Interagency Ecological Site

Handbook for Rangelands

January 2013
January 2013 Page 1

Authors

Dan Caudle

Rangeland Management Specialist 

(retired)

Natural Resources Conservation Service

Fort Worth, TX

Jeff DiBenedetto

Ecologist

Forest Service

Billings, MT

Michael “Sherm” Karl

Inventory and Monitoring 

Specialist/Rangeland Ecologist

Bureau of Land Management

Denver, CO

Homer Sanchez

Rangeland Management Specialist

Natural Resources Conservation Service

Fort Worth, TX

Curtis Talbot

Rangeland Management Specialist

Natural Resources Conservation Service

Lincoln, NE
January 2013 Page 2

Table of Contents

SECTION 1.0 INTRODUCTION............................................................................................................ 6

A. Purpose of Handbook ............................................................................................................. 6

B. Legal Authorities, Agency Policy, and Technical Guidance ............................................... 6

1. Bureau of Land Management (BLM).................................................................6

2. Forest Service (FS) ................................................................................................................. 7

3. Natural Resources Conservation Service (NRCS).................................................................. 8

C. Interagency Uses of Ecological Sites...................................................................................... 8

D. Interagency Coordination ...................................................................................................... 9

SECTION 1.1 ECOLOGICAL SITE RELATIONSHIPS WITH OTHER CLASSIFICATION AND 

MAPPING HIERARCHIES....................................................................................................................10

SECTION 2.0 ECOLOGICAL SITE CLASSIFICATION CONCEPTS..............................................12

A. Background............................................................................................................................ 12

B. Defining the Site Concept ..................................................................................................... 12

C. Interpreting Ecological Dynamics of the Site..................................................................... 14

1. Components of a State-and-Transition Model.......................................................................... 15

2. General Considerations in Producing State-and-Transition Models ........................................ 19

D. State Change versus Change in Ecological Site .................................................................. 20

SECTION 3.0 CLASSIFICATION, DIFFERENTIATION, AND DESCRIPTION OF 

ECOLOGICAL SITES..............................................................................................................................21

A. Purpose.................................................................................................................................... 21

B. Classification and Differentiation of an Ecological Site ..................................................... 21

SECTION 3.1 STEPS FOR CLASSIFICATION, DIFFERENTIATION, AND DESCRIPTION OF 

ECOLOGICAL SITES..............................................................................................................................23

Establish Local Work Groups................................................................................................... 23

SECTION 3.1.1 PRELIMINARY STAGES .........................................................................................23

A. Define Geographic/Ecological Extent................................................................................... 23

B. Gather Background Information.......................................................................................... 24
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C. Evaluate Existing Data .......................................................................................................... 24

D. Conduct Reconnaissance—Low Intensity Traverses.......................................................... 25

E. Develop State-and-Transition Model Concepts................................................................... 25

F. Develop Sampling Strategy.................................................................................................... 26

G. Select Sampling Methods...................................................................................................... 26

SECTION 3.1.2 ITERATIVE STAGES................................................................................................27

A. Data Collection—Medium Intensity Sampling ................................................................... 27

B. Data Analysis.......................................................................................................................... 28

C. Define Differentiating Characteristics of Ecological Sites ................................................. 28

D. Field Test the Classification .................................................................................................. 28

SECTION 3.1.3 FINAL STAGE............................................................................................................29

A. Data Collection—High Intensity Sampling ......................................................................... 29

B. Develop Management Interpretations.................................................................................. 30

C. Correlation.............................................................................................................................. 30

D. Quality Control and Assurance ............................................................................................ 30

1. Quality Control ......................................................................................................................... 30

2. Quality Assurance..................................................................................................................... 30

E. Certification ............................................................................................................................ 31

F. Publish the Ecological Site Description ................................................................................ 31

SECTION 3.2 ECOLOGICAL SITE KEY .............................................................................................32

SECTION 3.3 DESCRIBING STATES AND COMMUNITY PHASES OF ECOLOGICAL SITES

...................................................................................................................................................................33

SECTION 3.4 DATA STORAGE ..........................................................................................................34

SECTION 3.5 ECOLOGICAL SITE NAMING CONVENTION.........................................................34

SECTION 3.5.1 COMMUNITY PHASE NAMING CONVENTION.................................................35
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SECTION 3.6 REVISION OF ECOLOGICAL SITE DESCRIPTIONS.............................................35

SECTION 4.0 DELINEATION AND MAPPING OF ECOLOGICAL SITES...................................36

SECTION 4.1 ECOLOGICAL SITES AND ECOLOGICAL UNIT HIERARCHY MAPPING........37

SECTION 5.0 CONTENTS OF ECOLOGICAL SITE DESCRIPTIONS ..........................................38

A. Ecological Site Characteristics.............................................................................................. 38

1. Site Name:................................................................................................................................. 38

2. Site ID:...................................................................................................................................... 39

3. Hierarchical Classification Relationships................................................................................. 39

B. Physiographic Features.......................................................................................................... 39

C. Climatic Features................................................................................................................... 39

D. Influencing Water Features .................................................................................................. 40

E. Representative Soil Features................................................................................................. 40

F. States and Community Phases .............................................................................................. 40

1. Ecological Dynamics of the Site:.............................................................................................. 40

2. State-and-Transition Diagram:.................................................................................................. 41

3. Photos:....................................................................................................................................... 41

4. Narrative: .................................................................................................................................. 41

5. Supporting Community Phase Documentation:........................................................................ 42

6. Community Phase Composition: .............................................................................................. 42

7. Annual Production: ................................................................................................................... 42

8. Total Annual Production:.......................................................................................................... 42

9. Canopy or Foliar Cover: ........................................................................................................... 43

10. Structure:................................................................................................................................. 43

11. Ground Surface Cover: ........................................................................................................... 43

12. Community Phase Growth Curves: ........................................................................................ 43

G. Ecological Site Interpretations ............................................................................................. 44

1. Animal Community: ................................................................................................................. 44

2. Hydrology Functions: ............................................................................................................... 44

3. Recreational Uses: .................................................................................................................... 44

4. Wood Products:......................................................................................................................... 45

5. Other Products: ......................................................................................................................... 45

H. Supporting Information ........................................................................................................ 45

1. Associated Sites: ....................................................................................................................... 45

2. Similar Sites:............................................................................................................................. 45

3. Inventory Data References:....................................................................................................... 45

4. Agency/State Correlation:......................................................................................................... 46

5. Type Locality:........................................................................................................................... 46
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6. Relationship to Other Established Classification Systems: ...................................................... 46

7. Other References:...................................................................................................................... 46

8. Rangeland Health Reference Sheet:.......................................................................................... 46

I. Site Description Approval....................................................................................................... 46

1. Authorship: ............................................................................................................................... 46

2. Site Approval: ........................................................................................................................... 47

GLOSSARY ..............................................................................................................................................48

REFERENCES CITED ............................................................................................................................51

ACKNOWLEDGMENTS........................................................................................................................57

APPENDIX A. RELATIONSHIP OF ECOLOGICAL CLASSIFICATION AND MAPPING 

SYSTEMS .................................................................................................................................................59

APPENDIX B. EXAMPLE OF GROWTH FORMS THAT COULD BE USED TO CATEGORIZE 

PLANT SPECIES COVER (ADAPTED FROM FEDERAL GEOGRAPHIC DATA COMMITTEE 

2008). ......................................................................................................................................................70

APPENDIX C. EXAMPLE OF VERTICAL STRATA THAT COULD BE USED TO CATEGORIZE 

PLANT SPECIES COVER (ADAPTED FROM FEDERAL GEOGRAPHIC DATA COMMITTEE 

2008) .......................................................................................................................................................71

APPENDIX D. EXAMPLE ECOLOGICAL SITE KEY........................................................................72

APPENDIX E. EXAMPLE ECOLOGICAL SITE DESCRIPTION....................................................76
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SECTION 1.0 Introduction

A. Purpose of Handbook

The Interagency Ecological Site Handbook for Rangelands was developed to implement the 

policy outlined in the Rangeland Interagency Ecological Site Manual. This policy provides 

direction to Bureau of Land Management (BLM), Forest Service (FS), and Natural Resources 

Conservation Service (NRCS) to cooperatively identify and describe rangeland ecological sites 

for use in inventory, monitoring, evaluation, and management of the Nation’s rangelands. This

is a response, in part, to direction from Congress in the Department of the Interior and Related 

Agencies Appropriations Act of 2002. In that Appropriations Act, Congress expected the 

Secretary of Agriculture and the Secretary of the Interior to prepare a coordinated plan and 

budget that would identify the cost of completing standardized soil surveys and ecological 

classification on all rangeland for use at local management levels. This interagency handbook 

promulgates ecological sites as the component of ecological classification at local management 

levels (USDI and USDA 2003). 

This handbook provides a standardized method to be utilized by the BLM, FS, and NRCS to 

define, delineate, and describe terrestrial ecological sites on rangelands. Rangeland is defined as 

land on which the indigenous vegetation is predominantly grasses, grass-like plants, forbs, or 

shrubs, and is managed as a natural ecosystem. If plants are introduced, they are managed 

similarly. Rangelands include natural grasslands, shrublands, savannas, many deserts, tundra, 

alpine communities, marshes, and meadows (Society for Range Management 1998).

The BLM, FS, and NRCS have a common objective of utilizing science-based technical 

processes to sustain and enhance natural resources and the environment. They have used 

different methods to stratify landscapes into units for planning, analysis, and decision making. 

Their jurisdictions are intermingled throughout much of the United States, including both private 

and public lands; therefore, a standardized method to define, delineate, and describe terrestrial 

ecological sites is more efficient than each agency having their own method.

It is anticipated that future versions of this handbook will incorporate other ecosystems including 

forest, riparian, and culturally managed lands, such as cropland and pastureland.

B. Legal Authorities, Agency Policy, and Technical Guidance

Executive Order 13352—Facilitation of Cooperative Conservation (69 FR 167, 52989, August 

30, 2004). The purpose of this order is to ensure that the Departments of the Interior, 

Agriculture, Commerce, and Defense, and the Environmental Protection Agency implement laws 

relating to the environment and natural resources in a way that promotes cooperative 

conservation, with an emphasis on appropriate inclusion of local participation in Federal decision 

making, in accordance with their respective agency missions, policies, and regulations.

1. Bureau of Land Management (BLM) 

a. Legal Authorities

• The Taylor Grazing Act (TGA) of 1934 as amended (43 U.S.C. 315, 315a 

through 315r)
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• The Federal Land Policy and Management Act (FLPMA) of 1976 (43 U.S.C. 

1701 et seq.), as amended by the Public Rangelands Improvement Act of 1978 

(43 U.S.C. 1901 et seq.). 

• Executive Orders that transfer land acquired under the Bankhead-Jones Farm 

Tenant Act of July 22, 1937, as amended (7 U.S.C. 1012), to the Secretary and 

authorize administration under the Taylor Grazing Act.

• Section 4 of the Oregon and California Railroad Land Act of August 28, 1937 

(43 U.S.C. 1181d).

• The Public Rangelands Improvement Act of 1978 (43 U.S.C. 1901 et seq.).

b. Agency Policy

• Manual Handbook H-4410-1, National Range Handbook (USDI-Bureau of 

Land Management 1984, amended 1990).

• Manual 4400, Rangeland Inventory, Monitoring, and Evaluation (USDIBureau of Land Management 1989).

• Handbook H-4400-1, Rangeland Monitoring and Evaluation (USDI-Bureau of 

Land Management 1989, amended 1990).

c. Technical Guidance

• Technical Reference 4400-7, Rangeland Monitoring: Analysis, Interpretation, 

and Evaluation (USDI-Bureau of Land Management 1985). 

• Technical Reference 1737-7, Procedures For Ecological Site Inventory—With 

Special Reference to Riparian-Wetland Sites (USDI-Bureau of Land 

Management 1992).

• Interagency Technical Reference 1734-6, Interpreting Indicators of Rangeland 

Health, version 4 (Pellant et al. 2005).

• Technical Reference 1734-7, Ecological Site Inventory (Habich 2001).

2. Forest Service (FS)

a. Legal Authorities

• The Forest and Rangeland Renewable Resources Planning Act of 1974 

(Public Law 93-378, 88 Stat. 476, as amended; 16 U.S.C. 1601 (Note), 1600-

1614 and the National Forest Management Act of 1976 (Public Law 94-588, 

90 Stat. 2949, as amended; 16 U.S.C. 472a, 476, 500, 513-516, 518, 521b, 528 

(Note), 576b, 594-2 (Note), 1600 (Note), 1601 (Note), 1600-1602, 1604, 

1606, 1608-1614) 

• Public Rangelands Improvement Act of 1978 (Public Law 95-514, 92 Stat. 

1806; 43 U.S.C. 1752-1753, 1901-1908; 16 U.S.C. 1333(b)). 

b. Agency Policy

• Forest Service Manual 2060 Ecosystem Classification, Interpretation, and 

Application (USDA-Forest Service 2010)

• Ecological Classification and Inventory Handbook, Forest Service Handbook 

(FSH) 2090.11 (USDA-Forest Service 1991a)
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c. Technical Guidance

• Terrestrial Ecological Unit Inventory (TEUI) Technical Guide: Landscape and 

Land Unit Scales (Winthers et al. 2005)

• Existing Vegetation Classification and Mapping Technical Guide Version 1.0. 

(Brohman and Bryant 2005)

3. Natural Resources Conservation Service (NRCS)

a. Legal Authorities

• Soil Conservation and Domestic Allotment Act (Public Law 74-46) April 27, 

1935

• Secretary of Agriculture Memorandum 1396, April 10, 1956

• Rural Development Act of 1972 (Public Law 92-419, Section 302)

• Soil and Water Resources Act of 1977 (Public Law 95-192 Sections 2.3 and 

5)

b. Agency Policy and Technical Guidance

• Title 450, General Manual, Technology, Part 401 (USDA-Natural Resources 

Conservation Service 2010)

• Title 190, National Range and Pasture Handbook, Chapters 3 and 4 (USDANatural Resources Conservation Service 1997, amended 2003 and 2006 

respectively)

• Title 430, National Soil Survey Handbook, Part 622, Section 622.07, and 

Part 627, Section 627.09 (USDA-Natural Resources Conservation Service

2008 and 2012 respectively)

• Title 190, National Biology Manual, Part 512, Sections 512.30 through 512.32

(USDA-Natural Resources Conservation Service 2003)

• National Forestry Handbook Part 637.3 (USDA-Natural Resources 

Conservation Service 2004)

• Title 190, National Forestry Manual, Part 537, Section 537.3 (USDA-Natural 

Resources Conservation Service 2010)

C. Interagency Uses of Ecological Sites

Ecological site classifications and descriptions provide a consistent framework for stratifying and 

describing rangelands and their soil, vegetation, and abiotic features; thereby delineating units

that share similar capabilities to respond to management activities or disturbance processes. 

Ecological site descriptions provide land managers the information needed for evaluating 

suitability of the land for various land-use activities, the capability to respond to various 

management activities or disturbance processes, and the ability to sustain productivity over the 

long term. The BLM, FS, and NRCS each have business needs that are achieved with use of 

ecological sites. Below are a few examples of how ecological sites can facilitate common 

business needs across the agencies:

• Ecological site descriptions provide information to support land and resource 

assessments, planning, and monitoring including:

o descriptions of reference plant/soil relationships, 
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o disturbance processes, 

o associated ecosystem dynamics, that are critical to assessing and 

monitoring ecosystem and watershed function, conditions, and trend at the 

local, landscape, or watershed level.

• Ecological site descriptions provide a consistent framework for describing and 

communicating information about land capability and suitability for various land 

uses, such as

o total annual biomass production per year, 

o annual biomass production by species,

o various cover and structure values that can facilitate the understanding and 

management of wildlife habitat, soil functions and processes, and grazing 

management.

• Ecological site descriptions provide baseline resource information and/or benchmark 

data, plus alternative state resource information that can facilitate the planning 

process and the development of land management plans for resource use and 

monitoring condition.

D. Interagency Coordination

The Rangeland Interagency Ecological Site Manual identifies the establishment of an 

interagency, interdisciplinary workgroup. A national interagency workgroup, comprised of 

employees from BLM, FS, and NRCS provides leadership in the implementation of the 

Rangeland Interagency Ecological Site Manual and the Interagency Ecological Site Handbook

for Rangelands. This workgroup develops and recommends policy, procedures, and data 

management for the development and use of ecological site descriptions.

An interdisciplinary working group at the State level will be established under the direction of 

the NRCS State Conservationist, FS Regional Forester(s), and BLM State Director to discuss 

ecological site activities, consider the priorities of all agencies, and recommend actions. Their 

responsibility includes coordination and oversight for the development and maintenance of 

ecological site descriptions to ensure they meet unique agency business needs. The working 

group also identifies local resource interpretations specific to agency business needs, 

cooperatively prioritize ecological site description development needs, and provide guidance and 

support to the interdisciplinary working group at the local level to incorporate these priorities

into interagency local work plans. 

An interdisciplinary working group at the local level will be established to consolidate ecological 

site description needs into interagency local work plans. The interagency local work plan will be 

developed by Major Land Resource Area (MLRA) and will more specifically define 

interdisciplinary team membership, methods for the identification, inventory, analysis, 

documentation, and delineation of ecological sites, and should provide a crosswalk to other 

classification and mapping system hierarchies used by the agencies. The interagency local work 

plan will include review of ecological site descriptions to ensure they meet land and resource 

interpretation needs for each agency.
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SECTION 1.1 Ecological Site Relationships With Other Classification and Mapping 

Hierarchies

Ecological site classification and descriptions are one of many land potential and existing 

vegetation classification and mapping systems used in the United States (app. A). A number of 

the classification systems are organized within a nested hierarchy that describes ecosystem 

relationships at spatial scales ranging from continental to individual sites. Understanding the 

relationship between the NRCS Soil Geography hierarchy, the National Hierarchical Framework 

of Ecological Units (NHFEU), the National Vegetation Classification (NVC), and other 

classification systems will facilitate the comparison and use of existing classification 

descriptions and datasets for use in development and documentation of new ecological site 

descriptions.

Table 1.1 arrays spatial hierarchies currently used by the FS, NRCS, and BLM. Future 

development of a unified spatial hierarchy for interagency application will provide a consistent 

basis for classifying and mapping ecological sites across all lands. Ecological sites are 

appropriately used at the land unit level, (see Table 1.2) where fine scale abiotic and biotic 

factors are used to characterize ecosystems. Ecological sites are roughly equivalent in scale and 

landscape context to ecological units at the land type phase, and correspond with plant 

associations, and habitat type phases (Table 1.2), which are commensurate with soil series and 

soil series phase taxonomic units (Table 1.1). Land types are broader concepts delineated 

according to the origin and genesis of landforms, and the relationship of soil properties and 

floristic patterns and processes. An ecological site may be nested within a land type or land type 

association at the landscape and land unit planning and analysis levels. Appendix A contains a 

more detailed discussion of these classification systems.
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Table 1.1. Relationships of NRCS and Forest Service hierarchical mapping systems.

Ecological Mapping Systems

National Hierarchical Framework of Ecological 

Units1 NRCS Soil Geography Hierarchy2

Domain, Division, and Province 

(1:5,000,000-1:30,000,000)

Land Resource Region (LRR)/Common Ecological Region

(1:7,500,000)

Section (1:3,500,000) 

and

Subsection

(1:250,000)

Major Land Resource Area (MLRA)

(1:3,500,000)

Land Resource Unit (LRU)/Common Resource Area (CRA)

(1:1,000,000)

General Soil Map

(1:250,000)

Land type Association

(1:60,000)

NA

Land type

(1:24,000) 

Detailed Soil Map

(1:24,000)

Land type Phase3

(< 1:12,000)

Soil Series or SoilSeries Phase

(1:12,000)

Integrated Plot Soil Pedon

1 Map scale from: NHFEU (Cleland et al. 1997)

2

 USDA Natural Resources Conservation Service (2006). MLRA definitions 12/15/2005, Soil 

Geography Hierarchy, http://soils.usda.gov/survey/geography/hierarchy/index.html

3

 Terrestrial ecological unit inventory technical guide (Table 3.1) indicates soil series and phases 

of series can be incorporated into land type phase (Winthers et al. 2005).

Table 1.2. Relationships of existing ecological classification systems and planning levels.

Ecological Classification Systems

Hierarchical 

Planning and 

Analysis Levels

Ecosystem 

Classification

NRCS and 

BLM

Ecosystem 

Classification

FS 1

Potential Natural 

Vegetation 

Hierarchy4

National 

Vegetation 

Classification 

(NVC)3

Landscape Biophysical 

Settings 

(BLM)

Geomorphology

Geology, Relief, 

Biophysical Settings,

Potential Natural 

Community (PNC) Series;

Ecological type1

Plant Series;

Habitat Type Group

Group/Alliance;

(Dominance Type2)

Land Unit 

Ecological type1 Potential Plant 

Association;

Habitat type

Association/

Alliance

Ecological 

Site Ecological type1 Potential Plant Association Phase;

Habitat type phase

Association 

Individual 

Sample Sites

Vegetation 

plot and soil 

pedon

Sample site

(soil pedon/

vegetation plot)1 Vegetation plot Vegetation plot

1

 Terrestrial ecological unit inventory technical guide (Winthers et al. 2005).
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2

 Existing vegetation classification and mapping technical guide (Brohman and Bryant 2005)

3

 National Vegetation Classification Standard, version 2 (Federal Geographic Data Committee 

2008)

4

 An ecological land classification framework (Driscoll et al. 1984)

SECTION 2.0 Ecological Site Classification Concepts 

A. Background

An Ecological Site (ES) is a conceptual division of the landscape that is defined as a distinctive 

kind of land based on recurring soil, landform, geological, and climate characteristics that differs 

from other kinds of land in its ability to produce distinctive kinds and amounts of vegetation and 

in its ability to respond similarly to management actions and natural disturbances.

