United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-252

January 2011

Review of Fuel Treatment Effectiveness 

in Forests and Rangelands 

and a Case Study From the 

2007 Megafires in Central Idaho USA

Andrew T. Hudak, Ian Rickert, Penelope Morgan, 

Eva Strand, Sarah A. Lewis, Peter R. Robichaud, 

Chad Hoffman, Zachary A. Holden
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Hudak, Andrew T.; Rickert, Ian; Morgan, Penelope; Strand, Eva; Lewis, Sarah A.; 

Robichaud, Peter R.; Hoffman, Chad; Holden, Zachary A. 2011. Review of fuel 

treatment effectiveness in forests and rangelands and a case study from the 

2007 megafires in central, Idaho, USA. Gen. Tech. Rep. RMRS-GTR-252 Fort 

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

Research Station. 60 p.

Abstract

This report provides managers with the current state of knowledge regarding the 

effectiveness of fuel treatments for mitigating severe wildfire effects. A literature 

review examines the effectiveness of fuel treatments that had been previously 

applied and were subsequently burned through by wildfire in forests and 

rangelands. A case study focuses on WUI fuel treatments that were burned in the 

2007 East Zone and Cascade megafires in central Idaho. Both the literature review 

and case study results support a manager consensus that forest thinning followed 

by some form of slash removal is most effective for reducing subsequent wildfire 

severity.

Keywords: fire severity, fuel treatment, National Fire Plan, post-fire effects, 

wildland-urban interface (WUI)

Authors

Andrew T. Hudak, Research Forester, Rocky Mountain Research Station, Forest 

Service, U.S. Department of Agriculture, Moscow, Idaho

Ian Rickert, Squad Leader, Sawtooth Interagency Hotshot Crew, Sawtooth National 

Forest, Twin Falls, Idaho

Penelope Morgan, Professor, Department of Forest Resources, University of Idaho, 

Moscow, Idaho 

Eva Strand, Research Professor, Department of Rangeland Ecology and 

Management, University of Idaho, Moscow, Idaho

Sarah A. Lewis, Civil Engineer, Rocky Mountain Research Station, Forest Service, 

U.S. Department of Agriculture, Moscow, Idaho

Peter R. Robichaud, Research Engineer, Rocky Mountain Research Station, Forest 

Service, U.S. Department of Agriculture, Moscow, Idaho

Chad Hoffman, Instructor, Department of Forest Resources, University of Idaho, 

Moscow, Idaho

Zachary A. Holden, Spatial Analyst, Northern Region, Forest Service, U.S. 

Department of Agriculture, Missoula, Montana
Contents

Introduction 1

Literature Review 3

Forest Studies 3

Rangeland Studies 9

2007 Wildfires 12

Case Study 16

Study Areas 16

Incident Information 17

Fuel Treatments 22

Methods 22

Results 26

Discussion 40

Case Study of 2007 Central Idaho Wildfires 40

Are Expensive WUI Fuel Treatments Worthwhile? 46

Fuel Treatments in Forests: Implications and Conclusions 46

Grazing as a Fuel Treatment 49

Long-Term Ecological Effects of Fuel Treatments 50

Limitations and Future Needs 50

Unanswered Questions 51

Conclusion 55

Acknowledgments 55

References 56
USDA Forest Service RMRS-GTR-252. 2011. 1

Introduction

More forest burned in Idaho in 2007 than in any year 

since the historic massive blazes of 1910. Fortunately, 

no lives were lost and all communities were protected, 

with only a limited number of structures lost (McCarthy 

and others 2008). Most of these fires were in southern and central Idaho. The 190,577 ha and 98,467 ha 

burned on the Payette and Boise National Forests (NF), 

respectively, were the largest ever recorded in a single 

year. The East Zone and Cascade complexes both exceeded 120,000 ha. They burned across McCall and 

Krassel Districts (Payette NF) and Cascade District 

(Boise NF) and eventually joined. Their massive size, 

extreme fire conditions, and rugged terrain precluded 

containment as a viable strategy after some initial attempts. Instead, fire crews switched to Appropriate 

Management Response (AMR) strategy of wildlandurban interface (WUI) and point protection (McCarthy 

and others 2008).

Since 2000, there has been a significant increase 

in the amount and cost of wildfire suppression efforts 

due to changes in weather conditions, fuel build up, 

and growth of residential development in the WUI 

(National Wildfire Coordinating Group 2009). The 

cost of fire suppression was $2.0 billion in 2006 and 

$1.9 billion in 2007, and the number of hectares burned 

was 4.00 million in 2006 and 3.78 million in 2007. The 

10-year moving average of wildfire hectares doubled 

from 1.53 million in the 1990s to 2.89 million in the 

2000s. The scale of recent fire activity in the West and 

northern Midwest has not been observed since the 

early 1900s, and this trend is expected to continue as 

anticipated climate change worsens the effects of extended droughts in various regions of North America 

(National Wildfire Coordinating Group 2009).

The national media has increased public awareness 

of recent research findings that fires in the western 

United States have grown in size and severity in the 

past 15 to 20 years (Bartuska and Conard 2007, Pelley 

2007, Westerling and others 2006). Fire seasons have 

become longer west-wide (Westerling and others 

2006), and land use change, fire suppression, and fuel 

accumulation have contributed to increasingly large, 

severe wildfires in the western United States in recent 

decades. In the face of broad and growing scientific 

consensus that we will continue to have large, severe 

fires (Helms 2007, Running 2006), fuel treatments have 

been promoted as an important tool for fire managers 

who seek a compromise between the ecological utility 

and socioeconomic constraints of wildfire (Brose and 

Wade 2002, Covington and others 2001, Fulé and others 2001).

Since the inception of the National Fire Plan in 

2000, millions of dollars have been spent on fuel treatments in forests and rangelands to restore healthy 

ecosystems and to reduce hazardous fuel loads, especially in the WUI where people and property are likely 

to be threatened by wildfire. Under the National Fire 

Plan, 50 percent of treated lands must be in the WUI. 

Federal fuel treatments have grown to meet an annual 

target level of 1.2 million hectares treated, increased 

to 1.6 million hectares by including wildfire hectares 

that produce resource benefits, but this still amounts to 

less than half of the 3.2 to 4.0 million wildfire hectares 

that burn annually and the 4.0 to 4.9 million wildfire 

hectares that are projected to burn annually in the near 

future (National Wildfire Coordinating Group 2009).

In 2007, many large wildfires burned through fuel 

treatments, enabling an assessment of treatment effectiveness, which is the impetus for this and other reports 

(see Sidebar 3). The number of hectares treated is the 

current measure of success for hazardous fuel reduction projects, but this does not tell us whether and how 

much fuel treatments mitigate severe fire effects, what 

types of fuel treatments are most effective, or how long 

fuel treatments remain useful as fuels accumulate over 

time. Fuels may take 10 to 20 years to recover to pretreatment levels (Agee and Skinner 2005, Graham and 

others 2004), but this will vary by ecosystem, depending on rates of production, decomposition, and rates of 

plant establishment and mortality.

Fuel treatments include physical alteration of vegetation with the intent of reducing the probability of 

extreme fire behavior (Graham and others 1999, 2004). 

Treatments to reduce fire hazard often focus on thinning from below to reduce vertical (ladder fuels) and 

horizontal continuity of fuels as well as the amount 

of fuel on the ground. Mechanical treatments, such as 

mastication, chipping, piling by hand or machine, and 

compaction, and burning treatments, including piling 

and burning and broadcast burning, are designed to reduce the amount of fuel available to burn in subsequent 

wildfires (USDA FS 2005). Grazing is a common 

treatment in grasslands and shrublands. Treatments 

are designed to reduce the intensity and severity of 

fires (Graham and others 1999, 2004). All other fuel 
2 USDA Forest Service RMRS-GTR-252. 2011.

treatment goals such as improving firefighting efficiency, reducing risk, and mitigating fire severity are 

derivatives of moderating fire behavior.

In this paper, we focus on fuel treatment effectiveness in mitigating post-fire effects. Fuel treatment goals 

commonly include reducing wildfire risks to communities and the environment and improving ecosystem 

resiliency to wildfire effects (USDA USDOI WGA 

2002, 2006). Treatment effectiveness can be judged 

in terms of three criteria: (1) Did the treatment reduce 

crown fire behavior to improve firefighter safety? (2) 

Did the treatment protect people and their property? 

and (3) Did the treatment mitigate severe fire effects 

to valued vegetation and soil resources? Resources 

include forests, soils, fish and wildlife habitat, water quality, and recreation. This report focuses on the 

third criterion and documents not just our assessment 

of immediate fire effects (also termed “fire severity” 

measures by Lentile and others [2006]), such as ash 

deposition and soil alteration, but also extended fire effects (also termed “burn severity” measures by Lentile 

and others [2006]) assessed one year post-fire, such as 

delayed tree mortality and vegetation response.

This paper consists of three main sections. First, we 

review literature from forests and rangelands, focusing 

on case studies where there was a quantitative assessment of fuel treatments that were implemented and 

tested in fires. We summarize findings from multiple 

studies, including assessments of fuel treatment effectiveness in 2007 wildfires. Second, we summarize field 

and remotely sensed data that we collected and analyzed ourselves from two WUI areas in central Idaho 

where fuel treatments were burned through by massive wildfires. Our intent in the case study was to not 

just qualitatively assess whether or not the fuel treatments effectively mitigated severe fire but to quantify a 

number of specific post-fire vegetation and soil effects 

and statistically compare them between treated and 

untreated sites. Third, we discuss the management implications of our findings, integrate what we found in 

the case study with what we learned from the literature 

review, and articulate the knowledge gaps that should 

be emphasized in future assessments of fuel treatment 

effectiveness.
USDA Forest Service RMRS-GTR-252. 2011. 3

with 79 percent killed or severely damaged in untreated 

stands compared to only 17 percent killed or severely damaged in stands treated with prescribed fire.

Van Wagner (1968) evaluated tree mortality in 

southern California in plantations subjected to wildfire that 

had undergone fuel treatments with the explicit intent of 

minimizing the severity of subsequent wildfires. He evaluated two plantations that were burned in 1959 and 1960 

to determine treatment effectiveness for minimizing fireinduced tree mortality. The intent of this study was not to 

compare treated and untreated areas but to find the treatment method or fuel condition that effectively mitigated fire 

severity. Fuel treatment methods included brush removal 

within and around plantation perimeters, construction and 

maintenance of firebreaks, pruning of lower limbs, and scattering of slash from pruning. At the first site, pruning had 

been done three years prior to the fire, resulting in a canopy 

base height of 2.1 to 5.5 m and tree spacing of 3.0 to 3.7 m. 

Slash from thinning and pruning operations was scattered. 

Forest Studies Literature

Cumming (1964) compared the effectiveness of prescribed burning treatments to untreated, adjacent stands in 

the New Jersey Pine Barrens. Over the 10-year period prior 

to the wildfire, State lands within the wildfire perimeter had 

one to five prescribed fire treatments while private lands 

had no management action, resulting in different (although 

unquantified) stand structures and fuel compositions. Fire 

damage consisted of the following classifications: killed 

(stem killed or no sprouts at root collar), severe (crown 

reduced by two-thirds or more), moderate (one-third to 

two-thirds crown reduction), light (one-third or less), and 

unburned or no damage. Wildfire-induced tree canopy 

mortality was less in areas with prior prescribed burning, 

particularly in those units that had been treated within 

three years of the wildfire. Oak mortality was two to four 

times higher in untreated versus treated stands, with 97 percent either killed or severely damaged in untreated stands 

but only 46 percent killed or severely damaged in treated 

stands. Compared to oaks, pines were more fire tolerant, 

Literature Review

Forest Studies

Despite the broad scientific consensus that removing or reducing fuels can 

alter fire behavior (Graham and others 1999, Martinson and Omi 2008, Pollett 

and Omi 2002), there are few studies that quantitatively assess this assertion in 

treated areas subjected to wildfires. Evidence for effective fuel treatments comes 

predominantly from model simulations of fire spread and crown fire potential. 

Martinson and Omi (2008) found that 26 of the 49 studies they reviewed relied 

on simulations and 13 of the 26 employed hypothetical treatments in addition 

to hypothetical fires. Thus, these modeling study results might be best viewed 

as hypotheses that await empirical testing. Tests have taken the form of natural 

experiments, where wildfires have serendipitously encountered fuel treatments. 

There have been 22 published analyses of such; 11 of them included a statistical analysis of the treatment effect, and 7 attempted to control for the influences 

of topography and weather. According to Martinson and Omi (2008), there are 

only four published studies that include both a statistical test and adequate control to discern a fuel treatment effect in an actual wildfire.

Advances made in quantifying differences in treatments and resulting fire effects are evident when field-based case studies are reviewed (see Forest Studies 

sidebar) in chronological order. We only include case studies where vegetation 

treatments were tested in wildfires. Although some of the vegetation treatments 

evaluated were not specifically designed as fuel treatments, they are mentioned 

because they had the same effect.
4 USDA Forest Service RMRS-GTR-252. 2011.

The second site underwent a similar treatment, yet canopy 

base height was only increased 1.8 to 2.4 m. Slash was scattered and a 12 m wide fuel break was created around the 

plantation. Under the extreme burning conditions on both 

sites, there was no significant relationship between tree 

mortality and diameter at breast height (dbh) or pre-fire 

canopy base height. Given that both sites were dominated 

by Coulter pine (Pinus coulteri), species composition was 

not regarded as an influential factor on fire severity. Plots 

with the largest average tree diameter also had the highest 

survival percentage (92 percent). Across both sites, as shrub 

density increased, so did tree mortality. Plots with steep 

slopes and low brush densities still showed high percentages 

of tree mortality. Although canopy base height appeared to 

be significantly improved by pruning, severity was ultimately 

a function of surface fuels and/or slope acting as the mechanisms to carry fire into aerial fuels. As slope and surface 

fuels increase, so does flame length, representing a common cause and effect relationship of intensity and severity 

found in other studies within this review.

Wagle and Eakle (1979) evaluated how a prescribed 

burn one year prior to a wildfire affected tree mortality 

and fuels in east central Arizona. Fuels were quantified as 

the depth of loosely arranged fine and coarse surface litter, 

compacted fine and partially decomposed litter, and total 

litter depth. Their study site was dominated by ponderosa 

pine (Pinus ponderosa) with adjoining untreated and treated 

units on the same slope. Only one live tree was found in the 

untreated stand, while 83 percent of the trees in the treated 

areas survived the wildfire. Most of the dead trees were 

less than 20 cm dbh. One year after the wildfire, understory 

vegetation was twice as abundant in the treated area (9 

percent) than in the untreated area 

(5 percent).

Omi and Kalabokidis (1991) assessed the effects 

of a 1988 wildfire in lodgepole pine (Pinus contorta) and 

subalpine fir (Abies lasiocarpa) forests on the Targhee NF in 

Idaho. They compared fire severity in extensively managed 

sites versus intensively managed sites. Extensively managed 

areas were defined as having a mature overstory that was 

typically dominated by lodgepole pine, although species 

composition varied somewhat with elevation and included 

other tree species common to the Greater Yellowstone 

Ecosystem. Mountain pine beetle (Dendroctonus ponderosae) infestation had resulted in approximately 70 percent 

mortality of lodgepole pine throughout the extensively 

managed areas prior to the 1988 fire season. Intensively 

managed stands were naturally regenerated clearcuts 

composed of mostly lodgepole pine that had undergone 

harvest and slash disposal prior to 1988. Within intensively 

managed stands, tree densities increased with age, ranging 

from 15,000 trees/ha at a height of 0.9 to 5.0 m to 2000 

trees/ha at a height of 0.3 to 0.9 m. Burn severity within 

extensively managed areas and intensively managed sites 

was determined using ocular estimates based on the following criteria:

• unburned: fire did not enter stand

• light: surface burn without crown scorch

• spotty: irregular crown scorch

• moderate: intense burn with crown scorch

• severe: high intensity burn with crowns totally consumed

Fuel loadings were generally higher in extensively 

managed, mature stands compared with intensively managed stands across large (greater than 7.6 cm diameter) 

wood, small (less than 7.6 cm diameter) wood, and litter 

categories. In 89 percent of plots in the extensively managed 

areas, wildfire damage was moderate or severe compared 

to only 20 percent of plots in the intensively managed areas. 

Of the 45 regeneration sites, 38 had ratings of unburned, 

light, or spotty while adjacent, mature stands had ratings 

of moderate and severe. The authors attributed differences 

in fire damage to differences in fuel loading and fuel depth. 

Mature stands were more combustible due to the presence 

of beetle-killed lodgepole pine compared with significantly 

lower amounts of activity fuels in the intensively managed 

sites. Although this study was restricted to variations in 

loading among size classes, additional explanatory variables 

such as differences in stand continuity, crown diameter, 

aspect, slope, and elevation between the two management 

schemes/stand types/topographic conditions were suggested as influencing factors.

Weatherspoon and Skinner (1995) evaluated fire 

severity in northern California in plantations or partially cut 

stands with fuel treatments, partially cut stands without 

treatment, and uncut stands without treatment. Using aerial 

photography that was calibrated by forest records or interviews, the authors quantified fire damage to trees, including 

damage from crown scorch. The authors defined five classes 

of burn severity called fire damage classifications (FDC):

• 0 (did not burn)

• 1 (light underburn, less than 10 percent of trees with greater 

than 50 percent crown scorch)

• 2 (moderate damage, 10 to 50 percent of trees with greater 

than 50 percent crown scorch)

• 3 (greater than 50 percent of trees with greater than 50 percent 

crown scorch but less than 50 percent with crowns consumed)

• 4 (extreme damage, greater than 50 percent of trees with 

crowns consumed)

The following variables were also evaluated: presence 

of grasses and forbs, elevation, aspect, site preparation 

method, damage in adjacent stands related to plantations, 

uniformity of damage, and dominant tree species. In 

partially cut, treated stands, the slash had been broadcast 

burned, machine piled (all piles were burned prior to wildfire), or lopped and scattered. Areas that had been treated 

with broadcast burns (low intensity surface fires) suffered 
USDA Forest Service RMRS-GTR-252. 2011. 5

the least damage in the subsequent wildfire (half were 0 or 

1) compared with mechanically piled or lopped and scattered areas which had slightly higher fire damage ratings. 

By comparison, partially cut, untreated stands had an FDC 

of 3 or 4. Grass was more prevalent in pile and burn treatments than in broadcast treatments, while forbs were more 

prevalent in broadcast burn areas. Fire damage in treated 

plantations was also affected by fire damage in adjacent, 

untreated stands. As fire intensity and the resulting burn 

severity increased in untreated stands, it increased in the 

treated plantations. Treated plantations were relatively 

small (approximately 4 ha), and the authors stated that this 

likely affected the treatment’s effectiveness, particularly 

during extreme burning conditions. Additionally, partially cut 

stands or plantations were under a selection system where 

the large, fire-resistant trees were removed. The broadcast 

burned units showed a trend of damage that decreased 

from the edge inward, compared to the spotty burn pattern 

found in machine-piled treatments and uniform fire damage found in untreated stands. Grasses played a significant 

role in the FDC, as reduced fine fuel loading and continuity 

affected the spatial patterns of severity. Fire damage across 

management schemes increased in the following order: uncut and untreated, partially cut with treatment, and partially 

cut without treatment. Uncut and untreated stands were 

mature stands with less activity fuels than plantations, and 

the closed canopy resulted in a micro-climate that moderated burning conditions. Stands that were partially cut and 

untreated likely had continuous, relatively high loadings of 

activity fuels and fine fuels, resulting in substantial crown 

scorch.

Choromanska and DeLuca (2001) assessed the effects 

of prescribed fire and wildfire on microbial biomass recovery 

and carbon and nitrogen transformations. In August of 1996, 

a high intensity fire partially burned into an area treated 

by a prescribed fire that was applied in May of 1996 on the 

Bitterroot NF in Montana. Both the prescribed fire unit and 

the adjacent, untreated stand consisted of a ponderosa 

pine overstory with thickets of Douglas-fir (Pseudotsuga 

menziesii) regeneration. Prior to the prescribed fire and 

wildfire, this area had not seen fire since 1916. Topography 

and weather conditions were very similar between the 

two treatments at the time of the wildfire. The intent of 

this study was to characterize and evaluate fuel treatment 

effectiveness and to compare nutrient cycling between a 

prescribed fire (PB), wildfire (WF), and the portion of the 

area treated by prescribed fire that burned in a subsequent 

wildfire (PBWF), using an untreated, unburned stand as a 

control. The prescribed fire was conducted with the intent of 

reducing fuel and eliminating the Douglas-fir thickets. Fuel 

estimates were 1.5Mg/ha of fine material (0 to 8 cm diameter) and 0.2 Mg/haof fuels greater than 8 cm diameter. The 

prescribed burn resulted in 42 percent consumption of fine 

fuels and no tree canopy mortality. After the wildfire, the 

WF area showed 100 percent tree mortality and 100 percent 

fine fuel consumption compared to the PBWF where there 

was 50 percent tree mortality and 70 percent fine fuel consumption. Fuel consumption in the soil organic horizons was 

100 percent in the WF, 65 percent in the PBWF, and 42 percent in the PB. The PBWF area had significantly lower rates 

of net nitrogen mineralization and higher potentially mineralizable nitrogen in comparison to the WF area. Microbial 

recovery in the PBWF was faster than in the WF soils. 

Additionally, the PBWF area had double the carbon biomass 

and basal respiration of the WF area two years post-fire. 

Results show that prescribed fire treatment reduced wildfire 

burn severity in surface and aerial fuels, minimized losses 

of labile carbon and nitrogen, and improved soil microbial 

resilience to subsequent wildfire.

Pollett and Omi (2002) sought to empirically evaluate 

fuel treatments tested by recent wildfires. They selected 

sites with adjacent treated and untreated stands with accurate records and less than 15 years between treatment 

completion and subsequent wildfire. The four sites that met 

their selection criteria were the 1994 Webb fire in Montana 

that underwent a broadcast burn treatment in 1989; 

the 1994 Tyee fire in Washington that was treated with 

pre-commercial thinning in the 1970s and a subsequent 

underburn treatment in 1983; the 1994 Cottonwood fire in 

California that was treated with whole tree thinning in 1989 

and 1990; and the 1996 Hochderffer fire in Arizona that 

underwent a thinning treatment in the 1970s and broadcast 

burn in 1995. The authors measured aspect, slope (%), tree 

basal area (m2

/ha), density (stems/ha), average diameter 

(cm), fire severity rating, crown scorch (%), and crown 

weight (kg), and they used severity ratings derived from 

Omi and Kalabokidis (1991). Sites that received mechanical 

fuel treatment reduced wildfire severity rating and percent 

crown scorch more than broadcast burning. Severity rating 

and crown scorch did drop significantly across all treatments, but the Webb fire (broadcast burn only) showed 

the least difference between treated and untreated stands. 

