United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

General Technical Report 

RMRS-GTR-237

April 2010

The Sagebrush Steppe Treatment 

Evaluation Project (SageSTEP): A 

Test of State-and-Transition Theory

Prescribed fire—Seven Mile

Year after burn—Blue Mountain

Prescribed fire—Owyhee

Year after burn—Onaqui

Mastication—Stansbury

Mow—Rock Creek

Healthy sagebrush community—Steens Mountain
McIver, J.D.; Brunson, M.; Bunting, S.C., and others. 2010. The Sagebrush 

Steppe Treatment Evaluation Project (SageSTEP): a test of state-andtransition theory. Gen. Tech. Rep. RMRS-GTR-237. Fort Collins, CO: 

U.S. Department of Agriculture, Forest Service, Rocky Mountain Research 

Station. 16 p.

Abstract

The Sagebrush Steppe Treatment Evaluation Project (SageSTEP) is a 

comprehensive, integrated, long-term study that evaluates the ecological 

effects of fire and fire surrogate treatments designed to reduce fuel and 

to restore sagebrush (Artemisia spp.) communities of the Great Basin 

and surrounding areas. SageSTEP has several features that make it ideal 

for testing hypotheses from state-and-transition theory: it is long-term, 

experimental, multisite, and multivariate, and treatments are applied across 

condition gradients, allowing for potential identification of biotic thresholds. 

The project will determine the conditions under which sagebrush steppe 

ecological communities recover on their own following fuel treatment versus 

the communities crossing ecological thresholds, which requires expensive 

active restoration.

Keywords: fire surrogates, fire regimes, thresholds, resilience

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Fort Collins Service Center

Telephone (970) 498-1392

FAX (970) 498-1122

E-mail rschneider@fs.fed.us

Web site http://www.fs.fed.us/rm/publications

Mailing address Publications Distribution

Rocky Mountain Research Station

240 West Prospect Road

Fort Collins, CO 80526

Rocky Mountain Research Station

240 W. Prospect Road

Fort Collins, Colorado 80526
Authors

James McIver is a Senior Research Associate Professor with the Eastern Oregon Agricultural 

Research Station at Oregon State University in Union, OR.

Mark Brunson is a Professor with the Department of Environment and Society at Utah State 

University in Logan, UT.

Steve Bunting is a Professor with the Department of Rangeland Ecology and Management at 

University of Idaho in Moscow, ID.

Jeanne Chambers is a Research Ecologist with the USDA Forest Service, Rocky Mountain 

Research Station, in Reno, NV.

Nora Devoe is Research Coordinator for Nevada with the USDI Bureau of Land 

Management in Reno, NV.

Paul Doescher is a Professor with the Department of Forest Resources at Oregon State 

University in Corvallis, OR.

James Grace is a Senior Research Ecologist with the USGS National Wetlands Research 

Center in Lafayette, LA.

Dale Johnson is a Professor with the Department of Environmental and Resource Sciences 

at University of Nevada in Reno, NV.

Steve Knick is a Wildlife Ecologist with the USGS Forest and Rangeland Ecosystems Science 

Center in Boise, ID.

Richard Miller is a Range Ecologist with the Department of Rangeland Ecology and 

Management at Oregon State University in Corvallis, OR.

Mike Pellant is a Range Management Specialist with the USDI Bureau of Land Management 

in Boise, ID.

Fred Pierson is a Research Hydrologist with the Northwest Watershed Research Center, 

Agricultural Research Services, in Boise, ID.

David Pyke is a Research Ecologist with the USGS Forest and Rangeland Ecosystems 

Science Center in Corvallis, OR.

Kim Rollins is an Associate Professor with the Department of Applied Economics and 

Statistics at University of Nevada in Reno, NV.

Bruce Roundy is a Professor with the Department of Plant and Wildlife Sciences at Brigham 

Young University in Provo, UT.

Eugene Schupp is a Professor with the Department of Wildland Resources at Utah State 

University in Logan, UT.

Robin Tausch is a Research Ecologist with the USDA Forest Service, Rocky Mountain 

Research Station, in Reno, NV.

David Turner is a Statistician with the USDA Forest Service, Rocky Mountain Research 

Station, in Logan, UT.
Contents

Introduction..................................................................................................... 1

State-and-Transition Models (STMs).............................................................. 2

STMs for Sagebrush Steppe Systems............................................................ 2

SageSTEP DESIGN and STMs...................................................................... 6

Treatment Plot ............................................................................................ 8

Site Distribution.......................................................................................... 8

Treatments.................................................................................................11

Measured Variables .................................................................................. 12

Analyses................................................................................................... 13

Human Aspects.............................................................................................. 13

Sociopolitical ........................................................................................... 13

Economic ................................................................................................. 14

Outreach .................................................................................................. 14

Summary ........................................................................................................ 14

Acknowledgments......................................................................................... 15

References...................................................................................................... 15

ii
USDA Forest Service RMRS-GTR-237. 2010. 1

Introduction

Sagebrush (Artemisia spp.) habitats occupy 40 million ha in the western United States and Canada (Knick 

and others 2003). Home to more than 350 vertebrate 

species (Wisdom and others 2002), sagebrush steppe 

lands represent an important recreation area, are the 

primary forage base for the western rangeland livestock 

industry, and provide water in a semi-arid region with 

one of the fastest growing human populations in North 

America. Sagebrush ecosystems are considered to be 

among the most endangered in western North America 

(Noss and others 1995; Bunting and others 2002), with 

perhaps a third of the pre-settlement area of sagebrush 

already converted to other land uses or highly degraded. 

