

such as riparian corridors that do not fit well into the 

map topology. The best use of regionalization is classification and mapping at broad scales-dividing continents into domains (based on broad climatic zones), 

domains into divisions (based on regional climate), 

divisions into provinces (based on landforms, altitudinal zones and plant formations), provinces into sections (based on physiography) and sections into 
subsections (based on surficial geology). The National 

Framework of Ecological Units (Table 2.1) based on 

terms defined by Bailey (1995) is an excellent example 

of the geographical approach. 

In Bailey's (1995) approach, landtypes are divided 

into landtype phases or aggregated into landtype 

associations for landscape scale planning and analysis. At these detailed levels, forest and woodland 

stands as well as linear riparian ecosystems are recognized. Because these units can be observed on the 

ground, they are especially meaningful to managers 

and the public. The phase, landtype, and association 

are the smallest recognized divisions in the hierarchy 

of the National Framework of Ecological Units (Table 

2.1). Landtype and phase (land units) are useful for 

project planning and analysis and link to landscape 

units. Landtype associations (landscape units) are 

useful in forest planning and tier to the subregional 

units described by Bailey et al. (1994). 

Geographic classification is useful for strategic 

planning at regional or statewide levels. For planning 

and management at watershed, forest, and project 

levels, however, a fine-grain, taxonomic classification 

is required. The taxonomic approach (Pfister and 

Arno 1980) is a bottom-up aggregation of individual, 

sampled sites whch represent the population of all 

sites within an area and are intensively measured for 

a wide variety of ecological attributes. Aggregation 

uses multivariate statistical analysis to determine the 

similarity between units; mapping is a separate activity. The basis for classification may be potential or climax vegetation (habitat type) as developed by 

Daubenmire and Daubenmire (1968) and illustrated 

for Southwestern forests and woodlands by Stuever 

and Hayden (19%). Although vegetation alone well 

integrates numerous ecological and environmental 

factors, various other taxonomic systems explicitly 

use climatic, physiographic, edaphic, and vegetation 

data. An example of this approach is the Ecological 

Land Classification Framework for the United States 

(Driscoll et al. 1984). 

The comprehensive ecological classification system 

used in the Southwestern Region for analysis and 

planning is the Ecological Land Classification Framework for the United States (Driscoll et al. 1984) based 

on the Modified Ecoclass System. From this framework, the Southwestern Region developed the Terrestrial Ecosystem Survey (TES) procedures for 

Table 2.1 National Framework of Ecological Units for planning and analysis by the National 

Forest System. 

Planning and Ecological 

analysis scale Units 

Purpose, objectives, 

and general use 

General 

size range 

Ecoregion 

Global Domain 

Continental Division 

Regional Province 

Subregion Section 

Broad applicability 1,000,000s to 

for modeling and sampling. 10,000s of 

Strategic planning square miles. 

and assessment. 

International planning 

Strategic, multi-forest, 1,000s to 

statewide and multi-agency 10s of 

Subsection analysis and assessmen 

Landscape Landtype 

Association 

Land Unit 

Forest or area-wide 

planning, watershed 

analysis. 

Landtype Project and managemen 

area planning and 

analysis. 

Landtype Phase 

square miles. 

1,000s to 

100s of acres. 

100's to 

less than 

10 acres. 

Terms and concepts developed by Bailey (1995); table adapted from unpublished work by National [Forest Service] Ecomap Team. 

8 
classification, mapping of ecological units, and direction for interpreting the relationships of soil, vegetation, and climate. Two scales are available for 

mapping of ecological units. TES units are mapped as 

polygons at 1:24,000 and correspond to the land unit 

scale (Table 2.1). General Ecosystem Survey (Carleton 

et. a1 1991) units are mapped at 1:250,000 and correspond to the landscape scale (Table 2.1). These units 

are meaningful to resource managers and the public 

in that these units are observable spatial features that 

repeat themselves across the landscape. Managers can 

use these units to evaluate cause and effect relationships among management scenarios. The landscape 

scale and scales immediately above and below in the 

National Framework (Table 2.1) are those most appropriate for a regional assessment of forest ecosystem 

health. 

FORESTED PROVINCES OF THE SOUTHWEST 

Ecoregion provinces designate regional geographic 

areas with similar climates and landforms (Bailey 

1995). Within the National Hierarchical Framework of 

Ecological Units, the province is the appropriate scale 

for broad-level, strategic planning and assessment. 

The seven provinces (Bailey et al. 1994) mapped for 

the Southwest (Figure 2.2) are: 

American Semi-Desert and Desert Province, 

Arizona-New Mexico Mountains Semi-Desert 

- Open Woodland - Coniferous Forest - Alpine 

Meadow Province, 

Chihuahuan Semi-Desert Province, 

Colorado Plateau Semi-Desert Province, 

Great Plains - Palouse Dry Steppe Province, 

Southern Rocky Mountain Steppe - Open 

Woodland - Coniferous Forest - Alpine Meadow Province, and 

Southwestern Plateau and Plains Dry Steppe 

and Shrub Province. 

Because this is an assessment of forest and woodland ecosystems, the American Semi-Desert and 

Desert, the Chihuahuan Semi-Desert, and the Southwestern Plateau and Plains Dry Steppe and Shrub 

Provinces are excluded from further discussion. 

Provinces (and more specifically sections and subsections) delimit areas with like interactions among land 

units and which consequently form landscapes characteristic of the region. For example, because of differences in climate, landform, and history, succession 

proceeds differently in the Southern Rocky Mountain 

Province than in the Colorado Plateau Province. Differences in succession lead to the formation of regionally distinct landscapes, even though the same species 

are present in both provinces. Bailey (1995) describes 

the Southwestern provinces which include forest and 

woodland communities. 

Arizona-New Mexico Mountains Semi-Desert - 

Open Woodland - Coniferous Forest - Alpine 

Meadow Province 

The geomorphology includes mountains, hills, 

plains, and scarps across central Arizona, and western 

and southern New Mexico. The elevation starts at 

6,000 feet and goes up to 12,500 feet. Precipitation 

ranges from 12 to 35 inches annually. Potential vegetation includes pinyon (certain Pinus spp.), juniper 

(Juniperus), Gambel oak (Quercus gambelii), ponderosa 

pine (I? ponderosa), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menzesii). Aspen (Populus tremuloides) is an occasional species. The primary abiotic 

disturbance is fire; and the primary anthropological 

land use is forest management, including recreation, 

timber, aesthetics, and wildlife habitat. Portions of the 

Tonto, Coconino, Apache-Sitgreaves, Lincoln, Cibola, 

and Santa Fe National Forests are included in this 

province. 

Colorado Plateau Semi-Desert Province 

This province contains lower tablelands in Arizona 

and New Mexico; the Colorado River is the region's 

only large stream. The geomorphology of this 

province includes canyons, cliffs, scarps, plateaus, 

hills, and mountains. The elevation ranges from 3,000 

feet to 7,000 feet. Annual precipitation ranges from 6 

inches to 25 inches. In the lowest vegetation zone are 

arid grasslands and shrubs; sagebrush (Artemisia) is 

common over large areas. The woodland zone is the 

most extensive; pinyon and juniper are the dominant 

vegetation. The montane zone extends over the high 

plateaus and mountains; trees include ponderosa 

pine, Douglas-fir and aspen. Abiotic disturbances 

include wind, floods, drought, and fire. The principal 

anthropological land use is production of forage for 

livestock grazing and browsing. Portions of the 

Tonto, Prescott, Kaibab, Coconino, and Apache-Sitgreaves National Forests are included in this province. 

Southern Rocky Mountain Steppe - Open Woodland - Coniferous Forest - Alpine Meadow 

Province 

Landforms include mountains and valley plains of 

northern New Mexico. The elevations range from 

7,500 to 14,000 feet. Annual precipitation ranges from 

24 to 28 inches. Ponderosa pine, Douglas-fir, aspen, 

subalpine fir (Abies lasiocarpa) and Englemann spruce 

(Picea engelmannii) are common tree species. The primary abiotic disturbance is fire. Recreation, mining, 

and ranching are important land uses. This province 

includes significant portions of the Carson and Santa 

Fe National Forests. 

Great Plains - Palouse Dry Steppe Province 

Landforms include valley, lowlands, and elevated 

plains and hills in northern New Mexico. Elevation 

ranges from 6,800 to 8,800 feet. Precipitation varies 

from 6 to 8 inches annually and less than half of the 

precipitation falls during winter. Various species of 

forbs and grasses (graminoids) are found in the 

uplands; cottonwoods (Populus) and willows (Salix) 

along riparian corridors form the only forests in the 

province. Farming and ranching are the primary land 

uses. This province includes portions of the Carson 

and Santa Fe National Forests. 

LIFE ZONES OFTHE SOUTHWEST 

The General Ecosystem Survey (Carleton et al. 

1991) groups Southwestern ecosystems into life zones 

characterized by biotic community types including 

desert, grassland, chaparral, evergreen oak woodland, 

coniferous woodland, ponderosa pine, mixed conifer, 

spruce-fir, tundra, and riparian wetlands. Because 

ths is an assessment of forest, woodland, and associated riparian ecosystems, desert, grassland, chaparral, 

and tundra life zones are excluded from further discussion. The concept of a life zone is derived from a 

taxonomic classification system described first by 

Merriam (1898), revised by UNESCO (1973), and 

applied in the Southwest by the Terrestrial Ecosystem 

Survey. The General Ecosystem Survey life zones 

(Table 2.2) can be cross-referenced to the biotic communities described by Brown and Lowe (1977, 1980) 

and Brown (1994). Aspen is a component of the montane forest found mostly in the mixed conifer zone 

but also in the ponderosa pine and the spruce-fir 

zones. Riparian wetlands occupy little area but like 

aspen perform special and very important ecological 

and landscape functions within their life zone. 

Because of their uniqueness and value, aspen and 

riparian wetlands are treated here along with evergreen oak and coniferous woodlands, ponderosa pine, 

mixed conifer, and spruce-fir forests as forest biotic 

communities of the Southwest (Figure 2.3). 

A specific ecosystem can be located with reference 

to a geographic province; and if it is defined by the 

dominant vegetation, it can also be associated with 

other ecosystems of similar biotic composition (life 

zone). Whereas the province scale is the correct perspective for examining landscape dynamics, the life 

zone is the appropriate scale for describing aspects of 

community development such as disturbance regime 

and successional pattern. Every ecosystem is a unique 

entity with its own particular history, composition, 

structure, and potential. Although ecosystems of a 

common life zone tend to respond in similar ways, 

each is different. Some of this difference can be 

explained by location within a landscape and 

Table 2.2 Correspondence between General Ecosystem Survey Life Zones and 

Southwestern Biotic Communities. 

Life Zone Biotic Community 

Evergreen oak woodshedwatershed Madrean evergreen woodland 

Coniferous woodland Great Basin conifer woodland 

Ponderosa pine and mixed conifer Rocky MountainIMadrean montane coniferous forest 

Spruce-fir Rocky Mountain subalpine coniferous forest. 

Life zones defined by Carleton et at. (1991); biotic communities described by Brown and 

Lowe (1 977, 1980) and Brown (1 994). 

province. Because most of the available information 

for past and current ecosystems is cataloged or identified by life zone, this assessment primarily describes 

Southwestern ecosystems by life zone and notes differences by province where they are known. 

Evergreen Oak and Coniferous Woodlands 

Woodlands generally include evergreen oak and 

conifer species that occupy certain areas along an 

elevational gradient from low-elevation desert 

shrub / grasslands and short-grass prairies to high-elevation montane coniferous forests of ponderosa pine 

and Gambel oak. Oak woodlands occur within the 

range of 4,000 to 9,000 feet elevation. Gambel oak 

occurs at hgher elevations, and wavyleaf oak (Quercus undulata) occurs either below Gambel oak or intermingled with it in a transition zone. Woodlands were 

used extensively by prehistoric and historic populations for habitation and subsistence. Uses today 

include grazing, fuelwood harvest, and recreation. 

Evergreen oak woodland, characterized by wet 

summers and mild winters, extends from the Sierra 

Madre of Mexico into southeastern Arizona and 

southwestern New Mexico. In the United States, a 

variety of oak species such as Emory oak (Quercus 

emoryi), Arizona white oak (Q. arizonica), Mexican 

blue oak (Q. oblongifolia), gray oak (Q. grisea), silverleaf oak (Q. hypoleucoides), and netleaf oak (Q. rugosa) 

are found in conjunction with the following Madrean 

pine species-Apache pine (Pinus engelmannii), Chihuahua pine (I? leiophylla var. chihuahuana), and Arizona pine (I? arizonica) (Brown 1994). 

Pinyons and junipers, together or alone, dominate 

coniferous woodland communities. These woodlands 

occupy approximately 23 million acres in New Mexico, about 13 percent of which are on national forest 

lands, and 4.1 million acres in Arizona, 34 percent on 

national forest lands. The pinyons include Pinus 

edulis, the most common pinyon pine throughout the 

type, border pinyon (I? discolor), and Arizona singleleaf pinyon (I? californarium subsp. fallax). Junipers are 

frequently found at lower elevations than pinyons 

and typically occupy sites with deep soils. The most 

common junipers in the Southwest are one-seed 

juniper (luniperus monosperma) found in central and 

southern New Mexico and much of Arizona below 

the Mogollon Rim, the Rocky Mountain juniper 

(1. scopulorum) in the higher and colder woodlands 

of northern New Mexico and Arizona, Utah juniper 

(J. osteosperma) in northwestern New Mexico and 

northern Arizona, and alligator juniper (J. deppeana) 

associated with the Madrean woodlands of southern 

Arizona and New Mexico (Brown 1994, Gottfried 

1992). 

Ponderosa Pine 

Ponderosa pine (yellow pine or blackjack pine) is 

found from 6,500 to 8,000 feet elevation. At lower elevations, the ponderosa pine forest meets woodlands 

and at higher elevations transitions into the mixed 

conifer zone. Ponderosa pine forests of central and 

northern New Mexico and Arizona cover about 8.4 

million acres. The predominant form throughout the 

Southwest is the three-needled, Rocky Mountain ponderosa pine (P. ponderosa var. scopulorum). In lower 

elevations of southern Arizona, however, the five-needled, Arizona pine is more common. Other species 

associated with ponderosa pine at low elevations are 

Gambel oak and New Mexico locust (Robina neomexicana); at high elevations associates are southwestern 

white pine (Pinus strobiformis), Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca), Rocky 

Mountain white fir (Abies concolor var. concolor), and 

quaking aspen (Populus tremuloides) (Brown 1994). 

Uses include timber harvest, grazing, camping, and 

other types of recreation offering cool relief from hot 

urban areas. 

Mixed Conifer 

Mixed conifer forests dominated by Douglas-fir, 

white fir, and blue spruce (Picea pungens) occur at elevations from 8,000 to 9,500 feet. There are about 1.5 

million acres of mixed conifer forest in the Rocky 

Mountain and Madrean montane forests of southern 

Colorado, New Mexico, Arizona, and the Sierra 

Madre Occidental of Mexico (Brown 1994). Ponderosa 

pine, southwestern white pine, aspen, and a number 

of other tree species may occur in these forests. Uses 

are similar to the ponderosa pine community. 

Spruce-Fir 

Spruce-fir forests are found at high, subalpine, eleva tions in the Southwest from approximately 8,000 

feet to over 12,000 feet. Spruce-fir forests are typically 
restricted to areas receiving more than 25 inches of 

precipitation from winter snows and summer thunderstorms. The predominant spruce is Engelmann 

spruce which is found as far south as the Pinaleno 

Mountains in Arizona and the Sacramentos in New 

Mexico. The co-dominant species is subalpine fir 

(Abies lasiocarpa). Some populations of subalpine fir 

possess a distinctive outer cortex and are called corkbark fir (A. lasiocarpa var. arizonica). Small stands of 

aspen or blue spruce are found within the spruce-fir 

forest (Brown 1994). Uses include wilderness recreation, skiing, and the enjoyment of high places. 

Mountain peaks have special cultural and religious 

significance for many Southwestern Indian tribes. 

Aspen 

Quaking aspen occurs at elevations above 6,000 feet 

as small, transient patches in ponderosa pine, mixed 

conifer, or spruce-fir forests. There are close to 500,000 

acres of aspen in the Southwest, seventy-five percent in 

northern New Mexico and the ~mainder in the Mogollon 

Rim-Whte Mountains of Arizona (Brown 1994). 

Aspens can reproduce by cloning from an established 

root system and establish a new stand of trees quickly 

after a fire or other disturbance. Aspens, however, are 

intolerant of shade and eventually lose out to competition when they become overtopped by re-invading 

conifers. Aspen stands are especially valued for their 

scenic quality and use by traditional communities. 

Riparian Wetlands 

Riparian wetlands including cienegas make up less 

than 2 percent of the land of New Mexico and Arizona, but they are the most biologically diverse and 

productive ecosystems in the Southwest. Over 65 percent of Southwestern animals depend on riparian 

habitats during all or part of their life cycles. Millions 

of Southwestern residents use these areas for recreation and agriculture. The most important species of 

Southwestern riparian wetlands are the Fremont cottonwood (Populus fremontii) and the narrowleaf cottonwood (I? augustifolia) (Brown 1994). 
CHAPTER 3: THE HUMAN DIMENSION OF THE LAND 

"The replacement of Indians by predominantly European populations in New England [and the West] was as much an ecological as a cultural revolution, and the 

human side of that revolution cannotbe fully understood until it is embedded in the 

ecological one." William Cronon (1 983) 

The premise of this chapter is that the land, the biological processes, and the physical presence of all living and non-living things are reality; we humans are 

part of that reality. Where does the intellectual human 

stand in relation to this definition of reality? As we 

perceive the non-human through our numerous cultural filters, we create the ideas of nature, wilderness, 

and wildness; we re-create the animals, plants, sky 

and water by naming them and placing real and 

imagined boundaries around them. 

To understand the meaning of natural phenomena 

and one's own relation to nature, people create myths. 

The word "myth is not used here in a negative sense 

as a contrast to "real." Rather, myth stands for the cultural glue that binds people of like communities over 

time. Although myths evolve over generations, they are 

usually based on real people, places, and events. Myths 

become reality to the individuals and groups who create them. There is physical reality, and there is cultural 

reality. The latter consists of artificial codes, ideological 

identities, and objects re-invented by recombination and 

juxtaposition (Clifford 1988). Myths are shared within 

communities of interest and communities of place. 

READING MYTHS 

Solomon (1988) defines semiotics as the analysis of 

ordinary objects for signs of hdden cultural interests. 

His four principles of semiotics are: 

1. Always question the "common sense" view of 

things, because "common sense" is really 

"communal sense," i.e., the habitual opinions 

and perspectives of the tribe. 

2. The "common sense" viewpoint is usually 

motivated by a cultural interest that manipulates consciousness for ideological reasons. 

3. Cultures tend to conceal their ideologies 

behind the veil of nature, defining what they 

do as "natural" and condemning contrary cultural practices as "unnatural." 

4. In evaluating any system of cultural practices, 

one must take into account the interests 

behind it. 

Why is semiotics relevant to forest ecosystem 

health? Perceptions of wildlands continue to "re-create" wildlands. Science, environmentalism, wise-use, 

conservation, and popular culture interpret nature 

according to the mythologes of its own interest 

group. Behind all of these mythologies lies the physical reality of wildlands. Agencies concerned with forest ecosystem health must sift through the cultural 

constructs to find core reality. The Forest Service cannot manage mythological wildlands. 

Long before the arrival of Europeans to the New 

World, Native Americans interpreted their physical 

and mythc ties to the land through oral traditions 

and ceremonies. Guided by a sense of oneness with 

the earth (Allen 1986), they sought to balance their 

lives with all things through reciprocity, giving back 

to the earth as they took food and shelter from it. Ceremonialism was geared to seasonal change; the relation of the rising and setting of the sun, moon, and 

stars to special features on the landscape signalled 

new religious cycles. Mountains were places where 

sacred energy could be received from spiritual beings 

(Leeming 1990). The Southwestern landscapes in 

which Native Americans lived were sacred to them. 

Questing for gold, commerce, and converts, the 

Spaniards moved into the New World in the 16th century. Stories of Aztec and Inca gold hordes fueled 

imaginations and lured expeditions into what would 

later be named the Southwest. Attended by Fray Juan 

de Padilla, Coronado came to the New World to find 
the fabled wealthy and intellectually perfect Seven 

Cities of Antilla and reunite them with the Christian 

world (Kessell 1987). Although the golden civilizations of Mexico and Peru were never discovered in 

the northern lands, future converts to Catholicism for 

the greater glory of God and subjects and new lands 

for the King of Spain were found (Crosby 1972). For 

Spanish colonists, the Southwest was a harsh and 

inhospitable land, remote beyond compare (Kessell 

1989). It was, however, a land granted to them forever 

by their King, and as such it took on the deep cultural 

meaning of the Spanish homeland. 

Over 60 years after Coronado's expeditions in the 

Southwest, English settlements on the other side of the 

continent were thriving on materials grown in the New 

World and exported to Europe. Production of plants 

native to the Americas and plants and animals of European origins were the basis of this commerce (Crosby 

1972). By 1607, English enthusiasm for New World settlement was fueled by the opportunity for religous 

freedom and the potential for commerce between England and these new settlements (Miller 1956). The 

wilderness was not a passive concept to the new American settlers; it represented an historical challenge. From 

wilderness, American farmers could build a life of independence, freedom, and fulfillment-the Jeffersonian 

Arcadia, an ideal garden. As Tocqueville noted from a 

visit to America, "...the wilderness was precious to most 

Americans chiefly for what could be made of it-a terrain of rural peace and happiness" (Marx 1964). 

In the Southwest, these and many other contrasting 

mythologies came together in conflict and uneasy 

accommodation during the 17th, 18th, and 19th centuries as the territory passed from Spanish to Mexican 

to American rule. Mixing mythologies is the core of 

American life, and many mythologies relate to American perceptions of wildlands and wild processes. Preceptions have driven and continue to drive wildland 

management because people cannot be separated 

from the land and their myths of it. 

SOME POPULAR AMERICAN LAND MYTHS 

There Was No Land Management in America 

Before Europeans Arrived. 

To what extent lands of North America were managed by American Indians before Columbus arrived 

in the Americas is not precisely known. Nabhan 

(1995) states, 

"...we are often left hearing the truism, before the 

White Man came, North America was essentially a 

wilderness where the few Indian inhabitants lived 

in constant harmony with nature ... even though 

millions of people spealang over two hundred languages variously burned, pruned, hunted, hacked, 

cleared, irrigated, and planted in an astonishing 

diversity of habitats. And many people imagine 

that these indigenous peoples lived in some static 

homeostasis with all the various plants and animals 

they encountered." 

Although Nabhan may have overstated the scale of 

this impact, his basic point is well taken. Although 

hunter-gatherers who harvested seasonal plant and 

animal resources may have affected animal populations more than their habitats, this was not true for all 

cultures. Sedentary people, agriculturalists, most 

assuredly modified the landscapes around them, 

whether living in groups of ten or over a thousand. 

Before the horse was brought to the New World, 

land use was probably concentrated in localized areas 

around settlements. In the arid Southwest, settlements 

by native peoples or colonists concentrated close to 

the limited water sources, and exploited shallow, 

nutrient-poor soils for agriculture. Near these settlements, trees became building materials and firewood; 

and game was a major food source (Kohler 1992). 

How far might a resident of a 100-year-old village of 

1,000 people have walked to find new fields, firewood, or game-5 to 10 miles? 

Some scholars suggest that European diseases carried by the first explorers had an early and devastating effect on the native populations of eastern North 

America. By the time colonists and settlers first saw 

these "new lands," they may have been abandoned 

and untended for 50 to 200 years. What the colonists 

may have discovered was the regeneration of previously managed forests (Nabhan 1995, Cronon 1983). 

English visitors noted that large sections of the southern New England forest were burned twice a year by 

Indian villagers. According to Thomas Morton 

(Cronon 1983): 

"The Savages are accustomed to set fire of the 

Country in all places where they come, and to 

burne it twize a yeare, viz: at the Spring, and the 

fall of the leafe, [a practice that produced] open and 

parklike [forests where there were] more ground 

fires than forest fires.. ." 
Unlike the East and other parts of the West, ths degree 

of burning was not documented for Southwestern 

native cultures. Given the frequency of natural fires, 

deliberate burning probably would not have been 

necessary (Swetnam and Baisan 1996). It is likely, 

however, that fire was used on a local scale for specific purposes. The Europeans who had not witnessed 

American Indian forest and grassland management 

would probably not have expected or recognized the 

land as having been managed. 

American Wildlands are "Pristine" and 

"Untrammeled." 

As discussed above, American lands were far from 

untouched when Europeans arrived in the New 

World. The Europeans brought with them overwhelming forces of change. From the standpoint of 

the land, however, the most profound invasion force 

to enter North American was not clad in armor but in 

fur, hide, feathers, shells, rinds, and husks. Within 200 

years, much of the biology of North America was 

irrevocably altered by the cattle, oxen, horses, sheep, 

pigs, rats, birds, plants, insects, and fungi brought 

from the Old World. 

Overgrazing coupled with continued burning of 

grasslands provided fertile ground for exotic plants 

and reduced more palatable native species. Many 

plants were purposely introduced by Europeans to 

provide foods to which they were accustomed and 

ornamentals that reminded them of home (Crosby 

1972). The increase in crop plants like wheat, rice, and 

fruits, coupled with corn and potatoes, provided a 

rich food base that could support greater numbers of 

settlers. Using oxen, the rich sod of grasslands and 

meadows could be broken up to allow more intense 

cropping, large food supplies, and even more people 

(Crosby 1972). 

By 1800, the flora and fauna of New England were 

very different from the land described in the journals 

of early colonists. In southern New England, beaver, 

deer, turkey and wolves were near to extinction; 

hordes of cattle overgrazed lands opened by intensive 

burning; native grasses were striped off and soils desiccated. Once constant streams dwindled or disappeared as forests were removed (Cronon 1983). By the 

1830s, machines began to assist humans in the reshaping of landscapes (Marx 1964). 

Southwestern lands were not spared intensive use. 

In the 17th century Spanish demands for tribute compelled the Pueblo Indians of New Mexico to intensify 

agricultural production by expanding their irrigation 

farming. In addition to an array of domestic livestock 

(sheep, goats, cattle, horses, mules, hogs, chickens) 

and new crops (wheat, barley oats, onions, lettuce, 

watermelon, fruit trees), the Spanish also introduced 

native Mexican Indian crops such as tomatoes, chiles, 

cultivated tobacco, and new varieties of corn and 

beans. These introduced species along with the introduction of metal tools had a significant impact on 

native flora, fauna, and soils in the Southwest 

(Wozniak 1995, 1987). 

Early livestock use had an effect in the Southwest 

even before the later 1800s. By 1870, the sheep population in New Mexico increased to 619,000. By the 

1880s, nearly 5 million sheep were grazing in New 

Mexico, and this number did not decrease to 3.5 million until after the turn of the century (de Buys 1985). 

Because sheep graze higher up on steep slopes than 

cattle, their impact on fragile mountain soils is more 

destructive and eventually leads to flooding (de Buys 

1985). The number of cattle in New Mexico increased 

from 148,000 in 1870 to 1.32 million in 1890; in Arizona during the same period, the number of cattle 

increased from 249,000 to 970,000. As trampled and 

naked soils heated up without adequate plant cover, 

cool-season, perennial, native grasses could not reestablish and were sparsely replaced by annual weeds 

from southern deserts. The productivity of most 

northern New Mexican land was lost during this time 

of extreme use (de Buys 1985). Arroyo formation, long 

considered a natural, visual trademark of the Southwest, may have been accelerated by a combination of 

natural climatic fluctuation and overgrazing (Hastings 

and Turner 1965, Cooke and Reeves 1976). 

With the best of intentions, people introduced exotic 

plants into the Southwest to restore degraded natural 

areas. Saltcedar (Tamarix ramosissima), for example, 

was introduced to hold soils on floodplains left bare 

from overgrazing; and Russian-olive (Elaeagnus augustfolia) became a favorite landscaping plant because it 

thrives in arid landscapes with little rainfall. Contemporary diversity of Southwestern riparian ecosystems 

has been greatly reduced by these two plants that 

were so successful in their own reproduction (DickPeddie 1993). Native riparian species could not compete with these exotics; animals dependent on native 

species for food and shelter were impacted. 

Clearly American wildlands have been modified 

by intentional and unintentional human actions over 
thousands of years. Adjectives such as "pristine" and 

"untrammeled" seem idealistic for describing current 

wildland conditions, especially given the events of 

the past four centuries. Although some wildlands 

may still exhibit minimum human impact, the 

primeval, virginal conditions conjured up by the 

words "pristine" and "untrammeled" simply do not 

exist. 

Public Lands Were Created to Preserve 

America's Wildlands. 

The myth that public lands were created to preserve America's wildlands ignores the historical, 

philosophical, and political contexts within whch 

public lands were created. By 1832, America's infatuation with the machine had begun, and the impacts of 

the industrial age were evident on the landscape 

(Marx 1964). For 200 years, grazing, hunting, and timber harvesting gradually had re-shaped wilderness as 

"civilization" moved further west. But machines 

greatly accelerated this conversion of wildlands to 

farmlands and forest plantations as they facilitated 

the movement of raw resources to Eastern markets. 

As wildlands disappeared, some American artists, 

philosophers, poets, and naturalists noted with regret 

the decrease in wild America. Although seldom 

removing themselves from civilization, they realized 

that much of what was considered uniquely American, its wild landscapes, was being lost. They sounded an environmental and philosophical alarm that 

continues to be echoed today. If Americans lose their 

wildlands, do they lose their identity as well as their 

resources? From Thoreau to Bierstadt and Emerson to 

Moran, artists' views of nature profoundly affected 

Americans' perceptions of wildlands. Artists substituted American landscapes for European classical 

heritage (Novak 1980). A young nation could not 

compete with the classical heritage of Europe, considered fashonable by wealthy Americans. But everyone 

in America, rich or poor, could be proud of the spectacular and wild landscapes that rivaled the grandeur 

of the Old World's heritage. 

In 1872, Congress designated Yellowstone the first 

National Park; and by 1900, many more areas in the 

West were added. Parks were created for several reasons. First, with new technological developments in 

transportation, tourism for people of means was 

increasing. America's appetite for dramatic scenery 

was immense. It was now fashionable to see one's 

own country, and the railroads made it possible. Secondly, concerned citizens were fighting back against 

the land practices of "claim, grab, and raid" decried 

by Wallace Stegner (Athearn 1986). 

A motivation similar to that which supported 

national parks also prompted a group of Americans to 

press for the establishment of forest reserves. In 1895, 

a system of forest reserves was established from the 

public domain. Although these lands were also set 

aside to prevent their imminent destruction, the longrange management goals of forests were different 

from those of parks. Parks were managed for scenic 

beauty and historical content; and forests were 

intended for the sustained yield of timber, water, and 

forage. By 1905, Congress, at the urging of President 

Theodore Roosevelt and Gifford Pinchot, created the 

Forest Service to scientifically manage national 

forests. In 1916, Congress established the National 

Park Service to manage the parks for the pleasure and 

education of the American public. 