Mechanical treatments yielded more homogenous residual 

stand conditions than the broadcast burn treatment, 

resulting in lower density, larger trees, higher crown base 

heights, and reduced continuity in aerial fuels throughout 

the treatment area. The authors did not support the notion 

that more open stands would change the micro-climate and 

result in higher fire severity, as suggested by Weatherspoon 

and Skinner (1995). Pollett and Omi (2002) reasoned that 

treatments that reduced density and increased average tree 

diameter outweighed any increase in micro-climate effects, 

suggesting the degree of forest openness was not enough to 

sufficiently increase fire behavior and, thus, post-fire effects. 

However, they did state that under extreme burning conditions, fuel treatments may have minimal effect in mitigating 

fire severity. Nonetheless, all treatment types studied across 

sites significantly mitigated canopy scorch, with thinning 

treatments alone or in combination with prescribed fire 

reducing severity more than prescribed fire alone.
6 USDA Forest Service RMRS-GTR-252. 2011.

Martinson and others (2003) examined all natural 

and anthropogenic fuel alterations within the perimeter of 

the 2002 Hayman fire in Colorado, including past wildfires, 

prescribed fires, commercial tree harvests, pre-commercial 

stand improvements, plantations, and surface fuel treatments. Many of the treatments were not implemented with 

the intent of mitigating wildfire burn severity. The authors 

utilized a burned area severity map and verified results with 

field sampling, classifying severity as low, moderate, or high. 

The authors concluded that the extreme weather conditions 

and other abiotic factors that influenced burning conditions rendered most pre-wildfire stand treatments useless; 

although there were examples in which prescribed fires, old 

burns, thinning treatments, and timber harvests mitigated 

wildfire burn severity by changing fire behavior from crown 

to surface fire. In areas that were burned under moderate 

conditions, recent prescribed burns had lower wildfire 

severity than older prescribed burns, with a noticeable difference between units that had been burned multiple times. 

However, uncertainties in pre-fire forest structure made 

identifying specific attributes to predict treatment success 

impossible.

Skinner and others (2004) utilized the Cone fire of 

2002 to evaluate multiple treatment types within the Black 

Mountain Experimental Forest in northern California. Forest 

structure within treatments was grouped into two distinct 

ecological groups: late-seral stage and mid-seral stage. In 

late-seral treatments, only ladder fuels were removed. In 

mid-seral stands, large, mature trees greater than 41 cm 

dbh and smaller trees (ladder fuels) were removed, creating 

stands composed of intermediate age classes. Six of each 

of these units, ranging from 77 to 142 ha, were created 

within the Experimental Forest. Each of the six units was 

split in half; one received a prescribed fire treatment, and 

the other received no additional management activity 

with the exception of grazing prior to the wildfire. Of these 

experimental units, two mid-seral stands and one late-seral 

stand were burned in the 2002 wildfire. Pre-treatment surface fuels varied greatly across sites; 0- to 7.6-cm material 

ranged from 3.6 to 20.8 Mg/ha (mean of 9.4 Mg/ha), and 

material greater than 7.6 cm ranged from 1.1 to 86.8 Mg/ha 

(mean of 24.2 Mg/ha). The harvest system in the mid-seral 

treatments increased surface loading by an average of 7.8 

Mg/ha, particularly in the 0 to 7.6 cm size class, although 

this was also quite variable. Late-seral harvesting resulted 

in minimal fuel increases. The prescribed fire treatments 

essentially consumed all size classes less than 7.6 cm, 

except unburned islands, and significantly reduced larger 

surface fuels. Wildfire-induced tree mortality was highest 

in untreated stands (greater than 90 percent), and thinning 

only treatments that consisted of lop and scatter or that 

did not address surface fuels showed the second highest 

levels of mortality (40 to 60 percent). Similar to the results 

in Weatherspoon and Skinner (1995) and others, thinning 

treatments followed by prescribed fire two to four years 

prior to the wildfire showed the least fire-induced tree 

mortality compared with thin-only treatments. In addition, 

surface fuel loading and continuity again appeared to be 

key influences on post-fire tree mortality in ponderosa pine 

stands.

Based on the large area burned by the RodeoChediski fires in Arizona, Finney and others (2005) evaluated 

the effectiveness of prescribed burning on reducing burn 

severity in treatments that were completed between 1993 

and 2001. They used the differenced Normalized Burn Ratio 

(dNBR) that was interpreted from Landsat satellite imagery 

and the burn severity classes of Key and Benson (2005) to 

compare areas treated with prescribed fire versus untreated 

areas. Localized effects such as differences in fuel composition and consumption of different parts of the fuelbed were 

not addressed. Overall, burn severity was reduced where 

prescribed fires had occurred within the nine years prior 

to the wildfire. Burn severity was more consistently and 

significantly reduced in areas that were burned within four 

years before the wildfires. Burn severity was less where 

treatments were larger and in areas that had been burned 

multiple times. Because prescribed fires can yield patchy 

results, Finney and others (2005) suggested that increased 

treatment size may promote heterogeneity within the 

prescribed burn perimeter, thereby reducing overall burn 

severity across the treatment.

Raymond and Peterson (2005) measured fire damage 

across different treatment types when the Biscuit fire of 

2002 burned through two separate study sites in the mixed 

conifer forest of the Oregon Coast Range. The first site was 

divided into three treatment plots (6 to 8 ha) composed 

of stands that were thinned, thinned then broadcast 

burned, or untreated. The second site had three plots that 

were thinned, thinned with coarse woody debris left, or 

untreated. The treatments were a combination of crown 

thinning and thinning from below. Douglas-fir, the dominant 

species on the site, was thinned to a relative density of 0.25 

(proportion of standard volume for a given stand age and 

site quality), and evergreen broadleaf species were thinned 

to a spacing of 8 m. Fuel characteristics were quantified 

both pre- and post- treatment after the Biscuit fire. The 

authors measured 1-hr, 10-hr, and 100-hr fuel size classes, 

live woody and herbaceous fuels, fuel depth, and computed 

summary statistics. Additionally, aerial fuels were calculated 

from measured tree dbh, species, crown class, total tree 

height, and crown base height. Prior to the wildfire, thinning 

treatments across all sites decreased tree density, basal 

area, and crown bulk density and increased both crown 

base height and mean dbh. However, the effects on surface 

fuels differed with respect to treatment. There was more 

surface fuel in thinned-only stands, while the thin and burn 

treatment showed a net decrease in surface fuels. Fire 

damage was measured by crown scorch volume, height of 

crown scorch, and tree mortality. In thinned stands, crown 

base height and mean dbh were higher. Both crown scorch 
USDA Forest Service RMRS-GTR-252. 2011. 7

volume and crown scorch height increased in the following 

order: thin and burn, untreated, and thin only. Douglas-fir 

tree mortality two years post-fire was 80 to 100 percent in 

thinned stands, 53 to 54 percent in untreated stands, and 

5 percent in thinned and burned stands. Untreated stands 

also had the greatest variance in fire damage. The increased 

surface fuel loading in thinned only treatments outweighed 

any benefit of increased crown base height in reducing burn 

severity. Patterns of tree damage varied among tree species; 

yet without treating surface fuels, the overstory trees all had 

relatively high scorch heights and mortality. The fire burned 

around the thinned and burned treatments where surface 

fuels had been greatly reduced but burned through thinned 

treatments. Raymond and Peterson (2005) also concluded 

that crown scorch volume, or the percent of crown volume 

scorched, is a better indicator of mortality than scorch 

height.

Cram and others (2006) evaluated fuel treatment 

effectiveness across multiple vegetation types after Arizona 

and New Mexico wildfires in 2002 and 2003. They sampled 

sites with fuel treatments and adjacent untreated areas with 

similar vegetation, wildfire conditions, slope, and aspect. All 

treated and untreated areas sampled were greater than 16 

ha in size with no post-fire salvage cutting. Study sites were 

in the Oso and Borrego fires, which burned through mid- to 

high-elevation stands dominated by ponderosa pine with intermixed Douglas-fir and white fir (Abies concolor) that were 

treated by commercial harvest followed by prescribed fire. 

Two additional study sites were within the perimeter of the 

Rodeo-Chediski fire in Arizona, which burned at relatively 

low elevations in ponderosa pine and gambel oak (Quercus 

gambelli). The two sites consisted of a non-commercial 

lop, pile, and burn treatment and non-commercial lop and 

scatter treatment. Measurements that characterized the 

respective stands were basal area, density, dbh, tree height, 

crown length, height to pre-fire live crown, and canopy bulk 

density. Burn severity measurements included bole char 

height, crown scorch height, crown consumption height, 

percent crown scorch, and percent crown consumption. 

Burn severity was also quantified using the previously 

mentioned ocular estimates for crown damage developed 

by Omi and Kalabokidis (1991) in addition to the ocular 

estimates for surface damage modified after Ryan and Noste 

(1985). Results yielded a canopy fuel consumption threshold 

that consisted of canopy bulk density of 0.047 kg/m3

. Stands 

that underwent surface fuel treatments with canopy bulk 

density below this threshold showed no evidence of canopy 

fuel consumption. This threshold also applied to lop and 

scatter plots, although increased surface fuel load resulted 

in significant canopy scorch. The third lop and scatter plot 

that was above the crown bulk density threshold (0.084 kg/

m3

) showed evidence of torching characterized by canopy 

fuel consumption. All untreated stands showed evidence of 

torching or crown fire and were above this threshold, supporting the conclusion that canopy bulk density is a limiting 

factor in torching and crown fire initiation (Rothermel 1991). 

Cram and others (2006) concluded that as tree density and 

basal area decreased and mean tree diameter increased, fire 

effects decreased. They stated that canopy bulk density was 

perhaps the best quantitative indicator of potential crown 

damage, suggesting that aggressive treatments are needed 

to significantly reduce canopy fuels to achieve this loading. 

Additionally, mechanical treatments followed by prescribed 

fire provided the best manipulation of surface and aerial 

fuels and resulted in the most significant mitigation of fire 

effects. Accordingly, treatments where slash was scattered 

still left stands susceptible to high severity fire effects, even 

in recent treatments four years old or less.

Omi and others (2006) evaluated fuel treatments 

within the boundaries of five large, recent wildfires: the 

Hayman fire (2002) in Colorado, the Aspen fire (2003) 

in Arizona, the Davis fire (2003) in Oregon, the Power 

fire (2004) in California, and the Fischer fire (2004) in 

Washington. Across these study sites, a full range of treatments were tested, including thinning from above and 

from below both with and without slash removal and in 

conjunction with prescribed fire or pile burning. These sites 

spanned a large range of environmental and topographic 

conditions. The majority of the study sites were in dry, 

mixed conifer forests dominated by ponderosa pine, 

Douglas-fir, or Jeffrey pine (Pinus jeffreyi). Canopy severity 

ratings were derived from Omi and Kalabokidis (1991), and 

fire effects on surface and ground fuels were evaluated 

based upon Ryan and Noste (1985). The authors measured 

canopy cover of understory plants and characterized soils to 

determine any possible relationship between moisture and 

nutrient (carbon and nitrogen) availability and non-native 

plant abundance. Results showed that treated areas had 

lower tree density (484 versus 1110 trees/ha), lower crown 

bulk density (0.07 kg/m3 versus 0.10 kg/m3

), higher crown 

base height (8.0 m versus 4.1 m), and increased mean tree 

diameter (38.4 cm versus 28.6 cm) compared with adjacent 

untreated stands. With the exception of height to canopy (or 

canopy base height), differences in treated versus untreated 

stands were greatest in treatments that were intended to 

reduce canopy fuels. Across all study sites, treatments 10 

years old or less were generally effective if they reduced surface fuels. However, the most effective treatments not only 

reduced litter and other surface fuels but also served as low 

thinning treatments by reducing canopy bulk density and increasing both height to canopy and mean tree diameter. The 

treatment type that most effectively achieved this result was 

mechanical thinning followed by some type of slash removal 

and surface fuel treatment within two years of the thinning. 

Treatments at the Hayman and Davis fires that involved both 

thinning and slash removal produced the most dramatic 

results of all study areas, with 80 percent less canopy scorch 

in treated areas compared to adjacent, untreated stands.

Moghaddas and Craggs (2007) used the 2005 Bell 

fire to evaluate a private land fuel treatment adjacent to an 
8 USDA Forest Service RMRS-GTR-252. 2011.

untreated stand on the Plumas NF in northern California. 

Species composition was dominated by Douglas-fir, with 

the remainder of the species composed of incense cedar 

(Calocedrus decurrens), ponderosa pine, sugar pine (Pinus 

lambertiana), white fir, and California black oak (Quercus 

kelloggii). The area was subjected to a selection harvest. 

Pre-treatment stand basal area was 59 m2

/ha with a stand 

density of 1181 trees/ha. Post-treatment tree density averaged 181.1 trees/ha, 9.2 m canopy base height, and 23.7 

m2

/ha basal area. Surface fuels were characterized with an 

average depth of 3.6 cm and 11.9 Mg/ha for 1-hr, 10-hr, and 

100-hr fuels combined. The treatment resulted in reduced 

vertical and horizontal continuity of aerial fuels. Compaction 

of surface fuels from the harvesting operation changed the 

surface area to volume ratio, while chipping unmerchantable tops at the landing mitigated increasing post-treatment 

surface fuel loading. Although the focus of the study was 

fire behavior and suppression efficiency, the authors measured severity in terms of percent crown volume scorched. 

Crown scorch was 75 percent at the southern edge of the 

treatment and decreased to less than 10 percent within 60 

m as the fire moved to the interior of the treatment. The 

increased vertical and horizontal spacing of canopy fuels 

in the treated area greatly reduced passive crown fire and 

mitigated burn severity in the tree canopy. However, the 

treatment was situated on a ridgetop while the rest of the 

fire perimeter was on a relatively steep slope with a southerly aspect. Slope and aspect likely played significant roles 

in minimizing overall crown scorch and contributed to the 

spatial changes in severity across the treatment.

Strom and Fulé (2007) sampled treatments burned 

during the 2002 Rodeo-Chediski fire in Arizona that had 

been implemented with the explicit intent of mitigating fire 

effects. Fourteen sites were selected; all of which had adjacent treated and untreated stands with similar topography 

and no barriers to impede fire spread between them. Of 

the 14 sites, 12 were non-commercial thinning treatments 

where slash was piled and burned, and slash was either 

scattered or crushed in the remaining 2. All treatments 

were completed between 1990 and 1999. Post-fire tree 

measurements included tree species, condition, dbh, total 

height, canopy base height, bole char height (minimum and 

maximum), and a dwarf mistletoe rating (0 to 6) derived 

from Hawksworth (1977). Post-wildfire tree condition was 

also classified as either live, declining, or one of four stages 

of snags: recent, loose bark, clean, or broken above breast 

height (from Thomas and others 1979). Tree mortality was 

compared between treated and untreated stands. A subsample of increment cores was also collected to determine 

age and growth data of residual trees, while regenerating 

trees and shrubs were quantified by species, condition, and 

height class. Untreated stands had higher post-fire proportions of small trees, causing higher bole char, fire-induced 

increases in crown base height, and increased overall tree 

mortality, all of which contributed to a shift in the residual 

tree distribution toward larger trees. Treated areas had 

significantly higher live tree density and higher crown base 

height, with 50 percent mortality in treated stands compared to 95 percent in untreated stands. Due to similarities 

in pre-fire basal area and treatment-caused differences in 

fire effects, the authors concluded that the arrangement of 

canopy fuels—not the overall amount of fuels in the form 

of trees—was the determinant of burn severity. That is, fire 

effects differed greatly between stands with many small 

trees and those with a few larger trees. Initial measures of 

recovery were similar between treated and untreated areas, 

with the exception of the abundance of surface fuel and 

manzanita (Arctostaphylos spp.), both of which were more 

abundant in untreated areas. Ponderosa pine regeneration 

was patchy in both treated and untreated areas. Areas that 

were untreated prior to the wildfire would likely become 

shrubfields dominated by manzanita, gambel oak, and New 

Mexico locust (Robinia neomexicana). In contrast, areas 

that were treated prior to the wildfire would likely become 

dominated by ponderosa pine with larger trees, increased 

basal area, lower tree density, and a gambel oak understory 

in the coming decades. The authors concluded that fuel 

treatments are not only effective in mitigating fire severity 

but also contribute greatly to retaining the ecological functionality of southwestern ponderosa pine forests.

Martinson and Omi (2008) assessed the mitigating 

effect of fuel treatments on wildfire severity. The study 

site was on the Mississippi Sandhill Crane National Refuge, 

where slash pine is dominant and longleaf pine is present 

on flat topography. A prescribed fire in the prescribed firemaintained Fontainebleau Unit on 18 April 1999 escaped 

by spotting across a railroad and became a wildfire that exhibited extreme fire behavior in untreated fuels on adjacent 

private land. The team opportunistically collected post-fire 

data in September 1999 to quantify fuel and fire severity 

differences between treated and untreated stands. The 

authors did not sample ground fuels because these were 

largely consumed by the fire. They used nine variable radius 

plots in each condition, with plot centers separated by 60 m 

and surrounded by a 60-m buffer to minimize edge effects. 

They ocularly assessed height to post-fire live crown and 

maximum scorch height. They found that trees in treated 

plots were 50 percent taller than trees in untreated plots 

and had twice the girth. Crown base heights were nearly 

twice as high in treated plots, while shrubs were twice as tall 

in untreated plots. Shrub density did not differ significantly. 

Maximum needle scorch height was nearly twice as high in 

untreated plots. Martinson and Omi (2008) concluded by 

noting the rarity of empirical, retrospective studies of fuel 

treatment effectiveness, and they reiterated the need to 

continue collecting empirical data from other natural experiments where wildfire burns through fuel treatments.

• • • • •
USDA Forest Service RMRS-GTR-252. 2011. 9

Rangeland Studies

Prior to European settlement, fires in sagebrush communities typically 

burned in a patchy fashion, leaving unburned islands (Miller and Eddleman 

2001). Sagebrush and grass were probably dominant with a strong perennial 

grass and forb component in the understory. Excessive livestock grazing by 

Euro-American settlers in the late 1800s and early 1900s caused major changes 

in plant communities within a few decades. By the early 1900s, an estimated 26 

million cattle and 20 million sheep grazed in western rangelands. The grazing 

capacity of western lands had decreased by an estimated 60 to 90 percent by 

the 1930s (Miller and Eddleman 2001). From 1880 to 1912, when the number 

of cattle, sheep, and horses was particularly high, only 44 fires were reported 

in Great Basin rangelands, burning only 4500 ha (Miller and Narayanan 2008).

The Bureau of Land Management and the Forest Service reported that the 

annual area burned in wildfires is on a long-term upward trend (Davison 1996, 

Westerling 2006). The number of rangeland fires larger than 2000 ha has increased from 15 percent of all fires from 1960 to 1982 to 60 percent of all 

fires from 1983 to 2003 across the sagebrush (Artemisia spp.) steppe in the 

Snake River Plains and Northern Basin and Range ecoregions in the Great Basin 

(Kuchy 2008). In 2007, the Murphy complex burned over 240,000 ha of mainly 

sagebrush steppe in southern Idaho and northern Nevada; the Milford Flat fire 

burned over 120,000 ha of Utah rangelands in the same year. The predicted 

change in climate combined with the large fires that burned during the 2007 fire 

season and the need for reducing the likelihood of extensive fires in western 

rangelands have focused considerable attention on the effects of historical and 

current grazing regimes on fire fuels, fire effects, behavior, and post-fire soil and 

vegetation recovery. Because there are no explicit examples in the literature of 

wildfires that have burned across rangelands where fuel treatments have been 

conducted, this review (see Rangeland Studies sidebar) examines the potential 

effects of livestock grazing (removal of herbaceous fuels) on fuels, potential 

fire behavior, and fire effects. The geographic focus is on the sagebrush steppe 

ecosystems of the Great Basin, but examples are also included from the forestrangeland interface. The case studies (arranged in chronological order) have 

focused on the degree to which grazing could alter fire behavior.

Rangeland Studies Literature

Rummel (1951) examined long-term effects in 

vegetation differences between grazed and ungrazed ponderosa pine-dominated plateaus in central Washington. 

Vegetation characteristics were compared on two plateaus 

that were similar in geologic origin, elevation, climate, and 

timber type. Both plateaus were unaffected by fire, and 

grazing was identified as the only broad-scale disturbance. 

Meeks Table had never been grazed by livestock while 

Devil’s Table had been heavily utilized by livestock during 

the 40 years that led up to this study. Study plots were 

grouped into three classifications: (1) pinegrass-elk sedge 

(Calamagrostis rubescens-Carex geyeri) understory, open 

ponderosa pine overstory; (2) pinegrass-elk sedge understory, mixed ponderosa pine-Douglas-fir overstory; and 

(3) subalpine needlegrass (Achnatherum nelsonii)–

Sandberg bluegrass (Poa secunda) open grassland type. 

Herbaceous and shrubby understory vegetation density 

and composition were determined for both mesas. 

Herbaceous weight of pinegrass was also determined. All 

trees less than 10.2 cm dbh were tallied by species and 
10 USDA Forest Service RMRS-GTR-252. 2011.

height class, while all trees greater than 10.2 cm dbh were 

recorded by species and dbh class. Grassland openings 

on the grazed mesa had been invaded by ponderosa pine 

while openings on the ungrazed mesa remained free 

of seedlings. Pinegrass cover was high in the grassland 

openings on the ungrazed mesa. Herbaceous and shrubby 

understory cover beneath open ponderosa pine stands 

averaged 35 percent on ungrazed mesas and 14 percent on 

grazed mesas. The pinegrass biomass (grass fuels) was 

953 kg/ha on the ungrazed mesa and 269 kg/ha on the 

grazed mesa. On the ungrazed mesa, there were only 

210 trees/ha that were less than 10.2 cm dbh; on the 

grazed mesa, there were 8132 trees/ha that were less than 

10.2 cm dbh. The authors concluded that the vegetative 

ground cover and litter prevented the establishment of 

tree seedlings on the ungrazed mesa. In this ecosystem, 

the removal of understory vegetation by livestock 

facilitated tree propagation and growth. Livestock may 

have reduced fire potential by reducing grass and shrub 

biomass.

Madany and West (1983) examined the relative 

importance and interaction of fire cessation and livestock 

grazing on grazed and ungrazed mesas in southern Utah. 

