Uneven-Aged Management of

Longleaf Pine Forests: A Scientist

and Manager Dialogue

Dale G. Brockway, Kenneth W. Outcalt,

James M. Guldin, William D. Boyer, Joan L. Walker,

D. Craig Rudolph, Robert B. Rummer, James P.

Barnett, Shibu Jose, and Jarek Nowak

Southern

Research Station

General Technical

Report SRS–78

United States

Department of

Agriculture

Forest Service
Dale G. Brockway, Research Ecologist, U.S. Department of Agriculture Forest Service,

Southern Research Station, Auburn, AL 36849; Kenneth W. Outcalt, Research Plant

Ecologist, U.S. Department of Agriculture Forest Service, Southern Research Station,

Athens, GA 30602; James M. Guldin, Research Forest Ecologist and Project Leader, U.S.

Department of Agriculture Forest Service, Southern Research Station, Monticello, AR

71656; William D. Boyer, Research Forester Emeritus, U.S. Department of Agriculture

Forest Service, Southern Research Station, Auburn, AL 36849; Joan L. Walker, Research

Plant Ecologist, U.S. Department of Agriculture Forest Service, Southern Research

Station, Clemson, SC 29634; D. Craig Rudolph, Research Ecologist, U.S. Department of

Agriculture Forest Service, Southern Research Station, Nacogdoches, TX 75961; Robert

B. Rummer, Research Engineer and Project Leader, U.S. Department of Agriculture

Forest Service, Southern Research Station, Auburn, AL 36849; James P. Barnett, Chief

Silviculturist and Project Leader, U.S. Department of Agriculture Forest Service, Southern

Research Station, Pineville, LA 71360; Shibu Jose, Associate Professor of Forestry,

University of Florida, School of Forest Resources and Conservation, Milton, FL 32583;

and Jarek Nowak, Assistant Professor of Forestry, University of Florida, School of Forest

Resources and Conservation, Quincy, FL 32351.

The Authors

March 2005

Southern Research Station

P.O. Box 2680

Asheville, NC 28802

Uneven-aged longleaf pine forest in the sandhills of South Carolina, showing

developing pines in an overstory canopy gap and suppressed seedlings beneath the

crowns of nearby adult trees. Photo courtesy of William D. Boyer, Southern Research

Station, USDA Forest Service.

Cover Photo
i

Uneven-Aged Management of

Longleaf Pine Forests:

A Scientist and Manager Dialogue

Dale G. Brockway, Kenneth W. Outcalt,

James M. Guldin, William D. Boyer, Joan L. Walker,

D. Craig Rudolph, Robert B. Rummer,

James P. Barnett, Shibu Jose, and Jarek Nowak
ii
iii

Contents

Prologue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Part A. Methods for Converting Even-Aged Stands to

Uneven-Aged Stands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Part B. Growth and Yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Part C. Selection Harvest Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Part D. Optimum Logging Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Part E. Effects on Red-Cockaded Woodpeckers . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Part F. Prescribed Burning Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Part G. Regeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Part H. Optimum Stand Structure for Management Objectives . . . . . . . . . . . . 26

Part I. Competition Tolerance and Release Potential of

Various Age Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Part J. Viability of Interplanting and Underplanting . . . . . . . . . . . . . . . . . . . . . 31

Epilogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Glossary of Abbreviations and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Contributing Scientists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
iv
1

Uneven-Aged Management of Longleaf Pine Forests:

A Scientist and Manager Dialogue

Dale G. Brockway, Kenneth W. Outcalt, James M. Guldin,

William D. Boyer, Joan L. Walker, D. Craig Rudolph,

Robert B. Rummer, James P. Barnett, Shibu Jose, and Jarek Nowak

Abstract

Interest in appropriate management approaches for sustaining longleaf

pine (Pinus palustris Mill.) forests has increased substantially during the

recent decade. Although longleaf pine can be managed using even-aged

techniques, interest in uneven-aged methods has grown significantly as a

result of concern for sustaining the wide range of ecological values

associated with maintaining continuous crown cover in these ecosystems.

Indeed, land managers have recently sought to restore and sustain the

many habitat attributes upon which numerous at-risk species depend,

while simultaneously producing high-quality wood products from longleaf pine forest ecosystems. Although earlier research produced a substantial body of knowledge to guide even-aged management, less is known

about application of uneven-aged management methods in longleaf pine

forests. Much of this information is yet in the developmental stage.

However, managers from the Florida Division of Forestry and Florida

National Forests, having a keen interest in applying what is currently

known, encouraged scientists of the U.S. Department of Agriculture

Forest Service, Southern Research Station and faculty members from the

School of Forest Resources and Conservation at the University of Florida

to engage in a dialogue that focused on addressing 60 of their key questions concerning uneven-aged management of longleaf pine. This dialogue

addresses issues related to (1) methods for converting even-aged to unevenaged stands, (2) growth and yield, (3) selection harvest techniques, (4)

optimum logging practices, (5) effects on red-cockaded woodpeckers

(Picoides borealis), (6) prescribed burning approaches, (7) regeneration,

(8) optimum stand structure, (9) competition tolerance and release of

various seedling age classes, and (10) the viability of interplanting and

underplanting.

Keywords: Artificial regeneration, group selection, growth and yield,

natural regeneration, prescribed fire, red-cockaded woodpecker, singletree selection, stand structure.

Prologue

At a meeting held in Tallahassee, FL, on February 7–9, 2001,

U.S. Department of Agriculture Forest Service, Southern

Research Station (SRS) scientists and University of

Florida researchers met with managers from the Florida

Division of Forestry and the Florida National Forests to

discuss how to best apply uneven-aged management

methods to longleaf pine (Pinus palustris Mill.) stands on

State and Federal forests in Florida. In recent years, the

public has expressed its desire to have public forests

managed over longer rotations and with methods that

mimic natural processes. They are interested in maintaining

both the long-term sustainability and biological diversity

of these ecosystems. Although uneven-aged management

is one way to mimic the natural stand replacement dynamics that occur in longleaf pine forests, less information is

available for ensuring that the goals of sustainability and

biodiversity will be met. With few exceptions, forest

managers and researchers alike have little experience in

applying uneven-aged management to longleaf pine

forests. Because these forests traditionally have been

managed with even-aged practices, information related to

the economics of uneven-aged management in longleaf

pine forests is scarce.

The purpose of this report is to capture the individual

responses of scientists to questions raised by forest land

managers about the uneven-aged management of longleaf

pine forests and make this information available to a broad

range of interested parties. Two groups of research scientists participated, one group having expertise in the unevenaged management of southern pines generally (but not

longleaf pine specifically) and the other having expertise in

longleaf pine ecology and management generally (but only

limited exposure to uneven-aged management methods).

The approach taken in this publication is that of a question

and answer format, where practicing field foresters and

natural resources managers who routinely face decisions

about application of uneven-aged silviculture in longleaf

pine stands were invited to ask questions of the scientists.

The scientists then responded to any questions about which

they could provide useful information, whether based on

the findings from specific research studies and long-term

demonstrations or, in many instances, based on their scientifically informed opinions (i.e., their “best guess”). As

presented here, the resulting document more closely resembles a roundtable dialogue than a synthesis focused on

providing a precise answer. Instances of disagreement

were retained to underscore the currently developmental

nature of this body of knowledge. These questions and

answers have been organized into the following categories.
2

Part Subject Questions

A Methods for converting even-aged 1 – 7

stands to uneven-aged stands

B Growth and yield 8 – 14

C Selection harvest techniques 15 – 22

D Optimum logging practices 23 – 24

E Effects on red-cockaded woodpeckers 25 – 29

(Picoides borealis)

F Prescribed burning approaches 30 – 40

G Regeneration 41 – 43

H Optimum stand structure for 44 – 51

management objectives

I Competition tolerance and release 52 – 56

potential of various age classes

J Viability of interplanting and 57 – 60

underplanting

Longleaf pine forests have been managed for many

purposes and using several different techniques. Before

deciding to implement one approach or another, managers

should consider the following stand reproduction methods

and management options and select the ones that best

meet their goals:

• Longleaf pine forests can be sustainably managed with

even-aged management methods. Uniform shelterwood

and irregular shelterwood methods most closely mimic

stand-replacing hurricane-type disturbances. Both

shelterwood methods are easy to apply, and there is an

extensive body of research to support their use in longleaf pine forests.

• Much research has been devoted to demonstrating the

effectiveness of the uniform shelterwood method in

regenerating longleaf pine stands. Even though the

responses to the following questions focus on the application of uneven-aged management, we must recognize

that even-aged management in the form of the uniform

shelterwood method remains a viable alternative for

application by many landowners on a variety of longleaf pine sites.

• The irregular shelterwood method is one way to begin

shifting a stand toward uneven-aged management over

time. Irregular shelterwood can be used to convert evenaged stands to a two-aged condition and eventually to

an uneven-aged structure. The structure resulting from

irregular shelterwood often results in excellent redcockaded woodpecker habitat and retains large trees

characteristic of old-growth forests. If desired, irregular

shelterwood can be used indefinitely to sustain longleaf

pine forests and the many ecological, economic, and

social values associated with the longleaf pine

ecosystem.

• Patch clearcutting is another method that can be used

to successfully sustain longleaf pine forests. In application, it creates numerous dispersed small openings in

the forest, and these should facilitate natural regeneration. Although technically considered an even-aged management method, it creates a mosaic of small even-aged

patches within an uneven-aged forest matrix (much as

group selection does where area regulation is employed).

It may be considered a transitional method having the

characteristics of an even-aged management method

but producing results similar to those obtained by means

of uneven-aged management. This method is easier to

apply than either single-tree selection or group selection (with the volume regulation option). Most foresters

can lay out an array of 0.25- to 2-acre patch clearcuts,

thereby creating the initial gaps for longleaf pine regeneration. However, foresters would be wise to guard

against creating unnaturally evenly spaced small clearcut patches across the landscape in a robotic fashion,

since this would impose an artificially uniform pattern on

forest structure that could degrade ecological values and

aesthetic qualities. As field personnel acquire training

and gain experience with application of the uneven-aged

management volume regulation concepts of volumeguiding diameter limit (VGDL) or BDq (explained in

the dialogue section below), a shift from small patch

clearcutting to an uneven-aged management program is

possible.

• We do not have enough long-term research on unevenaged management in longleaf pine stands to state

categorically that these methods will provide for the

long-term sustainability of longleaf pine forests, but our

long-term research on uneven-aged management in

other southern pine forests suggests that it can be applied

in this forest type as well. Public land managers must be

committed to a system of monitoring these ecosystems

over time to ensure that various measures of health in

longleaf pine ecosystems are maintained over time.

Studies and management experience from other forest

types indicate that uneven-aged management is generally more expensive to implement and requires that
3

field personnel possess a higher level of expertise and

training than is required to apply even-aged methods.

• Limited research suggests that group selection is the

uneven-aged management method that most closely

mimics the natural gap-phase stand replacement dynamics typical of longleaf pine ecosystems (e.g., smallscale disturbances such as lightning strikes, localized

fires, insects, or pathogens causing gap formation).

More research is needed on group selection to confirm

these preliminary findings and further refine their

application to longleaf pine forests.

• Single-tree selection has yet to be clearly demonstrated

as an effective method for sustaining longleaf pine

forests. Although single trees do die naturally in longleaf pine forests, there is little evidence to suggest that

longleaf pine juveniles can regenerate in the very small

space resulting from the death of a single longleaf pine

tree. Most evidence indicates that several longleaf pine

trees must fall from the canopy before sufficient space

is available to allow longleaf pine juveniles to begin

growing into the canopy. Group selection is more likely

to provide the required minimum opening size (0.25 to

0.5 acre). Single-tree selection has never been comprehensively tested against all the other stand reproduction

methods listed above. More research is needed before

this method can be recommended for sustaining longleaf pine forest ecosystems.

It should be noted that longleaf pine forests grow on a wide

range of site types (e.g., wet flatwoods, mesic uplands,

xeric sandhills, and mountains), each characterized by a

distinctly different ambient environment. Across its range,

longleaf pine is often found growing in association with

slash pine (P. elliottii Engelm.) on flatwoods sites, loblolly

pine (P. taeda L.) and shortleaf pine (P. echinata Mill.) on

upland sites, and various hardwood species on many site

types. Therefore, no single management prescription is

appropriate for sustaining longleaf pine forests everywhere. In pursuing their objectives, prudent managers

will typically select a combination of approaches that is

appropriate for the specific environment and that allows

for the trajectory of forest development from current status

to future desired conditions. Prior to implementing any of

the above methods, it is desirable to restore the native

plant community by an appropriate application of mechanical, chemical, and burning methods. In the absence of a

restored ecosystem, forest management activities may

simply increase competition from woody plants in the

midstory and understory, thereby jeopardizing longleaf

pine regeneration success.

In implementing the above methods, forest managers may

consider using artificial regeneration to supplement seedling stocking when natural regeneration is inadequate.

However, planting should not be viewed as an infallible

remedy for improper application of these forest reproduction methods. Regardless of the stand reproduction method

selected, managers should be mindful of the crucial importance of using prescribed fire to sustain longleaf pine forest

ecosystems over the long term. Periodic fire is essential

for maintaining longleaf pine forest composition, structure, and function, primarily by curtailing the proliferation

of woody plants in the understory and midstory and

creating seedbed conditions favorable for the regeneration

and development of longleaf pine seedlings.

Part A. Methods for Converting

Even-Aged Stands to

Uneven-Aged Stands

Forest Manager: (1) What are the best or most

efficient methods for converting from even-aged

management to uneven-aged management?

Brockway: The quickest way for a land manager to convert an even-aged longleaf pine forest to an uneven-aged

longleaf pine forest is through application of the irregular

shelterwood stand reproduction method. Although shelterwood methods are generally thought to result in even-aged

stand structures, the irregular shelterwood method allows

rapid development of multiple age classes in a forest. As

with application of the uniform shelterwood method, the

seedcut will reduce stand basal area to 25 to 30 square feet

per acre. However, the overwood is not removed once the

regenerated seedlings have become established, as it is in

the uniform shelterwood method. Rather, the overwood

harvest is deferred, and it is retained onsite throughout the

entire next rotation. As a bonus, the damage done to seedlings during harvest of the overwood is eliminated. Retaining wind-firm trees of this long-lived species presents little

problem in implementing this method. Seed dispersed from

overstory trees initially results in a two-storied forest

structure. However, as additional seed trees mature and

disperse seed across the site in ensuing decades, multiple

waves of seedlings emerge, and an uneven-aged forest

structure develops. Advantages of this method include

(1) sustainable harvest of usable, often high-quality wood

fiber; (2) continuous maintenance of a canopy of tree

cover to achieve ecological and aesthetic objectives; and

(3) easy implementation using existing machine technology

and forest resource information. Once in an uneven-aged
4

condition, the forest can be so maintained in a number of

ways.

A somewhat slower but ecologically sound silvicultural

method for converting from an even-aged to uneven-aged

forest structure is through the group selection method.

Creation of numerous 0.25- to 2-acre gaps in an even-aged

forest encourages regeneration of varying ages to develop,

much as in natural gap-phase regeneration, which is

common in longleaf pine forests. The end product of this

process is a series of small even-aged patches that constitute an uneven-aged forest across the landscape. This stand

reproduction method probably comes closest to the manner

in which natural longleaf pine forests have historically

renewed and sustained themselves for thousands of years.

Of course, periodic fire must be used to ensure that proper

seedbed conditions are maintained for regeneration of longleaf pine seedlings and control of competing woody plants.

Advantages of this method include (1) sustainable harvest

of usable, often high-quality wood fiber and (2) continuous

maintenance of a canopy of tree cover to achieve ecological

and aesthetic objectives. This uneven-aged management

method can be applied to a forest in perpetuity without

degradation of resource values.

Boyer: The most rapid way to change from even-aged to

uneven-aged stand structure, given a mature or maturing

even-aged stand, is to create an irregular shelterwood, or

two-aged stand. The typical reverse-J curve of size-class

distribution is rapidly established. In one study on an average Coastal Plain site, the largest ingrowth was 14 inches

in diameter at breast height (d.b.h.) at 40 years, only 2

inches less than the smallest of the residual trees. This

occurred only in stands with a low density (10 square feet

per acre) of residuals. Once a reverse-J curve is established,

it can be maintained indefinitely through any of several

strategies.

Guldin: Two stand reproduction cutting methods and one

method that grades between intermediate treatments and

reproduction cutting have been used successfully to convert

from even-aged management to uneven-aged management

in loblolly-shortleaf pine stands on the upper West Gulf

Coastal Plain.

Group Selection or Single-Tree Selection

Regardless of whether you choose group selection or

single-tree selection, one of two regulation methods is

called for, BDq regulation or volume regulation. For BDq

regulation, the forester must inventory the existing stand

and generate a stand-and-stock table by 1-inch or 2-inch

d.b.h. classes. Separately, a hypothetical uneven-aged

target stand structure is created using the basal area (B),

maximum d.b.h. (D), and age class distribution coefficient

(q) parameters. The stand is then harvested to conform to

this target. Many publications provide the detail necessary

to properly implement the BDq method. Some of these

studies and publications contain short-term research results.

The VGDL method can also be adapted to conversion of

even-aged stands, but since it is a sawtimber regulation

method, separate attention must be paid to ensure adequate

regeneration in smaller size classes. This is also true to a

lesser extent with the BDq method.

The method of regulation is independent of whether singletree or group selection is used. Regulating group selection

with any other method (such as area regulation) is much

less supported in the uneven-aged silviculture literature

and comes uncomfortably close to patch clearcutting or

some other form of patch-based even-aged management.

Nor should it be assumed that the group selection method

requires that an opening be cleared of all trees (as in patch

clearcutting). Residual seed-producing trees can be left

within group openings at the equivalent of seed-tree or

shelterwood residual basal area levels (10 to 30 square feet

per acre) if this is desired and more appropriate for the

silvics of the species involved, and this might allow group

openings to be made larger than 2 acres. Given the success

that Tom Croker and his colleagues experienced in the

1960s and 1970s at the Escambia Experimental Forest

(EEF) in southern Alabama, the group shelterwood with

group openings varying from 2 to 5 acres might be a very

effective means of managing longleaf pine using the selection method. (This does, however, deviate from current

Forest Service Region 8 guidelines that specify a 2-acre

maximum size for group selection).

