A Comprehensive Guide to Fuels Treatment 

Practices for Ponderosa Pine in the Black 

Hills, Colorado Front Range, and Southwest

M.E. Hunter, W.D. Shepperd, L.B. Lentile, J.E. Lundquist, 

M.G. Andreu, J.L. Butler, and F.W. Smith

United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-198

September 2007
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Hunter, M.E.; Shepperd, W.D.; Lentile, J.E.; Lundquist, J.E.; Andreu, M.G.; Butler, J.L.; Smith, 

F.W. 2007. A comprehensive guide to fuels treatment practices for ponderosa pine in 

the Black Hills, Colorado Front Range, and Southwest. Gen. Tech. Rep. RMRS-GTR-198. 

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

Station. 93 p.

Abstract

The objective of this paper is to present recommendations for fuels treatments in ponderosa 

pine forests in the Southwest, Colorado Front Range, and Black Hills of South Dakota. We 

have synthesized existing knowledge from the peer-reviewed literature and administrative 

studies and acquired local knowledge through a series of discussions with fuels treatment 

practitioners. We describe specific treatments, the circumstances under which they can be 

applied, and treatment effects. We provide recommendations related to where, how, and how 

often fuels treatments may be prescribed to achieve desired outcomes. Desired outcomes 

address social, political, economic, and ecological factors. 

Key words: southwest, Black Hills, ponderosa pine, wildfire, forest thinning, prescribed fire

Authors

Molly E. Hunter School of Forestry, Northern Arizona University, Flagstaff, AZ

Wayne D. Shepperd (retired) USDA Forest Service, Rocky Mountain Research Station, Fort 

Collins, CO

Leigh B. Lentile Department of Forestry and Geology, The University of the South, 

Sewanee, TN

John D. Lundquist USDA Forest Service, Pacific Northwest Research Station, Anchorage, 

AK

Michael G. Andreu School of Forest Resources and Conservation, University of Florida, 

Plant City, FL

Jack L. Butler USDA Forest Service, Rocky Mountain Research Station, Rapid City, SD

Frederick W. Smith Forest, Rangeland, and Watershed Stewardship, Colorado State 

University, Fort Collins, CO
Executive Summary

This comprehensive status of knowledge summary of fuels treatment practices in ponderosa 

pine forests of the Black Hills, Front Range and Southwest is the final report of Joint Fire Science 

Program Project 05-S-03. The authors gratefully acknowledge the support and encouragement 

of the Joint Fire Science Program Board of Directors and staff in completing this publication.

Historically, fire has been important in shaping the vegetation composition, succession, and 

structure of forests throughout the western United States. Low elevation ponderosa pine 

forests have been particularly vulnerable to altered fire regimes and much of the wildlandurban interface in the west is found among or adjacent to this forest type. In the past, relatively 

frequent low-severity surface or mixed-severity fires burned throughout ponderosa pine forests. 

Fire acted as a natural restorative agent by reducing litter, removing unhealthy trees, snags, 

and woody debris, thinning small trees, and creating diversity in landscapes at a spectrum of 

scales.

Over the past century and a half, changes in forest structure, understory and overstory 

conditions, fuel biomass conditions, and fire frequency have created a situation where large, 

infrequent, and intense fires are now the norm. Fire research has shown that physical setting, 

fuels, and weather combine to determine fire behavior. Recent research has addressed the role 

of stand and fuel structure to reduce wildfire behavior, severity, and extent. Although the need 

to restore historical disturbance processes is now recognized, management practices to assist 

hazardous fuels treatment project design and implementation have not yet been developed for 

fuels treatments in ponderosa pine forests.

The objective of this paper is to present management recommendations for fuels treatment 

based on a synthesis of existing knowledge acquired from the literature and the expertise of 

practitioners. We bring the expertise of fire scientists and managers in the Southwest, Colorado 

Front Range, and Black Hills of South Dakota together in a collaborative effort to produce a 

reference that provides science-based decision support for ongoing fuel reduction activities in 

ponderosa pine forests of these regions. We document specific conditions and practices where 

management intervention is appropriate to reduce fuels hazards while attempting to restore the 

forest community to a more natural condition. To achieve these goals, we have synthesized 

existing knowledge from the peer-reviewed literature and administrative studies, and acquired 

local knowledge through a series of interviews and discussions with local fuels treatment 

practitioners. We describe specific treatments, the circumstances under which they can be 

applied, and the expected reductions in fuels hazard. We provide recommendations related to 

where, how, and how often fuels treatments may be prescribed to achieve desired outcomes. 

Desired outcomes address social, political, economic, and ecological factors. Finally, deficits in 

the existing knowledge are identified.
Contents

Section I: Introduction...............................................................................................................1

Spatial Scales ......................................................................................................................1

Integrated Approach ............................................................................................................3

Background..........................................................................................................................3

Section II: Fire and Fuels Issues..............................................................................................5

Past Land Use and Management Activities .........................................................................5

Fire Regimes .......................................................................................................................7

Impacts of Altered Fire Regimes........................................................................................17

Section III: Fuel Treatment Objectives...................................................................................23

Reduced Wildfire Hazard...................................................................................................23

Restoration ........................................................................................................................24

Commercial Revenue ........................................................................................................25

Other Objectives ................................................................................................................25

Summary ...........................................................................................................................25

Section IV: Fuel Treatment Techniques.................................................................................27

Developing Landscape-wide Fuel Treatment Strategies ...................................................27

Prescribed Fire Techniques ...............................................................................................28

Thinning Techniques..........................................................................................................36

Other Mechanical and Combination (Fire + Mechanical) Techniques ...............................44

Livestock Grazing and Chemical Treatment Techniques...................................................47

Section V: Fuel Treatment Requirements..............................................................................49

Planning.............................................................................................................................49

Prescribed Fire ..................................................................................................................49

Thinning .............................................................................................................................51

Other Mechanical and Combination Treatments ...............................................................51

Livestock Grazing and Chemical Treatments ....................................................................52

Limitations and Examples of Overcoming Them ...............................................................53

Section VI: Fuel Treatment Impacts, Mitigation, and Monitoring........................................61

Undesirable Impacts of Fuel Treatments ...........................................................................61

Mitigation of Undesirable Fuel Treatment Impacts ............................................................65

Monitoring ..........................................................................................................................68

Section VII: Comprehensive Management Principles..........................................................71

Integrating Ecological Knowledge and Principles into Fuel Projects .................................71

Planning Fuel Treatments Within a Broad Landscape Context .........................................72

Encouraging Innovative Approaches to Fuels Treatment ..................................................72

Monitoring Treatment Effects and Effectiveness of Fuel Projects......................................73

Collaboration with Other Resource Managers and Interested 

Parties to Improve Results .............................................................................................73

Conclusion .........................................................................................................................74

References ................................................................................................................................75

Appendix A: Models Used in Fuel Treatment Planning and Implementation............................89

Appendix B: Species Referenced in Best Management Practices Guide.................................91

Appendix C: Managers Interviewed..........................................................................................92

ii
USDA Forest Service RMRS-GTR-198. 2007 1

Historically, fire was a keystone ecological process 

that shaped the composition and structure of plant 

communities across the extensive range of ponderosa 

pine forests (refer to Appendix B for scientific names of 

species listed in text). Relatively frequent, low-intensity 

surface fires acted as a natural thinning agent by reducing litter, burning small trees, and reducing ladder fuels. 

These fires were largely limited to the understory, killed 

few mature pines, and created an uneven-aged structure composed of small, relatively even-aged groups. In 

some parts of the range of ponderosa pine, small-scale 

stand-replacing fires were also historically significant 

components of the disturbance regime.

Fire suppression, grazing, and intensive forest management over the past 100+ years have altered forest 

structure to eliminate much of this diversity, creating 

uniformly stocked landscapes of even-aged stands, 

many of which are densely stocked or contain dense 

understories of regeneration. As a result, contemporary 

wildfires have increased in severity across the range of 

ponderosa pine. The dispersal of private land holdings 

throughout publicly managed lands further complicates 

fuel treatment efforts. Fire exclusion has had other 

negative effects, including increased susceptibility of 

ponderosa pine forests to outbreaks of mountain pine 

beetle (MPB). Large-scale MPB outbreaks may further 

dramatically increase fuel loadings and the severity of 

fire effects.

Creation of forest structures resistant to crown fire 

initiation and bark beetle attack and spread is an increasingly important objective of forest management in 

ponderosa pine communities. Forest managers must integrate social, political, and economic values, in addition 

to ecological considerations, when evaluating fuels and 

restoration treatments. In many cases, ecological restoration and wildfire hazard reduction can be achieved 

simultaneously, but in other cases, these goals may be 

conflicting. In this document, we highlight areas where 

these goals may not be fully compatible and discuss how 

goals associated with restoration and fuel reduction can 

still be incorporated in management practices. Although 

prescribed fire and mechanical fuels treatments have 

been used in varying degrees across the extensive range 

of ponderosa pine forests, comprehensive management 

practices have not yet been described for fuels treatments. Nor have these treatments been evaluated in 

terms of landscape-scale hazard and risk reduction.

The intent of this publication is to develop management practice recommendations for fuels treatment 

activities in Southwest, Colorado Front Range, and 

Black Hills ponderosa pine. While the range of ponderosa pine forests is much larger (fig. 1) we focus our 

discussion on this region as it reflects the broad scope 

of historical fire regimes and forest structure seen in 

ponderosa pine forests. Recommendations are based on 

collaboration of research and managerial experience. It 

has been a joint effort between RMRS staff and collaborators at Colorado State University, University of Idaho, 

and University of Florida using shared data, expertise, 

and resources obtained from interviews with fire specialists in the Southwest, Front Range, and Black Hills. 

This multi-faceted approach involved all collaborators 

and used both published data and information from current management activities and other sources to identify 

appropriate management practices that can both reduce 

immediate fuels hazards and restore attributes of historical forest conditions in ponderosa pine forests.

Spatial Scales

The large and catastrophic wildfires found in many 

ponderosa pine forests today pose significant direct 

threats to humans and structures, as well as many natural 

resources considered valuable to humans, including water 

resources, wildlife habitat, recreation areas, and so forth. 

Restoration and fuel reduction treatments in ponderosa 

pine systems should focus on reducing the likelihood 

of catastrophic wildfires impacting values at risk while 

improving or maintaining the ecological integrity of the 

system. To effectively achieve this, restoration and fuel 

reduction treatments should be conceptualized at multiple scales, from local stands to landscapes. On the stand 

level, treatment prescriptions should be designed to reduce fuel loading to a level that will reduce the potential 

for spread of crown fire. To ensure long-term ecosystem sustainability, this is best achieved in the context of 

the historical stand structure and processes. Forests are 

Section I:

Introduction
2 USDA Forest Service RMRS-GTR-198. 2007

0 1 75 50 300

Miles

Figure 1. Shaded areas show the distribution of ponderosa pine in North America. The darker shading shows the distribution of ponderosa pine in the Black Hills, Colorado Front Range, and Southwest (Arizona, New Mexico, and southwestern Colorado), areas that are the focus of this report.
USDA Forest Service RMRS-GTR-198. 2007 3

managed for many resources that are more appropriately 

addressed at spatial scales larger than individual stands. 

Forested landscapes, for example, are usually composed 

of a mosaic of forest stands, which vary in fuel management and restoration needs.

Even though many areas across ponderosa pine landscapes may have deviated from historical conditions 

and thus be in need of restoration or fuel management, 

there are likely to be significant economic and logistical constraints to treating all areas. In addition, other 

management objectives, such as protection of sensitive 

wildlife habitat or structures in urban settings, may necessitate prioritization of restoration and fuel treatments 

across landscapes. Management needs vary across the 

landscape, thus what is done is just as important as where 

to do it. Therefore, spatial planning is critical for effectiveness in restoration, hazardous fuel reduction, and 

meeting other resource management objectives across 

ponderosa pine landscapes. In this comprehensive management practices guide, we include effective strategies 

for planning and implementing restoration and fuel reduction treatments at both landscape and stand scales. 

While the information in this guide is specific to the 

ponderosa pine type in the southwestern United States, 

Front Range of Colorado, and Black Hills of South 

Dakota, many aspects would be applicable in ponderosa 

pine forests found in other regions.

Integrated Approach

A wealth of information on various aspects of restoration and fuel reduction treatments in ponderosa pine 

forests is available in peer-reviewed literature, government reports, and other publications. However, this 

information has yet to be summarized in a comprehensive guide to restoration and fuel reduction treatments in 

ponderosa pine forests. In addition, many effective strategies for restoration and fuels reduction commonly used 

by managers remain undocumented and known only to 

the local practitioners who use them. We attempted to 

capture and document this information through a series 

of discussions with fire and fuel managers from various 

land management agencies throughout Arizona, New 

Mexico, Colorado, and South Dakota. To obtain a broad 

range of perspectives, we also spoke with a variety 

people from different organizations including researchers, state and private foresters, and conservationists. 

Appendix C provides a list of people we interviewed. 

We used information gained from the literature, discussions with practitioners and interested parties, as well as 

our own expertise to develop recommendations for management practices for restoration and fuels treatments in 

ponderosa pine forests of the Southwest, Front Range, 

and Black Hills.

Background

Ponderosa pine forests in many western states currently have the potential to burn with much higher fire 

intensity than they would have 100 years ago (Brown 

and Cook 2006; Covington and others 1994; Kaufmann 

and others 2003). This is largely because of management and land use practices throughout the 19th and 20th

centuries, particularly those that lead to alteration of natural fire regimes. While past management practices have 

played a dominant role in altering natural fire regimes, 

changing climate throughout the 19th and 20th centuries 

has also been significant (Westerling and others 2006). 

Knowledge of the historical fire regime and resultant 

forest structure is thus important as it represents the 

conditions under which plant and animal populations in 

these forest communities have evolved and provides a 

standard for restoration (Swetnam and others 1999). A 

complete return to pre-Euro-American settlement conditions may not always be desirable or even possible 

given today’s societal needs and attitudes toward forests 

and the possibility of a changing climate. However, presettlement forest structure does provide a benchmark for 

which current, unsustainable forest conditions can be 

compared. In cases where historical fire regimes were 

dominated by frequent, low intensity fires, altering current forest structure such that it more closely resembles 

historical forest structure should lead to forests that are 

ultimately less susceptible to large-scale crown fires 

and safer for the reintroduction of prescribed fire. The 

historical fire regimes, past land use and management activities, and current forest structure and its implications 

for current fire regimes and other ecological attributes 

are all presented in Section II—Fire and Fuels Issues.

While reduced risk of severe wildfire spread is generally the primary objective of fuel reduction treatments, 

many other resource management objectives can be met 

concurrently. In many ponderosa pine forests, restoration 

as a general rule is conducive to hazardous fuel reduction. When restoration is not a specific objective, other 

natural resource objectives, such as wildlife habitat or 

watershed health improvement or protection, can also 

be met in fuel reduction treatments without significantly 

compromising the objective of reducing wildfire hazard. 

Specific objectives that can be considered in restoration 

and fuel treatments are presented in Section III—Fuel 

Treatment Objectives. Several tools can be used to 

meet these objectives, including prescribed fire and mechanical, chemical, and biological treatments. However, 
4 USDA Forest Service RMRS-GTR-198. 2007

certain techniques will be more appropriate than others depending on the specific treatment objectives. 

Techniques and tools used to successfully achieve fuel 

treatment, restoration, and other resource objectives are 

presented in Section IV—Fuel Treatment Techniques.

Fuel treatments alone are not always effective in 

meeting resource management objectives. Many factors 

need to be considered in the planning stages to ensure 

effectiveness. Part of the challenge of implementing 

effective fuel treatments is overcoming other resource 

limitations or logistical constraints, such as limited time 

and funding. While restoration and fuel treatments are 

often meant to improve the health of forested systems, 

they can also have adverse effects on other resources 

or values, such as sensitive species habitat. The effectiveness of various treatments in meeting objectives, 

resources needed to complete effective treatments, and 

limitations on use of various treatments are presented in 

Section V—Fuel Treatment Requirements.

It is also possible that additional work may be needed 

to offset the effects of some fuel treatment activities. 

Examples may include control of invasive species or 

excess tree regeneration, or modifying activities for sensitive plants or wildlife habitat. Techniques for mitigating 

various undesirable consequences of fuel treatment activities are discussed in Section VI—Fuel Treatment 

Impacts, Mitigation, and Monitoring.

Throughout our discussions with managers, we encountered many different approaches to achieving the 

same resource management objectives. Despite these 

differences, we noticed that successful treatments 

seemed to be accomplished when managers adhered 

to some common principles. We attempt to summarize 

those commonalities here as “management principles” 

that should be considered in any management program. 

In the final section of the document, we present several 

over-arching themes that we believe should be paramount in any fuel reduction or restoration treatment in 

ponderosa pine forests.
USDA Forest Service RMRS-GTR-198. 2007 5

Humans and natural processes, such as climatic cycles and geologic substrates, have shaped ponderosa pine landscapes for long periods of time. In some 

cases, human impacts have been subtle and localized; 

while in other cases they have been profound and extensive. The latter impacts, in particular, have altered 

current vegetation structure, which in turn influences 

how disturbances such as fire are currently manifested 

in the landscape. It is imperative for managers to have an 

appreciation for how natural processes and humans have 

shaped forest structure and disturbance processes in the 

past. Understanding the historical influences of humans 

and natural processes on the landscape is vital for planning and implementing land management practices 

under a wide range of conditions. We provide that context in this section by discussing how different groups of 

people (Native Americans and Euro-Americans) shaped 

landscapes in the past. We then discuss how forest structure and fire regimes have varied with natural changes 

in climate and topography. Finally, we discuss how past 

management practices and natural factors have shaped 

current forest conditions and disturbance regimes in the 

Southwest, Front Range, and Black Hills.

Past Land Use and Management 

Activities

Southwest

Humans began settling the southwestern United 

States at least 12,000 years ago, but their populations 

probably did not reach large numbers until 2000 to 1000 

B.C. when cultivated plants spread throughout the region 

and societies shifted from nomadic to agrarian (Allen 

2002). It is estimated that 100,000 Native Americans 

occupied the upper Rio Grande Valley of New Mexico 

at the height of their population. Similar numbers of 

people settled in other population centers throughout the 

Southwest (Parker 2002).

These Native Americans likely had substantial impacts on forest structure around their large settlements. 

For example, as many as 200,000 trees of ponderosa 

pine, Engelmann spruce, and subalpine fir harvested 

up to 75 km from the population center were used for 

construction of pueblos at Chaco Canyon, a large settlement in northern New Mexico (Betancourt and others 

1986). However, the imprint Native Americans had on 

forest structure in other areas was likely somewhat limited. Native Americans did venture into ponderosa pine 

forests throughout the region for hunting and gathering. 

Historical accounts suggest they intentionally set fires 

to these forests for purposes of herding game, clearing 

travel routes, improving forage production, or warfare 

(Allen 2002). While these actions certainly increased the 

frequency with which fires burned in some areas (Baisan 

and Swetnam 1997; Kaye and Swetnam 1999), it is not 

likely that these human ignitions significantly altered 

the natural fire regime over landscape or regional scales 

given the high frequency of lightning-caused fires in the 

Southwest (Allen 2002).

Euro-American and Hispanic settlers left a much 

more significant imprint on the landscape than Native 

Americans when they began settling in the region in 

large numbers in the late 1800s. Upon their arrival in 

the Southwest, they introduced domesticated sheep and 

cattle to the ponderosa pine forests to take advantage 

of the abundant forage in the open forest understory. 

While limited grazing began earlier in the 19th century in certain areas (Savage and Swetnam 1990), the 

number of livestock on the range exploded throughout 

the region around 1880 (Denevan 1967; Dutton 1953). 

There were an estimated 4 million sheep in the state of 

New Mexico by 1880 (Denevan 1967) and 200,000 in 

the San Francisco Peaks area of Northern Arizona in 

1887 (Friederici 2003). With the rangeland largely open 

and unregulated, overgrazing became rampant (Cooper 

1960; Denevan 1967; Kaufmann and others 1998). The 

ubiquitous overgrazing, coupled with a severe drought in 

the 1890s lasting several years, caused substantial reductions in grass cover and changes in species composition 

in the understory of ponderosa pine forests throughout 

the region (Arnold 1950; Cooper 1960; Dutton 1953; 

Weaver 1951). By the 1910s, more active grazing management began with the creation of the Forest Service 

(Allen 1989; Kaufmann and others 1998). While sheep 

grazing has declined over the years, cattle grazing has 

continued in the 1990s on public and private lands in 

the Southwest with 0.5 million head in Arizona and 

Section II:

Fire and Fuels Issues
6 USDA Forest Service RMRS-GTR-198. 2007

1.2 million head in New Mexico grazing annually 

(Dahms and Geils 1997).

Other significant land use and management activities common in the Southwest throughout the 20th

century include commercial logging and fire suppression. Commercial logging began in the region around 

the same time that large-scale livestock grazing was 

initiated (Allen 1989; Friederici 2003; Kaufmann and 

others 1998). The level of timber extraction increased 

steadily throughout the 20th century and peaked in 1990 

with roughly 433 million board feet extracted from 

public and private forests in Arizona and New Mexico 

in 1 year (Covington 2003). Due to lack of large trees, 

changing economic conditions, and increasing environmental concerns, commercial timber harvest levels 

have declined in much of the region since 1990, but 

such programs have remained active in certain areas 

(Friederici 2003). Organized fire suppression also began 

in the Southwest with the creation of the Forest Service 

in the 1910s (Pyne 2004). The road network created 

to aid timber harvest throughout the 20th century has 

also greatly improved firefighting efficiency (Dahms 

and Geils 1997) while concurrently increasing accessibility and the potential for human caused ignitions. 

With the exception of some extensive and long-term 

wildland fire use programs (for example, Gila National 

Forest, Grand Canyon National Park, Saguaro National 

Park), most wildland fires in the Southwest continue to 

be suppressed (Covington 2003).

Colorado Front Range

Nomadic Native Americans traveled through the 

Rocky Mountains of Colorado beginning 10,000 to 

15,000 years ago (Buchholtz 1983). However, it was 

not until 650 to 1000 A.D. that the Ute, Arapaho, and 

Cheyenne began settling in the Front Range more permanently, returning to the mountains from the plains 

each summer to take advantage of the abundant game 

(Buchholtz 1983; Peet 1981). While Native American 

populations throughout the Rocky Mountains reached up 

to 30,000 (Baker 2002), populations were much smaller 

in Colorado, probably peaking around 2,500 to 10,000 

in the 1700s (Baker 2002; Buchholtz 1983). Early EuroAmerican settlers of Colorado recounted widespread 

intentional burning by Native Americans (Veblen 2000). 

However, the reliability of these accounts has been questioned (Baker 2002). While Native Americans certainly 

used fire for herding game in this region (Buchholtz 

1983; Peet 1981), given their low population density, 

they were not likely to have had a significant impact on 

the historical fire regime in the ponderosa pine forests of 

the Front Range (Baker 2002).

Euro-American settlers were first lured to Colorado 

by the discovery of gold in the late 1850s (Buchholtz 

1983; Rueth and others 2002). Thousands of prospectors from all over the country descended upon Colorado 

and towns such as Boulder, Golden, and Denver boomed 

overnight. Extensive cattle grazing and logging soon 

followed on the Front Range to support the rapidly 

growing population and industry (Veblen and Lorenz 

1986; Veblen 2000). Historical photographs reveal that 

disturbance in the Front Range forests during this period 

was severe and extensive (Veblen and Lorenz 1991). 

Forests in the montane zone (including ponderosa pine 

and mixed conifer forests) were extensively logged and 

miners routinely set fires to these forests to facilitate 

prospecting (Veblen and Lorenz 1986, 1991). Although 

a rather large number of old trees still exist, few oldgrowth forests remain in the montane zone of the Front 

Range today (Kaufmann and others 2000).

With the creation of the Forest Service and the Park 

Service in the early 1900s, sustainable management of 

natural resources became a priority. Effects of rampant 

logging, human caused fires, and over-grazing started to 

lessen with tighter management of these activities and 

the beginning of the era of fire suppression (Brown and 

others 2000; Veblen and Lorenz 1991). Since the 1960s, 

both logging and cattle grazing have decreased dramatically throughout the region (Veblen and Lorenz 1991). 

Although prescribed fire programs began in the 1970s, 

implementation has been limited in extent (Pyne 1997). 

Suppression of wildfires has occurred throughout the 20th

century and most wildfires continue to be suppressed in 

the region. Because of its proximity to the largest cities 

in Colorado, the forested montane zone has been one of 

the most heavily used areas in the state for recreation 

(Myers 1974).

Black Hills

Native Americans inhabited the Dakotas in large 

numbers as early as 1500, although there is no evidence 

of these cultures living in the Black Hills during that 

time (Froiland 1990). Many groups lived near the Black 

Hills in the 1600s and 1700s including the Cheyenne, 

Kiowa, and Arapaho (Froiland 1990). However, they 

were likely to have only occasionally ventured into the 

forests of the Black Hills to harvest minimal amounts of 

forest products (Froiland 1990; Gartner and Thompson 

1973). In addition, these groups most likely preferred 

the open habitat and abundant game in the nearby plains 

(Gartner and Thompson 1973) and thus were not likely 

to have had an impact on the historical fire regime of the 

Black Hills. These groups left the region in the 1780s 

when they were forced westward by the Sioux (Froiland 
USDA Forest Service RMRS-GTR-198. 2007 7

1990). The Sioux likely used the interior of the Black 

Hills to a greater extent, as early explorers found evidence of Native American presence in the Black Hills 

in the 1870s (Progulske 1974). There is some evidence 

that suggests the Sioux disrupted the natural fire regime 

in the foothills of the Black Hills by intentionally setting 

fires to herd game (Fisher and others 1987).

Word of the discovery of gold in the Black Hills in 

1874 quickly spread to Euro-Americans in the east and 

they soon migrated to the region in large numbers forcing Native Americans to move out of the Black Hills 

(Froiland 1990). In addition to mining resources, the 

region also offered abundant timber, game, and forage 

for livestock, and these resources were soon extracted to 

support the growing population. With no land management agency in place, these resources quickly became at 

risk of depletion. Many large game animals including bison, pronghorn, and elk were eliminated from the Black 

Hills around this time. By the early 20th century, much 

of the Black Hills had been logged (Raventon 1994) 

and as a result, very few old growth forests remain today (Boldt and Van Deusen 1974). To curb the rampant 

use of resources by early settlers and manage resource 

extraction, in 1897 the Black Hills forest reserve was 

created. With the creation of this reserve, the first of its 

kind in the United States, suppression of wildfires began 

in the Black Hills (Raventon 1994).

Today, the Black Hills National Forest is the most 

intensively managed national forest in the country, has 

the highest allowable timber sale quantity of any forest 

in the Rocky Mountain region, and supports extensive 

livestock grazing. However, the method and degree of 

resource extraction has changed dramatically since the 

days of the early explorers. Although unmanaged logging, grazing, and hunting were common practice in the 

late 1800s and early 1900s (Froiland 1990; Raventon 

1994), timber harvests and livestock numbers are closely managed today (USDA Forest Service 1994). Some 

of the game species eliminated in the early 1900s have 

been reintroduced in the Black Hills (Raventon 1994). 

Habitat management for these populations is currently 

a priority (USDA Forest Service 1994). The practice 

of suppression continues, but acknowledgment of the 

ecological importance of fire and its potential benefit 

to different resources has led to increasing use of prescribed fire.

Fire Regimes

Many characteristics can be used to describe a fire regime. The characteristics we consider in this document 

are fire frequency, magnitude, extent, and seasonality. 

Frequency can be thought of as the number years between fire events in a given area. Magnitude is often 

described as fire intensity or the rate of release of energy 

along a flaming front. However, since fire intensity can 

be difficult to measure, magnitude can also be assessed 

through fire severity, which can be thought of as the 

magnitude of the effects of fire on dominant organisms. 

For example, in high-severity fire regimes, the effect of 

the fire may be the killing of dominant trees over large 

areas in a stand-replacing event. In a low-severity fire 

regime, the effect of a fire may be relatively benign to 

most organisms not resulting is substantial mortality. In 

a mixed-severity fire regime, the effects of a fire may 

be a diverse array of severe and benign effects. The distinction between mixed- and high-severity fire regimes 

is often partly a function of the extent or scale of highseverity patches (Agee 1998).

The historical fire regime (prior to Euro-American 

settlement) and resultant forest structure of ponderosa 

pine forests is a useful reference as it reflects the states 

and processes under which many of the plant and animal populations found in these forests have evolved 

(Swetnam and others 1999). Thus, restoring the historical structure and processes of ecosystems to the extent 

possible provides the best alternative for sustainable 

ecosystem management.

Depending upon the region, ponderosa pine forests 

historically burned with frequent low- to more infrequent mixed-severity fire regimes, depending upon the 

region. Restoring historical fire regimes in many cases 

should therefore reduce the risk of high-severity wildfires. However, in areas where historical fire regimes 

may have been composed of infrequent, small-scale and 

patchy crown fires, restoration may not be fully conducive to reducing wildfire hazard. In such cases, fuel 

treatments that focus on creating conditions that promote 

low-intensity surface fires may reduce wildfire hazard, 

but may not have an ecological justification.

In forested systems, dendroecology is the most widely used tool for reconstructing historical fire regimes. 

Dendroecology applies dendrochronology, or the dating of tree rings, to ecological questions (Fritts and 

Swetnam 1989). Ponderosa pine trees are particularly 

adapted to the use of dendroecology to reconstruct fire 

histories. Ponderosa pine has thick bark that allows it 

to survive low-intensity surface fire and trees are able 

to grow new rings over injuries caused by fire, creating fire scars. By examining fire scars in the annual 

growth rings on individual trees and comparing them 

with established tree ring chronologies, the years, and 

in some cases, the season in which a fire burned, can 

be determined.
8 USDA Forest Service RMRS-GTR-198. 2007

Fire scars represent an incomplete record of fire history since some fires do not scar every tree. However, 

by examining fire scars on multiple trees within a stand 

or in several stands, mean fire return intervals (MFI), or 

the mean number of years between recorded fires, can be 

calculated at multiple scales. Fire historians often calculate different estimates of MFI based on the number of 

trees in a stand that record fire, for example, at least 25 

percent of trees or just a few trees in a stand (Swetnam 

and Baisan 1996). The former is likely to represent more 

extensive fires that may have had a greater ecological effect on the landscape than the latter, which may indicate 

more localized fires.

Dendrochronology can also be used to reconstruct the 

historical stand structure of forests (Brown and Cook 

2006; Moore and others 2004). The occurrence of highseverity fires can be determined by examining the age 

of trees that likely initiated in unison following such an 

event (Johnson and Gutsell 1994).

There are other sources of information commonly 

used to determine historical fire regimes. For example, 

historical accounts and photographs of early settlers can 

be used to characterize historical forest structure when 

lack of tree ring evidence makes dendroecological studies difficult. Such accounts can also be used to augment 

findings from tree ring studies. In addition, evidence of 

past wildfires can be recorded as deposits of ash and 

charcoal in lake beds. These deposits can also be extracted to determine extent and timing of past fire events.

Fire history studies in ponderosa pine forests have identified disturbance patterns that are synchronous across 

broad spatial scales (Swetnam and Baisan 1996). These 

disturbances are likely driven by regional climatic patterns that influence fuel accumulation and fuel moisture. 

