U.S. Department of the Interior

U.S. Geological Survey

Fire Patterns in the Range of the Greater Sage-Grouse, 

1984–2013—Implications for Conservation and Management

Open–File Report 2015–1167
Cover: Fire in sagebrush shrubland, southwestern Idaho, June 2010. 

Photograph by Douglas J. Shinneman, U.S. Geological Survey.
U.S. Department of the Interior

U.S. Geological Survey

Fire Patterns in the Range of the Greater Sage-Grouse, 

1984–2013—Implications for Conservation and 

Management

By Matthew L. Brooks, John R. Matchett, Douglas J. Shinneman, and Peter S. Coates

Open-File Report 2015-1167
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit

http://www.usgs.gov/ or call 1–888–ASK–USGS (1–888–275–8747).

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply

endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may

contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items

must be secured from the copyright owner.

Suggested citation:

Brooks, M.L., Matchett, J.R., Shinneman, D.J., and Coates, P.S., 2015, Fire patterns in the range of greater sagegrouse, 1984–2013—Implications for conservation and management: U.S. Geological Survey Open-File Report 

2015-1167, 66 p., http://dx.doi.org/10.3133/ofr20151167.

ISSN 2331-1258 (online)
iii

Contents

Abstract ...................................................................................................................................................................... 1

Introduction................................................................................................................................................................. 2

Study Purpose ........................................................................................................................................................ 2

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

Methods...................................................................................................................................................................... 4

Study Area .............................................................................................................................................................. 4

Greater Sage-Grouse Management Zones ......................................................................................................... 6

Western and Eastern Regions............................................................................................................................. 6

Vegetation Types ................................................................................................................................................ 6

Soil Temperature and Moisture Regimes as Indicators of Resilience/Resistance............................................. 10

Sources of Fire Data ............................................................................................................................................. 11

Analyses ............................................................................................................................................................... 12

Fire Pattern Results .................................................................................................................................................. 14

Rangewide Fire Area ............................................................................................................................................ 14

Western Regional Fire Area and Other Fire Regime Characteristics .................................................................... 17

Eastern Regional Fire Area and Other Fire Regime Characteristics ..................................................................... 27

Discussion of Fire Patterns....................................................................................................................................... 35

Fire Area ............................................................................................................................................................... 35

Fire Area Amount and Percentage of Available Area ........................................................................................ 35

Fire Area Trends ............................................................................................................................................... 36

Fire Recurrence .................................................................................................................................................... 37

Fire Size................................................................................................................................................................ 38

Fire Rotation ......................................................................................................................................................... 38

Fire Season........................................................................................................................................................... 39

Fire Threats Assessment for Greater Sage-Grouse Habitat ..................................................................................... 40

Acknowledgments..................................................................................................................................................... 44

References Cited...................................................................................................................................................... 44

Appendix 1. Crosswalk of Greater Sage-Grouse Management Zones with Other Bioregional Classifications ........ 50

Appendix 2. Proportion of Land Ownership in the Greater Sage-Grouse Management Zones................................ 51

Appendix 3. Soil Temperature and Moisture Regimes in the Study Area ................................................................ 52

Appendix 4. Aerial Extent of the Major Vegetation Types in the Four Western Management Zones and Their 

Constituent LANDFIRE Biophysical Setting Types That Were Previously Identified as Capable of Supporting 

Sagebrush Vegetation and Providing Suitable Seasonal Habitat for Greater Sage-Grouse in the Greater SageGrouse Monitoring Framework ................................................................................................................................. 53

Appendix 5. Aerial Extent of the Major Vegetation Types in the Three Eastern Management Zones and Their 

Constituent LANDFIRE Biophysical Setting Types That Were Previously Identified as Capable of Supporting 

Sagebrush Vegetation and Providing Suitable Seasonal Habitat for Greater Sage-Grouse in the Greater SageGrouse Monitoring Framework ................................................................................................................................. 55

Appendix 6. Crosswalk of Soil Temperature and Moisture Regimes with Potential Resilience to Fire and 

Resistance to Annual Grass Invasion ....................................................................................................................... 57
iv

Appendix 7. Proportions of Total Available Area Represented by Each Soil Temperature and Moisture Regime 

Class in Each Vegetation Type Rangewide and in the Eastern and Western Regions............................................. 58

Appendix 8. Limitations of Fire Point Occurrence, Burn Severity, and Fire Perimeter Data...................................... 59

Appendix 9. Annual Precipitation Means (in millimeters per year) over the Long Term (1895–2013) and in the Years 

Encompassed by the Fire Data (1984–2013) ........................................................................................................... 62

Appendix 10. Annual Precipitation Means (mm/yr) During Each of the 30 Years of the Study (1984–2013) 

Compared with the Previous 117 Years (1895–2012) .............................................................................................. 63

Appendix 11. Proportion of Fire Area Represented by Each Soil Temperature and Moisture Regime Class in 

Each Vegetation Type Rangewide............................................................................................................................ 64

Appendix 12. Proportion of Fire Area Represented by Each Soil Temperature and Moisture Regime Class in 

Each Vegetation Type in Each Greater Sage-Grouse Management Zone in the Western Region ........................... 65

Appendix 13. Proportion of Fire Area Represented by Each Soil Temperature and Moisture Regime Class in 

Each Vegetation Type in Each Greater Sage-Grouse Management Zone in the Eastern Region ............................ 66

Figures

Figure 1. Study area showing boundaries of each of the seven greater sage-grouse management zones 

(based on Stiver and others, 2006) that were a primary strata for analyses in this study. ......................................... 5

Figure 2. Vegetation types that were a primary strata for analyses in this study....................................................... 9

Figure 3. Polygons of all fires used in this study overlaid to create recurrence classes.......................................... 15

Figure 4. Fire area for each year 1984–2013 within each major vegetation type throughout the 

range of the greater sage-grouse ............................................................................................................................ 16

Figure 5. Fire area for each year 1984–2013 within major vegetation types and the four management 

zones in the western region of the greater sage-grouse range................................................................................ 19

Figure 6. Cumulative fire area as a function of fire size in the four management zones in the western 

region of the greater sage-grouse range.................................................................................................................. 23

Figure 7. Cumulative fire area as a function of fire size in the western and eastern regions of the 

greater sage-grouse range ...................................................................................................................................... 23

Figure 8. Fire size at the 25th, 50th, and 75th percentiles of the cumulative fire area distribution for each year 

1984–2013 in the western region of the greater sage-grouse range ....................................................................... 24

Figure 9. Fire season length for each year 1984–2013 in the four management zones in the 

western region of the greater sage-grouse range .................................................................................................... 26

Figure 10. Fire area for each year 1984–2013 within major vegetation types and the three 

management zones in the eastern region of the greater sage-grouse range........................................................... 29

Figure 11. Cumulative fire area as a function of fire size in the three management zones in the 

eastern region of the greater sage-grouse range..................................................................................................... 30

Figure 12. Fire size at the 25th, 50th, and 75th percentiles of the cumulative fire area distribution 

for each year 1984–2013 in the eastern region of the greater sage-grouse range .................................................. 31

Figure 13. Fire season length for each year 1984–2013 in the three management zones in the 

eastern region of the greater sage-grouse range..................................................................................................... 34
v

Tables

Table 1. Aerial extent of the major vegetation types within the study area and their constituent LANDFIRE 

biophysical setting types that were previously identified as capable of supporting sagebrush vegetation and 

providing suitable seasonal habitat for greater sage-grouse in the Greater Sage-Grouse Monitoring Framework .... 7

Table 2. Fire area and percentage of fire area for each vegetation type rangewide (1984–2013) .......................... 14

Table 3. Fire area, percentage of fire area, and percentage of available area for each vegetation type in the 

management zones of the western region of the greater sage-grouse range (1984–2013)..................................... 18

Table 4. Fire recurrence area among fire recurrence classes within each vegetation type and management 

zone in the western range of the greater sage-grouse (1984–2013) ....................................................................... 21

Table 5. Fire rotation (years) in each vegetation type and management zone in the western range of the

greater sage-grouse (1984–2013) .......................................................................................................................... 25

Table 6. Fire season beginning (day of year), ending (day of year), and length (days) in each 

management zone in the western range of the greater sage-grouse (1984–2013) ................................................. 26

Table 7. Fire area, percentage of total fire area, and percentage of available area for each vegetation 

type in the management zones of the eastern region of the greater sage grouse range (1984–2013).................... 28

Table 8. Fire recurrence area among fire recurrence classes in each vegetation type and management 

zone in the eastern region of the greater sage-grouse (1984–2013)....................................................................... 32

Table 9. Fire rotation (years) in each vegetation type and management zone in the eastern 

region of the greater sage grouse (1984–2013)....................................................................................................... 33

Table 10. Fire season variables (mean values) in each management zone in the eastern range 

of the greater sage grouse (1984–2013) ................................................................................................................. 34

Table 11. Fire threats assessment on a scale from low to high (0–4) within nine regime categories ...................... 42
vi

Conversion Factors

International System of Units to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

hectare (ha) 2.471 acre

square hectometer (hm2) 2.471 acre

hectare (ha) 0.003861 square mile (mi2) 

square hectometer (hm2) 0.3861 square mile (mi2)

Precipitation rate

millimeter per year (mm/yr) 0.03937 inch per year (in/yr)

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
1

Fire Patterns in the Range of the Greater Sage-Grouse, 

1984–2013—Implications for Conservation and 

Management

By Matthew L. Brooks, John R. Matchett, Douglas J. Shinneman, and Peter S. Coates

Abstract

Fire ranks among the top three threats to the greater sage-grouse (Centrocercus urophasianus) 

throughout its range, and among the top two threats in the western part of its range. The national 

research strategy for this species and the recent U.S. Department of the Interior Secretarial Order 3336 

call for science-based threats assessment of fire to inform conservation planning and fire management 

efforts. The cornerstone of such assessments is a clear understanding of where fires are occurring and 

what aspects of fire regimes may be shifting outside of their historical range of variation. This report 

fulfills this need by describing patterns of fire area, fire size, fire rotation, and fire season length and 

timing from 1984 to 2013 across the range of the greater sage-grouse. This information need is further 

addressed by evaluating the ecological and management implications of these fire patterns. Analyses are 

stratified by major vegetation types and the seven greater sage-grouse management zones, delineated 

regionally as four western and three eastern management zones. Soil temperature and moisture 

indicators of resilience to fire and resistance to cheatgrass invasion, and the potential for establishment 

of a grass/fire cycle, are used as unifying concepts in developing fire threat assessments for each 

analysis strata.

The results indicate that fire threats are higher in the four western than in the three eastern 

management zones. Among the four western management zones, the Snake River Plain and the 

Columbia Basin ranked somewhat higher than the Southern Great Basin and Northern Great Basin in 

terms of fire effects on sage-grouse habitat. These results support the previous high ranking of fire as a 

threat to the greater sage-grouse in the western region. In contrast, considering the low rankings for fire 

threats in the eastern region, it may be useful to reconsider the relative importance of wildfire as a threat 

to greater sage-grouse in those three management zones.
2

Introduction

Study Purpose

The greater sage-grouse (Centrocercus urophasianus) was initially considered for listing by the 

U.S. Fish and Wildlife Service in 2005 (U.S. Fish and Wildlife Service, 2005). Although listing was 

determined not to be warranted at that time, the decision document acknowledged that fire posed a 

significant threat. Wildland fire (hereinafter referred to as fire) was ranked third only to invasive species 

and human infrastructure among the greatest threats across its range, and second in the western part of 

its range (U.S. Fish and Wildlife Service, 2005). The subsequent 2010 decision concluded that listing 

the greater sage-grouse was warranted based on a similar threats analysis, but emphasized that most 

threats including fire had become increasingly more prominent (U.S. Fish and Wildlife Service, 2010).

The greater sage-grouse is currently listed as a candidate species throughout its range, meaning 

that its listing as Threatened or Endangered under the Endangered Species Act of 1973 is warranted, but 

a final decision is currently precluded by higher priority species (U.S. Fish and Wildlife Service, 2010). 

A lawsuit in 2011 challenged the timeframe for a listing decision on the greater sage-grouse and the 

associated court decision established a deadline of September 30, 2015, for a final decision on whether 

or not to list this species. In preparation for this listing decision, the U.S. Fish and Wildlife Service has 

been compiling and synthesizing the best current information to update their state-of-science 

understanding of the ecology, threats, and potential recovery actions for this species.

Chief among the information needed for the current listing decision is an updated understanding 

of the threats posed by fire. The national research strategy for the greater sage-grouse specifically calls 

for information to “assess fire history and fire-recovery rates in a way that informs planning efforts and 

deployment of resources for future fire events” (Hanser and Manier, 2013, p. 7). In January 2015, a U.S. 

Department of the Interior Secretarial Order was issued on rangeland fire prevention, management, and 

restoration that calls for a “science-based strategy to reduce the threat of large-scale rangeland fire to 

habitat for the greater sage-grouse and the sagebrush-steppe ecosystems” (U.S. Department of the 

Interior Secretarial Order 3336, 2015a, Section 6a). Soon following that Executive Order was a report 

released in May 2015 titled, “An Integrated Rangeland Fire Management Strategy”, with the purpose 

“... to improve the efficiency and efficacy of actions to address rangeland fire, to better prevent and 

suppress rangeland fire, and improve efforts to restore fire-impacted landscapes” (U.S. Department of 

the Interior, 2015b). Science-based threats assessments are integral to efficient and effective fire 

management, and the cornerstone of these assessments is a clear understanding of where fires are 

occurring and what aspects of fire regimes may be shifting outside of their historical range of variation. 

The purpose of the current report is to provide a scientific assessment of recent spatio-temporal 

patterns in the amount of fire area and other fire regime characteristics during the most recent 30-year 

period with comprehensive fire data (1984–2013), and to evaluate implications of these findings for 

conservation and management of the greater sage-grouse in wildland areas across the species’ range. A 

complementary assessment using a subset of the same fire dataset was published in parallel with this 

report, and is focused on fire and climatic effects on sage-grouse population growth derived from 30 

years of lek-count data in the Great Basin portion of the species’ range (Coates and others, 2015).
3

Background

The greater sage-grouse occurs in the cold desert ecoregion of Western North America 

(Schroeder and others, 2004). It is considered a sagebrush (Artemisia spp.) obligate species (Connelly 

and others, 2004), because it depends on sagebrush plants to provide most of its life-history needs 

including winter forage, nesting sites, and predator avoidance cover (Rowland and others, 2006; Knick 

and Connelly, 2011). Most sagebrush species such as big sagebrush (Artemisia tridentata), black 

sagebrush (Artemisia nova), and low sagebrush (Artemisia arbuscula) lack post-fire re-sprouting 

capabilities and have poor seed dispersal rates, resulting in high mortality and slow recovery following 

fire (Bunting and others, 1987; Baker, 2009). Two notable exceptions are silver sagebrush (Artemisia 

cana) and threetip sagebrush (Artemisia tripartita), which survive fire by vigorous resprouting from 

roots and rhizomes and can therefore tolerate periodic fire (White and Currie, 1983). The fire-intolerant 

sagebrush species are much more widespread and abundant than the fire-tolerant species, thus fire is 

generally considered to be a threat to sagebrush ecosystems and habitat quality for the greater sagegrouse.

Some studies have identified direct relationships between sage-grouse and fire, but have been 

limited to local sites (Connelly and others, 2000), movements and habitat associations (Fischer and 

others, 1996, 1997; Nelle and others, 2000; Rhodes and others, 2010), relatively short time frames (< 10 

year) (Blomberg and others, 2012), habitat suitability (Davis and Crawford, 2015), or relied primarily 

on simulations (Pedersen and others, 2003). A recent published report clearly demonstrates adverse 

long-term effects of wildfire on sage-grouse population growth rate across the Great Basin (Coates and 

others, 2015).

Although large and severe fires historically occurred in many sagebrush ecosystems, they were

typically infrequent, especially in the warmer-drier, fuel-limited sagebrush community types. Mean fire 

return intervals may have ranged from decades in colder-moister sagebrush ecosystems (Miller and 

Heyerdahl, 2008) to hundreds of years in hotter-drier sagebrush ecosystems (Bukowski and Baker,

2013), allowing for recovery and persistence of sagebrush communities adapted to those conditions. 

However, during recent decades, fire probability and occurrence have increased across large portions of

the cold desert ecoregion of Western United States (Whisenant, 1989; Knick and Rotenberrry, 1997;

Chambers, 2008; Miller and others, 2011; Baker, 2013; Balch and others, 2013), hindering recovery of 

sagebrush and threatening sage-grouse habitat.