Over the past 100 years, fire suppression, inappropriate livestock grazing, expansion of native conifers like 

juniper and pinyon pine (Juniperus occidentalis, J. osteosperma; Pinus monophylla, P. edulis), and invasion 

of exotic weeds such as cheatgrass (Bromus tectorum) 

have contributed most to the decline of sagebrush communities in the Intermountain Region (Pellant 1994; 

Miller and Tausch 2001). In more mesic locations, 

conifer expansion and depletion of fine fuels due to inappropriate livestock grazing has shifted fire regimes 

from relatively frequent and low to mixed severity (10 

to 50 years mean fire return interval) to more infrequent and high severity (>50 years mean fire interval) 

(Miller and Rose 1999; Miller and Tausch 2001; Miller 

and Heyerdahl 2008). In some places, this shift has resulted in nearly a six-fold increase in fuel loads (from 7 

to 40 tons/ha) (Tausch and others 2004). In more xeric 

sagebrush ecosystems, exotic annual grasses have become more dominant at the expense of native perennial 

species, and these annuals have shifted mean fire return 

intervals from >50 years to <10 years in some places 

(Whisenant 1990). Under current climatic conditions, 

both pinyon and juniper woodlands and exotic annual 

grasses have the potential to dominate an even greater 

area (Betancourt 1987; West and Van Pelt 1987; Miller 

and others 2000; Wisdom and others 2002), and global warming is likely to exacerbate this trend (Tausch 

and Nowak 2000; Pyke and Knick 2003; Neilson and 

others 2005). Millions of taxpayer dollars are spent 

annually for fire suppression as a result of increased 

fire risk and sagebrush steppe degredation. The cumulative effects of degrading sagebrush habitats include 

increased threat to property and life, higher erosion and 

sedimentation, decreased water quality, declines in the 

forage base for domestic livestock, and decreased habitat for big game and threatened wildlife species (Knick 

and others 2003).

Federal land managers are attempting to arrest the 

conversion of sagebrush steppe communities into 

woodland and cheatgrass, restore a desirable herbaceous understory, and reduce fuel loads by applying 

treatments such as prescribed fire, mowing, chaining, cutting, masticating, and/or herbicides. Although 

site-specific information exists on the effectiveness of 

some treatments, there is scant multidisciplinary scientific information available on treatment outcomes 

over the range of environmental and ecological conditions that occur across sagebrush habitats. Further, 

little is known about the actual costs of these treatments, particularly relative to fire suppression efforts, 

or how acceptable they are to society for reducing fuels and restoring more desirable ecological conditions. 

Managers need multidisciplinary scientific information on the recovery potential of sagebrush ecosystems 

exhibiting different degrees of degradation and on the 

effectiveness of available treatments. Increasingly, 

managers rely on state-and-transition models (STMs) 

to determine recovery potentials and treatment alternatives for shrubland and grassland ecosystems (Briske 

and others 2005, 2006). In sagebrush ecosystems, the 

multisite, multidisciplinary scientific data necessary to 

The Sagebrush Steppe Treatment 

Evaluation Project (SageSTEP): A Test of 

State-and-Transition Theory
2 USDA Forest Service RMRS-GTR-237. 2010.

Developing STMs for managed landscapes is important for both management and research. Coupled with 

information from ecological site descriptions, STMs 

enhance managers’ abilities to predict treatment effects 

and outcomes and to determine what risks they might 

take if they decide to do nothing (Briske and others 

2006). From a research perspective, the construction 

of STMs encourages ecologists to think clearly about 

ecosystem structure and ecological processes and the 

influence of human and natural disturbances, species 

invasions, and management actions. STMs can be 

used both to identify relevant management hypotheses 

(Briske and others 2005) and to design experiments 

to test them. SageSTEP is a management experiment 

that is specifically designed to test hypotheses related 

to STMs and threshold crossings in sagebrush steppe 

ecosystems.

STMs for Sagebrush Steppe 

Systems

SageSTEP consists of two similarly designed experiments. The woodland experiment focuses on pinyon 

and/or juniper expansion into more mesic sagebrush 

steppe sites (12 to 14 inches precipitation), and the 

sage/cheat experiment focuses on cheatgrass invasion 

into more xeric sites (10 to 12 inches precipitation). We 

present a standard STM for each experiment, but we 

recognize that details of treatment response will vary 

among sites due to differences in vegetation composition and abundance, soils, elevation, aspect, slope, and 

climate (Tables 1 and 2). In addition, inherent site differences will likely influence the timing and trajectory 

of vegetation recovery. Thus, it is important to evaluate 

treatment responses for at least 10 years after treatment 

to capture the pattern and timing of recovery and to 

develop accurate STMs for each site.

For the woodland experiment, the sagebrush steppe 

reference state can be represented by three phases 

(Figure 1). Phase Ia depicts an herbaceous plant community consisting primarily of annual and perennial 

grasses and forbs that can persist on a site indefinitely 

with proper grazing and periodic low-intensity fire. 

If fire is suppressed and/or inappropriate grazing occurs, perennial herbaceous species decrease, sagebrush 

and other woody shrubs increase, and the site moves 

to Phase Ib. Pinyon and juniper seedling recruitment 

is facilitated by sagebrush and other woody shrubs 

(Chambers and others 1999; Chambers 2000), and 

after an increase in shrubs, trees are able to establish and begin to increase their dominance on the site 

evaluate the existing states and transitions and to develop appropriate prescriptions are lacking.

The Sagebrush Steppe Treatment Evaluation Project 

(SageSTEP) is a unique and unprecedented effort designed to collect these data and fully develop STMs 

for managing sagebrush steppe lands in the Interior 

West. SageSTEP tests specific predictions from STMs 

experimentally by evaluating the ecological effects of 

prescribed fire and its surrogates (mechanical and herbicide treatments) at 21 sagebrush steppe sites in the 

Great Basin and surrounding areas. The project also 

evaluates social acceptability of fire and fire surrogate 

treatments, measures costs and benefits of treatment 

application, and explores ways to place information in 

the hands of land managers. In this report, we briefly 

introduce the concept and value of state-and-transition 

modeling for management and research, present STMs 

that represent the two ecological experiments within 

SageSTEP, and describe the research design in the 

context of those STMs. We then describe the human 

aspects of SageSTEP research, including its sociopolitical, economic, and outreach components.

State-and-Transition Models 

(STMs)

With his observation that ecosystems could develop 

alternate stable states at different times on the same 

piece of ground, Holling (1973) set the stage for current thinking in rangeland ecology and its focus on 

threshold dynamics and STMs. Since their introduction 

about 20 years ago (Westoby and others 1989; Laycock 

1991), STMs have become increasingly popular for 

vegetation evaluation and rangeland management in 

the western United States (Briske and others 2005; 

Bestelmeyer 2006). In contrast to traditional “range 

models” (Dyksterhuis 1949), STMs recognize and accommodate multiple successional pathways on single 

sites. Some pathways lead to alternate community 

phases within a single stable state, and the ecosystem 

can move among these phases without changing state. 