Irregular Shelterwood

An irregular shelterwood approach can be used to establish

three age classes. This approach would lead to an imbalanced uneven-aged structure with fewer age classes. Experimental use of the shelterwood method in longleaf pine at

the EEF is well documented. Some modifications of the

method would be needed to allow us to apply what we know

about the silvical characteristics of longleaf pine. For example, longleaf pine’s adaptation to advance growth could be

used to compensate for its erratic seed production. A third

age class could be obtained by retaining the first age class

while conducting another shelterwood reproduction cut

shortly after the second age class starts to produce cones.

By this method the minimum of three age classes that

defines uneven-aged condition would be obtained. A fourth

iteration of shelterwood might also be possible. Prescribed

fire would be needed to effectively manage these classes.
5

Rehabilitation Technique

Methods similar to those pioneered for rehabilitation of

understocked loblolly-shortleaf pine stands at the Crossett

Experimental Forest (CEF) could be used to move the

stand toward an uneven-aged condition. The VGDL regulation method is one possibility. In its early stages, this

prescription resembles classic improvement cutting, but as

time goes on the practice graduates to the selection reproduction cutting method.

This combination of prescriptions evolved as follows.

Stands at the CEF originated in about 1915 following pine

high-grading to a 15-inch stump limit. Uncontrolled fire

followed on an irregular interval. After 20 years, the

Southern Forest Experiment Station established the CEF

in 1934, and Station scientists began to control hardwood

competition and encourage development of better pines by

cutting the poorer ones using volume-control regulation

methods. After 15 years of this management, pine stands

were producing 400 board feet per acre (Doyle log rule)

sawlog volume annually. Volume regulation (cutting-cycle

harvests based on growth or a proportion thereof) has been

used in these stands for the succeeding 50 years, and

periodic yields in the vicinity of 400 board feet per acre

have been maintained. There are good empirical and

research data for this.

One might consider applying this sequence of techniques

to the recently acquired longleaf stands in Florida and

elsewhere. If those stands have a history of mismanagement

that resembles high-grading but still have reasonable

stocking levels of longleaf, they may be candidates for this

rehabilitation prescription. Similarly, if stands have a

history of being damaged by storms such as hurricanes,

managing existing stands may be an easier proposition

than starting over with new stands. Some simple research

would be in order to establish the minimum acceptable

stocking levels from which recovery can be expected.

Forest Manager: (2) What cutting method is best

for regenerating longleaf pine under an unevenaged management system—single-tree selection,

group selection, or another method?

Guldin: During his tenure at the CEF, founding scientist

Russ Reynolds explicitly refused to identify his VGDL

method as single-tree or group selection. He simply called

it selection. Sometimes this selection method would result

in large openings in the forest; sometimes small ones would

suffice. Following the guideline of cutting the worst and

leaving the best, situations can be imagined where from

one to many adjacent trees would be harvested. I’d propose

that one approach for longleaf pine is probably a combination of group and single-tree selection after Reynolds’s

description of selection.

Both single-tree selection and group selection can be

adapted for use in longleaf pine early in the process of

converting stands to uneven-aged structure. Experimentation with cutting-cycle lengths, after-cut target stands,

opening size, residual basal area, and so on will be needed,

and in some cases data from existing studies of longleaf

pine may be applicable. On drier sites such as the sandhills,

group selection is probably more likely to produce desired

results. Single-tree selection may be feasible on better

sites, but more research is needed before we can recommend

one method over the other for such sites.

The single best source for information on uneven-aged

management is Bob Farrar’s (1996) uneven-aged management guide, which is based on a combination of empirical

experience and research. Farrar cites both the VGDL and

BDq regulation methods as feasible in longleaf pine, but

only under modified group selection and with cyclic

prescribed burning. The burning program is required to

keep competing hardwoods in check and to keep seedbeds

prepared for any seedfall that might occur. When seedlings

become established at acceptable densities within an area

(local distributions equivalent to 700 to 800 trees per acre),

a cutting-cycle harvest to remove the overstory trees will

allow the seedlings to initiate height growth. Subsequent

cutting-cycle harvests can be used to expand existing

groups or to establish new groups and as a free thinning in

the matrix of the stand between the group openings. This

varied approach should ensure that the method does not

become patch clearcutting.

How can one tell whether a given cutting-cycle harvest

more closely resembles group selection or patch clearcutting? Ideally a group selection harvest should have the

following attributes: (a) openings are created in a random

rather than geometric pattern, (b) the total area in groups

is not obtained by using an area/rotation length calculation,

and (c) there is variation in the size and shape of the

openings created by harvesting.

Finally, the more experience one has with these methods,

the more one will feel comfortable with following the

marking rule “cut the worst trees and leave the best.” This

is difficult to do consistently over time under group selection. However, the greater one’s experience with the selection method, the easier it will be to obtain regeneration in

openings.
6

To better understand longleaf developmental dynamics, we

need better data on the establishment and development of

longleaf seedlings in openings of varying size and beneath

residual basal areas that vary from 10 to 60 square feet

per acre. Such data would help us understand the kinds of

conditions under which longleaf regeneration can become

established and, more important, develop in an acceptable

manner.

Forest Manager: (3) At what age would a planted

longleaf pine stand be capable of producing

enough viable cones and seeds to reproduce

itself through natural regeneration?

Boyer: Longleaf tree size (dominant or codominant members of a stand) rather than age indicates the cone-bearing

potential of a tree. Within shelterwood stands, a 9-inch

d.b.h. tree produced an average of 4 cones annually, a

12-inch tree averaged 12 cones annually, a 15-inch tree

averaged 32 cones annually, and an 18-inch tree averaged

58 cones annually. A shelterwood stand with 30 square feet

per acre could have 68 trees of 9-inch d.b.h. or 24 trees of

15-inch d.b.h. Cones per acre, on average, will amount to

272 with the 9-inch trees and 768 with the 15-inch trees.

The recent increase in size and frequency of longleaf cone

crops, if continued, will likely increase the long-term averages noted here. At least 750 cones per acre are required

for successful natural regeneration. The larger the seed

trees, the more frequent the usable cone crops, but cone

production per acre increases more slowly for trees with

d.b.h. > 15 inches than for trees with d.b.h. from 9 to 15

inches.

Forest Manager: (4) What is the most effective

regimen for accomplishing the conversion of

even-aged stands to uneven-aged stands,

beginning at various age or size classes and

stocking levels? Also, we need to distinguish

between a plantation and a natural stand.

Boyer: For an explanation of the most effective way to

convert even-aged stands to uneven-aged condition, see

the replies to question 1 above. The stand should contain

sufficient numbers of trees of seed-bearing size before you

attempt to utilize natural regeneration, which is the most

economical way to provide a stand with recruitment on a

regular basis.

Guldin: The most effective way to convert an even-aged

stand to an uneven-aged stand depends on the specific circumstances of the stand in question. Suggestions offered

in my answer to question 1 might help the manager decide

the direction for a particular stand. We could probably come

up with some reasonable guesses (they might also be called

guidelines) for various age classes and stocking levels and

also for converting plantations. As a starting point, I would

suggest the CEF standard for loblolly pine (see the following tabulation), perhaps reducing the residual basal area

slightly to account for the greater intolerance of longleaf

regeneration.

Variable Value

B, residual basal area 60 square feet per acre

D, maximum diameter retained 18 to 20 inches

q, diminution quotient 1.2 for 1-inch classes or

1.44 for 2-inch classes

Cutting cycle 5 to 7 years, perhaps 7 to

10 years for longleaf pine

Volume 5,000 board feet per acre

(Doyle log rule)

Residual stand parameters must be tailored to cutting-cycle

harvest lengths so that residual stand conditions do not

become dense enough to arrest regeneration development.

Practitioners should keep in mind that these parameters for

applying the BDq method are a starting point. It is apparent

from the CEF work and other work that the most important

element of the target curve to achieve is B, the residual

basal area. The maximum retained diameter, D, can be set

at whatever d.b.h. class the landowner is willing to establish. A key factor in this decision is whether a landowner

believes that the many ecological benefits provided by

leaving large trees (under a large D) are worth the risk of

financial loss that could result from the deaths of large

residual trees, which may be lost to lightning and other

mortality factors. Some have advocated tracking the target

diameter distribution, but then allowing some trees to

“escape” from the target BDq curve by simply retaining

them as relict trees above the D. If this silvicultural tactic

is employed, one key element is needed: the basal area of

these larger relict trees must be accounted for in the retained

B, the target residual basal area. For example, one cannot

simply configure the target BDq curve using the target

parameters of B, D, and q and then allow relict trees to

exist outside the parameters of the target curve. The reason

for that is that those relict trees carry significant basal area

that must be accounted for in development of the target

curve lest the residual basal area be too high for adequate

regeneration development. If x square feet per acre of basal
7

area are left in relict trees above the D, the BDq target curve

at and below the D should have its B reduced by x as well,

to retain the overall target basal area for all trees in the

stand. Finally, attaining the proper q is of least importance,

especially early in converting an even-aged stand to an

uneven-aged structure. During conversion, it is more important to leave the best trees in the stand at the suggested

residual basal area, and the best trees in a stand with an

even-aged structure will generally not be distributed among

all size classes. However, not leaving some trees in all size

classes increases the likelihood of irregular product yields

through time.

Forest Manager: (5) How long does it take to

establish a truly uneven-aged stand, beginning at

various age or size classes and stocking levels?

Guldin: The answer to this question depends on the definition of a “truly” uneven-aged stand, and on the age and

stocking levels at the start of the conversion. Generally

speaking, different age classes of trees (10-year groupings)

are distinguishable by tree size in uneven-aged stands. This

rule of thumb would suggest that the textbook requirement

of three age classes to define an uneven-aged stand would

require a minimum of 10 years to develop: the first age

class would exist on the site at year 0 of management, the

second would be obtained through reproduction cutting at

year 0, and the third would be obtained after a cuttingcycle harvest at year 10.

More realistically, the length of time required to establish

an uneven-aged stand depends on the number of size classes

present in the initial stand after the first cut and the length

of time to obtain two more seed crops from the longleaf

pine overstory. This estimate assumes that seedlings could

germinate and become established after each seed crop. As

a practical matter, it is likely that from 10 to 30 years will

be required to produce the minimal age class and structural

attributes that define an uneven-aged stand, depending on

initial stand condition and the time needed to obtain two

new age classes of reproduction.

Forest Manager: (6) How do different methods for

converting even-aged stands to uneven-aged

stands compare with respect to efficiency, growth

and yield, prescribed fire, pine regeneration, and

ground cover quality and diversity?

Boyer: As can be seen below, the most rapid development

of longleaf pine ingrowth occurred under lightest residual

overstory (i.e., even-aged stands with initial stand basal

area = 0).

Residual pine Ingrowth pine Total pine

Initial stand

Basal area Basal area Volume Basal area Volume Basal area Volume

square feet square feet cubic feet square feet cubic feet square feet cubic feet

per acre per acre per acre per acre per acre per acre per acre

Block A:

 0 0 0 79.1 1884.3 79.1 1884.3

 0 0 0 73.9 1795.7 73.9 1795.7

 9 9.6 265.7 50.9 1005.7 60.5 1271.4

18 31.7 885.7 29.6 430.0 61.3 1315.7

27 38.7 1067.1 10.0 88.6 48.7 1155.7

36 56.1 1565.7 3.5 62.9 59.6 1628.6

45 67.0 1811.4 0.9 15.7 67.9 1827.1

Block B:

 0 0 0 87.4 1998.6 87.4 1998.6

 9 10.9 305.7 51.3 981.4 62.2 1287.1

18 27.4 767.1 20.0 251.4 47.4 1018.5

27 40.4 1125.7 7.8 74.3 48.2 1200.0

36 55.2 1527.1 1.7 21.4 56.9 1548.5

45 70.0 1940.0 0.4 2.9 70.4 1942.9
8

closure when foliage of the pines is above the normal

flame length of the fire, to minimize sapling mortality.

Pine Regeneration

The success of the shelterwood approach in achieving

regeneration is well documented for longleaf pine. I see no

reason that a third age class couldn’t be established in such

a stand. The same comment applies to group selection, an

example being Farrar’s modified approach. Few data are

available on the success of single-tree selection or whether

one would obtain longleaf pine seedlings when converting

understocked even-aged stands of longleaf pine to an

uneven-aged structure.

Ground Cover Quality and Diversity

Those methods that create the greatest diversity of microhabitats should result in the greatest diversity of ground

cover. Modified group selection is such a method. A more

important question would be, how much ground layer

diversity is desired?

Forest Manager: (7) What criteria should be used

to determine when to convert which even-aged

stands to uneven-aged stands?

Guldin: Landscape attributes and management implications

are important factors in these determinations.

At the stand level, though, several structural attributes can

be used to identify those stands more likely to be quickly

converted to an uneven-aged condition. First, stands with

more than one size class of trees are easier to convert since

the second age class is already present. Second, stands that

were high-graded or overcut in the past may be good candidates for converting to uneven-aged condition. If these

stands are understocked but have sufficient volume to

rehabilitate, they can be quickly converted to productive

uneven-aged stands. Third, experience in a number of

forest types suggests that uneven-aged silviculture is more

easily done on sites of poor quality (i.e., those with site

indices ranging from 50 to 70) rather than on good-quality

sites (i.e., those with site indices of 80 or more), because

competing vegetation is more vigorous on good sites.

Supplemental release treatments to enhance seedling development are less likely to be needed on poor sites, and thus

chances of success are higher there. Finally, stands with a

great deal of within-stand heterogeneity in density, pockets

where few trees exist, and other pockets where an excess

of the most common age class exists would be better

candidates for conversion than fully stocked even-aged

stands.

Growth rate was compared with that of even-aged stands

at or near the same age as ingrowth in the two-aged stands

(i.e., initial stand basal area > 0), at last remeasurement of

36 years in block A and 40 years in block B. Competition

with the residual parent trees resulted in rapid establishment

of the reverse-J diameter class distribution, with the largest

number of stems in the small diameter classes, but also a

fair number of sawlog size trees by age 40. The parent trees

average about 90 years in age. This appears to be the most

rapid way to obtain uneven-aged stand structure with a

growth rate (in these tests) close to that of even-aged stands.

For the last 5-year remeasurement interval, the two-aged

stands have been growing at nearly 80 percent of the rate

of even-aged stands, although total volume yield of the

two-aged stand is still slightly under 50 percent of that of

the even-aged stands. A note of caution is appropriate here.

The stands used in tests of uneven-aged management on

the EEF consist largely of mature trees, while the two-aged

stands are largely young trees, mostly still below merchantable size classes. The next remeasurement of these stands

will give us more information. See also my answer to

question 28 for information on the effects of uneven-aged

management with appropriate fire regimes on the diversity

of natural communities.

Guldin: The effectiveness of different treatments in producing uneven-aged characteristics in longleaf pine stands

can be discussed in terms of efficiency, growth and yield,

prescribed fire, pine regeneration, and ground cover quality

and diversity, as follows.

Efficiency

Most studies show that if one wants to convert an even-aged

stand to an uneven-aged condition, it is more biologically

and economically efficient to convert poorly stocked evenaged stands than fully stocked even-aged stands. Directly

converting fully stocked even-aged stands to uneven-aged

ones (especially those stands nearing maturity) is the most

wasteful way to convert the stand. Group selection or the

irregular shelterwood method might offer a compromise.

Growth and Yield

The same comments offered regarding efficiency apply

here.

Prescribed Fire

I don’t see any difference in the ability to maintain prescribed fires under any of these alternatives. The only exception would be that fire should be excluded when using the

irregular shelterwood approach between the period of

emergence from the grass stage and the point after crown
9

Part B. Growth and Yield

Forest Manager: (8) What volume growth rates

can be expected from longleaf pine seedlings

established on a variety of common soil types

and vegetation communities?

Boyer: The nature and degree of competition largely determines the early growth rate of longleaf pine seedlings. The

form of height-over-age curves of young longleaf pine is

affected by competition level (both seedling density and

site quality). Plantation site index curves differ among old

fields, prepared sites, and unprepared cutover sites (Boyer

1983). All plantation site index curves differ from those

for natural stands. Natural stands, while lagging greatly in

growth during early years, tend to catch up with planted

cousins in later years. Also, natural longleaf pine stands

released early in their development get a substantial growth

jump on same-aged seedling stands that are not released

until later, but both types of stands reach small pole size

(age 30) with no difference in tree size or volume yield

per acre. This result was replicated on both poor and

average Coastal Plain sites (Boyer 1985).

Forest Manager: (9) What volume growth rates can

be expected from merchantable longleaf pine

stands consisting of at least three age classes on

a variety of common soil types and vegetation

communities at various densities?

Boyer: The oldest stand for which we have data on this

issue, the EEF Farm Forty, had a mean annual increment

of 36 cubic feet per acre per year over 50 years. Now this

stand appears to have reached a steady state in terms of

growth. Growth is 42 percent of that expected for an evenaged stand on the same site, maintained at the same average

density, over an 80-year rotation. The gap between growth

in these two types of stands would be smaller if the rotation of the even-aged stand were extended to 120 years,

although information on average yield up to 120 years is

not yet available. Permanent plots of a longleaf pine

growth-and-yield study will soon supply these data.

Guldin: Here are some rules of thumb that are based on

our Arkansas work with loblolly-shortleaf pine and other

citations from the literature.

When properly configured, well-balanced uneven-aged

stands can be managed by cutting growth. The growth to be

expected depends on the conditions associated with determining balance. Annual growth expectations for sawtimber

(Doyle log rule), using simple interest rate projections, at

different rates and cutting-cycle lengths, assuming an

initial volume of 5,000 board feet per acre, are shown

below.

Interest rate (percent) Length of

cutting cycle 4 6 8

 years board feet per acre per year

 5 217 338 469

 7 226 360 510

 10 240 395 579

Our experience with yields from loblolly-shortleaf pine

stands in Arkansas suggests that sawtimber volume production over 36 years of uneven-aged management parallels

that expected from natural even-aged stand management.