Deviations from regional scale patterns have also been 

seen on local scales (Madanay and West 1983; Touchan 

and others 1996). For example, a higher or lower historical fire frequency can be a function of Native American 

burning, isolation of ridge tops, or other factors (Kaye 

and Swetnam 1999; Madanay and West 1983). Fire regimes also tend to vary with topographical features such 

as elevation, aspect, and steepness of slope. This variation in fire regimes likely created landscapes that were 

naturally heterogeneous in structure and disturbance processes. This heterogeneity is important for maintaining 

biodiversity (Reice 1994). Thus, in fuel and restoration 

treatments, it is imperative to have an appreciation for 

the range of variability in fire regimes and historical 

forest structure in both time and space within a given region and to incorporate this variability in treatments at 

the stand and landscape scale. Doing so should ensure 

broader goals, such as restoration and maintenance of 

wildlife habitat, are met. Tables of documented mean fire 

intervals found in the Southwest, Front Range, and Black 

Hills and resultant forest stand structure show the variation in these metrics across landscapes with changes in 

elevation, aspect, and latitude (tables 1, 2, 3, and 4).

Southwest

Prior to major Euro-American and Hispanic settlement of the region in the late 19th century, the fire regime 

of ponderosa pine forests in the Southwest was characterized by frequent occurrence of low-intensity surface 

fires (Cooper 1960; Covington and Moore 1994a; Weaver 

1951). Such fires would have burned mainly through the 

understory, consuming grasses, forbs, shrubs, litter, and 

tree seedlings and causing little damage to larger trees. 

Crown fires were not a component of the historical fire 

regime (Cooper 1960). Across the region, less conservative estimates of historical MFI ranged from 2 to 12 

years (fires recorded by at least a few trees in a stand), 

while more conservative estimates ranged from 5 to 23 

years (fires recorded by at least 25 percent of trees in a 

stand) (table 1). While MFI estimates varied across the 

region, fire regimes in all locales were characterized by 

frequent low intensity fire with an absence of crown fire. 

The majority of fires occurred in late spring and early 

summer, prior to the summer monsoon storms that occur July and August (Brown and others 2001b; Fule and 

others 2003b).

While most fire history studies have reported MFIs 

that fall within the regional average, certain deviations 

from the mean exist on a local scale. Numerous local factors can influence the fire regime in a particular 

area. Although rare, longer fire free intervals have been 

found in areas that were geographically isolated (for example, mesa tops) where fire spread would be limited 

from distant fire starts (Madany and West 1983; Touchan 

and others 1996). Fire occurrence also tends to be less 

frequent at higher elevations and on more northerly aspects where fuel moisture tends to be higher (Baisan and 

Swetnam 1990; Brown and others 2001b; Swetnam and 

Baisan 1996). The condition of the forests on ridge tops, 

where lightning is most likely to strike and ignite fires, 

can also be an important factor determining the historical fire frequency. For example, fire may be more likely 

to ignite and spread on forested ridge tops compared to 

rocky ridge tops (Baisan and Swetnam 1990). In certain areas, intentional burning by Native Americans may 

have significantly increased the historical fire frequency 

on a local scale (Baisan and Swetnam 1997; Kaye and 

Swetnam 1999).

At regional and landscape scales, long- and shortterm climatic fluctuations influenced the frequency and 
USDA Forest Service RMRS-GTR-198. 2007 9

extent of fires. Historically, large fire years, defined as 

years in which fires occurred throughout much of the 

landscape, occurred in conjunction with severe droughts 

(Grissino-Mayer and Swetnam 2000). In particular, 

large fire years occurred in drought years preceded 

by one or two wet years—a pattern consistently seen 

with El Nino/Southern Oscillation cycles. This pattern 

has been observed in several studies throughout the 

Southwest (Brown and others 2001b; Fule and others 

2003a; Grissino-Mayer and Swetnam 2000; Swetnam 

and Baisan 1996; Swetnam and Betancourt 1998). The 

wet years allowed for high grass production, which 

provided an abundant source of fine fuel conducive to 

ignition and surface fire spread during subsequent dry 

(La Nina) years. Many fire history studies also report an 

unusually long fire-free interval in the 1820s and 1830s, 

most likely due to wetter than average conditions seen 

during this period (Brown and others 2001b; Swetnam 

and Dieterich 1985).

The historical fire regimes described above, in part, 

maintained a very characteristic forest structure in 

ponderosa pine forests of the southwestern United States. 

On a landscape scale, forests were likely a mixture of 

open woodlands, meadows, and more dense forested 

stands (Savage 1991). Studies of historical forest structure in northern Arizona suggest that these forests were 

fairly open with clumps of even- or uneven-aged forests 

interspersed with large tree-free openings where grasses 

were dominant (Cooper 1960; White 1985). Clumps of 

trees were typically no more than half an acre in size 

(Cooper 1960). Grasses in the openings provided an ideal 

fuel for carrying low intensity surface fires, particularly 

when dry. Higher fuel loadings of larger fuels occurred 

near and in clumps of trees. This would have resulted in 

an occasional high intensity fire on a local scale near tree 

clumps, thus creating microsites favorable for pine regeneration (Arnold 1950; Cooper 1960). This dynamic 

led to a persistence of the clumping tree pattern as tree 

seedlings would have had difficulty establishing in the 

grassy openings (Cooper 1960; White 1985). Density 

of ponderosa pine trees varied throughout the region 

(see table 2). It is important to note that these numbers 

Table 1. Mean fire intervals (MFI) and their range, estimated in fire history studies at different elevations throughout 

the Southwest. The table includes conservative (25 percent of trees in a stand scarred) and less conservative (a few 

trees in a stand scarred) estimates of MFI.

MFI (years)

Site Elevation (m) MFI (years) Range Conservative Range

Southern AZa 1970 to 2100 8.0 1 to 31 13.1 4 to 31

Southern AZa 2270 to 2400 6.6 2 to 18 9.6 2 to 30

Southern AZa 2330 to 2530 5.5 1 to 15 7.3 2 to 16

Southern AZa 2260 to 2840 3.0 1 to 9 7.3 2 to 13

Southern NMa 2400 to 2600 5.5 1 to 23 13.7 3 to 20

Southern NMa 2550 to 2600 3.5 1 to 10 6.9 2 to 26

Southern NMa 2600 to 2730 2.9 1 to 15 7.8 4 to 31

Southern NMa 2670 to 2800 5.4 1 to 16 16.5 4 to 41

Southern NMa 2800 to 3100 3.0 1 to 15 13.1 2 to 21

Northern AZb 2130 3.7 2 to 8 6.5 2 to 15

Northern AZa 2300 2.5 1 to 12 5.4 2 to 24

Northern AZc 2300 to 2370 3.7 1 to 11 6.4 2 to 11

Northern AZa 2440 to 2480 2.6 1 to 13 7.1 2 to 22

Northern AZc 2427 to 2537 5.5 1 to 15 9.0 4 to 21

Northern AZa 2930 to 2970 3.9 1 to 23 9.3 4 to 16

Northern NMa 2220 to 2250 8.3 1 to 25 17.1 3 to 42

Northern NMa 2430 to 2470 9.2 2 to 38 19.0 3 to 30

Northern NMa 2500 12.0 2 to 31 16.3 8 to 37

Northern NMd 2600 5.5 1 to 12 8.4 3 to 18

Northern NMd 2700 5.0 1 to 16 11.5 5 to 19

Northern NMa 3040 to 3070 10.1 2 to 29 23.0 7 to 35

a

 From (Swetnam and Baisan 1996) 

b

 From (Fule and others 1997) 

c

 From (Fule and others 2003b) 

d

 From (Touchan and others1996) 
10 USDA Forest Service RMRS-GTR-198. 2007

represent estimates of tree density at a specific period of 

time and may not reflect the range of tree density seen 

prior to Euro-American settlement over longer time 

scales and climate variability.

With the combined effect of overgrazing and drought 

in the late 19th century, grass cover decreased considerably in ponderosa pine forests throughout the Southwest 

(Arnold 1950; Denevan 1967). An abrupt decline in fire 

frequency began around 1880 concurrent with the reduction of this fine fuel that would readily carry surface fire 

(Baisan and Swetnam 1990; Brown and others 2001b; 

Covington and Moore 1994a; Dieterich 1980; Swetnam 

and Baisan 1996). Fire frequency was also reduced with 

the practice of fire suppression that began with the creation of the Forest Service in the early 20th century (Pyne 

2004).

With the absence of fire and an explosive pine regeneration event in 1919 and 1920, tree density increased 

throughout southwestern ponderosa pine forests (Fule 

and others 1997; Moore and others 2004; Schubert 

1974). As a result, the current forest structure deviates 

considerably from the historical structure. For example, 

in northern Arizona, estimates of number of trees per acre 

have increased from about 20 to 60 in the early 1900s 

to 270 to 850 currently (Covington and Moore 1994b; 

Fule and others 1997). When averaged across the region, 

the average number of trees per acre has increased from 

roughly 30 in the 1910s to 220 in the 1990s (Moore and 

others 2004). However, tree density also varies by substrate. For example, higher historical and contemporary 

tree densities occur in areas with limestone substrates 

(Covington and Moore 1994a).

Tree species composition has also changed in many 

places, from a dominance of shade-intolerant ponderosa pine trees to more shade-tolerant species such as 

white fir and Douglas-fir (Covington and Moore 1994b; 

Fule and others 1997). Tree size class distribution has 

changed from a structure with few large to medium 

diameter trees to many small diameter trees (Fule and 

others 1997; Moore and others 2004). There are also 

more standing dead trees and higher surface fuel loading in the current forests compared to historical levels, 

Table 2. Reported density of presettlement ponderosa pine trees as evidenced by age structure studies of old 

growth ponderosa pine forests.

Site Elevation (m) Density (trees/acre) Citation

Central AZ 2400 ~120* Cooper 1960

Northern AZ 2120 to 2570 23 Covington and Moore 1994a

Northern AZ 2270 to 2600 56 Covington and Moore 1994a

Southern UT 2150 to 2260 38* Madnay and West 1983

Northern AZ 2255 15 White 1985

Northern AZ 2600 to 2670 40 to 45 Rasmussen 1941

Northern AZ 2400 to 2470 23 Covington and others 1997

Northern AZ 2175 to 2450 26 Fule and others 1997

Northern AZ 2290 18 to 43 Fule and others 2002a

Northern AZ 2125 to 2290 19 to 32 Fule and others 2006

Central NM 2610 32 Moore and others 2004

Central NM 2,500 50 Moore and others 2004

Northern AZ 2,240 11 Moore and others 2004

Northern AZ 2,240 10 Moore and others 2004

Northern AZ 2,250 33 Moore and others 2004

Northern AZ 2,250 29 Moore and others 2004

Northern AZ 2,300 19 Moore and others 2004

Northern AZ 2,300 23 Moore and others 2004

Northern AZ 2,060 35 Moore and others 2004

Northern AZ 2,050 25 Moore and others 2004

Northern AZ 2,290 8 Moore and others 2004

Northern AZ 2,250 34 Moore and others 2004

Central NM 2,760 27 Moore and others 2004

Northern NM 2,150 36 Moore and others 2004

Northern NM 2,620 89 Moore and others 2004

*Reflects both presettlement and postsettlement trees greater than or equal to 2 inches dbh in forests not impacted by 

postsettlment fire suppression.
USDA Forest Service RMRS-GTR-198. 2007 11

although there are no data available on the size of snags 

present in historical forests (Moore and others 2004). On 

a landscape scale, many forests are much more structurally homogenous (Savage 1991).

The current forest structure has led to an altered fire 

regime such that forests are now more likely to burn 

with infrequent, intense stand-replacing fires. This has 

been shown with increasing occurrence of large and severe fires in the Southwest since the middle of the 20th

century (Swetnam 1990), including the Rodeo-Chediski 

fire that burned over 400,000 acres in central Arizona 

in 2002.

According to coarse scale assessments, many of the 

ponderosa pine forests in the Southwest are considered to 

be outside of their historical range of variability in terms 

of fire disturbance and forest structure (Aplet and Wilmer 

2003). Currently, an estimated 61 percent of ponderosa 

pine/dry Douglas-fir forests in New Mexico have high 

potential for crown fire spread (Fiedler and others 2002). 

These areas should benefit from fuel treatments for purposes of restoration or fire hazard reduction. Given the 

vast areas in need of treatments and the constraints on 

available resources, priorities areas considered for fuel 

reduction treatments should be prioritized.

Colorado Front Range

Prior to the start of Euro-American settlement in the 

mid-19th century, the fire regime of ponderosa pine forests of the Front Range exhibited both similarities and 

differences to those of the Southwest. Here, fires have 

been characterized as mixed-severity, with both surface 

and small-scale, stand-replacing crown fires occurring 

at intervals anywhere between 5 and 118 years (Brown 

and others 1999; Brown and others 2000; Brown and 

Shepperd 2001; Donnegan and others 2001; Goldblum 

and Veblen 1992; Hadley 1994; Veblen and others 2000). 

The mean fire interval for surface fires (MFI) historically 

varied throughout the Front Range depending on latitude, elevation, and aspect (table 3). Across the region, 

less conservative estimates of MFI varied from 8 to 64 

years (fires recorded by a few trees in a stand), while 

more conservative estimates ranged from 14 to 59 years 

(fires recorded by at least 25 percent of trees in a stand) 

(table 3). We note, however, that use of MFI alone does 

not consider the spatial extent of recorded fires, which 

is especially important in the Front Range where fires 

that were ecologically important at the landscape scale 

occurred less frequently and at a spectrum of severities 

(Kaufmann and others 2006)

In general, the historical frequency of surface fires 

decreased with elevation with more frequent surface 

fires in the low elevation grassland/forest ecotone and 

less frequent fires in higher elevation forests (table 3) 

(Brown and Shepperd 2001; Sherriff and Veblen, in 

press). The historical MFI, in general, also increased with 

latitude from southern Colorado to southern Wyoming 

(table 3). Low intensity surface fires were also likely 

more frequent on south-, east-, and west-facing slopes 

where conditions were more xeric and stands less dense 

(Goldblum and Veblen 1992; Veblen 2003). Historically, 

fires occurred throughout the growing season, but occurred slightly earlier in the southern portion of the 

range (Baker 2003; Brown and others 1999; Brown and 

Shepperd 2001; Veblen and Kitzberger 2002).

Currently, ponderosa pine forests in the Front Range 

include few openings and stands with conspicuous age 

and size limits (Brown and others 1999; Brown and others 2000; Ehle and Baker 2003; Huckaby and others 

2001; Kaufmann and others 2000; Sherriff and Veblen 

2007). Spatial patterns and age structure characteristics 

associated with past stand-replacing disturbance events 

appear to be an important part of the historical fire regime in ponderosa pine forests in some parts of the Front 

Range (Kaufmann and others 2006).

The nature of mixed-severity fire regimes and the extensive logging and burning in the Front Range during the 

19th century make assessment of the historical crown fire 

component of this fire regime extremely difficult. Thus, 

the historical extent and frequency of stand-replacing 

fires in the Front Range is not well understood. Only one 

study to date has examined historical fire regimes across 

the full elevational range of ponderosa pine in the Front 

Range. This study found that low-severity surface fires 

were common on only 20 percent of the landscape studies (in areas below 2100 m in elevation) (Sherriff and 

Veblen 2007). However, this study represents a unique 

and small portion of the Front Range.

Kaufmann and others (2006) examined the available historical fire data for the Front Range in an effort 

to bring some understanding to the apparent conflicts 

among the various studies reported in the literature. They 

conclude that historical fires in the Front Range were 

complex and burned in response to variations in weather 

conditions, fuels, and topography. Historical fire regime 

of low-severity fires that maintained savannas and open 

woodlands in ponderosa pine forests applies only to portions of the lowest elevations of the Front Range. At 

middle and higher elevations, mixed-severity fires were 

the most important in maintaining the structure and spatial distribution of ponderosa pine in the Front Range 

landscape. They further note that steep topographic and 

elevation gradients strongly affected the fire regime. It 

is likely that stand-replacing fires were more common 

in mesic sites at higher elevations and on north-facing 
12 USDA Forest Service RMRS-GTR-198. 2007

aspects where tree density is typically high and shadetolerant species such as Douglas-fir are more common 

(Romme and others 2000; Veblen and others 2000).

Historically, fire frequency, severity, and extent in the 

Front Range varied with long- and short-term climatic 

fluctuations. As in the Southwest, large fire years (years 

where fires occurred across much of the landscape) 

tended to occur when the growing season was drier than 

average and was preceded by 1 to 3 wetter than average years, a common pattern when El Nino-Southern 

Oscillation (ENSO) years (wet) are followed by La Nina 

years (dry) (Donnegan and others 2001; Veblen 2000; 

Veblen and others 2000). Live fine fuels (grasses) likely 

accumulated during wet years and subsequently cured 

during dry years, providing an abundant dry fuel source 

conducive to ignition and fire spread. However, this 

pattern was less pronounced in the northern portion of 

the Front Range where sensitivity to ENSO patterns is 

weaker (Veblen 2000). Long-term climatic changes may 

also have been responsible for decadal shifts in the historical fire regime. Increased fire activity was observed 

during decades with pronounced ENSO activity, and 

decreased fire activity was observed for decades when 

ENSO activity was weak (Donnegan and others 2001; 

Veblen 2000).

Fewer studies have examined historical tree density in old growth forests in the Front Range than in 

the Southwest. However, studies suggest that historical 

Table 3. Summary of historical mean fire intervals (pre-1850) and their range of variability found in fire history studies at 

different elevations throughout the Front Range. The table includes conservative estimates of MFI (25 percent of trees 

in a stand scarred) and less conservative estimates of MFI (a few trees in a stand scarred).

MFI (years)

Site Elevation (m) MFI (years) Range Conservative Range

Southern WYa 1920 to 1960 26 to 33.5 8 to 82 n/a n/a

Northern COb 2090 to 2200 16.0 3 to 50 n/a n/a

Northern COb 2220 to 2250 25.5 4 to 52 n/a n/a

Northern COb 2420 to 2590 29.5 8 to 79 n/a n/a

Northern COb 2600 to 2230 29.0 11 to 69 n/a n/a

Northern COb 2610 to 2630 21.5 3 to 54 n/a n/a

Central COc 1996 9.0 1 to 51 n/a n/a

Central COd 1884 to 2015 8.3 1 to 29 14.4 2 to 46

Central COd 2048 to 2177 13.4 1 to 47 23.6 14 to 47

Central COd 2189 to 2432 17.7 1 to 63 19.3 1 to 63

Central COd 2440 to 2488 22.4 1 to 125 43.4 7 to 125

Central COe 2100 to 2520 9.2 1 to 29 59.2 27 to 128

Central COf 2375 to 2685 15.2 2 to 49 n/a n/a

Central COb 2380 to 2390 22.5 2 to 72 n/a n/a

Central COb 2390 to 2410 7.5 2 to 82 n/a n/a

Central COg 2500 to 2800 20.9 11 to 145 41.7 5 to 63

Central COh 2450 to 2750 22.4 8 to 38 n/a n/a

Central COc 2621 18.0 4 to 76 48.0 4 to 102

Central COb 2630 to 2670 64.0 24 to 79 n/a n/a

Central COc 2743 31.0 2 to 116 n/a n/a

Central COc 2865 23.0 1 to 88 n/a n/a

Southern COi 2100 to 2500 7.5 2 to 37 n/a n/a

Southern COa 2590 to 2640 9.5 2 to 41 n/a n/a

Southern COb 2670 to 2690 10.0 4 to 41 n/a n/a

Southern COb 2720 to 2740 19.0 4 to 54 n/a n/a

a

 Brown and others 2000 

b

 Brown and Shepperd 2001

c

 Donnegan and others 2001

d

 Veblen and others 2000

e

 Brown and others 1999 

f

 Goldblum and Veblen 1992

h

 Hadley 1994

g

 Laven and others 1980

i

 Wieder and Bower 2004
USDA Forest Service RMRS-GTR-198. 2007 13

forest structure varied widely throughout the range with 

estimates of historical tree density ranging from 16 to 

1380 trees per acre (Baker and others 2007). The mixedseverity fire regime likely resulted in a complex forest 

structure composed of openings with no trees, persistent 

clumps of old-growth trees, forest patches with nearly 

pure ponderosa pine, and patches with ponderosa pine 

and Douglas-fir (Kaufmann and others 2001). This complexity is the result of the wide range of environmental 

conditions where ponderosa pine occurs in the Front 

Range. Mixed-conifer forests containing ponderosa pine, 

lodgepole pine, limber pine, Douglas-fir, aspen, spruce, 

and fir can be found in various combinations in the Front 

Range (Kaufmann and others 2006). Historically, these 

mixed conifer forests were found in more mesic areas 

at higher elevations on north-facing aspects, and likely 

had higher tree density than the drier pure ponderosa 

pine forests found at lower elevations (Baker and others 

2007; Kaufmann and others 2000). In the drier forests, 

both high and low intensity fires would have resulted in 

tree mortality and would have created openings with no 

trees and stands with low tree density (Kaufmann and 

others 2001; Kaufmann and others 2003). Old-growth 

forests likely persisted in areas where intervals between 

stand-replacing events were long. In the central portion 

of the Front Range, delayed tree recruitment following 

stand-replacing disturbance events would have allowed 

for openings and low density stands (< 30 percent canopy cover) to persist across the landscape (Huckaby and 

others 2003; Kaufmann and others 2003). It is estimated 

that these openings may have accounted for up to 25 

percent of the landscape in lower elevation montane forests in the central Front Range, (Kaufmann and others 

2001). However, in the northern Front Range at higher 

elevations, others have argued that dense ponderosa 

pine forests may have historically made up a significant 

portion of the upper montane forests (Baker and others 

2007; Ehle and Baker 2003; Sherriff and Veblen 2007).

Large-scale human disturbance in the mid-19th century (logging, grazing, burning), along with favorable 

climatic conditions, prompted synchronized tree regeneration events in the Front Range (Ehle and Baker 2003; 

Kaufmann and others 2003; Veblen and others 2000). 

This resulted in a rather even-aged and even-sized distribution of ponderosa pine and Douglas-fir trees in forests 

throughout the Front Range. Because fire suppression 

in the 20th century limited mortality of trees following 

these recruitment pulses, current forests have much 

higher tree density than historical forests (Kaufmann 

and others 2000; Veblen and others 2000). Tree species 

composition has changed from dominance of shadeintolerant ponderosa pine trees to more shade-tolerate 

species such as Douglas-fir (Kaufmann and others 2000). 

Forest structure has changed from a mosaic of dense forests, openings, and old growth to a homogenous forest 

structure of dense trees of similar age and size classes and higher tree canopy cover (Huckaby and others 

2003; Kaufmann and others 2000; Veblen and Lorenz 

1991). Thus, current forest structure, particularly in low 

elevation forests, contains much higher tree density 

than historical levels in drier forests (Kaufmann and 

others 2000). Yet, forest structure of more mesic upper 

montane ponderosa pine – Douglas-fir forests at higher 

elevations and on north-facing slopes may not have been 

as severely altered, particularly in the northern Front 

Range (Baker and others 2007). In fact, some have argued that fire suppression has resulted in decreased tree 

regeneration throughout the 20th century through the development of thick forest canopies that limit successful 

seedling establishment in the understory in some areas 

of the Front Range (Ehle and Baker 2003; Sherriff and 

Veblen, in press).

In places where forest structure has been severely altered, the increased forest density has led to an altered 

fire regime where wildfires today are more likely to burn 

with more severe fire effects. While stand-replacing fires 

certainly were a part of the historical fire regime, the 

stand-replacing portion of any given fire is likely much 

higher under current forest conditions (Kaufmann and 

others 2000; Schoennagel and others 2004). This has 

been evidenced by several high-severity wildfires that 

have occurred in the Front Range in recent years, including the 130,000+ acre Hayman Fire, which was 

unprecedented in terms of size of high-severity patches in this landscape, at least over the past 5 centuries 

(Kaufmann and others 2003) (fig. 2). While fire regimes 

may not have been significantly altered in higher elevation montane forests in the northern Front Range 

(Sherriff and Veblen 2007), the extent to which fire regimes have changed high elevation montane forests in 

other portions of the Front Range remains largely unknown (Kaufmann and others 2006).

According to a recent report by the Front Range Fuel 

Treatment Partnership Rountable (2006), close to 1 million acres of fire-prone forests fall in the wildland urban 

interface in the Front Range of Colorado and are thus a 

high priority for treatment. Of these, about 400,000 acres 

are in the lower montane ponderosa pine zone roughly 

split between public and private ownership. Thus, fuel 

treatment strategies that cross jurisdictional boundaries 

are needed in this region to truly protect communities 

from the threat of wildfire. For purposes of restoration, 

the lower elevation forests (below 2100 m) are more 

likely to have significantly higher tree density today than 
14 USDA Forest Service RMRS-GTR-198. 2007

they would have had historically (Kaufmann and others 

2006). Thus, restoration efforts should be prioritized in 

these areas. By some estimates, this makes up only 20 

percent of the ponderosa pine forests in the Front Range 

(Sherriff and Veblen 2007). However, these estimates 

come from the northern Front Range in Boulder County, 

which has relatively little lower montane ponderosa pine, 

and it is unclear if similar proportions can be applied to 

other forests in the Front Range (Kaufmann and others 

2006). In any case, lower elevation ponderosa pine forests are more likely to occur near developed urban areas 

in the Front Range, further underscoring the need for 

fuels treatment intervention in the urban interface.

Black Hills

While similarities exist in historical fire regimes of 

ponderosa pine forests of the Black Hills, Front Range 

and Southwest, certain characteristics distinguish the 

Black Hills ponderosa pine type forests from those of 

the Front Range and Southwest. The Continental climate in the Black Hills is much more conducive to the 

establishment and growth of ponderosa pine, owing 

to persistent seed crops and abundant summer rainfall (Shepperd and Battaglia 2002). The result is forest 

structures and fire regimes that were historically different from those in the Front Range and Southwest. While 

only a few studies have been conducted on the historical 

fire regime of the Black Hills, current evidence suggests 

that prior to Euro-American settlement, the fire regime 

of the Black Hills would have been of mixed-severity, with both surface and crown fires being important 

components of the ecosystem (Brown and Sieg 1996; 

Brown 2003; Shinneman and Baker 1997). However, 

most fire history studies in this region have focused on 

questions regarding the historical frequency of surface 

fires. With mean annual precipitation increasing from 

south to north in the Black Hills, historical surface fire 

frequency was higher in the southern portion compared to the northern and central portions (Brown 2003; 

Shinneman and Baker 1997). Less conservative estimates of the mean fire interval (MFI) ranged from 10 to 

15 years in the southern Black Hills, to 30 to 33 years in 

Figure 2. An example of the severe fire effects seen from the Hayman Fire, Colorado. Photo credit: Molly Hunter.
USDA Forest Service RMRS-GTR-198. 2007 15

the central and northern Black Hills (table 4). In Devils 

Tower National Monument, MFI varied through time 

with a higher MFI occurring from 1600 to 1770 (MFI = 

27 years) compared to 1779 to 1900 (MFI = 14 years) 

(Fisher and others 1987). The author attributed this to 

the presence of the Sioux who may have intentionally 

set fires to herd game. Historical MFI also increased 

with elevation (table 4) along with precipitation and 

colder temperatures (Shepperd and Battaglia 2002).

Many studies report evidence of a crown fire component in this system. Evidence for this comes from 

historical accounts and photos from early Euro-American 

explorers. Journals from early explorers reveal that large 

treeless areas with charred snags were commonly encountered (Graves 1899). Historical photographs reveal 

this as well (Grafe and Horsted 2002; Progulske 1974). 

Pine regeneration can be prolific in the Black Hills, especially after stand-replacing disturbance (Bonnet and 

others 2005; Brown and others 2000; Lentile 2004; 

Lundquist and Negron 2000). Early explorers to the 

Black Hills commonly found dense, even-aged stands 

of ponderosa pine seedlings or saplings (Grafe and 

Horsted 2002; Kime 1996; Progulske 1974) or two-aged 

stands with dense understories of younger trees (Graves 

1899). While such stands can be a result of a variety 

of disturbance agents (wind, disease, insects), other 

Table 4. Summary of historical mean fire intervals (MFI) and their range of variability for a given aspect and elevation found in fire 

history studies in the northern, central, and southern portions of the Black Hills. Table includes more conservative (25 percent of 

trees in a stand scarred) and less conservative (a few trees in a stand scarred) estimates of MFI, although most studies only report 

the less conservative estimate.

MFI (years)

Site Elevation (m) Aspect MFI (years) Range Conservative Range

Northerna n/a n/a 27 n/a n/a n/a

Northerna n/a n/a 14 n/a n/a n/a

Northernb 1520 to 1550 S 22 11 to 41 n/a n/a

Northernb 1520 to 1500 N 11 3 to 30 n/a n/a

Northernb 1350 to 1390 E 16 4 to 34 n/a n/a

Northernb 1830 to 1860 S 13 22 to 42 n/a n/a

Northernb 1850 to 1890 E 21 4 to 64 n/a n/a

Northernb 1840 to 1880 W 31 14 to 64 n/a n/a

Northernb 1870 to 1910 SE 13 8 to 19 n/a n/a

Northernb 1730 to 1760 E 20 7 to 37 n/a n/a

Northernb 1740 to 1780 SW 17 2 to 33 n/a n/a

Northernf 1200 to 1280 n/a 13 1 to 43 15 4 to 42

Centralc 1660 to 1690 n/a 23 11 to 74 n/a n/a

Centralc 1670 to 1720 n/a 22 13 to 72 n/a n/a

Centrald 1585 to 1768 n/a 16 1 to 45 16 1 to 45

Centralb 2070 to 2090 S 24 10 to 41 n/a n/a

Centralb 1660 to 1690 E 27 15 to 42 n/a n/a

Centralb 1670 to 1720 S 27 15 to 46 n/a n/a

Centralb 1670 to 1710 N 20 1 to 47 n/a n/a

Centralb 1720 n/a 23 6 to 45 n/a n/a

Centralb 1680 to 1740 S 20 1 to 47 n/a n/a

Centralb 1580 to 1670 SW 19 7 to 37 n/a n/a

Southerne 1100 to 1530 n/a 12 3 to 32 n/a n/a

Southerne 1100 to 1530 n/a 10 2 to 23 n/a n/a

Southern 1100 to 1530 n/a 12 3 to 34 n/a n/a

Southernb 1470 to 1510 E 11 3 to 29 n/a n/a

Southernb 1340 to 1350 E 10 2 to 18 n/a n/a

Southernb 1220 to 1260 N 12 3 to 34 n/a n/a

a

 Fisher and others 1987

b

 Brown 2003

c

 Brown and others 2000

d

 Brown and Sieg 1996

e

 Brown and Sieg 1999

f

 Wienk and others 2004
16 USDA Forest Service RMRS-GTR-198. 2007

evidence (charred snags) suggests that wildfire was the 

cause (Grafe and Horsted 2002; Kime 1996). However, 

one study shows that pulses of pine recruitment may be 

driven more by climate than disturbance (Brown 2003). 

Unlike ponderosa pine forests in other parts of the United 

States, long fire-free periods were historically common 

in the Black Hills (Brown and Sieg 1996), which may 

have led to fuel build-up and high tree density - conditions conducive to crown fire spread. Because much of 

the Black Hills was repeatedly logged during the 20th

century (Boldt and Van Deusen 1974; Raventon 1994, 

Shepperd and Battaglia 2002), it is difficult to determine 

the historical extent and frequency of crown fires in this 

system.