Climate, geomorphology, and soils interact to govern how plant species are distributed along 

environmental gradients and how the resulting associations of plant species (plant communities) 

respond to disturbances and management. More than a century of observation and experimental 

research have established the importance of climate, landscape position, soil characteristics, and 

disturbance regimes in determining how changes in disturbances and management actions can be 

expected to affect plant community composition and structure. A systematic understanding of 

how management and disturbance processes interact with abiotic and biotic factors is a critical

element to understanding ecological processes and function. This understanding is also 

necessary to assess degradation risk, implement appropriate management practices, and assess 

land capability.

An ES incorporates abiotic and biotic environmental factors such as climate, soils/landform, 

hydrology, vegetation, and natural disturbance regimes that together define the site. Each 

ecological site is identified, differentiated, and described based on the relationships between 

these environmental factors and how they influence plant community composition. The

characteristics differentiating ecological sites and their abiotic and biotic features are 

documented in ecological site descriptions (ESD). The ESD documentation includes:

• data used to define the distinctive properties and characteristics of the sites

• biotic and abiotic characteristics that differentiate the site (i.e., climate, physiographic, 

soil characteristics, plant communities)

• ecological dynamics of the site that describes how changes in climate, disturbance 

processes and management can affect the site. 

An ESD also provides interpretations about the land uses and ecosystem services that a particular 

ES can support and management alternatives for achieving land management objectives.

B. Defining the Site Concept

The identification and classification of ES’s are based on a fundamental premise that the 

composition, structure, and function of plant communities are governed by energy, moisture, and 

nutrient gradients, as well as disturbance regimes. In decreasing order of scale, these gradients 

vary due to differences in macroclimate, geology, geomorphology, topography (elevation, slope, 
January 2013 Page 13

aspect, and landform position), and soil physical and chemical characteristics. Collectively, 

these factors determine soil temperature, moisture, and nutrient regimes that affect patterns and 

processes associated with particular ES’s.

At the local scale, soil temperature, moisture, and nutrient regimes are characterized based on 

key soil physical and chemical properties that are used as differentiating criteria in defining an 

ES. Key soil properties are identified using direct measures of edaphic conditions including soil 

morphology, depth, texture, water holding capacity, pH, and so forth. Key soil properties are 

also determined based on our knowledge of plant-soil relationships, and include the use of 

vegetation as an indirect indicator of environmental gradients. 

The floristic criteria used in combination with environmental factors to define an ES are 

ecologically significant associations of plant species, or indicator plant communities, which 

serve as indicators of important environmental conditions. Indicator plant communities are 

composed of species that are strongly associated with narrow ranges of environmental 

conditions. When used in combination with direct measurements of environment, indicator 

species provide features that can be readily observed in field applications such as on-site 

investigations or ecological site mapping. Knowledge of these associations of indicator species 

and their relationship to environmental conditions may come from expert opinion following field 

investigations, through the incorporation of existing vegetative classifications, or it may be more 

objectively developed through analyses of floristic and soils data collected from sites 

representing the site concept. These relationships define soil moisture and nutrient gradients 

associated with differences in inherent land capability to support specific kinds of vegetation,

and provide detectible environmental thresholds that allow for separation of one ES from 

another.

The inherent complexities of vegetation dynamics (e.g., how vegetation originated in an area and 

how it might change in the future) require an understanding of historical vegetation, disturbance 

regimes, climatic variability, and existing (current) vegetation. Long-term trends in historic 

vegetation can be examined over long time periods using pollen analysis and other 

dendroecological techniques. The relevance of such data diminishes the further back in time one 

goes due to increasing differences in climate, disturbance regimes, and species distributions. A 

500-year or shorter period immediately preceding European settlement is a reasonable time 

period for establishing reference conditions within the United States (Winthers et al. 2005).

The ES concept is defined based on reference conditions representing natural states. The state 

changes and transitions are subsequently estimated based on our understanding of succession and 

ecological thresholds. Reference states and their component community phases represent the 

historical range of variability due to successional dynamics following disturbances. Within this 

natural, historical, or reference state, the community phase used to define an ecological site is 

termed the reference community phase.

The reference community phase is identified as that community phase which exhibits the 

characteristics of the reference state, and contains the full complement of plant species that 

historically occupied the site (Bestelmeyer et al. 2010, Briske et al. 2008). The reference 

community phase formed as a result of interacting environmental gradients, natural disturbance 

regimes, and physiological characteristics of species comprising the community. Within 

landscapes that historically experienced relatively infrequent disturbances, late successional 
January 2013 Page 14

communities that required long-time periods to develop are typically selected as the reference 

community phase. However, in landscapes where frequent natural disturbances occurred, the 

geographically dominant community in the reference state may be more relevant and therefore 

selected as the reference community phase, since the latter stages of succession seldom occurred. 

For example, the former tall grass prairie occurs within a relatively moist macroclimatic zone 

that would have succeeded to woodlands or forests in the absence of disturbance, but frequent 

fires maintained the prairie over the majority of its natural geographic extent for thousands of 

years. 

C. Interpreting Ecological Dynamics of the Site 

Ecological dynamics describe the changes to vegetation and soils, and the causes of those 

changes that can occur on an ecological site. Details on the alternative states, ranges of 

variability within states, and the processes that cause plant community shifts within states as well 

as transitions among states are described in the text and diagram of a state-and-transition model

(STM).

STMs can include single or multiple states, depending upon the nature of the system, and 

incorporates the concepts of ecological resilience and resistance. Ecological resilience is a 

measure of the amount of change or disruption that is required to transform a system from being 

maintained by one set of mutually reinforcing processes and structures to a different set of 

processes and structures (Peterson et al. 1998). This definition is distinct from that of 

engineering resilience, which describes the rate at which ecosystems return to their original 

stable state following disturbance (Holling 1996). The conditions sufficient to modify the 

structure and function of a state beyond the limits of ecological resilience result in the formation 

of an alternative state. 

STMs are organized as a collection of community phases and states that communicate 

information about the ecological dynamics of an ES and can provide management alternatives 

and information about restoration (Fig. 2.1). Alternative states are separated by thresholds that 

can be induced by natural or human-caused events. Crossing a threshold from one state to 

another (the transition) indicates persistent changes in vegetation and, often, dynamic soil 

properties. The persistence or resilience (Peterson et al. 1998) of alternative states is caused by 

feedbacks between environmental conditions and vegetation or long-time lags in vegetation

responses to natural or management drivers(e.g. grazing pressure). In such cases, even if the 

management or environmental drivers (such as grazing pressure or high rainfall) returns to 

earlier values, the vegetation may not return to its earlier state, or does so only slowly or in 

response to unusual events. When transitions are undesirable, costly restoration approaches are 

typically required to return to the earlier state within management timeframes, or restoration may 

not be possible given current technology. 

Each state may contain one or more community phases representing system dynamics within the 

limits of the state. The dynamics among community phases may be driven independently or in 

combination by natural events (e.g., succession or disturbances) or human activities (e.g., land 

management (Walker et al. 2004)).

STMs are a means of communicating about plant succession, ecological thresholds, nonequilibrium dynamics, and functional and structural change in response to disturbances and 
January 2013 Page 15

management actions. STMs describe relationships between vegetation, soil, animals, hydrology, 

disturbance (e.g., fire, lack of fire, grazing and browsing, drought, unusually wet periods, insects 

and disease), and management actions. This information is used to describe existing soilvegetation relationships, document historical vegetation and dynamics as well as restoration 

outcomes, and measurements of ecosystem properties and processes occurring within states (e.g.,

cover, soil aggregate stability, erosion rates, net primary production).

STMs are developed using published literature, expert knowledge, existing agency datasets (e.g.,

National Resources Inventory, Forest Inventory and Analysis data, agency legacy datasets), 

newly collected inventory data, and research data. STMs begin as a working hypothesis based 

largely on expert knowledge and available inventory data. STMs should be refined with 

empirical information obtained through research, monitoring, and data collection. STMs are 

ideally developed using four kinds of information: 1) inventory data of soil properties and 

vegetation, 2) historical reconstructions using long-term monitoring data, historical records, or 

photography, 3) recent monitoring data, including responses to climate variability and 

management interventions, and 4) process-based research and studies that test for the 

mechanisms causing or constraining ecosystem responses. The goal in producing STMs is to 

provide a conceptual understanding of:

• the ecological dynamics that can occur on an ES, 

• the drivers and mechanisms of ecosystem change, and 

• the management actions that can be used to influence change.

1. Components of a State-and-Transition Model

An STM for an ecological site has five fundamental components (fig. 2.1). Characteristics of 

the components follow Stringham et al. (2003), Briske et al. (2008), and Bestelmeyer et al. 

(2010).

a. The state (large boxes in fig. 2.1) is a suite of community phases that interact with the 

environment to produce a characteristic composition of plant species, functional and 

structural groups, soil functions, and a characteristic range of variability. The state is defined 

with reference to community phases, dynamic soil properties, and animal populations that 

are linked to one another via feedback mechanisms. Inherent natural ranges of variability of 

plant species composition (production, canopy or foliar cover), soil properties (inherent and 

dynamic), ground cover, and disturbance processes should be described. Alternative states 

differ in the operation of one or more primary ecological processes including the hydrologic 

(water) cycle, nutrient cycle, the process of energy capture and transformation (energy flow). 

Because the designation of alternative states in STMs denotes changes in ecosystem 

properties that require intensive efforts—or are practically impossible—to reverse within 

management timeframes, the presence of alternative states can be used to support changes in 

management approaches. Given such a potentially important role, evidence for the existence 

of alternative states should be carefully identified (Bestelmeyer 2006). The assumptions, 

methods, and supporting data or literature used for the definition of alternative states and 

thresholds in STMs should be documented, peer reviewed, and further developed if needed. 

These include:

• careful description of the properties of reference and alternative states, 
January 2013 Page 16

• description of the ecological mechanisms causing transitions and precluding recovery 

of reference or other states, 

• identification of evidence sources and assumptions, and 

• level of confidence in portions of the STM given the evidence. 

Care should be taken not to confuse dynamics between community phases, with transitions 

between states.

Persistent changes in vegetation and related processes recognized via states and transitions 

can involve several interacting causes (Allen 2007). The causes of state changes can be 

associated with processes at different spatial scales (e.g., land use changing at site scales that 

is interacting with directional changes in climate occurring at broader scales.), involve 

episodic events (e.g., extreme rainfall events), and time lags (e.g., gradual plant recruitment 

following episodic events). Consequently, the assertion of an alternative state is often 

inherently uncertain and should be treated as an hypothesis that can be tested via long-term 

observations of ecosystem behavior (e.g., evidence of slow or episodic recovery of formerly 

dominant species) and repeated application of conservation and restoration practices (e.g., the 

successful recovery of ecosystem structure with a change in fire management). The 

designation of alternative states should be subjected to constant reevaluation and refinement. 

Evidence for existence of alternative states, and the varying constraints to recovery of desired 

conditions, should be pursued and evaluated over long time periods.

A reference state (fig. 2.1) is recognized in each STM that describes the ecological 

potential and natural or historical range of variability of the ecological site. The reference 

state should also incorporate information on dynamic soil properties as well as native 

plant and animal populations. 

Due to natural disturbance and climatic processes, reference conditions can be 

represented by more than one community phase depending on the time period in which 

an ecological site is observed. In some ecological sites (e.g., some grass-dominated sites) 

only one community phase may be recognized in the reference state. Ecological sites 

featuring natural fire regimes will most likely have more than one community phase in 

the reference state. In such cases, a cessation of natural disturbance may lead to 

transitions. 

b. Transitions (arrows starting with T) describe the biotic or abiotic variables or events, 

acting independently or in combination, that contribute directly to loss of state resilience and 

result in shifts between states. A transition can be triggered by natural events (e.g., climatic 

events or fire), management actions (e.g., grazing, burning, fire suppression, recreational use) 

or both. Whereas transitions describe the drivers and mechanisms of shifts between states, 

the term “threshold” indicates set of conditions separating two states where conditions 

sufficient to modify ecosystem structure and function beyond the limits of ecological 

resistance or resilience results in the formation of alternative states (Briske et al. 2008). 

Because alternative states are persistent and exhibit characteristic differences in feedbacks 

and primary ecological processes, transitions may be irreversible, or at least do not reverse 

themselves within management timeframes (e.g., several decades). Transitions can occur 

quickly as in the case of catastrophic events like fire, flood, or a hurricane event whereas 

others may unfold over a long period of time in response to long-term management 
January 2013 Page 17

conditions and gradual changes in the environment. In practical terms, changes that warrant 

the use of intensive management practices and restoration technologies to return to the 

previous state are considered to be transitions.

Changes in dynamic soil properties (e.g., soil organic carbon, bulk density, pH, salinity, and 

aggregate stability) can parallel changes in community phases or transitions between states. 

These coupled changes may be due to feedbacks between plant cover and composition and 

dynamic soil properties. Thus, dynamic soil properties can be used to help understand the 

risk of transition, especially when it is not easily understood via observations of vegetation.

Description of transitions should emphasize soil and vegetation indicators that are related to 

feedbacks and the processes that reduce the resilience of states. The approximate time period 

required for triggers and feedbacks to reduce resilience and for alternative states to develop 

should be estimated.

c. Restoration pathways (arrows starting with R) describe the environmental conditions and 

practices that are required to recover a state that has undergone a transition. Ecosystem 

properties that promote restoration should be identified. Such ecosystem properties (e.g., 

seed sources, species composition, nutrient distribution, and hydrologic function) greatly 

influence the rate, probability of success, and prescriptions required for restoration, including 

remediation. Environmental conditions, for example, may include relatively high rainfall 

years. Practices include significant management inputs (e.g., chemical/mechanical treatments 

or planting) coupled to facilitating and management practices (e.g., prescribed fire, wildland 

fire managed for resource benefit, fencing and grazing management prescriptions).

d. Community phases (small boxes within states) are unique assemblages of plants and 

associated dynamic soil property levels that can occur over time within a state. In states that 

attain equilibrium, community phases are equivalent to seral or successional stages that may 

undergo orderly changes in response to natural disturbance, management, and succession. In 

states that do not attain equilibrium, community phases may shift from one to the other in 

complex ways depending on the interactions of climate, natural disturbance, and 

management. Community phases included in a single state may have similar floristic or 

functional groups, but may differ in dominant or subordinate species. However, the 

community phases may be quite different in floristic or functional groups when disturbance 

drivers cause changes in plant composition and structure (e.g., fire). Collectively, the 

community phases represent the range of variation within a state, including conditions that 

place the state at risk of a transition.

An at-risk community phase is a community phase that can be designated within the 

reference state and also in alternative states. This community phase is the most vulnerable 

to transition to an alternative state. The at-risk community phase can be considered as 

part of a transition process that is reversible with changes in management. Indicators 

should be identified and described for this phase in order to help managers recognize 

increasing likelihood of a transition. For example, the presence of large bare gaps or 

small shrubs may be used to indicate that a grassland state is at risk of transition to a 

shrub-dominated state in semi-arid and arid ecosystems. It is also important to identify 

management changes that can cause or are needed to avert a transition. Management 

changes prior to a transition may be more effective and more economical than 
January 2013 Page 18

implementing restoration practices after a transition has taken place. In some states, 

designation of an at-risk community phase is not needed when transitions are equally 

likely in multiple community phases or when a state has only one community phase or 

state. Indicators of imminent transition and management needs to avert a transition 

should be explicitly described for the state. 

e. Community pathways (arrows between community phases within a state) describe the 

causes of shifts between community phases. Community pathways can include the concepts 

of episodic plant community changes as well as succession and seral stages. Community 

pathways in state-and-transition models can be used to represent both linear and non-linear

plant community changes. In contrast to transitions between alternative states, shifts in 

community phases are easily reversed due to succession, natural disturbances, short-term 

climatic variation, and facilitating practices such as grazing management. 
January 2013 Page 19

Figure 2.1 Example of a state-and-transition diagram for an ecological site.

2. General Considerations in Producing State-and-Transition Models

The following issues, as applicable, should be considered when developing STMs.

• All states and community phases that are known to occur on an ecological site should be 

described in STMs. In cases where empirical data are lacking, states and community 

phases can be described based on expert knowledge and should be identified as 

provisional. The long term goal is to support each state and community phase description 

with empirical data.

• Abandoned cropland that has been allowed to naturally revegetate, and seeded rangeland 

can be considered as alternative states when important native species or soil functions do 
January 2013 Page 20

not recover to the former state without restoration actions. Such intensively modified 

systems may change to another state.

• Naturalized communities, plant communities that have become established naturally and 

dominated by non-native or exotic species, will always be considered as belonging to an 

alternative state, except when used to define a site (see Section 2.0 D). Examples include 

timothy, smooth brome, or annual bromes.

• Describe “at-risk community” phases where possible and useful.

• STMs should make explicit reference to dynamic soil properties and rangeland health 

indicators in narratives for states and transitions.

• In cases where the time scales of community pathways or transitions are known, they 

should be described in the narratives. 

• Consider all relevant drivers and disturbance agents in models, including the impacts of 

native and domesticated animals, wildland fire and lack of fire, recreation activities, and 

other management actions.

D. State Change versus Change in Ecological Site 

Alternative states often persist for many decades without evidence of recovery to the reference 

state. This persistence certainly extends beyond practical timeframes for land use and 

management planning. As long as the soil and physiographic characteristics that defined the 

ecological site remain unchanged, a change to another ecological site need not be considered. 

The ecological potential for the site is not considered to have been altered permanently merely 

because the alternative state is persistent. The inability of current knowledge and technology or 

economics to restore alternative states does not warrant a new ecological site designation or 

description. Alternative states are recognized and described that deal with severely altered 

locations within ecological sites. 

Some ecological sites have been invaded or planted with non-native species. These non-native 

species may become well-established, or naturalized, on the site. They may dominate the site, or 

may persist within community phases in states that have recovered much of its historic structure 

and composition. In these cases of invasion or introduction of non-native species, a change in 

ecological site is not recognized. 

In some parts of the United States naturalized plant communities have become established on 

some ecological sites and it is impossible to reconstruct the reference state with any degree of 

reliability. A naturalized plant community is a plant community that is dominated by naturalized 

exotic plant species and is a relatively stable community resulting from secondary succession 

after disturbance. In these regions, ecological site descriptions will be developed using the 

naturalized plant communities for the site. Examples of areas in the United States where this 

may be used are the State of Hawaii, the Caribbean Area, and the annual grasslands of 

California. 
January 2013 Page 21

Approval to utilize naturalized plant communities to define the site concept must be obtained 

jointly by the Chief, Forest, Rangeland, Riparian, and Plant Conservation Division, BLM; 

Director of Rangelands Management, FS; and Director, Ecological Sciences Division, and 

Director, Soil Survey Division, NRCS; or their official designee(s).

SECTION 3.0 Classification, Differentiation, And Description of Ecological Sites 

A. Purpose

Ecological sites are classified and their concepts are assembled into a written document called an 

ecological site description (ESD) (see app. E). ESD development includes two complementary 

efforts or processes. The first process is to identify the abiotic and biotic relationships that help 

define the unique soil, geomorphic, vegetation, and climate characteristics of the ecological 

site. The classification and differentiation of the ecological site centers on the identification of

the abiotic and biotic factors associated with the reference community phase within the reference 

state. The second part of ESD development is the process of classifying or describing other

community phases and states of the ecological site. After the site has been classified, community 

phase and state information is incorporated into the ecological site descriptions. The natural 

disturbances and management actions that cause shifts between community phases and/or states 

are described using the STM diagram and the associated narratives of transitions and community 

pathways.

B. Classification and Differentiation of an Ecological Site

Ecological sites integrate a variety of information sources, including expert knowledge, historical 

reconstructions, and inventory and monitoring data to help establish or understand 

soil/plant/landform relationships and management considerations for different ecological sites. 

A well-organized plan is essential to characterizing the ecological site concept and in developing 

an ESD. 

Site classification and differentiation are based on the reference community phase and associated 

soil, climate, geologic, topographic, and landform properties. Replicated observation of the 

reference community phase within the reference state and associated soils are needed to classify 

an ecological site. Replicated observations should be geographically distributed in order to 

capture the range of environmental variability associated with the ecological site. 

The use of integrated plot data is preferred for classifying and differentiating ecological sites. 

Integrated plots are plots in which vegetation, soil, and other physical data are collected 

concurrently. When integrated plot data are not available, initial differentiation may be 

estimated through use of expert knowledge, analysis of soil survey pedon, transect or traverse 

data and vegetation data that may have been collected at different times and for different 

purposes. It is critical that the supporting data be adequately described so that the strength of 

evidence can be evaluated.

Plots used to characterize the reference community phase should be sampled from multiple

locations representing the reference community phase. Plot locations should not have 

experienced recent disturbance, nor should have been protected from natural disturbance for long 

periods of time. These data sets are used to identify relationships between vegetation, soils, and 
January 2013 Page 22

other environmental factors. Data on plant species composition, soil properties, and other

environmental factors are analyzed to document the distinctive characteristics of, and variability 

within, each ecological site, and serve as documentation for the site. Data or expert knowledge 

on disturbance and management responses should also be considered. The initial outcome of 

data analysis is the identification of attributes that differentiate, classify, and characterize the 

ecological site concept. Data analysis for ecological site classification is a systematic process to 

detect patterns of similar vegetation composition and relationships between vegetation, soil 

properties, and other environmental elements within a dataset. 

Where changes in soils, aspect, topography, or climate are abrupt, ecological site boundaries are 

usually well-defined. Boundaries are broader and more subtle where plant communities and 

environmental gradients change more gradually. Making distinctions between ecological sites 

that vary along a gradual continuum is difficult, and site differentiation may not be readily 

apparent until the cumulative effects of soil, topography, and climate on vegetation are examined 

over a broad area. 

No single factor or criterion is used to differentiate an ecological site. Criteria should be 

considered in combination rather than individually. The following criteria should be considered 

in differentiating one ecological site from another when developing an ecological site 

description:

• Abiotic factors that influence plant production, composition, ecological processes of the 

water cycle, nutrient cycles, and energy flow,

• Significant differences in the presence of species or ecologically significant species groups,

• Significant differences in the relative proportion of species or species groups,

• Significant differences in the total annual production, and.