These stands showed slightly lower yields, but with higher

log quality than that expected from plantations managed

for similar lengths of time. Uneven-aged stands produce

from 50 to 75 percent of the total merchantable cubic volume expected from plantations. Uneven-aged silviculture

does not compare with plantations as a prolific producer of

pulpwood, but it produces large volumes of high-quality

sawtimber.

Forest Manager: (10) How can we create growthand-yield tables for balanced, uneven-aged

longleaf pine stands on various sites?

Guldin: Individual tree growth-and-yield models will be

required. Our research work unit in Arkansas (SRS-4106) is

just completing a 15-year study to provide data to develop

a model such as this for loblolly-shortleaf pine stands. Bob

Farrar initiated a growth-and-yield study in even-aged longleaf pine stands that is being maintained by Ralph Meldahl

at Auburn University. While neither of these can be used

directly to estimate growth and yield of uneven-aged longleaf pine stands, they provide a starting place. Bill Boyer

tells me that scientists in the Auburn research unit (SRS4105) are currently tracking growth and yield for several

uneven-aged longleaf pine stands on the EEF (different

compartments managed with different techniques). These

compartments should provide data that could be used to

create a growth-and-yield table for uneven-aged longleaf

pine stands sometime in the future.
10

Forest Manager: (11) How can we create growthand-yield tables for various combinations of

unbalanced, uneven-aged stands on various

sites?

Guldin: Individual tree growth-and-yield models will be

required (refer to my answer to question 10).

Forest Manager: (12) What are the growth rates

of trees of different diameter classes under the

canopy of an uneven-aged stand?

Boyer: Rates of volume growth of different diameter classes

depend on crown class, stand density, and site quality.

Rates for intermediate or suppressed trees are very slow.

Rates of 20 to 25 years per inch d.b.h. have been observed.

Growth of young trees depends on the proximity of older,

dominant trees. Longleaf pine is the most intolerant of the

southern pines and does best when free from all competition.

Guldin: Data that could be applied to this question should

be available once the ongoing longleaf pine growth-andyield studies noted in the responses to question 10 are

completed.

Forest Manager: (13) Can we develop an unevenaged extension for the Forest Vegetation

Simulator (FVS) for longleaf pine and slash pine?

Nowak: I have been in touch with the Forest Service staff

at the Forest Management Service Center in Fort Collins,

CO, who developed the existing FVS. I have not heard back

from them yet, but would be interested in cooperation on

this question if anyone else is interested in working on

this. FVS is an age-independent model, and the recently

developed Southern Variant of FVS includes models for

longleaf pine and slash pine that would handle growth

projections in uneven-aged stands. A near-term need is

accuracy testing of the current models for longleaf pine

and slash pine.

Forest Manager: (14) What are the growth rates of

individual diameter classes under uneven-aged

management?

Boyer: We currently have studies on the EEF in unevenaged longleaf pine stands that may help answer this and

other questions (10, 11, and 12) concerning growth and

yield for uneven-aged longleaf pine. These data do not yet

provide enough information to answer these questions, but

stay tuned.

Part C. Selection Harvest Techniques

Forest Manager: (15) Can methods be developed

to mark uneven-aged timber sales in one pass?

Guldin: Yes, but not according to regulation approaches

that stand the test of time. Both the BDq and the VGDL

techniques require inventories in advance of harvest. (But

then again, so would ideally prescribed even-aged thinnings and reproduction cuttings.)

Scientists at research work unit SRS-4106 have discussed

one possibility but have not tested it in the field. The theory

is that one could mark an uneven-aged stand in a single

pass if one intended to apply the uneven-aged marking rule

of cutting the worst trees and leaving the best. The key

would be to take the unusual step of marking trees to leave.

This would require keeping a tally of every tree marked,

then periodically checking the tally of marked residual

trees against the cumulative area of the stand that had been

covered by the marking crew. To do this, it would be necessary to keep electronic marking tallies such that cumulative

tallies could be instantly generated in the woods; be able

to subdivide the stand into subdivisions of known stand

area, and be able to recognize the subunit boundaries in

the field; and cut the worst trees and leave the best trees,

regardless of spacing.

A second possibility would be to mark a stand and to

frequently check one’s marking using a prism. Using this

approach, one would make an ocular estimate of or a very

cursory prism cruise to provide a rough estimate of basal

area. One would then mark and tally to a residual basal

area using the “cut the worst trees and leave the best”

approach such that the desired residual basal area would

be attained. This process would resemble a low thinning

that would leave an understocked stand having a residual

basal area of 50 to 60 square feet per acre. One would

expect regeneration to develop in those portions of the

stand where residual basal area is less than the average. To

execute this marking, one would use the prism frequently

to confirm that marking has retained the target residual

stand basal area and cut the worst trees and leave the best

trees, regardless of spacing.

There are two compromises associated with these

approaches. Firstly, they violate all of the rules thought to

be important to encourage development of structure through

adherence to guiding curves or attention to sub-sawtimber

diameter classes. Thus, these techniques suffer from the

same limitation as the VGDL technique in requiring implementation by highly skilled crews. Secondly, there is no
11

way other than by experience to tell whether an operable

cut will be obtained.

The “mark to leave” procedure has been applied by Bureau

of Indian Affairs foresters in uneven-aged ponderosa pine

stands in the Rocky Mountains and Intermountain West.

Field tests have been limited in the Southern Region by

the need to mark trees being cut for timber sale contract

administration purposes.

Forest Manager: (16) Can a group selection

technique be developed that is simple to

implement and that guarantees adequate

regeneration and residual old growth?

Boyer: Yes, provided that volume yield is not a consideration. I suggest you read the paper by Farrar and Boyer

(1991), which describes in detail the VGDL method. This

method was developed by Russ Reynolds and applied to

loblolly-shortleaf pine stands on the CEF. Under this

method, diameter class distribution is not a concern and is

not monitored as in the BDq method. This saves a lot of

time. Board-foot volume is used to regulate the stand under

the VGDL method, so the actual harvest tends to occur

only in trees 9.6 inches and larger, with much of the cut

based on trees of larger diameter. The manager has wide

latitude for exercising his or her own judgment. In this

regard, it is similar to the Stoddard-Neal variant of singletree selection uneven-aged management. Compared to the

EEF Farm Forty, the VGDL method has had lower total

volume increment so far but higher sawtimber increment.

Brockway: Authorities typically recommend that silviculturists who implement the group selection reproduction

method use one of the principal volume regulation techniques, VGDL or BDq. While these approaches may be

modified to reduce the administrative workload and somewhat simplify their application, implementation of unevenaged procedures requires greater information, more

planning, and increased skill levels for field crew members

than does even-aged management. Area regulation may be

an alternative to volume regulation in applying the group

selection method.

Implementation of group selection with area regulation is

not very different from implementing small patch clearcuts. At the appropriate time, field staff mark the boundary

of each small unit (0.25 to 2 acres) on the ground, and some

or all mature trees within the defined unit can be harvested.

Although tracking progress on a large land base for numerous 2-acre units is a complex task, currently available

computer hardware and software (including geographic

information system and global positioning system technology) should render this work manageable. The forest land

base would thus be divided into a large number of small

units, and forest regulation could proceed based on these

units. Under area regulation, managers establish a rotation

of field visits to individual units on a regular periodic basis.

For example, each unit will be inspected in the field and

its management status and needs assessed once every 10

years (or another time interval if that were more suitable).

At the time of inspection, a harvest or no-harvest decision

will be made based on the current condition in relation to

a desired condition. Each year a certain proportion of your

units can be scheduled for harvest. For example, the number

of units to be harvested each year would not exceed 0.5

percent of the total number of land units if you had a goal

of maintaining the age range of trees on the forest between

0 and 200 years old. On a forest with 400,000 acres (and

200,000 units) under such management, 1,000 units, or

2,000 acres, might be regenerated each year on the average.

Of course there would be opportunity to deviate from such

a schedule, should a natural or man-made disturbance

necessitate intervention for restoration purposes. Note that

the above scenario assumes a fully regulated forest condition. One key to making such a system work successfully

would be the proper dispersion of units to be harvested

during any single year. It is important not to cluster the

harvest units too closely or the saturation effect could

greatly degrade resource values in that area in the short

term. Harvesting in adjacent units should be avoided during

the same year or during any time frame that results in a

large opening in the forest canopy. Obvious exceptions

could be made for natural disturbance events that resulted

in the mortality of trees over large areas. The great peril in

this approach is that it essentially functions like small patch

clearcutting and brings with it the potential for abuse previously associated with large block clearcutting. Therefore,

managers should resist the temptation to expand individual

unit sizes over time unnecessarily, to cut trees in regularly

dispersed geometric patterns that appear aesthetically

unnatural, to use area regulation as a cover for cutting the

best trees and leaving the worst trees (i.e., high-grading),

and to strictly limit the maximum tree age to an arbitrarily

chosen “rotation age.” Since longleaf pine is long-lived, it

is entirely appropriate to plan for growth of individual

trees and development of some stands to reach advanced

ages (200 to 400 years) in parts of the forest.

Group selection, as a stand reproduction method, has been

used in Europe to restore and sustain forests for hundreds

of years. The methodology is well documented and taught

in the forestry curricula at major academic institutions
12

around the world. It is, however, a method that has been

less applied operationally in the United States. A land

manager is most fortunate to find longleaf pine regeneration already established before creating 0.25- to 2-acre

gaps in the forest. However, if advanced regeneration is

not present, this should not prevent the manager from

harvesting timber and creating the gaps, generally cutting

the worst trees and leaving the best trees. As long as

periodic fire is applied to the forest, gaps unoccupied by

longleaf pine seedlings can be maintained brush-free (or at

least brush invasion will be discouraged) until longleaf

pine can seed into the area. Gaps may be occupied by

grasses and forbs (and a few shrubs) until a favorable seed

year arrives. Alternatively, forest gaps created by this

method need not have all adult trees removed at once.

Residual seed trees may be retained within gaps to aid in

regeneration and then removed during a future stand entry.

Old-growth forests in many environments renew and sustain themselves through the death of individual trees and

groups of trees. Longleaf pine is generally too intolerant

of competition to benefit from the death of individual trees

(too small a gap is created). However, when a group of

trees dies and creates a sufficiently large gap in the canopy

and root zone, longleaf pine seedlings decades old are

known to be responsive to release. Therefore, group selection is the forest reproduction method that most closely

corresponds to the natural gap-phase regeneration dynamics that have been common in longleaf pine ecosystems

for thousands of years. While old growth is technically

forest that has never been harvested by humans, group

selection is the single reproduction method that most

closely resembles the structure and regeneration dynamics

of old-growth longleaf pine forests. Thus, it is a method

that will likely be increasingly used in the future to provide old-growth like stand conditions and to sustain over

the long term the numerous ecological, economic, and

social values of longleaf pine forest ecosystems.

Guldin: Farrar’s (1996) modified group selection approach

comes closest to having the characteristics you seek. His

uneven-aged marking guidelines contain a description of

how it would be implemented for longleaf pine.

In the BDq method, the standard marking rule for unevenaged stands is to cut the worst trees and leave the best in

diameter classes at or below D, the maximum retained

diameter, and to cut all trees above D. No active research

specifically tests whether trees larger than D can be

retained. In the volume-control method, the diameter limit

is a guide, and trees above the limit can be retained at the

discretion of the marker, provided that an equivalent

volume is then marked below the guiding diameter limit.

In either method, any tree whose retention is desired by

the forester can be retained. But provision must be made

to account for it. In the BDq method, the basal area of

retained trees must be included in the calculations of stand

structure. For example, a 24-inch tree has a basal area of

3.1 square feet. If two 24-inch trees per acre are retained

for whatever reason in the stand, that 6.2 square feet of

basal area must be accounted for in the development of the

marking tally, since retaining them reduces the amount of

growing space that can be used by trees of other sizes. For

example, if the target BDq structure is 60-20-1.2, any trees

above the maximum diameter must be added to the BDq

target curve. Otherwise, too much basal area will be

retained, and seedling development will be suppressed.

Similarly, under the VGDL method, the volume and the

volume growth of those big trees must be averaged into the

calculation used to determine the guiding diameter limit.

In my opinion, area regulation should not be used. It

becomes difficult to state unequivocally that one is

conducting group selection rather than patch clearcutting

under the area regulation approach.

Forest Manager: (17) When, what, and how do

you thin within each of the following groups:

regeneration (saplings), intermediate, mature, and

old trees?

Guldin: Reynolds had a simple marking rule: Cut the

worst trees and leave the best trees across all diameter

classes. This is done as described in Marquis (1978) by

generating a stand inventory that counts the number of

trees in each diameter class, developing the marking tally

by diameter class, and calculating a percentage of each

class to be marked. Then when marking, the marker’s duty

is to mark the poorest given percentage of trees in each

diameter class. If dense stands of pulpwood-and-smaller

longleaf pine don’t stagnate (like slash pine does), little

deliberate thinning has to be done in the pulpwood-orsmaller size classes. Nature will thin these over time. In

commercial harvests, there’s no need to precisely control

stem density in the submerchantable component. However,

if too much regeneration exists, the practical methods that

have been applied in even-aged natural regeneration

methods (i.e., fell mature trees into overly dense patches

of regeneration or skid through them) can be applied to

uneven-aged stands as well. Under the VGDL method, all

thinning below the guiding diameter limit must be done

using field experience and thus is difficult to quantify for

marking crews.
13

Forest Manager: (18) How do selection harvest

methods (single-tree and various sized, shaped,

and spaced groups of trees) affect long-term overstory structure, pine regeneration, prescribed fire,

ground cover, and red-cockaded woodpeckers?

Guldin:

Long-Term Overstory Structure

The effect of different selection harvest methods varies

and is locally determined. In an average fully stocked

southern pine stand, the same after-cut diameter distribution on a per-acre basis can be obtained, but the stands can

look entirely different depending on how the trees are

distributed throughout the stand after harvest.

Pine Regeneration

After a group selection harvest that leaves openings, regeneration would be concentrated in openings. Regeneration

would not be present in the matrix between openings

because residual basal area would be too high. After a

single-tree-selection harvest, in which residual basal area

of the overstory is heterogeneously distributed across the

stand and regeneration is presumably more uniformly

distributed, there will be local pockets of increased density

and other pockets of sparse regeneration.

Prescribed Fire

We only have empirical evidence about the effects of prescribed fire in stands that have been harvested by different

methods. I’ve seen prescribed fires that burn through the

matrix of an uneven-aged stand of ponderosa pine but that

will not carry through the group opening. Bill Boyer tells

me that he has seen this in longleaf pine stands as well. As

brush becomes established in openings in the stand, there

is less fuel to carry a fire (no grass or needle litter). Boyer

recommends leaving a shelterwood overstory until a seedling stand is established in the targeted opening, when the

remainder of the overstory can be removed. The shelterwood overstory will provide enough needle litter fuel to

carry the fires needed to retard brush development.

Ground Cover

Different patterns of selection harvest (single-tree versus

group) would result in different ground cover conditions

and species composition. Ground cover species composition can probably be predicted by others more familiar

with the longleaf forest type.

Red-Cockaded Woodpeckers

We have some interesting empirical data on the effects of

different harvest techniques on red-cockaded woodpeckers.

We have active colonies of red-cockaded woodpeckers in

the Good Forty at the CEF. The Good Forty has been

subject to uneven-aged silviculture since the late 1930s

and has the classic multilayered characteristics of unevenaged forest. I’m not convinced that generally accepted

thoughts about what red-cockaded woodpeckers can

tolerate are consistent with their use of habitat in the Good

Forty.

Forest Manager: (19) How do various selection

and marking techniques compare with respect to

administrative efficiency?

Guldin: The standard rule in working with uneven-aged

methods is to assume that annual management costs per

acre are double those for even-aged stands, with cited

figures in the ballpark of $4 per acre per year.

Forest Manager: (20) What are statistically robust

and administratively efficient sampling techniques for describing the structure of unevenaged stands in order to determine management

prescriptions?

Guldin: Which sampling technique to use depends on the

degree of heterogeneity of tree diameter in the initial stand

and on the degree of variation in the sample with which

the forester is comfortable. For example, Farrar recommends a 100-percent tally for stands < 100 acres in size.

Under conditions where this is not possible, the sample

design depends on the heterogeneity of the stand condition.

Heterogeneous stands with trees of many sizes should be

sampled using methods that sample trees of all sizes with

equal probability, such as fixed-area plots or strips rather

than a prism. Even though small trees may not be of value

economically, they are important silviculturally in making

marking decisions about uneven-aged stands. If the stand

is an older and more homogeneous stand, such as an evenaged stand with a high proportion of sawlogs, a prism

cruise can be used. Nevertheless, a 10-percent to 20-percent sample using strips, 0.1-acre or 0.2-acre fixed-radius

plots, or a similar number of 10-BAF prism plots will give

fairly reliable estimates of stand condition. Crew time can

be saved with a minimum effect on marking efficiency if

crews tally using 2-inch size classes.

Finally, some estimate of regeneration condition must be

obtained as well. A systematic sample of 100 nested plots,
14

using milacre plots (0.001 acre) to tally trees in the 0-inch

class and 0.01-acre plots to tally trees in the 1-inch, 2-inch,

and 3-inch classes, should give acceptable information

about the adequacy of the submerchantable component of

the stand in terms of both regeneration density and

uniformity of distribution.

Forest Manager: (21) What are the effects of heavy

equipment on the ground cover within the

openings created by uneven-aged management?

Rummer: There are very few data on the direct effect of

heavy logging equipment on ground cover plants. Most

studies have documented the extent of soil disturbance

after the logging operation is complete. Generally, after a

ground-based clearcut logging operation, about 30 to 40

percent of the area will be undisturbed, 10 to 15 percent

will be in trails, and about 50 percent will have been moderately disturbed, but without much mineral soil exposed.