Much of the precipitation in the Black Hills falls as 

rain from April to September (Brown 2003; Shepperd 

and Battaglia 2002). Thus, historically, most wildfires 

burned in the late summer and early fall when fuels 

would have been sufficiently dry to promote fire spread 

(Brown and Sieg 1996, 1999). In the higher elevations in 

the northern and central portions of the Black Hills, fires 

occurred more rarely and may have spread mostly in 

years that were drier than average. Fires did not typically occur in years that were wetter than average. Unlike 

ponderosa pine forests in other regions, there appears to 

be no effect of El Nino/La Nina cycles on the historical 

fire regime (Brown 2003).

The occurrence of surface fires and stand-replacing 

fires, coupled with other disturbance agents, led to a 

complex mosaic of forest structure composed of dense 

forests, moderately stocked forests, and treeless openings. In 1899, Henry S. Graves conducted an extensive 

inventory of timber resources in the Black Hills for the 

U.S. Geological Survey. While this assessment occurred 

after substantial logging had occurred in certain areas, it 

still provides an invaluable insight into the historical forest structure of the Black Hills. Graves identified three 

classes of timber: 1) less than 2,000 board feet per acre, 

2) 2,000 to 5,000 board feet per acre, and 3) 5,000 to 

10,000 board feet per acre. The first class was the most 

common in the Black Hills and the third class was the 

least common. Evidence of disturbance was not seen in 

the third class and the dense forest structure was likely a 

result of long fire-free periods (Graves 1899). Density of 

trees in classes one and two was probably limited by frequent disturbance from fire and insects. In the absence 

of disturbance, stands in class three would have become 

very dense and more susceptible to crown fire spread. 

In more frequently disturbed forests, stands were likely 

multi-aged and tree density varied from 7 to almost 300 

trees per acre (Brown and Cook 2006; McAdams 1995). 

In forests with longer intervals between disturbances, 

sapling density may have been as high as 8,000 trees per 

acre (Baker and others 2007). As these dense, even-aged 

forests matured, density decreased to 150 to 200 trees 

per acre (Baker and others 2007).

The historical fire regime of the Black Hills has been 

disrupted as a result of human influence. While Native 

Americans were likely to have had little effect on the 

historical fire regime, there is some evidence that their 

burning practices increased the fire frequency in certain 

portions of this region (Fisher and others 1987). The biggest disruption in the fire regime was a sharp decrease in 

the fire frequency as a result of fire exclusion, logging, 

and grazing by Euro-Americans beginning around 1900. 

Given the naturally long fire-free periods in some parts 

of the Black Hills, the historical fire regime may not have 

changed on some local scales. However, across the Black 

Hills landscape, fires have become less frequent during 

the 20th century. In addition, the current fire-free periods 

are longer than the longest fire-free periods found in fire 

history studies (Brown and Sieg 1996, 1999).

The altered fire regime, along with other human disturbances, has led to dramatic changes in forest structure 

in the Black Hills since the end of the 19th century. On 

a regional scale, ponderosa pine density is much higher 

today compared to conditions when Euro-American’s 

first settled in the region (Grafe and Horsted 2002; 

McAdams 1995; Progulske 1974). In areas where tree 

density would have been naturally high (north-facing 

slopes and higher elevation forests), forest structure may 

not have been significantly altered since fire exclusion. 

While dense second-growth forests would historically 

have been common, old-growth forests, openings, and 

frequently disturbed forests of low density were also significant components of the landscape (Parrish and others 

1996). As a result of extensive logging, old-growth forests are almost completely removed from the Black 

Hills landscape (Boldt and Van Deusen 1974). Early 

explorers accounted large tree-free areas presumably resulting from crown fires (Grafe and Horsted 2002; Kime 

1996; Progulske 1974). Fewer of these areas exist today 

as a result of fire exclusion (Grafe and Horsted 2002; 

Progulske 1974). Areas that were formerly frequently disturbed stands with historically low tree density 

are now very dense stands (Grafe and Horsted 2002; 

McAdams 1995; Progulske 1974; USDA Forest Service 

1994). There is also evidence to suggest that current average tree size is lower than historical levels (Brown and 

Cook 2006). While historically much of the Black Hills 

would have been composed of a mosaic of stands with 

even- or multi-aged structure, today, the Black Hills are 

predominantly managed with an even-aged shelterwood 

silvicultural system (Shepperd and Battaglia 2002).
USDA Forest Service RMRS-GTR-198. 2007 17

The increases in fuel loads and tree density and the 

homogenous nature of current Black Hills forest landscapes have changed the fire regime so ponderosa pine 

forests are now more likely to burn with infrequent and 

large stand-replacing fires. This is evidenced by several 

large wildfires that occurred in the Black Hills in the 

19th and 20th centuries (Raventon 1994, Shepperd and 

Battaglia 2002). In the 1890s two large fires burned about 

74,000 acres in the northern Black Hills. In the 1930s, 

the Rochford and McVey fires burned about 40,000 acres 

on the Limestone Plateau. Since 2000, seven fires have 

burned about 140,000 acres, including large areas of 

both privately- and publicly-managed forests and grasslands. This includes the largest fire to occur in recorded 

history in the Black Hills, the Jasper fire, which burned 

81,000 acres in 2000 (Lentile 2004).

To reduce wildfire hazard, managers in the Black Hills 

estimate that 15,000 to 20,000 acres per year should be 

burned in the Black Hills using prescribed fire (USDA 

Forest Service 1994). Currently, fewer acres are actually 

burned in a given year (USDA Forest Service 2004a). Up 

to 44,000 acres that are commercially thinned are in need 

of additional fuel treatment every year and up to 13,000 

acres per year of natural fuels are in need of mechanical 

fuel treatment in the Black Hills. About 5,000 parcels 

of private land are intermingled within the Black Hills 

National Forest, making up 19 percent of the area within 

the forest boundary (USDA Forest Service 1994) (fig. 3). 

The potential for wildfires and escaped prescribed fires 

occurring within this extensive wildland-urban interface 

poses significant challenges for managers.

For purposes of restoration, not all areas of the Black 

Hills would be in need of treatment. Since ponderosa 

pine forests in the Black Hills historically contained a 

mosaic of structures and stocking conditions, from relatively open stands to dense forested patches (Brown and 

Cook 2006), care should be taken to re-create this heterogeneity in forest structure across the landscape.

Impacts of Altered Fire Regimes

While there are differences in historical forest structure and fire regimes in ponderosa pine forests in the 

Southwest, Front Range, and Black Hills, all of these 

regions have experienced drastic changes in forest 

structure and subsequent changes in fire regimes in the 

past century. Forests that historically were relatively 

open once burned with frequent low- or mixed-severity 

fire regimes. Presently, these forests have much higher 

tree density and fuel loading and are more likely to 

burn with infrequent, severe crown fires (Brown and 

others 1999; Covington 2003; Covington and Moore 

1994a; Huckaby and others 2003; Kaufmann and others 2000; Veblen and others 2000). However, historical 

forest structure and the resulting fire regime may not 

have changed significantly in certain areas in the Front 

Range and Black Hills where tree density has always 

been naturally high (north-facing slopes, higher elevations) (Baker and others 2007). At landscape scales, 

however, the fire regime has likely been altered as 

forests have become more dense and homogenous 

in nature (Huckaby and others 2003; Kaufmann and 

others 2000; Schoennagel and others 2004; Veblen 

and others 2000). Records indicate that fires across 

the Southwest have become larger and more severe 

since the mid-20th century (Swetnam 1990). Crown 

fires in the Front Range seem to be less localized and 

more extensive than in the past (Huckaby and others 

2003). Similarly, large wildfires that have occurred in 

the Black Hills in recent years are likely a function of 

the more homogenous nature of forest structure today 

(Brown and Cook 2006).

These large and severe wildfires have very significant consequences for a variety of resources managed in 

these forests, including hydrology and soils, community 

and fire-fighter safety, insect and disease outbreaks, and 

bidoversity. Even with the absence of fire, the altered 

forest structure can also have negative consequences for 

valued resources. The dense and homogenous nature of 

ponderosa pine landscapes in these regions today can 

also have negative impacts on hydrology, insect and disease outbreaks, biodiversity, and forage production.

Hydrology and Soils

Large and severe wildfires result in more negative 

impacts on hydrology and soils compared to fires of lowseverity. Severe wildfires result in sudden and complete 

reductions in vegetative cover, which leads to increased 

water runoff and soil erosion (DeBano and others 1998). 

Such changes in hydrology can be severe enough to 

significantly reduce site fertility and water quality and 

degrade stream communities (DeBano 1991; Keane and 

others 2002; Landsberg and Tiedemann 2000). Full recovery of soil microbial communities reduced by severe 

wildfire can take up to 2 years or longer, and this can 

have detrimental impacts on availability of soil carbon 

and nitrogen (Choromanska and DeLuca 2001).

Another effect of dense and homogenous forest structure is increased evapotranspiration and interception 

resultant from increased tree density. This can significantly reduce the water yield from watersheds when 

averaged across the landscape, limiting supply for humans and riparian communities (Keane and others 2002; 

Stednick 1996).
18 USDA Forest Service RMRS-GTR-198. 2007

0 4 2 8 12 16

Miles

Figure 3. Map of Black Hills NF, including land ownership patterns.
USDA Forest Service RMRS-GTR-198. 2007 19

Non-native Plants

Non-native, invasive plants are often well-adapted to 

disturbance, and establish rapidly in recently disturbed 

areas. High intensity disturbance events in particular 

promote establishment of invasive plants. Thus, severe 

wildfires in ponderosa pine forests create ample opportunities for establishment of non-native invasive plants 

(Crawford and others 2001; Hobbs and Huenneke 1992; 

Hunter and others 2006; Keeley and others 2003) (fig. 

4). Since native plants are often not well-adapted to such 

high intensity disturbance, recovery of these species 

may be slow. With the absence of potentially competing native plants, non-native invasive plants may more 

readily become permanently established. If invasive 

plants become well-established, they may prevent reestablishment of native species and ultimately reducing 

biodiversity.

Community and Fire-fighter Safety

The severe wildfires commonly seen in ponderosa 

pine landscapes often burn as crown fires with high 

flame lengths. These conditions preclude direct fire suppression. Such fires need to be fought using equipment 

such as planes and dozers, making them considerably 

more costly to suppress than low-intensity surface fires 

(Snider and others 2003). These fires are also inherently 

more dangerous and pose greater threats to firefighters 

and communities than low intensity fires.

Insect and Disease Outbreaks

Insects and pathogens are natural components of forest ecosystems where they play many roles—some are 

able to damage or kill trees. The distribution, abundance, 

and community composition of these pests commonly 

Figure 4. Burning of piles results in high fire intensity on a small scale and the resultant severe fire effects can encourage establishment of invasive species. In the Black Hills, it is common for Cirsium arvense to establish in burn pile scars. Photo credit: 

Molly Hunter.
20 USDA Forest Service RMRS-GTR-198. 2007

depend on the structure of the stands within the forest 

landscape and the condition of the trees within these 

stands. Under endemic conditions, they affect single or 

small groups of individuals, helping to sustain succession, nutrient cycling, energy flows, biodiversity, and 

other ecosystem processes. At other times, however, 

these pests erupt into outbreaks that kill thousands of 

trees over vast areas, lasting several years, and impacting aesthetic values, water production, recreation, 

timber production, wildlife habitat, and other valuable 

resources.

Severe wildfires can impact the potential for insect 

and disease outbreaks. High intensity fires are more 

likely to damage overstory trees, which makes them 

more susceptible to bark beetle attack (Wallin and others 2003). Fire seldom eliminates root disease pathogens 

from a site, but it can reduce woody substrates that support pathogen growth and/or shift stand composition 

toward more disease tolerant seral species. Fire can also 

create scars on the boles of surviving trees, impact tree 

health, stimulate germination of heat resistant spores 

(for example, Rhizina root disease), or otherwise change 

conditions to increase diseases.

The current forest structure resultant from the altered fire regime can have detrimental consequences 

for other ecological processes (fig. 5). Several studies 

have attempted to describe conditions preferred by various insect pests and thus conducive to insect outbreaks 

(Furniss 1965; Negron and Popp 2004; Reynolds and 

Holsten 1996; Rudinsky 1966). One product of this 

research has been infestation hazard models. These 

models commonly show that infestations are associated 

with such factors as basal area, stand density, age, stem 

diameter, the sequential or concurrent presence of other 

disturbance agents (for example, root diseases; Lessard 

and others 1985), dwarf mistletoe (McCambridge and 

others 1982), and other variables. What triggers such 

outbreaks has been a source of speculation by generations of entomologists and pathologists. However, it is 

fairly clear that exclusion of fire in forest ecosystems 

is one such trigger. In locations where fire has been 

excluded and stands become overstocked or stand composition shifts toward shade-tolerant species, or both, 

root diseases often increase (Hansen and Goheen 2000; 

Otrosina and Ferrell 1995). Additionally, homogenous 

forest structure may cause insect outbreaks to be more 

synchronous across the landscape (Kaufmann and others 

2000; Lundquist and Negron 2000; Schmid and Mata 

1996; Swetnam and Lynch 1993).

Biodiversity and Forage Production

Increased canopy cover and duff accumulations limit opportunities for establishment and growth of plant 

species in the forest understory, which in turn, has negative impacts on both forage production and biodiversity 

(Alexander 1987; Keane and others 2002; Laughlin and 

others 2004, 2005; Severson and Uresk 1988; Uresk 

and Severson 1988). By some estimates, the increase in 

forest canopy cover throughout the 20th century has led 

to as much as a 92 percent reduction in forage production in some pine stands in Arizona. Forests with high 

tree density may also reduce habitat quality for wildlife species adapted to forest openings and stands with 

large trees and snags (Dahms and Geils 1997). Some aspects of the altered forest structure may also negatively 

impact threatened and endangered species such as the 

Mexican spotted owl, northern goshawk, and Pawnee 

montane skipper (Colorado State Forest Service 2004; 

Reynolds and others 1996; Sheppard and Farnsworth 

1997). Furthermore, many species of wildlife and plants 

are adapted to a variety of forest structural stages, from 

forest openings to forests with dense canopy cover 

(Anderson 1994). Thus, landscapes that contain a diverse mosaic of structural stages tend to support more 

species of birds and mammals than landscapes that are 

more homogenous (Finch and others 1997; Keane and 

others 2002).
USDA Forest Service RMRS-GTR-198. 2007 21

Figure 5. Example of overly stocked, homogenous forest in the Black Hills National Forest. This 

type of forest structure can have negative consequences for a variety of ecological attributes 

including hydrology, insect and disease outbreaks, and wildfire hazard. Photo credit: Molly 

Hunter.
22 USDA Forest Service RMRS-GTR-198. 2007
USDA Forest Service RMRS-GTR-198. 2007 23

The goal of any fuel treatment project is to alter fuels to reduce the potential for catastrophic wildfire 

spread. Depending on the objective, this can be achieved 

by practices that reduce fuel loading, continuity, and 

depth. While wildfire hazard reduction is a valid goal, 

agencies are also charged with meeting many other resource management objectives, such as wildlife habitat 

improvement and maintenance of species diversity. 

Restoring landscapes to conditions present prior to major disruptions by Euro-Americans may best meet these 

goals. For example, conditions under which the large 

variety of plants and animals found in ponderosa pine 

forests have evolved and adapted. In some cases, goals of 

forest restoration can be conducive with reducing wildfire hazard, especially for areas that historically burned 

with frequent low-severity fire regimes. However, where 

mixed-severity fire regimes were the norm, restoration 

may result in moderately dense forests with the potential 

to burn with high intensity on a small scale. The needs 

of reduced fire hazard may have to be balanced against 

the needs for restoration in such cases. However, other 

resource management objectives may still be met by altering fuel treatment prescriptions. Treatments that are 

multifaceted and consider many resource management 

objectives, along with fuel reduction, are likely more 

sustainable in the long term.

Reduced Wildfire Hazard

Wildfire hazard can be thought of as the potential fire 

behavior and effects based on existing fuel condition. 

Reduced wildfire hazard is the primary goal of forest 

fuel reduction treatments. In order to effectively achieve 

this goal, fuel treatments need to address needs at both 

local and landscape scales with attention to requirements 

for long-term sustained management. On the stand level, 

prescriptions need to be designed to reduce the potential for initiation of active crown fires. On the landscape 

scale, fuel treatments need to be strategically placed to 

protect values at risk from catastrophic fire. Long-term 

planning must take into account sustained management 

so that treatments maintain their effectiveness over time. 

In all cases, the goal is to reduce wildfire hazard, not 

to eliminate fire altogether. The degree of reduction that 

can be achieved requires consideration of a variety of 

factors and ecosystem values.

On the stand level, reduced fire hazard is accomplished through reductions in surface, ladder, and canopy 

fuels. Surface fuels include litter, duff, and woody debris 

that lie on the soil surface, as well as standing grasses, 

forbs, shrubs, and small trees. High fuel loading contributes to the potential for high intensity surface fire that 

can, in turn, have adverse effects on soil and vegetation 

through elimination of protective organic matter, and 

heat damage to soil organisms, roots and stems. Ladder 

fuels include large woody debris, large shrubs, small 

trees, and lower branches on large trees, all of which 

act to carry fire from the surface up into the canopy of 

trees, otherwise known as passive crown fire (Agee and 

Skinner 2005; Brown and others 2004). Canopy fuels 

include branches, leaves, and other materials that are 

in the forest canopy. Canopy bulk density, or the mass 

of material in a given volume of canopy space, contributes directly to the potential for fire to spread from tree 

canopy to tree canopy, otherwise known as active crown 

fire spread (Agee and Skinner 2005). To reduce wildfire 

hazard at the stand level, fuels need to be manipulated 

to reduce the potential for initiation of both active and 

undesired passive crown fire behavior. The appropriate 

level of hazard reduction will vary with any given treatment. Many have used the general rule of altering fuels 

such that surface fire is promoted under 90 percent fire 

weather conditions. A number of treatments are available 

that can be used to reduce loading of surface, ladder, and 

canopy fuels (see Section IV—Treatment Techniques) 

and thus, affect fire behavior.

Even though most fuel treatments occur on a stand 

level, it is important to consider each treatment in a landscape context, especially since many current wildfires 

dwarf the size of individual fuel treatment projects and 

cross jurisdictional boundaries (Sisk and others 2004). 

Placement of fuel treatments on every square inch of 

ponderosa pine landscapes will never be feasible nor 

would it be desirable given other resource management 

needs. Strategies for fuel treatment placement should be 

designed to maximize benefit gained from treatments in 

terms of meeting goals of reduced wildfire hazard. Not 

Section III:

Fuel Treatment Objectives
24 USDA Forest Service RMRS-GTR-198. 2007

every acre requires treatment to effectively reduce the 

potential for severe wildfire spread. Researchers have 

modeled fire growth under different fuel treatment scenarios to determine how fuel treatments can be optimally 

placed to reduce fire spread. Results show that separate 

treatments that overlap slightly in the heading fire direction can reduce overall rate of fire spread (Finney 2001). 

Placement of linear fuel breaks in strategic locations (for 

example, ridgetops) has also been proposed to break up 

fuel continuity and aid in fire suppression tactics (Agee 

and others 2000).

Management of landscapes does not end with the 

initial implementation of strategically-placed fuel treatments across the landscape. Long-term planning is 

needed to ensure that the effectiveness of treatments is 

maintained. For example, prescribed fires are shown to 

reduce the severity of wildfires for up to 4 years in Arizona 

and New Mexico (Ffolliott and Guertin 1988; Finney 

and others 2005; Omi and others 2005) and 6 years in 

Colorado (Omi and others 2005). Once initial fuel treatments have sufficiently reduced fuel loads to promote 

low intensity fire, maintenance of low fuel loads should 

then be accomplished with repeated fuel treatments. The 

frequency of maintenance treatments will vary by region 

and can be determined by the historical fire frequency 

or rates of fuel accumulation. For example, it is recommended that maintenance treatments be conducted every 

3 to 10 years in the Southwest where fires historically 

occurred with high frequency (Allen and others 1968; 

Biswell and others 1973; Harrington and Sackett 1990; 

Sackett and others 1996). This is also consistent with 

the rates of accumulation of surface fuels in this region 

(Ffolliott and others 1977; Ffolliott and Guertin 1988). 

In the Black Hills and Front Range where fire was historically less frequent, maintenance treatments occur at 

longer intervals. In the Black Hills, maintenance treatments are recommended every 15 to 25 years in the 

lower elevation forests (Bachelet and others 2000). In 

the Front Range, maintenance treatments should be conducted in intervals of 3 to 20 years or more depending on 

location and elevation (City of Boulder 1999; Kaufmann 

and others 2005). Tree seedling establishment and crown 

growth rates vary with locality, site conditions, and associate vegetation and may require modification of these 

maintenance treatment intervals.

Restoration

Restoring forests to their historical structure and reintroducing important ecological processes, such as 

fire, should promote viability of species that evolved 

under the historical forest conditions (Allen and 

others 2002; Brown and others 2004; Landres and others 

1999; Swetnam and others 1999). Since pre-settlement 

ponderosa pine forests in the Southwest, Front Range, 

and Black Hills generally burned under low- to mixedseverity fire regimes, restoring historical forest structure 

should reduce the potential for large-scale crown fires 

(Allen and others 2002; Brown and others 2000; Brown 

and others 2001a; Fiedler and Keegan 2003; Fule and 

others 2001; Kaufmann and others 2003; Wienk and 

others 2004). However, adhering to strict restoration 

objectives will not result in reduced wildfire hazard in 

all stands since some ponderosa pine forests historically burned with infrequent fires of high severity (Baker 

and others 2007). Pre-Euro-American settlement forest 

structure provides a useful reference for thinning targets 

(Landres and others 1999), but there are limitations in 

the use of historical data since site specific information is 

often not available (Landres and others 1999; Swetnam 

and others 1999). However, there is general knowledge 

of the range of variability in historical forest structure 

and disturbance processes and this can be considered 

when planning site-specific fuels treatment activities.

Restoration projects at the stand level should attempt to mimic historical stand conditions in terms of 

tree density, tree age and size distribution, tree species 

composition, and spatial pattern (Allen and others 2002; 

Kaufmann and others 2003; Moore and others 1999). 

Since these conditions likely varied across the landscape, care should be taken to consider that variability 

and use local historical data when available. Managers 

should also consider other important historical components of stands, such as understory species and wildlife. 

Restoration involves much more than returning historical forest structure. For example, historical processes 

also require attention. Thus, dominant disturbance processes such as fire also need to be returned to the system 

in a manner that reflects historical disturbance regimes 

(Allen and others 2002; Moore and others 1999).

To approach historical conditions on a landscape 

level, managers should attempt to achieve the spatial 

heterogeneity in forest structures that were evident in the 

past. Although ponderosa pine forests in these regions, 

on the whole, have higher fuel loadings today, these forests did not historically exhibit homogenous structure on 

the landscape scale. In the Southwest, landscapes were 

likely composed of a mosaic of meadows, savannahlike forests with low tree density interspersed with more 

dense forests with higher canopy cover (Savage 1991). 

In the Front Range, forests were composed of a mixture of persistent old growth, openings, and dense stands 

(Kaufmann and others 2001). The Black Hills historically exhibited similar heterogeneity in forest structure 
USDA Forest Service RMRS-GTR-198. 2007 25

(Parrish and others 1996). The variety of species of 

plants and wildlife found in these ponderosa pine forests 

were probably adapted to a wide range of forest structures (Finch and others 1997; Keane and others 2002). 

To maintain diverse wildlife and plant habitat, managers should strive to create habitat diversity across the 

landscape within the bounds of the historical range of 

variability in forest structure. This can be achieved by 

designing different treatment prescriptions (including 

no treatment) that result in structural and spatial patterns 

across the landscape that are consistent with historical 

conditions.

Commercial Revenue

Although commercial timber production can be 

obtained from silviculture treatments designed for restoration or hazardous fuel reduction, it is not the primary 

goal of these treatments. Maximizing commercial revenue is often contrary to wildfire hazard reduction and 

other resource management objectives (Allen and others 

2002; Arno and Fiedler 2005; Brown and others 2004; 

Covington and others 1997; Graham and others 1999). 

This does not mean that cutting large fire-resistant trees 

should never be done. In some cases, larger, commercially viable trees need to be removed in order to create 

openings or to reduce canopy bulk density to levels 

that would significantly reduce the probability of active 

crown fire spread (Arno and Fiedler 2005; Hollenstein 

and others 2001; Lynch and others 2000; Scott 1998). 

The revenue gained from commercially viable trees in 

these cases can then be used to offset the cost of removing non-commercial trees and slash. Any silviculture 

treatment that reduces crown bulk density and surface 

or ladder fuels will have some effect on mitigating fire 

behavior. However, overstory removal and individual 

tree selection cuts that do not remove excess small- and 

intermediate-sized trees have previously been reported 

as ineffective in reducing the potential for extreme fire 

behavior (Graham and others 1999; Martinson and Omi 

2003; Scott 1998; Stephens and Mogahaddas 2005a).

There is some potential to use conventionally nonmerchantable material (small trees, tree tops, branches, 

and shrubs) for bioenergy or other wood products such 

as particle board or paper (Graham and others 1998; 

Harrison 1975; Hollenstein and others 2001; Le VanGreen and Livingston 2003). With careful planning, 

development of a sustainable long-term biomass harvest 

cycle may be compatible with decreasing wildfire hazard while maintaining ecological integrity (Hollenstein 

and others 2001). However, selling biomass for energy 

is often not economically feasible when other sources of 

energy are inexpensive, processing plants are scarce, and 

access to biomass is restricted (Stokes 1992). Biomass 

heaters have been successfully used on a small scale in 

buildings at the Community College of Santa Fe, NM, 

and in Boulder County, CO. Chipped material can also 

be sold for garden mulch, but again the economical feasibility of this depends on available markets (USDA 

Forest Service 2003c).

Other Objectives

A host of other resource management objectives can 

be met with fuel management treatments. For example, 

fuel treatments can be used to increase forage or shrub 

production and nutritional quality important for a variety of wildlife species and domesticated animals (Harris 

and Covington 1983; Sieg and Severson 1996; Sieg and 

Wright 1996). Prescribed fire has been used to improve 

grass quality and quantity in the Southwest and Front 

Range (Biswell and others 1973), and to encourage 

shrub resprouting of mountain mahogany in the Front 

Range and bur oak in the Black Hills (Harper and others 1985; Sieg and Severson 1996). Fuel treatments can 

also be used to control outbreaks of insects and diseases. Heavier thinning targets have been justified in areas 

severely infested by dwarf mistletoe (Heidmann 1968; 

Myers 1974) and mountain pine beetle (McCambridge 

and Stevens 1982). Fuel treatments have been used to 

increase water yield from watersheds. Heavy cutting of 

trees in patches or strips have been justified for this purpose (Ffolliott and Malchus 2001; Orr 1975).

Summary

In concluding this section, we remind readers that 

forest ecosystems are not static, but dynamic systems 

that are constantly changing. Realistically, forests are 

populations of living organisms where new seedlings are 

constantly establishing, old trees are dying, and all trees 

are increasing in biomass through time. Management activities that alter the numbers, sizes, and species of trees 

on a site will have consequences in terms of resource 

allocation and the population dynamics of all organisms 

using the site. For example, a standard fuels treatment 

is a thinning from below to remove ladder fuels and 

reduce crown bulk density. This closely approximates 

the seed cut of a two-step shelterwood harvest where 

the objective is to open the forest canopy and provide 

a seed source to establish a new even-aged forest. We 

must therefore expect abundant natural regeneration to 

establish following the initial entry and be prepared to 
26 USDA Forest Service RMRS-GTR-198. 2007

periodically re-treat the stand to keep the seedlings from 

growing into ladder fuels. We must also consider the 

remaining overstory trees. Although they are likely to 

live many decades, they will eventually die and require 

replacement to maintain the desired forest structure. In 

the long term, we must therefore balance the need for reducing wildfire risk with the need to maintain a healthy 

viable population of trees along with other resource considerations.
USDA Forest Service RMRS-GTR-198. 2007 27

Even though most fuel treatments occur on a stand level, it is important to consider each treatment in a 

landscape context, especially since wildfires commonly 

dwarf in size individual fuel treatment projects (Sisk and 

others 2004). Historically, the primary scale of forest 

structural variation may have been broad and driven by 

landscape-level fire effects. Structural variation in contemporary forests exists at the stand level due to harvests 

and other management activities including fire exclusion 

(Hudak and others 2006). Historical ponderosa pine forests were seldom homogeneous in structure (Savage 

1991). Thus, managers should strive to achieve greater 

landscape heterogeneity within the bounds of the historical range of variability in forest structure. Yet, landscape 

scale fuel management and restoration treatments have 

been slow to develop (Miller and others 2000). A highly 

heterogeneous landscape is associated with many desirable resource conditions, but achieving and sustaining 

this condition requires an understanding of the spatial 

dynamics of the factors that structure the environment. 

These include adequate tools to make good decisions 

about managing these factors, and a management philosophy that incorporates the long term and large scale 

(Lundquist 2005). Recently, much effort has been spent 

on developing landscape scale spatially explicit fuel 

distributions (for example, Reich and others 2004) and 

fire spread models, socioeconomic perceptual models 

of people affected by disturbances (for example, Flint 

2006), and long-term impacts on functions and structure 

of landscapes (Keane and others 2006).

Diseases, insects, and other biotic and abiotic factors 

influence fire regimes, singly or in combination, sequentially or concurrently. Different biotic disturbances, for 

instance, commonly cause characteristic patterns of 

mortality and stand structure across the forest landscape 

that, in turn, change ignition potential, rate and direction 

of spread, and intensity of wildfires. The relative importance of different disturbance agents would probably 

vary among stands and/or landscapes. Wildfires, in turn, 

change a forest landscape in ways that often influence 

the occurrence, distribution, and epidemiology of forest 

diseases, insect pests, and other small-scale disturbances. This reciprocal relationship is well recognized, but 

is not well-studied primarily because quantitative tools 

to characterize such interactions are lacking. Ecological 

surprises arise when these events interact with other 

perturbations or agents. Understanding the role of compound disturbances is imperative, yet little research 

exists on this topic (Paine and others 1998).

Models Used to Derive Landscape Strategies

Several tools are available to help managers derive strategies for achieving maximum benefit for fuel 

treatments. One such approach is the Forest Ecological 

Restoration Analysis (ForestERA) project implemented by researchers at Northern Arizona University (Sisk 

and others 2004). In a pilot project conducted in northern Arizona, the researchers have amassed GIS spatial 

data layers that include vegetation composition, canopy cover, basal area, stem density, elevation, historical 

fires, ignition points, invasive plant locations, hydrology, and soil characteristics. These layers are used to 

develop models that predict risks (for example, fire 

risk, watershed effects, invasive plants) and values (for 

example, wildlife habitat, wilderness, recreation, and 

infrastructure) on the forested landscape. A framework 

is then developed where landscape scale objectives 

and criteria for meeting objectives are defined, and 

then through an iterative modeling process, fuel treatment locations are optimized across the landscape to 

maximize protection of values at risk while achieving 

management objectives.

The Wildfire Alternatives (WALTER) project is 

an approach developed at the University of Arizona 

and currently has assessments available for the Santa 

Catalina Mountains, Chiricahua Mountains, Huachuca 

Mountains in Arizona, and the Jemez Mountains in 

northern New Mexico (University of Arizona 2002). 

This model assesses fire risk across these landscapes 

based on climate, fire history, vegetation, fuels, and societal values. WALTER allows managers to assess fire risk 

in these landscapes under different climatic scenarios, 

making it useful for developing strategies for optimizing 

placement of fuel treatments across a landscape.