In 1913, an event that had been unfolding over 

many years reached its conclusion. In the arena of 

public land management, philosophical lines were 

drawn on the banks of the Hetch-Hetchy River in 

Yosemite National Park. Yosemite was the crown 

jewel of John Muifs many travels through American 

wildlands. An advocate of a national park system, 

Muir was incensed when the City of San Francisco 

applied to the federal government for water rights in 

the Hetch-Hetchy Valley. A dam would be needed to 

impound the water within the already established 

boundaries of Yosemite. Muir waged a running battle 

in the news media to keep all utilitarian projects out 

of Yosemite. But Gifford Pinchot, the new Chief of the 

Forest Service, supported the use of public water to 

meet the needs of a growing San Francisco. Muir lost 

the battle to preserve Hetch-Hetchy Valley, and his 

loss sealed his distrust of Pinchot's conservation ideology. If Pinchot was a conservationist (see Pinchot 

1947), then Muir would be a preservationist (see Muir 

1916). Muir and Pinchot, now mythic figures, symbolize the dichotomy of land use philosophies that had 

began over 100 years before (Nash 1967). 

MYTH IN FOREST MANAGEMENT 

Just as forest ecosystems have ecological mechanisms for maintaining stability, human cultural systems have myths to correct imbalances. When 

commodity forestry is perceived as too destructive, 
environmental groups are motivated to action by 150 ed. The interdependence of natural resources, adapting 

years of concern for the preservation of wildlands. to change, and non-commodity uses may be recognized 

When protection of plants and animals is perceived to 

lock out economically dependent local residents, 

some individuals and groups rally around 150 years 

of myths that the Western garden provides their living and freedom. When the availability of natural 

resources for industry and business is perceived as 

threatened, the myth of endless Western resources 

and the American right to convert raw material into 

domestic products are perceived as violated. And 

when the interests and actions of outside groups are 

perceived as threats to traditional cultures, community and spiritual leaders respond in terms of beliefs 

about the sacredness of the land and prior land use 

rights. 

Mythologies are also prominent within the Forest 

Service. Consider, for example, the myths surrounding the ideal of "multiple use." Although the term 

itself came later, the concept of multiple use is derived 

from Pinchot's (1947) utilitarian social philosophy of 

forestry, "the greatest good for the greatest number in 

the long run." Historically multiple use assumes that 

there existed an array of discrete forest interests and 

commodities which could be objectively weighed and 

allocated by a public agency in a wise and fair manner. This allocation is to be made at the local level and 

in such a way as to ensure a continuous flow of use 

and commodity into the future. National forests are 

thus seen as storehouses of resources to be managed 

and regulated for the public good. The agency, it is 

assumed, with its cadre of trained foresters knows 

best how to accomplish this. 

Fire fighting is also steeped in mythology. According to the 1905 Forest Reserves Use Book, "Officers of 

the Forest Service, especially Forest Rangers, have no 

duty more important than protecting the Reserves 

from forest fire." Armed with this belief, the Forest 

Service and other public agencies launched an aggressive and highly effective fire suppression program 

that has dominated forestry for over 60 years. The 

myth that fire is the greatest enemy of the forest was 

reinforced over the years by the powerful symbol of 

Smokey Bear and the most effective public service 

campaign ever waged. 

Both the mythologes of multiple use and Smokey 

Bear influence land managers' perceptions of the land 

as well as their perceptions of a role as stewards of the 

nation's forests. Under these myths, management tends 

to be functional, technology-based, and output-orientbut are gven less weight. Professionalism and agency 

autonomy are highly valued. Public dissatisfaction, 

when encountered, is attributed to the public's failure to 

understand and the need to better educate the public. 

THE SITUATION TODAY 

How do mythologies play out today? The population in the Southwest has been increasing rapidly (see 

Figure 5.5). Unless states, counties, and towns place 

moratoriums on new growth and housing, populations will continue to grow. Many people and businesses moving into the Southwest bring entirely new 

mythology-based perceptions of wildlands with them. 

New mythologies are also at work within the Forest 

Service. As stated in the beginning of this chapter, 

mixing mythologies is at the core of American life. A 

diversity of mythologies may also be a source of 

insight and creativity in finding solutions to problems. Although it may not be an easy process, recognizing and respecting where others are coming from 

is a crucial step in the communication challenge now 

facing the Southwestern Region. 

A review of Solomon's (1988) principles of semiotics may be helpful in looking into what people are 

really trying to say about their forests and themselves. 

Numerous people inside and outside the Forest Service continue to express a desire for national forests to 

be returned to "pre-settlement" conditions. Some 

individuals go so far as to want the Forest Service "to 

get out of the woods and let Nature heal herself." Still 

others see their independent way of life as loggers, 

ranchers, or farmers threatened by outsiders, both the 

government and the urban elite. 

CONCLUSION 

There were vibrant native cultures using Southwestern forests long before Europeans arrived; and 

words like pristine and untrammeled are more idealistic than practical in the context of forest health. 

Nonetheless, public perceptions of the land and what 

it should provide cannot be discounted. Neither can 

an agency's own perceptions of management responsibility go unexamined. Forest health depends on the 

ability of people to communicate and collaborate to 

find not the "right answer" from a single perspective, 
but a range of useful solutions and experiments from 

which we all can learn. 

Aldo Leopold (1949) observes that "the outstanding 

discovery of the 20th century is not radio, or television, but rather the complexity of the land organisms." Are human ideologies and relations any less 

complex? Sustaining forest ecosystems requires all of 

us to recognize that the land and the culture are one. 

Nature matters because we are nature. There is a 

human dimension to ecosystem management. This is 

a difficult task in an already complex and contentious 

social and political environment. A collaborative 

approach to internal and external communications 

seems essential, although it may seem at odds with 

the former Forest Service myth of autonomy. New 

visions that better serve the times can, perhaps, better 

serve public land stewardship. The basic challenge is 

whether we can align our internal mythologies and 

external relationships to successfully address the issue 

of forest health. 
CHAPTER 4: HISTORIC CONDITIONS 

"Evaluating the status of existing ecosystems requires a standard or set of reference points that characterize sustainable ecosystems." Kaufmann et al. (1 994) 

Thousands of years of human occupation preceded 

the first written accounts, paintings, and photographs 

of Southwestern landscapes. We can only guess what 

the earliest occupants thought of their landscape. We 

know that prehistoric peoples altered vegetation by 

farming and burning; they shaped the land by terracing, field leveling, and stream channeling. Archeologists are just beginning to understand the extent of 

prehistoric occupation and do not know how prehstoric activities over the centuries have resonated 

across the landscape. For example, we know little of 

how burning or nutrient depletion by repeated cultivation affects vegetative patterns hundreds or thousands of years later. We need to view the whole 

notion of naturalness in the Southwest through the filter of prolonged and sometimes intensive human 

occupation. In the present and historical past, it is 

often very difficult to distinguish between natural and 

human-caused effects. For instance, what did cause 

widespread arroyo cutting in Southwestern deserts? 

Was it over-grazing, climate change, or a combination 

of both (Hastings and Turner 1965, Cooke and Reeves 

1976)? 

The period used to characterize historic conditions in this chapter is that prior to the MexicanAmerican War of 1848. This date is selected as a 

central point between the 1845 annexation of Texas 

and the 1853 Gadsden Purchase. These events mark 

the political transition from Hispanic to American 

sovereignty in the Southwest and its opening to new 

and increasing waves of settlement. The view 

through time's fuzzy lens becomes a little clearer as 

we approach the present. After the Civil War, members of various expeditions and surveys began to 

photograph the Southwestern landscape. General 

agreement between 18th century photographs and 

16th century written accounts indicate that the 

landscape had maintained some degree of consistency over those centuries. If this agreement were 

valid, then photographs taken in the 1880s (and possibly as late as the 1920s for the Colorado Plateau) 

could represent the general forest character during 

at least the last few centuries. The consistency of 

forest attributes in early Colorado Plateau photographs supports this hypothesis (Hastings and 

Turner 1965, USDA Forest Service photographs 

1901-19683). There is, however, one note of caution 

in use of old photos to characterize the past. Artistic 

bias and commercial interests may have favored certain landscapes and views over more common ones; 

historic photographs may not be representative of 

earlier landscapes. 

CLIMATE 

A description of past forest conditions in the Southwest begins with a review of climate history. 

A1 though regional climates persist for centuries, they 

do change and vegetation responds on a similar scale 

(Delcourt et al. 1983). The forest ecosystems we see 

today or in hundred-year-old photographs are the 

products of species evolution and migration over 

aeons of time on a constantly shifting landscape driven by changes in climate. From a broader perspective and context, the climate during the few centuries 

before 1848 was unique. 

Climates change at a variety of scales (Delcourt 

et al. 1983). Long-term, persistent trends in temperature and humidity determine the extent and location of the various life zones, the elevation at 

which one biotic community replaces another. 

On file at the Cline Librar~ Northern Arizona Universit~ 

Flagstaff, AZ. 
Shifts from one climatic regime to a new pattern FIRE 

can be abrupt. Evidence from Greenland ice cores 

suggests the 1300-year cold spell of the Younger 

Dyras (11,200-10,000 B.P.) ended over a period of 

only a few years (Betancourt et al. 1993). Shortterm fluctuations in the order of years to decades 

determine drought cycles, fire frequencies, and 

pulses of tree reproduction. The Southwest is 

strongly influenced by oscillations in the Pacific 

ocean-atmosphere system; years of El Nino bring 

increased annual precipitation (but less rain in 

summer) and years of La Nina bring the opposite 

(Betancourt et al. 1993). 

Data from geology, paleobotany, and dendrochronology studies at Potato Lake and Chaco 

Canyon permit a reconstruction of the climate history of the Southwest. Potato Lake (Anderson 1993) is 

a high elevation site (7,500 feet) in the Arizona-New 

Mexico Mountains Province. In the mid-Wisconsin 

Period (35,000-21,000 B.P.), the area was dominated 

by mixed conifer species; in the late-Wisconsin 

(21,000-10,400 B.P.) by spruce alone; and for the past 

10,400 years by ponderosa pine. The Chaco Canyon 

and San Juan Basin (Betancourt et al. 1993) is a lower 

elevation region in the Colorado Plateau Province. 

Before 8,000 B.P. a relatively cold and moderately 

wet climate prevailed; the canyons contained a 

mixed conifer forest and the mesa tops a cold desert 

steppe. During the Altithermal Period (8,000-4,000 

B.P.) pinyon and juniper migrated into the area and 

replaced the mixed conifer forests; warm desert 

grasses replaced the sagebrush of the cold desert 

steppe. The cause of these vegetation changes is 

thought to have been the arrival under generally 

warmer conditions of a monsoonal circulation with 

warm wet summers. A cooler and dryer Neoglacial 

Period lasted from 5,000 to 2,000 B.P. The climate of 

the past 2,000 years is considered modern 

(Cartledge and Propper 1993), but it includes several notable, global events-the Medieval Warm 

Period from 1000 to 1350 A.D. and the Little Ice 

Age from 1450 to 1850 A.D. (Nielson 1986). In the 

Southwest, higher average summer temperature 

and precipitation persisted from 950-1130 A.D. 

and prolonged summer droughts occurred from 

1130-1180 A.D. (Cartledge and Propper 1993). 

Cycles are not only in the past. In 1996, Arizona 

endured one of the worst droughts since 1904; tree 

damage was detected on 57,000 acres of Federal 

forests (USDA Forest Service 1996a). 

Both lightning and human-caused fires, once started, could burn until extinguished by rain, or until they 

ran out of fuel (typically when they reached an area 

that had recently burned). Fires could burn for months 

and cover thousands of acres (Swetnam 1990, Swetnam and Baisan 1996). As a result, most forest stands 

(except spruce-fir) burned every 2 to 30 years as lowintensity, area-wide fires. Fire reconstructions in the 

Pinaleno Mountains of southern Arizona demonstrate 

that pre-settlement mixed-conifer forests could have 

burned as frequently as the ponderosa pine forests 

(Grissino-Mayer et al. 1995). With greater moisture levels but heavier fuel loads, spruce-fir forests burned 

much less frequently but at high, stand-replacing, 

intensity (Grissino-Mayer et al. 1995, Veblen et al. 

1994). Research by Cable (1975), Dieterich (1980, 1985), 

Grissino-Mayer et al. (1995), Leopold (1924), and 

Weaver (1951) establish the range of pre-settlement fire 

frequencies for Southwestern forest communities 

(Table 4.1). The role of native peoples in modifying fire 

regimes of the interior West is examined by Arno 1985, 

Gruel1 1985, Barrett 1988, Savage and Swetnam 1990, 

and Veblen and Lorenz 1991. Native cultures used fire 

for a variety of purposes (Pyne 1982, Phllips 1985). In 

addition to incidental burning, there is ample evidence 

that fires were intentionally set for increasing desired 

plant species, improving wildlife habitat, driving 

game animals, and clearing transportation routes. Pinchot (1947) describes a scene where: 

"We looked down and across the plain. And as we 

looked there rose a line of smokes. An Apache was 

getting ready to hunt deer. And he was setting the 

woods on fire because a hunter has a better chance 

under cover of smoke." 

Table 4.1 Frequency of area-wide fires in Southwestern forests prior to European settlement. 

Biotic Community Fire frequency (years) 

Pinion-juniper 

Ponderosa Pine 

Mixed conifer 

Spruce-fir 

Based on data from Cable (1 975), Dieterich (1 980, 

1985), Grissino-Mayer et al. (1 995), Leopold (1 924), and 

Weaver (1 951 ). 
In many areas of the West, American Indians Grande and in the Zuni and Hopi areas. The Hohokam 

altered succession using fire (Gruel1 1985). In the and Salado populations, however, appear to have 

Southwest, however, the historic fire regime does not 

depend on native burning (Swetnam and Baisan 

1996). Lightning is common in many parts of the 

Southwest during periods of high fire hazard; these 

rates and patterns would have prevailed in earlier 

times as well (Schroeder and Buck 1970). Lightning 

ignition alone is sufficient to produce the fire frequencies revealed in various fire-scar chronologies. The 

effect of native peoples on fire in the Southwest 

would probably have been very site- and time-specific 

(Swetnam and Baisan 1994). 

The ecological role of fire in Southwestern forests 

has always been significant. Where fire was more frequent forest communities even developed a dependency on fire as a mechanism for ecosystem 

regulation (Wright and Heinselman 1973). Where fire 

was infrequent such as in the spruce-fir forest, fire 

was still a major abiotic factor, but its effects and integration into the ecosystem had a very different character. Like all disturbances (such as grazing, fuelwood 

collection, mortality from insects and diseases) fire 

affected species composition, the amount, distribution, and proportion of living and dead biomass, and 

various ecosystem functions (e.g., nutrient cycling). 

DEMOGRAPHICS AND LAND USE 

For more than 12,000 years, humans have been an 

integral component of Southwestern forest ecosystems; but the archaeological record is fragmentary 

and poorly sampled. Precise estimates of regional 

populations in prehistoric times do not exist, although 

information on general population trends are evident 

(Dean et al. 1994). For at least 10,000 years, a sparse 

population dependent on wild plants and animals 

occupied the Southwest. Beginning around 300 A.D., 

the population in certain areas of the Southwest 

increased with a shift to greater reliance on domesticated plants and development of more permanent settlements. By 600 A.D., the increase was regionwide. 

With the growth of larger, more complex communities 

throughout the region, the population peaked at perhaps 130,000-150,000 in the 11 th to 13th centuries 

(Dean et al. 1994). Beginning about 1300 A.D., many 

areas of the Southwest were abandoned; and the 

regional population probably declined, although to 

what degree is uncertain. Anasazi populations appear 

to have re-aggregated into large pueblos along the Rio 

- - 

dispersed. such shifts in population and settlement 

had probably been repeated throughout prehistory in 

various ways and at various scales as societies 

responded to changes in climate, resource availability, 

and political, economic, and social pressures (Cordell 

1984, Gumerman 1988, Tainter and Tainter 1996). 

These fluctuations in late prehistoric times, however, 

were dwarfed by the major reduction of native populations that began with the arrival of Spanish 

colonists. 

Impacts of prehistoric populations are thought to 

have been minimal or highly localized until the 11 th 

and 12th centuries. At that time, farming, fuelwood 

cutting, and game hunting greatly increased around 

new, dense settlements. There is evidence in the 

Phoenix Basin that main irrigation canals during the 

Classic Hohokam Period (1200-1400 A.D.), totalled 

more than 500 kilometers (Spoerl and Ravesloot 1994) 

and that irrigated fields covered 150 square kilometers (Nicholas and Neitzel 1984). In other areas where 

dry farming and floodwater farming were practiced, 

similar intensive use and alteration of the landscape is 

apparent (Fish and Fish 1992, Lang 1995). Impacts on 

the environment in late prehistoric times, along with 

drought, crop failure, and population stress, probably 

contributed to local and regional cycles of settlement 

abandonment, and relocation. 

In the Southwest, as elsewhere in the New World, 

the arrival of Europeans had a catastrophic impact on 

native populations. Epidemics, starvation, hostilities, 

subjugation, and relocation devastated native peoples. 

Pueblo populations in New Mexico, for example, 

were reduced from perhaps as many as 60,000 in the 

1500s to fewer than 7,000 by 1706 (Schroeder 1979). 

Some groups disappeared entirely, including the Piro 

of central New Mexico and the Sobaipuri of southern 

Arizona. The degree to which the effects of disease 

may have preceded the actual arrival of Spanish 

colonists is unknown. 

The Spanish population during the Colonial Period 

remained relatively small, due to their dependence on 

irrigation agriculture and hostile relations with the 

Apaches, Navajos, Utes and Comanches. The Spanish 

population in New Mexico is estimated to have been 

only 2,500-3,000 in 1680, and was perhaps no more 

than 20,000-25,000 by the late 18th century (Simmons 

1979). Because the population was small except along 

certain permanent streams, regional impacts during 
the Colonial Period were not much different from 

those of late prehistoric times. The notable changes 

were the shift to more intensive irrigation and the 

introduction of new crops and animals. The population grew during the later Mexican Period; sheep 

grazing increased significantly; and mining expanded 

in certain areas. 

TIMBER AND FUELWOOD RESOURCES 

Prehistoric populations used wood for fuel, tools, 

and construction. In late prehistoric times, pinyon and 

juniper were locally depleted in some areas (Bahre 

1991, Betancourt et al. 1993, Cartledge and Propper 

1993, Kohler 1992, Stiger 1979). As many as 200,000 

ponderosa, spruce, and fir beams were used for construction of the 10 major puebloes and kivas at Chaco 

Canyon (Betancourt et al. 1986). At least near large 

settlements, impacts on adjacent upland forests may 

have been significant. 

In historic times prior to 1848, only small-scale utilization of timber resources was possible because of 

technological and transportation limitations. Native 

American and Hispanic populations used the forests 

for lumber in domestic construction and for firewood. 

Woodland and riparian forests were affected, especially near areas of population growth. The riparian 

bosque of the Middle Rio Grande Valley, for instance, 

had been virtually eliminated by Puebloan and Hispanic farmers before 1848 (Abert 1848a, Wozniak 

1987). But impacts on upland forests were probably 

negligible before the introduction of commercial logging, mining, and railroads in the late 19th century. 

FOREST INSECTS AND PATHOGENS 

For millennia, trees of Southwestern forests have 

been host to numerous species of herbivorous insects, 

pathogenic or saprophytic fungi, and parasitic plants. 

These species co-evolved with their hosts as members 

of dynamic, interacting communities. Through their 

ability to cause widespread tree mortality, defoliation, 

decay or deformity, some of these species achieved significant ecological importance as disturbance agents. 

Along with fire, these agents are among the more 

important regulators of forest density, composition, 

and structure. Forest conditions in turn affect the distribution and reproduction of forest insects and pathogens. Directly and indirectly, these species interact 

with other members of the ecological community 

influencing various ecosystem processes, providing 

food and creating habitat for other organisms, affecting nutrient recycling, and influencing fire behavior. 

The species of primary interest in the Southwest 

include bark beetles, several species of defoliating 

insects, dwarf mistletoes, and root decay fungi. Bark 

beetles and defoliators are usually present in low populations, but they will periodically increase to outbreak 

levels. Although populations of dwarf mistletoe and 

root decay fungi fluctuate, their rates of change are 

much slower. These species, however, are very persistent and affect forests annually rather than periodically. 

Descriptions of previous outbreak patterns for 

insects or distribution and abundance of pathogens 

are developed from inference or observation. Details 

for prior disturbance regimes of insects and 

pathogens may be inferred if one assumes their fundamental biology (e.g., host preferences) has not 

changed and if one has data on past climate and vegetation. Observations on the distribution and severity 

of outbreaks prior to the past few decades are limited 

to early written reports and photographs and to later 

reports of forests little affected by harvest, grazing, 

and fire. Some characteristics of prehistoric outbreaks 

can also be determined by various reconstruction 

techniques (e.g., paleobotany and dendrochronology). 

The host and environmental requirements of native 

insects, fungi, and parasitic plants has probably 

changed little over the recent centuries, so it is reasonable to expect that where and when conditions were 

suitable, these disturbance agents would have been 

active. Systematic surveys and reporting of insect outbreaks and disease occurrence only began in recent 

decades (unpublished reports4 and USDA Forest Service 1972). As mentioned previously in reference to 

old photographs, the early reports must be interpreted with caution, not because they are inaccurate, but 

early entomologists may have viewed forests with 

different objectives and values ("conceptual filters.") 

Bark Beetles 

Numerous species of bark beetles attack and lull 

trees (Furniss and Carolin 1977). Bark beetles generally 

have a narrow host preference wihn several related 

Forest insect conditions, R-3, 1918- 1952; photocopied letters 

and annual reports on file; Flagstafl: AZ: U. S. Department of Agriculture, Forest Service, Arizona Zone Entomology and Pathology 
genera or a single genus; wihn portions of a beetle's 

range only a single host species may be available 

(Wood 1982). In the Southwest, the most important 

bark beetles on ponderosa pine are the roundheaded 

pine beetle (D. adjunctus), western pine beetle (D. brevicornis), mountain pine beetle (Dendroctonus ponderosae), 

pine engraver (Ips pini), and the Arizona fivespined ips 

(I. lecontei). The Douglas-fir beetle (D. pseudotsugae) on 

Douglas-fir, the fir engraver (Scolytus ventralis) on 

white fir, the spruce beetle (Dendroctonus rufpennis) on 

Engelmam spruce, and the western balsam bark beetle 

(D yocoetes confisus) on subalpine fir are also important 

bark beetles. Successful attack usually leads to rapid 

tree death, but if attack is restricted to only a portion of 

the bole, top-killing or strip-lulling may occur (Stark 

1982). At low population levels, bark beetles are usually restricted to scattered individual trees that have been 

weakened by disease, old age, or competition and to 

fresh logs and slash caused by windthrow or snow 

breakage. In outbreaks, small groups of killed trees 

eventually merge into large stands of dead trees. 

Bark beetles affect and are affected by the forest 

community in numerous ways. By selectively hlling 

trees of certain sizes and species, bark beetles change 

tree density species composition, and size structure of 

the forest (Schmid and Frye 1977). Extensive and 

severe outbreaks can increase fire hazard (Martin and 

Mitchell 1980). The beetles, their associates, and successors provide food for insectivorous birds (especially woodpeckers); the resulting snags provide habitat 

for cavity-dependent species. Changes in forest conditions brought on by beetle-caused mortality modify 

the environment for numerous other species. Principal factors that influence bark beetle outbreaks are 

susceptible host population, weather, and natural enemies. Factors that lower tree resistance, such as poor 

site, overcrowding, drought, injury and disease, favor 

outbreaks. Depletion of suitable hosts, extreme cold 

temperature, and natural enemies (insect predators 

and parasites, fungal diseases, and birds) contribute 

to population declines. 

The earliest published reports of bark beetles in the 

Southwest date from the early 1900s; information 

prior to 1848 is scarce. In the early 1900s, entomologists from the USDA Bureau of Entomology conducted the first detailed investigations on various species 

of Dendroctonus beetles in Arizona and New Mexico 

(Hopluns 1909). From their reports, it appears that 

large outbreaks occurred in certain forest types and 

regions but were rare or insignificant in others. 

Hopkins (1909) reports an outbreak of spruce beetle 

on the slopes of Sierra Blanca Peak, south central New 

Mexico. Baker and Veblen (1990) use historic photos 

and dendrochronology data to reconstruct disturbance regimes. They determined that the spruce beetle has been a major disturbance agent, comparable to 

fire, from central New Mexico to Colorado since the 

19th century. Because fire suppression and logging 

have had less effect on spruce-fir forests than other 

communities, disturbance regimes observed today are 

probably a good reflection of what they had been in 

earlier historic times. 

Hopluns (1909) notes that levels of pine beetle 

activity were less in the Southwest than he had 

observed in other Western regions. Woolsey (1911) 

concurs that mortality from the mountain pine beetle 

was less continuous and extensive in Arizona and 

New Mexico than elsewhere. These are curious 

reports considering that at the time (early 1900s) the 

Southwest was experiencing a severe drought whch 

ought to have stressed trees and made them susceptible to attack. On the other hand, even today, forests of 

large, widely-spaced pines and few understory trees 

rarely support outbreaks. 

The exception to observations of limited pine beetle 

activity in the Southwest is found on the Kaibab 

Plateau of northern Arizona. Blackman (1931) provides 

evidence for early outbreaks of mountain pine beetle in 

ponderosa pine. This section of the Colorado Plateau 

Province seems to have had a long hstory of large outbreaks by the mountain pine beetle. The largest outbreak occurred between 1917 and 1926 and lulled 

about 12 percent of the ponderosa pine growing stock. 

Five earlier outbreaks dating back to 1837 were identified, but neither their extent nor magnitude are well 

documented. Why pine bark beetles were so active 

here and not so elsewhere is an intriguing question. 

Defoliating Insects 

Western spruce budworm 

The western spruce budworm (Choristoneura occidentalis) feeds on foliage of true firs, Douglas-fir, and 

spruce throughout the western United States. In the 

Southwest, its principal hosts are white fir and Douglas-fir (Linnane 1986). Larvae feed primarily in buds 

and on foliage of the current year. Complete defoliation occurs when outbreaks persist for several years. 

Sustained heavy defoliation results in decreased 
growth, tree deformity, top-killing, and death. Standlevel effects include changes in stand structure and 

composition. Tree mortality is generally more prevalent in the smaller, suppressed, understory trees, so 

outbreaks result in fewer understory trees and 

increases in the average diameter. Species composition shifts to nonhost or less susceptible species. In 

mixed-species stands where true fir, spruce, or Douglas-fir are climax species, budworm outbreaks 

increase the relative abundance of early seral species 

such as ponderosa pine or southwestern white pine 

(Wulf and Cates 1987). In stands with only late seral 

hosts, outbreaks are a natural thinning from below, 

removing understory trees and stimulating growth of 

overstory trees. 

In addition to the direct effects on forest trees, western spruce budworm affects other members of the forest community. Twenty-six species of birds are known 

to feed on budworm. Some of these consume large 

numbers of budworm, and their populations may 

increase in outbreak areas (Garton 1987). Outbreaks of 

Douglas-fir beetle sometimes follow after those of the 

western spruce budworm. 

Swetnam and Lynch (1989,1993) use dendrochronology to reconstruct the long-term, regional outbreak 

hstory of western spruce budworm in northern New 

Mexico (Southern Rocky Mountain Province). Nine 

regional outbreaks are identified from 1690 to 1989, 

with a periodicity of 20 to 33 years, and duration within 

stands of approximately 11 years. Most stands, including one over 700 years old, had endured multiple infestations, suggesting that Douglas-fir and budworm may 

coexist in the same stands over long periods. Budworm 

activity tends to coincide with increased spring precipitation. Budworm hstory and behavior in other Southwestern provinces is expected to be different, but 

research in these areas is not complete. 

Western tent caterpillar 

The western tent caterpillar (Malacosoma californicum) 

is a native insect that feeds on the foliage of aspen and 

is an important defoliator in the Southwest. Outbreaks 

occur sporadically and can result in extensive defoliation, growth loss, top kill, or even mortality. Outbreaks 

typically persist in an area for several years and flare 

up in one stand and then another. In a few areas, however, there have been repeated sustained outbreaks 

(Jones et al. 1985). Outbreaks eventually subside from a 

variety of biotic factors, particularly natural enemies 

such as viruses, insect parasites and predators, and 

birds. The most important control is a nucleopolyhedrosis virus which affects larvae (Furniss and Carolin 

1977). The authors are unaware of any reports of the 

incidence or activity of hs insect prior to 1848, but if 

aspen were more extensive then, outbreaks could also 

have been more common. 

Root Decay Fungi 

Root diseases are common throughout the Southwest in many stands of mixed conifer and spruce-fir 

forests and some pinyon or ponderosa pine stands 

(Wood 1983). The most important root diseases are 

caused by the decay fungi Heterobasidion annosum 

(affecting ponderosa pine and white fir), Phaeolus 

schweinitzii (primarily affecting Douglas-fir), lnonotus 

tomentosus (affecting spruce) and Armillaria spp. 

(affecting nearly all species). These fungi injure trees 

by decaying and killing roots. Spread occurs by winddisseminated spores which infect through basal 

wounds, through root contacts between healthy and 

infected trees, or through rhizomorphs (only for 

Armillaria). These fungi can persist for decades in the 

roots of stumps and snags and infect susceptible 

regeneration through root contact (Shaw and Kile 

1991, Otrosina and Cobb 1989, Tkacz and Baker 1991). 

Root disease infection reduces growth and survival 

and increases risk of mortality by bark beetles or 

wind throw. 

Although some seedling and sapling trees are 

killed by root disease fungi, their principal ecological 

effect is through the death of canopy trees, either as 

single individuals or groups in slowly expanding 

patches. Disease centers persist for hundreds of years 

and appear as openings with progressively more 

recently-killed trees at the edge. Some regeneration 

may establish within a disease center, but these trees 

only escape mortality for a few years. Because there 

are species differences in susceptibility and tolerance, 

affected stands may exhibit species conversion (even 

from trees to brush). Increases in canopy diversity 

greatly impact habitat quality; whether the change 

benefits or harms a species depends on its individual 

requirements. 

Although the authors know of no early reports 

describing the distribution and extent of root disease 

centers in the Southwest, their longevity and ubiquity 

suggest that root disease fungi have always been 

important disturbance agents, especially on more 

mesic sites (Wood 1983). 
Dwarf Mistletoes 

The dwarf mistletoes (Arceuthobium) are highly specialized dicotyledonous parasites of conifers 

(Hawksworth and Wiens 1996). Most conifers species 

in the Southwest are parasitized by one or another 

species of Arceuthobium. Because of their abundance 

and severe damage to infected trees, the most important dwarf mistletoes are the southwestern dwarf 

mistletoe (A. vaginaturn subsp. cryptopodurn) on ponderosa pine and the Douglas-fir dwarf mistletoe (A. 

douglasii) on Douglas-fir. Mistletoes acquire their 

water, mineral nutrients, and carbohydrates from a 

living host (Tocher et al. 1984), thereby reducing and 

re-allocating host growth. Many species of mistletoe, 

including the southwestern dwarf mistletoe and the 

Douglas-fir mistletoe, induce proliferation of dormant 

buds, localized swellings, and retention of infected 

branches; leading to the formation of distinctive 

witches brooms. Although intensification within an 

infected tree is slow (Geils and Mathiasen 1990), survival is greatly reduced (Hawksworth and Geils 

1990). 

Dwarf mistletoes affect wildlife habitat both directly and indirectly (Hawksworth and Wiens 1996). 

Mistletoes provide food, foraging sites, and nesting 

for numerous species; structural changes from 

brooms, snags, and openings (Parmeter 1978, Tinnin 

1984) benefit the abundance and richness of nesting 

passerine birds (Bennetts et al. 1996). 