Uneven-aged management will affect the amount of

disturbed area. Residual trees will constrain traffic and

limit the amount of disturbed area, but the severity of the

disturbance that does occur may be increased. The amount

of soil disturbance varies with the type of uneven-aged

management practiced. In a study of uneven-aged management on the Ouachita National Forest, we found 42 percent, 17 percent, and 10 percent undisturbed area under

single-tree, shelterwood, and clearcut prescriptions, respectively. The amount of area with mineral soil exposed did

not differ significantly among the treatments, but the

amount of area in moderately disturbed categories did so

differ.

The amount of soil disturbance also varies with the type of

harvesting system used. Ground skidding with clambunks,

cable skidders, or grapple skidders creates the most soil

disturbance due to the sweeping action of limbs and tops

dragged along the trail. A forwarder, however, carries

wood off the ground and minimizes soil exposure. Swing

machines, which lift and rotate (feller bunchers or shovel

loggers), also reduce soil exposure.

As mentioned above, these data represent the effects of

heavy equipment on soil disturbance and not on ground

cover. Does crushing of plants by wheeled traffic result in

damage? This probably depends on other factors such as

plant species, time of year, weather, etc. Tracked machines

tend to minimize soil compaction but may have a greater

impact on the herbaceous understory than rubber-tired

machines. Cut-to-length systems minimize soil disturbance

by creating a mat of limbs and tops to drive over. This mat

may protect soil but may also affect herbaceous plants. We

need to study whether heavy equipment may have residual

impacts on the herbaceous layer that are not readily evident

immediately after the logging operation. Disturbance to

the soil may result in immediate reduction in herbaceous

cover but could lead to increased amounts of herbaceous

cover if regeneration is encouraged by exposure of mineral

soil.

Available research information will indicate extent of soil

disturbance, but additional research should be considered

relating to the effect of traffic on herbaceous plant cover.

Outcalt: I am not aware of any research specifically looking at the effect of equipment on understory plants during

uneven-aged harvests. However, I have conducted two

research studies looking at the effect of clearcutting operations on understory plants in longleaf pine communities.

Both studies were in Florida, one on the Ocala National

Forest and the other on the Withlacoochee State Forest. In

both cases, the only impact occurred on main skid trails.

Even in these areas, however, the understory was recovering within a couple of years after harvest (Outcalt 2002).

As shown by another study, where scalped strips were

created through an existing longleaf pine understory, the

understory plants are pretty resilient (Outcalt 1995). If the

understory is healthy before a disturbance occurs, these

plants will reinvade the areas in which they have been

extirpated. Prescribed burning prior to a logging operation

will improve the health and resilience of the understory,

thereby speeding recovery from any damage that does

result from selective harvesting.

Jose: I have great interest in exploring this issue further. I

suspect that the wiregrass community would be very susceptible to any kind of disturbance. However, it would be

important to examine how resilient the understory is and

how long it would take to revert it back to the desired

condition if we alter the composition.

Forest Manager: (22) Is there soil compaction

within the opening created by uneven-aged

management?

Guldin: Loggers tend to use group openings as places to

concentrate operations. Group openings are commonly

used to deck logs harvested in the opening and from the

matrix surrounding the opening. That added physical impact

associated with log decks would presumably increase compaction in the group opening. However, if amelioration

treatments are applied, they need only be applied in the

openings. Further, the degree of mineral soil exposure that
15

results from intensive use of the opening often provides a

good seedbed for natural regeneration. Group openings

used in this manner often develop a very dense sapling

cohort.

Rummer: This seemingly simple question is very complex.

Soil compaction is a function of the machine size, number

of passes, soil type, and moisture content. Not all evenaged management systems have the same combination of

these factors, and thus any resulting compaction is highly

variable. Generally, very dry soils or very wet soils will

not significantly compact. Coarse-textured soils (sands)

are not as susceptible to compaction. For example, a study

of pine thinning in Florida found no compaction after the

operation on a sandy soil. Additionally, the vertical and

horizontal distribution of the compaction is important.

Compaction varies with soil depth, with most compaction

from forest operations occurring in the upper 4 to 6 inches,

although the surface 2 inches is often loosened by traffic.

A landing area becomes a heavily impacted continuous

patch of compaction. The same amount of compacted area

arranged as wheel tracks is significantly less detrimental.

Thus, the traffic pattern associated with a particular type

of uneven-aged management (group selection, single-tree

selection) and logging system (skidders, forwarders, animals) is important in assessing impact. Soil compaction

will also vary with time. Natural processes restore soil

porosity over time. Depending on rotation length and the

entry interval, compaction may or may not persist in the

stand.

It is also important to understand why compaction may be

a concern to the resource manager. Compaction can (1)

reduce infiltration and thus increase runoff and erosion,

(2) impede subsurface flow and thus alter water table

depth, (3) reduce porosity and thus affect soil biological

processes, and (4) damage roots directly by shearing.

Forest Service long-term site productivity studies have

attempted to evaluate the long-term effects of soil compaction on forest productivity for different forest sites in the

United States. Thus, more specific information may be

available for Florida.

Part D. Optimum Logging Practices

Forest Manager: (23) What logging techniques are

most efficient and provide minimum damage to

residual trees when harvesting is conducted in

uneven-aged stands?

Guldin: Points to remember regarding logging techniques:

• Efficiency increases with average log size, and average

log size is high in uneven-aged harvests.

• Skidding of logs that are 16 to 32 feet in length is

preferable to tree-length skidding, because shorter logs

can be more easily maneuvered through the residual

stand by careful operators.

• Use small mobile harvesting equipment (e.g., small

three-wheeled harvester, grapple skidders).

• Careful contract administration can keep damage to the

residual stand at a minimum. Careless administration

can result in problems.

Forest Manager: (24) How do different methods of

logging affect prescribed fire and ground cover

quality and diversity?

Rummer: Fire behavior would be affected by the volume,

size distribution, and spatial arrangement of residual fuels.

Logging systems vary in how they affect these parameters.

Whole-tree logging, in which the stem is felled by a feller

buncher and then skidded to a roadside for processing, tends

to leave very little volume in the stand. Gate delimbing

removes the limbs and tops at some point near the landing.

Pull-through delimbers and whole-tree processors concentrate all the limbs and tops at the landing. Often whole-tree

systems are so effective at removing material that logging

specifications require that slash be carried back into the

stand and scattered. The amount of this material can be

specified and controlled by fire specialists to obtain any

desired fuel conditions. Cut-to-length (CTL) logging systems process trees “at the stump.” This type of logging

leaves the entire volume of limbs and tops distributed

across the stand. Some CTL systems concentrate the processing along the trails, driving over the residual material.

This results in a slash mat that can be a fire risk (creates

hot spots during prescribed fire) as well as impacting regeneration and ground cover. Use of any logging system can

be followed by applications of fuel treatment prescriptions.

Mulching machines drive through the stand and reduce

material to smaller fuel classes in order to promote decomposition and minimize smoke. Hand lopping and scattering

operations can be used to cut submerchantable material

and arrange it appropriately for burning. The most efficient

approach is to have a clear stand-specific prescription that

considers desired post treatment fuel conditions prior to

logging.

See my answer to question 21 for a discussion of the

effects of logging operations on ground cover.
16

Rudolph: In longleaf pine communities, the herbaceous

ground cover is dominated by perennials. A large portion

of the diversity is contributed by perennial species, many

of which may be quite rare. Soil disturbance may temporarily eliminate species that may then require extended

periods to re-establish. Logging procedures that minimize

damage to the soil surface would be preferable.

Brockway: The understory plants of longleaf pine ecosystems have been reported to be vulnerable to mechanical

damage. Actions such as double-chopping with a rollerchopper have been shown to significantly reduce the cover

of wiregrass. Wiregrass and other understory plants may

also be reduced (at least for several years if not permanently)

by machines that scrape away topsoil. Therefore, it is

reasonable to conclude that mechanical disturbance of the

soil either by the direct action of a machine or by dragging

logs across the soil surface could be deleterious to understory plants. Adverse changes in the understory plant community not only lead to declines in the total biological

diversity in the forest, but also would very likely decrease

the effectiveness with which prescribed fire can maintain

the ecosystem. Reduction of the understory plant community diminishes one of the principal carriers of fire. Burning

stands in which this has occurred may be more difficult

and give very spotty results. Fortunately, most of the impact

of logging machines is normally confined to skid trails,

decks, and roads, all of which normally constitute only a

portion of any particular site. Ideally, to minimize ecological damage to any longleaf pine forest, harvesting should

be performed with equipment that produces the least practical amount of surface soil disturbance. This may require

the use of smaller machines that have a lighter “footprint”

and can transport logs from the site without causing excessive soil damage. Log suspension is preferred to dragging,

wherever possible.

Part E. Effects on Red-Cockaded

Woodpeckers

Forest Manager: (25) How do we implement

uneven-aged management of longleaf pine while

leaving adequate recruitment trees and foraging

substrate for red-cockaded woodpeckers? Will

this require alteration of harvest guidelines, stand

tables, and desired outcome?

Rudolph: The recovery plan for red-cockaded woodpeckers

has been completed and contains some general guidelines

(U.S. Fish and Wildlife Service 2003). However, some

additional comments are necessary. Most existing stands

do not contain adequate potential cavity trees; the stands

are too young. The goal is to grow and retain sufficient

numbers of old trees. Single-tree selection with a diameterlimit approach requires careful attention to tree ages. With

new silvicultural regimes, the growth rates may change

with time, so monitoring is necessary, and adjustment of

the diameter limit may be required. The goal is to produce

sufficient numbers of trees at least 120 years of age to

provide potential cavity trees. Minimal data are available

to predict the response of red-cockaded woodpeckers to

forests with older trees. Consequently, it will also be

necessary to monitor cavity excavation dynamics as older

trees become available to ensure that 120-year-old trees,

for example, are sufficient. A possible alternative would

be to allow some of the older trees to escape the diameter

limit and be retained in the stands in perpetuity. It is also

important to set silvicultural parameters (entry intervals, q)

so that the stands contain relatively little midstory, including pine midstory. This is possibly the most significant

deviation required from management based solely on

timber objectives. Similar considerations apply to group

selection approaches. In both of these approaches, attention must be given to basal areas and group sizes to ensure

adequate regeneration.

Although not strictly an uneven-aged technique, irregular

shelterwood offers many of the advantages of uneven-aged

management. In irregular shelterwood, most or all of the

leave trees are retained throughout the succeeding rotation.

With a 120-year rotation, the leave trees would reach 240

years of age at the next harvest. Any survivors could then

be retained as leave trees for the next rotation, with the

deficit made up with 120-year-old trees. Substantial numbers of potential cavity trees would then be possible. This

approach has the advantage of minimal suppression of the

regeneration, few harvest entries to disturb the herbaceous

flora, known age of residual pines, and simplicity.

Regardless of the approach used, fire is critical. Very

frequent fire maintains many other ecosystem functions,

controls midstory vegetation, enhances foraging habitat

(recent data suggest that prey abundance is tied to a welldeveloped herbaceous layer), and reduces risks associated

with severe wildfire (or prescribed fire).

Clearly, implementation of these methods to produce suitable red-cockaded woodpecker habitat will require alteration of silvicultural guidelines. Most important, it will

require adjustment of maximum tree ages, reduction in the

number of midstory trees (including pines), and modification of guidelines for basal area.
17

Forest Manager: (26) What is the maximum height

and stocking of premerchantable trees within a

cluster or foraging zone before the cluster is no

longer suitable for red-cockaded woodpeckers?

Rudolph: Maximum height is not an issue for red-cockaded

woodpeckers. However, midstory density (stocking) is an

issue. The U.S. Fish and Wildlife Service recovery plan

(2003) should be consulted. There is not necessarily a hard

threshold for midstory density. Midstories typically need

to be sparse enough to provide a generally open midstory

and a healthy herbaceous layer. Low levels of midstory,

including hardwoods, that are consistent with a fire-maintained pine ecosystem are not detrimental to red-cockaded

woodpeckers and provide many other ecosystem benefits.

See the reference section for papers that relate to management of red-cockaded woodpeckers.

Forest Manager: (27) How do uneven-aged stand

conditions affect red-cockaded woodpecker

reproductive output, foraging behavior, nesting

behavior, and demography?

Rudolph: Uneven-aged stand conditions do not necessarily

differ from even-aged stand conditions in relation to redcockaded woodpecker biology. However, factors such as

midstory development, tree ages, and herbaceous understory should be within the acceptable levels. Again, the

U.S. Fish and Wildlife Service recovery plan covers these

issues in some detail. Demographic integrity of red-cockaded woodpecker populations and landscape fragmentation

are also considerations. This issue is more easily addressed

under uneven-aged management because the silvicultural

treatments involved do not contribute to fragmentation.

Forest Manager: (28) What are the effects of

uneven-aged management of longleaf pine and

slash pine on the biodiversity of natural

communities?

Boyer: Given appropriate fire regimes, group selection

should have minimal impact on natural communities. This

uneven-aged stand reproduction method mimics natural

processes in place for thousands of years (natural attrition

in mature trees through lightning strikes and insect outbreaks, fire-related mortality, and limited blowdown).

Rudolph: The biodiversity of natural communities should

be enhanced by uneven-aged silviculture, since it more

nearly approximates natural disturbance regimes. A possible exception would be early successional species that

require openings of substantial size (e.g., certain avian

species).

A two-aged shelterwood (irregular shelterwood) mimics

uneven-aged management to some extent because residual

trees are held until the next regeneration cut or even longer.

If residual longleaf pines are left beyond the second rotation, this can produce a three-aged stand with substantial

numbers of quite old trees, a limited pine midstory, and

new pine regeneration. The resulting two-aged or threeaged stand structure can result in good red-cockaded woodpecker habitat throughout the next rotation. By contrast, in

loblolly pine and shortleaf pine stands, reproduction after

a shelterwood cut can be abundant and result in a dense

pine midstory until the regeneration grows into the canopy.

Prescribed fire to reduce the density of regeneration

(thermal thinning) or mechanical thinning can substantially reduce the midstory problem. At worst, this is a

problem for only a fraction of the rotation cycle. The pine

midstory is generally less dense in longleaf pine stands

than in stands of loblolly or shortleaf pines, but the midstory in longleaf pine stands should be reduced if and

when it becomes too dense for red-cockaded woodpecker

habitat requirements.

A large literature exists specific to individual taxa. However, most is not specifically in reference to uneven-aged

management. We need to explore the literature for information relevant to these taxa.

Forest Manager: (29) What uneven-aged stand

conditions support both expanding and stable

red-cockaded woodpecker populations?

Rudolph: See my answer to question 25 above.

Part F. Prescribed Burning Approaches

Forest Manager: (30) What is the best indicator of

potential tree mortality from prescribed fire

during prolonged dry periods?

Boyer: The best indicators of potential tree mortality from

fire are tree size, fuel load, time since last burn, and fire

intensity.

Nowak: I have tried to reach Todd Engstrom of The Nature

Conservancy (formerly of Tall Timbers Research Station)

about the possibility of working together on this question.

I have not heard back from him yet. The people at Tall

Timbers burn some tracts of longleaf pine every year and

have tagged their trees. It would be ideal to do this

research there, if they are interested.
18

Outcalt: The best indicator of potential tree mortality is a

combination of the duff moisture level and the Keetch and

Byram (1968) drought (or burn) index (KBDI). Prolonged

periods of drought dry the duff layer sufficiently for it to

ignite and burn completely via smoldering combustion

following prescribed burning. The long residence time of

this smoldering combustion will cause significant cambial

and root damage, especially to larger trees. This leads to

abnormally high mortality rates. Use of the KBDI alone

can lead to problems, since rainfall sufficient to lower this

index will not necessarily rewet the duff layer enough to

prevent smoldering combustion. In summary, be very

cautious during and following a prolonged period of

drought. It is best to confine prescribed burning to areas

that are fully restored with a grass-dominated understory

and a minimal duff layer. Avoid any areas that have not yet

adjusted to frequent prescribed burning.

Forest Manager: (31) What are the optimum techniques

for ensuring the protection of regeneration during

burning in uneven-aged stands?

Boyer: Regeneration can survive and develop with a

frequency of one fire every 2 or 3 years, with best results

from periodic spring fires. Survival is best in stands of

relatively low density, as young trees there reach fireresistant size sooner, and needle litter serving as fuel is at

a lower level. Data below show longleaf pine ingrowth in

shelterwood stands of varying residual overwood densities

that are unburned or subjected to biennial winter, spring,

or summer fires.

Overstory Winter Spring Summer No

density burn burn burn burn Average

square feet - - - - - - - - - - - stems per acre - - - - - - - - - - -

per acre

Longleaf pine ingrowth (d.b.h. > 1.5 inches)

20 218 582 400 369 392

30 138 613 227 253 308

40 0 89 4 116 52

50 0 31 0 53 21

Average 89 329 158 198 193

All hardwood trees (d.b.h. > 1.5 inches)

20 116 9 31 716 218

30 4 0 0 436 110

40 18 0 31 333 96

50 27 0 67 342 109

Average 41 2 32 457 133

Principal findings were that (1) longleaf pine seedling development was better with spring burning than with summer

or winter burning; (2) hardwood development was inhibited by burning and became virtually nonexistent with

spring burning; (3) development of pine, and to some extent

of hardwood, was inhibited by increasing overstory density;

and (4) at low overstory densities, periodic spring burning

results in the best combination of maximum development

of pine regeneration with minimal hardwood encroachment.

Also note that many longleaf pine grass-stage seedlings

can sprout from the root collar if top-killed by fire.

Forest Manager: (32) What burning techniques

best enhance diversity and maintain native

ground cover and understory?

Brockway: We know from research studies that dormantseason burning and growing-season fire affect the diversity

and productivity of native understory plants quite differently. Dormant-season fires generally burn under cooler

conditions and are less effective in stimulating seed production of native herbs and controlling encroachment by

woody vegetation. Woody vegetation directly competes

with herbaceous plant species and tends to depress native

plant diversity. Thus dormant-season burning alone is generally thought to be less effective in maintaining native

plant diversity in the understory of longleaf pine ecosystems. By contrast, growing-season fires stimulate herbaceous seed production and more effectively discourage the

invasion of longleaf pine sites by woody plants. Burning

during May is especially effective. Growing-season fires

are generally more effective than dormant-season burns in

enhancing and maintaining native diversity in the understories of longleaf pine forests.