Ungrazed study sites had been isolated from both fire and 

grazing. The study sites were located in Zion National Park 

in Utah. The area was dominated by ponderosa pine and 

gambel oak (Quercus gambelii), however, Rocky Mountain 

juniper (Juniperus scopulorum), pinyon pine (Pinus edulis), 

and bigtooth maple (Acer grandidentatum) were also present in the area. In addition to gathering historical land use 

information for this area, the authors collected sapling, 

shrub, forb, and graminoid cover data. A fire history was 

constructed from cross sections taken from 111 fire-scarred 

trees. A reduction in herbaceous cover and increases in 

woody species density were attributed to livestock grazing. 

While changes in vegetation composition and structure 

resulted in decreased fire frequency on the grazed mesa, 

ungrazed mesas retained savanna-like conditions despite 

the absence of frequent fires. The authors suggested that 

heavy grazing may lead to an increase in gambel oak stem 

density because oak more readily establishes when the 

grassy interspaces are disturbed. The dense sod associated 

with perennial grasses is likely the main controlling factor of 

ponderosa pine regeneration, however allelopathic interactions between grasses and pine seedlings, and competition 

for limited soil moisture, may also play important roles in 

pine regeneration. In summary, livestock grazing may help 

to accelerate functional and structural changes in ponderosa pine forests. As grazing depletes the herbaceous layer, it 

reduces fire frequency while simultaneously enabling pine 

seedling regeneration.

Zimmerman and Neuenschwander (1984) focused 

on the influences of livestock grazing on plant community structure, fire frequency, and fire intensity in the 

Douglas-fir/ninebark (Pseudotsuga menziesii/Physocarpus 

malvaceous) habitat type of northern Idaho. The area was 

grazed by cattle, sheep, and native ungulates since the 

1920s, heavily from 1945 to 1967. Vegetation was sampled 

in 18 15- by 25-m plots in grazed and ungrazed areas (exclosures), including number of trees, tree basal area, shrub 

density, herbaceous plant cover and frequency, herbaceous 

biomass, and accumulation of downed woody fuels. Trees 

in size classes less than 40 cm dbh were significantly more 

numerous in the grazed plots compared to ungrazed plots, 

particularly in the 5- to 20-cm dbh classes. Douglas-fir seedlings were more abundant than ponderosa pine seedlings in 

grazed plots, indicating that long-term heavy grazing favors 

Douglas-fir rather than ponderosa pine. No significant effects were reported in the larger size classes of trees. Tree 

basal area was significantly higher in grazed compared to 

ungrazed stands, which was attributed to the larger number 

of young trees in the grazed stands. Total shrub density did 

not differ between grazed and ungrazed stands. Service 

berry (Amelanchier alnifolia), ninebark (Physocarpus spp.), 

and white spiraea (Spiraea betulifolia) had a greater density 

in grazed stands, while the remaining nine shrub species 

showed a higher density in ungrazed stands; however, only 

the density for redstem ceanothus (Ceanothus sanguineus), 

chokecherry (Prunus virginiana), and yerba buena (Sarureja 

douglasii) were significantly different. Total shrub cover 

was significantly lower in grazed stands—15.8 percent 

in grazed stands compared to 24.5 percent in ungrazed 

stands. Herbaceous biomass of bluebunch wheatgrass 

(Pseudoroegneria spicata), Idaho fescue (Festuca idhoensis), and pinegrass was significantly lower in grazed plots, 

while biomass of Columbia brome (Bromus vulgaris) and 

Kentucky bluegrass (Poa pratensis) was higher in grazed 

stands. Total forb cover was not significantly different 

between grazed and ungrazed stands. Downed woody 

fuel loadings of all size classes, including duff, was higher 

in grazed stands. Live herbaceous fuels were significantly 

lower (467 kg/ha) in grazed compared to ungrazed stands 

(719 kg/ha). The authors concluded that livestock grazing 

has the ability to alter vegetation structure and composition and also the composition of all fuel classes in the 

Douglas-fir/ninebark habitat type. The modifications result 

in a forest that is less likely to burn in frequent surface fires; 

that is conducive to vertical fire spread; and, in the absence 

of fuel treatments, promotes the occurrence of infrequent, 

high intensity fires.

Sapsis and Kauffmann (1991) measured fuel load, 

fuel moisture, fire weather, fire behavior, and consumed 

biomass during prescribed burning in sagebrush steppe 

in Oregon. Two fire treatments were conducted and 

compared: a fall burn (four plots) and a spring burn (five 

plots). The overstory was dominated by basin big sagebrush 

(Artemisia tridentata subsp. tridentata), and the understory 

was dominated by Idaho fescue and bluebunch wheatgrass. 

Each burn unit was at least 30 to 50 m in size and the burn 

treatments were randomly assigned; 1-hr, 10-hr, 100-hr, 
USDA Forest Service RMRS-GTR-252. 2011. 11

herbaceous, and downed woody fuels were measured prior 

to the treatments. Sagebrush cover was estimated by the 

line-intercept method. Shrub volume was measured and 

sagebrush biomass was calculated, as was the biomass of 

the herbaceous material. Post-fire fuels were estimated in 

a similar manner. The fall burn resulted in a longer flame 

length (4.1 compared to 1.7 m in the spring), higher rate of 

spread (1.6 compared to 0.3 m/s in the spring), and higher 

fire line intensity (6400 compared to 880 kW/m). Sagebrush 

foliar moisture was 186 percent in the spring and 97 

percent in the fall. The consumption of fine fuel was not 

significantly different between treatments. However, consumption of 10-hr and 100-hr fuels was significantly higher 

in the fall burn. Biomass consumption was 93 percent in 

the fall burns compared to 84 percent in the spring burns. 

The largest difference in fuel consumption was found in the 

10-hr fuels (85 percent for the fall burn and 52 percent for 

the spring burn) possibly due to the higher foliar moisture 

in the spring.

Link and others (2006) explored fire-plant-grazing 

interactions in a field in Saddle Mountain National Wildlife 

Refuge in Grant County, Washington. Relationships among 

fire ignition probability, cheatgrass (Bromus tectorum) 

cover, native perennial plants, and grazing are complex. 

The percent cover of vascular plant species, bare soil, soil 

cryptograms, litter, and cheatgrass was estimated in late 

August and early September 2002 in 176 plots. Fires were 

ignited on the upwind side of the plots and were considered a sustained fire if they grew to an area of 100 m2

. 

Fine-scale aerial photos taken in September 2002 were 

used to estimate cheatgrass cover in the plots. Fire ignition 

risk was 100 percent when the cover of cheatgrass was 

45 percent or more, while the fire ignition risk dropped to 

46 percent when cheatgrass cover was 12 percent or less. 

When ground cover of native perennials, litter, and soil 

approached 31 percent, the risk of ignition and sustainable 

fire was significantly reduced. Wind speeds greater than 

5.7 km/hr increased fire risk, while fuel moistures greater 

than 7.5 percent decreased fire risk. Cheatgrass cover 

dramatically affected fire spread. The authors concluded 

that management strategies aimed at reducing cheatgrass 

cover and promoting perennial plants would reduce the risk 

of fire spread.

Nader and others (2007) presented techniques 

that have been explored to prevent the start and spread 

of wildfires in rangelands. The objective of fuel reduction 

is to change the fire behavior by changing the fuel bed 

depth, fuel loading, vegetative cover, and ladder fuels such 

that the flame length never reaches 1.2 m. Methods for 

fuels management were discussed, including mechanized 

treatment, herbicides, prescribed fire, hand cutting, and 

prescribed grazing. The authors compared the effectiveness and costs for the different methods in rangelands. 

Prescribed grazing was discussed in much detail, and the 

authors compared effects of grazing animal species, grazing 

intensity, season of grazing, animal condition, and desired 

outcome of the grazing treatment. The authors found 

that grazing is an appropriate tool when addressing smalldiameter (1-hr and 10-hr) fuels. Grazing can impact these 

fuels by ingestion and trampling. Many factors affect the 

success of using grazing for fuels management, including 

species of livestock, the animal’s previous grazing experience, time of year in relation to plant physiology, grazing 

intensity, grazing duration, plant secondary compounds, 

and animal physiological state. Grazing before seed set can 

change seed bank dynamics. Repeated grazing of perennial 

species can deplete root carbohydrates and cause mortality 

that can shift species composition. Each species of grazing 

animal has a unique utilization pattern. Cattle are effective 

in grass removal, while sheep and goats are effective on 

forbs and browse. Lactating and young animals are not 

recommended for fire fuel control because the animals may 

be required to eat below their nutritional needs. Care must 

be taken to select the appropriate combination of animal 

species, animal condition, season, duration, and intensity 

of grazing in order to reach desired fuel management 

objectives.

• • • • •
12 USDA Forest Service RMRS-GTR-252. 2011.

for commercial logging or fire hazard reduction activities. 

Areas subjected to commercial logging, salvage logging, or 

other treatments not designed as fuel treatments mostly 

burned with high intensity crown fire. One partially treated 

unit where handpiles had been created but not burned 

exhibited fire behavior and effects similar to the untreated 

stands. Murphy and others (2007) found that most of the 

area fuel treatments reduced fire behavior from a crown 

fire to a surface fire. Area fuel treatments adjacent to subdivisions provided important safety zones for firefighters, 

which increased fire suppression effectiveness and helped 

firefighters save houses. Urban lot treatments reduced 

ember production, and reduced heat and smoke, allowing 

firefighters to be more effective. A large number of houses 

burned from firebrands that were generated from other 

burning houses rather than wildland fuel. Fuel treatment 

units on steep slopes burned at higher intensities than 

those on flat ground. Some fuel treatment units burned 

at high fire intensity because they were adjacent to and 

downwind from untreated units. Crown fire momentum 

carried high fire intensity partway into these treated areas 

before the more widely spaced crowns and reduced surface fuel load caused the fire to transition to the surface.

The lightning-ignited Antelope complex started 

5 July 2007 and burned 9478 ha on the Plumas NF in 

California. Fites and others (2007) present findings and 

recommendations derived from evaluating the use and 

effectiveness of fuel treatments and fire behavior inside 

treated and untreated areas of dense, mixed conifer 

forest and shrubs. Their report is based on firsthand 

observation of fire behavior and suppression. Post-fire, the 

team quantified fire behavior and effects from field plots 

and Landsat satellite imagery. The fire burned through 

areas treated for fuel hazard reduction, untreated areas, 

and areas protected for California spotted owl (Strix occidentalis) and goshawk (Accipiter gentillis) habitat, as 

well as Riparian Habitat Conservation Areas. More than 

2007 Wildfires Literature

Murphy and others (2007) assessed fuel treatment 

effectiveness at the 1243-ha Angora fire, which started 

from an unattended campfire southwest of South Lake 

Tahoe in California on the afternoon of 24 June 2007. The 

fire burned under some of the most severe fire danger 

conditions experienced in that area during the previous 20 

years. The fire spread 6.4 km in three hours and burned 

over 250 structures on private property; most of the fire 

growth was under hot, dry, and windy conditions. U.S. 

Forest Service (USFS) lands constituted 89 percent of the 

area burned, about 50 percent of which was treated. 

Treatments covered 8 percent of the area on state and 

private land. About 300 urban lots and 93 ha of private 

property burned. The USFS Region 5 Fire Director sent a 

team to evaluate the effects of fuel treatments (mostly 

thinning with surface fuels piled and then burned) on 

fire behavior, fire suppression, structure ignition, and 

public safety/egress, as well as fire behavior in untreated 

areas and in other vegetation management treatment 

units (commercial thinning or salvage logging). Using 

on-the-ground and aerial reconnaissance; interviews with 

homeowners, firefighters, fire scientists, and fire behavior 

experts; and videos and photos taken prior to, during, 

and after the Angora fire, the team evaluated 16 fuel 

treatments (194 ha) on USFS land, 84 percent of which 

burned with surface fires. Of the 150 urban lots the team 

assessed, 80 percent burned with surface fire. About 

164 ha of USFS fuel treatments burned with surface fire 

intensity. Many of the untreated stands were on steep 

ground with heavy fuel, and most burned in crown fires 

that consumed 95 to 100 percent of the tree crowns and 

surface vegetation. Untreated stands were mostly dense 

and multi-storied stands with abundant ladder fuels and 

moderate to heavy woody fuel and shrubs in the understory, including manzanita, bitterbrush (Purshia tridentata), 

and sagebrush. Untreated areas had trees with little 

commercial timber value, poor access, or adverse terrain 

2007 Wildfires

Wildfires were extensive in the summer and fall of 2007. Many burned through 

fuel treatments, providing the opportunity for assessment of fuel treatment 

effectiveness. Several reports already published by a number of teams are summarized (see 2007 Wildfire sidebar) both to increase their visibility and because 

they contribute to this synthesis of case studies. Compared to the previously 

reviewed journal articles, these reports communicate less about ecological fire 

effects and more about the influence of fuel treatments on fire behavior because 

they are targeted primarily at wildland firefighters who are more concerned with 

safety and are charged with protecting people and property.
USDA Forest Service RMRS-GTR-252. 2011. 13

half of the area burned during the first two days when 

there were few firefighters working on the fire. Areas with 

fuel treatments had significantly reduced fire behavior, 

higher tree survival, and less impact on soils compared to 

untreated areas. Treated areas and recently burned areas 

had significantly lower burn severity than untreated areas, 

and burn severity was significantly higher in protected 

areas (owl and goshawk core and nest stands) than in 

other untreated portions of the landscape. Firefighters 

reported using treated areas in fire suppression. Treated 

areas provided safe escape routes for firefighters when 

other routes were not available. Even treated areas that 

burned intensely when few firefighters were present had 

reduced fire effects. Observations of fire behavior during 

the first two days suggested that large untreated areas 

allowed the fire to build momentum and contributed to 

increased rate of spread and intensity, making it more 

likely that suppression resources would be overwhelmed 

and treated areas would be threatened. As the wildfire 

burned in treated areas, it transitioned from crown fire or 

high intensity surface fire to moderate intensity surface 

fire. Fites and others (2007) recommended that more of 

the landscape be treated to reduce the likelihood of fires 

gaining momentum and increasing in behavior to a point 

where suppression and nearby fuel treatments become 

less effective. They also recommended treating protected 

areas to make them more resilient to fires and to prevent 

them from contributing to increased severe fire behavior 

across the landscape.

Dailey and others (2008) assessed fire behavior 

and effects on treated and untreated lands on the 2007 

Moonlight fire, adjacent to the Antelope complex on the 

Plumas NF in California. Plume-dominated fire and longrange spotting exemplified intense fire behavior. From 3 

September to 15 September, the wildfire burned 64,997 

ha, including protected areas for California spotted owl and 

goshawk. Data from both randomly stratified field plots 

and Landsat satellite imagery were used in the assessment. 

Satellite dNBR data were instrumental in showing that 

most (68 percent) of owl core habitat areas had 75 to 100 

percent canopy cover change, while about half (46 percent) of goshawk core areas had 75 to 100 percent canopy 

cover change, possibly rendering them inviable. Fire intensity and crown consumption were higher in the untreated 

protected areas than in treated areas. A smaller proportion 

of lands burned in the Moonlight fire had been treated 

compared to lands in the Antelope complex, rendering the 

fuel treatments less effective and making fire suppression 

more difficult. Daily and others (2008) recommended that 

larger portions of the landscape be treated to reduce the 

likelihood of fires gaining momentum and burning with 

high intensity into protected areas. They also suggested 

watershed-scale prescribed burns as a practical means to 

reduce fuel loads across broad areas of difficult terrain 

and in sensitive areas where other treatment options are 

limited.

Rogers and others (2008) assessed the Grass Valley 

fire, which burned in southern California in October 2007 

under warm, dry weather and fuel conditions (relative 

humidity of 8 percent, live woody fuel moistures of 56 

percent), Santa Ana winds of 29 to 64 kph, and gentle to 

steep slopes (less than 10 to greater than 60 percent). 

Many homes were threatened, and 199 structures were 

damaged or destroyed by the fire. Most of the area and 

many of the houses burned on the first day of the fire. The 

oak-shrub vegetation had an oak and pine overstory with 

dense white fir in the understory, was interspersed with 

chaparral dominated by manzanita, and had surface fuels 

of pine needles and oak leaves. Fuels had been treated on 

30 percent of the 503 ha that were burned by the fire. Fuel 

treatments were designed to reduce crowning potential 

and ember production. Treatments varied but generally 

included removal of dead, dying, and diseased trees 

combined with thinning, pruning, chipping, and burning to 

reduce surface litter, woody fuel, and ladder and canopy 

fuel. More conifers than oaks were removed and more 

understory trees than overstory trees were removed, leaving widely spaced woodlands that were dominated by oaks 

and had discontinuous surface fuels. Along roads, removal 

of dead trees prior to the fire lessened the risk to firefighters working in and around structures, made evacuation 

routes safer, and reduced ember production and spot fires. 

Other treatments were intended to make public 

evacuations safer while improving visibility and access for 

firefighters. The Grass Valley fire burned with lower flame 

lengths, slower rate of spread, fewer instances of transition 

to crown fire, and less spotting in treated areas than in 

adjacent untreated wildland fuels. As a result, firefighters 

were able to concentrate on evacuating people, protecting structures, and limiting fire spread. Fuel treatments 

improved visibility for the firefighters, but the fire burned 

more intensely within the residential area than in adjacent 

wildland fuels. Mass ember production from structures 

ignited adjacent and downwind structures in many cases. 

Lack of surface fire evidence in vegetation that surrounded 

burned homes provided strong evidence that house-tohouse ignitions by airborne firebrands were responsible for 

many of the destroyed homes. Homes were close together 

and on steep slopes, and many had multiple wooden 

decks. The pre-fire removal of large-diameter dead trees 

from urban lots did little to reduce fire behavior once 

homes ignited. A Spotted Owl Protected Activity Center 

(PAC) burned in the fire. Trees survived in the portion of 

the PAC that had fuel treatments, while tree mortality 

was high in the untreated portion of the PAC. The authors 

identified three factors that contributed most to treatment 

effectiveness. First, the fuel treatments had been prioritized based on an integrated landscape look at hazardous 

fuels and terrain, fire weather and history, access, egress, 

and communities at risk. Second, treatments were planned 

and implemented to meet specific fire behavior objectives. 
14 USDA Forest Service RMRS-GTR-252. 2011.

Third, treatments that were applied along roads and power 

lines and in urban areas all helped enhance suppression 

actions and enabled safe evacuation of the public.

Harbert and others (2007) interviewed local 

firefighters and fuel and vegetation managers, made 

field observations, collected relevant photographs, and 

reviewed fire operation and burn plan documents on three 

large 2007 fires east of the Cascade Range in Oregon: 

the Monument fire, the GW fire, and the Egley complex. 

Following is a summary of each fire.

The Monument fire burned 21,673 ha in July 

2007 across a landscape with extensive but relatively 

low intensity fuel treatments that reduced severe fire 

effects. Most of the area affected by the Monument fire 

had previously been selectively logged. Since 1998, the 

Umatilla NF had implemented prescribed burns on 5487 

ha within the fire perimeter. Areas that were previously 

underburned supported two-storied stands with light to 

moderate woody fuels and grass in the understory, while 

the untreated areas were dominated by multistoried 

stands with some plantations and meadows. Some areas 

had been prescribed burned more than once, and the 

interval between the most recent prescribed burn and the 

wildfire varied from 9 to 17 years. Few trees in treated 

areas died in crown fires, and the fire burned with less 

intensity and severity in treated areas. Of the fuel and 

vegetation treatments that had been applied on Umatilla 

NF lands prior to the Monument fire, only the underburn 

treatments significantly mitigated burn severity compared 

to the untreated areas.

The 2974-ha GW fire burned 2382 ha on the 

Deschutes NF and 591 ha of private timberland. Twentyfive percent of the USFS lands that burned had received 

prior fuel or other vegetation treatments. Dense, multistory stands dominated where no treatments had been 

applied. The fire burned into intensive fuel treatments 

that were designed to reduce wildfire threat to Black Butte 

Ranch and was stopped with the help of favorable weather 

and effective fire suppression. The fuel and other vegetation treatments were useful for fire suppression in part 

because the Incident Commander knew about them and 

used them and several large, recent fires in fire operations.

The Egley complex burned 56,802 ha from 6 to 22 

July 2007 under some of the most severe fire danger conditions experienced in the area in the previous 20 years. 

Fires in the complex threatened towns, private in-holdings, 

ranches, and Federal administrative sites. Harbert and 

others (2007) analyzed 39,872 ha burned on Malheur NF 

lands that supported open shrublands at low elevations, 

grass with sage and juniper, open ponderosa pine, and 

dense pine. Within the Egley complex, fuel and other 

vegetation treatments encompassed 42 percent of the 

burned areas assessed by the team. Treatment prescriptions were designed to accomplish ecosystem restoration 

and to improve firefighting effectiveness. Treatments 

generally included thinning with fuel treatment (fuels 

were usually piled and burned with underburning about 

five years later), commercial harvests, and underburning. 

These treatments were not intended to stop fire spread 

but to keep fires on the surface and enhance firefighter 

effectiveness. Where the Egley complex burned in treated 

areas, surface fire behavior predominated with only occasional torching, resulting in little firebrand production and 

overstory tree mortality and few spot fires. In areas where 

commercial thinning and piling had occurred and the 

piles were unburned at the time of wildfire, tree mortality 

was significant, particularly at the top of steep slopes. 

In contrast, tree mortality and burn severity were much 

lower in similar forests that had been treated with thinning 

and burning before the wildfire. Areas treated less than 

12 years prior exhibited 15 percent less area with high 

and moderate fire severity effects. This was likely because 

the older treatments had more vegetation growth since 

treatment and, therefore, more available fuel. The more 

recent treatments also had more aggressive treatment 

prescriptions that removed more vegetation and fuel than 

the older prescriptions. In some areas, even well-designed 

and well-implemented fuel treatments were ineffective, 

as active crown fire caused significant tree mortality. The 

authors attributed this to extremely low live fuel moisture, 

very high winds, high slopes, or a combination of all three 

of these factors.

Harbert and others (2007) concluded that fuel treatments—both prescribed burning and more intensive fuel 

treatments, including thinning and burning—reduced fire 

intensity and severity. Intensive fuel treatments that were 

located along major ridgetop road systems were particularly useful in increasing fire suppression effectiveness. 

Thus, on all three fires, fuel treatments seemed to increase 

suppression effectiveness. Additionally, when Incident 

Management Teams had knowledge of treatments, they 

used the treated areas to plan and implement fire suppression. Harbert and others (2007) also evaluated treated 

and untreated areas with respect to burn severity inferred 

from satellite imagery using Burned Area Reflectance 

Classification (BARC) maps produced by the USFS Remote 

Sensing Applications Center and modified by local Burned 

Area Emergency Response (BAER) teams (Orlemann and 

others 2002). On the three fires studied, a higher proportion of hectares burned severely on untreated lands than 

on lands where fuel or other vegetation treatments had 

been applied prior to the fires. More recent treatments 

and higher intensity treatments reduced fire behavior and 

fire effects more effectively than older and less intense 

treatments.