Other pathways may result in threshold crossings to alternative stable states. Once a threshold is crossed, the 

ecosystem typically does not return to its previous state 

without active management (Briske and others 2006). 

Rangeland professionals are knowledgeable enough to 

link soil and vegetation characteristics with STMs and, 

in fact, these are essential elements of Ecological Site 

Descriptions (Pyke and others 2002; Bestelmeyer and 

others 2004).
USDA Forest Service RMRS-GTR-237. 2010. 3

Table 1. List of 14 SageSTEP sites within three woodland regions, plus current native vegetation, soils, elevation range, slope, aspect, and year treatments were 

applied. (For each site, prescribed fire was applied first, followed by mechanical and herbicide treatments.)

Site Current native vegetation Soils Elevation range Slope/ aspect Year treated

Western Juniper Region Blue Mountain Site

Mountain Big Sage,

Idaho fescue, Sandberg bluegrass, 

Bluebunch wheatgrass

Loamy, mixed, mesic, Lithic to Pachic 

Argixerolls 1500 - 1700 m 5%

N 2007

 Bridge Creek

Basin Big Sage,

Bluebunch wheatgrass, Sandberg 

bluegrass, Idaho fescue

Sandy loam, frigid Typic Haploxerolls 

to frigid Torriorthents 800 - 900 m 25%NW 2006

 Castlehead(Hydrology only) Same as Blue Mountain site Loamy, mixed frigid, Lithic to Pachici Argixerolls and Haploxerolls 1600 - 2000 m 5-8% SE, W 2007 Devine Ridge

Mountain Big Sage,

Sandberg bluegrass, Thurber needlegrass,

Squirreltail

Coarse grained sandy loam, frigid 

Torriorthents 1600 - 1700 m 0-8%

W 2007

 Five Creeks (Birds only)

Mountain Big Sage,

Idaho fescue, Sandberg bluegrass

Clayey, smectitic, frigid, Lithic 

Argixerolls 1770 - 1920 m 0 -27% NE, SE, W 2008

 Walker Butte

Mountain Big Sage

Idaho fescue, Thurber needlegrass,

Squirreltail

Sandy loam, frigid Typic Haploxerolls 1400 - 1500 m Flat 2006

Pinyon-Juniper Region

 Marking Corral Wyoming Big Sage, Thurber needlegrass Loamy, mixed, mesic, Aridic and Haploxerollic Durargids 2300 - 2400 m 6-20% NW, NE, SE 2006 Seven Mile Mt. Mahogony/Mountain Big Sage, Bluebunch wheatgrass, muttongrass Loamy-skeletal, mixed, frigid Lithic and Typic Argixerolls 2300 - 2500 m 6-15% NW , E, SE 2007 South Ruby

Wyoming Big Sage/Bitterbrush,

Bluebunch wheatgrass, Sandberg 

bluegrass, Thurber needlegrass

Loamy-skeletal, carbonatic, mesic 

Lithic Xerollic Calciorthrids 2100 - 2200 m 8-30% All aspects 2008

 Spruce Mountain Wyoming Big Sage, Black Sage, Bluebunch wheatgrass, Indian ricegrass Loamy-skeletal, carbonatic, mesic Lithic Xerollic Calciorthrids 2200 - 2500 m 3-35% NE, E, S 2009

Utah Juniper Region

 Greenville Bench Wyoming Big Sage, Needle and Thread, Bluebunch wheatgrass Decca, very gravelly to cobbly sandy loam 1750 - 1850 m 2-28%

N 2007

 Onaqui Wyoming Big Sage, Bluebunch wheatgrass Loamy-skeletal, carbonatic, mesic, shallow Aridic Petrocalcic Palexerolls 1700 - 2100 m 2-30%

E 2006

 Scipio Same as Onaqui site Loamy-skeletal, mixed, mesic, shallow Calcic Petrocalcids 1700 - 1800 m 2-28%

W 2007

Stansbury Mountains Mountain Big Sage/Antelope Bitterbrush, Bluebunch wheatgrass Loamy-skeletal, mixed, mesic Aridic Calcixerolls 1700 - 1850 m 8-30%

W 2007
4 USDA Forest Service RMRS-GTR-237. 2010. Table 2. List of seven SageSTEP sites within three sagebrush steppe regions, plus current native vegetation, soils, elevation range, slope, aspect, and year treatments were applied. (For each site, prescribed fire was applied first, followed by mechanical and herbicide treatments.) Site Current native vegetation Soils Elevation range Slope/ aspect Year treated Humboldt/Bonneville Region Onaqui Wyoming Big Sage/Antelope bitterbrush, Bluebunch wheatgrass, Slender wheatgrass Fine-loamy, mixed, mesic Xerollic Calciorthids 1750 - 1850 m 3-4%E 2006 Owyhee Wyoming Big Sage, Bluebunch wheatgrass, Squirreltail, Thurber needlegrass, Sandberg bluegrass, Wildrye Fine-silty to fine-loamy, mixed, mesic, shallow, Xerollic Durargids, Durixerollic Camborthids, and Durixerollic Haplargids 1700 - 1750 m 0-10% All aspects 2008 Roberts Wyoming Big Sage, Bluebunch wheatgrass Fine- to coarse-loamy, mixed, superactive, frigid Xeric Haplocalcids 1550 - 1600 m 0-10% All aspects 2007 High Desert Region Hart Mountain Gray Butte Wyoming Big Sage, Squirreltail, Thurber needlegrass Brace: Fine-loamy, mixed, frigid Xeric Argidurids Raz: Loamy, mixed, superactive, frigid, shallow Xeric Haplodurids 1450 - 1600 m 0-10% All aspects 2008 Hart Mountain Rock Creek Same as Gray Butte site Same as Hart Mountain Gray Butte site 1450 - 1600 m 0-10% All aspects 2007 Low Desert Region Moses Coulee Wyoming Big Sage, Bluebunch wheatgrass, Squirreltail, Sandberg bluegrass Skaha: Loamy-skeletal, mixed, superactive, mesic Aridic Haploxerolls Strat: Loamy-skeletal, mixed, superactive, mesic Vitritorrandic Haploxerolls Tubspring: Coarse-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Calcidic Haploxerolls 515 – 530 m 0-10%S 2008/2009 (mechanical, herbicide—2008; fire—2009) Saddle Mountain Wyoming Big Sage, Bluebunch wheatgrass, Indian ricegrass, Bottlebrush squirreltail Coarse-silty, mixed, superactive, mesic Xeric Haplocambids 262 – 286 m 1-5%S 2008
USDA Forest Service RMRS-GTR-237. 2010. 5

Figure 1. State-and-transition model for the woodland system (12- to 14-inch precipitation zone) focusing on vegetation only. 