However, the story is not quite so simple. The logistical

problems involved in conducting all burns during the

growing season make it necessary for managers to also

consider dormant-season fires as a management option. In

forests where the rough has accumulated to dangerously

high levels, burning during the cooler dormant season is

the only safe management alternative. Also, it is important

to recognize that while most natural fires may have historically occurred during the growing season, natural fires

did occur at all times of the year. Native ecosystems developed as a product of fire with a variable frequency, not a

constant growing-season-only fire with a fixed return

interval. Therefore, managers who wish to maximize

native plant diversity in longleaf pine forests may want to

consider burning mostly during the growing season, but

also during the dormant season once in a while and at

intervals that vary over time. This variable fire regime will
19

most closely simulate the natural fire pattern and provide

the best opportunity for the greatest number of native

organisms to occupy the widest range of high-quality

habitats.

Outcalt: I see this as two separate questions. The first

question is, How can fire be used to maintain native ground

cover in longleaf pine communities? Once you are at the

maintenance phase (i.e., you have a healthy overstory of

longleaf pine with a grass- and forb-dominated understory),

you can pretty much use prescribed fire as best suits your

particular situation to keep the ecosystem healthy and

productive. Large areas can be burned with aerial ignition.

Strip head fires from ground ignition can also be used and

are more appropriate for smaller areas. Practitioners of

prescribed burning pretty much already know how to burn

these areas to minimize damage to overstory trees while

controlling the growth of the woody understory species.

The key is to burn often enough to maintain the dominance

of the grasses and forbs and prevent a big increase in woody

species. The more productive the site, the more frequently

it must be burned. Thus, relatively infertile xeric sandhills

only need one fire every 4 to 6 years, while mesic uplands

may need one fire every 2 to 3 years to control woody

species (Glitzenstein and others 2003). In all cases, there

should be variability in both timing and frequency, to

mimic what happened with natural ignitions. An emphasis

should be placed on growing-season burns, but dormantseason burns are also acceptable every third or fourth burn.

The second question is, How should prescribed burning be

used to enhance diversity? I am interpreting this to refer to

the restoration of diversity in longleaf communities that

have an understory that has been captured by woody species. If the soil has not been heavily disturbed by mechanical means, there should be a viable assortment of native

grasses and forbs available either as remnant populations

or in the soil seed bank. What is needed is a reduction in

the woody understory species cover that will allow the

grasses and forbs to increase and eventually become the

dominant understory species groups. Prescribed fire is one

tool that can be used to accomplish this transition. Research

shows that growing-season burns are better than, or at least

as good as, dormant-season burns for readjusting understory composition (Robbins and Myers 1992). Thus, they

should be favored, but dormant-season fire may be necessary to reduce fuel loads before switching to growingseason burns. Thus, a dormant-season burn or two may be

used to gradually reduce litter buildup before a growingseason burn is applied. In addition, it is usually best to

conduct these burns at short intervals (i.e., within 2 years

or less) to minimize fuel accumulations between burns.

Expected results depend on the community type and your

starting conditions. Sandhill sites where scrub oaks are the

major problem tend to respond quite quickly, with noticeable oak top-kill after only a couple of growing-season

burns (Rebertus and others 1989b). Flatwoods understories

dominated by saw-palmetto [Serenoa repens (Bartr.) Small],

gallberry [Ilex glabra (L.) Gray], and Lyonia [Lyonia

ferruginea (Walt.) Nutt. are more resistant to burning.

Research indicates that only repeated burns at short return

intervals over a long period significantly reduce these

woody species (Glitzenstein and others 2003). Thus, burning every 2 years for a period of 10 to 20 years may be

required to readjust the understory composition on flatwoods sites. This may seem like a long time to wait for

results. However, if it took more than 30 years of dormantseason burns at intervals of at least 4 to 6 years for the

understory to reach its current composition, there is no

reason to expect that this condition can be reversed with

one burn or in a 5-year period. As long as the plant community is moving toward recovery, then worthwhile

progress is being made. A similar scenario of frequent

growing-season burns is needed for mesic uplands with

better soils where the woody competition is often in the

form of hardwoods, many of which are now of midstory

size. Other tools like herbicides and mechanical reduction

of woody species may be used to speed the process of

readjusting understory species composition and dominance

(Brockway and Outcalt 2000).

Walker: By choosing the fire season, the conditions under

which to burn, and the firing techniques (including pattern

and methods), the prescribed fire manager exercises considerable control over fire effects. Making the best choices

depends on a solid understanding of the effects of fire on

target species or communities. Understanding how vegetation is expected to respond to certain kinds of fire (e.g.,

fire at different seasons, intensities, and spatial patchiness)

provides the basis for prescribing the best fire to achieve

objectives. Note that a single fire will not enhance diversity or maintain a desirable plant community. Therefore, it

may be most productive to consider management in terms

of a prescribed fire regime. Additionally, even with the

best information available and the best prescriptions written

and applied, outcomes are uncertain. Some effects are

unknown or not well understood, and second-order effects

caused by factors other than the fire itself (i.e., post-fire

weather events, insect and disease outbreaks, and unusual

levels of herbivory) may contribute to unexpected outcomes. I am not a fire application specialist, so I will not

address the technical aspects of setting fires. I am a plant

ecologist, so I will attempt to highlight important fire

effects on understory plants in longleaf pine woodlands.
20

Once the manager understands these effects, they can be

used to guide management and to describe the outcomes

of certain prescribed fire regime choices, for example,

choices of fire season, frequency, and “on-average” intensity.

Fire Effects on Ground-Layer Vegetation in

Fire-Maintained Communities

It is widely accepted that frequent burning increases

species richness and enhances the vigor of the herbaceous

layer in longleaf pine woodlands. Various authorities have

suggested that burning does this by (1) increasing light by

reducing the canopy, (2) providing a pulse of nutrients that

are rapidly taken up by ground-layer species, (3) stimulating flower and seed production, and (4) increasing populations of ground-layer species. There are differing opinions

about the relative importance of these mechanisms

(Brockway and Outcalt 1998; McGuire and others 2001;

Means 1997; Platt and others 1988a, 1988b). All are

probably important to some degree. Regardless of specific

mechanisms, changes in resource availability associated

with burning will benefit or enhance only those populations already present when the burning occurs. If the vegetation consists of large numbers of native species, they

will benefit. If the vegetation includes populations of oldfield species, these too will likely benefit from increased

resource availability.

Maintaining and Enhancing an

Existing Native Ground Layer

In general, fire management recommendations to enhance

existing ground cover are to burn frequently (every 2 to 3

years) and make sure that some of those fires occur during

the growing season or during the lightning season, which

is considered May to August in much of Florida (Robbins

and Myers 1992). This general recommendation focuses

on seasonality and frequency of burning, but choices about

these two components of the prescribed fire regime will

influence fire intensity by maintaining moderate fine fuel

loads and by burning when air temperatures vary from

cool winter temperatures (50 oF) to hot spring days (90 °F).

Efforts to maintain and enhance ground layers and understories generally include operations that are designed to

(1) remove midstory woody species or reduce them to

ground layer components and (2) provide opportunities

for sexual reproduction of understory plants, at least

periodically.

Midstory Tree and Shrub Control

Many studies indicate that burning hardwood species in

the early spring when trees are leafing out top-kills a

greater proportion of stems than burning during other

seasons (Glitzenstein and others 1995; Rebertus and others

1989a, 1989b; Robbins and Myers 1992). Top-kill rates

vary with stem diameters. Smaller stems can be killed with

relatively cool fires, while hotter fires are more likely to

increase the kill of larger stems. However, if larger stems

can be top-killed, they are less likely to resprout than

smaller stems. Although top-kill success varies with season

of burning, long-term studies show that repeated burns

over long periods of time (even winter burns) reduce

hardwoods to the ground layer and ultimately reduce the

numbers of stems (Waldrop and others 1987). While fire

may be used to manage hardwood and shrub stems, there

may not be adequate fuels to carry fire through the stand

where such stems are dense. In such cases, it may be

necessary to couple a pre-fire mechanical treatment that

puts woody fuel on the ground with prescribed burning.

Ordinarily, a treatment that minimizes disturbance of the

ground layer would be preferred over one that disrupts

soils. However, exposing mineral soil (as where a tractor

or drum chopper turns a corner) may provide establishment sites for grasses and forbs.

Increasing the General Vigor, Flowering, and

Seed Production of Grasses and Forbs

Published accounts show that lightning-season burning

results in abundant flowering of dominant bunchgrasses,

such as wiregrass (Aristida spp.), toothache-grass (Ctenium

spp.), and Indiangrass (Sorghastrum spp.), and many forbs

in longleaf pine woodlands (Platt and others 1988a, 1988b).

There is some evidence that a strong flowering response to

growing-season burns results in greater viable seed production and seedling establishment of grasses or forbs than

that obtained by burning at other times (Brewer and Platt

1994, van Eerden 1997). Evidence is increasing to indicate

that species characteristic of longleaf pine ground layers

exhibit a variety of responses to season of burning. In a

recent publication, Hiers and others (2000) reported that

the effects of season of burning vary among the legumes

(one of the most diverse groups in Gulf Coastal Plain longleaf pine communities). At least one species showed maximum flowering production in each of the three experimental

treatments: lightning-season fire, late winter burning, and

no burning. Both the time of flowering and the duration of

flowering period for some species were affected by fire

treatment. Hermann and others (1998) provide more evidence of species-specific variation related to season of

burn.

Collectively such studies support the proposal of Robbins

and Myers (1992) for varying the return interval and season

of prescribed burns on a site. Appendix II in their publication includes tables for scheduling a series of prescribed
21

fires for a selected site. Scheduling tables allow longer

return intervals for xeric sites than for more mesic sites.

If burn units are large enough to contain a variety of sites

types, schedule prescribed fires to maintain the most mesic

sites. Dry sites where enough fuel has not accumulated to

carry fire simply will not burn. If low fuel accumulations

interrupt the spread of fire through the landscape, ignition

patterns may have to be modified. Although this approach

is based on fire season and frequency, variations in intensity are likely to occur across large burn units, and if

special resources require special conditions, burning

techniques can be modified to accomplish specific

objectives.

In summary, overall plant community responses to burning

are very dependent on (1) what is there when the fire is

set, (2) what prescribed fire regime has been applied in the

recent past, and (3) what fire regime is established for the

ensuing decade. Responses to single fires may be interesting, but maintaining and enhancing the ground layer in

longleaf pine communities is really a cumulative effect of

multiple fires and the climatic context in which they are

embedded.

Research Needs and Opportunities

Existing information provides adequate general guidance

for using fire to maintain the ground layers of longleaf

pine communities. Longleaf pine communities, however,

harbor a large number of rare plant species. Research may

not yet be able to provide specific information about fire

effects for all included special plants. Two kinds of new

information are needed: (1) information about fire effects

for individual understory plant species, both at the individual plant level and the plant population level, and (2) a

better understanding of the mechanisms by which plants

respond to burning. The species-specific work must also

include possible effects of fire on necessary mutualists like

pollinators and seed dispersers.

Forest Manager: (33) Where feeder roots have

extended into unburned duff layers for 60 years or

more, can we use fire to gradually reduce the duff

layer with resultant regrowth of feeder roots in the

upper soil layers, without unacceptable damage

to overstory trees?

Outcalt: Research and practical experience to date indicate the answer may be no. Nearly everyone who has

reintroduced growing-season fires into longleaf pine communities that have not been burned for a long period has

had increased mortality of large trees. Are there things that

can be done to minimize these losses? I believe there are.

First, a couple of dormant-season burns (timed as closely

together as the availability of fuels needed to carry the fire

will allow) under cool conditions with relative humidity of

60 to 70 percent can be used to reduce litter buildup. This

should be followed by a growing-season burn, again as

soon as there is sufficient fuel to carry a good fire. It is

also important to pay attention to duff moisture levels, as

this determines whether the duff layer around larger longleaf pines will ignite and burn, causing excessive feeder

root damage and possibly even girdling the tree by killing

the cambium at the root collar. Often in the early part of

the growing season, many areas in Florida are coming out

of the spring dry period, and the duff layer around the base

of the trees is dry all the way to the mineral soil. As the

summer rains begin and the drought index drops, conditions

are suitable for prescribed burning. However, if there has

not been sufficient rainfall to completely re-wet the duff

layer at the base of trees, there is often enough heat from a

prescribed burn to dry out the moist top portion of the

layer. This allows the layer to ignite and slowly burn for

many hours, producing temperatures high enough to cause

cell death in roots and at the base of the tree. Thus, when

determining whether it is safe to burn, it is important to

make sure that the duff at the base of larger trees is wet on

the bottom, with only the very top layer being dry. This

may not occur until July in Florida, as it takes substantial

precipitation to re-wet the duff layer once it has become

completely dry. This technique of checking for moisture

deep in the duff layer should allow you to burn these areas

when conditions are optimal, so the fire only consumes the

dry top layer of the duff, while the wet lower layer will

protect the roots and root collar. If carefully applied, this

technique may be used to gradually reduce the duff layer

at the base of trees after four or five burns and still keep

tree mortality at an acceptable level. This is only a possibility, and the procedure has not been tested on a large

scale to see if it really works. It may turn out that high

mortality in older longleaf pine trees is something that is

going to happen when we reintroduce growing-season fires

to long unburned sites. Such mortality may simply be the

cost of doing business. These fire-killed trees can be

salvaged to realize some of their economic value, and the

ecosystem will eventually replace them over time. The

negative impact on the forest plant community from not

burning is going to be much worse than the loss of some

of the older trees. Without prescribed burning, the problem

will only continue to get worse with time, and if a wildfire

occurs, most of the older trees will be killed.

Forest Manager: (34) What are the best methods

for reintroducing prescribed fire into stands

where fire has been excluded for over 20 years?
22

Brockway: After such a prolonged period of fire exclusion,

an accumulation of potentially hazardous fuel is likely present. Increased fuels not only include a larger mass of finer

fuels (leaves on the forest floor and suspended needles) but

also a changed understory and midstory. The understory and

midstory probably now contain a greater number and mass

of woody plants that form a fire ladder to the tree canopy.

Burning such a forest during the growing season could

result in a catastrophic stand replacement fire. If a longunburned stand is burned using a cooler fire during the

winter months, major damage to the ecosystem might be

avoided (but then there are no guarantees, and burning such

a stand at any time is dangerous). If a fuel ladder is present,

the stand structure should be altered by mechanical or

chemical methods prior to burning with prescribed fire.

Mechanical treatment will immediately reduce the catastrophic fire hazard, while chemical treatment will require 2 to

3 years for mortality and decomposition processes to reduce

the undesirable woody plants. Perhaps the safest strategy is

to mechanically reduce the woody plants and soon follow

this treatment with at least one cool winter burn to reduce

the fuel load. Growing-season burns on about a 2- to 5-year

cycle can thereafter be implemented for ecosystem maintenance. The actual burning technique used will be based on

ambient conditions, with backing fire, flanking fire, and

strip headfire all being possible alternatives. If a headfire

method is selected, it should be a strip headfire (with a

short burning width to avoid the adverse cumulative downwind effects of a fire that begins moving too fast and burns

out of control) that burns toward a reliable firebreak (i.e.,

a river, lake, tilled cropland, transportation corridor, or

wide blackline) that will safely stop a runaway fire.

Jose: Under certain circumstances, it may be desirable to

remove a hardwood midstory by using herbicides and mechanical methods. If the expense of herbicide treatments and

mechanical treatments is a constraint, initial cool-season

burnings would be preferable. Once the fuel load reaches a

manageable level, growing-season fire can be introduced

(Provencher and others 2001).

Forest Manager: (35) What are the best ways to

monitor the long-term effects of prescribed fires

on ground cover, soils, hydrology, timber

stocking, and root zones of trees?

Boyer: To monitor the long-term effects of prescribed fire,

establish and periodically monitor permanent plots in areas

of concern. However, under most management schemes,

this should not be necessary. Considerable data on longterm fire effects are already available for the plant communities and soils of Coastal Plain sites (Boyer 1990, 1993a,

1993c, 2000; Boyer and Miller 1994; Brockway and Lewis

1997; Haywood and others 1998; Heyward 1936, 1939;

Kush and others 1999, 2000; McKee 1982; Ralston and

Hatchell 1971; Wells 1971).

Forest Manager: (36) What are the effects of

dormant-season and early growing-season fires

on postburn survival and growth of grass-stage

longleaf pine seedlings (2-year-old plantations or

naturally regenerated seedlings)?

Boyer: At least two published papers indicate that grassstage seedlings burned in the spring (i.e., May) grow significantly better than seedlings burned during the winter or

not burned at all (Grelen 1978, Maple 1977). Refer once

again to above data showing improved ingrowth survival

with spring burns as compared with winter burns, summer

burns, and no burns.

Forest Manager: (37) What is the most efficient

spatial configuration of timber stand and

prescribed burning unit boundaries, in terms of

both staff management efforts and ecological

integrity?

Boyer: The most efficient configuration of prescribed

burning units is one that makes maximum use of existing

boundaries such as streams and roads in order to minimize

the need for supplemental fire lines. For longleaf pine, any

number of management units may be included within a

single burn unit. The size of burn units and management

units will depend on management goals and total area

under management.

Outcalt: For ecological integrity, artificial boundaries must

be kept to a minimum. This means avoid putting roads and

fire lines around every stand. It also means burning in

large blocks. Naturally ignited fire was once able to burn

across the landscape until it came to a natural barrier or

was extinguished by rain. Managers can mimic this natural

process by burning blocks between existing roads and

natural fire breaks on the landscape. This allows fire to burn

into areas as it should and skip those that will not burn at

that particular time. This lets fire determine where transition zones should be and how often wetter areas are burned.

It also avoids all of the problems and expense of plowing

lines around areas the manager thinks should not be burned.