The spread and intensification of dwarf mistletoe 

are affected by numerous host, stand, and environmental factors. Site quality, host vigor and age, stand 

density composition, and structure are several of the 

more important factors (Parmeter 1978) in determining the rate of mistletoe increase. In the historic period, fire had been a significant factor in determining 

mistletoe distribution and persistence (Alexander and 

Hawksworth 1976). Although severe crown fires can 

sanitize an infested stand, partial burns leave scattered infected seed trees and insure early re-infection 

of the regeneration. Increased fine fuels and brooms 

on infected trees provide a fuel ladder to carry 

ground fire into the crown, thereby leading to complete, stand-replacing fire. Even in low-intensity fires, 

mistletoe reduces the survival of infected trees (Harrington and Hawksworth 1990). 

Although there is little information on the previous 

abundance of dwarf mistletoes, they were probably 

already well distributed throughout the forests of the 

Southwest by historic times. Paleobotanical evidence 

supports the hypothesis that these parasites have 

been in western North America since the Miocene 

Epoch (Hawksworth and Wiens 1996). Because 

spread is relatively slow and long-distance dispersal 

rare, the extent of mistletoe distribution in the historic period is probably well reflected by the current 

distribution. Based on present understanding of 

mistletoe ecology (Parameter 1978) and evidence of 

previous forest conditions and fire frequency one can 

infer that mistletoe abundance may have been lower 

in the historic period. 

HISTORIC CONDITION BY 

FOREST COMMUNITY 

Woodlands 

Prior to 1848, many of the areas now occupied by 

dense woodlands were predominantly open, diverse 

communities of trees, shrubs, and perennial grasses 

and forbs. However, there were dense woodlands 

reported early in the 19th century. Abert (1848a, 

1848b), for example, describes a trip between Santa Fe 

and Taos which began in a pinyon woodland with no 

grass. From the plateau east of the Rio Grande, he 

entered the canyon at Embudo where he reports little 

pasturage and that residents raised goats because 

there was insufficient vegetation for cattle. Leopold 

(1951) compares 20 pairs of photographs in stands of 

pinyon-juniper from nine different geographic localities. The earliest of the pairs were taken between 1895 

and 1903; the latter were taken between 1937 and 

1946. The number of trees increased in 7 pair, 

remained unchanged in 10 pair, and decreased in 3 

pair. 

Woodlands consist of dispersed groups of pinyon, 

juniper, or oak; the areas between tree patches may 

be mostly bare or covered by sparse litter, shrubs, or 

grasses. The pattern of tree patches is strongly influenced by ecosystem conditions and processes both 

below ground and above. Variations in soil depth, 

nutrients, and microbes interact with seasonal annual drought, plant competition, fire, grazing, and 

insect-pathogen attack (Gehring and Whitham 1995, 

Klopatek et al. 1990, Leopold 1924). In the historic 

period, native use of woodlands for timber and fuelwood had a significant effect (Betancourt et al. 

1986). 
Ponderosa Pine 

Numerous documents (e.g., Biswell et al. 1973, 

Brown and Davis 1973, Cooper 1960) refer to historic 

ponderosa pine stands as open, parklike, and with a 

vigorous and abundant herbaceous understory. Captain Sitgreaves in 1854 describes an apparently typical 

ponderosa pine scene where "the ground was covered 

with fresh grass, and well timbered with tall pines." 

Photographic and written records of historic forest conditions and archaeological reconstructions suggest that 

the characteristic vegetation was a grass matrix with 

individuals, clumps, and stringers of large and variously-sized trees of almost exclusively ponderosa pine. 

An area now wihn the Coconino National Forest is 

described in a U.S. Geological Survey (1904) report as: 

"A yellow-pine forest, as nearly pure as the one in 

this region, nearly always has an open growth, but 

not necessarily as lightly and insufficiently stocked 

as in the case in this forest reserve. The open character of the yellow-pine forest is due partly to the 

fact that the yellow pine flourishes best when a considerable distance separates the different trees or 

groups of trees. It is very evident that the yellowpine stands, even where entirely untouched by the 

ax, do not carry an average crop of more than 40 

per cent of the timber they are capable of producing 

... The yellow-pine forest in the reserve is, broadly 

speaking, a forest long since past its prime and now 

in a state of decadence ... Apparently there has been 

an almost complete cessation of reproduction over 

very large areas during the past twenty or twentyfive years (due mostly to sheep use), and there is no 

evidence that previous to that time, it was at any 

period, very exuberant." 

Although the popular early descriptions of the ponderosa pine forest call attention to the parklike stands, 

there are also descriptions which refer to dense cover 

(Woolsey 1911). An accurate picture of the pre-settlement ponderosa pine forest would most likely 

describe a mosaic not only with an open, grass savanna and clumps of large, yellow-bark ponderosa pine, 

but also with a few dense patches and stringers of 

small, blackjack pines (young ponderosa pine). Ponderosa pine naturally regenerates rarely, but then 

reproduces with an over abundance of seedlings and 

a high rate of juvenile mortality (Pearson 1931). The 

large yellow-bark ponderosa pine of late 1800s were 

probably survivors that emerged from dense patches 

established during rare episodes of successful reproduction (climatically unusual periods of high moisture and infrequent fires). These patches would have 

provided needed cover for not only various wildlife 

species (e.g., wild turkey Meleagris gallopava) but also 

the conditions for mistletoes and bark beetles to persist and even locally flourish. 

The typical climate over the several centuries prior 

to 1848 and the development of a fire-dependent vegetation reinforced a fire regime of frequent, low-intensity burns (Covington and Moore 1994b). On an 

area-wide basis, surface fires burned within the montane zone where ponderosa pine is either climax or 

sera1 every 4.8 to 11.9 years (Weaver 1951). Fires of 

ths frequency were sufficient to normally prevent 

reproduction by ponderosa pine or other species of 

the mixed conifer community. These fires, however, 

encouraged development of grassy understories and 

retention of large, open-grown ponderosa pine. 

The typical climate of the ponderosa pine zone 

includes an adequate, annual amount of moisture for 

good vegetative growth and conditions favorable for 

frequent early summer fires (Harrington and Sackett 

1992). Winters are relatively mild (average slightly 

above 30 F) and precipitation as snow saturates the soil 

(Schubert 1974). Rainfall minimums occur in May and 

June (some areas receive less than 0.5 inch). The spring 

dry season is accompanied by increasing air temperatures, low humidity, and persistent winds. The drought 

is broken in early to mid-July with development of 

almost daily thunder and lightning storms; July and 

August are the wettest, warmest months. A second dry 

season occurs in the fall. Ths climatic pattern is particularly conducive for development of a pine-grass 

savanna maintained by frequent surface fires. 

Open stands of ponderosa pine under a frequent 

fire regime are capable of supporting a productive 

understory and associated grazing populations. Clary 

(1975) reports that open pine stands can produce at 

least 200 to 300 pounds per acre of herbaceous material; Cooper (1960) estimates that production could 

exceed 1,600 pounds per acres in frequently burned 

stands. These high levels are the result of surface fires 

which increase nutrient cycling and reduce competition from woody reproduction. Needle cast and litter 

from the previous yeafs grassy and herbaceous growth 

form a highly flammable fuel that is easily dried out 

in the spring and ignited in the early dry lightning 

storms (Pyne 1982). Because fires are frequent, large 
amounts of woody fuel do not accumulate and crown 

fires are uncommon. These frequent, surface fires kill 

small trees, but the still dormant grasses and forbs 

survive, and large trees escape damage because of 

their high crowns and thick barks (Biswell et al. 1973). 

These forests (Biswell 1972, Cooper 1960, Hall 1976, 

Weaver 1947) support elk and deer as the dominant 

grazers; disease, predators, and other population regulation mechanisms keep vegetation and herbivores 

in balance. 

The more dense and younger stand structures of 

the historic ponderosa pine forest were the result of 

special circumstances in the interaction of climate and 

site. Even though ponderosa pine reproduction was 

rare, there were occasional wet cycles as long as 15 to 

20 years without fires when ponderosa pine could 

regenerate (Swetnam and Dieterich 1985). The regeneration cycle required seed production, establishment, 

and survival to an age at which the young tree could 

successfully compete and endure surface fires. In the 

historic period, most large trees were killed by lightning (and associated fire), dwarf mistletoe, bark beetles, windthrow, or senescence. When single or small 

groups of trees died and fell, they were inevitable 

consumed by surface fires. Ths more severe, but 

localized, fire treatment produced mineral soil 

seedbeds and reduced grass competition, thereby creating a favorable microsite for establishment (Cooper 

1960). Within these severely burned microsites with 

little competition and fuel, seedlings could survive, 

grow, and develop their competitive ability and resistance to fire. Replication of this pattern within the 

pine-savanna resulted in an uneven-aged forest composed of small, relatively even-aged groups (Cooper 

1960). 

Mixed Conifer 

Early descriptions of the mixed conifer forest indicate 

they included a variety of conditions depending on 

the time since and the severity of the most recent 

burn. Lang and Stewart5 describe the mixed conifer 

forest on the North Kaibab Plateau (Colorado Plateau 

Province) in 1909. Although the date is later than 

1848, this particular region had been only sparsely 

Unpublished report titled Reconnaissance of the Kaibab 

National Forest, unpublished survey report circa 1910 on file 

Williams, AZ: U. S. Department of Agriculture, Forest Service, 

Kaibab National Forest. 

settled by that time. They describe most mature Douglas-fir (as well as white fir and blue spruce) as "deteriorating"; they probably mean these trees were 

decayed, had poor crown form, broken tops, and hollow bases typical of repeatedly fire-damaged trees. 

Lang and Stewart also note that Douglas-fir regeneration was "healthy and vigorous"; and often dense 

stands of pole-sized trees covered large areas, especially on more mesic sites and under aspen. The older 

stands had probably survived numerous, light fires. 

On xeric or warm-dry sites (white fir and Douglas-fir 

habitat types, and those with sera1 ponderosa pine) 

mixed conifer stands burned about every 5 to 12 years 

(Weaver 1951). On mesic or cool-moist sites 

(spruce-fir habitat types) in the Whte Mountains of 

Arizona, area-wide fires occurred with an average 

return interval of 22 years (Dieterich 1983). As the 

interval between fires increases more fuel accumulates and the likelihood of a stand-destroying crown 

fire increases. The younger stands described by Lang 

and Stewart had probably established following a 

severe fire. Moir and Ludwig (1979) declare that most 

mixed conifer stands are established in this manner. 

These severe fires may either directly produced a 

stand of conifers or a stand which first goes through 

an aspen stage (Pearson 1931, Pearson and Marsh 

1935). 

Spruce-Fir 

Because many spruce-fir forests in the Southwest 

had been little affected by logging, grazing, or fire 

suppression until very recently, the historic conditions 

and disturbance regimes of this community can be 

reconstructed with good precision and reliability. 

The major disturbances in the spruce-fir forests of 

the Southwest are fire and bark beetles (Baker and 

Veblen 1990, Schmid and Frye 1977). Although these 

agents are capable of reshaping whole landscapes by 

conflagration or outbreak, these events are relatively 

infrequent (loo+ years between major disturbances, 

see Veblen et al. 1994). In these wet forests, ignitions 

are rare, but heavy fuel accumulations and steep 

slopes result in high-intensity, crown fires lethal to the 

subalpine vegetation (Grissino-Mayer et al. 1995). The 

different species of bark beetles are selective for either 

spruce (usually developing in blowdown) or subalpine fir (often associated with root disease). Snags 

created by these events can remain for decades 

(Schmid and Hinds 1974). The species and patterns of 
regeneration are highly variable and depend in the 

long term on climate (Anderson 1993) and in the short 

term by site conditions and immediate disturbance 

hstory (Rebertus et al. 1992, Fatten and Stromberg 

1995). On wetter sites protected from intense radiation, Engelmann spruce and subalpine fir usually take 

and hold early dominance of the site (Fowells 1965). 

On drier sites, aspen, Douglas-fir, and southwestern 

white pine may become established initially and 

spruce and fir later emerge as dominants (Lebarron 

and Jemison 1953). 

Aspen 

Although aspen is usually successional to conifers, 

the aspen community has always been an important 

component of Southwestern forests. Precise estimates 

of forest area occupied by aspen before the mid-19th 

century are not available, but since that time acreages 

have declined with cessation in burning (Jones and 

DeByle 1985). The successional dynamics and ecological role of aspen stands are well known and little 

changed since the historic period. 

Aspen stands are usually very quite wet and do not 

readily burn; aspen stems, however, have only a thin 

bark and are easily killed by a light fire (Baker 1925). 

After a fire, aspen re-sprout or sucker from shallow 

lateral roots (Gruel1 and Loope 1974). Although aspen 

is a climax species on some sites, it is usually sera1 to 

conifers (Mueggler 1976). This replacement is gradual 

and can take from 100 to 200 or more years (Bartos et 

a1 1983). If an aspen stand is within a mixed conifer 

forest, conifers can become established'within a single 

decade (Jones 1974). Because aspen stands are so different from conifer stands, they are very important for 

landscape diversity and wildlife habitat. Although 

aspen stems are short lived and snags do not stand 

long, the wood is soft, often decayed, and therefore 

useful to cavity-dependent species. Young sprouts are 

heavily browsed by elk and deer. 

Riparian Wetlands 

The Colorado and Rio Grande River systems in Arizona and New Mexico extend from headwater tributaries in high, forested mountains to the lowlands of 

the subtropical Sonoran and Chihuahuan Deserts 

(Minckley and Rinne 1985). Continuous corridors of 

riparian vegetation once covered hundreds of miles 

along desert rivers in the Southwest. Besides forested 

riparian communities, there were riparian shrublands, 

marshlands, and grasslands. These plant communities 

were found at elevations from high wet meadows and 

cienegas, to tree-banked streams, to slack water 

sloughs and marshes-the alpine, montane, and 

floodplains-plains riparian ecosystems (Dick-Peddie 

1993). 

Riparian ecosystems served as permanent habitat 

and seasonal migration routes for many species of 

birds and mammals. Rivers and spring-fed cienegas 

supported specialized, endemic fish species. Beaver 

(Castor canadensis) required water and created ponds 

to retain it during periods of low flow. Open water for 

drinlung was essential for some animals such as 

doves and bats (e.g., the spotted bat, Euderma maculatum). Other species like the southwestern willow flycatcher (Empidonax trailii extimus) and the ferruginous 

pygmy owl (Glaucidium brasillianum) depended on the 

special plant and animal communities of a riparian 

wetland. 

Alpine plant associations in the Southwest are dominated by graminoids-especially, sedges or Carex, 

other aquatic plants in the genera Cyperus, Juncus, and 

Scirpus, and grasses of the genera Deschampsia, 

Agrostis, and Glyceria. By trapping sediments moving 

over the channel bottom these native aquatic plants 

are important for protecting the long-term stability of 

alpine meadows or cienegas. 

A large proportion of the Southwest's "live" streams 

pass through the upland montane forests of the mixed 

conifer and ponderosa pine communities. The riparian zones themselves are usually narrow, often following relatively steep stream channels in restricted 

valleys. The watercourses are flanked by hardwood 

and coniferous riparian plant communities. Narrowleaf cottonwood, box-elder (Acer negundo), bigtooth maple (Acer grandidentatum), Scouler willow 

(Salix scouleriana),. and arroyo willows (Salix lasiolepis) 

are typical hardwoods. White fir and blue spruce are 

the common conifers in and adjacent to riparian 

ecosystems (Szaro 1989, Minckley and Brown 1994). 

These streams usually flood from snowmelt in the 

spring; and many riparian species depend on overbank flooding for seed transport and burial in fresh, 

fertile alluvial sediments. Historically seed shedding 

and flooding usually coincided. 

The vegetation and stream channels between the 

montane and subtropical floodplains are markedly 

diverse. In steep terrain, watercourses are often 
confined to narrow canyon areas where riparian 

vegetation is restricted. Broader riparian zones 

occur in wider valley bottoms. This warm, temperate, mid-elevational zone supports mixed broadleaf 

forests of Arizona sycamore (Platanus wrightii), Arizona walnut (Juglans major), velvet ash (Fraxinus 

velutina), and Bonpland willow (Salix bonplandiana) 

(Szaro 1989, Minckley and Brown 1994). 

Historically, the low desert, subtropical zone riparian areas supported gallery forests of Fremont cottonwood and Gooding willow (Salix gooddingii). 

Understory communities include bosque-forming 

mesquite (Prosopis) on terraces and coyote willow 

(Salix exigua) in wetter areas. Historical records state 

that major rivers in the hot desert zone flowed 

through riparian gallery forests, densely vegetated 

flood plains, and substantial marshlands (Minckley 

and Rinne 1985). 

WILDLIFE 

As forest vegetation and landscapes evolved over 

millennia, so did their accompanying wildlife. Little is 

known about the history of many wildlife species. 

Grass and shrub communities of the intermountain 

portions of the West evolved largely in the absence of 

large hoofed herbivores (Mack 1989). Elk (Cervus 

elphus), mule deer (Odocoileus hemionus), pronghorn 

(Antilocarpa americana), bighorn sheep (Ovis 

canadensis), and occasionally bison (Bison bison) were 

the dominant grazing and browsing animals. The 

more open canopies in woodland, ponderosa pine, 

and mixed conifer forests favored wildlife species 

such as deer, turkey, some songbirds, and small 

rodents. Some species such as the northern goshawk 

(Accipiter gentilis atricapillus) preferred forests with 

more closed canopies; others such as the Mexican 

spotted owl (Sirix occidentalis lucida) preferred habitats 

with vertical structure, as provided in steep canyons 

or tall, diverse forests. 

Numerous authors (Kay 1990,1992,1994a, 1994b; 

Koch 1941; Rawley 1985) report that deer, elk, antelope, and bighorn sheep were rare or absent in the 

Rocky Mountains during the early 1800s. Davis (1982) 

reviews the status of wildlife and hunting in Arizona 

from 1824 to 1865. Mule deer and pronghorn were the 

game animals most often encountered, but hunting 

success was no better than today. Bighorn sheep 

remained in rugged mountainous districts that were 

avoided by early travelers so few encounters were 

reported. Davis (1982) goes on to state that antelope 

had been reduced to small scattered bands by World 

War I and that native elk were gone by 1900. He 

describes hunting in early Arizona: 

"Most of us harbor the notion that game in a virgin 

wilderness is always abundant, tame, and easy to 

kill-a hunter's paradise. No such assessment could 

possibly be made from the writings of the American explorers of Arizona. More often than not they 

complained that game was scarce and wary and on 

a number of occasions several were forced to kill 

and eat their horses and mules." 
CHAPTER 5: CHANGES IN ECOLOGICAL PROCESSES 

AND FOREST CONDITIONS 

"Ecosystems are dynamic entities whose basic patterns and processes were and 

are shaped and sustained on the landscape not only by natural successional 

processes, but also by natural abiotic and disturbances such as fire, drought, and 

wind. - Collectively, these features influence the range of natural variability of 

ecosystem structure, composition and function." Kaufmann et al. (1 994) 

Ths chapter describes the changes in ecological 

processes that occurred after the Mexican-American 

War in 1848 (the beginning of the Territorial Period) to 

the present. We discuss in particular-grazing and 

browsing; fire; demographics and land use; recreation; 

alteration of watershed processes, including erosion, 

stream course effects, and floods; introduction of exotic (non-native) plants; disturbance by forest insects 

and pathogens; timber harvest; succession; wildlife 

population dynamics; and air quality. How various 

ecosystem functions have changed within each forest 

community follows the descriptions of selected disturbances. The next chapter discusses how these disturbances have changed Southwestern forest ecosystems 

in terms of their biotic diversity, integrity and 

resilience, and ability to accommodate human needs. 

Although climate affects forest conditions and may 

have shifted in the past 100 years, climate change on a 

global scale is beyond the scope of this assessment 

and is not discussed. 

GRAZING AND BROWSING 

One of the earliest changes that occurred as a result 

of European settlement was the introduction of 

domestic livestock, beginning with the Spanish occupation. Juan de Onate brought sheep to the Rio 

Grande pueblos in 1598; cattle, horses, and goats soon 

followed. By 1880, cattle herds in Arizona and New 

Mexico were estimated at 172,000 head (Baker et al. 

1988) and articles in Western Range reported that overgrazing was depleting the range. By 1890, cattle numbers in the Southwest increased to more than 1.5 

million head; and additional large numbers of sheep 

were being grazed. The once lush grasslands were in 

danger of disappearing. The Governor of Arizona 

stated in 1893, "In nearly all districts, owning to overstocking, many weeds have taken the place of the best 

grasses" (Baker et al. 1988). 

By the time forest reserves were proclaimed in 1891, 

ranchers had become accustomed to unregulated use 

of forest lands for summer range. At the turn of the 

century there were so many livestock grazing the 

public lands that signs of range deterioration began to 

appear even in the "good years." In 1901, overstocking of sheep brought forest regeneration to a standstill. The forest floor in some places was "as bare and 

compact as a roadbed" (Baker et al. 1988): 

"They [cattlemen and sheepmen] knew nothing of 

grazing capacity and there was no fund of technical 

knowledge about forage management to rely on. 

Overgrazing could not readily be recognized until 

in an advanced stage. Thus, when the Forest Service came into being on February 1, 1905, the most 

complex problems facing southwestern foresters 

related to grazing rights and range management." 

By 1912, livestock pressures had penetrated the most 

remote, timbered and mountainous areas. Theodore 

Rixon (Roberts 1965), one of the first foresters in the 

Southwest, portrays the dismal situation: 

"At the beginning the mountains and heavily timbered areas were used but little, but as the situation 

grew more acute in the more accessible regions the 

use of these areas became more general and in 

course of time conditions withn them were more 

grave than elsewhere ... The mountains were denuded of their vegetative cover, forest reproduction was 

damaged or destroyed, the slopes were seamed with 
deep erosion gullies, and the water-conserving 

power of the drainage basins became seriously 

impaired. Flocks passed each other on the trails, one 

rushing in to secure what the other had just abandoned as worthless, feed was deliberately wasted to 

prevent its utilization by others, the ranges were 

occupied before the snow had left them. Transient 

sheepmen roamed the country robbing the resident 

stockmen of forage that was justly theirs." 

Not only were there pressures from range livestock 

but also from domestic and feral horses and burros. 

For over 70 years, heavy grazing reduced community 

diversity and plant competition; as a result there were 

no fine fuels to carry surface and ground fires. Grazing, reducing competition from herbaceous species, 

allowed rapid growth of pinyon, juniper, and oaks in 

adjacent communities (Nabi 1978). 

The numbers of range cattle and sheep in the 

Southwest peaked during or shortly after World War I 

and have since declined (Figure 5.1). About 1920 the 

numbers of range cattle reached about 1.6 million 

head in Arizona and in New Mexico. Currently there 

are 0.5 million head in Arizona and 1.2 million head 

in New Mexico. Sheep numbers are only available 

after 1920 and for New Mexico which has a substantial commercial market. Sheep populations have experienced a steady and dramatic decline from 2.3 

million head in 1920 to only 0.2 million head in 1996. 

Range management was one of the most difficult 

resource management situations for the Forest Service 

during its first five to six decades. Ecosystems grazed 

by domestic livestock, and to a lesser extent by 

wildlife, suffered significant damage. Only substantial 

investment could save some plant communities. In 

the early 1960s, the Forest Service began to gain some 

control over grazing. Since then, livestock numbers 

were reduced and more intensive management systems were initiated on many grazing allotments. 

Annual grazing reports document the decreases in 

permitted numbers of cattle and horses and numbers 

of sheep and goats in Arizona and New Mexico (Figure 5.2). Permitted numbers for cattle and horses in 

both states have declined by more than half their peak 

numbers in 1919. Sheep and goat permitted numbers 

are a small fraction of their 1919 levels. 

At the same time that livestock numbers have 

decreased, populations of wild ungulates have 

increased. Mule deer populations and range have 

increased with development of stock tanks and 

increases of woody vegetation (Davis 1982). By 1900, 

elk had been extirpated in Arizona; but they were 

reintroduced from 1913 to 1928 by transplanting animals from Wyoming. Elk populations reached such 

numbers by 1995 that the annual harvest in Arizona6 

was 10,000 animals and in New Mexico7 12,000 animals. In some areas, such as the Apache and Gila 

National Forests, livestock numbers have been adjusted to respond to resource damage; but overall impacts 

Wnpublished data from Supplee, 1996, Arizona Game and 

Fish Department, Phoenix, AZ. 

Unpublished data from Goldsteine, 1996, New Mexico Game 

and Fish Department, Santa Fe, NM. 

Arizona New Mexico 

2,800,000 2,800,000 

2,400,000 2,400,000 - D, a\ 

a 'S 

Figure 5.1 Estimated number of range cattle and sheep in Arizona and New Mexico since 1870. Values are derived from 

annual, January estimates provided by the USDA National Agricultural Statistics Service, 1996. Data for numbers of 

sheep in Arizona and number of sheep in New Mexico before 1920 are not available. Number of range cattle is 

determined by subtracting the number of dairy cows and cattle on feed from the total number of cattle. Estimates 

for number of cattle on feed are only available after 1930, about the time feed operations in the Southwest became 

significant. 
Arizona New Mexico 

Figure 5.2 Numbers of permitted livestock as cattle and horses and as sheep and goats in selected years from 1909 to 

1992 for Arizona and New Mexico. Data provided by USDA Forest Service, Southwestern Region. 

remain the same or increase as elk subsequently move 

into the area. In these areas, there is much public controversy concerning whether the land should be managed for cattle or for elk. 

Grazing and browsing pressures in the Southwest 

have changed over time, and affected the forest 

ecosystem both directly and indirectly. Forest ecosystems have gone from light grazing pressure during 

the 1800s, to severe pressure for the first several 

decades of this century, to current levels that attempt 

to balance numbers with capacity. The result of this 

grazing history has been to reduce the amount and 

diversity of the forest understory and its ability to 

carry surface fires. 

FIRE 

Except for climate, fire probably had the largest single impact in shaping the ecology of the Southwest 

prior to European settlement. It continues today to be 

the greatest potential force controlling ecosystems. 

The historic fire regimes characterized in the previous 

chapter changed dramatically with the coming of 

European and American settlers. Livestock removed 

much of the grassy fuels that carried frequent, surface 

fires; roads and trails broke up the continuity of forest 

fuels and further contributed to reductions in fire frequency and size (Covington and Moore 1994b). 

Because settlers saw fire as a threat, they actively suppressed it whenever they could. Initially, fire suppression was very successful because of low fuel loadings; 

but without fires to consume them, fuels accumulated 

over time. By the early 1900s, fire exclusion began 

altering forest structure and fire regime (Covington et 

al. 1994b). Forests with historically frequent, lowintensity fires were those initially most affected (Arno 

and Ottmar 1993, Covington and Moore 1994a). 

Woodland, ponderosa pine, and drier mixed conifer 

forests shifted from a fire regime of frequent, surface 

fires to one of stand-replacing, high-intensity fires. 

Fire had already been infrequent but high-intensity in 

the spruce-fir forest, so suppression there had less 

effect (Covington et al. 1994a). 

Fire suppression has contributed to the buildup of 

organic materials (fuels) on the forest floor. Logging 

added heavy fuels in the form of limbs, tree tops, and 

cull logs. In some areas, these heavy fuels have been 

removed by slash disposal (fuel treatment), prescribed fire, or firewood collection. The areas with 

the greatest fire hazard are those with the greatest fuel 

accumulations, such as stands never logged or logged 

without fuel treatment, and stands inaccessible to firewood collectors. 

The disruption of natural fire regimes has 

decreased the diversity of stands across the landscape. 

Frequent fires have killed conifer seedlings encroaching into forest meadows. Fire exclusion permits this 

encroachment, and meadow acreage has decreased 

(Arno 1985, Gruel1 1985). Establishment of young 

trees in older stands provides a fuel ladder for carrying fires into the canopy. With more s tand-replacing 

fires, average stand age is reduced; the diversity 

inherent in old stands is lost. 

Because of heavy fuel accumulations, fires that 

occur now are more intense and more difficult to contain. Certainly there are more, large fires. The number 

of fires burning more than 10 acres has increased each 

decade since the 1930's (Figure 5.3). The average size 

of fires since the 1970s has ranged from 14 to 16 acres 

per fire, double the average size of fires in earlier 

decades, 1940s to 1960s (Figure 5.4). 
Figure 5.3 Average number of fires per year in the Southwest since 1930. Fires included are only those 

larger than 10 acres; annual data are reduced to 

an average for each decade or period. (USDA Forest Service 1996a). 

Figure 5.4 Average number of acres burned per fire start 

in the Southwest from 1940 to 1987 (Swetnam 

1988) 

The role of fire in specific communities is discussed further under "Resultant Changes in Forest 

Condition." 

DEMOGRAPHICS AND LAND USE 

It was not until the Territorial Period that both population and associated impacts on the environment 

increased dramatically. Population growth and 

resource extraction were spurred by construction of 

the transcontinental railroads. In the late 1870s and 

early 1880s, the long-awaited railroad arrived in the 

Southwest and linked it to population centers and 

commercial markets on the east and west coasts. Connections to the East promoted and expanded new 

industries, including sheep and cattle ranching, mining, and timber. The railroads supported population 

growth through homesteading and employment for 

construction and operations. The exploitation of 

minerals, grasslands, and forests as part of the new, 

commercial economy opened the Southwest to more 

intensive use than the preceding, subsistence economy had found possible or necessary. The new Southwestern settlers introduced changes to the economy 

that altered settlement and land use patterns, along 

with natural resources. The consequences were depletion of forage, degradation of riparian areas, and 

changes to water tables, forest communities, wildlife 

habitats, and wildlife populations (de Buys 1985, 

Bahre 1991). The centuries-old system of irrigation 

farming with acequias had changed little before the 

1920s; frustrated by antiquated farming methods, the 

new settlers introduced "modern" farming approaches and techniques. 

Within decades of the arrival of the railroad, the 

population of the Southwest increased rapidly. Population levels soon exceeded the carrying capacity of 

the land using only traditional technologies. To meet 

subsistence and economic needs, new practices in 

farming, irrigation, ranching, and timber harvesting 

were initiated. Resource extraction increased exponentially, not only for use within the Southwest but 

also for export throughout the United States. Consequently resource demands exceeded the system's 

capacity of renewal and led to unsustainable practices such as-the excessive trapping of beaver from 

the early 1800s, overuse of forage by domestic livestock from the mid-1800s, and depletion of oldgrowth trees and forests in this century (Covington 

and Moore 1994a, Johnson 1994, Allen 1989, Cooper 

1960, Dick-Peddie 1993). Extensive and unregulated 

mining led to degradation of upland slopes, riparian 

areas, and streams. Hydroelectric dams, over-harvesting, and loss of habitat impacted fisheries. Onceflowing streams were de-watered to satisfy irrigation 

needs. 

Especially in the past few decades, the population 

of the Southwest has boomed and become more 

urban. The population of Arizona first exceeded that 

of New Mexico in the 1930s; since then Arizona has 

grown more quickly than New Mexico and by 1960 

surpassed a million (Figure 5.5, data from de Gennaro 

1990, Vest 1996, Bureau of Business and Economic 

Research 1994). If expected trends continue, by 2010 

there will be two million people in New Mexico and 

three times as many in Arizona. The majority of residents live in the most urban counties of each state 

(those with the largest cities). Maricopa County 

(including Phoenix) has a population of 2,355,900; and 
Figure 5.5 Population growth in Arizona and New Mexico 

1870-1 990 and projected population for the year 

201 0. (de Gennaro 1990, Vest 1996, Bureau of 

Business and Economic Research 1994). 