Increased prevalence of fire in the sagebrush ecosystem is strongly associated with the influence 

of non-native invasive annual grasses, especially cheatgrass (Bromus tectorum) in the more arid regions 

of the western part of the greater sage-grouse range. Cheatgrass can fill the interspaces between native 

perennials and facilitate fire spread where it would not otherwise occur, especially in more arid regions 

where native plant productivity is low (Whisenant, 1989). This is a particular concern for more arid 

sagebrush shrublands, dominated by Wyoming big sagebrush (Artemisia tridentata ssp. wyomensis) and 

basin big sagebrush (Artemisia tridentata ssp. tridentata) (Brooks and others, in press). These 

landscapes often have a minimal perennial grass component and low resilience (that is, ability to 

recover) of sagebrush vegetation following fire and low resistance to cheatgrass invasion (Chambers 

and others, 2014a, 2014b; Brooks and others, in press). These conditions can result in greatly reduced

fire-free intervals and prevent reestablishment of the native sagebrush community. This dynamic leads 

to a self-perpetuating “grass/fire cycle” (D’Antonio and Vitousek, 1992) that favors the dominance and 

spread of invasive annual grasses, which in turn facilitate more frequent fire (Brooks and others, 2004;

Brooks, 2008).
4

Decreased prevalence of fire also can pose a threat to the greater sage-grouse in portions of its 

range, especially in Mountain Big Sagebrush (Artemisia tridentata ssp. vaseyana) communities, which 

are more productive and include more perennial grasses than in arid regions. These landscapes have 

moderate to high resilience of sagebrush vegetation following fire and resistance to cheatgrass invasion 

(Chambers and others, 2014a, 2014b). Reduction of fuels caused by livestock grazing and fire 

suppression activities are thought to have increased fire return intervals to the point where conifer 

species (especially juniper and pinyon) can establish and eventually outcompete sagebrush, leading to a 

reduction of perennial grasses and forbs (Miller and Tausch, 2001). This reduction in habitat quality for 

the greater sage-grouse (Miller and Rose, 1999; Miller and Heyerdahl, 2008) has led to avoidance of 

areas with trees (Casazza and others, 2011) and declines in population persistence (Baruch-Mordo and 

others, 2013). Conifer encroachment was ranked tenth among threats across the range of the species, 

and fourth in the western part of its range in the 2005 listing decision (U.S. Fish and Wildlife Service,

2005).

Although fire area generally is reported to have increased during the past few decades in the cold 

deserts of North America, these patterns are often characterized using broad-scale, regional assessments 

integrated across diverse ecoregions and vegetation types (for example, Littell and others, 2009). 

Research specific to fire patterns in sagebrush ecosystems have included analysis of area burned relative 

to cheatgrass dominance in a large portion of the Great Basin (Balch and others, 2013), and assessments

of spatial and temporal trends in fire area, fire size, and fire frequency in floristic provinces across the 

sagebrush biome (Baker, 2011; Miller and others, 2011; Baker, 2013). To best inform conservation and 

management efforts for the greater sage-grouse, there is a need to more precisely analyze fire area and 

other fire regime characteristics in landscapes most relevant to this species. To facilitate the evaluation 

of habitat responses to these fire patterns and ultimately fire threats, they also should be evaluated 

specifically in landscapes that the greater sage-grouse occupies and at scales that match current 

understanding of the fire ecology of major vegetation types.

Methods

The primary objective of this study was to evaluate spatio-temporal patterns of fire in greater 

sage-grouse population areas throughout the species’ range. Fire area was evaluated at rangewide, 

regional (western vs. eastern), and greater sage-grouse management zone scales. Fire size, fire 

recurrence, fire rotation, and fire season length and timing were evaluated at regional and management 

zones scales. All analyses were stratified by major sagebrush vegetation types. Fire threats analyses 

were based on the relative resilience to fire and resistance to cheatgrass invasion of these vegetation 

types, as inferred from their soil temperature and moisture regimes (Campbell, 2014) and the general 

fire ecology literature. 

Study Area

The study area is defined as the greater sage-grouse population areas in the Western United

States, spanning the current range of the species as defined by Schroeder and others (2004) (fig. 1). 

These population areas include some urban, agricultural, and other developed lands that are typically 

under private or municipal ownership, generally do not constitute habitat for the greater sage-grouse, 

and are poorly represented in the fire database used in this study. Thus, developed areas and unburnable 

areas (for example, open water) were excluded from the study area and not analyzed. We refer to the

remaining 77,308,081 ha (298,487 mi2

) area which was the focus of this study as “sage-grouse wildland 

area.” 
5

Figure 1. Study area showing boundaries of each of the seven greater sage-grouse management zones (based on 

Stiver and others, 2006) that were a primary strata for analyses in this study. The greater sage-grouse population 

areas also are shown which represent the geographic extent of landscapes include in the analyses. 
6

Greater Sage-Grouse Management Zones

The study area was partitioned into the seven management zones (fig. 1) identified by the 

Western Association of Fish and Wildlife Agencies, Conservation Strategy for Greater Sage-Grouse 

(Stiver and others, 2006). Each of the seven greater sage-grouse management zones correspond to a 

major floristic province (Miller and Eddleman, 2001) and EPA Level III ecoregion(s) (Wilken and 

others, 2011) (appendix 1), and the constituent vegetation in each management zone is expected to

respond similarly to environmental factors and management actions. The proportion of lands under 

Federal, State, and local governmental jurisdiction varied widely among these management zones, with 

government lands covering equal to or greater than 75% of the Southern Great Basin, Northern Great 

Basin, Snake River Plain, and Colorado Plateau management zones, but encompassing less than 50% of 

the Great Plains and Columbia Basin management zones (appendix 2).

Western and Eastern Regions

The four western management zones were distinguished from the three eastern management 

zones (fig. 1) in the listing decisions (U.S. Fish and Wildlife Service, 2005, 2010). Their primary 

ecological distinction is based on the predominance of Xeric soil moisture regimes and winterdominated rainfall in the West, versus Ustic soil moisture regimes and summer-dominated rainfall in the 

East (appendix 3). This difference in rainfall seasonality can significantly affect landscape resilience to 

fire and resistance to cheatgrass (Chambers and others, 2014a, 2014b). Thus, in addition to the seven 

management zones, fire patterns also were analyzed and compared between the western and eastern 

regions, due to their potential to support substantially different fire regimes and fire effects.

Vegetation Types

We analyzed fire patterns among seven major vegetation types in the study area (table 1, fig. 2), 

each based on an amalgam of LANDFIRE biophysical settings (Rollins, 2009). LANDFIRE biophysical 

settings are derived in part using the same 30-m resolution Landsat satellite imagery also used to 

generate the fire data in this study (see section, “Sources of Fire Data”), which facilitated the spatial 

intersection of the data layers without a need for resampling. Biophysical settings represent potential 

vegetation based on the current biophysical environment and an approximation of the historical 

disturbance regime prior to Euro-American settlement (Rollins, 2009), essentially approximating the 

vegetation that might be present if disturbance regimes had not been altered post-settlement. We chose 

not to evaluate fire patterns among current vegetation types, such as those represented by the 

LANDFIRE existing vegetation type product. Current vegetation is the result of both the conditions 

represented by potential vegetation and the various ways that disturbance regimes have been altered 

since Euro-American settlement, including the influences of livestock grazing, plant invasions, 

anthropogenic ignitions, and altered fire regimes. Thus, the recent 30-year patterns of fire that is the 

focus of this study could have resulted in, or been a product of, patterns of current vegetation. Using 

potential vegetation avoided these cause-and-effect confounders and allowed us to more easily interpret 

recent patterns of fire among the vegetation types.
7

Table 1. Aerial extent of the major vegetation types in the study area and their constituent LANDFIRE biophysical 

setting types that were previously identified as capable of supporting sagebrush vegetation and providing suitable 

seasonal habitat for greater sage-grouse in the Greater Sage-Grouse Monitoring Framework. 

[From Interagency Greater Sage-Grouse Disturbance and Monitoring Subteam (2014, table 4). The first two vegetation types 

are predominantly sagebrush, whereas the latter four are pre-dominantly other plant taxa. All six differ in terms of floristics, 

fire regimes, and as potential habitat for the greater sage-grouse. The Non-Sagebrush type does not contain any sagebrush 

species as a potential dominant in the constituent biophysical settings descriptions and were not previously identified as 

supporting sagebrush vegetation or greater sage-grouse habitat. Dominant Artemisia spp: Artemisia species listed as a 

dominant in the biophysical settings descriptions of in the mapping zones used in the current study]

Biophysical setting Area 

hectares) Dominant Artemisia spp

Big Sagebrush

Inter-Mountain Basins Big Sagebrush Steppe 10,468,051 A. tridentata ssp. wyomensis

A. tridentata ssp. tridentata

Inter-Mountain Basins Big Sagebrush Shrubland - Wyoming 

Big Sagebrush

7,896,148 A. tridentata ssp. wyomensis

Inter-Mountain Basins Montane Sagebrush Steppe 6,748,739 A. tridentata ssp. vaseyana

A. tripartita ssp. tripartita

Inter-Mountain Basins Big Sagebrush Shrubland 5,141,354 A. tridentata ssp. wyomensis 

A. tridentata ssp. tridentata

Inter-Mountain Basins Big Sagebrush Shrubland - Basin Big 

Sagebrush

634,153 A. tridentata ssp. tridentata

Inter-Mountain Basins Montane Sagebrush Steppe - Mountain 

Big Sagebrush

871,684 A. tridentata ssp. vaseyana

Black/Low Sagebrush

Great Basin Xeric Mixed Sagebrush Shrubland 6,984,654 A. nova

A. bigelovii

Columbia Plateau Low Sagebrush Steppe 246,249 A. arbuscula 

A. arbuscula ssp. longiloba

Inter-Mountain Basins Montane Sagebrush Steppe - Low 

Sagebrush

147,456 A. nova

Colorado Plateau Mixed Low Sagebrush Shrubland 73,503 A. arbuscula 

A. nova

A. cana

Wyoming Basins Dwarf Sagebrush Shrubland and Steppe 4,282 A. nova

A. arbuscula

A. pedatifida

A. tripartita

Desert Mixed Shrub

Inter-Mountain Basins Mixed Salt Desert Scrub 2,698,410 A. tridentata ssp. wyomensis

A. tridentata ssp. tridentata

Columbia Plateau Scabland Shrubland 194,873 A. rigida

Inter-Mountain Basins Semi-Desert Shrub-Steppe 95,500 A. tridentata ssp. wyomensis

A. tridentata ssp. tridentata

Floodplain

Western Great Plains Floodplain Systems 893,044 A. cana ssp. cana
8

Biophysical setting Area 

hectares) Dominant Artemisia spp

Grassland

Northwestern Great Plains Mixed Grass Prairie 12,785,292 A. cana ssp. cana

Northwestern Great Plains Shrubland 1,004,669 A. cana ssp. cana

Columbia Plateau Steppe and Grassland 809,650 A. spp.

Western Great Plains Sand Prairie 194,122 A. cana ssp. cana

Mountain Brush

Inter-Mountain Basins Curl-leaf Mountain Mahogany Woodland 

and Shrubland

517,666 A. tridentata ssp. vaseyana

Rocky Mountain Gambel Oak-Mixed Montane Shrubland 401,983 A. tridentata ssp. vaseyana

Rocky Mountain Lower Montane-Foothill Shrubland 140,959 A. tridentata ssp. vaseyana

Non-Sagebrush

remaining biophysical setting types combined (n=117) 18,356,248 none
9

Figure 2. Vegetation types that were a primary strata for analyses in this study. Descriptions of LANDFIRE 

biophysical settings (Rollins, 2009) that comprised each vegetation type are listed in table 1. 
10

Each vegetation type we defined was comprised of multiple biophysical settings that were 

distinct from each other in terms of vegetation structure, dominant sagebrush species, and historical fire 

regimes according to LANDFIRE’s descriptions. Each vegetation type also has distinct enough 

physiographic characteristics, which we felt were accurately differentiated by LANDFIRE’s biophysical 

settings classification model. LANDFIRE did not attempt a formal accuracy assessment of the 

biophysical settings layer; however, their accuracy assessments of existing vegetation layers indicated 

difficulty distinguishing between sagebrush types having similar physiognomy. This latter point is the 

primary reason we did not further split the Big Sagebrush vegetation category into shrubland, steppe, 

montane, basin, and/or Wyoming big sagebrush types.

Two vegetation types (Big Sagebrush and Black/Low Sagebrush) are comprised mostly of 

sagebrush-dominated communities, whereas four (Desert Mixed Shrub, Floodplain, Grassland, and 

Mountain Brush) are characterized by mostly Non-Sagebrush dominated communities, but which have 

potential for at least one sagebrush species to be co-dominant (table 1). The Non-Sagebrush vegetation 

type included 117 biophysical settings that do not support sagebrush-containing communities. 

The Big Sagebrush vegetation type comprised 41% of the total sage-grouse wildland area in this 

study (table 1), slightly more of which (55%) occurred in the western region (appendix 4). Grassland 

comprised 19% of the total study area (table 1), with the vast majority (95%) in the eastern region 

(appendix 5). Black/Low Sagebrush and Desert Mixed Shrub comprised 10% and 4% of the study area 

respectively (table 1), nearly all (92% and 99%, respectively) occurring in the western region (appendix 

4). Floodplain and Mountain Brush each comprised 1% of the study area (table 1), with virtually all for 

the former (99%) in the eastern region (appendix 5) and slightly more (52%) of the latter in the western 

region (appendix 4). Non-Sagebrush vegetation comprised 24% of the total study area (table 1), slightly 

more of which (59%) was in the western region (appendix 4). Thus, the western region contained the 

majority of Black/Low Sagebrush and Desert Mixed Shrub vegetation, the eastern region contained 

most of the Grassland and Floodplain vegetation, whereas Big Sagebrush, Mountain Brush, and NonSagebrush were more evenly distributed between the two regions.

Soil Temperature and Moisture Regimes as Indicators of Resilience/Resistance

We used the seven soil temperature and moisture regime classes of Campbell (2014) (appendix 

3) to help infer the relative resilience to fire and resistance to invasive annual grasses in each analysis 

stratum. In general, soil moisture is positively associated with resilience to fire and soil temperature is 

negatively associated with resistance to annual grasses (Chambers and others, 2007, 2014a, 2014b). 

More specifically, the hotter-drier, winter-rainfall dominated, Mesic/Aridic and Frigid/Aridic regimes 

are associated with lower resilience/resistance, whereas the Cryic, Frigid/Ustic, and Frigid/Xeric 

regimes are associated with higher resilience/resistance (appendix 6) (Chambers and others, 2014a, 

2014b). Winter rainfall regimes (that is, Aridic) generally are negatively associated with resistance 

because non-native annual grasses are well adapted to Mediterranean climatic conditions (Bradford and 

Lauenroth, 2006; Bradley, 2009). In contrast, summer rainfall regimes (that is, Ustic) generally are 

positively associated with resistance because they facilitate growth of perennial grasses that help to 

competitively exclude non-native annual grasses. The raster layer of soil temperature and moisture 

regimes was created using 5-m pixel resolution, which we upscaled to 30-m resolution using a nearest 

neighbor approach in order to match the resolutions of the vegetation and fire layers.
11

The majority of area in Big Sagebrush, Black/Low Sagebrush and Desert Mixed Shrub

vegetation types is classified as Mesic/Aridic or Frigid/Aridic, and thus relatively low resilience and 

resistance, especially in the western region (appendix 7). In contrast, most of the Floodplain, Grassland, 

and Mountain Brush vegetation types are classified as Cryic, Frigid/Ustic, or Mesic/Ustic, and thus 

relatively high resilience/resistance.

Sources of Fire Data

Fire data produced by the Monitoring Trends in Burn Severity (MTBS) program 

(http://www.mtbs.gov/) were used as the basis for all analyses in this study, largely because of their 

mapping precision, accuracy, and consistent methodology across the study area (appendix 8). The 

MTBS program is focused on documenting fires equal to or greater than 405 ha (1,000 acres) in the 

Western United States. Although small fire (<405 ha) data were available from point occurrence 

datasets, these data were not used because of known errors and inconsistencies. For example, the 

relative level of completeness of point fire occurrence data varies widely across different types of public 

and private land ownership (appendix 8), which would skew results across the management zones used 

in this study (appendix 2). In addition, point data are not amenable to spatial analyses that parse the 

landscape by vegetation or soil temperature and moisture regime (appendix 8).

The MTBS fire perimeter data slightly over-represent area burned because they include 

unburned inclusions; however, they also under-represent overall burned area by not including smaller 

fires (<405 ha) (appendix 8). These smaller fires typically represent about 5% of the total area burned in 

a given area (Eidenshink and others, 2007), which is similar to estimates of small fire area not 

represented in the dataset used in the current study (appendix 8). The net result of not accounting for 

unburned inclusions and not using smaller fires is that the final estimates of fire area in this study are 

likely to be highly representative of actual burned area (appendix 8).

Utilizing only MTBS fires also is supported by their greater ecological relevance compared to 

smaller fires. Some of the most significant ecological impacts on sagebrush ecosystems may be 

associated with relatively large fires. For instance, a recent study within the boundaries of the 

hydrographic Great Basin estimated adverse effects on greater sage-grouse population growth rates 

when fires are adjacent to lek sites and fire sizes reached more than 916 ha (2,265 acres) (Coates and 

others, 2015). Additionally, significant rates of soil erosion in sagebrush landscapes have been reported 

for most fires more than 4,047 ha (10,000 acres) and rarely for smaller fires (Matt Germino, U.S. 

Geological Survey, written commun., February 10, 2015).

The fire data we used from the MTBS program spanned the years 1984 through 2013. The 

beginning of this time interval represented the first year that a consistent form of Landsat satellite 

imagery at 30 × 30 m resolution was available (Eidenshink and others, 2007). The last year represented 

the most recent in which completed data were available.
12

Analyses

Fire Area.—We focused on fire area, rather than fire numbers, based on the premise that the 

amount of fire area is more relevant to the ecology and management of the greater sage-grouse. A given 

fire’s area was based on the portion of its perimeter that intersected our study area, and was calculated 

by summing all pixels classified as unburned-to-low, low, moderate, high, increased greenness, and 

non-processed in the fire’s thematic burn severity raster. We did not exclude unburned-to-low pixels 

from a fire’s area because of biases in initial versus extended assessment fires (see appendix 8), and we 

included non-processed pixels (typically clouds or missing pixels in Landsat 7 scenes following the 

failure of its scan line corrector) in the total because MTBS analysts chose to include them within the 

fire’s perimeter. These fire area pixels were then used to extract and summarize pixels from the 

sagebrush types and soil moisture and temperature regime rasters.