Burning larger blocks also promotes efficiency of scale

because aerial ignition can be used to get many acres done

on days with suitable conditions. What you want to avoid

is trying to burn individual stands. Some managers have
23

done this in the past in an attempt to protect newly planted

seedlings or small regeneration. With the selection harvest

method and uneven-aged management, you are going to

have regeneration everywhere. Thus, a more efficient

system is to periodically concentrate selective harvest in a

portion of the large blocks, creating gaps in all the stands

in a selected block that are ready for removals. Then, if

you later get a good seedfall and catch, you can keep fire

out of those blocks for a period to allow seedlings to

become large enough to survive a burn. This has the added

advantage of limiting disturbance from harvest to a short

period followed by a longer period when there would be

no entry into the entire area.

Guldin: Prescribed burn unit boundaries should be much

larger than timber stand unit boundaries. Timber stands

must be managed to be robust under landscape applications

of prescribed fire. The acreage that should be burned

annually far exceeds the acreage that can be custom burned

on the average district. This suggests that stands under

regeneration should be clustered together for management

purposes more than is currently the case on most national

forests.

Forest Manager: (38) How do various burn

frequencies affect pine regeneration, ground

cover quality, and diversity in uneven-aged

stands? Can a desirable range of frequencies be

defined for different ecosystem types (e.g.,

sandhills, mesic flatwoods, scrubby flatwoods)?

Outcalt: I think the real question some managers have is,

If we need to burn every 3 to 5 years to maintain the

ground cover diversity and health, will we get any longleaf

pine regeneration? The answer is most definitely yes. If

longleaf pine (which we consistently state is a fire-adapted

species) were unable to reproduce with frequent fire, it

would not have dominated over 90 million acres in North

America when the Europeans first arrived. Frequent burning is required for readjustment of understory composition

in communities where it is out of balance. However, once

this has occurred, maintenance burning does not have to

be quite so frequent. In addition, fire frequency depends on

site productivity, with better sites needing more frequent

burning to control competition and maintain forest health.

Thus, mesic upland sites need fire about once every 3 years,

flatwoods once every 3 to 4 years, and xeric sandhills once

every 4 to 6 years. It is quite likely that the frequent burning that is required to readjust understory composition will

kill many longleaf pine seedlings. However, in the maintenance mode, when the community is in a healthy state,

we already know how to get all the regeneration we want.

Managers have been doing exactly this with the shelterwood stand reproduction method (Boyer 1993b). Burns

should be timed to match seedfall in the stands where regeneration is desired. Then, if you get a good catch, exclude

fire for 3 or 4 years to allow a good portion of the seedlings to become large enough to survive the next prescribed

burn. These same techniques will work just as well with

group selection in an uneven-aged management approach.

Even burning every 3 years will allow 1 to 2 percent of the

seedlings to survive fire, and this is enough to fill gaps

created by group selection harvests (Outcalt 1998). It

should be noted that with uneven-aged approaches, it is

not necessary to immediately obtain regeneration within

the gaps of a stand. Longleaf pine is a long-lived tree, and

the growth is going to be occurring on the larger trees and

not the seedlings (Boyer 1993a). The seedlings are only

needed to replace trees that are harvested or die in the

areas surrounding the gaps. Thus, if a cycle of regeneration only occurs once every 20 years, this is not a problem

because the manager can compensate by not enlarging

gaps until regeneration is obtained. Trees harvested in the

interim should be from the matrix between gaps, and

harvesting should be designed to reduce competition for

superior trees and to capture potential mortality.

Forest Manager: (39) What prescribed burning

regime is best to establish slash pine

regeneration in uneven-aged stands?

Boyer: There is very little information on this. A firereturn interval of about 8 years supports slash pine regeneration in stream bottoms and wet flats in Coastal Plain

longleaf pine forests. The same burn interval also supports

development of canebrakes, which were once so common

in the Southeastern United States. Exclusion of fire from

wet flats and bottoms has resulted in a hardwood invasion

trend that has been very detrimental to the ecosystems that

originally occupied these sites.

Outcalt: By the time slash pine seedlings reach 8 to 10

years old, they are quite resistant to fire-caused mortality.

Slash pine is also a fairly consistent seed producer. Therefore, whenever slash pine regeneration is wanted in forest

openings, the manager needs to keep fire out of the area

for at least 8 years. This will allow adequate time for the

regeneration to become large enough to survive prescribed

burning. The first burning following this period should be

a dormant-season fire conducted under mild conditions to

reduce fuel loads. A second burning should be applied

about 2 or 3 years later. Then the normal maintenance fire

regime, with burning once every 3 to 5 years, can be

resumed until another wave of regeneration is desired.
24

Forest Manager: (40) What factors and relationships influence tree mortality, morbidity, and pest

attack as a result of fire (prescribed burning and

wildfire) where fuels have accumulated over a

long period of time and during periods of

drought?

Rudolph: I am not familiar with the literature in this area.

However, several individuals dealing with management of

these types of situations have experienced problems with

tree mortality. Bill Boyer has some insight, especially

from the Flomaton, AL, site. Ike McWorter of The Nature

Conservancy in Texas has also had experience with tree

mortality problems associated with fires in areas with a long

history of fire suppression. Anecdotal observations suggest

that fire can increase tree susceptibility to bark beetles. Kier

Klepzig of the Southern Research Station in Pineville, LA,

is considering a proposal to investigate this issue.

Boyer: The principal factor affecting pine mortality seems

to be fire intensity. For longleaf pine, tree age also seems

to be a factor. In one study, a summer burn that was

intended to wipe out some hardwoods killed a substantial

number of pines, but mortality varied by size class (Boyer

1990). The summer burn killed a large number of longleaf

pines in the 4-inch and smaller d.b.h. classes, didn’t kill

any pines in the 5-inch to 15-inch d.b.h. classes, killed 12

to 13 percent of longleaf pines in the 16-inch to 21-inch

d.b.h. classes, and killed 25 percent of the longleaf pine in

22-inch and larger d.b.h. classes. The fire was a hot fire

with high air temperatures (99 o

F) and low humidity (34

percent). The area had been burned by a winter fire 2

years earlier. Crown scorch on the large trees was not a

factor in this mortality, averaging < 10 percent.

A growing-season wildfire burned through part of the oldgrowth longleaf pine stand at Flomaton, AL, in August

1992. This fire killed all trees, which were up to 350 years

old and 36 inches d.b.h.. Some of the younger pines (50 to

60 years old) survived briefly but were soon killed by

black turpentine beetles. Fire had been excluded from this

stand for more than 40 years. However, another study has

shown that organic litter on the forest floor reaches a

steady-state after a time, with a balance between accretion

and decay. The load is much less in low-density than highdensity stands, with sunlight seeming to speed the decay

process. Accumulation did not exceed 2 years’ deposition

in any of the stands observed (Boyer and Fahnestock 1966).

These results were found in longleaf pine stands on a

sandy Coastal Plain site with densities not exceeding 50

square feet per acre. Results may differ on other site types.

These results do, however, suggest that fuel loads (organic

litter on forest floor, not living material) 2 to 3 years after

a burn in these low-density stands could be as great as

those found in stands not burned for 20 to 30 years.

Observations of a late summer burn at a study area on the

Kisatchie National Forest in Louisiana indicated that the

fire was so intense that saplings of 4 inches and smaller

d.b.h. were killed along with many large grass-stage seedlings, which are normally resistant to fire-kill. These results

suggest that surface soil temperatures reached lethal levels

at the ground line, girdling seedlings at the root collar. I

believe this may be the factor responsible for the death of

large trees in the summer burn study. Older trees with

slower growth and thinner bark near ground line are

susceptible to damage or mortality from an intense, lingering fire in the accumulated bark and needles found at

the bases of the trees. These large trees were in essence

thermally girdled. This possible relationship is the reason

some managers like to rake around red-cockaded woodpecker cavity trees before burning. Without raking, these

old trees would be more vulnerable to fire kill. Another

hypothesis that has been advanced to explain high mortality of old trees in long unburned stands has to do with

fine root density. This theory suggests that increased fine

root density near the surface, just under or in the lowest

litter layer, is susceptible to damage from high-intensity

fire. Damage to these roots presumably leads to the death

of trees. While this could have been a factor in the

Flomaton old-growth stand, it was not a factor in the Boyer

(1990) study or the Kisatchie study, since both of these sites

were burned regularly, and burning removed the accumulated litter. Obviously, more research is needed on this

subject. Based on my experience, I would guess that high

fire intensity produces lingering lethal temperatures at the

ground line, girdling the trees, with greatest impact on

those trees with thinnest bark near the ground line. Summer

burns generally produce the highest fire intensities, which

is probably why H.H. Chapman once said that August was

the most dangerous month to burn in longleaf pine forests.

For that reason, I would avoid summer burning. Besides,

spring burns are more effective for hardwood control.

Normal mortality in mature longleaf pine stands, based on

observations in our shelterwood stands throughout the

South, averages 0.4 trees per acre per year (Boyer 1979).

The causes of about 60 percent of this mortality could be

identified. Of this 60 percent, about two-thirds was caused

by lightning, about one-tenth by wind, and the remaining

portion by beetles and pathogens. This is normal attrition.

All study areas were subjected to careful prescribed

burning, and no fire-related mortality was observed.
25

Outcalt: Mortality following prescribed burns or wildfire

is a function of fuel loads, fuel moisture content, weather

during the burn, burning technique, tree condition prior to

burning, and postfire conditions. High mortality can result

from high-intensity fires caused by high fuel loads, low

fuel moisture, low humidity, high winds, and high temperatures. In these situations the burn will be intense enough to

cause significant mortality from crown and bole damage.

Excessive tree mortality can also result from low-intensity

but high-severity fires that creep or back through a stand

with high loads of very dry forest floor fuels. Even though

intensity may be low with very little crown damage, the

long residence time of smoldering combustion can cause

significant cell death in root and bole cambium. This loss

of roots or actual girdling results in high morality. For

guidance on how to deal with stands that have not been

burned for long periods and have high fuel loads, see

Wade (2002).

Part G. Regeneration

Forest Manager: (41) What is seedling survival in

relationship to opening size, shape, and solar

path?

Boyer: Longleaf pine seedling survival is independent of

opening size, shape, and solar path. A study of seedling

survival in relation to overstory density indicated that after

8 years, survival under overstories of 90 square feet per

acre was as high as in clearcut openings (Boyer 1963).

The same was true for all overstory densities in between

these extremes. The only variable affecting seedling

survival was the timing of fire. The seedling survival study

referred to here was unburned. Burns should be deferred

until longleaf pine seedlings have reached a fire-resistant

size (> 0.3-inches in diameter at root collar). Many if not

most grass-stage seedlings larger than this can sprout at

the root collar if top-killed by fire.

Jose: I do not believe the shape of the opening has anything to do with survival patterns. Brockway and Outcalt

(1998) found that the size of the opening is an important

factor for seedling survival in xeric longleaf pine forests.

However, I observed no significant correlation between

opening size and seedling survival in an open longleaf

pine–wiregrass forest community in northwestern Florida.

Guldin: The experience in Coastal Plain loblolly-shortleaf

pine stands suggests that with good mineral soil exposure,

minimal openings are needed to establish pine regeneration. Certainly I’d expect similar results in longleaf pine

during good seed years, but I defer to Bill Boyer and his

experience on the EEF for any data relating to longleaf

pine.

Perhaps it would be useful to compare the effects of seedbed condition (such as exposed mineral soil) in good to

poor seed years and to determine whether supplemental

scarification can result in acceptable establishment of

longleaf pine seedlings during marginal seed production

years. It is easier to manipulate overstory conditions above

an established regeneration cohort than it is to configure

openings when regeneration is absent.

Forest Manager: (42) What is the best timing and

frequency of prescribed burning after seed-fall to

reforest group-selection openings?

Boyer: The best time to regenerate a group-selection

opening is before it is created. New gaps should be created

to release seedlings already present. Conduct a seedbed

burn prior to a good seed crop. Do not burn again until at

least 2 years after trees are cut (give seedlings time to

respond to release and logging slash a chance to decay,

eliminating the extra fuel load).

Forest Manager: (43) How much exposed mineral

soil is necessary to get regeneration within

group-selection openings?

Boyer: A good seedbed burn within a year of seedfall

exposes sufficient mineral soil for seedling establishment.

Two-year and older roughs create a problem for establishment. Longleaf pine has a large seed that retains its wing

and is easily suspended in even a relatively light ground

cover. Understory hardwoods should be controlled in

advance of regeneration.

Guldin: Group openings get heavy use by loggers. Experience in the Ouachita Mountains suggests that loggers use

the group openings as in-the-woods decks to concentrate

loads from the adjacent between-group matrix. As a result,

group openings are characterized by a high degree of

mineral soil exposure. Moreover, empirical evidence and

inspections show that the mineral soil exposure that occurs

as a result of skidding is sufficient to support seedling

establishment. Because of this, it has been suggested that

one should avoid supplemental rehabilitation of skid roads

by direct seeding with wildlife grass and forb mixtures.
26

Part H. Optimum Stand Structure for

Management Objectives

Forest Manager: (44) How many openings should

be created when group selection is used to

regenerate longleaf pine and slash pine, and how

large should the openings be?

Brockway: There is no single answer to this question, since

the optimum size and number of openings in longleaf pine

and slash pine regenerated with the group selection reproduction method will depend on the forest site type (i.e.,

xeric sandhills, mesic uplands, flatwoods, etc.), competition intensity, and current stand conditions. With group

selection, the general size range for gap openings created

by cutting varies from 0.25 to 2 acres. On xeric sandhills,

where the zone of intraspecific competition between adults

and seedlings is relatively wide (about 52 feet), larger gap

sizes are probably more appropriate. On more mesic sites,

where this competitive zone is thought to be somewhat

narrower, smaller gap sizes may suffice. When properly

executed, the group selection method will result in gaps

of a number that is not predetermined, of a size that is

variable, and of a spatial distribution that reflects the practice of generally taking the worst trees and leaving the best

trees within the age classes that the prescription specifies.

Our research on gap-phase regeneration in longleaf pine

forests on xeric sandhill sites indicates that minimum diameters for circular gaps should range from 131 to 165 feet

to ensure adequate seedling relief from competition with

overstory adults (Brockway and Outcalt 1998). Measured

from tree bole to tree bole (not canopy edge to canopy edge),

these dimensions produce forest gaps that are approximately

0.3 to 0.5 acre in size. The lower portion of our recommended size range concurs with studies on mesic uplands

(Palik and others 1997); however, other studies conducted

on mesic uplands and flatwoods suggest that gaps as small

as 0.25 acre may be suitable for longleaf pine regeneration

(Gagnon and others 2003, McGuire and others 2001).

Forest gap diameters > 328 feet would exceed the 2-acre

upper limit typically used in the group selection method

and therefore should be considered with caution. In

observing the geometry of naturally occurring forest gaps,

researchers generally agree that gaps created by cutting

can range widely in shape from circles to ellipses to

various irregular polygons.

Outcalt: We have done research directly on the question

of opening size for regeneration in longleaf pine stands on

xeric sandhills. The mature trees surrounding gaps reduce

seedling survival near the gap edge. The minimum size for

an opening is about 0.25 acre, with a diameter of 118 feet

if circular, on sandhill sites (Brockway and Outcalt 1998).

However, the ideal size is about 0.5 acre for a round gap

with a diameter of 165 feet, because a 0.5-acre gap has 27

percent of its area in the zone where seedlings are likely to

survive vs. just 11 percent for a 0.25-acre gap. When gaps

larger than 0.5 acre are desired, they should be elliptical

with a maximum width of 165 feet so longleaf pine seeds

do not have to travel more than twice the height of dominant seed trees. On more moist sites, it is possible to obtain

regeneration in even small openings, because intraspecific

competition for soil moisture is lower and thus has less

adverse influence on seedling survival and growth. Palik

and others (1997), however, recommend gaps exceeding

0.35 acre in size to minimize overstory competition with

regeneration in uneven-aged management of longleaf pine

on moist sites in southwestern Georgia.

Not all trees need to be cut in groups. If there are poor trees

or at-risk trees that need removal, they can be included in

the selection harvest. Also, not all gaps need be created in

a single cut. It is okay to select trees from groups to partially open up the area and then remove the remainder of

the group during subsequent entries to actually create the

gap. The key thing to avoid is high-grading the stand during

the marking and harvest phase (i.e., do not take out the

good trees and leave the bad ones).

The number of openings to create depends on site productivity and minimum harvest level to make an entry

economical. This can be handled using standard silvicultural techniques. If you want to reduce the basal area from

80 square feet per acre to 65 square feet per acre, then you

need to create enough gaps to cover 10 to 15 percent of

the area and take additional trees from intervening areas to

yield the 15 square feet per acre you want removed. This

translates to one 0.5- to 0.75-acre gap per 5 acres of the

stand plus some single-tree selections. Then the stand is

not entered until the average basal area has again reached

80 square feet per acre. This can be continued indefinitely,

always keeping trees of many size classes on the land, yet

having fairly even harvests and a system that can easily be

taught to marking crews.

Guldin: Optimum size would be determined by silvical

characteristics for optimum longleaf pine development.

The question of the optimum number of openings is not

the way to approach the layout of groups. Group selection

is implemented according to the BDq and the VGDL regulation methods, as is single-tree selection. Therefore, there

should be no plan prior to marking with regard to the

number or size of openings. It is especially important to

avoid installing regularly shaped openings in a regular
27

pattern, since such an approach is properly classified as

patch clearcutting rather than group selection.

Forest Manager: (45) What is the smallest forest

opening in which a longleaf pine seedling can

become established, survive, and grow into a

codominant or dominant tree?

Brockway: According to our research on the xeric sandhills of Florida, any circular gap with a diameter < 98 feet

and an area < 0.17 acre is probably too small (because of

fine root competition from nearby adult longleaf pine trees)

to allow many longleaf pine seedlings to survive and eventually ascend into the overstory. This is why we recommend

that the smallest circular gaps created in the longleaf pine

forest through harvest range from 131 to 165 feet in diameter (0.3 to 0.5 acre). Note that this recommended minimum gap size should be smaller on higher quality mesic

sites, where adult tree roots may be less widespread and

the corresponding competition for seedlings may be somewhat diminished.

