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BLM/OC/ST-16/005+4400
Bureau of Land Management

Rangeland Resource Assessment—2011

Michael G. “Sherm” Karl

U.S. Department of the Interior–Bureau of Land Management

National Operations Center, Denver, CO

Emily Kachergis

U.S. Department of the Interior–Bureau of Land Management

National Operations Center, Denver, CO

Jason W. Karl

U.S. Department of Agriculture–Agricultural Research Service

Jornada Experimental Range, Las Cruces, NM

September 2016 
Suggested citations:

Karl, M.G. “Sherm,” E. Kachergis, and J.W. Karl. 2016. Bureau of Land Management Rangeland Resource 

Assessment—2011. U.S. Department of the Interior, Bureau of Land Management, National Operations 

Center, Denver, CO. 96 pp.

U.S. Department of the Interior. 2016. Bureau of Land Management Rangeland Resource 

Assessment—2011. Bureau of Land Management, National Operations Center, Denver, CO. 96 pp.
Rangeland Resource Assessment—2011 iii

Acknowledgments

Many individuals contributed behind the scenes to 

the creation of the “Bureau of Land Management 

Rangeland Resource Assessment—2011.” Gordon Toevs 

and Carol Spurrier, of the BLM’s Washington Office, 

provided overall guidance, critical strategic support, 

and the necessary funding. Cindy Yu, Sarah Nusser, 

Todd Krueger, Steve Roberts, and Jie Li, with the 

Center for Survey Statistics and Methodology at 

Iowa State University, and Veronica “Roni” Lessard, 

with the Natural Resources Conservation Service, 

provided expertise in the survey design, sample 

selection, and statistical processing and estimation of 

the attributes and indicators.

Comments from John Carter, Jeff Herrick, 

Sarah Lamagna, Richard Mayberry, Scott Miller, 

Mike Pellant, David Pyke, Tony Svejcar, Curtis Talbot, 

and Kenneth Visser improved the focus and content 

of the rangeland resource assessment.

Linda Hill of the BLM’s National Operations Center 

provided expert editing that in immeasureable ways 

improved the organization and readability of the 

rangeland resource assessment.

To all of these individuals, the authors express their 

gratitude. 

Rangeland Resource Assessment—2011 v

Contents

Introduction .

Purpose and Background .

Rangeland Productivity .

Methods .

Sample Design and Selection .

Data Collection .

Data Summarization .

Extrapolation of Sample Data to BLM Rangelands . 

Rangeland Resources Status and Condition . 

Arizona/New Mexico Mountains Ecoregion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Central Basin and Range Ecoregion . 

Eastern Cold Deserts Ecoregion . 

Madrean Archipelago Ecoregion . 

Northern Cold Deserts Ecoregion . 

South Central Semi-Arid Prairies Ecoregion . 

Warm Deserts Ecoregion . 

West Central Semi-Arid Prairies Ecoregion . 

Western Cordillera Ecoregion . 

Conclusion . 

Literature Cited . 

Appendix A: List of Nonnative Invasive Plant Species . 

Appendix B: Attributes and Indicators Measured and Associated Statistics for Each Ecoregion . 

Appendix C: Overall Comparison of Attribute and Indicator Estimates Across Ecoregions . 

Appendix D: Pairwise Comparisons Across Ecoregions for Each Attribute or Indicator . 

Rangeland Resource Assessment—2011 vii

List of Figures and Tables

Figure 1 Ecoregions and the number of points sampled in each ecoregion for the 2011 BLM RRA . 

Figure 2 Agua Fria National Monument, Arizona, within the Arizona/New Mexico Mountains ecoregion . 

Figure 3 Mean and 80% confidence interval for attributes and indicators in the Arizona/New Mexico 

Mountains ecoregion . 

Figure 4 Proportion of BLM rangelands where soil aggregate stability is ranked 4 or less (80% 

confidence interval) within ecoregions . 

Figure 5 Proportion of BLM rangelands where biotic integrity shows moderate departure from 

reference conditions (80% confidence interval) within ecoregions . 

Figure 6 Black Rock Desert–High Rock Canyon Emigrant Trails National Conservation Area, 

north of Gerlach, Nevada, within the Central Basin and Range ecoregion . 

Figure 7 Mean and 80% confidence interval for attributes and indicators in the Central Basin 

and Range ecoregion . 

Figure 8 Average amount of bare ground (80% confidence interval) on BLM rangelands 

within ecoregions . 

Figure 9 Proportion of BLM rangelands with at least 20% bare ground (80% confidence interval) 

within ecoregions . 

Figure 10 Proportion of BLM rangelands with at least 30% bare ground (80% confidence interval) 

within ecoregions . 

Figure 11 Proportion of BLM rangelands with at least 40% bare ground (80% confidence interval) 

within ecoregions . 

Figure 12 Proportion of BLM rangelands with at least 50% bare ground (80% confidence interval) 

within ecoregions . 

Figure 13 Proportion of BLM rangelands with at least 20% of the land having intercanopy gaps of 

at least 2 meters in length (80% confidence interval) within ecoregions . 

Figure 14 Proportion of BLM rangelands with nonnative invasive plant species present (80% 

confidence interval) within ecoregions . 

Figure 15 Proportion of BLM rangelands with abundant nonnative invasive plant species (80% 

confidence interval) within ecoregions . 

Figure 16 Proportion of BLM rangelands where hydrologic function shows moderate departure 

from reference conditions (80% confidence interval) within ecoregions . 
viii Bureau of Land Management

Figure 17 Head of Sinbad, San Rafael Swell, Utah, within the Eastern Cold Deserts ecoregion . 

Figure 18 Mean and 80% confidence interval for attributes and indicators in the Eastern Cold 

Deserts ecoregion . 

Figure 19 Proportion of BLM rangelands where biotic integrity shows moderate-to-extreme or 

extreme-to-total departure from reference conditions (80% confidence interval) 

within ecoregions . 

Figure 20 Proportion of BLM rangelands where hydrologic function shows moderate-to-extreme or 

extreme-to-total departure from reference conditions (80% confidence interval 

within ecoregions . 

Figure 21 Proportion of BLM rangelands where soil/site stability shows moderate-to-extreme or extremeto-total departure from reference conditions (80% confidence interval) within ecoregions . 

Figure 22 Sandy lowland was near Safford, Arizona, within the Madrean Archipelago ecoregion . 

Figure 23 Mean and 80% confidence interval for attributes and indicators in the Madrean 

Archipelago ecoregion . 

Figure 24 Northwest of Frenchglen, Oregon, near Fish Lake, within the Northern Cold Deserts ecoregion . 

Figure 25 Mean and 80% confidence interval for attributes and indicators in the 

Northern Cold Deserts ecoregion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Figure 26 Proportion of BLM rangelands where soil/site stability shows moderate departure 

from reference conditions (80% confidence interval) within ecoregions . 

Figure 27 Shortgrass prairie at the U.S. Department of Agriculture–Agricultural Research Service, 

Central Plains Experimental Range near Nunn, Colorado, within the South Central 

Semi-Arid Prairies ecoregion . 

Figure 28 Mean and 80% confidence interval for attributes and indicators in the South Central 

Semi-Arid Prairies ecoregion . 

Figure 29 California desert, within the Warm Deserts ecoregion . 

Figure 30 Mean and 80% confidence interval for attributes and indicators in the Warm Deserts ecoregion . 

Figure 31 Mixed-grass prairie near Battle Creek, Montana, within the West Central Semi-Arid 

Prairies ecoregion . 

Figure 32 Mean and 80% confidence interval for attributes and indicators in the West Central 

Semi-Arid Prairies ecoregion . 

Figure 33 Northeast of Crested Butte, Colorado, within the Western Cordillera ecoregion . 

Figure 34 Mean and 80% confidence interval for attributes and indicators in the Western 

Cordillera ecoregion . 

Table 1 Number of sample points by state .

Table 2 Indicators calculated for the 2011 BLM RRA and the methods used to measure the indicators .

Table 3 Combined assessments of the 17 rangeland indicators produce ratings of biotic integrity, 

hydrologic function, and soil/site stability .

Table 4 The number of points sampled and the acres of BLM rangelands within each ecoregion . 
Rangeland Resource Assessment—2011 1

renewable resources in the Federal Land Policy and 

Management Act of 1976 (Public Law 94-579). As a 

way to determine if the BLM was achieving sustained 

yield, Congress directed the agency to periodically 

and systematically inventory the public rangelands, 

identify current public rangeland conditions and 

trends, and report this information to Congress and 

the public. This report meets the requirements of 

section 201(a) (43 U.S.C. 1711(a)) of the Federal 

Land Policy and Management Act, as amended, 

and sections 1901 (b)(1) and 1903(a) of the Public 

Rangelands Improvement Act (Public Law 95-514).

Purpose and Background

The 2011 rangeland resource assessment (RRA) is a 

first-of-its-kind report on the status and condition of 

renewable resources on federal rangelands managed 

by the BLM. The BLM based the RRA on a statistical 

survey of 879 locations 

across BLM rangelands 

in 13 western states. 

Future RRAs will 

report the trend 

(change across time) in 

status and condition of 

renewable resources on 

BLM rangelands. 

Several aspects of this assessment make it 

unique. The 2011 RRA uses a standardized set 

Introduction

Rangelands are the largest ecosystem type in the 

United States, covering 830 million acres in the 

lower 48 states and 205 million acres in Alaska 

(The Heinz Center 2008). The Bureau of Land 

Management (BLM), 

within the Department 

of the Interior, manages 

nearly 194 million 

acres of rangelands in 

the lower 48 states and 

Alaska (USDI–BLM 

2013). Rangelands in the 

United States are diverse, 

including the prairies 

of the Midwest and 

Great Plains, sagebrush 

shrublands, deserts, 

mountain meadows, 

pastures and haylands, 

and tundra in Alaska. 

Although rangelands 

can appear barren and 

unproductive, rangelands 

provide us with minerals; 

food and fiber; huntable 

and watchable wildlife; 

clean, fresh water; open 

space and views; wilderness experiences; and 

inspiration (The Heinz Center 2008).

Congress directed the BLM to manage public 

lands for multiple uses and the sustained yield of 

Rangelands are lands on which 

the climax or potential plant 

cover is composed of grasses, 

grasslike plants, forbs, and 

shrubs managed as a natural 

ecosystem. Lands with introduced 

perennial grasses such as crested 

wheatgrass and managed as 

rangelands are also considered 

rangelands. Rangelands include 

grasslands, savannas, shrublands, 

deserts, tundra, alpine plant 

communities, marshes, wet 

meadows, and oak and pinyonjuniper woodlands.

Sustained yield means 

achievement and maintenance in 

perpetuity of a high-level annual 

or regular periodic output of the 

various renewable resources 

of the public lands consistent 

with multiple use (as defined 

in the Federal Land Policy and 

Management Act).

Status is an amount of a 

renewable resource at a point 

in time.

Condition is the status of a 

renewable resource in comparison 

with a reference value for that 

renewable resource.
2 Bureau of Land Management

of attributes and 

indicators to portray 

the status and condition 

of renewable resources 

on BLM-managed 

public rangelands. The 

BLM used standardized 

field methods and 

a statistically valid 

study design to 

measure attributes and 

indicators of rangeland 

status and condition 

consistently across all 

rangelands sampled. 

This consistency allowed 

the computation of 

statistically valid 

estimates of rangeland 

status and condition and the interpretation of those 

results across BLM rangelands.

The 2011 BLM RRA is a product of a partnership 

among the BLM, the United States Department of 

Agriculture–Natural Resources Conservation Service 

(NRCS), and the Center for Survey Statistics and 

Methodology (CSSM) at Iowa State University. 

The 2011 BLM RRA augments the National 

Resources Inventory (NRI) RRA, conducted by the 

NRCS, which estimates the status and condition 

of rangeland resources and describes trends on 

nonfederal rangelands. The NRCS conducts the NRI 

RRA in cooperation with the CSSM, which generates 

the statistics and survey design methods used in the 

NRI. The NRCS has conducted on-the-ground NRI 

sampling on nonfederal rangelands since 2003.

The BLM, NRCS, and CSSM developed this 

partnership to use funds and the existing workforce 

efficiently to provide a unified estimate of rangeland 

status and condition on nonfederal rangelands and 

BLM-managed public rangelands. The 2011 BLM 

RRA and the 2011 NRI used the same sampling 

design and the same trained data collectors. Field 

methods used in the 2011 BLM RRA were used also 

in the 2011 NRI. The CSSM provided statistical 

support for the selection of samples, support for the 

survey design, and statistical processing and estimates 

of the attributes and indicators for the 2011 BLM 

RRA (Nusser et al. 2013).

Rangeland Productivity

The attributes and indicators in this report tell a 

story about the productivity of BLM rangelands. 

The productivity of rangelands is the capacity of 

rangelands to produce commodities and satisfy 

values (National Research Council 1994). Sustaining 

rangeland productivity depends on ecological 

processes such as soil development, water cycling (the 

capture, storage, and safe release of precipitation), 

nutrient cycling (movement of nutrients through air, 

water, soil, and animals), energy flow (conversion of 

sunlight to plant matter and then animal matter), 

and the structure and dynamics of plant and animal 

communities (National Research Council 1994). The 

status and condition of the attributes and indicators 

give us a way to determine whether these processes 

are maintaining their functionality, degrading, 

or improving. For example, large areas with low 

soil aggregate stability or abundant bare ground 

demonstrate high potential for soil erosion, degrading 

productivity. Likewise, large areas free of invasive 

plants show that the structure of plant communities 

may be relatively stable, maintaining productivity. 

Multiple indicators tell a more complete story than 

one alone, and thus, any conclusions drawn about 

rangeland productivity should consider all indicators.

An attribute is a biological or 

physical component that provides 

information about the functional 

status of the ecological processes 

(soil development, water and 

nutrient cycling, and energy 

flow) on rangelands. Ecological 

processes are often complex 

and difficult to measure directly; 

attributes reduce the complexity 

of ecological processes to 

measureable components that 

show the status of these processes.

An indicator is a component 

of rangeland that has a 

characteristic (such as presence or 

absence, amount, or distribution) 

used to infer the status of 

productivity of rangeland.
Rangeland Resource Assessment—2011 3

Methods

Sample Design and Selection

The assessment team designed the 2011 BLM RRA 

to assess the status and condition of renewable 

resources on BLM rangelands in 13 western states: 

Arizona, California, Colorado, Idaho, Montana, 

New Mexico, Nevada, North Dakota, Oregon, 

South Dakota, Utah, Washington, and Wyoming. 

The assessment team did not assess the status and 

condition of renewable resources on BLM-managed 

public rangelands in Alaska because the NRI RRA 

did not sample Alaska. NRCS personnel and NRCScontracted personnel measured attributes and 

indicators of rangeland status and condition at 

sample points (i.e., locations) in these 13 western states.

For 2011, the BLM RRA relied on the existing 

sample design of the NRI. The NRI uses a stratified 

two-stage design where Public Land Survey System 

quarter-sections called segments are randomly 

selected within each township and three sample 

points are selected within each segment using a 

restricted randomization procedure that encourages a 

geographic spread of the points (Nusser et al. 2013).

The sampling universe for the BLM RRA sample was 

BLM-managed public land in the 13 western states. 

The BLM provided a geographic information system 

layer to the CSSM that defined the extent of BLMmanaged public land in each state. Segments eligible 

for sampling were those that had at least one point 

located on BLM-managed public land within the 

13 western states.

The target sample size of the 2011 BLM RRA was 

1,070 points on BLM-managed public rangelands, 

based on the constraints of the number of eligible 

segments and a sample design constraint of a 

maximum of 2 points per eligible segment. The CSSM 

selected a larger sample size of 1,200 points on BLMmanaged public lands to try to yield a final sample of 

1,070 BLM rangeland points. The CSSM allocated 

the 1,200 points to the 13 western states in proportion 

to the number of BLM-managed acres in each state 

and calculated the number of segments selected from 

this allocation. States having a small amount of BLMmanaged public lands had few to no segments, and 

states having greater amounts of BLM-managed public 

lands had a greater number of segments.

Of the three points within each segment, the CSSM 

selected a maximum of two points. If a segment 

contained one or two points located on BLMmanaged public land, the CSSM selected these 

points with certainty for the BLM RRA sample. If a 

segment had three points on BLM-managed public 

land, then the CSSM randomly selected two of the 

three points to be included in the sample.

Of the original sample of 1,200 points on BLMmanaged public land, NRCS personnel and NRCScontracted personnel actually sampled 883 points 

(table 1). The CSSM removed points from the 

sample that were (1) not on BLM-managed public 

land; (2) not on rangeland, such as those on roads, 

in water, or on forest land; and (3) on rangeland but 

could not be sampled, such as those requiring access 

across private land where permission was not granted, 

those in inaccessible terrain, and those on steep slopes 

that posed a safety hazard for sampling.
4 Bureau of Land Management

Table 1. Number of sample points by state.