Section IV:

Fuel Treatment Techniques

Developing Landscape-wide Fuel 

Treatment Strategies
28 USDA Forest Service RMRS-GTR-198. 2007

While the above approaches are currently only available for specific landscapes in the Southwest, another 

approach currently in progress in southern New Mexico 

uses spatial data layers developed from the LANDFIRE 

project. While the data developed in LANDFIRE is less 

detailed than in the previous two examples, it will eventually be available for all of North America, making this 

process easily adapted to landscapes in other regions. 

The LANDFIRE project uses biophysical settings and 

simulation modeling to describe historical successional 

vegetation classes and estimates the proportion of the 

landscape that historically existed in each succession 

class. Simulation modeling, satellite imagery, and other 

tools are then used to determine existing vegetation and 

departure from historical conditions. With this process, 

GIS spatial data layers are developed that can be directly 

imported into FARSITE and FlamMap, allowing one to 

evaluate potential fire behavior and spread patterns. The 

data are easily accessible on the LANDFIRE website 

(www.landfire.gov).

Managers and researchers on the Gila National Forest 

have used LANDFIRE data and spatial data locating 

values at risk, including wildland urban interface and 

threatened and endangered species habitat, to develop 

strategies for placing fuel treatments across the landscape. Fuel treatment placement is prioritized adjacent 

to values at risk (for example, wildland urban interface, 

Mexican spotted owl habitat) to minimize the threat 

of damage from severe wildfire in areas where fuel 

hazard is greatest. Factors such as prevailing wind, dominant slope, and fuel condition, along with models like 

FlamMap and FARSITE, are considered to determine 

the likelihood of severe fire occurrence and spread in 

any given area. An imperative component of this process 

is the inclusion of land managers that have worked in 

the area for a long time and are able to evaluate the accuracy of the LANDFIRE data and output from models 

like FlamMap and FARSITE based on their experience 

in, and knowledge of, fire behavior in the region.

Lundquist (in press) developed a method of measuring 

the relative importance of individual agents as drivers 

of wildfire using structural equation modeling when 

compound disturbances occur together in the landscape. 

The method was able to separate out the individual impacts of various agents acting concurrently. The method 

developed by Lundquist would certainly be able to identify the most important factors affecting the ecosystem, 

which might be the type of information needed to prioritize fire and fuel treatments (fig. 6).

Prescribed Fire Techniques

Differing levels of fire intensity may be desirable in 

a prescribed fire depending on the amount and type of 

fuel targeted for reduction and different secondary resource objectives that may be considered (DeBano and 

others 1998). Fire intensity can be controlled partly by 

environmental conditions in the prescription window. For 

example, higher fire intensity can be expected when fuel 

moisture is low, temperature is high, and winds are strong 

(Pyne and others 1996). Fire intensity can also be controlled through ignition techniques and firing patterns.

Figure 6. An example of how structural 

equation modeling can be used to 

measure the relative importance 

of individual agents (for example, 

insects and diseases) as drivers of 

wildfire. The effects of fuel generating disturbances are modeled and 

the predicted results can be used in 

a fire spread model.
USDA Forest Service RMRS-GTR-198. 2007 29

Low Intensity Prescribed Fire

Low intensity prescribed fire can be used to reduce the 

potential for severe fire spread by reducing fuel loads, 

particularly for surface fuels, including litter, duff, and 

woody debris (Bastain 2001; Biswell and others 1973; 

Cooper 1961; Covington and Sackett 1984; Davis and 

others 1968; Harrington 1981; Sackett 1980) (fig. 7). 

They can also be used to consume small tree seedlings to 

slow development of ladder fuels (Arno and Harrington 

1997; Arno and Fiedler 2005; Harrington 1981) (fig. 8) 

or to scorch the lower limbs of trees and saplings to increase crown base height and reduce the potential for 

torching of trees (Agee and Skinner 2005; Gaines and 

others 1958). Reduction in these fuels should reduce the 

potential for severe wildfire spread (fig. 9).

Low intensity prescribed fire may also be used to 

reduce unusually large accumulations of surface fuels, such as slash loadings after a thinning operation. 

However, excessively high fuel loading can promote surface fires of high intensity and undesirable fire effects, 

particularly on soil resources. Although many managers 

feel uncomfortable using prescribed fire in these situations, some have used broadcast burns to reduce slash 

loading within a year of the thinning operation. This can 

be safely done when larger diameter fuels and duff are 

sufficiently wet to prevent high intensity fire, but red 

needles attached to branches will facilitate the rate of 

fire spread. These fires generally consume only 1- and 

10-hour fuels, limiting fire intensity and damage to trees 

(Biswell and others 1973; Orozco and Carrillo 1992-

93). Consumption of remaining slash and duff can be 

achieved with subsequent burns. Managers have been 

successful in experimentally burning red slash in the 

summer 2 to 4 days following rain events (Orozco and 

Carrillo 1992-93). Alternatively, the excess material can 

be put into piles that can then be burned. This generally 

carries less risk than broadcast burning, as piles can be 

burned in the winter when fire risk is lower.

Restoration objectives can be met by using low intensity prescribed fire. In most ponderosa pine forests, 

low intensity surface fire made up some component of 

the historical disturbance regime. Thus, returning low 

intensity fire to the landscape is a vital component of 

restoration. Fire can be effective in creating diversity 

in habitat structure on the stand scale (Severson and 

Rinne 1990) (fig. 10). Returning fire would be important 

for other ecological processes such as nutrient cycling 

and understory production (Covington and Sackett 

1992; Harris and Covington 1983). The burning cycle 

conducted by managers should be consistent with the 

historical range of variability in fire frequency of a site 

(Arno and Fiedler 2005). Since surface fuels accumulate 

at relatively rapid rates in southwestern ponderosa pine 

forests (Ffolliott and others 1977; Ffolliott and Guertin 

1988), researchers have recommended burning every 3 

to 10 years, consistent with the historical range of variability in fire frequency (Allen and others 1968; Biswell 

and others 1973; Harrington and Sackett 1990; Sackett 

and others 1996). However, rates of surface fuel accumulation vary by region. In the Black Hills and Front 

Range, where natural fire was historically less frequent, 

prescribed fire can be repeated with longer intervals between fires. Here, conducting low intensity prescribed 

fire every 15 to 25 years in lower elevation forests is 

recommended (Bachelet and others 2000). In the Front 

Figure 7. Low intensity prescribed 

fire consuming litter, duff, and 

woody debris. Photo credit: 

Paul Summerfelt.
30 USDA Forest Service RMRS-GTR-198. 2007

Figure 8. Low intensity prescribed 

fire kills tree saplings and can 

therefore slow development 

of ladder fuels. Photo credit: 

Mike Battaglia.

Figure 9. Relatively low to moderate intensity prescribed fire 

consumes the lower limbs of 

trees and can therefore reduce 

ladder fuels. Photo credit: Mike 

Battaglia.

Figure 10. Prescribed fire can 

be used to create or maintain important wildlife habitat features. In this example, 

prescribed fire creates habitat 

by providing openings while 

maintaining important habitat 

components such as large trees 

and woody debris. Photo credit: Mike Battaglia.
USDA Forest Service RMRS-GTR-198. 2007 31

Range, low intensity prescribed fires are recommended 

at intervals of 3 to 20 years or more, consistent with the 

historical fire return interval at various locations and 

elevations (City of Boulder 1999; Kaufmann and others 2005). Historical fire regime can vary widely within 

a given region (see tables 1, 3, and 4). This variability should be considered in fuel treatments in order to 

achieve heterogeneity at the stand and landscape level.

High Intensity Prescribed Fire

High intensity prescribed fire that often exhibits some 

torching can be used to reduce the potential for highseverity wildfire spread by reducing ladder and some 

canopy fuels (Biswell and others 1973; Fule and others 2002a; Fule and others 2004; Harrington and Sackett 

1990; Lindenmuth 1960; Morris and Mowat 1958; 

Woodridge and Weaver 1965) (fig. 11). Prescribed fire 

treatments with some torching may be appropriate when 

the use of mechanical equipment to thin trees is not feasible because of limited access or other restrictions (Aplet 

and Wilmer 2003; DellaSalla and Frost 2001; Fule and 

others 2002a). Opportunities for use of high intensity 

prescribed fire may be limited because of the risk of fire 

escape and the proximity of ponderosa pine forests to 

population centers in the Southwest, Front Range, and 

Black Hills. However, use of small-scale (< 5 acres in 

size) high intensity fire has been achieved successfully 

in limited areas including ponderosa pine forests in the 

Arapaho-Roosevelt, San Juan, Prescott, Santa Fe, and 

Black Hills National Forests, and Bandelier National 

Monument. The torching pattern can create forest openings, stands with lower tree density, and increased 

structural diversity.

High intensity prescribed fire can also be used to meet 

restoration objectives. Relatively small-scale crown 

fires were a component of the historical fire regimes in 

certain ponderosa pine forests in the Front Range and 

Black Hills (Baker and others 2007; Huckaby and others 

2001; Kaufmann and others 2000; Sherriff and Veblen 

2007). From a restoration perspective, it may be desirable to duplicate some of this fire behavior and resultant 

fire effects where possible. High-severity crown fires 

were likely more common in higher elevation forests 

and on north-facing aspects where conditions were more 

mesic (Sherriff and Veblen 2007). The size of patches 

in these forests that experienced high fire severity is 

not well understood, but were likely variable in size 

(Kauffmann and others 2003). Since such events likely 

occurred with long return intervals and the historical 

extent of such events is not well understood, using this 

technique extensively under the guise of restoration is 

not recommended. Instead, high intensity prescribed fire 

may be used to a limited extent where feasible to create landscape heterogeneity that would have been more 

characteristic of historical forests (fig. 12).

Figure 11. Higher intensity prescribed fire, which exhibits some torching, can be a 

useful tool for reducing tree 

density and ladder fuels and 

creating important wildlife 

habitat features. Photo credit: Gale Gire.
32 USDA Forest Service RMRS-GTR-198. 2007

Prescribed fires that exhibit some torching can be 

used to meet other resource management objectives 

as well. Such fires may be more effective in reducing 

dwarf mistletoe infection on trees in the Southwest 

and Front Range (Alexander and Hawksworth 1976; 

Conklin and Armstrong 2001). High intensity surface 

fires may be effective in stimulating sprouting of shrubs 

that are important browse for wildlife (Bock and Bock 

1984; Harrington 1985; Sieg and Wright 1996; Young 

and Baily 1975). Higher intensity surface fire may also 

be needed to control dense thickets of Gambel oak in 

the Southwest that can act as a ladder fuel (Harrington 

1985) (fig. 13).

Controlling Fire Intensity

Prescription window—Fire intensity can be controlled 

by burning under specific conditions of fuels, weather, 

and topography, all of which affect fire behavior and 

make up the prescription window. If lower fire intensity is desired, burns can be conducted when relative 

humidity and fuel moisture contents are high and wind 

speeds are low. Burning on a steep slope will result 

in faster rate of spread and fire intensity compared to 

burning on a gentle slope. A fire will burn with higher 

intensity when more heavy fuel is available to burn. Fuel 

loading or arrangement can be altered through various 

Figure 12. Higher intensity prescribed 

fire can be used to create a more 

heterogeneous landscape. Photo 

credit: Gale Gire.

Figure 13. Gambel oak, particularly in 

southwestern Colorado, can grow 

in dense thickets in the understory 

of ponderosa pine forests creating 

ladder fuels. Photo credit: Todd 

Gardiner.
USDA Forest Service RMRS-GTR-198. 2007 33

mechanical means (discussed elsewhere in this publication) to achieve desired fuel conditions and subsequent 

prescribed fire behavior. Less intensive actions can also 

be taken to alter fuel loading or structure. For example, 

managers on the Colorado State Forest often hand-remove heavy fuels from selected portions of a burn unit 

prior to ignition to prevent high fire intensity around 

sensitive areas (for example, old trees, fire lines, and so 

forth). This practice is common when managers conduct 

low intensity fires in open ponderosa pine forests with 

grassy understories.

Firing patterns and ignition techniques—Fire intensity can also be controlled on the ground through use 

of alternate firing patterns. Although many patterns are 

available, the most commonly used patterns are backing 

fires and strip head fires. Backing fires are set along a fuel 

break and allowed to spread against the wind or down a 

moderate slope (Brown and Davis 1973; Chandler and 

others 1983; Kilgore and Curtis 1987; Pyne and others 

1996) (fig. 14). They generally result in a slow moving 

fire of minimal intensity with more complete combustion of fuels. This technique requires a steady wind and 

is often not suitable for very steep slopes. Backing fires 

are not often used exclusively in a project, as it takes a 

considerable amount of time to burn a large unit using 

this method. They are more commonly used to create 

black lines or to burn portions of units where extreme 

fire behavior poses a threat.

In contrast to backing fires, strip head fires are set so 

that the flaming front spreads in the direction of the wind 

or slope (Brown and Davis 1973; Chandler and others 

1983) (fig. 15). Typically, a broad fuelbreak is burned at 

Figure 14. Backing 

fires tend to move 

relatively slowly 

with low flame 

lengths and tend 

to result in more 

complete combustion of surface fuels. Photo 

credit: Unaweep 

FUM.

Figure 15. Example 

of a strip head fire. 

The rate of spread 

and intensity depends on the 

length between 

strips and type 

of fuel burning. 

Photo credit: Paul 

Summerfelt.
34 USDA Forest Service RMRS-GTR-198. 2007

the top of the unit before a head fire is 

set, or a natural firebreak is used as an 

anchor point. Head fires tend to be very 

intense and burn with a rapid rate of 

spread. For more control, head fires can 

be set in portions (strips). For example, 

a head fire can be lit somewhere below 

the fire break at the top of the unit and 

allowed to burn to the fire break. This 

process can then be repeated until the 

entire unit is burned. Fire intensity can 

be controlled by the spacing interval between strips, but will also vary with fuel 

loading and fuel moisture. Wide strips 

may reduce fire intensity in light fuels, 

but can increase intensity in heavier fuels. For example, wide spacings have 

been used in the Black Hills to complete 

a stand replacement prescribed burn in 

areas with heavier fuels (Henry Goehle, 

personal communication). Intervals between strips can 

range from 10 to 200 feet depending on desired fire behavior and fuel loading. Different firing patterns, such as 

jackpot and spot firing, can also be used to create higher 

fire intensity to thin stands (fig. 16).

Fire intensity can also be controlled by use of different ignition techniques. Certain ignition tools allow for 

more fire to be placed on the ground in a short amount 

of time, thereby increasing fire intensity (Brown 1984). 

Aerial ignition devices (for example, helitorch, pingpong balls) are likely to result in higher fire intensity 

than hand ignition devices (for example, drip torch, fuses) (fig. 17). Different ignition devices are discussed in 

the Tools Used in Burning section below.

Wildland Fire Use

In certain areas, managers use fires that are naturally 

ignited by lightning to achieve resource benefit. This 

practice is termed wildland fire use for resource benefit, 

or wildland fire use (WFU). Such fires typically burn for 

multiple days or weeks and exhibit varied fire behavior 

and resultant fire effects. WFU is often practiced in remote areas where risk of wildfire impacting humans is 

low and cost to suppress is high (fig. 18).

Tools Used in Burning

Burning and fuel break tools—Most prescribed fire 

treatments can be accomplished with hand crews using 

drip torches. For larger areas, aerial ignition devices may 

be used. These include delayed aerial ignition devices 

(DAID), or ping-pong ball system, and the helitorch, 

Figure 16. Example of spot firing. Depending on the type of fuel 

targeted and the number of ignitions, this firing technique 

can be used to create higher intensity. Photo credit: Paul 

Summerfelt.

Figure 17. Drip torches can be used for implementing a variety 

of firing patterns. Photo credit: Mark Roper.
USDA Forest Service RMRS-GTR-198. 2007 35

or flying drip torch system. Aerial systems reduce the 

amount of time it takes to light an area and thus may 

be most efficiently used on large treatment units. For 

example, managers on the San Juan National Forest 

have found it cost effective to use aerial ignition devices 

when units are greater than 500 acres. Aerial ignition devices have also been used on smaller units in Wind Cave 

National Park in areas where topography creates unsafe 

conditions for hand crews. The ping-pong ball system is 

particularly useful when a mosaic burn pattern is desirable. In northern Arizona, the gentle terrain allows for 

frequent use of ATVs with mounted drip torches, which 

also can decrease the amount of time required to burn an 

area. ATVs have also been used in the Front Range on 

the Pike-San Isabel NF.

For building fuel breaks, hoses, foam, hand crews, or 

dozers can be used. Dozers are generally needed only 

to create fuel breaks if fuel treatments are conducted in 

heavily stocked stands and if there are values at risk near 

the treatment area. In northern Arizona, smaller fuel 

breaks are constructed with an ATV by dragging a truck 

wheel rim filled with concrete. This technique is more 

productive than hand crews, yet does not cause as much 

disturbance as dozers (soil compaction and tree damage). ATVs are more easily used on gentle terrain with 

light surface fuels where soils are not excessively rocky. 

Dozers are more suited to construct fuel breaks in situations where fire intensities will be greater and terrain and 

soils are conducive to their use, as in the Black Hills.

Models used in planning—Different models can be 

used for planning prescribed fires at stand and landscape 

scales. On the stand level, the fire behavior prediction systems BehavePlus and NEXUS can be used to 

evaluate the effects of a range of fuel, weather, and topography variables on surface and crown fire behavior 

characteristics such as flame lengths, rate of spread, and 

fire intensity (Burgan and Rothermel 1984; Scott 1999). 

BehavePlus, in particular, is commonly used to derive 

a range of weather variables that will achieve desired 

fire behavior for a particular prescribed fire. NEXUS is 

commonly used to ensure treatments have effectively 

reduced the potential for active and passive crown fire 

initiation and spread. The effects of projected fire behavior characteristics on important fire effects such as 

tree mortality, fuel consumption, smoke production, and 

soil heating can be evaluated using the First Order Fire 

Effects Model (FOFEM) (Reinhardt and others 1997).

On a landscape scale, models like FlamMap and 

FARSITE can be used for a variety of planning purposes. FlamMap assesses wildlife risk across a landscape by 

creating maps of potential fire behavior characteristics 

(rate of spread, flame length) based on fuel structure, 

Figure 18. A wildland fire use (WFU) event (Taylor fire) on the Gila National Forest. WFU events often exhibit 

variable fire behavior and result in a wide array of fire effects. Photo credit: Michael Andreu.
36 USDA Forest Service RMRS-GTR-198. 2007

weather, and topography. FARSITE predicts spread patterns of fires over landscapes based on fuels, weather, 

and topography (Finney 1998). FARSITE is often used 

in management of large or complex fires to inform, for 

example, where resources may be best placed. Both 

models can also be used to assess the potential effectiveness of fuel treatments in reducing the potential for 

severe fire spread across a landscape (Stratton 2004). 

In the past, a limitation on the use of these models has 

been the availability of spatial GIS data layers needed to 

run the models. However, the LANDFIRE project is in 

the process of making such data available for the entire 

country. It is imperative to consult managers with a great 

deal of experience in, and knowledge of, a particular region to help verify model results. Models are useful, but 

they are often imprecise as is the data that goes into them 

and thus, they should never substitute for practitioner 

knowledge and experience.

Thinning Techniques

Silviculture Background

In the context of fuel treatment, thinning refers to the 

reduction of above-ground biomass by the removal of 

trees from a forest. Thinning affects fire behavior by 

changing both the amount and distribution of fuel available to burn. It is used primarily to lower the risk of 

crown fire by reducing crown bulk density. Although 

tree boles aren’t often consumed in crown fires, increasing the spacing between trees and removing smaller 

trees whose crowns serve as ladder fuels can dramatically alter potential crown fire behavior in a conifer forest. 

Thinning also affects how trees grow and can profoundly affect how forests develop in the future, including 

how fuels will be distributed in those future forests. Use 

of traditional silvicultural methods is practical for fuels 

reduction because prescriptions can be communicated 

effectively across disciplines and agencies (Arno and 

Fiedler 2005). Therefore, we feel a short discussion of 

thinning from a silviculture standpoint will be beneficial 

in understanding its effects from a fuel treatment standpoint.

Thinning is an intermediate silviculture treatment 

intended to improve growing conditions in forests managed under even-aged systems where mature trees will 

eventually be removed and replaced by a new forest. 

There are six general methods of thinning originally developed for management of commercial timber, but they 

can also be used for restoration and to promote reduced 

crown fire potential. These methods include crown thinning or thinning from above, low thinning or thinning 

from below, selection thinning, free thinning, geometric thinning, and variable density thinning (Graham and 

others 1999; Peterson and others 2005; Smith and others 1997). In crown thinning, trees in the upper crown 

classes are targeted for removal to release trees in the 

same size class from competition and increase their 

growth rates. In low thinning, trees in the lower crown 

classes are mostly targeted for removal, although some 

co-dominant trees can be targeted depending on the 

intensity of the treatment. Free thinning is a highly variable treatment in which individual trees are targeted for 

removal for the purposes of releasing desirable trees 

from competition. In selection thinning, the most economically viable trees are removed to stimulate growth 

of suppressed and intermediate trees in the understory. In 

geometric thinning, tree removal is based on spacing or 

geometric pattern. Variable density thinning utilizes low 

thinning in combination with at least one of the other 

methods. In all cases, thinning under even-aged management is intended to promote the health and vigor of 

the forest until it matures, is harvested, and is replaced 

with a new forest.

In contrast to even-aged management, forests under 

uneven-aged management are maintained through time 

within a range of desired spatial and structural conditions where trees of all sizes and ages are represented in 

the overall forest structure. Periodic removals similar to 

thinning are used to maintain the desired conditions in 

uneven-aged forests, but differ in that trees of all sizes 

are typically removed.

Fuel reduction or restoration treatments may be applied in forests under both even- and uneven-aged 

management systems. Uneven-aged management is 

more appropriate when the intention is to maintain a 

diverse forest structure containing trees of various age 

classes continuously through time on a site to mimic 

historic conditions as occurred at various scales in ponderosa pine stands in the Black Hills, Front Range, and 

Southwest. On the other hand, even-aged systems, such 

as shelterwood and seed tree methods, are relatively 

easy to implement and have been used widely in the 

Black Hills, Front Range, and Southwest on lands suitable for timber production (Schubert 1974; Shepperd 

and Battaglia 2002). In both cases, when trees reach maturity they are removed in one or more entries after a 

new crop of seedlings has been established.

Periodic removals under uneven-aged management 

take the place of both thinning and harvest cuts under 

even-aged management. Although some old, large trees 

are removed in each entry, at no point in time are all 

mature trees harvested from the stand. Control of growing stock under uneven-aged management methods is 
USDA Forest Service RMRS-GTR-198. 2007 37

a bit more complicated than with even-aged management. Stocking is controlled by diameter/age classes 

using either the BDQ method (Alexander and Edminster 

1977) or Stand Density Index (SDI) (Long 1995; 

Shepperd 2007). In both methods, one needs to determine the range of diameters and the residual stocking 

desired for a given stand. The techniques differ in their 

method for determining the distribution of trees in different size classes, but both enable an infinite variety of 

stand configurations from very open to heavily-stocked. 

Uneven-aged removals can accomplish many of the fuels 

treatments done with even-aged thinning, although fuels 

managers need to appreciate the differences between the 

two management systems. Application of uneven-aged 

silviculture on the ground is not much harder than evenaged treatments, as diameter-class removals can often be 

collapsed into broad structure or size classes. Although 

both even- and uneven-aged management are appropriate for ponderosa pine forests, from a fuels standpoint, 

both systems will require periodic treatments to maintain desired fuels conditions. The main difference will 

be what the stand will look like in the long term and 

what mix of resource use and management emphasis is 

placed on a particular piece of ground.

Reducing Wildfire Hazard

Certain thinning methods can be used to reduce the 

potential for active crown fire spread through reductions 

in canopy fuel loading, in particular canopy bulk density. 

However, while all thinning treatments technically result 

in reductions in canopy fuels, they will not all be effective in reducing the potential for torching and crown fire 

spread (Graham and others 1999; Peterson and others 

2005). Thinning treatments that use low, free, or variable density thinning methods are most likely to result in 

reduced potential for crown fire spread (Graham and others 1999; Peterson and others 2005; Scott 1998; Smith 

and others 1997; Stephens and Moghaddas 2005a), as 

are uneven-aged treatments that emphasize removal 

of small trees (Skog and others 2006). These methods 

can effectively increase canopy base height, decrease 

canopy bulk density, and decrease canopy continuity, 

factors that are needed to reduce the potential for torching, crown fire initiation, and crown fire spread (Agee 

and Skinner 2005; Skog and others 2006). Any removal 

of trees that results in reductions in canopy bulk density 

and continuity can be effective in reducing the potential 

for active crown fire spread. However, if these reductions only occur in the upper levels of the canopy, high 

crown fire spread rates may still be a factor in lower portions of the canopy. Tree removals often are not effective 

in increasing canopy base height unless smaller trees 

and lower limbs are removed as well. Thus, the potential for torching is generally not reduced after treatments 

that utilize crown, selection, or geometric thinning techniques where only large trees are removed. Subsequent 

treatment or removal of slash created by thinning operations is critical to maximize the benefits of the thinning. 

Slash left on ground will significantly increase fire behavior, even after 20 years and especially during drought 

conditions (Henry Goehle, personal communication).

Intensive treatments in which a great deal of material 

is removed in a short time period may be problematic as 

they can have detrimental impacts on native microbial 

and vegetation composition and diversity. For example, 

as disturbance intensity increases in fuel treatments, the 

potential for invasive species establishment tends to increase (Martinson and others, in press). However, if too 

little is removed, the treatment may be ineffective in reducing wildfire hazard. In order to be effective, multiple 

entries may be needed, increasing costs and prolonging 

environmental impacts.

There may be instances where reducing the threat 

of wildfire trumps other objectives. For example, in 

the wildland urban interface, protection of communities from wildfires is generally the primary objective. 

In such cases, the level of tree removal may justifiably 

be more intensive. Definitions of wildland urban interface vary, but it generally extends to at least 200 feet 

from structures and in some cases up to 1.5 miles from 

communities (Gatewood and Summerfelt 2005). In the 

wildland urban interface, particularly in areas within 200 

feet of structures, thinning treatments may be designed 

to reduce the potential for crown fire spread and create 

“defensible space” that provide firefighters safe conditions for battling oncoming wildfires (Gatewood and 

Summerfelt 2005; Nowicki 2001). Some have recommended that treatments in the defensible zone include 

removal of ladder fuels and thinning so that tree canopy 

spacing is a minimum of 10 feet (Dennis 1999; Nowicki 

2001). This should sufficiently reduce the potential for 

spread of crown fire in the wildland urban interface. 

Other treatment techniques may accomplish the same 

objectives, but many have not been sufficiently tested.

Restoration

Certain thinning techniques can be used to achieve 

objectives of restoring historical forest structure. 

Prescriptions designed to restore historical forest structure vary across the range of ponderosa pine, as historical 

disturbance processes and forest structures were very 

different in different regions (see Section II—Fire and 

Fuels Issues). Even within a region, landscapes were 

likely heterogeneous in forest structure and disturbance 
38 USDA Forest Service RMRS-GTR-198. 2007

processes in both time and space. Such heterogeneity 

should be met in current landscapes by creating variable 

prescriptions that fit within the natural variability in historical forest structure.

Southwest—Evidence of historical forest structure 

in a stand, such as pre-settlement trees, downed logs, 

stumps, and snags, should be used to restore historical structure in southwestern ponderosa pine forests. 

All pre-settlement trees should be retained in a thinning operation. Retaining post-settlement trees around 

pre-Euro-American settlement trees is recommended to 

restore the historical spatial pattern of trees (clumps of 

trees and openings), (Covington and others 1997; Fule 

and others 2002a; Moore and others 1999). The number 

of post-settlement trees retained can vary depending on 

historical tree density (table 2). It has also been recommended that post-settlement trees should be retained as 

replacement trees around large downed logs, stumps, or 

snags, which provide evidence as to where pre-settlement trees existed in the stand (Covington and others 

1997; Fule and others 2002a; Moore and others 1999) 

(fig. 19).

In many cases, restoration options may be limited 

because of lack of old-growth trees and site specific historical data. In such cases, information about historical 

tree density, species composition, and other attributes 

from similar forests can be used as a guide. It is important to understand that historical forest structure likely 

varied throughout the Southwest at local and landscape 

scales, and local conditions should be considered when 

designing restoration treatments. For example, historical tree density in the northern Arizona ranged from 25 

to 100 trees per acre and basal area varied from 34 to 

125 ft2

 per acre (Fule and others 1997; Fule and others 2002a; Moore and others 2004). Trees were into 

0.05 to 0.7 acre clumps of 2 to 40 trees (Covington and 

others 1997; White 1985). As a result, there has been a 

wide range in target basal areas (40 to 70 ft2/acre) and 

tree density (35 to 110 trees/acre) in restoration treatments throughout the Southwest (Edminster and Olsen 

1996; Fiedler and Keegan 2003; Fight and others 2004; 

Schumann 2004). To mimic historical forest structure as 

best possible, most treatment prescriptions involve retaining the largest trees and leaving trees in a clumped 

distribution. In areas where tree density would likely 

have been higher historically, such as on north aspects 

or in canyon bottoms, basal area targets may be higher 

(fig. 20).

Most ponderosa pine forests in the Southwest historically exhibited uneven-aged forest structure at some 

scale. Treatments should be designed to mimic this 

structure as best possible. Uneven-aged management 

Figure 19. Thinned and recently prescribed burned forest stand in the Gila National Forest. Retaining large trees and trees in multiple size classes and maintaining low tree density are common prescriptions for restoration treatments. Photo credit: Michael 

Andreu.
USDA Forest Service RMRS-GTR-198. 2007 39

methods have been developed to create historical forest structures (Edminster and Olsen 1996) and to meet 

specific fuels treatment objectives (Shepperd and others 

2005; Skog and others 2006) (see Techniques section).

On a landscape scale, ponderosa pine forests in the 

Southwest were historically composed of a mosaic 

of openings and forested stands with variable density 

(Savage 1991). For the purposes of restoration, managers 

should strive to recreate this landscape heterogeneity by 

designing and utilizing a variety of treatment prescriptions 

(including no treatment) across the landscape. Different 

management objectives (for example, wildlife habitat protection, and wildland urban interface) may facilitate use 

of different treatment strategies in different areas on the 

landscape and this may encourage landscape heterogeneity in forest structure. When available, localized data on 

historical forest structure should guide treatment prescriptions. If historical data is not available, managers can vary 

treatment prescriptions based on topographic features. 

For example, forests may have been denser historically 

on sites at higher elevations, on north-facing aspects, or 

on sites with productive soils.

Colorado Front Range—Based on historical forest 

structure and composition of low elevation montane forests in the central Front Range, Kaufmann and others 

(2003) recommends treatments that will create openings of various sizes so that they account for 15 to 25 

percent of the landscape, reduce tree density so canopy 

cover is 10 to 30 percent across the landscape, remove 

Douglas-fir trees except on north aspects, and retain oldgrowth trees. Managers in the Front Range often take 

these recommendations into account for fuel reduction 

projects (USDA Forest Service 2004b, 2004c). Patch 

cuts are used to create openings up to 5 acres in size. 

Between patch cuts, stands are thinned from below to 

reduce tree density by 20 to 30 percent. Managers focus on achieving stand structure with a variety of age 

classes and spatial patterns, as forests were historically 

uneven-aged in structure (fig. 21). Both the BDQ and 

SDI methods can be used to develop targets for numbers 

Figure 20. Recent mastication treatment in the Jemez Mountains, NM. Residual tree density was higher in drainages 

where historical tree density was also likely higher. Photo 

credit: Molly Hunter.