Outcalt: See my answer to question 44, as this question

is essentially a subset of that question. Our research at

sandhill sites indicates that the smallest opening that is

likely to allow the establishment of longleaf pine seedlings

is 0.25 acre. On sites with higher soil moisture levels, it

may be possible to get seedlings established directly

beneath the crowns of mature trees. These seedlings have

the potential to become dominants or codominants if the

mature trees are later removed.

Guldin: I have a bit of a problem with the wording of this

question. Available canopy space does not remain constant

over the life of a seedling. In the absence of further harvest, crown space narrows with lateral development of the

crowns of adjacent trees. But it’s difficult to imagine a

situation under any even-aged or uneven-aged silvicultural

system where timely harvests could not be made that would

expand the size of the canopy gap within which the new

tree was growing. The key to ensuring that longleaf pine

seedlings and saplings maintain acceptable height growth

is to develop studies that relate height growth of trees of

different d.b.h. classes to overstory basal area affecting

those trees. Then, silvicultural tactics can be developed to

ensure that periodic cutting-cycle harvests maintain overstory conditions that permit continued seedling and sapling

development.

Forest Manager: (46) What is the understory

vegetation response to the creation of forest

openings?

Brockway: Since the canopy of a longleaf pine forest is

typically quite open (< 60 percent cover), the forest floor

is almost never shrouded in dark shadows as long as periodic fire continues to exclude invasive woody plants. So

increased light to the forest floor within a canopy gap may

increase the growth of understory plants only marginally.

However, removing overstory trees creates a below-ground

gap in the adult root systems that typically extend throughout a site. This root gap is a refuge where longleaf pine

seedlings more easily survive and grow. Thus, it is quite

reasonable to expect that understory plants might also

benefit from the competition relief afforded within a root

gap. To date, little is known about such understory plant

dynamics in canopy gaps created through harvesting.

Jose: After a forest opening is created, the understory vegetation responds positively to increased light availability.

This increase in understory can significantly reduce light

availability to young longleaf pine seedlings, especially

when they are in the grass stage. Larger gap size and

increased light availability may not translate into successful establishment and growth of longleaf pine seedlings in

the presence of severe understory competition.

Outcalt: The understory response depends on understory

composition before the opening is created. If you have a

healthy grass- and forb-dominated understory, it will

respond with some increase in growth. If the understory is

shrub dominated, it can and often does respond with prolific growth in the newly created opening. This can be a

real problem, since these woody plants inhibit longleaf

pine regeneration. They are also difficult to control with

prescribed burning, because fuel levels of grass and needle

litter are often too low to carry an intense fire through the

opening. Therefore, it is better to readjust plant composition before creating openings; if this is not done, it will be

necessary to undertake site preparation to control woody

vegetation before adequate regeneration can be obtained.

Forest Manager: (47) How do we favor longleaf

pine in uneven-aged management when we are

starting with a mixed longleaf pine and slash pine

stand?

Brockway: First, slash pine trees that are too large to be

killed by fire should be removed by harvesting, in one or

more entries depending on the rate at which the manager

wishes to reduce the slash pine component of the forest.
28

This will yield a volume of usable wood and prevent additional dissemination of slash pine seed. Second and perhaps

most important, keep burning the site at frequent intervals

(every 2 to 3 years) during the growing season so that young

fire-susceptible slash pines are killed before they reach

sexual maturity. This combination of actions should cause

slash pine numbers to decline and longleaf pine numbers

to increase over time. From the larger ecological perspective, slash pine is known to naturally occur in mixed stands

with longleaf pine on flatwoods sites. Therefore, on these

forest site types, a component of slash pine may be retained

(at the landowner’s option) and managed along with the

longleaf pine.

Outcalt: First, we should realize that slash pine is native

to Florida and did co-occur with longleaf pine on many

flatwoods sites (Schultz 1983). On wetter sites, where the

interval between fires is at least 8 years, slash pine seedlings can become large enough to survive subsequent

ground fires and remain part of the stand. Thus, we do not

need to remove it from all stands. Alternatively, there are a

number of areas where changes in the natural fire regime

or past management, or both, have favored slash pine over

longleaf pine. On these sites, use your management and

silvicultural actions to favor longleaf pine. This means

preferentially selecting slash pine for harvest when the

stands are marked for partial harvest. It also means burning

on a regular basis, allowing fire to determine which longleaf pine and which slash pine seedlings will survive to be

part of the next overstory.

Guldin: There are several ways that this can be done,

through alteration of the proportion of longleaf pine to

slash pine in the overstory and in the regeneration cohorts

of various ages. Overstory treatments that favor longleaf

pine and discriminate against slash pine increase the proportion of overstory longleaf pine immediately and also

change the proportion of natural seedfall in favor of longleaf pine. If this is the desired outcome, one should manage

the stand so that the longleaf pine component becomes

acceptably stocked as soon as possible. If there is enough

longleaf pine in the stand so that minimum stocking standards in the pine component can be met with longleaf pine

alone, the situation is simple—remove the slash pine component as soon as possible (through commercial harvest or

injection).

If there is not enough longleaf pine in the overstory to meet

minimum stocking standards, some proportion of slash

pine must be retained to bring the stand up to acceptable

minimums. If this is the case, remember that cone production is a highly inherited trait genetically. Tom Croker’s

colorful advice for longleaf pine seed producers was to

“leave fruiters, not neuters” in order to enhance longleaf

pine seed production. Croker sought to leave longleaf pines

that showed evidence of past seed production. If you must

leave some slash pine overstory, try taking the inverse of

Croker’s advice. Leave the slash pines that are growing

fastest (so volume production remains acceptable) but show

evidence of being poor cone producers. In this way, the

proportion of slash pine in the annual pine seedfall should

be minimized.

Finally, there will probably be a need to influence the species composition of existing regeneration as well. Practices

that kill more slash pine seedlings and saplings than longleaf pine seedlings should be employed. Prescribed fire

may be highly effective in increasing the relative proportion of longleaf pine to slash pine. However, you could use

other release treatments also, such as selective chemical

(injection) or mechanical (chain-saw felling) treatments.

Forest Manager: (48) What are the optimum

ranges for the size, distribution, and frequency

of harvests and new openings during the

maintenance phase?

Guldin: These ranges depend on a balance between aftercut

stand structure, the expected growth of the stand, and the

number of years between cutting-cycle harvests. The longer

the time between cutting-cycle harvests, the bigger the

expected growth and volume that can be cut, and therefore

the lower will be the after-cut volume and basal area.

For example, suppose you want either 7,000 board feet per

acre or 75 square feet per acre in basal area or both immediately before a cutting-cycle harvest. The intensity of the

marking prescription depends on the anticipated length of

the subsequent cutting cycle. Assuming that stands grow at

400 board feet per acre per year and 3 square feet per acre

per year (which is the case for Coastal Plain loblolly-shortleaf pine stands), the following stand conditions would be

needed to grow back to 7,000 board feet per acre and 75

square feet per acre.

 Cutting-cycle

 length Volume Basal area

board feet square feet

 years per acre per acre

 3 5,800 66

 5 5,000 60

 7 4,200 54

 10 3,000 45
29

You can plug in your own estimates of longleaf pine

volume and basal area growth and obtain similar estimates

of after-cut volumes and basal area.

Forest Manager: (49) At what density (basal area

or trees per acre) can you get the best balance

between merchantable timber growth and

continuous longleaf pine regeneration?

Boyer: The best density (basal area) for merchantable

longleaf pine timber growth on average Coastal Plain sites

is 60 to 90 square feet per acre. The best basal area for

obtaining longleaf pine regeneration is 25 to 30 square

feet per acre. This density will maximize cone production

per acre. Cone production is very low under the higher

densities that maximize timber volume growth per acre.

Few seedlings established under the higher densities (60 to

90 square feet per acre) will survive any burning regime

with less than a 5-year return interval.

Guldin: My experience is in using uneven-aged management on loblolly-shortleaf pine stands. In managing these

forests, residual stands of 45 to 75 square feet per acre are

best for establishment and development of loblolly pine

and shortleaf pine regeneration. However, simply reducing

overstory density is not enough. These reductions must

also be coupled with effective competition control. I would

suggest similar basal areas, perhaps slightly lower (40 to

70 square feet per acre during any point in the cutting

cycle) as a starting point for implementing uneven-aged

management in longleaf pine stands. This recommendation is subject to revision if empirical experience, new

research, or application of new growth-and-yield models

suggests otherwise.

Forest Manager: (50) At what density (basal area

or trees per acre) can you get the best balance

between merchantable timber growth and

vegetation diversity?

Guldin: Density is less likely to be important than withinstand habitat diversity in balancing growth and vegetation

diversity. If you want to maximize vegetation diversity,

you should maximize within-stand heterogeneity. Methods

such as group selection or patch clearcutting might be most

appropriate for achieving this objective. On the other hand,

if you want a large block of similar habitat condition, the

single-tree selection method might be better. Specific targets for vegetation diversity may also influence the form

and intensity of site preparation and release treatments that

are applied in a stand. Moreover, in both cases, questions

about vegetation diversity should include assessments of

conditions in adjacent stands and on larger spatial scales.

Forest Manager: (51) How do stand structural

characteristics (spatial orientation, size, shape,

density, age distribution, and diameter distribution)

interact with each other and with management

functions (timber inventory, prescribed burning,

monitoring, administration)?

Guldin:

Timber Inventory, Monitoring, and Administration

Stand structural characteristics are mostly independent of

these administrative issues. Inventory work is conducted

using plots and standards as described previously, and these

are independent of whether stands are managed using single-tree or group selection. Age distribution is independent

of inventory issues, but diameter distribution can be used

as an indicator of stand heterogeneity and may affect the

decision to use fixed area plots or prism samples. In group

selection, there is no need to sample regeneration in the

matrix between groups.

Prescribed Burning

Prescribed burning may be conducted differently in longleaf pine stands where group selection is employed than in

those where single-tree selection is used. In the Ouachita

Mountains, fire prescriptions for shortleaf pine are implemented in the same way in group-selection stands and

single-tree-selection stands. However, large even-aged

regeneration blocks (clearcut, seed-tree, and shelterwood

blocks) are preburned in January prior to landscape burns

in March. This tactic ensures that the March fires do not

burn uncontrollably and do not damage regeneration

severely in the preburned areas. Group openings in group

selection stands are too small to be treated in the way.

Part I. Competition Tolerance and Release

Potential of Various Age Classes

Forest Manager: (52) Will suppressed longleaf

pine saplings and pulpwood respond once they

are released?

Boyer: Suppressed saplings will usually respond to release,

but the time required will depend on their condition. Codominants will respond immediately, intermediates will

take longer, and suppressed saplings will take much longer.
30

I don’t believe there have been any studies on response of

suppressed saplings and pulpwood-size material to release

in terms of their initial crown condition, but it takes years

for full response. More information is available on seedlings, as noted in the responses to earlier questions.

Guldin: Both loblolly pine and shortleaf pine respond to

release if some degree of apical dominance is still apparent

in the seedling or sapling. The standards that indicate potential for acceptable recovery are quite low for pulpwoodsized suppressed trees. If a suppressed loblolly pine has a

live-crown ratio > 20 percent and an outside bark diameter

of at least 2 inches at the base of the live crown, it will

respond. Some research in understocked longleaf pine

stands would be needed to obtain similar indications of the

ability to respond to release.

Forest Manager: (53) What degree(s) and duration(s) of shading can seedlings and saplings

survive and, when released, still recover their full

growth potential?

Boyer: Longleaf pine seedlings can survive an extended

period of suppression by overstory competition and still

respond promptly to release and achieve full growth potential. Studies have reported response after 8 years of suppression, and informal observations have noted rapid

recovery after 15 years of suppression and survival (of

grass-stage seedlings) through 22 years of suppression.

Guldin: In loblolly and shortleaf pine stands, height growth

of regeneration is a useful indication of the ability to

recover full growth potential. Minimum acceptable annual

height growth in these species is 0.5 foot. If seedlings or

saplings < 4.5 feet in height are not growing at this rate,

they will probably not survive.

Also the residual basal area that remains after a low thinning to the point at which accidental regeneration just

begins to suffer suppression approximates the highest acceptable before-cut basal area in uneven-aged stands. In evenaged Coastal Plain loblolly pine stands thinned to 70 square

feet per acre, regeneration of pine often becomes established. But by the time the stand grows above 75 square

feet per acre, the regeneration ceases to make acceptable

height growth. In uneven-aged stands, that 75 square feet

per acre is distributed much less uniformly than it is in

low-thinned even-aged stands, and the regeneration will

not be suppressed in the holes in the uneven-aged stands.

But repeated cutting-cycle harvests are needed to enlarge

any existing holes in the stand and to create new openings

and new zones of lower basal area within which regeneration can become established and develop.

Forest Manager: (54) At what maximum age is

release still possible?

Boyer: There is probably no age limit for response to

release. Observations of growth rings have shown that

200-year-old trees have responded rapidly to release.

Guldin: In loblolly-shortleaf pine stands, maximum age is

less important than minimum size, as has been discussed

in the responses to question 52.

Forest Manager: (55) How shade tolerant are

longleaf pines at different ages, spacings, and

densities?

Brockway: Shade tolerance (or more precisely competition tolerance) is an inherent physiological characteristic

of each tree species. In some tree species, tolerance varies

over the life span of the organism. For example, some

species may be intermediate in tolerance as juveniles and

then become intolerant as adults. However, this is not the

case with longleaf pine. Longleaf pine is classified as very

intolerant by most silvicultural authorities and apparently

retains that status at all ages. The very intolerant status of

longleaf pine is not altered by spacing or density within a

forest stand. Because juvenile longleaf pines sometimes

persist for many years beneath the crowns of adults, some

people have come to regard these suppressed offspring as

shade-tolerant. They are not. They are simply suppressed

young awaiting an opportunity for release following a

canopy-altering disturbance.

Boyer: One study showed that light shading (about a 33

percent reduction in sunlight intensity) did not significantly affect the height growth of longleaf pine saplings

over a single growing season.

Forest Manager: (56) Does shade tolerance make

any ecological or silvicultural difference over the

long term in uneven-aged stands?

Guldin: No. The most intolerant species can be managed

using uneven-aged methods. However, once an unevenaged prescription is initiated with intolerant species, cuttingcycle harvests must be made in a regular and timely way.

Failure to execute cutting-cycle harvests means that the

stand will continue to grow and that basal area will exceed

the maximum at which regeneration development can be

maintained.
31

Part J. Viability of Interplanting and

Underplanting

Forest Manager: (57) At what stocking level is

underplanting economical?

Barnett: Underplanting is probably not an economic management practice for most species. Research has shown

that underplanted loblolly pine and slash pine seedlings

never catch up with the original stand and usually become

suppressed stock. However, longleaf pine’s grass stage

delays early height growth. This makes natural regeneration harder and makes underplanting or interplanting an

option. The seedlings should be planted in openings,

because they die or develop very poorly if they are planted

within about 50 feet of a mature tree or in stands of trees

that will be retained. However, if a stand has openings at

least 0.25 acre in area, then underplanting or interplanting

or both may be effective in increasing the stocking of that

stand and developing a multi-aged condition.

Guldin: See my answer to question 60. There probably is

a minimum number of seedlings that is operationally

feasible to plant. If natural regeneration is inadequate and

planting is needed, be sure to plant enough seedlings to

ensure that there is a fully stocked stand of planted seedlings. That way, in the event that naturally regenerated

seedlings fail to survive, the site will be fully stocked.

Many of the existing naturally regenerated seedlings will

not survive the site preparation necessary to ensure a

successful planting job.

My views on this reflect my background as a dyed-in-thewool natural-regeneration silviculturist. If efforts are being

made to manage a stand using any of the even-aged or

uneven-aged reproduction methods that leave residual trees

on the site, natural regeneration should have two chances

for success prior to planting. The first chance is associated

with the initial harvest. The hope is that the harvest would

occur in conjunction with a good seed year. However, the

administration of sales on National Forest System lands

makes it almost impossible to guarantee harvest in conjunction with seed crops, since logging contractors are typically given several years to harvest a timber sale.

The second chance is the first good seed crop after the sale

closes. Site preparation can be conducted so as to catch the

seed crop. This, too, is constrained by administrative procedures. The Knutsen-Vandenberg (KV) Act of 1933 allows

national forests to retain a portion of the sale receipts from

timber harvested within a sale area to reinvest in that sale

area. Reforestation needs such as site preparation activities

associated with obtaining natural regeneration qualify for

such funding. However, these KV funds can generally be

held for only 5 years, with some special exceptions. Thus,

national forest managers must respond to a bumper seed

crop within 5 years. Longleaf pine doesn’t always produce

a bumper seed crop every 5 years, so managers must sometimes decide whether to plant stands that show little likelihood of seedfall. Moreover, money for site preparation

must be requested during the fiscal year before that in

which it would be spent, and there is no way to predict a

good seed year that far in advance.

Practically, then, a silviculturist with a national forest has

4 years after the harvest to try twice to obtain natural

regeneration; the 5th year must be devoted to spending the

available KV funds to prepare sites in advance of planting.

We should tell silviculturists what conditions are likely to

cause great difficulties with natural regeneration. Such

conditions include the presence of poor seed producers left

on the site, an absence of advanced growth, and the lack of

adjacent stands that can contribute seed to cutover areas.

Silviculturists could use this information to identify sites

that might be good candidates for underplanting, and

avoid the problem of timing site preparation to take

advantage of seedfall.

Some research should be conducted on how to choose seedlings to use when underplanting. Efforts in genetic improvement and progeny testing have focused on developing

seedlings designed to make rapid early height growth

under open conditions with intensive site preparation. Will

those families that have been successful under open conditions of intensive forestry be equally successful when

underplanted beneath a residual overstory? Are there other

families with desirable form and growth attributes that

might better withstand the more challenging environment

that seedlings face under partial overstories? I guess this

would involve progeny tests under similar conditions, and

I know of no such tests being conducted anywhere in the

nation.