State Number of Sample Points

Arizona 59

California 47

Colorado 29

Idaho 52

Montana 33

Nevada 274

New Mexico 75

North Dakota 0

Oregon 86

South Dakota 1

Utah 118

Washington 3

Wyoming 106

Total 883

Data Collection

NRCS personnel and NRCS-contracted personnel 

collected all data for the 2011 BLM RRA following 

NRI protocols and the BLM’s core terrestrial 

methods (MacKinnon et al. 2011). Before receiving 

authorization to collect data, these field personnel 

received training and performed calibration on the 

methods for data collection and the attributes and 

indicators to be measured. Data collection occurred 

primarily in the summer and fall of 2011 for most 

states. Data collection occurred from 2011 through 

the spring of 2012 in Arizona and from December 

2011 to October 2012 in California.

The data collectors conducted rangeland health 

assessments at each sample location using the 

protocol from Pellant et al. (2005). They completed 

measurements for the BLM’s core terrestrial 

indicators (MacKinnon et al. 2011) using 

protocols from Herrick et al. (2009). Each sample 

location consisted of a 0.4-acre (0.16-hectare) area 

encompassed by a 150-foot (45.7-meter) diameter 

circular plot centered on the intersection of two 

perpendicular 150-foot (45.7-meter) line transects.

The data collectors used the following five methods 

to measure the rangeland attributes and indicators:

1. Rangeland health assessment protocol (Pellant et 

al. 2005)

2. Line-point intercept supplemented with plot-area 

species inventory

3. Canopy gap intercept

4. Height of woody and herbaceous vegetation

5. Soil aggregate stability

Data provided by this suite of methods allows for 

the calculation of myriad attributes and indicators 

of rangeland resources. For the BLM RRA, however, 

the assessment team reported on a limited suite 

of indicators related to national-scale rangeland 

resource productivity (table 2) and did not produce 

an exhaustive set of estimates from all methods. 

For example, although the data collectors recorded 

vegetation height data at each sample location, 

the assessment team did not report height-related 

indicators in this BLM RRA (but might report 

them in future RRAs). Descriptions of each method 

(excluding vegetation height) and the attributes or 

indicators measured with each method follow.
Rangeland Resource Assessment—2011 5

Table 2. Indicators calculated for the 2011 BLM RRA and the methods used to measure the indicators.

Indicator Method

Average amount of bare ground on BLM rangelands Line-point intercept

Proportion of BLM rangelands with at least 20% bare ground Line-point intercept

Proportion of BLM rangelands with at least 30% bare ground Line-point intercept

Proportion of BLM rangelands with at least 40% bare ground Line-point intercept

Proportion of BLM rangelands with at least 50% bare ground Line-point intercept

Proportion of BLM rangelands where soil aggregate stability is Soil aggregate stability 

ranked 4 or less

Proportion of BLM rangelands with at least 20% of the land having 

intercanopy gaps of at least 2 meters in length

Canopy gap intercept

Proportion of BLM rangelands with nonnative invasive 

plant species present

Line-point intercept with 

plot-area species inventory

Proportion of BLM rangelands with abundant nonnative invasive 

plant species*

Line-point intercept

Proportion of BLM rangelands where biotic integrity shows moderate 

departure from reference conditions

Rangeland health 

assessment

Proportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsRangeland health 

assessment

Proportion of BLM rangelands where hydrologic function shows moderate 

departure from reference conditions

Rangeland health 

assessment

Proportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsRangeland health 

assessment

Proportion of BLM rangelands where soil/site stability shows moderate 

departure from reference conditions

Rangeland health 

assessment

Proportion of BLM rangelands where soil/site stability shows moderate-toextreme or extreme-to-total departure from reference conditionsRangeland health 

assessment

* ≥25% of foliar intercepts of vegetation are nonnative invasive plant species

Rangeland Health Assessment

Rangeland health assessments characterize three 

attributes of the ecological processes of rangeland 

ecosystems: biotic integrity, hydrologic function, 

and soil/site stability (Pellant et al. 2005). For each 

rangeland health assessment, the data collectors 

qualitatively compared 17 biological and physical 

indicators (table 3) at the sample location to reference 

conditions for each indicator at that location. 

Reference conditions are those that occur where 

the biotic integrity, hydrologic function, and soil/

site stability are at their potential under the natural 

disturbance regime. A detailed reference sheet specific 

to the type of land, or ecological site, at the sample 

location describes reference conditions for each 

indicator. A team of experts uses the best available 

information to develop the reference sheets contained 

within the ecological site descriptions.

The data collectors 

recorded the degree 

of departure from 

reference conditions in 

five rating categories: 

none to slight, slight 

to moderate, moderate, 

moderate to extreme,

and extreme to total.

They combined 

departure ratings for 

Moderate departure from 

reference conditions suggests 

that the attribute is “at risk” of 

declining in condition on the 

rangeland.

Moderate-to-extreme departure 

or extreme-to-total departure 

suggests that the attribute has 

declined in condition on the 

rangeland.
6 Bureau of Land Management

the 17 indicators to produce composite ratings of 

departure from reference conditions for each of the 

three rangeland health attributes:

•	 Biotic integrity is the capacity of the biotic

community to support ecological processes (the 

water cycle, energy flow, and nutrient cycle) within 

the normal range of variability expected for the 

ecological site, to resist a loss in the capacity to 

support these processes, and to recover this capacity 

when losses do occur. The biotic community 

includes plants, animals, and microorganisms 

occurring both above and below ground (Pellant 

et al. 2005). Biotic integrity, as measured, is a 

compilation of the ratings of departure from 

reference conditions for nine indicators (table 3).

•	 Hydrologic function is the capacity of an area to

capture, store, and safely release water from rainfall, 

run-on, and snowmelt; to resist a reduction in 

this capacity; and to recover this capacity when 

a reduction does occur (Pellant et al. 2005). 

Hydrologic function, as measured, is a compilation 

of the ratings of departure from reference 

conditions for 10 indicators (table 3).

•	 Soil/site stability is the capacity of an area to limit

redistribution and loss of soil resources (including 

nutrients and organic matter in the soil) by wind 

and water (Pellant et al. 2005). Soil/site stability, 

as measured, is a compilation of the ratings of 

departure from reference conditions for 

10 indicators (table 3).

Table 3. Combined assessments of the 17 rangeland health indicators produce ratings of biotic integrity, 

hydrologic function, and soil/site stability (Pellant et al. 2005).

Rangeland

Health Indicator DescriptionBiotic IntegrityHydrologic FunctionSoil/Site Stability

Soil surface 

resistance to 

erosion

The resistance of the surface of the soil to erosion. X X X

Soil surface loss 

or degradation The loss or degradation of the soil surface layer. X X X

Compaction layer

Presence of a near-surface layer of dense soil caused by 

repeated impacts on or disturbances of the soil surface, and 

the thickness of this layer.

X X X

Functional/

structural groups

Abundance and relative dominance of groups of plant 

species; groups are based on similarity in characteristics 

such as height, volume, root structure, type of 

photosynthesis, or life cycle. 

X

Plant mortality/

decadence

The proportion of dead or decadent (for example, moribund 

or dying) plants, compared with young or mature plants, in 

the plant community.

X

Litter amount

The cover of litter and the depth of litter, which is any dead 

plant material that is detached from the base of the plant 

and is in contact with the soil surface.

X X

Annual 

production

The net quantity of aboveground plant material produced 

within a year.

X
Rangeland Resource Assessment—2011 7

Rangeland

Health Indicator DescriptionBiotic IntegrityHydrologic FunctionSoil/Site Stability

Invasive plants

Plants that are invasive to the sample location, with invasive 

plants being plants that are not part of, or are a minor 

component of, the original plant community and that have 

the potential to become a dominant or codominant species 

on the sample location if their future establishment and 

growth are not actively controlled by management actions.

X

Reproductive 

capability of 

perennial plants

The seed production of sexually reproducing plants and tiller 

or rhizome production of asexually reproducing plants.

X

Rills The number and extent of rills, which are small, generally 

linear erosional water flows across the surface of the soil.

X X

Gullies The number of gullies, which are channels cut into the soil 

by moving water, and the erosion associated with gullies.

X X

Water flow 

patterns

The presence of water flow patterns, which is the path that 

water takes across the soil surface during overland flow 

caused by rainstorms or snowmelt.

X X

Pedestals and/or 

terracettes

The number and height of pedestals and terracettes caused 

by erosion. Pedestals are rocks or plants that appear 

elevated as a result of soil loss by wind or water erosion. 

Terracettes are benches of soil deposition caused by water 

movement and located behind obstacles.

X X

Bare ground

The amount and distribution of bare ground, which is 

exposed mineral or organic soil that is susceptible to 

raindrop splash erosion.

X X

Plant community 

composition and 

distribution relative 

to infiltration and 

runoff

The distribution of the amount and type of vegetation in 

relation to its ability to control infiltration of water and 

runoff of water.

X

Wind-scoured, 

blowout, and/or 

depositional areas

The extent of wind-scoured, blowout, and depositional areas 

caused by accelerated wind erosion of soil.

X

Litter movement

The degree and amount of litter movement caused by 

erosion by wind or water, with litter being dead plant 

material that is in contact with the soil surface.

X

Table 3. Continued.

identifying reference conditions was not available at 

all sampling locations. The 2011 BLM RRA reported 

on six indicators derived from the rangeland health 

assessment protocol (table 2).

The assessment team used the attributes of rangeland 

health to characterize the condition of renewable 

resources on BLM rangelands. The data collectors 

collected rangeland health assessment data on 

only 828 points because requisite soils data for 
8 Bureau of Land Management

Line-Point Intercept with PlotArea Species Inventory

Line-Point Intercept:

The line-point intercept (LPI) method estimates foliar 

and basal plant cover as well as the proportion of the 

plot that is bare ground or otherwise nonvegetated 

(e.g., rock). The 2011 RRA used LPI to describe the 

presence and relative abundance of plants and soil 

features in a plot. At 3-foot (0.9-meter) intervals along 

each plot transect, the data collectors dropped a long, 

narrow pin and recorded aerial foliage of vegetation 

touching the pin by species. They also recorded any 

plant species intercepted by the pin at the ground 

surface as well as litter, rock, and the soil surface. For 

a more detailed description of the LPI technique, see 

Herrick et al. (2009).

The data collectors used the LPI method to collect 

data on bare ground and foliar and basal cover of 

nonnative invasive plant species. The CSSM used 

these data to calculate the average amount of bare 

ground on BLM rangelands, the proportion of BLM 

rangelands with equal to or more than 20%, 30%, 

40%, and 50% bare ground, and the proportion of 

BLM rangelands with abundant nonnative invasive 

plant species (table 2). The data collectors recorded 

bare ground for pins that did not hit plants and did 

not hit rock or gravel. The CSSM calculated bare 

ground for each plot as the number of pins that 

hit bare ground at the soil surface, divided by the 

total number of pin drops along the two transects, 

and then multiplied by 100. The assessment team 

considered nonnative invasive plant species abundant 

when ≥25% of foliar intercepts of vegetation on the 

line transects in a plot were nonnative invasive 

plant species.

Plot-Area Species Inventory:

The plot-area species inventory captured the 

presence of a majority of plant species occurring 

in the plot. The data collectors searched the entire 

plot area systematically to identify all plant species 

encountered. Searches lasted 15 minutes.

The data collectors used LPI supplemented with the 

plot-area species inventory method to collect data 

on nonnative invasive plant species. The CSSM used 

these data to calculate the proportion of rangelands 

with nonnative invasive plant species present (table 2). 

The data collectors recorded the presence of 

nonnative invasive plant species in the plot if at least 

one nonnative invasive plant species was detected 

either on the line transects or on the walking search 

of the plot area. Appendix A lists nonnative invasive 

plant species included in the search of all plots.

Canopy Gap Intercept

The canopy gap intercept method (Herrick et 

al. 2009) estimates the proportion of a plot with gaps 

(i.e., areas without plant cover) of different sizes. 

An abundance of large canopy gaps can indicate 

decreased rangeland forage production, low-quality 

wildlife habitat, and an increased susceptibility to 

wind erosion. Potential for wind erosion is a function 

of canopy gap size and vegetation height, and most 

rangelands with canopy gaps of greater than 2 meters 

are at high risk for wind erosion (Okin 2008). 

The data collectors used the canopy gap intercept 

method on the same transects where they used the 

LPI method, measuring gaps in vegetation between 

the boundaries of the plant canopies along both plot 

transects. The canopy gap intercept method allowed 

the CSSM to calculate the proportion of BLM 

rangelands where vegetation gaps of at least 2 meters 

in length accounted for 20% or more of the length of 

the line transects (table 2). 

Soil Aggregate Stability

Soil aggregate stability measures the ability of soils to 

hold together despite disturbance. Unstable soils are 

more susceptible to wind and water erosion (Pellant 

et al. 2005; Herrick et al. 2001). 

The data collectors conducted a rangeland soil 

aggregate stability test (Herrick et al. 2001) at nine 

locations within each plot area. They collected surface 

soil samples at five locations along one transect and at 

four locations along the other transect. They exposed 
Rangeland Resource Assessment—2011 9

surface soil samples of about 6 millimeters (0.24 inches) 

in diameter to rapid wetting with water to determine 

the length of time it took for the soil sample to 

dissolve or crumble. The data collectors ranked the 

soil samples on a scale of 1 to 6. They based the 

rankings on observations of dissolving or crumbling 

during the first 5 minutes after immersion in distilled 

water and the percent of the soil sample remaining 

on a 1.5-millimeter (0.06-inch) sieve after five 

dipping cycles at the end of the 5-minute period. The 

higher the ranking, the greater the stability of the soil 

aggregate. The soil aggregate stability method allowed 

the CSSM to compute the average ranking for the 

nine soil aggregate tests for each plot area and calculate 

the proportion of BLM rangelands having an average 

soil aggregate stability ranking of 4 or less (table 2). 

Data Summarization

The assessment team summarized the attribute and 

indicator data by ecoregions as defined by the 

U.S. Environmental Protection Agency (EPA) 

(https://www.epa.gov/eco-research/ecoregions-northamerica). Ecoregions are areas that contain 

geographically distinct rangelands (USDI–BLM 

2008). Ecoregions in the 2011 RRA were either 

EPA level II ecoregions, EPA level III ecoregions, or 

ecoregions created from a combination of EPA level 

III ecoregions. The ecoregions selected for the 2011 

RRA balance the need to report on units that are 

meaningful for BLM rangelands with the available 

sample size. Figure 1 identifies the ecoregions and the 

number of locations sampled within each of them. 

Two ecoregions, the Marine West Coast Forest 

and Mediterranean California, had few to no 

data collection points. The assessment team 

could not confidently say that the attribute and 

indicator estimates from the few points sampled 

represented conditions across these two ecoregions, 

so they excluded the ecoregions from the 2011 

RRA. Removing the four points sampled in these 

ecoregions from the 883 total sampled points left 

879 points in this RRA. If future data collection 

efforts include 

additional sample 

points, future RRAs 

may include these 

ecoregions.

Ecoregions in this 

2011 RRA included 

the Arizona/New 

Mexico Mountains, 

Central Basin and 

Range, Eastern Cold 

Deserts, Madrean 

Archipelago, Northern 

Cold Deserts, South 

Central Semi-Arid 

Prairies, Warm Deserts, 

West Central Semi-Arid 

Prairies, and Western 

Cordillera. The CSSM 

calculated attributes and 

indicators within each 

of these ecoregions with 

statistics of mean 

(average), standard error (SE), coefficient of 

variation (CV), and an 80% confidence interval. 

Appendix B contains the attribute and indicator 

estimates by ecoregion.

The assessment team interpreted the calculated 

attributes and indicators to describe the status and 

condition of rangeland resources for each ecoregion. 

The ecoregion interpretations also highlight any 

differences between that ecoregion and other 

ecoregions for each attribute or indicator.

The assessment team determined differences in 

attributes or indicators across ecoregions or between 

pairs of ecoregions using an omnibus F test. The results 

of the omnibus F test showed that the estimates for 

each attribute or indicator were not all the same across 

the ecoregions (appendix C). The assessment team 

also performed pairwise comparisons of attribute and 

indicator estimates to determine significant differences 

between ecoregions (appendix D).

What Is a Confidence Interval?

A confidence interval represents 

the uncertainty associated with 

an indicator estimate due to 

sampling. A confidence interval of 

80% means that if the sampling 

and measurements were repeated 

many times, 80% of the time the 

true value of the indicator would 

lie within the interval.

The width of a confidence 

interval is determined by the 

underlying variability of the 

indicator being estimated as 

well as the number of samples. 

Wide-ranging confidence intervals 

are typically associated with 

very heterogeneous ecoregions 

or ecoregions with small 

sample sizes—both cases where 

the sampling effort may be 

insufficient. Narrow confidence 

intervals are typically associated 

with ecoregions with larger 

sample sizes.
10 Bureau of Land Management

Figure 1. Ecoregions and the number of points sampled in each ecoregion (= ct) for the 2011 BLM RRA.
Rangeland Resource Assessment—2011 11

Extrapolation of Sample 

Data to BLM Rangelands

The 2011 RRA reports on rangeland resource status 

and condition based on a sample of 879 locations. 

The 879 locations in the sample are representative 

of rangeland resources on about 150 million acres of 

BLM lands across the ecoregions (table 4).