• Significant differences in an ecological site’s response to management actions or disturbance 

processes.

Examples of guidelines (adapted from Miles and Leonard 1984, Winthers et al. 2005) that have 

been used for determining significant differences are:

• Differences in abiotic factors (soil factors and/or climate, geomorphology, surficial geology, 

and hydrology),

• Differences in biotic factors including indicator plant communities that have been correlated 

with abiotic factors,

• Presence (or absence) of one or more species that make up 10 percent or more of the

reference community phase, by air dry weight,

• A 20-percent change in composition, by air dry weight, between any two species in the 

reference community phase, and

• A percent difference in average annual herbaceous production potential in the reference 

community phase of:

o plus or minus 50 percent, when the potential is 200 to 500 pounds (lbs)/acre (ac),

o plus or minus 30 percent, when the potential ranges between 500 to 1,000 lbs/ac,

o plus or minus 20 percent, when the potential is greater than 1,000 lbs/ac, and

o a difference in average annual production of 100 lbs/ac is of minor importance on 

ecological sites capable of producing 2,000 lbs/ac. This difference, however, is highly 

significant on sites capable of producing only 200 to 300 lbs/acre.
January 2013 Page 23

Ecological sites may be differentiated using finer or broader differences than those described 

above. Overall, the attributes used to distinguish ecological sites should indicate significant 

differences of site capability for management. 

SECTION 3.1 Steps For Classification, Differentiation, And Description of Ecological Sites 

The process and methods for classification, differentiation, and description of ecological sites 

involve several steps. The steps are grouped into preliminary stages, iterative stages, and final 

stages (fig. 3.1). The process is adapted from the Existing Vegetation Classification and 

Mapping Technical Guide (Brohman and Bryant 2005), Terrestrial Ecological Unit Inventory 

Technical Guide (Winthers et al. 2005), the National Range and Pasture Handbook, Chapter 3 

(USDA Natural Resources Conservation Service 1997, amended 2003). 

The preliminary and iterative stages focus on classification and differentiation of ecological sites. 

Ecological site concepts are formulated and differentiating abiotic and biotic factors are 

identified and tested. The final stage focuses on completing an ecological site description. It 

includes the classification and characterization of community phases, description of ecosystem 

dynamics associated with the site, and documentation of reference and alternative states. 

Strong interdisciplinary participation is critical to the ESD development process. This process is 

best performed concurrently with soil survey projects. In areas where soil survey activities have 

been completed or where published soil surveys exist, validation of existing ecological site 

classification will be conducted concurrently by soil scientists and vegetation specialists. 

Establish Local Work Groups

To bring expert knowledge together, an interdisciplinary working group should be formed at the 

local level. Persons who interact with the land on a regular basis may have gained practical 

knowledge about how ecosystems function by living and managing them and thus can be 

included in this group. Where ecological sites cover both private and public lands the local work 

group will include public land agency personnel. Every effort should be made to invite and 

involve local experts from sources, such as, scientists, academia, agency professionals, 

conservation partners, land owners, and land managers.

SECTION 3.1.1 Preliminary Stages

A. Define Geographic/Ecological Extent

For immediate development needs, the geographic/ecological extent covered by a single 

ecological site classification effort will be a Major Land Resource Area (MLRA)/Land Resource 

Unit (LRU) or ecological sections/subsections. Future development of a unified spatial 

hierarchy that resolves differences between NRCS’s and FS’s spatial hierarchies will provide an 

interagency application for establishing the geographic extent of ESDs. Once developed, the 

unified spatial hierarchy will enable a one-to-one crosswalk of respective agency systems and 

will be utilized to describe the appropriate geographic extent for sets of related ecological sites. 

Needed adjustments to the boundaries and descriptions of MLRAs or FS ecoregions will be 
January 2013 Page 24

coordinated through the interagency teams under the direction of the national interagency 

workgroup. 

B. Gather Background Information

Review ecological literature, data, and local expert knowledge relevant to the area covered by the 

classification, including information on local climate, geology, soils, and current and historical

vegetation. Published literature as well as mapping for the region should be reviewed. Existing 

ecological and vegetation classifications provide knowledge and information useful for 

developing site concepts. These classifications, such as potential natural vegetation (PNV) or 

habitat type classifications, often describe ecologically significant plant species (indicator 

species) or potential plant communities associated with soil moisture-nutrient-temperature 

gradients and differences in ecological potential within landscapes.

Types of background information include, but are not limited to:

• current ecological (synecological) information

• past vegetation history

• past vegetation data

• vegetation and ecological classifications and descriptions

• plant species (autecological) information 

• natural disturbance regimes

• botanical references 

• physical environment 

• soil surveys and other land system inventories

• hydrologic information

• zoological information

• farm, ranch and research station data or records

• interviews with long-time residents and land managers

C. Evaluate Existing Data

Existing data sources previously collected from an area can be used for various aspects of the 

ecological site classification and description. Depending on the source of the data and its 

quality, some data may be suitable for:

• the classification itself, 

• stratifying the landscape for reconnaissance or further sampling, and

• providing interpretations for the descriptions such as wildlife habitat, fuels, etc. 

Existing data may include integrated plots (vegetation, soil data, and other physical data 

collected concurrently), or vegetation data only. Plot data may differ in how plant species 

attributes were collected (e.g., species production, species canopy cover, species foliar cover, 

basal cover, vegetation structure). Sources of existing data include maps, remote sensing, 

ecological classification publications, and inventory and monitoring plots from government 

agencies and nongovernment organizations within the area.

A resulting product of information and literature research should be a rudimentary grouping of 

climate zones/elevation zones, parent materials, soil properties, and vegetation communities. 
January 2013 Page 25

Literature-based research should be combined with field reconnaissance and resulting data 

collection strategies covering the extent over which an ecological site concept applies.

D. Conduct Reconnaissance—Low Intensity Traverses 

Reconnaissance is used to develop ecological site concepts. It helps determine the sampling 

strategy and design for ecological site classification. Reconnaissance is a low intensity inventory 

(traverse) technique to become familiar with the general features of the landscape, such as

landforms, surficial geology, soils, vegetation patterns, and plant species. Reconnaissance 

employs a rapid characterization of plant communities and associated environmental settings 

(e.g., slope, aspect, landform, slope shape) to formulate the initial ecological site concepts.

Reconnaissance observations should be gathered across the extent of an ecological site 

development effort.

In reconnaissance, a large number of sampling points are observed. At these points, soil augers 

or shallow pits are dug to examine the soils and classify them to soil taxonomic family or series.

Soil characteristics, landform, slope, aspect, and plant community characteristics are 

documented. Often these points are selected by driving along roadways that cover the extent of 

the study area and to traverse major landforms, landform components, and distinct plant 

assemblages. Review of previous soil surveys, digital elevation models, or coarse-scale 

vegetation maps provide insight into patterns associated with environmental gradients and 

disturbance processes; and help identify traverse routes. Several representatives of specific soil 

map units or ecological map units established in previous soil surveys or ecological unit 

inventories may be targeted for observation. 

It is important to recognize that the primary objective of this phase is to cover the range of 

environmental gradients within the geographic extent of the project area, to gain understanding 

about vegetation, soil, and landscape patterns. Notations about possible sample site locations to 

be visited for medium intensity sampling (see sec. 3.1.2A) should be documented. 

E. Develop State-and-Transition Model Concepts

STMs are developed utilizing historical information, local and professional knowledge, and 

inventory, monitoring, and experimental data (see Bestelmeyer et al. 2010). Background 

information and existing data previously gathered can be linked with local and professional 

knowledge from local workgroups to develop initial diagrams and narratives for each component 

of a STM for an ecological site. 

STM development typically begins with the grouping of community phases associated with the 

ecological site concept that were identified during the review of existing data and field 

reconnaissance. Community phases are sorted based on structures (e.g., dominant species and 

functional groups) that control feedback mechanisms and ecological processes to develop the 

state concepts. Then, narratives describing the states, community phases, community pathways, 

transitions, and restoration pathways, are developed. (see sec. 3.3).

As the ecological site development process continues and new information or data is collected, 

STMs should be revised as necessary.

 
January 2013 Page 26

F. Develop Sampling Strategy

Initial ecological site concepts identified during the reconnaissance phase are used to develop the 

sampling strategy and design the medium intensity (see sec. 3.1.2.A) field inventory to test and 

refine the site concept. Sample locations across the project area are selected using maps, aerial 

photography, or applicable Web services, and locations documented during the reconnaissance 

phase. It is important to determine and document the data collection strategy that will best 

capture the spatial and temporal variations of ecological sites across the landscape. Sample sites 

should be relatively uniform in landform, topographic position, and vegetation (Federal 

Geographic Data Committee 2008, Winthers et al. 2005). The specific protocol or combination 

of protocols used should be sufficient to characterize the soil diagnostic horizons and their 

properties (e.g., soil texture, soil texture modifiers, soil depth to a restrictive horizon), landform,

topographic features (slope and aspect), complete species lists, variations in plant species cover

and structure, and soil surface properties.

The sampling strategy selected depends on whether soil surveys have been completed or not. 

Where soil surveys have been completed and ESDs are being developed or revised, sampling can 

be stratified by soil map unit component. On National Forest System lands where terrestrial 

ecological unit inventories are used in place of soil map units sample sites would be stratified by 

ecological map unit. Where soil surveys and ESDs have not been completed, samples are 

stratified by elevation, landform, slope, aspect, geologic parent material, and vegetation patterns

via information gathered during reconnaissance and using aerial photography and other spatial 

data. Aerial photography and remote sensing can be useful tools for stratifying the landscape 

prior to or during field reconnaissance This approach is applicable for areas without an active 

soil survey and where soil survey or terrestrial ecological unit inventory is being completed 

concurrently with ESD development. 

G. Select Sampling Methods

Select sampling methods best suited for meeting the classification criteria, descriptive attributes,

and interpretations chosen for the ecological site classification and description. Vegetation plots 

and soil pedon descriptions comprise an integrated plot. Detailed descriptions of appropriate plot 

size, plot shape, and vegetation sampling methods are found in existing agency and interagency 

handbooks and technical guides/references, including:

• Sampling Vegetation Attributes (USDI Bureau of Land Management, Cooperative 

Extension Service, USDA Forest Service, and USDA Natural Resources Conservation 

Service 1996, revised 1997,1999)

• Monitoring Manual for Grassland, Shrubland, and Savanna Ecosystems (Herrick et al. 

2009)

• BLM Ecological Site Inventory (Habich 2001)

• National Vegetation Classification Standard (NVCS) Version 2 (Federal Geographic 

Data Committee 2008)

• Terrestrial Ecological Unit Inventory Technical Guide (Winthers et al. 2005)

• Existing Vegetation Classification and Mapping Technical Guide (Brohman and Bryant

2005)

• National Range and Pasture Handbook, Chapter 4 (USDA Natural Resources 

Conservation Service 1997, amended 2003)
January 2013 Page 27

Methods for soils data collection are found in:

• Field Book for Describing and Sampling Soils Version 2.0 (Schoeneberger et al. 2002)

• Soil Survey Manual (USDA Soil Survey Division Staff 1993)

• National Soil Survey Handbook (USDA Natural Resources Conservation Service 1996)

• Soil Taxonomy, A Basic System of Soil Classification for Making and Interpreting Soil 

Surveys Second Edition (USDA Soil Survey Staff 1999). 

SECTION 3.1.2 Iterative Stages

The iterative stages implement the sampling strategy and methods identified in the preliminary 

stages. It involves initial field sampling, analysis, defining ecological site characteristics, field 

testing of the classification, and modification as needed. Classification of ecological sites, as 

well as associated community phases in reference or alternative states, can be best thought of as 

testing a working hypothesis. The classification of ecological sites and their associated 

community phases can be refined or augmented as new information or knowledge becomes 

available. Medium intensity sampling is required in order to formalize the site concept. 

 

A. Data Collection—Medium Intensity Sampling

Medium intensity sampling is intended to be rapid and focused on sampling the environmental 

range associated with initial ecological site concepts. Data are collected to test for relationships 

between climate, vegetation, soil properties, landforms, and relief. Relationships between 

disturbance processes and vegetation composition, structure, and soil dynamic properties can 

also be considered.

Collect field data according to the sampling strategy using the appropriate sampling methods

identified in section 3.1.1(F) and (G) of this publication. Ideally, soil scientists, range 

management specialists, vegetation ecologists, biologists, and other specialists (as needed) work 

together as interdisciplinary teams. 

The following data are typically utilized to validate the ecological site concept:

• full species list for each described community phase

• canopy cover, by species, growth form (see example definitions, app. B), and vertical 

strata (see example definitions, app. C)

• production by species (e.g., dry-weight rank/comparative yield)

• vegetation vertical structure (see sec. 5.0 F.10)

• inherent soil properties 

• topography (i.e., landform, slope, aspect, elevation, slope shape)

• ground cover (bare ground , basal vegetation cover, litter, gravel, rock, biological soil 

crust, includes mosses and lichens and cyanobacteria)

• photographs that capture landscape setting as well as dominant vegetation components
January 2013 Page 28

Integrated sample plots are located to represent relatively homogenous vegetation, landform, and 

topographic position that reflect similar environments. Data are collected within fixed area plots 

(e.g., 20 x 20 meter or 1/10th acre plot) so that soil properties, site factors, and plant species can 

be related to one another. Partial soil profile descriptions obtained with soil augers or shallow 

soil pits can be used to identify key soil/site characteristics. Ecologically important soil 

attributes are observed (e.g., soil horizons, soil structure, rock fragments, soil depth-to-argillic 

layer, root-restrictive layer) and samples of horizons are gathered for possible laboratory analysis 

(Bestelmeyer et al. 2009, Moseley et al. 2010). This information is used to test and refine initial

ecological site concepts by identifying key soil properties, site factors, and indicator plant 

species relationships that differentiate sites. 

Ocular estimation coupled to quantitative calibration in medium intensity sampling is important 

to establish consistency and minimize variability between examiners. Variability associated with 

ocular estimates is often negated with the larger sample size obtained with medium intensity 

sampling. Calibration of ocular estimation is conducted at the start of an inventory project and 

periodically throughout the field season and duration of the project. Methods for conducting 

ocular estimation calibration can be found in Sampling Vegetation Attributes (USDI Bureau of 

Land Management, Cooperative Extension Service, USDA Forest Service, and USDA Natural 

Resources Conservation Service 1996, revised 1997, 1999).

B. Data Analysis 

There are a variety of analytical methods and tools used for classification and differentiation of 

sites based on biotic and abiotic factors. Rather than specifying one standard analysis method or 

tool, it is best to select the method or methods that will best meet the objectives for completing 

the classification. Procedures used to classify ecological sites may be different than analysis 

methods used to classify community phases for describing ecological site dynamics. Examples 

of analysis methods include gradient analysis, ordination programs, cluster analysis, and 

resulting plant association (e.g., constancy/cover) tables. References for classification analysis 

include Mueller-Dombois and Ellenberg (1974), Gauch (1982), Ludwig and Reynolds (1988),

Kent and Coker (1992), Jongman et al. (1995), McCune and Mefford (1999), Podani (2000), and 

McCune et al. (2002).

C. Define Differentiating Characteristics of Ecological Sites

Differentiating characteristics of ecological sites are determined using existing information and 

synthesis, or through more objective analyses of abiotic and biotic data collected in the 

ecological site development process. The central concepts and the range of variation for the 

ecological site are described (i.e., the range of soil and plant community properties).

Characteristics include a summary of soil properties and/or soil map unit components to which 

the site is provisionally correlated, site characteristics (i.e., slope, aspect, landform, elevation, 

and climate), and vegetation composition of associated community phases. This step is based on 

more than one integrated plot sample.

D. Field Test the Classification

Test the differentiating characteristics in the field to validate the ecological site concepts and 

differentiating characteristics. The classification process is complete when the differentiating 
January 2013 Page 29

characteristics used to define the ecological site concept work well in the field with a variety of 

end users. Final soil-site correlation and field review with soil scientists and vegetation 

specialists (ecologists or range management specialists) can occur during this step.

SECTION 3.1.3 Final Stage

A. Data Collection—High Intensity Sampling

High intensity sampling is used to provide additional, detailed information on a few modal sites

once the ecological site concept is established. Modal sites are those that adequately represent 

the properties of an ecological site. Once a number of site locations have been observed and 

concepts of states are firmly established, several areas may be chosen as modal types to provide 

quantitative values used to communicate state concepts. 

The sample site should be uniform in vegetation, soils, and landform, and large enough to 

completely include the vegetation plot and soil pit. Obvious ecotones or sites lacking uniformity 

are not suitable for sampling. Soil and vegetation specialists should jointly conduct the detailed 

characterization. Intensive soil characterizations are combined with high-intensity measurements

of vegetation. While the number of vegetation and soil characterizations that represent the 

concept of the reference state may vary, a minimum number of characterizations should be 

agreed upon in the local work plan. Minimum sampling criteria for alternative states and 

community phase should also be defined in the work plan. These characterizations should 

represent the geographic extent, environmental range, disturbance regimes, and temporal 

variability (e.g., within year, yearly, decadal) of the ecological site.

High-intensity vegetation and soil measurement methods can include line-intercept for canopy 

cover, and basal and/or canopy gap intercept; line-point intercept of basal and foliar cover;

production estimates/species composition utilizing double sampling or total harvest techniques; 

and surface/subsurface soil stability tests. The following data are required for data supported 

community phases:

• full species list

• canopy or foliar cover, by species, growth form (see example definitions, app. B), and 

vertical strata (see example definitions, App. C )

• production by species 

• vegetation vertical and horizontal structure (see sec. 5.0 F. 10)

• inherent and dynamic soil properties 

• topography (i.e., landform, slope, aspect, elevation, slope shape)

• ground cover (bare ground , basal vegetation cover, litter, gravel, rock, biological soil 

crust, includes mosses, lichens and cyanobacteria)

• photographs that capture landscape setting as well as dominant vegetation components

The resulting values and associated ranges derived from high intensity sampling data are used to 

provide quantitative benchmarks to aid in the documentation of states/community phases in 

ESDs. These quantitative benchmarks can support development of rangeland health reference 

sheet and other management interpretations.
January 2013 Page 30

B. Develop Management Interpretations

Management interpretations are based on the vegetation, soil, and environmental characteristics 

of the ecological site that are relevant to land use and resource management decisions. 

Interpretations may be based on vegetation attributes, soil properties, successional relationships 

between community phases, or expected response to disturbance regimes or management 

practices. Additional information may be obtained from monitoring or observing vegetation, soil 

properties, wildlife habitat, and animal’s response to management or disturbance processes. This 

information can be incorporated into the ecological site description to validate and quantify 

assumptions about ecosystem properties and dynamics associated with STMs.

C. Correlation

Correlation is a process for ensuring consistency in the classification, delineation, description, 

and interpretation of ecological sites. Correlation needs to be a result of interdisciplinary and 

interagency input and should include a formal review and quality control process. 

D. Quality Control and Assurance

Quality control and quality assurance are important to ensure delivery of a technically sound 

ESD that meets the defined standards in this handbook. Formal designation of these roles should 

be identified in documents such as memorandums of understanding, performance work 

statements, etc. 

The interagency workgroup (USDI BLM and USDA FS and NRCS 2010) will develop and 

recommend policy, procedures, and data management for the development and use of rangeland 

ESDs. In addition, this workgroup will provide support and quality control/assurance to 

appropriate state and regional agency leadership coordinating the development and use of 

rangeland ESDs.

1. Quality Control

Quality control is primarily the responsibility of the first-line supervisor in the field. This is 

expected to vary between agencies, but will typically be a project leader, party leader, or some 

similar work position. As much as possible, this individual will have daily contact with the field 

specialists who are conducting the varied activities associated with the development of an 

ecological site and its accompanying description. All work is inspected to meet technical 

standards, although the degree of inspection will vary depending upon the experience and 

demonstrated skills of the field specialists. Typically, quality control will be the responsibility of 

the agency(ies) performing or controlling the actual tasks being completed.

2. Quality Assurance

Quality assurance is primarily the responsibility of a technical specialist with oversight duties for 

the disciplines involved in the development of ESDs. Typically, this individual will be 

employed at the State or regional levels, providing possible interaction among multiple work 

parties. Frequency of contact is dictated by the level of work party experience, time 
January 2013 Page 31

management associated with project deadlines, project complexity, etc. Work should be 

inspected or spot-checked, but certain circumstances could require a full work inspection. The 

task of quality assurance is shared among all agencies with a vested interest in the ecological 

site. An agency should perform quality assurance tasks before signing or approving the ESD.

E. Certification

After the ESD is completed, and quality control and quality assurance measures have been met, 

the document is ready for certification. If a particular ESD pertains only to lands administered or 

serviced by a single agency, then a certification by that unique agency is sufficient for release to 

the public. If two or more agencies share responsibilities over land covered by a particular ESD, 

then all affected agencies will share signatory duties. Multiple signatures would be required, in 

this case, before the document should be released for use by both agency personnel and the 

public.

F. Publish the Ecological Site Description

Approved ecological site descriptions that have completed quality control and quality assurance 

reviews are to be published electronically in one national system, such as Ecological Site 

Information System (ESIS), which is supported by all agency partners. Approved ESDs are 

accessible to the agencies and public, and reports may be customized to meet individual needs. 
January 2013 Page 32

Figure 3.1 Ecological Site Classification & Development Process

Yes

No:

Repeat 1 or more steps

Establish Local Work Group

Sec. 3.1

Evaluate Existing Data:

Sec. 3.1.1.C

Gather Background Information

Sec. 3.1.1.B

Reconnaissance-Low Intensity Traverses

Sec. 3.1.1.D

Develop Sampling Strategy

Sec. 3.1.1.F

Select Sampling Methods

Sec. 3.1.1.G

Data Collection – Medium Intensity 

Sampling

Sec. 3.1.2.A

Publish Ecological Site Description

Sec. 3.1.3.F

Preliminary Stages

Sec. 3.1.1

Iterative Stages

Sec. 3.1.2

Data Analysis

Sec. 3.1.2.B

Define Differentiating Characteristics

Sec. 3.1.2.C

Develop Management Interpretations

Sec. 3.1.3 B

Field Test Classification

Sec 3.1.2.D

• Does site concept & key work in the field?