Harbert and others (2007) had several key recommendations. They felt that land management agencies 

needed to develop and articulate a clear strategy for 

guiding treatments in order to reduce hazardous fuels, 
USDA Forest Service RMRS-GTR-252. 2011. 15

that monitoring must continue, and that information on 

the location and status of fuel treatments should be used 

in wildfire management strategies. The latter could be 

facilitated by providing maps of treated areas to Incident 

Management Teams. Further, Harbert and others (2007) 

recommended that quantitative data (not just anecdotal 

information and retrospective analyses) were needed, 

particularly regarding when and where fuel treatment 

performance was tested by wildfires.

Graham and others (2009) assessed the 2007 

Cascade complex that burned through a variety of fuel 

treatments that were designed to protect over 70 summer 

homes and other buildings near Warm Lake in central 

Idaho. The fuel treatments modified fire intensity and 

allowed firefighters to protect all but two uninhabited 

structures. Beginning in 1996, treatments were designed 

to reduce the risk of wildfire affecting structures and other 

values at risk around Warm Lake. The prevailing winds 

were from the southwest, so priority areas for treatment 

were Boise NF lands immediately west of the residences 

along the western shore of Warm Lake. Both mechanical and prescribed fire treatments were used to reduce 

surface, ladder, and crown hazardous fuels. Mechanical 

treatments were usually hand-pile and burn treatments 

that thinned trees to a spacing of 3.0 to 4.6 m, pruned 

the lower limbs of residual trees up to 1.5 m high, and 

removed ladder and surface fuels. The covered piles were 

burned in the late fall or early spring and were monitored 

to ensure that at least 80 percent of the material was 

consumed. In a 61-ha mulch treatment, a vertical shaft 

machine was used to masticate fuels that were not subsequently burned. The cost to treat 3680 ha in the Warm 

Lake Basin in some fashion from 1996 to 2006 was over 

$1.65 million ($448/ha).

These WUI fuel treatments were tested by the 

2007 Monumental and North Fork fires that merged near 

Warm Lake as part of the Cascade complex. These and at 

least 25 other wildfires were ignited by dry lightning from 

thunderstorms on 17 July on the Boise or Payette NFs in 

central Idaho. On 13 August, southwest winds pushed the 

Monumental fire into fuel treatments west and east of 

Warm Lake. On 14 August, west winds pushed the North 

Fork fire to the northwest of Warm Lake; from there, it 

spotted into the two northernmost treatment units on the 

west side of Warm Lake. Meanwhile, the Monumental fire 

burned farther into the treatment units east of Warm Lake. 

Both wildfires continued to progress, eventually merging 

on 17 August on both the northwest and northeast sides 

of Warm Lake. The merged fires continued to burn to the 

northeast and were not extinguished until snow arrived 

in early October. Graham and others (2009) provided a 

detailed narrative of the day-to-day fire behavior and 

spread as it burned through the Warm Lake vicinity. 

Intense crown fire behavior in the untreated forest along 

the river caused many spot fires into the treatment units, 

which fire crews could easily suppress. Knowledge that 

the fuel treatments reduced fire intensity to a manageable level helped Incident Command develop an AMR of 

strategic point protection. The treatment units provided 

an area of relative safety, from which firefighters could 

more safely and effectively conduct burnout operations 

and protect the structures and other values at risk in the 

Warm Lake community. The treatment units did not stop 

the fire progression but greatly modified fire behavior. 

Severe fire effects on vegetation and soils were more 

prevalent in areas that were not treated than in areas 

that were treated. Trees near the edge of treatment units 

were often scorched by the radiative heat from crown fires 

adjacent to the units or were burned by surface fires that 

spotted into the treatment units. The location of the fuel 

treatment units in relation to the fire progression, wind 

direction, roads, and topography was an obvious factor in 

fire suppression activities—one that greatly influenced the 

resulting pattern in burn severity in the post-fire landscape.

• • • • •
16 USDA Forest Service RMRS-GTR-252. 2011.

Case Study

Study Areas

The Secesh Meadows community (45.245°; 

-115.822°) is located about 48 km north-northeast 

of McCall, Idaho, within the area that was burned 

by the 2007 East Zone complex (figure 1). The 

community stretches out along the Secesh River 

valley and is surrounded by steep, forested terrain 

on both sides of the riparian zone (figure 2). Several 

homeowners have implemented Firewise fuel treatments around their homes. A USFS campground is 

situated at the south end of the WUI area. The forest 

type is subalpine with lodgepole pine, Engelmann 

spruce (Picea engelmannii), and subalpine fir.

The Warm Lake community (44.645°; -115.688°) 

is located about 43 km east-northeast of Cascade, 

Idaho, within the area that was burned by the 2007 

Cascade complex (figure 1). The community consists of over 70 structures, including summer cabins 

on leased Government land that surrounds Warm 

Lake. Lessees were unable to treat fuels near their 

homes on Government land. Two lodges, three public campgrounds, a youth camp, a church camp, and 

a USFS project camp were threatened by the wildfire. The forest type is mixed conifer with lodgepole 

pine, Douglas-fir, and ponderosa pine.

Figure 1. Location and extent of 

the East Zone and Cascade 

Complexes within central Idaho 

(inset). The city of McCall and 

the RAWS with weather data 

considered in this analysis 

are shown, as are the Secesh 

Meadows and Warm Lake study 

areas.
USDA Forest Service RMRS-GTR-252. 2011. 17

Incident Information

On 7 July 2007, lightning strikes 40 km northeast 

of McCall, Idaho, ignited the wildfire(s) that grew 

and eventually merged into the 121,415-ha East 

Zone complex. The individual wildfires that merged 

were the Loon, Zena, Raines, Profile, and Horton 

fires (figure 3). The cost to fight these fires was over 

$32,500,000 (Independent Large Wildfire Cost Panel 

2008), and the fires were contained on 30 September 

2007.

Lightning ignited the first wildfire(s) of the Cascade 

complex 43 km east of Cascade, Idaho, 17 July 2007 

at 1700. The North Fork, Monumental, and Riordan 

fires (figure 4) eventually merged into the 122,367-

ha Cascade complex, with containment declared on 

30 September 2007. The cost to fight the fires was 

over $40,700,000 (Independent Large Wildfire Cost 

Panel 2008). The East Zone and Cascade complexes 

eventually merged, and comprise a subset of the 2007 

wildland fires that occurred in central Idaho (figure 1).

A point protection strategy was adopted to defend 

threatened structures in the local rural communities 

of Secesh Meadows (figure 5) and Warm Lake (figure 

6). Difficult terrain, extreme fire weather, and exceptionally low fuel moisture (figure 7) all contributed to 

the strategy. The size of the wildfires and their severe 

fire behavior, added to the fact that 2007 was a very 

busy fire year and resulted in a shortage of firefighting resources, made point protection the only viable 

option to the incident management team (McCarthy 

and others 2008). The lack of distinct topographic 

ridgelines that were perpendicular to the prevailing 

winds and fire direction and close to the WUI made 

the WUI fuel treatment units important for effective 

fire suppression.

Figure 2. Secesh Meadows from the air, looking south toward Loon Lake and the Loon fire ignitions. Photo: 

Roger Staats.
18 USDA Forest Service RMRS-GTR-252. 2011.

Figure 3. Loon Fire 

smoke plume on 

the first day the 

wildfire pushed 

into Secesh 

Meadows, looking 

southeast. Photo: 

Roger Staats.

Figure 4. Monumental Fire 

smoke plume in mid 

August 2007 east of 

Cascade, Idaho. Photo: 

Ian Rickert.
USDA Forest Service RMRS-GTR-252. 2011. 19

Figure 5. East Zone Complex progression map in the Secesh Meadows WUI area, with fuel treatment 

units and field plot locations from paired field sites (n = 13) overlaid.
20 USDA Forest Service RMRS-GTR-252. 2011.

Figure 6. Cascade Complex progression map in the Warm Lake WUI area, with fuel treatment units and field plot 

locations from paired field sites (n = 7) overlaid.
USDA Forest Service RMRS-GTR-252. 2011. 21

Figure 7. (1) Energy Release Component (ERC) and (2) 1000-hr Fuel Moisture in the west-central 

Idaho mountains where the 2007 East Zone and Cascade complexes occurred. From May 

through September, the extreme 2007 trends are plotted along with the 2006 trends, the 

1993 to 2006 average trend, and the maximum ERC or minimum 1000-hr fuel moisture 

trends for the sake of comparison (http://gacc.nifc.gov/egbc/index.htm). Energy Release Component

5/1

3 Day Periods

0

10

20

30

40

50

60

70

80

90

Avg

Max

2007

2006

97%

90%

6/1 7/1 8/1 9/1

Model: 7G

2139 Wx Observations

FF+3.0.5 09/27/2007-09:34

SIG - EB01

1993 - 2006

(1)

1000-Hour Fuel Moisture

5/1

3 Day Periods

0

5

10

15

20

25

30

35

Avg

Min

2007

2006

10% 3%

6/1 7/1 8/1 9/1

Model: 7G

2139 Wx Observations

FF+3.0.5 09/27/2007-09:34

SIG - EB01

1993 - 2006

(2)
22 USDA Forest Service RMRS-GTR-252. 2011.

Fuel Treatments

Pile and burn fuel treatments were implemented in 

2006 at Secesh Meadows. Thinned trees were piled in 

preparation for burning (figure 8). The piles in eight 

units had been burned prior to the wildfire; however 

in five units, the piles had not yet been burned as prescribed (“Rx Piles”) but instead were burned in the 

wildfire (“WF Piles”) (table 1). A wider variety of fuel 

treatments were implemented at Warm Lake over a period of 10 years, including pile and burn, mastication, 

and underburn treatments (table 1).

Figure 8. Activity fuels prior to pile burning (top left), being ignited (top right), and burning prior to the wildfire (bottom left and 

right). Photos: Paul Klasner.

Methods

Initial field assessment

Fire effects on vegetation and soils were assessed 

initially in the field from 18 to 21 September 2007. We 

used paired field sites to compare fire effects in treatment units relative to adjacent untreated lands. NF 

managers helped locate fuel treatments that had burned 

through by wildfires. Once a fuel treatment unit was 

selected for sampling, five 1-m2

 subplots were used to 

measure charred and uncharred ground cover fractions, 

litter and duff depths, and overstory canopy closure; 
USDA Forest Service RMRS-GTR-252. 2011. 23

the five subplots were situated in a systematic pattern 

per site (figure 9), with the rule that no subplot should 

be closer than 5 m from the edge of the fuel treatment 

unit. The central subplot was situated in a random location near the center of the treatment unit, and the four 

other subplots were placed 30 m away from the central 

subplot in the four cardinal directions (figure 9). We 

recorded tree species, diameter at breast height (dbh), 

and condition in a 1/50-ha fixed-radius (8.0 m) plot 

situated at the center of the field site. An identical plot 

configuration was randomly placed in an adjacent untreated site that had a similar topographic position.

Extended field assessment

We conducted a more thorough field assessment in 

August 2008, one year after the fires. There were several notable differences between our initial and extended 

assessments. We expanded our field site count from 10 

paired sites in 2007 to 20 paired sites in 2008, with the 

2008 assessment including re-measurement of all of 

the 2007 sites. We learned late in the 2007 assessment 

Table 1. Fuel treatment description, year (if applicable), and hectares treated for the (A) Secesh Meadows 

and (B) Warm Lake WUI areas.

Area description Treatment year Hectares

(A) Secesh Meadows WUI Area

Firewise (private lands; 5 units) 2005 277

Pile and Burn (Rx piles; 8 units) 2006 156

Pile and Burn (WF piles; 5 units) 2006 63

Untreated 5774

Secesh River (50-m buffer)a 130

Total 6400

(B) Warm Lake WUI Area

Mastication

Warm Lake Highway 2004 61

Pile and Burn

Warm Lake South 2000 76

Warm Lake North 2003 16

Warm Lake East 2005 38

Pile and Burn, followed by Prescribed Surface Fire

Church Camp 2004 28

Paradise Valley 2005 72

Underburn

Warm Lake Creek 1996 268

Chipmunk Creek 1997 461

Reeves Creek 1998 486

Kline Mountain 2006 122

Untreated 4502

South Fork Salmon River (50-m buffer)a 69

Warm Lake (50-m buffer)a 201

Total 6400

a

 The riparian zone near the water was excluded from the BARC map data analysis.

Figure 9. Systematic plot and subplot configuration at a field 

sampling site.

1-m x 1-m ground cover subplot

(five per site, separated by 30 m)

1/500-ha vegetation subplot

1/25-ha tree subplot

30 m

15-m surface fuels transect

(two per site)
24 USDA Forest Service RMRS-GTR-252. 2011.

that both sites in one of our site pairs were actually 

within a treatment unit, just on opposite sides of a road 

that was used as a firebreak. We resolved this complication in 2008 by reclassifying both sites as “treated” 

and establishing two new untreated sites to complement the treated sites, resulting in two paired sites. In 

other words, of the 20 field sites measured in 2007, 11 

sites were treated and 9 were untreated. We expanded 

the 1/50-ha fixed-radius (8.0 m) plots from our 2007 

assessment to 1/25-ha fixed-radius (11.3 m) plots in 

order to tally more trees (figure 9). In 2008, we also 

measured tree, crown base, maximum scorch, and bole 

char heights using a laser rangefinder. We measured 

one year post-fire vegetation re-growth in a 1/500-ha 

(2.5 m radius) subplot that was situated at the center 

of each field site (figure 9), where we ocularly estimated the percent cover of each plant functional type 

and listed the species encountered. We added Brown’s 

(1974) transects to our sampling protocol to measure 

surface fuels following a slightly modified FIREMON 

sampling protocol (Lutes and others 2006). The 30-m 

coarse woody debris (CWD) transect was divided into 

two 15-m sections situated on either side of plot center 

in order to preclude any directional bias (figure 9). Fine 

woody debris (FWD) was sampled along the central 

2-m section of each 15-m CWD transect. We doubled 

our field site count, expanded the tree plot size, and 

measured additional variables in 2008 because we had 

more time to sample than in 2007 when the East Zone 

and Cascade complexes were still officially active and 

we needed to work expediently.

We used the tree diameter and sapling tallies in our 

1/25-ha fixed-radius plots to estimate the plot-level 

basal area of trees and saplings. To retrospectively estimate the basal area of trees and saplings that were 

removed by either the fuel treatment or natural disturbance, we tallied the stumps in each plot within three 

diameter classes with the following midpoints: small 

(5.1 cm), medium (17.8 cm), and large (30.5 cm). We 

excluded any remaining bark on the stump from the 

diameter measurement. To convert the stump diameters to estimates of dbh, we multiplied by a ratio of 0.9 

based on Bones (1960), who found dbh/stump ratios of 

0.937 for lodgepole pine, 0.865 for subalpine fir, and 

0.832 for Engelmann spruce in the Pacific Northwest. 

Thus, 0.9 served as a good average approximate ratio for the primary species encountered in this study. 

Rescaling the stump diameter measures to dbh allowed 

us to equitably compare the basal area of standing trees 

and saplings to those that were removed or were otherwise absent. Species could not be reliably called from 

just the stumps, but was recorded for the trees and saplings so that biomass could be estimated from the dbh 

measures and allometric equations (Jenkins and others 

2003). The FWD and CWD fractions were combined 

for a total downed woody debris (DWD) estimate, 

which was converted to biomass following Brown 

(1974) for FWD and Harmon and Sexton (1996) for 

CWD.

Data collected at the five subplots per site (figure 9) 

were averaged to represent the site, which was our experimental unit. The paired site sampling design made 

pairwise comparisons a simple yet powerful method to 

assess the significance of differences between treated 

and untreated sites. Furthermore, separate tests were 

applied to each field variable measured to determine 

clearly which specific vegetation or soil measures were 

influenced by the fuel treatment and/or the wildfire and 

which were not. The Shapiro-Wilk statistic (Royston 

1982, 1995) was used to test the normality of the field 

measures from both the treated and untreated sites, 

and the histograms were inspected. Most (70 percent) 

of the distributions were significantly non-normal (pvalue less than 0.1, Royston [1995]); therefore, the 

non-parametric Wilcoxon signed rank test (Bauer 

1972) and a significance level of α = 0.05 was used to 

assess the significance of differences between paired 

sites. All statistics presented in this paper were run 

in R (R Development Core Team 2005) unless stated 

otherwise.

Satellite assessment

The NBR was developed as an index of burn severity that could be simply calculated by taking the 

difference between Landsat Thematic Mapper (TM) 

bands 4 and 7 and then dividing that quantity by their 

sum (Key and Benson 2005). Typically, this operation 

is applied to both pre- and post-fire images acquired 

at nearly the same time of year (to control for variable 

sun angle and vegetation phenology). Then, the postfire NBR image is subtracted from the pre-fire NBR 

image to produce the dNBR, which is the most widely 

used index of burn severity (Key and Benson 2005, 

Hudak and others 2007). The USFS Remote Sensing 

Applications Center (RSAC) produces preliminary 

BARC maps from continuous dNBR values. The maps 

are delivered to incident management teams on important wildfires and are used as preliminary inferences of 
USDA Forest Service RMRS-GTR-252. 2011. 25

unburned, low, moderate, and high burn severity classes, as defined by Key and Benson (2005). If necessary, 

the thresholds that demarcate the four preliminary burn 

severity classes are adjusted by BAER teams working 

on the incident in order to more accurately represent 

conditions observed on the ground (Hudak and others 

2007).

Because the East Zone and Cascade complexes were 

such high priority fires, RSAC produced three BARC 

maps using dNBR values derived from an 11 October 

2004 Landsat 5 Thematic Mapper pre-fire image and 

either Landsat 5 TM or Landsat 7 Enhanced Thematic 

Mapper Plus (ETM+) post-fire images that were acquired 25 August (ETM+), 2 September (TM) and 26 

September 2007 (ETM+) in the case of the East Zone 

complex and on 25 August (ETM+), 10 September 

(ETM+), and 26 September 2007 (ETM+) in the case 

of the Cascade complex. We used the latest ETM+ 

image in a BARC map data analysis of immediate 

post-fire severity because local wildfire activity within 

our two study areas had ceased by 26 September 2007. 

In this analysis, we calculated the areal percentage 

of hectares that burned at high severity on untreated 

lands, assumed this to be the percentage expected to 

burn at high severity in the absence of any fuel treatment, and then compared the expected percentage to 

the observed percentage of hectares that burned at high 

severity within each fuel treatment, as observed in the 

immediate post-fire BARC map. We considered each 

treatment unit as a replicate. Because the observed percentages were not normally distributed according to 

the Shapiro-Wilk statistic (Royston 1982, 1995), we 

tested the significance of differences between observed 

and expected percentages using Wilcoxon rank sum 

tests (Bauer 1972) and a significance level of α = 0.05.

A problem with ETM+ imagery since 31 May 2003 

is the failure of the scan line corrector mechanism on 

board Landsat 7, which causes data voids in the image 

parallel to the scan direction (perpendicular to the satellite path) that widen toward the edges of the scene. A 

majority filter is employed to fill the categorical data 

gaps in the classified BARC map and produce a more 

visually satisfying result, but this technique is inappropriate for filling the gaps in the continuous dNBR 

images. Unfortunately, a large proportion of our field 

sites (40 percent) fell into those dNBR data voids. To 

solve the problem, two successive ETM+ images that 

were collected on 10 July 2008 and 26 July 2008 were 

merged. The data gaps in the two scenes fortunately 

offset just enough to produce a composite one year 

post-fire image with continuous coverage over all 

of our field sites. A 13 July 2006 Landsat TM image 

provided the pre-fire NBR values needed to calculate dNBR. These one year post-fire dNBR data were 

more appropriate than immediate post-fire dNBR data 

for our paired site comparisons because the bulk of 

our field data were collected one year post-fire. After 

confirming that both the treated and untreated dNBR 

distributions were normal with the Shapiro-Wilk test 

(Royston 1982), we used paired t-tests and a significance level of α = 0.05 to assess the significance of 

differences between treated and untreated sites.

Fire weather assessment

We were able to obtain weather data online (http://

mesowest.utah.edu/index.html) from nine Remote 

Automated Weather Stations (RAWS) located in or 

near the East Zone or Cascade complexes, as well as 

from three portable RAWS (Flat Creek, Warm Lake, 

and North Fork) deployed near the wildfires to provide up-to-date local weather data to fire managers 

(figure 1). Variables recorded at RAWS on an hourly 

basis included air temperature, dewpoint temperature, 

relative humidity, precipitation, wind speed, and wind 

gust speed. We computed daily means from the hourly 

data that were available within the 63-day period from 

18 July to 18 September 2007. Plotting the daily means 

against Julian Date revealed considerable daily variation among the 12 RAWS, which would be attributable 

to their wide geographic separation that encompassed a 

range of local weather conditions. Nevertheless, we averaged the daily means across the 12 RAWS to generate 

regional daily means for the 6 weather variables named 

above. The response variable (area burned per day; ha/

day) was tallied from the East Zone and Cascade fire 

progression data that were obtained from the incident 

camp GIS team located just outside of Cascade, Idaho.

We employed ordinary least squares (OLS) regression 

to predict area burned per day from the weather variables, 

not for the purpose of prediction but to quantify the influence of the weather variables on fire activity (Hawkins 

2004). Care is needed when using linear regression with 

time series data (Chambers 1992). Therefore, we examined the OLS model residuals for autocorrelation at time 

lags ranging from one to five days, and tested the significance of the autocorrelation using the Durbin-Watson 

statistic (Vinod 1973) in SAS. This test was imbedded 

in the SAS AUTOREG procedure (Gallant and Goebel 
26 USDA Forest Service RMRS-GTR-252. 2011.

1976) that generated OLS models based on the six 

weather variables in all possible combinations (n = 63) 

and tested the residuals from every model for significant 

autocorrelation. In the models that exhibited significant 

autocorrelation, backward elimination of one- to fiveday autoregressive (AR) error terms was employed until 

only the significant AR error terms remained. The best 

subset model from among the 63 possible models that 

were estimated using maximum likelihood was selected 

based on the lowest Akaike Information Criterion statistic (Burnham and Anderson 1998). This resulted in a best 

subset model that was parsimonious in that it consisted 

of only significant RAWS variables and significant AR 

error terms. All residual Durbin-Watson test statistics 

were non-significant after fitting the autoregressive error 

models, and the histograms of residuals were inspected 

to confirm normality.