Table 4. The number of points sampled and the acres 

of BLM rangelands within each ecoregion.

Ecoregion

Number 

of Sample 

Points

Acres of BLM 

Rangelands*

Arizona/New Mexico 

Mountains

9 1,147,998

Central Basin and 

Range

259 42,027,281

Eastern Cold Deserts 218 34,546,049

Madrean Archipelago 12 1,094,849

Northern Cold 

Deserts

158 25,903,037

South Central 

Semi-Arid Prairies

9 1,623,357

Warm Deserts 139 28,328,632

West Central 

Semi-Arid Prairies

36 7,756,129

Western Cordillera 39 7,696,398

Total 879 150,123,730

* Acres of BLM rangelands estimated by the CSSM (Nusser et al. 2013).

Rangeland Resource Assessment—2011 13

Rangeland Resources Status and Condition

Arizona/New Mexico 

Mountains Ecoregion

Overview

The Arizona/New Mexico Mountains ecoregion is 

an EPA level III ecoregion (figure 2). The climate 

is variable, but generally characterized by warm 

to hot summers and mild winters. Mean annual 

temperatures vary with elevation, ranging from 

19 °C in lower southern valleys to 3 °C at high 

elevations. More than half the precipitation occurs 

with thunderstorms in July, August, and September. 

The remaining precipitation occurs from December 

through March with frontal storms from the Pacific. 

Mean annual precipitation is 477 mm, ranging from 

270 mm at lower elevations to more than 1,000 mm 

on higher peaks. Steep foothills, mountains, and 

high plateaus characterize the terrain. Chaparral 

shrublands dominate the vegetation in the lowlands. 

At middle elevations, pinyon-juniper woodlands are 

common, and higher elevations have evergreen forests 

(Wiken et al. 2011).

Figure 2. Agua Fria National Monument, Arizona, within the Arizona/New Mexico Mountains ecoregion 

(BLM photo). 
14 Bureau of Land Management

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is the amount of a 

renewable resource at a point in time. Condition 

is the status of a renewable resource in comparison 

against a reference value. The assessment team 

reported all indicators using an 80% confidence 

interval. An 80% confidence interval means that 

there is an 80% chance that the true population 

mean lies within that range. Average conditions for 

an attribute or an indicator in this ecoregion will fall 

within this range. For more information, see “Data 

Summarization.” Differences in climate, vegetation 

type, physiography, and similar broad-scale factors 

likely drive differences in ecoregion status (e.g., 

bare ground). Differences in management factors 

likely drive differences in condition (e.g., rangeland 

health attributes).

Figure 3 shows the means and 80% confidence 

intervals for each indicator. Within the Arizona/

New Mexico Mountains ecoregion, average bare 

ground on BLM rangelands was between 10% and 

33%. Bare ground refers to bare mineral soil with 

no vegetation, rocks, litter, or other cover above it. 

Greater amounts of bare ground suggest an increased 

risk of soil erosion (Smith and Wischmeier 1962, 

Morgan 1986, Benkobi et al. 1993, Blackburn and 

Pierson 1994, Pierson et al. 1994, Gutierrez and 

Hernandez 1996, and Cerda 1999 in Pellant et al. 2005).

Between 18% and 89% of the rangelands here had 

at least 20% bare ground. Some rangelands had at 

least 30% bare ground, but the sample size was not 

large enough to confidently estimate the proportion 

of BLM rangelands. No BLM rangelands sampled in 

this ecoregion had at least 40% bare ground.

Soil stability and occurrence of large canopy gaps 

are notable indicators of the status of the Arizona/

New Mexico Mountains ecoregion. Most soils in 

this ecoregion had low aggregate stability, suggesting 

high erosion potential. Between 89% and 100% 

of BLM rangelands had soils that are susceptible to 

breaking apart and eroding from wind and water. 

Only the Madrean Archipelago and Warm Deserts 

ecoregions had as much rangeland with unstable soils 

as the Arizona/New Mexico Mountains ecoregion 

(figure 4). Between 29% and 92% of the rangelands 

in the Arizona/New Mexico Mountains ecoregion 

had large gaps (≥2 meters) between plant canopies 

that comprised more than 20% of the soil surface. 

The “openness” of the vegetation suggests that BLM 

rangelands in this ecoregion may be more vulnerable 

to soil erosion by water and wind. Most rangelands 

with canopy gaps of greater than 2 meters are at high 

risk for wind erosion (Okin 2008).

Nonnative invasive plant species had colonized an 

estimated 6% to 100% of BLM rangelands in the 

Arizona/New Mexico Mountains ecoregion. Some 

BLM rangelands had abundant nonnative invasive 

plants, but the sample size was not large enough 

to confidently estimate the proportion of BLM 

rangelands. Nonnative invasive plant species often 

outcompete native plant species for growing space, 

causing a decline in abundance of native plant 

species. This decline in turn causes changes in wildlife 

habitat availability, wildfire frequency and severity, 

and susceptibility of soil to erosion. 

An estimated 19% to 52% of the rangelands in the 

Arizona/New Mexico Mountains ecoregion were at 

risk of declining biotic integrity relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that these rangelands and their associated plant, 

animal, and microorganism communities may be 

starting to have trouble cycling water and nutrients, 

capturing energy from sunlight, and sustaining 

other ecological processes. More rangelands are at 

risk of declining biotic integrity here than on nearly 

all remaining BLM rangelands (figure 5). Some 

BLM rangelands had diminished biotic integrity 

relative to reference conditions (rating of moderateto-extreme or extreme-to-total departure), but the 

sample size was not large enough to confidently 

estimate the proportion. 
Rangeland Resource Assessment—2011 15

Some BLM rangelands in the Arizona/New Mexico 

Mountains ecoregion were at risk of declining 

hydrologic function relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005), but the sample size was not 

large enough to confidently estimate the proportion. 

Likewise, some BLM rangelands sampled in this 

ecoregion had diminished hydrologic function 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure). The sample size 

was not large enough to confidently estimate the 

proportion of rangelands.

No BLM rangelands sampled in the Arizona/New 

Mexico Mountains ecoregion were at risk of declining 

soil and site stability relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005). Some BLM rangelands sampled 

in this ecoregion had diminished soil and site stability 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure), but the sample size 

was not large enough to confidently estimate the 

proportion of rangelands.

Implications for Productivity

Rangeland health assessments showed that declining 

biotic integrity was a primary threat to productivity 

in the Arizona/New Mexico Mountains, with at 

least one-fifth of the ecoregion at risk of decline. 

In addition, low soil aggregate stability and large 

intercanopy gaps present on large proportions of 

the rangelands suggest further declines in soil and 

site stability and hydrologic function and, thus, 

future productivity.
16 Bureau of Land Management

0 10 20 30 40 50 60 70 80 90 100

Percent

Arizona/New Mexico Mountains (n = 9)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions

Figure 3. Mean and 80% confidence interval for attributes and indicators in the Arizona/New Mexico Mountains ecoregion.
Rangeland Resource Assessment—2011 17

Figure 4. Proportion of BLM rangelands where soil aggregate stability is ranked 4 or less (80% confidence 

interval) within ecoregions.
18 Bureau of Land Management

Figure 5. Proportion of BLM rangelands where biotic integrity shows moderate departure from reference 

conditions (80% confidence interval) within ecoregions.
Rangeland Resource Assessment—2011 19

Central Basin and Range 

Ecoregion

Overview

The Central Basin and Range ecoregion is an EPA 

level III ecoregion (figure 6). Hot summers and mild 

winters are typical in this ecoregion. Mean annual 

temperatures vary with elevation, ranging from 

14 °C in lowlands to 2 °C in the mountains. Mean 

annual precipitation is 277 mm, ranging from 4 mm 

to more than 1,000 mm. Most of the rainfall occurs 

in the summer. Broad basins and valleys interrupted 

by mountain ranges characterize the terrain. Basin 

vegetation is shrub-dominated with primarily coolseason native grasses. Mountain vegetation ranges 

from shrublands at lower elevations to forests at 

higher elevations (Wiken et al. 2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition is the 

status of a renewable resource in comparison against 

a reference value. The assessment team reported all 

indicators using an 80% confidence interval. An 80% 

confidence interval means that there is an 80% chance 

that the true population mean lies within that range. 

Average conditions for an attribute or an indicator 

in this ecoregion will fall within this range. For more 

information, see “Data Summarization.” Differences 

in climate, vegetation type, physiography, and similar 

broad-scale factors likely drive differences in ecoregion 

status (e.g., bare ground). Differences in management 

factors likely drive differences in condition (e.g., 

rangeland health attributes).

Figure 6. Black Rock Desert–High Rock Canyon Emigrant Trails National Conservation Area, north of 

Gerlach, Nevada, within the Central Basin and Range ecoregion (BLM photo).
20 Bureau of Land Management

Figure 7 shows the means and 80% confidence 

intervals for each indicator. Within the Central Basin 

and Range ecoregion, average bare ground on BLM 

rangelands was between 16% and 25%. Bare ground 

refers to bare mineral soil with no vegetation, rocks, 

litter, or other cover above it. Greater amounts of 

bare ground suggest an increased risk of soil erosion 

(Smith and Wischmeier 1962, Morgan 1986, 

Benkobi et al. 1993, Blackburn and Pierson 1994, 

Pierson et al. 1994, Gutierrez and Hernandez 1996, 

and Cerda 1999 in Pellant et al. 2005). A large 

proportion of BLM rangelands, between 30% and 

46%, had at least 20% bare ground, and only 8% to 

20% of BLM rangelands had at least 40% bare ground.

BLM rangelands in the Central Basin and Range had 

less bare ground than BLM rangelands in the Eastern 

Cold Deserts and Warm Deserts ecoregions (figure 8). 

Likewise, a smaller proportion of BLM rangelands in 

this ecoregion had large amounts of bare ground (i.e., 

at least 20%, 30%, or 40% bare ground) than in the 

Eastern Cold Deserts and Warm Deserts (figures 9, 

10, and 11). BLM rangelands in the Central Basin 

and Range had greater amounts of bare ground than 

BLM rangelands in the West Central Semi-Arid 

Prairies (figure 8). More of the BLM rangelands here 

had large amounts of bare ground (at least 40% or 

50% bare ground on average) than in the Northern 

Cold Deserts (figures 11 and 12).

Many soils in the Central Basin and Range 

had low soil aggregate stability, suggesting high 

erosion potential. Between 35% and 52% of BLM 

rangelands had soils that are susceptible to breaking 

apart and eroding from wind and water. However, 

the proportion of BLM rangelands with unstable soils 

was less than in the Arizona/New Mexico Mountains, 

Eastern Cold Deserts, Madrean Archipelago, and 

Warm Deserts (figure 4).

Between 52% and 66% of BLM rangelands in the 

Central Basin and Range ecoregion had large gaps 

(≥2 meters) between plant canopies that comprised 

more than 20% of the soil surface. This greater 

“openness” of the vegetation suggests that BLM 

rangelands in this ecoregion may be more vulnerable 

to soil erosion by water and wind. Most rangelands 

with canopy gaps of greater than 2 meters are at 

high risk for wind erosion (Okin 2008). Large gaps 

between plant canopies were more prevalent on 

BLM rangelands in the Central Basin and Range 

than in the Eastern Cold Deserts, Northern Cold 

Deserts, and West Central Semi-Arid Prairies, but less 

prevalent than in the Warm Deserts (figure 13).

The presence and abundance of nonnative invasive 

plant species is a notable indicator of the condition 

of BLM rangelands in the Central Basin and Range 

ecoregion. Nonnative invasive plant species had 

colonized a large proportion of BLM rangelands in 

this ecoregion, on average between 66% and 80%. 

Between 34% and 52% of BLM rangelands had 

abundant nonnative invasive plants. Nonnative 

invasive plant species often outcompete native 

plant species for growing space, causing declines in 

abundance of native plant species. This decline in 

turn causes changes in wildlife habitat availability, 

wildfire frequency and severity, and susceptibility 

of soil to erosion. The Central Basin and Range 

ecoregion had a greater proportion of BLM 

rangelands colonized by nonnative invasive plant 

species than the Eastern Cold Deserts, South Central 

Semi-Arid Prairies, Warm Deserts, West Central 

Semi-Arid Prairies, and Western Cordillera (figure 14). 

The Central Basin and Range also had a greater 

proportion of BLM rangelands with abundant 

nonnative invasive plant species than the Eastern 

Cold Deserts, Warm Deserts, and Western Cordillera 

(figure 15).

An estimated 3% to 8% of the BLM rangelands 

in the Central Basin and Range ecoregion were at 

risk of declining biotic integrity relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that these rangelands and their associated plant, 

animal, and microorganism communities may be 

starting to have trouble cycling water and nutrients, 
Rangeland Resource Assessment—2011 21

capturing energy from sunlight, and sustaining other 

ecological processes. Some BLM rangelands in this 

ecoregion had diminished biotic integrity relative 

to reference conditions (moderate-to-extreme or 

extreme-to-total departure), but the proportion 

could not be confidently estimated attributable to 

insufficient sample size. 

An estimated 1% to 5% of BLM rangelands in the 

Central Basin and Range ecoregion were at risk of 

declining hydrologic function relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that the soils and vegetation on these rangelands 

may be starting to have trouble capturing, storing, 

and safely releasing water. A lower proportion of 

rangelands were at risk of declining hydrologic 

function in Central Basin and Range than in the 

Eastern Cold Deserts, Warm Deserts, and West 

Central Semi-Arid Prairies (figure 16). No BLM 

rangelands sampled in this ecoregion had diminished 

hydrologic function relative to reference conditions 

(moderate-to-extreme or extreme-to-total departure).

An estimated 0.4% to 3% of BLM rangelands in the 

Central Basin and Range ecoregion were at risk of 

declining soil and site stability relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that excessive amounts of soil may be eroding by 

wind and water on these rangelands. No BLM 

rangelands sampled in this ecoregion had diminished 

soil and site stability relative to reference conditions 

(moderate-to-extreme or extreme-to-total departure).

Implications for Productivity

Rangeland health assessments showed that less than 

10% of the Central Basin and Range ecoregion was 

at risk of declining productivity, with biotic integrity 

at risk of the largest declines. However, abundant 

nonnative invasive plant species and frequent large 

plant canopy gaps represent potential threats to 

biotic integrity, soil and site stability, and hydrologic 

function and, thus, future productivity. 
22 Bureau of Land Management

Figure 7. Mean and 80% confidence interval for attributes and indicators in the Central Basin and Range ecoregion.

0 10 20 30 40 50 60 70 80 90 100

Percent

Central Basin and Range (n = 259)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
Rangeland Resource Assessment—2011 23

Figure 8. Average amount of bare ground (80% confidence interval) on BLM rangelands within ecoregions.
24 Bureau of Land Management

Figure 9. Proportion of BLM rangelands with at least 20% bare ground (80% confidence interval) 

within ecoregions.
Rangeland Resource Assessment—2011 25

Figure 10. Proportion of BLM rangelands with at least 30% bare ground (80% confidence interval) 

within ecoregions.
26 Bureau of Land Management

Figure 11. Proportion of BLM rangelands with at least 40% bare ground (80% confidence interval) 

within ecoregions.
Rangeland Resource Assessment—2011 27

Figure 12. Proportion of BLM rangelands with at least 50% bare ground (80% confidence interval) 

within ecoregions.
28 Bureau of Land Management

Figure 13. Proportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 

2 meters in length (80% confidence interval) within ecoregions.
Rangeland Resource Assessment—2011 29

Figure 14. Proportion of BLM rangelands with nonnative invasive plant species present (80% confidence 

interval) within ecoregions.
30 Bureau of Land Management

Figure 15. Proportion of BLM rangelands with abundant nonnative invasive plant species (80% confidence 

interval) within ecoregions.
Rangeland Resource Assessment—2011 31

Figure 16. Proportion of BLM rangelands where hydrologic function shows moderate departure from 

reference conditions (80% confidence interval) within ecoregions. 
32 Bureau of Land Management

Eastern Cold Deserts 

Ecoregion

Overview

The Eastern Cold Deserts ecoregion is composed 

of three EPA level III ecoregions: Wyoming Basins, 

Colorado Plateaus, and Arizona/New Mexico Plateau 

(figure 17). Warm to hot summers and cold winters 

are typical in the Eastern Cold Deserts ecoregion. 

Mean annual temperatures get slightly warmer as 

you move from north to south, ranging from 

0 °C to 8 °C in the Wyoming Basins, 5 °C to 

15 °C in the Colorado Plateau, and 5 °C to 16 °C 

in the Arizona/New Mexico Plateau. Mean annual 

precipitation averages 290 to 300 mm across all three 

subregions, with lows around 130 mm and highs 

up to 800 mm at higher elevations. Plains, plateaus, 

mesas, steep canyons and valleys are characteristic 

landforms. Grasslands and shrublands are the most 

common vegetation types. Some woodlands occur 

at higher elevations. Grasslands are more common 

in the northern and southern areas of the ecoregion 

(Wiken et al. 2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition is the 

status of a renewable resource in comparison against 

a reference value. The assessment team reported all 

indicators using an 80% confidence interval. An 

80% confidence interval means that there is an 

80% chance that the true population mean lies within 

that range. Average conditions for an attribute or an 

indicator in this ecoregion will fall within this range. 