(See Table 1 for site differences in vegetation, soils, and other inherent site features.) Font size indicates relative dominance of 

vegetation life form within each phase. *Fire is assumed to be severe enough to kill most of the woody vegetation.

WOODLAND

Sagebrush Steppe

State-and-Transition Model

Phase Ib:

Sagebrush/Native

Forbs/Grasses

~Cheatgrass

Phase Ia:

Native Perennial

Forbs/Grasses

~Cheatgrass

Phase II

Sagebrush/Native

Forbs/Grasses/Trees

~Cheatgrass

Phase III

TREE-Dominated

Sagebrush/Native Forbs/Grasses

Cheatgrass

Fire *

No Fire

Fire

Fire

???

Tree

Growth

Tree

Encroachment

Moderate

Grazing

Impact

Biotic

THRESHOLD

Fire

???

REFERENCE STATE

Sagebrush Steppe (12-14” Precipitation)

DEGRADED STATE 1

Phase IVa:

Native Annual/

Residual Herbaceous

Phase IVb:

Invasive Annual

Grass/Perennial

Forbs

Fire*/

Weed

Seeds

Fire/

Weed Seeds

Fire

Abiotic

THRESHOLD

Significant Erosion/

Nutrient and Soil Loss

DEGRADED STATE 2

Eroded

Phase Vb:

Invasive Annual

Grass/Perennial

Forbs

Phase Va:

TREE-Dominated/

No Understory

Fire/

Weed

Seeds
6 USDA Forest Service RMRS-GTR-237. 2010.

(Phase II). Low to moderate grazing and fire of adequate severity to kill woody vegetation can result in a 

shift from Phase II back to Phase I. The successional 

process then repeats itself. The predominate feedback 

mechanism that maintains the plant community within 

the reference state is negative as fire returns at relatively frequent intervals due to steadily increasing fuel 

loads that accumulate with plant succession. As long 

as the understory herbaceous vegetation layer remains 

relatively abundant and well-distributed, fuel continuity is generally sufficient to support surface fires over a 

fairly wide range of weather conditions. Heavy grazing 

or lack of fire can result in tree dominance and depletion of both shrubs and herbaceous understory species 

(Phase III). Fine fuels may be insufficient for surface 

fire and the system may not return to more seral phases 

within the reference state. As a result of the changes 

in the plant community at this point, the system is at 

risk of crossing a biotic threshold to Degraded State 1. 

The plant community is now either dominated by invasive annuals such as cheatgrass or is characterized by 

the expansion of native annual cover. The threshold is 

“triggered” by tree competition or overgrazing, both of 

which are processes that decrease the ecological role 

of the herbaceous understory. This biotic threshold is 

characterized by the dominance of a positive feedback 

mechanism by which continued tree growth makes 

the system more impervious to surface fire. Even if 

the trees are removed, the residual plant community 

may be so depleted that it will not return to the reference state without re-seeding. Phase III will persist 

indefinitely with trees gradually acquiring more of the 

available resources until canopy structure, fuel loads, 

and weather conditions are conducive to a crown fire. 

A Phase IV plant community typically then results, 

dominated either by native annual grasses and forbs 

(Phase IVa) or by invasive plants if seeds are available 

(Phase IVb). Degraded State 2 may occur on steeper 

slopes and under certain soil conditions. To reach this 

state, an abiotic threshold is crossed in which erosion 

causes soil and nutrient loss (Phase V). The worst-case 

scenario is Phase Vb, an eroded state where crown fire 

eventually occurs and leaves a condition in which only 

native or invasive species that can tolerate the altered 

conditions can establish and persist.

The sage/cheat experiment is focused on a sagebrush 

steppe reference state that occurs in the 10- to 12-inch 

precipitation zone, an ecological site in which trees almost never establish and persist. This reference state 

has the same two phases (Ia and Ib) as the woodland 

model (Figure 2). However, instead of tree expansion, 

both phases (particularly Phase Ib) are vulnerable to 

cheatgrass invasion. If grazing is absent or at low levels, native herbaceous vegetation typically remains 

dominant in the system even though cheatgrass becomes part of the plant community. With moderate 

grazing, both phases (particularly Phase Ib) experience a decline in the preferred perennial grasses. In 

Phase II, fire kills most shrub species, and the community returns to Phase Ia. As long as native herbaceous 

perennials remain sufficiently abundant, periodic fire 

acts as a negative feedback mechanism that maintains 

the reference state and a plant community dominated 

by native perennial species. However, with heavy 

grazing the community transitions to Phase III, in 

which perennial herbaceous vegetation is reduced to 

relatively low cover values and cheatgrass abundance 

increases. Introduction of stand-replacement fire can 

return the community to Phase Ia, but most likely will 

cause the community to cross a biotic threshold to a 

degraded state dominated by cheatgrass (Phases IV 

and V). Cheatgrass is highly flammable for a longer 

period of time during the late spring and summer than 

native perennials, and it typically creates a highly continuous fine fuel bed. Thus, fire operates once again 

as a negative feedback mechanism, this time returning the community to cheatgrass dominance with each 

repeated burn. Remnant perennial shrubs that cannot 

tolerate fire are progressively eliminated, while perennial herbaceous species exhibit reduced capacity to 

produce seeds and establish in the highly competitive 

environment. Exotic perennial invasion can result in 

Phase V, a plant community codominated by cheatgrass, other annual grasses, and weedy perennial forbs. 

Repeat fire may return the community to Phase IV or 

may perpetuate Phase V, but further research is needed 

to determine this. Active restoration is required to return either Phase IV or V to the reference state, but 

even significant efforts may fail to achieve restoration 

success in these systems.