Figure 21. Recent thinning treatment in the Front Range. Photo 

credit: Wayne Shepperd.
40 USDA Forest Service RMRS-GTR-198. 2007

of trees desired in various age or size classes (Brown 

and others 2001a; Shepperd 2007; Shepperd and others 

2005). To promote development of old growth conditions, large and old-growth trees should be retained 

(Brown and others 2001a; Kaufmann and others 2003; 

USDA Forest Service 2004b, 2004c). Managers can use 

the guide developed by Huckaby and others (2003) to 

identify old ponderosa pine trees.

In some portions of the northern Front Range, researchers have found that higher elevation forests 

(above 2100 m) historically had much longer fire return intervals and thus, were likely controlled more by 

an infrequent high-severity fire regime (Ehle and Baker 

2003; Sherriff and Veblen, in press). In these forests, 

dense even-aged cohorts of trees likely followed high 

intensity disturbance events. In such forests, researchers 

have recommended a more gentle approach to restoration. Such thinning will likely have some effect on 

crown fire risk factors, but will likely be inadequate to 

meet all fire risk reduction needs in areas where this type 

of ponderosa pine forest occurs in an urban interface. It 

is also unclear if this approach is appropriate for higher 

elevation montane forests in other portions of the Front 

Range (Kaufmann and others 2006) since the data from 

the above studies is limited.

Ponderosa pine forests in most of the Front Range 

were historically composed of a mosaic of persistent old 

growth, openings, and forests of pure ponderosa pine and 

mixtures of ponderosa pine and Douglas-fir with variable density (Huckaby and others 2001; Kaufmann and 

others 2000; Sherriff and Veblen, in press). For restoration purposes, managers should attempt to recreate this 

landscape heterogeneity in forest structure by designing 

a variety of treatment prescriptions appropriate for different conditions. For example, forests in the grassland/

forest ecotone and lower montane forests, ranging from 

1700 m elevation in the southern Front Range to 2100 

m in the northern Front Range (Kaufmann and others 

2006), likely had much lower tree density historically. 

Thus, heavier treatment prescriptions may be appropriate (Huckaby and others 2001; Kaufmann and others 

2000; Mast and others 1998; Sherriff and Veblen 2007). 

In higher elevation montane forests and on north-facing 

aspects, tree density was likely higher historically (Ehle 

and Baker 2003; Huckaby and others 2001; Kaufmann 

and others 2000; Sherriff and Veblen 2007) and less 

intensive treatments would be more appropriate. The 

trade-off is that historically these latter forests were more 

likely subject to crown fires and would continue to be at 

higher risk to crown fire if higher densities are maintained. The key to dealing with this risk at the landscape 

scale is to make sure denser forests are isolated within 

the landscape by stands at lower risk to crown fire so that 

the risk of a landscape-wide crown fire is reduced.

Black Hills—The historical forest structure of the 

Black Hills included dense stands that may have been 

conducive to crown fire (Graves 1899; Parrish and others 1996; Progulske 1974). Given that crown fires were 

a component of the historical fire regime (Brown and 

Sieg 1996; Shinneman and Baker 1997), complete forest 

restoration may not be realistic for the Black Hills as it 

would conflict with current management objectives and 

land use. However, attempting to restore some aspects 

of historical forest structure and processes in Black Hills 

forests is likely to benefit native species that evolved 

with historical forest conditions and will positively affect current fire risk.

The current condition of the Black Hills has deviated from historical conditions in a variety of ways. 

Landscapes within the Black Hills are more homogenous 

in forest structure today than historically (Parrish and 

others 1996; Progulske 1974). Thus, thinning treatments 

can be designed to make the landscape more heterogeneous with stands of varying age structures interspersed 

throughout the landscape. In the drier portions of the 

Black Hills and in meadows, tree density is higher today 

than it was historically (McAdams 1995; Parrish and 

others 1996; Progulske 1974). In these cases, restoring 

historical forest structure would be consistent with reducing the potential for crown fires (fig. 22). Average 

tree size across the Black Hills is lower today than it was 

historically (Brown and Cook 2006; McAdams 1995). 

Recruitment of larger trees would not only reduce the 

potential for catastrophic wildfire, as large trees are 

more resistant to fire-induced mortality and have higher 

crown base heights, but it would also benefit many wildlife species that prefer large diameter trees and snags. 

This is particularly important for the northern goshawk, 

brown creeper, northern flying squirrel, and many woodpecker species (Shepperd and Battaglia 2002; USDA 

Forest Service 2003b).

Other Thinning Objectives

Reducing forest density also meets other resource 

management objectives. For example, the Flagstaff 

Fire Department treats mistletoe infested stands by 

completely removing small pockets of infestation (less 

than 1⁄4 acre) or by isolating larger patches with a barrier of 50 feet to reduce further spread (Farnsworth 

and Summerfelt 2001). Pockets that are infested with 

Ips beetles or mountain pine beetles are often targeted 

for heavier thinning treatments (USDA Forest Service 

2003a). Both of these treatments will reduce the potential for crown fire spread as well.
USDA Forest Service RMRS-GTR-198. 2007 41

As we mentioned earlier, regeneration of tree and 

shrub species in the forest understory may be a concern 

for land managers when the canopy is opened up. This 

can be particularly important for shrub species such as 

Gambel oak and Rocky Mountain juniper. These species act as ladder fuels, increasing fire hazard in open 

ponderosa pine stands. To prevent this, some managers 

maintain higher basal area targets in a thinning operation. For example, foresters in the Colorado State Forest 

often used higher residual stocking levels (Basal area = 

80 ft2

/acre) when there are many shrubs in the understory 

and lower stocking levels (Basal area = 40 ft2/acre when 

there is mostly grass in the understory. The trade-off between maintaining open forests at lower risk to crown 

fire and avoiding buildups of surface and ladder fuels 

may be more frequent prescribed burning or mechanical 

treatments to keep regeneration and shrubs in check.

Harvest Methods

Trees can be cut, processed, and removed from the 

forest using a variety of methods, including whole-tree 

harvesting, cut-to-length systems, or cable yarding (Fight 

and others 1999; Hartsough and others 1998; Windell 

and Bradshaw 2000). Processing harvested trees involves 

removing the limbs and tops of trees and cutting them 

into merchantable lengths and can occur in the woods, or 

at a landing. With each method, a variety of equipment 

can be used to cut and remove the trees (Holtzscher and 

Lanford 1997). In whole-tree harvesting, trees are felled 

and immediately removed to a landing area where they 

are processed. In cut-to-length systems, trees are felled 

and processed at the stump before being transported to a 

landing. In cable yarding, trees are felled and removed via 

a skyline cable system and can be processed at the stump 

or at the landing. Cable yarding is generally reserved 

for steep slopes, where use of other types of mechanical 

equipment is restricted (Fiedler and others 1999). Smaller 

trees can be hand or machine felled, or processed using 

masticators, which grind trees to the stump and disperse 

the resulting small material on the site.

Tools Used for Thinning

Chainsaws—Hand felling of trees of many different 

sizes can be accomplished effectively using chainsaws 

(Arno and Fiedler 2005; Larson and Hallman 1980; Scott 

1998; Stephens and Moghaddas 2005b). Using chainsaws 

is advantageous as it requires very little capital investment in equipment and they can be used in areas that are 

not accessible to mechanical equipment (for example, 

steep slopes and remote areas). However, hand felling 

is inherently dangerous as crews are directly exposed to 

multiple hazards during the logging. Furthermore, hand 

felling is labor intensive and generally not as productive 

as mechanical equipment. Thus, mechanical equipment 

is more economical, especially on large treatment units 

(Wang and others 1998). For large treatments accessible 

by road and in operable topography, mechanical equipment may be most appropriate.

Feller-bunchers and tree shears—Trees can be harvested mechanically using feller-bunchers or tree 

shears. Feller-bunchers use hydraulic grapple arms to 

hold the tree while it is cut (fig. 23). On some machines, 

a gathering device makes it possible to cut and collect 

several trees before they are dropped in a bunch. The 

cutting devices (for example, feller buncher and tree 

shear) can be attached to an articulating arm or boom, 

or directly to a tractor or other vehicle. A boom allows 

the machine to reach into stands to collect trees and 

minimizes travel over the site (fig. 24). Some mastication equipment can also be used to remove small trees. 

Commonly used mastication equipment is described 

in the following Other Mechanical and Combination 

Techniques section.

Figure 22. A recently thinned stand in the Black Hills National 

Forest. Photo credit: Molly Hunter.
42 USDA Forest Service RMRS-GTR-198. 2007

Prime movers—Vehicles serving as prime movers 

for harvesting heads (for example feller-bunchers and 

tree shears) generally include excavators, all surface 

vehicles, or four-wheel drive tractors, and they provide 

both the maneuverability and power supply for the cutting heads. Smaller machines, appropriate for small 

diameter material, are generally more maneuverable and 

apply less ground pressure than large machines. Rubbertired machines disturb soil less than skid-steer tracked 

machines but have a smaller footprint and thus, may 

compact the soil to a greater extent. Use of larger machines is generally only appropriate and economical if 

large diameter material is being removed. It is important 

to contact the manufacturer to ensure a head is matched 

with an appropriate machine that will provide sufficient 

power. Windell and Bradshaw (2000) and Jones and 

Stokes (2004) provide a summary of commonly used 

feller-bunchers and tree shears and their specifications.

Tree harvesters—Trees can also be felled using tree 

harvesters (Larson and Hallman 1980). Use of these 

machines is advantageous because they can also delimb, sort, and buck logs in the woods. A disadvantage 

of harvesters is that they often have limited maneuverability and thus can cause considerable residual stem 

damage. Also, they are generally not effective in delimbing trees with large branches (Hartsough and others 

1998) and often are not as productive as other methods 

(Holtzscher and Lanford 1997; Wang and others 1998). 

Tree harvesters leave branches and un-merchantable 

portions of trees scattered in the woods, which can significantly increase surface fuel loadings. Windell and 

Bradshaw (2000) and Jones and Stokes (2004) provide 

a summary of commonly used tree harvesters and their 

specifications.

Tree processors—Tree processing involves removal 

of limbs and tree tops and cutting logs to merchantable 

Figure 23. Feller-buncher head attached to a rubber-tired 

prime mover. Photo credit: Molly Hunter.

Figure 24. Mastication head attached to a 

boom or articulated arm of a Timbco© 

tracked timber harvester. Photo credit: 

Kristen Garrison.
USDA Forest Service RMRS-GTR-198. 2007 43

lengths. This can be accomplished at the stump or at the 

landing. Tree processing can be accomplished effectively using hand crews with chain saws. Alternatively, 

tree processing can be achieved using a mechanized processor. Here again, using chainsaws is advantageous as 

it requires little capital investment, although their use 

poses a safety risk for hand crews and they are often not 

as productive as mechanical processors (Holtzscher and 

Lanford 1997). Mechanized equipment may be more 

appropriate for treating large areas. Landing-based processors, such as boom delimbers, process whole trees 

that have been skidded to a central landing, separating 

merchantable material from tops, branches, and unmerchantable sections of logs and piling the debris in large 

piles at the landing for later disposal by burning or further processing. This equipment has the advantage of 

concentrating all slash into one location and will not increase surface fuel loadings in the woods. Disadvantages 

of this system include concentrated machine activity 

around landings, with associate soil compaction and 

modification of the soil environment under burned piles 

(Massman and others 2003, 2006).

Skidders and forwarders—Once trees are felled, they 

need to be removed to a landing. This can be achieved 

through skidding, forwarding, or cable yarding (fig. 

25). In skidding, logs or whole trees are dragged on the 

ground singly or in bunches by a skidder or crawler tractor. Traditional skidding uses wire rope or chain chokers 

to attach logs to the skidder, but modern grapple skidders 

are equipped with large hydraulic tongs that can pick up 

bunches of trees in one operation without the operator 

leaving the cab, making them much more productive. 

Skid trails should be strategically placed to minimize soil 

disturbance over the site. If disturbance is a concern, logs 

can be removed with a forwarder. Forwarders pick up 

material and carry it to a landing. Forwarders can generally carry much more material than skidders, thus fewer 

passes across the site are needed. However, forwarders 

are designed to remove processed logs and are normally 

used in situations where unmerchantable material and 

slash is left scattered on-site. In cable yarding, trees are 

removed via a skyline cable system. Because this treatment is expensive, it is generally reserved for removing 

commercial material from steep slopes or where use of 

mechanical equipment is restricted (Fiedler and others 

1999). At the landing, trees are loaded onto trucks or 

trailers using log loaders.

Computer models—The fire and fuels extension of the 

forest vegetation simulator (FVS-FFE) can be used to 

assess the impacts of various stand treatment options on 

potential fire behavior and fire effects (Reinhardt and 

Crookston 2003). This model can also be used to assess 

how different fuels, including trees, snags, and coarse 

woody debris, will change over time. FSVeg can also 

be used to assess how many trees need to be removed 

from a site. Both of these models require reliable stand 

exam data. When this is not available, the nearest neighbor analysis in INFORMS can be used to assess stand 

condition. FMAPlus can then be used to assess potential 

fire behavior of a treated stand. Models like FlamMap 

and FARSITE can be used to assess how fuel treatments 

will impact fire spread on a landscape scale. Models 

commonly used in fuel treatment projects are listed in 

Appendix A.

Figure 25. Cut trees can be removed from site using relatively 

simple technology such as this 

ATV and skidding arch. Photo 

credit: Wayne Shepperd.
44 USDA Forest Service RMRS-GTR-198. 2007

Other Mechanical and Combination 

(Fire + Mechanical) Techniques

Piling and Burning

As discussed earlier, a common method of removing 

or reducing surface fuel loading is moving it into piles 

that are then individually burned (fig. 26). This mostly 

occurs with logging slash that is generated from thinning operations (Brown and Davis 1973; Fuller 1991). 

Relative to a broadcast burn, the potential for an escaped 

fire is low and the prescription window is wide, as piles 

can be kept dry by covering them with plastic and burning them when environmental conditions are likely to 

prevent fire spread (fall or winter). The piles should be 

strategically placed such that fire induced damage to trees 

is minimized (Allen and others 1968). Depending on the 

amount of fuel, the average size of fuel, size of the treatment unit, and accessibility of the site, fuels can be piled 

by hand or with a machine. Use of mechanical equipment 

is generally more appropriate for large units with large 

diameter material. Hand crews are also more appropriate 

when accessibility limits use of mechanical equipment, 

either because of lack of roads or steep slopes (Jones and 

Stokes 2004; USDA Forest Service 1973; Windell and 

Bradshaw 2000).

The Flagstaff Fire Department has developed very 

specific guidelines for constructing slash piles to be 

burned in the wildland urban interface (Flagstaff Fire 

Department 2005). According to their best management 

practices guide, piles should be between 5 and 8 feet 

in height and diameter. Smaller branches and tree tops 

should be on the bottom, followed by larger branches in 

the middle of the pile and small diameter material on the 

top. Piles should be in the shape of a cone. In the wildland urban interface, hand piles can be burned any time 

of year, but larger machine piles are typically burned 

when there is some snow on the ground.

Given the heat fluxes that can occur when piles are 

burned (Massman and others 2003), care should be taken to locate piles far enough away from residual trees to 

avoid damage to foliage and roots.

Removal

Surface and ladder fuels in the form of slash can also 

be mechanically removed from a site. Merchantable 

trees can be removed from a site before removing tree 

tops and limbs via whole tree-skidding or cable yarding (Scott 1996; Windell and Bradshaw 2000). Tree tops 

and limbs can then be removed from harvested trees at 

a landing rather than on site. This material can then be 

piled and burned at the landing as described earlier, or 

chipped or bundled as biomass for other uses (fig. 27). 

This may be appropriate when burning on site is not 

feasible. If markets are available, this material can also 

be used for bioenergy or composted and used for garden mulch (Graham and others 1998; Hollenstein and 

Figure 26. Excess surface fuels can be piled and 

burned when broadcast burning presents too 

much risk. Photo credit: Wayne Shepperd.

Figure 27. Excess fuels on Boulder County land are chipped and used for heating county offices. Photo credit: Molly Hunter.
USDA Forest Service RMRS-GTR-198. 2007 45

others 2001; Jones and Stokes 2004; LeVan-Green and 

Livingston 2003; Stokes 1992). If material is to be sold 

commercially, it is generally more cost efficient to collect material at a landing (Stokes 1992).

Chipping, Mowing, and Mastication

In mowing or mastication treatments, mechanical 

equipment is used to cut surface and ladder fuels into 

small chunks or chips that are then left on site (Jones and 

Stokes 2004; USDA Forest Service 2003c; Windell and 

Bradshaw 2000). Depending on the type of equipment 

used, slash or standing small trees and shrubs can be 

targeted in mastication/mowing treatments. Generally, 

mechanical equipment is effective for material averaging 10 inches in diameter; however, some equipment 

can be used on material up to 18 inches in diameter 

(Jones and Stokes 2004). The residual material can vary 

in size depending on the equipment used. Slower moving equipment with rapidly rotating blades will result in 

smaller material (Busse and others 2005). Mastication 

and mowing can be used to prepare sites for broadcast 

burns, as the treatments result in reduced ladder fuels (Bradley and others 2003; Busse and others 2005; 

Stephens and Moghaddas 2005b). Crushing understory 

biomass involves driving over material with heavy machinery to compact understory fuels (Jones and Stokes 

2004; Windell and Bradshaw 2000). This is generally 

useful for treatment of cured slash or very brittle brush 

species, but is not effective in treating tree seedlings and 

saplings. Crushing generally results in reduced fuel bed 

depth and increased compactness.

Tools Used in Mechanical and Combination 

Treatments

Prime movers and cutting heads—Mechanical equipment used for mastication/mowing or piling of material 

involves a prime mover vehicle and a head or cutting/

moving attachment (Jones and Stokes 2004; Ryans and 

Cromier 1994). Prime movers generally include excavators, all surface vehicles, or four-wheel drive tractors. 

The prime mover is the power source and the carrier for 

the mastication head. A head can be attached directly to 

the prime mover or can be attached via an articulating 

arm or boom. Cutting heads can be classified according 

to the orientation of the main power shaft, vertical or 

horizontal, and the type of cutter, fixed or free swinging/

pivotal, containing knife blades, flails, hardened cutter 

teeth, and so forth mounted on rotating drums or disks. 

Some brush-cutting equipment is built for specific carriers while other equipment is sold as attachments for 

multi-purpose carriers. It is important to check with 

the manufacturer to ensure a given head will be appropriate for a prime mover. There are advantages and 

disadvantages of using vertical versus horizontal cutting 

heads and fixed versus free-swinging cutters for changing the fuel structure of small trees, brush, and slash. 

These trade offs should be carefully evaluated before a 

decision is made on which type of equipment is to be 

used. Windell and Bradsaw (2000) and Jones and Stokes 

(2004) provide a summary of common equipment used 

in fuel reduction treatments.

Prime movers can have rubber tires, rubber track, 

steel tracks, or can be stationary. It is important that the 

machine have enough power capability to move effectively at slow speeds while supplying adequate hydraulic 

or mechanical power to the cutting head (McKenzie 

1991; Ryans and Cromier 1994). Tracked machines are 

advantageous because they apply less ground pressure 

than wheeled machines and they can operate on steeper 

slopes (McKenzie 1991; Windell and Bradshaw 2000). 

However, excessive soil compaction does not seem to be 

a problem on many of the soil types in the Front Range 

and Southwest. Tracked machines are also generally 

more maneuverable than wheeled machines, but wheeled 

machines are generally less expensive and more productive (Windell and Bradsahw 2000).

Vertical shaft cutting heads are generally lighter, and 

thus require less energy than horizontal shaft cutting 

heads (Ryans and Cromier 1994; Windell and Bradshaw 

2000). Use of vertical shaft cutting heads requires a 

large safety zone because debris tends to be ejected in 

all directions. Thus, vertical shaft cutting heads may 

not be appropriate for use near structures (McKenzie 

1991; Windell and Bradshaw 2000). Vertical shaft cutting heads can be attached to an articulating arm on an 

excavator that allows the machine to process material 

standing higher off the ground than horizontal-shaft machines. Standing trees can be ground to stumps with little 

damage to desirable trees and vegetation. The articulating arm also minimizes travel across the site (Windell 

and Bradshaw 2000). Mulching can be improved on vertical shaft cutters by reducing the size of rock guards on 

the shaft or increasing the rotating speed (fig. 28).

Horizontal shaft cutting heads provide more mulching action than vertical shaft cutting heads but are also 

more sensitive to wear and if bladed, will require more 

frequent sharpening than heads with hardened teeth. 

Horizontal shaft cutting heads are generally attached 

to a tracked machine or articulated tractor. These can 

be used to walk over brush, small trees, and slash. In 

general, front-mounted machine attachments provide 

better operator visibility than rear-mounted attachments 

(McKenzie 1991; Ryans and Cromier 1994) (fig. 29).
46 USDA Forest Service RMRS-GTR-198. 2007

Fixed cutters are typically circular saws and discs with 

fixed teeth (Ryans and Cromier 1994). Free swinging 

cutters consist of pivoted knives mounted on a central 

disc or bar. Fixed cutters generally have less mulching capability, but improved mulching often comes at a 

cost of higher energy requirements and possibly lower 

productivity (McKenzie 1991). Fixed cutters often require frequent sharpening as the blades easily dull with 

frequent contact with rocks and soil. Damage to knives 

is less likely with free swinging cutters. Fixed cutters 

do not throw material as far as free swinging cutters 

(McKenzie 1991).

Pruning and piling equipment—Pruning, piling of 

slash, and lop and scattering of slash can also be accomplished effectively with hand crews (Jones and Stokes 

2004; USDA Forest Service 1973). Hand pruning saws 

and loppers can be used to prune the lower branches of 

trees. Managers have recommended that no more than 50 

percent of the live crown should be removed. Chainsaws 

can be used to cut material (USDA Forest Service 1973; 

Jones and Stokes 2004). Biomass can then be placed into 

piles or scattered across the site by hand. If material is 

to be burned, it is important to place piles and scattered 

material away from residual trees to avoid fuel buildup 

under crowns or near the base of tree boles. When a high 

quantity of large diameter material is on site, piling by 

hand can be difficult. In such cases, piling can be better 

accomplished with a tractor, loader, or dozer with rake 

or grapple attachments. Grapples attached to excavators 

can also be used if tree spacing limits movement of larger equipment. Considerable amounts of dirt can be piled 

with the debris with certain types of equipment, making the piles more difficult to burn (Cammack 1978). 

Less dirt tends to accumulate in piles when material is 

picked up with rakes rather 

than dragged across the 

ground.

Woody biomass and slash 

can also be fed into chippers. 

Material can be processed at 

a landing where the chips 

can be loaded into trucks 

or trailers. This is appropriate if chips are to be sold as 

garden mulch or for a bioenergy product. Alternatively, 

chips can be processed on 

site and distributed over the 

area. Whole tree chippers or 

hand fed chippers, made by 

a variety of manufacturers, 

Figure 28. Example of a vertical shaft masticator, a Quadco© 

brush cutter on a Timbco© tracked harvester. Photo credit: 

Kristen Garrison.

Figure 29. Example of a horizontal shaft masticator, a Wag Way© drum grinder. 

Photo credit: Kristen Garrison
USDA Forest Service RMRS-GTR-198. 2007 47

are generally used at landings, although some specialized equipment can be used in the woods.

Livestock Grazing and Chemical 

Treatment Techniques

Livestock grazing and chemical treatments in association with fuels reduction treatments in ponderosa pine 

forests have been used to a very limited extent in the 

Southwest, Front Range, and Black Hills. Thus, an extensive list of treatment options is not available. However, 

there has been some experimentation with these treatments to control excessive sprouting of Gambel oak, 

which can develop into a ladder fuel if left unchecked, 

particularly in the southern Rocky Mountains.

Livestock Grazing

Livestock grazing can be an important management tool for manipulating the amount and extent of 

understory woody (shrubs and small trees) and herbaceous vegetation (Archer and Smeins 1991). Low 

to moderate levels of grazing can reduce tree and 

shrub establishment on a site by promoting growth 

in grasses, which increases their ability to preempt 

resources from trees and shrubs while increasing 

biomass and continuity of fine fuels and hence, fire 

frequency (Borman 2005; Madany and West 1983; 

Rummell 1951). In contrast, higher levels of grazing 

reduce the amount of fine fuels, which decreases fire 

frequency and intensity (Bachelet and others 2000), 

but can lead to increased establishment of trees and 

shrubs (Archer and Smeins 1991).

Two studies have documented successful use of 

goats to control dominance of Gambel oak in dense 

shrub thickets in the Southwest (Davis and others 1975; 

Riggs and Urness 1989). Goats are generally better to 

use than cattle or sheep because they will preferentially browse on Gambel oak. Use of 1,300 to 1,800 goat 

days per hectare (526 to 729 per acre) in the summer 

for two seasons was successful in defoliating oak (Riggs 

and Urness 1989). Since Gambel oak has low carbohydrate reserves in June and August, this may be the best 

time to graze goats (Davis and others 1975). Generally, 

more than one grazing season is needed to successfully 

control oak sprouts (Davis and others 1975; Riggs and 

Urness 1989). Alternatively, goats can be used following another treatment such as mechanical removal, 

herbicides, or prescribed fire (Davis and others 1975). 

This is particularly useful when much of the oak foliage 

is tall and not within reach of goats. More studies on 

use of goats to control Gambel oak are needed to better 

evaluate the effectiveness of this treatment in reducing 

wildfire risk. Obviously, the technique is not appropriate 

for use on large areas, but may have applicability in situations where other options are not available.

Herbicides

Several herbicides have been tested on Gambel oak to 

control dominance in dense shrub thickets in southwestern Colorado, including Silvex (2,4,5-T and 2,4,5-TP), 

Picloram, and glyphosate and glyphosate:triclopyrpicloram combinations (Lauver and others 1989). Foliar 

application of Tordon has also been effective (Marquiss 

1973). Foliar applications are effective while soil treatments are generally not effective (Van Epps 1974). 

However, treatment results tend to be highly variable 

year to year (Harper and others 1985). Applications in 

July may be effective as this is when plants begin storage of carbohydrates and herbicides may be transported 

more easily through the plants (Kufeld 1983). More 

studies on use of herbicides to control Gambel oak are 

needed to better evaluate the effectiveness of this treatment in reducing wildfire risk. One of us (Shepperd) is 

aware of another test of the herbicide Arsenal© that effectively killed Gambel Oak in the San Juan NF in the 

1980s.

Control of invasive weeds is a more common use 

of herbicides associated with fuels treatments in Black 

Hills, Front Range, and Southwest ponderosa pine 

forests. Managers typically spot-spray herbicide on 

individual plants or populations of invasive plants associated with areas disturbed by skid trails, landings, and 

pile burn sites. Application is usually accomplished by 

backpack, ATV, or truck mounted spraying equipment 

and is sometimes done cooperatively by trained personnel from other agencies or resources in collaboration 

with the fuels treatment program.
48 USDA Forest Service RMRS-GTR-198. 2007
USDA Forest Service RMRS-GTR-198. 2007 49

The success in meeting fuel treatment objectives as well as broader resource management objectives in 

each fuel treatment depends on how well a project treatment prescription is planned and implemented. While 

reduced wildfire risk is generally the primary objective, 

well planned projects tend to consider this objective 

in a broad framework that includes a suite of resource 

management objectives in a landscape context. Well implemented projects are successful in meeting objectives 

despite several limitations that are commonly encountered. In this section, we present information that should 

be considered in the planning and implementation of any 

fuel treatment project to ensure treatment and resource 

management objectives are met. This includes discussion of factors that influence treatment effectiveness in 

reducing severe wildfire risk and the resources needed 

to complete these treatments. We also discuss common 

limitations to effectively achieving resource and fuel 

treatment objectives and present examples of how managers have successfully overcome these limitations.

Planning

Before implementation of any fuel treatment can begin, most agencies require a thorough analysis of the 

potential effects of various treatments. Laws such as 

the National Environmental Policy Act, Endangered 

Species Act, and Clean Air Act often dictate these analyses. While the requirements for planning projects vary 

by agency, at least on federal lands, managers generally 

need to consult various resource management specialists (for example, wildlife biologists, archeologists, and 

hydrologists) and solicit public comments for each proposed treatment. Thorough surveys of valued resources 

in proposed treatment areas may be needed to fully understand the potential impacts of treatments on these 

resources. These actions can help determine what type of 

treatment would be most appropriate for any given situation and how it should be scheduled and implemented. 

It can also help identify critical factors to monitor posttreatment. In many cases, it can take a year or more to 

complete this process.

Prescribed Fire

Effectiveness

As described earlier, prescribed fire is generally 

used to reduce loading of surface, ladder, and canopy 

fuels with the ultimate goal of reducing the potential 

for spread of catastrophic wildfire. Prescribed fires are 

generally effective in reducing loading of surface fuels, 

and have been shown to reduce the size, severity, and 

resultant ecological effects of wildfires (Choromasnska 

and DeLua 2001; Kallander 1969; Pollet and Omi 2002; 

Omi and others 2005; Wagle and Eakle 1979). However, 

not all prescribed fires are equally effective in reducing 

wildfire hazard. This may be because prescribed fire does 

not always result in sufficient fuel reduction. The size of 

a prescribed fire may also be a factor. While small prescribed fires (less than 100 acres) are generally easier to 

implement and carry less risk of escape, large prescribed 

fires (greater than 800 acres) are more likely to be effective in reducing the potential for severe wildfire spread 

(Finney and others 2005; Martinson and others 2003). 

Use of prescribed fires also requires sustained management as effectiveness decreases with time since fire 

(Finney and others 2005). Prescribed fires were found to 

be effective in reducing subsequent wildfire severity for 

up to 4 years in Arizona and New Mexico (Ffolliott and 

Guertin 1988; Finney and others 2005; Omi and others 

2005) and 6 years in Colorado (Omi and others 2005). 

Prescribed fires are less likely to be effective in sufficiently reducing fuel loads if they are conducted when 

fuels are too wet (Fernandes and Betelho 2003).

Prescribed fires have also been used effectively to reduce tree density. Because prescribed fire is relatively 

ineffective in reducing canopy bulk density (Agee and 

Skinner 2005; Fule and others 2002a; Sackett and others 

1996), multiple high to moderate intensity fires may be 

needed to sufficiently reduce tree density before low intensity fires can be used exclusively to maintain desired 

conditions (USDA Forest Service 2003c). Similarly, 

multiple prescribed fires or fires of high intensity may be 

needed to reduce fuel loads to levels that would significantly impact wildfire behavior (Fule and others 2002a; 

Section V:

Fuel Treatment Requirements
50 USDA Forest Service RMRS-GTR-198. 2007

Fule and others 2004; Harrington and Sackett 1990; 

Windell and Bradshaw 2000).

If reduction of shrub fuels is the objective, prescribed 

burns should be conducted with greater frequency to 

keep up with shrub sprouting (Harrington and Sackett 

1990). For Gambel oak, control burns should be conducted every other year in the summer (Harrington 

1985). Stimulation of new shrub sprouts may be desirable for wildlife forage. To stimulate shrub sprouting, 

prescribed burns generally need to be conducted in the 

dormant season when carbohydrate reserves that are 

stored in the roots should facilitate sprouting (Bock and 

Bock 1984; Harrington 1985; Sieg and Wright 1996; 

Young and Baily 1975).