Bernalillo County (including Albuquerque) has 

650,000 residents. 

RECREATION 

The transcontinental railroads not only opened the 

Southwest for resource extraction and settlement, but 

also opened a market for tourism. In the last quarter 

of the 19th century the Santa Fe Railroad expanded 

its ridership through tourism to the Grand Canyon in 

Arizona and the Indian pueblos in New Mexico. In its 

efforts to encourage tourism of the Southwest, the 

railroad was aided and assisted by the Fred Harvey 

Company (Howard and Pardue 1996): 

"The Fred Harvey Company and the Santa Fe Railway joined forces at an auspicious hstorical 

moment. Borrowing new techmques in marketing 

and advertising, the companies promoted the American Southwest as an exotic destination. The railroad, 

the travelers, and the indigenous communities of the 

region were all integral elements in a partnershp 

that spanned more than three-quarters of a century." 

Still, much of the recreation potential of Southwest 

remained undiscovered. Only the most spectacular 

sites that were easily accessible from the railroads 

attracted significant visitation. Recreation facilities 

and services in most of the region's arid landscape 

were sparse and primitive, simply because there was 

little demand before 1940 (USDA Forest Service 1980): 

"Recreation use of the forest reserves grew slowly 

at first, then more rapidly as automobiles became 

numerous and roads penetrated further into what 

had previously been remote and inaccessible areas. 

General prosperity and more leisure time increased 

the human flow into the national forests, a flow 

which eventually became a flood." 

Beginning in the 1970s, the Southwest was "discovered." The population expansion of the Phoenix and 

Tucson metropolitan areas was unparalleled anywhere in the United States. At the same time, the 

mystique of the "Land of Enchantment" and the 

"Santa Fe" style captured the attention of trend-setters 

throughout the country and tourism to New Mexico 

exploded. Because of the mild weather, the Southwest 

also became a winter mecca for retired people as well 

as those with the freedom of long vacations. The 

Southwest became the nation's number-one target 

destination for the retired and recreational vehicle 

(RV) traveler, malung it a year-round recreation area. 

The Southwest has a diversity of high-quality recreation opportunities ranging from the primitive settings of the Gila Wilderness (first wilderness in the 

National Forest System) to the urban settings of the 

Salt River Chain of Lakes outside of Phoenix, Arizona. 

With the large increase in population and the attraction of the Southwest's climate, culture, and scenery, 

recreation use has increased tremendously over the 

past 20 years. Recreation use (as recreation-visitordays, RVD, see glossary for defination) on National 

Forest System lands since 1965 has increased fourfold: 

Year Recreation-visitor-days 

1965 10,147 

1976 15,565 

1985 21,742 

1996 44,342 

Developed Site Recreation 

There has been an increase in demand for highquality developments that include toilets, showers, 

lights, and reservation systems. Modern campers are 

seeking spaces designed for 40-foot RVs with individual hookups for sewage, water, power, and cable television. They also want trails, mountain bike paths, 

and interpretive nature walks. Their expectations on 

safety and security far surpass traditional offerings. 

The effects on forest health of this localized use 

include soil compaction, loss of vegetative cover, and 

soil erosion. 
Wilderness 

At the other end of the spectrum, there has been 

an increase in numbers seelung solitude in backcountry and wilderness areas. The idea, concept, and 

spirit of wilderness found their beginning in the 

Southwest. Heroes of the wilderness movement, 

Arthur Carhart and Aldo Leopold, worked in New 

Mexico and were influential in creating the first 

administratively designated wilderness, the Gila. 

The Forest Service in the Southwest now administers 

52 designated Wildernesses with a combined total of 

2,736,500 acres and an additional 175,112 acres in the 

Blue Range Primitive Area. These areas are ecologically diverse and range in size from 5,200 acres to 

558,065 acres. Some are adjacent to the major cities of 

Phoenix, Tucson, and Albuquerque. These present 

complex management situations of protecting the 

resource from overuse, and resolving issues of nonconforming uses such as structures, illegal motorized 

access, overflights, and cultivation of cannabis. With 

more and more people using wildernesses there has 

been a noticeable effect on forest health including 

introduction of exotic weeds and an increase in 

human-caused fires. From 1992 through 1996, there 

were 18,747 human-caused fires in the Southwest (all 

ownerships) compared to 12,988 lightning-caused 

fires. 

Heritage Sites 

Of all the many tourist destinations in the West, 

few combine the landscapes and the romance of the 

Western experience as strikingly as the archaeological ruins of the Southwest. A recent study of heritage 

tourism by the New Mexico Office of Cultural 

Affairs (1995) indicates that visiting heritage sites 

and learning about American Indian culture ranked 

second only to scenic beauty, and higher than outdoor recreation, in reasons given for why people 

visit the state. Similar findings have been reported 

by Kaufman8 for Arizona. In a market overview of 

the Four Corners region, sightseeing at cultural and 

historic sites was noted as the number one purpose 

of trips to the area (Lillywhite 1994). In New Mexico 

alone, over 12 million visits are made each year to 

Tourism and archaeology in Arizona: assessing the economic 

impacts; unpublished manuscript dated 1996 on file Albuquerque, 

NM: U, S. Department of Agriculture, Forest Service, Southwestern Region. 

heritage sites and events, and the total economic 

impact of heritage resources is estimated to be $1.6 

billion. 

Interest in the heritage resources on national 

forests is increasing as people seek out opportunities 

to discover and explore Southwestern cultures in 

more remote, uncrowded settings. Over 50,000 heritage sites have been inventoried on national forests 

in Arizona and New Mexico. These include cliff 

dwellings, massive pueblo ruins, and a vast array of 

other historic and prehistoric remains. Heritage sites 

hold important cultural, educational, and scientific 

values for many people and contain clues for reconstructing prehistoric landscapes and past ecosystems. 

Many of these sites are threatened by natural and 

human forces, including erosion, vandalism, and the 

cumulative effects of visitation. Southwestern Indian 

tribes continue to express concern about the protection and appropriate use of these resources. Experience gained through programs like "Passport in 

Time" shows the public is eager for opportunities to 

assist in the preservation and study of heritage 

resources. Balancing the public's desire to experience 

the past with the exigency of protecting sites and the 

need to be sensitive to tribal concerns is an important 

challenge. 

River Use 

Another example of the public's attraction to the 

Southwest is reflected in the tremendous growth of 

whitewater river use during the past five years. 

Rafters, canoeists, and kayakers, both individually 

and through outfitter guide services, have discovered 

that the Southwest has miles of fine whitewater and 

attractive riparian habitats. As a result, river management needs to balance increased use with a need to 

protect the ecosystem on which the use is dependent. 

River use brings new health issues including disposal 

of human waste, water pollution, litter, and wildlife 

disturbance. 

Hunters, Anglers, and Wildlife Viewers 

The diversity of wildlife in the Southwest has 

attracted large numbers of hunters, anglers, and 

wildlife viewers. The Southwest serves as a major 

staging and stopover area for great numbers of 

migrating North American waterfowl. Only in the 
Southwest can four species of quail (Lophorfyx) be 

found and hunted. Arizona and New Mexico are 

known for the last of the really great trophy elk as 

well as two kinds of bighorn sheep (desert and mountain). Other major game species are deer, black bear 

(Ursus americanus), pronghorn, mountain lion (Felis 

concolor), javelina (Tayassu tajacu), wild turkey doves, 

grouse, and squirrel. In 1991, approximately 291,000 

hunters spent 2.6 million days (8 hour days) pursuing 

game in Arizona and New Mexico (compiled data 

from various federal and state statistics). Fishing is an 

even more popular activity in the Southwest with 

761,000 anglers and 6 million fishing days estimated 

for 1991 alone (same data sources as above). The 

major species taken are bass, trout, catfish, crappie, 

and sunfish. But the most popular activity, undertaken by 1.6 million people (9.2 million days in 1991), 

was observing and photographing the over 500 

species of birds found in the Southwest. 

Outfitter Guide Services 

Outfitter and guide permits are issued for a variety 

of recreational pursuits. These include special events, 

horseback and llama-supported wilderness trips, jeep 

tours of backcountry areas, big game hunting, caving, 

whitewater rafting, and environmental awareness 

training. Many exotic types of dispersed recreation 

activities, which are provided by the private sector, 

such as bungee jumping, rock climbing, hang gliding, 

scuba diving, gold panning, and caving continue to 

gain in popularity and pose unique, new management challenges. Major impacts of these newer uses 

tend to be concentrated in the same areas as the more 

traditional activities such as hiking, bikmg, off-highway vehicle (OHV), water-oriented recreation, and 

horseback riding. Conflicts are on the rise in a region 

where there was once sufficient land capacity to 

accommodate all requests. The challenge is to find a 

sustainable balance. 

Winter Use 

Winter sports activities include destination, alpine 

slu areas such as Taos Ski Valley, Santa Fe Ski Area, 

Arizona Snow Bowl Ski Area and several Nordic ski 

centers. There are 10 alpine sk areas wholly or partially on national forest lands. In 1990, use on these 

areas totaled 620,000 RVDs with over a million slu 

visits. Ski resorts have significant, although local, 

impacts on the land. In addition, cross-country skiing, 

snowmobiling, and tubing attract many people. 

Recreation Impacts 

Many years ago, the numbers of people recreating 

on the national forests were so few and undemanding that they were little burden on the land. Now, 

people come in such great numbers and with such a 

wide variety of demands that their presence has 

brought significant impacts. Negative impacts 

include introductions of exotic weeds, increased 

human-caused fires, vandalism, littering, and stealing 

the artifacts of ancient human cultures. On the positive side, recreationists stimulate local economies and 

the tourism industry and provide numerous social 

and psychological benefits to themselves, their families and communities. Finally as a result of their use 

and enjoyment of the forest, recreationists increase 

their awareness and possibly their involvement in 

forest health issues. 

WATERSHED PROCESSES 

Grazing and browsing, which reduced the ground 

cover of grasses and litter and reduced the frequency 

of fires, have also changed hydrologic cycles. Reduction in fire frequency has resulted in increased density 

of trees in most forest communities. Increased tree 

density has increased transpiration and interception 

of precipitation thereby making less water available 

for long-term stream flow. On the other hand, soil 

compaction caused by grazing of domestic and wild 

animals slows infiltration of surface water. Construction of roads increases runoff through interception 

and concentration of surface flows. These factors 

taken together can generate rapid runoff and powerful floods. Although total stream flow is reduced by 

increased evapotranspiration, periodic floods may 

generate peak flows greater than historic levels. 

Flooding occurs because water runs off the surface 

rapidly rather than being absorbed into the soil and 

released slowly to the watercourse. A flood may be 

powerful enough to remove the entire flood plain and 

its riparian vegetation. Floods may also cut deep, 

incised channels through old alluvial deposits. In a 

wet meadow, this channel cutting can lower the water 

table and drain hydric soils. 
Impoundments and diversions on large rivers significantly modify the channel dynamics of erosion 

and deposition. The regeneration of cottonwoods and 

willows is dependent on natural floods to create 

seedbeds and moist conditions required for germination and establishment. Below large flood control 

dams, floods that would have supported this regeneration no longer occur. 

Because arroyo formation in the late 19th century 

coincided with hgh livestock numbers, overgrazing has 

been portrayed as the primary cause of arroyos in the 

Southwest. However, cycles of arroyo cutting and filling 

have occurred repeatedly since prehstoric times (Cooke 

and Reeves 1976, Dean et al. 1985). Prehstoric arroyos 

are usually attributed to climatic variations. But, identifying the cause of arroyo formation in hstoric times has 

been difficult. Hastings and Turner (1965) and Cooke 

and Reeves (1976) conclude that arroyos probably arose 

from several interrelated environmental changes, 

including rainfall pattern, moisture regime and vegetation change. Although human-induced land disturbance may have played a role in arroyo formation, it 

was probably neither the sole nor primary cause. 

Apparently, various combinations of initial conditions 

and environmental changes can form similar appearing 

arroyos in different areas (Cooke and Reeves 1976). 

INTRODUCTION OF EXOTIC PLANTS 

In the early to mid 1800s, European and Asian 

immigrants to the Southwest brought from their 

native lands not only animals and material items but 

also various ornamental plants and plants of cultural 

significance. In their native environment, these plants 

had been subject to control by various insects and diseases not present in America. In their new home, 

these plants were carefully cultivated; many found a 

suitable climate in which they could thrive even without care. By the early 1900s, the most aggressive 

species were out of control. Many were causing economic losses by competing with desirable plants, poisoning animals, hosting insect and disease agents, and 

altering various ecosystem attributes, such as fire 

regime (Dick-Peddie 1993). 

Exotic weeds continue to invade rangelands, 

forests, and riparian ecosystems at an alarming rate. 

Control of infestations has been difficult, and the ecological consequences have been serious. The rapid 

expansion of exotic weed populations is a great deterrent, if not the greatest deterrent, to restoring native 

plant communities and re-establishing historic conditions. If exotic plants are not kept in check, long-term 

devastating effects to forest ecosystems can occur. The 

ecological effects include replacement of native plant 

species and reduction in ground cover which leads to 

loss of biodiversity, forage, habitat and scenic quality, 

and even soil productivity. 

The Forest Service noxious weed strategy provides 

short-term direction for the containment, control, and 

management of noxious weeds through the Federal 

Noxious Weed Act of 1974, the 1990 Farm Bill Amendment, and USDA Departmental Regulation 9500-10. 

Species which are aggressive, difficult to control, toxic, 

parasitic, or hosts to serious disease or insect pests 

may be designated as noxious weeds. The Arizona 

Interagency Noxious Weed Committee has designated 

37 native and exotic species as noxious weeds (Table 

5.1); the New Mexico Interagency Noxious Weed 

Committee has designated 21 exotic species (Table 5.2). 

FOREST INSECTS AND PATHOGENS 

Forest insects, fungi, and parasitic plants continue 

to play important ecological roles in the re-structuring 

of forest communities (Holling 1992). The tree mortality that results directly or indirectly from their activity 

provides habitat, promotes nutrient cycling, drives 

plant succession, and contributes to biological diversity. Although their fundamental roles remain unaltered 

since historic times, the frequency, extent, or synchroneity of outbreaks may have changed for some of 

these disturbance agents. Insect and pathogen populations are ultimately limited by the availability of susceptible host trees. Therefore, changes in stand 

density, composition, and structure caused by fire 

suppression and logging would likely have affected 

outbreak patterns. Disturbance regimes of native 

insects and pathogens may also be affected by the 

introduction of exotics such as white pine blister rust 

(Cronartium ribicola). Detailed, standardized, regional 

reports of annual insect and disease conditions are 

available for only the past 25 years. Before then, 

reports9 of forest insect and disease activity were sporadic and emphasized situations where valuable economic or visual resources were threatened. In spite of 

limited information prior to 1900, there are good 

descriptions of more recent outbreaks and epidemics. 

Forest insect conditions, R-3, 1918- 1952; photocopied letters 

and annual reports on file; Flagstafl AZ: U. S. Department of Agriculture, Forest Service, Arizona Zone Entomology and Pathology 
Table 5.1 Designated noxious plants of Arizona. 

Scientific name Common name Origin Life Cycle 

A egilops cylindrica 

Alhagi pseudalhagi 

Ambrosia trifida 

Asclepias subverticilla 

Asphodelous fistulosus 

Cannabis sa tiva 

Cardaria chalepensis 

Cardaria draba 

Cardaria pubescens 

Carduus nutans 

Centaurea calcitrapa 

Centaurea diffusa 

Centaurea repens 

Centaurea maculosa 

Centaurea solstitialis 

Cirsium arevense 

Cirsium vulgare 

Convolvulus arvensis 

Drymaria arena rioides 

Echhornia azurea 

Euphorbia esula 

Halogeton glomeratus 

Hydrilla verticillata 

Hymenoxys richardsonii 

Kochia scoparia 

Linaria dalma tica 

Lina ria vulgaris 

Onopordum acanthium 

Rorippa a ustriaca 

Salsola iberica 

Solanum carolinense 

Solanum elaeagnifolium 

Sonchus arvensis 

Sorghum halepense 

Tribulus terres tris 

Verbascum thapsus 

Zigadenus paniculatus 

Jointed goatgrass 

Camelthorn 

Giant ragweed 

Poison milkweed 

Onion weed 

Marijuana 

Lens-podded hoary cress 

Whitetop or hoary cress 

Globe-potted hoary cress 

Musk thistle 

Purple starthistle 

Diffused knapweed 

Russian knapweed 

Spotted knapweed 

Yellow starthistle 

Canada thistle 

Bull thistle 

Field bindweed 

Alfombrilla 

Anchored waterhyacinth 

Leafy spurge 

Halogeton 

Hydrilla 

Pinque 

Kochia 

Dalmation toadflax 

Yellow toadflax 

Scotch thistle 

Austrian field cress 

Russian thistle 

Carolina horsenettle 

Silver nightshade 

Perennial sowthistle 

Johnson grass 

Puncture-vine 

Mullein 

Death camas 

So. Europe 

Asia 

Native 

Native 

Mexico 

Asia 

Eurasia 

Eurasia 

Eurasia 

So. Europe 

Europe 

Eurasia 

Eurasia 

Eurasia 

Europe 

Eurasia 

Eurasia 

Europe 

Mexico 

Brazil 

Eurasia 

Asia 

So. Africa 

Native 

Asia 

Europe 

Eurasia 

Europe 

Eurasia 

Russia 

Native 

Native 

Eurasia 

Mediterranean 

So. Europe 

Asia 

Native 

Annual 

Perennial 

Annual 

Perennial 

Perennial 

Annual 

Perennial 

Perennial 

Perennial 

Biennial 

Annual 

Perennial 

Perennial 

Perennial 

Annual 

Perennial 

Biennial 

Perennial 

Perennial 

Perennial 

Perennial 

Annual 

Perennial 

Annual 

Annual 

Perennial 

Perennial 

Biennial 

Perennial 

Annual 

Perennial 

Perennial 

Perennial 

Perennial 

Annual 

Biennial 

Perennial 

Native and exotic plants listed by the Arizona Interagency Noxious Weed Committee for their poisonous or invasive properties. 

Bark Beetles 

The known outbreak history of the roundheaded 

pine beetle in the Sacramento Mountains in southeastern New Mexico suggests an increasing trend during 

this century. At least six outbreaks have been reported 

in the Sacramento Mountains since 1937 (Bennett et 

al. 1994). From 1937 to the late 1960s, these outbreaks 

involved small acreages. In the early 1970s, an estimated 400,000 second-growth ponderosa pine trees 

were killed over 150,000 acres (Massey et al. 1977). 

This outbreak killed between 11 and 54 percent of 

ponderosa pines in sampled stands (Stevens and 

Flake 1974). Although the average diameter of ponderosa pine before and after the outbreak was 

unchanged, species dominance shifted to Douglas-fir 

and white fir. In the early 1990s, another outbreak of 

both the roundheaded pine beetle and the western 

pine beetle lulled an estimated 100,000 trees over 

87,000 acres. About the same time, two smaller yet 

still significant outbreaks of roundheaded pine beetle 

occurred in the Pinaleno Mountains of southeastern 
Table 5.2 Designated noxious plants of New Mexico. 

Scientific name Common name Origin Life Cycle 

Alhagi pseudalhagi 

Cardaria draba 

Carduus nutans 

Cen ta urea calcitrapa 

Cen taurea diffusa 

Centaurea ma culosa 

Centaurea melitensis 

Centaurea repens 

Centaurea solstitialis 

Cirsium atvense 

Cirsium vulgare 

Dipsacus sylvestris 

Euphoria esula 

Halogeton glomeratus 

Hydrilla verticillata 

Lepidium latifolium 

Linaria dalmatica 

Lina ria vulgaris 

Lythrum salica ria 

Onopordum acanthium 

Peganum harmala 

Camelthorn 

Whitetop or hoary cress 

Musk thistle 

Purple starthistle 

Diffused kn,apweed 

Spotted knapweed 

Malta starthistle 

Russian knapweed 

Yellow starthistle 

Canada thistle 

Bull thistle 

Teasel 

Leafy spurge 

Halogeton 

Hydrilla 

Perennial peppeweed 

Dalmation toadflax 

Yellow toadflax 

Purple loosestrife 

Scotch thistle 

African Rue 

Asia 

Eurasia 

So. Europe 

Europe 

Eurasia 

Eurasia 

Europe 

Eurasia 

Europe 

Eurasia 

Eurasia 

Europe 

Eurasia 

Asia 

So. Africa 

So. Europe 

Europe 

Eurasia 

Europe 

Europe 

No. Africa 

Perennial 

Perennial 

Biennial 

Annual 

Perennial 

Perennial 

Annual 

Perennial 

Annual 

Perennial 

Biennial 

Biennial 

Perennial 

Annual 

Perennial 

Perennial 

Perennial 

Perennial 

Perennial 

Biennial 

Perennial 

Exotic plants listed by the New Mexico Interagency Noxious Weed Committee for their poisonous 

or invasive properties. 

Arizona (Flake 1970, Wilson 1993); no prior outbreaks 

in the area are known. At least for these two areas, 

increases in outbreak size and frequency may have 

resulted from changes in stand conditions, especially 

increased density of susceptible host trees. 

Elsewhere in the Southwest, large pine-beetle outbreaks have occurred only on the Kaibab Plateau 

(Colorado Plateau Province). A mountain pine beetle 

outbreak in this northern Arizona forest covered over 

75,000 acres at its largest extent in the mid- to late1970s. Otherwise, outbreaks in the pine forests have 

generally been less extensive and of shorter duration. 

The susceptibility of the pine communities to bark 

beetles, however, continues to increase slowly over 

time so larger, more severe outbreaks may occur in 

the future. 

In other pine forests and in mixed conifer forests, 

extensive, sustained outbreaks have been rare, even 

though stands there are at historically high levels of 

risk due to increased tree densities. 

Large, spruce beetle outbreaks occurred in northern 

New Mexico, the Jemez Mountains during 1970s and 

the Pecos Wilderness between 1982 and 1985, and in 

Arizona, the White Mountains in the 1980s (USDA 

Forest Service 1976, Bennett et al. 1994). Infrequent, 

large outbreaks, however, are considered typical of 

natural disturbance regimes in spruce-fir forests 

(Veblen et al. 1994, Schmid and Frye 1977). 

Western Spruce Budworm 

Although the frequency of western spruce budworm outbreaks has not changed in this century compared to the past, their spatial and temporal pattern 

has changed (Swetnam and Lynch 1989,1993). The 

most recent outbreaks in northern New Mexico 

(Southern Rocky Mountain Province) have been more 

synchronous and therefore more extensive and perhaps more severe than previous outbreaks. Fire suppression, grazing, and harvesting preferences to 

remove pines have favored establishment of multistoried stands of young shade-tolerant species that are 

preferred hosts for the budworm. These changes in 

forest composition and structure may well account for 

the observed changes in budworm outbreak patterns. 

Root Decay Fungi 

A recent survey of commercial timber-producing 

lands on six national forests in Arizona and New 

Mexico (Wood 1993) indicates that root diseases and 
associated pests are responsible for mortality of 34 

percent of trees (> 5 inches dbh). Although it is 

impossible to determine whether the relative importance of root disease as a mortality factor has 

increased recently, it is likely that root disease fungi 

are responding to the greater abundance of host material (living and dead). Species conversion allows new 

opportunities for host-preferring fungi; increased tree 

density permits greater root contact; increased competition and insect activity further weakens trees; and 

more stumps provide additional and long-lasting 

sources of inoculum. The life histories of root disease 

fungi and bark beetles complement each other as a 

positive feedback system that could potentially lead 

to larger and more persistent outbreaks. The extent or 

distribution of root disease is also likely to expand to 

those areas where Douglas-fir and white fir have 

recently replaced ponderosa pine (Johnson 1994). 

White Pine Blister Rust 

White pine blister rust is caused by the fungus 

Cronartium ribicola, introduced in the Northwest about 

1910. The fungus has spread across the coastal and 

northern states and has caused serious economic and 

ecological impacts on western white pine (Pinus monticola), sugar pine (I? lambertiana), and whitebark pine 

(P albicaulis). In 1990, the rust was discovered in the 

Southwest on southwestern white pine (Hawksworth 

1990); the rust probably first became established 

about 1970 near Cloudcroft, New Mexico. Surveys 

indicate the rust is now present throughout the Sacramento Mountains (Hawksworth and Conklin 1990) 

and adjacent Capitan Mountains. The fungus rapidly 

kills seedlings and saplings. Larger trees are initially 

flagged (infected branches killed); later, the bole is 

cankered and eventually girdled. Because southwestern white pine is highly susceptible and environmental conditions are especially suitable in the 

Sacramento Mountains, the epidemic is expected to 

severely impact the white pine population there. A 

large inoculum source in the Sacramento Mountains 

increases the threat to other white pine populations in 

the Southwest and northern Mexico. The loss of 

southwestern white pine from the mixed conifer 

forests of the Sacramento Mountains not only reduces 

species diversity but also may result in greater damage by other disturbance agents. 

Dwarf Mistletoes 

More than 2 million acres of national forest lands in 

the Southwest are currently infested with dwarf 

mistletoes (Johnson and Hawksworth 1985). Surveys 

of ponderosa pine forests conducted in the 1950s and 

1980s suggest that the incidence of southwestern 

dwarf mistletoe in ponderosa pine may have 

increased in some areas due to past fire suppression 

and timber harvesting (Andrews and Daniels 1960, 

Maffei and Beatty 1988). Although basic principles of 

mistletoe control have long been known (Koristian 

and Long 1922, Pearson 1950), intermediate cutting 

practices that leave infected trees and infrequent use 

of final removal cuts and understory sanitation may 

have increased mistletoe abundance. Fire suppression 

may also have resulted in the retention of additional 

infected trees that serve as inoculum sources to the 

developing understory. Because mistletoe spreads 

rapidly from overstory to understory trees, improper 

use of uneven-aged management could also increase 

mistletoe abundance. Dwarf mistletoe is a native 

member of the plant community and it provides 

numerous ecological benefits where host-pathogen 

levels are within a natural range. Unfortunately, present forest conditions are especially suitable for development of infestation levels not previously 

experienced in these forests. A consequence of greater 

infestation is an increase in the risk and severity of 

insect outbreaks and wildfire. 

TIMBER HARVEST 

Logging has been conducted in the Southwest for 

over 100 years. Major efforts began with the harvest 

of railroad ties and other products for construction of 

the transcontinental railroad in the 1870s and 1880s 

(Schubert 1974). During the early days, logs were 

removed from the forests by expensive rail transport. 

To make these operations economically feasible, 70 to 

80 percent of the volume had to be removed (Schubert 

1974). When trucks became available for hauling, 

lighter cuts became economical. To insure continued 

timber supplies until young trees could establish and 

grow to adequate size, harvests of large trees were 

further reduced by distributing the cut to two or more 

entries (Myers and Martin 1963). During this time, 

typical harvests removed one-third to two-thrds of 

the available volume (Myers and Martin 1963) and 

averaged about 50 percent (Schubert 1974). At these 
residual stocking rates, reproduction was good to 

excellent (Schubert 1974), so stem density increased 

while tree size and age deceased. 

Logging in the Southwest has been practiced 

over many acres with various methods and associated activities. Harvest practices have ranged from 

high-grading which removed quality trees and left 

poor trees to clearcutting and group selection 

which established even-aged stands or clusters of 

vigorous trees. The result has been a number of 

different environmental effects, good or bad, that 

vary from site to site. Although not a universal 

practice, logging slash is commonly piled and 

burned. The effect of this treatment is to reduce 

habitat for small mammals and material that might 

have contributed to soil organic content (Harvey et 

al. 1987). Where this treatment was not used, habitat and soil organic material increased, but so also 

did fire hazard. 

Timber harvest levels on National Forest System 

lands in the Southwest have been tracked since 1908. 

Harvest levels gradually increased through the 1950s 

and, under sustained-yield management, remained 

relatively flat through the 1980s: 

Average annual cut, 

Decade million board feet 

1908-1910 40 

1971-1980 375 

1981-1990 402 

There has been an steady decline in the amount of 

timber cut in the 1990s. The timber cut in 1996 was 

almost exclusively fuelwood: 

Annual cut, 

Year million board feet 

1991 344 

1992 291 

1993 190 

1994 115 

1995 100 

1996 46 

The net annual growth rate of all size classes of saw 

timber in the Regon, currently around 700 million 

board feet, is substantially greater than historic harvest levels (Johnson 1994). 

Roads associated with logging have made human 

access to the forest easier. This has several effects, 

including improved fire fighting efficiency, increased 

recreational use, and easier access to helwood. Roads, 

however, also provide better access for poachers and 

may increase habitat fragmentation for some 

species. Improperly located roads can result in 

increased soil erosion, stream siltation, and meadow 

degradation. 

Through the harvest of dead and dying trees, the 

number of snags may have been reduced in some 

areas. Snags are important habitat components for 

some wildlife species. On the other hand, logging has 

occasionally been used to reset succession to an early 

stage for the benefit of specific plants and animals 

adapted to these conditions. 

Harvesting fuelwood in woodlands has resulted in 

removal of many of the larger trees in some areas. The 

combined effects of removal of large trees, intensive 

grazing, and fire exclusion have resulted in extremely 

dense stands in some forests. The dense cover of trees 

and grazing pressure have reduced the density of 

grasses and forbs, resulting in increased rates of soil 

erosion over large areas. 

SUCCESSION 

Plant succession and disturbance are now recognized 

as closely connected processes that together determine 

vegetation dynamics. This section focuses on forest 

succession, the factors affecting it, and the resulting 

vegetation patterns and ecological consequences. 

Definitions and Theories 

Following a disturbance that lulls or removes a significant portion of the dominant vegetation, succession 

is the recolonization and replacement of plant species 

that occupy and eventually dominate a site. Characteristic sequences of species (seres) develop. Early dominants modify environmental conditions, that affect 

subsequent immigration and reproduction. Succession 

continues until a regional and climatic climax develops. Various ecological mechanisms drive the process 

(McCook 1994), and succession may follow various 

pathways at varying rates and directions (Hagle and 

Williams 1995, McCune and Allen 1985). Although climax species are able to reproduce under conditions 

they create, further disturbance is common every- 
where so a climax community may never develop on 

some sites (van der Maarel 1993). Succession is usually 

seen as species turnover, but it can also be described as 

changes in physiognomy or ecosystem processes. Forest succession characteristically proceeds through four 

physiognomic stages-stand initiation, stem exclusion, 

understory re-initiation, and old growth (Oliver 1981). 

As succession proceeds, ecosystem processes such as 

nutrient cycling progress through phases of exploitation and conservation; Holling (1992) integrates disturbance into this model by adding two short but critical 

phases, release and reorganization. 

Succession is a fundamental process operating at a 

fine scale. Together with disturbance that can operate 

at a range of scales, these processes determine vegetation dynamics from single-tree canopy gaps to forest 

landscapes (Delcourt et al. 1983, Holling 1992). Succession is a gap and patch scale process because it is 

the result of various tree-to-tree interactions such as 

competition and allopathy (Shugart 1984, Watt 1947). 

Coarse-scale landscape patterns arise from the replication of these patches over large areas. Turner et al. 