Define Geographic/Ecological Extent

Sec. 3.1.1.A

Correlation

Sec. 3.1.3 C

Quality Control/Quality Assurance

Sec. 3.1.3 D

Final Stages

Sec. 3.1.3

Develop STM Concept

Sec. 3.1.1.E

High Intensity Sampling

Sec. 3.1.3 A

ESD Certification

Sec. 3.1.3 E
January 2013 Page 33

SECTION 3.2 Ecological Site Key 

Keys to ecological sites are an important tool for accurate identification of ecological sites in the 

field. Although soil maps may indicate ecological sites associated with soil map units, individual 

ecological sites are not always spatially delineated within a map unit. In many situations,

ecological sites may occur as one or more major components or as a minor inclusion of a map 

unit. A key is based on soil, site, and vegetation characteristics that differentiate ecological sites

and facilitate identification of individual ecological sites within a map unit.

Areas without a soil survey may have ESDs. In these situations, an ecological site key will 

facilitate the identification of individual ecological sites.

A key may be constructed using a dichotomous format or by simply leading the reader through 

diagnostic characteristics. Since many ecological sites may represent a range of community 

phases, the key should be based on abiotic factors that are stable and not subject to change 

because of management or disturbance. Abiotic factors may include soil properties (i.e., texture, 

depth, presence of claypan, etc.), topographic features (i.e., landform, slope, aspect, slope 

position, elevation) or climate (i.e., precipitation zone, etc.). Indicator species that are persistent 

features of the site should also be included.

Ecological site keys should be developed for each MLRA. Similar MLRA’s may have similar 

keys or even identical keys. Keys need to be cross-walked to ecological sections/subsections

where the national hierarchical framework of ecological units is used by the FS. Examples of 

ecological site keys are contained in appendix D.

SECTION 3.3 Describing States and Community Phases of Ecological Sites

Descriptions of states and community phases should include data representing the influence of 

different disturbance regimes, seasonal differences, and differences between years on plant 

species, dynamic soil properties, and ecological processes. Descriptions based on a single plot 

are not adequate. Data from integrated plots should be used to describe community phases and 

states. The steps and process for understanding and documenting states and associated 

community phases is similar to that outlined for the classification of ecological sites.

Consideration must be given to many factors including the effects of:

• fire or lack of fire

• grazing or lack of grazing

• rodent activity

• insect activity

• soil erosion or deposition by wind and/or water

• drought or unusually wet periods

• variations in hydrology and storm events 

• plant disease

• introduced plant and animal species

The following methods are used to describe characteristic states and community phases of an 

ecological site: 
January 2013 Page 34

1. Review of historical accounts, survey and military records, and botanical literature of the 

area. The information may be combined with expert knowledge to develop vegetation 

state concepts.

2. Identification and evaluation of reference sites featuring similar community phases and 

associated soils. 

• Sample locations used to describe community phases and soils for the reference state 

should be exposed to natural disturbances regimes, within the natural range of 

variability.

• When describing the community phases and soils for alternative states, sample

locations should characterize the range of variability of the alternative state.

3. Data collected by soil scientists and vegetation specialists must be from the same location 

and preferably collected concurrently. See figure 3.1 and sections 3.1.1.G, 3.1.2.A, 

3.1.2.B, and 3.1.3.A, for direction about sampling methods, data collection, and analysis 

associated with describing community phases associated with describing states.

• Evaluation and interpretation of existing research and classification data dealing with 

the ecology, management, and soils can be used to support state and community 

phase characterization.

• In situations where reference community phases cannot be confidently identified, 

historical references or data from other ecological sites with similar vegetation, soil, 

and climatic characteristics may be used as supporting data.

• Evaluate and compare the same ecological site at various locations that have 

experienced different levels of management and disturbance to differentiate states. 

SECTION 3.4 Data Storage

The data collected and used to support the classification, description, data extraction, and report 

generation ability of ESDs will be entered and stored in an appropriate database. Examples of 

existing databases include the Ecological Site Inventory Information System (ESIS) and the 

National Soil Information System (NASIS) within NRCS; the Natural Resources Information 

System (NRIS-Inventory and Mapping) within FS; and the Inventory Data System (IDS) within 

the BLM. The national interagency workgroup identified in section 1.0.D will develop policy 

and procedures for common data management.

SECTION 3.5 Ecological Site Naming Convention

The naming convention includes a common, descriptive abiotic name as well as a biotic plant 

community name (scientific and common name), and a site identification number (ID). The 

abiotic name can include modifiers (elevation, aspect, precipitation, etc.) as needed to adequately 

describe and differentiate the ecological site. 

The biotic plant community name may be composed of up to three strata, consisting of a primary 

and a secondary tree, shrub and herbaceous species representing the reference community phase. 
January 2013 Page 35

Biotic names shall contain both scientific and English common names. Vascular plant scientific 

names will follow the accepted name in USDA PLANTS database. Among the taxa that are 

chosen, those occurring in the same strata or growth form are separated by a hyphen (-), and 

those occurring in different strata are separated by a slash (/).

 

The recommended naming convention is similar to the following example. 

Site Name: Clay Loam Upland 13-17" precipitation zone (p.z.)

Artemisia tridentata ssp. wyomingensis / Pascopyrum smithii - Bouteloua gracilis

(Wyoming big sagebrush / western wheatgrass - blue grama) 

Site ID: 035XF603

The Ecological Site Identification/Numbering System—The site ID consists of an eight-digit 

alpha numeric character code. The site ID begins with a three-digit number and followed by a 

one-digit letter (default is “X”) that designates the MLRA. Next comes a single-digit letter 

(default is “Y”) that designates the Land Resource Unit (LRU) or another State-designated 

subdivision of the MLRA. This is followed by a three-digit number, unique to the site—for 

example, 123XY987. Only one name and site ID will be given to a common ecological site that 

occurs within the same MLRA.

SECTION 3.5.1 Community Phase Naming Convention

Community phases should be named based on dominant overstory and understory species. 

When appropriate, plant communities recognized within the NVC may be used. When 

alternative naming conventions are used, the community phases that are data supported must be 

able to be crosswalked to vegetation types in the NVC. Minimum core vegetation data (canopy 

or foliar cover by species, growth form, and vertical strata; production by species) as mentioned 

in section 3.1.2.A, must be available to crosswalk community phases. 

The following naming conventions and definitions are adapted from Federal Geographic Data 

Committee (2008). Community phase names shall contain both scientific and English common 

names in ESDs. However, STM diagrams should only display either the common or the 

scientific name. The relevant dominant and ecologically significant indicator species that are 

used in naming a community phase should be selected from the tabular summaries of the 

community phases. Dominant species and indicator species should include at least one from the 

dominant stratum of the plant community. Vascular plant scientific names will follow the 

accepted name in the USDA PLANTS database (USDA Natural Resources Conservation Service 

1995), coupled with the specific date of observation of the website. Among the taxa that are 

chosen to name the community phases, those occurring in the same strata or growth form are 

separated by a hyphen (-), and those occurring in different strata are separated by a slash (/). 

Taxa occurring in the uppermost stratum are listed first, followed successively by those in lower 

strata. The order of taxon names within stratum or growth form generally reflects decreasing 

levels of dominance, constancy, or other measures of diagnostic value.

SECTION 3.6 Revision of Ecological Site Descriptions

Analysis and interpretation of new information may reveal a need to revise or update ESDs. 

Because the collection of such information through resource inventories and monitoring is a 
January 2013 Page 36

continuous process, ESDs should be periodically reviewed for needed revision. It is especially 

important that ESDs be reviewed by all signatory agencies when new data on composition, 

production, or response to disturbance become available. Documented production and 

composition data, along with related soil, climate, and physiographic data, will be the basis of 

the ESD revisions. Changes need to be tracked through time, including former classifications

and the descriptions of an ecological site and the previous names of the ecological site.

SECTION 4.0 Delineation and Mapping of Ecological Sites

Delineation of an ecological site is the process of determining where boundaries between 

different ecological sites occur. Delineation is the process of separating map units using 

consistent criteria (Winthers et al. 2005), which consist of multiple factors. In field application, 

these factors include observable landscape features such as soil morphology, texture and

drainage class, indicator plant communities, landform position, slope, aspect, or elevation, and so 

forth. The criteria may differ according to specific map scale, and the importance of factors will 

vary depending on broader-scale influences such as macroclimate. For example, the importance 

of aspect becomes greater in moisture-limited climatic zones.

Ecological sites can be mapped using a number of approaches. One approach is to use existing 

map products to estimate ecological site occurrence. Maps produced through the National 

Cooperative Soil Survey (NCSS) are a primary information source across private, State, and 

many Federal lands. Terrestrial ecological unit inventories (TEUI) conducted on National 

Forests are another information source. 

In areas where soils have been mapped as part of the NCSS, ecological site delineation depends 

on the relationship of ecological sites to soil map unit components. Ecological sites may be 

identified and delineated as single components where soils are mapped as soil consociations 

(generally Order 2 soil surveys). Many similar soil map unit components may be grouped into 

one ecological site. However, a single soil component (phase) of a named soil series will not 

occur in more than one ecological site.

Where soils are mapped as soil associations, soil complexes, or soil undifferentiated groups, 

individual ecological sites are identified, yet they may not be delineated separately (generally 

Order 3 or Order 4 soil surveys). In these situations, ecological sites are usually associated with 

the soil map unit delineation; however, the actual physical location of the ecological site within 

the soil map unit might not be identifiable. 

In areas where TEUIs have been completed in accordance with NCSS standards, ecological sites 

may be identified at different levels of a spatial hierarchy (tables 1 and 2, app. A). At the finest 

level, ecological land-type phases can often be directly related to an ecological site, since both 

systems recommend incorporating use of the same biotic and abiotic factors in map unit design. 

At the land-type level, one or more ecological sites may occur, depending on the variability in 

local conditions. 
January 2013 Page 37

Table 4. Relationship of soil survey intensity to ecological site delineation. Adapted from table 

2-1 in USDA-Soil Survey Division Staff (1993). See table 1.1 of this document to see the 

relationships to the National Hierarchical Framework of Ecological Units and Soil Geography.

Soil Survey 

Order

Map Scale Minimum 

Delineation 

Size (acres)

Kinds of 

Map Units

Map Unit 

Components

(soils)

Map Unit 

Components

(ecological sites)

2nd Order

(Intensive; 

general 

agriculture, 

urban planning)

1:12,000 –

1:31,680

1.4 – 10.0 Mostly soil 

consociations 

Soil series 

phase

Single ecological 

site associated with 

soil series phase.

3rd Order

(Extensive; 

range, 

community 

planning)

1:20,000 –

1:63,360

4.0 – 40.0 Mostly soil 

associations 

or soil 

complexes

Soil series or 

soil series 

phase

Multiple ecological 

sites may be 

associated with soil 

map unit 

components. 

Individual ecological 

sites in a soil 

association or soil 

complex are not 

delineated within 

the soil map unit.

4th Order 

(Extensive; 

general landuse potential 

and land 

management)

1:63,360 –

1:250,000

40.0 – 623.0 Mostly soil 

associations

Soil series or 

taxa above 

the series

Ecological sites are 

generally not 

delineated at this 

soil survey order.

Depending on the availability and quality of soil surveys or TEUIs, these areas previously 

mapped as part of the NCSS, present an opportunity to utilize geospatial technologies to 

delineate and map ecological sites. Maps of soil polygons sharing common soil properties can 

be combined with other spatial information not considered in the original map unit design. 

Morphometric characteristics of aspect or slope position, or important differences in bedrock or 

surficial geology, for example, can be combined with soil property polygons to render 

unsupervised ecological site delineation. An example of a GIS application that would be useful 

in delineating and mapping ecological sites is the Terrestrial Ecological Unit Inventory (TEUI) 

Geospatial Toolkit (Fisk et al. 2007, Benton 2008).

In areas where ecological sites are being developed in conjunction with the initiation of a new 

soil survey, TEUI, or update of an existing soil survey, attributes used to develop ecological sites

should be incorporated in map unit design. This approach uses existing information, 

classification results, or expert knowledge in establishing ranges of characteristics in mapping 

legends.

SECTION 4.1 Ecological Sites and Ecological Unit Hierarchy Mapping

There is increasing recognition that cross-scale relationships and factors are important to 

understanding ecosystem processes and influences on patterns at different spatial and temporal 

scales. Knowledge about hierarchical relationships is needed to better understand and describe 

ecosystem dynamics associated with ecological sites (Bestelmeyer et al. 2011). An ecological 
January 2013 Page 38

unit hierarchy provides a framework for characterizing landscapes and cross-scale ecosystem 

processes. They also provide a framework for assessing resource conditions at multiple scales 

and addressing indirect, direct, and cumulative effects of management activities (Cleland et al.

1997).

Bestelmeyer et al. (2009) discusses the use of a spatial hierarchy to structure inventory and to 

identify cross-scale interactions. The levels of the hierarchy in Bestelmeyer et al. (2009) are 

similar and easily related to the National Hierarchical Framework of Ecological Units (Cleland et 

al. 1997) (see appendix A). Middle levels stratify landscapes within climate zones into distinct 

soil-geomorphic systems (SGSs), capturing soil-geomorphic relationships encompassing mosaics 

of ecological sites. Landscape and land-type ecological units in Cleland et al. (1997) and 

Winthers et al. (2005) are comparable to SGSs described by Bestelmeyer et al. (2009) to describe 

the landscape context, relationships, and cross-scale processes. At the ecological site level, an 

ecological site is considered a spatial unit associated with distinct soils and topographic positions 

within a landscape (e.g., soil-geomorphic system, land-type ecological unit), linked to soil map 

unit components (e.g., soil series phase) or land-type phase ecological units. Ecological sites can 

be associated with the land-type association, land type, and land-type phase ecological units at 

the landscape and land-unit planning and analysis levels of the hierarchy.

SECTION 5.0 Contents of Ecological Site Descriptions 

This section highlights each element of an ESD (see app. E). Each element will be described by 

both required and recommended information. Agencies using this template may add additional 

requirements for their own use, but will not remove any element from the site description. 

A. Ecological Site Characteristics

1. Site Name:

Required: The naming convention includes a common, descriptive abiotic name as well as a 

biotic plant community name (scientific and common name). The abiotic name can include 

optional modifiers (elevation, aspect, precipitation, etc.) as needed to adequately describe and 

differentiate the ecological site.

The biotic name may be composed of up to three strata, consisting of a primary and a secondary 

tree, shrub, and herbaceous species representing the reference community phase. Biotic names 

shall contain both scientific and English common names. The relevant dominant and diagnostic 

species that are used in naming the reference community phase should be selected from the 

tabular summaries. Vascular plant scientific names will follow the accepted name in the USDA 

PLANTS database. Among the taxa that are chosen, those occurring in the same strata or growth 

form are separated by a hyphen (-), and those occurring in different strata are separated by a 

slash (/).

The recommended naming convention is similar to the following example.

Site Name: Clay Loam Upland 13-17" p.z. (precipitation zone)

Artemisia tridentata ssp. wyomingensis / Pascopyrum smithii - Bouteloua gracilis
January 2013 Page 39

(Wyoming big sagebrush / western wheatgrass - blue grama) 

Site ID: 035XF603

Recommended: None

2. Site ID:

Required: The site ID consists of an eight-digit alpha numeric character code. The site ID

begins with a three-digit number and followed by a one-digit letter (default is “X”) that 

designates the MLRA. Next comes a single-digit letter (default is “Y”) that designates the LRU 

or another state-designated subdivision of the MLRA. This is followed by a three-digit number, 

unique to the site—for example, 123XY987. Only one site ID will be given to a common

ecological site that occurs within the same MLRA.

Recommended: None

3. Hierarchical Classification Relationships

Required: List the name (and code, if applicable) of the higher land classification element. This 

would include classification systems such as the MLRA (USDA Natural Resources Conservation 

Service 2006) and the Ecological Subregions: Section or Subsection (McNab et al. 2007) of the 

National Hierarchical Framework of Ecological Units (Cleland et al. 1997).

Recommended: None

B. Physiographic Features

Required: Describe the position of the site on the landscape. Physiographic features include 

landscape, landform, geology (lithology, stratigraphy), aspect, site elevation, slope, water table, 

flooding, ponding, and runoff class. Use standard physiographic terminology and definitions 

from the National Soil Survey Handbook (USDA Natural Resources Conservation Service 1996) 

and Field Book for Describing and Sampling Soils (Schoeneberger et al. 2002). Document the 

capability of the site to generate runoff, receive runoff from other sites, or both receive and 

generate runoff. 

Recommended: None

C. Climatic Features

Required: Climatic information will be developed and included in the description of the site. 

Include climatic features that typify the site, relate to its potential, and characterize the dynamics 

of the site: storm intensity, frequency of catastrophic storm events, drought cycles. Climatic 

features include frost-free period, freeze-free period, mean annual precipitation, monthly 

moisture and temperature distribution, and location of climate stations. If climate data exist, 

include information (averages and ranges) from throughout the entire area where the ecological 

site occurs. Climate data may be extrapolated using climate models (e.g., Parameter-elevation 

Regressions on Independent Slopes Model (PRISM)). Distinguish between information that is 

supported by weather station data and information that is extrapolated from existing weather 
January 2013 Page 40

stations (for example, PRISM data). Include a link to local weather stations if available. Many 

sites occur in areas without appropriate climate station data. 

Recommended: None

D. Influencing Water Features

Required: Describe any water features existing on the site or adjacent wetland/riparian 

ecological sites that influence the vegetation and/or management of the site: streams, springs, 

wetlands, or depressions. Use terminology associated with the Cowardin Wetland Classification

(Cowardin et al. 1979) and Rosgen Stream Classification (Rosgen 1996).

Recommended: None

E. Representative Soil Features

Required: Describe the inherent soil properties that define a site as distinctive from other sites. 

Differentiate between inherent, attainable, and actual values for the selected properties as 

appropriate. Give special attention to properties that significantly affect plant-soil-water 

relationships and the site hydrology. Representative soil features that need to be described 

include: parent materials, surface and subsurface texture, surface and subsurface fragments, 

drainage class, hydrologic conductivity (permeability class), depth, electrical conductivity, 

sodium adsorption ratio, calcium carbonate equivalent, soil reaction (pH), and available water 

capacity. 

Describe the soil and hydrologic rangeland health indicators that characterize the reference 

community phase: for example, extent of rills and gullies; extent of water flow patterns across 

the soil surface during overland flow; amount and patterns of pedestalling and terracettes caused 

by wind or water; size and frequency of wind-scoured areas susceptibility of the site to 

compaction; expected nature of the surface organic layer; and expected physical and chemical 

crusts that might be present. 

Recommended: Provide a list of soil map unit components which are correlated to the ecological 

site.

F. States and Community Phases

1. Ecological Dynamics of the Site:

Required: Describe the general ecological dynamics of the site. Describe states based on growth 

form, life form, or functional group. Where appropriate, identify successional or seral stages. 

Describe the changes that are expected to occur because of variation in weather, and what effects 

this might have on the dynamics of the site. Identify the disturbances and disturbance intervals

affecting site development (fire regime, fire dependent or not, native herbivory, and other 

disturbances). Other general information regarding the dynamics of the site in general should be 

included. Cite scientific literature and experts consulted in describing ecological dynamics of the 

site in the Other References section of the ESD (sec. 5.0.H.7).
January 2013 Page 41

Recommended: None

2. State-and-Transition Diagram:

Required: Include a diagram of the STM for the site. The diagram should include States, 

Community Phases, Community Pathways, Transitions, and Restoration Pathways. Label all 

parts of the STM. See section 2.0.C.1 for further guidance on components of STMs.

The assumptions, methods and supporting data or literature used in defining alternative states of

STMs should be documented, peer reviewed, and further developed, if needed. These include 

careful description of the properties of reference and alternative states, description of the 

ecological mechanisms causing transitions and precluding recovery of reference or other states, 

the identification of evidence sources and assumptions, and the level of confidence in portions of 

the STM given the evidence.

Recommended: None

3. Photos: 

Required: None

Recommended: One or more photos should be included for each state and/or community phase 

described in the STM for the ecological site. Landscape photos are desirable. However, 

consider adding other photos to capture unique properties of the site, such as vegetative structure, 

soil surface, etc. Photographs should focus on conveying characteristics of the natural landscape 

setting and should be free of people, livestock, vehicles, etc. If reference to scale is important 

use a tool such as a range pole. 

4. Narrative:

Required: Describe each community phase and state identified in the STM diagram. Document 

whether the community phases are supported by empirical data or whether they are provisional 

communities. Describe the rationale for separating community phases in different states based 

on ecological processes. As a minimum, the narrative should describe the dynamics of the 

community phase and causes or triggers of community pathways and transitions. Identify and 

describe the thresholds between states. Provide information on the water cycle, nutrient cycle, 

and energy flow, and evaluation of the functioning of these ecological processes. Explain causes 

of shifts or changes, and relate how these changes will affect ecological functions. Describe 

changes in hydrologic and erosion characteristics of the site resulting from these shifts. Include 

descriptions of these elements: amount and distribution of expected litter, patterns of plant 

mortality, expected or measured changes to dynamic soil properties. 

Recommended: None
January 2013 Page 42

5. Supporting Community Phase Documentation:

Required: For community phases supported by empirical data, document the number and type of 

plots used. For provisional community phases, document the source of information used as the 

basis for describing the community phase.

Recommended: Where permissible, identify the sampling site locations used to describe the 

community phases.