Trends in annual fire area were evaluated by summing the fire area within a given stratum, and 

then performing one-tailed tests for monotonic increasing trends using the non-parametric MannKendall statistic (Mann, 1945; Kendall, 1975). To display trends in annual fire area, we plotted the 

proportion of total area burned each year of the study period in each strata. Rangewide analyses 

included 8 strata (7 vegetation types plus all types combined), western regional analyses included 35 

strata (6 vegetation types—because Floodplains were absent—plus all types, multiplied by 4 

management zones plus all zones), and eastern regional analyses included 32 strata (7 vegetation types

plus all types, multiplied by 3 management zones plus all zones). Given the large number of separate 

statistical tests, one might expect some significant trends to occur merely by chance. To control for this 

test multiplicity, we adjusted the p-values of individual tests to minimize the overall false discovery 

rate, which is the expected proportion of tests declared to be “significant” that are truly not significant. 

We used a conservative approach for false discovery rate p-value adjustment recommended by 

Benjamini and Yekutieli (2001) because some tests in the overall set are likely strongly correlated

because some strata are aggregations of other strata. We present both the unadjusted and adjusted pvalues, thus bracketing our estimates of significance by the least and most conservative statistical 

approaches. 

Fire Recurrence.—Fire recurrence is defined as the number of times that fire occurred in a 

specific area during 1984–2013. We created a fire recurrence raster layer by calculating the total number 

of times each pixel was within a fire area over this 30-year period. The fire recurrence raster was then 

intersected with the vegetation and soil raster layers to calculate both the total and the percentage of fire 

area that burned one or more times in each vegetation type and soil temperature/moisture regime class.

Fire Size.—Fire size is the total burned and unburned area within the perimeter of a particular 

fire (Sugihara and others, 2006). Determining average fire size, as well as addressing the question of 

whether fires are getting bigger over time, is complicated by the highly non-normal distribution of fire 

sizes. This is because small fires are the most abundant, permitting a few large fires to greatly influence 

measures of central tendency. Statistical techniques (for example, log-transformation, trimmed means, 

quantile regression) can address some of these concerns; however, such calculations are further 

complicated by incomplete point data for smaller fires (<405 ha; see appendix 8). Alternatively, we 

characterized how the proportion of total fire area is distributed across fire sizes because the dataset of 

large fires we used likely encompasses all the area burned despite the exclusion of small fires. We 

developed cumulative distribution curves for a given stratum of interest by plotting the size of 

individual fires (ordered from smallest to largest) versus the cumulative proportion of total fire area. We 

evaluated directional shifts in these fire size–cumulative area curves over time by determining the fire 

sizes at the 25th, 50th, and 75th percentiles of the cumulative fire area distributions calculated for each 

of the 30 years of the study. We did this for the western management zones combined and the eastern 
13

management zones combined. We were not able to conduct this analysis separately for all seven 

management zones, because most had too many years with too few MTBS fires to create reasonable 

cumulative distribution curves. We tested for increasing trends of fire sizes at the 25th, 50th, and 75th 

percentiles using one-tailed Mann-Kendall trend tests and present p-values that are both unadjusted and 

adjusted (for false discovery rates).

Fire Rotation.—Fire rotation is defined as the time necessary to burn an area equal in size to a 

particular area of interest (Sugihara and others, 2006). Fire rotation was calculated within the various 

strata by taking the timespan of the dataset (30 years) and dividing it by the proportion of area that 

burned during that period (Agee, 1993). Because the 30-year study period is shorter than all fire rotation 

values calculated and reported in this study, our estimates of fire rotations are only considered to be 

estimates because they are based on recent fire trends only, and might differ if reliable fire data were 

available for longer periods. Moreover, these estimates are reflective of the climate patterns over a 

recent 30-year period and do not incorporate the likely influence of projected future climate change on 

wildfire. Insufficient data were available to estimate fire rotation for strata that either had 0 ha burned 

during the 30-year study period, or in the case of Black/Low Sagebrush and Mountain Brush in the 

Columbia Basin, the amount of available area was very small (appendix 4).

Fire Season Timing and Length.—Various definitions of fire season have been used for firerelated research (for example, Westerling and others, 2006; Jolly and others, 2015). Here we define the 

beginning of the fire season for a given year as the start date of the first large fire (≥405 ha) and the 

ending of the season as the start date of the last large fire. The actual end of a fire can be defined various 

ways that are somewhat subjective (for example date of containment or control), but only the start date 

is unambiguous and recorded in the metadata of the fire database we used. We calculated fire season 

length for each year by subtracting the beginning from the ending Julian dates. Years that had fewer 

than two fires equal to or greater than 405 ha resulted in a 0-day fire season length. For each strata, 

mean annual fire season beginning and ending dates were calculated over the 30-year period. We tested 

for increasing trends in fire season length using one-tailed Mann-Kendall trend tests and presented pvalues that were both unadjusted and adjusted for false discovery rates using the method of Benjamini 

and Yekutieli (2001).
14

Fire Pattern Results

Rangewide Fire Area

Within all sage-grouse wildland areas, fire area totaled 10,270,949 ha (25,380,067 acres; 39,656

mi2) during the 30-year study period (1984–2013), constituting 13% of the total available area (table 2, 

fig. 3). The total wildland fire area presented in table 2 includes some area that burned more than once 

during the 30-year period, which we refer to as “recurrent fire” (≥2 fires in the same place). Thus, 

although the total fire area represents 13% of the total available study area, only 11% of the available 

surface area burned during the 30-year period. 

Three-quarters of the total fire area rangewide occurred in Big Sagebrush (56%), Black/Low

Sagebrush (14%), and Desert Mixed Shrub (4%) (table 2). Although Desert Mixed Shrub represented 

the smallest amount of fire area, the percentage of available area burned was similar to that of Big 

Sagebrush and Black/Low Sagebrush: 14% for the former, and 18% and 19%, respectively, for the other 

two. These three vegetation types were comprised of mostly low resilience/resistance landscapes 

characterized by Mesic/Aridic or Frigid/Aridic soil temperature and moisture regimes (appendix 11). 

Non-Sagebrush represented 15% of the total fire area and burned at a rate of 9% of the total 

available area (table 2). Grassland was next at 10% of total fire area, and burned at a rate of 7% of the 

total available area. Floodplain and Mountain Brush represented less than 1% and 1% of the fire area, 

respectively, and were burning at a rate of 5% and 6% of the available area. These four vegetation types 

were comprised of high resilience/resistance landscapes of Cryic, Frigid/Ustic, and Frigid/Xeric soil 

temperature and moisture regimes (appendix 11).

All vegetation type displayed some degree of increasing annual fire area during the 30-year 

study period (fig. 4). The differences among them were related to the strength and level of certainty in 

each trend. In two cases, Big Sagebrush and Black/Low Sagebrush, the p-values were relatively high 

even though there was an apparent increasing trend. This was likely due to relatively low 30-year 

sample size of the trends analyses. In another case, Desert Mixed Shrub, the p-value was relatively high 

and there was no obvious trend in annual fire area, so the lack of significance seemed to accurately 

reflect the absence of a trend. It is therefore important to evaluate both the pattern of the plots and the 

statistical p-values when evaluating trends.

Table 2. Fire area and percentage of fire area for each vegetation type rangewide (1984–2013).

Vegetation type Fire area 

(hectares)

Percentage of

total fire area

Percentage of 

available area

Big Sagebrush 5,794,604 56 18

Black/Low Sagebrush 1,409,797 14 19

Desert Mixed Shrub 403,579 4 14

Floodplain 45,783 <1 5

Grassland 988,726 10 7

Mountain Brush 62,821 1 6

Non-Sagebrush 1,565,639 15 9

Rangewide Total 10,270,949 100 13
15

Figure 3. Polygons of all fires used in this study overlaid to create recurrence classes. Data were obtained from the 

Monitoring Trends in Burn Severity Program and are characterized by fires equal to or greater than 405 ha from 

1984 to 2013.
16

Figure 4. Fire area for each year 1984–2013 in each major vegetation type throughout the range of the greater 

sage-grouse. P-values are unadjusted and (adjusted for false discovery rate) to bracket the range of statistical 

confidence in the trends.

Non-Sagebrush vegetation had the highest level of certainty (unadjusted p=0.01), followed by 

Floodplain (p=0.03); Grassland, Mountain Brush, and all vegetation types combined (p=0.05); and Big 

Sagebrush (p=0.09). Desert Mixed Shrub (p=0.13) and Black/Low Sagebrush (p=0.22) displayed 

unadjusted p-values that were too large to be considered even low reliability indicators of increased fire 

area. Although as mentioned above, the high interannual variability in fire area for Black/Low 

Sagebrush may have statistically masked an otherwise apparently increasing trend. It should also be 

noted that p-values that were conservatively adjusted to control for false discovery rates associated with 

test multiplicity (n=718 tests) all displayed very low levels of certainty (adjusted p=0.50 to p=1.00). The 

high number of separate tests that were adjusted for and the lack of highly significant unadjusted pvalues are the likely reason for the high adjusted p-values.
17

Western Regional Fire Area and Other Fire Regime Characteristics

Fire Area.—Within the sage-grouse wildland areas of the western region, fire area totaled

8,374,864 ha (20,701,824 acres; 32,347 mi2) during the 30-year study period (table 3, fig. 3), 

constituting 21% of the total available area in the western region (39,649,711 ha, appendix 4).

Accounting for recurrent fire, 17% of available surface area in the western region was burned one or 

more times. The total western region fire area (table 3) represented the greatest majority (82%) of the 

total fire area across all sage-grouse wildland areas in this study, even though the western region 

constituted only one-half (51%) of the total area in this study.

More than one-half (60%, 5,029,815 ha) of the fire area in the western region was in the Snake 

River Plain management zone, and 88% (4,459,799 ha) of that area was in Big Sagebrush and 

Black/Low Sagebrush vegetation types (table 3). The Southern Great Basin was next in prominence 

constituting 21% (1,727,767 ha) of the fire area, with 63% (1,093,305 ha) in Big Sagebrush and 

Black/Low Sagebrush, 16% (268,897 ha) in Desert Mixed Shrub, and 20% (345,611 ha) in NonSagebrush. The Northern Great Basin constituted 16% (1,348,223 ha) of the fire area, with 78% 

(1,045,352 ha) in Big Sagebrush and Black/Low Sagebrush. The Columbia Basin rounded out the total 

fire area at 3% (271,925 ha), with 57% (153,400 ha) in Grassland and 26% (71,150 ha) in Big 

Sagebrush.

Although the Columbia Basin represented the smallest amount of fire area, it burned at the same 

overall rate as the Snake River Plain (31% of available area) (table 3). Big Sagebrush in the Columbia 

Plateau burned at a particularly high rate at 49% of available area, whereas Big Sagebrush in the Snake 

River plain burned at 38% of available area, and in each of the other two western management zones 

burned at 20% of available area.

Over three-quarters of the fire area in the western region occurred in areas of relatively low 

resilience/resistance (Mesic/Aridic or Frigid/Aridic) (appendix 12). These fire areas were mostly in Big 

Sagebrush, and to a lesser extent Black/Low Sagebrush, which together represented 80% of the total fire 

area (table 3). Non-Sagebrush vegetation accounted for 13% of the western region total (table 3) and 

was split evenly between the high and low ends of the resilience/resistance gradient (appendix 12), 

similar to what was observed in the rangewide fire summaries (appendix 11).

The strongest evidence of increasing fire area across the western region (fig. 5) was for NonSagebrush (unadjusted p=0.01), Mountain Brush (p=0.04), and all vegetation types combined (p=0.05) 

(fig. 5). These patterns were mostly driven by the Snake River Plain and Columbia Basin management 

zones, which also provided evidence of increasing trends with Big Sagebrush (p=0.05) and Desert 

Mixed Shrub (p=0.09) in the former and Big Sagebrush (p=0.04), Black/Low Sagebrush (p=0.07), and 

Grassland (p=0.09) in the latter. The Southern Great Basin also displayed evidence of increasing trends 

in Non-Sagebrush (p=0.01) and Mountain Brush (p=0.07) vegetation types. The Northern Great Basin 

only showed weak evidence of increasing fire area in Non-Sagebrush (p=0.11). The remaining 

vegetation types in each management zones displayed unadjusted p-values greater than 0.10. All pvalues that were conservatively adjusted to control for false discovery rates associated with test 

multiplicity displayed very low levels of certainty (adjusted p=0.50 to p=1.00). Again, the very high 

number of separate tests that were adjusted for and the lack of highly significant unadjusted p=values 

are the likely reasons for the high adjusted p-values.
18

Table 3. Fire area, percentage of fire area, and percentage of available area for each vegetation type in the 

management zones of the western region of the greater sage-grouse range (1984–2013).

Vegetation Type Fire Area

(hectares)

Percentage of

Fire Area

Percentage of 

Available Area

Columbia Basin

Big Sagebrush 71,150 26 49

Black/Low Sagebrush 3 0 1

Desert Mixed Shrub 20,937 8 20

Floodplain 0 0 0

Grassland 153,400 57 28

Mountain Brush 3 0 11

Non-Sagebrush 25,934 10 23

Columbia Basin Total 271,426 100 31

Northern Great Basin

Big Sagebrush 672,343 50 20

Black/Low Sagebrush 373,009 28 22

Desert Mixed Shrub 28,367 2 10

Floodplain 0 0 0

Grassland 21,230 2 11

Mountain Brush 12,007 1 29

Non-Sagebrush 240,216 18 11

Northern Great Basin Total 1,347,172 100 18

Snake River Plain

Big Sagebrush 3,636,638 72 38

Black/Low Sagebrush 823,161 16 31

Desert Mixed Shrub 83,767 2 17

Floodplain 0 0 0

Grassland 16,550 0 21

Mountain Brush 19,978 0 15

Non-Sagebrush 448,935 9 12

Snake River Plain Total 5,029,028 100 31

Southern Great Basin

Big Sagebrush 880,825 51 20

Black/Low Sagebrush 212,480 12 7

Desert Mixed Shrub 268,897 16 14

Floodplain 0 0 0

Grassland 0 0 0

Mountain Brush 19,424 1 5

Non-Sagebrush 345,611 20 7

Southern Great Basin Total 1,727,237 100 12

Western Management Zones Combined

Big Sagebrush 5,260,956 63 30

Black/Low Sagebrush 1,408,653 17 19

Desert Mixed Shrub 401,968 5 15

Floodplain 0 0 0

Grassland 191,180 2 23

Mountain Brush 51,411 1 9

Non-Sagebrush 1,060,696 13 10

Western Management Zones 

T l 8,374,864 100 21
19

Figure 5. Fire area for each year 1984–2013 in major vegetation types and the four management zones in the 

western region of the greater sage-grouse range. P-values are unadjusted and (adjusted for false discovery rate) to 

bracket the range of statistical confidence in the trends.
20

Fire Recurrence.—Recurrent fire area encompassed 1,412,673 ha, or 22% of the total fire area

in the western region (table 4). The majority (65%) of the recurrent fire area occurred in the Snake River 

Plain management zone (fig. 3). The Southern Great Basin (19%), Northern Great Basin (11%), and the 

Columbia Basin (5%) round out the percentages of recurrent fire area in the western region.

Big Sagebrush encompassed 1,010,671 ha, or 72% of all recurrent fire area in the western region

(table 4). Black/Low Sagebrush (13%), Non-Sagebrush (8%), Desert Mixed Shrub (5%), Grassland 

(2%), and Mountain Brush (<1%) rounded out the percentages of recurrent fire area among western 

region vegetation types.

Although the smallest amount of recurrent fire area occurred in the Columbia Basin (64,811 ha), 

it represented one-third (34%) of the total fire area in that management zone (table 4). The vegetation 

types that were most responsible for the high proportion of recurrent fire were Non-Sagebrush (46%), 

Big Sagebrush (45%), and Desert Mixed Shrub (40%). 

Fire Size.—The size distributions of total fire area across fire sizes in the western region over 

the 30-year study period all differed somewhat among the four management zones (fig. 6). Fire sizes at 

the 25th, 50th, and 75th percentiles of cumulative fire area generally were highest for the Northern 

Great Basin at 4,211; 23,328; and 66,108 ha, respectively. The Snake River Plain was a second in fire 

size with 5,362; 17,436; and 59,826 ha fires at each of the three percentiles. The Southern Great Basin 

was slightly lower at 4,667; 16,877; and 51,858 ha, followed by the Columbia Basin at 4,119; 13,901;

and 31,547 ha on the Columbia Basin at each of the three percentiles. The very largest fires in Columbia 

Basin did not exceed about 30,000 ha whereas in the other three management zones they exceeded 

100,000 ha.

Fires were generally larger in the western region than in the eastern region (fig. 7). Fire sizes at 

the 25th, 50th, and 75th percentiles of cumulative fire area were 4,945; 17,436; and 56,460 ha in the 

western region compared to 2,903; 11,578; and 41,713 ha in the eastern region. This translated into fire 

sizes that were 41%, 34%, and 26% higher in the western region at each of the three percentile levels.

Another way of describing this difference is that one-half of the total fire area in the western region was 

represented by fire sizes greater than 17,436 ha, ranging from greater than 13,901 in the Columbia Basin 

to greater than 23,328 ha in the Northern Great Basin, whereas one-half of the fire area in eastern region 

was in fire sizes that were greater than 11,578 ha.