Resources Needed

The personnel required to implement a prescribed 

fire is highly variable and dependent on the complexity 

of the prescribed fire, level of experience of available 

personnel, and perception of risk, among other things. 

For example, more people may be needed for prescribed 

fires that are closer to communities, in areas where fuel 

loading is particularly high, or in situations where more 

precise control of the burning process is needed to mitigate other resource needs. Internal agency policies are 

also a factor. The personnel needed to complete prescribed fires seems to be increasing, as some agencies 

now require contingency resources to be on site of the 

prescribed fire. Thus, enough resources need to be on 

hand to hold a fire should it go out of prescription. This 

will almost always include at least one engine, but the 

number often depends on the maximum area that will 

be allowed to burn. These requirements will increase the 

cost of conducting a prescribed fire, but will decrease 

the probability of fire having detrimental impacts to values at risk.

Cost of prescribed burning can be highly variable. 

Factors such as size of burn, type of equipment used, 

accessibility, and type firing pattern use all influence the 

cost of a prescribed fire. On the Gila National Forest, 

prescribed fire can cost anywhere from $25 to $200 per 

acre (Lolley and others 2006). Costs have been has high 

as $500 per acre on the Santa Fe National Forest and 

average $300 per acre on the Black Hills National Forest 

(table 5). A complete analysis of costs for various treatments in the Front Range was also recently compiled 

and is a valuable reference (Front Range Fuel Treatment 

Partnership Rountable 2006).

For many reasons, wildland fire use events tend to be 

much less expensive on a per acre basis than management ignited prescribed fires (Lolley and others 2006). 

Since wildland fire use fires tend to burn over multiple 

days or weeks, more acres are generally burned in a 

given event relative to a management ignited prescribed 

fire. As the number of acres burned increases in an event, 

Table 5. Examples of treatment implementation costs. Numbers do not reflect cost of planning fuel treatments.

Treatment Cost/acre Year Site

Prescribed firea $300 2006 Black Hills NF

Masticationa $350 2006 Black Hills NF

Prescribed fireb $75 to 150 2006 Colorado State Forest

Thinning (no utilization) + prescribed fireb $600 to 1200 2006 Colorado State Forest

Broadcast burnc $114 2004 CO Front Range

Pile burnc $132 2004 CO Front Range

Masticationc $341 2004 CO Front Range

Thinning (utilization)c $364 2004 CO Front Range

Thinning (no utilization)c $654 2004 CO Front Range

Broadcast burnd $100 2003 San Isabel NF

Masticationd $250 2003 San Isabel NF

Broadcast burne $450 to 500 2006 Santa Fe NF

WFUf $25 2004 Gila NF

Broadcast burnf $25 to 100 2004 Gila NF

Thinningf $200 to 500 2004 Gila NF

a

 Interview with Gwen Lipp, 2006

b

 Interview with Christy Berggren and Andi Perry

c

 Front Range Fuel Treatment Partnership 2006

d

 USDA Forest Service 2003a

e

 Interview with Lawrence Garcia, David Isackson, and Tom Johnston, 2006

f

 Lolley and others 2006
USDA Forest Service RMRS-GTR-198. 2007 51

the cost per acre generally decreases as the same level of 

resources are used in each case (Wood 1988). Wildland 

fire use fires also do not generally require construction 

of fuel breaks, which can be costly.

Wildland fire use events require an upfront planning 

process in the fire management plan, but not a separate and lengthy environmental analysis for each event 

(USDA and USDI 2005). This would be impossible 

given that one cannot predict when and where wildland 

fire use opportunities will present themselves. This more 

streamlined planning process, relative to management 

ignited prescribed fires, also reduces the overall cost of 

wildland fire use events.

Thinning

Effectiveness

Thinning treatments have been tested in wildfire scenarios in ponderosa pine forests throughout the west 

and have been shown to be effective in mitigating fire 

severity (Cram and others 2006; Martinson and Omi 

2003; Martinson and others 2003; Pollet and Omi 2002). 

However, different thinning treatments are not equally 

effective in reducing the potential for wildfire spread 

and intensity. For example, in treatments where only a 

few small trees are removed, the potential for crown fire 

spread may not be significantly reduced (Fule and others 

2006). Treatments that focus on removal of smaller trees 

will generally be more effective than treatments that focus 

on overstory removal (Arno and Fiedler 2005; Graham 

and others 1999; Martinson and Omi 2003; Scott 1998), 

although specific effects are strongly dependent upon 

the number and distribution of tree sizes present before 

treatment (Shepperd and others 2005). However, some 

large trees may need to be removed to effectively reduce 

the potential for crown fire spread (Scott 1998; Arno and 

Fiedler 2005). Many studies (for example, Callaway and 

Davis 1993; Cram and others 2006; Odion and others 

2004) have found that patterns of fire effects (severity) 

and post-fire vegetation recovery may be predisposed by 

topographical position and pre-fire vegetation structure. 

Stand density index, the number of large trees, and slope 

were the variables most closely associated with low and 

moderate burn severity under the severe weather conditions during a large, contemporary wildfire in Black 

Hills ponderosa pine forests (Lentile and others 2006). 

Although many stands were thinned, sapling and small 

tree density remained high and stands with low numbers 

of large trees on gentle slopes were most likely to burn at 

low or moderate burn severity. High density stands with 

either many large or small trees, in other words, with 

high canopy bulk density or fuel ladders, were more 

likely to burn severely (Lentile and others 2006).

Thinning operations can often dramatically increase 

surface fuel loading in the form of tree tops and limbs 

or slash and are generally not effective in reducing the 

potential for severe fire spread if the resultant slash is 

not subsequently treated (Graham and others 1999; 

Martinson and others 2003; Peterson and others 2005). 

If residual slash burns under hot and dry conditions, it 

can result in very extreme fire behavior (Martinson and 

others 2003). It is therefore necessary to remove or alter 

the structure of these surface fuels using prescribed fire 

or mechanical treatments in conjunction with thinning.

Resources Needed

The resources needed to complete a thinning operation 

depend on the treatment area size, the size and amount 

of treated material, and the accessibility and topography of the site. For example, on smaller treatment areas, 

hand crews using chainsaws or small, maneuverable 

equipment of low horsepower are generally sufficient. 

On larger treatment areas, larger mechanical equipment 

may be needed as they have higher production rates. 

The size of the material being removed can also dictate 

what type of equipment is needed (see previous Tools 

section). Mechanical equipment may be needed when 

there is a great deal of material that needs to be removed, 

again because of higher production rates. Use of mechanical equipment becomes problematic in areas that 

are inaccessible or have complex terrain. In such cases, 

hand crews may be needed. Alternatively, mechanical 

equipment specially made for complex terrain may be 

used (see previous Tools section).

Costs for thinning operations can be highly variable. Thinning operations in ponderosa pine forests on 

the Gila National Forest cost between $200 and $500 

per acre (Lolley and others 2006). Treatments have cost 

up to $1,000 per acre on the Santa Fe National Forest 

and up to $1,200 per acre for projects managed by the 

Colorado State Forest. Treatments in the Black Hills 

National Forest on average cost around $350 per acre 

(table 5).

Other Mechanical and Combination 

Treatments

Effectiveness

One of the more common ways to dispose of excess 

surface fuel is to move the material into piles constructed 

by hand or machine. These piles are then burned under 
52 USDA Forest Service RMRS-GTR-198. 2007

relatively benign conditions. If trees are to be used commercially, the unusable portions of the tree (for example, 

tops, limbs) can be cut after the tree has been removed 

from the site, a process called whole tree removal. Both 

methods are effective in reducing the loading of slash.

In other methods, larger surface and ladder fuels are 

processed with chippers or masticators. The resultant 

material is then spread out over the site. This process is 

relatively new and the effectiveness of these methods in 

reducing fire risk has not been adequately tested. Such 

treatments have been shown to reduce the height of ladder fuels and thus the potential for initiation of torching 

and crowning fire behavior (Jerman and others 2004). 

However, others have found that chipped and masticated 

fuels in particular can burn completely with relatively 

high intensity during prescribed fires and this has been 

shown to have adverse effects on soil properties and tree 

mortality (Bradley and others 2003; Busse and others 

2005; Stephens and Moghaddas 2005b). Concentrations 

of chips on the ground have also been found to dramatically alter the soil environment, even if they are not 

burned (Massman and others 2006) (fig. 30).

Fuels that are scattered or crushed have not been shown 

to burn with the same effect, perhaps because these fuels generally do not burn completely during a prescribed 

fire (Jerman and others 2004). Prescott National Forest 

personnel have found that burning masticated fuels with 

very high fuel moisture contents and high relative humidity (35 percent) results in rather complete consumption 

of surface fuels without detrimental impacts on soils. 

These treatments were conducted in chaparral fuels, 

and thus it is unclear if similar fuel consumption would 

be achieved in less volatile fuels. However, Shepperd 

(2004) reported that burning heavy surface fuels on saturated soils had no apparent detrimental effect on aspen 

roots at a low elevation mixed conifer site in southern 

Colorado that contained ponderosa pine. More research 

is needed to fully understand the impacts of mastication 

treatments on the potential for severe wildfire spread 

and other resources or ecological processes.

Resources Needed

Surface fuels can be treated using a variety of tools, 

from fire to mechanical treatments. Both hand crews and 

mechanical equipment can be used to cut ladder fuels 

such as large shrubs and small trees. Both can also be 

used to place material into piles that can later be burned. 

The necessity of using hand crews versus mechanical 

equipment will depend on the size of the treatment area 

and the type and amount of material being removed. 

In addition, there is a wide range of useful equipment 

that varies in power capacity and other features (see 

previous Tools section). More powerful mechanical 

equipment may be needed when a lot of material over 

a large area needs to be treated. Specialized equipment 

may be needed on steeper terrain. The type of equipment used will also depend on the desired condition of 

fuels after treatment. For example, a chipper would be 

preferred if smaller material, a neater appearance, and 

low-intensity burning conditions were wanted while a 

hydro-axe would suffice if larger material could be left 

on-site. Costs of combined treatments may vary widely 

as well. Mastication treatments can range from $100 to 

$1,000 per acre and pile burning can range from $100 to 

$750 per acre (USDA Forest Service 2003c) (table 5). 

Chipping is generally more expensive than mastication 

or pile burning. Programs such as My Fuel Treatment 

Planner (MyFTP) can be used to assess and compare the 

costs of various treatments (Fight and Barbour 2005).

Livestock Grazing and Chemical 

Treatments

Effectiveness

The use of livestock grazing and chemical treatments 

for fuels reduction has been limited in ponderosa pine 

systems, thus it is difficult to fully evaluate the effectiveness of these treatments along with the resource needs and 

limitations. There seems to be some potential to reduce 

fuel loading in dense thickets of Gambel oak. Gambel 

oak grows in the understory of ponderosa pine forests 

in Arizona, New Mexico, and Colorado. This species is 

very important as browse and habitat for a variety of 

wildlife species (Reynolds and others 1996). However, 

Figure 30. Compact layers of wood chips may have adverse effects on the soil environment. Wood chip layers (2 to 3 inches in depth) did not appear to inhibit seedling establishment 

of ponderosa pine in Boulder County. Photo credit: Molly 

Hunter.
USDA Forest Service RMRS-GTR-198. 2007 53

after decades of fire exclusion, stands of Gambel oak can 

become impenetrable to wildlife, produce poor browse 

quality, prevent regeneration of ponderosa pine trees, and 

develop into potentially threatening ladder fuels (Harper 

and others 1985). Thus, in some regions, managers have 

attempted to control the density and height of Gambel 

oak stands using herds of goats and herbicides to control 

dense thickets of Gambel oak, but such treatments have 

been limited and have not been sufficiently evaluated to 

determine their effectiveness in reducing the potential 

for severe fire spread and their effects on other resources 

or processes.

Limitations and Examples of 

Overcoming Them

Access and Topography

Mechanical equipment is more restricted by access 

and terrain than are hand crews. Use of mechanical 

equipment is generally not feasible on slopes greater than 

35 percent (Fight and others 1999). Some machines can 

be used on steeper slopes, but such machines generally 

require greater capital investment that can only be recuperated if sustained commercial products are obtained 

from treatments (Fight and others 1999; Fight and others 2003). Mechanical treatments are also restricted by 

access and cannot be used on isolated sites surrounded 

by other ownerships unless owners agree to let equipment cross their land. Costs of treatments increase as 

distance to roads increases, yet constructing new roads 

to facilitate mechanical fuel treatments may have detrimental effects on other ecological resources (DellaSalla 

and Frost 2001; Hartsough and others 1998; Trombulak 

and Frissell 2000) and will require extensive study in 

some jurisdictions.

Use of prescribed fire is less restricted by access and 

topography and thus may be more feasible than use of 

mechanical treatments in certain situations. However, it 

can be more difficult to construct fuel breaks in inaccessible terrain, and steep and rugged topography can 

make conditions unsafe for firefighters. Despite the 

need, implementation of fuel treatments is not an option 

in certain areas because of access and topography.

Allowing wildfires to burn and reduce fuel loads may 

be a viable option in such cases. These limitations necessitate development of strategies to determine where 

to implement fuel treatments across a landscape while 

maximizing the benefits gained from such treatments. An 

example of this process is taking place in management 

units such as the Prescott and Coconino National Forests 

in northern Arizona. Intensive mechanical treatments, 

often in combination with prescribed fire, are being 

focused around values at risk, including power lines, 

municipal water sources, and communities. Access and 

topography are generally not restrictive factors around 

such infrastructure in these areas. Once these values are 

sufficiently protected from the risk of severe wildfire, 

there should be greater opportunities to use natural or 

management ignited fire to treat fuels in more remote 

areas. While use of fire alone without mechanical treatments carries some risk of extreme fire behavior, such 

events should be less threatening to communities or 

other values at risk if a buffer of intensively treated forest surrounds them. This practice has also been endorsed 

by others (Aplet and Wilmer 2003; DellaSalla and Frost 

2001).

Resource Limitations

Most management agencies have limited resources 

available for fuel treatment activities and this often restricts the number of acres that can be treated and can 

dictate the type of treatment used. Ideally, managers 

would have enough resources to treat all the acres that 

are in need of fuel reduction and to use the tools that are 

most appropriate for meeting all resource management 

objectives. In reality, managers need to derive strategies 

for maximizing benefits for natural resources given the 

capital they have because available funding will always 

be an issue.

One strategy for maximizing benefit of resources is to 

leverage funds for fuels treatments with funds allocated 

for other resources, such as wildlife habitat or timber 

management, thereby increasing the number of acres 

that are treated. For example, fuel managers on the Black 

Hills National Forest and in Custer State Park, both in 

South Dakota, coordinate efforts with their timber management staffs. This allows managers to share resources 

while meeting multiple objectives (for example, timber 

targets and fuels reduction). Managers are also able to 

partially offset the cost of treatments by producing some 

commercially viable material.

The ability to use merchantable material from 

fuel reduction treatments is often limited by availability of processing plants and consistent long-term 

markets (Hollenstein and others 2001; Le Van-Green 

and Livingston 2003; USDA Forest Service 2003c). 

The proportion of material removed that is sawlog-sized 

versus product other than logs (POL) often determines 

whether or not there is profit from restoration or fuel 

reduction treatments. In southwestern Colorado, for 

example, treatments have been profitable when a maximum of 60 percent of the material removed from a site is 

POL (Lynch 2001). Even in areas where selling timber is 
54 USDA Forest Service RMRS-GTR-198. 2007

not a viable option because of poor markets or absence 

of viable material, there may be unique opportunities 

to offset costs. For example, in Boulder County, CO, 

small diameter material harvested from county lands is 

processed as chips that are then used to heat some county-owned buildings.

While prescribed fires are generally less expensive 

than mechanical treatments on a per acre basis, the cost 

of such treatments can still be substantial. There are 

many things that can be done to minimize burning costs. 

For example, the Colorado State Forest Service minimizes costs by using local volunteer fire departments 

for their prescribed fires. This helps the volunteer fire 

departments by allowing their personnel to gain experience and advance in their training. Costs of prescribed 

fires can be highly variable depending on numerous factors. For example, larger prescribed fires generally cost 

less on a per acre basis (Cleaves and others 2000; Wood 

1988). Smaller fires can be more costly than large fires, 

even though the required crew sizes may be smaller, 

because the same level of holding equipment (for example, engines, dozers) is needed as on larger fires (Wood 

1988).

Construction of fireline also affects prescribed fire 

costs. The proportion of fireline created per area burned 

is higher for smaller fires (Wood 1988) and can significantly effect prescribed fire cost. The cost of burning 

can be reduced substantially if fireline construction is 

minimized by using natural or existing fuel breaks. This 

can include roads, trails, rivers, and snow. Managers of 

the Coconino National Forest organize prescribed fire 

units in stacked blocks so that prescribed fires conducted 

early in the season can be used as fire breaks for subsequent prescribed fires later in the season.

Distance traveled to a treatment site can substantially 

increase the cost of prescribed fire treatments as well. If 

units are far away, care should be taken to ensure that 

the prescribed fire can be completed in the fewest number of days possible to minimize travel time and costs. 

This can be achieved by increasing the size of crews, 

using aerial ignition, or burning for longer periods of 

time each day.

High Fuel Loading

Use of prescribed fire is often restricted in areas where 

fuel loading is unusually high. In such cases, if prescribed 

fire is initiated under relatively benign conditions (for 

example, high relative humidity, low temperature), then 

resulting fire behavior often does not achieve the desired 

effect in terms of reduction in tree density or loading of 

surface fuels. Conversely, if prescribed fires are initiated 

under drier and warmer conditions, there is a greater risk 

of extreme fire behavior. Such intense prescribed burns 

may have undesirable effects on watershed and ecological processes and can increase threats to firefighter and 

community safety (DellaSalla and Frost 2001; Fule and 

others 2002b; USDA Forest Service 2003c).

If high fuel loadings are present in areas adjacent 

to communities, prescribed fire may be implemented 

only after significant amounts of fuel are removed or 

rearranged mechanically (Allen and others 2002). For 

example, some managers on the Coconino National 

Forest told us they feel more comfortable using prescribed fire in or near the wildland urban interface when 

canopy cover is less than 50 percent and fuel bed depth 

is less than 1-foot conditions that can only be met by applying mechanical treatments prior to burning. The city 

of Flagstaff also conducts broadcast burns in and around 

the city after areas have been treated mechanically and 

heavy fuels have been burned in piles (Farnsworth and 

Summerfelt 2001) (fig. 31).

Use of prescribed natural fire may be appropriate in 

more remote areas with high fuel loading. For example, 

in the Gila National Forest, managers have been very 

successful in using naturally ignited fires to treat areas 

with excessively high fuel loads. This practice has been 

going on in this area since the 1970s. Several areas have 

burned in two or three fire events since the program began. Since the fires initiate with natural lightning strikes, 

they typically start during the summer monsoon season 

when relative humidity and fuel moisture is high, which 

may prevent very extreme fire behavior. Managers have 

noticed that while the initial fire is generally not very 

effective in reducing fuel loads (particularly tree density) areas that have seen multiple fires have significant 

reductions in fuel loads.

Prescribed fire has also been used in stands with high 

fuel loads in areas that are not as remote. Examples of 

this can be seen in the Black Hills National Forest, Santa 

Fe National Forest, and Bandelier National Monument 

(fig. 32). Using fire to reduce fuel loads often means accepting the possibility of some extreme fire behavior, 

such as tree torching and crowning, within the treated 

area. This process creates heterogeneity on the landscape 

that restores some of the historical diversity of ponderosa pine forests and is beneficial for wildlife habitat and 

other resource uses. Such pockets of intense prescribed 

fire can be created with individual ignitions or as part of 

a larger prescribed fire.

Prescription Windows

Prior to conducting a prescribed fire, managers need to 

define a set of objectives (for example, percent tree mortality or percent black) and fire behavior characteristics 
USDA Forest Service RMRS-GTR-198. 2007 55

(for example, flame length, rate of spread) that will allow 

fuel treatment goals to be met without severe risk of escape fire or extreme fire behavior. Managers then define 

a prescription window, or a range of values for relative 

humidity, temperature, wind, and slope that will result in 

the desired fire behavior. Managers should bear in mind 

that it can be very difficult to complete prescribed fires 

if a prescription window is very narrow, or if there are 

few days during a burning season when a prescription 

window can be met. This is particularly problematic in 

areas with high fuel loading. Narrow prescription windows can ultimately restrict the number of acres that can 

be treated in a given year. This is especially true if all 

planned projects have the same narrow prescription window. If such is the case, managers need to realistically 

assess the likelihood of completing planned projects and 

investigate other fuels treatment alternatives.

Managers have learned to overcome such obstacles 

by designing their prescription windows to be as wide as 

possible. The general approach of managers on the San 

Juan National Forest, for example, is to start with desired fire behavior (from BehavePlus output) and work 

backward to find a wide range of weather parameters 

that will produce the desired fire behavior. Another approach is to burn as many acres as possible when you 

are in prescription. For example, managers in northern 

Figure 31. The Flagstaff Fire 

Department has been 

successful in implementing prescribed fire in the 

wildland urban interface. 

Broadcast burns or burning of piles near structures is typically done 

only after a thinning 

operation. Photo credit: 

Paul Summerfelt.

Figure 32. High intensity 

prescribed fire, with 

some torching and small 

scale crowning, has 

been used to reduce tree 

density in more remote 

forested areas. Photo 

credit: Mike Battaglia.
56 USDA Forest Service RMRS-GTR-198. 2007

Arizona sometimes will burn piles concurrent with a 

broadcast burn if prescription windows are very narrow, 

or extend the burn period if prescription window conditions persist. Widening the prescription window can 

also be achieved by expanding the burning season into 

summer and winter and planning to expanding the hours 

in a day when burning is typically done. For example, 

managers with the Coconino National Forest often 

burn at night to be within their prescription. San Juan 

National Forest personnel have considered broadcast 

burning on south-facing slopes when they are snow-free 

in dry winters. Innovative thinking can result in strategies like these to help widen the prescription window. 

It is important to note however that burning in a season 

not consistent with the historical fire regime may result 

in very different fire effects. For example, certain species may be more susceptible to fire damage during the 

growing season (Harrington 1987).

Overcoming the limitations of narrow prescription 

windows requires planning. Treatments can be planned 

with flexibility so an entire treatment area does not need 

to be shut down when only a portion of it is out of prescription. In the past, managers on the Santa Fe National 

Forest have often broken up treatments into units based 

on topography. Breaking up a treatment area in this fashion decreases the likelihood that a burn will be cancelled 

because average conditions do not fit a prescription window. For example, one portion of the unit may be out 

of prescription (south aspect), yet another portion may 

be in prescription (north aspect). This approach may 

require more intensive collection of fuel moisture and 

weather data than normal, but may result in accomplishments that otherwise could not be achieved.

Another very innovative approach is currently in 

the planning process on the Coronado National Forest. 

Managers there are attempting to plan for several projects across a broad scale. Having several projects ready 

to be implemented would allow some flexibility in treating areas in a given year. If, for example, if they are 

not able to conduct a planned prescribed fire because 

prescription windows are not met, they can instead use 

available resources to implement a planned thinning 

project. Having several implementation-ready projects 

on hand allows for this flexibility. In order to accomplish 

this, they have had to expand the scope of fuel treatment 

planning from the ranger district level to the forest level 

and beyond.

Public and Agency Resistance

Both the general public and agency personnel can be 

resistant to fuel treatments for a variety of reasons. In 

some cases, prescribed fires and mechanical treatments 

have had detrimental impacts on valued resources. For 

example, the 2000 Cerro Grande fire in northern New 

Mexico was a prescribed fire that went out of prescription and resulted in the evacuation of the city of Los 

Alamos and the destruction of over 200 structures. Fires 

in the Southwest (including wildland fire use fires) have 

also necessitated the emergency removal of threatened 

fish species in effected streams. Inadvertent loss of 

property in prescribed fires has resulted in the threat of 

criminal prosecution of personnel conducting the burn. 

Even though such events are rare, their high profile and 

the attention given by the media give the public and resource managers within agencies the impression that the 

risk of detrimental effects of such treatments outweigh 

the benefits. Since comments from the public and other 

resource managers are solicited in any fuel treatment 

project, this resistance can create substantial barriers to 

implementating fuel treatments.

Managers are more successful in gaining acceptance 

for fuel treatments when they actively engage the public and agency officials during the entire fuel treatment 

or restoration process, from planning to implementation. While collaborative projects often require a lot 

of up-front investment in time, these efforts generally 

pay off by reducing overall resistance to prescribed fire 

and other fuel treatments. Ultimately, engaging multiple stakeholders forces managers to consider multiple 

resource management objectives and thus operate in a 

framework that considers sustainability of the whole 

forest system.

There are many examples of planning processes 

that have involved multiple collaborators. On the Gila 

National Forest, a landscape pre-planning process was 

designed to provide recommendations to the forest service on where to place fuel treatments. This involved 

a collaborative effort that included managers with the 

Forest Service, non-profit groups, local governments, 

environmental advocacy groups, and forest industry 

companies that use small diameter material. Another 

collaborative effort on the Coronado National Forest 

included members from agencies with adjoining land 

units, including the National Park Service, Department 

of Defense, Nature Conservancy, and Audubon Society. 

Our interviews with practitioners have shown repeatedly 

that outside resistance to proposed projects is reduced 

when multiple stakeholders have played a key role in 

planning fuel treatment activities and feel their concerns 

have been addressed.

Another important aspect of acceptance of fuel 

treatments is the level of trust that is given to those 

implementing and planning treatments. Generally, trust 

in agency officials is not given easily and often only 
USDA Forest Service RMRS-GTR-198. 2007 57

develops over time and after relationships based on 

mutual respect have been established with the public 

and other resource managers. Once trust is established, 

it is imperative to maintain it by following through 

with intended treatments, monitoring their success or 

failings, and openly sharing the results. Once trust is 

lost, it is extremely difficult to regain again. Managers 

on the San Juan National Forest invest a great deal of 

time and energy in actions that establish and maintain 

trust with the public. They take time to ensure that the 

public and other interested parties understand exactly 

what they plan to do and why they plan to do it. For 

example, prior to implementing a restoration project, 

personnel organize field trips to the proposed treatment 

area. They also bring historical photos to show what 

the area might have looked like prior to Euro-American 

settlement and discuss the consequences of the proposed change. They provide photos of treatment areas 

1, 2, and 3 years after treatment so that people have a 

sense of what the area will look like after treatment. 

This helps avoid the public perception that agency officials can not be trusted, a perception that can develop 

when there are misconceptions about what fuel treatments are supposed to accomplish.

Smoke

Depending on the region, smoke from a prescribed 

fire can be subject to regulation by various state and 

federal laws. Smoke production is a serious matter because it can affect public health, visibility for road and 

air traffic, and contribute to “bad air” days in metropolitan areas subject to EPA regulations. The public can also 

have low tolerance for smoke in their communities even 

when smoke production is within acceptable limits. Both 

of these factors can seriously limit the number of areas 

that can be burned in a season. In addition, managers 

often have to consider factors that affect smoke dispersal 

to ensure that sensitive municipalities are not adversely 

impacted by smoke.

As with other limiting factors, innovative thinking is 

key to dealing with smoke production. Recognizing this 

limitation, managers from different agencies in northern 

Arizona coordinate their burns to ensure that certain areas do not receive excessive smoke impacts in any given 

period of time. Conversely, if conditions are favorable 

for smoke dispersal, they will coordinate to accomplish 

as much burning as possible. To comply with air quality 

standards imposed by state and federal laws, in northern Arizona, managers coordinate prescribed fire plans 

on a daily basis to ensure that certain areas do not receive excessive smoke impacts in any given period of 

time. This can be challenging, especially when adjacent 

management units tend to have the same narrow prescription windows in northern Arizona. Managers have 

also been able to take advantage of local weather phenomenon to maximize smoke dispersal. For example, 

the Coconino National Forest has experimented with, 

and been successful in, implementing prescribed fires 

ahead of approaching cold fronts, which disperse smoke 

away from sensitive areas during windy periods before 

the front passes. To contain the fires, they also take advantage of colder, wetter, and calmer conditions after the 

front. This type of detailed knowledge and understanding of local weather processes and fire behavior patterns 

is gained only after years of working in a particular locale, and emphasizes the value of confident, experienced 

personnel in completing fuels treatment projects.

In some cases, it will be impossible to limit smoke 

impact from prescribed fire on communities. The public can become more accepting of smoke if they fully 

understand its necessity, and if agencies take steps to 

minimize smoke impacts on communities. For example, 

the city of Flagstaff, AZ, has been successful in increasing public acceptance of smoke through an extensive 

public outreach and education program that emphasizes the need for prescribed fire to reduce the risk of 

severe wildfire. They also take care to minimize smoke 

impacts to sensitive areas, such as schools and hospitals, and coordinate activities as discussed above to 

limit the number of smoky days. They maintain a call 

list to notify those individuals in the community that 

are particularly sensitive to smoke several days before 

they conduct a prescribed fire. They have noticed that 

when people are forewarned, there is general tolerance 

of smoke for 1 day, but after 2 or 3 days, people begin 

to complain (Farnsworth and Summerfelt 2001). Thus, 

they take several additional steps in the wildland urban 

interface to minimize the number of days impacted by 

smoke. For example, they will burn no more than 150 

piles per day no more than once a week in a neighborshed, an area they define as within a neighborhood or 

geographic area where smoke will accumulate and remain visible for at least four hours following the burn 

(Flagstaff Fire Department 2005).

Wildlife Habitat

While it is recognized that high-severity wildfire 

poses a serious threat to threatened and endangered 

species habitat, there is also some concern for the impacts of fuel treatments on these species (Ganey and 

others 1999). Thus, restrictions are often imposed on 

use of some treatments in sensitive wildlife habitat. 

For example, fuels treatment activities are restricted in 

Mexican spotted owl habitat in some national forests of 
58 USDA Forest Service RMRS-GTR-198. 2007

the Southwest. The owl is a federally threatened species 

that occurs throughout the Southwest and is a significant 

focus of management efforts in the region. These owls 

typically breed from March to August in mixed conifer 

forests and pine-oak forests. Because they are thought 

to have a low tolerance for heat, they generally prefer 

closed canopy forests with old-growth characteristics 

such as large trees, snags, and down woody material. The 

primary threats to the long-term survival of the species 

include timber harvest, particularly even-aged harvest 

methods, and catastrophic wildfire. Yet, the objectives 

of thinning to reduce wildfire hazard need to be balanced 

against the need to maintain critical owl habitat, which 

consists of rather dense forests stands. Guidelines developed in the Mexican spotted owl recovery plan (USDI 

Fish and Wildlife Service 1995) are aimed at maintaining Mexican spotted owl habitat and protecting it from 

catastrophic wildfire. Since Mexican spotted owls generally do not nest in pure ponderosa pine stands, the 

restrictions on fuel treatments in owl habitat generally 

apply only to pine forests that have a Gambel oak component, or those in steep canyons (slope >40 percent). 

The guidelines suggest restricting thinning operations in 

100 acre areas surrounding identified nest sites. In addition, thinning should be limited to trees that are less 

than 9 inches dbh and restricted to the non-breeding season (Sept. to Feb.) in protected activity centers (PACs) 

that are 600 acre areas surrounding designated nest sites. 

Pine forests with a significant Gambel oak component 

are considered “restricted habitat” where thinning should 

be limited to trees less than 24 inches dbh and removal 

of trees between 18 inches and 24 inches dbh should be 

minimal. It is also recommended that large oak trees be 

protected and that canopy cover should be at least 40 

percent. Similar restrictions on fuel treatments are recommended in northern goshawk habitat (Reynolds and 

others 1992) as well. Some fire managers have found 

that these restrictions limit opportunities to reduce wildfire risk at landscape scales.