6. Community Phase Composition:

Required: For the reference community phase within the reference state, as well as all other 

data-supported community phases, a detailed species list will be entered and incorporated into 

plant association or constancy cover tables. Both common and scientific names and plant 

symbol will be included for all species. Plant scientific names and symbols will be obtained 

through the USDA PLANTS database (USDA Natural Resources Conservation Service 1995). 

If plant groups are used, plant groupings must identify whether individual species within the 

group will have a production limitation or whether a single species can account for the entire 

group allowable. Numerous items must be considered when placing plant species into groups for 

the purpose of ESD development. Items include kind of plant, structure, size, rooting structure, 

life cycle, production, niche occupied, and photosynthetic pathway. Plant groups could include 

cool-season tall grasses, cool-season midgrasses, warm-season tall grasses, warm-season 

midgrasses, warm-season short grasses, annual grasses, perennial forbs, biennial forbs, annual 

forbs, shrubs, half-shrubs, deciduous trees, evergreen trees, cacti, yucca and yucca-like plants, 

succulent forbs, and leafy forbs. This list is not exhaustive. Professionals describing sites may 

identify additional attributes and relationships that can be used to define useful groupings. For

example, two or more groups of warm-season midgrasses may be described because of different 

niches and differences in production, structure, elevation, and climatic adaptations.

Recommended: Develop a detailed species composition list for all other community phases.

7. Annual Production:

Required: For the reference community phase within the reference state, as well as all other 

data-supported community phases, show the range of production by species (designating the 

range of variability for the species across the extent of the community phase) in two values (low 

and high), expressed in pounds air-dry weight/acre.

Recommended: To capture differences in annual production, by species across the extent of the 

community phase, it is recommended to collect annual production over multiple years for all

other community phases.

8. Total Annual Production:

Required: For the reference community phase within the reference state, as well as all other 

data-supported community phases, show total annual production by growth form, expressed in 

pounds air-dry weight/acre, and the fluctuations to be expected during favorable, normal, and 

unfavorable years (climatic variability, primarily by precipitation). Total annual production is not 
January 2013 Page 43

to be confused with annual production by species above (see 7) which accounts for variability by 

species across the extent of the community phase.

Recommended: Collect total annual production for all other community phases described for the 

ecological site.

9. Canopy or Foliar Cover:

Required: For the reference community phase within the reference state, as well as all other 

data-supported community phases, use either canopy or foliar cover. Be sure to identify the type 

of cover and the data collection method. Methods should be standardized and documented. 

Summarize the range of canopy or foliar cover and constancy by species for each community 

phase.

Recommended: Include canopy or foliar cover estimates with line-intercept or line-point 

intercept methods for all other community phases described for the ecological site. Note the 

presence of rare plant species and whether or not they occurred on one, a few, many, or all sites 

sampled.

10. Structure:

Required: Characterize vertical structure for the reference community phase within the reference 

state, as well as all other data-supported community phases. Vertical structure will be collected

by recording cover by growth form and vertical strata for each species (see section 3.1.3.A). Be 

sure to define both the height of the respective vertical strata, as well as the type of cover 

(canopy or foliar). Characterize horizontal structure for the reference community phase, as well 

as all other data-supported community phases. A combination of basal gaps, canopy gaps, 

canopy or foliar cover can be used to characterize horizontal structure. Horizontal structure is 

the distribution of vegetation patterns and gaps within an ecological site. 

Recommended: Include both vertical and horizontal structure for all other community phases 

described for the ecological site. 

11. Ground Surface Cover:

Required: For the reference community phase within the reference state, as well as all other 

data-supported community phases, record ground surface cover. Ground surface cover is the 

percentage of the ground surface actually occupied by bare soil, basal vegetation, litter, gravel, 

rock, or soil biological crust, including mosses and lichens.

Recommended: Include ground surface cover for all other community phases described for the 

ecological site.

12. Community Phase Growth Curves:

Required: None
January 2013 Page 44

Recommended: For the reference community phase within the reference state, as well as all 

other data-supported community phases, include a generalized chart or graph showing percent 

growth by month or season. Include growth curves for all other community phases described for 

the ecological site.

G. Ecological Site Interpretations

1. Animal Community:

Required: None

Recommended: Include information on landscape descriptions, area-sensitive species, 

transitory/migratory animals, invasive species, thresholds by animal species, species guilds, 

keystone species, aquatic elements/inclusions (e.g., mineral springs/seeps, riparian areas), 

essential habitat elements across plant communities, and potential species (e.g., extirpated, 

historical, incidental). Specific species related to a community phase should be described along 

with any known interactions. The following information, when provided, will be shown in the 

order listing lowest-to-highest trophic level: invertebrates, fish, reptiles/amphibians, birds, 

mammals, essential habitat elements, and variations impacting wildlife. General descriptions for 

use of the site by livestock, domesticated wildlife, wild horses, and burros should also be 

included. Suitability of this site for grazing, by kind and class of livestock, and potential 

management problems that exist (poisonous plants, topography, and physical barriers) should be 

described. Describe wildlife-livestock interactions and competition. Include forage preferences 

for livestock and wildlife by plant species and/or various parts of a plant species for each season 

of the year. Much of this information is likely more relevant at a higher order of land 

classification. If this information is contained in a description at a higher order, then a reference 

to that description is acceptable.

2. Hydrology Functions:

Required: None

Recommended: Indicate changes in hydrology functions that may occur with shifts in 

community phases within states. For each community phase, describe the changes in infiltration 

and runoff characteristics expected because of changes in plant species composition and soil 

surface characteristics. For example, when a plant community composition shifts from blue 

grama to buffalo grass, runoff is typically accelerated because of a change in plant growth form 

and root morphology characteristics. Information about water budgets for each community 

phase can be included.

3. Recreational Uses:

Required: None

Recommended: Indicate the potential uses that the site can support or that may influence the 

management of the site. List the plant species that have special aesthetic or landscape value. Be 

sensitive to disclosure of species affected by over harvesting. Much of this information is likely 
January 2013 Page 45

more relevant at a higher order of land classification. If this information is contained in a 

description at a higher order, then a reference to that description is acceptable.

4. Wood Products:

Required: None

Optional: Indicate use or potential use of significant species that may influence the management 

of the site. Describe the potential for woody species that have commercial value on sites where 

this is a management consideration.

5. Other Products:

Required: None

Recommended: Indicate the use or potential use of other products of the site. These may 

include such things as landscape plants, nuts and berries, mushrooms, and biomass for energy 

potentials. Be sensitive to disclosure of species affected by over harvesting.

H. Supporting Information

1. Associated Sites:

Required: Identify and describe other sites that are commonly located in conjunction with the 

site. 

Recommended: None

2. Similar Sites:

Required: Identify and describe sites that resemble or can be confused with the site.

Recommended: None

3. Inventory Data References:

Required: Enter a listing of plots supporting the site identification. Record the data source (i.e.,

sample methods) and sample identification of each plot. This is a compilation of data types and 

numbers as described in section 5.0.F.5, Supporting Plant Community Phase Documentation. 

On non-Federal land, ensure privacy of the landowner by not listing specific locations.

Recommended: Enter a listing of inventory plots supporting the community phases in STMs in 

ecological site descriptions. On non-Federal land, ensure privacy of the landowner by not listing 

specific locations. 
January 2013 Page 46

4. Agency/State Correlation:

Required: Enter the agencies and/or States which have reviewed and approved the site 

description.

Recommended: None

5. Type Locality:

Required: For Federal lands, enter the location of a typical example of the ecological site.

Recommended: For non-Federal lands, enter the location of a typical example of the site.

Indicate township, range, section, or longitude, latitude, and specific location. On non-Federal 

land, ensure privacy of the landowner by not listing specific locations.

6. Relationship to Other Established Classification Systems:

Required: None

Recommended: Describe how the ecological site description may relate to other established 

classification systems. Crosswalk each data supported community phase to the existing 

vegetation type(s) in the National Vegetation Classification (NVC). Where applicable, include a 

description of how the ecological site is related to existing PNV classifications, habitat type 

classifications, and Biophysical Setting classifications. This information is particularly 

important on some Federal lands where other classification systems and mapping hierarchies are 

used in multilevel or above site-level resource assessments, land and resource management 

planning, and monitoring.

7. Other References:

Required: Record other reference information used in site development or in understanding 

ecological dynamics of the site.

Recommended: None

8. Rangeland Health Reference Sheet:

Required: Provide reference state conditions for the 17 indicators included in Interpreting 

Indicators of Rangeland Health (Pellant et al. 2005).

Recommended: None

I. Site Description Approval

1. Authorship:

Required: Record the original authors’ names and date. Record any revisions with authors’ 

names and date.
January 2013 Page 47

Recommended: None

2. Site Approval:

Required: Indicate site approval by the appropriate authorized agency representative before final 

distribution. Record the approver’s name, date, and agency affiliation.

Recommended: None
January 2013 Page 48

GLOSSARY

At-Risk Community Phase—A community phase that can be designated within the reference 

state and also in alternative states. This community phase is the most vulnerable to transition to 

an alternative state.

Canopy Cover—The percentage of ground covered by a vertical projection downward of the 

outermost perimeter of the natural spread of foliage of plants. Small openings within the canopy 

are included. It may exceed 100 percent. Canopy cover is synonymous with crown cover.

Community Pathway—Community pathways describe the causes of shifts between community 

phases. Community pathways can include the concepts of episodic plant community changes as 

well as succession and seral stages. Community pathways can represent both linear and nonlinear plant community changes. A community pathway is reversible, attributable to succession, 

natural disturbances, short-term climatic variation, and facilitating practices such as grazing 

management.

Community Phase—A unique assemblage of plants and associated dynamic soil property levels 

that can occur within a state.

Constancy—The percentage of plots in a given data set that a taxon occurs in (Jennings et al. 

2009).

Dominant Species—Plant species or species groups that exert considerable influence upon a 

community by its size, abundance or coverage.

Ecological Resilience—1) Amount of change or disruption in functioning of ecological 

processes (nutrient cycling, hydrologic cycle, energy flow, succession) caused by disturbance(s) 

that is required to transform a community phase or a state from one community phase to another 

community phase or from one state to another state. 2) Also, has been defined not as a quantity 

of change but as a rate of change . . . ecological resilience is the rate of recovery of predisturbance(s) functioning of ecological processes of a community phase or a state, after 

disturbance(s).

Ecological Site (ES)—An ecological site is a conceptual division of the landscape, defined as a 

distinctive kind of land based on recurring soil, landform, geological, and climate characteristics 

that differs from other kinds of land in its ability to produce distinctive kinds and amounts of 

vegetation and in its ability to respond similarly to management actions and natural disturbances.

Ecological Site Classification—The process used to identify and define distinct ecological sites.

Ecological Site Descriptions (ESD)—The documentation of the characteristics of an ecological 

site. The documentation includes the data used to define the distinctive properties and 

characteristics of the ecological site; the biotic and abiotic characteristics that differentiate the 

site (i.e., climate, physiographic, soil characteristics, plant communities); and the ecological 

dynamics of the site that describes how changes in disturbance processes and management can 

affect the site. An ESD also provides interpretations about the land uses and ecosystem services 
January 2013 Page 49

that a particular ecological site can support and management alternatives for achieving land 

management.

Ecological Type—A category of land with a distinctive (i.e., mappable) combination of 

landscape elements. The elements making up an ecological type are climate, geology, 

geomorphology, soils, and potential natural vegetation. Ecological types differ from each other 

in their ability to produce vegetation and respond to management and natural disturbances 

(Winthers et al. 2005).

Foliar Cover—The percentage of ground covered by a vertical projection downward of the 

aerial portion of plants. Small openings in the canopy and intraspecific overlap are 

excluded. Foliar cover is always less than canopy cover. It may exceed 100 percent.

Indicator species —A species whose presence, abundance, or vigor indicates certain 

environmental conditions. Indicator species may represent either qualitative or quantitative 

distinctions between types (Winthers et al. 2005).

Integrated Plots—Plots in which vegetation, soil, and other physical data, are collected 

concurrently, for the purposes of classifying ecological sites and classifying plant community 

phases in ecological site descriptions.

Naturalized Plant Community—A plant community that is dominated by naturalized exotic 

plant species and is a relatively stable community resulting from secondary succession after 

disturbance. Annual grasslands of California are an example of a naturalized plant community 

(adapted from USDA Natural Resources Conservation Service 1997, amended 2003; Habich 

2001).

Potential Natural Community—A potential natural community is a biotic community that 

would become established on an ecological site if all successional sequences were completed 

without interference by humans under contemporary environmental conditions. The potential 

natural community recognizes past influences by humans, including past land use and including 

exotic species of plants or animals. Human influence is excluded from the present onward to 

eliminate the complexities of future management. A potential natural community explicitly 

recognizes that naturalized exotic species may persist in the final stage of secondary succession 

and that succession after disturbance does not always reestablish the original vegetation (adapted 

from Habich 2001).

Potential Natural Vegetation—The plant community that would become established if all 

successional sequences were completed without human interference under contemporary 

environmental and floristic conditions, including those created by man (Tuxen 1956, as cited in 

Mueller-Dombois and Ellenberg 1974, and modified by Winthers et al. 2005).

Rangeland—Land on which the indigenous vegetation is predominantly grasses, grass-like 

plants, forbs, or shrubs and is managed as a natural ecosystem. If plants are introduced, they are 

managed similarly. Rangelands include natural grasslands, shrublands, savannas, many deserts, 

tundra, alpine communities, marshes, and meadows (Society for Range Management 1998).
January 2013 Page 50

Reference Community Phase—The reference community phase is identified as that community 

phase which exhibits the characteristics of the reference state, and contains the full complement 

of plant species that historically occupied the site (Bestelmeyer et al. 2010, Briske et al. 2008). 

The reference community phase formed as a result of interacting environmental gradients, 

natural disturbance regimes, and physiological characteristics of species comprising the 

community. It is the community phase in the reference state that is used to classify an ecological 

site.

Reference state—A reference state is recognized in each state-and-transition model that 

describes the ecological potential and natural or historical range of variability of the ecological 

site.

Restoration Pathways—Restoration pathways describe the environmental conditions and 

practices that are required to recover a state that has undergone a transition.

State—A state is a suite of community phases and their inherent soil properties that interact with 

the abiotic and biotic environment to produce persistent functional and structural attributes 

associated with a characteristic range of variability (adapted from Briske et al. 2008). 

State-and-Transition Model—A method to organize and communicate complex information 

about the relationships between vegetation, soil, animals, hydrology, disturbances (fire, lack of 

fire, grazing and browsing, drought, unusually wet periods, insects and disease), and 

management actions on an ecological site. 

Thresholds—Conditions sufficient to modify ecosystem structure and function beyond the limits 

of ecological resilience, resulting in the formation of alternative states (Briske et al. 2008).

Transition—Transitions describe the biotic or abiotic variables or events, acting independently 

or in combination, that contributes directly to loss of state resilience and result in shifts between 

states. Transitions are often triggered by disturbances including natural events (climatic events 

or fire) and/or management actions (grazing, burning, fire suppression). They can occur quickly 

as in the case of catastrophic events like fire or flood, or over a long period of time as in the case 

of a gradual shift in climate patterns or repeated stresses like frequent fires.

Triggers—Events, processes, and drivers that initiate a transition to an alternative state.
January 2013 Page 51

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Terrestrial ecological unit inventory technical guide. U.S. Department

of Agriculture, Forest Service, Washington Office, Ecosystem Management

Coordination Staff. Washington, D.C. 245 p.
January 2013 Page 57

ACKNOWLEDGMENTS

Department of Agriculture Natural Resources Conservation Service:

Administrative Support:

Michael Golden, Director, Soil Survey Division, Washington, D.C.

Dennis Thompson, National Range and Grazing Lands Ecologist, Washington, D.C.

Ronald Williams, Director, Central National Technology Support Center, Fort Worth, TX

(retired)

Major Contributors to Content of Handbook: 

Stan Boltz, Rangeland Management Specialist, Huron, SD

Joel Brown, Rangeland Management Specialist, National Soil Survey Center, Las Cruces, NM

Wendell Gilgert, Biologist, West National Technology Support Center, Portland, OR (retired)

Lori Metz, Rangeland Management Specialist, Temple, TX

Kendra Moseley, Ecological Site Inventory Specialist, Portland OR

Steve Nelle, Biologist, San Angelo, TX (retired)

George Peacock, Team Leader, Grazing Lands Team, Fort Worth, TX

Jim Robinson, Forester, Central National Technology Support Center, Fort Worth, TX (retired)

Josh Saunders, Rangeland Management Specialist, Fort Morgan, CO

Pat Shaver, Rangeland Management Specialist, West National Technology Support Center, 

Portland, OR

Mike Stellbauer, Rangeland Management Specialist, Bryan, TX

Ray Stoner, Forester, Central National Technology Support Center, Fort Worth, TX 

Lyn Townsend, Forester, West National Technology Support Center, Portland, OR (retired)

Arlene Tugel, Soil Scientist, National Soil Survey Center, Las Cruces, NM (retired)

Bruce Wight, National Forester, Washington, D.C.

Craig Ziegler, Forester, West National Technology Support Center, Portland, OR

Other Significant Contributors to Content of Handbook:

Steve Brady, Biologist, Central National Technology Support Center, Fort Worth, TX (retired)

Justin Clary, former Rangeland Management Specialist, Temple, TX

Dave DeWald, Biologist, Bismarck, ND (retired)

Gene Fults, Rangeland Management Specialist, West National Technology Support Center, 

Portland, OR

Bob Gillaspy, Rangeland Management Specialist, Portland, OR

Steve Glasgow, State Resource Conservationist, Stillwater, OK

Shane Green, Rangeland Management Specialist, Salt Lake City, UT

Jon Gustafson, State Rangeland Ecologist, Davis, CA 

Karl Hipple, National Leader Soil Survey Interpretations, National Soil Survey Center, 

Lincoln, NE (retired)

Rhett Johnson, Director, Grazing Lands Technology Institute, Fort Worth, TX (retired)

Patti Novak, Rangeland Management Specialist, Reno, NV

Richard Oliver, Forester, East National Technology Support Center, Greensboro, NC (retired)

Jeff Printz, Rangeland Management Specialist, Bismarck, ND

Jeff Repp, Rangeland Management Specialist, West National Technology Support Center, 

Portland, OR (retired)
January 2013 Page 58

Department of The Interior Bureau of Land Management:

Administrative Support:

Robert Bolton, Senior Rangeland Management Specialist, Division of Rangeland Resources, 

Washington, D.C.

Bud Cribley, State Director, Alaska State Office, Anchorage, AK

Rob Roudabush, Division Chief, Division of Rangeland Resources, Washington, D.C. (retired)

Contributors to Content of Handbook:

Bruce Call, Soil Scientist, Las Cruces District Office, Las Cruces, NM (retired)

Ed Horn, Soil Scientist, Prineville District Office, Prineville, OR (retired)

Stephen Klessens, Rangeland Management Specialist, Glasgow Field Office, Glasgow, MT

Burk Rhodes, Rangeland Management Specialist, Malta Field Office, Malta, MT

Phil Smith, Rangeland Management Specialist, Las Cruces District Office, Las Cruces, NM

William Volk, Montana State Soil Scientist, Montana State Office, Billings, MT (retired)

William Ypsilantis, Acting Division Chief, Division of Environmental Quality and Protection, 

Washington, D.C. (retired)

Department of Agriculture Forest Service

Administrative Support:

Ricardo Lopez, Assistant Director, National Vegetation Ecology, Washington, D.C.

Wayne Padgett, Vegetation Ecologist, Washington, D.C. (now Ecologist, Utah State Office, Salt 

Lake City, UT, BLM)

Larry Bryant, Assistant Director Rangeland Management, Washington, D.C. (retired)

Janette Kaiser, Director Rangeland Management, Washington, D.C. (retired)

Contributors to Content of Handbook:

Dave Cleland, Assistant National Vegetation Ecologist, Washington, D.C.

Randy Davis, National Soils Program Leader, Washington, D.C. (retired)

Eric Winthers, Soil Scientist, Bridger-Teton National Forest, Jackson, WY

Wayne Robbie, Ecological Inventory Coordinator, Southwestern Region, Albuquerque, NM

Steve Strenger, Terrestrial Ecosystem Survey Project Leader, Albuquerque, NM

George Robertson, Terrestrial Ecosystem Survey Project Leader, Phoenix, AZ

Daniel Uresk, Senior Research Biologist, Rapid City, SD

Other Agencies/Organizations:

Contributors to Content of Handbook:

Brandon Bestelmeyer, Research Ecologist, Jornada Agricultural Experiment Station, 

Agricultural Research Service, Las Cruces, NM

Pete Biggam, Soil Scientist, National Park Service, Lakewood, CO

Jeff Herrick, Research Soil Scientist, Jornada Agricultural Experiment Station, Agricultural 

Research Service, LasCruces, NM

Jim O’Rourke, Professor emeritus, Chadron State College, Chadron, NE
January 2013 Page 59

APPENDIX A. Relationship of Ecological Classification and Mapping Systems

A number of ecological classification and mapping systems are currently used by various 

agencies and organizations. These systems are designed to provide information specific to an 

agency’s or organization’s land and resource management mission and business needs. Most 

systems strive to understand the inherent biological and physical potential of the land in terms of 

the capability to support desired resource values, as well as the response of the land to 

management actions or disturbance regimes.

Many of the classification systems are part of a nested hierarchy that address ecosystem 

relationships at multiple spatial scales, and provide information appropriate for different levels of 

planning and analysis (table 1). The upper (broader spatial scale) planning and analysis levels in 

the hierarchy are based on general relationships and described in broad terms, (e.g., regional or 

continental climate patterns, soil order or great group) while the lower (finer spatial scale) 

planning and analysis levels are described in finer detail, using specific soil, vegetation, and/or

landform characteristics associated with a site (e.g., soil series, soil series phase, plant 

association). 

There is a distinction between classification and mapping systems. Classification is a formal 

process of organizing ecosystem elements into naturally occurring classes or categories. 