SageSTEP DESIGN and STMs

SageSTEP has five key features that make it ideal for 

testing hypotheses developed from state-and-transition 

theory and for applying new knowledge in a management context. SageSTEP is:

• Experimental—allows for controlled manipulation 

of ecological factors that are considered to be drivers 

in the two experimental systems;

• Long-term (10 years post-treatment)—provides 

sufficient ecological post-treatment time to measure 

and interpret ecological response;
USDA Forest Service RMRS-GTR-237. 2010. 7

Figure 2. State-and-transition model for the sage/cheat system (10- to 12-inch precipitation zone) 

focusing on vegetation only. (See Table 2 for site differences in vegetation, soils, and other inherent 

site features.) Font size indicates relative dominance of vegetation life form within each phase. *Fire is 

assumed to be severe enough to kill most of the woody vegetation.

SAGE/CHEAT

Sagebrush Steppe

State-and-Transition Model

Phase Ib:

Sagebrush/Native

Forbs/Grasses

Cheatgrass

Phase Ia:

Native Perennial

Forbs/Grasses

Cheatgrass

Phase II

Sagebrush/Native

Forbs/Grasses

Cheatgrass

Phase III

Sagebrush/Native

Forbs/Grasses

Cheatgrass

Fire *

No Fire

Fire

Fire

???

Heavy

Grazing

Impact

Moderate

Grazing

Impact

Biotic

THRESHOLD

Fire

???

REFERENCE STATE

Sagebrush Steppe (10-12” Precipitation)

DEGRADED STATE

Phase IV:

CheatgrassDominated

Fire

Phase V:

Cheatgrass+

Invasive Perennials

Invasive

Perennial

Seeds

Frequent

Fire*
8 USDA Forest Service RMRS-GTR-237. 2010.

• Multisite—evaluates responses across the range 

of environmental conditions that characterize the 

region;

• Multivariate—measures both dependent and independent variables to not only characterize response 

but also to identify mechanisms behind that response; 

and

• STM-based—applies treatments across the range of 

ecological conditions that characterize the states and 

phases within the woodland and sage/cheat STMs.

These five features are incorporated into both the 

woodland and sage/cheat experiments. Each experiment is comprised of several replicate sites (N = 12 

for woodland; N = 7 for sage/cheat), and each site represents a block where alternative fire or fire surrogate 

treatments are applied at the plot level. Each treatment 

plot includes between 15 and 24 measurement subplots established to span a wide gradient of ecological 

conditions. We describe this study design in detail, 

starting with the treatment plot, which is designed to 

study treatment response across the condition gradient.

Treatment Plot

The current management focus in sagebrush steppe 

is to maintain or restore native sagebrush ecosystems. 

The dominant shrubs (Artemisia spp.) and trees are 

not fire-tolerant, and initial ecosystem recovery following wildfires or management treatments depends 

on native perennial herbaceous species that resprout 

or reestablish following fire and that decrease the susceptibility of these ecosystems to cheatgrass invasion 

(Chambers and others 2007). Total or partial removal 

of trees and shrubs through fire or one of its surrogates 

and removal of cheatgrass by applying herbicides can 

result in competitive release of perennial herbaceous 

species. Thus, vegetation recovery may depend on the 

relative abundance of native perennial herbaceous species and trees, shrubs, and cheatgrass in woodland and 

sage/cheat ecosystems and on their responses to the 

different treatments. SageSTEP is designed to examine 

vegetation response to specific treatments over these 

abundance gradients in woodland and sage/cheat ecosystems. Sub-plots are positioned and sized (relatively 

large) to capture the range of vegetation conditions 

within a plot. For example, the Greenville Bench control plot (woodland experiment) has an area of 25 ha 

(1250 by 200 m), and the differences in tree abundance 

can easily be seen on the National Agriculture Imagery 

Program image (Figure 3a). Because tree cover is the 

primary driver behind declines in understory cover 

(Figure 3b), an opposing response curve for understory 

vegetation is evident in each treatment plot. Recovery 

potential can be assessed with this design by applying 

the selected treatments across the entire plot, measuring vegetation response within the sub-plots, and then 

interpreting the response within the context of the vegetation gradient. If a threshold exists in herbaceous 

vegetation cover, below which recovery does not occur 

without further intervention, it likely will be identified 

with this design. After examination of many landscapes prior to site selection, we found that typically 

at least 15-ha treatment plots were necessary to capture 

a meaningful gradient for stands encroached by woodland species, and at least 30-ha plots were necessary 

for the more xeric stands in the sage/cheat experiment.

Site Distribution

While treatment of a single large plot can identify 

thresholds for that particular place at that particular 

time, managers need to know if application of the same 

treatment elsewhere will produce similar results. The 

issues of site-specific responses to treatments and variation in the position of the biotic threshold (and other 

STM characteristics) were addressed by conducting 

the same experiment across a wide range of environmental conditions. The two experiments in SageSTEP’s 

core study are applied at 19 sites located across much 

of the land area occupied by sagebrush steppe vegetation in the western United States (Figure 4). All sites 

fall within the same Major Land Resource Area (i.e., 

lands that have similar vegetation and land use patterns (Bestelmeyer and others 2009). Each of these 

19 sites received the full suite of treatments. Although 

all sites are classified as Cool Desert, weather patterns 

differ markedly across this geographic range. Sites 

in California, Oregon, Washington, and southwest 

Idaho have a Pacific Maritime climate, with nearly 

all precipitation originating in the Pacific Ocean and 

falling between November and June. The majority of 

the western juniper ecosystem lies north of the polar 

front gradient where temperatures are cooler, summer 

precipitation is decreased, and winter precipitation is 

increased (Mitchell 1976). In contrast, sites in Nevada 

and Utah have a more Continental climate, with less 

precipitation falling from November to June, and relatively more summer rains originating from the Gulf 

of Mexico, usually in July and August. Since weather 

systems in the Pacific and in the Gulf are somewhat independent, we expect different patterns of inter-annual 

weather variation across the SageSTEP network, and 

we expect that this variation may affect recovery after 
USDA Forest Service RMRS-GTR-237. 2010. 9

Figure 3. Greenville Bench control plot. (a) Map of plot showing location of measurement sub-plots, 

weather station, soil moisture stations, soil cores, bird point counts, and butterfly transects. (b) 

Relationship between tree cover and understory cover over the plot’s condition gradient.