Research at the Hitchiti Experimental Forest in central

Georgia suggests that slash pine seedlings that are interplanted a few years after the initial planting have a very

low probability of surviving to become part of the codominant canopy unless the initial spacing is very wide. In

longleaf pine, interplanted seedlings of good vigor might

become part of the subsequent stand if the longleaf pine

seedlings established previously have not yet initiated

height growth. But, like slash pine, longleaf pine is an

intolerant species. The likelihood of a newly planted seedling finding its way into the main canopy is probably low,
32

although no research has been conducted in longleaf pine

to verify this. On balance, interplanting as a supplement to

natural regeneration is probably less effective than considering inadequate natural regeneration a failure, site-preparing the entire stand, planting, and relying on the planted

seedlings to develop into the fully stocked condition.

Forest Manager: (58) What are the growth characteristics of longleaf pine seedlings that are either

interplanted with other seedlings or underplanted

in more mature stands?

Barnett: Longleaf pine seedlings are very intolerant and

require almost full sunlight to quickly initiate height

growth and become vigorous saplings. The success of

interplanting in young stands of established seedlings or

saplings that are in height growth depends greatly on

access to full sunlight and control of both woody and grass

competition. If favorable conditions do not exist, planted

stock will be slow to come out of the grass stage and will

be slow to develop in competition with surrounding plants.

Even when openings exist that are sufficient for good

establishment and early growth, use of fire before and

after planting will be important in controlling competition

that will delay or prevent seedling development. Frequent

prescribed fires will be an important management tool to

make these plantings successful.

Jose: If there are further research questions here, I would

be interested in working with someone on this important

question.

Forest Manager: (59) Do interplanting and underplanting have any long-term silvicultural or

ecological advantages?

Barnett: When they are used with an understanding of the

ecology of longleaf pine, interplanting and underplanting

can have both silvicultural and ecological advantages.

Such planting should be done in openings of sufficient size

to allow successful establishment and development of longleaf pine seedlings. The appropriateness of this approach

depends on the condition of existing stands and the management objectives of the organization. If objectives include

the development of forest stands with potential for wood

products production or restoration of longleaf pine ecosystems, you must establish stocked stands with which to

work. If economics and time are not a principal concern,

filling in the openings in existing stands is an option that

should be considered. The management of such stands is

more time consuming and expensive than harvesting the

stands and planting, but it is an option that may be attractive if an uneven-aged condition is desired.

Brockway: Artificial regeneration is generally more

expensive than natural regeneration. If time is crucial, then

the higher expense of artificial regeneration may be justified. But if timber yield is not a priority, it is perfectly

acceptable that openings in the longleaf pine forest persist

for many years or even decades. As long as an aggressive

program of prescribed fire keeps woody plants from invading and occupying these openings, longleaf pine seedlings

will eventually establish there if a parent tree is nearby. In

natural longleaf pine ecosystems, persistent openings are

simply part of the normal landscape condition. We do not

always have to obtain 300 evenly spaced longleaf pine trees

per acre to fully occupy the site. The density of natural

longleaf pine stands varies widely; for example, there are

sparsely stocked stands in savannas and well-stocked

stands on uplands. All of these conditions are perfectly

acceptable and are good stewardship objectives for the

prudent natural resources manager. Some managers are

much more concerned about planting wiregrass and various forbs under their longleaf pine trees. It seems they are

quite successful at restoring the longleaf pine trees, but the

understory has been so degraded that many of the native

plants that act as the most effective carriers of fire and add

the greatest amount of biological diversity to the ecosystem are missing.

Guldin: Part of this question was addressed in my response

to question 58. Many of the advantages of planting relate

to timeliness of reforestation, ease of administration,

reductions in the length of time a stand is understocked,

better control of species composition, better control of tree

spacing, and overall improvement in the genetic quality of

a longleaf pine stand. Disadvantages relate to cost, spatial

appearance (though spacing of underplantings could be

varied in creative ways), and the opportunity to stock the

site with progeny of trees that have been genetically

successful on that given site.

Forest Manager: (60) What are acceptable rates of

regeneration such that interplanting or underplanting are not necessary?

Barnett: The answer to this question depends on the stage

of regeneration being considered. Planting rates depend

greatly on the type of stock being planted and may vary

from 700 to 1,200 seedlings per acre. If bareroot stock is

being used, the higher planting rates in this range should

be used because levels of initial mortality are higher. Container stock can be planted in the 700 to 900 seedlings per
33

acre portion of this range if adequate site preparation has

been done.

A minimum of 400 to 500 seedlings per acre should have

initiated height growth within 3 to 4 years to obtain a good,

manageable stand. However, interplanting should be considered only in stand openings of about 0.25 acre or larger.

Boyer: The amount of regeneration needed so that reinforcement planting is not necessary varies with the management

technique used. The goal with even-aged management is

3,000 seedlings per acre at least 1 year old after removal

of the parent overstory. Since about 10 percent of the

seedlings in a natural stand are resistant to the brown-spot

needle blight, this will result in about 300 disease-resistant

trees per acre for the next generation. The goal in an unevenaged management method is much lower because a seed

source is always available to supplement a limited population of established seedlings. A new stand in an opening

may consist of seedlings from three or more different cone

crops. Supplemental planting might be considered if part

of the opening has < 250 well-distributed seedlings per acre

and is beyond seeding range of the nearest mature trees.

Guldin: Minimum acceptable standards for regeneration

(the 0-inch, 1-inch, 2-inch, and 3-inch size classes) in

uneven-aged loblolly-shortleaf pine stands in the western

gulf region and in shortleaf pine stands in the Interior

Highlands are 200 stems per acre and 20 percent milacre

stocking. By comparison, a plantation established at an 8-

by 10-foot spacing has 544 seedlings per acre and a milacre

stocking rate of 54 percent. Minimum acceptable standards

for natural regeneration in even-aged stands in the Ouachita

Ecosystem Management research study are 300 seedlings

per acre at 30 percent milacre stocking. These are minimum

standards, and the closer a stand is to them the more likely

you will need to consider supplemental release treatments.

Standards similar to those described above for loblollyshortleaf pine stands might be a place to start for assessing

regeneration success in longleaf pine stands. A forester

who is guided by these standards will not engage in underplanting or supplemental planting if natural regeneration

in stands exceeds these levels.

Epilogue

As the above discussion shows, not all questions posed by

forest managers can be fully answered at this time. In

many instances, scientific study has already developed a

considerable body of knowledge about longleaf pine that

may be useful to managers. In other instances, only partial

answers can be provided, since the topic under consideration has been only partly explored, and studies concerning

the subject may yet be in progress. Clearly, this dialogue

among managers and scientists was an opportunity to

assess the current status of longleaf pine research and

consider possible directions for its future development.

The interaction during this dialogue not only enhanced the

awareness of managers, but also stimulated the natural

curiosity that encourages scientists to investigate those

questions that, at this time, remain partially answered.

This positive synergism is the very essence of a beneficial

scientific research and technology transfer process.

That not all scientists are in complete agreement concerning the answers to some of these questions is also noteworthy. Although the authors hope to avoid creating

confusion for those managers who may be seeking a single

right answer, it should be recognized that such honest

disagreements are not uncommon in scientific disciplines.

Scientific research is a developmentally iterative process,

in which the participating individuals often have differing

viewpoints, areas of expertise, and levels of insight. Therefore, complete agreement is often rare until the preponderance of evidence allows preliminary findings and

provisional concepts to coalesce into broader agreement

among the many investigators. Through the process of (1)

thesis, (2) antithesis, (3) synthesis, and (4) new thesis,

scientific knowledge deliberately progresses through its

developmental stages. The lack of complete agreement

often means that scientists are working at the cutting edge

of knowledge and that the synthesis needed to resolve

differing viewpoints has not occurred yet but is likely to

occur in the future.

A great deal of useful information about longleaf pine

ecology and management has already been developed by

scientists in a wide variety and large number of research

organizations. Continuing research will improve our understanding of these longleaf pine forest ecosystems and the

management options available for sustaining them in perpetuity. Ongoing longleaf pine research efforts are currently focused on a variety of subjects, including (1) safe

reintroduction of prescribed fire into long-unburned

forests, (2) methods for restoring native understory plants

as well as overstory trees, (3) comparative analysis of

even-aged and uneven-aged forest reproduction methods

across a wide range of ecological site types, (4) natural

gap-phase regeneration dynamics, (5) impacts of management treatments on biological diversity and wildlife habitat

quality, (6) growth-and-yield modeling, and (7) carbon

sequestration. The authors of this dialogue look forward to
34

a bright future for longleaf pine forest ecosystems as they

are restored and are more suitably managed to ensure that

the ecological, economic, and social values associated

with them are sustained well into the future.

Acknowledgments

The authors thank Todd Engstrom, James Baker, Rhett

Johnson, Charlie Marcus, and Gary Hegg for technical

review comments useful in improving this manuscript and

Nancy Herbert, Carol Whitlock, Paul Smith, Alan Salmon,

and Louise Wilde for administrative and editorial support

of this project.

Literature Cited

Baker, J.B.; Cain, M.D.; Guldin, J.M. [and others]. 1996. Uneven-aged

silviculture for the loblolly and shortleaf pine forest cover types. Gen.

Tech. Rep. SO–118. Asheville, NC: U.S. Department of Agriculture,

Forest Service, Southern Research Station. 65 p.

Boyer, W.D. 1963. Development of longleaf pine seedlings under parent

trees. Res. Pap. SO–4. New Orleans: U.S. Department of Agriculture,

Forest Service, Southern Forest Experiment Station. 5 p.

Boyer, W.D. 1979. Regenerating the natural longleaf pine forest. Journal

of Forestry. 77: 572–575.

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36

GLOSSARY OF ABBREVIATIONS AND ACRONYMS

A/r: area (A) divided by rotation length (r), normally yielding a rate of harvest in acres

per year.

BDq: an uneven-aged method of regulating stand volume based on basal area (B),

maximum d.b.h. (D), and the diminution coefficient (q).

CEF: Crossett Experimental Forest in southern Arkansas.

CTL: cut-to-length.

d.b.h.: diameter at breast height.

EEF: Escambia Experimental Forest in southern Alabama.

FVS: Forest Vegetation Simulator.

KV: Knudson-Vandenberg Act of 1933 and the funds allocated by this legislation to

ensure that harvested sites on national forests are reforested.

VGDL: volume-guiding diameter limit method of regulating uneven-aged stands.
37

James P. Barnett is Project Leader of the Ecology and

Management of Even-Aged Southern Pine Forests research

work unit, Southern Research Station, U.S. Department of

Agriculture (USDA) Forest Service, Alexandria Forestry

Center, 2500 Shreveport Highway, Pineville, LA 71360.

During many years his research has focused on the study

of longleaf pine ecosystems, including seed and seedling

physiology, seedling establishment, and forest stand

ecophysiology. He can be contacted by telephone at (318)

473-7214 or by email at jpbarnett@fs.fed.us.

William D. Boyer is Research Forester Emeritus,

Southern Research Station, USDA Forest Service, G.W.

Andrews Forestry Sciences Laboratory, 520 Devall Drive,

Auburn, AL 36849. During more than 40 years of study,

his silviculture research has concentrated on numerous

aspects of the regeneration and management of longleaf

pine forests. He can be contacted by telephone at (334)

826-8700 or email at bboyer@fs.fed.us.

Dale G. Brockway is Research Ecologist, Southern

Research Station, USDA Forest Service, G.W. Andrews

Forestry Sciences Laboratory, 520 Devall Drive, Auburn,

AL 36849. His research work has included biogeochemical cycling, ecological classification of forest communities,

and restoring fire as an ecological process in xeric woodlands and grasslands. His research has more recently

focused on analyzing plant community responses to mechanical, herbicide, and prescribed burning treatments for

improved fuels management and fire danger mitigation;

evaluating physical, chemical, and pyric methods for

restoring longleaf pine ecosystems; and comparatively

analyzing forest reproduction methods (including natural

gap-phase regeneration dynamics) to develop improved

silvicultural approaches for sustaining the biological

diversity and long-term productivity of longleaf pine

ecosystems. He can be contacted by telephone at (334)

826-8700 or by email at dbrockway@fs.fed.us.

James M. Guldin is Project Leader of the Managing

Upland Forest Ecosystems in the Midsouth research work

unit, Southern Research Station, USDA Forest Service,

Arkansas Forestry Sciences Laboratory, 211 Forest

Resources Building, University of Arkansas, Monticello,

AR 71656. His research has included the development of

even-aged and uneven-aged reproduction cutting methods

that rely on natural regeneration in pine, pine-hardwood,

and hardwood stands in the west Gulf Coastal Plain and

Interior Highlands of Arkansas and Oklahoma and is

currently focused on extending and adapting regulation

methods for uneven-aged forest types in the United States.

He can be contacted at by telephone at (501) 623-1174 or

email at jguldin@fs.fed.us.

Shibu Jose is Associate Professor of Forestry, School of

Forest Resources and Conservation, University of Florida,

5988 Highway 90, Building 4900, Milton, FL 32583. His

research is focused on production ecology and ecophysiology of intensively managed pine and hardwood forests,

restoration of longleaf pine ecosystems, and ecological

and ecophysiological interactions in tree-crop mixed

systems. He is also developing an educational course in

restoration ecology which features longleaf pine ecosystems. He can be contacted by telephone at (850) 983-2632

or email at sjose@ufl.edu.

Jarek Nowak is Assistant Professor of Forestry, School of

Forest Resources and Conservation, University of Florida,

North Florida Research and Education Center, 30 Research

Road, Quincy, FL 32351. His research studies and extension work are focused on the silviculture of southern pine

forests and include restoration of longleaf pine ecosystems.

He can be contacted by telephone at (850) 875-7142 or

email at jnowak@mail.ifas.ufl.edu.

Kenneth W. Outcalt is Research Plant Ecologist,

Southern Research Station, USDA Forest Service, Forestry

Sciences Laboratory, 320 Green Street, Athens, GA 30602.

His research work has included the silviculture of sand

pine, slash pine, and longleaf pine and more recently has

concentrated on understanding the natural dynamics of

mortality and regeneration in longleaf pine ecosystems,

developing techniques for maintaining and restoring

biological diversity in the plant communities of longleaf

pine forests, and determining the effects of fire and other

disturbances on longleaf pine ecosystems. He can be

contacted by telephone at (706) 559-4309 or email at

koutcalt@fs.fed.us.

D. Craig Rudolph is Research Ecologist, Southern

Research Station, USDA Forest Service, Wildlife Habitat

and Timber Resources Laboratory, 506 Hayter Street,

Nacogdoches, TX 75961. His research is focused on the

biology of red-cockaded woodpeckers, Louisiana pine

snakes, and interactions of various taxa with alteration of

fire regimes in fire-maintained pine ecosystems. He can be

contacted by telephone at (936) 569-7981 or email at

crudolph01@fs.fed.us.

CONTRIBUTING SCIENTISTS
38

Robert B. Rummer is Project Leader of the Forest

Operations to Achieve Sustainable Management research

work unit, Southern Research Station, USDA Forest

Service, G.W. Andrews Forestry Sciences Laboratory,

520 Devall Drive, Auburn, AL 36849. His research is

focused on developing new technology for forest work,

forest operations safety, and the ecological effects of

forest operations. He can be contacted by telephone at

(334) 826-8700 or email at rrummer@fs.fed.us.

Joan L. Walker is Research Plant Ecologist, Southern

Research Station, USDA Forest Service, Endangered,

Threatened and Sensitive Wildlife and Plants Laboratory,

Department of Forest Resources, Clemson University,

Clemson, SC 29634. Her research has included studies of

the structure and composition of longleaf pine ecosystems

in Florida, Georgia, South Carolina, and North Carolina

and currently focuses on the biology and management of

rare plant species and their habitats and on restoration of

ground-layer vegetation in upland sandhills. She can be

contacted by telephone at (864) 656-4822 or email at

joanwalker@fs.fed.us.
Brockway, Dale G.; Outcalt, Kenneth W.; Guldin, James M.; Boyer, William D.;

Walker, Joan L.; Rudolph, D. Craig; Rummer, Robert B.; Barnett, James P.; Jose,

Shibu; Nowak, Jarek. 2005. Uneven-aged management of longleaf pine forests: a

scientist and manager dialogue. Gen. Tech. Rep. SRS-78. Asheville, NC: U.S.

Department of Agriculture, Forest Service, Southern Research Station. 38 p.

Interest in appropriate management approaches for sustaining longleaf pine (Pinus

palustris Mill.) forests has increased substantially during the recent decade. Although

long-leaf pine can be managed using even-aged techniques, interest in uneven-aged

methods has grown significantly as a result of concern for sustaining the wide range of

ecological values associated with maintaining continuous crown cover in these ecosystems. Indeed, land managers have recently sought to restore and sustain the many habitat

attributes upon which numerous at-risk species depend, while simultaneously producing

high-quality wood products from longleaf pine forest ecosystems. Although earlier

research produced a substantial body of knowledge to guide even-aged management,

less is known about application of uneven-aged management methods in longleaf pine

forests. Much of this information is yet in the developmental staage. However, managers

from the Florida Division of Forestry and Florida National Forests, having a keen interest

in applying what is currently known, encouraged scientists of the U.S. Department of

Agriculture Forest Service, Southern Research Station and faculty members from the

School of Forest Resources and Conservation at the University of Florida to engage in a

dialogue that focused on addressing 60 of their key questions concerning uneven-aged

management of longleaf pine. This dialogue addresses issues related to (1) methods for

converting even-aged to uneven-aged stands, (2) growth and yield, (3) selection harvest

techniques, (4) optimum logging practices, (5) effects on red-cockaded woodpeckers

(Picoides borealis), (6) prescribed burning approaches, (7) regeneration, (8) optimum

stand structure, (9) competition tolerance and release of various seedling age classes, and

(10) the viability of interplanting and underplanting.

Keywords: Artificial regeneration, group selection, growth and yield, natural regeneration, prescribed fire, red-cockaded woodpecker, single-tree selection, stand structure.
The Forest Service, United States Department of

Agriculture (USDA), is dedicated to the principle of

multiple use management of the Nation’s forest

resources for sustained yields of wood, water, forage,

wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the National Forests and National Grasslands, it

strives—as directed by Congress—to provide increasingly

greater service to a growing Nation.

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