Mapping utilizes classifications to develop map unit legends to estimate the spatial distribution 

of ecosystem elements (i.e., components) or integrated multifactor ecosystem classes that occur 

across the landscape (Winthers et al. 2005). Mapping includes a map unit design process to 

establish relationships between classification and mapping. Map units do not necessarily have a 

one-to-one relationship with classification units. Often it is necessary to include two or more 

classification units into a single map unit because of the heterogeneity or mosaic nature of 

vegetation and soil features on any given landscape. Through the map unit design process,

decisions are made about the thematic and spatial level of map detail, which classified 

components comprise each map unit, and what delineation criteria will be used to differentiate 

map units (Winthers et al. 2005).

Driscoll et al. (1984) describes two kinds or approaches to ecological classification for assessing 

natural resources, integrated and component, or ecosystem element. Integrated classification 

unites elements of the land (i.e., vegetation, soil, landform, climate, and water) to describe a 

united entity. Integrated classifications express the interactive character of the land’s elements as 

a unit in relation to surrounding land units in a spatial hierarchy. Integrated ecological 

classifications are based on known functional relationships among land elements. Examples of 

integrated classification and mapping systems include the lower levels (land unit) of the NHFEU 

(Cleland et al. 1997), the ecological type classification (Winthers et al. 2005), and ecological 

systems (Comer et al. 2003).

Component or ecosystem element classifications describe parts of the land (i.e., soil, vegetation, 

landform, water, and climate) separately, with each element as an entity based on their primary 

characteristics. Examples of component or ecosystem element classifications include Soil 

Taxonomy (USDA Soil Survey Staff 1999), Potential Natural Vegetation Classification 

Hierarchy (Brewer and Pfister 2006, Brohman and Bryant 2005, Driscoll et al. 1984) and the 

NVCS (Federal Geographic Data Committee 2008). An ecosystem element classification 

approximates integrated land classification as the classification of each element may consider 
January 2013 Page 60

integration of physical and biotic factors. For example, effects of moisture and temperature are 

considered in soil and vegetation classifications, such as boreal forests (forests developed in cool 

climates) and Aridisol soils (soils formed in aridic climates). Further integration is accomplished 

by selecting classification criteria from several ecosystem element classifications to form a new 

ecological entity. Examples of ecosystem classifications and mapping derived through the 

combination of ecosystem element classifications are the upper levels of the NHFEU (i.e.,

Domain, Division, Province, Section, Subsection) (Cleland et al. 1997).

Table 1 arrays different ecological classification systems and ecological mapping systems used 

by the FS, NRCS, BLM, and NatureServe. The table provides context for where ecological sites 

and their descriptions reside within hierarchical planning and analysis levels (which themselves 

represent various spatial scales). Ecological sites are associated with land unit planning and 

analysis level, where fine spatial scale ecosystem elements are used to characterize ecosystems. 

Ecological sites are appropriate for fine scale planning and analysis and are roughly equivalent to 

ecological types associated with land type phases, plant associations, and habitat type phases.
Table 1. Relationships of ecological classification and mapping systems across various hierarchical planning and analysis levels.

Ecological Classification Systems Ecological Mapping Systems

Hierarchical 

Planning and 

Analysis Levels

Ecosystem 

Classification

NRCS and 

BLM

Ecosystem 

Classification

FS1, 2

Potential Natural 

Vegetation 

Hierarchy6

National 

Vegetation 

Classification 

(NVC)5

National Hierarchical 

Framework of 

Ecological Units1

NRCS

Soil Geography 

Hierarchy3

NatureServe

Ecological 

Systems7

Continental and 

Region 

(Ecoregion)

NA

Macro Climate

PNV 

Series Groups1

PNV 

Groups, SubclassesFormation/Division

Domain, Division, and 

Province 

(1:5,000,000-

1:30,000,000)

Land Resource Region 

(LRR)/Common 

Ecological Region

(1:7,500,000)

Macroecosystem 

scale

Subregion NA

Macro Climate,

Physiography,

PNC – Series, 

Formation

Plant Series; 

Formation

Division/

Macrogroup

Section (1:3,500,000) 

and

Subsection

(1:250,000)

Major Land Resource 

Area (MLRA)

(1:3,500,000)

Land Resource Unit 

(LRU)/Common 

Resource Area (CRA)

(1:1,000,000)

General Soil Map

(1:250,000)

Landscape

(watershed—5th

unit of 

Hydrologic Unit 

Code)

Biophysical 

Settings 

(BLM)

Geomorphology

Geology, Relief, 

Biophysical 

Settings,

Potential Natural 

Community 

(PNC) Series;

Ecological type2

Plant Series;

Habitat Type 

Group

Group/Alliance;

(Dominance 

Type4

)

Landtype Association

(1:60,000)

NA Ecological 

Systems

(Mesoecosystem

Scale)

Land Unit 

(subwatershed—

6th unit of 

Hydrologic Unit 

Code), grazing 

allotment, 

farm/ranch)

NA Ecological type2 Potential Plant 

Association;

Habitat type

Association/

Alliance

Landtype

(1:24,000) 

Detailed Soil Map

(1:24,000)

Microecosystem

Scale Ecological 

Site Ecological type2 Potential Plant 

Association 

Phase;

Habitat type phase

Association 

Landtype Phase

(< 1:12,000)

Soil Series, Soil Series 

Phase

(1:12,000)

Individual 

Sample Sites

Vegetation 

plot and soil 

pedon

Sample site

(soil pedon/

vegetation plot)2 Vegetation plot Vegetation plot

Integrated Plot Soil Pedon NA
January 2013 Page 62

1 Map scale from: NHFEU (Cleland et al. 1997)

2

 Terrestrial ecological unit inventory technical guide indicates soil series can be incorporated into landtype phase (see table 3.1 in Winthers et 

al. 2005)

3

 USDA Natural Resources Conservation Service 2006. MLRA definitions 12/15/2005, Soil Geography Hierarchy, 

http://soils.usda.gov/survey/geography/hierarchy/index.html

4 Existing vegetation classification and mapping technical guide (Brohman and Bryant 2005)

5

 National Vegetation Classification Standard, version 2 (Federal Geographic Data Committee 2008)

6

 An ecological land classification framework (Driscoll et al. 1984)

7

 Ecological Systems of the United States: A Working Classification of US Terrestrial Systems (Comer et al. 2003)
January 2013 Page 63

Forest Service Ecological Classification and Unit Mapping

The FS utilizes ecological classification and mapping to classify ecological types and map 

ecological units at multiple spatial scales. Ecological units are relatively stable environments 

associated with repeating patterns of landscape elements (e.g., geology, climate, landform, 

topographic feature, vegetation, soils), with similar combinations of ecological sites and types as 

map unit components (Winthers et al. 2005). They delimit areas of similar biological and 

physical potentials at different levels of resolution (i.e., continental to land unit) within a nested 

hierarchy (Cleland et al. 1997).

The NHFEU (Cleland et al. 1997) outlines eight levels of ecological unit classification and 

mapping which support four planning and analysis levels used by the FS (table 2). The hierarchy 

provides a framework for describing and assessing ecosystems from continental to local scales. 

Ecoregion and subregion are the two upper planning and analysis levels typically used for 

national and regional assessments and planning. Domain, division, and province are ecological 

units used to describe and communicate ecosystem processes in regional and national

assessments and planning (Cleland et al. 1997). Mapping and classification criteria used for 

these broad ecological units include continental climatic regimes and physiography (Winthers et 

al. 2005). Section and subsection are ecological units used in regional assessments and planning 

(Cleland et al. 2007). Mapping and classification criteria used for these regional ecological units 

include regional climate, geomorphic processes, topography, and stratigraphy (Winthers et al.

2005). Section and subsection ecological units are roughly at the same spatial scale as Major 

Land Resource Areas and Land Resource Units (table 1). 

Landscape and land unit are the two lower planning and analysis levels used by the FS for local 

assessments and planning. At the landscape planning and analysis level, land-type association 

ecological units describe and communicate ecosystem processes for forest-wide and watershed 

analysis and planning. Differentiating criteria for land-type associations and associated 

ecological types include broad patterns of soil families or soil sub groups, potential natural 

vegetation series (i.e., vegetation series), geomorphic processes, landforms, geology, and local 

climate. Land-type association ecological units are roughly at the same map unit size as map 

units in a 4th order soil survey (table 2). 

Land type and land-type phase ecological units at the land unit planning and analysis level are 

used to describe and communicate ecosystem processes at local scales for project, small 

landscape (subwatershed) analysis and planning, resource inventories, and effectiveness 

monitoring. Land types are roughly at the same map unit size as map units in a 3rd order soil 

survey and land-type phases are roughly at the same map unit size as map units in a 2nd order soil 

survey (see table 2). Land types and land-type phases are characterized by repeating patterns of 

one or more ecological types. Ecological unit inventories are designed and completed in 

cooperation with the NRCS and meet the mapping conventions and soil classification standards 

of the NCSS (Winthers et al. 2005, Cleland et al. 1997).
January 2013 Page 64

Table 2. Relationship of land-type association, land type, and land-type phase ecological units of 

the NHFEU, to associated ecological type criteria, ecological sites, and soil survey classification 

and mapping.

National 

Hierarchical 

Framework of 

Ecological 

Units 

Components4 Ecological Type 

Criteria

Ecological Site 

Correlation

Soil 

Taxonomic 

Unit 

Component 

(SRI)1,3,6 

Soil Survey/

Soil 

Resource 

Inventory

(SRI) Order1, 

3

NRCS

Soil Geography 

Hierarchy 5 and 

Soil Map Unit 

Components1

Subregion:

Section 

(1:3,500,000) 

and

Subsection

(1:250,000)

Regional climate, 

geology, 

geomorphology, soil 

great groups and 

subgroups,

Land Resource 

Unit

NA 5th Order Land Resource 

Units

1:250,000 –

1:1,000,000 or 

smaller

Land-type 

association

(1:60,000 –

1:250,000) 

Climate, geology, 

geomorphology, soil 

great groups and 

subgroups, potential 

vegetation series 

and subseries

NA Phases of soil 

families or soil 

subgroups

4th Order General Soil Map

(1:63,360 -

1:250,000)

Land type

(1:24,000 –

1:60,000) 

One (i.e., soil 

consociation) 

or more 

ecological 

types (i.e., soil 

association or 

soil complexes)

Potential natural 

vegetation, soils, 

local climate, 

geomorphology, 

surficial geology, 

and hydrology. 

Based on integrated 

field plot sample

Correlated with 

soil series and 

differences in 

species 

composition of 

the reference 

community 

phase.

Mapped as soil 

series, soil 

associations, or 

soil complexes. 

Phases of soil 

series or soil 

families

3rd Order Detailed soil map 

mostly of soil 

series, soil

associations, or soil 

complexes.

(1:20,000 -

1:63,360)

Land-type 

phase

(<1:24,000) 

One (i.e., soil 

consociation); 

sometimes 

more than 1 

ecological type 

(i.e., soil 

association or 

soil complexes)

Potential natural 

vegetation, soils, 

local climate, 

geomorphology, 

surficial geology, 

and hydrology.

Based on integrated 

field plot sample

Correlated with 

soil series, soil 

series phase, 

and reference 

community 

phase.

Mapped as 

single soil series, 

some soil 

associations.

Soil series,

Soil series 

phase

2nd Order Detailed soil map 

mostly single soil 

series, soil series 

phase, some soil 

associations

(1:12,000 –

1:31,680)

NA NA Correlated with 

soil series phase 

and reference 

community 

phase.

Mapped as 

single soil series 

phase.

Soil series 

phase

1st Order Detailed soil map, 

mostly single soil 

series phase map 

units

(1:15,840 or larger)

1 USDA Soil Survey Division Staff (1993). 
January 2013 Page 65

2 Terrestrial Ecological Unit Inventory Technical Guide indicates soil series can be incorporated 

into landtype phase (see table 3.1 in Winthers et al. 2005).

3 USDA Forest Service (1991b)

4 Map scale from: NHFEU (Cleland et al. 1997)

5 USDA Natural Resources Conservation Service 2006. MLRA definitions 12/15/2005, Soil 

Geography Hierarchy http://soils.usda.gov/survey/geography/hierarchy/index.html

6 USDA Soil Survey Staff (1999)

An ecological type is similar to an ecological site at the land unit level (e.g., landtype phase, soil 

series phase). It is a category of land with a distinctive (that is, mappable) combination of 

landscape elements. The elements making up an ecological type are climate, geology, 

geomorphology, soils, and potential natural vegetation. Ecological types differ from each other 

in their ability to produce vegetation and respond to management and natural disturbances 

(Winthers et al. 2005). An ecological type classification is associated with the landscape and 

land unit planning and analysis levels of the hierarchy. As components of land-type associations, 

ecological type classifications describe relationships between broader landscape elements. 

Geomorphology is a primary differentiating criteria, rather than soil properties. Local climate 

(modified by elevation, aspect), geology, parent material, soil subgroups, and vegetation series 

are also used as differentiating criteria for land-type association ecological types. As 

components of land type and land-type phase ecological units, local site relationships become 

more important as differentiating criteria. Primary differentiating criteria are soil properties, 

local climate modified by terrain (slope, aspect, elevation), parent material (surficial geology), 

potential natural vegetation, hydrology, and geomorphology.

Ecological type classifications are derived through analysis of field data comprised of integrated 

plots to determine which site characteristics or properties best differentiate the types. Integrated 

plots include data about the geology, geomorphology, soil properties, and potential natural 

vegetation of a sample site. Ecological type classifications and descriptions, where completed, 

can provide information useful in the formation and documentation of ecological site concepts 

and descriptions. Information and associated data they provide can help stratify the landscape 

along environmental gradients, define plant-soil-site relationships, identify differentiating factors 

between ecological sites, and provide additional supporting documentation for ecological site 

descriptions. 

At the land unit planning and analysis level ecological types are similar to ecological sites 

because both describe and communicate information about the lands capability to support similar 

vegetation, and the lands response to management actions and disturbance regimes. Soils and 

abiotic factors, together with vegetation, are used to differentiate ecological types and ecological 

sites. Classification of ecological types and ecological sites differs in some key aspects. 

Ecological type classifications are defined at multiple spatial scales and are applicable at both the 

landscape and land unit planning and analysis levels of the hierarchy. However, criteria for 

differentiation of ecological types vary across the spatial scales. Ecological sites are associated 

to a single spatial scale, the site level. In terms of spatial scale, ecological types and ecological 

sites are most comparable at the land-type phase and 1st and 2nd order soil survey levels.
January 2013 Page 66

Relationship to Habitat Type Classifications

Habitat types have historically been defined as all parts of the land surface supporting, or capable 

of supporting, the same kind of climax plant association (Daubenmire 1978). Habitat type

classifications have been developed and used extensively in the western United States to define 

and describe differences in land capability for land and resource management analysis and 

planning. Wellner (1989) noted that 127 habitat type classifications for forests and rangelands 

had been published in the western United States between 1970 and 1987. Habitat type 

classifications differ from potential natural vegetation classifications in that habitat type 

classifications include two components, vegetation and associated abiotic characteristics. The 

vegetation component is defined by potential natural vegetation (i.e., late successional or 

potential plant association), thus the vegetation component is a potential natural vegetation 

classification. In practice, however, habitat types have been developed for fire-dependent 

ecosystems based on dominant seres, not the endpoint of succession in the absence of 

disturbance. For example, habitat types have been developed for jack and red pine ecosystems 

(Kotar et al. 2002), which originated from and are maintained by relatively frequent crown or 

surface fire regimes. In Montana and northern Idaho, Pfister and Arno (1980) considered 70-

year-old forested sites as late successional communities for interpreting and describing 

ecological potential, that is, sites where understory species composition has achieved stability 

with the environment. Jensen (1990) similarly considered minimally disturbed sites to classify 

and describe ecological potential for grassland and shrubland types. The abiotic component is 

comprised of climate, soils, terrain, and landform. Together, the potential natural vegetation 

community and the abiotic components define the environmental setting or the habitat type. An 

underlying premise of habitat type classification is that vegetation is the integrated expression of 

the environment that reflects the environmental potential of a land area (Pfister 1989). 

Habitat types differ from ecological sites in that soils are not explicitly used to differentiate 

habitat types, which are differentiated on the basis of indicator species. Soils information is 

often included in habitat type descriptions as part of the environmental setting description. More 

detailed investigation and documentation of the relationship of key soil properties to indicator 

species is needed to meet ESD standards.

Relationship with Ecological Systems and Biophysical Settings

Ecological systems is a mid-level ecosystem classification and mapping system developed by 

NatureServe to address information needs in support of assessments of ecological integrity and 

biological diversity, and to inform conservation and resource management decisions. Ecological 

systems represent recurring groups of biological communities that are found in similar physical 

environments and are influenced by similar dynamic ecological processes (e.g., fire, flooding 

etc.) (Comer et al. 2003). Spatially, they are defined as mesoscale ecosystems. They are

somewhat comparable to land-type associations but are more narrowly defined as a landscape 

unit intermediate between the group and the alliance level of the NVC (table 1). They are a 

broader land unit than an ecological site, being focused on landscape elements and patterns

rather than site-level ecosystem element relationships. Ecological systems use plant associations 

(i.e., plant associations within the NVC, which are existing vegetation types) which co-occur as a 

differentiating criteria. In addition to existing vegetation types, other factors to differentiate 

ecological systems include disturbance regimes, substrates (i.e., soil, geology), and 
January 2013 Page 67

environmental gradients (i.e., local climate, desert, arid grassland, montane, alpine zones). 

Conversely, disturbance regimes are not differentiating criteria for ecological sites, ecological 

types, nor land-type association ecological units.

Biophysical Settings, a classification used to map fire regimes, uses the scale and nomenclature 

of ecological systems in describing vegetation communities at the time of European settlement 

(LANDFIRE 2010). Within LANDFIRE, unique STM’s were developed for each Biophysical 

Setting which depicts development stages, successional pathways, and natural disturbance effects 

in the absence of human interference.

Relationship with the National Vegetation Classification

The United States Federal Geographic Data Committee developed a geospatial data standard 

called the National Vegetation Classification (Standard) (Federal Geographic Data Committee 

2008). The purpose of the Standard is to support the development and use of a consistent 

national vegetation classification system for the United States and its Trust Territories. The U.S. 

National Vegetation Classification allows uniform statistics to be generated about vegetation 

resources in the United States, based on vegetation data gathered at local, regional, or national 

levels. The Standard requires that agencies be able to crosswalk other vegetation classifications 

to the NVC to facilitate the compilation of regional and national summaries. 

In addition, all federal vegetation classification efforts must meet core data requirements that 

are the same across all Federal agencies to permit aggregation of data from all Federal 

agencies. The NVCS will require that vegetation inventory units crosswalk to the NVC. 

Therefore, the composition of any vegetation inventory unit has to be describable in terms of one 

or more vegetation types within the NVC. The NVC contains a standardized list of vegetation 

types in each of several hierarchical levels, with the most detailed hierarchical levels 

characterized by vegetation types that are floristic (plant species) based. The NVCS and NVC

apply to existing vegetation and existing vegetation types, regardless of their relationship to

potential natural vegetation.

Ecological sites contain differing kinds and amounts of vegetation that are categorized into 

community phases. Community phases are floristic and are existing vegetation types. 

Therefore, ecological sites are subject to necessary crosswalking to the NVC. Community 

phases that are data-supported and not provisional need minimum data to be collected to 

facilitate crosswalking of community phases to vegetation types in the NVC. Specifically, 

minimum data associated with plots used to classify ecological sites, and data associated with

plots used to identify community phases that can exist on ecological sites will need to be 

collected.

The NVC does not replace classification of vegetation types (community phases) in an 

ecological site classification. Therefore, community phases identified in ecological sites do not 

have to be named exactly as vegetation types in the NVC. However, by whatever means

community phases are identified for ecological sites, minimum data associated with those 

community phases must be available so that each community phase can be crosswalked to one or 

more existing vegetation types in the NVC.
January 2013 Page 68

Ecological Site Relationship with National Cooperative Soil Survey (NCSS)

The National Soil Survey Handbook (NSSH) (USDA Natural Resources Conservation Service 

1996) establishes responsibility for planning soil surveys on rangeland. Soil scientists and 

vegetation specialists (ecologists or rangeland management specialists) and cooperating agencies 

will work together to map soils and ecological sites in rangeland areas. Essential activities 

include development of soil survey work plans, determination of soil mapping unit composition, 

preparation of map legends, determination of mapping intensity, and necessary field reviews. 

The NSSH, part 627.02 (USDA Natural Resources Conservation Service 1996), describes the 

delineation of major landform units and landform components as a preliminary procedure in field 

mapping. The next step is the identification, description, and classification of the kinds of soils 

associated with the landform components. 

A soil map unit is a collection of areas defined and named the same in terms of their soil 

components and is uniquely identified on a soil map as a delineation (USDA Soil Survey 

Division Staff 1993). Map unit design establishes relationships between soil-landscape 

elements, ecological site characteristics (as defined by the classification), and soil taxonomic unit 

to define map unit components. There are four kinds of soil map units: soil consociations, soil 

associations, soil complexes, and soil undifferentiated groups (USDA Soil Survey Division Staff 

1993). Soil consociations are soil map units composed of a single component (i.e., soil series, 

soil series phase) that makes up at least 75 to 85 percent of the map unit. Soil associations and 

soil complexes are soil map units that may have two or more major dissimilar components which 

together make up 75 to 85 percent of the map unit and consistently occur together. Major 

components of a soil association can be delineated at larger scales, while components of soil 

complexes cannot be delineated separately. Soil undifferentiated groups are soil map units that 

consist of two or more components that do not consistently occur together. They may be 

grouped together, however, because of some common map feature (landform, topography) that 

may determine similar management interpretations. Regardless of map unit kind, soil map units 

may contain 15 to 25 percent inclusions of dissimilar components.