Results

Our quantitative case study results consider all three 

components of the fire behavior triangle to some extent 

and are divided into six sections:

(1) the influence that fire weather had on landscapelevel fire activity;

(2) whether mitigation of severe fire effects by fuel 

treatments was detected by satellite imagery that 

was acquired immediately post-fire and one year 

afterward;

(3) whether our paired site design controlled for topographic effects;

(4) a retrospective comparison of treatment effects on 

pre-fire fuel loads between treated and untreated 

field sites;

(5) a comparison of one year post-fire effects between 

treated and untreated field sites; and

(6) a comparison of immediate versus one year postfire effects to compare site recovery between treated 

and untreated field sites.

Fire weather assessment

Temporal autocorrelation trends were evident not just 

in the individual RAWS records but in the means calculated across all 12 RAWS. Temporal autocorrelation 

indicates stability in weather patterns during the burning 

period, such as from inversions, and supports the fact 

that temperature can be more reliably predicted at a regional scale than cloud conditions or precipitation that 

vary more at finer scales. We found that daily burned 

area across the full regional extent of the East Zone and 

Cascade complexes could not be significantly predicted 

from autoregression models based on the daily mean 

weather time series variables averaged across the 12 

RAWS (R2

 = 0.10, p-value = 0.213).

Fire weather conditions vary greatly at local scales. 

Therefore, we used the same approach to predict area 

burned within each of the local WUI areas using the 

daily means from just the local RAWS. The Flat Creek 

portable RAWS in the northern portion of the Secesh 

Meadows WUI area (figure 5) provided the most complete and proximal weather dataset for analysis. Trends 

in the weather variables recorded there most closely resembled the trend in area burned per day, particularly the 

spike on the big blowup day of 14 August (Julian Date 

226, figure 10). The best subset autoregression model that 

predicted daily area burned within the Secesh Meadows 

WUI area was based on relative humidity, precipitation, and four- and five-day autoregressive terms (table 

2). The next closest RAWS with a complete record was 

the Zena RAWS that was located approximately 21 km 

south-southeast; however, the best subset model based 

on dewpoint temperature and four- and five-day autoregressive terms was non-significant (table 2).

The Warm Lake portable RAWS was deployed just 1 

km southeast of the Warm Lake WUI area, but the wildfire actually destroyed it on 17 August 2007 after only 

10 days of recording, which was too short a period for 

meaningful analysis. The Knox Ranch RAWS was situated in the northern portion of the Warm Lake WUI area 

(figure 6), but weather records from this RAWS only began on 27 August 2007, almost entirely after the wildfire 

already had burned through the WUI area. The closest 

meaningful record was from the North Fork portable 

RAWS that was located about 9 km northwest, which 

explained much of the variation in area burned within 

the Warm Lake WUI (table 2) based on dewpoint temperature, wind gust speed, and a four-day autoregressive 

term. The closest RAWS with a complete record was the 

Tea Pot RAWS that was located approximately 24 km 

north-northeast; the best subset model was significant 

based on dewpoint temperature and a four-day autoregressive term (table 2).

Satellite assessments

The size of both the Secesh Meadows and Warm 

Lake WUI analysis areas was delimited at 6400 ha 

to include not just the treatment units but also the 
USDA Forest Service RMRS-GTR-252. 2011. 27

Figure 10. Daily averages of six weather variables recorded hourly at the Flat Creek Fire RAWS at Secesh Meadows 

from 4 August to 17 September 2007. Area burned per day (ha/day) is plotted as a solid blue line in each graph 

to assist in comparing trends.

Table 2. Best subset multiple linear regression models with autoregressive (AR) terms for predicting area burned in the (A) Secesh 

Meadows and (B) Warm Lake WUI areas from RAWS variables (daily means). Significant differences (α = 0.05) are indicated in 

boldface.

WUI area and RAWS Significant model parametersa Days sampled AIC Total R2 P-value

(A) Secesh Meadows WUI Area

Flat Creek Portable RAWS Relative Humidity, Precipitation, 63 859.74 0.34 0.029

AR4, AR5

Zena RAWS Dewpoint Temperature, AR4, 63 863.01 0.28 0.121

AR5

(B) Warm Lake WUI Area

North Fork Portable RAWS Dewpoint Temperature, Wind 31 472.82 0.44 0.004

Gust Speed, AR4

Tea Pot RAWS Dewpoint Temperature, AR4 63 926.51 0.25 0.046

a

 AR4 indicates significant four-day autocorrelation, and AR5 indicates significant five-day autocorrelation. Air Te

mperature (C)

0 5 10 20 15 25

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

Wind Speed (km/hr)

0 1 2 4 3 5

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

6

Wind Gusts (km/hr)

5 10 20 15 25

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

Dew Point Te

mperature (C)

-5 0 5 10

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

Relative Humidity (%)

20 40 60

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

80

Precipitation (mm)

0 2 8 6 10

200

Julian Date

210 220 230 240 250 260

0 500 1000 1500

Area burned (ha/day)

4
28 USDA Forest Service RMRS-GTR-252. 2011.

surrounding areas of relevance (table 1). At Secesh 

Meadows (figure 11), private lands with Firewise treatments comprised 277 ha, while treatments funded by 

the National Fire Plan (NFP) on Payette NF land comprised 220 ha (3.5 percent) of the WUI area (excluding 

a 50 m buffer zone on either side of the Secesh River). 

At Warm Lake (figure 12), NFP-funded treatments 

on Boise NF land covered 1645 ha (26.5 percent) of 

the WUI area (excluding a 50-m buffer zone on either side of the South Fork Salmon River and around 

Figure 11. BARC classification 

of dNBR values derived from 

11 October 2004 Landsat TM 

pre-fire and 26 September 2007 

Landsat ETM+ post-fire images, 

indicating immediate post-fire 

burn severity across the Secesh 

Meadows study area.

Warm Lake). Based on the BARC map data at Secesh 

Meadows, a significantly lower areal percentage of 

hectares within pile and burn treatment units burned at 

high severity (provided the piles were burned as prescribed) compared to untreated lands (p-value = 0.008) 

(figure 13). Firewise treatments on private lands were 

most effective for significantly reducing high severity 

fire at Secesh Meadows (p-value = 0.007). At Warm 

Lake, there were too few treatment units to result in 

any significant differences by treatment type (table 1), 
USDA Forest Service RMRS-GTR-252. 2011. 29

Figure 12. BARC classification of dNBR 

values derived from 11 October 2004 

Landsat TM pre-fire and 26 September 

2007 Landsat ETM+ post-fire images, 

indicating immediate post-fire burn 

severity across the Warm Lake study 

area.

Figure 13. Areal percentages of immediate post-fire BARC map severity classes in different fuel treatment 

types at the (1) Secesh Meadows and (2) Warm Lake study areas. Significance: **, p-value<0.01.

Unburned

Low

Moderate

High

Areal Percentage (%)

0

Firewise

(Private)

Pile and Burn

(Rx Fire)

Pile and Burn

(Wildfire)

 

Untreated

BARC Map Severity Class

(1)

10

20

30

40

50

60

70

80

Unburned

Low

Moderate

High

Areal Percentage (%)

0

Mastication Pile and Burn Pile and Burn +

Rx Surface Fire

Underburn

BARC Map Severity Class

(2)

10

20

30

40

50

60

Untreated
30 USDA Forest Service RMRS-GTR-252. 2011.

but when the 10 units were considered together, there 

was a significantly lower percentage of high severity 

hectares inside treatment units compared to outside 

(p-value = 0.001). Based on the BARC map data, the 

combination of pile and burn and prescribed surface 

fire treatments was slightly more effective for mitigating high burn severity than piling and burning only; 

the mastication treatment was less effective; and the 

underburns were least effective (figure 13).

This evidence from the immediate post-fire BARC 

map data assessment that the fuel treatments mitigated 

fire severity was corroborated by the paired site comparison of one year post-fire dNBR. The dNBR was 

significantly lower at treated sites than at untreated 

sites at Warm Lake (p-value = 0.014), as well as at the 

“Rx Pile” treated sites at Secesh Meadows (p-value = 

0.025). The “WF Pile” treated sites at Secesh Meadows 

exhibited the opposite trend, although this difference 

was not significant (p-value = 0.764) based on only 

four paired sites.

Topographic effects

The intent of the paired site design was to minimize 

the confounding influences of the fire weather and topography components of the fire behavior triangle to 

isolate the fuels component (figures 14 through 19). 

The spatial distribution of the RAWS was much too 

sparse to know if fire weather differed significantly 

between our treated and untreated site pairs. We can 

only assume that it did not, which is reasonable given 

Figure 14. Secesh Meadows pile and burn treated site (left) where the fuel piles were burned prior to the wildfire (“Rx Piles”) 

versus its paired untreated site (right) nearby, one month after the wildfire. The fuel treatment effect on fire severity at this 

site pair was positive. Photos: Andrew Hudak.

Figure 15. Secesh Meadows pile and burn treated site (left) where the fuel piles were burned prior to the wildfire (“Rx Piles”) 

versus its paired untreated site (right) nearby, one month after the wildfire. The fuel treatment effect on fire severity at this 

site pair was neutral. Photos: Andrew Hudak.
USDA Forest Service RMRS-GTR-252. 2011. 31

Figure 16. Secesh Meadows treated site (left) where the fuel piles burned in the wildfire (“WF Piles”) versus its paired untreated 

site (right) nearby, one month after the wildfire. The fuel treatment effect on fire severity at this site pair was negative. 

Photos: Andrew Hudak.

Figure 17. Warm Lake South pile and burn treated site (left) versus its paired untreated site (right) nearby, one month after the 

wildfire. Photos: Andrew Hudak.

Figure 18. Warm Lake Highway mastication treated site (left) versus its paired untreated site (right) nearby, one month after the 

wildfire. Photos: Andrew Hudak.
32 USDA Forest Service RMRS-GTR-252. 2011.

that the distance separating the paired sites ranged 

from 100 to 350 m. Most site pairs were within sight 

of each other unless a hillslope intervened. While we 

could not test for differences in fire weather, we tested 

whether elevation, slope, and aspect as recorded in the 

field differed between treated and untreated site pairs. 

Wilcoxon signed rank tests of these variables revealed 

no significant differences at either Secesh Meadows or 

Warm Lake, with the exception of elevation at Secesh 

Meadows (p-value = 0.01). Although statistically significant, the mean difference between untreated and 

treated sites at Secesh Meadows was only 11 m. This 

was because the Secesh Meadows community is situated in a valley along the Secesh River where, in 10 of 13 

cases, the untreated sites were situated upslope of the 

treated sites placed in WUI treatment units that were 

designed to protect structures along the valley bottom. 

Steeper slopes appeared to interact with fuel load and 

contributed to more severe fire effects at some paired 

sites; in other words, the site that had higher surface 

fuel loads sometimes burned more severely, whether 

treated (figure 16) or untreated (figure 19).

Treatment effects

The fuel treatments removed nearly all of the saplings and many of the trees at Secesh Meadows and 

Warm Lake (figures 20 and 21). We did not record 

whether or not stumps had been cut by a chain saw, 

but at both Secesh Meadows and Warm Lake, the density and basal area of stumps plus saplings and trees at 

treated sites was approximately twice that of saplings 

and trees at untreated sites, meaning the fuel treatments 

might have accounted for only half of the stumps we 

tallied (figures 20 and 21). Wilcoxon signed rank tests 

indicated that the differences in tree/sapling/stump 

density and basal area between treated and untreated 

sites were significant at Secesh Meadows but not at 

Warm Lake (table 3). Treatment effects on tree density, basal area, and biomass were not as pronounced 

at Warm Lake as at Secesh Meadows. Had the number of site pairs at Warm Lake (n = 7) matched that of 

Secesh Meadows (n = 13), it is likely that the density, 

basal area, and biomass of saplings would have significantly differed (table 3). It is likely that fewer stumps 

remained in the treatment units at Warm Lake because 

of the nature of the fuel treatments (for example, mastication and underburn) and because the 2000 to 2005 

Warm Lake fuel treatments were one to six years older 

than the 2006 Secesh Meadows fuel treatments.

Estimates of tree and sapling biomass (figure 22) 

might better reflect pre-fire biomass than post-fire biomass, because the Jenkins and others (2003) allometric 

equations were based on live trees. Nevertheless, the 

relative differences are still useful and informative. 

Tree and sapling biomass was lower at treated sites 

than at untreated sites at both Secesh Meadows and 

Warm Lake (figure 22), although this treatment effect was significant only at Secesh Meadows (table 3). 

DWD biomass was higher at untreated sites at Secesh 

Meadows and, in contrast, at treated sites at Warm Lake 

(figure 22). However, these opposing trends were not 

significant for DWD or for the FWD or CWD components of DWD (table 3). These differences in post-fire

surface fuels (DWD) does not preclude the possibility 

Figure 19. Warm Lake Kline Mountain underburn treated site (left) versus its paired untreated site (right) nearby, one month 

after the wildfire. Photos: Andrew Hudak.
USDA Forest Service RMRS-GTR-252. 2011. 33

Figure 20. Mean (+SE, vertical lines) 

one year post-wildfire stem density 

of trees and saplings measured 

on treated versus untreated site 

pairs at Secesh Meadows (n = 13) 

and Warm Lake (n = 7). Stumps 

were also tallied to estimate stems 

removed from the site due to 

treatment effects on treated sites or 

natural disturbance and mortality 

effects on both treated and 

untreated sites. Significance: ** , 

p-value<0.01; ***, p-value<0.001.

Figure 21. Mean (+SE, vertical lines) one 

year post-wildfire basal area of trees 

and saplings measured on treated versus 

untreated site pairs at Secesh Meadows 

(n = 13) and Warm Lake (n = 7). Stumps 

were also tallied to estimate basal area 

lost from the site due to treatment effects 

on treated sites or natural disturbance 

and mortality effects on both treated 

and untreated sites. Significance: **, 

p-value<0.01; ***, p-value<0.001.

Secesh Meadows, Treated

Secesh Meadows, Untreated

Warm Lake, Treated

Warm Lake, Untreated

Tree, Sapling, or Stump Density (stems/ha)

0 1000 2000 3000

Trees Saplings Sapling Stumps

**

***

**

Tree Stumps

***

2500 1500 500
34 USDA Forest Service RMRS-GTR-252. 2011.

Figure 22. Mean (+SE) one year post-wildfire 

biomass of trees, saplings, and DWD 

measured on treated versus untreated 

site pairs at Secesh Meadows (n = 13) 

and Warm Lake (n = 7). Significance: **, 

p-value<0.01; ***, p-value = 0.001.

Table 3. WUI treatment effects measured retrospectively at Secesh Meadows and Warm Lake. Significant differences (α = 0.05) indicated in 

boldface.

Secesh Meadows Warm Lake

Site Treated Untreated Wilcoxon Site Treated Untreated Wilcoxon

Variable description pairs mean (SE) mean (SE) p-value pairs mean (SE) mean (SE) p-value

Tree Density (trees/ha) 13 432.7 (39.6) 775.0 (66.2) 0.00 7 507.1 (29.2) 396.4 (48.6) 0.20

Tree Stump Density (stumps/ha) 13 430.8 (40.7) 111.5 (20.9) 0.00 7 253.6 (76.1) 107.1 (41.4) 0.07

Sapling Density (saplings/ha) 13 13.5 (5.4) 1094.2 (245.9) 0.00 7 275.0 (158.9) 2271.4 (732.7) 0.08

Sapling Stump Density (stumps/ha) 13 1673.1 (203.5) 475.0 (134.8) 0.00 7 1214.3 (389.0) 800.0 (318.1) 0.38

Tree Basal Area (m2/ha) 13 16.9 (2.0) 26.9 (2.2) 0.00 7 19.0 (2.8) 18.7 (5.3) 0.94

Tree Stump Basal Area (m2

/ha) 13 12.3 (1.1) 4.5 (1.0) 0.00 7 7.5 (2.6) 3.5 (1.3) 0.38

Sapling Basal Area (m2

/ha) 13 0.0 (0.0) 3.5 (0.8) 0.00 7 0.9 (0.5) 7.2 (2.3) 0.08

Sapling Stump Basal Area (m2/ha) 13 4.3 (0.5) 1.2 (0.3) 0.00 7 3.1 (1.0) 2.1 (0.8) 0.38

Tree Biomass (Mg/ha) 13 71.1 (9.5) 110.8 (10.8) 0.01 7 86.1 (19.4) 107.8 (40.2) 0.58

Sapling Biomass (Mg/ha) 13 0.1 (0.0) 8.1 (1.8) 0.00 7 2.2 (1.3) 16.5 (5.1) 0.08

Fine Woody Debris Biomass (Mg/ha)a 13 1.4 (0.5) 2.3 (0.9) 0.51 7 3.2 (0.8) 1.6 (1.0) 0.08

Coarse Woody Debris Biomass (Mg/ha)a 13 8.7 (2.8) 13.4 (3.1) 0.22 7 8.8 (3.1) 1.8 (0.8) 0.08

Downed Woody Debris Biomass (Mg/ha)a 13 10.1 (2.7) 15.7 (2.7) 0.19 7 12.0 (3.0) 3.4 (1.5) 0.08

Tree Height (m) 13 17.4 (0.6) 17.2 (0.7) 0.84 7 15.3 (1.0) 15.2 (2.0) 0.94

Crown Base Height (m)b 13 8.0 (0.9) 9.1 (0.9) 0.54 5 7.9 (1.2) 8.4 (1.3) 0.44

a

 These are post-wildfire forest floor fuel measures; pre-fire forest floor fuel loads are unknown.

b

 These are post-wildfire measures that exclude one site pair and one untreated site at Warm Lake where crown base height could not be assessed because no 

needles remained.
USDA Forest Service RMRS-GTR-252. 2011. 35

that pre-fire surface fuels did differ significantly between treated and untreated sites. This is because the 

wildfire consumed virtually all DWD, especially at 

more severely burned sites. Further obfuscating the 

surface fuel comparison is the fact that much of the 

DWD that was measured post-fire fell to the ground 

soon after the wildfire.

Tree and crown base heights that were measured 

post-fire did not differ significantly between treated 

and untreated sites at either Secesh Meadows or Warm 

Lake (table 3). However, pre-fire crown base height 

might have differed more between treated and untreated sites but could not be retrospectively assessed 

on high severity sites where the needles on the lower 

branches were consumed by the wildfire. For any tree 

crown in which all the needles had been consumed all 

the way to the top, or could not be inferred by the presence of charred cones, crown base height was recorded 

as “NA” so as not to bias the analysis.

Wildfire effects

Crown base height likely influenced maximum 

scorch and bole char heights because all three variables exhibited similar patterns (figure 23). At Secesh 

Meadows, where the fuel piles burned in the wildfire 

(“WF Pile,” figures 23 through 26), both maximum 

scorch and bole char heights were higher on the treated sites than on the paired untreated sites, although 

not significantly based on only four site pairs (table 4). Maximum scorch and bole char heights were 

higher on untreated sites compared to treated sites 

at Secesh Meadows; in those treatment units where 

the fuel piles had been burned as prescribed (“Rx 

Pile,” figures 23 through 26); and at the pile and burn, 

mastication, and underburn treatment units sampled 

at Warm Lake (figure 23). The only significant difference found was bole char height at Warm Lake 

(table 4). Note that for any scorched tree crown where 

no green needles remained, maximum scorch height 

was recorded as equal to the tree height, but this made 

for a less meaningful measure that did not differ significantly between treated and untreated sites at either 

Secesh Meadows or Warm Lake (table 4). Raymond 

and Peterson (2005) found that scorch volume was a 

better indicator of tree mortality than scorch height. 

We agree because areas of crown scorch often occur 

at variable heights.

The patterns in bole char height (figure 23) that 

were just described were repeated for tree mortality (figure 24). Indeed, tree mortality and bole char 

height were significantly correlated (r = 0.68, pvalue<0.0001) across all sites. Tree mortality was 

Figure 23. Mean (+SE) one year postwildfire crown base, maximum scorch, 

and bole char heights on treated versus 

untreated site pairs at Secesh Meadows 

(SM) pile and burn treatment units, 

where the piles were burned by either 

the wildfire (WF, n = 4) or before the 

wildfire as prescribed (Rx, n = 9). Site 

pairs at Warm Lake (WL, n = 7) are also 

included. Significance: *, p-value<0.05.

SM, WF Pile

SM, WF Untreated

SM, Rx Pile

SM, Rx Untreated

WL, Treated

WL, Untreated

Height (m)

0 5 10 15 20

Crown Base Max Scorch Bole Char

*
36 USDA Forest Service RMRS-GTR-252. 2011.

Figure 25. Mean (+SE) one year postwildfire tree crown condition on 

treated versus untreated site pairs 

at (1) pile and burn treatment units 

at Secesh Meadows (SM), where 

the piles were burned by either the 

wildfire (WF, n = 4) or before the 

wildfire as prescribed (Rx, n = 9), 

and (2) at Warm Lake (WL, n = 7). 

Significance: *, p-value<0.05; **, 

p-value<0.01.

Figure 24. Mean (+SE) one year 

wildfire-induced tree mortality 

and post-wildfire canopy closure 

and needlecast on treated versus 

untreated site pairs at Secesh 

Meadows (SM) pile and burn 

treatment units, where the piles 

were burned by either the wildfire 

(WF, n = 4) or before the wildfire 

as prescribed (Rx, n = 9). Paired 

sites at Warm Lake (WL, n = 7) 

are also included. Significance: *, 

p-value<0.05; ** p-value<0.01.

SM, WF Pile

SM, WF Untreated

SM, Rx Pile

SM, Rx Untreated

WL, Treated

WL, Untreated

Percent (%)

0 20 40 60 80 100

Tree Mortality Canopy Closure Needlecast

**

*

*

SM, WF Pile

SM, WF Untreated

SM, Rx Pile

SM, Rx Untreated

WL, Treated

WL, Untreated

Percent (%)

0 20 40 60 80 100

Live Scorched Charred

**

*

*

*
USDA Forest Service RMRS-GTR-252. 2011. 37

Figure 26. Mean one year post-wildfire ground cover fractions on treated versus untreated site pairs at Secesh Meadows, where 

the fuel piles from pile and burn treatments were burned by either the wildfire (WF, n = 3) or as prescribed (Rx, n = 10), and 

at Warm Lake (n = 7), where pile and burn, mastication, and underburn treatments were applied. There were no statistically 

significant differences (α = 0.05).

higher on the treated sites at Secesh Meadows where 

fuel piles remained for the wildfire to consume (in 

other words, “WF Piles”) than on untreated sites. 