(1993) describe a conceptual model that integrates disturbance and succession on both spatial and temporal 

scales. The temporal dimension is represented as the 

ratio of time between disturbance events and time 

required for recovery; the spatial dimension is represented as the ratio of area disturbed to total landscape 

area. Various regions on this spatial-temporal graph 

identify where the interactions of disturbance and 

succession lead to landscape stability, oscillation, or 

destruction. Veblen et al. (1994) provide a more concrete example of disturbance-succession interactions 

using observations from a spruce-fir forest. They 

describe a complex pattern of vegetation patches as 

the outcome of snow avalanches, fire, and spruce beetle acting on two tree species, subalpine fir and Englemann spruce, with very different survival and 

reproduction strategies. 

Competing theories by Clements and Gleason were 

proposed early hs century to explain succession (see 

reviews by McIntosh 1980, McCook 1994, Cook 1996). 

Clements (1916) emphasizes the importance of competition and the effect of vegetation on modifying environmental conditions ("reaction"). He argues that 

succession proceeded unidirectionally to commonly 

occurring self-replicating stages characteristic of a 

region and climate (climax vegetation). He discounts 

the role of disturbance and thought that before settlement most sites supported climax vegetation. These 

ideas were repeated in many early textbooks and once 

widely accepted; but later evidence has accumulated to 

challenge this simple, deterministic explanation (Drury 

and Nisbet 1973). The alternative theory presented by 

Gleason (1926) recognizes greater significance of individual species differences (life history) and chance 

events (variation in seed source). With modification 

and elaboration, these ideas became incorporated into 

many subsequent theories and models of succession. 

Numerous studies confirm the importance of life history and disturbame on succession. 

The differences between Clements (1 91 6) and Gleason (1926) opened a debate on succession that has continued throughout the century. Tansley (1935) proposes 

that more than one climax may result on a given site. 

Watt (1947) identifies the importance of patches and 

disturbance cycles for creating vegetation mosaics. 

Egler (1954) notes that species did not always invade a 

site in relay but may be initially on the site and sequentially assume dominance. Pickett (1976) recognizes the 

importance of natural selection and disturbance. Connell and Slatyer (1977) propose three alternative mechanisms of species interaction for driving successionfacilitation, tolerance, and intubition. Grime (1979) 

expands on explanations of succession due to life history characteristics and recognized three strategies-rudera1 (in early stages), competitive (in middle stages), 

and stress-tolerant (at later stages). Cattelino et al. 

(1979) further refine the life hstory concept and integrated succession with disturbance regme; they 

demonstrate the possibility of multiple outcomes on a 

single site. Huston and Smith (1987) construct a general 

simulation model to explore species interactions and 

successional pathways. Expanding on the mechanisms 

of Connell and Slatyer (1977), Huston and Smith (1987) 

demonstrate how five successional patterns could 

emerge: sequential succession, divergence, total suppression, convergence, and pseudo-cyclic replacement. 

A number of books (e.g., Glenn-Lewin et al. 1992) provide a modern synthesis of successional theories that 

tend to be mechanistic (Shugart 1984) rather than holistic and to allow for non-equilibrium (chaotic) cycles 

(Oliver and Larson 1990) rather than require stable, 

determinis tic outcomes. 

Factors Affecting Succession and Resulting 

Patterns 

The principal factors that determine the direction 

and rate succession are climate, site conditions (such 
as landform, elevation, and soil), and life history species in many mixed conifer habitat types of the 

strategies. Various random influences (e.g., initial Southwest (Moir and Ludwig 1979). But southwestern 

species mix and invasion opportunities) and disturbances also have a significant effect on succession 

(McCune and Allen 1985). 

Climate, site conditions, and life strategies usually 

evolve slowly relative to successional rates, although 

there are exceptions. Climatic change has been relatively gradual throughout the present interglacial 

period; but future climatic warming could be more 

rapid (Delcourt et al. 1983). Pearson (1931) not only 

describes climate and forest types across the Southwest, but he also relates vegetation and soils. For 

example, he observes that substrates such as those 

with high clay content can be detrimental to pine 

reproduction and therefore limit the potential vegetation on a site. Because soils that develop in prairies 

are distinct from those that develop in forests, it is 

sometimes possible to determine that trees have 

recently invaded or retreated from an area. Life history strategies are the product of evolution and represent the integration of numerous physiological and 

morphological adaptions. Especially for long-lived 

trees in tightly connected ecosystems, life history 

attributes of a species probably change only very 

gradually most of the time. Rapid changes in genetics, 

however, can happen as when local populations are 

reduced to low numbers. Climate change, soil development, evolution, and human activities all provide a 

context for succession; sequences of species turnover 

that had occurred in one era may be impossible in the 

next. 

Successional patterns reflect species accommodations to established environmental conditions and disturbance regimes. If the intensity, return interval, and 

area affected do not exceed limits imposed by rates of 

soil development, species longevity, and dispersal, 

even stand-replacing crown fires can be integrated 

into evolutionary and ecological systems (Pickett 

1976, Odum 1969, Turner et al. 1993). This integration 

has occurred in fire-dependent systems such as northern coniferous forests (Wright and Heinselman 1973). 

New successional patterns, however, are established 

following novel, extreme (catastrophic or cusp) 

events (Jameson 1994). Introduction of new, nonnative species (e.g., domestic livestock, weeds, insects 

and pathogens) may so re-sort species relations and 

environmental conditions that whole new vegetation 

emerges (see Sprugel1991 for several examples). 

Southwestern white pine is a minor or major seral 

white pine is susceptible to blister rust. This stem disease is lethal to seedlings and saplings and has recently become established in southern New Mexico 

(Hawksworth and Conklin 1990). In some areas, 

southwestern white pine could even be extirpated. 

The effect in the Southwest of eliminating this seral 

species on successional pathways is unknown; but in 

the northern Rockies the ecologcal consequences of 

blister rust has been significant (Monnig and Byler 

1992). 

Succession and Ecosystem Trends 

Ecosystem processes such as nutrient cycling are 

expected to respond with changes in the dominant 

vegetation of a site. Although it is quite evident that 

there are environmental and biotic differences 

between seral stages (if not, they wouldn't be recognized), there is a lack of agreement on which ecosystem trends are linked to succession and how they are 

linked. Odum (1969) categorizes ecosystem trends as 

community energetics, community structure, life history, nutrient cycling, selection pressure, and overall 

homeostasis. Some obvious and well-observed trends 

in the physical environment (especially light and 

moisture) result directly from changes in community 

structure as succession proceeds through the various 

physiognomic stages (Oliver 1981). Commonly 

observed trends are biomass accumulation, reduction 

of radiation below the canopy, and moderation of 

environmental extremes. Forest sites become more 

mesic as succession proceeds. Odum (1969) goes further in his contrast of young (early seral) and mature 

(later seral or climax) ecosystems. He suggests that 

production, growth, and quantity are associated with 

young systems and protection, stability, and quality 

are associated with mature systems. Observations of 

specific attributes such as ratios of production to respiration, species diversity, organism size, and nutrient 

conservation in actual ecosystems, however, do not 

always support the predictions (see Odum 1985). 

Even greater controversy arises from differences in 

explanations of the mechanisms responsible for 

observed trends. For example, DeAngelis and Waterhouse (1987) suggest that species stability is not fundamentally a property of ecological systems, but that 

an equilibrium state can emerge with extrapolation to 

sufficiently large spatial scales. 
Succession in the Southwest 

Many disturbance events like fires and insect outbreaks have not been allowed to run their natural 

courses over the past century. Consequently, they 

have become less frequent but more severe. Suppression of natural disturbances like fires and insects and 

deliberate removal of some late seral communities 

through logging may have resulted in an artificial 

over abundance of mid-sera1 communities. 

Johnson (1994) reports that the area of both aspen 

and ponderosa pine decreased on national forests in 

the Southwest by more than 425,000 acres between 

1962 and 1986. Most of the land that had been occupied by these early seral communities became part of 

the mixed conifer forest through succession. While 

ths vegetation was succeeding to a later sere, average 

stand age decreased as harvest removed older trees 

and encouraged regeneration. The result has been a 

more homogeneous forest that lacks stands in the 

youngest and oldest classes. 

In 1987, only 7 percent of national forest timberlands in the Southwest were nonstocked or in 

seedling and sapling age classes (Conner et al. 1990, 

Van Hooser et al. 1993). Reynolds et al. (1992) estimate that approximately 20 percent of timberlands 

would need to be in these condition classes to provide 

all age classes, including old growth, on a balanced, 

sustained basis. 

RESULTANT CHANGES IN 

FOREST CONDITIONS 

The changes in disturbance regimes and other forest 

processes listed previously have resulted in a transformation of forest conditions such as structure and composition. These changes in forest condition further 

contribute to changes in processes in a feedback cycle. 

Some of the structural changes that have been 

observed in Southwestern forests are listed below. 

Forest OverstorylUnderstory Relationships 

Structural diversity in the forests of the Southwest 

has changed considerably, including understory 

plants. Heavy livestock grazing not only removed the 

fine fuels needed to carry a fire but shifted the competitive advantage from the herbaceous understory to 

tree seedlings. This increased tree density within the 

forest and allowed tree expansion into meadows. As 

the large ponderosa pine and Douglas-firs trees were 

harvested, they were replaced by numerous seedlings 

which were not thinned by fire as in the past. Expanding coniferous thickets suppressed understory plants. 

Over large areas, important components of structural 

diversity, namely meadows, open-canopy and oldgrowth forests, have been converted to pine and fir 

thickets (Moir and Fletcher 1996). 

The relationship between overstory density and 

understory productivity has been documented in 

numerous studies. Covington and Moore'' estimate 

the increase in overstory canopy density in the past 

century has reduced herbage production by 92 percent within some ponderosa pine stands. 

Moore and Deiter (1992) report on the relation 

between stand density index and understory productivity in a ponderosa pine forest on the Kaibab 

Plateau. Productivity of grasses, sedges, forbs, and 

shrubs decreased with stand density index; the rate of 

decrease was steepest at stand density index values 

from 0-500 (Figure 5.6). These results support earlier 

lo Unpublished repod for Water Resources Operations, Salt 

River Project. 

I Grasses 

Sedges 

Forbs 

Shrubs 

0 200 400 600 800 1000 1200 1400 

Stand Density Index 

Figure 5.6 Understory productivity of grasses, sedges, 

forbs, and shrubs by stand density index of ponderosa pine on the Kaibab Plateau, Arizona 

(redrawn from Moore and Dieter 1992). 
findings by Jameson (1967) for overstory-understory 

relations in ponderosa pine in northern Arizona and 

pinyon-juniper in northern and central Arizona. The 

understory within the ponderosa pine stands was 36 

percent by weight Arizona fescue (Festuca arizonica) 

and 49 percent mountain muhly (Muhlenbergia montana). Productivity declined with increasing overstory 

basal area and with percent canopy cover; the 

decrease was steepest from 0 to 40 sq. ft. per acre (Figure 5.7) or 0 to 20 percent canopy cover (Figure 5.8). 

The understory within the pinyon-juniper stands was 

dominated by blue grama (Bouteloua gracilis) and 

broom snakeweed (Gutierrezia sarothrae). Productivity 

declined with percent canopy cover (Figure 5.9), but 

the decrease was less steep than in the ponderosa 

pine stands. Although these relations should apply 

generally throughout the Southwest, herbage production at any given forest density will vary from area to 

area depending on the site's capacity and history. 

Variations in overstory-understory relations are 

due to differences in fire regime, grazing history, 

species composition, climate, and parent material. 

The decline in productivity displayed in Figures 

5.6-5.9 may not have been as steep if these stands 

had been more frequently burned (especially, the 

ponderosa pine) and not as heavily grazed (both the 

ponderosa pine and pinyon-juniper). A variety of 

cool-season grasses are well adapted to the 

pinyon-juniper understory and some species even 

increase in abundance as canopy cover increases. 

Clary and Morrison (1973) find that cool-season 

grasses such as mutton grass (Poa fendleriana), squirreltail (Elymus elymoides), Junegrass (Koeleria macrantha) and western wheatgrass (Pascopyrum smithii) 

were more abundant in northern New Mexico under 

the canopy of large alligator junipers than in open 

spaces. Pieper (1994) reports pinyon ricegrass (Piptochaetum fimbriatum) and New Mexico needlegrass 

(Stipa neomexicana) were positively related to canopy 

cover. During his 12-year study, end-of-season, 

herbaceous, standing crops varied from 200 to 1000 

kg per ha; differences in July-August precipitation 

explained over 40 percent of the variation in crop levels. Jameson (1966) examines differences in the effect 

of cover by one-seed juniper on growth of blue grama 

at sites either derived from granite or from limestone. 

Canopy densities up to 13 percent on the granite site 

and up to 31 percent of the limestone site had either 

no effect or even a positive effect on blue grama productivity. These relatively low canopy densities may 

I Basal Area (sqwacre) 

Figure 5.7 Herbage production of Arizona fescue and 

mountain muhly in relation to basal area of ponderosa pine in northern Arizona (redrawn from 

Jameson 1967). 

Canopy Cover (percent) 

Figure 5.8 Herbage production of Arizona fescue and 

mountain muhly in relation to canopy cover of 

ponderosa pine in northern Arizona, (redrawn 

from Jameson 1967). 

I Canopy Cover (percent) 

- 

Figure 5.9 Herbage production of blue grama and broom 

snakeweed in relation to canopy cover of pinyon 

and juniper in northern and central Arizona 

(redrawn from Jameson 1967). 
have benefited the understory by reducing evapotranspiration or ameliorating temperature; higher 

tree densities may have impacted understory growth 

by shading or various belowground effects. 

Although little is known of how belowground 

processes may have changed since the Territorial Period, mycorrhizae, nutrient cycling, and carbon cycling 

are fundamental ecosystem processes that strongly 

interact with both the overstory trees and the understory vegetation. Perry et al. (1989) describe the 

ecosystem relation between plants and soils, especially soil microbes, as a self-generating positive feedback 

system. A large share of the primary productivity of 

plants is allocated to roots and symbiotic fungi that 

form specialized root-fungus structures called mycorrhizae (Allen 1991, Brundrett 1991). Most plants and 

all conifers studied in natural ecosystems are mycorrhizal (Perry et al. 1989). Mycorrhizae increase plant 

nutrients and water and provide protection against 

some pathogens (Klopatek 1995). Mycorrhizae are 

important for seedling establishment and growth. 

Nutrient cycling, especially nitrogen which is essential for plant growth, depends on various soil 

microbes. Organic material in the soil affects its texture and water-holding capacity (Harvey et al. 1987). 

The breakdown and release of carbon in the soil is 

effected through shredding by arthropods and other 

macroorganisms, cellulose digestion by fungi, and 

additional decomposition by other microbes. Grazing 

affects these soil processes by reducing the carbohydrates available to mycorrhizae, the litter input to the 

soil, and the mulching effect of ground cover. Fire 

affects these processes by lethal temperatures and 

rapid mineralization. Both grazing and fire can lead to 

excessive soil erosion or leaching. As with various 

aboveground processes, the effects of disturbances and 

belowground responses vary by forest community. 

Oak Woodland 

Harrington (1985) claims that summer burns 

repeated at frequent intervals reduces the density of 

Gambel oak. At least in the lower elevations, oak density has probably increased during the last century 

because of fuelwood harvesting and decreased frequency and severity of fire (McPherson 1992). 

Studies in the oak woodlands of southeastern Arizona document a decrease in the number of trees, particularly large trees, an increase in mesquite and juniper 

in the lower elevations, and a decline in grasses, all of 

which are related, at least to some degree, to human 

factors (Bahre and Bradbury 1984, Hadley et al. 1991). 

Fuelwood harvesting in historic times was a major 

extractive activity. Over-grazing was also prevalent, and 

fire suppression in more recent times no doubt affected 

the composition of the oak woodlands (Propper 1992). 

The normal result of increased tree density in 

forested ecosys tems is reduced density and diversity 

of other plant species. In many woodland areas, the 

ability of understory grasses to control erosion is not 

offset by greater tree density. The result is increased 

surface erosion with permanent loss of productive 

capacity for the site. If allowed to progress, it may be 

impossible to replace the original plant community in 

less than geological time. If understory species 

become extinct, then the original community can 

never be replaced. 

Coniferous Woodland 

Pieper and Lymberry (1983) describe changes to the 

coniferous woodlands: 

"Prior to widespread settlement of the Southwest, 

pinyon-juniper stands were more open and were 

confined largely to the rocky ridges or more level 

sites with shallow soils-tree densities have increased 

with subsequent invasion into adjacent grasslands." 

The pinyon-juniper woodlands may not have been as 

confined to rocky shallow sites as this description suggests. The General Ecosystem Survey identifies vast 

areas of established coniferous woodlands on deep, 

productive soil of level sites (i.e., GES Map Unit 130). 

But the GES data also support the view that the extent 

of coniferous woodlands has increased. Pieper and 

Lymberry (1983) attribute ths increase to lack of periodic fires, increased spread of seed by livestock, overgrazing and resultant reduction in competition by 

grasses, and a shift in climate favoring the woody 

species. These factors have accelerated succession to 

woody species, especially during wet years favorable 

for regeneration of shade-tolerant trees (Johnsen 1962). 

Heavy grazing led to a reduction in the numbers and 

intensities of fire that has resulted in a significant 

expansion of junipers (Wright 1990). Since the historic 

period, coniferous woodlands have generally become 

more dense and extensive, primarily by expansion into 

shrubsteppe and grasslands. As in the oak woodlands, coniferous woodlands have experienced 
reduced diversity of understory species, increased erosion, reduced productivity and possible permanent 

changes in dependent plant and animal communities. 

Invasion of other plant communities by woodland 

species reduces biodiversity on a landscape scale. 

In some areas, coniferous woodlands have been 

manually converted to grasslands. From 1960 to about 

1970, there was a widespread but controversial effort 

to convert woodlands to grasslands. de Buys (1985) 

describes an incident near Pecos, New Mexico where 

the Forest Service cleared 13,000 acres of woodland 

and reseeded them to grasses. This action was warmly received by grazing permittees, but upset village 

residents who depended on the area for fuelwood. 

These reactions typify the contrast in attitudes over 

woodlands-some people value woodlands for aesthetic or utilitarian reasons whereas others view 

woodlands as a mere impediment to livestock grazing 

(Lanner 1977). 

Grazing has affected cryptogamic soil crust present 

in some woodland areas. Cryptogamic soil crust has a 

stabilizing influence on the soil surface (Bailey et al. 

1973, Anantani and Marthe 1974a, 1974b). The 

increased porosity typical of crusted soils improves 

infiltration of rainwater, thus reducing runoff and 

subsequent erosion (Booth 1941, Loope and Gifford 

1972). Additional benefits are increased fixation of 

atmospheric nitrogen and improved soil water and 

nutrient levels (Durrell and Shields 1961). Trampling 

of cryptogamic soil crust significantly disrupts this 

process. Research by St. Clair et al. (1984) indicates 

that an intact or recovered crust enhances seedling 

development, regardless of the crust composition. 

Ponderosa Pine 

Striking changes have occurred in the ponderosa 

pine forests of the Southwest. Over large areas, the 

open structure of historic forests has been replaced by 

dense thickets of sapling and pole stands (Harrington 

and Sackett 1990). A disturbance regime of frequent, 

low-intensity fires has been replaced with one of 

stand-replacing, high-intensity fires. 

These changes had their beginning in the intensive 

livestock grazing of the late 19th century (Faulk 1970). 

Much of the herbaceous vegetation could not survive 

the grazing pressure, and its coverage declined drastically. Because of a decrease in fine fuels, this vegetation decline led to a reduction in fire spread that 

preceded organized fire suppression by one or two 

decades (Touchan et al. 1996). Forestry practices in the 

early 1900s further reduced the spread of fires. 

Because virtually all Southwestern fire history studies 

(Weaver 1951, Dieterich 1980, Swetnam 1990, Allen 

1989, Savage and Swetnam 1990) report a similar pattern, a reduction in fire frequency of the early 20th 

century was probably common throughout the ponderosa pine forests of the Southwest. 

In addition to a reduction in fires, ponderosa pine 

forests also experienced increased logging and 

reduced growth of herbaceous understory. With less 

herbaceous competition, improved soil conditions for 

seed germination, and better seedling survival, ponderosa pine regeneration, particularly in wet years, 

increased dramatically (Cooper 1960). Before, densities had been 3 to 56 trees per acre (Covington and 

Moore 1992); by 1986 ponderosa pine density on 

National Forest lands was 294 trees per acre (Johnson 

1994). Many of these trees occur as stagnant thickets 

of saplings and poles; fuels are at unprecedented levels (Biswell et al. 1973). 

An increase in stand density alone does not 

describe the changes to the forest structure of Southwestern ponderosa pine. Changes in size class distribution and numbers of large, yellow pine are also 

important but controversial. Although different areas 

were surveyed or different size classes were used, 

there are a number of inventories that can be used to 

examine changes in forest size structure (Figure 5.10). 

Woolsey (1911) reports the results of inventories on 

three national forests, and Lang and Stewart" report a 

inventory of what is now the North Kaibab Ranger 

District. These inventories can be compared with data 

of Conner et al. (1990) and Van Hooser et al. (1993) as 

re-compiled by Woudenberg (Intermountain Research 

Station, personal communication). 

Early surveys by Woolsey (1911) and by Lang and 

Stewart and recent surveys by Conner et al. (1990) 

and Van Hooser et al. (1993) include relatively large 

acreages of Southwestern ponderosa pine and use 

similar size classes. The Woolsey (1911) survey represents 1,888 acres of well-watered, rolling malpais flats 

with good stocking (Coconino National Forest), 5,920 

acres on southeastern exposure, with dry soil, volcanic cinder, and light stocking (Tusayan Forest), and 

128 acres on the Prescott National Forest. 

" Unpublished report titled Reconnaissance of the Kaibab 

National Forest, unpublished survey report circa 1910 on file 

Williams, AZ: U. S. Department of Agriculture, Forest Service, 

Kaibab National Forest, 
Circa 191 0 Circa 1985 

Figure 5.10 Change in size-class distribution of ponderosa pine 1910 to 1985. The number of trees per 

acre are estimated from several forest inventories 

circa 1910 (Lang and Stewart unpublished on 

North Kaibab Plateau and Woolsey 191 1 in northern Arizona) and circa 1985 (Conner et al. 1990 in 

Arizona and Van Hooser et. all993 in New Mexico). Size classes for the early inventories are 

small, 4 to 18 inches dbh; medium, 18 to 24 inches dbh; and large, greater than 24 inches dbh. 

Size classes for the later inventories are small, 6 

to 18 inches dbh; medium, 18 to 23 inches dbh; 

and large, greater than 23 inches dbh. 

Lang and Stewart surveyed eight acres per quarter 

section across the North Kaibab Ranger District. 

These early surveys grouped trees 4 to 18 inches in a 

small-diameter class, trees 18 to 24 inches in the medium-diameter class, and trees over 24 inches in the 

large-diameter class. Conner et al. (1990) reports 

inventory totals for all forested lands in Arizona (survey 1985), and Van Hooser et al. (1993) reports inventory totals for New Mexico (survey 1986-1987). These 

recent surveys grouped trees 6 to 18 inches in the 

small class, 18 to 23 inches in the medium class, and 

trees over 23 inches in the large class. 

Changes in the stand structure of Southwestern 

ponderosa pine from the early 1900s to the 1980s are 

illustrated by size-class distributions (Figure 5.10) 

using data from Woolsey (1911), Lang and Stewart, 

Conner et al. (1990), and Van Hooser et al. (1993). The 

most obvious change has been the increase in smalldiameter trees (less than 18 inches dbh) from 17 trees 

per acre to 140 trees per acre. The number of mediumdiameter trees (18 to 23 or 24 inches dbh) increased 

slightly from 5 to 6 trees per acre. The number of 

large-diameter trees (over 23 or 24 inches), however, 

decreased slightly from 3 to 2 trees per acre. Because 

of disparities in survey area and methods, no statistical significance can be placed on these differences, but 

they probably well reflect actual changes from a forest 

dominated by few but large trees to a forest of many 

small and few large trees. 

Probably the largest effect on forest health in Southwestern ponderosa pine is due to the increase in the 

density of the trees. This effect is expressed in several 

ways: 

Increased tree density reduces the abundance 

and diversity of understory plants. 

Since most of the increase is in smaller trees, 

there is an increase in ladder fuels, so that 

crown fires, once rare in ponderosa pine, are 

now common. 

Increased tree density increases susceptibility 

to bark beetles. 

Dense, multi-storied stands provide suitable 

conditions for rapid spread and intensification 

of dwarf mistletoe. 

Increased density results in lower water yields, 

which has a negative impact on riparian areas. 

In addition to increased density, ponderosa pine 

forests have tended to become more uniform, with the 

loss of structural and compositional diversity (see 

Chapter 5). We do not have good inventories of the 

amount of land in old-growth condition, either prior 

to European settlement or now. However, many people believe that there is less old growth now than 

there was before logging began. The lack of a commonly accepted definition of old growth and a lack of 

information on pre-settlement conditions makes this 

difficult to verify. If true, it may indicate that in recent 

times there have been too many minor disturbances 

and too few major disturbances. A major disturbance 

could move an area into a condition where the trees 

would be both young and would consist of early seral 

species. Minor disturbances like selective harvest or 

thnning could result in the loss of only certain 

species or certain age classes. They could move an 

area from late seral to a middle seral condition or 

from a stand of old trees to a stand of middle-aged 

trees but fail to take it all the way back to an early 

seral condition or a very young age. The lack of early 

and late seral conditions and young and old stands 

could cause reduced populations of plants and animals that depend on these conditions, thereby reducing the biodiversity of the forest. 

All of this indicates that attempts by managers 

to reduce disturbances like low-intensity fires and 
periodic insect outbreaks are at the heart of the 

unhealthy conditions existing in ponderosa pine 

forests today. The future health of these forests 

demands more disturbance, not less. However, these 

disturbances must reflect the historic variability in 

terms of frequency, intensity, and size to insure that 

the resulting forest structure and composition are 

sustainable. 

Mixed Conifer 

Although we do not have the detailed early inventories for mixed conifer forests that we have for ponderosa pine forests, it is reasonable to assume that 

many of the same types of changes have also occurred 

there. Whereas fires previously occurred at intervals 

of 5 to 25 years (Table 4.1), they now occur at much 

longer intervals and with much hgher intensity. As in 

ponderosa pine, increased overall density and 

increased numbers of small trees contribute to the frequency of crown fires and the susceptibility to bark 

beetle attacks. An additional change in mixed conifer 

stands, however, is a trend toward larger numbers of 

late seral species such as white fir and Douglas-fir 

and reduced numbers of early seral species such as 

ponderosa pine and aspen. 

Increased tree densities and multi-storied stands of 

late seral species are very favorable conditions for 

attack by the western spruce budworm. Increasing the 

proportion of Douglas-fir in a stand also makes it easier for Douglas-fir dwarf mistletoe to spread and 

intensify. Loss of ponderosa pine and aspen from 

mixed conifer stands further reduces biodiversity. 

Increased overall density will also reduce the abundance and diversity of understory plants. 

The 1962 and 1986 forest inventories for the Southwest indicate the extent of meadows within the mixed 

conifer forest. In some areas, there is evidence that 

these open montane grasslands are shrinking, with 

some small openings disappearing altogether. In the 

Jemez Mountains of northern New Mexico, for 

instance, more than 55 percent of the high elevation 

grasslands have been lost since the early 1900s. This 

loss is attributed to conifer encroachment caused by 

overgrazing and the removal of fire (Allen 1989). Over 

40 percent of the species found in meadows are not 

found in adjacent mixed-conifer forests. The fragmentation of meadow habitats into smaller, more isolated 

parcels limits the ability of the ecosystem to support 

hstoric wildlife populations. 

Spruce-Fir 

The spruce-fir forest has always been an area of 

both rare but high-intensity disturbances and frequent 

patch-scale disturbances. Grissino-Mayer et al. (1995) 

reports that a severe fire every 300 to 400 years 

returns the spruce-fir of the Pinaleno Mountains to an 

early successional stage. The spruce beetle, hgh 

winds, and root disease can also rarely cause standreplacing disturbances or patch-scale openings in the 

spruce-fir forest. 

Due to the low product value and the difficulty of 

building roads, relatively little logging was done 

before 1950 in spruce-fir forests (Alexander and 

Edminster 1980). Because these forests were neither 

roaded nor cut, large portions were designated as 

Wildernesses. Spruce forests outside of reserved areas, 

however, have been extensively logged over the past 

50 years. Because the natural disturbance regime of 

spruce-fir forests includes infrequent but high-intensity events like windthrow, fire, and spruce beetle epidemics, the current stand age-class structure of the 

spruce forest is probably not outside the historic 

norm. 

Aspen 

Johnson (1994) reports a 46 percent decline in aspen 

forest cover during the period from 1962 to 1986. This 

decline represents a substantial reduction in landscape biodiversity. The enormous aspen stands 

reported by Pearson (1931) no longer exist, and the 

number of smaller ones has decreased. Aspen is an 

early seral species that requires high-intensity disturbances such as stand-replacing fires or clearcut logging for successful regeneration. Because elk, deer, 

and livestock heavily browse young aspen sprouts 

and can destroy entire areas of regeneration, restoration of aspen is difficult. Some forests (e.g., Coconino 

and Apache-Sitgreaves) have resorted to installing 

very expensive fences capable of excluding not only 

cattle, but also deer and elk. If large fires were to 

occur in the mixed conifer forest, so much of the area 

may regenerate to aspen that animal damage would 

be widely dispersed and aspen could re-establish. 

This has not yet been demonstrated. Once established, 

aspen stands can usually persist for about 100 years 

before they deteriorate and are replaced by conifers. 

Although aspen is little used in the Southwest for 

timber (except locally for house logs), aspen is an 
important ecological feature and recreation attraction. 

Aspen groves provide important foraging, nesting, 

breeding, and resting sites for over 200 wildlife 

species. Fall coloration by aspen draws numerous visitors to the Southwest, especially northern New Mexico. If current trends of reducing acreage of aspen 

continue, these values would be lost. 

Riparian Wetlands 

In alpine riparian systems, including montane 

cienegas, the process of trapping sediments moving 

over channel bottoms by native aquatic vegetation is 

important to their long-term stability. Under impacts 

such as livestock grazing starting in the late 1800s, 

native ungulate grazing, and the reduction of aquatic 

plants, high-elevation stream systems initiated a 

process of degradation and stream-channel down cutting. Introduced graminoids such as Poa, Agropyron, 

and Dactylis are able to invade riparian areas. But 

they are less able to withstand the various impacts of 

grazing, and their root systems are less able to prevent channel aggradation (Neary and Medina 1995). 

The floodplains-plains riparian systems of the 

Southwest have suffered more from human activities 

than other riparian associations (see Chpater 5). The 

floodplains portion is typically found on older, meandering river systems with extensive flats. One manifestation of human activity is the explosion of exotic 

shrubby species such as Russian-olive in the northern 

river sections and saltcedar in the southern parts of 

the regon and northwestern New Mexico. The gallery 

forests that covered the floodplains riparian systems 

were composed of large trees and were often close to 

human settlements. Trees were initially cut for fuel 

and shelter. Riparian trees were also cut to clear land 

for agriculture and settlement. The natural resiliency 

of riparian vegetation might have eventually resulted 

in the restoration of the former forests, if it had not 

been for the impoundment of the streams and rivers. 