Mapping scale, soil survey order, and kinds of map unit delineations have a bearing on whether 

ecological sites are delineated or how precise or general the delineations may be. Ecological 

sites may be identified and delineated as single components where soils are mapped as soil 

consociations (generally order 2 soil surveys). Where soils are mapped as soil associations, soil 

complexes, or soil undifferentiated groups, individual ecological sites are identified, yet they 

may not be delineated separately (generally order 3 or order 4 soil surveys). In these situations, 

ecological sites are usually associated with the soil map unit delineation; however, the actual 

physical location of the ecological site might not be identifiable from the soil map. Ecological 

sites associated with the different soil components within map units with multiple components 

are expressed as a percent of the map unit soil taxonomic composition.

Ecological site delineation depends on the relationship of ecological sites to the order of soil 

survey mapping. There is a many-to-one relationship between soil series phase and ecological 

sites. This is represented most frequently at order 2 soil survey mapping. Many similar soil 

taxonomic components may be grouped into one ecological site. However, a single soil 

component (phase) of a named soil series will not occur in more than one ecological site. 
January 2013 Page 69

Broadly mapped soil components (i.e., soil series or higher taxonomic units, soil family, in an 

order 3 soil survey), may include more than one ecological site.

Order 3 mapping describes individual soil and plant map unit components at soil association or 

soil complex levels. This requires that map unit descriptions be developed that describe each soil 

association component and assign locations and percentages to each. Individual ecological sites 

must be described at a level equivalent to the individual components of the order 3 soils map. 

Where order 2 soil surveys are completed and ecological site interpretations have been made, 

boundaries of ecological sites can generally be determined directly from the soil map.
January 2013 Page 70

APPENDIX B. Example of Growth Forms That Could Be Used To Categorize Plant 

Species Cover (adapted from Federal Geographic Data Committee 2008).

Growth Form Definition

Trees Woody plants that generally have a single main stem and have more or less 

definite crowns. In instances where growth form cannot be determined, 

woody plants equal to or greater than 5 meters (m) in height at maturity 

shall be considered trees.

Shrubs Woody plants that generally exhibit several erect, spreading, or prostrate 

stems which give it a bushy appearance. In instances where growth form 

cannot be determined, woody plants less than 5 m in height at maturity shall 

be considered shrubs.

Herbs Vascular plants without significant woody tissue above the ground, with 

perennating buds borne at or below the ground surface. Includes 

graminoids, forbs, ferns, club mosses, horsetails, and quillworts.

Nonvascular A plant or plant-like organism without specialized water or fluid conductive 

tissue (xylem and phloem). Includes mosses, liverworts, hornworts, 

lichens, and algae.

Floating Rooted or drifting plants that float on the water surface.

Submerged Rooted or drifting plants that by-and-large, remain submerged in the water 

column or on the aquatic bottom.

Epiphyte A vascular or nonvascular plant that grows by germinating and rooting on 

other plants or other perched structures, and does not root in the ground.

Liana A woody, climbing plant that begins life as terrestrial seedlings but relies on 

external structural support for height growth during some part of its life, 

typically exceeding 5 m in height or length at maturity.
January 2013 Page 71

APPENDIX C. Example of Vertical Strata That Could Be Used To Categorize Plant 

Species Cover (adapted from Federal Geographic Data Committee 2008)

Stratum Definition

Tree The layer of vegetation where woody plants are typically more than 

5 m in height, including mature trees, shrubs over 5 m tall, and 

lianas. Epiphytes growing on these woody plants are also included 

in this stratum.

Shrub The layer of vegetation where woody plants are typically more than 

0.5 m tall but less than 5 m in height, such as shrubs, tree saplings, 

and lianas. Epiphytes may also be present in this stratum. Rooted 

herbs are excluded even if they are over 0.5 m in height, as their 

stems often die back annually and do not provide a consistent 

structure.

Herb The layer of vegetation consisting of herbs, regardless of height, as 

well as woody plants less than 0.5 m in height.

Nonvascular (Ground) The layer of vegetation consisting of nonvascular plants growing on 

soil or rock surfaces. This includes mosses, liverworts, hornworts, 

lichens, and algae.

Floating The layer of vegetation consisting of rooted or drifting plants that 

float on the water surface.

Submerged The layer of vegetation consisting of rooted or drifting plants that 

by-and-large remain submerged in the water column or on the 

aquatic bottom. Emergent plant growth forms are excluded (for 

example, cattails would be placed in the herb stratum).
January 2013 Page 72

APPENDIX D. Example Ecological Site Key

Soil Based Key

To the Ecological Sites within the 16-20 inch Precipitation Zone within the 

AZ1 Land Resource Unit within 

Major Land Resource Area (MLRA) 41, Southeastern Arizona Basin and 

Range

Major Land Resource Area (MLRA) 41, Southeastern Arizona Basin and Range, is found in 

southeastern Arizona and southwestern New Mexico within the Mexican Highland Section of the 

Basin and Range Province of the Intermontane Plateaus. 

The climate of the area is warm (thermic) and dry to wet (typic aridic to typic ustic). Elevations 

range from 2600 feet to 10,700 feet or more in the higher mountainous areas found within the 

MLRA.

The MLRA is separated into three Land Resource Units (LRU’s), the 41.AZ1 – Mexican OakPine Forest and Oak Savannah, the 41.AZ2 – Chihuahuan – Sonoran Desert Shrubs LRU, and 

the 41.AZ3 – Chihuahuan – Sonoran Semidesert Grasslands LRU. This key example displays 

only one of the three LRU’s, the 41.AZ1, Mexican Oak – Pine Forest and Oak Savannah, and 

displays one of the three precipitation zones, 16-20 precipitation zone within that LRU: 

Land Resource Unit 41.AZ1 

Mexican Oak-Pine Forest and Oak Savannah

LRU 41.AZ1 – Mexican Oak-Pine Forest and Oak Savannah

Elevations range from 4500 to 10,700 feet and precipitation ranges 

from 16 to 30 inches. Vegetation includes Emory oak, Mexican 

blue oak, Arizona white oak, one-seed juniper, alligator juniper, 

sacahuista, California bricklebush, skunkbush sumac, Arizona 

rosewood, wait-a-bit mimosa, sideoats grama, blue grama, purple 

grama, wooly bunchgrass, plains lovegrass, squirreltail, and pinyon 

ricegrass. The soil temperature regime ranges from thermic to 

mesic and the soil moisture regime ranges from aridic ustic to typic 

ustic. This unit occurs within the Basin and Range Physiographic 

Province and is characterized by numerous mountain ranges that 

rise abruptly from broad, plain-like valleys and basins. Igneous and 

metamorphic rock classes dominate the mountain ranges and 

sediments filling the basins represent combinations of fluvial, 

lacustrine, colluvial and alluvial deposits.
January 2013 Page 73

Land Resource Unit 41.AZ1, Mexican Oak – Pine Forest and Oak 

Savannah, Ecological Site List for 16-20” PZ

Site ID Number Site Name

041XA101 Clayey Swale16-20" p.z.

041XA102 Granitic Hills16-20" p.z.

041XA103 Limestone Hills16-20" p.z.

041XA104 Limy Slopes16-20" p.z.

041XA105 Limy Upland16-20" p.z.

041XA107 Loamy Slopes16-20" p.z.

041XA108 Loamy Upland16-20" p.z.

041XA109 Clay Loam Upland16-20" p.z.

041XA110 Sandy Loam Upland16-20" p.z.

041XA111 Volcanic Hills16-20" p.z.

041XA112 Sandy Wash, QUEM, QUAR

041XA113 Sandy Bottom, PLWR2, POFR2

041XA114 Loamy Bottom16-20" p.z.

041XA117 Granitic Upland16-20" p.z.

041XA126 Clayey Upland16-20" p.z.

041XA127 Sandy Loam Upland16-20" p.z.Deep
January 2013 Page 74

Key to Ecological Sites found in the 16-20” PZ within Land Resource Unit

41.AZ1, Mexican Oak-Pine Forest and Oak Savannah

I. Flooded (bottom position, flooded from the valley-side or over-bank)

A. Soils with a perennial high water-table (3-15 ft.)

1. Soils sandy and gravelly with redox features –

Sandy Bottom, PLWR2, POFR2 (041XA113)

2. Soils loamy to clayey with redox features - Cienega **

B. Soils with seasonal (summer) water table (3-15 ft.) –

1. Soils sandy loam to clay loam - Loamy Bottom (041XA114)

C. Soils without a high water table (3-15 ft)

1. Soils sandy - Sandy Wash, QUEM, QUAR (041XA112)

2. Soils sandy loam to clay loam - Loamy Bottom (041XA114)

3. Soils clayey (vertic) - Clayey Swale (041XA101)

II. Not Flooded (upland position, receives only precipitation)

A. Slopes less than 15%

1. Soils calcareous throughout

a. Soils shallow (less than 20 inches deep)

1. Soils with a lime cemented hardpan –

Limy Upland (041XA105)

b. Soils moderately deep to deep (30 to 60 inches)

2. Soils with an argillic horizon - Loamy Upland, limy **

2. Soils non calcareous in upper 10 inches

a. Soils shallow (less than 20 inches deep)

1. Soils underlain by granite, schist, rhyolite bedrock -

Granitic Upland (041XA117)

b. Soils moderately deep to deep (30 to 60 inches)

1. Soils without an argillic horizon

a. Soils loamy fine sand to sandy loam –

Sandy Loam Upland, Deep (041XA127)

2. Soils with an argillic horizon

a. Soils with sandy loam surface 4 in. or thicker 

Sandy Loam Upland (041XA110)

b. Soils with sandy loam surface less than 4 in. 

Loamy Upland (041XA108)

c. Soils with clay loam surface (not vertic) -

Clay Loam Upland (041XA109)

d. Soils with a clayey surface (vertic) –

Clayey Upland (041XA126)

B. Slopes greater than 15%

1. Soils shallow (less than 20 inches deep)
January 2013 Page 75

a. Soils calcareous throughout

1. Soils over limestone parent materials –

Limestone Hills (041XA103)

b. Soils non calcareous 

1. Soils over granite, schist, gneiss, rhyolite (acid 

igneous) - Granitic Hills (041XA102)

2. Soils over basalt, andesite, welded tuff (basic 

igneous) - Volcanic Hills (041XA111)

2. Soils moderately deep and deep (30 to 60 inches)

a. Soils calcareous throughout

1. Soils dark colored in the surface 5 inches (10YR, 

4/2) – Limy Slopes (041XA104)

b. Soils non calcareous in the upper 10 inches

1. Soils sandy loam to clay loam –

Loamy Slopes (041XA107)

2. Soils clayey - Clayey Slopes **

** These sites may occur, but have not yet been confirmed
January 2013 Page 76

APPENDIX E. Example Ecological Site Description

ECOLOGICAL SITE DESCRIPTION

(Portions of this ecological site description have been fabricated for presentation purpose in an effort to 

display the applicable contents of an ESD as defined in the Interagency ESD handbook) 

ECOLOGICAL SITE CHARACTERISTICS

Site Name: Deep Sand Savanna 13-16 P.Z.

Artemisia filifolia/Andropogon hallii-Schizachyrium scoparium, (sand sagebrush/sand 

bluestem-little bluestem) 

Site ID: 045CY999 

Hierarchical Classification Relationships:

Major Land Resource Area (MLRA) 045C-Central New Mexico Highlands. This 

MLRA lies within the Sacramento Section of the Basin and Range Province of the 

Intermontane Plateaus. It is characterized by block-faulted ranges separated by intermountain 

basins. Tablelands and mesas are capped by sedimentary rocks. Many local terraces are near 

small streams. Steep escarpments and breaks are common. Elevation generally ranges from 

5,000 to 7,400 feet (1,525 to 2,255 meters). In some mountainous areas, however, it is more 

than 8,500 feet (2,590 meters). 

Crosswalk MLRA 045C with Ecological Subregions:

Section M313B—Sacramento-Monzano Mountains

Section M315A—Pecos Valley
January 2013 Page 77

Physiographic Features

This site occurs as coarse-textured eolian and alluvial sediments on upland plains. Slopes are nearly 

level to gently undulating, generally less than 5 percent. Low stabilized hummocks or dunes may 

occur. Exposure varies but is not significant. Elevations range from 4,500 to 7,200 feet above sea 

level.

Landform: (1)Plain

(2)Sand sheet

Climatic Features

Climatic features are of the general area within which the Deep Sand Savanna ecological site is 

located, and do not necessarily apply to exact locations of the Deep Sand Savanna ecological site. 

The climate of the area is semi-arid continental. The average annual precipitation ranges from 13 to 

16 inches. Variations of 5 inches, more or less, are common. Seventy-five percent of the 

precipitation falls from April through October. Most of the summer precipitation falls in the form of 

high-intensity, short-duration thunderstorms. Drought (less than 75% of average annual 

precipitation) years occur about 1 in 10 years.

Distinct seasonal changes and large annual and diurnal temperature changes characterize 

temperatures. The average annual temperature is about 50 degrees F with extremes of –29 degrees F 

in the winter and 103 degrees F in the summer. 

Both temperature and precipitation favor warm-season, perennial plant species. However, about 40 

percent of the precipitation falls at a time favorable for cool-season plant growth. This allows the 

cool-season species to occupy an important component in this site. Because of the coarse texture of 

the soil, the plant community can respond rapidly to any precipitation during the frost-free season. 

Strong winds blow from February through June, drying the soil during a critical stage for plant 

growth and causing the soil to blow, which can damage plants. 

Minimum Maximum

Elevation (feet): 4500 7200

Slope (percent): 0 5

Slope Shape:

Hillslope – Profile Position:

Water Table Depth (inches):

Linear

Not applicable

Flooding:

 Frequency:

 Duration: None None

Ponding:

 Depth (inches):

 Frequency:

 Duration: None None

Runoff Class: Negligible Medium

Aspect: No Influence on this site
January 2013 Page 78

The average frost-free period varies between 131 and 173 days, with at least 50% of the years having 

a frost-free period within that range. The average freeze-free period varies between 155 and 187 

days, with at least 50% of the years having a freeze-free period within that range. The last killing 

frost typically occurs in early May and the first killing frost typically occurs in early October. 

Minimum (days) Maximum (days)

50% Probability Frost-Free Period (32.5oF or greater) 131 173

50% Probability Freeze-Free Period (28.5oF or greater) 155 187

Mean Annual Precipitation: 13.0 to 16.0 inches per year

Monthly Precipitation (inches) and Temperature (oF) Distribution 

Month

Temperature

Average Precipitation Average Low Average High

January 0.63 15.6 42.1

February 0.58 19.9 52.9

March 0.60 24.4 59.7

April 0.68 31.4 68.9

May 1.23 39.2 77.7

June 1.26 46.9 87.1

July 2.26 53.1 88.5

August 2.84 51.9 85.7

September 1.90 44.3 80.4

October 1.26 32.8 70.5

November 0.80 22.2 57.5

December 0.75 15.9 49.3
January 2013 Page 79

0

0.5

1

1.5

2

2.5

3

0

10

20

30

40

50

60

70

80

90

100

Precipitation (inch)

Temperature (F)

Monthly Precipitation and Temperature

Average Precipitation Average Low Temperature Average High Temperature
January 2013 Page 80

Referenced Climate Stations

Clines Corners 7 SE, NM

Corona 11 SSW, NM

Estancia, NM

Gran Quivira Natl. Monument, NM

Mountainair, NM

Vaughn, NM

Influencing Water Features

This site is not influenced by water from a wetland or stream.

Wetland Description: System Subsystem Class

(Cowardin System) None

0

5

10

15

20

25

30

197219741976197819801982198419861988199019921994199619982000

Precipitation (in)

Year

30 Year Precipitation Patterns (1972 to 2001)

Annual Precipitation

Average Precipitation Across

Years

Drought
January 2013 Page 81

Representative Soil Features

The soils on this site are deep and excessively drained. Key features that typify the site are: surface 

textures that are of loamy fine sand or fine sandy loams; soils that extend to a depth of 60 inches or 

more; soil surface stability class ratings of 3.5 to 4.5 in interspaces, and soil surface stability ratings 

of 4 to 5 under shrub or grass plant canopies; soils are rapidly permeable and have a low waterholding capacity. The average soil organic matter (SOM) is 1 to 3%. Surface runoff is very slow. 

Drying of the surface is fast and soil-blowing hazard is high.

Characteristic Soils Are: Flugle, Mespun, Otero, Palma, Trail

Parent Materials:

 Kind: Eolian deposits

 Origin: Sandstone and Shale

Surface Texture: (1) Loamy fine sand 

(2) Fine sandy loam 

(3) Loamy sand 

Subsurface Texture Group: Loamy

Minimum Maximum

Surface Fragments <=3" (% Cover):

Surface Fragments > 3" (% Cover):

Subsurface Fragments <=3" (% Volume): 15 35

Subsurface Fragments > 3" (% Volume): 15 35

Drainage Class: Well drained To Excessively drained 

Permeability Class: Moderately slow To Rapid 

Minimum Maximum

Depth (inches): 60 72

Electrical Conductivity (mmhos/cm): 0 4

Sodium Absorption Ratio:

Calcium Carbonate Equivalent (percent):

Soil Reaction (1:1 Water): 6.1 8.4

Soil Reaction (0.01M CaCl2):

Available Water Capacity (inches): 3.0 6.0

States and Community Phases

Ecological Dynamics of the Site 

A state-and-transition model was developed using archeological and historical data, professional 

experience, and scientific studies. A brief summary of the information used is included here. The 

model was refined using professional experience and expert knowledge gained from 1990 to 2012. 

Scientific knowledge gained from long term and expanded studies (Shaver 2010b) and scientific and 

historical literature was also used.
January 2013 Page 82

In the early 1600's Gran Quivira (Jumano Pueblo) may have had as many as 1,000 inhabitants. These 

people traded with the Pueblo peoples in the Rio Grande valley to the west, the Comanche in the east 

and the Apache in the south. Vivian (1961) quotes Spanish documents in which Nicolas de Aguilar, 

a Spanish “Encomendero”, in 1663 states: 

“It has never been possible to keep livestock in said Pueblo because there is not water, for what there 

is comes only from wells which are a quarter of a league (~850 – 900 m) from the place, forty or 

fifty estados (~70 - 85 m) in depth. And therefore it costs a great deal to get water and it makes a lot 

of work for the Indians in obtaining it, and the wells are exhausted and there is an insufficient water 

supply for the people, for their lack of water is so great they are accustomed to save their urine to 

water the land and to build walls.” 

Excavations of the ruin of Gran Quivira show that over half of the animal bones found were 

blacktailed jackrabbit (Lepus californicus) and pronghorn antelope (Antilocapra americana). Desert 

cottontail rabbits (Sylvilagus audubonii), domestic and wild sheep (Ovis spp), mule deer (Odocoileus

hemionus), domestic horse (Equus caballus) and bison (Bison bison) were also present in much 

smaller amounts. Trace amounts of bones were found from various birds, cougar (Felis concolor), 

gray fox (Urocyon cinereoargenteus) and black-tailed prairie dog (Cynomys ludovicianus) (Vivian 

1961). The indication is that native herbivory prior to European influence, and even after Spanish 

reconquest and colonization in 1692, was mainly by lagomorphs and pronghorn antelope.

This area has historically been described as grassland with few junipers dotting the landscape. Oneseed juniper (Juniperus monosperma) was confined to ridge tops and the foot slopes of adjoining 

mountains (Bandelier 1884, Horgan 1954, McLeullough 1982). While not specific to the peoples of 

the Jumano Pueblo, Stewart (2002) states that the Apache, Navajo and Pueblo inhabitants of this 

area used fire as a management tool for hunting, to draw game into the area, for clearing crop fields 

and to increase the yield of grass seeds used for grain. Other authors support this contention with fire 

frequencies for the area ranging from 4 – 20 years (Allen 1989, Baisan and Swetnam 1997, Frost 

1998). This fire regime would be frequent enough to create and maintain a grassland aspect and 

herbaceous dominated plant community. Wright (1990) indicated that fires every 10 – 30 years kept 

juniper on shallow, rocky, rough places. He also indicated that non-sprouting junipers less than four 

feet tall are readily killed by ground fires of herbaceous fuel. Dwyer and Pieper (1967) show that 

one-seed juniper less than four feet tall were killed with a ground fire. 

Given this description, it is very unlikely that large numbers of domesticated or native herbivores

were grazing in this region until the Anglo expansion into New Mexico occurred in the mid 1800's. 

It is estimated that there were several hundred thousand head of sheep in New Mexico from 1788 

onward to about 1870 (Denevan 1967). Domestic livestock grazing increased rapidly following 

Anglo expansion. From 1870 to 1890 sheep numbers increased to around 5 million state wide 

(Denevan 1967). Cattle numbers were approximately 137,000 in 1880 and reached 1.3 million by 

1889. Numbers of sheep and cattle increased from the 1880s to the end of World War I and have 

been decreasing since 1920 (Schickedanz 1980). In 1906 there were approximately 1 million cattle 

and 6 million sheep in New Mexico. By 1979, cattle had increased to 1.5 million, while sheep had 

decreased to 600,000. This historical increase in livestock numbers undoubtedly impacted the natural 

disturbance regime of frequent fires by lessening the frequency, and increasing the pre-Anglo low 

levels of herbivory. Many studies have linked juniper expansion to increased livestock and decreased 

fire frequency (Jameson 1962, Johnsen 1962, Arnold 1964, Arnold et al. 1964, White 1965, Jameson 

1967, Jameson 1970, Clary and Jameson 1981, Pieper 1983, Miller and Wigand 1994, Allen and 

Breshears 1998, Lanner and Van Devender 1998). 
January 2013 Page 83

Historical information and existing data (Shaver 2010a, 2010b) indicate these physical and 

environmental conditions have led to ecological dynamics that have produced an ecological site 

characterized by tall and mid warm season grasses. Warm and cool season mid and short grasses

were the sub-dominant plant functional groups on this ecological site. Observation indicates the forb 

component was variable depending on timing and amount of precipitation and with the season. The 

woody plant component was both spatially and temporally variable depending on time since the last 

fire, but was always a minor component of the plant community (Allen 1989, Baisan and Swetnam 

1997, Frost 1998, Stewart 2002). The production of a continuous fine fuel load and resulting fires 

were important negative feedbacks that limited the abundance of the woody components and 

maintained an herbaceous dominance on the site. The resilience of the ecological site was 

maintained by the continued input of organic matter primarily from root turnover of the herbaceous

species (Gill and Jackson 2000) and herbaceous litter. Development and maintenance of stable soil 

aggregates is a function of the interactions of soil microbes and organic inputs, and the continuation 

of herbaceous litter production and root turnover. The resulting soil aggregate stability is integral to 

the negative feedback mechanisms responsible for ecological resilience. High soil aggregate stability 

provides optimal rates of infiltration, water holding capacity, aeration and mineral cycling, which 

maintains herbaceous production. Herbaceous production provides for a uniform distribution of soil 

nutrients and water throughout the soil profile (Schlesinger et al. 1990). This uniform distribution 

maintains uniform organic matter inputs (Kemper and Koch 1966, Tisdall and Oades 1982, 

Goldberg et al. 1988, Topp et al. 1996, Bird et al. 2007) and strengthens the resilience of the site to 

the periodic fires that were necessary to control the establishment and increase of one-seed juniper. 