Whereas, tree mortality was lower on fully treated 

sites at Secesh Meadows (in other words, “Rx Piles”) 

and Warm Lake than on untreated sites (figure 24). 

However, Wilcoxon signed rank tests indicated that 

none of these differences was significant (table 4). 

Tree canopy closure was lower in treated sites than 

in untreated sites at Secesh Meadows—significantly 

in the “WF Pile” units but not significantly in the 

“Rx Pile” units. In contrast, tree canopy closure at 

Warm Lake was significantly higher in treated sites 

than in untreated sites (figure 24, table 4). We assert 

that differences in canopy closure were more influenced by treatment effects than by wildfire effects 

at Secesh Meadows, where treatment effects were 

more pronounced than at Warm Lake (see preceding 

subsection). This assertion is supported by observed 

differences in needlecast. In the “WF Pile” units at 

Secesh Meadows, needlecast was significantly lower 

in treated sites than in untreated sites. On the other 

hand, in the “Rx Pile” units at Secesh Meadows and 

at Warm Lake, needlecast was significantly higher on 

treated sites than untreated sites (figure 24, table 4). 

Needlecast can protect the soil against erosion, although the up to 35 percent coverage observed across 

all of our sites was below the 50 to 70 percent coverage deemed sufficient for erosion control (Pannkuk 

and Robichaud 2003). Furthermore, needlecast returns some essential nutrients to the soil. If the 

needles are consumed, as in a high severity fire, then 

much of the essential nutrients can be volatilized, depleting the site and slowing re-vegetation (Garrison 

and Moore 1998).

The observed trends in bole char height (figure 23) 

and tree mortality (figure 24) also were reflected in 

the percentage of charred tree crowns (figure 25), 

which significantly differed between treated and 

untreated sites for the “Rx Pile” treatment units at 

Secesh Meadows and at Warm Lake (table 4). The 

percentage of scorched tree crowns also significantly 

Secesh Meadows, WF Pile

Litter

Green

Soil

Ash

Litter

Green

Soil

Ash

Litter

Green

Soil

Ash

Litter

Green

Soil

Ash

Litter

Green

Soil

Ash

Litter

Green

Soil

Ash

Secesh Meadows, Rx Pile Warm Lake, Treated

Secesh Meadows, WF Untreated Secesh Meadows, Rx Untreated Warm Lake, Untreated
38 USDA Forest Service RMRS-GTR-252. 2011. Table 4. Wildfire effects measured one year post-fire on WUI fuel treatments at Secesh Meadows and Warm Lake. Significant differences (a = 0.05) indicated in boldface. Wildfire (WF) burned fuel piles Prescribed fire (Rx) burned fuel piles Warm Lake fuel treatments Site Treated Untreated Wilcoxon Site Treated Untreated Wilcoxon Site Treated Untreated Wilcoxon Variable description pairs mean (SE) mean (SE) p-value pairs mean (SE) mean (SE) p-value pairs mean (SE) mean (SE) p-value Max Scorch Height (m) 4 17.5 (1.5) 12.6 (1.4) 0.13 9 14.3 (1.4) 14.6 (1.8) 0.30 7 14.5 (1.0) 15.2 (2.0) 0.94 Bole Char Height (m) 4 9.2 (2.3) 5.0 (2.6) 0.25 9 6.1 (1.7) 9.5 (2.5) 0.20 7 5.1 (2.0) 14.5 (2.2) 0.02 Tree Mortality (%) 4 79.9 (11.7) 55.4 (19.1) 0.25 9 55.6 (10.8) 70.7 (12.4) 0.11 7 68.2 (11.3) 95.4 (3.1) 0.08 Canopy Closure (%) 4 25.2 (5.0) 44.8 (6.8) 0.13 9 29.9 (3.7) 32.6 (4.2) 0.50 7 26.9 (3.6) 17.7 (1.0) 0.02 Needlecast (%)a 4 20.0 (5.3) 30.9 (2.6) 0.13 9 23.8 (3.1) 14.4 (3.1) 0.01 4 18.6 (4.2) 3.6 (1.9) 0.13 Green Crown (%) 4 4.6 (4.6) 39.3 (20.6) 0.18 9 22.1 (9.6) 22.7 (13.7) 0.83 7 19.9 (9.2) 0.0 (0.0) 0.06 Scorched Crown (%) 4 54.8 (18.2) 32.5 (7.7) 0.63 9 53.1 (10.5) 15.5 (6.3) 0.00 7 59.2 (12.2) 0.7 (0.5) 0.04 Charred Crown (%) 4 40.6 (20.0) 28.1 (16.5) 0.88 9 24.8 (12.1) 61.7 (13.8) 0.02 7 20.8 (13.5) 99.3 (0.5) 0.04 Green Overstory (%) 4 17.5 (17.5) 38.0 (22.2) 0.18 9 25.7 (10.8) 22.8 (13.0) 1.00 7 24.0 (11.9) 0.0 (0.0) 0.06 Scorched Overstory (%) 4 46.2 (19.2) 42.0 (16.6) 0.88 9 50.9 (10.7) 20.9 (7.5) 0.02 7 52.4 (13.8) 1.0 (0.7) 0.03 Charred Overstory (%) 4 36.2 (22.0) 20.0 (16.8) 0.79 9 23.4 (12.0) 56.3 (14.1) 0.05 7 23.6 (14.6) 99.0 (0.7) 0.03 Green Understory (%) 4 24.8 (12.1) 26.2 (9.9) 0.88 9 29.8 (7.3) 36.6 (8.2) 0.44 7 39.4 (9.8) 27.3 (9.6) 0.58 Scorched Understory (%) 4 37.5 (13.0) 48.2 (8.5) 1.00 9 37.1 (6.0) 23.7 (4.3) 0.12 7 41.4 (7.8) 18.7 (10.5) 0.08 Charred Understory (%) 4 37.8 (17.8) 25.5 (10.7) 1.00 9 33.1 (8.2) 39.8 (11.6) 0.83 7 19.1 (11.2) 54.0 (11.2) 0.09 Green Surface Vegetation (%) 4 7.1 (3.2) 6.9 (2.3) 1.00 9 9.6 (2.5) 11.0 (3.7) 0.82 7 18.8 (9.2) 10.0 (3.7) 0.58 Litter/DWD (%) 4 41.6 (14.0) 49.4 (7.4) 0.63 9 51.8 (3.9) 59.9 (5.1) 0.13 7 35.4 (6.8) 22.8 (6.3) 0.30 Ash (%) 4 7.3 (4.9) 0.6 (0.6) 0.18 9 4.0 (3.7) 2.0 (1.1) 0.92 7 0.6 (0.4) 0.3 (0.2) 0.79 Mineral Soil/Rock (%) 4 44.0 (13.3) 43.1 (8.3) 0.88 9 34.7 (5.7) 27.1 (6.8) 0.13 7 45.2 (10.8) 66.9 (7.1) 0.16 Char (%) 4 55.9 (9.1) 68.4 (6.4) 0.63 9 62.6 (3.3) 71.5 (6.3) 0.20 7 52.1 (9.5) 59.3 (11.3) 0.47 Litter Depth (mm) 4 2.2 (0.6) 2.5 (0.3) 0.88 9 2.0 (0.3) 2.6 (0.5) 0.21 7 2.3 (0.3) 1.3 (0.1) 0.03 Duff Depth (mm) 4 2.5 (1.7) 1.8 (0.6) 1.00 9 1.7 (0.7) 3.0 (1.0) 0.23 7 1.2 (0.8) 0.1 (0.0) 0.10 Water Infiltration Rate at 1 cm 4 4.5 (1.6) 3.4 (1.2) 0.88 9 8.5 (2.3) 4.8 (1.5) 0.30 6 10.8 (2.5) 9.7 (1.2) 1.00 Soil Depth (ml/min)b Water Infiltration Rate at 3 cm 4 2.5 (0.8) 3.6 (1.4) 0.63 9 2.6 (0.5) 3.7 (0.9) 0.57 6 5.7 (1.5) 7.9 (2.0) 0.44 Soil Depth (ml/min)b Live Seedling Density 4 2625.0 (1143.4)125.0 (125.0) 0.18 9 1388.9 (570.0) 944.4 (536.5) 0.60 7 1714.3 (1159.1) 0.0 (0.0) 0.10 (seedlings/ha) Vegetation Plot Cover (%) 4 11.8 (2.6) 10.2 (2.8) 0.79 9 17.6 (4.6) 24.4 (7.7) 0.44 7 26.3 (9.5) 24.0 (7.4) 0.74 Plot Species Richness (count) 4 9.0 (2.6) 5.2 (0.9) 0.18 9 6.1 (1.1) 8.2 (1.2) 0.11 7 6.0 (0.9) 5.9 (1.5) 0.80 a Excludes one treated and two untreated sites at Warm Lake where wheat straw was applied for post-fire rehabilitation prior to the 2008 field visits. b Excludes one site pair at Warm Lake where soil conditions were too wet at the time of the 2008 field visits to measure water infiltration reliably.
USDA Forest Service RMRS-GTR-252. 2011. 39

differed in the same cases, while in no cases did the 

percentage of green tree crowns significantly differ (figure 25, table 4). Note that the percentage of 

charred, scorched, and green tree crowns must sum to 

unity; they are not independent. We estimated crown 

condition ocularly (Omi and Kalabokidis 1991) for 

every tree crown within the 1/25-ha tree plot and averaged them; whereas the live, scorched, and charred 

overstory (and understory) variables (table 4) were a 

single ocular estimate of the overstory (and understory) canopy condition across the entire field site. The 

high redundancy between the tree crown and overstory condition results (table 4) indicates that the trees in 

the tree plots are representative of the field sites and 

that the quicker overstory (and understory) estimates 

are sufficient for rapid response assessment.

The fractional ground cover components of green 

surface vegetation, litter/DWD, ash, and mineral soil/

rock were also constrained to sum to unity. Unlike the 

tree crown condition variables, however, none of the 

ground cover variables differed significantly between 

treated and untreated sites (figure 26, table 4). The 

most dramatic contrast was at Warm Lake where, as 

has been indicated by the other field measures presented above, wildfire effects were more pronounced 

than at Secesh Meadows. The char fraction of surface materials did not significantly differ between any 

paired site groups (table 4).

The more marked contrast in burn severity between 

treated and untreated sites at Warm Lake may have 

contributed to one significant difference in a surface 

fuel variable--litter depth was significantly greater (pvalue = 0.03) on treated sites than on untreated sites 

at Warm Lake (table 4). However, the significance of 

this result may have been driven by the mastication 

treatment, where a good share of the wood chips that 

resulted from the fuel treatment remained on the forest floor following the wildfire. Duff depths did not 

differ significantly between any paired site groups 

(table 4). We also compared the soil infiltration rates 

(Robichaud and others 2008) between treated and untreated sites but found no significant differences in 

infiltration rate for any paired site groups at either 1 

cm or 3 cm depth (table 4).

We estimated there were 1300 more tree seedlings/

ha on treated sites than on untreated sites—a significant difference when compared across all 20 site pairs 

(p-value = 0.03) but not significant within any particular paired site group (table 4). Neither total vegetation 

cover nor understory plant species richness assessed 

within our 1/500-ha vegetation subplots differed significantly between treated and untreated sites, either 

as a whole or for any paired site groups (table 4).

Site recovery

All of the field assessment results presented so far 

are based on data collected one year after the 2007 

wildfires—in August 2008. However, we established 

half of our field sites during our initial, rapid assessment in September 2007. We compared treated versus 

untreated sites and used Wilcoxon signed rank tests to 

assess the significance of the differences in 2007, but 

the results did not differ appreciably from the 2008 results presented earlier. Only the differences in sapling 

density, basal area, and biomass; tree stump density; 

and tree mortality were significant, probably because 

only nine paired sites were available. With the exception of tree mortality, these significant differences 

reflected treatment effects rather than wildfire effects.

The real value of the 2007 initial assessment was to 

allow an assessment of site recovery, even if for only 

half the number of field sites as were characterized in 

2008. Fewer field variables were measured in 2007 

than in 2008, further limiting the number of comparisons that could be made. Many of the 2007 measures 

that were re-measured in 2008 did not change significantly, according to Wilcoxon signed rank tests. 

Such measures included variables that were related 

mainly to treatment effects (in other words, tree/sapling/stump density/basal area/biomass) and would not 

be expected to change after only one year (figure 27). 

Not surprisingly, percent tree mortality also did not 

change appreciably. However, a slight yet significant 

4.1 percent increase in canopy closure was measured 

across both treated and untreated sites (table 5). This 

is counterintuitive, especially given that significantly 

more needlecast cover (5.7 percent) fell to the ground 

between the 2007 and 2008 assessments (table 5). 

Foliar regrowth could explain some of the observed 

increase in canopy closure, but given the high tree 

mortality rates observed, the more likely explanation 

was measurement bias. Different field crew personnel 

measured canopy closure in 2007 than in 2008, and 

spherical densiometer measurements are highly variable and, therefore, vulnerable to user bias. Overstory 

tree canopy condition changed little between 2007 

and 2008, whereas understory canopy condition 

changed greatly from being predominantly charred in 
40 USDA Forest Service RMRS-GTR-252. 2011.

2007 to having equal proportions of live, scorched, 

and charred canopy in 2008 (figure 28). The increase 

in live understory canopy and concomitant decrease 

in charred understory canopy was significant, regardless of whether the sites had been treated (table 5).

Changes in ground cover from 2007 to 2008 did 

not differ between treated and untreated sites (figure 

29) but were significant in either case (figure 30), with 

significant increases in green vegetation cover concomitant with significant decreases in surface litter/

DWD and charred material (table 5). Grasses, forbs, 

and some resprouting shrubs were the main plant 

types recovering one year after the wildfire. Litter 

depth decreased 4.1 mm across all 20 re-measured 

sites (table 5), which may point to physical degradation and incorporation of organic material into the 

soil after a year of weathering. Although the trends 

in site recovery from 2007 to 2008 across treated and 

untreated sites were broadly similar, there was weak 

but significant evidence that soil water repellency and 

seedling density recovered more quickly on treated 

sites than on untreated sites (table 5), which may be 

indicative of less soil heating on treated sites than on 

untreated sites.

Discussion

Case Study of 2007 Central 

Idaho Wildfires

Field assessments

We are confident that the paired site design strengthened our inferences. One could argue that the large 

number of significant paired test results (n = 50; tables 

3 through 5) increases the risk of falsely rejecting the 

null hypothesis of no difference between treated and 

untreated sites. However, at the significance level of 

α = 0.05, this would be expected to amount to only 

50 x .05 = 2.5 false positives, which would be unlikely to change our general conclusion that the fuel 

treatments did mitigate severe fire effects. From our 

standpoint, the cost of committing a Type I error by 

our analytical approach was greatly outweighed by the 

benefit of being able to point to specific fuel treatment 

and/or fire effects that may warrant greater attention by 

fuel and fire managers.

Martinson and Omi (2008) concluded that retrospective studies of fuel treatment effectiveness can be 

limited by such caveats as a firebreak between treated 

Figure 27. Secesh Meadows pile and burn treated site (left) versus its paired untreated site (right) nearby, one year after the fire. 

Post-fire revegetation did not show a treatment effect. Photos: Andrew Hudak.
USDA Forest Service RMRS-GTR-252. 2011. 41 Table 5. Comparisons of immediate and one year post-wildfire effects to assess site recovery at Secesh Meadows and Warm Lake. Significant differences (a = 0.05) indicated in boldface. Treated sites Untreated sites All sites Site 2007 2008 Wilcoxon Site 2007 2008 Wilcoxon Site 2007 2008 Wilcoxon Variable description pairs mean (SE) mean (SE) p-value pairs mean (SE) mean (SE) p-value pairs mean (SE) mean (SE) p-value Tree Mortality (%) 11 57.2 (13.6) 62.8 (9.7) 0.68 9 90.4 (3.2) 82.0 (10.1) 0.59 20 72.1 (8.4) 71.4 (7.2) 0.98 Canopy Closure (%) 11 22.9 (2.5) 26.5 (3.7) 0.01 9 22.0 (2.9) 26.7 (4.6) 0.04 20 22.5 (1.9) 26.6 (2.8) 0.00 Needlecast (%)a 11 14.0 (4.1) 20.9 (4.2) 0.07 7 7.9 (4.2) 11.5 (4.9) 0.24 18 11.6 (3.0) 17.3 (3.3) 0.02 Green Overstory (%) 11 26.8 (12.8) 20.8 (10.3) 0.79 9 8.9 (8.9) 11.2 (11.0) 0.37 20 18.8 (8.1) 16.5 (7.4) 0.93 Scorched Overstory (%) 11 39.1 (11.8) 46.1 (10.9) 0.57 9 13.6 (5.7) 12.4 (9.6) 0.27 20 27.6 (7.4) 30.9 (8.2) 0.87 Charred Overstory (%) 11 34.1 (12.7) 33.1 (11.8) 1.00 9 77.6 (11.2) 76.3 (13.6) 0.40 20 53.6 (9.7) 52.5 (10.0) 0.61 Green Understory (%) 11 2.4 (1.6) 38.4 (7.8) 0.00 9 1.1 (1.1) 30.4 (9.3) 0.01 20 1.8 (1.0) 34.8 (5.9) 0.00 Scorched Understory (%) 11 24.5 (5.6) 31.5 (5.7) 0.39 9 14.4 (4.0) 27.7 (9.7) 0.12 20 20.0 (3.7) 29.8 (5.2) 0.11 Charred Understory (%) 11 73.1 (6.9) 30.1 (9.8) 0.01 9 84.4 (4.4) 41.9 (11.6) 0.01 20 78.2 (4.4) 35.4 (7.4) 0.00 Green Surface Vegetation (%) 11 0.8 (0.5) 16.3 (6.0) 0.00 9 0.8 (0.7) 13.5 (4.0) 0.00 20 0.8 (0.4) 15.0 (3.7) 0.00 Litter/DWD (%) 11 69.5 (7.0) 42.6 (4.8) 0.00 9 55.7 (9.4) 38.4 (8.3) 0.02 20 63.3 (5.8) 40.7 (4.5) 0.00 Ash (%) 11 2.0 (1.4) 4.1 (3.0) 0.44 9 2.0 (0.7) 1.5 (1.1) 0.57 20 2.0 (0.8) 3.0 (1.7) 0.98 Mineral Soil/Rock (%) 11 27.7 (6.8) 37.0 (6.7) 0.28 9 41.5 (9.8) 46.6 (10.6) 0.30 20 33.9 (5.8) 41.3 (5.9) 0.10 Char (%) 11 85.8 (5.5) 55.8 (6.0) 0.00 9 91.3 (3.4) 61.0 (7.9) 0.00 20 88.3 (3.4) 58.1 (4.8) 0.00 Litter Depth (mm) 11 6.5 (1.3) 2.3 (0.3) 0.00 9 6.2 (1.3) 2.2 (0.5) 0.01 20 6.3 (0.9) 2.2 (0.3) 0.00 Duff Depth (mm) 11 1.9 (1.0) 1.5 (0.7) 0.64 9 1.7 (1.1) 1.8 (1.1) 0.10 20 1.8 (0.7) 1.6 (0.6) 0.97 Water Infiltration Rate at 1 cm 9 0.4 (0.1) 9.8 (2.6) 0.00 6 4.0 (2.8) 7.6 (1.9) 0.22 15 1.9 (1.2) 8.8 (1.7) 0.00 Soil Depth (ml/min)b Water Infiltration Rate at 3 cm 10 1.3 (0.5) 4.1 (1.1) 0.02 8 2.3 (1.0) 6.2 (1.4) 0.04 18 1.8 (0.5) 5.0 (0.9) 0.00 Soil Depth (ml/min)b Live Seedling Density 11 0.0 (0.0) 1545.5 (739.9) 0.02 9 55.6 (55.6) 611.1 (551.4) 0.37 20 25.0 (25.0) 1125.0 (476.9) 0.01 (seedlings/ha) a Excludes two untreated sites at Warm Lake where wheat straw was applied for post-fire rehabilitation between the 2007 and 2008 field visits. b Excludes field sites at Warm Lake where soil conditions were too wet at the time of either the 2007 or 2008 field visits to measure water infiltration reliably.
42 USDA Forest Service RMRS-GTR-252. 2011.

Figure 28. Mean post-wildfire overstory and understory canopy condition on treated (n = 11) 

and untreated (n = 9) sites, immediately post-fire (2007) versus one year post-fire (2008). 

Significant changes from 2007 to 2008 are indicated on the right: *, p-value<0.05; **, 

p-value<0.01.

Overstory in 2007, Treated

Scorched

Charred

Live

Overstory in 2008, Treated

Scorched

Charred

Live

Overstory in 2007, Untreated

Scorched

Charred

Live

Overstory in 2008, Untreated

Scorched

Charred

Live

Understory in 2007, Treated

Scorched

Charred

Live

Understory in 2008, Treated

Scorched

Charred

Live

Understory in 2007, Untreated

Scorched

Charred

Live

Understory in 2008, Untreated

Scorched

Charred

Live

**

**

**

*
USDA Forest Service RMRS-GTR-252. 2011. 43

Figure 29. Secesh Meadows pile and burn treated site (left) versus its paired untreated site (right) nearby, one year after the fire. 

Ground cover fractions changed but similarly between treated and untreated sites. Photos: Andrew Hudak.

Figure 30. Mean post-wildfire ground cover fractions on treated (n = 11) and 

untreated (n = 9) sites, immediately post-fire (2007) versus one year post-fire 

(2008). Significant changes are indicated on the right: *, p-value<0.05, **, 

p-value<0.01; ***, p-value = 0.001.

Surface Cover in 2007, Treated Surface Cover in 2008, Treated

Litter Litter ***

***

Surface Cover in 2007, Untreated Surface Cover in 2008, Untreated

Green

Green

Soil

Soil

Ash

Ash

Litter Litter *

**

Green

Green

Soil Soil

Ash

Ash
44 USDA Forest Service RMRS-GTR-252. 2011.

and untreated sites (for example, a railroad track in their 

study) or pseudo-replicated samples that are caused by 

having multiple sites within a single treatment unit. 

We sampled two treatment units at Secesh Meadows 

twice, two treatment units at Warm Lake twice, and another at Warm Lake thrice (figure 12), but these were 

larger treatment units in which different site pairs were 

separated by either ample distance perpendicular to 

the direction of the advancing crown fire or by roads/

powerlines that acted as firebreaks between different 

paired sites. Strom and Fulé (2007) also found that a 

paired sampling approach was powerful for focusing 

attention on the fuels component of the fire behavior 

triangle as fire weather and topography at a given pair 

of sites were otherwise very similar.