The hydrology of dammed rivers was altered in 

ways that thwarted some of the reproductive mechanisms of native riparian species. Wells and drains 

dropped water tables and reduced the number and 

extent of phreatophytic habitats. Not only were flow 

rates below dams reduced, but annual flooding of 

benches and terraces bordering channels was eliminated. This drastically curtailed the major reproductive mechanisms for cottonwoods. The decline in the 

number of native trees and the altered available water 

regime on rivers and streams, coupled with livestock 

grazing, have eliminated some wet meadows and set 

the stage for the establishment of exotics such as 

Siberian elm (Ulmus pumila), Russian-olive, and 

saltcedar (Dick-Peddie 1993). Costs of eradication, if 

desirable, are high. For example, removal of all the 

saltcedar along the Lower Colorado River and 

restoration of native vegetation have been estimated 

at between $45 and $450 million (USDI Bureau of 

Reclamation 1992). 

These impacts and others, such as the removal of 

beavers from many waterways, have caused an overall deterioration of riparian ecosystems. Those 

wildlife species dependent on riparian ecosystems 

that are currently at reduced population levels are at 

risk for further declines in population as threatened, 

endangered, or sensitive species (TES ). The influence 

of brown-headed cowbird (Molothrus ater) parasitism 

to many small songbirds continues to be pervasive 

due to readily detectable nest sites caused by the lack 

of dense riparian vegetation. Insectivorous bird 

species that prefer slow-moving insect-rich boggy 

areas will continue to decline due to the lack of vegetation and beaver activity. The majority of species currently on the Regional Forestel's Sensitive Species list 

for the Southwestern Region are riparian-dependent 

species or species which thrive in healthy riparian 

ecosystems. 

WILDLIFE POPULATION DYNAMICS 

In the past 150 years, significant changes have 

occurred to wildlife populations of the West. In general, some species have been extirpated, some have 

increased in abundance, and some new species have 

been introduced. Despite the lack of data, there is consensus that as resource management intensified, 

ecosystems were simplified, habitats were fragmented, and animal populations declined (Harris 1984). 

Virtually all of the game animals are at significantly 

increased levels compared to the 1890s. Wildlife population estimates are difficult to obtain and are seasonally dependent. Populations in the spring, after 

the peak of reproduction and prior to juvenile mortality can be several times greater than populations after 

hunting and winter mortality. Wildlife estimates for 

Arizona are estimates from the Arizona Game and 

Fish Department for post-hunt adults; estimates for 

New Mexico are from the New Mexico Department of 

Game and Fish. Since populations fluctuate yearly 
with variations from site to site, population estimates 

at this broad scale should be used in the context of 

understanding overall trends through time, not sitespecific analysis. 

Large predators were aggressively persecuted until 

as recently as 1960. Gray wolves (Canis lupus), mountain lions, and grizzly bears (Ursus arctos) were largely 

extirpated from most Western states. Mountain lion 

populations have rebounded in most Western states 

since 1970. Black bears and mountain lions are managed through regulated hunts in New Mexico and 

Arizona. Black bear numbers were estimated to be 770 

in New Mexico in 1926 and increased under hunting 

regulation to about 3,000 by the early 1960s (Ames 

1967). Information from ongoing research indicates 

that the current New Mexico population may be 4,000 

to 6,000 animals. The black bear population in Arizona has apparently remained stable over the last 10 

years and is estimated at about 2,500 animals. 

Thomas and Toweill (1982) report on the history of 

elk populations. Unregulated hunting, including market hunting, reduced elk populations to low numbers 

by the 1890s; a few years later, elk were extirpated 

from Arizona. Tragically, Merriam's elk (Cervus elphus 

merriami), a subspecies found in southern New Mexico and Arizona, became extinct by 1900. Rocky Mountain elk were extirpated from northern New Mexico 

around 1909. Reintroduction efforts began in 1910 and 

continued through 1966 (Gates 1967). After 1900, following a four-decade period of low or no legal hunting, elk populations began to recover. Today elk 

numbers in some areas appear higher than during 

any period in recorded history (Irwin et al. 1993). The 

1994 estimate of elk in Arizona was 29,000 adults. In 

New Mexico, elk numbers were estimated to be 712 in 

1926 and grew to about 11,000 to 12,000 in the early 

1960s (Ames 1967). The current elk population in 

New Mexico is estimated at 30,000 to 50,000 adults. 

Deer populations are more variable in number. 

Irruptions occur periodically in which large populations are observed that subsequently crash. Causes for 

these irruptions were varied and probably interdependent (Caughley 1976, Pengelly 1976, Mitchell and 

Freeman 1993). Causes include such factors as predator control, protection from hunting, drought, disruptions of the natural fire regime, logging, and 

competition with cattle. In Arizona, from extreme low 

numbers in the 1890s, deer peaked about 1960. After 

an extended drought in the 1970s, they peaked again 

in the mid-1980s. The current population is again at 

the relatively low level of the 1970s. 1994 Arizona 

population estimates for mule deer and white-tailed 

deer (Odocoileus virginianus) are 120,000 and 82,000 

respectively. In New Mexico, mule deer reached a low 

population around 1926 at an estimated 41,000 animals. Numbers increased until about 1960 at an estimated 318,000 animals (Ames 1967). Mule deer 

populations fluctuate grea tly due to the influence of 

weather on reproduction and survival. Post-hunt population numbers for all age classes have probably 

fluctuated between 235,000 to 300,000 animals during 

the past 10 years. 

In the late 1890s, big game seasons were closed for 

bighorn sheep and pronghorn in Arizona. At this 

time, mountain bighorn sheep were estimated at no 

more than 1,500 animals in Arizona. By the early 

1900s, mountain bighorn sheep were extirpated from 

New Mexico (Sands 1967). Restoration of bighorn 

sheep began in 1932 in New Mexico and continues to 

the present day. Currently five populations exist totaling an estimated 570 animals, with the majority located in the Pecos Wilderness. Desert bighorn sheep in 

the San Andres and Big Hatchet Mountains in New 

Mexico reached a low in about 1955. Transplants have 

been made to the Peloncillo, Hatchet, and Ladrone 

Mountains between 1979 and 1993 from the Red Rock 

captive population. Total numbers in 1994 are estimated at 360 animals. The 1994 estimate of bighorn sheep 

in Arizona is 6,500-about 6,000 desert bighorn sheep 

and about 500 mountain bighorn sheep. 

In the Southwest, pronghorn numbers reached a 

low in the early 1900s. At that time, there were an 

estimated 1,200 animals in New Mexico (Larsen 1967). 

The transplant program begun in 1937 has been 

responsible for reintroducing pronghorn to most suitable habitats in New Mexico. The 1993 New Mexico 

population estimate is 36,000 animals (Gleadle 1994), 

and the 1994 Arizona estimate is 7,800. Pronghorn 

populations are subject to great fluctuations due to 

changes in habitat quality. 

Javelina in New Mexico received protection as a 

game species in 1937 (Donaldson 1967). Numbers 

were then estimated to be 400 and 3,500 by 1964 

(Ames 1967). It has been noted that their distribution 

has been expanding through natural dispersal to the 

San Andres and Guadalupe Mountains. Current numbers are unknown but may be increasing. The Arizona 

estimate for javelina in 1994 is 38,000 animals. 

Wild turkey populations can fluctuate widely from 

year to year. In New Mexico, turkey numbers reached 
a low by about 1926 and were estimated to be 21,000 

statewide. The population was estimated to be about 

25,000 in 1964. No current statewide estimate has 

been made. In Arizona, there are currently between 

30,000 and 40,000 turkeys. 

Another influence that altered Southwestern 

ecosystems was the removal of beaver by aggressive 

fur trapping. Tens of thousands of beaver were 

removed from riparian areas. Their removal encouraged channelization and reduced the hydrologic effect 

of pooling. The loss of beaver affected native fish such 

as the Apache trout (Salmo apache) and Rio Grande 

cutthroat trout (Salmo clarki), and birds dependent 

upon insect-rich boggy conditions. It also narrowed 

the riparian corridor due to decreased water infiltration. In many areas of the Southwest, beaver have not 

returned to many historic waterways. 

Numerous activities of management and resource 

use have had detrimental effects on populations of 

native fish. Poisoning "undesirable" fish and stoclung 

popular game species such as the rainbow trout 

(Salmo garidneri), reduced native populations and 

introduced competitors and predators. Mining, timber 

harvesting, and livestock grazing have all affected 

water quality and riparian habitat. In the warm and 

sunny Southwest, riparian vegetation is especially 

important for cooling and shading forest streams. The 

native fish most sensitive to these changes include the 

Apache trout, Gila trout (Salmo gilae), Little Colorado 

spinedace (Lepidemeda vittata), spikedace (Meda 

fulgida), loach minnow (Tiaroga cobitis), and Sonora 

chub (Gila ditaena). 

Each forest type and its respective successional stages 

have specific wildlife communities associated with 

them. As cover type and/or successional stages change, 

there are corresponding changes in the composition of 

wildlife communities. The BISON-M habitat relationships database was queried to analyze the numbers of 

birds and mammals in different cover types and successional stages to evaluate effects of vegetation trends. 

Seventy-three percent of birds and mammals found in 

grasslands are not found in pinyon-juniper woodlands. 

Therefore, increasing acreages in pinyon-juniper woodland will negatively affect some grassland species. Likewise, shifts from ponderosa pine to mixed conifer also 

affect wildlife composition. 

The rapid change of aspen to mixed conifer is one 

of the most significant concerns to wildlife management. Although both communities have many species 

in common, there is a distinct suite of birds and mammals that occur only in aspen. In addition, aspen provides a broadleaf component that is important to certain invertebrates, such as the western tiger swallowtail (Papilio rutulus) and red-spotted purple (Basilarchia 

astyanax) butterflies. 

The size and abundance of meadows is declining in 

the Southwest as conifers encroach. Forty-six percent 

of the species found in meadows are not found in 

mixed conifer forests. The fragmentation of meadows 

limits the habitat's ability to support wildlife species 

that require large meadows. 

AIR QUALITY 

In Arizona the number of areas that do not meet 

National Ambient Air Quality Standards has 

increased over time, while by comparison air quality 

in New Mexico remains more pristine. However, 

efforts to maintain good air quality in New Mexico 

have increased, as demonstrated by mandatory noburn policies during air temperature inversions that 

affect Albuquerque. Most Forest Service resource 

inventory and monitoring for air pollution effects has 

focused on establishing current conditions. Few longtrend analyses have been conducted. However, the 

National Acid Precipitation Assessment Program and 

the Interagency Monitoring of Protected Visual Environments (IMPROVE) network have summarized 

long-term data for western states. 

Terrestrial and aquatic ecosystems and visibility 

have been affected by atmospheric pollutants. Sensitivity to acidic deposition is a function of geologic 

characteristics of the watershed, soil and vegetation 

type, hydrologic characteristics, chemical and biological characteristics of the ecosystem, and precipitation 

volume. Mercury, which could be from the atmosphere, and other trace metals have bio-accumulated 

in fish tissue, and health advisories have been issued 

in some areas. A loss of acid-neutralizing capacity 

due to high sulfur or nitrogen deposition has been 

documented in the Southwest. Episodic acidification 

has been detected at some high elevation lakes or 

streams. Paleobotanical reconstructions infer changes 

in lake species that may relate to changes in lake 

chemistry caused by atmospheric pollutants. These 

changes indicate a shift to more acid-tolerant species 

may be occurring in some high elevation lakes in 

New Mexico. Ozone, which is toxic to plants, is also a 

concern, particularly near large urban areas where 

combustion from various sources generates ozone 

precursors. 
Sulfate aerosols from all sources (including power 

plants and copper smelters) and other fine particles 

and gases in the atmosphere impair scenic vistas in 

the Southwest. For example, data from the Interagency Monitoring of Protected Visual Environments 

network show that in autumn sulfur concentrations 

have steadily increased since 1980 at Grand Canyon 

National Park. The National Academy of Sciences 

(1993) state that "the average visual range in most of 

the western United States ... is about one-half to twothirds of the natural visual range that would exist in 

the absence of air pollution." 
CHAPTER 6: A SUMMARY OF CURRENT 

ECOSYSTEM CONDITIONS 

"...a society and its biophysical environment are interactive, interadaptive, and interdependent in a single biosocial system of constant mutual adjustment." 

R. W. Behan (1995) 

This documents the current status of selected 

ecosystem indicators for forests and woodlands of the 

Southwest. The integration and interpretation of these 

indicators from the conditions described in chapters 3 

to 5 provide both a summary for specific biotic communities and a statement of professional expertise 

and judgement of the team. Ecosystem conditions in 

this chapter are defined by the following questions: 

Is adequate provision made for the conservation of biological diversity? The maintenance of 

biodiversity includes, at a broad scale, maintaining the composition and arrangement of 

species and ecosystems across the landscape 

and, at a lower level of organization, maintaining the diversity of gene pools within a species. 

Diversity is important in forested ecosystems 

because a loss of species is associated with an 

increased potential for species extinction or 

genetic loss of species with known or unforeseen ecological or societal value. Also, diverse 

ecosystems may be less susceptible to devastation by disturbance events. 

2. Is ecosystem integrity and resilience maintained in the long term? These are respectively 

defined as the ability of the ecosystem: (a) to 

maintain vital ecological processes, such as 

energy flows, nutrient cycling, hydrologic 

cycling, soil development, plant community 

succession, animal population movements 

(i.e., migration), and unimpaired flow of 

genetic material at rates within the range of 

historic variability and (b) to recover biotic 

integrity following disturbance. 

3. Are human needs for ecosystem resource use 

and landscape occupancy being adequately 

accommodated? 

WOODLANDS 

Biological Diversity 

A decreased diversity in grasses and forbs has 

resulted from less frequent burning than the hstoric fire regime. 

Herbivore use is above historic levels (prior to Territorial Period), resulting in decreased biotic and 

genetic diversity in native species. 

Past land disturbances have permitted increases 

in introduction and establishment of exotic 

species. 

Integrity and Resilience 

Soil erosion today is greater than in the past, resulting in decreased upland site productivity. 

Soil infiltration rates are below historic levels, 

resulting in greater overland flows, higher peak 

flows, reduced length of base flows in intermittent 

streams, and more confinement of channels. 

Some wildlife populations such as pronghorn have 

been isolated because of the construction of major 

hghways. 

Culling of dying, standing dead, and downed 

pinyon and juniper trees through fuelwood gathering and salvage operations has reduced available snags and downed logs needed by many 

species of wildlife (e.g., insects, woodpeckers, 

bats, nuthatches, titmice, small rodents, and many 

reptiles). Opportunities are also lost for other benefits, such as the release of nutrients to the soil 

and increased plant growth adjacent to these 

structures. 

Stock tanks and ponds provide for increased habitat 

for species such as woodpeckers, frogs, elk, bats, 
and other animals. These waters not only provide 

water for wildlife, but also attract insects, a source 

of food, and help disperse populations of wildlife. 

Human Needs and Uses 

Coniferous woodlands have changed from a visually diverse mosaic of tree-covered patches and corridors to a matrix of trees with more homogeneous 

tree cover and reduced overall scenic diversity and 

quality. 

Roads and utility corridors have changed the 

appearance of the landscape by adding foreign line 

elements that span wide areas. 

Past attempts at improving grazing conditions 

through chaining and pushing resulted in some 

large, geometric, linear, unnatural-looking patterns 

on the landscape. 

Controversies resulting from resource allocations 

between threatened species and traditional community uses, such as firewood gathering, have resulted 

in disputes be tween cultures. 

Woodlands are especially rich in heritage sites whch 

have been susceptible to damage from human activities and natural processes such as erosion. 

PONDEROSA PINE 

Biological Diversity 

Because of changes in fire regime and forest management, there have been significant changes in the 

diversity of vegetation and wildlife. Many wellspaced groups of large yellow-bark ponderosa pine 

have been replaced with closed thickets of small, 

blackjack ponderosa pine or with mesic mixed 

conifer species. 

These changes have been accompanied by 

decreased diversity of grasses, forbs, and shrubs 

and by increased levels of surface organic material. 

Although wildlife species (some small mammals) 

that benefit from increases in mixed conifer or surface litter are more abundant, many other species 

dependent on open stands and large trees, and 

especially on large snags (cavity-dwelling birds and 

mammals), are found in fewer areas. 

Overall, the loss of large ponderosa pine trees has 

resulted in a reduction of vegetation and wildlife 

diversity. 

Integrity and Resilience 

Reductions in low-intensity fires, changes in species 

composition, and increases in stand density have 

altered both physical and biotic processes in ponderosa pine forests. 

Mortality of large trees by dwarf mistletoe, root disease fungi, bark beetles, and wildfire has replaced 

the understory thnning action of low-intensity 

ground fires as the principal forest disturbance. 

In general, the scale at which tree death and regeneration occurs has been altered from that of the rare 

loss of mature individuals (appearing as a constant, 

uniform change) to more common destruction of 

groups of trees (appearing as a more variable or 

chaotic change). 

Impacts from grazing and browsing of livestock 

and wildlife have resulted in decreased watershed 

cover and riparian stability in some areas. 

Human Needs and Uses 

Ponderosa pine forests have changed from a grass 

matrix with individuals, clumps, and stringers of 

various-sized trees (many large), to stands of mostly 

smaller trees with only an occasional grassy opening. Large trees are no longer found in well-spaced, 

open groves, but primarily as individuals, surrounded by smaller trees. The visual depth of forest landscapes has decreased due to these changes. 

Increased road densities have resulted in more visual opportunities, but also more visually displeasing 

road scars. 

Tree decline and mortality due to increased dwarf 

mistletoe infestations have negatively affected aesthetic qualities at recreation sites and withn visual 

corridors. 

Increased dwarf mistletoe infestations have had a 

negative effect on timber production. 

Mortality of trees from pine bark beetle outbreaks 

has resulted in lost opportunities for timber production in the Sacramento Mountains. Outbreaks 

have occurred in dense stands of ponderosa pine 

primarily affecting trees of low-vigor, i.e., highlystressed trees. 

Competition for forage and water between cattle 

and elk has created controversy over appropriate 

resource use. 

Controversy over resource allocations between 

threatened species and timber harvesting has 
resulted in reduced viability for forest-dependent 

industries and increased demands for protection. 

Urban development in forested ecosystems has 

increased risks related to fire. 

Sulfate aerosols and other fine particles and gases 

in the atmosphere have impaired scenic vistas. 

Scenic and recreation values and expectations are 

often in conflict with extractive uses and timber 

management activities. 

MIXED CONIFER 

Biological Diversity 

The increase in mixed conifer acreage is likely to 

have slightly increased the diversity of vegetation 

types and possibly the diversity of wildlife species 

in some areas. 

With the decline of the aspen component in the 

mixed conifer, a broadleaf component that is important to some invertebrates such as the western tiger 

swallowtail and red-spotted purple butterflies is 

reduced. 

Populations of some bird species have increased 

due to increased spruce budworm infestations. 

Habitat for cavity-nesting birds has increased following spruce budworm infestations. 

Integrity and Resilience 

Due to widespread harvests and fire suppression, 

younger, multi-storied stands composed of more 

shade-tolerant trees are more common and more susceptible to western spruce budworm attacks. Sustained heavy defoliation by budworm has resulted in 

decreased growth, tree deformity, top lalling and 

death. Stand level effects include changes in stand 

structure, reduction of understory, and a composition shift toward nonhost or less susceptible species. 

Spruce budworm infestations have decreased thermal cover and forage for wildlife but sometimes 

have increased water yield. 

Forest openings are fewer and smaller than in the 

past, resulting in reduced snow accumulation and 

faster spring snow-melt. 

The risks of acidification of high-elevation lakes 

have increased due to high sulfur or nitrogen deposition. Ozone toxicity to plants, particularly near 

urban areas, is a concern. 

Human Needs and Uses 

The visual diversity in the mixed conifer forests has 

decreased due to reduced regeneration of aspen 

stands. Seasonal color and textural contrasts 

between aspen and conifer have been reduced. 

Due to western spruce budworm infestations, visual quality and recreation use has been affected. 

Heavy defoliation, discoloration, top-killing, and 

tree mortality has reduced the visual quality of 

scenic corridors and heavily used recreation areas. 

In addition, the presence of large numbers of larvae 

has been a nuisance in campgrounds, picnic sites, 

and summer home areas. 

Sulfate aerosols and other fine particles and gases 

in the atmosphere have impaired scenic vistas. 

SPRUCE-FIR 

Biological Diversity, Integrity, and Resilience 

Relative to other vegetation communities, little 

change has occurred in these communities. 

The risks of acidification of hgh elevation lakes have 

increased due to high sulfur or nitrogen deposition. 

Ozone toxicity to plants, particularly near urban 

areas, is a concern. 

Human Needs and Uses 

Installations, such as radio towers, microwave facilities, and ski lifts, are the most notable visual 

changes to the spruce-fir and alpine meadow visual 

characteristics. 

Sulfate aerosols and other fine particles and gases 

in the atmosphere have impaired scenic vistas. 

Mountain peaks hold special cultural and religious 

value for many Southwestern Indian tribes giving 

rise to conflicts between traditional uses and other 

uses and development. 

ASPEN 

Biological Diversity 

There has been a 46 percent decline in the aspen 

cover type between 1962 and 1986, representing a 

loss of biodiversity at the landscape level. 
lntegrity and Resilience 

Aspen regeneration has declined due to continued 

elk browsing of aspen sprouts, resulting in the 

death of the sucker root system. 

With the loss of the aspen component in the mixed 

conifer, we are losing a broadleaf component that is 

important to some invertebrates such as the western tiger swallowtail and red-spotted purple butterflies. 

Human Needs and Uses 

People are concerned about the loss of aspen as 

they are valued for their scenic beauty. They are 

also excellent sites for viewing wildlife and wildflowers. 

In many of the mountain towns and villages of 

northern New Mexico and Arizona, homes are still 

heated with aspen. 

Many rural people continue to depend on the sale of 

aspen wood products for part of their livelihoods. 

MONTANE RIPARIAN WETLANDS 

Biological Diversity 

Grazing and browsing in riparian areas have resulted in decreased diversity and cover in riparian vegetation. 

The number of impoundments and diversions and 

the level of grazing is greater than in the past, 

resulting in increases in the number and extent of 

exotic species in riparian areas. 

lntegrity and Resilience 

Riparian corridors have been interrupted due to 

grazing and agricultural practices, resulting in 

decreased wildlife movement corridors, increased 

water temperatures, and decreased transport of 

organic materials. 

Disturbance due to flooding has been reduced 

below historic levels, resulting in decreased potentials for regeneration and reduced biomass production from native species. Channel stability has also 

changed due to reduced vegetative cover and 

changes in sediment transport. 

The risks of acidification of high elevation lakes 

have increased due to high sulfur or nitrogen deposition. Ozone toxicity to plants, particularly near 

urban areas, is a concern. 

Human Needs and Uses 

Riparian uses such as grazing, recreation, and agriculture frequently result in water quality not meeting standards for designated beneficial uses. 

Grazing and browsing in riparian areas has had a 

negative effect on scenic qualities and recreation 

experiences in some areas. 

Increasing competition for scarce water resources 

has resulted in conflicts between traditional uses, 

such as community acequias, and other uses and 

developments. 

FLOODPLAIN-PLAINS RIPARIAN WETLANDS 

Biological Diversity 

Riparian area structure and composition have 

changed due to irrigation diversions, reservoirs, 

farming, grazing, and human settlement. Consequently, some species diversity has been lost, and 

channel functions such as sediment transport have 

changed. 

Due to changes in larger river channel dynamics, 

many of the native fish species have been lost. 

lntegrity and Resilience 

Riparian corridors have been interrupted due to 

grazing, agriculture, recreation, industrial, and 

urban uses, resulting in decreased wildlife corridors, increased water temperatures, increased sediment transport, and decreased transport of organic 

materials. 

Due to channel confinement and floodplain constrictions, peak flows have been frequently higher, 

velocity has been increased, and flood residence 

time has decreased, thus decreasing groundwater 

recharge. 

Disturbance due to flooding has been reduced 

below historic levels, resulting in decreased potential for regeneration of native species and reduced 

biomass production from native species. Channel 
stability has also changed due to reduced vegetative cover and changes in sediment transport. 

Agricultural conversion, livestock grazing, invasion 

of exotic plants, structural alterations of habitats, 

pollution, and replacement of native cottonwood, 

willow, mesquite, and marshes by urban environments and croplands have influenced the availability of foraging, breeding, and wintering habitats and 

food resources for migratory birds. These impacts 

have also altered the composition, structure, and 

dynamics of plant and animal communities in 

riparian ecosystems. 

Increased presence of saltcedar has resulted in 

increasingly drier riparian systems. The salt residue 

in the leaf litter tends to prevent native plants from 

re-establishing. Dense saltcedar thickets form barriers to wildlife, livestock, and human access to 

water. Bird species richness and abundance in 

saltcedar-dominated communities are substantially 

lower than in native plant communities. 

The spread of saltcedar and other exotic woody 

ornamentals such as Russian-olive and Siberian elm 

has resulted in the creation of new plant communities with different vertical and horizontal layers, 

understory species composition, age class distribution, and mixes of native and exotic overstory 

species. 

Human Needs and Uses 

Use of riparian areas, such as grazing, recreation, 

agriculture, industrial, and urban uses has frequently resulted in water quality not meeting standards 

for designated beneficial uses. 

American Indian communities along the Colorado 

River and in northern Mexico have been concerned 

that their mesquite is not regenerating well enough 

to ensure sustained supplies for religious and commercial needs. 

CONCLUSION 

Is Adequate Provision Being Made for the Conservation of Biological Diversity? 

Species numbers for many species that are intensively managed appear to be stable or even increasing. However, the population dynamics of many less 

intensively managed species are unknown; others are 

considered to be on the decline. Habitat fragmentation of the landscape appears to have increasingly isolated many plant and animal populations to the 

degree that their long-term viability is in question. As 

intensive human use of ecosystem resources increases 

with a corresponding rise in our population, the survival of these species will remain in doubt. 

Is Ecosystem Integrity and Resilience Being 

Maintained in the Long Term? 

Generally yes. However, in certain ecosystems such 

as deciduous riparian forests along major rivers, 

integrity and resilience has declined to a degree that 

seriously jeopardizes ecosystem structure and function. Similar degradation has occurred in coniferous 

woodlands (pinyon-juniper), where loss of understory plant cover has greatly accelerated soil erosion 

rates beyond historical levels. In coniferous forests 

(i.e., ponderosa pine), stand structure has changed to 

conditions that place these forests increasingly at risk 

of loss from catastrophic (stand replacement) fires relative to past time periods. 

Are Human Needs for Ecosystem Resource Use 

and Landscape Occupancy Being Adequately 

Accommodated? 

Human population has been growing and human 

interest in and demands upon ecosystem resources 

have expanded and caused a significant rise in pressure upon the landscape. Increased human occupancy 

of the land has resulted in greater numbers of people 

being adversely impacted by disasters such as fires 

and floods. Increasing human presence upon and use 

The history of human occupation in the Southwest of the land by a wide variety of groups often holding 

has resulted in many changes that are pervasive contrasting views and values concerning the land 

across all provinces. Many forest health issues are have resulted in a heightened degree of conflict. This 

problems at scale levels below the province level. is especially true between groups who favor traditionHowever, at a broad analysis resolution, we can a1 utilitarian uses of the land and those for which 

address the following questions on the status of forest preservation and protection are highest priorities. Traecosystems: ditional extractive uses of land resources have 
declined, resulting in the closing of forest-based by our inability to resolve issues related to balancing 

industries. American Indian tribes are spealung out the needs and desires of humans with the biological 

more forcefully on traditional cultural and religious needs of nonhuman organisms in the ecosystem. 

concerns. The clash of cultures, whether rural versus Thus, it seems that human needs are inadequately 

urban or utilitarian versus protection, appears driven accommodated. 
CHAPTER 7: OPPORTUNITIES 

"The world's ecosystems respond to the aggregate of both anthropogenic and natural stresses on their well-being, but our attempts to protect them are fragmented 

and unduly reductionist." John Cairns, Jr. (1991) 

On a broad scale, a blend of management styles 

across the landscape will be needed to accommodate 

human and landscape needs over time and space. For 

instance, the intensity of management in wilderness is 

typically lower than in non-wilderness to enhance 

recreational experiences. Some areas will be managed 

more intensively for commodity production to meet 

landowners' management objectives and resource 

demands. In determining the appropriate blend of 

management regimes at the landscape level, managers must consider the dynamics of the entire landscape; forest ecosystem health can be achieved only 

within the context of adaptive ecosystem management. This philosophy requires managers to integrate 

the biophysical and human dimensions of the landscape and restore ecosystem structure and processes 

essential to its integrity and long-term sustainability. 

The "Forest Service Ethics and Course to the Future" 

(USDA Forest Service 1994b) states that the national 

forests and grasslands will be managed as models of 

ecosystem management. 

Forest health must be a priority in developing management actions. Ecosystems need not be returned to 

some pristine condition, but good management will 

create situations that are sustainable-that work with, 

not against the underlying processes (Allen and 

Hoekstra 1992). One of the Forest Service's national 

priorities is to restore or rehabilitate deteriorated 

ecosystems; the challenge is to translate national policy into on-the-ground management. Attempting to 

address all restoration needs is impossible. The continuing decline of personnel and budgets of land 

management agencies necessitates the setting of priorities of forest ecosystem health needs. 

In establishing restoration priorities, both social concerns and ecological needs will need to be evaulated. 

Rather than exclusively targeting the most severely 

deteriorated ecosystems, it may be more cost-effective 

to focus restoration efforts on ecosystems that are at 

risk but only moderately degraded. Proactive management can head off further deterioration. 

To make these determinations, the setting of forest 

health priorities must be an issue included in assessment efforts. One way this can be achieved within the 

Forest Service is through forest plans. Assessments of 

forest ecosystem health to support forest plan revision 

efforts should establish priorities for restoration needs 

for each forest. In addition, Ecosystem Management 

Areas (EMAs) at the landscape scale have been delineated for each forest in the Southwestern Region; the 

assessment of each EMA should include forest health 

priorities. Desired conditions for the EMAs developed 

in conjunction with each assessment should incorporate the concept of ecosystem health. Large area 

assessments at the regional or subregional scale are 

another opportunity to incorporate forest health 

needs into the planning process. Large area assessments provide the context for setting priorities at the 

forest plan level. 

The assessment process includes the development 

of potential management practices that will incrementally move the landscape toward desired conditions 

for ecosystem health. Fast and ongoing research studies and management restoration projects are invaluable in identifying innovative and practical 

techniques for reconstructing naturally functioning 

ecosystems. Several of the Region's ecosystem management demonstration projects have been partnerships efforts to restore pinyon-juniper ecosystems, 

e.g. the Carrizo Project on the Lincoln National Forest 

and the Flying V and H Project on the Tonto. Innovative pilot projects for road construction have led to a 

guidebook on managing roads for wet meadow 

ecosystem recovery (USDA Forest Service 1996b). 
Restoration studies in ponderosa pine forests of the 

Southwest are ongoing at the land unit scale near 

Flagstaff, Arizona and are being initiated at the landscape scale in the Mount Trumbell Resource Conservation Area north of the Grand Canyon (Covington et 

al. 1997). New information that results form these and 

other restoration project activities needs to be synthesised and made widely available to land managers. 

Information management is another area rich in 

opportunities. Ecosystem and adaptive management 

require data appropriate to the issues of the area and 

at the appropriate scale. The Southwestern Region has 

not developed data requirements to support forest 

ecosystem health assessments. The Region should 

review data requirements to see if appropriate information related to ecosystem health is being collected 

at the appropriate spatial scales. Where possible, ties 

to national efforts should be made. Often, projects 

stall because the information identified in the information needs assessment process is unavailable. This 

is particularly true for projects requiring information 

on the historic conditions of an area. The amount and 

quality of information on historic conditions is highly 

variable, and historic documents and inventories have 

limited value for reconstructing landscape appearance 

prior to minimal human influence (Kaufmann et al. 