For more information, see “Data Summarization.” 

Differences in climate, vegetation type, physiography,

Figure 17. Head of Sinbad, San Rafael Swell, Utah, within the Eastern Cold Deserts ecoregion (BLM photo).
Rangeland Resource Assessment—2011 33

and similar broad-scale factors likely drive differences 

in ecoregion status (e.g., bare ground). Differences 

in management factors likely drive differences in 

condition (e.g., rangeland health attributes).

Figure 18 shows the means and 80% confidence 

intervals for each indicator. Within the Eastern Cold 

Deserts ecoregion, average bare ground on BLM 

rangelands was between 27% and 31%. Bare ground 

refers to bare mineral soil with no vegetation, rocks, 

litter, or other cover above it. Greater amounts of 

bare ground suggest an increased risk of soil erosion 

(Smith and Wischmeier 1962, Morgan 1986, 

Benkobi et al. 1993, Blackburn and Pierson 1994, 

Pierson et al. 1994, Gutierrez and Hernandez 1996, 

and Cerda 1999 in Pellant et al. 2005). Bare ground 

was widespread on BLM rangelands in this ecoregion, 

with between 56% and 66% of the rangelands having 

at least 20% bare ground. Bare ground was more 

widespread in the Eastern Cold Deserts than on 

nearly all other BLM rangelands. Only rangelands 

in the Warm Deserts, South Central Semi-Arid 

Prairies, and Arizona/New Mexico Mountains had 

as much or more bare ground than the Eastern Cold 

Deserts (figure 8).

Many soils in the Eastern Cold Deserts had low soil 

aggregate stability, suggesting high erosion potential. 

Between 59% and 68% of BLM rangelands had soils 

that are susceptible to breaking apart and eroding from 

wind and water. Only rangelands in the Arizona/New 

Mexico Mountains, Madrean Archipelago, and Warm 

Deserts had more rangelands with erodible soils than 

the Eastern Cold Deserts (figure 4).

Between 30% and 38% of BLM rangelands in the 

Eastern Cold Deserts had large gaps (≥2 meters) 

between plant canopies that comprised more than 

20% of the surface. This “openness” of the vegetation 

suggests that BLM rangelands in this ecoregion may 

be more vulnerable to soil erosion by water and 

wind. Most rangelands with canopy gaps of greater 

than 2 meters are at high risk for wind erosion 

(Okin 2008). Large gaps between plant canopies were 

more prevalent in the Eastern Cold Deserts than in 

the Northern Cold Deserts and West Central SemiArid Prairies. However, large gaps were less prevalent 

here than on BLM rangelands in the Central Basin 

and Range and Warm Deserts (figure 13).

Nonnative invasive plant species had colonized a 

large proportion of BLM rangelands in the Eastern 

Cold Deserts, between 48% and 61%. However, 

a relatively small proportion of these rangelands, 

between 7% and 12%, had abundant nonnative 

invasive plant species. Only BLM rangelands in the 

Central Basin and Range and Northern Cold Deserts 

had greater presence and abundance of nonnative 

invasive plant species than those in the Eastern Cold 

Deserts (figures 14 and 15).

An estimated 6% to 12% of BLM rangelands in 

the Eastern Cold Deserts ecoregion were at risk 

of declining biotic integrity relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that these rangelands and their associated plant, 

animal, and microorganism communities may be 

starting to have trouble cycling water and nutrients, 

capturing energy from sunlight, and sustaining other 

ecological processes. Biotic integrity had declined 

on between 1% and 3% of BLM rangelands in the 

Eastern Cold Deserts relative to reference conditions 

(moderate-to-extreme or extreme-to-total departure). 

This finding suggests that these rangelands may 

have lost some capacity to cycle water and nutrients, 

capture sunlight, and sustain other ecological 

processes. Only BLM rangelands in the Warm 

Deserts had lost more biotic integrity than those in 

the Eastern Cold Deserts (figure 19).

An estimated 7% to 13% of BLM rangelands in 

the Eastern Cold Deserts ecoregion were at risk of 

declining hydrologic function relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that soils and vegetation on these rangelands may 

be starting to have trouble capturing, storing, and 
34 Bureau of Land Management

safely releasing water. Hydrologic function had 

declined relative to reference conditions on between 

1% and 4% of the rangelands (moderate-to-extreme 

or extreme-to-total departure). This finding suggests 

that soils and vegetation on these rangelands may 

have lost some capacity to capture, store, and safely 

release water. Only BLM rangelands in the Warm 

Deserts had lost more hydrologic function than those 

in the Eastern Cold Deserts (figure 20).

An estimated 6% to 11% of BLM rangelands in 

the Eastern Cold Deserts ecoregion were at risk of 

declining soil and site stability relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that excessive amounts of soil may be eroding by 

wind and water on these rangelands. Soil and site 

stability had declined relative to reference conditions 

on between 1% and 4% of the BLM rangelands 

(moderate-to-extreme or extreme-to-total departure). 

This finding suggests that excessive amounts of 

soil may have been lost on these rangelands. Only 

rangelands in the Warm Deserts have lost more soil 

and site stability than those in the Eastern Cold 

Deserts (figure 21).

Implications for Productivity

Rangeland health assessments showed that up to 

one-tenth of the Eastern Cold Deserts ecoregion 

was at risk of declining productivity attributable to 

declines in all three attributes of rangeland health: 

soil and site stability, hydrologic function, and biotic 

integrity. Only the Warm Deserts ecoregion exceeded 

the proportion of rangelands with declines in health. 

Large amounts of bare ground, unstable soils, and 

broad colonization of nonnative invasive plant 

species represent threats to rangeland health and, 

thus, future productivity.
Rangeland Resource Assessment—2011 35 Figure 18. Mean and 80% confidence interval for attributes and indicators in the Eastern Cold Deserts ecoregion. 0 10 20 30 40 50 60 70 80 90 100 Percent

Eastern Cold Deserts (n = 218)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
36 Bureau of Land Management

Figure 19. Proportion of BLM rangelands where biotic integrity shows moderate-to-extreme or extreme-tototal departure from reference conditions (80% confidence interval) within ecoregions.
Rangeland Resource Assessment—2011 37

Figure 20. Proportion of BLM rangelands where hydrologic function shows moderate-to-extreme or 

extreme-to-total departure from reference conditions (80% confidence interval) within ecoregions.
38 Bureau of Land Management

Figure 21. Proportion of BLM rangelands where soil/site stability shows moderate-to-extreme or extremeto-total departure from reference conditions (80% confidence interval) within ecoregions.
Rangeland Resource Assessment—2011 39

Madrean Archipelago 

Ecoregion

Overview

The Madrean Archipelago is an EPA level III 

ecoregion characterized by hot summers and mild 

winters (figure 22). Mean annual temperature 

ranges from 7 °C to 19 °C, making this ecoregion 

among the warmest of all ecoregions in the RRA. 

Mean annual precipitation is 421 mm, but ranges 

with elevation from 260 to 950 mm. Much of the 

precipitation occurs as rain during thunderstorms 

from July to September. The terrain consists 

of mountain ranges and intermountain basins. 

Vegetation varies with elevation, from shrublands and 

warm season grasslands at low elevations, to oakjuniper woodlands on mountain slopes, to ponderosa 

pine forests at high elevations (Wiken et al. 2011).

Figure 22. Sandy lowland wash near Safford, Arizona, within the Madrean Archipelago ecoregion 

(BLM photo).
40 Bureau of Land Management

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition 

is the status of a renewable resource in comparison 

against a reference value. The assessment team 

reported all indicators using an 80% confidence 

interval. An 80% confidence interval means that 

there is an 80% chance that the true population 

mean lies within that range. Average conditions for 

an attribute or an indicator in this ecoregion will fall 

within this range. For more information, see “Data 

Summarization.” Differences in climate, vegetation 

type, physiography, and similar broad-scale factors 

likely drive differences in ecoregion status (e.g., bare 

ground). Differences in management factors likely 

drive differences in condition (e.g., rangeland 

health attributes).

Figure 23 shows the means and 80% confidence 

intervals for each indicator. Within the Madrean 

Archipelago ecoregion, average bare ground on BLM 

rangelands was between 9% and 23%. Bare ground 

refers to bare mineral soil with no vegetation, rocks, 

litter, or other cover above it. Greater amounts of 

bare ground suggest an increased risk of soil erosion 

(Smith and Wischmeier 1962, Morgan 1986, 

Benkobi et al. 1993, Blackburn and Pierson 1994, 

Pierson et al. 1994, Gutierrez and Hernandez 1996, 

and Cerda 1999 in Pellant et al. 2005). An estimated 

4% to 54% of BLM rangelands in the Madrean 

Archipelago had at least 20% bare ground. Some 

BLM rangelands had at least 30%, 40%, and 50% 

bare ground, but the sample size was not sufficient 

to confidently estimate the proportion of BLM 

rangelands. There was less bare ground on BLM 

rangelands in the Madrean Archipelago than in the 

Eastern Cold Deserts and Warm Deserts (figure 8).

Most BLM rangelands in the Madrean Archipelago 

ecoregion had low soil aggregate stability, suggesting 

high erosion potential. Between 81% and 100% of 

BLM rangelands had soils that were susceptible to 

breaking apart and eroding from wind and water. 

Only rangelands in the Arizona/New Mexico 

Mountains and Warm Deserts had as high a 

proportion of unstable soils as those in the Madrean 

Archipelago (figure 4).

Between 25% and 80% of BLM rangelands in the 

Madrean Archipelago ecoregion had large gaps 

(≥2 meters) between plant canopies that comprised 

more than 20% of the surface. This greater 

“openness” of the vegetation suggests that BLM 

rangelands in this ecoregion may be more vulnerable 

to soil erosion by water and wind. Most rangelands 

with canopy gaps of greater than 2 meters are at 

high risk for wind erosion (Okin 2008). Large gaps 

between plant canopies were more prevalent in the 

Madrean Archipelago than in the Northern Cold 

Deserts and West Central Semi-Arid Prairies (figure 13).

Nonnative invasive plant species had colonized 

some BLM rangelands in the Madrean Archipelago 

ecoregion, but the sample size was not large enough 

to confidently estimate the proportion of BLM 

rangelands. None of the sampled BLM rangelands 

had abundant nonnative invasive plants. Nonnative 

invasive plant species often outcompete native 

plant species for growing space, causing a decline in 

abundance of native plant species. This decline in 

turn causes changes in wildlife habitat availability, 

wildfire frequency and severity, and susceptibility of 

soil to erosion.

An estimated 1% to 31% of BLM rangelands in 

the Madrean Archipelago were at risk of declining 

biotic integrity relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005). This finding suggests that these 

rangelands and their associated plant, animal, and 

microorganism communities may be starting to 

have trouble cycling water and nutrients, capturing 

energy from sunlight, and sustaining other ecological 

processes. None of the BLM rangelands sampled in 

the Madrean Archipelago ecoregion had diminished 

biotic integrity relative to reference conditions 
Rangeland Resource Assessment—2011 41

(moderate-to-extreme or extreme-to-total departure).

Some BLM rangelands in the Madrean Archipelago 

ecoregion were at risk of declining hydrologic 

function relative to reference conditions based on a 

qualitative rating of moderate departure (Pellant et 

al. 2005), but the sample size was not large enough 

to confidently estimate the proportion of rangelands. 

Likewise, some BLM rangelands sampled in this 

ecoregion had diminished hydrologic function 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure), but the sample size 

was not large enough to confidently estimate the 

proportion of rangelands.

Some BLM rangelands in the Madrean Archipelago 

ecoregion were at risk of declining soil and site 

stability relative to reference conditions based on a 

qualitative rating of moderate departure (Pellant et 

al. 2005), but the sample size was not large enough 

to confidently estimate the proportion of rangelands. 

Likewise, some BLM rangelands sampled in this 

ecoregion had diminished soil and site stability 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure), but the sample size 

was not large enough to confidently estimate the 

proportion of rangelands.

Implications for Productivity

Rangeland health assessments showed that the 

Madrean Archipelago was at risk of declining 

productivity primarily attributable to declines in 

biotic integrity. However, the risk of declining 

productivity was less here than in nearly all other 

ecoregions. Low soil aggregate stability present 

on large proportions of the rangelands represents 

a potential threat to soil and site stability and 

hydrologic function and, thus, future productivity. 
42 Bureau of Land Management

Figure 23. Mean and 80% confidence interval for attributes and indicators in the Madrean Archipelago ecoregion.

0 10 20 30 40 50 60 70 80 90 100

Percent

Madrean Archipelago (n = 12)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
Rangeland Resource Assessment—2011 43

Northern Cold Deserts 

Ecoregion

Overview

The Northern Cold Deserts ecoregion is composed 

of three EPA level III ecoregions: Columbia Plateau, 

Snake River Plain, and Northern Basin and Range 

(figure 24). Warm to hot summers and cold winters are 

typical in this ecoregion. Mean annual temperatures 

are very similar across the three subregions, ranging 

from 7 °C to 12 °C in the Columbia Plateau, 6 °C to 

10 °C in the Snake River Plain, and 5 °C to 9 °C in 

the Northern Great Basin. Mean annual precipitation 

is also similar, but slightly lower in the Snake River 

Plain (316 mm) than the Columbia Plateau (334 mm) 

and Northern Great Basin (351 mm). Annual 

precipitation ranges from 110 mm at low elevations 

and in rain shadows to more than 1,000 mm at high 

elevations. Topography consists of plains (including 

lava plains), valleys, low hills, and tablelands, 

sometimes interrupted by mountain ranges. Vegetation 

is primarily sagebrush shrublands and cool-season 

grasslands. Aspen and conifer forests occur at higher 

elevations (Wiken et al. 2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition 

is the status of a renewable resource in comparison 

against a reference value. The assessment team reported 

all indicators using an 80% confidence interval. 

An 80% confidence interval means that there is 

an 80% chance that the true population mean 

lies within that range. Average conditions for an 

attribute or an indicator in this ecoregion will fall 

within this range. For more information, see “Data 

Summarization.” Differences in climate, vegetation

Figure 24. Northwest of Frenchglen, Oregon, near Fish Lake, within the Northern Cold Deserts ecoregion 

(BLM photo).
44 Bureau of Land Management

type, physiography, and similar broad-scale factors 

likely drive differences in ecoregion status (e.g., bare 

ground). Differences in management factors likely drive 

differences in condition (e.g., rangeland health attributes).

Figure 25 shows the means and 80% confidence 

intervals for each indicator. Within the Northern 

Cold Deserts ecoregion, average bare ground on 

BLM rangelands was between 17% and 20%. Bare 

ground refers to bare mineral soil with no vegetation, 

rocks, litter, or other cover above it. Greater amounts 

of bare ground suggest an increased risk of soil 

erosion (Smith and Wischmeier 1962, Morgan 1986, 

Benkobi et al. 1993, Blackburn and Pierson 1994, 

Pierson et al. 1994, Gutierrez and Hernandez 1996, 

and Cerda 1999 in Pellant et al. 2005). There is less 

bare ground on BLM rangelands here than in the 

Eastern Cold Deserts and Warm Deserts (figure 8). 

A smaller proportion of BLM rangelands in the 

Northern Cold Deserts had large amounts of bare 

ground (at least 30%, 40%, or 50% bare ground) 

than in the Central Basin and Range, Eastern Cold 

Deserts, and Warm Deserts (figures 10, 11, and 12). 

There was more bare ground on BLM rangelands 

here than on those in the West Central Semi-Arid 

Prairies (figure 8).

Many soils in the Northern Cold Deserts had 

low soil aggregate stability, suggesting high 

erosion potential. Between 30% and 48% of BLM 

rangelands had soils that were susceptible to breaking 

apart and eroding from wind and water. However, 

the proportion of BLM rangelands with unstable soils 

was less than in the Arizona/New Mexico Mountains, 

Eastern Cold Deserts, Madrean Archipelago, and 

Warm Deserts (figure 4).

Between 3% and 10% of BLM rangelands in the 

Northern Cold Deserts ecoregion had large gaps 

(≥2 meters) between plant canopies that comprised 

more than 20% of the soil surface. Less “open” 

vegetation suggests that BLM rangelands in this 

ecoregion may be less vulnerable to soil erosion by 

water and wind. Most rangelands with canopy gaps 

of greater than 2 meters are at high risk for wind 

erosion (Okin 2008). Large gaps between plant 

canopies were less prevalent in the Northern Cold 

Deserts than in the Arizona/New Mexico Mountains, 

Central Basin and Range, Eastern Cold Deserts, 

Madrean Archipelago, and Warm Deserts (figure 13).

The presence and abundance of nonnative invasive 

plant species are notable indicators of the condition 

of BLM rangelands in the Northern Cold Deserts. 