Fuel treatment effects on tree density, basal area, and 

biomass were more pronounced at Secesh Meadows 

than at Warm Lake (table 3), perhaps in part because the 

Secesh Meadows treatments were more recent (2006) 

compared to the Warm Lake treatments sampled (2000 

to 2005). The nine treated sites at Secesh Meadows 

where the piles had been prescribed burned prior to the 

wildfire burned less severely than their paired untreated 

sites. Fuel piles that burned in the wildfire contributed 

to more severe fire effects than at untreated sites (figure 31)—a result noted in other assessments (Harbert 

and others 2007, Murphy and others 2007). At Warm 

Lake, all seven treated sites burned less severely than 

their paired untreated sites regardless of treatment type 

(figures 17-19), so all seven paired sites at Warm Lake 

were grouped together for the statistical comparison 

(table 4).

Our vegetation recovery results after a single year 

indicated little differential ability in the sites to recover 

from wildfire after one year, based on how and whether 

fuels had been treated (table 5). However, one year is 

not an adequate period of time to consider tree and understory plant recovery. Because vegetation recovery 

following fuel treatments can be rapid, most fuel treatments need repeated maintenance to remain effective 

(Graham and others 1999, 2004). Longer-term monitoring of fuel treatments is needed to understand the 

duration of treatment effectiveness in different ecosystems, whether or not a wildfire actually burns through.

Satellite assessments

The dNBR and potentially other burn severity 

indices may be useful for assessing fuel treatment effectiveness consistently across large areas. Wimberly 

and others (2009) found that thinning treatments that 

used prescribed fires to reduce fuel loads were more 

effective than thinning alone in reducing subsequent 

burn severity for three western wildfires. The data used 

by Wimberly and others (2009) were dNBR maps developed by the national-scale Monitoring Trends in 

Burn Severity (MTBS) project from 1984 to present 

Landsat imagery, and geospatial data layers from the 

LANDFIRE project to control for pre-fire variability 

in canopy cover, fuels, and topography, which can confound efforts to assess treatment effects from remotely 

sensed data. The MTBS project uses one year post-fire 

imagery because it provides a more accurate indicator 

of burn severity, defined as the ecological impact of the 

fire (Lentile and others 2006), than immediate post-fire 

imagery.

We found that one year post-fire dNBR, the most 

common remotely sensed indicator of burn severity, 

significantly differed between our treated and untreated sites. This and other indices derived from satellite 

images are sensitive to burn severity, as characterized 

by fire effects on vegetation and soils (Key and Benson 

2005, Hudak and others 2007). Considering all 20 

paired sites, one year post-fire dNBR correlated more 

strongly to bole char height (r = 0.84, p-value<0.0001), 

percent charred overstory canopy (r = 0.85, p-value<0.0001), percent charred tree crowns (r = 0.82, 

p-value<0.0001), and tree mortality (r = 0.66, p-value<0.0001) than to any other field measures. These 

field measures were especially high at the untreated 

sites at Warm Lake, again indicating that severe wildfire effects were more pronounced there than at Secesh 

Meadows (table 4). This result supports the finding of 

Hudak and others (2007) that vegetation canopy reflectance has more influence than soil reflectance on the 

dNBR signal integrated over a 30- by 30-m pixel area.

The immediate post-fire BARC map data analysis of 

treated versus untreated lands also showed that the fuel 

treatments significantly reduced high severity fires (figure 13). This agreed with similar findings by Harbert 

and others (2007) on three large 2007 fires in central 

Oregon. However, simple BARC map analyses such 

as these do not control for complicating factors such 

as topography and local fire weather as effectively as a 

paired site sampling strategy. For example, local USFS 

fire and fuel managers were doubtful that the weather 

data recorded at the Flat Creek portable RAWS (figure 

10), situated between the northernmost treatment units 

at Secesh Meadows (figure 5), would well represent the 
USDA Forest Service RMRS-GTR-252. 2011. 45

entire WUI because of the way the wind swirled within 

the constricted valley during the fire. Similarly, eddies 

produced by the local topography were undoubtedly a 

factor at Warm Lake. On the other hand, the RAWS 

variables that we considered explained a large proportion of the variance in area burned per day in both WUI 

areas. The significant explanatory power of most of the 

spatial autoregressive models based on RAWS records 

that were collected within 25 km of the local WUI areas demonstrated that local weather is an important 

determinant of fire activity (table 2).

Fuel treatment effectiveness

The combination of mechanical treatment followed 

by prescribed surface fire was the most effective type 

of fuel treatment for mitigating severe fire effects 

(figures 12 and 13). While this result confirms many 

other findings (Cram and others 2006, Martinson and 

others 2003, Omi and others 2006, Prichard and others 2010, Raymond and Peterson 2005, Ritchie and 

others 2007, Skinner and others 2004, van Wagner 

1968, Weatherspoon and Skinner 1995), it was probably influenced by several local variables that merit 

discussion. First, the effectiveness of the underburn 

treatments at Warm Lake depended on time since 

treatment. The areal percentage of high severity 

hectares was 16 percent in the 2006 Kline Mountain 

underburn unit but ranged from 18 to 34 percent 

in the three other underburns applied from 1996 to 

1998. Even more dramatically, the areal percentage 

of low severity hectares was 40 percent in the Kline 

Mountain underburn but only 11 to 24 percent in the 

older underburn units.

Fire direction was another factor. The treatment 

units west of Warm Lake were most severely tested 

by the advancing wildfire, namely the Warm Lake 

Highway mastication treatment (tested by the North 

Fork fire that approached from the west); the Warm 

Lake South pile and burn treatment (tested by the 

Monumental fire that approached from the south); and 

the Kline Mountain underburn treatment in between, 

where steeper slopes and variable aspects appeared 

to interact with the converging wildfires. These treatments all worked as designed to slow the momentum 

of the advancing crown fire. The observed west to 

east gradient of high to low burn severity that was 

captured by the BARC map across the treatment units 

(figure 12) was the immediate post-fire expression 

of a similar gradient in fire intensity, as crown fires 

dropped down to surface fires as they moved through 

the treatment units. The many (more than 100) bucket drops from helicopters into the treatment units in 

close proximity to structures was also a factor in the 

high percentage of unburned hectares in pile and burn 

Figure 31. Left: Backing fire igniting unburned fuel piles at Secesh Meadows, which contributed to more severe fire effects. 

Photo: Roger Staats. Right: Contrasts in crown condition, tree mortality, and understory re-vegetation at Secesh Meadows 

one year post-fire, looking north up the hill toward the Pioneer Cemetery. Photo: Andrew Hudak. Area upslope to the left 

had residual fuel piles burned by the wildfire (WF Piles), while most of the piles in the area in the foreground and to the 

right were burned prior to the wildfire as prescribed (Rx Piles). More severe fire effects persisted one year later on the left 

than on the right as evidenced by greater crown scorching, higher tree mortality, and less re-vegetation.
46 USDA Forest Service RMRS-GTR-252. 2011.

treatment units at Warm Lake and in Firewise-treated 

private lands at Secesh Meadows.

Whether or not these fuel treatments would have 

protected homes without the added fire suppression 

measures may not be as important as determining 

how fuel treatments can be optimally located and 

distributed across the landscape to allow fire suppression crews to gain control more effectively and 

safely. Maps of fuel treatment units should be made 

available to incident commanders to use as potential 

fire breaks, similar to roads and streams. Other assessments have promoted planning fire suppression 

efforts around fuel treatment units (Fites and others 

2007, Graham and others 2009, Harbert and others 

2007, Murphy and others 2007, Rogers and others 

2008).

Are Expensive WUI Fuel 

Treatments Worthwhile?

We are rapidly learning about fuel treatments, 

though we need better monitoring and communication of successes and lessons learned. The interagency 

Joint Fire Science Program has funded multiple studies on fuel treatments, including some user guides 

(Graham and others 1999, 2004) and recent projects 

that are focused on the life cycle of fuel treatments. 

Fuels synthesis tools are also useful. While there is 

general agreement that removing and reducing fuels 

reduces fire intensity, not all agree that fuel treatments 

are effective, and many assessments of treatment effectiveness are qualitative or based on simulation 

models with little empirical data.

Rhodes and Baker (2008) found that fuel treatments 

only have a mean probability of 2.0 to 7.9 percent of 

being encountered by moderate or high severity fire 

within 20 years following treatment, and they argue 

that the millions of dollars spent on fuel treatments 

is, therefore, not justified. Rhodes and Baker (2008) 

argue that, even if those areas benefited from reduced 

burn severity, they are too small to counterbalance the 

adverse effects of fuel treatments on watersheds.

However, Rhodes and Baker (2008) oversimplified their analysis by assuming that ignitions, and 

fuel treatments, are randomly distributed across the 

11 western states. Neither assumption is correct, as 

50 percent of fuel treatments are mandated to occur 

in the WUI (but see Schoennagel and others 2009 

and discussion below). Ignitions, all of which except 

lightning are human-caused, are more probable where 

human populations are denser, as in the WUI. Rhodes 

and Baker’s (2008) findings are instructive for regional or national level planning but are less helpful 

to local fuel managers who design and implement fuel 

treatments. Simulation models provide valuable planning tools for decision makers. For example, Ager and 

others (2010) found that fuel reduction treatments on 

just 10 percent of the landscape resulted in a 70 percent reduction of large tree mortality to help preserve 

highly valued, old forest stands. Many fuel treatments 

will not be challenged by fire, and so they need to 

be well designed for other vegetation management 

objectives that are appropriate to the biophysical and 

socio-economic setting.

Schoennagel and others (2009) looked at the 

44,000 fuel treatments implemented across the western United States and found that only 3 percent of the 

treated areas were within the WUI and only 8 percent 

within 2.5 km of the WUI, which falls far short of 

the 50 percent mandated by the National Fire Plan. 

Only 17 percent of the area within 2.5 km of the WUI 

is under Federal ownership. Therefore, Schoennagel 

and others (2009) concluded that the focus for treating fuels needs to shift from public to private lands.

The costs and benefits of fuel treatments—particularly in the WUI—are likely to continue to be debated. 

Our primary goal in this report is not to add to this 

debate but to look at cases where fuel treatments were 

tested by wildfire and ask, “Were these treatments 

effective?” Our qualified answer is “Yes.” We now 

summarize the important implications of our findings.

Fuel Treatments in Forests: 

Implications and Conclusions

Fuel treatments mitigate fire effects. Of the case 

studies we reviewed that had been tested in wildfires, 

only Weatherspoon and Skinner’s (1995) showed that 

fuel treatments were not effective. However, in their 

study, the untreated stands were simply more fire resistant than treated stands.

We can draw some broad conclusions from our case 

study and the diverse studies we reviewed. These conclusions apply most directly to the dry forests of the 

western United States where most of the studies have 

been conducted.
USDA Forest Service RMRS-GTR-252. 2011. 47

First, fire effects on the overstory trees were most 

effectively mitigated by treatments that addressed 

both surface and crown fuels through combination 

treatments such as thinning followed by a prescribed 

burn or by removing slash after thinning (Cram and 

others 2006, Martinson and others 2003, Omi and 

others 2006, Prichard and others 2010, Raymond and 

Peterson 2005, Ritchie and others 2007, Skinner and 

others 2004, van Wagner 1968, Weatherspoon and 

Skinner 1995). Thinning alone can certainly alter the 

amount and arrangement of crown fuels (Omi and 

others 2006, Pollet and Omi 2002), but the presence 

of abundant activity fuels or slash (Skinner and others 2004), grasses (Weatherspoon and Skinner 1995), 

and shrubs (van Wagner 1968) contribute to tree canopy damage or mortality when those fuels burn. Field 

observations and fire behavior modeling studies have 

demonstrated that increased surface and ladder fuels 

increase crown fire risk (Vaillant and others 2009). 

From our own case study, we found that the most effective treatments combined forest thinning and reduction 

of surface fuels (figures 12 and 13).

Second, prescribed burn treatments varied in their 

effectiveness. Pollet and Omi (2002) found that prescribed burning was the least successful of alternative 

fuel treatments in mitigating fire severity, and our 

BARC map data comparison of treatment types at 

Warm Lake confirm this finding (figure 13). However, 

Omi and others (2006) found that prescribed fire 

treatments that removed small-diameter trees in addition to surface fuel consumption resulted in a canopy 

structure similar to thinning from below and that this 

proved highly successful compared with thinning 

treatments that did not affect surface fuels. Given the 

variability in prescribed fires, repeated entry may be 

necessary to achieve desired fuel amount and composition (Martinson and others 2003). It is difficult to 

kill most medium-sized trees and many small trees by 

fire alone. Multiple rounds of prescribed fire are more 

effective in reducing burn severity of subsequent wildfires than single entry treatments (Finney and others 

2005, Harbert and others 2007).

Third, treatments become less effective with time 

since treatment. This was the case with the 1996 to 2006 

underburn treatments at Warm Lake (figure 12). Fuels 

accumulate because vegetation production outweighs 

decomposition; fires maintain a balance between fuel 

accumulation and consumption (van Wagtendonk and 

Moore 2010). The rate of forest fuels accumulation 

varies as a function of forest type, climate, and disturbance regime, particularly fire disturbance (Graham 

and others 1999). Keifer and others (2006) found that 

fuels in ponderosa pine stands in California accumulated to 84 to 88 percent of pre-fire levels 10 years after 

burning and 150 to 180 percent 31 years after burning. Skinner and others (2004) found that treatments 

conducted two to four years prior to wildfires showed 

the least tree mortality. Finney and others (2005) 

found treatments completed within four years before 

the fire reduced severity most consistently and more 

significantly than those completed nine years prior to 

wildfires. Omi and others (2006) took this a step further, stating that treatments that removed slash, which 

significantly reduced surface fuel loading, were effective for 10 years, while thinning-only treatments were 

only found to be effective if they were 1 year old or 

less. Although it is clear that fuel treatment effectiveness declines with time, more studies are needed. It is 

likely that longevity of treatments is site-specific and 

constrained by climate. Re-treatment or other maintenance of treated areas will be necessary for continued 

effectiveness. Landscape-scale prescribed burning and 

maintenance of treated areas must be part of longterm vegetation and fuel treatment strategies, and the 

need for maintenance treatments will continue to escalate as more lands are restored (Harbert and others 

2007). Firewise communities (www.firewise.org) need 

to be part of developing fire smart landscapes—landscapes that are resilient to the effects of future fires. 

Collaborative efforts will be key, as will treatment of 

public lands immediately adjacent to private lands like 

we observed at Secesh Meadows (figure 11).

Fourth, we know little about the importance of 

spatial arrangement and spatial heterogeneity of fuels and fuel treatments. Finney and others (2005) and 

Weatherspoon and Skinner (1995) found that larger 

treatments generally mitigated fire effects more effectively than smaller treatments. Where post-treatment 

fuels were homogeneous, burn severity decreased 

with distance from treatment edge. Weatherspoon and 

Skinner (1995) found that in broadcast burn treatments, 

burn severity decreased with distance from treatment 

edge, while machine-piled and -burned treatments did 

not show this effect but rather a “spotty” burn pattern. 

The relatively uniform treatment tested by Moghaddas 

and Craggs (2007) showed a 65 percent decrease in 

crown scorch within 60 m from the edge of the treatment, although topography likely influenced this. 
48 USDA Forest Service RMRS-GTR-252. 2011.

 Omi and Kalabokidis (1991) did not find this edge 

effect in the relatively uniform fuels of regenerating 

lodgepole pine clearcuts. In our case study at Warm 

Lake, distance from the edge was an observable factor 

in the mechanical treatment units with homogeneous 

fuel conditions but not in the underburn units with 

more heterogeneous fuel conditions (figure 12).

Fifth, placement of treatments with respect to topography, wind, and existing fuels can influence treatment 

effectiveness. Treatments need to be carefully prioritized in a landscape-scale context (Rogers and others 

2007). Both less intense, landscape-scale treatments 

(for example, prescribed burning and wildland fire 

use for resource benefit) and more intense treatments 

(for example, thinning combined with piling, masticating, or otherwise treating surface fuels) will be part of 

strategic choices. Tools such as ARCFUELS (http://

www.fs.fed.us/wwetac/arcfuels/index.html, Ager and 

others 2006, Finney and others 2007) can help managers strategically place future treatments with respect to 

topography and existing vegetation, thereby minimizing the effects of extreme fire weather on fire behavior. 

Although placement was not a variable included in 

their discussion, the ridgetop placement of the thinning 

treatment evaluated by Moghaddas and Craggs (2007) 

should be viewed as an example of maximizing the 

effect of a fuel treatment with regard to topographic 

influences on burning conditions. This agrees with earlier findings by van Wagner (1968), who documented 

slope effects that contributed to increased fire behavior 

and severity; and Weatherspoon and Skinner (1995), 

who noted that aspect was a significant variable that 

contributed to fire severity. We also observed slope 

effects that contributed to more severe fire effects at 

Secesh Meadows and Warm Lake (figures 16 and 19). 

Additional studies are needed to prioritize the locations where treatments can be most effective and to test 

placement empirically.

Sixth, there is no magic formula. While thinning 

from below is a common treatment and thresholds in 

tree density, crown base height, crown bulk density, 

tree spacing, and other fuel composition descriptors 

exist for a given stand, there is no general prescription 

that will work in all or even most stands. The great variety of stand conditions, topography, wildfire burning 

conditions and other variables make it impossible to 

identify target thresholds for fuel treatment effectiveness. Targets have been suggested, such as the crown 

bulk density threshold isolated by Cram and others 

(2006) of 0.047 kg/m3

 or the threshold identified by 

Agee (1996) of 0.10 kg/m3

 for torching and crown fire 

propagation. However, the conditions that will make 

a given stand resilient to wildfire depend on many 

factors.

Seventh, fuel treatments are not designed to stop 

fires but rather to modify fire behavior. Firefighters can 

often use treated areas in effective fire suppression to 

limit fire spread. Fuel treatments can assist fire managers in burn operation strategies when treatments reduce 

fire intensity (Fites and others 2007). Fuel treatments 

are designed to be used together with fire suppression 

and Firewise principles to effectively reduce the likelihood that wildfires will burn homes. Fuel treatments 

can be designed to change fire behavior from crown fire 

to surface fire, thereby reducing spotting distances and 

convective and radiant heat (Murphy and others 2007). 

Short of removing all fuel, we cannot design fuel treatments that will not burn, especially under extreme fire 

conditions (Pollett and Omi 2002). However, we can 

readily design and implement sustainable, visually appealing fuel treatments that will be resilient when they 

burn and that will help fire managers charged with protecting key resource values while also providing for 

ecological restoration and health. It is worth repeating 

that fuel treatments need to be more intensive (more 

surface fuels removed and wider crown spacing) on 

slopes to achieve the same effect as on flat ground.

Eighth, whether fuel treatments exacerbate undesirable fire behavior has been a point of contention. 

Within treated areas, the lower tree canopy cover and 

higher light and nutrient availability on the forest floor 

may lead to increased grass or other conditions that 

favor rapidly spreading fires of high intensity (Agee 

1996, Covington and others 1997). Increased wind velocity can decrease fuel moisture and increase flame 

lengths and rates of spread, thereby increasing the 

magnitude of post-fire effects (Agee 1996, Covington 

and others 1997, Weatherspoon and Skinner 1995). On 

the other hand, Faiella and Baily (2007) examined fuel 

moisture in thin and burn and burn-only ponderosa 

pine restoration treatments in Arizona and compared 

them to untreated sites. They found no significant differences in the moisture content of fuels in the 0 to 6, 

6 to 25, and 25 to 100 mm size classes and concluded 

that concerns of decreased fuel moisture in treated ponderosa pine forests appear to be unwarranted. Though 

it is certainly possible for fuel treatments to increase 

fine fuel temperature and create a micro-climate that 
USDA Forest Service RMRS-GTR-252. 2011. 49

favors increased winds and lower relative humidity. 

Future research should explore these factors as well 

as the scale at which they affect fire behavior. In addition, managers must recognize that fuel treatments 

are not intended as one time actions and an increase 

in fine fuels can be planned for and dealt with using 

maintenance treatments. For example, a high loading 

of grasses following prescribed fire can be controlled 

by periodic grazing or maintenance burns.

Ninth, fuels are just one leg of the fire behavior triangle. Weather and topography affect fire behavior; 

in some cases they render the most robust fuel treatments useless (Bessie and Johnson 1995). Firefighting 

tactics and fuels management treatments are all based 

upon the recognition that fuels are the one aspect of 

the fire environment that humans can most readily 

alter. Researchers acknowledge that the interaction 

of weather and topography is difficult to adequately 

quantify in empirical studies. More recent studies have 

attempted to control those variables through statistical tests and sample design (Cram and others 2006, 

Martinson and Omi 2006, Omi and others 2006, Pollet 

and Omi 2002, Raymond and Peterson 2005). Future 

treatments will likely be more effective if topography 

and potential micro-climate effects are considered 

in treatment prescription and location (Agee 1996, 

Weatherspoon and Skinner 1995). Recent efforts to 

statistically test the variables should be applauded, but 

more definitive controls are needed to apply fuel treatment parameters with confidence. Whether treatments 

are effective or not will vary with fire weather conditions. We expect fuel treatments to be less effective in 

hot, dry, and windy conditions. In other words, fuel 

treatments may successfully dampen the behavior of 

fires that are fuel-driven, but wind-driven fires carry 

tremendous momentum and are much more difficult to 

control.

Tenth, there is much to be learned in fuel treatment 

design and implementation from the many years of experience gained by forest and rangeland managers who 

manage vegetation for other objectives. Vegetation 

treatments, if thoughtfully designed, can often accomplish multiple objectives. For instance, promoting 

the resilience of vegetation to future disturbance, especially in the face of climate change, may become 

increasingly important. Much of the vegetation surrounding the WUI is valued for recreation, aesthetics, 

and songbird habitat, and there are often ways to adapt 

treatment design to enhance those ecosystem services 

(Graham and others 1999, 2004).

Grazing as a Fuel Treatment

The removal of biomass during grazing (particularly 

heavy grazing) reduces fine fuels and decreases risk 

of fire occurrence and spread. Livestock grazing has 

the ability to alter the vegetation structure and composition of all fuel classes in the Douglas-fir/ninebark 

habitat type (Zimmerman and Neuenschwander 1984). 

Those modifications result in a forest that is less likely 

to burn and is less conducive to vertical fire spread.

Disturbances that affect the heterogeneity of fuel loads 

(for example, grazing) affect the total area burned and 

the complexity of the perimeter in a fire. Fire behavior modeling in tallgrass prairie indicates that fires are 

smaller and have more complex shapes in heterogeneous landscapes (Kerby and others 2006). Grazing 

and browsing can be targeted to manage long-term 

vegetation structure and composition (Davison 1996, 

Nader and others 2007, Taylor 2006). Such targeted 

grazing often requires intensive management of livestock, including careful selection of appropriate animal 

species, animal condition, season, duration, and intensity of grazing, and does not often result in optimum 

livestock production.