There was a notable shift in the distribution of fire area across fire sizes, with significant trends 

in the annual fire sizes at the at the 25th (unadjusted p=0.02), 50th (p=0.00), and 75th (p=0.00) 

percentiles of the cumulative fire area distributions calculated for each of the 30 years of the study (fig.

8). All p-values that were conservatively adjusted to control for false discovery rates also displayed high 

levels of certainty (adjusted p=0.01 to p=0.04). There also appeared to be an increase in annual fire size 

beginning in 2005, especially at the 50th and 75th percentiles.
21

Table 4. Fire recurrence area among fire recurrence classes in each vegetation type and management zone in the western range of the greater 

sage-grouse (1984–2013).

[ha, hectare; ≥, greater than or equal to; %, percent; ×, times]

Vegetation type

Fire recurrence (ha) Fire area ≥2×

Recurrent (ha)

Fire area ≥2×

1 2 3 4 5 6 7 Recurrent (%)

Columbia Basin

Big Sagebrush 24,808 15,326 5,223 5 0 0 0 20,554 45

Black/Low Sagebrush 3 0 0 0 0 0 0 0 0

Desert Mixed Shrub 8,575 4,951 796 16 2 0 0 5,764 40

Floodplain 0 0 0 0 0 0 0 0 0

Grassland 82,658 22,275 8,452 201 6 0 0 30,935 27

Mountain Brush 3 0 0 0 0 0 0 0 0

Non-Sagebrush 8,879 5,123 2,430 4 0 0 0 7,558 46

Columbia Basin Total 124,926 47,675 16,901 227 8 0 0 64,811 34

Northern Great Basin

Big Sagebrush 490,367 78,202 8,281 183 0 0 0 86,666 15

Black/Low Sagebrush 276,447 33,929 9,469 75 0 0 0 43,472 14

Desert Mixed Shrub 22,136 2,785 214 4 0 0 0 3,004 12

Floodplain 0 0 0 0 0 0 0 0 0

Grassland 17,523 1,612 153 6 0 0 0 1,771 9

Mountain Brush 8,288 1,564 197 0 0 0 0 1,761 18

Non-Sagebrush 196,314 19,015 2,306 1 0 0 0 21,322 10

Northern Great Basin Total 1,011,074 137,107 20,620 268 0 0 0 157,996 14

Snake River Plain

Big Sagebrush 1,850,933 499,526 169,577 49,858 11,748 2,780 438 733,928 28

Black/Low Sagebrush 587,712 101,234 8,990 1,425 62 0 0 111,712 16

Desert Mixed Shrub 48,377 9,407 1,708 2,156 390 141 4 13,807 22

Floodplain 0 0 0 0 0 0 0 0 0

Grassland 12,699 1,440 106 93 23 28 1,690 12

Mountain Brush 15,335 1,941 254 0 0 0 0 2,195 13

Non-Sagebrush 315,108 39,775 11,069 4,034 945 136 26 55,985 15
22

Vegetation type

Fire recurrence (ha) Fire area ≥2×

Recurrent (ha)

Fire area ≥2×

1 2 3 4 5 6 7 Recurrent (%)

Snake River Plain Total 2,830,163 653,324 191,705 57,566 13,168 3,086 468 919,316 25

Southern Great Basin

Big Sagebrush 511,660 141,712 25,771 1,772 268 0 0 169,523 25

Black/Low Sagebrush 156,745 22,166 3,635 122 2 0 0 25,925 14

Desert Mixed Shrub 180,361 38,111 3,467 469 8 0 0 42,054 19

Floodplain 0 0 0 0 0 0 0 0 0

Grassland 0 0 0 0 0 0 0 0 0

Mountain Brush 18,768 304 12 3 0 0 0 319 2

Non-Sagebrush 277,375 29,558 3,038 126 6 0 0 32,729 11

Southern Great Basin Total 1,144,909 231,852 35,923 2,491 284 0 0 270,551 19

Western Management Zones Combined

Big Sagebrush 2,877,767 734,767 208,852 51,818 12,016 2,780 438 1,010,671 26

Black/Low Sagebrush 1,020,907 157,329 22,094 1,621 64 0 0 181,108 15

Desert Mixed Shrub 259,449 55,255 6,185 2,645 400 141 4 64,630 20

Floodplain 0 0 0 0 0 0 0 0 0

Grassland 112,880 25,328 8,712 299 29 28 0 34,396 23

Mountain Brush 42,394 3,809 463 3 0 0 0 4,274 9

Non-Sagebrush 797,676 93,472 18,843 4,166 951 136 26 117,593 13

Western Management Zones Total 5,111,072 1,069,959 265,150 60,552 13,460 3,086 468 1,412,673 22
23

Figure 6. Cumulative fire area as a function of fire size in the four management zones in the western region of the 

greater sage-grouse range. Each distribution is based on all fires 1984–2013 in each management zone.

Figure 7. Cumulative fire area as a function of fire size in the western and eastern regions of the greater sagegrouse range. Each distribution is based on all fires 1984–2013 in each region.
24

Figure 8. Fire size at the 25th, 50th, and 75th percentiles of the cumulative fire area distribution for each year 

1984–2013 in the western region of the greater sage-grouse range. P-values are unadjusted and (adjusted for false 

discovery rate) to bracket the range of statistical confidence in the trends.

Fire Rotation.—Estimated fire rotation in the western region was shortest for Big Sagebrush at 

99 years (table 5). Management zone values for this vegetation type ranged from a low of 61 and 78 

years in the Columbia Basin and Snake River Plain, respectively, to highs of 148 and 150 years in the 

Northern Great Basin and Southern Great Basin, respectively. Fire rotation in Grassland was slightly 

longer at 127 years, ranging from a low of 106 years in the Columbia Basin, to a high of 146 years in 

the Snake River Plain, to 268 years in the Northern Great Basin. Black/Low Sagebrush had a fire 

rotation of 158 years ranging widely from 97 years in the Snake River Plain to 435 years in the Southern 

Great Basin. Desert Mixed Shrub displayed the next longest fire rotation at 206 years. Values ranged 

from lows of 152 and 176 years in the Columbia Basin and Snake River Plain, respectively, to highs of 

208 and 315 years in the Southern Great Basin and Northern Great Basin, respectively. Mountain Brush 

represented the longest fire rotation in the western region at 320 years, ranging from extremes of 102 

years in the Northern Great Basin to 580 years in the Southern Great Basin. 
25

Table 5. Fire rotation (years) in each vegetation type and management zone in the western range of the greater 

sage-grouse (1984–2013).

[Estimates for Non-Sagebrush were not reported (NR) because they represented an amalgam of numerous biophysical setting 

types with widely disparate fire regimes. Insufficient data (ID) existed to calculate fire rotation for some strata, either 

because 0 ha of fire area burned the strata or, in the case of Black/Low Sagebrush and Mountain Brush in the Columbia 

Basin, the amount of available area was very small (appendix 4)]

Vegetation type

Columbia 

Basin

Northern 

Great Basin

Snake River 

Plain

Southern Great 

Basin

Western 

Management 

Zones Combined

Modern Fire Rotation (Current Study)

Big Sagebrush 61 148 78 150 99

Black/Low Sagebrush ID 134 97 435 158

Desert Mixed Shrub 152 315 176 208 206

Floodplain ID ID ID ID ID

Grassland 106 268 146 N/A 127

Mountain Brush ID 102 198 580 320

Non-Sagebrush NR NR NR NR NR

Fire Season.—Fire season was longest in the Snake River Plain, followed by the Northern Great

Basin, Southern Great Basin, and Columbia Basin (table 6). The Snake River Plain also had the earliest 

mean beginning date and latest ending date. Beginning dates for the Northern Great Basin and Southern 

Great Basin were similar, but ending dates were later for the former than the latter. The Columbia Basin 

by far had the latest beginning date and earliest end date in the western region. These estimates are 

considered to be fairly robust because of the high number of years in a given management zone that had 

two or more fires equal to or greater than 405 ha (1,000 acres): Snake River Plain (n=30 years), 

Southern Great Basin (n=29 years), Northern Great Basin (n=28 years), and Columbia Basin (n=24 

years).

The length of the fire season was fairly constant during the 30-year study period for all except 

the Southern Great Basin, which displayed a significantly increasing trend towards longer fire seasons 

(fig. 9).

Inferring the ecological significance of differences in fire season beginning, ending, and length 

among management zones is somewhat complicated by the fact that regions with greater numbers of 

fires will have increasing probability of some fires occurring very early or very late in the season. Thus, 

the mean beginning and ending dates, and season length, may therefore all be more extreme in 

geographic regions with more fires. This is particularly evident when comparing the values for 

individual management zones to those of all management zones combined with the western and eastern 

regions (see fire season results below),
26

Table 6. Fire season beginning (day of year), ending (day of year), and length (days) in each management zone in 

the western range of the greater sage-grouse (1984–2013). 

[Beginning and ending days are defined by the start date of the first and last fires equal to or greater than 405 ha (1,000 

acres) each year and equal to or greater than two fires in a year are required to generate a fire season length value]

Columbia 

Basin

Northern 

Great Basin

Snake River

Plain

Southern Great 

Basin

Western 

Management Zones 

Combined

Length (days) 26 85 111 72 138

Beginning (day of year) 189 172 165 171 144

Ending (day of year) 222 264 275 245 282

Years with ≥2 Fires (count) 24 28 30 29 30

Figure 9. Fire season length for each year 1984–2013 in the four management zones in the western region of the 

greater sage-grouse range. P-values are unadjusted and (adjusted for false discovery rate) to bracket the range of 

statistical confidence in the trends.
27

Eastern Regional Fire Area and Other Fire Regime Characteristics

Fire Area.—In the eastern region, fire area encompassed 1,891,979 (4,678,244 acres; 7,310 mi2)

(table 7, fig. 3), constituting 5% of the total available area in the eastern region (37,658,979 ha, 

appendix 5). Even accounting for recurrent fire, 5% of available surface area in the eastern region 

burned one or more times. This fire area represented a small fraction (18%) of the total fire area across 

all sage-grouse wildland areas rangewide, even though the eastern region contributed almost one-half 

(49%) of the total area in this study. 

Two-thirds (66%) of the fire area in the eastern region was in the Great Plains management 

zone, and 62% of that area was in Grassland (table 7). The other one-third (31%) was in the Wyoming 

Basin, mostly in Big Sagebrush (57%) and Non-Sagebrush (39%) vegetation types. The remaining 2% 

of the fire area occurred in the Colorado Plateau. The rates of burning were all relatively low across the 

eastern region, most around 5% of total available area.

Most of the fire area in the eastern region occurred in areas of relatively high 

resilience/resistance (Cryic, Frigid/Ustic) (appendix 13). These fire areas were mostly in Grassland, 

Floodplain, Mountain Brush, and Non-Sagebrush vegetation types. Only fire area in Big Sagebrush in 

the Wyoming Basin occurred on relatively low resilience/resistance landscapes (Frigid/Aridic, 

Mesic/Aridic). 

The strongest evidence of increasing fire area were in Non-Sagebrush (unadjusted p=0.01), 

Grassland (p=0.03), and Floodplain (p=0.03) (fig. 10). These patterns were mostly due to the Great 

Plains and Wyoming Basin. The former also displayed some evidence of increasing fire area in Big 

Sagebrush (p=0.06) and Black/Low Sagebrush (p=0.07). All p-values that were conservatively adjusted 

to control for false discovery rates associated with test multiplicity (Benjamini and Yekutieli, 2001) 

displayed very low levels of certainty (adjusted p=0.50 to p=1.00). The very high number of separate 

tests that were adjusted for and lack of high significant unadjusted p=values are the likely reasons for 

the high adjusted p-values.
28

Table 7. Fire area, percentage of total fire area, and percentage of available area for each vegetation type in the 

management zones of the eastern region of the greater sage grouse range (1984–2013).

Vegetation type

Fire area 

(hectares)

Percentage of 

fire area 

Percentage of 

available area 

Colorado Plateau

Big Sagebrush 4,175 10 4

Black/Low Sagebrush 57 0 <1

Desert Mixed Shrub 230 1 1

Floodplain 0 0 0

Grassland 0 0 0

Mountain Brush 5,580 14 7

Non-Sagebrush 30,601 75 8

Colorado Plateau Vegetation 

Total 40,643 100 6

Great Plains

Big Sagebrush 191,560 15 7

Black/Low Sagebrush 0 0 <1

Desert Mixed Shrub 0 0 0

Floodplain 44,732 4 5

Grassland 779,665 62 6

Mountain Brush 1,734 0 6

Non-Sagebrush 238,566 19 11

Great Plains Vegetation Total 1,256,257 100 7

Wyoming Basin

Big Sagebrush 337,913 57 3

Black/Low Sagebrush 1,088 0 3

Desert Mixed Shrub 1,382 0 1

Floodplain 1,050 0 2

Grassland 17,881 3 5

Mountain Brush 4,096 1 1

Non-Sagebrush 231,669 39 5

Wyoming Basin Vegetation 

Total 595,079 100 4

Eastern Management Zones Combined

Big Sagebrush 533,648 28 4 

Black/Low Sagebrush 1,144 0 3 

Desert Mixed Shrub 1,612 0 1 

Floodplain 45,783 2 5 

Grassland 797,546 42 6 

Mountain Brush 11,410 1 2 

Non-Sagebrush 500,836 26 7 

Eastern Zones Vegetation Total 1,891,979 100 5 
29

Figure 10. Fire area for each year 1984–2013 in major vegetation types and the three management zones in the 

eastern region of the greater sage-grouse range. P-values are unadjusted and (adjusted for false discovery rate) to 

bracket the range of statistical confidence in the trends.
30

Fire Recurrence.—Recurrent fire area encompassed 123,479 ha, or 22% of the total fire area in 

the eastern region (table 8). The majority (80%) of the recurrent fire area occurred in the Great Plains 

management zone. The Wyoming Basin (19%) and Colorado Plateau (1%) round out the percentages of 

recurrent fire area in the eastern region. Most of the recurrent fire area occurred in Grassland (52%) 

(table 8). Big sagebrush (25%) was the other major contributor of recurrent fire.

Fire Size.—The size distributions of fire area across fire sizes in the eastern region over the 30-

year study period differed widely among management zones (fig. 11). Fire sizes at the 25th, 50th, and 

75th percentiles of cumulative fire area were much higher in the Great Plains at 3,568; 16,348; and 

50,424 ha than in the Wyoming Basin at 1,991; 6,027; and 19,042 ha. Thus, one-half of the fire area in 

the Great Plains occurred in fires greater than 16,348 ha, whereas in the Wyoming Basin one-half of the 

fire area was in fires greater than 6,027 ha. Cumulative fire area in the Colorado Plateau was not 

comparable to the other regions because there was only a few fires greater than 1,000 ha (fig. 11).

As mentioned above in the western regional results for fire size, the fires were much smaller in 

the eastern region than in the western region (fig. 7). Also, in contrast to the western region which

displayed notable shifts in fire area size distribution over time (fig. 8), the eastern region displayed no 

such trend (fig. 12). 

Figure 11. Cumulative fire area as a function of fire size in the three management zones in the eastern region of 

the greater sage-grouse range. Each distribution is based on all fires 1984–2013 in each management zone.
31

Figure 12. Fire size at the 25th, 50th, and 75th percentiles of the cumulative fire area distribution for each year 

1984–2013 in the eastern region of the greater sage-grouse range. P-values are unadjusted and (adjusted for false 

discovery rate) to bracket the range of statistical confidence in the trends.
32

Table 8. Fire recurrence area among fire recurrence classes in each vegetation type and management zone in the 

eastern region of the greater sage-grouse (1984–2013).

[ha, hectare; ≥, greater than or equal to; %, percent; ×, times]

Vegetation type

Fire Recurrence Fire Area ≥2×

Recurrent (ha)

Fire Area ≥2×

1 2 3 4 Recurrent (%)

Colorado Plateau

Big Sagebrush 3,896 139 0 0 139 3

Black/Low Sagebrush 54 1 0 0 1 2

Desert Mixed Shrub 217 6 0 0 6 3

Floodplain 0 0 0 0 0 NA

Grassland 0 0 0 0 0 NA

Mountain Brush 4,897 342 0 0 342 7

Non-Sagebrush 28,047 1,277 0 0 1,277 4

Colorado Plateau Vegetation Total 37,111 1,766 0 0 1,766 5

Great Plains

Big Sagebrush 158,439 15,880 453 0 16,333 9

Black/Low Sagebrush 0 0 0 0 0 NA

Desert Mixed Shrub 0 0 0 0 0 NA

Floodplain 38,617 2,843 142 1 2,986 7

Grassland 653,100 59,221 2,672 27 61,920 9

Mountain Brush 1,651 42 0 0 42 2

Non-Sagebrush 203,371 15,873 1,109 30 17,013 8

Great Plains Vegetation Total 1,055,178 93,859 4,376 58 98,293 9

Wyoming Basin

Big Sagebrush 308,969 14,307 110 0 14,417 4

Black/Low Sagebrush 951 68 0 0 68 7

Desert Mixed Shrub 1,290 46 0 0 46 3

Floodplain 982 34 0 0 34 3

Grassland 13,833 2,024 0 0 2,024 13

Mountain Brush 3,631 232 0 0 232 6

Non-Sagebrush 218,472 6,594 3 0 6,597 3

Wyoming Basin Vegetation Total 548,128 23,306 113 0 23,419 4

Eastern Management Zones Combined

Big Sagebrush 471,305 30,327 563 0 30,890 6

Black/Low Sagebrush 1,004 70 0 0 70 7

Desert Mixed Shrub 1,507 52 0 0 52 3

Floodplain 39,599 2,877 142 1 3,020 7

Grassland 666,933 61,245 2,672 27 63,944 9

Mountain Brush 10,178 615 0 0 616 6

Non-Sagebrush 449,889 23,744 1,112 30 24,887 5

Eastern Zones Vegetation Total 1,640,416 118,931 4,489 58 123,479 7
33

Fire Rotation.—Estimated fire rotation in the eastern region was shortest for Grassland at 526 

years (table 9). Management zone values for this vegetation type ranged from 524 years in the Great 

Plains to 603 years in the Wyoming Basin. Floodplain was slightly higher at 585 years, but ranged more 

widely from 555 years in the Great Plains to 1,853 years in the Wyoming Basin. Big Sagebrush was a 

couple hundred years longer at 810 years, ranging from 445 years in the Great Plains to 1,017 years in 

the Wyoming Basin (table 9). Black/Low Sagebrush displayed a fire rotation of 1,251 years, with 883

years in the Wyoming Basin and 7,533 years in the Colorado Plateau. Mountain Brush was a bit higher 

at 1,348 years, ranging from 516 years in the Great Plains to 2,433 in the Wyoming Basin. Desert 

Mixed Shrub had the longest fire rotation by far at 4,366 years, ranging from 3,672 years in the 

Colorado Plateau to 4,481 years in the Wyoming Basin.