Nonnative invasive plant species had colonized nearly 

all of the rangelands, on average between 77% and 

88%. Between 29% and 41% of BLM rangelands 

had abundant nonnative invasive plants. Nonnative 

invasive plant species often outcompete native 

plant species for growing space, causing a decline in 

abundance of native plant species. This decline in 

turn causes changes in wildlife habitat availability, 

wildfire frequency and severity, and susceptibility 

of soil to erosion. Nonnative invasive plant species 

are pervasive on BLM rangelands here. Only BLM 

rangelands in the Central Basin and Range had as 

high a proportion of colonization and abundance 

of nonnative invasive plant species as those in the 

Northern Cold Deserts (figures 14 and 15).

An estimated 8% to 18% of the rangelands in 

the Northern Cold Deserts ecoregion were at risk 

of declining biotic integrity relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that these rangelands and their associated plant, 

animal, and microorganism communities may be 

starting to have trouble cycling water and nutrients, 

capturing energy from sunlight, and sustaining other 

ecological processes. Biotic integrity had declined 

relative to reference conditions on between 1% and 

6% of BLM rangelands (moderate-to-extreme or 

extreme-to-total departure). This finding suggests 

that these rangelands may have lost some capacity 

to cycle water and nutrients, capture sunlight, and 

sustain other ecological processes. Only rangelands in 

the Warm Deserts had lost more biotic integrity than 

in the Northern Cold Deserts (figure 19).
Rangeland Resource Assessment—2011 45

An estimated 4% to 9% of BLM rangelands in the 

Northern Cold Deserts were at risk of declining 

hydrologic function relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005). This finding suggests that soils 

and vegetation on these rangelands may be starting to 

have trouble capturing, storing, and safely releasing 

water. Some BLM rangelands in this ecoregion had 

diminished hydrologic function relative to reference 

conditions (moderate-to-extreme or extreme-to-total 

departure), but the sample size was not large enough 

to confidently estimate the proportion of rangelands. 

An estimated 2% to 6% of BLM rangelands in the 

Northern Cold Deserts ecoregion were at risk of 

declining soil and site stability relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that excessive amounts of soil may be eroding by 

wind and water on those rangelands. Only rangelands 

in the Warm Deserts, Eastern Cold Deserts, and 

South Central Semi-Arid Prairies had greater risk of 

declining soil and site stability than in the Northern 

Cold Deserts (figure 26). Some BLM rangelands in 

this ecoregion had diminished soil and site stability 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure), but the sample size 

was not large enough to confidently estimate the 

proportion of rangelands.

Implications for Productivity

Rangeland health assessments showed that up to 

one-fifth of the Northern Cold Deserts ecoregion 

was at risk of declining productivity attributable to 

biotic integrity. This risk was greater here than in 

all ecoregions except the Warm Deserts and Eastern 

Cold Deserts. Abundant nonnative invasive plant 

species represent a potential threat to biotic integrity 

and, thus, future productivity. 
46 Bureau of Land Management

Figure 25. Mean and 80% confidence interval for attributes and indicators in the Northern Cold Deserts ecoregion

0 10 20 30 40 50 60 70 80 90 100

Percent

Northern Cold Deserts (n = 158)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
Rangeland Resource Assessment—2011 47

Figure 26. Proportion of BLM rangelands where soil/site stability shows moderate departure from 

reference conditions (80% confidence interval) within ecoregions.
48 Bureau of Land Management

South Central Semi-Arid 

Prairies Ecoregion

Overview

The South Central Semi-Arid Prairies ecoregion is 

an EPA level II ecoregion (figure 27). Hot summers 

and cool to cold winters are typical in this ecoregion. 

Mean annual temperatures range from 8 °C to 21 °C, 

among the warmest of all ecoregions in the RRA. 

Mean annual precipitation ranges from 255 to 

1,170 mm. Landforms consist of smooth as well as 

irregular plains and tablelands. Shortgrass prairie 

dominates the vegetation in the north, blended with 

mesquite juniper and oak woodlands further south 

Wiken et al. (2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition is the 

status of a renewable resource in comparison against 

a reference value. The assessment team reported all 

indicators using an 80% confidence interval. An 

80% confidence interval means that there is an 

80% chance that the true population mean lies within 

that range. Average conditions for an attribute or an 

indicator in this ecoregion will fall within this range. 

For more information, see “Data Summarization.” 

Differences in climate, vegetation type, physiography, 

and similar broad-scale factors likely drive differences 

in ecoregion status (e.g., bare ground). Differences 

in management factors likely drive differences in 

condition (e.g., rangeland health attributes).

Figure 28 shows the means and 80% confidence 

intervals for each indicator. Within the South Central 

Semi-Arid Prairies ecoregion, average bare ground 

Figure 27. Shortgrass prairie at the U.S. Department of Agriculture–Agricultural Research Service, Central 

Plains Experimental Range near Nunn, Colorado, within the South Central Semi-Arid Prairies 

ecoregion (photo by Emily Kachergis).
Rangeland Resource Assessment—2011 49

on BLM rangelands was between 17% and 29%. 

Bare ground refers to bare mineral soil with no 

vegetation, rocks, litter, or other cover above it. 

Greater amounts of bare ground suggest an increased 

risk of soil erosion (Smith and Wischmeier 1962, 

Morgan 1986, Benkobi et al. 1993, Blackburn and 

Pierson 1994, Pierson et al. 1994, Gutierrez and 

Hernandez 1996, and Cerda 1999 in Pellant et al. 

2005). BLM rangelands here had greater amounts of 

bare ground than those in the West Central SemiArid Prairies (figure 8). No BLM rangelands sampled 

in the South Central Semi-Arid Prairies had extreme 

amounts (at least 40% or 50%) of bare ground.

Some soils in the South Central Semi-Arid Prairies 

had low soil aggregate stability, suggesting high 

erosion potential. Between 16% and 74% of BLM 

rangelands had soils that were susceptible to breaking 

apart and eroding from wind and water. A smaller 

proportion of rangelands here have unstable soils 

than in the Arizona/New Mexico Mountains, 

Madrean Archipelago, and Warm Deserts (figure 4).

Some BLM rangelands in the South Central Semi-Arid 

Prairies ecoregion had large gaps (≥2 meters) between 

plant canopies that comprised more than 20% of the 

surface. However, the sample size was not sufficient to 

confidently estimate the proportion of rangelands.

Nonnative invasive plant species had colonized an 

estimated 12% to 51% of BLM rangelands in the 

South Central Semi-Arid Prairies. Nonnative invasive 

plant species often outcompete native plant species 

for growing space, causing a decline in abundance 

of native plant species. This decline in turn causes 

changes in wildlife habitat availability, wildfire 

frequency and severity, and susceptibility of soil 

to erosion. Nonnative invasive plant species had 

colonized a smaller proportion of rangelands here 

than in the Central Basin and Range, Eastern Cold 

Deserts, and Northern Cold Deserts (figure 14). Some 

BLM rangelands in the South Central Semi-Arid 

Prairies ecoregion had abundant nonnative invasive 

plant species, but the sample size was not sufficient to 

confidently estimate the proportion of rangelands.

Some BLM rangelands in the South Central SemiArid Prairies ecoregion were at risk of declining biotic 

integrity relative to reference conditions based on a 

qualitative rating of moderate departure (Pellant et 

al. 2005), but the sample size was not large enough 

to confidently estimate the proportion of rangelands. 

No BLM rangelands sampled had diminished biotic 

integrity relative to reference conditions (rating of 

moderate-to-extreme or extreme-to-total departure).

Some BLM rangelands in the South Central SemiArid Prairies ecoregion were at risk of declining 

hydrologic function relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005), but the sample size was not 

large enough to confidently estimate the proportion 

of rangelands. No BLM rangelands sampled in 

this ecoregion had diminished hydrologic function 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure).

An estimated 5% to 41% of BLM rangelands in the 

South Central Semi-Arid Prairies ecoregion were 

at risk of declining soil and site stability relative to 

reference conditions based on a qualitative rating 

of moderate departure (Pellant et al. 2005). This 

finding suggests that excessive amounts of soil may 

be eroding by wind and water on these rangelands. 

No BLM rangelands sampled in this ecoregion had 

diminished soil and site stability relative to reference 

conditions (moderate-to-extreme or extreme-tototal departure).

Implications for Productivity

Rangeland health assessments showed that soil and 

site stability was a primary threat to productivity in 

the South Central Semi-Arid Prairies ecoregion. In 

contrast, relatively low proportions of rangelands 

with declines in the other rangeland health attributes, 

or with prevalence of other indicators such as large 

plant canopy gaps and colonization by nonnative 

species, suggested that this ecoregion may be less at 

risk for declining productivity than other ecoregions. 
50 Bureau of Land Management

Figure 28. Mean and 80% confidence interval for attributes and indicators in the South Central Semi-Arid Prairies ecoregion.

0 10 20 30 40 50 60 70 80 90 100

Percent

South Central Semi-Arid Prairies (n = 9)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
Rangeland Resource Assessment—2011 51

Warm Deserts Ecoregion

Overview

The Warm Deserts ecoregion is an EPA level II 

ecoregion (figure 29). Hot summers and mild 

winters are typical in this ecoregion. Mean annual 

temperatures range from 5 °C to 25 °C. Mean annual 

precipitation is generally low, but ranges from 50 mm 

to over 900 mm on high mountain peaks. The Warm 

Deserts ecoregion is the warmest and driest of all 

ecoregions in the RRA. Dominant landforms are 

open plains interspersed with low to high mountain 

ranges. Vegetation consists of shrublands mixed with 

grasslands (Wiken et al. 2011). 

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition 

is the status of a renewable resource in comparison 

against a reference value. The assessment team 

reported all indicators using an 80% confidence 

interval. An 80% confidence interval means that 

there is an 80% chance that the true population 

mean lies within that range. Average conditions for 

an attribute or an indicator in this ecoregion will fall 

within this range. For more information, see “Data 

Summarization.” Differences in climate, vegetation 

type, physiography, and similar broad-scale factors 

likely drive differences in ecoregion status (e.g., bare 

ground). Differences in management factors likely 

drive differences in condition (e.g., rangeland 

health attributes).

Figure 30 shows the means and 80% confidence 

intervals for each indicator. Within the Warm Deserts

Figure 29. California desert, within the Warm Deserts ecoregion (BLM photo). 
52 Bureau of Land Management

ecoregion, average bare ground on BLM rangelands 

was between 25% and 32%. Bare ground refers to 

bare mineral soil with no vegetation, rocks, litter, or 

other cover above it. Greater amounts of bare ground 

suggest an increased risk of soil erosion (Smith and 

Wischmeier 1962, Morgan 1986, Benkobi et 

al. 1993, Blackburn and Pierson 1994, Pierson et 

al. 1994, Gutierrez and Hernandez 1996, and 

Cerda 1999 in Pellant et al. 2005). Large amounts of 

bare ground occurred on a significant proportion of 

BLM rangelands in the Warm Deserts, with between 

46% and 60% of the rangelands having at least 

20% bare ground. Bare ground was more prevalent 

here than on most other BLM rangelands. Only 

rangelands in the Eastern Cold Deserts, Arizona/

New Mexico Mountains, and South Central SemiArid Prairies had as much bare ground as those in the 

Warm Deserts (figure 8).

Many soils in the Warm Deserts had low soil 

aggregate stability, suggesting high erosion potential. 

Between 82% and 93% of BLM rangelands had 

soils that were susceptible to breaking apart and 

eroding from wind and water. Only rangelands in 

the Arizona/New Mexico Mountains and Madrean 

Archipelago had as high a proportion of rangelands 

with erodible soils as the Warm Deserts (figure 4).

Between 69% and 82% of BLM rangelands in the 

Warm Deserts have large gaps between plant canopies 

(≥2 meters) that comprised at least 20% of the soil 

surface. This greater “openness” of the vegetation 

suggests that BLM rangelands in this ecoregion may 

be more vulnerable to soil erosion by water and 

wind. Most rangelands with canopy gaps of greater 

than 2 meters are at high risk for wind erosion 

(Okin 2008). Only rangelands in the Arizona/New 

Mexico Mountains and Madrean Archipelago had 

large gaps between plant canopies as prevalent as 

those in the Warm Deserts (figure 13).

Nonnative invasive plant species had colonized 

between 24% and 37% of BLM rangelands in the 

Warm Deserts ecoregion, but only a small proportion 

of these rangelands had abundant nonnative invasive 

plant species. Nonnative invasive plant species often 

outcompete native plant species for growing space, 

causing a decline in abundance of native plant 

species. This decline in turn causes changes in wildlife 

habitat availability, wildfire frequency and severity, 

and susceptibility of soil to erosion. Nonnative 

invasive plant species had colonized or were abundant 

on a smaller proportion of BLM rangelands in the 

Warm Deserts than in the Central Basin and Range 

and Northern Cold Deserts (figures 14 and 15).

An estimated 3% to 10% of BLM rangelands in 

the Warm Deserts were at risk of declining biotic 

integrity relative to reference conditions based on 

a qualitative rating of moderate departure (Pellant 

et al. 2005). This finding suggests that these 

rangelands and their associated plant, animal, and 

microorganism communities may be starting to 

have trouble cycling water and nutrients, capturing 

energy from sunlight, and sustaining other ecological 

processes. Biotic integrity had declined relative to 

reference conditions on an estimated 10% to 22% of 

BLM rangelands (moderate-to-extreme or extremeto-total departure). This finding suggests that these 

rangelands may have lost some capacity to cycle 

water and nutrients, capture energy, and sustain other 

ecological processes. A larger proportion of BLM 

rangelands had diminished biotic integrity in the 

Warm Deserts than in any other ecoregion (figure 19).

An estimated 6% to 18% of BLM rangelands in the 

Warm Deserts ecoregion were at risk of declining 

hydrologic function relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005). This finding suggests that soils 

and vegetation on these rangelands may be starting to 

have trouble capturing, storing, and safely releasing 

water. Hydrologic function had declined relative to 

reference conditions on an estimated 8% to 20% of 

the rangelands (moderate-to-extreme or extreme-tototal departure). This finding suggests that soils and 

vegetation on these rangelands may have lost some 

capacity to capture, store, and safely release water. 
Rangeland Resource Assessment—2011 53

A larger proportion of BLM rangelands had 

diminished hydrologic function in the Warm Deserts 

than in any other ecoregion (figure 20).

An estimated 7% to 20% of BLM rangelands in the 

Warm Deserts were at risk of declining soil and site 

stability relative to reference conditions based on 

a qualitative rating of moderate departure (Pellant 

et al. 2005). This finding suggests that excessive 

amounts of soil may be eroding by wind and water on 

these rangelands. Soil and site stability had declined 

relative to reference conditions on an estimated 7% 

to 17% of BLM rangelands (moderate-to-extreme or 

extreme-to-total departure). This finding suggests that 

excessive amounts of soil may have been lost on these 

rangelands. A larger proportion of rangelands had 

diminished soil and site stability in the Warm Deserts 

ecoregion than in any other ecoregion (figure 21).

Implications for Productivity

Rangeland health assessments showed that up to 

one-fifth of the Warm Deserts ecoregion was at risk 

of declining productivity attributable to declines in 

all three attributes of rangeland health: soil and site 

stability, hydrologic function, and biotic integrity. 

This ecoregion has a greater proportion of rangelands 

with declines in health and, thus, productivity than 

any other ecoregion. Large amounts of bare ground, 

unstable soils, and large gaps between plant canopies 

represent threats to rangeland health and, thus, 

future productivity.
54 Bureau of Land Management

Figure 30. Mean and 80% confidence interval for attributes and indicators in the Warm Deserts ecoregion.

0 10 20 30 40 50 60 70 80 90 100

Percent

Warm Deserts (n = 139)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
Rangeland Resource Assessment—2011 55

West Central Semi-Arid 

Prairies Ecoregion

Overview

The West Central Semi-Arid Prairies ecoregion is 

an EPA level II ecoregion (figure 31). Warm to 

hot summers and cold winters are typical in this 

ecoregion. Mean annual temperatures range from 

2 °C to 9 °C, among the coolest of all ecoregions in 

the RRA. Mean annual precipitation varies from 

250 mm to 580 mm. Irregular plains, tablelands, and 

low hills characterize the terrain. Native vegetation is 

grassland with a mix of short and mid-height grasses 

(Wiken et al. 2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition is the 

status of a renewable resource in comparison against 

a reference value. The assessment team reported all 

indicators using an 80% confidence interval. An 

80% confidence interval means that there is an 80% 

chance that the true population mean lies within 

that range. Average conditions for an attribute or an 

indicator in this ecoregion will fall within this range. 

For more information, see “Data Summarization.” 

Differences in climate, vegetation type, physiography, 

and similar broad-scale factors likely drive differences 

in ecoregion status (e.g., bare ground). Differences 

in management factors likely drive differences in 

condition (e.g., rangeland health attributes).

Figure 32 shows the means and 80% confidence 

intervals for each indicator. Within the West Central 

Semi-Arid Prairies ecoregion, average bare ground on 

BLM rangelands was between 11% and 18%. Bare 

ground refers to bare mineral soil with no vegetation, 

rocks, litter, or other cover above it. Greater amounts 

of bare ground suggest an increased risk of soil 

erosion (Smith and Wischmeier 1962, Morgan 1986, 

Benkobi et al. 1993, Blackburn and Pierson 1994, 

Pierson et al. 1994, Gutierrez and Hernandez 1996, 

and Cerda 1999 in Pellant et al. 2005). Bare ground 

Figure 31. Mixed-grass prairie near Battle Creek, Montana, within the West Central Semi-Arid Prairies 

ecoregion (BLM photo). 
56 Bureau of Land Management

was less in the West Central Semi-Arid Prairies than 

in Central Basin and Range, Eastern Cold Deserts, 

Northern Cold Deserts, South Central Semi-Arid 

Prairies, and Warm Deserts (figure 8).