40

Shrubs + Perennial Grasses

Shrubs

Perennial Grasses

20

30

Threshold? Sub-plots

% Understory Cover

10

% Tree Cover

0

0 10 20 30 40 50 60

(a)

(b)
10 USDA Forest Service RMRS-GTR-237. 2010.

Figure 4. Map of SageSTEP Network of 21 sagebrush steppe sites, 19 of which are used in the core experiment focused on 

vegetation responses, and two of which are only used for wildlife (5-Creeks) or hydrology (Castlehead) research.
USDA Forest Service RMRS-GTR-237. 2010. 11

treatment. If among-site recovery rates and/or patterns 

mirror vulnerability, then more xeric sites, or sites with 

higher inter-annual variation in weather, may be slower 

to recover relative to more mesic, or less variable, sites 

(Chambers and others 2007). We collect weather data at 

each site throughout the study period from weather stations located in the control plot of each site (Figure 3a). 

These data are used as a covariate in the analyses to 

help explain vegetation response.

The 12 woodland sites can be organized into 

three regions, each reflecting the dominant tree species (Figure 4). With four sites located in Oregon and 

Northern California, the Western Juniper Region is 

roughly defined by a triangle 300 km on the side. The 

four sites within the Pinyon-Juniper Region are more 

tightly clustered in east-central Nevada. The Utah 

Juniper Region consists of four sites in western Utah, 

spanning a north to south geographic range of roughly 

400 km. Altogether, the 12 woodland sites span a geographic range of more than 800 km, from Bridge Creek 

in the northwest to Greenville Bench in the southeast, 

and represent conditions that vary considerably in elevation, topography, soils, current vegetation, and climate 

(Table 1).

The cheatgrass experiment consists of seven sites, all 

within the sagebrush biome but separated by more than 

1000 km from south-central Washington to west-central 

Utah (Figure 4). Four of these sites are located in the 

western part of the sagebrush range, two are in central Oregon (High Desert Region), and two are in the 

Columbia Basin of southern Washington (Low Desert 

Region). Three of the sites are located in the eastern 

portion of the range (Bonneville Region), with one in 

Utah, one in eastern Idaho, and one in northern Nevada. 

Although all seven sites are typical sagebrush steppe 

systems, they also encompass a range of soil types, 

plant communities, and weather patterns (Table 2).

While most sampling occurs within the plots and 

sub-plots, analyses are conducted not only at the plot 

level, but at the site, region, and network levels. The 

hierarchical organization of the study reflects the sampling orientation and sets the stage for different kinds 

of analyses. If native perennial herbaceous vegetation 

has an effect on recovery and thresholds as originally 

predicted, we will be able to determine its relative importance at both site and regional levels for the woodland 

and sage/cheat experiments. Because other factors like 

soil characteristics, weather patterns, and abundance of 

other plant life forms, especially cheatgrass, likely have 

additional effects, we also will be able to determine 

their relative contribution to recovery and thresholds.

Treatments

For both the woodland and sage/cheat core experiments, a full set of treatments were applied at each 

site to achieve a statistical block. These treatments are 

commonly used to decrease woody fuels and to maintain or restore sagebrush ecosystems. The woodland 

experiment features three plot-level treatments: prescribed fire, cut and fell, and mastication. Treatment 

plots range in size from 10 to 30 ha, each of which 

has 15 measured sub-plots positioned to cover a broad 

condition gradient. Prescribed fire was applied first, 

between August and November of 2006, 2007, or 2008 

(Table 1). The goal was to accomplish 100 percent 

tree mortality within each treatment plot. However, 

due to considerable variation in weather conditions, 

prescribed fires only burned between 20 and 95 percent area. For those plots in which percent area burned 

was low, we blackened every sub-plot where the low 

measurements were taken. Cut and fell and mastication treatments were implemented within six months 

of fire treatments. All trees >2 m tall were cut down 

and left on the ground across the contour. An additional 

treatment was applied at the four Utah juniper sites—

all trees >2 m tall were masticated with the Bullhog®, 

a machine with a rotary mower capable of shredding 

even the largest juniper trees. An untreated plot serves 

as a control to complete the three-treatment ensemble 

for each woodland site (four treatments for the Utah 

juniper region).

The sage/cheat experiment includes four plot-level 

treatments per site: prescribed fire, application of the 

herbicide tebuthiuron, rotary mowing, and application 

of the herbicide imazapic nested within each of the 

other treatments. Treatment plots range in size from 20 

to 80 ha, each of which has 18 measured sub-plots positioned to cover a broad condition gradient. Prescribed 

fire was applied first, from May to October of 2006, 

2007, or 2008 (Table 2). The goal was to accomplish 

100 percent fire coverage. In some cases, weather conditions did not cooperate, with the result that some 

plots were not completely burned. In these cases, fire 

crews blackened every sub-plot where measurements 

occurred. Once fire was implemented for each site, 

both herbicide and mowing treatments were applied to 

two other plots within the following eight months. Both 

treatments were designed to remove about 50 percent 

of sagebrush cover to reduce woody fuels and release 

the understory herbaceous species. The herbicide 

tebuthiuron (N -[5-1,1-dimethylethyl-1,3,4-thiadiazol2-yl]- N,N’ –dimethylurea) was applied over the entire 
12 USDA Forest Service RMRS-GTR-237. 2010.

plot at a rate dictated by prior testing to remove 50 

percent of the overstory. Rotary mowers were set at a 

pre-determined height to remove 50 percent of sagebrush biomass over the entire plot. An untreated plot 

served as the control to complete the four-treatment 

ensemble of plot-level applications for each site. The 

pre-emergent herbicide imazapic (3-Pyridinecarboxylic 

acid, 2-(4,5-dihydo-4-methyl-4-(1-methylethyl)-5–

oxo-1H-imidazol-2-yl)-5-methyl-monoammonium 

salt) was applied to half of the sub-plots within each 

of the three or four plots per site (including control) 

simultaneous to each of the other treatments. At low 

rates, imazapic selectively acts on annual plants.