Fire Season.—Fire season length was similar in the Great Plains (mean = 100 days) and 

Wyoming Basin (mean = 96 days) (table 10). Beginning dates were earlier for the Great Plains (mean = 

147 days, day of year = May 27) than for the Wyoming Basin (mean = 163 days, day of year = June 12), 

and so, too, were the ending dates for the former (mean = 255 days, day of year = September 12) than 

the latter (mean = 265 days, day of year = September 22). The Colorado Plateau was anomalous in 

having mean beginning and ending dates for the fire season the same (mean = 194 days, day of year = 

July 13), and the mean season length 0 days. This was due to the very small number of years with at 

least two fires equal to or greater than 405 ha (1,000 acres) (n=10 years). The other two eastern region 

management zones each had n=28 years with two or more of these fires.

The length of the fire season significantly increased during the 30-year study period for both the 

Great Plains and the Wyoming Basin (fig. 13). Fire seasons were shorter in the first decade than in the 

latter two decades of the study period.

Table 9. Fire rotation (years) in each vegetation type and management zone in the eastern region of the greater 

sage grouse (1984–2013). 

[Estimates for Non-Sagebrush were not reported (NR) because they represented an amalgam of numerous biophysical setting 

types with widely disparate fire regimes. Insufficient data (ID) existed to calculate fire rotation for some strata, either 

because 0 ha of fire area burned the strata or, in the case of Black/Low Sagebrush and Mountain Brush in the Columbia 

Basin, the amount of available area was very small (appendix 4)]

Vegetation type Colorado Plateau Great Plains Wyoming Basin Eastern Management 

Zones combined

Modern Fire Rotation (Current Study)

Big Sagebrush 833 445 1,017 810 

Black/Low Sagebrush 7,533 ID 883 1,251 

Desert Mixed Shrub 3,672 ID 4,481 4,366 

Floodplain ID 555 1,853 585 

Grassland ID 524 603 526 

Mountain Brush 811 516 2,433 1,348 

Non-Sagebrush NR NR NR NR
34

Table 10. Fire season variables (mean values) in each management zone in the eastern range of the greater sage 

grouse (1984–2013). 

[Beginning and ending days are defined by the start date of the first and last fires equal to or greater than 405 ha (1,000 

acres) each year and equal to or greater than two fires in a year are required to generate a fire season length value]

Colorado Plateau Great Plains Wyoming Basin

Eastern 

Management 

Zones Combined

Length (days) 0 100 96 142

Beginning (day of year) 194 147 163 131

Ending (day of year) 194 255 265 273

Years with ≥2 Fires (count) 10 28 28 30

Figure 13. Fire season length for each year 1984–2013 in the three management zones in the eastern region of 

the greater sage-grouse range. P-values are unadjusted and (adjusted for false discovery rate) to bracket the range 

of statistical confidence in the trends.
35

Discussion of Fire Patterns

Fire Area

Fire Area Amount and Percentage of Available Area

We know of no published studies that are comparable with the results we present for fire area 

and fire area as a percentage of available area in sage-grouse management zones and vegetation types. 

The only possible comparison might be a series of figures (Miller and others, 2011; figs. 10.11–10.15),

which suggest similar ordinal ranking of total fire area as those reported for some of the sage-grouse 

management zones in the current study. We therefore focus below on the potential ecological 

implications of the fire area patterns we reported, rather than comparisons with other studies. 

The significant amount fire area in Big Sagebrush, and to a lesser degree Black/Low Sagebrush 

and Desert Mixed Scrub, across the range of the greater sage-grouse should be a great concern for 

conservation efforts. These relatively hot/dry, low productivity landscapes recover more slowly 

following fire and are more susceptible to invasion by non-native invasive grasses than are higher 

resilience/resistance vegetation types in the sagebrush biome (Chambers and others, 2014a, 2014b, 

Brooks and others, in press). In addition, increased dominance by non-native grasses such as cheatgrass 

can increase fire frequency and promote a grass/fire cycle (D’Antonio and Vitousek, 1992; Brooks and 

others, 2004; Brooks, 2008), potentially leading to type-conversion of native sagebrush into non-native 

annual grasslands (Brooks, 2008, fig. 3.7), and thus significantly reducing habitat quality for the greater 

sage-grouse (Knick and others, 2013). 

As mentioned in the introduction to this report, invasive species and fire are among the top three 

greatest threats to the greater sage-grouse (U.S. Fish and Wildlife Service, 2005). However, it is actually 

the interaction between the two, via the grass-fire cycle, which is arguably the single greatest threat, at 

least in the western regions. The steps of inference to determine that an altered fire regime has occurred 

include: (1) documenting that a plant invasion or set of invasions has altered fuelbed characteristics; (2) 

demonstrating that these fuelbed changes alter the spatial and/or temporal distribution of fire on the 

landscape; and (3) showing that the new fire regime promotes the dominance of the fuels that drive it 

(Brooks, 2008; fig. 3.6). Cheatgrass is known to increase fine fuel loads, horizontal continuity, and 

ignitability of fuels (Brooks and Pyke, 2001; Rice and others, 2001; Brooks, 2008). These fuelbed 

characteristics can lead to increased fire size, frequency, and seasonal window of burning. These 

changes make it increasing difficult for woody sagebrush steppe species to recover, leading to 

replacement of coarse woody fuels by fine herbaceous grasses. Cheatgrass can recover very quickly 

producing fuel beds that can carry fire after as few as 5 years (Whisenant, 1989), but most native woody 

species are adapted to a longer fire-return intervals ranging from many decades to over a century or 

more (Rice and others, 2001). Thus, cheatgrass both promotes frequent fire and recovers soon following 

fire, creating a grass/fire cycle that has converted vast landscapes of native sagebrush vegetation types

to nonnative annual grasslands (Rice and others, 2001; Menakis and others, 2003). 
36

Few would argue that the grass/fire cycle is not a substantial threat to the greater sage-grouse

habitat, but it can be difficult to define exactly where thresholds have been crossed and a self-sustaining 

grass/fire cycle has become established. In fact, there are relatively few studies published from around 

the world that specifically document evidence for cases where a grass/fire cycle has become established 

(for example Rossiter and others, 2003; Setterfield and others, 2013; Bowman and others, 2014). 

Although this task is beyond the scope of the current study, the information we present on patterns of 

fire regime characteristics provide critical pieces of the puzzle that ultimately can be used to develop 

risk assessments for the establishment potential of a grass/fire cycle across the range of the greater sagegrouse.

The concern regarding the preponderance of fire area in vegetation types of low resistance and 

resilience is clearly well justified, but other evidence somewhat tempers this concern. For example, the 

strongest evidence suggesting an increasing trend in annual fire area is from relatively high 

resilience/resistance vegetation types, specifically Floodplain, Grassland, and Mountain Brush, and 

especially for Non-Sagebrush. These types may actually benefit from increased fire area after a century 

or more of reduce fire conditions. Such a situation has been documented in Grasslands where 

inappropriate grazing practices reduced fuel loads below the threshold that could easily carry fire, 

resulting in reduced fire frequency and increased abundance of woody species (Ratajczak and others,

2014). Thus, not all increasing trends in fire area are necessarily cause for alarm and fire threats 

analyses should take into account the differing implications of increased fire in low resilience/resistance 

versus high resilience/resistance landscapes.

Fire Area Trends

Increasing trends in annual fire area have been widely cited to occur in the Western United 

States (Balch and others, 2013; Dennison and others, 2014), but few estimates have focused on the 

regions that generally coincided with the geographic range of the greater sage-grouse, and those that do 

are not exactly comparable with the current study. One such study was based on an incomplete and 

inconsistently derived fire dataset and a different time interval (1980–2007) and did not parse the 

analyses by vegetation type (Miller and others, 2011). Another study was based on a more complete and 

consistent dataset (≥405 ha MTBS fires), across another time interval (1984–2008), but utilized current 

rather than potential vegetation layers and may therefore be susceptible to potential cause-and-effect 

confounders when interpreting the resulting fire patterns (Baker, 2013). Neither of those previous 

studies focused specifically on what we define as sage-grouse wildland areas, relevant for habitat 

conservation across the range of sage-grouse (see section, “Study Area” for description of this term). 

Those differences aside, Miller and others (2011) and Baker (2013) provide the closest estimates of 

recent patterns of fire area that are comparable for this current study.

The current study reported evidence of increased fire area for all vegetation types combined in 

the Wyoming Basin, Snake River Plain, Columbia Basin, and Great Plains, but not in the Northern

Great Basin, Southern Great Basin, and Colorado Plateau. Miller and others (2011) reported increased 

fire area in all regions except the Snake River Plain, but also reported increases in the Northern Great 

Basin and Southern Great Basin. Baker (2013) reported increasing fire area in the Colorado Plateau and 

Columbia Basin, but not in other regions. The current study also highlighted relatively strong evidence 
37

of increases in fire area in Big Sagebrush of the Columbia Basin and Snake River Plain, and weaker 

evidence in the Great Plains. Baker (2013) reports similar fire area increases in Big Sagebrush of the 

Columbia Plateau, but not in the Snake River Plain. There are many other examples of relatively poor 

concurrence in results between these previous two studies (Miller and others, 2011; Baker, 2013) and 

the current study in trends in fire area integrated across all vegetation types in the range of greater sagegrouse. 

Difference among study findings reflect a common difficulty when comparing the results of fire 

history studies that are based on differing spatial and temporal scales, or that use different datasets.

However, because of our specific focus on greater sage-grouse habitat across its entire range, our use of 

a longer fire period and more accurate fire dataset, and our focus on the biophysical conditions capable 

of supporting sagebrush communities, we suggest that our results are appropriate for use in planning 

efforts focused on greater sage-grouse conservation. 

Fire Recurrence

The prevalence of recurrent fire in Big Sagebrush is of similar concern as that explained above 

for fire area patterns. This vegetation type is dominated by relatively hot/dry, low productivity 

landscapes that have relatively low resilience/resistance. As a result, it has higher probability of 

transitioning to a grass/fire cycle than cooler/wetter landscapes. The presence of recurrent fire, rather 

than simply fire per se, serves as an additional source of concern because shortened fire-return intervals 

are a hallmark of the grass/fire cycle (D’Antonio and Vitousek, 1992) and a key piece of evidence that 

indicates its presence (Brooks, 2008). Thus, areas with recurrent fire in Big Sagebrush and other low 

resilience/resistance vegetation types such as Black/Low Sagebrush and Desert Mixed Shrub are at a 

high probability of transitioning to a grass/fire cycle.

As fire recurrence over a given time period increases and the average fire return interval 

decreases, conditions become increasing more suitable for the persistence of annual plants such as 

cheatgrass and less suitable for the persistence of woody perennials such as sagebrush. A seminal study 

documented this dynamic in Big Sagebrush on the Snake River Plain (Whisenant, 1989). Declines were 

reported in fire return intervals from 60 to 110 years historically to 3–5 years during the 1960s through 

1980s across large portions of that region. Increased fire frequency was associated with increased 

frequency of cheatgrass and other annuals, decreased frequency of sagebrush, others shrubs, and 

perennial grasses, and decreased plant species diversity. These changes all represent dramatic declines 

in habitat quality for the greater sage-grouse.

Of the total recurrent fire area, we reported (1.4 million ha), roughly two-thirds of that area 

(919,316 ha) occurred in the Snake River Plain management zone (table 4) during the 30-year study 

period. Most of that recurrent fire area burned twice (71%) resulting in an average fire return interval of 

15 years for those areas, and the remainder (29%) burned three or more times for an average fire return 

interval of 7.5 years or less. However, an analysis of recurrent fire area as a proportion of total available 

sage-grouse wildland area in the Snake River Plain (16,496,669 ha; appendix 4) indicates that only 6% 

of the total available area was affected by recurrent fire, and 8% of the available Big Sagebrush area 

was affected by recurrent fire. We cannot directly compare our values to those previously reported by 

Whisenant (1989) because that study does not report exactly what proportion of the Snake River Plain 

burned recurrently, only that “large areas” burned every 3–5 years. Finally, the percentage of fire area 

classified as recurrent was the highest for the Columbia Basin (34%), potentially indicating an even 

greater risk of conversion to a grass-fire cycle than the Snake River Plain (with 25% of fire area 

classified as recurrent).
38

Fire Size

Larger fires generally are considered to be of greater ecological concern, although the evidence 

supporting that conclusion is limited and varies among ecosystems (Keane and others, 2008). Historical 

fire sizes in sagebrush ecosystems are poorly understood. Some suggest that infrequent large fires were 

part of historical sagebrush fire regimes (Baker, 2011; Bukowski and Baker, 2013), although others 

suggest that the sizes of sagebrush fires during recent decades may be unprecedented (Keane and others,

2008). In terms of conservation efforts for the greater sage-grouse, it is arguably less important to know 

how current fire sizes compare to historical, than it is to understand how current fire sizes affect the 

species and its current remaining habitat. 

One of the greatest concerns with large sagebrush fires is that, as fire size increases, so too does 

the dispersal distance that is required for seeds of non-resprouting native sagebrush species to reach 

ever-larger interiors of burned landscapes. Fire behavior in larger fires also may generate higher 

temperatures and more complete burning, leaving fewer patches of unburned vegetation that could 

otherwise serve as seed sources in the fire perimeter, thus further reducing capacity for recolonization of 

native species.

The higher proportions of larger fires that we report in the Northern Great Basin, Snake River 

Plain, and Southern Great Basin, and the increasing trend in fire area in the western region, are 

additional cause for concern. Miller and others (2011) also reported increasing fire size for the Southern 

Great Basin, but not for the other two regions. Baker (2013) did not analyze fire size directly, but did 

compare the top fire years in sagebrush vegetation types in the Western United States based on area 

burned among two consecutive 12-year periods (1985–1996, 1997–2008), and suggested that fire sizes 

may be increasing. Balch and others (2013) reported that a large proportion (39 of 50) of the largest 

fires that occurred in the Great Basin during 1980–2008 were associated with cheatgrass and, along with 

other evidence, they suggested this represented conversion to a grass/fire cycle in that region. Analysis 

of recent fire data across a broader array of ecosystem types also have suggested fire size has increased 

with time throughout most ecoregions of the Western United States (Dennison and others, 2014).

Fire Rotation

Fire rotation has great importance for the sustainability of sagebrush ecosystems, particularly if 

rotations are too short for sagebrush plants to regenerate and provide adequate habitat conditions for 

sage-grouse and other sagebrush-dependent species. Most sagebrush species generally are slow to 

recover after fire, due to limited seed dispersal, inability to resprout, and poor seed viability (Young and 

Evans, 1989; Miller and others, 2011). Thus, if fire rotations are too short (even without the influence of 

cheatgrass), many sagebrush stands would be unable to persist or to develop to mature stages (Lesica 

and others, 2007).

Estimates of historical fire rotation in sagebrush communities have varied widely, depending on 

community type, location, methods used, and assumptions made. Many previous studies focused on 

sagebrush-woodland ecotones, using fire-scarred trees to estimate fire return intervals for adjacent 

sagebrush stands. However, such estimates assume that fire behavior and history at these ecotones are 

consistent with those of broad expanses of shrubland and steppe that characterize sagebrush vegetation 

types. This assumption could result in biased fire rotation estimates that are uncharacteristic of most 

sagebrush communities. For instance, dated fire scars on trees that were used to estimate that fire 

rotation for mountain big sagebrush stands in Oregon were as short as 15 years or less (Miller and Rose,

1999), whereas a similar study suggested sagebrush fire rotations generally were decades or longer 

depending on biophysical conditions (Miller and Heyerdahl, 2008). Other studies have documented that 

at least a few to several decades are required for sagebrush ecosystems to recover after fire (for 
39

example, Welch and Criddle, 2003; Lesica and others, 2007), which would suggest even longer mean 

fire rotations are required to maintain a dominance of mature sagebrush communities on the broader 

landscape (Baker, 2006; Lesica and others, 2007). Supporting this notion, Bukowski and Baker (2013) 

used historical General Land Office Survey data from the late 1800s to early 1900s that documented fire 

evidence and vegetation types for large areas of the Western United States, and estimated that historical 

fire rotations were 171–342 and 137–217 years for Wyoming Big Sagebrush and Mountain Big 

Sagebrush, respectively.