Some soils in the West Central Semi-Arid Prairies had 

low soil aggregate stability, suggesting high erosion 

potential. Between 16% and 43% of BLM rangelands 

had soils that are susceptible to breaking apart and 

eroding from wind and water. A smaller proportion 

of BLM rangelands in the West Central Semi-Arid 

Prairies had unstable soils than in the Arizona/New 

Mexico Mountains, Eastern Cold Deserts, Madrean 

Archipelago, and Warm Deserts (figure 4).

Between a trace (less than 1%) to 19% of BLM 

rangelands in the West Central Semi-Arid Prairies had 

large gaps between plant canopies (≥2 meters) that 

comprise more than 20% of the surface. The greater 

the “openness” of the vegetation, the more vulnerable 

BLM rangelands in this ecoregion are to soil erosion by 

water and wind. Most rangelands with canopy gaps of 

greater than 2 meters are at high risk for wind erosion 

(Okin 2008). Large gaps between plant canopies were 

less prevalent in the West Central Semi-Arid Prairies 

than in the Arizona/New Mexico Mountains, Central 

Basin and Range, Eastern Cold Deserts, Madrean 

Archipelago, and Warm Deserts (figure 13).

Nonnative invasive plant species had colonized 

between 17% to 39% of BLM rangelands in the 

West Central Semi-Arid Prairies ecoregion, but 

no rangelands were sampled that had abundant 

nonnative invasive plant species. Nonnative invasive 

plant species often outcompete native plant species 

for growing space, causing a decline in abundance 

of native plant species. This decline in turn causes 

changes in wildlife habitat availability, wildfire 

frequency and severity, and susceptibility of soil 

to erosion. Nonnative invasive plant species had 

colonized a smaller proportion of rangelands in 

the West Central Semi-Arid Prairies than in the 

Central Basin and Range, Eastern Cold Deserts, and 

Northern Cold Deserts (figure 14).

Some BLM rangelands in the West Central SemiArid Prairies ecoregion were at risk of declining biotic 

integrity relative to reference conditions based on a 

qualitative rating of moderate departure (Pellant et 

al. 2005), but the sample size was not large enough 

to confidently estimate the proportion of rangelands. 

No BLM rangelands sampled had diminished biotic 

integrity relative to reference conditions (rating of 

moderate-to-extreme or extreme-to-total departure).

An estimated 3% to 18% of BLM rangelands in 

the West Central Semi-Arid Prairies were at risk of 

declining hydrologic function relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that soils and vegetation on these rangelands may be 

starting to have trouble capturing, storing, and safely 

releasing water. No rangelands sampled had diminished 

hydrologic function relative to reference conditions 

(moderate-to-extreme or extreme-to-total departure).

Some BLM rangelands in the West Central SemiArid Prairies ecoregion were at risk of declining soil 

and site stability relative to reference conditions 

based on a qualitative rating of moderate departure 

(Pellant et al. 2005), but the sample size was not 

large enough to confidently estimate the proportion 

of rangelands. No BLM rangelands sampled in this 

ecoregion had diminished soil and site stability 

relative to reference conditions (moderate-to-extreme 

or extreme-to-total departure).

Implications for Productivity

Rangeland health assessments showed that declines 

in hydrologic function were a primary threat to 

productivity in the West Central Semi-Arid Prairies 

ecoregion. In contrast, relatively low proportions of 

rangelands where other rangeland health attributes 

were at risk, or with prevalence of other indicators 

such as large plant canopy gaps and unstable soils, 

suggest that this ecoregion may be less at risk for 

declining productivity than other ecoregions. 
Rangeland Resource Assessment—2011 57 Figure 32. Mean and 80% confidence interval for attributes and indicators in the West Central Semi-Arid Prairies ecoregion. 0 10 20 30 40 50 60 70 80 90 100 Percent

West Central Semi-Arid Prairies (n = 36)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions
58 Bureau of Land Management

Western Cordillera 

Ecoregion

Overview

The Western Cordillera ecoregion is an EPA level II 

ecoregion (figure 33). Warm to hot summers and cold 

winters are typical in this ecoregion. Mean annual 

temperatures range from -5 °C to 17 °C. Precipitation 

varies with elevation and latitude, ranging from 

150 to 6,000 mm per year. This is the coolest and 

wettest ecoregion in the RRA. The terrain is primarily 

high mountains interspersed with high-elevation 

broad valleys. Vegetation at low elevations consists of 

shrublands and grasslands. Conifer and aspen forests 

occur at higher elevations (Wiken et al. 2011).

Status and Condition

Results of this RRA represent a bird’s-eye view of 

the status and condition of BLM rangelands within 

each ecoregion in 2011. Status is an amount of a 

renewable resource at a point in time. Condition 

is the status of a renewable resource in comparison 

against a reference value. The assessment team 

reported all indicators using an 80% confidence 

interval. An 80% confidence interval means that 

there is an 80% chance that the true population 

mean lies within that range. Average conditions for 

an attribute or an indicator in this ecoregion will fall 

within this range. For more information, see “Data 

Summarization.” Differences in climate, vegetation 

Figure 33. Northeast of Crested Butte, Colorado, within the Western Cordillera ecoregion (photo by Emily 

Kachergis).
Rangeland Resource Assessment—2011 59

type, physiography, and similar broad-scale factors 

likely drive differences in ecoregion status (e.g., bare 

ground). Differences in management factors likely 

drive differences in condition (e.g., rangeland 

health attributes).

Figure 34 shows the means and 80% confidence 

intervals for each indicator. In the Western Cordillera 

ecoregion, average bare ground on BLM rangelands 

was between 15% and 23%. Bare ground refers to 

bare mineral soil with no vegetation, rocks, litter, or 

other cover above it. Greater amounts of bare ground 

suggest an increased risk of soil erosion (Smith and 

Wischmeier 1962, Morgan 1986, Benkobi et al. 1993, 

Blackburn and Pierson 1994, Pierson et al. 1994, 

Gutierrez and Hernandez 1996, and Cerda 1999 

in Pellant et al. 2005). Bare ground occurred in 

smaller amounts on Western Cordillera rangelands 

than on the rangelands in the Eastern Cold Deserts 

and Warm Deserts (figure 8). Likewise, a smaller 

proportion of BLM rangelands here had large 

amounts of bare ground (at least 30% or 40% bare 

ground) than in the Eastern Cold Deserts and Warm 

Deserts (figures 10 and 11). An estimated 8% to 

27% of BLM rangelands in the Western Cordillera 

had at least 30% bare ground, and trace (less than 

1%) to 17% of BLM rangelands here had at least 

40% bare ground.

Many soils in the Western Cordillera ecoregion 

had low soil aggregate stability, suggesting high 

erosion potential. Between 36% and 58% of BLM 

rangelands had soils that are susceptible to breaking 

apart and eroding from wind and water. However, 

the proportion of BLM rangelands with unstable soils 

was less than in the Arizona/New Mexico Mountains, 

Eastern Cold Deserts, Madrean Archipelago, and 

Warm Deserts (figure 4).

Some BLM rangelands in the Western Cordillera 

ecoregion had large gaps between plant canopies 

(≥2 meters) that comprised more than 20% of the 

soil surface. However, the sample size was not sufficient 

to confidently estimate the proportion of rangelands. 

Nonnative invasive plant species had colonized an 

estimated 21% to 45% of BLM rangelands in the 

Western Cordillera ecoregion. However, a small 

proportion of these rangelands, between a trace (less 

than 1%) and 14%, had abundant nonnative invasive 

plant species. Nonnative invasive plant species often 

outcompete native plant species for growing space, 

causing a decline in abundance of native plant 

species. This decline in turn causes changes in wildlife 

habitat availability, wildfire frequency and severity, 

and susceptibility of soil to erosion. Nonnative 

invasive plant species colonized a smaller proportion 

of rangelands, and were less abundant, in the Western 

Cordillera than in the Central Basin and Range and 

Northern Cold Deserts (figures 14 and 15).

An estimated trace (less than 1%) to 9% of BLM 

rangelands in the Western Cordillera ecoregion 

were at risk of declining biotic integrity relative to 

reference conditions based on a qualitative rating of 

moderate departure (Pellant et al. 2005). This finding 

suggests that these rangelands and their associated 

plant, animal, and microorganism communities 

may be starting to have trouble cycling water and 

nutrients, capturing energy from sunlight, and 

sustaining other ecological processes. No BLM 

rangelands sampled in the Western Cordillera had 

diminished biotic integrity relative to reference 

conditions (moderate-to-extreme or extreme-tototal departure).

An estimated 2% to 14% of BLM rangelands in the 

Western Cordillera are at risk of declining hydrologic 

function relative to reference conditions based on 

a qualitative rating of moderate departure (Pellant 

et al. 2005). This finding suggests that the soils and 

vegetation on these rangelands may be starting to 

have trouble capturing, storing, and safely releasing 

water. Some BLM rangelands in this ecoregion had 

diminished hydrologic function relative to reference 

conditions (moderate-to-extreme or extreme-to-total 

departure), but the sample size was not sufficient to 

confidently estimate the proportion of rangelands.
60 Bureau of Land Management

An estimated trace (less than 1%) to 11% of BLM 

rangelands in the Western Cordillera were at risk of 

declining soil and site stability relative to reference 

conditions based on a qualitative rating of moderate 

departure (Pellant et al. 2005). This finding suggests 

that excessive amounts of soil may be eroding by 

wind and water on these rangelands. Some BLM 

rangelands in this ecoregion had diminished soil 

and site stability relative to reference conditions 

(moderate-to-extreme or extreme-to-total departure), 

but the sample size was not sufficient to confidently 

estimate the proportion of rangelands.

Implications for Productivity

Rangeland health assessments showed that up to onetenth of the Western Cordillera ecoregion was at risk 

of declining productivity attributable to declines in 

all three rangeland health attributes: biotic integrity, 

hydrologic function, and soil and site stability. 

However, relatively low proportions of rangelands 

with prevalence of indicators such as bare ground 

and colonization by nonnative invasive plants suggest 

that this ecoregion may be less at risk for declining 

productivity than other ecoregions. 
Rangeland Resource Assessment—2011 61 Figure 34. Mean and 80% confidence interval for attributes and indicators in the Western Cordillera ecoregion. 0 10 20 30 40 50 60 70 80 90 100 Percent

Western Cordillera (n = 39)

Average amount of bare ground on BLM rangelandsProportion of BLM rangelands with at least 20% bare groundProportion of BLM rangelands with at least 30% bare groundProportion of BLM rangelands with at least 40% bare groundProportion of BLM rangelands with at least 50% bare groundProportion of BLM rangelands where soil aggregate stability is ranked 4 or lessProportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in lengthProportion of BLM rangelands with nonnative invasive plant species presentProportion of BLM rangelands with abundant nonnative invasive plant speciesProportion of BLM rangelands where biotic integrity shows moderate departure from reference conditionsProportion of BLM rangelands where biotic integrity shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where hydrologic function showsmoderate departure from reference conditionsProportion of BLM rangelands where hydrologic function shows moderateto-extreme or extreme-to-total departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderate departure from reference conditionsProportion of BLM rangelands where soil/site stability shows moderateto-extreme or extreme-to-total departure from reference conditions

Rangeland Resource Assessment—2011 63

Conclusion

This first-of-its kind BLM RRA provides a snapshot 

of renewable resource status and condition on BLM 

rangelands. Indicators and attributes reported relate 

to ecological processes responsible for sustaining 

the productivity of BLM rangelands or the capacity 

of rangelands to produce commodities and satisfy 

values (National Research Council 1994). This report 

fulfills Congress’s direction in the Federal Land Policy 

and Management Act and the Public Rangelands 

Improvement Act to periodically and systematically 

inventory the public rangelands, identify current 

conditions, and report that information to Congress 

and the public.

Results from 2011 show that status and condition, 

and thus productivity, vary in different ecoregions 

on BLM rangelands. Generally, the Warm Deserts, 

Eastern Cold Deserts, and Northern Cold Deserts 

ecoregions exhibited the largest risks to and declines 

in productivity. In contrast, the Madrean Archipelago, 

West Central Semi-Arid Prairies, and South Central 

Semi-Arid Prairies had lower risks to and declines 

in productivity. However, every ecoregion had some 

rangelands with declines in productivity.

The variability in status and condition in each 

ecoregion can inform a targeted approach to land use, 

management, and restoration focused on sustaining 

ecological processes within that ecoregion. For 

example, efforts towards nonnative invasive plant 

species control may be most justified in the most 

invaded ecoregions, the Central Basin and Range 

and Northern Cold Deserts. Likewise, efforts to 

improve soil stability may have the most benefit in 

the Warm Deserts, Arizona/New Mexico Mountains, 

and the Madrean Archipelago, where soils were the 

least stable.

The information from the RRA helps the BLM better 

understand its rangelands via remote sensing and 

provides contextual information for local monitoring 

results. Subsequent RRAs will report on trend or 

changes in renewable resource status and condition 

over time.

Rangeland Resource Assessment—2011 65

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L.M. Burkett, and W.G. Whitford. 2009. 

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08_Vol1.pdf. Accessed 26 January 2015.

Herrick, J.E., W.G. Whitford, A.G. de Soyza, 

J.W. Van Zee, K.M. Havstad, C.A. Seybold, and 

M. Walton. 2001. Field soil aggregate stability kit 

for soil quality and rangeland health evaluations. 

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MacKinnon, W.C., J.W. Karl, G.R. Toevs, J.J. Taylor, 

M. Karl, C.S. Spurrier, and J.E. Herrick. 2011. 

BLM core terrestrial indicators and methods. 

Technical Note 440. BLM/OC/ST-11/003+1735. 

U.S. Department of the Interior–Bureau of Land 

Management, National Operations Center, Denver, 

CO. http://www.blm.gov/style/medialib/blm/wo/

blm_library/tech_notes.Par.83785.File.dat/TN_440.

pdf. Accessed 26 January 2015.

National Research Council. 1994. Rangeland health: 

New methods to classify, inventory, and monitor 

rangelands. National Academy Press, Washington, 

DC. 200 pp.

Nusser, S.M. and J.J. Goebel. 1997. The National 

Resources Inventory: A long-term multi-resource 

monitoring programme. Environmental and 

Ecological Statistics 4:181–204.

Nusser, S., C. Yu, T. Krueger, S. Roberts, and 

J. Li. 2013. Sample design, survey data collection 

systems, and statistical estimation for the 2011 

Bureau of Land Management rangeland survey. 

Iowa State University, Center for Survey Statistics 

and Methodology, Ames, IA. 46 pp.

Okin, G.S. 2008. A new model of wind erosion in 

the presence of vegetation. Journal of Geophysical 

Research 113: F02S10.

Pellant, M., P. Shaver, D.A. Pyke, and J.E. Herrick. 

2005. Interpreting indicators of rangeland health. 

Version 4. Technical Reference 1734-6. BLM/WO/

ST-00/001+1734/REV05. U.S. Department of the 

Interior–Bureau of Land Management, National 

Science and Technology Center, Denver, CO. 122 pp.

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blm_library/tech_refs.Par.10940.File.dat/TR_1734-

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The Heinz Center. 2008. The state of the nation’s 

ecosystems 2008: Measuring the lands, waters, 

and living resources of the United States. The 

H. John Heinz III Center for Science, Economics 

and the Environment. Island Press, Washington 

DC. 352 pp.
66 Bureau of Land Management

U.S. Department of the Interior–Bureau of Land 

Management. 2008. Bureau of Land Management 

science strategy. BLM/RS/PL-00/001+1700. 

Denver, CO. 24 pp.

U.S. Department of the Interior–Bureau of Land 

Management. 2013. Public land statistics 2012. 

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statistics/pls12/pls2012.pdf. Accessed 2 August 2016.