1994). Although it is useful to expand research of historic conditions from agency records, libraries, and 

other sources, it is necessary to develop that understanding of historic conditions using information 

which can be obtained within the time frame of the 

planned assessment. 

New technologies have become available in data 

collection, modeling, and information transfer. 

Remote sensing data are being acquired nationally to 

support Forest Service activities, and other agencies 

have typically made their data available over the 

Internet. GIs technology is already being used by 

most land management agencies, although the data 

available to support GIs analysis is often lacking. 

Decision support systems for modeling alternative 

scenarios are currently being developed; the Forest 

Service has identified approximately 20 systems used 

within the agency e.g., Spectrum, RELM, SNAP, 

EMDS. To coordinate activities across ownership 

boundaries, efficient communication between different parties is essential. Using computers to communicate via the Internet, videoconferencing, and satellite 

conferencing are technologies readily available today, 

but they are often inadequately used. 

Ecosystem management integrates both the human 

dimension and the biophysical aspects of the ecosystem. Although the Forest Service, or any other entity, 

has limited knowledge of the ecological processes in 

ecosystems, the agency's greater weakness is understanding the social context of an ecosystem assessment. In forest ecosystem health assessments, the 

values and uses of the communities of place, communities of interest, and the public should be characterized. Traditional and cultural perspectives should be 

included. The public should be involved in the assessment process; innovative techniques to keep the public informed, such as posting information on the 

Internet, should be explored. Partnerships with various agencies and groups to accomplish mutually beneficial forest ecosystem health objectives should be 

pursued. The ability to initiate restoration projects is 

dependent on the level of support for the project, both 

internally and externally. At all levels of the Region 

(Regional Office, forests, and districts), the Forest Service needs to implement collaborative stewardship by 

aggressively pursuing opportunities to communicate 

and collaborate among themselves and with the public about forest ecosystem health issues. 

Public land managers can work closely with environmental educators to promote forest health based 

on ecosystem sustainability. Roggenbuck and Driver 

(1996) identify several key aspects of a successful 

environmental education program. Public land managers must reach out and form partnerships with a 

wide variety of educators, including teachers at all 

levels of the school system, professors at univerisities, 

media leaders, and directors of zoos, museums, and 

art centers. Effective use of the news media (primarily 

radio, television, and newspapers) as an educational 

tool is critical to reach the large segment of the American public that does not visit public lands. It is also 

inportant to intensify our contact with the visting 

public by encouraging longer stays in forests and providing more frequent opportunitites (short loop hikes, 

for instance) to demonstrate forest ecosystem health 

practices and issues. We should also use our existing 

partners, e.g. outfitters, industry leaders, campground 

hosts, in environmental education workshops and to 

individually promote forest health. Focused opportunities for reaching young people, both in the classroom and in outdoor settings (field trips, residential 

camp programs) should be intensified. 

The adaptive management approach views management as a learning experience. Management 
actions must be coupled with monitoring to evaluate 

ecosystem responses. Projects must specifically state 

objectives to establish monitoring needs at the onset 

of the project, not as an afterthought. Projects should 

not be initiated unless monitoring needs can be met. 

In determining monitoring needs, three types of monitoring should be considered: 1) Did the project do 

what it said it would do (implementation)? 2) Did it 

work (effectiveness)? 3) Were the assumptions that 

were made valid (validation)? Validation monitoring 

is often, but not necessarily, the role of research. After 

monitoring takes place, the results need to be scientifically evaluated and applied to successive projects in 

a continuous feedback loop. Learning from monitoring and evaluation is an important aspect of adaptive 

management, but it is not the only one. In active 

adaptive management, management determines 

knowledge gaps and deliberately initiates management experiments to fill in those gaps to better understand the complexities of ecosystems. Since there is an 

infinite list of potential management experiments, 

ones should be selected where the consequences are 

meaningful enough to justify the cost. In deciding 

what changes to try, managers should look at the 

importance of the problem, not at the certainty of the 

answer; and they should be committed to going on to 

other potential solutions if the first one tried is a "surprise." Surprising results are legitimate, not signs of 

failure. Experimentation requires a clear understanding of scientific methodology. It involves the development of hypotheses and quantifiable objectives, 

designing a sampling scheme, establishing control 

areas, and setting rules for deciding when to adjust 

management. Results of management experiments 

need to be widely disseminated to avoid duplication 

of effort and extend use of new knowledge. Active 

adaptive management may result in different research 

techniques being used than have been used in the 

past. The ideal design of a management experiment 

may not be the most rigorous design possible, since it 

may be impractical to implement. The need for 

research scientists to be part of this approach is obvious; they can provide expertise and guidance on 

experimental design, the process used to collect and 

interpret data, and methods for monitoring ecosystem 

responses. Therefore, a close collaboration with 

research is essential, as well as more effective technology transfer between management and science. 
CHAPTER 8: TOOLS TO ACHIEVE DESIRED RESULTS 

"The only way to determine the most appropriate strategy for particular situations is 

for the manager to begin implementing natural experiments in the field." Unknown 

This chapter presents a Forest Service perspective 

(that of the assessement team) on a general strategy 

for improving the long-term condition of the forests 

in Arizona and New Mexico at the forest and district 

level. The Forest Service has authority for stewardship 

of National Forest System land-maintaining habitat 

for wildlife species, providing recreational opportunities, and managing commodity uses; the U.S. Fish and 

Wildlife Service and state game and fish departments 

are responsible for managing species populations. The 

approach advocated in this report blends vegetation 

management, where and when appropriate, with natural forest processes. The best opportunity to maintain and improve forest soils, watershed conditions, 

recreation opportunities, wildlife habitats, indeed, all 

attributes of the forest ecosystem, is through sound 

vegetation management. Southwestern forests are 

indeed treasures; their management is both an art and 

a science. 

There are many different ideas over what constitutes a healthy forest; opinions of how our federal 

lands should be managed differ even more. The strategy presented here is largely based on three premises 

which enjoy some general agreement (e.g., Sampson 

Over the last century there have been rather 

dramatic changes in the structures of Southwestern forests (Figure 8.1). 

The demand for aesthetic values from Southwestern forests will continue to increase. People prefer to see large trees and open stands 

(Brown and Daniel 1984). Although they dislike views of dead and dying forests, people 

can appreciate the value of snags and toplulled trees for wildlife (Baker and Rabin 1988, 

Orland et al. 1992). 

3. Even with greater conservation and recycling, 

there is an increasing local, national, and global demand for wood products. 

We may never fully understand the complexities of 

ecosystems, but we know enough to manage Southwestern forests more appropriately than in the past. 

We have learned much from research, from the public, 

and from our past mistakes-and our successes! Over 

time, we will learn more and can adjust accordingly 

with adaptive management. Some of the suggestions 

presented here are already being practiced by Forest 

Service land managers. 

Although historic conditions may not be "desired 

conditions" and may not be feasible to re-create over 

large areas, they do provide us much insight. There is 

a growing consensus that forests have become overcrowded and that there are too many small- and 

medium-size trees. Moreover, in some parts of the 

Southwest, there are few, old forests of large trees. 

As discussed in preceding chapters, some past 

management, particularly fire exclusion, overgrazing, and high-grade logging, has led to unhealthy 

conditions in some areas. However, it is important 

for resource managers and the public to understand that other practices over the past century, 

including improvement selection cutting and the 

thinning of small trees, have not harmed and have 

probably improved the condition of the forest over 

time. 

In discussing forest health among resource professionals and the public, we (the Forest Service) should 

accurately describe forest conditions and not overstate 

the case. Forests in some portions of the western United States have experienced dramatic episodes of tree 

mortality in recent years. For the most part, forests in 

the Southwest have remained green and appear 

healthy to many people. 
Figure 8.1 Ponderosa pine forests of the Southwest during the horse and buggy days was a grass matrix with individual, 

clumps, and stringers of large and variously-sized trees of almost exclusively ponderosa pine (see chapter 4). 

We should keep in mind, however, that the largescale tree mortality seen elsewhere had occurred during or following extended periods of drought 

(Wickman 1992). Overall precipitation in the Southwest has been well above average the past couple of 

decades. But given the unprecedented tree densities 

throughout much of the Southwestern forests, what 

might happen during the next extended drought? Did 

the next drought cycle begin in 1996? 

The following recommendations are the informed, 

professional judgements of the assessment team. 

Although the team believes these actions should be 

taken where and when appropriate, these recommendations are not policy statements directing managers 

to specific decisions. For the most part, these recommendations are compatible with guidelines recently 

developed for management of the northern goshawk 

and the Mexican spotted owl (Reynolds et al. 1992, 

USDI Fish and Wildlife Service 1995). They are primarily intended for ponderosa pine and mixed 

conifer forests, which make up the great majority of 

Southwestern forested lands. Spruce-fir ecosystems 

are thought to be relatively unaffected by past management; and for the most part, these forests appear 

to be in good condition and functioning normally. 

Sound management activities are appropriate in 

spruce-fir forests, but the majority of this forest type 

occurs in designated wilderness with limited management opportunities. Most of the recommendations 

discussed here, such as low thinning, also apply to 

pinyon-juniper woodlands, which have also been 

greatly affected by human activity. Recommendations 

for specific management situations, such as management of aspen and riparian areas, channel stabilization, recreation, exotic plants, and soil amendment, 

are also included. 
Density Management 

The long-term condition of Southwestern forests 

can often be improved with prudent thinning. In most 

areas, the emphasis should be on "low thinning" or 

"thinning from below." Often, a combination of 

mechanical thinning and prescribed fire can be used 

to work toward a desired condition. 

As in the past, thinning will include both commercial (sawtimber, pulp, and multi-product sales) and 

non-commercial treatments. The focus should be on 

removing smaller trees, and leaving a high proportion 

of the larger trees in most areas. 

As a silvicultural term, "low thinning" means 

removal of trees from the lower crown classes. In 

some locations, this can simply involve removal of 

trees from the understory (Smith 1962); but in many 

areas it can involve removal of some overstory trees 

as well. Suppressed, intermediate, and often some codominant trees are cut; dominant and at least some 

co-dominant trees are left. Simply stated, the largest 

trees are left, and other trees are thinned as appropriate. This approach is described as focusing on what is 

left (the residual) instead of what is cut (the removal). 

In many respects, low thinning is the opposite of high 

grading in which the best trees are removed first and 

the inferior trees are left. 

Prudent thinning has numerous benefits. The 

growth rate of ihe remaining trees usually 

improves significantly. Obtaining large trees is a 

function of time and site productivity, but also of 

competition. Similarly, by reducing competition, 

the longevity of the oldest and largest trees may 

increase (Barclay and Layton 1990). A more open 

canopy allows better growth of grasses, forbs, and 

shrubs, which, in turn, helps maintain forest soils. 

Some insect and disease damage can be averted, 

and the risk from fire reduced. The long-term 

appearance of the forest can be enhanced-possibly 

the greatest benefit of all, at least from a human 

perspective. 

Well-thinned, relatively open areas scattered 

across the landscape, interspersed with denser, 

less intensively managed areas, would provide a 

wide array of wildlife habitat, and would be a forest less prone to large-scale catastrophic wildfire. 

There are some documented cases where large 

wildfires have behaved as non-destructive ground 

fires as they moved into thinned forests (Barbouletos and Morelan 1995). 

Many thinning projects in the past, especially noncommercial thinning of young stands, achieved 

rather uniform spacing, resulting in a "tree-farm" 

appearance. Spacing should be highly variable to 

favor the best trees and provide more heterogeneous 

conditions. 

Good selection of residual trees is a simple practice 

that should be done to counter the effects of past high 

grading. Terms like "crop-tree selection," developed 

for timber production, can have much broader application; trees can be selected as future wildlife snags. 

Selection and marking greatly affect the outcome of 

treatments and, ultimately, what the forest will look 

like long into the future. 

Thinning by hand (cutting, chopping, grubbing) is a 

useful tool due to its selective nature and minimal 

ground disturbance. However, since it has a high 

labor cost per acre, it is usually suitable for initial 

treatment of small trees in light to moderate densities 

or in areas where mechanical treatments with heavy 

equipment are not acceptable. 

Within timber sale areas, to return stand densities 

to the level of historic variability, it will be necessary 

to remove at least 90 percent of the volume in the 

form of small trees, those less than 18 inches dbh (see 

Figure 5.10). Guidelines should allow flexibility to 

account for site differences and conditions, but in 

most areas the majority of the larger trees should be 

left. 

An aggressive program for thinning small-diameter trees is required to reduce stand densities. Much 

progress in this area would be achieved if the majority of the Knutson-Vandenberg (K-V) funds generated by most timber sales were used for thinning. 

Additional sources of funding and channelling as 

much existing funding as possible into thinning 

dense, small-diameter stands would further improve 

the condition. Thinning small-diameter trees will 

either require a non-commerical entry or market 

development. 

If sawtimber were harvested at a sustainable 

growth rate, acreage of pulpwood harvest and smalldiameter thinning were increased, and prescribed 

burning activities were greatly increased, there should 

be significant improvements in forest conditions within a few decades. 

If we take this approach (and explain what we are 

doing), we are apt to gain more widespread public 

support. Over time, this should lead to greater efficiency in developing and implementing projects, and, 
ultimately, more rapid progress in restoring forest 

ecosystem health. 

Efforts to improve forest conditions could be assisted by the development and application of new technologies in the Southwest, including the manufacture 

of engineered wood products and the biomass industry. Creating new markets for the vast amounts of 

pulpwood and other small-dimension material available in the Southwestern Region could be more 

aggressively pursued. 

The agency hopes that the increased attention on 

forest health, both nationally and regionally will allow 

more flexibility and help alleviate budgetary constraints. Some forest health treatments will be belowcost in the short term but, considering long-term 

values of forests, both commodity and non-commodity, will be sound investments. Forest condition and 

commodity products need to be equally weighted. 

Even-aged vs Uneven-aged Management 

True even-age management has seldom been practiced in the Southwest. The great majority of stands, 

including most of those that have received silvicultura1 treatment in the last 20 years, contain multiple age 

and size classes. Thus, articulation of the use of evenaged management regmes in the forest plans is somewhat inaccurate and, in some respects, self-defeating. 

The terms "even-aged" and "uneven-aged" are 

scale-dependent, relative to the size of the area, and 

may not be the best terminology (Bradshaw 1992). 

Generally, a better approach is to work with and 

enhance existing stand conditions rather than to rigidly adhere to an idealized system. 

Combination Silvicultural Methods 

Both even-aged and uneven-aged silviculture have 

application and often can be used in combination. 

For example, when group selection is chosen for certain objectives, it is often appropriate to use low thinning between the groups to achieve a wider array of 

benefits. 

Individual tree selection has some important 

advantages over group selection. Selection of individual trees to be left after harvesting can improve 

stand quality and genetic tree quality. Growth rates 

typically increase throughout a stand after individual-tree selection thinning, whereas only trees on the 

edges of the groups (or within groups if some were 

removed) show any release. Species composition can 

be manipulated with either method, but with individual-tree selection, this can often be accomplished 

more directly. For example, the proportion of ponderosa pine can be increased in many mixed conifer 

forests by selecting white fir and Douglas-fir for 

removal. Also, basal area can be lowered to encourage pine regeneration. Stand susceptibility to bark 

beetles can often be lowered using individual-tree 

selection or by group selection augmented with thinning between groups. 

As discussed previously, more open conditions 

achieved by low thinning can reduce susceptibility to 

wildfire, and can make it more feasible (i.e., less 

risky) to reintroduce fire with prescribed burning. In 

some instances, however, open conditions can make 

it more difficult to execute a prescribed fire. On the 

other hand, group selection which opens a canopy 

more than individual selection often provides more 

heterogeneity in stand structure and increases habitat 

diversity. Similarly, the openings created usually 

encourage the development of grasses, forbs, and 

shrubs. These effects can be achieved, although to a 

lesser degree, by varying spacing with single-tree 

selection. Group selection can also be used to regenerate shade-intolerant species like ponderosa pine 

and aspen. 

Damage to the remaining trees from felling or skidding is usually less using group selection, although in 

most areas damage can be minimized with either 

method (Figure 8.2). Road densities needed for management are probably similar for both methods. Individual tree selection is an ineffective method for 

long-term control of dwarf mistletoe. Group selection 

appears to have promise in ths respect because of the 

"groupy" spatial distribution of the parasite; however, 

in most cases regeneration within the openings will 

be exposed to infected trees on the edges of the group 

(or reserve trees left within the groups). 

Slash, Woody Debris, and Snags 

Timber harvest and other forest thinning typically 

generates large quantities of slash and thereby creates numerous problems. Non-commercial thinning 

of dense stands can result in very high fuel loads, 

making the sites hazardous in wildfire or prescribed 

fire. Fresh slash, particularly in ponderosa pine 

forests, can lead to rapid buildups of bark beetle 
Figure 8.2 Even large-sized material can be handled with horse and small-equipment; these heritage methods may still be 

useful for operating at low cost and without damage to the soil and and residual trees. 

populations, especially ips species, which may then 

attack and kill green standing trees. To reduce this 

potential, thinning is best carried out from July to 

December (ideally in mid- to late summer), allowing 

the slash to dry out and making it less favorable for 

the beetles (Parker 1991). Lopping and scattering is 

recommended for some sites, particularly when thinning is done in the spring. This practice hastens drying of the slash and generally improves the 

appearance of a site, although it increases treatment 

costs. Public fuelwood gathering can reduce the 

amount of green slash, reducing both fuel loading 

and the chance for beetle outbreaks. Large slash piles 

also have a visual impact. 

Although large amounts of slash can create problems, it is becoming evident that coarse woody debris 

has great importance for forest soils and wildlife habitat. Management recommendations, using ectomycorrhizae as indicators, have been developed for forests 

in the Rocky Mountains (Harvey et al. 1987, Graham 

et al. 1994). These suggest leaving roughly 10 to 15 

tons per acre of coarse woody debris after timber harvesting to maintain long-term productivity. Some 

ponderosa pine sites may require less material, 

whereas some mixed conifer and spruce-fir sites may 

benefit from larger amounts. 

Snags, essential habitat for many species, including 

cavity-dependent species, are deficient in many 

forested areas. Rigorous efforts in the past to fell 

dead trees to remove ignition sources, as well as 

efforts to harvest declining trees before they die, are 

largely responsible for snag deficiencies. These policies have been modified in recent years; over time, 

we can expect to have higher snag densities in 

forests. 

Although not recommended as a widespread 

practice, snag recruitment may be appropriate on 

some sites (Figure 8.3). For example, large, dwarf 
Figure 8.3 Most wildlife cavities are constructed in the 

decayed wood of old-growt h trees. Second-growt h 

trees, even while still alive, can be inoculated with 

wood-decay fungi to accelerate their developement into desirable wildlife trees. In this experimanta1 demonstration project, a hole is drilled 

into the upper bole of a large tree, a plastic pipe is 

inserted (to retard wound closure), and the tree is 

inoculated with a wooden dowel. 

mistletoe-infected trees might be selectively killed to 

make snags in areas where significant amounts of 

young regeneration can be protected from infection. 

Salvage 

Although often linked with the forest health issue, 

salvage is primarily an economic activity. Salvage 

sales supply wood to mills and benefit local 

economies; but they generally do little to improve forest conditions, except for reducing fuel loading. However, K-V funds can and should be used to pay for 

non-commercial thinning, tree planting, prescribed 

fire, and other restoration treatments. Salvage operations need to be done in a way that minimizes soil 

damage and loss, and leaves an adequate number of 

standing snags and fallen logs. 

Prescribed Fire 

Significant increase in the use of prescribed fire is 

needed in appropriate areas on Southwestern forests. 

Prescribed fires can be natural or management-ignited. In most parts of the Southwest and until very 

recently, prescribed fire has mostly been used to burn 

slash piles and for small broadcast burns. An increase 

in the number of acres of broadcast burning would 

enhance forest health. 

The potential benefits from broadcast burning are 

numerous and include-reduction in fuel loads; stimulation of understory vegetation including grasses, 

£orbs, and shrubs; thnning of overcrowded stands; 

and nutrient cycling. Over time, prudent use of prescribed burning could reduce the damage caused by 

wildfire, as well as the costs associated with fire suppression (Moody et al. 1992). 

Thinning stands with fire can potentially be done at 

a much lower cost than with mechanical thinning, 

although past attempts to do this in the Southwest 

have met with varying degrees of success (Harrington 

and Sackett 1990). Generally fire increases structural 

heterogeneity and diversity, creating mosaics within 

stands and over larger areas. It recycles nutrients for 

use by surviving trees and new vegetation. No other 

silvicultural technique fully mimics the ecological 

effects of historical fire regimes. 

Burning tends to promote natural regeneration 

of ponderosa pine, providing favorable seedbeds 

and enhancing the growing environment for survival (Harrington and Sackett 1990). Repeated 

burning of the same area is expected to maintain a 

sparse understory and relatively open forest conditions by killing some of the previously established regeneration. 

A few studies indicate a tendency for understory 

burning to reduce stand dwarf mistletoe infection levels (Harrington and Hawksworth 1990); significant 

amounts of crown scorch are probably needed to 

achieve this effect. 

One of the obstacles to more widespread use of 

broadcast burning in the Southwest is the risk 

involved both to resources and property. In many 

forests, fuel loads are so high that prescribed burning 
alone could lead to stand-replacement fires. These 

areas need to be mechanically thinned first, with 

much of the cut stems removed from the site, before 

fire can be safely reintroduced. One of the other risks 

is to old-growth trees; their protection may require 

either removing accumulated duff, protecting the 

trees and surrounding duff with foam, or establishing 

a fire-line around them. 

Broadcast burns are recommended following most 

mechanical thinning operations on ponderosa pine 

and lower mixed conifer sites. Generally such fires 

should be designed to reduce fine fuels, leave coarser 

fuels, and cause minimal damage to the remaining 

stand. As with any prescribed burn, timing is critical. 

Occasionally stands may benefit from understory 

burns prior to mechanical thinning, to reduce ground 

fuels before the additional slash is generated. 

Because of crown scorch and needle fall after 

understory burning, fuel loads can increase to hgh 

levels within a year or two after treatment. Thus, reburns are often needed to reduce these fuels. 

Burning intervals appropriate for various forest 

types, based on current knowledge of natural fire history (Table 4.1), are: 

Pinyon-juniper 10-30 years 

Ponderosa pine 2-10 years 

Xeric mixed conifer 5-12 years 

Mesic mixed conifer 20-25 years 

Spruce-fir usually not recommended 

Like other management practices, prescribed burning is both an art and a science. Every prescribed burn 

can be a learning tool; the acquired experience of 

practitioners is invaluable. Documentation and monitoring of prescribed burning activities and their 

effects is also be crucial for developing and improving 

burning programs. 

Smoke Management 

Fires within forested ecosystems naturally create 

smoke. Smoke is or can be hazardous to those who 

live near burn areas, either wildfires or prescribed 

fires. Smoke entering the atmosphere can create hazards through visibility reductions and, in some 

cases, increase breathing difficulties for individuals. 

Smoke can also create "smoke odors" inside of 

homes. For individuals living within the wildland /urban interface, visible smoke clouds can also 

create mild or intense apprehension and fear for 

safety and property. 

Because of smoke concerns, some are opposed to 

fire of any kind, including management-ignited fires 

or those naturally started through lightning. Often 

when fuels reduction proposals are made within the 

wildland / urban interface, opposition is raised during 

public meetings, through an appeals process, or some 

means of litigation. Long delays can result while fire 

hazard continues to increase. As the urban interface 

continues to grow and expand, opposition to smokerelated activities is expected to increase. 

Prescribed natural fire programs are often acceptable to large segments of rural population areas as 

long as the "smoke duration" is relatively short. 

Smoke is normally tolerated if the event doesn't 

exceed 10 to 14 days. After this period of time, the tolerance level declines rapidly. Individuals living within larger population centers are less tolerant to smoke 

from any source. Despite these concerns, people 

should recognize that all forests will eventually burn 

whether management-ignited or as wildfires. 

Currently the Environmental Protection Agency 

(EPA) guidelines for smoke emissions are based upon 

PM-10 standards (particulate matter exceeding 10 

microns). Current standards for air quality are a maximum of 150 micrograms/ cubic meter of air. EPA is 

now studying the possibility of adopting a PM-2.5 

standard. Since approximately 70 percent of the particulate emissions from fire are less than 2.5 microns 

in diameter, the standards proposed by EPA will provide significant challenges to the Forest Service and 

other users of prescribed fire. 

In implementing forest health strategies, it will be 

important to increase the amount of aceage that can 

be treated for fuels reduction. The current proposal 

for fuels reduction projects nationally is 3,000,000 

acres per year by the year 2000. 

Insect and Pathogen Considerations 

Extensive tree decline and mortality from insects 

and pathogens are often equated with an unhealthy 

forest. At the same time, dead and dying trees are 

important components of healthy forest ecosystems. 

Because the effects of forest insects and pathogens 

have often been and should be considered in the 

development of management practices, we include a 

brief discussion and some general recommendations 

in this area. 
It may be useful to consider high levels of forest 

insect or disease activity to be an indicator of an 

unhealthy condition (Bennett et al. 1994). Typically, 

they would indicate overcrowded conditions, or, 

sometimes, unusual or unnatural changes in species 

composition. 

Ecologically, some insects and pathogens appear to 

act as regulators of forest condition, i.e., nature's 

response, via feedback mechanisms, to restore previous conditions or ecological balance. In extreme cases, 

this process can lead to socially undesirable consequences such as large-scale tree mortality followed by 

catastrophic fire. 

Generally, emphasis in managing forest insects and 

pathogens should be on prevention rather than direct 

suppression. Some strateges to prevent Ips beetle 

problems were discussed previously. Thnning can 

limit mortality from other bark beetles in many forest 

situations (Fiddler et al. 1995, Schmid and Mata 1992); 

it appears to be a way of preventing unacceptable 

damage on specific sites and, presumably, across 

landscapes. Thinning in mixed conifer forests, particularly where ponderosa pine can be retained, may 

well lessen the severity and impact of unsightly 

spruce budworm outbreaks. 

Dwarf mistletoes present a difficult situation that 

should be recognized in efforts to maintain or 

improve forest health. Fairly aggressive efforts to 

control these parasites in the 1980s generated much 

controversy and opposition. Nevertheless, decades 

of research indicate that a rather aggressive 

approach is required for effective control in some situations (Heidmann 1983, Beatty 1986, Hawksworth 

and Johnson 1989). Regenerating stands and creating 

openings at least 20 acres in size are needed to provide effective, long-term control where infestation is 

severe. 

Low thinning and prescribed burning may be the 

best ecological approach for managing dwarf mistletoes on many ponderosa pine and mixed conifer sites. 

It is probably best to defer many heavily infested 

stands from treatment. Occasionally, on recently 

regenerated sites, it is prudent to remove all sources 

of infection. In some cases, this may involve the creation of fairly extensive openings. Specific recommendations for dwarf mistletoes should be based on the 

characteristics of individual sites, considering the surrounding landscape. 

Some sites may need to be managed in consideration of the effects of root diseases. Thinning may 

increase the incidence of root disease on some sites; 

however, this has seldom been a significant problem 

in the Southwest. Management recommendations 

tend to be very site-specific (Hagle and Goheen 1988). 

Efforts should continue to limit the potential for 

white pine blister rust to spread to other parts of the 

Southwest. Working with natural host resistance may 

be the best approach for reducing its impact in the 

Sacramento Mountains. Removing diseased trees 

through salvage or thinning will have little value, 

since infection of pine occurs through an alternate 

host. Large-scale salvage logging of white pine might 

reduce genetic variation in the host population. 

Treatment Priorities 

In general, treatment priorities should be established, not by focusing on where the biggest problems 

are (as is often suggested), but by where the greatest 

improvements can likely be achieved, at a reasonable 

cost. For example, it usually makes more sense to thin 

a middle-aged forest that has been thinned within the 

last 20-30 years than one of similar age that has never 

been thinned and is severely stagnated. Thinning 

healthy ponderosa pine stands is often more beneficial than thinning dwarf mistletoe infested stands. 

However, the removal of infected seed trees or residuals in newly regenerated areas should be given a high 

priority on many sites. 

Areas where healthy ponderosa pine can be favored 

over fir are often excellent candidates for thinning. 

Inter-planting with site-compatible pine has merit, 

particularly on some previously logged mixed conifer 

sites. Creating open parklike stands of ponderosa pine 

should be a priority for some areas. In some locations, 

this could be done with one or two heavy thinnings. 

On other sites, it could be done gradually, using a 

series of treatments over 20 years or more. 

Sampson et al. (1995), in a discussion of the condition of national forests throughout the inland West, 

eloquently states: 

"These lands, so highly important for so many reasons, to so many people, deserve better care than 

we have been willing-as a public-to give them ... 

If we continue to spend all our time in preparing 

studies and fighting over whether or not to address 

these treatment needs, the natural forces such as 

wildfire will take those decisions out of our 

hands ..." 
As part of the Southwestern Region's Forest 

Health Restoration Initiative (USDA Forest Service 

1993b), 742,000 acres in Arizona and 583,000 acres in 

New Mexico, were recommended for treatment over 

a 5-year period. The Initiative suggests this be 

accomplished by increasing the use of prescribed 

fire, reducing fire hazard in wildland /urban interfaces, and pursuing as much small-diameter thinning as possible, consistent with overall forest 

health. 

Aspen 

Unlike conifers, aspen has a strong tendency to be 

self-thinning, mostly due to a number of fungal diseases. Moreover, because this species is very susceptible to wounding and subsequent introduction of 

pathogens, thinning is usually not recommended 

(Jones and Shepperd 1985, Hinds 1976). However, 

sapling-size aspen (less than four inches dbh) can 

usually be thinned without much damage to the 

remaining trees (Jones and Shepperd 1985) to provide 

small products such as latillas (i.e., small diameter 

roundstock used in the ceiling and roofing of traditional Southwestern homes). 

A major decrease in aspen type suggests an urgent 

need for treatments to regenerate the species. Group 

selection cuts, small clearcuts which fit into the landscape, or, in some areas, prescribed fire, can be used 

to regenerate aspen. Although aspen readily resprouts following such treatments, grazing, browsing, 

and trampling by both wildlife and livestock can be a 

serious problem in establishing regeneration. Fencing 

is needed in many areas. Aspen can be regenerated 

and promoted by reducing populations of browsing 

animals, at least temporarily. Removal of "invading" 

conifer understories is suggested as a way of mainate and for a long enough period protect plant cover, 

facilitate regeneration, and prevent damage to stream 

banks and channels. In the long term, however, we 

should strive for conditions where fenses are not 

needed. Generally, any tree cutting within a riparian 

area would be very selective, and appropriate road 

construction and channel diversions would be 

designed to minimize adverse effects. Where opportunities exist, developed recreation sites can be moved 

out of sensitive riparian areas. Good riparian restoration minimizes use of structures and relies more on 

vegetation recovery. 

Channel Stabilization 

The goal of channel stabilization is to achieve a 

long lasting effect with vegetation. Mechanical measures are used to supplement or accelerate stabilization but they are not the best, long-term approach. 