Our estimates of modern rotations are not entirely comparable to other fire studies that focused 

on estimating modern rotations in sagebrush ecosystems. Estimates among studies vary, in part, due to 

differences in fire period (this study had a slightly longer temporal extent than other studies), 

geographic/vegetation delineations, vegetation datasets, and quantitative approaches used. For instance, 

our estimate of the modern fire rotation for Black/Low Sagebrush is 134 years for the Northern Great 

Basin, whereas Baker’s (2013) estimates for Dwarf/Xeric Sagebrush and Low Sagebrush types (the 

most similar to our Low/Black Sagebrush type) in that region were 168 and 231 years, respectively.

However, there also were similarities. Baker’s (2013) estimate of modern fire rotation for Big 

Sagebrush Shrubland and Steppe in the Wyoming Basin and the Snake River Plain was very similar to 

our Big Sagebrush rotation estimates of 78 and 1,017 years in those two regions, respectively.

Despite these differences, the key issue is whether contemporary fire rotations for sagebrush

communities are different from historical rotations, and whether differences between the two periods 

suggest rotations are either moving away from or are already outside of their historical ranges of 

variability. To make this assessment, we generally were hindered by a lack of historical fire rotation 

estimates for the different vegetation types among different regions. However, we can draw a few 

tentative conclusions based on estimates we do have of historical fire rotations for big sagebrush 

communities in different regions as presented in Baker (2013) and Bukowski and Baker (2013). For Big 

Sagebrush in the western region, our calculated modern fire rotations for all management zones (61–150 

years across the entire region) likely represent a substantial reduction compared to historical fire 

rotations, which were estimated to be 171–342 (Bukowski and Baker, 2013). In contrast, the very long 

fire rotations (445–1,017 years) calculated for Big Sagebrush in the eastern region could suggest just the 

opposite trend, although credible historical fire rotation estimates for Big Sagebrush communities in this 

region are largely lacking. Black/Low Sagebrush fire rotations are more difficult to assess relative to 

historical rotation estimates. If compared to Baker’s (2013) estimates for Dwarf/Xeric Sagebrush 

ecosystems, they are considerably shorter in the western region (potentially by a factor of 10 or greater),

but they may be similar to historical fire rotations in the eastern region. However, this comparison is 

complicated by the disparities in vegetation types used between the two studies, as well as a paucity of 

empirically derived historical rotation estimates for low sagebrush in particular and sagebrush in the 

eastern region in general. 

Fire Season

Fire season is a variable that is rarely analyzed in the scientific literature, partly because it has no 

standardized definition. However, a few studies have analyzed changes in large fire seasons over time 

across the Western United States. Westerling and others (2006) documented a trend toward longer fire 

seasons and earlier large fire start dates at higher elevations that were correlated with earlier spring 

snowmelt, while Dennison and others (2014) did not find significant trends in large fire start dates 

between 1984 and 2011 across large ecoregions of the Western United States. However, neither of these 

studies focused on data from sagebrush-dominated landscapes as we have here. 
40

In this study we define fire season as beginning with the first large fire (≥405 ha) and ending 

with the last large fire each year. Although this specific fire size is predetermined solely based on the 

reporting parameters of the MTBS program, we provide some evidence in the section “Methods”

suggesting that fires above this general size may represent greater threats to the greater sage-grouse than 

do smaller fires (for example Coates and others, 2015). In addition, most of the annual area burned is 

due to large fires, and larger fires are thought to have greater ecological effects, especially for sagegrouse populations, as explained in the section, “Discussion” on fire size.

Fire seasons typically are reported in very broad terms, such as “summer-early fall” which was 

reported for sagebrush landscapes in northeastern California (Riegel and others, 2006) and peak fire 

season is reported as June–September throughout much of our study area (Littell and others, 2009; 

table 1). The beginning and ending dates that we reported occurred in May and June through September 

and October, and are fairly comparable to these previous studies, although those previous studies do not 

provide specific definitions for what constitute the beginning and ending of the fire season.

Changes in fire season lengths were significant for three of the management zones in this study, 

somewhat differing from the findings of Dennison and others (2014) which did not find a trend toward 

fires beginning earlier in the season, perhaps due to our more specific focus on sagebrush dominated 

landscapes. The increasing fire season length that we reported in the Southern Great Basin might be of 

primary concern, considering the relatively low resilience/resistance of that management zone. In 

contrast, increasing fire season length in the Great Plains may be considered a potential positive 

development, considering the apparent lack of fire compared to historical conditions, especially in 

Grassland vegetation of that management zone.

Fire Threats Assessment for Greater Sage-Grouse Habitat

Plants do not evolve in response to fire per se, but rather to the spatial and temporal patterns of 

fire, which are referred to as a fire regime (Pausas and Keeley, 2009). Some individual fire regime 

variables reported in this study may provide more information than others relative to the threats fire

pose to vegetation. However, any single variable does not provide as much information as do all 

variables considered together. 

We combined our various results of spatial and temporal patterns of fire reported in this study 

into an overall fire threats assessment. This assessment is focused on the implications of fire patterns on 

sage-grouse habitat, defined as vegetation types that contain sagebrush as a dominant or subdominant 

component. It is specifically related to landscape resilience to fire and resistance to annual grass 

invasion as inferred from soil temperature and moisture regimes (Campbell, 2014) and the general fire 

ecology literature. The assessment was not intended to specifically evaluate potential threats that fire 

may pose to greater sage-grouse population vital rates. That type of analysis ideally requires models 

linking direct and indirect effects of fire with demographic characteristics of greater sage-grouse 

populations linked through intermediate pathways (see Coates and others, 2015, for an example). 

Nevertheless, understanding the implications of fire patterns over the past 30 years on sagebrush habitat 

is clearly and important component of conservation plans for the greater sage-grouse.
41

The fire threats assessment clearly indicates that threats are higher in the four western

management zones than in the three eastern management zones (table 11), which are cause for concern 

in the western region of sage-grouse range. Among the four western zones, the Snake River Plain and 

the Columbia Basin ranked somewhat higher than the Southern Great Basin and Northern Great Basin

in terms of their effects on sage-grouse habitat. Overall, our findings corroborate a recent demography 

study using a subset of same fire data in the western region of sage-grouse range and was published in 

parallel with the current report. Specifically, Coates and others (2015) studied annual patterns of 

wildfire, variation in precipitation, and soil conditions over 30 years to evaluate how these factors

influence sage-grouse population vital growth rates using lek count data. The amount of area burned 

near sage-grouse leks, which is typically dominated by sagebrush communities, has adverse and longlasting effects on sage-grouse population growth. Importantly, fire near leks nullifies increases in 

population growth that are normally associated with periods of high precipitation. Thus, loss of 

sagebrush habitat through increasing wildfire, especially in low resilient and resistant systems as 

supported by our analysis, offer an explanation for long-term negative impacts of wildfire on sagegrouse populations. Their models also projected that approximately one-half of the current population of 

sage-grouse will remain in the Great Basin by the mid-2040s if current fire trends continue unabated. 

Collectively, this report and our findings clearly illustrate how sage-grouse habitat and their population 

persistence may be compromised as sagebrush ecosystems become more impacted by fire, and 

increasingly invaded by annual grasses, at least in the western portion of the species’ range. Thus, the 

high rankings we report here for fire threats in the western region (table 11) support the previous high 

ranking of fire as a threat to the greater sage-grouse in that region (U.S. Fish and Wildlife Service,

2005). In contrast, considering the low rankings that we report for fire threats in the eastern region 

(table 11), it may be useful to reconsider the relative importance of wildfire as a threat to greater sagegrouse in those three management zones where it currently ranks among the top 5 of 19 total threats 

(U.S. Fish and Wildlife Service, 2005).

This threats assessment can be customized to include any subset of the multiple fire regime 

categories by simply adding them and recomparing the management zones. However, doing so in 

various combinations does not change the difference between the western and eastern regions, and only 

slightly changes differences among the western zones. Thus, we feel this threats assessment is a fairly 

robust summary of the overall implications of the fire patterns reported in this study.
42

Table 11. Fire threats assessment on a scale from low to high (0–4) in nine regime categories.

[Ranking of amount of fire area and fire recurrence are based on both absolute values among management zones and relative values in each zone. Increasing 

annual amount, proportion, and length are each based on the one-tailed test of increasing trends during the 30-year study period. Deviation from historical is 

based on comparisons with the literature. Fire season length was not included in this assessment because there were no historical baselines to compare it with]

Management 

Zone

Fire area 

(amount in

low resilience

/resistance areas)

Fire area 

(percentage of available in 

low resilience/resistance 

areas)

Fire area

(increasing annual 

amount in low 

resilience/resistance 

areas)

Fire recurrence

(amount in low 

resilience/resistance 

areas)

Fire recurrence

(percentage in low 

resilience/resistance 

areas)

Western Region 

Columbia Basin 2 4 3 3 4

Northern Great Basin 3 2 0 2 1

Snake River Plain 4 3 4 4 3

Southern Great Basin 3 2 0 2 2

Eastern Region

Colorado Plateau 0 0 0 0 0

Great Plains 0 1 0 0 1

Wyoming Basin 1 0 0 0 0

Location of Information Used for Ranking

Tables 3, 7; Appendixes 

10, 11

Tables 3, 7; Appendixes 

10, 11

Figs. 6, 9; Appendixes 

10, 11

Tables 4, 8; Appendixes 

10, 11

Tables 4, 8; Appendixes 

10, 11
43

Fire size

(higher proportion of 

fire areas in larger fires)

Fire size

(increasing proportion 

of fire area in larger 

fires)

Fire rotation 

(deviation from 

historical)

Fire season (increasing 

annual length in low 

resilience/resistance areas)

Cumulative Fire 

Threat Score

Western Region 

Columbia Basin 1 4 4 0 25 

Northern Great Basin 4 4 2 0 18

Snake River Plain 3 4 4 0 29

Southern Great Basin 2 4 2 2 19

Eastern Region

Colorado Plateau 0 0 0 0 0

Great Plains 1 0 0 0 3

Wyoming Basin 0 0 0 1 2

Location of Information Used for Ranking

Figs. 6, 11 Figs. 8, 12 Tables 5, 9 Figs. 8,11; Appendixes 10, 

11

sum of individual 

categories
44

Acknowledgments

We thank M. Reeves, M. Rollins, and J. Yee who provided helpful reviews of earlier drafts of 

this report. 

References Cited

Abatzoglou, J.T., and Kolden, C.A., 2013, Relationships between climate and macroscale area burned in 

the western United States: International Journal of Wildland Fire, v. 22, p. 1003–1020.

Agee, J., 1993, Fire ecology of Pacific Northwest forests: Washington, D.C., Island Press, 493 p.

Baker, W.L., 2006, Fire and restoration of sagebrush ecosystems: Wildlife Society Bulletin, no. 34, p. 

177–185.

Baker, W.L., 2009, Fire ecology in Rocky Mountain landscapes: Washington, D.C, Island Press, 632 p.

Baker, W.L., 2011, Pre-EuroAmerican and recent fire in sagebrush ecosystems, in Knick, S.T., and

Connelly, J.W., eds., Ecology and conservation of greater sage-grouse—A landscape species and its 

habitats: Studies in Avian Biology, v. 38, p. 185–201.

Baker, W.L., 2013, Is wildland fire increasing in sagebrush landscapes of the western United States?, 

Annals of the Association of American Geographers, v. 103, issue 1, p. 5-19.

Balch, J.K., Bradley, B.A., D'Antonio, C.M., and Gómez-Dans, J., 2013, Introduced annual grass 

increases regional fire activity across the arid western USA (1980–2009): Global Change Biology, v. 

19, p. 173–183.

Baruch-Mordo, S., Evans, J.S., Severson, J.P., Naugle, D.E., Maestas, J.D., Kiesecker, J.M., Falkowski, 

M.J., Hagen, C.A., and Reese, K.P., 2013, Saving sage-grouse from the trees—A proactive solution to 

reducing a key threat to a candidate species: Biological Conservation, v. 167, p. 233–241.

Benjamini, Y., and Yekutieli, D., 2001, The control of the false discovery rate in multiple testing under 

dependency: Annals of Statistics, v. 29, p. 1165–1188.

Blomberg, E.J., Sedinger, J.S., Atamian, M.T., and Nonne, D.V., 2012, Characteristics of climate and 

landscape disturbance influence the dynamics of greater sage-grouse populations: Ecosphere, v. 3, 

issue 6, article 55.

Bowman, D.M.J.S., MacDermott, H.J., Nichols, S.C., and Murphy, B.P., 2014, A grass-fire cycle 

eliminates an obligate-seeding tree in a tropical savanna: Ecology and Evolution, v. 4, p. 4184–4194.

Bradford, J.B., and Lauenroth, W.K., 2006, Controls over invasion of Bromus tectorum—The 

importance of climate, soil, disturbance and seed availability: Journal of Vegetation Science, 

v. 17, p. 693–704.

Bradley, B.A., 2009, Regional analysis of the impacts of climate change on cheatgrass invasion shows 

potential risk and opportunity: Global Change Biology, v. 15, p. 196–208.

Brooks, M.L., 2008, Plant invasions and fire regimes, in Zouhar, K., Kapler Smith, J. Sutherland, S.,

and Brooks, M.L., eds., Wildland fire in ecosystems—Fire and nonnative invasive plants: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station, Ogden, Utah, RMRSGTR-42-volume 6, p. 33–46.

Brooks, M.L., Brown, C.S., Chambers, J.C., D’Antonio, C.M., Keeley, J.E., and Belnap J., in press,

Exotic annual Bromus invasions—Comparisons among species and ecoregions in the Western United 

States, in Germino, M.J., Chambers, J.C., and Brown, C.S., eds., Exotic brome-grasses in arid and 

semi-arid ecosystems of the Western United States—Causes, consequences and management 

implications: Springer Press.
45

Brooks, M.L., D'Antonio, C.M., Richardson, D.M., Grace, J.B., Keeley, J.E., DiTomaso, J.M., Hobbs, 

R.J., Pellant, M., and Pyke, D., 2004, Effects of invasive alien plants on fire regimes: Bioscience, v.

54, p. 677–688.

Brooks, M.L., and Pyke, D., 2001, Invasive plants and fire in the deserts of North America, in Galley,

K., and Wilson, T., eds., Proceedings of the Invasive Species Workshop—The Role of Fire In the 

Control and Spread of Invasive Species. Fire Conference 2000—The First National Congress on Fire 

Ecology, Prevention, and Management, Miscellaneous Publications No. 11, Tall Timbers Research 

Station, Tallahassee, Florida, p. 1–14. 

Bukowski, B.E., and Baker, W.L., 2013, Historical fire regimes, reconstructed from land-survey data, 

led to complexity and fluctuation in sagebrush landscapes: Ecological Applications, v. 23, p. 546–

564.

Bunting, S.C., Kilgore, B.M., and Bushey, C.L., 1987, Guidelines for prescribed burning sagebrushgrass rangelands in the northern Great Basin: U.S. Department of Agriculture, Forest Service, 

Intermountain Research Station, Ogden, Utah, General Technical Report INT-231, 33 p.

Campbell, S.B., 2014, Soil temperature and moisture regime data for the range of greater sage-grouse—

Data product: USDA Natural Resources Conservation Service, Portland, Oregon, Web site, accessed 

February 2, 2015, at

https://www.sciencebase.gov/catalog/folder/537f8be5e4b021317a872f1b?community=LC+MAP+-

+Landscape+Conservation+Management+and+Analysis+Portal.

Casazza, M.L., Coates, P.S., and Overton, C.T., 2011, Linking habitat selection and brood success in 

greater sage-grouse, in Sandercock, B.K., Martin, K., and Segelbacher, G., eds., Ecology, 

conservation, and management of grouse—Studies in avian biology (no. 39): Berkeley, University of 

California Press, p. 151–167.

Chambers, J.C., 2008, Fire and the Great Basin. in Chambers, J. C., Devoe, N., and Evenden, A., eds.,

Collaborative management and research in the Great Basin—Examining the issues and developing a 

framework for action: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research 

Station, Fort Collins, Colorado, General Technical Report RMRS-GTR-204, p. 33–37.

Chambers, J.C., Bradley, B.A., Brown, C.S., D’Antonio, C., Germino, M.J., Grace, J.B., Hardegree, 

S.P., Miller, R.F., and Pyke, D.A., 2014a, Resilience to stress and disturbance, and resistance to 

Bromus tectorum L. invasion in cold desert shrublands of western North America: Ecosystems, v. 17, 

no. 2, p. 360–375.

Chambers, J.C., Pyke, D.A., Maestas, J.D., Pellant, M., Boyd, C.S., Campbell, S.B., Espinosa, S., 

Havlina, D.W., Mayer, K.E., and Wuenschel, A., 2014b, Using resistance and resilience concepts to 

reduce impacts of invasive annual grasses and altered fire regimes on the sagebrush ecosystem and 

greater sage-grouse—A strategic multi-scale approach: U.S. Department of Agriculture, Forest

Service, Rocky Mountain Research Station, Fort Collins, Colorado, General Technical Report RMRSGTR-326, 73 p.

Chambers, J.C., Roundy, B.A., Blank, R.R., Meyer, S.E., and Whittaker, A., 2007, What makes Great 

Basin sagebrush ecosystems invasible by Bromus tectorum? Ecological Monographs, v. 77, 

no. 1, p. 117145.