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Rangeland Resource Assessment—2011 67

Appendix A: List of Nonnative Invasive 

Plant Species

The BLM recognizes the following list of species 

compiled from legally declared noxious weed species 

PLANTS 

symbol1 Scientific Name

ABTH Abutilon theophrasti

ACPA8 Acacia paradoxa

ACNO7 Acaena novae-zelandiae

ACPA14 Acaena pallida

ACBR5 Achnatherum brachychaetum

ACRE3 Acroptilon repens 

AECY Aegilops cylindrica

AEGE Aegilops geniculata

AETR Aegilops triuncialis

AEIN6 Aeginetia indica

AERU Aeschynomene rudis

AGAD2 Ageratina adenophora

AIAL Ailanthus altissima

ALMA12 Alhagi maurorum

ALPE4 Alliaria petiolata

ALNE3 Allium neapolitanum

ALPA20 Allium paniculatum

ALVI Allium vineale

ALMY Alopecurus myosuroides

ALPH Alternanthera philoxeroides

ALSE4 Alternanthera sessilis 

AMAR4 Ammophila arenaria

ANAR16 Anchusa arvensis

ANOF Anchusa officinalis

ANAR6 Anthemis arvensis

ANCO2 Anthemis cotula 

ANSY Anthriscus sylvestris

ARSE8 Araujia sericifera

PLANTS 

symbol1 Scientific Name

ARMI2 Arctium minus

ARCA45 Arctotheca calendula

ARAB3 Artemisia absinthium

ARDO4 Arundo donax

ASFI2 Asphodelus fistulosus

AVST Avena sterilis

BAHY Bassia hyssopifolia

BASC5 Bassia scoparia

BRSY Brachypodium sylvaticum 

BRNI Brassica nigra

BRTO Brassica tournefortii

BRAR5 Bromus arvensis

BRDI3 Bromus diandrus

BRRU2 Bromus rubens 

BRTE Bromus tectorum

BRAL4 Bryonia alba

BUDA2 Buddleja davidii

BUUM Butomus umbellatus

CAGI Caesalpinia gilliesii

CACH42 Cardaria chalepensis 

CADR Cardaria draba 

CAPU6 Cardaria pubescens

CAAC Carduus acanthoides 

CANU4 Carduus nutans

CAPY2 Carduus pycnocephalus

CATE2 Carduus tenuiflorus

CACH38 Carpobrotus chilensis 

CAED3 Carpobrotus edulis

lists in the western states and invasive plant species 

recognized by the Weed Science Society of America.
68 Bureau of Land Management

PLANTS 

symbol1 Scientific Name

CALA20 Carthamus lanatus 

CAOX6 Carthamus oxyacanthus

CACA19 Carum carvi

CECA2 Centaurea calcitrapa

CECY2 Centaurea cyanus 

CEDI3 Centaurea diffusa 

CEIB Centaurea iberica

CEJA Centaurea jacea 

CEMA9 Centaurea macrocephala

CEME2 Centaurea melitensis 

CEMO Centaurea montana

CENI2 Centaurea nigra

CENI3 Centaurea nigrescens 

CESO3 Centaurea solstitialis 

CESTM Centaurea stoebe ssp. micranthos

CESU Centaurea sulphurea

CETR12 Centaurea trichocephala

CEVIS2 Centaurea virgata ssp. squarrosa

CHMI Chaenorhinum minus

CHJU Chondrilla juncea

CHTE2 Chorispora tenella

CIIN Cichorium intybus 

CIAR4 Cirsium arvense

CIVU Cirsium vulgare

CLOR Clematis orientalis

CLVI6 Clematis vitalba

COBE2 Commelina benghalensis

COMA2 Conium maculatum

COAR4 Convolvulus arvensis

COSQ Coronopus squamatus

COJU2 Cortaderia jubata

COSE4 Cortaderia selloana

CRSE2 Crepis setosa 

CRVU2 Crupina vulgaris 

CUMY Cucumis myriocarpus

CUAP2 Cuscuta approximata

CURE Cuscuta reflexa

CYCA Cynara cardunculus

CYDA Cynodon dactylon

CYPL2 Cynodon plectostachyus 

CYTR Cynodon transvaalensis

CYOF Cynoglossum officinale

PLANTS 

symbol1 Scientific Name

CYRO Cyperus rotundus

CYSC4 Cytisus scoparius

CYST7 Cytisus striatus

DACA6 Daucus carota

DEOD Delairea odorata

DIPU Digitalis purpurea

DIFU2 Dipsacus fullonum

DILA4 Dipsacus laciniatus

DISA9 Dipsacus sativus

ECPL Echium plantagineum

ECVU Echium vulgare

EGDE Egeria densa

EHCA Ehrharta calycina

EICR Eichhornia crassipes

ELAN Elaeagnus angustifolia

ELRE4 Elymus repens

EMAU Emex australis

EMSP Emex spinosa

EPHI Epilobium hirsutum

ERLE Eragrostis lehmanniana

ERGL8 Erechtites glomerata 

ERCI6 Erodium cicutarium

EUCY2 Euphorbia cyparissias

EUES Euphorbia esula 

EUESU Euphorbia esula var. uralensis

EUMY2 Euphorbia myrsinites

EUOB4 Euphorbia oblongata

EUSE12 Euphorbia serrata

EUTE10 Euphorbia terracina

FICA Ficus carica 

FOVU Foeniculum vulgare

GAOF Galega officinalis

GATE2 Galeopsis tetrahit

GAPA2 Galinsoga parviflora

GEMO2 Genista monspessulana

GYPA Gypsophila paniculata

HAHA8 Halimodendron halodendron

HAGL Halogeton glomeratus

HEHE Hedera helix

HEMA17 Heracleum mantegazzianum

HEMA3 Hesperis matronalis 

HITR Hibiscus trionum
Rangeland Resource Assessment—2011 69

PLANTS 

symbol1 Scientific Name

HIFL3 Hieracium × floribundum 

HIAU Hieracium aurantiacum

HICA10 Hieracium caespitosum

HIPI Hieracium pilosella 

HIPI2 Hieracium piloselloides

HYVE3 Hydrilla verticillata 

HYMO6 Hydrocharis morsus-ranae

HYNI Hyoscyamus niger 

HYPE Hypericum perforatum

HYRA3 Hypochaeris radicata 

IMGL Impatiens glandulifera

IPAQ Ipomoea aquatica

IPHE Ipomoea hederacea

IPPU2 Ipomoea purpurea

IRPS Iris pseudacorus

ISTI Isatis tinctoria 

KNAR Knautia arvensis

LALA4 Lathyrus latifolius 

LELA2 Lepidium latifolium

LEHO7 Lepyrodiclis holosteoides

LEVU Leucanthemum vulgare

LIDAD Linaria dalmatica ssp. dalmatica 

LIGE Linaria genistifolia

LIVU2 Linaria vulgaris 

LUGRH Ludwigia grandiflora ssp. hexapetala

LYFE4 Lycium ferocissimum

LYVU Lysimachia vulgaris

LYSA2 Lythrum salicaria 

LYVI3 Lythrum virgatum

MAVU Marrubium vulgare

MEPO3 Medicago polymorpha

MENO2 Mesembryanthemum nodiflorum

MIVE3 Milium vernale

MOVA Monochoria vaginalis

MUKE Murdannia keisak

MYAQ2 Myriophyllum aquaticum

MYSP2 Myriophyllum spicatum

NAST3 Nardus stricta

NYPE Nymphoides peltata

ONAL5 Ononis alopecuroides

ONAC Onopordum acanthium

ONTA Onopordum tauricum 

PLANTS 

symbol1 Scientific Name

ORMI Orobanche minor

ORRA Orobanche ramosa

ORRU Oryza rufipogon

OTAL Ottelia alismoides

PAAN4 Panicum antidotale

PAMI2 Panicum miliaceum

PARE3 Panicum repens

PEHA Peganum harmala 

PECI Pennisetum ciliare

PECL2 Pennisetum clandestinum

PEMA80 Pennisetum macrourum

PEPO14 Pennisetum polystachion

PESE3 Pennisetum setaceum

POCU6 Polygonum cuspidatum

POPO5 Polygonum polystachyum

POSA4 Polygonum sachalinense

POOL Portulaca oleracea

PORE5 Potentilla recta

PRST3 Prosopis strombulifera

PUMOL Pueraria montana var. lobata

REMO2 Retama monosperma

ROAU Rorippa austriaca

ROSY Rorippa sylvestris

ROMU Rosa multiflora

ROCO6 Rottboellia cochinchinensis

RUAR9 Rubus armeniacus

SACO8 Salsola collina

SAPA8 Salsola paulsenii

SATR12 Salsola tragus

SAVE6 Salsola vermiculata

SAAE Salvia aethiopis

SAPR2 Salvia pratensis

SASC2 Salvia sclarea

SAMO5 Salvinia molesta

SAOF4 Saponaria officinalis 

SCTE Schinus terebinthifolius

SCAR Schismus arabicus 

SCBA Schismus barbatus

SCHI Scolymus hispanicus

SECE Secale cereale

SEJA Senecio jacobaea

SESQ Senecio squalidus
70 Bureau of Land Management

PLANTS 

symbol1 Scientific Name

SEFA Setaria faberi

SILAA3 Silene latifolia ssp. alba

SIMA3 Silybum marianum

SOCA19 Solanum cardiophyllum

SODU Solanum dulcamara 

SOLA Solanum lanceolatum

SOMA Solanum marginatum

SOSE2 Soliva sessilis

SOAR2 Sonchus arvensis

SOBI2 Sorghum bicolor

SOHA Sorghum halepense

SPAN5 Spartina anglica

SPDE2 Spartina densiflora 

SPJU2 Spartium junceum

SPSA3 Sphaerophysa salsula 

SYAS Symphytum asperum

TACA8 Taeniatherum caput-medusae 

TAMI3 Tagetes minuta

TAAF Tamarix africana

TAAP Tamarix aphylla

TAAR6 Tamarix aralensis

TACA9 Tamarix canariensis

TACH2 Tamarix chinensis 

TAGA Tamarix gallica

TAPA4 Tamarix parviflora 

TAVU Tanacetum vulgare

THPA7 Thymelaea passerina

TOAR Torilis arvensis

TRTE Tribulus terrestris

TRPE21 Tripleurospermum perforata

TUFA Tussilago farfara

ULEU Ulex europaeus 

ULPU Ulmus pumila 

URPA Urochloa panicoides

VEBL Verbascum blattaria

VETH Verbascum thapsus

VIAL2 Viscum album

XASP2 Xanthium spinosum

ZYFA Zygophyllum fabago

1

 The symbol for the nonnative invasive plant species found in the 

U.S. Department of Agriculture PLANTS database at http://plants.

usda.gov/java/.
Rangeland Resource Assessment—2011 71

Appendix B: Attributes and Indicators 

Measured and Associated Statistics for 

Each Ecoregion

Attribute and indicator statistics with a single asterisk 

denote that there is an 80% chance that the actual 

percent of BLM rangeland acres in the ecoregion 

ranged between values that included zero. In such 

situations, the actual percent of BLM rangeland 

acres could not confidently be stated to differ from 

zero. Attribute and indicator statistics with a double 

asterisk denote that the attribute or indicator was not 

detected on BLM rangelands within the ecoregion.
72 Bureau of Land Management Attribute or Indicator Statistics Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archi- pelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Average amount of bare ground on BLM 

rangelands

Average percent on BLM rangeland acres

21.38 20.42 28.57 15.68 18.39 22.59 28.75 14.53 18.75

SE 8.92 3.37 1.59 5.38 0.92 4.67 2.72 2.61 3.20

CV 0.42 0.16 0.06 0.34 0.05 0.21 0.10 0.18 0.17

80% confidence interval

9.94-32.81 16.10-24.73 26.53-30.61 8.78-22.58 17.21-19.57 16.60-28.57 25.27-32.24 11.19-17.87 14.65-22.85

Proportion of BLM rangelands with at least 20% bare ground

Average percent of BLM rangeland acres

53.88 37.74 61.34 28.66 34.54 56.38 53.07 29.55 43.40

SE 27.81 6.08 3.88 19.52 4.41 16.03 5.57 8.40 9.37CV 0.52 0.16 0.06 0.68 0.13 0.28 0.10 0.28 0.2280% confidence interval

18.24-89.52 29.95-45.54 56.36-66.32 3.64-53.67 28.89-40.20 35.83-76.92 45.93-60.21 18.79-40.31 31.39-55.42

Proportion of BLM rangelands with at least 30% bare ground

Average percent of BLM rangeland acres

36.53* 24.40 36.04 12.89* 17.30 33.41 38.85 18.55 17.86

SE 41.05 5.69 3.87 10.29 2.25 22.52 5.72 7.97 7.41

CV 1.12 0.23 0.11 0.80 0.13 0.67 0.15 0.43 0.4280% confidence interval

0-89.13 17.11-31.69 31.08-41.01 0-26.07 14.42-20.18 4.55-62.28 31.51-46.18 8.33-28.76 8.36-27.35
Rangeland Resource Assessment—2011 73

Attribute or Indicator Statistics

Ecoregion

Arizona/ 

New 

Mexico 

Mountains

Central 

Basin and 

Range

Eastern 

Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold 

Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West 

Central 

Semi-Arid 

Prairies

Western 

Cordillera

Proportion of BLM rangelands with at least 40% bare ground

Average percent of BLM rangeland acres

** 13.95 25.79 4.28* 6.80 ** 30.73 2.90* 8.65

SE 5.02 3.68 4.78 1.81 5.58 3.09 6.39

CV 0.36 0.14 1.12 0.27 0.18 1.07 0.7480% confidence interval

7.52-20.38 21.08-30.50 0-10.41 4.48-9.13 23.57-37.88 0-6.87 0.46-16.84

Proportion of BLM rangelands with at least 50% bare ground

Average percent of BLM rangeland acres

** 10.31 14.57 2.14* 2.82 ** 20.07 2.90* 2.94*

SE 4.92 3.19 2.39 1.41 4.59 3.09 3.05CV 0.48 0.22 1.12 0.50 0.23 1.07 1.04

80% confidence interval

4.01-16.62 10.48-18.66 0-5.20 1.02-4.62 14.18-25.96 0-6.87 0-6.86

Proportion of BLM rangelands where soil aggregate stability is ranked 4 or less

Average percent of BLM rangeland acres

95.93 43.47 63.70 91.96 39.12 44.72 87.22 29.81 46.87

SE 5.19 6.59 3.58 8.86 7.15 22.52 4.14 10.45 8.50CV 0.05 0.15 0.06 0.10 0.18 0.50 0.05 0.35 0.18

80% confidence interval

89.27-100 35.03-51.92 59.11-68.28 80.61-100 29.96-48.28 15.86-73.58 81.91-92.53 16.42-43.20 35.98-57.77
74 Bureau of Land Management Attribute or Indicator Statistics Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archi- pelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Proportion of BLM rangelands with at least 20% of the land having intercanopy 

gaps of at least 2 meters in length

Average percent of BLM rangeland acres

60.73 59.01 33.71 52.44 6.76 22.11* 75.60 9.75 2.36*

SE 24.54 5.13 3.23 21.16 2.79 23.96 4.89 7.56 2.43CV 0.40 0.09 0.10 0.40 0.41 1.08 0.06 0.78 1.03

80% confidence interval

29.28-92.18 52.44-65.57 29.57-37.86 25.32-79.56 3.18-10.33 0-52.82 69.34-81.86 0.06-19.45 0-5.48

Proportion of BLM rangelands with nonnative invasive plant species present

Average percent of BLM rangeland acres

55.49 73.16 54.62 23.20* 82.80 31.43 30.43 28.08 33.10

SE 38.68 5.60 4.95 24.97 4.43 15.29 4.93 8.44 9.58

CV 0.70 0.08 0.09 1.08 0.05 0.49 0.16 0.30 0.2980% confidence interval

5.92-100 65.98-80.34 48.28-60.96 0-55.20 77.12-88.48 11.83-51.03 24.11-36.75 17.26-38.91 20.83-45.38

Proportion of BLM rangelands with abundant nonnative invasive plant species

Average percent of BLM rangeland acres

18.26* 43.18 9.76 ** 34.83 9.07* 6.86 ** 6.89

SE 20.52 6.84 2.07 4.93 10.48 2.70 5.28CV 1.12 0.16 0.21 0.14 1.16 0.39 0.7780% confidence interval

0-44.57 34.41-51.95 7.11-12.41 28.52-41.14 0-22.50 3.40-10.32 0.12-13.67
Rangeland Resource Assessment—2011 75

Attribute or Indicator Statistics

Ecoregion

Arizona/ 

New 

Mexico 

Mountains

Central 

Basin and 

Range

Eastern 

Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold 

Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West 

Central 

Semi-Arid 

Prairies

Western 

Cordillera

Proportion of BLM rangelands where biotic integrity shows moderate departure from reference conditions

Average percent of BLM rangeland acres

35.61 5.27 8.93 15.77 13.29 11.30* 6.57 3.79* 4.72

SE 12.62 2.08 2.26 11.64 3.74 12.23 2.86 3.83 3.49CV 0.35 0.40 0.25 0.74 0.28 1.08 0.44 1.01 0.74

80% confidence interval

19.44-51.79 2.60-7.93 6.04-11.82 0.85-30.69 8.50-18.08 0-26.98 2.89-10.24 0-8.70 0.25-9.20

Proportion of BLM rangelands where biotic integrity shows moderateto-extreme or extremeto-total departure from reference conditions

Average percent of BLM rangeland acres

17.35* 0.10* 1.96 ** 3.38 ** 15.80 ** **

SE 19.69 0.11 0.96 2.05 4.52CV 1.14 1.05 0.49 0.61 0.29

80% confidence interval

0-42.58 0-0.24 0.73-3.19 0.75-6.01 10.01-21.60
76 Bureau of Land Management Attribute or Indicator Statistics Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archi- pelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Proportion of BLM rangelands where hydrologic function 

shows moderate departure from reference conditions

Average percent of BLM rangeland acres

17.35* 3.08 10.13 2.14* 6.49 11.30* 11.73 10.67 7.95

SE 19.69 1.83 2.11 2.39 2.02 12.23 4.75 5.69 4.68CV 1.14 0.59 0.21 1.12 0.31 1.08 0.40 0.53 0.59

80% confidence interval

0-42.58 0.73-5.42 7.42-12.83 0-5.20 3.90-9.07 0-26.98 5.64-17.81 3.38-17.96 1.95-13.94

Proportion of BLM rangelands where hydrologic function shows moderateto-extreme or extremeto-total departure from reference conditions

Average percent of BLM rangeland acres

17.35* ** 2.49 8.04* 1.12* ** 13.99 ** 2.29*

SE 19.69 1.10 8.86 1.13 4.42 2.41

CV 1.14 0.44 1.10 1.00 0.32 1.0580% confidence interval

0-42.58 1.07-3.90 0-19.39 0-2.57 8.32-19.66 0-5.38
Rangeland Resource Assessment—2011 77

Attribute or Indicator Statistics

Ecoregion

Arizona/ 

New 

Mexico 

Mountains

Central 

Basin and 

Range

Eastern 

Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold 

Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West 

Central 

Semi-Arid 

Prairies

Western 

Cordillera

Proportion of BLM rangelands where soil/site stability shows moderate departure from reference conditions

Average percent of BLM rangeland acres

** 1.50 8.54 2.14* 4.19 22.96 13.57 3.79* 5.51

SE 0.83 1.91 2.39 1.65 13.74 4.95 3.83 4.01CV 0.55 0.22 1.12 0.39 0.60 0.36 1.01 0.73

80% confidence interval

0.44-2.56 6.09-10.99 0-5.20 2.07-6.30 5.35-40.57 7.23-19.91 0-8.70 0.37-10.65

Proportion of BLM rangelands where soil/site stability shows moderateto-extreme or extremeto-total departure from reference conditions

Average percent of BLM rangeland acres

17.35* ** 2.55 8.04* 1.12* ** 12.14 ** 2.29*

SE 19.69 1.10 8.86 1.13 3.79 2.41

CV 1.14 0.43 1.10 1.00 0.31 1.0580% confidence interval

0-42.58 1.15-3.96 0-19.39 0-2.57 7.28-17.00 0-5.38

Rangeland Resource Assessment—2011 79

Appendix C: Overall Comparison of 

Attribute and Indicator Estimates 

Across Ecoregions

Results of the omnibus F-test, which tests whether 

the estimates for an attribute or indicator across 

different ecoregions are the same or are not all 

the same.