Management strategies that successfully achieve 

multiple management objectives are often accomplished 

only when different resource managers work closely 

together and recognize the need to balance these objectives. One example comes from the Gila National Forest 

in New Mexico. Here, during wildland fire use events, 

fire managers constantly consult with wildlife biologists to ensure that the fire not only reduces fuel loads 

but also benefits or does not adversely impact wildlife 

habitat. This exchange has allowed the development of 

strategies to allow fire to move into Mexican spotted owl 

habitat. But achieving desired results may require altering fire behavior to ensure that important owl habitat 

components (for example, large snags, logs, oaks) are 

protected. By working together, fire managers and wildlife biologists developed fuels treatments that would be 

acceptable from both the perspective of fuels reduction 

and wildlife habitat improvement.

Wildland Urban Interface

The risk of escaped prescribed fire threatening structures is higher when burning in the wildland urban 

interface (WUI). This often makes managers uncomfortable conducting prescribed burns in these areas. In 

addition, many managers we interviewed suggested that 

the public is generally unhappy with the increased risk 

and exposure to smoke. However, many of these areas 

are in need of treatment in order to adequately protect 

communities from the threat of wildfire. Mechanical 

treatment is an option, but is expensive and cannot meet 

management objectives in all cases.

Management agencies around Flagstaff, AZ, have 

been very successful in conducting broadcast and pile 

burns near structures (Gatewood and Summerfelt 2005). 

Almost all treatments require some mechanical treatment prior to burning. A typical treatment in ponderosa 

pine forests near Flagstaff includes a thinning operation, 

followed by pile burning, and then broadcast burning, 

all completed within a year. The mechanical treatments 

reduce canopy and ladder fuels and alter potential fire 

behavior during subsequent prescribed burning. The 

managers’ perception of risk is low because their experience igniting fire under such conditions is extensive. 

As further insurance, they use more personnel on these 

urban projects than they would to treat areas farther 

away from structures. An extensive outreach and public 

education program has been key in gaining public support for these mechanical fuel treatments and prescribed 

burns in the Flagstaff wildland urban interface. In fact, 

agencies managing neighboring public lands (for example, the Forest Service) have likely benefited from these 

efforts as well.

Cross-agency Issues and Collaboration

Wildfires occur on landscape scales and do not obey 

jurisdictional boundaries. In order to be most effective, 

managers therefore need to derive strategies that reduce 

wildfire risk across landownership boundaries. Yet, there 

are often no incentives in place for working outside 

one’s management unit. Collaboration among adjacent 

landowners can greatly increase the effectiveness of 

fuel treatments across landscapes. Collaboration can 

allow partners to share resources (for example, equipment, personnel, money). Collaboration can also lead to 
USDA Forest Service RMRS-GTR-198. 2007 59

greater effectiveness of fuel treatments as strategies for 

mitigating fire spread patters are developed at more appropriate scales (in other words, landscapes).

We encountered several examples of managers successfully working across jurisdictional boundaries to 

more effectively reduce wildfire hazard. For example, 

the Gila National Forest allowed a wildland fire use 

event to spread onto adjacent private land with the support of the landowner to reduce surface fuels. The city 

of Flagstaff, AZ, will also conduct prescribed fires on 

private land with the landowner’s cooperation to reduce 

surface fuel loading. Because managers facilitated treatments closer to structures, both of these examples did 

much more to protect structures from wildfire than if 

they had occurred exclusively on federal or city land. 

The sharing of resources essentially provided greater leverage for implementing fuel treatment projects.

A similar process is occurring on a much broader scale 

on the Coronado National Forest and surrounding lands 

in southern Arizona where future fuel treatments across 

the landscape are being planned. Rather than complete 

the process in isolation, the Forest has invited managers from adjacent landowners to the table. This includes 

managers from the Nature Conservancy, Department of 

Defense, Audubon Society, and National Park Service. 

Their joint environmental analysis will cover all 

jurisdictions and allow all agencies to use the information in their own planning process. Thus, strategies for 

fuel treatment placement can be developed across jurisdictional boundaries to more effectively reduce wildfire 

hazard on a landscape scale.

A stellar example of interagency collaboration in the 

Front Range would be the Front Range Fuels Treatment 

Partnership, comprising a collation of federal, state, and 

local agencies working with private landowners, conservation organizations, and other stakeholders to reduce 

wildfire risk. The partnership has sponsored workshops, 

compiled data on forest condition and treatment techniques, needs, and costs (Front Range Fuel Treatment 

Partnership Roundtable 2006), and has served as clearinghouse to educate stakeholders on fuels treatment issues.

Coordinating fuel treatments across agency boundaries through efforts like these will maximize benefits 

gained in reducing wildfire risk and improve ecological 

integrity across landscapes, regardless of ownership. If 

the collaborative effort is extended to sharing resources 

during implementation, further savings will result. This 

could include extending fuel treatment contracts across 

jurisdictional boundaries, or conducting joint prescribed 

burns using personnel and equipment from cooperating 

agencies.
60 USDA Forest Service RMRS-GTR-198. 2007
USDA Forest Service RMRS-GTR-198. 2007 61

While the overall outcome of fuel or restoration 

treatments may be beneficial in terms of reducing wildfire hazard and improving ecosystem health, 

unintended and undesirable effects, such as introduction of invasive species or excessive tree mortality can 

also occur. However, measures can be taken to ensure 

undesirable effects do not materialize or to mitigate unintended effects should they occur. In this section, we 

review several unintended outcomes of fuel and restoration treatments and present some successful measures 

taken to mitigate these effects.

Monitoring of treatment effects is vital to ensure 

that restoration and fuel reduction treatments have the 

intended effect. When undesirable effects do occur, 

the monitoring data allows documentation of the effect and modification of treatment prescriptions so the 

undesirable effect does not occur in future treatments. 

Monitoring of treatment effects should be an integral 

part of any restoration or fuel reduction treatment and 

should include post-treatment recovery as well as evaluation of direct treatment objectives. Despite this need, 

it is not uncommon for managers to neglect monitoring 

because of operational time and resource constraints. Yet 

in many cases, sufficient information can be gained from 

simple protocols that require relatively little investment 

in time and resources.

Undesirable Impacts of Fuel 

Treatments

Tree Mortality

Protection of large and old growth trees and those with 

other desirable characteristics is often a priority of restoration treatments because such trees provide important 

ecosystem amenities including wildlife habitat, opportunities for large snag recruitment, greater genetic diversity, 

retention of cultural artifacts, and enhanced aesthetics. 

Under certain conditions, smoldering duff can damage 

tree roots and ultimately cause high levels of mortality of 

old growth trees (Graham and others 2004; Lindenmuth 

1960; Sackett and others 1996). Burning stands with high 

loading of surface fuels can also cause excessive tree 

scorch that can result in tree mortality (Harrington 1987; 

Jerman and others 2004; Swezy and Agee 1991; Wienk 

and others 2004; Wyant and others 1986). High levels of 

tree scorch can also leave trees more susceptible to bark 

beetle attack (Wallin and others 2003). Use of prescribed 

fire can be tenuous when there is high density of saplings. Under safe burning conditions, it is often difficult 

to achieve fire behavior hot enough to kill tree seedlings 

and saplings under dense forest canopies and thus meet 

treatment objectives (Agee and Skinner 2005; Sackett 

and others 1996). However, burning under more extreme 

conditions can lead to undesirable ecological effects. If 

smaller trees ignite, they can act as ladder fuels, carrying fire into the canopy of larger trees. Tree mortality is 

not limited to prescribed fire treatments alone. Undesired 

mortality and damage to residual trees can also occur during mechanical treatments (fig. 33). Large equipment can 

knock over trees and damage roots, bark, and branches to 

the point of causing tree mortality.

Section VI:

Fuel Treatment Impacts, Mitigation, and 

Monitoring

Figure 33. Care should be taken to limit damage to residual 

trees when maneuvering mechanical equipment through 

forests. Photo credit: Molly Hunter.
62 USDA Forest Service RMRS-GTR-198. 2007

Non-native Species

Non-native species are often adapted to disturbed 

environments with increased availability of resources 

such as light, nitrogen, and water (Hobbs and Huenneke 

1992). Since fuel treatments constitute a disturbance, 

they can also encourage establishment of invasive species that may ultimately have negative consequences to 

native species and biodiversity (Mack and others 2000). 

Cover of non-native plants has been found to increase 

following prescribed fire and mechanical treatments 

in ponderosa pine forests (Crawford and others 2001; 

Griffis and others 2001; Hunter and others 2006; Keeley 

and others 2003; Metlen and Fiedler 2006) (fig. 4). If 

disturbance intensity is high, non-native plants do seem 

to be even more likely to establish and spread. For example, non-native plants have been found to establish 

following high intensity wildfires (Crawford and others 2001; Griffis and others 2001; Hunter and others 

2006; Keeley and others 2003) and following particularly aggressive mechanical treatments where a great 

deal of the existing basal area is removed (Abella and 

Covington 2004; Fule and others 2005). Establishment 

of non-native species is also a function of the number of 

available propagules, or seeds, of non-native species at a 

site. Areas with a long history of disturbance have been 

reported to have more non-native species stored in the 

seedbank than in more pristine areas (Korb and others 

2005). This may explain why non-native species have 

not been found following wildfires in more remote areas 

in northern Arizona (Laughlin and others 2004, 2005). 

Fuel treatments also carry the risk of transporting seeds 

of non-native species attached to mechanical equipment 

or people to a site.

Air Quality

Smoke produced from prescribed fires is problematic 

because it can pose threats to human health and impair 

visibility and thus, is regulated under state and federal 

laws. In addition, the public’s negative reaction to smoke 

can threaten prescribed fire programs. When fuels burn 

efficiently, the smoke is composed mostly of carbon dioxide and water. While these are greenhouse gasses, 

they are not considered pollutants and are not regulated 

as such. Fuels burn efficiently when most of the fuel is 

combusted in the flaming stage (DeBano and others 1998; 

Mahaffey and Miller 1994). When fuels are combusted 

during a smoldering fire, they burn inefficiently, more 

smoke is produced, and other pollutants, such as particulates, carbon monoxide, and nitrogen and sulfur oxides, 

are released with the smoke. These pollutants are often 

subject to regulation under federal and state laws.

Aesthetics

There are several aspects of prescribed fire and mechanical fuel treatments that should be considered from 

an aesthetics perspective. This is particularly important 

for treatment areas that are readily visible by the public. Public acceptance of fuel treatment programs is vital 

for long-term support of these programs and is often a 

function of the perceived aesthetics (Winter and others 

2002). Managers with the Flagstaff Fire Department have 

noticed that the public tends not to support prescribed 

fire efforts when they result in excessive tree scorch or 

mortality, particularly of large trees. Many managers 

have found that the public does not like the way treated 

areas look immediately after prescribed fires, but find 

the aesthetics acceptable 1 or 2 years later. Managers of 

the Colorado State Forest have noticed that residual tree 

damage from mechanical equipment is also a factor that 

can impact the public’s perception of aesthetics. Freshly 

shredded trees, scattered debris, and disturbed soil also 

affect aesthetics in mechanically treated areas, especially when large volumes of material remain (fig. 34).

Wildlife Habitat

Prescribed fire and mechanical treatments can have 

negative impacts on many important components of wildlife habitat, such as snags, downed logs, and old growth 

or large trees (Horton and Mann 1988; Randall-Parker 

and Miller 2002). Snags are particularly important for 

cavity nesting birds and bats. Downed logs provide habitat for small mammals, reptiles, amphibians, and insects. 

Large trees are used by a variety of wildlife species for 

nesting, feeding, foraging, and roosting. Prescribed fires 

tend to consume snags and downed logs and can cause 

mortality of large trees through damage to fine roots. 

While some new snags can be recruited from killed trees 

and downed logs can result from fallen snags, the gain in 

new snags and downed logs generally does not offset the 

loss from prescribed burning (Randall-Parker and Miller 

2002). This is particularly true for large snags (Horton 

and Mann 1988). The impacts of multiple prescribed 

fires on snags and downed logs are not well understood. 

However, Holden and others (2006) found that even after multiple burns, snag density was within the range 

adopted by the U.S. Forest Service as necessary to maintain viable populations of cavity nesting birds.

While control of dense thickets of Gambel oak is 

sometimes desirable in ponderosa pine forests (see 

Livestock Grazing and Chemical Treatment section), 

large and isolated Gambel oak trees provide very important wildlife habitat in ponderosa pine forests of the 

Southwest (Harper and others 1985). Bird diversity tends 
USDA Forest Service RMRS-GTR-198. 2007 63

to be higher in ponderosa pine forests that have some 

Gambel oak component (Rosenstock 1998), and small 

mammals tend to prefer large Gambel oaks (Chambers 

2002). There is some indication that prescribed burning may increase mortality of large and old Gambel oak 

trees (Randall-Parker and Miller 2002).

Wildlife species found throughout ponderosa pine 

forests can be adapted to a wide variety of forest conditions, from openings to relatively dense forest stands. 

For example, while many ungulates prefer open stands 

or small openings for feeding, they also need more dense 

stands for protective and thermal cover (Ffolliott 1997). 

It is important to maintain a variety of stand structures 

and spatial distributions across the landscape to maintain 

sufficient habitat for the wide range of species in these 

forests. When uniform treatment prescriptions are used, 

there is danger in creating a homogenous landscape in 

which important habitat for many species is lost.

Cultural Resources

Preservation of prehistoric and historical sites and 

artifacts is important for understanding past societies 

and our cultural heritage. Such sites and resources are 

prominent in western landscapes. Prehistoric cultural 

resources include artifacts, ceremonial or residential 

sites, and rock art panels including pictographs and 

petroglyphs. Historical resources include old cabins, homesteads, logging camps, battlegrounds, trails, 

mining claims, and artifacts from such sites (Hanes 

1994). Prescribed fire and mechanical fuel treatment 

activities have the potential to damage these resources 

in a variety of ways. Cultural resources can be directly 

scorched, altered, or consumed by prescribed fire and 

heavy equipment. The potential for damage depends 

on the type of artifact material, whether it is above or 

below ground, the intensity of a fire, or the type of mechanical treatment. For example, organic materials have 

much less capacity to retain heat than stone or ceramic 

materials. Stone is subject to damage at temperatures 

above 700° F, while ceramic is subject to damage at 

temperatures above 925° F (Hanes 1994). Pictographs 

are especially vulnerable to damage from prescribed 

fire. However, prescribed fire is not likely to reach temperatures that would result in damage to artifacts that are 

buried below the surface. In general, higher fire intensity will increase the potential for damage to cultural and 

historical resources. Mechanical treatment activities and 

equipment that does not disturb or compact the soil will 

have minimal effect on artifacts compared to tracked vehicles, bulldozers, fire line plows, and so forth.

Accurate dating of prehistoric sites and artifacts 

can also be compromised by prescribed fire. For example, carbon dating of charcoal remains is often done 

to determine the approximate age of prehistoric sites. 

However, this process can be compromised if the charcoal is contaminated with ash and charcoal from more 

recent fires. Pollen preserved in prehistoric sites can be 

Figure 34. Scattered debris 

left after a thinning operation is generally not considered aesthetically pleasing 

to the public. Photo credit: 

Deb Tinker.
64 USDA Forest Service RMRS-GTR-198. 2007

used in paleoenvironmental and dietary studies. Pollen 

is generally destroyed when exposed to temperatures 

above 600° F. Similarly, dating of pottery fragments, 

obsidian, and other materials becomes highly inaccurate if these materials are subject to intense heat (Hanes 

1994). Both prescribed fire and mechanical treatments 

can destroy valuable tree ring records of past climate, 

fires, insect outbreaks, and other disturbances. This occurs most often when sound stumps, logs, and snags are 

burned or destroyed. For example, the 2002 Hayman 

Fire in Colorado destroyed nearly all dead wood that 

was sampled to develop fire history chronologies presented in Brown and others (1999). Evidence of early 

fires no longer exists in the severely burned portion 

of the Hayman Fire where all surface fuels were consumed.

Soil Resources

When heavy equipment drives over the soil surface, it 

may compact or physically displace soil. Increased soil 

compaction can make it harder for plants to extract water 

and nutrients from the soil and thus decrease the productivity of a site (Poff 1996). This effect is dependent upon 

the number and type of vehicle passes and can last years 

to decades (Shepperd 1993). However, soil compaction 

is not a serious problem on all soil types. For example, 

soils containing high levels of organic matter, surface 

rock fragments, and sand or clay content are generally 

less susceptible to compaction (Greacean and Sands 

1980; Lull 1959; Poff 1996). Displaced soil also has 

long-term consequences for site productivity. Displaced 

soil can ultimately be deposited in lakes or streams and 

impair water quality. Since scarified seedbeds favor natural ponderosa pine seedling establishment (Shepperd 

and others 2006), excessive soil disturbance in fuels 

treatment areas can result in quicker re-establishment of 

ladder fuels.

Mastication, chipping, and mowing all result in large 

increases in woody material on the soil surface. This increase in woody biomass has the potential to impact a 

variety of ecological attributes. For example, the availability of nitrogen in the system may initially decrease 

as nitrogen is tied up in decomposing organisms and 

a subsequent increase in nutrient availability once the 

material is completely decomposed (Resh and others 

2005). However, if the layer of material is excessively 

thick, decomposition may be slow and nutrients may 

be tied up for some time (Graham and others 2004). 

This material often acts as mulch, resulting in increases in soil moisture and decreases in daily temperature 

fluctuations. It may also prevent establishment of tree 

seedlings and understory vegetation, particularly if 

material is left in a thick layer. There is some evidence 

to suggest that the wood material provides habitat for 

insects and pathogens that may then impact standing 

trees.

Often, masticated fuels are subsequently burned to increase the rate of decomposition. There is some concern 

that burning high loadings of masticated fuels can result in high fire intensity and thus, adverse fire effects on 

soils and vegetation. Burning thick layers of masticated 

fuels often results in large heat pulses to the soil that 

can potentially kill soil organisms, seeds, and plant roots 

(Busse and others 2005). Similar effects can be seen under burned slash piles (Korb and others 2004; Massaman 

and others 2003). The resultant conditions may provide 

ideal opportunities for establishment of invasive species 

(Korb and others 2004; Wolfson and others 2005). In 

addition, there is some concern that burning masticated 

material would smolder and create smoke management 

problems.

Insect and Disease Outbreaks

Several studies have been conducted on how fire affects the risk and hazard of insect infestations and how 

insects influence the probability of fire ignition, spread, 

and severity (Billings and others 2004; Cunningham 

and others 2005; Mathew 2003; Moretti and Barbalat 

2004). Some of these studies have examined the impacts of fuels treatments, especially prescribed fires 

(Boyle and others 2004; Sullivan and others 2003). 

These studies have shown that fire can injure or kill 

insects directly, cause them to leave burning areas, 

or attract them (Evans 1971). Different insect species 

respond differently to fire. Huff and Smith (2000) list 

six responses of animal communities to fire: invade, 

exploit, resist, endure, avoid, and vacillate. These categories are applicable to insects as well. Some insects 

are vulnerable only at certain stages of their life cycle. 

For example, bark beetles can be protected from fire 

and many other threats while feeding under bark. Some 

insects live for periods of their life, or even their entire life, underground where their survival during a fire 

depends on the fire severity. Many insects can flee an 

approaching fire. Others are attracted to the heat, smoke, 

or carbon dioxide emitted by a fire. Understanding 

these behavioral responses offers a core for developing fire management options aimed at reducing fire risk 

and hazard by managing insect populations or managing the probability of insect infestation.
USDA Forest Service RMRS-GTR-198. 2007 65

Mitigation of Undesirable Fuel 

Treatment Impacts

Tree Mortality

Some researchers have recommended mechanically 

removing duff around the base of old growth trees before 

prescribed fire is initiated (Covington and others 1997). 

While such treatments have been successful in reducing tree mortality, many managers find this practice very 

labor intensive and too expensive given the resources 

they have to complete projects. Thus, this practice may 

not be feasible in all situations. Others have been able 

to achieve appropriate mortality levels without duff removal by conducting prescribed fires under conditions 

that promote low fire intensity (for example, high relatively humidity and low air temperature) (Bastain 2001; 

Davis and others 1968; Kaufmann and Covington 2001; 

Swezy and Agee 1991). However, such fires may not 

be effective in reducing surface fuel loadings to levels 

sufficient for reducing wildfire hazard. Thus, multiple 

prescribed fires may be needed. Season of burning can 

also be taken into account, as trees are often more susceptible to the stress of fire during the growing season 

(spring and summer) (Harrington 1987).

Even when density of saplings is high, there seems to 

be some potential for use of high intensity fire exhibiting 

some torching to reduce tree density. This may also pose 

a threat to mortality of larger and desirable trees, especially if torching of smaller trees occurs and increases 

the potential for fire to spread into the canopies of larger 

trees. Reintroduction of fire may be possible only after 

some of the smaller trees have been mechanically removed (Covington and others 1997; Fule and others 

2001; Graham and others 2004; Wallin and others 2004). 

Alternatively, it may be used under conditions that promote a fire that mainly affects smaller trees through 

cambial damage or some scorching of tree canopy, while 

posing little impact on larger trees. Burning under such 

moderate conditions may not be sufficient in killing 

smaller trees and reducing stand density as many trees 

can survive these burning conditions. Instead, multiple 

low intensity prescribed fires may be needed to successfully kill small trees and reduce tree density without 

harming overstory trees (Fule and others 2002a).

Non-native Plants

Spread of non-native plants can be handled by taking 

measures to limit seed dispersal and establishment, or by 

eliminating populations of non-natives before they establish and spread throughout the treatment area. A very 

effective pre-emptive measure is to limit the degree to 

which people and mechanical equipment disperse seeds 

in a site. For example, many management agencies 

require that equipment be washed to remove seeds before entering a treatment unit. On the Prescott National 

Forest, managers take further measures to ensure that 

seed spread by humans will be minimal by avoiding 

obvious non-native plant populations when placing 

landings and fuel breaks or holding personnel briefings.

Spread of non-native plants following fuel treatments 

can be expected if seeds are already on site. To mitigate 

these potential impacts, individual non-native plants 

should be quickly controlled before populations spread 

and reach uncontrollable levels. Managers in northern 

Arizona have successfully controlled for non-native 

species in slash pile scars by amending them with arbuscular mycorrhizal fungi and seeds from native species 

(Korb and others 2004). In Custer State Park, SD, large 

machine pile scars are generally sprayed with herbicide 

to control non-natives and then amended with native 

seeds. Several years after the treatment, the former burn 

scars were indistinguishable in a native grass meadow 

in the park. Only certified weed-free native seed mixes 

should be used. Further caution is needed as some mixes 

have been suspected of contamination with seeds from 

non-native plants (Hunter and others 2006; Springer and 

others 2001). Mechanical removal of invasive plants, 

mowing to prevent seed ripening, or introduction of 

biological agents that kill specific invasive plants are 

all additional measures that can control non-native plant 

populations.

Air Quality

Problems associated with smoke can be alleviated by 

burning under conditions that result in more efficient 

combustion of fuels (DeBano and others 1998; Mahaffey 

and Miller 1994). The efficiency of combustion can be 

influenced by ignition techniques, fuel structure, and 

burning conditions. For example, head fires tend to be 

fast moving while back fires move much more slowly. 

Little fuel is burned in the flaming front of a fast moving 

head fire compared to a slow moving backing fire. In 

a heading fire, more fuels tend to burn in a smoldering 

manner after the flaming front has passed. Thus, head 

fires tend to produce more smoke and pollutants than 

back fires.

Fuel structure also determines the amount of smoke 

and pollutants produced in a fire (Mahaffey and Miller 

1994). Fine fuels tend to burn efficiently while large diameter fuels tend to smolder. Tightly packed fuels tend to 

smolder more than loosely packed fuels. Dry fuels tend 

to burn more completely than wet fuels. The amount of 

smoke produced from a fire can be controlled by burning 
66 USDA Forest Service RMRS-GTR-198. 2007

when conditions favor certain fuels and not others. For 

example, if reduction of fine fuels is the primary goal, 

a fire can be set when fuel moisture of the fine fuels is 

low and fuel moisture of the large fuels is high. Smoke 

production would thus be lessened if larger fuels were 

not available to burn.

When large amounts of smoke production are inevitable from a prescribed fire, care should be taken to ensure 

that smoke does not drift into sensitive areas such as scenic vistas, urban areas, or road corridors (DeBano and 

others 1998; Mahaffey and Miller 1994). This can be accomplished by burning when wind is not blowing in the 

direction of the sensitive area. If smoke drifts into sensitive areas, care should be taken to ensure that the smoke 

plume mixes with substantial amounts of air before it 

reaches the sensitive area. This can be accomplished by 

burning when the atmosphere is somewhat unstable and 

will promote rapid mixing. However, burns should not 

be conducted when the atmosphere is extremely unstable, as this can promote extreme fire behavior. Mixing 

of the smoke with air can also be encouraged by creating burning conditions that promote development of 

a convection column that allows smoke to rise rapidly 

to the upper atmosphere. For example, mass ignitions 

are more likely to create convective conditions than line 

ignitions.

The Flagstaff Fire Department has been very successful in managing smoke production from prescribed fires 

in the wildland urban interface by adhering to several 

management practices (Flagstaff Fire Department 2005). 

In general, prescribed burns are avoided adjacent to sensitive areas such as medical centers and nursing homes. 

If burns are conducted near schools, they are done when 

school is not in session. If possible, burns are conducted 

in the summer when day lengths are long. This reduces 

the risk of nighttime smoke inversions. Burns are also 

conducted when forecasts for ventilation are good or 

excellent. To reduce smoke emission, backing fires are 

normally used and some woody material may be removed or isolated prior to burning. Managers adhere to 

maximum burn guidelines by burning no more than 150 

piles per day no more than once a week in a neighborshed and no more than 50 acres per week on a broadcast 

burn in a neighborshed. In addition, managers notify 

the media and the public about planned prescribed fires 

and possible smoke impacts before burns are conducted. 

One of the reasons the program is so successful is the 

time and energy put into the extensive public outreach 

and education program.

Smoke management is an integral part of the prescribed 

fire planning process. With careful planning and experience, problems associated with smoke can be avoided 

or at least minimized. Several models are available to 

help predict the amount of smoke likely to be released 

from a fire and the direction the smoke should spread although they have had varying success. A relatively new 

model increasingly being used by managers, the Smoke 

Impact Spreadsheet (SIS), has shown some success in 

accurately predicting particulate matter emissions from 

prescribed fires. This model incorporates the First Order 

Fire Effects Model (FOFEM) and CONSUME to predict downwind emissions of particulate matter from 

wildfires, broadcast burns, and pile burns (Wickman and 

Acheson 2005).

Aesthetics

In general, a fuels treatment that is good for the ecosystem can also be aesthetically pleasing, if applied 

properly. Avoiding excessive scorch or mechanical 

damage to residual trees is beneficial from a variety of 

resource standpoints. Excessive residual surface fuel 

loading is probably not acceptable from either an aesthetic or a fire hazard perspective. In heavily used or 

visible areas, care should be taken to maintain stand 

characteristics that contribute to the aesthetic quality 

of the forest, including retention of large trees, spatial 

and structural diversity, and minimizing surface debris. Measures can also be taken in such areas to limit 

tree mortality. For example, managers in Bandelier 

National Monument have removed heavy loadings of 

duff around old growth trees in highly visible areas to 

limit mortality from prescribed fires. While this practice is generally too labor intensive to practice on all 

prescribed fires, it has been done in areas that are more 

visible. To avoid residual tree damage, foresters with 

the Colorado State Forest Service recommend being 

very specific in contracts about acceptable residual 

tree damage and holding contractors responsible for 

unacceptable levels of damage. Negative results can 

be avoided by having a detailed contract, stringent 

enforcement, and a mutual understanding with the 

contractor as to what is expected. In some cases, the 

Colorado State foresters will treat a test plot prior to 

treating the entire unit to ensure the contractor understands the desired treatment effects.

The choice of fuel treatment technique can also affect resulting aesthetics. For example, the Pike National 

Forest uses public firewood sales to clean up tree boles 

dropped by Forest Service crews in accessible (and 

highly visible) units along highways. This highly effective technique meets public demand for firewood, builds 

goodwill and acceptance of fuels treatments, and dramatically reduces heavy fuel loading. Subsequent low 

intensity prescribed burns are then used to eliminate 
USDA Forest Service RMRS-GTR-198. 2007 67

remaining surface fuels with minimal adverse smoke effects and residual tree damage.

Wildlife Habitat

Measures can be taken to ensure prescribed burns do 

not result in excessive loss of these important wildlife 

habitat components. Burning snags can be prevented by 

removing fuels from the base of snags prior to burning 

(Anderson 1994; Randall-Parker and Miller 2002), or by 

black lining snags prior to burning the entire unit. Large 

diameter snags, which are often preferred by cavity nesting birds, may be in particular need of protection as there 

is little potential for large snag recruitment given the lack 

of large diameter trees in many areas (Horton and Mann 

1988). The same can be done to large or old growth trees 

to prevent mortality. Foresters with the Colorado State 

Forest occasionally removed fuels around large pieces of 

coarse woody debris to protect them in prescribed fires. 

Burns can also be conducted when moisture contents of 

fuels are such that only small diameter fuels will burn 

and large fuels will be spared (Anderson 1994; RandallParker and Miller 2002). Burning in early spring shortly 

after snowmelt can be effective in accomplishing this 

result (Shepperd 2004). If surface fuels are to be removed through burning of piles, large diameter logs can 

be intentionally left out of the piles to create wildlife 

habitat. To limit mortality of large oak trees during prescribed fire, managers in northern Arizona often create 

fuel breaks around large oak trees prior to burning. To 

do this in a cost effective manner, they use an innovative 

ATV fire line plow created from an old truck wheel (see 

SECTION IV, Tools Used in Burning). In addition, care 

can be taken so that oak litter is not directly ignited and 

instead, fire is allowed to creep through it. Managers on 

the Coconino National Forest have found that this practice limits mortality of large oak trees.

When treating ponderosa pine landscapes to reduce 

fire hazard, it is important to ensure such activities result 

in a mosaic of forest cover types across the landscape 

that are likely to be the most beneficial in providing 

habitat for a variety of species (Fiedler and Cully 1995; 

Shepperd and Battaglia 2002; Sieg and Severson 1996). 

Heterogeneity in stand structure should also be a management goal on the stand level. Rather than promoting 

a uniform treatment prescription, managers should strive 

to create heterogeneity by using a variety of treatment 

prescriptions and in some cases, conducting no treatment 

at all. Historical forest structure can be used as a guide in 

this process. For example, heavier thinning prescriptions 

may be justified in areas that would have had low tree 

density historically (for example, south-facing slopes, 

meadows), while less intensive thinning prescriptions 

may be more appropriate in other portions of the landscape (for example, north-facing slopes). Managers on 

the Santa Fe National Forest have accomplished this by 

designing treatment prescriptions so areas in the forest 

that may have historically had higher tree density, like 

drainages, would have fewer trees removed.

Cultural Resources

Damage to cultural and historical resources from 

prescribed fire can be easily avoided by knowing the 

number, type, and distribution of cultural resources in 

a management area. Extensive archeological surveys 

in proposed treatment areas can substantially increase 

the cost of fuel treatments, but must be done if artifacts 

are suspected in the area. Sensitive materials can be 

removed from a site prior to treatment. If this is not possible, sensitive areas can be excluded from prescribed 

burning or mechanical treatment efforts. Fuel breaks can 

also be constructed around sensitive areas or high fuels 

loads can be manually removed around sensitive areas. 