Measured Variables

SageSTEP measures well over 100 distinct variables that can be roughly classified as response 

(dependent) or explanatory (independent) variables. 

To evaluate ecological response, a comprehensive 

set of variables are measured within each of the 1050 

sub-plots, capturing both structural and compositional 

elements of the system. These variables are measured 

pre-treatment and for at least 10 years post-treatment 

within each of the 0.1-ha sub-plots (30 by 33 m) in the 

two experiments. Cover and density of trees, shrubs, 

forbs, and grasses are measured, and analyses focus 

on how these vegetation components respond to treatment in relation to the vegetation gradients. Biological 

crust cover, bare ground cover, harvester ant mounds, 

and ant community structures are also measured within each sub-plot because of their potential relevance to 

vegetation recovery. A number of critical explanatory 

variables are measured to aid in interpretation of vegetation response, including: (1) inherent features of the 

sub-plot, such as slope, aspect, topographic position, 

and elevation; (2) all components of the fuel bed within sub-plots, such as standing and down woody fuel, 

litter, duff, and live fuels; (3) inherent soil properties, 

such as depth, texture, and moisture; (4) soil chemistry, with a focus on nitrogen availability and carbon; 

and (5) air temperature and precipitation, at weather 

stations placed in the center of each control plot. Each 

time a sub-plot is measured, two photo points are 

taken at the 0- and 30-m marks of the central (15 m) 

transect using a digital camera. These geo-referenced 

photo points are used to document vegetation recovery over the long term and to aid in interpretation of 

vegetation response. This suite of variables will aid 

in quantifying STM differences among sites because 

recovery processes likely will largely depend on how 

different variables interact in the context of climate 

zones and weather patterns. Including variables that 

managers or scientists believe are potentially relevant 

maximizes the likelihood of capturing indicator patterns that are connected to critical processes (Pyke and 

others 2002). Finally, it is imperative that variables be 

measured for at least 10 years post-treatment because 

of uncertainty about the length of time required for 

vegetation recovery and because of the community’s 

potential to return to the reference state. In fact, time 

frames must be fully understood in order to complete 

an STM (Bestelmeyer and others 2004).

Faunal response was also measured at the treatment 

plot level, particularly passerine bird and butterfly 

response. Passerine bird point counts are conducted annually in each treatment plot for the woodland 

experiment only, while 1000-m butterfly transect surveys are conducted within treatment plots for both the 

woodland and sage/cheat experiments. Thus, the effects of fire and fire surrogates on both passerine bird 

and butterfly abundances can be assessed with this design. Because average home range size for passerine 

birds is too large to study populations within typical 

SageSTEP treatment plots, bird research also includes 

intensive demographic work on seven species of sageobligate passerine birds within 10 400-ha plots—one 

control and one prescribed burn plot for each of five 

woodland sites (Figure 4). Because sage-obligate 

passerines are known to have similar habitat preferences to sage grouse (a species of concern), research 

on these birds should provide insight into treatment 

effects on grouse populations. More generally, an 

important rationale for measuring faunal response to 

treatment is to understand the extent to which other 

components of the system not directly related to vegetation management track the response of vegetation 

over time. Understanding faunal effects will provide 

managers with more confidence on how their treatments influence the whole system. SageSTEP can 

identify inconsistencies in treatment response between 

the flora and fauna and potential time lags in faunal 

response as key components of habitat recovery after 

treatment. SageSTEP biodiversity research will help 

patch the schism that has developed in recent years between rangeland professionals focused exclusively on 

vegetation and production and those more interested 

in the health of whole ecosystems, which is commonly expressed as various measures of biodiversity 

(Bestelmeyer 2006).

Finally, the extent to which woodland encroachment affects water relations has been a significant 

concern in recent years among managers of the sagebrush biome. Variations in site infiltration, runoff, 
USDA Forest Service RMRS-GTR-237. 2010. 13

and erosion are closely correlated with variations in 

vegetation and surface soil conditions (Pierson and 

others 2002; Rau and others 2005). In particular, pinyon and juniper trees are highly competitive for soil 

water, and tree dominance typically results in major 

declines in understory vegetation (Figure 3b). Under 

these conditions, undesirable hydrological conditions 

can develop on steep slopes, causing increased erosion 

and sediment transport (Degraded State 2; Figure 1). 

SageSTEP hydrology research focuses on the conditions under which the most deleterious effects occur 

to determine if critical thresholds exist in vegetation 

and ground cover that significantly influence hillslope 

erosion and if management treatments influence these 

thresholds.

Analyses

Both univariate and multivariate analyses are being 

used for the two ecological experiments. For univariate 

analyses, we will use PROC GLIMMIX (SAS Institute 

Inc. 2004), with replication provided at the site level 

for both woodland (n = 12) and sage/cheat (n = 7) experiments. This ensures a statistically valid design for 

the overall experiment in which differences among 

sites, treatments, and treatment years can be tested for 

the suite of ecological variables examined. Variables 

believed to be influencing ecosystem trajectories, like 

tree cover, cheatgrass biomass, or soil texture, will be 

treated as covariates to examine their overall influence 

on other response variables. To capture whole system 

responses to fire and fire surrogate treatments, we will 

use multivariate methods. Information on whole system response is valuable to managers because it allows 

them to evaluate treatment tradeoffs for key variables. 

Multivariate methods such as ordination and classification are best used for investigations on how plant and 

animal communities vary along spatial gradients and 

how they respond to treatments (McCune and Grace 

2002).

To evaluate how relationships among components 

within a system respond to treatment, we will use 

structural equation modeling (SEM) (Grace 2006). 

This analysis tool requires that the investigator build 

hypothetical models from prior knowledge that include the key variables and their causal relationships 

not only to the dependent variable but to one another, 

and then test the models with data from the experiment. For example, we can examine how soil type 

influences the degree to which fire and fire surrogates 

affect plant species diversity. Factors such as slope, 

elevation, aspect, and initial fuel loads can also be 

evaluated in the context of a structural equation model. In summary, analytical results are used not only to 

identify significant differences in responses among 

sites, but also to provide confidence intervals for the 

more detailed STMs that will emerge from the study.