Attribute or Indicator F Statistic P-value

Degrees 

of 

Freedom

Number of 

Ecoregions 

Compared

Average amount of bare ground on BLM rangelands 69.77 0.0000 (8, 20) 9

Proportion of BLM rangelands with at least 20% bare ground 27.56 0.0000 (8, 20) 9

Proportion of BLM rangelands with at least 30% bare ground 48.41 0.0000 (6, 22) 7

Proportion of BLM rangelands with at least 40% bare ground 51.05 0.0000 (4, 24) 5

Proportion of BLM rangelands with at least 50% bare ground 36.43 0.0000 (3, 25) 4

Proportion of BLM rangelands where soil aggregate stability 

is ranked 4 or less

163.34 0.0000 (8, 20) 9

Proportion of BLM rangelands with at least 20% of the land 

having intercanopy gaps of at least 2 meters in length

296.28 0.0000 (6, 22) 7

Proportion of BLM rangelands with nonnative invasive plant 

species present

148.06 0.0000 (7, 21) 8

Proportion of BLM rangelands with abundant nonnative 

invasive plant species

49.19 0.0000 (4, 24) 5

Proportion of BLM rangelands where biotic integrity shows 

moderate departure from reference condition

8.67 0.0001 (6, 22) 7

Proportion of BLM rangelands where biotic integrity shows 

moderate-to-extreme or extreme-to-total departure from 

reference conditions

9.35 0.0009 (2, 26) 3

Proportion of BLM rangelands where hydrologic function 

shows moderate departure from reference conditions

14.24 0.0000 (5, 23) 6

Proportion of BLM rangelands where hydrologic function 

shows moderate-to-extreme or extreme-to-total departure 

from reference conditions

6.03 0.0208 (1, 27) 2

Proportion of BLM rangelands where soil/site stability shows 

moderate departure from reference conditions

35.83 0.0000 (5, 23) 6

Proportion of BLM rangelands where soil/site stability shows 

moderate-to-extreme or extreme-to-total departure from 

reference conditions

5.48 0.0269 (1, 27) 2

Rangeland Resource Assessment—2011 81

Appendix D: Pairwise Comparisons Across 

Ecoregions for Each Attribute or Indicator

These comparisons show whether estimates are 

significantly different or not for each pair of 

ecoregions. Values in tables are F statistics.
82 Bureau of Land Management Indicator: Average amount of bare ground on BLM rangelands Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains 0.01 0.63 0.30 0.11 0.02 0.59 0.57 0.08 Central Basin and Range 6.69* 0.49 0.45 0.14 3.81* 2.72* 0.11 Eastern Cold 

Deserts

5.10* 38.02* 1.47 0.00 23.26* 6.35*

Madrean Archipelago

0.24 0.95 3.97* 0.04 0.17

Northern Cold Deserts

0.74 14.94* 2.03* 0.01

South Central SemiArid Prairies 1.44 1.83* 0.57Warm Deserts

12.59* 5.98*

West Central Semi-Arid Prairies

0.96

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.
Rangeland Resource Assessment—2011 83

Indicator: Proportion of BLM rangelands with at least 20% bare ground

Ecoregion

Arizona/

New Mexico 

Mountains

Central 

Basin and 

Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

0.32 0.08 0.59 0.47 0.01 0.00 0.75 0.13

Central Basin and Range

11.51* 0.16 0.59 1.36 3.52* 0.86 0.23

Eastern Cold Deserts

2.72* 21.26* 0.09 1.58 9.97* 2.55*

Madrean Archipelago

0.08 0.98 1.27 0.00 0.38

Northern Cold Deserts

1.53 7.35* 0.36 0.62

South Central SemiArid Prairies 0.04 1.92* 0.59Warm Deserts

6.11* 0.87

West Central Semi-Arid Prairies

1.37

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.
84 Bureau of Land Management Indicator: Proportion of BLM rangelands with at least 30% bare ground Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains **   **  **   **  Central Basin and Range 3.27* ** 1.84* 0.14 4.11* 0.40 0.43 Eastern Cold 

Deserts

** 19.40* 0.01 0.14 3.78* 3.62*

Madrean Archipelago

**   **  **

Northern Cold Deserts

0.50 14.22* 0.02 0.01

South Central SemiArid Prairies 0.05 0.34 0.50Warm Deserts

4.52* 5.32*

West Central Semi-Arid Prairies

0.00

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion and the Madrean Archipelago ecoregion because the indicator estimates for these ecoregions could not confidently be stated to differ from zero.
Rangeland Resource Assessment—2011 85

Indicator: Proportion of BLM rangelands with at least 40% bare ground

Ecoregion

Arizona/

New Mexico 

Mountains

Central 

Basin and 

Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

*** *** ** *** *** *** ** ***

Central Basin and Range

3.74* ** 1.92* *** 5.91* ** 0.37

Eastern Cold Deserts

** 24.39* *** 0.54 ** 4.30*

Madrean Archipelago

**   **  **

Northern Cold Deserts

*** 19.71* ** 0.09

South Central SemiArid Prairies *** ** ***Warm Deserts

** 6.53*

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion and the West Central Semi-Arid Prairies ecoregion because the indicator estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion and the South Central Semi-Arid Prairies ecoregion, because the indicator was not detected on BLM rangelands within these ecoregions.
86 Bureau of Land Management Indicator: Proportion of BLM rangelands with at least 50% bare ground Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi-Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains *** *** ** *** *** ***   Central Basin and Range 0.58 **  2.06* *** 2.25* ** ** Eastern Cold 

Deserts

** 14.36* *** 0.89  

Madrean Archipelago

**  **   ** 

Northern Cold Deserts

*** 15.31* ** **

South Central SemiArid Prairies ***  Warm Deserts

**  **

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion, the West Central Semi-Arid Prairies ecoregion, and the Western Cordillera ecoregion because the indicator estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion and the South Central Semi-Arid Prairies ecoregion because the indicator was not detected on BLM rangelands within these ecoregions.
Rangeland Resource Assessment—2011 87

Indicator: Proportion of BLM rangelands where soil aggregate stability is ranked 4 or less

Ecoregion

Arizona/

New Mexico 

Mountains

Central 

Basin and 

Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central 

Semi-Arid 

Prairies

Warm 

Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

37.42* 23.66* 0.15 40.47* 4.68* 1.35 36.07* 27.24*

Central Basin and Range

7.39* 18.83* 0.14 0.00 49.84* 1.21 0.11

Eastern Cold Deserts

7.60* 8.31* 0.68 17.20* 9.64* 3.81*

Madrean Archipelago

23.64* 3.94* 0.20 19.90* 12.56*

Northern Cold Deserts

0.05 27.19* 0.53 0.51

South Central SemiArid Prairies 3.06* 0.34 0.01Warm Deserts

22.35* 18.15*

West Central Semi-Arid Prairies

1.35

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.
88 Bureau of Land Management Indicator: Proportion of BLM rangelands with at least 20% of the land having intercanopy gaps of at least 2 meters in length Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi- Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains 0.00 1.14 0.08 4.66* ** 0.30 3.82* ** Central Basin and Range 19.04* 0.09 90.24* ** 4.93* 31.51* ** Eastern Cold Deserts 0.82 49.41* ** 56.91* 11.00* **

Madrean Archipelago

4.49* ** 1.11 3.58* **

Northern Cold Deserts

** 171.28* 0.17 **

South Central SemiArid Prairies   ** Warm Deserts

52.98* **

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the South Central Semi-Arid Prairies ecoregion and the Western Cordillera ecoregion because the indicator estimates for these ecoregions could not confidently be stated to differ from zero.
Rangeland Resource Assessment—2011 89

Indicator: Proportion of BLM rangelands with nonnative invasive plant species present

Ecoregion

Arizona/

New Mexico 

Mountains

Central Basin 

and Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central SemiArid Prairies Warm Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

0.21 0.00 ** 0.49 0.27 0.41 0.64 0.32

Central Basin and Range

6.89* ** 1.71 5.76* 23.48* 19.83* 20.99*

Eastern Cold Deserts

** 15.24* 2.15* 15.04* 6.68* 3.34*

Madrean Archipelago

**   **  **

Northern Cold Deserts

11.65* 55.32* 30.31* 24.75*

South Central SemiArid Prairies 0.00 0.03 0.01Warm Deserts

0.05 0.05

West Central Semi-Arid Prairies

0.14

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion because the indicator estimate for this ecoregion could not confidently be stated to differ from zero.
90 Bureau of Land Management Indicator: Proportion of BLM rangelands with abundant nonnative invasive plant species Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi- Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains   **  **   **  ** Central Basin and Range 20.31* *** 0.83 ** 19.23* *** 14.27* Eastern Cold Deserts *** 21.47* ** 0.93 *** 0.24

Madrean Archipelago

*** ** *** *** ***

Northern Cold Deserts

** 28.97* *** 16.79*

South Central SemiArid Prairies **  Warm Deserts

** * 0.00

West Central Semi-Arid Prairies

***

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion and the South Central Semi-Arid Prairies ecoregion because the indicator estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion and the West Central Semi-Arid Prairies ecoregion because the indicator was not detected on BLM rangelands within these ecoregions.
Rangeland Resource Assessment—2011 91

Attribute: Proportion of BLM rangelands where biotic integrity shows moderate departure from reference conditions 

Ecoregion

Arizona/

New Mexico 

Mountains

Central Basin 

and Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central SemiArid Prairies Warm Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

5.80* 4.35* 1.55 2.86* ** 4.74* ** 5.61*

Central Basin and Range

1.19 0.79 2.58* ** 0.17 ** 0.02

Eastern Cold Deserts

0.31 1.21 ** 0.42 ** 1.06

Madrean Archipelago

0.04 ** 0.50 ** 0.84

Northern Cold Deserts

** 1.71 ** 2.41*

South Central SemiArid Prairies **  Warm Deserts

**  0.16

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the South Central Semi-Arid Prairies ecoregion and the West Central Semi-Arid Prairies ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.
92 Bureau of Land Management Attribute: Proportion of BLM rangelands where biotic integrity shows moderate-to-extreme or extreme-to-total departure from reference conditions Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi- Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains   **  **   **  ** Central Basin and Range   **  **   **  Eastern Cold Deserts *** 0.31 *** 9.15* *** ***

Madrean Archipelago

*** *** *** *** ***

Northern Cold Deserts

*** 5.83* *** ***

South Central SemiArid Prairies *** *** ***Warm Deserts

*** ***

West Central Semi-Arid Prairies

***

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion and the Central Basin and Range ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion, the South Central Semi-Arid Prairies ecoregion, the West Central Semi-Arid Prairies ecoregion, and the Western Cordillera ecoregion because the attribute was not detected on BLM rangelands within these ecoregions.
Rangeland Resource Assessment—2011 93

Attribute: Proportion of BLM rangelands where hydrologic function shows moderate departure from reference conditions

Ecoregion

Arizona/

New Mexico 

Mountains

Central Basin 

and Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central SemiArid Prairies Warm Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

  **  **   **  **

Central Basin and Range

5.25* ** 1.40 ** 2.96* 2.37* 0.89

Eastern Cold Deserts

** 1.15 ** 0.09 0.01 0.17

Madrean Archipelago

  **  ** **

Northern Cold Deserts

** 0.92 0.45 0.07

South Central SemiArid Prairies   ** Warm Deserts

0.02 0.41

West Central Semi-Arid Prairies

0.13

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion, the Madrean Archipelago ecoregion, and the South Central Semi-Arid Prairies ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.
94 Bureau of Land Management Attribute: Proportion of BLM rangelands where hydrologic function shows moderate-to-extreme or extreme-to-total departure from reference conditions Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi- Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains   **  **   **  ** Central Basin and Range ***   ** * *** *** ** Eastern Cold Deserts   ** * 6.03* *** **

Madrean Archipelago

  **  ** **

Northern Cold Deserts

  **  **

South Central SemiArid Prairies *** *** **Warm Deserts

*** **

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion, the Madrean Archipelago ecoregion, the Northern Cold Deserts ecoregion, and the Western Cordillera ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Central Basin and Range ecoregion, the South Central Semi-Arid Prairies ecoregion, and the West Central Semi-Arid Prairies ecoregion because the attribute was not detected on BLM rangelands within these ecoregions.
Rangeland Resource Assessment—2011 95

Attribute: Proportion of BLM rangelands where soil/site stability shows moderate departure from reference conditions

Ecoregion

Arizona/

New Mexico 

Mountains

Central Basin 

and Range

Eastern Cold 

Deserts

Madrean 

Archipelago

Northern 

Cold Deserts

South 

Central SemiArid Prairies Warm Deserts

West Central 

Semi-Arid 

Prairies

Western 

Cordillera

Arizona/New Mexico Mountains

*** *** ** *** *** *** ** ***

Central Basin and Range

11.17* ** 3.01* 2.48* 5.75* ** 0.94

Eastern Cold Deserts

** 2.96* 0.98 0.93 ** 0.44

Madrean Archipelago

  **  ** **

Northern Cold Deserts

1.76* 2.57* ** 0.08

South Central SemiArid Prairies 0.44 ** 1.58Warm Deserts

** 2.02*

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Madrean Archipelago ecoregion and the West Central Semi-Arid Prairies ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion because the attribute was not detected on BLM rangelands within this ecoregion.
96 Bureau of Land Management Attribute: Proportion of BLM rangelands where soil/site stability shows moderate-to-extreme or extreme-to-total departure from reference conditions Ecoregion Arizona/ New Mexico Mountains Central Basin and Range Eastern Cold Deserts Madrean Archipelago Northern Cold Deserts South Central Semi- Arid Prairies Warm Deserts West Central Semi-Arid Prairies Western Cordillera Arizona/ New Mexico Mountains   **  **   **  ** Central Basin and Range ***   ** * *** *** ** Eastern Cold Deserts   ** * 5.48* *** **

Madrean Archipelago

  **  ** **

Northern Cold Deserts

  **  **

South Central SemiArid Prairies *** *** **Warm Deserts

*** **

West Central Semi-Arid Prairies

**

Western Cordillera

* Statistically significant at 80% confidence level; F critical value (degrees of freedom (df) 1, 27; α = 0.8) = 1.73.** Pairwise comparisons were not conducted with the Arizona/New Mexico Mountains ecoregion, the Madrean Archipelago ecoregion, the Northern Cold Deserts ecoregion, and the Western Cordillera ecoregion because the attribute estimates for these ecoregions could not confidently be stated to differ from zero.*** Pairwise comparisons were not conducted with the Central Basin and Range ecoregion, the South Central Semi-Arid Prairies ecoregion, and the West Central Semi-Arid Prairies ecoregion because the attribute was not detected on BLM rangelands within these ecoregions.
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