Coates, P.S., Ricca, M.A., Prochazka, B.G., Doherty, K.E., Brooks, M.L., and Casazza, M.L., 2015, 

Long-term effects of wildfire on greater sage-grouse—Integrating population and ecosystem concepts

for management in the Great Basin: U.S. Geological Survey Open-File Report 2015–1165, 42 p.,

http://dx.doi.org/10.3133/ofr20151165.

Connelly, J.W., Reese, K.P., Fischer, R.A., and Wakkinen, W.L., 2000, Response of a sage grouse 

breeding population to fire in southeastern Idaho: Wildlife Society Bulletin, v. 28, p. 90–96.
46

Connelly, J.W., Knick, S.T., Schroeder, M.A., and Stiver, S.J., 2004, Conservation assessment of 

greater sage-grouse and sagebrush habitats: Western Association of Fish and Wildlife Agencies,

Cheyenne, Wyoming, http://sagemap.wr.usgs.gov/docs/Greater_Sagegrouse_Conservation_Assessment_060404.pdf.

D'Antonio, C.M., and Vitousek, P.M., 1992, Biological invasions by exotic grasses, the grass/fire cycle, 

and global change: Annual Review of Ecology and Systematics, v. 23, p. 63–87.

Davis, D.M., and Crawford, J.A. 2015, Case study: Short-term response of greater sage-grouse habitats 

to wildfire in mountain big sagebrush communities: Wildlife Society Bulletin, v. 39, issue 1, 

p. 129-137.

Dennison, P.E., Brewer, S.C., Arnold, J.D., and Moritz, M.A., 2014, Large wildfire trends in the 

western United States, 1984–2011, Geophysical Research Letters, v. 41, doi:10.1002/2014GL059576.

Eidenshink, J., Schwind, B., Brewer, K., Zhu, Z., Quayle, B., and Howard, S., 2007, A project for 

monitoring trends in burn severity: Fire Ecology, v. 3, p. 3–21.

Fischer, R.A., Reese, K.P., and Connelly, J.W., 1996, An investigation on fire effects within xeric sage 

grouse brood habitat: Journal of Range Management, v. 49, p. 194–198.

Fischer, R.A., Wakkinen, W.L., Reese, K.P., and Connelly, J.W., 1997, Effects of prescribed fire on 

movements of female sage grouse from breeding to summer ranges: The Wilson Bulletin, v. 109, p. 

82–91.

Interagency Greater Sage-Grouse Disturbance and Monitoring Subteam, 2014, The greater sage-grouse 

monitoring framework: Bureau of Land Management and U.S. Forest Service, 47 p., 

https://eplanning.blm.gov/epl-front-office/projects/lup/21152/48421/52584/GRSG-FINALMonitoring_Framework_20140530.pdf.

Hanser, S.E., and Manier, D.J., 2013, Greater Sage-Grouse National Research Strategy: U.S. Geological 

Survey Scientific Investigations Report 2013-5167, 46 p. plus appendix.

Jolly, W.M., Cochrane, M.A., Freeborn, P.H., Holden, Z.A., Brown, T.J., Williamson, G.J., and 

Bowman, D.M.J.S., 2015, Climate-induced variations in global wildfire danger from 1979 to 2013:

Nature Communications, v. 6, no. 7537, 11 p.

Keane, R.E., Agee, J.K., Fule, P., Keeley, J.E., Key, C., Kitchen, S.G., Miller, R., and Schulte, L.A.,

2008, Ecological effects of large fires on US landscapes—Benefit or catastrophe?: International 

Journal of Wildand Fire, v. 17, p. 696–712.

Kendall, M.G., 1975, Rank correlation methods (4th ed.): London, Charles Griffin Publishers.

Knick, S.T., and Connelly, J.W., eds., 2011, Greater sage-grouse—Ecology and conservation of a 

landscape species and its habitats—Studies in avian biology (no. 38): Berkeley, University of 

California Press, 664 p.

Knick, S.T., Hanser, S.E., and Preston, K.L., 2013, Modeling ecological minimum requirements for 

distribution of greater sage-grouse leks—Implications for population connectivity across their western 

range, U.S.A: Ecology and Evolution, v. 3, no. 6, p. 1539–1551. 

Knick, S.T., and Rotenberry, J.T., 1997, Landscape characteristics of disturbed shrubsteppe habitats in 

southwestern Idaho (U.S.A.): Landscape Ecology, v. 12, p. 287–297.

Lesica, P., Cooper, S.V., and Kudray, G., 2007, Recovery of big sagebrush following fire in southwest 

Montana: Rangeland Ecology and Management, v. 60, p. 261–269.

Littell, J.S., McKenzie, D., Peterson, D.L., and Westerling, A.L., 2009, Climate and wildfire area 

burned in western U.S. ecoprovinces, 1916–2003: Ecological Applications, v. 19, p. 1003–1021.

Mann, H.B., 1945, Non-parametric tests against trend: Econometrica, v. 13, p. 163–171.
47

Menakis, J.P., Osborne, D., and Miller, M., 2003, Mapping the cheatgrass-caused departure from 

historical natural fire regimes in the Great Basin, USA, in Proceedings, Fire, Fuel Treatments, and 

Ecological Restoration Conference, April 16–18, 2002, Fort Collins, Colorado: USDA Forest Service, 

Rocky Mountain Research Station online publication RMRS-P-29.

Meyer, S.E., Garvin, S.C., and Beckstead, J., 2001, Factors mediating cheatgrass invasion of intact salt 

desert shrubland, in McArthur, D.E., and Fairbanks, D.J., compilers, Proceedings—Shrubland 

ecosystem genetics and biodiversity: Proceedings RMRS-P-21, Ogden UT, U.S. Department of 

Agriculture, Forest Service, Rocky Mountain Research Station, p. 224-232.

Miller, R.F., and Eddleman, L.L., 2001, Spatial and temporal changes of sage grouse habitat in the 

sagebrush biome: Oregon State University, Agricultural Experiment Station, Technical Bulletin 151, 

35 p.

Miller, R.F., and Heyerdahl, E.K., 2008, Fine-scale variation of historical fire regimes in sagebrushsteppe and juniper woodland—An example from California, USA: International Journal of Wildland 

Fire, v. 17, p. 245–254.

Miller, R.F., Knick, S.T., Pyke, D.A., Meinke, C.W., Hanser, S.E., Wisdom, M.J., and Hild, A.L., 2011,

Characteristics of sagebrush habitats and limitations to long-term conservation, in Knick, S.T., and 

Connelly, J.W., eds., Greater sage-grouse—Ecology and conservation of a landscape species and its 

habitats: Berkeley, University of California Press, p. 145–184.

Miller, R.F., and Rose, J.A., 1999, Fire history and western juniper encroachment in sagebrush steppe:

Journal of Range Management, v. 52, p. 550–559.

Miller, R.F., and Tausch, R.J., 2001, The role of fire in pinyon and juniper woodlands—A descriptive 

analysis, in Galley, K.E.M., and Wilson, T.P., eds., Proceedings of the Invasive Species Workshop—

The Role of Fire in the Control and Spread of Invasive Species: Fire Conference 2000—The First 

National Congress on Fire Ecology, Prevention, and Management, Miscellaneous Publication No. 11, 

Tall Timbers Research Station, Tallahassee, Florida,

p. 15–30.

Nelle, P.J., Reese, K.P., and Connelly, J.W., 2000, Long-term effects of fire on sage-grouse habitat:

Journal of Range Management, v. 53, p. 586–591.

Pausas, J.G., and Keeley, J.E., 2009, A burning story—The role of fire in the history of life: Bioscience, 

v. 59, p. 593–601.

Pedersen, E.K., Connelly, J.W., Hendrickson, J.R., and Grant, W.E., 2003, Effect of sheep grazing and 

fire on sage grouse populations in southeastern Idaho: Ecological Modelling, v. 165. p. 23–47.

Ratajczak, Z., Nippert, J.B., Briggs, J.M., and Blair, J.M., 2014, Fire dynamics distinguish grasslands, 

shrublands, and woodlands as alternative attractors in the Central Great Plains of North America:

Journal of Ecology, v. 102, p. 1374–1385.

Rhodes, E.C., Bates, J.D., Sharp, R.N., and Davies, K.W., 2010, Fire effects on cover and dietary 

resources of sage-grouse habitat: Journal of Wildlife Management, v. 74, p. 755–764.
48

Rice, P.M., McPherson, G.R., and Rew, L.J., 2001, Fire and nonnative invasive plants in the Interior 

West Bioregion, in Zouhar, K., Smith, J.K., Sutherland, S., and Brooks, M.L., eds., Wildland fire in 

ecosystems: fire and nonnative invasive plants. Fort Collins, CO, USA: US Department of 

Agriculture, Forest Service, Rocky Mountain Research Station, General Technical Report, 

RMRSGTR-42, v. 6. p. 141–171.

Riegel, G.M., Miller, R.F., Skinner, C.N., and Smith, S.E., 2006, Northeastern plateaus bioregion, in

Sugihara, N.G., van Wagtendonk, J.W., Shaffer, K.E., Fites-Kaufman, J., and Thode, A.E., eds., Fire 

in California’s ecosystem: Berkeley and Los Angeles, University of California Press.

Rollins, M.G., 2009, LANDFIRE—A nationally consistent vegetation, wildland fire, and fuel 

assessment: International Journal of Wildland Fire, v. 18, p. 235–249.

Rossiter, N.A., Setterfield, S.A., Douglas, M.M., and Huntley, L.B., 2003, Testing the grass-fire cycle—

Alien grass invasion in the tropical savannas of northern Australia: Diversity and Distributions, v. 9, 

p. 160–176.

Rowland, M.M., Wisdom, M.J., Suring, L.H., and Meinke, C.W., 2006, Greater sage-grouse as an 

umbrella species for sagebrush-associated vertebrates: Biological Conservation, v. 129, p. 323–335.

Schroeder, M.A., Aldridge, C.L., Apa, A.D., Bohne, J.R., Braun, C.E., Bunnell, S.D., Connelly, J.W.,

Deibert, P.A., Gardner, S.C., Hilliard, M.A., Kobriger, G.D., McAdam, S.M., McCarthy, C.W., 

McCarthy, J.J., Mitchell, D.L., Rickerson, E.V., and Stiver, S.J., 2004, Distribution of sage-grouse in 

North America: The Condor, v. 106, p. 363–376.

Setterfield, S.A., Rossiter-Rachor, N.A., Douglas, M.M., Wainger, L., Petty, A.M., Barrow, P.,

Shepherd, I.J., and Ferdinands, K.B., 2013, Adding fuel to the fire—The impacts of non-native grass 

invasion on fire management at a regional scale: PLoS ONE, v. 8, no. 5, e59144,

doi:10.1371/journal.pone.0059144.

Sparks, A., Boschetti, L., Smith, A., Tinkham, W., Lannom, K., and Newingham, B., 2014, An accuracy 

assessment of the MTBS burned area product for shrub–steppe fires in the northern Great Basin, 

United States: International Journal of Wildland Fire, v. 24, no. 1, p. 70–78.

Stiver, S.J., Apa, A.D., Bohne, J.R., Bunnell, S.D., Deibert, P.A., Gardner, S.C., Hilliard, M.A., 

McCarthy, C.W., and Schroeder, M.A., 2006, Greater sage-grouse comprehensive conservation 

strategy: Cheyenne, Wyoming, Western Association of Fish and Wildlife Agencies, 442 p., 

http://wdfw.wa.gov/publications/01317/wdfw01317.pdf.

Strand, E.K., Bunting, S.C., and Keefe, R.F., 2013, Influence of wildland fire along a successional 

gradient in sagebrush steppe and western juniper woodlands: Rangeland Ecology and Management, v. 

66, p. 667–679.

Sugihara, N.G., van Wagtendonk, J.W., and Fites-Kaufman, J., 2006, Fire as an ecological process, in

Sugihara, N.G., van Wagtendonk, J.W., Shaffer, K.E., Fites-Kaufman, J., and Thode, A.E., eds., Fire 

in California’s ecosystem: Berkeley and Los Angeles, University of California Press.

U.S. Department of the Interior, 2015a, Secretarial Order 3336—Rangeland Fire Prevention, 

Management, and Restoration, accessed August 2015, at 

http://www.fws.gov/greatersagegrouse/documents/Threats/20150106DOI-Fire-Order.pdf. 
49

U.S. Department of the Interior, 2015b, An integrated rangeland fire management strategy—Final report 

to the Secretary of the Interior: Rangeland Fire Task Force, 82 p., 

http://forestsandrangelands.gov/rangeland/.

U.S. Fish and Wildlife Service, 2005, Endangered and threatened wildlife and plants; 12-month finding

for petitions to list the greater sage-grouse as threatened or endangered: Federal Register, v. 70, p.

2244–2282, accessed August 2015, at https://www.federalregister.gov/articles/2005/01/12/05-

583/endangered-and-threatened-wildlife-and-plants-12-month-finding-for-petitions-to-list-the-greater.

U.S. Fish and Wildlife Service, 2010, Endangered and threatened wildlife and plants; 12-month findings 

for petitions to list the greater sage-grouse (Centrocercus urophasianus) as threatened or endangered: 

Federal Register, v. 75, no. 55, p. 13909–14014, accessed August 2015, at

https://www.federalregister.gov/articles/2010/03/23/2010-5132/endangered-and-threatened-wildlifeand-plants-12-month-findings-for-petitions-to-list-the-greater.

Young, J.A., and Evans, R.A., 1989, Dispersal and germination of big sagebrush (Artemisia 319 

tridentata) seeds: Weed Science, v. 37, p. 201–206.

Welch, B.L., and Criddle, C., 2003, Countering misinformation concerning big sagebrush, USDA Forest 

Service, Rocky Mountain Research Station, Fort Collins, Colorado, Research Paper RMRS-RP-40, 

28 p.

Westerling, A.L., Hidalgo, H.G., Cayan, D.R., and Swetnam, T.W., 2006, Warming and earlier spring 

increase Western U.S. forest wildfire activity: Science, v. 313, p. 940–943.

Whisenant, S.G., 1989, Changing fire frequencies on Idaho’s Snake River Plains—Ecological and 

management implications, in McArthur, E.D., Romney, E.M., Smith, S.D., and Tueller, P.T., 

compilers, Proceedings—Symposium on Cheatgrass Invasion, Shrub Die-Off, and Other Aspects of 

Shrub Biology and Management: USDA Forest Service, Intermountain Research Station, Ogden, 

Utah, General Technical Report INT-276, p. 4–10.

White, R.S., and Currie, P.O., 1983, The effects of prescribed burning on silver sagebrush: Journal of 

Range Management, v. 36, p. 611–613.

Wilken, E., Nava, F.J., and Griffith, G., 2011, North American terrestrial ecoregions—Level III:

Montreal, Canada, Commission for Environmental Cooperation.
50

Appendix 1. Crosswalk of Greater Sage-Grouse Management Zones with Other 

Bioregional Classifications

[Floristic Province: Miller and Eddleman (2001); http://greatbasin.wr.usgs.gov/LWG/Floristic_Provinces.asp accessed 

March 16, 2015. Level III Ecoregions: Wilken and others (2011)]

Management Zone Floristic Province Level III Ecoregion(s)

Western Management Zones

Columbia Basin Columbia Basin Columbia Plateau 10.1.2

Northern Great Basin Northern Great Basin Northern Basin and Range 10.1.3

Snake River Plain Snake River Plain Snake River Plain 10.1.8, 

Northern Basin and Range 10.1.3

Southern Great Basin Southern Great Basin Central Basin and Range 10.1.5

Colorado Plateau Colorado Plateau Colorado Plateaus 10.1.6

Western Management Zones

Great Plains Silver Sagebrush Subdivision Northwestern Great Plains 9.3.3, 

Northwestern Glaciated Plains 9.3.1 

Wyoming Basin Wyoming Basin Wyoming Basin 10.1.4
51

Appendix 2. Proportion of Land Ownership in the Greater Sage-Grouse 

Management Zones
52

Appendix 3. Soil Temperature and Moisture Regimes in the Study Area
53

Appendix 4. Aerial Extent of the Major Vegetation Types in the Four Western Management Zones and 

Their Constituent LANDFIRE Biophysical Setting Types That Were Previously Identified as Capable of 

Supporting Sagebrush Vegetation and Providing Suitable Seasonal Habitat for Greater Sage-Grouse in 

the Greater Sage-Grouse Monitoring Framework 

[From Interagency Greater Sage-Grouse Disturbance and Monitoring Subteam (2014, table 4). The first two vegetation types are predominantly sagebrush, 

whereas the latter four are pre-dominantly other plant taxa. All six differ in terms of floristics, fire regimes, and as potential habitat for the greater sage-grouse. 