Similarly, tree ring collections can be made prior to 

treatment, or potential sample specimens can be avoided. On the other hand, we should not forget potential 

positive cultural resource benefits resulting from fuels 

treatments. Managers at Bandelier National Monument 

have actually justified use of prescribed fire to protect 

sensitive areas that would otherwise be subject to much 

more extreme heat from a wildfire.

Soil Resources

Soil disturbance and compaction can be easily avoided by using hand crews in lieu of machines to fell and 

process trees. This may be a valid choice in very sensitive areas or on smaller treatment units. However, in 

some cases, use of mechanical equipment may be justified. While some soil compaction and disturbance is 

inevitable when heavy equipment is used for thinning 

or understory biomass alteration/removal, certain procedures or equipment can minimize the amount of soil 

compaction across a site. For example, using equipment 

that has longer reach and more maneuverability reduces 

the percentage of the area that the equipment needs to 

traverse. If boom-mounted machines are not available, 

care should be taken to ensure that machines stay in designated paths designed to minimize machine movement 

across the site. Felling trees in the direction of the skid 

trail can also minimize soil disturbance and compaction 

by minimizing skidding distance (Minard 2003).

Several agencies in northern Arizona limit damage 

to soil resources using a technique developed on the 

Mormon Lake Ranger District of the Coconico National 
68 USDA Forest Service RMRS-GTR-198. 2007

Forest (Farsworth and Summerfelt 2001). With this 

method, trees are directionally felled into a windrow 

and are then pushed into large piles by a dozer during a 

single pass. Few ruts are made because the dozer is not 

constantly spinning and turning. Smaller, more maneuverable machines apply less ground pressure and lead 

to less soil compaction than larger machines. However, 

the effects of large machines are not as severe if the 

ground pressure is applied over a larger area (Poff 1996; 

Windell and Bradshaw 2000). Track-mounted machines 

tend to lead to less soil compaction than wheel-mounted 

machines as they allow the machine weight to be distributed over a larger area, but their skid-steering design can 

disturb soil to a greater extent. Soil compaction can also 

be minimized by conducting treatments when the soil 

is frozen or extremely dry, or by driving machines over 

protective layers of litter, slash, or snow (Poff 1996; 

Windell and Bradshaw 2000). Even on gentle slopes, 

road access or landings should be downhill of the treatment area. Skidding or forwarding logs uphill can result 

in substantial soil erosion and treatment costs (Fight and 

others 2003).

Some of the effects of burning masticated fuels may 

be avoided by burning multiple times under relatively 

wet conditions so that fuels are removed in stages. For 

example, a first burn can be accomplished when the top 

layer of masticated fuel is dry but the bottom layers are 

wet and thus, not readily ignited. Residual fuels can then 

be burned in subsequent burns, at 2- to 3-year rotations. 

Managers on the San Juan National Forest have achieved 

some success by using this technique. Adverse effects 

of burning slash piles can be avoided by keeping piles 

relatively small or burning larger piles when the soil is 

frozen or there is some snow on the ground (Farnsworth 

and Summerfelt 2001). This results in fewer piles per 

acre that can be ignited under snowier and wetter conditions than traditional hand piles. This method is also 

more productive than hand piling. However, managers 

should note that burning any pile results in very high 

soil temperatures and associated adverse soil effects 

(Massman and others 2003, 2006).

Insect and Disease Outbreaks

Few studies have examined insect-fire interactions at 

the landscape scale, although this subject has recently 

received increased attention (Howe and Baker 2003; 

Saint-Germain and others 2004; Sturtevant and others 

2004). At the landscape scale, insects create, and are affected by, the spatial patterns of suitable and unsuitable 

habitat patches. Large fires seldom affect all burned areas 

equally, but the burned area usually arises from crown 

fires, severe surface fires, stand replacing fires, and 

understory fires that create a patchy spatially patterned 

environment composed of a variety of potential insect 

habitats. This spatial heterogeneity and variety of habitats 

helps to maintain insect populations, diversity of insect 

behavioral traits including wood-feeders, and genetic diversity among local insect populations. The configuration 

of suitable habitat, distance between suitable patches, 

and the nature of the landscape matrix between patches 

all influence the abundance, dispersal, and survivability 

of insect populations. These landscape attributes also determine the potential for insect outbreaks. Understanding 

how to make use of spatial patterns to manage fire and 

insect risk and hazard are fundamental to landscape fire 

and insect management, but much still needs to be developed.

Monitoring

Agencies often implement fuel treatment activities 

without fully knowing about their effectiveness or their 

potential impact on other values at risk. Monitoring of 

treatment effects is imperative to determine treatment 

effectiveness and to ensure undesirable effects do not 

materialize. Managers who have made monitoring efforts a priority have been able to operate more in an 

adaptive management framework by altering management actions when ineffectiveness or undesirable 

outcomes have been documented. Such data helps build 

public confidence and acceptance of fuels treatments, 

especially when it is shared openly among stakeholders 

and is used to help plan and implement future activities.

Several monitoring protocols have been developed 

specifically for monitoring the effects of fuels treatments. 

The most commonly used protocols within government 

agencies include the fire effects monitoring guide developed by the National Park Service (USDI National Park 

Service 2003) and FIREMON (Lutes and others 2006). 

While both protocols were developed for monitoring of 

prescribed fires, wildfires, and wildland fire use fires, 

they could be easily adapted for other fuel treatments 

(for example, thinning and grazing). These monitoring 

protocols recommend a basic level of monitoring that 

includes data on vegetation (for example, species composition and cover), stand structure (for example, tree 

density and size class distribution), fuels (for example, 

loading and depth), and basic fire effects (for example, 

scorch height and char height). These programs also 

provide detailed instruction for plot layout, data organization, and analysis.

This basic level of monitoring allows one to assess 

a wide variety of fuel treatment objectives. Data on 

fuels can be used to determine whether treatments are 
USDA Forest Service RMRS-GTR-198. 2007 69

effective in reducing fuel loading to desired levels. Data 

on fire effects can be used to assure treatments result in 

desirable levels of tree mortality. Data on vegetation can 

be used to ensure treatments result in desirable levels of 

understory production while discouraging establishment 

of non-native, invasive species. Of course, in order to 

assess change, one must collect data before treatments 

are implemented, immediately after treatments are 

implemented, and again at regular time intervals following treatment, typically every year for up to 5 years or 

more.

Our observation in gathering information for this 

report is that with the exception of the National Park 

Service, most agencies struggle to allocate time and 

money to monitoring efforts, even while recognizing their importance. In response to this shortcoming, 

some have designed protocols that are flexible and can 

be altered depending on resources available for monitoring. For example, FIREMON describes three levels 

of monitoring designed for different levels of resources 

(Lutes 2006). Managers can alter monitoring protocols 

depending on resources available in several ways. If few 

resources are available for monitoring, managers may 

decide to collect data from fewer plots or not to collect 

data from a control plot. This will likely mean that it 

will be more difficult to detect treatment effects statistically, and results will have to be described in qualitative 

rather than quantitative terms. While this may not be 

ideal, it is still more desirable than collecting no data 

in conjunction with fuel treatments. FIREMON specifically discusses the number of plots that should be 

assessed given the level of resources available and the 

desired robustness of data. Managers can also collect 

data on fewer variables if resources for monitoring are 

scarce. However, some have noted that much of the cost 

associated with monitoring can be attributed to transporting crews to and from monitoring sites. It is often a 

more efficient use of resources to collect as much data 

as possible while at the monitoring site (USDI National 

Park Service 2003).

The level of monitoring recommended by the National 

Park Service and other agencies may still be too detailed for the needs of other smaller organizations. The 

Collaborative Forest Restoration Program (CFRP) has 

attempted to meet monitoring needs of other organizations in New Mexico. This granting program supports 

restoration projects on federal, state, municipal, and 

tribal lands in New Mexico. An integral requirement for 

funding under this program is a multiparty monitoring 

protocol. Simple protocols for a variety of variables are 

available at http://www.fs.fed.us/r3/spf/cfrp/ (accessed 

10-25-06). While developed in New Mexico, these protocols could also be adapted for other regions.

In some cases, the basic protocols discussed above 

may not be useful for meeting other monitoring objectives. This may particularly be true if a management area 

is managed for a very specific resource such as Native 

American ruins or sensitive wildlife habitat. These 

monitoring protocols will not be useful for determining 

whether or not prescribed fire damages sensitive Native 

American artifacts. In such special cases, more specific 

monitoring protocols need to be developed to assure 

treatments are benefiting the desired resource, or at least 

not harming it.

Responsibility for monitoring does not end with the 

field data collection. It should include archiving and 

cataloging of results in a permanent database available 

and readable to future generations of fuel managers. 

Another advantage of using developed programs such 

as FIREMON and the National Park Service monitoring 

protocol is that data archiving and analysis applications 

have been developed with the protocols. This allows for 

a systematic framework for archiving data.
70 USDA Forest Service RMRS-GTR-198. 2007
USDA Forest Service RMRS-GTR-198. 2007 71

During our conversations with managers throughout the Southwest, Front Range, and Black Hills, 

we discovered that while many managers are driven by 

similar resource management objectives, very different 

approaches are taken to achieve these objectives. There 

is no one method for effectively meeting management 

objectives, but we have noticed that success is more 

likely to be achieved when several broad management 

principles are followed. We attempt to summarize those 

principles here as broad guidelines that can be applied 

to any management scenario and are imperative to consider in any fuel treatment or restoration project. We also 

present specific examples we encountered of how managers are implementing these principles.

Integrating Ecological Knowledge 

and Principles into Fuel Projects

Fuel treatments should be designed to accomplish 

more than reduced wildfire risk or hazard. When other resource management objectives are incorporated 

into projects, fuels treatments will ultimately be more 

ecologically sustainable. This is best achieved through 

restoration of forested systems to conditions that were 

seen prior to major disruptions often associated with 

Euro-American settlement. We recognize that restoration will not always be compatible with reducing wildfire 

hazard. However, where reducing wildfire hazard takes 

precedent over restoration, attempts can still be made to 

restore certain features of historical stands. For example, 

in areas where habitat features such as large trees and 

snags have been lost, development of these important 

habitat components should be encouraged.

In ponderosa pine forests adapted to historical surface fire regimes, ecological restoration goals include 

surface and canopy fuel reduction, protection of old 

trees, recovery of native understory vegetation, and the 

reintroduction of surface fire as a key ecological process 

(Allen and others 2002; Covington and others 1997; Fule 

and others 2006). If managers are to mimic the effects 

of natural disturbances, they must integrate the timing 

and severity of prescribed disturbances with the ecological requirements of the desired landscape composition 

and condition (Hudak and others 2006). Understanding 

the effects of different types of disturbances and associated alteration of key processes may help to promote 

ecosystem resiliency through improved management decisions. Fuel reduction treatments influence vegetation 

succession, and the individual and cumulative effects 

of these treatments may have positive and negative implications for ecosystem character and function (Noss 

and others 2006). Development of sustainable relationships between humans and their environments requires 

knowledge of successional consequences and planning 

on a broad spatial scale.

Goals of restoration and reduced wildfire hazard may 

not always overlap in mixed-severity fire regimes more 

commonly found in the Front Range and Black Hills. 

While some portions of these forests burned historically with low intensity surface fire, pockets with high 

intensity crown fire on a small scale were also common (Brown and Sieg 1996; Brown and others 1999; 

Huckaby and others 2001). This likely resulted in a 

landscape mosaic composed of openings, stands with 

low tree density, and stands with relatively high tree 

density. Thus, a fully restored landscape is not likely to 

result in acceptable levels of wildfire hazard reduction 

given the patchwork of public and private land found in 

these landscapes. However, certain aspects of historical 

structure and processes can and should be incorporated 

into fuel treatments, particularly on a landscape scale. 

For example, care may be taken to maintain patches of 

densely stocked forest in areas where they would not 

pose an undue hazard to human communities.

Case Study

Many fire managers recognize that re-establishing 

appropriate fire regimes to fire-adapted ecosystems is 

imperative for allowing natural processes to shape ecosystems. Fire is likely the best tool available to create 

the natural heterogeneity in forest structure at stand and 

landscape scales. Managers on the Gila National Forest 

have been very successful in allowing naturally ignited 

fire to shape the landscape. Since their wildland fire use 

program has been implemented (over 30 years ago), 

multiple areas have burned in two or three wildland 

Section VII:

Comprehensive Management Principles
72 USDA Forest Service RMRS-GTR-198. 2007

fire use events. This has created a forest structure that 

is more characteristic of historical conditions. Managers 

here work closely with wildlife biologists and adjacent 

landowners to ensure that wildland fire use events do 

not threaten sensitive wildlife habitat or communities. 

Allowing natural fires to return to these ponderosa pine 

forests will allow the many plants and animals adapted 

to this system to thrive under current and future climatic 

conditions.

Planning Fuel Treatments Within a 

Broad Landscape Context

The degree to which fuels treatments and other vegetation conditions have influenced fire effects across 

landscapes is little understood, yet has tremendous implications for the efficacy of fuels management designed 

to achieve multiple resource objectives, including the 

moderation of future fire effects. Planning fuel treatments 

on a landscape scale and across jurisdictions is needed 

because most wildfires dwarf the size of individual fuel 

treatment projects and don’t obey human defined boundaries. It will never be feasible to treat every square inch 

of fire-prone landscapes. Strategies should be developed 

to maximize benefit gained from fuel treatments, both in 

terms of reducing the threat of wildfire and improving 

ecological integrity. Fuel treatments can be strategically 

placed across landscapes so the historical heterogeneity 

in forest structure can also be recreated. Many studies 

(for example, Callaway and Davis 1993; Cram and others 

2006; Odion and others 2004) have found that patterns 

of fire effects (for example, severity) and post-fire vegetation recovery may be predisposed by topographical 

position and pre-fire vegetation structure. These studies 

suggest that, at the very least, forest managers should 

consider the spatial arrangement and size of harvest and 

other management units, as well as topographic characteristics, when planning for fuel treatments and other fire 

mitigation measures.

Case Study

Managers with the Coronado National Forest are 

currently involved with multiple parties in a planning 

process that will strategically place fuel treatments 

across the landscape. This effort is in collaboration 

with managers from neighboring landowners, including Department of the Defense, National Park Service, 

Nature Conservancy, Audubon Society, Bureau of Land 

Management, and Arizona State Parks. Collaborators 

are planning future fuel treatment projects to maximize 

benefit across jurisdictional boundaries. This approach 

has several other benefits: the costs per acre are kept 

low with broad-scale projects; natural and logical project boundaries (rather than jurisdictional) can be used 

for fire management; staff and equipment are used more 

efficiently across agencies; monitoring efforts can be coordinated; and a consistent message is delivered to the 

public.

Encouraging Innovative Approaches 

to Fuels Treatment

Many areas in ponderosa pine landscapes in most 

need of treatment are also the most difficult to treat because of topography or proximity to values at risk. While 

innovative approaches can be used to treat such areas, 

there often is no agency incentive for pursuing innovative options. Innovative and perhaps somewhat risky 

approaches need to be attempted in order to learn what 

can effectively reduce the threat of severe wildfire in 

some landscapes. Managers should not be penalized for 

attempting innovative treatments or be held personally 

liable if such treatments fail. Encouraging innovation 

means using an adaptive management approach that allows managers to try new approaches and learn from 

the experience. Restricting them to fuels treatments that 

are without risk stifles innovation. The probability of 

innovative treatments failing can be reduced by using 

experienced fire managers and resource specialists on 

the project team. Our conversations with managers revealed that the most successful fuel treatment programs 

always had a cadre of experienced personnel participating in the planning and on-the-ground execution of fuel 

treatment projects. Their knowledge of local conditions 

and confidence in what could be done strongly influenced the success of their programs.

Case Study

Managers on the Santa Fe National Forest advocate the 

pairing of very experienced fire managers with younger 

individuals in the field. The experienced managers often 

provide the detailed knowledge of a particular region 

and typical fire behavior in different circumstances in 

that locality. Working with younger members in the field 

ensures that this knowledge is passed to the next generation of fire managers. The working relationship is not a 

one way interaction, however. Younger managers often 

have the advantage of training in newer methods and 

models being used in the field of fire management. When 

this mix of expertise and new perspectives is combined, 

there is generally more confidence in the outcome and 

less aversion to the risks that are always associated with 
USDA Forest Service RMRS-GTR-198. 2007 73

prescribed fire. While managers should always proceed 

with caution and be fully aware of the risks associated 

with their activities, they should focus on the importance 

of innovation in order to effectively achieve objectives.

Monitoring Treatment Effects and 

Effectiveness of Fuel Projects

Managers can not truly determine whether they are 

meeting management objectives with their treatments 

without monitoring their effectiveness. Quantitative data 

showing that treatments have been effective in meeting 

management objectives can serve to justify the need for 

more and similar treatments. Similarly, monitoring can 

document whether treatments are having adverse effects on other resource values such as wildlife habitat 

or biodiversity. Justification can be made for altering 

treatment prescriptions if monitoring data suggest that 

desired results are not being achieved. This allows managers to work in an adaptive management framework. 

Monitoring should not be restricted to fire weather and 

behavior, but should document treatment effects on other resources and ecosystem values as well. Monitoring 

should not begin with the treatment action, but should 

first document pre-treatment conditions to serve a 

benchmark for anticipated outcomes. Responsibility 

for monitoring does not end with the final data collection. It should include archiving and cataloging results 

in a permanent database available and readable to future 

generations of fuel managers.

Case Study

The fire effects monitoring protocol developed by the 

National Park Service and FIREMON provide very effective monitoring protocols that can be easily adapted to 

monitor for a variety of treatment effects. The protocols 

describe in detail every step of the monitoring process, 

including developing monitoring objectives, randomization, plot layout, data collection, data archiving and 

analysis, and more. These protocols can also be adapted 

depending on the level of resources devoted to monitoring. FIREMON, in particular, provides strategies for 

adapting monitoring protocols based on the level of resources available to conduct monitoring and the need for 

robust data. Both protocols also provide computer applications for archiving data that also include basic data 

analysis procedures.

The Collaborative Forest Restoration Program, a 

granting program that facilitates restoration projects on 

federal and tribal lands in New Mexico, requires monitoring be included in all proposed projects. To facilitate 

this process, the program members have developed protocols for monitoring a variety of ecological attributes. 

These protocols provide a common framework for monitoring, ensure treatments have been effective in meeting 

objectives, and document any detrimental impacts on 

other resources. Recognizing that many managers often have limited time and resources to do monitoring, 

these protocols have been designed to be relatively easy 

to implement. The monitoring guide developed by the 

program is available at http://www.fs.fed.us/r3/spf/cfrp/

(accessed 06-21-07).

Collaboration with Other Resource 

Managers and Interested Parties to 

Improve Results

Fuel treatment projects that are multi-faceted will best 

meet the needs of sustaining forested ecosystems. To 

be effective in meeting multiple resource management 

objectives, managers should solicit input from resource 

specialists with expertise in varying fields and from 

other interested parties outside the management agency. 

Establishing relationships with managers and stakeholders within and outside the agency, including the general 

public and non-profit organizations, can take a great 

deal of time and energy and reaching consensus can be 

difficult. However, we have noticed that managers who 

invested time in these relationships benefit immensely in 

the long run. With collaboration, fuel treatment projects 

are generally better in meeting multiple objectives and 

internal and external resistance to fuel treatments is lessened. Collaboration gives stakeholders ownership in the 

process and pride in the outcome.

Collaboration has a long history in fire management, 

evidenced by partnerships like the National Interagency 

Fire Center and the National Wildfire Coordinating 

Group. More recent policy directives (for example the 

National Fire Plan and Healthy Forest Restoration Act) 

have further emphasized the need for collaboration in 

fuel treatment projects, particularly on a local level. 

There are several benefits to collaborative efforts in the 

context of wildland fire. Collaboration tends to mobilize 

people to generate funds, allows for sharing of data and 

expertise, leads to a broader understanding of different 

attitudes and values toward natural resources, and allows for increased efficiency and effectiveness of fuel 

treatments (Sturtevant and others 2005). Collaboration 

tends to be effective in relatively small groups of people. 

Collaboration is time consuming and can be difficult if 

there is a history of unresolved conflict, if partners are 

not willing to compromise, or if partners have no power 
74 USDA Forest Service RMRS-GTR-198. 2007

to implement decisions. However, overcoming these obstacles builds trust and ownership in the process and will 

inevitably lead to a successful outcome.

Case Study

Gila National Forest managers are developing strategies for implementing fuel treatments on the Silver City 

Ranger District. Multiple stakeholders are involved in 

the process including environmental advocates, local 

government officials, commercial wood products users, and scientists. This collaborative process ensures 

that the concerns of all interested parties are addressed. 

Working together in this setting, members from different parties often gain a better understanding for the 

needs and concerns of other stakeholders and compromises are more easily attained. In this case, we find 

that all collaborative partners understand the need to 

balance protection of communities, sensitive wildlife 

habitat, and important watersheds with other resource 

management needs and they work together to make 

sure these needs are met.

A number of excellent resources are available on establishing and maintaining collaborative relationships, 

including handbooks and guides specifically structured 

to the requirements and policies of Federal agencies. The 

following website has links to a number of publications 

and documents on collaboration and building partnerships. This website includes materials specific to fuels 

treatment projects and Forest Service agreements: http://

www.partnershipresourcecenter.org/resources

A particularly useful publication available at this site is 

the Partnership Guide, published jointly by the National 

Forest Foundation and USDA Forest Service National 

Partnership Office (National Forest Foundation and USDA 

Forest Service 2005). Yet another publication specific to 

building collaboration and preparing and implementing 

community wildfire protection plans is the handbook 

published by the Society of American Foresters, which 

can be found at: http://www.safnet.org/policyandpress/

cwpp.cfm.

We urge readers to use these resources to plan, build, 

and maintain collaborative relationships with stakeholders that have an interest in fuels treatment activities. 

Our experiences in completing this document have convinced us that including stakeholder ideas and input in 

a project and acknowledging their need for ownership 

in the decision-making process will ultimately ensure a 

successful outcome to any fuels treatment activity.

Conclusion

In our attempt to elucidate comprehensive management practices for fuels treatments in ponderosa pine 

forests in the Black Hills, Front Range, and Southwest, 

we have combed all available published literature and 

have journeyed throughout the regions where these forests grow to gather information from managers and fuels 

treatment practitioners. Our experiences have convinced 

us that while much is known, there is more to be learned. 

On the one hand, there are physical, biologic, regulatory, 

and societal limitations on what can be done to reduce 

the risk of catastrophic wildfire in these systems. On the 

other, there is innovation, collaboration, and a wealth of 

experience that can be drawn upon to find solutions to 

those limitations. What we have presented here is a static 

summary of existing knowledge. It is useful to a point – 

today. Management practices will, and should, evolve as 

we gain new knowledge in the future. Our efforts should 

therefore be viewed only as a beginning point in that 

continuum.
USDA Forest Service RMRS-GTR-198. 2007 75

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BehavePlus

BehavePlus uses inputs of fuel characteristics and 

weather and topography to predict surface fire and 

crown fire spread and intensity. This model has a 

variety of applications for wildland fire suppression 

and training. For prescribed fire, it is typically used 

to develop prescription windows that will result 

in desired fire behavior. This model is available to 

download at www.fire.org.

CONSUME

CONSUME is a model that predicts fuel consumption 

and emission based on fuel and weather conditions. 

This model is available to download at http://www.

fs.fed.us/pnw/fera/products/consume.html.

FARSITE

FARSITE uses spatial information on fuels and 

topography and weather indices to simulate fire 

spread across a landscape. This model is particularly 

useful for simulating spread of fires used for resource 

benefit and for landscape planning of fuel treatments. 

This model is available to download at www.fire.org.

FFE-FVS

The Fire and Fuels Extension of the Forest Vegetation 

Simulator (FFE-FVS) links the growth and yield 

models of FVS with models that predict fire behavior, 

fire effects, fuel loading, and snag dynamics. This 

model is particularly useful for examining the potential 

short- and long-term effects of fuel treatments. This 

model is available to download at www.fs.fed.us/

fmsc/fvs/index.shtml.

FIREMON

FIREMON is monitoring program designed to enable 

managers to develop a monitoring protocol, collect 

data, and store and analyze fire effects. This model is 

available to download at www.fire.org.

FlamMap

FlamMap computes potential fire behavior 

characteristics over a FARSITE landscape. FlamMap is 

particularly useful for prioritizing fuel treatment areas 

across a landscape and assessing their effectiveness 

in preventing severe wildfire spread. This model is 

available to download at www.fire.org.

FMAPlus

Fuels Management Analyst (FMAPlus) is a model 

that can estimate loading of surface and canopy fuels 

and then predict surface and canopy fire behavior and 

fire effects. This model is available to purchase at 

http://www.fireps.com/fmanalyst3/index.htm.

FOFEM

The First Order Fire Effects Model (FOFEM) 

predicts the effects of fire on tree mortality, fuel 

consumption, smoke production, and soil heating. 

This model is useful for ensuring prescribed fires will 

result in desired fire effects. This model is available to 

download at www.fire.org.

FSVeg

FSVeg is a program that can be used by managers in the 

Forest Service. It contains data on trees, surface cover, 

down woody material, vegetation composition, and 

fuel loading for stands on Forest Service land. FSVeg 

data can be used directly in the Forest Vegetation 

Simulator (FVS) and the Integrated Forest Resource 

Management System (INFORMS). This program is 

very useful for fuel treatment planning. Information 

on this program is available at http://www.fs.fed.us/

emc/nris/products/fsveg/index.shtml.

INFORMS

The Integrated Forest Resource Management System 

(INFORMS) was designed for the Forest Service 

to support the entire NEPA process. This model is 

particularly useful in generating maps of fire hazard 

for different treatment alternatives. It also generates 

Appendix A: Models Used in Fuel Treatment 

Planning and Implementation
90 USDA Forest Service RMRS-GTR-198. 2007

FARSITE ready data. This model is available to 

download at http://www.fs.fed.us/informs/index.php.

MYFTP

My fuel treatment planner (MyFtp) can be used to 

assess the cost associated with mechanical treatments 

and prescribed fire. It is available for downloading 

at http://www.fs.fed.us/fire/tech_transfer/synthesis/

economic_utilization_team/MyFTP_home.htm.

NEXUS

NEXUS links surface and crown fire behavior models 

to create indices of relative crown fire potential. This 

model can be used to examine the crown fire potential 

of stands treated for fuels reduction. This model is 

available to download at www.fire.org.
USDA Forest Service RMRS-GTR-198. 2007 91

Plants

Scientific Name Common Name Distribution

Abies concolor white fir AZ, CO, NM

Abies lasiocarpa subalpine fir AZ, CO, NM

Cercocarpus montanus mountain mahogany AZ, CO, NM, SD

Juniperus scopulorum Rocky Mountain juniper AZ, CO, NM, SD

Picea engelmannii Engelmann spruce AZ. CO, NM

Pinus ponderosa ponderosa pine AZ, CO, NM, SD

Populus tremuloides quaking aspen AZ, CO, NM, SD

Pseudotsuga menziesii Douglas-fir AZ, CO, NM

Quercus gambellii Gambel oak AZ, CO, NM

Quercus macrocarpa bur oak NM, SD

Birds

Accipiter gentiles northern goshawk AZ, CO, NM, SD

Cervus canadensis elk AZ, CO, NM, SD

Odocoileus spp. deer AZ, CO, NM, SD

Strix occidentalis lucida Mexican spotted owl AZ, NM

Mammals

Antilocarpa Americana pronghorn AZ, CO, NM, SD

Bison bison American bison SD

Cervus elaphus elk AZ, CO, NM, SD

Sciurus aberti Abert’s squirrel AZ, CO, NM

Insects

Choristoneura occidentalis spruce budworm AZ, CO, NM

Dendroctonus spp. bark beetles AZ, CO, NM, SD

Dendroctonus ponderosae mountain pine beetle AZ, CO, NM, SD

Ips spp. Ips beetles AZ, CO, NM, SD

Hesperia leonardus montana Pawnee montane skipper CO

Fish

Oncorhynchus gilae Gila trout AZ, NM

Diseases

Arceuthobium spp. dwarf mistletoe AZ, NM, CO

Appendix B: Species Referenced in Best 

Management Practices Guide
92 USDA Forest Service RMRS-GTR-198. 2007

Name Title Agency

Craig Allen Research Ecologist USGS

Goeff Bell Fire Management Officer Arapaho-Roosevelt National Forest

Kristy Berggren Forester Colorado State Forest Service

Anne Bradley SW fire learning network The Nature Conservancy

Blaine Cook Forest Silviculturalist Black Hills National Forest

Russ Copp Forest Fuels Specialist Coconino National Forest

Michael Creach Fuels Management Specialist Prescott National Forest

Don Falk Adjuct Professor University of Arizona

Lawrence Garcia District FMO Santa Fe National Forest

Steve Gatewood Program Director Greater Flagstaff Forests Partnership

Brook Gebow Preserves The Nature Conservancy

Gale Gire Silviculturalist Black Hills National Forest

Craig Goodell Assistant FMO San Juan National Forest

William Hill Silviculturalist Custer State Park

David Isackson Assistant District FMO Santa Fe National Forest

Tom Johnston Forest Fuels Specialist Santa Fe National Forest

Gary Kemp FMO Bandelier National Monument

Lowell Kendall Assistant FMO Coconino National Forest

Paul Langowski Branch Chief—Fuels/Fire ecology USFS—Rocky Mountain Region

Andrew Leiendecker Assistant FMO Coronado National Forest

Randy Lewis Natural Resource Specialist Bureau of Land Management

Gwen Lipp Fuels Specialist Black Hills National Forest

John Lissoway Fire Program Manager National Park Service

Dennis Mauch Forest Technician Black Hills National Forest

Cecilia McNicoll Forest Planner Gila National Forest

Dan Morford Prescribed fire specialist Wind Cave National Park

Shane Olpin Assistant FMO Black Hills National Forest

Andy Perri Forester Colorado State Forest Service

Toby Richards District FMO Gila National Forest

Marla Rodgers Assistant FMO Bandelier National Monument

Orlando Romero Senior Forester Forest Guild

Melissa Savage Four Corners Institute

Paul Schmidtke Fire Staff Officer Lincoln National Forest

Todd Schulke Center for Biological Diversity

Martha Schumann SW NM field rep. The Nature Conservancy

Scott Spleiss Assistant FMO Prescott National Forest

Paul Summerfelt Fuel Management Officer Flagstaff Fire Department

Appendix C: Managers Interviewed
USDA Forest Service RMRS-GTR-198. 2007 93

Tracy Swenson Zone FMO Arapaho-Roosevelt National Forest

Walker Thornton Fuels Specialist Coconino National Forest

Jeff Thumm Natural Resource Specialist Coconino National Forest

Terry Tompkins Assistant FMO Black Hills National Forest

Russell Truman Assistant FMO Kaibab National Forest

Sherry Tune Forest Fire and Fuels Planner Coronado National Forest

Scott Wagner Forester San Juan National Forest

Gordon West Santa Clara Woodworks

Brenda Wasielewski Assistant District Forester Colorado State Forest Service

Craig Wilcox Assistant FMO Coronado National Forest

Jim Williams Forest Technician Black Hills National Forest

Ros Wu Fire ecologist San Juan National Forest
Publishing Services Staff

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The Rocky Mountain Research Station develops scientific 

information and technology to improve management, protection, 

and use of the forests and rangelands. Research is designed to 

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industry, and individuals.

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