Bed control measures, using nonporous or porous 

structures, are generally used to stop bed erosion or 

headcuts upstream. Bank treatments such as armor, 

flow deflectors, or flow separators stop or reverse lateral bank erosion. Flow separation structures, used 

only where the river system has a floodplain wide 

enough to allow for sediment deposition, yield the 

greatest benefit for riparian ecosystems (DeBano and 

Schmidt 1989). It may be necessary to partially or 

totally reconstruct a channel to meet desired geomorphc characteristics. Good channel design maintains 

smooth transitions of flow at all points upstream and 

downstream. Vegetation recovery is the key to channel stabilization. 

Recreation Tools 

taining aspen and may be appropriate for some areas. Proper recreation facilities are designed to minimize However, the effects of such treatment is typically resource damage. Reclamation of damaged areas (for short-lived. Moreover, unlike low thinning in pine or instance, mine tailings) are a high priority in areas of mixed conifer forests, which largely mimics the effects 

visual interest. Annual hazard tree surveys identify of fire, the removal of conifer understories from aspen 

stands does not resemble natural processes. 

trees with safety hazards for subsequent trimming or 

removal. Areas highly impacted by dispersed use, 

such as hunting camps, can be hardened by having 

Riparian Areas their boundaries marked or fenced to prevent further 

expansion and reducing the number of fire pits. 

Grazing pressure from ungulates (cattle and elk) Desired trails are monitored and maintained; those 

can be reduced within degraded areas, on a site-by- that have been poorly designed requre closing and resite basis. Enclosures (fencing) used where appropri- construction. 
Exotic Plants 

Management of exotic plants, especially those 

designated as noxious weeds, is essential to maintain ecosystem health, particularly within forest 

grasslands and riparian areas. Even with strategic 

planning and project implementation, the expansion 

and spread of aggressive weeds will continue. Management and treatment of exotic plants is and will 

continue to be a never ending process. As a first 

step, all noxious weed infestations are identified 

and mapped. Risk assessments are performed and 

used as a baseline for monitoring. Integrated weed 

management programs and plans are developed and 

implemented (with appropriate NEPA analysis) to 

address situations prior to infestations getting further out of control. Control efforts must be designed 

to protect native vegetation, achieve desired conditions, and maintain biodiversity. Management areas 

are designed to treat infested ecosystems regardless 

of jurisdictional boundaries. To facilitate this 

process, memorandums of understanding (MOU) 

with other federal and state agencies, county governments and private landowners can be developed 

and implemented. 

Soil Amendment Techniques 

Scattering slash and woody debris is used to add 

nutrients to the soil, as discussed previously. Research 

on the use of fertilizer to improve the status of nutrients and plant growth has shown mixed results. Fertilizers should be limited to sites where an andlysis 

indicates a nutrient deficiency and where soil moisture conditions are favorable. The application of treated municipal sludge as a soil amendment is becoming 

more popular, although opportunities to use sludge 

may be limited by its availability. Sludge has been 

tested in New Mexico where it has been used successfully to reduce runoff and improve plant growth 

(Aguilar and Loftin 1992). 
CHAPTER 9: RESEARCH NEEDS 

Although there is an adequate scientific basis to justify the need for maintaining and restoring healthy 

forests, numerous information gaps remain in the 

understanding of Southwestern ecosystems, application of techniques, and assessment of cultural and 

social values. Evans (1997) presents the conclusions of 

a review and workshop to identify research needs for 

management of National Forest lands in the Southwest. That effort categorizes research needs and current work into four priorities: l) inventory, 

monitoring, and assessment; 2) ecosystem health, disturbance, and restoration; 3) wildlife habitat relations 

with emphasis on TES; and 4) human needs and values. Many of the information gaps identified in Evans 

(1997) relate directly or indirectly to forest ecosystem 

health issues and concerns described in the previous 

chapters of this assessment. The following research 

needs are those specifically identified by the assessment team as critical for implementing adaptive management to maintain and restore forest ecosystem 

health in the Southwest. 

UNDERSTANDING HISTORIC VARIABILITY 

Improved information concerning reference conditions for Southwestern forests is needed, specifically 

the historical ranges and rates of change of numerous 

ecosystem variables. Information which characterizes 

ecosystem composition, structure, and function 

through time, including the frequency intensity, 

duration, and spatial patterns of disturbance at multiple scales is fundamental. This information provides managers with a better understanding of the 

historic variability of these complex ecosystems. 

This hstoric variability should be described both in 

terms of mean (central tendency) and variation (dispersion). Models can present this information in 

graphical form similar to normal distribution curves 

(histograms) and display the frequency with which 

these systems remain near average status or deviate 

toward extremes under slowly or rapidly changing 

conditions. Such information contributes to improving our overall understanding of the dynamic behavior of these ecosystems in the absence of human 

disturbance and management. 

In view of the substantial changes brought about in 

Southwestern forests by European settlement, an 

improved understanding of ecological succession, as 

modified and influenced by these changes, is needed. 

In ecosystems that have undergone significant change 

or degradation, successional pathways have been 

altered and plant communities are currently proceeding along trajectories for which no historical analog 

exists. The ultimate result of such successional change 

is largely unknown. A better understanding of this 

dynamic change is crucial to the success of ecological 

restoration and efforts to achieve desired conditions 

in the ecosystems of the future. 

A much improved working model of forest ecosystems in the Southwest is needed, one which explains 

dynamic behavior across multiple levels of the ecological hierarchy. The basic ecological building blocks of 

genes, genotypes, and species need to be functionally 

integrated with populations, communities, and landscapes to more fully identify emergent system properties characteristic of each forest ecosystem. Numerous 

modeling approaches could be used to achieve this 

integration, including individualist models, process 

models, and spatial models. Just the exercise of constructing such models should provide improved 

insights into the mechanisms wlch influence ecosystem behavior such as decomposition, nutrient cycling, 

growth and development, patch dynamics, and 

species dispersal and migration. 

Even though humans have been an integral component of the Southwestern landscape for over 12,000 

years, the archaeological and paleoenvironmental 

record of human habitation is often sparse and fragmentary. It is generally recognized that humans have 

significantly affected ecosystem conditions within the 

last century, but little is known about the impacts of 

prehistoric cultures on the landscape. Additional 

research is needed to better understand the interactions of prehistoric cultures and forest ecosystems 

through time. 

UNDERSTANDING FOREST ECOSYSTEM 

HEALTH 

Ecological variables which serve as appropriate 

indicators of ecosystem health are needed. These variables must be affordable, measurable, and reliable 

indicators of the health status of the ecosystem. 
Whether these variables are structural or functional 

characteristics, a reference database that describes 

acceptable (i.e., normal) and pathological (i.e., abnormal) ranges for each greatly enhances the utility of 

such measurements. Models which improve managers' understanding of species populations and 

trends, patch dynamics, disturbance effects, and 

human interactions need to be developed. Comparative analyses of the effects of wildfire and prescribed 

fire on resource values, air quality, and human health 

are also needed. 

UNDERSTANDING INSECT AND PATHOGEN 

INTERACTIONS 

More needs to be learned concerning how landscapes and ecosystems, under various management 

regimes, are affected by and respond to insects and 

pathogens at different temporal and spatial scales. Better hazard rating and damage prediction models need 

to be developed that describe the effects of insects and 

pathogens in a manner readily understandable by 

agency personnel and members of the public. 

The most critical needs vary by ecosystem and 

insect or pathogen. In woodland and riparian ecosystems, we need an inventory of potentially harmful 

insects and pathogens, their effects on various 

resource values, and in particular the effects of dwarf 

mistletoe on pinyon nut production. We need to know 

how thinning may prevent ips beetle outbreaks in 

woodland ecosystems or reduce the susceptibility of 

mixed conifer forests to western spruce budworm. For 

southwestern white pine, we need reliable estimates 

for the rates of spread and intensification of blister 

rust and levels of natural resistance to blister rust. We 

need to quantify the effects of uneven-aged management on the spread and intensification of dwarf 

mistletoe in ponderosa and mixed conifer forests. 

Information is lacking on the causes of aspen regeneration dieback and how to prevent it. 

UNDERSTANDING WILDLIFE HABITAT 

REQUIREMENTS 

Information concerning the habitat requirements of 

TES species is needed, (e.g., the Mexican spotted owl). 

Models which address the needs of multiple wildlife 

species would also be highly useful. These should 

include provisions for the influences of climate, competition, predation, and disturbance on community 

niche sizes and overlaps. 

The scales at which each wildlife species are best 

managed and the habitat components that influence 

each species and group at each scale need to be identified. A better understanding of the influence of management practices on ecological processes at multiple 

scales is also needed. This information allows managers to ascertain the effects of management applied 

at one scale uplm other scales and determine where to 

optimally apply management for the most desirable 

results across the hierarchy. 

In the interest of maintaining viable wildlife populations, information concerning the spatial distribution of 

habitat necessary for unimpaired movement of populations and individuals is needed. Information relevant to 

the effects of size, shape, and juxtaposition of patches 

and corridors on specific species and communities is 

essential. Critical population thresholds that threaten 

viability need to be determined. Specific data types relevant to the determination of species viability needs to 

be added to habitat relationship databases. And finally, 

quantifiable data are required on effects of bark beetle 

outbreaks to TES species populations and habitat. 

DEVELOPING TECHNIQUES TO RESTORE AND 

MAINTAIN ECOSYSTEMS 

Additional research is required in several areas 

before an improved understanding of forest ecosystems can be implemented. In particular, these areas 

include use of prescribed fire, wood utilization of 

small trees, and weed detection and control. Information is needed to ensure safe and effective use of prescribed fire in fuel reduction and vegetation 

management. Equipment technologies for economical 

harvesting of small trees (3 to 4 inches dbh) needs to 

be developed or imported from other regions and 

adapted to Southwestern conditions. Economic markets for small trees, such as poles and posts, chip-andsaw, chips, pressure composites, and pulp need to be 

developed. New product development in cooperation 

with the Forest Products Laboratory in Madison, Wisconsin, may be helpful in this matter. Work is needed 

in the detection of exotic plant infestations and the 

evaluation of the efficacy of mechanical, chemical, 

biological, and natural control methods. 
CULTURAL AND SOCIAL ASSESSMENTS standing of the expectations of forest visitors and users. 

Better models for tribal consultation and a better 

A better understanding of the cultural context for knowledge base for evaluating hstoric and contempoforest health is needed. Improved insight into public rary traditional uses is important to facilitate collaboraperceptions concerning what constitutes a healthy for- tive partnershps. A greater understanding of the 

est and what lands and levels of management activities effects of various recreational activities on forest health, 

are acceptable is essential, as well as a better under- especially in riparian ecosystems, is also crucial. 
LITERATURE CITED 

Abert, J.W. 1848a. Report of his examination of New 

Mexico in the years 1846-1847.30th Congress, 1st Session, Senate Executive Document 23. Washington, DC: 

Government Printing Office. 

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GLOSSARY 

Acequia: an irrigation ditch or channel, a term commonly used in northern New Mexico. 

Adaptive management: a process for implementing policy decisions as an ongoing activity that requires monitoring and adjustment. Adaptive management applies 

scientific principles and methods to improve resource 

management incrementally as managers learn from 

experience and as new scientific findings and social 

changes demand. 

Allopathy: an interaction between plant species in 

which one species inhibits the establishment or growth 

on the second species through production of a selectively inhibitory chemical agent. 

B.P.: before present. 

Biotic community: a group of interacting organisms 

within a given area. Plant communities are characterized 

by a distinctive physiognomy or appearance, such as 

woodland or forest. At a regional scale, the biotic community is called a biome (e.g., the western coniferous 

forest biome). 

Biodiversity: the variety of life and its processes. Biodiversity includes the diversity of landscapes, communities, and populations (genetic variation). Also called 

biological diversity or biotic diversity. 

Biotic integrity: the ability of a community to recover 

and maintain system processes within historic variability. 

Browsing: the consumption by livestock and wildlife of 

leaves and shoots from woody plants. See grazing. 

Catastrophic: a property of non-linear dynamic systems 

(such as biotic communities) in which what appears to 

be a small disturbance (introduction of an exotic species) 

initiates large changes and establishes a new set of stable 

conditions (see Jameson 1994). 

Cienega: a Southwestern, non-forested wetland. Cienegas 

are dominated by graminoids and may be seasonally dry. 

Climax: the state of a biotic community attained when constituent species populations fluctuate rather than exhibit 

successional replacement and thereby self-perpetuate as 

long as climatic, edaphic, and biotic conditions continue. 

Community of interest: a social group that shares common perspectives, vulnerabilities, and preferences with 

respect to resource management issues (eg., hunters, 

anglers, permittees, and environmentalists). 

Community of place: a social group bounded by geographic locality. 

DBH: diameter at breast height, a measure of tree diameter determined at the standard height of 4.5 feet. 

Dendrochronology: the technique of dating events with 

use of tree rings. 

Disturbance: a discrete event or process which kills or 

removes vegetation. From an ecological and hierarchical 

perspective, disturbance is a change in the minimal 

structure of an ecosystem caused by a factor external to 

the reference structure (see Pickett et al. 1989). 

Dwarf mistletoes: plants of the genus Arceuthobium (Viscaceae). Dwarf mistletoes are shrubby aerial parasites of 

gymnosperms, distinguished by hydrostatically explosive fruits and sticky seeds. 

Ecological approach: a method of natural resource planning and management that provides due consideration 

for the interrelationships between all species, including 

humans, and their environment. 

Ecological assessment: a process for describing the status of ecosystems, their components, related processes 

and effects, and associated interactions. An ecological 

assessment should address social, cultural, and political 

issues relevant to resource management and use scientifically supportable data. 

Ecoregion: a continuous geographic area over which 

the macroclimate is sufficiently uniform to permit 

development of similar ecosystems on sites with similar 

geophysical properties. Ecoregions contain multiple 

landscapes with different spatial patterns of ecosystems. 

Ecosystem: a complex of interacting plants and animals 

with their physical surroundings. Ecosystems are isolated from each other by boundaries which confine and 

restrict the movement of energy and matter; for example, an ecosystem could be recognized at a watershed 

scale by designating an area of common drainage (i.e., 

topography determines movement of water). 

Ecosystem function: the processes through which the 

constituent living and nonliving elements of ecosystems 

change and interact. The term ecological function is 

often used in reference to the role or specific contribution of a entity to system behavior. 

Ecosystem management: a concept of natural resources 

management wherein human activities are considered 
within the context of economic, ecological, and social 

interactions within a defined area or region over both 

the short and long term. Its purpose is to meet human 

needs while maintaining the health, diversity, and productivity of ecosystems. 

Ecosystem restoration: actions taken to modify an 

ecosystem for the purpose of re-establishing and maintaining desired ecological structures and processes. 

Ecosystem structure: the physical elements and spatial 

arrangement of the living and nonliving elements within 

an ecosystem. 

Ecosystem sustainability: the capacity of an ecosystem 

for long-term maintenance of ecological processes and 

functions, biological diversity, and productivity. Also 

called ecological sustainability. 

Endangered species: any species that is in danger of 

extinction throughout all or a significant portion of its 

range. 

Exotic species: a non-native or non-indigenous species, 

usually introduced as the result of human activities. 

Fire hazard: the fuel complex defined by kind, arrangement, volume, condition, and location that form a special threat of ignition or suppression difficulty. 

Forage: food for livestock and wildlife, especially taken 

by browsing or grazing. 

Forb: an herbaceous plant other than a graminoid. 

Forest health: a condition wherein a forest has the 

capacity across the landscape for renewal, for recovery 

from a wide range of disturbances, and for retention of 

its ecological resiliency while meeting current and future 

needs of people for desired levels of values, uses, products, and services. 

Forest: in general, an area or biotic community dominated 

by trees of any size (usually, at least 10 percent of the area 

is covered by trees). If distinction is made to woodlands, 

forests are composed of taller, more closely-spaced trees. 

Fragmentation: a process by which large, contiguous 

blocks of habitat are broken into smaller patches isolated 

from each other by a landscape matrix dissimilar to the 

original habitat. 

Fuels: the organic materials that support ignition and 

spread of a fire (duff, litter, grass, weeds, forbs, brush, 

trees, snags, and logs). 

Fuel treatment: the re-arrangement or disposal of fuels 

to reduce the fire hazard. 

Fuelwood: the round, split, or sawed wood of general 

refuse material, which is cut into short lengths for burning as fuel. 

GIs: geographic information system, a computer-assisted method for organizing, analyzing, and displaying 

spatial data. 

Graminoid: a grass or grass-like plant. 

Grazing: the consumption by livestock and wildlife of 

range or pasture forage. Although strictly grazing refers 

to consumption of forbs and graminoids, it is often used 

in a general sense to include both grazing and browsing. 

Habitat: the natural environment of a plant or animal; 

the locality where an organism may generally be found 

and where the essentials of its survival and reproduction 

are present. Habitats are typically described by geographic boundary, biotic community, or various physical 

characteristics. 

Habitat type: the collective term for all land areas potentially capable of supporting the same climax, biotic communi ty. 

Healthy ecosystem: an ecosystem in which structure 

and functions allow the desired maintenance over time 

of biological diversity, biotic integrity, and ecological 

processes. 

Hierarchical: a description of ecosystems referring to 

their nested and scale-dependent organization. See Allen 

and Hoekstra (1992). 

High-grading: a harvesting practice in which the most 

valuable trees are removed with little provision for 

regeneration or subsequent entries. 

Historic variability: the variation in spatial, structural, 

compositional, and temporal characteristics of ecosystem 

elements during a reference period prior to intensive 

resource use and management. In the Southwest, this 

reference period is typically considered the recent climatic and ecological era before the Territorial period 

(resource use and management by native and Hispanic 

cultures are integrated with, other ecological process). 

Homeostasis: the maintenance of a steady state by use 

of feedback control processes. In homeostatic systems, a 

change outside the normal range is seen as a decline in 

the health of that system. 

Human dimension: an integral component of ecosystem 

management that recognizes people are part of ecosystems; that people's pursuits of past, present, and future 

desires, needs, and values (including perceptions, 
beliefs, attitudes, and behaviors) have and will continue 

to influence ecosystems; and that ecosystem management must include consideration of the physical, emotional, mental, spiritual, social, cultural, and economic 

well-being of people and communities. 

Indicator: a quantitative or qualitative variable which 

can be measured or described and which when 

observed periodically demonstrates trends. Ecosystem 

indicators track the magnitude of stress, habitat characteristics, exposure to the stressor, or ecological response 

to exposure. 

K-V Act: Knutson-Vandenberg Act of 1930 which established a funding mechanism for wildlife and fisheries, 

timber, soil, air, and watershed restoration and enhancement projects. Projects are restricted to timber sale areas 

and are funded from receipts generated on those areas. 

Landscape: a heterogeneous area composed of a cluster 

of interacting ecosystems that are repeated in similar 

form throughout the area. Forest landscapes of the 

Southwest usually range from hundreds to thousands of 

acres and are the result of geologic, edaphic, climatic, 

biotic, and human influences. 

Life zone: a broad class of vegetation and climatic condition based on temperature and precipitation. Merriam's 

(1898) life zones in the Southwest include the Hudsonian, 

Canadian, and Transitional (from cool wet to warm dry; 

terms are nominal rather than specifically geographic). 

Malpais: a Southwestern term for rough country underlain by basaltic lava. 

Management scenario: a description of future conditions 

expected to result from the general implementation of a 

broad resource management strategy. Management scenarios are developed to explore the biological and social 

implications, tradeoffs, and uncertainties of ecosystem 

management rather than present a range of options for 

site specific adoption (management alternatives). 

Monitoring: the component of adaptive management in 

which information is collected to track system behavior 

and its response to management. 

NEPA: National Environmental Protection Act. 

Nonstocked: a site condition in which the area is less 

than 10 percent stocked with live trees. 

Noxious weed: a plant species that possesses one or 

more of the following attributes - aggressive and difficult to manage, poisonous, toxic, parasitic, a carrier or 

host of serious insect or disease and being native or new 

to or not common to the United States or parts thereof. 

OHV: off-highway vehicle. 

Old growth: a late stage of forest succession. Although 

the specific characteristics of old-growth stands vary with 

species composition and history, some commonly expected attributes in mesic forests on productive sites include 

-an abundance of large trees at least 180 to 200 years 

old; a multi-layered, multi-species canopy dominated by 

large overstory trees with moderate to high closure; 

numerous trees with broken tops, snags, and large logs. 

Paleobotany: the study of lake sediments, pollens, and 

microfossils to determine ancient climate and vegetation. 

Phreatophyte: a deep rooted plant that obtains its water 

from the water table. 

Prescribed fire (or burning): the intentional burning of 

forest fuels under conditions specified in an approved 

plan to meet management objectives and confined to a 

predetermined area; ignition may be either the result of 

a scheduled management activity or from other sources 

(e .g., lightning). 

Province: an ecological unit at the regional scale of 

assessment controlled mainly by continental weather 

patterns. 

Resilience: the ability of an ecosystem to maintain or 

restore biodiversity biotic integrity and ecological structure and processes following disturbance. 

Riparian ecosystem: a transitional ecosystem located 

between aquatic (usually riverine) and terrestrial 

(upland) environments. Riparian ecosystems are identified by distinctive soil characteristics and vegetation 

communities that require free water. 

Rhizomorph: a highly differentiated, fully autonomous, 

apically growing aggregation of hyphae produced by a 

few fungal species. Rhizomorphs of Armillaria resemble 

black "shoestrings" and function in extension of the fungus to new substrate. 

Ruderal: plant species adapted to sites with recent disturbance. Some characteristics of ruderal species are - a 

potentially high relative growth rate during the seedling 

phase, early onset of flowering, self-pollination, rapid 

maturation and release of seeds, and sustained seed production at expense of ability for competition and tolerance to stress. 

RVD: recreation visitor day. A recreation visitor day is 

use of a site or area for 12 visitor-hours, aggregated as 1 

person for 12 hours, 12 persons for 1 hour, or any equivalent combination of continuous or intermittent use. 
Salvage harvest: removal of dead and dying trees resulting from insect and disease epidemics or wildfire. 

Sapling: a tree 1 to 4.9 inches DBH. 

Scale: the degree of resolution from a spatial or temporal 

perspective at which ecological processes, structures, 

and changes across space and time are observed and 

measured. 

Sediment: solid material, both mineral and organic, that 

is in suspension, being transported, or has been moved 

from its site of origin by air, water, gravity, or ice. 

Seedling: a tree less than one inch DBH. 

Sensitive species: those plant and animal species identified by a Regional Forester for which population viability is a concern as evidenced by: (a) significant current or 

predicted downward trends in population numbers or 

density; or (b) significant current or predicted downward trend in habitat capability that would reduce a 

species' existing distribution. 

Sere: a transitional stage in plant succession. Environmental conditions, species, or biotic communities may be 

described as sera1 in contrast to climax. 

Slash: debris such as logs, bark, branches, and stumps 

left after logging, pruning, thinning, brush cutting, or 

windstorms. 

Snag: a standing dead tree from which the leaves and 

fine branches have fallen. 

Soil productivity: the capacity of a soil, in its normal 

environment, to produce a specific plant or sequence of 

plants under a specific system of management. 

Stability: a condition whereby system variables return 

to equilibrium after being disturbed. Stability within 

ecosystems results from various population feedback 

mechanisms and integration of disturbances at larger 

spatial scales (see DeAngelis and Waterhouse 1987). 

Stand: a biotic community, particularly of trees, possessing sufficient uniformity of composition, age, and spatial 

arrangement to be distinguishable from adjacent communities. Stand structure refers to the composition, age, and 

arrangement of the trees in a delimited biotic community. 

Stand density index: a relative measure of competition 

in a forest stand based on number of trees per unit area 

and average tree size. 

Stewardship: caring for land and associated resources and 

maintaining healthy ecosystems for future generations. 

Succession: the ecological process of sequential replacement by plant communities on a given site as a result of 

differential reproduction and competition. 

Sustained yield: the perpetual output of a renewable 

resource, achieved and maintained at a given management intensity, without impairment of the productivity 

of the land. 

TES: threatened, endangered, or sensitive species. Also, 

Terrestrial Ecosystem Survey. 

Thinning: the silvicultural practice of removing selected 

trees in a stand to reduce competition for light, water, 

and nutrients and thereby promote the growth and survival of remaining trees. 

Threatened species: any species that is likely to become 

an endangered species with the foreseeable future 

through all or a significant portion of its range. 

Watershed: an area of land with a characteristic drainage 

network that contributes surface or ground water to 

flow at a designated location; a drainage basin or a 

major subdivision of a drainage basin. 

Woodland: an area or biotic community dominated by 

widely-spaced trees of short stature growing on warm, 

dry sites. In the Southwest, common woodland species 

are oak, pinyon, and juniper; these woodlands usually 

occur below 8,000 feet elevation. 
COMMON AND SCIENTIFIC NAMES 

PLANTS 

Common Name 

alligator juniper 

Apache pine 

Arizona fescue 

Arizona pine 

Arizona singleleaf pinyon 

Arizona sycamore 

Arizona walnut 

Arizona white oak 

arroyo willow 

aspen 

bigtooth maple 

blue grama 

blue spruce 

Bonpland willow 

border pinyon 

box-elder 

broom snakeweed 

Chihauhua pine 

corkbark fir 

coyote willow 

Douglas-fir dwarf mistletoe 

Emory oak 

Engelmann spruce 

Fremont cottonwood 

Gambel oak 

Goodding's black willow 

gray oak 

Junegrass 

Mexican blue oak 

mountain muhly 

mutton grass 

narrowleaf cottonwood 

netleaf oak 

New Mexico locust 

New Mexico needlegrass 

one-seed juniper 

pinyon 

pinyon ricegrass 

quakmg aspen 

Scientific Name 

Juniperus deppeana Steud. 

Pinus engelmannii Carr. 

Festuca arizonica Vasey 

Pinus arizonica Engelm. 

Pinus californiarum subsp. fallax (Little) 

D.K. Bailey 

Platanus wrightii S. Wats. 

Juglans major (Torr.) Heller 

Quercus arizonica Sarg. 

Salix lasiolepis Benth. 

Populus tremuloides Michx. 

Acer grandidentaturn Nutt. 

Bouteloua gracilis (Kunth) Griffiths 

Picea pungens Engelm. 

Salix bonplandiana 

Pinus discolor D.K. Bailey & Hawkws. 

Acer negundo L. 

Gutierrezia sarothrae (Pursh) Britt. & 

Rusby 

Pinus leiophylla Schiede & Deppe 

var. chihuahuana (Engelm.) G.R. Shaw 

Abies lasiocarpa (Hook.) Nutt. var. 

arizonaica (Merr.) Lemmon 

Salix exigua Nutt. 

Arceuthobium douglasii Engelm. 

Quercus emoryi Torr. 

Picea engelmannii Parry ex Engelm. 

Populus fremontii S. Wats. 

Quercus gambelii Nutt. 

Salix gooddingii C. Ball 

Quercus grisea Liebm. 

Koeleria macrantha (Ledeb.) J.A. Schultes 

Quercus oblongifolia Torr. 

Muhlenbergia montana (Nutt.) A. Hitchc. 

Poa fendleriana (Steudel) Vasey 

Populus angustfolia James 

Quercus reticulata Humb. & Bonpl. 

Robina neomexicana A. Grey 

Stipa neomexicana (Thurb.) Scribn. 

Juniperus monosperma (Engelm.) Sarg. 

Pinus edulis Engelm. 

Piptochaetium fimbriatum (H. B. K.) Hitchc. 

Populus tremuloides Michx. 
Rocky Mountain Douglas-fir 

Rocky Mountain juniper 

Rocky Mountain ponderosa pine 

Rocky Mountain white fir 

Russian-olive 

saltcedar 

Scouler willow 

Siberian elm 

silverleaf oak 

southwestern dwarf mistletoe 

southwestern white pine 

squirreltail 

subalpine fir 

sugar pine 

Utah juniper 

velvet ash 

wavyleaf oak 

western wheatgrass 

western white pine 

whitebark pine 

FUNGI 

annosus root disease 

schweinitzii butt rot 

tomentosus root rot 

white pine blister rust 

ANIMALS 

Insects 

Common name 

Arizona fivespined ips 

fir engraver 

Douglas-fir beetle 

mountain pine beetle 

pine engraver 

red-spotted purple 

roundheaded pine beetle 

spruce beetle 

western balsam bark beetle 

western pine beetle 

Pseudotsuga menziesii (Mirbel) Franco var. 

glauca (Mayr) Franco 

Juniperus scopulorum Sarg. 

Pinus ponderosa Doug. ex Laws. var. 

scopularum Engel. 

Abies concolor (Gord. & Glend.) 

Hildebrand var. concolor 

Elaeagnus augustifolia L. 

Tamarix ramosissima Ledeb. 

Salix scouleriana Barratt 

Ulmus pumila L. 

Quercus hypoleucoides A. Camus 

Arceuthobium vaginatum (Willd.) Presl 

subsp. cryptopodum (Engelm.) Hawksw. 

& Wiens 

Pinus strobiformis Engelm. 

Elymus elymoides (Rafin) Swezey 

Abies lasiocarpa (Hook.) Nutt. 

Pinus lambertiana Dougl. 

Juniperus osteosperma (Torr.) Little 

Fraxinus vel u tina Torr. 

Quercus undalata Torr. 

Pascopyrum smithii (Rydb.) A. Love 

Pinus monticola Dougl. ex D. Don 

Pinus albicaulis Engelm. 

Heterobasidion annosus (Fr.) Bref. 

Phaeolus schweinitzii (Fr.) Pat. 

Inonotus tomentosus (Fr.) Gilbn. 

Cronartium ribicola Fisch. 

Scientific name 

Ips lecontei Swaine 

Scolytus ventralis LeConte 

Dendroctonus pseudotsuga Hoplans 

Dendroctonus ponderosae Hopkins 

Ips pini (Say) 

Basilarchia astyanax 

Dendroctonus adjunctus Blandford 

Dendroctonus rufipennis (Kirby) 

D yocoetes confirsus Swaine 

Dendroctonus brevicomis LeConte 
western spruce budworm 

western tent caterpillar 

western tiger swallowtail 

Fish 

Apache trout 

channel catfish 

Gila trout 

Little Colorado spinedace 

loach minnow 

rainbow trout 

fio Grande cutthroat trout 

Sonoran chub 

spikedace 

Choris toneura occiden talis Freeman 

Malacosoma calvornicum (Packard) 

Papilio rutulus Lucus 

Salmo apache Miller 

Ictalurus punctatus (Rafinesque) 

Salmo gilae Richardson 

Lepidomeda vittata Cope 

Tiarogo cobitis Girard 

Salmo gairdneri Richardson 

Salmo clarki Richardson 

Gila ditaenia Miller 

Meda fulgida Girard 

Birds 

brown-headed cowbird Molothrus ater 

ferruginous pygmy owl Glaucidium brasillianum 

Mexican spotted owl Stris occidentalis lucida 

northern flicker Colaptes auratus 

northern goshawk Accipiter gen tilis atricapillus 

southwestern willow flycatcher Empidonax trailii extimus 

wild turkey Meleagris gallopavo 

Mammals 

beaver 

bighorn sheep 

bison 

black bear 

elk 

gray wolf 

grizzly 

javelina 

Merriam's elk 

mountain lion 

mule deer 

pronghorn 

spotted bat 

white-tailed deer 

Castor canadensis 

Ovis canadensis 

Bison bison 

Ursus americanus 

Cervus elaphus 

Canis lupus 

Ursus arctos 

Tayassu tajacu 

Cervus elaphus merriami (extinct) 

Felis concolor 

Odocoileus hemionus 

Antilocapra americana 

Euderma maculcltaum 

Odocoileus virgininnus 

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