The Non-Sagebrush type does not contain any sagebrush species as a potential dominant in the constituent biophysical settings descriptions and were not 

previously identified as supporting sagebrush vegetation or greater sage-grouse habitat]

Biophysical Setting

Area (hectares)

Columbia Basin Northern Great 

Basin

Snake River 

Plain

Southern Great 

Basin

Western 

Management 

Zones 

Combined

Big Sagebrush

Inter-Mountain Basins Big Sagebrush Steppe 122,974 2,002,658 5,529,428 38,133 7,693,192

Inter-Mountain Basins Big Sagebrush Shrubland - Wyoming 

Big Sagebrush 0 0 1,124 0 1,124

Inter-Mountain Basins Montane Sagebrush Steppe 19,374 916,680 2,958,342 751,474 4,645,870

Inter-Mountain Basins Big Sagebrush Shrubland 2,594 407,808 970,249 3,078,812 4,459,463

Inter-Mountain Basins Big Sagebrush Shrubland - Basin Big 

Sagebrush 0 0 1,331 0 1,331

Inter-Mountain Basins Montane Sagebrush Steppe - Mountain 

Big Sagebrush 0 0 2,437 545,987 548,425

Black/Low Sagebrush

Great Basin Xeric Mixed Sagebrush Shrubland 0 1,564,488 2,531,070 2,860,024 6,955,582

Columbia Plateau Low Sagebrush Steppe 314 107,706 124,439 12,454 244,913

Inter-Mountain Basins Montane Sagebrush Steppe - Low 

Sagebrush 0 0 13 147,431 147,444

Colorado Plateau Mixed Low Sagebrush Shrubland 0 0 4 60,500 60,505

Wyoming Basins Dwarf Sagebrush Shrubland and Steppe 0 0 0 0 0

Desert Mixed Shrub

Inter-Mountain Basins Mixed Salt Desert Scrub 0 251,235 447,578 1,800,540 2,499,353

Columbia Plateau Scabland Shrubland 105,944 38,562 22,297 0 166,803
54

Biophysical Setting

Area (hectares)

Columbia Basin Northern Great 

Basin

Snake River 

Plain

Southern Great 

Basin

Western 

Management 

Zones 

Combined

Inter-Mountain Basins Semi-Desert Shrub-Steppe 4 7,755 20,815 59,491 88,064

Floodplain

Western Great Plains Floodplain Systems 0 41 0 41

Grassland

Northwestern Great Plains Mixed Grass Prairie 0 0 183 0 183

Northwestern Great Plains Shrubland 0 0 705 0 705

Columbia Plateau Steppe and Grassland 540,127 189,684 79,839 0 809,650

Western Great Plains Sand Prairie 0 0 0 0 0

Mountain Brush

Inter-Mountain Basins Curl-leaf Mountain Mahogany 

Woodland and Shrubland 26 40,836 111,101 330,203 482,166

Rocky Mountain Gambel Oak-Mixed Montane Shrubland 0 0 34 11,996 12,030

Rocky Mountain Lower Montane-Foothill Shrubland 0 0 20,576 33,091 53,667

Non-Sagebrush

remaining biophysical setting types combined 115,513 2,202,923 3,675,063 4,785,702 10,779,201
55

Appendix 5. Aerial Extent of the Major Vegetation Types in the Three Eastern Management Zones and 

Their Constituent LANDFIRE Biophysical Setting Types That Were Previously Identified as Capable of 

Supporting Sagebrush Vegetation and Providing Suitable Seasonal Habitat for Greater Sage-Grouse in 

the Greater Sage-Grouse Monitoring Framework. 

[From Interagency Greater Sage-Grouse Disturbance and Monitoring Subteam (2014, table 4). The first two vegetation types are predominantly sagebrush, 

whereas the latter four are pre-dominantly other plant taxa. All six differ in terms of floristics, fire regimes, and as potential habitat for the greater sage-grouse. 

The Non-Sagebrush type does not contain any sagebrush species as a potential dominant in the constituent biophysical settings descriptions and were not 

previously identified as supporting sagebrush vegetation or greater sage-grouse habitat]

Biophysical Setting

Area (hectares)

Colorado Plateau Great Plains Wyoming Basin

Eastern 

Management

Zones Combined

Big Sagebrush

Inter-Mountain Basins Big Sagebrush Steppe 25,365 2,583,626 165,868 2,774,859

Inter-Mountain Basins Big Sagebrush Shrubland - Wyoming Big 

Sagebrush 0 69,807 7,825,217 7,895,024

Inter-Mountain Basins Montane Sagebrush Steppe 963 188,443 1,913,463 2,102,869

Inter-Mountain Basins Big Sagebrush Shrubland 66,914 350 614,627 681,892

Inter-Mountain Basins Big Sagebrush Shrubland - Basin Big Sagebrush 0 763 632,059 632,822

Inter-Mountain Basins Montane Sagebrush Steppe - Mountain Big 

Sagebrush 22,703 0 300,556 323,259

Black/Low Sagebrush

Colorado Plateau Mixed Low Sagebrush Shrubland 14,085 0 14,986 29,071

Columbia Plateau Low Sagebrush Steppe 0 0 1,336 1,336

Great Basin Xeric Mixed Sagebrush Shrubland 0 0 12 12

Inter-Mountain Basins Montane Sagebrush Steppe - Low Sagebrush 130 0 12,868 12,999

Wyoming Basins Dwarf Sagebrush Shrubland and Steppe 0 1,464 2,819 4,282

Desert Mixed Shrub

Inter-Mountain Basins Mixed Salt Desert Scrub 28,054 17 0 28,070

Columbia Plateau Scabland Shrubland 0 0 199,057 199,057

Inter-Mountain Basins Semi-Desert Shrub-Steppe 84 22 7,330 7,436
56

Biophysical Setting

Area (hectares)

Colorado Plateau Great Plains Wyoming Basin

Eastern 

Management

Zones Combined

Floodplain

Western Great Plains Floodplain Systems 0 828,117 64,886 893,003

Grassland

Northwestern Great Plains Mixed Grass Prairie 0 12,440,726 344,383 12,785,109

Northwestern Great Plains Shrubland 0 1,000,166 3,798 1,003,965

Columbia Plateau Steppe and Grassland 0 0 0 0

Western Great Plains Sand Prairie 0 183,137 10,984 194,122

Mountain Brush

Inter-Mountain Basins Curl-leaf Mountain Mahogany Woodland and 

Shrubland 918 11,046 23,535 35,500

Rocky Mountain Gambel Oak-Mixed Montane Shrubland 143,034 0 246,919 389,953

Rocky Mountain Lower Montane-Foothill Shrubland 6,811 18,763 61,718 87,292

Non-Sagebrush

remaining biophysical setting types combined 382,977 2,213,457 4,980,614 7,577,048
57

Appendix 6. Crosswalk of Soil Temperature and Moisture Regimes with 

Potential Resilience to Fire and Resistance to Annual Grass Invasion

[Temperature and moisture regime class: From Campbell (2014). Potential resilience and resistance gradient: Derived 

from information in Meyer and others, 2001; Bradford and Lauenroth, 2006; Chambers and others, 2007, 2014a, 2014b; and 

Bradley, 2009]

Common name

Temperature and moisture 

regime class

Potential resilience and 

resistance gradient

Cold Cryic highest

Cool and Moist (summer) Frigid/Ustic intermediate

Cool and Moist (winter) Frigid/Xeric intermediate

Warm and Moist (summer) Mesic/Ustic intermediate

Warm and Moist (winter) Mesic/Xeric intermediate

Cool and Dry Frigid/Aridic intermediate

Warm and Dry Mesic/Aridic lowest
58

Appendix 7. Proportions of Total Available Area Represented by Each Soil 

Temperature and Moisture Regime Class in Each Vegetation Type Rangewide 

and in the Eastern and Western Regions
59

Appendix 8. Limitations of Fire Point Occurrence, Burn Severity, and Fire 

Perimeter Data

Fire data are typically available in point occurrence, burn severity, and fire perimeter formats. 

Point occurrence data include various attributes included in fire agency reports (size, cause, dates, etc.),

which are typically georeferenced to the estimated point of origin of a fire. Many older records only 

reference the fire location using the Public Land Survey System (that is, township, range, section), and 

early electronic databases limited the spatial resolution at which locations were recorded, resulting in 

points being snapped to a regularly spaced grid. Burn severity data are derived using satellite imagery 

and stored in raster format at the pixel resolution associated with the satellite sensors they were derived 

from. Burn severity is estimated using satellite-sensor evidence of fire consumption rates of both living 

and dead plants which are used to infer fire severity or the magnitude of the effect that fire has on the 

environment (Sugihara and others, 2006). Fire perimeter data were traditionally produced by sketching 

estimated fire boundaries onto paper maps, manually interpreting them from aerial photographs, or 

connecting a series of GPS points generated by walking or flying around the fire perimeter. More 

recently, fire perimeters have been generated by digitizing raster-based imagery, especially burn 

severity data. Each of these source of fire data have their limitations that must be fully understood to 

avoid inappropriate uses. Some of their primary limitations are described below, in addition to our 

reasoning for only utilizing one type in this study, specifically fire perimeter data derived from rasterbased satellite imagery.

Limitations of Fire Point Occurrence Data

Point occurrence data have the advantage of encompassing all fires, regardless of size. However, 

they have many characteristics that limit their utility. Although point data may be relatively complete 

for areas under Federal jurisdiction, they are often less complete for other areas, especially private lands. 

Thus, as the spatial scope of an area increases encompassing multiple management types (for example

Federal, State, local, and private jurisdictions), so too does the internal consistency of the point 

occurrence data. The wide range of proportions of governmental lands versus private lands among the 

management zones in this study (appendix 2) would confound comparisons among these zones if point 

data were to be used. The areas associated with each fire record also are only estimates of total fire area 

and not actual burned area, because unburned inclusions are not quantified. The methodologies used to 

estimate fire area can vary among fires and among years based on variable reporting standards and 

evolving technologies. Reported fire areas can sometimes: (1) alternatively represent the containment 

area rather than actual fire area; (2) extend to include outlying spots as contiguous in the fire 

boundaries; (3) be incomplete and estimated before the end of burning; and (4) be reported only in 

public agency boundaries. Point data also often contain errors associated with the initial recording, or 

subsequent transcription from paper to electronic records, of the point of origin of a fire. Point datasets 

also can contain redundancies, such as the same fire being reported by multiple responding agencies that 

can affect derived statistics such as fire area. Additionally, because points are one dimensional, the area 

they conceptually represent can not be readily parsed using other fine-scale spatial data (for example

vegetation types or soil temperature and moisture regimes). The most comprehensive and annually 

updated online source of point data in the Western United States is the Federal Wildland Fire 

Occurrence database (http://wildfire.cr.usgs.gov/firehistory/data.html), and the metadata for these point 

data contain explicit warnings regarding potential errors and limitations of their use.
60

Limitations of Burn Severity Data

Burn severity data have the advantage of providing precise estimates of actual burned area based 

on the resolution of the satellite sensors. These data are generated on a continuous scale, which is often 

summarized into thematic severity classes (for example unburned-to-low, low, moderate, high). 

However, these data have significant limitations, mostly notably associated with inferring burn severity 

levels from satellite sensor data. It also can be problematic to translate burn severity data that are based 

largely on estimates of fuel consumption into fire severity estimates, which represents the ecological 

effects of fire on plant and animal populations and communities, soil characteristics, etc. Additional 

limitations of burn severity data are discussed in the following section on fire perimeter data as they 

relate to distinguishing between unburned-to-low and other burn severity classes. 

The most comprehensive and consistent source of burn severity data in the United States is 

produced by the Monitoring Trends in Burn Severity (MTBS) program (http://www.mtbs.gov/). The 

MTBS program produces burn severity mapping products based on Landsat satellite imagery at 30 m ×

30 m resolution dating back to 1984 (Eidenshink and others, 2007). This database includes the majority 

of fires ≥405 ha (1,000 acres) that have occurred in the Western United States. Various fire reports and 

other records from Federal and State sources are used by MTBS program staff to guide their searches 

for fire perimeters on satellite imagery. Thus, although the MTBS data focus on large fires that occur on 

Federal lands, they also include most large fires on State lands. The MTBS database also includes many 

large fires that occur on private lands because large fires typically involve some response by Federal or 

State fire suppression agencies, in turn generating a fire report likely captured by MTBS.

Limitations of Fire Perimeter Data

In the past, fire perimeters were generated by relatively imprecise, inaccurate, and variable 

methods, but more recently the perimeters have been digitized by the MTBS program from more precise 

and accurate raster imagery using standardized methods for the entire United States. The MTBS 

perimeter data have far less limitations compared to those described above for point occurrence data, but 

because they are based on burn severity data, they are limited by most of the same issues associated 

with that technology. 

Virtually all fires have some degree of unburned and partially or lightly burned (that is, low 

severity) inclusions in their outer perimeter. The term “fire area” rather than “burned area” is sometimes 

used in reference to the area in a fire perimeter to emphasize that it is not necessarily all burned. An 

MTBS fire record contains a thematic burn severity raster that includes an unburned-to-low class, which 

could be removed to potentially generate a more precise calculation of actual burned area in a fire 

perimeter. This approach is designed to reduce errors of commission, which occur when assuming a 

pixel in a perimeter was burned when it really was not burned. At least one recent study of fire patterns 

in the Western United States adopted this approach to reduce errors of commission (Abatzoglou and 

Kolden, 2013). However, this approach can lead to equally concerning errors of omission, which occur 

when assuming a pixel was unburned when it really was burned. Both of these types of errors can occur 

in MTBS burn severity products, or derivations of them.

A recent study by Sparks and others (2014) evaluated burned/unburned classification accuracies 

of MTBS products compared with visual interpretations of false color Landsat composites. The focus 

was on four fires in sagebrush steppe in the Northern Great Basin that ranged in the degree to which 

they had unburned inclusions. One fire had few actual unburned inclusions, another had some unburned 

areas, and the other two had many unburned areas. The MTBS fire product with few unburned 

inclusions had 98% accuracy, with 4% errors of commission and 5% errors of omission of burned areas 

(Sparks and others, 2014, table 1). The other three fire perimeters for fires with moderate to high 
61

amounts of unburned area had 94–97% accuracy, with 8–16% errors of commission and 5–8% errors off 

omission of burned areas. Adjusting the MTBS fire perimeters by removing unburned inclusions 

(unburned-to-low thematic class) decreased errors of commission, but increased errors of omission, 

resulting in negligible changes in overall accuracy (Sparks and others, 2014). The take home message 

was that attempts to increase precision of burned area estimates by removing unburned-to-low pixels 

may not substantially improve overall accuracy in sagebrush steppe, and may simply replace 

overestimates with underestimates of fire area.

The accuracy of burn severity products also can differ greatly among those derived from postfire satellite imagery taken 1 month, 1 year, and 2 years post-fire (Strand and others, 2013, table 2). In 

sagebrush steppe, a significant correlation of severity estimates with on-the-ground composite burn 

index (CBI) values was only observed for imagery captured within a month following the fire, and not 

with imagery from 1 or 2 years post-fire (Strand and others, 2013). It was explained that in areas burned 

at low to moderate severity in sagebrush steppe, the regrowth of vegetation during the initial growing 

seasons following fire can produce enough biomass to look very similar to unburned areas, and 

therefore be classified as such using imagery captured 1 or 2 years post-fire. The implications are that 

burn severity products generated using post-fire imagery beyond the growing season in which the fire 

occurred may include substantial misclassifications of actual burned pixels as being unburned, leading 

to increased errors of omission. 

MTBS protocols call for using post-fire imagery from the current growing season (called an 

“initial assessment”) when a fire occurs primarily in herbaceous and/or non-resprouting shrubland

vegetation and imagery from the subsequent growing season (called an “extended assessment”) in all 

other vegetation types. The prairie, steppe, and shrubland fires included in the current study were 

characterized by MTBS staff using a mix of initial (70% of fires) and extended (30% of fires) 

assessment data, even though one would have thought that only initial assessment data would have been 

used. The 30% of fires that used extended assessment imagery in our study also encompassed larger 

expanses of Non-Sagebrush types for which extended assessments were deemed most appropriate (for 

example woodlands and forests). This is a common limitation of analyzing only portions of fires. As 

would be predicted, across the fire areas in our study we found much higher proportions of unburned-tolow pixels in extended assessment compared to initial assessment fires (13% unburned-to-low pixels in 

initial and 35% in extended assessment fires for areas in the Big Sagebrush, Black and Low Sagebrush, 

and Grassland vegetation types where initial assessment would be most appropriate). This observation 

corroborates the conclusion that some areas that actually burned were likely classified as unburned 

when using extended assessment imagery in our study area.
62

Appendix 9. Annual Precipitation Means (in millimeters per year) over the Long

Term (1895–2013) and in the Years Encompassed by the Fire Data (1984–2013)

Management Zone Long-term 

(1885–2013)

Fire data years

(1984–2013)

Deviation from

long-term

Western Management Zones

Columbia Basin 250 250 0.1

Northern Great Basin 316 317 0.1

Snake River Plain 362 364 0.5

Southern Great Basin 323 328 1.5

Eastern Management Zones

Colorado Plateau 395 414 4.6

Great Plains 357 365 2.1

Wyoming Basin 367 375 2.2
63

Appendix 10. Annual Precipitation Means (mm/yr) During Each of the 30 Years 

of the Study (1984–2013) Compared with the Previous 117 Years (1895–2012)
64

Appendix 11. Proportion of Fire Area Represented by Each Soil Temperature 

and Moisture Regime Class in Each Vegetation Type Rangewide
65

Appendix 12. Proportion of Fire Area Represented by Each Soil Temperature 

and Moisture Regime Class in Each Vegetation Type in Each Greater SageGrouse Management Zone in the Western Region
66

Appendix 13. Proportion of Fire Area Represented by Each Soil Temperature 

and Moisture Regime Class in Each Vegetation Type in Each Greater SageGrouse Management Zone in the Eastern Region
Publishing support provided by the U.S. Geological Survey

Science Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the

 Director, Western Ecological Research Center

U.S. Geological Survey

3020 State University Drive East

Sacramento, California 95819 

http://werc.usgs.gov/
Brooks and others—Fire Patterns in the Range of the Greater Sage-Grouse, 1984–2013—Implications for Conservation and Management—Open–File Report 2015–1167

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151167