Cheatgrass is a flammable annual grass that has 

significantly altered the fire regimes in the sagebrush 

steppe. It would be inadequate to discuss fire patterns 

in sagebrush ecosystems without including a discussion of cheatgrass and its interactions with grazing. 

Cheatgrass is an invasive annual grass that was introduced to North America in the Eighteenth century, 

likely as a contaminant in grain seed (Mack 1981). 

Cheatgrass forms a fine-textured, continuous fuel bed 

that is highly flammable when dry and that can support rapidly spreading fires (Klemmendson and Smith 

1964, Link and others 2006). Cheatgrass typically 

cures by early June, expanding the fire season by nearly 

two months in sagebrush communities (Klemmendson 

and Smith 1964). Cheatgrass dominance has changed 

the fire regime in many areas of the sagebrush steppe 

enough to significantly alter succession, create a more 

homogeneous landscape, and decrease species diversity (Peters and Bunting 1994). Historically, grazing 

and agriculture were significant disturbances within 

the Snake River Plain; however, fire is now the primary disturbance that allows for and perpetuates the 
50 USDA Forest Service RMRS-GTR-252. 2011.

invasion of cheatgrass (Peters and Bunting 1994). Fire 

frequency changed from 35 to 110 years to 3 to 5 years 

due to cheatgrass invasion, and because of the continuity it provides, fires burned more uniformly, leaving 

less unburned vegetation (Whisenant 1990). However, 

cheatgrass does not do as well in black sage (Artemisia 

nova) communities (Miller and Eddleman 2001), nor 

does it readily dominate in more mesic and cool areas 

that are typified by mountain big sagebrush and low 

sagebrush (Artemisia arbuscula) (above 1500 m in the 

northern portion of the sagebrush biome and above 

1600 m in the southern portion). 

While the fire frequency has changed greatly in areas 

that are invaded by annual grasses such as cheatgrass, 

conifer expansions in the mesic portion of the sagebrush 

steppe have decreased fire frequency (Miller and Rose 

1999). Post-settlement western juniper (Juniperous occidentalis) expansion is associated with an increase in 

domestic livestock, a reduction in fire frequency, and 

an increase in precipitation (Miller and Rose 1999). 

Increased sagebrush cover, resulting from intensive 

grazing and other vegetation modifications that are designed to increase forage for domestic livestock, may 

provide safe sites for juniper establishment and sapling 

growth. Interactions among grazing regimes, invasive 

plants, and a changing climate contribute to the complexity of fuels management in rangelands. The legacy 

of the land and potential future trajectories in vegetation composition must be carefully considered when 

deciding whether or not to apply fuel treatments in 

rangelands.

Long-Term Ecological Effects 

of Fuel Treatments

Fuel treatments can have long-term ecological effects, whether or not the treated area burns in wildfires. 

Choromanska and DeLuca (2001) showed that prescribed fire can minimize carbon and nitrogen losses 

from subsequent wildfires, improve soil microbe resistance, increase soil organic carbon, and increase basal 

respiration. Wagle and Eakle (1979) concluded that 

after wildfire, understory plants recovered more rapidly in areas treated with prescribed fire prior to the 

wildfire. Cram and others (2006) demonstrated that 

when wildfires burned in areas with prior treatments, 

there was less bare soil, more litter, and improved herbaceous plant recovery.

Fulé and others (2007) modeled different post-fire 

successional trajectories for treated and untreated areas 

in Arizona. Their results suggested that thinning and 

prescribed burning encouraged ponderosa pine, while 

untreated areas that burned in the same wildfires became dominated by manzanita, gambel oak, and New 

Mexican locust with few areas dominated by ponderosa pine.

Invasive plant species can increase in abundance 

following fuel treatments or wildfires, especially if disturbances are severe (Brooks and others 2004, Hunter 

and others 2006). Omi and others (2006) found higher 

cover of non-native plant species in areas that burned 

more severely. Where fuel treatments mitigated fire 

effects on canopy and ground fuels, native species 

richness was higher and species were more abundant 

than in areas that wildfires burned with high severity. 

However, post-fire invasive species are likely to be 

most abundant where they were abundant pre-fire, such 

as along roadsides or in other disturbed areas.

Limitations and Future Needs

These case studies cannot represent all types of fuel 

treatments or ecosystems, making it difficult to draw 

generalizations. Most case studies are based on thinning and prescribed burning in dry pine forests. There 

are few such studies in woodlands, shrublands, and 

grasslands (though the SageSTEP project [http://www.

sagestep.org/] will soon provide useful information 

for sagebrush and juniper woodlands). Despite their 

limitations, simulation modeling and case studies will 

continue to be used to evaluate fuel treatments. More 

landscape-level studies that exploit remotely sensed 

data are also needed (for example, Dailey and others 

2008, Fites and others 2007, Harbert and others 2007, 

Wimberly and others 2009).

Because there are few studies of the effectiveness of 

fuel treatments that are subjected to actual wildfires, our 

literature review reflected not only fuel treatments but 

also fuel modifications or management practices that 

altered vegetation composition and, thus, the fuelbed. 

It is important to recognize that many fuel treatments 

are similar to the vegetation manipulation treatments 

that have long been applied in forests and rangelands. 

That is an advantage because most treatments will 

not be tested by fires. Thus, it is important that fuel 

treatments be thoughtfully matched to the ecological 
USDA Forest Service RMRS-GTR-252. 2011. 51

conditions for long-term sustainability, as well as to be 

feasible and socially acceptable.

More consistent and specific quantitative data are 

needed to assess treatment effectiveness. For instance, 

burn severity is measured in many different ways. 

Weatherspoon and Skinner (1995) use 50 percent 

crown scorch as their measure of extreme fire damage, 

while Omi and Kalabokidis (1991) define severe damage as 100 percent crown consumption. Rating systems 

such as that outlined by Omi and Kalabokidis (1991) 

and Ryan and Noste (1985) for quantifying tree canopy 

scorch and consumption of surface and ground fuels 

have been used by many. The Composite Burn Index 

provides a generalized rating of post-fire conditions in 

the field and includes fire effects on both vegetation 

and soils (http://www.nrmsc.usgs.gov/science/fire/

cbi/description). Other measures of burn severity include methods from Brown (1974), Ffolliott and others 

(1968), and Keeley (2009).

Unanswered Questions

Are fuel treatments less effective in standreplacing fire regimes?

Most studies regarding fuel treatment efficacy 

focus on dry forest types where fire exclusion and climatic fluctuations have affected vegetation on a grand 

scale (Allen and others 2002, Pollet and Omi 2002, 

Westerling and others 2006). Therefore, fuel treatments 

that reduce burn severity and, in some cases, promote 

ecological restoration have been widely accepted in 

those regions. However, in subalpine forests, current 

fire regimes have been significantly less impacted by 

fire exclusion, meaning that fuel composition is more 

typical of historical conditions (Schoennagel and 

others 2004, Turner and others 2003). Climate fluctuations that result in periods of prolonged warm, dry 

conditions have contributed to the large, severe fires 

of recent decades in cold forests (Morgan and others 

2008, Swetnam and Westerling 2007).

Therefore, if fire intensity and severity are dictated 

more by the weather leg of the fire triangle than by fuels, are fuel treatments likely to be less effective outside 

of dry forests? Weather affects the availability of fuels, 

not the abundance of the tree canopy fuels that are necessary to carry fire across the landscape. It stands to 

reason that reducing canopy fuel loading and tree spacing would reduce the potential for stand-replacing fires. 

Our case study results in the lodgepole pine-dominated 

forests of central Idaho suggest that fuels management 

in those forests can mitigate post-fire effects.

In subalpine forests, new ecological problems may 

result if stands are maintained outside of their natural 

range of variability (Schoennagel and others 2004), 

for example by promoting large areas of low severity 

burn through fuel treatments. This should be considered when determining treatment size, location, and 

prescription. Spatial data such as the historical burn 

severity data made available through the nationalscale MTBS project (www.MTBS.gov) are available 

to evaluate patterns of burn severity across large areas (Wimberly and others 2009). Wilderness areas that 

tend to be at higher altitudes are logical places to focus 

such efforts. Such data could also be used to inform 

models of where on the landscape high severity burns 

are most likely to occur (Holden and others 2009)—information useful in both planning fuel treatments and 

fire management.

What about masticated fuels, biochar, and 

other innovative treatments?

We concur with Graham and others (2009) that the 

single mastication treatment (Warm Lake Highway) 

that was tested by an intense wildfire under extreme 

weather conditions worked to reduce the intense crown 

fire to a low intensity surface fire, although fire suppression measures undoubtedly played a role. Being a 

relatively new method, precious little is known regarding the effectiveness of mastication treatments. This 

will surely change, because as more and more mastication treatments are implemented, some will inevitably 

be tested by wildfires. In theory, masticated fuels are 

more likely to smolder than to flame, compared to 

natural fuel. Mastication usually results in a relatively 

compact layer of fuel. If it burns, long-term smoldering would likely result in deep soil heating (Haase and 

Sackett 1998, Hungerford and others 1991). Busse and 

others (2005) found that soil temperatures at a depth 

of 10 cm under burning residues from mastication of 

7.5 cm or more surpassed the 60 °C threshold that is 

lethal for most living plant tissue.

There are other good reasons to implement fuel treatments besides reducing hazardous fuel accumulations 

and lowering the risk of catastrophic fire. Implementing 

fuel treatments can provide jobs and help people feel 

safer. Fuel treatments may improve habitat for wildlife 

species of interest. Treatments also may benefit forest 
52 USDA Forest Service RMRS-GTR-252. 2011.

carbon management beyond the treatment effects on 

aboveground biomass measured in this study. Biofuels 

may increase in marketability in the future. Another future management objective may be to increase carbon 

sequestration by mimicking the more active historical 

fire regime with periodic prescribed fires. North and 

others (2009) found that fire suppression causes surface and standing, small-diameter fuels to accumulate, 

which contributes to higher emissions from either fuels 

treatment activities or possible wildfire combustion. 

The same forest maintained with frequent fires, as was 

the historical norm, emits less carbon.

How far away?

The distance that fuel treatments should be from 

the values they are intended to protect is of particular 

importance in the WUI where fuel treatments are commonly justified as reducing wildfire threats to homes. 

Wildfires that transition to structure fires are becoming 

more common and costly, which is as a major challenge and hazard for wildfire management. Solving 

this problem requires bridging the gap between structural and wildland fire management and research.

Maranghides and Mell (2009) collected post-fire data 

following the 2007 Witch and Guejito fires in The Trails 

development of Rancho Bernardo north of San Diego, 

where 74 of 245 homes within the fire perimeter were 

destroyed and 16 were damaged. Fifteen of the 16 damaged homes were defended; it is likely they would have 

been destroyed had they not been defended. One out of 

every three homes was defended, which probably reduced losses from over 37 to 30 percent. Early findings, 

based on field work, are that 40 percent of homes on the 

edge of the development were destroyed compared to 20 

percent in the interior. Direct flame impingement from 

structure to structure was not identified as a significant 

contributor to fire spread within The Trails. Nineteen 

of the destroyed structures were categorized as having 

possibly ignited due to the fire carrying through uninterrupted vegetation on the edge of the development; 20 

destroyed structures were categorized as having ignited 

from embers, both at the edge and in the interior of the 

development; 35 destroyed structures were categorized 

as having vegetation near the structure that may have 

ignited from embers, if the structures were not directly 

ignited from embers. It is possible that all of the homes 

destroyed may have been ignited from embers. The 

majority of damage was caused not by embers preceding the main fire front but by embers from the main 

fire front. Structure ignitions peaked at 21 per hour 

when the main fire front reached the community, with 

29 (40 percent) of the structures burning at the same 

time. Structure ignitions continued for nine hours following the arrival of the main fire front.

Understanding exactly how structures ignite from 

wildfires is critical to both fire managers and homeowners. Cohen (2000) concluded that the construction 

of the home and the fuels within 40 m of it determine 

ignitibility. Modeling and case studies suggest that if 

firebrands and/or flames do not come within approximately 40 m of structures, ignition is unlikely (Cohen 

1999, 2000, 2004; Cohen and Stratton 2008). The 

most common source of home or structure ignition is 

firebrands from other homes, not direct flame impingement from a wildfire (Cohen 2000, Cohen and Stratton 

2008). In many cases, homes act as the fuel that carries fire through communities in lieu of wildland fuels 

(Cohen and Stratton 2008).

These conclusions have several implications for fuels management. First, fuel treatments do not need to 

be very large in order to significantly lower the probability of structure ignition. Second, when a home 

ignites, it becomes the fuel that can continue the spread 

of fire to surrounding homes. Thus, Firewise communities that apply Cohen’s findings will likely be more 

resilient than poorly constructed homes surrounded by 

a large fuel treatment. Third, because the home ignition zone is in close proximity to the structure, Cohen 

(2000) concluded that “the WUI fire loss problem can 

be defined as a home ignitibility issue largely independent of wildland fuels management issues.”

There is no substitute for fire-resistant home construction and improvements within the WUI that 

ultimately lower home ignition potential. Fuels management and Firewise treatments can complement each 

other but will not replace one another. Applying fuels 

management outside of the home ignition zone may be 

more necessary where complex topography and the potential for extreme fire behavior can complicate exactly 

how far a Firewise-treated area should extend from the 

home. Fire intensity and spotting distance are affected 

by slope (Murphy and others 2007), and topographic 

features such as canyons increase fire intensity and can 

facilitate home ignition. In some situations, a larger 

Firewise-treated zone and more resistant structure are 

necessary to sufficiently minimize ignition potential. 

Certainly, the existence of the 2005 Firewise treatments 

on private lands at Secesh Meadows, not just the 2006 
USDA Forest Service RMRS-GTR-252. 2011. 53

Figure 32. Structure protection at Secesh Meadows. Photo: Roger Staats.

treatments on surrounding NF lands (table 1; figures 11 

and 13), was a factor that enabled firefighters to protect all of the homes (figures 32 and 33). Similarly at 

Warm Lake, the fuel treatments in the WUI did not 

stop the fire progression, but they directly impacted 

home survivability, allowed for safer and more efficient fire suppression, and played an integral role in 

the point-protection management strategy (Graham and 

others 2009). The treatment units west of Warm Lake 

(figure 12) effectively slowed down the eastward momentum of the Monumental and North Fork crown fires 

and exemplified how strategically placed fuel treatments can help firefighters save structures in the WUI.

How does one consider spatial patterns of 

fuels and treatments?

Determining the optimal spatial pattern of fuel treatments across a landscape brings together all of the 

factors of fuel treatment efficacy discussed thus far (for 

example, Moghaddas and Craggs 1997, Ritchie and 

others 2007, Skinner and others 2004, Weatherspoon 

and Skinner 1995). Strategic locations, prescription, 

temporal thresholds, and fire regimes must all be considered to decide where and when to implement fuel 

treatments for maximum effect. Because of the cost 

and magnitude of testing various spatial patterns of 

fuel treatments, most studies are limited to modeling.

By simulating treatment shapes and arrangements, 

Finney (2001) determined that separate, partially overlapping treatments (similar to a checkerboard) was the 

most effective spatial pattern for slowing the growth 

of large fires. Within this pattern, fuel treatments were 

rectangular and oriented so that the short axis of the 

treatment units were parallel to the primary direction of 

fire spread. This spatial pattern resulted in lower intensity head fires progressing through the fuel treatments 

and primarily flanking fires in the untreated areas. This 

pattern also resulted in fire moving across the landscape in a uniform manner, minimizing the areas where 

two flame fronts converge and produce high intensities 

and rapid rates of spread (Finney 2001).

However, accounting for multiple directions of fire 

spread complicates how fuel treatments should be arranged. By locating treatments in areas of high fire 
54 USDA Forest Service RMRS-GTR-252. 2011.

susceptibility, Parisien and others (2007) determined 

that clustered treatments were the most efficient in 

reducing the spread of fires burning from several directions. Using fuel treatments to connect lakes and other 

natural barriers further reduces fire spread potential 

(Parisien and others 2007). Temporal limitations further 

complicate the spatial arrangement of fuel treatments as 

there needs to be a balance between maintaining existing 

treatments and implementing new treatments to sufficiently reduce the threat of large fire events. Assuming 

that all individual treatments are effective in moderating fire behavior and are placed in optimal locations, 

Finney and others (2007) found that only 1 to 2 percent 

of the landscape must be treated annually to sufficiently 

lower rate of spread and intensity. Randomly located 

fuel treatments with identical prescriptions required 

approximately 4 percent of the landscape be treated to 

reduce large fire growth to the same level. This means 

that fewer maintenance treatments would be necessary 

to achieve the desired result. If 2 percent of the landscape is treated annually, then fewer than 5 percent of 

the treated areas would receive three or more treatments 

over five decades (Finney and others 2007).

Because most landscapes are heterogeneous, designing optimal fuel treatments is not simple. Fuel 

treatments must consider where and how fires are likely 

to spread in landscapes with variations in topography, 

vegetation, land uses, and land management objectives. 

Tools such as ARCFUELS can be useful in evaluating 

alternative treatment scenarios.

The paradox of fire suppression is that the more we 

suppress fires, the more intensely they may burn in the 

fuels that have accumulated. A related issue is the degree to which many valued ecosystem services benefit 

from fire. Landscape-scale fuels management must be 

thoughtfully designed to protect resources at risk and to 

promote other objectives such as water quality, wildlife 

corridors, and habitat diversity (figure 34).

Figure 33. Crews foaming to defend a home at Secesh Meadows. Photo: Roger Staats.
USDA Forest Service RMRS-GTR-252. 2011. 55

Figure 34. Aerial view of fire severity patterns across the Secesh Meadows landscape soon after the wildfire. Photos: Tim Sexton.

Are fuel treatments less effective in extreme 

weather conditions?

Probably. This is a widely held assumption, but 

Omi and others (2006) found that the effectiveness of 

combined surface and canopy fuel treatments actually increased with weather severity, as indicated by 

the Burning Index of the National Fire Danger Rating 

System. More quantitative assessments are required.

What about climate change?

Fires will burn under conditions greatly altered by 

people—long fire seasons, extreme weather conditions, 

expanding urban interface, and many invasive species 

will test the resilience of western ecosystems. Decades 

of fire suppression across the West have promoted unnatural fuel accumulations in many areas, especially in 

some dry ponderosa pine forests that historically experienced frequent, low intensity fires that were ignited 

by lightning and Native Americans (Schoennagel and 

others 2004). Fuels are often abundant in mixed conifer and subalpine fir forest types, but the effects of 

fire exclusion are much less pronounced than in dry 

forests. Another perception that is gaining acceptance 

is that we are observing the effects of climate change, 

as evidenced by the growing number of large fires in 

the western United States (Westerling and others 2006). 

Whether the pervasive drought that has afflicted much 

of the West is part of a long-term trend remains to be 

seen. Both climate change and land use change will 

continue to interact and influence fire regimes, but 

the relative importance will vary with ecosystem and 

location.

Conclusion

Fuel treatments altered fire behavior and subsequent 

fire effects in multiple large fires in 2007, usually in 

desirable ways but not always. Our results confirm the 

widely held notion that mechanical thinnings are the 

most effective fuels treatment, provided the activity fuels are treated. Prescribed burn treatments may be the 

most cost effective maintenance treatments for keeping 

fuel accumulations in check over time and for lowering 

the risk of severe fires. Further quantitative research 

studies and more consistent protocols are needed to 

assess fuel treatment effectiveness, especially over 

the longer term to evaluate the duration of treatment 

effectiveness and the cumulative effect of multiple 

treatments in the same location.

Acknowledgments

We foremost thank Tim Sexton and Rich Lasko from 

USFS Fire and Aviation Management for the USFS 

Washington Office funding that made this research 

possible. This research was supported by funds provided by the USFS Rocky Mountain Research Station 

through Joint Venture Agreement 03-JV-111222065-

279 with the University of Idaho. We are grateful to 

the many managers who helped us accomplish work on 

the ground, including Paul Klasner, Fuels Specialist, 

Payette NF; Sam Hescock, Fire Management Officer, 
56 USDA Forest Service RMRS-GTR-252. 2011.

Payette NF, Krassell Ranger District; Roger Staats, Fire 

Management Officer, Payette NF; Mark Loseke, Fuels 

Specialist, Boise NF; Guy Pence, Fire and Aviation 

Management Officer, Boise NF; and Dusty Pence, 

Fuels Planner, Boise NF. We benefited from discussion 

of fuel treatments and fire effects with Terrie Jain, Russ 

Graham, Steve Bunting, and others. Maike Holthuijzen 

and Joe Hulbert did the bulk of the 2008 field work. 

We thank Jess Clark, Remote Sensing Analyst at the 

Remote Sensing Applications Center, for doing additional Landsat image processing. We thank Terrie 

Jain and Russ Graham for sharing the North Fork 

and Warm Lake portable RAWS data and locations, 

Jonathan Sandquist for editing the Warm Lake treatment unit boundaries for accuracy, and Mike Bobbitt 

and John Parker-Mcglynn for assisting with map figures. We thank Crystal Kolden and Nicole Vaillant for 

their helpful technical reviews and Trevor Miller for 

his user review. RMRS Statistician Scott Baggett performed the SAS runs and provided statistical advice; 

and RMRS Editor Lindy Myers thoroughly edited the 

document.

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Rocky

 Mountain

 Research Station

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 meet the needs of 

the National Forest managers, Federal and State agencies, public and 

private organizations, academic institutions, industry, and individuals. 

Studies accelerate solutions to problems involving ecosystems, range, 

forests, water, recreation, fire, resource inventory, land reclamation, 

community sustainability, forest engineering technology, multiple use 

economics, wildlife and fish habitat, and forest insects and diseases. 

Studies are conducted cooperatively, and applications may be found 

worldwide.

Station Headquarters

Rocky Mountain Research Station

240 W Prospect Road

Fort Collins, CO 80526

(970) 498-1100

Research Locations

Reno, Nevada

Albuquerque, New Mexico

Rapid City, South Dakota

Logan, Utah

Ogden, Utah

Provo, Utah

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and where applicable, sex, marital status, familial status, parental status, religion, 

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or part of an individual’s income is derived from any public assistance program. 

(Not all prohibited bases apply to all programs.) Persons with disabilities who 

require alternative means for communication of program information (Braille, 

large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 

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Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, 

DC 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA 

is an equal opportunity provider and employer.

Flagstaff, Arizona

Fort Collins, Colorado

Boise, Idaho

Moscow, Idaho

Bozeman, Montana

Missoula, Montana