Human Aspects

SageSTEP is largely a comprehensive field study 

focused on ecological aspects of woodland expansion 

and cheatgrass invasion on sagebrush steppe lands 

of the Interior West. However, to improve public understanding of invasion and recovery processes in 

sagebrush steppe and to gain acceptance of applying 

recommended treatments, certain socioeconomic aspects need to be addressed. For instance, treatments 

will not be applied if the public doesn’t accept them 

or if they are too costly relative to other land management options. Further, research results must be 

communicated to key stakeholders in order for the results’ full potential to be realized. In this section, we 

briefly outline activities underway to assess sociopolitical, economic, and outreach aspects of SageSTEP.

Sociopolitical

Each management treatment evaluated in this 

project is a potentially controversial practice that 

might meet resistance from citizens and/or managers when applied to public lands. Because National 

Environmental Policy Act (NEPA) prescribes that 

Federal land managers must closely involve the public 

whenever treatment decisions are made, it is important 

to understand how treatments are perceived and accepted by various sectors of the public.

The sociopolitical component of SageSTEP assesses the social and political feasibility of alternative 

treatments, with feasibility defined as a function of 

positive or negative perceptions of the general public, interest group members, and land managers. Our 

intent is to identify factors in the treatments, or the 

conditions those treatments produce, that constrain or 

facilitate implementation of practices. Also included in 

those factors is the current state of ecological systems 

relative to ecological thresholds. While the research 

questions focus on the practical issue of choosing 

among potential restoration actions, the study also 

explores more basic questions about decisionmaking with uncertainty and about using the foundations 

of social acceptability (Shindler and others 2002) as 

guiding principles of contemporary land management.
14 USDA Forest Service RMRS-GTR-237. 2010.

Economic

The goal of SageSTEP economics work is to provide 

a comprehensive understanding of the tradeoffs and 

incentives that face decisionmakers at various levels 

when they consider whether to treat sagebrush steppe 

lands. The economic research consists of four parts:

1. A dynamic bioeconomic model that combines 

features of a state-and-transition ecological model 

with fire, invasives, and economic decision variables (treatment and grazing levels) to predict how 

system resilience changes with management decision variables

2. A ranch-level model to predict ranchers’ incentives 

in decisions regarding treatment options

3. A model to predict county-level impacts on employment and income by sector associated with 

alternative landscape characteristics caused by 

treatment or lack of treatment

4. A valuation of expected changes in flows of nonpriced goods and services brought about by decisions to treat sagebrush steppe lands that have 

been degraded by cheatgrass invasion or woodland 

encroachment

Outreach

Although SageSTEP will generate information for 

a wide variety of people, its principal outputs will 

consist of applied ecological and socioeconomic information designed to be useful to land managers. 

A Communication Plan has been developed that can 

adapt to the needs of practitioners and the public. The 

purpose of the Communication Plan is to guide the 

project through the outreach process by providing both 

conceptual and process frameworks at the network and 

site levels. Principal products and activities include:

• A Web site that is designed and maintained by a 

dedicated outreach coordinator

• A newsletter produced three times per year that 

informs stakeholders on the progress of SageSTEP

• Annual workshops for managers to maintain clear 

lines of communication

• Field tours for a variety of audiences

• Presentations at scientific and management-oriented 

meetings

• Scientific publications in which primary findings are 

published

• Other outreach materials that are developed as 

opportunities arise in order to serve a variety of 

audiences, including general or specific publics and 

land managers

• A set of three User’s Guides to be used by managers 

in the field

The User’s Guides exemplify the approach we have 

chosen: to deliver scientific information to managers’ hands. Each User’s Guide is focused on a Land 

Resource Unit with similar characteristics and issues 

to the perspective of the land manager (e.g., Western 

Juniper, Pinyon-Juniper, Wyoming Big Sagebrush). 

Each is grounded in scientific literature and provides 

a list of key publications that support its perspective 

and can be cited in NEPA documents. Each leads the 

user through a series of questions designed to help 

the manager make decisions on a particular stand or 

watershed. We anticipate that results from both experiments will be used to update and expand Ecological 

Site Descriptions for each of the distinct sites within 

the SageSTEP network and will update each of the 

three User’s Guides. Finally, the effectiveness of the 

outreach program will be evaluated regularly with surveys taken at the annual manager workshops.

Summary

As a single study focused on sagebrush steppe ecosystems of the Interior West, SageSTEP has several 

features that make it unique as a research project that 

tests hypotheses associated with state-and-transition 

theory. SageSTEP is: (1) Experimental—allows for 

controlled manipulation of ecological factors that are 

considered to be drivers in the woodland and sage/

cheat experimental systems; (2) Long-term (10 years 

post-treatment)—provides sufficient ecological posttreatment time to measure and interpret ecological 

response; (3) Multisite—evaluates responses across 

the range of environmental conditions that characterize 

the region; (4) Multivariate—measures both dependent and independent variables, not only to evaluate 

response but to identify mechanisms behind that response; and (5) STM-based—applies treatments across 

the range of ecological conditions that characterize the 

states and phases within the woodland and sage/cheat 

STMs. Information from SageSTEP will improve existing Ecological Site Descriptions, including details 

on among-site soil variation, vegetation, threshold 

dynamics, and the form of state-and-transition models, as they apply to both the flora and the fauna of 
USDA Forest Service RMRS-GTR-237. 2010. 15

sagebrush steppe systems. SageSTEP also explores human aspects of the invasion on sagebrush steppe lands, 

including the social acceptability of alternative treatments, the economic tradeoffs and incentives that face 

land managers dealing with woodland and cheatgrass 

invasion, and alternative methods for disseminating research results to key stakeholders.

Acknowledgments

This is Contribution Number 5 of the Sagebrush 

Steppe Treatment Evaluation Project (SageSTEP), 

funded by the U.S. Joint Fire Science Program 

(JFSP Grant #05-S-08). Substantial funds are provided by the research institutions with which the 

principal investigators are affiliated. We are also 

grateful to our management partners who bore the 

full cost of treatment implementation: the Bureau of 

Land Management, Forest Service, Fish and Wildlife 

Service, and The Nature Conservancy. This manuscript was considerably improved by comments from 

Pat Kennedy (Oregon State University), David Briske 

(Texas A&M), and two anonymous reviewers.

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