As European settlement progressed, domestic livestock numbers increased rapidly and the resulting 

grazing pressure decreased fine fuel for fires (Savage and Swetnam 1990, Swetnam et al. In Press). 

One-seed juniper increased in density and cover with an increase in the time since the last fire, also 

causing a decrease in herbaceous production (Jameson 1962, Johnsen 1962, Arnold 1964, Arnold et 

al. 1964, White 1965, Jameson 1967, Jameson 1970, Clary and Jameson 1981, Pieper 1983, Miller 

and Wigand 1994, Allen and Breshears 1998, Lanner and Van Devender 1998). Decreased 

herbaceous production caused a decline in organic matter inputs, resulting in lowered soil aggregate 

stability (Tisdall and Oades 1982). As herbaceous production and cover were reduced and bare 

ground and erosion increased, fine fuels for fire became inadequate and resilience was weakened. 

Soil moisture, nutrients and organic matter decreased in the interspaces and increased under the trees 

and shrubs (Padien and Lajtha 1992, Davenport et al. 1996, Weltzin and McPherson 1997, Breshears 

and Barnes 1999, Reid et al. 1999, Bird et al. 2002, McIntyre and Tongway 2005, Bestelmeyer et al. 

2006, Bird et al. 2007). Decreased herbaceous production and organic matter in the interspaces 

likely decreased soil aggregate stability, infiltration, water holding capacity and mineral cycling. As 

the redistribution of resources continued the strength of the feedback mechanisms began to shift and 

site resilience decreased. 

Plant interspaces continued to lose resources resulting in a lower proportion of root biomass 

available for annual turnover (Gill and Jackson 2000) further concentrating resources under the oneseed juniper. Gill and Jackson (2000) discussed the difference in root turnover from grasses and 

shrubs and state that the turnover from woody plants is much less proportionately than that of 

grasses. When juniper increases, the resulting reallocation of underground resources is well 

documented (Padien and Lajtha 1992, Davenport et al. 1996, Weltzin and McPherson 1997, 

Breshears and Barnes 1999, Reid et al. 1999, Bird et al. 2002, McIntyre and Tongway 2005, 

Bestelmeyer et al. 2006, Bird et al. 2007). This change develops abiotic feedback mechanisms 

controlled by wind and water erosion, leading to desertification that builds very strong resilience 
January 2013 Page 84

feedback mechanisms and resistance to change (Schlesinger et al. 1990, Whisenant 1999, 

Bestelmeyer et al. 2006).

State and Transition Diagram

Reference State 1.0

The reference state consist of two community phases, 1.1 and 1.2, each being maintained by frequent 

fire (6 to 20 year fire frequency) and weather fluctuations (drought and wet years). Community 

phase 1.1 is designated as the reference community phase while community 1.2 is the most at-risk 

community phase when bare ground increases and organic matter inputs decline.
January 2013 Page 85

Indicators: High perennial grass cover and production. Litter accumulation. 

Feedbacks: Organic matter inputs allow for increased soil moisture, production, root turnover and 

litter increasing soil surface stability. 

Reference Community Phase 1.1

Artemisia filifolia/Andropogon hallii-Schizachyrium scoparium (Sand Sagebrush/Sand 

Bluestem-Little Bluestem)

Reference Community Phase 1.1

The description for community phase 1.1 is based on data from medium and high intensity 

sampling. This community phase is characterized by an open stand of pinyon and/or one-seed 

juniper with grass understory. The overstory tree canopy cover ranges from 1 to 10 percent. Both 

warm/cool season mid and tall grasses characterize the understory grasses. Sand bluestem and little 

bluestem are the most common and abundant grass species in the understory. Sand sagebrush is the 

most common and abundant understory shrub. Other shrub species occur in minor amounts. Halfshrubs and forbs are a minor part of the community phase. The open stand of pinyon and juniper at 

one time may have been maintained by natural fire. The foliar cover for overstory tree is less than 8 

percent (see Plant Species Composition table). 

Other uncommon grasses that could appear on this site include: switchgrass, mesa dropseed, alkali 

sacaton, threeawns, sandhill muhly, purple lovegrass, ring muhly, bottlebrush squirreltail, western 

wheatgrass, plains bristlegrass, green sprangletop, littleseed ricegrass, and prairie junegrass. 

Other woody plants include: feather dalea, cholla, ephedra, winterfat, rubber rabbitbrush, broom 

snakeweed, fourwing saltbush, yucca, and algerita. Other forbs include: tansymustard, locoweed, 

redstem milkvetch, scarlet globemallow, mariola, sand verbena, goldenrod, and threadleaf groundsel.
January 2013 Page 86

Reference Community Phase Plant Species Composition:

Reference Community Phase Composition Table grouped by Growth Form, Functional Group 

membership, annual production, foliar cover, and constancy and canopy cover for common species 

found in the reference community phase. Production and foliar cover values are derived from high 

intensity sampling. Canopy cover values derived principally from medium intensity sampling.

Annual 

Production 

(lbs/ac)

Foliar 

Cover

Constancy/Canopy 

Cover

Sample Number: 10

Group 

Number

Functional

Group Name

Common 

Name Symbol Scientific Name Low High Low High Constancy

Canopy 

Cover

Range Mean

1-Tree 35 75 1-10 5

one-seed juniper JUMO Juniperus 

monosperma

35 75 3 8 100 1-7 5

pinyon pine PIED Pinus edulis 35 75 80 1-3 1

Shrub/Vine 0 – 5 3

2 – Evergreen Shrubs 35 75

sand sagebrush ARFI2 Artemisia filifolia 35 75 2 3 100 5 – 15 10

fourwing saltbush ATCA2 Atriplex canescens 10 55 1 3 80 1 - 15 5

algerita MATR3 Mahonia trifoliolata 10 35 0 1 50 1 - 3 1

yucca spp. YUCCA Yucca 10 25 0 1 30 1 - 3 1

3 – Deciduous Shrubs 32 75

oak spp. QUERC Quercus 22 40 0 3 50 1 - 10 5

skunkbush sumac RHTR Rhus trilobata 10 35 0 2 50 1 - 3 1

thistle cholla CYDA4 Cylindropuntia 

davisii 0 30 0 1 50 1 - 3 1

Grass/Grasslike 1-60 50

4 –Warm Season Tall Grasses, Dense 250 400

sand bluestem ANHA Andropogon hallii 200 285 100 10 – 30 20

little bluestem SCSC Schizachyrium 

scoparium 250 425 100 10 – 40 30

Indiangrass (yellow) SONU2 Sorghastrum nutans 50 75 80 1 – 5 3

big bluestem ANGE Andropogon gerardii 105 160 80 5 – 20 10

5 –Warm Season Tall Grasses, Open 50 250

cane bluestem BOBA3 Bothriochloa 

barbinodis 100 150 30 5 - 20 10

prairie sandreed CALO Calamovilfa 

longifolia 25 100 10 1 - 5 3

6 - Mid Grasses 40 100

sideoats grama BOCU Bouteloua 

curtipendula 40 100 40 1 – 5 3

7 – Other Mid Grasses 10 200

spike dropseed SPCO4 Sporobolus 

contractus

50 125 40 1- 5 3 

sand dropseed SPCR Sporobolus 

cryptandrus 40 160 40 1 - 5 3

giant dropseed SPGI Sporobolus giganteus 24 60 40 1 - 5 3
January 2013 Page 87

8 -- Other Mid Grasses 105 158

blue grama BOGR2 Bouteloua gracilis 0 80 30 1 - 3 1

needleandthread HECO26 Hesperostipa comata 32 53 30 1 - 3 1

New Mexico feathergrass HENE5 Hesperostipa 

neomexicana 0 26 30 1 - 3 1

galleta PLJA Pleuraphis jamesii 0 40 20 1 - 3 1

9 -- Other Mid Grasses 5 20

black grama BOER4 Bouteloua eriopoda 53 105 60 1 - 5 3

10 – Other Mid Grasses 5 20

Indian ricegrass ACHY Achnatherum 

hymenoides 5 20 60 1 - 3 1

11 - Forb 0 55 1 – 5 3

winterfat KRASC Krascheninnikovia 5 10 100 1 - 3 2

sand verbena ABRON Abronia 0 10 80 1 - 3 1

wooly loco ASMO7 Astragalus 

mollissimus 0 3 50 1 - 3 1

broom snakeweed GUSA2 Gutierrezia sarothrae 0 40 50 1 - 5 3

Community Pathway 1.1a

Community Pathways: Characterized by time since last fire and fluctuations in weather. 

Community pathway 1.1a is driven by time since last fire or by a series of dry years followed by wet 

years. As time since the last fire increases, the opportunity for one-seed juniper seedling 

establishment increases. A series of dry years that decreases herbaceous production, cover and 

organic matter input into the soil, when followed by a wet cycle allow opportunity for one-seed 

juniper seed germination and establishment, and the development of community phase 1.2.

One-seed juniper seedlings may increase in response to disturbances such as a series of dry years 

followed by wet years, or an interruption or delayed period from the normal fire frequency. A 

normal fire frequency allows ground fires to remove one-seed juniper seedlings and other 

established woody plants less than 1.5 meter in height. The site shifts from community phase 1.2 

back to reference community phase 1.1.

As time since the last fire increases, the one-seed juniper increases in size and density and the site 

moves toward community phase 1.2. The negative feedback mechanisms associated with site 

resilience are weakened. Positive feedbacks associated with degradation increase, making 

community phase 1.2 the at-risk community phase in the Reference State.
January 2013 Page 88

Total Annual Production:

Total Annual Production (lbs/ac)

Year

Growth Form Unfavorable Normal Favorable

Grass/Grasslike 475 700 1125

Forb 80 145 240

Shrub/Vine 5 20 35

Tree 75 150 300

Total: 635 1015 1700

Vertical Structure (percentages for each species are canopy cover)_ 

Species

Vertical Strata

Tree (> 

5m height)

Shrub (> 

0.5m to 5m 

height)

Herb (< 

0.5m 

height)

One-seed 

juniper

1-2% 1-6%

Pinyon pine 0-1% 1-3%

Sand sagebrush 3-11% 2-4%

Oak spp. 1-8% 0-2%

Fourwing 

saltbush

1-11% 0-4%

Sand bluestem 2-5% 8-25%

Little bluestem 3-10% 7-40%

Big bluestem 2-5% 3-15%

Cane bluestem 1-5% 4-15%

Indiangrass 1-3% 2-7%
January 2013 Page 89

Horizontal Structure

Ground Surface Cover Minimum Maximum

Basal Cover

Litter

7%

10%

14%

20%

Surface Fragments > 0.25” and <= 3”

Surface Fragments > 3”

Bedrock

Water

Bare Ground 35% 40%

Biological Soil Crust
January 2013 Page 90

Community Phase 1.2

Warm season mid and tall grasses and one-seed juniper < 4' tall

This community phase is provisional because a plant species list and plant abundance data are 

lacking. 

Community phases, 1.1 and 1.2, are both maintained by frequent fire (6 to 20 year fire frequency) 

and weather fluctuations (drought and wet years). 

Indicators: High perennial grass cover and production. Litter accumulation. 

Feedbacks: Organic matter inputs allow for increased soil moisture, production, root turnover and 

litter increasing soil surface stability.

The average surface soil stability rating in community phase 1.2 was 3.7, well within the range for 

the Reference State, but the average subsurface soil stability rating was 1.9, at the low end of the 

Reference State range.

The following data is based on summarizing nine transects. Canopy gaps >200 cm and basal gaps 

>200 cm were 20% and 25% respectively, both within the range for the Reference State. Juniper 

foliar cover averaged 12%, inside the range of the Reference State but outside the range of the 

reference community phase. This data seems to indicate that this community phase 1.2 is at risk of 

crossing an ecological threshold.

Community Pathway 1.2a

This community pathway is driven by fire. Short fire frequency intervals allow ground fires that 

cause high mortality of one-seed juniper seedlings and established plants less than 1.5 meters tall. 

Community pathway 1.2a represents the feedback mechanisms that maintain the resilience of the 

Reference State. As time since the last fire increases, the one-seed juniper in community phase 1.2 

increases in size and density and the negative feedback mechanisms associated with site resilience 

weaken. Positive feedbacks associated with degradation increase, making this the at-risk community 

phase in the Reference State.

As the one-seed juniper increases in size and density, soil and water resources begin to concentrate 

under and around the juniper plants, reducing herbaceous production in the interspace areas. This 

reduction in herbaceous production increases gap size, reduces fine fuel for fires and reduces organic 

matter inputs for soil aggregate stability. This agrees with Archer (1989) who suggested that changes 

to natural disturbance regimes might cause increases in woody plants. Bestelmeyer et al. (2006) 

showed that as the size of bare patches increased, aggregate stability decreased. Shaver (2010b) 

showed that the results of herbicide treatment on these treated plots, although long lasting, were 

beginning to decline. This suggests that without the reintroduction of fire, the feedback mechanisms 

of increased organic matter inputs were not able to limit the increase or encroachment of one-seed 

juniper onto the site. 

The resilience of the Reference State was weakened and the processes of infiltration, nutrient 

cycling, aggregate stability and annual production were nearing a threshold into the Juniper State. 
January 2013 Page 91

Threshold values from the Reference State to the Juniper State for surface soil stability were 

between 3.4 and 2.8 and for subsurface soil stability at 1.8. Once the threshold is crossed, along the 

transition (T1a) the positive feedbacks for change become negative feedbacks strengthening the 

resilience of the Juniper State.

Transition - T1A

The triggers for this transition are the elimination of fire, and overgrazing, causing increased oneseed juniper canopy. The threshold values are as follows: 

Increasing bare ground > 20%, and an increase in juniper canopy cover to 15%. 

Slow variables and triggers for this transition are the elimination of fire attributable to decrease in

fine fuels. The increasing canopies of juniper restrict or limit sunlight and moisture critical for 

herbaceous cover. The threshold values are: surface soil stability < 3.4, basal cover > 5%, juniper 

foliar cover > 15% and juniper > than 4' tall.

Juniper State 2.0

Juniper canopy cover controls the soil moisture, herbaceous production and organic matter inputs. 

Management practices applied to maintain current canopy cover and herbaceous production. 

Manipulation of shrub/tree species and prescribed fire and grazing management planned to maintain 

or improve warm season mid and tall grass production. 

Indicators: Juniper foliar cover>15%, bare ground 35 to 50% summarized from line transect.

Feedbacks: Juniper use of soil moisture, decreasing herbaceous production, decreasing organic 

matter inputs. 

At-risk Community Phase: Either community phase 2.1 or 2.2 is at risk if juniper seedlings increase 

and canopy cover increases.

Community Phase 2.1

Juniperus monosperma/Artemisia filifolia/Schizachyrium scoparium (One-seed Juniper/Sand 

Sagebrush/Little Bluestem)
January 2013 Page 92

The description for community phase 2.1 is based on data from medium and high intensity sampling. 

This community phase consists of a tree overstory dominated by one-seed juniper (canopy cover 20-

40%) and pinyon pine (canopy cover 5-10%). Sand sagebrush is the most common and abundant 

shrub species in the understory (canopy cover 5 -15%). The herbaceous layer contains a mix of tall 

and mid grass species with little bluestem (canopy cover 3-15%) being the most common and 

abundant grass species (see Plant Species Composition table). 

Plant Species Composition:

Plant Species Composition Table grouped by Growth Form, Functional Group membership, annual 

production, foliar cover, and constancy and canopy cover for common species found in community 

phase 2.1. Foliar cover derived from high intensity sampling. Canopy cover values derived 

principally from medium intensity sampling.

Annual 

Production

(lbs/ac)

Foliar 

Cover

Constancy/Canopy Cover

Sample Number: 15

Group

Number

Functional

Group 

Name

Common 

Name Symbol Scientific Name Low High Low High Constancy

Canopy Cover

Range Mean

1-Tree 15 - 45 25

one-seed juniper JUMO Juniperus monosperma 35 75 18 28 100 20 - 40 35

pinyon pine PIED Pinus edulis 20 60 100 5 -10 8

Shrub/Vine 5 - 15 10

2 – Evergreen Shrubs 35 75

sand sagebrush ARFI2 Artemisia filifolia 35 75 2 3 100 5 - 15 10

Community Phase 2.1
January 2013 Page 93

3 – Deciduous Shrubs 32 75

oak spp. QUERC Quercus 22 40 0 3 50 1 - 10 5

skunkbush sumac RHTR Rhus trilobata 10 35 0 2 50 1 - 3 1

Grass/Grasslike 1 - 30 15

4 –Warm Season Tall Grasses, Dense 100 220

sand bluestem ANHA Andropogon hallii 10 30 80 1 - 5 3

little bluestem SCSC Schizachyrium scoparium 50 85 100 3 - 15 10

5 –Warm Season Tall Grasses, Open 0 30

cane bluestem BOBA3 Bothriochloa barbinodis 0 15 30 1 - 3 1

prairie sandreed CALO Calamovilfa longifolia 0 25 10 1 - 3 1

6 -Mid Grasses 0 40

sideoats grama BOCU Bouteloua curtipendula 0 40 40 1 - 3 1

7 –Other Mid Grasses 10 200

sandhill muhly MUPU2 Muhlenbergia pungens 10 50 60 1 - 3 1

8 – Other Mid Grasses 105 158

blue grama BOGR2 Bouteloua gracilis 20 40 60 1 - 3 1

9 – Other Mid Grasses 5 20

perennial threeawn ARIST Aristida 15 45 60 1 - 5 3

sixweeks grama BOBA2 Bouteloua barbata 0 15 50 0 - 3 1

10 – Other Mid Grasses 5 20

Indian ricegrass ACHY Achnatherum hymenoides 0 10 60 1 - 3 1

spike dropseed SPCO4 Sporobolus contractus 0 30 40 1 - 3 1 

sand dropseed SPCR Sporobolus cryptandrus 0 40 40 1 - 3 1

11 - Forb 0 55 1 – 5 3

Forb, annual 2FA 5 10 100 1 - 3 2

Community Pathway 2.1a

Community Pathway 2.1a is characterized by a decrease in shrub and herbaceous production and 

cover. Shrubs and tall grasses decrease or are eliminated. Juniper canopy cover increases as time 

lengthens since the last fire or since the last management action intended to reduce juniper canopy 

cover. Drought years followed by wet years will allow for increase in juniper establishment.
January 2013 Page 94

Total Annual Production:

Total Annual Production (lbs/ac)

Year

Growth Form Unfavorable Normal Favorable

Grass/Grasslike 330 425 585

Forb 100 300 400

Shrub/Vine 75 155 290

Tree 75 100 125

Total: 580 980 1400

Vertical Structure (percentages for each species are canopy cover)

Species

Vertical Strata

Tree (> 

5m height)

Shrub (> 

0.5m to 5m 

height)

Herb (< 

0.5m 

height)

One-seed 

juniper

8-18% 10-17% 2-5%

Pinyon pine 3-5% 1-3% 1-2%

Sand sagebrush 4-12% 1-3%

Oak spp. 1-5% 0-3% 0-2%

Sand bluestem 0-2% 1-3%

Little bluestem 1-4% 2-11%
January 2013 Page 95

Horizontal Structure

Ground Surface Cover Minimum Maximum

Basal Cover

Litter

5% 10%

Surface Fragments > 0.25” and <= 3”

Surface Fragments > 3”

Bedrock

Water

Bare Ground 35% 50%

Biological Soil Crust
January 2013 Page 96

Community Phase 2.2

One-seed juniper and warm season mid grasses

This community phase is provisional because a plant species list and plant abundance data are 

lacking.

 

Community Phase 2.2

Community Pathway 2.2a

Management actions that decrease juniper canopy and increase herbaceous and shrub production. 

These can include prescribed burning, chemical or mechanical brush management, while grazing 

management is aimed at increasing production.

Transition - T2A

The trigger for this transition is the increase in juniper seedling establishment and/or juniper canopy 

cover. This is caused by management actions that lead to decreased herbaceous production and 

decreased organic matter inputs into the soil. This can also be caused by lack of management actions 

that actively reduce juniper canopy cover. Threshold values for this transaction are: Bare ground > 

50% and soil surface stability <3.0.

Restoration Pathway - R2A
January 2013 Page 97

Removal of juniper foliar cover to < 15% with minimal soil surface disturbance. Grazing 

management that increases herbaceous production and favors the establishment and growth of warm 

season tall and mid grasses is essential for success of this pathway.
January 2013 Page 98

Eroded State 3.0

Active wind and water erosion taking place. 

Indicators: Closed juniper canopy, soil surface stability indicators < 3.0, active wind and water 

erosion prevalent. 

Feedbacks: Juniper use of all available moisture, elimination of organic matter inputs, decrease in 

soil surface stability

Community Phase 3.1

One-seed juniper

This community phase is provisional because a plant species list and plant abundance data are 

lacking.

Community Phase 3.1 

Restoration Pathway - R3A

Management and restoration practices planned must decrease juniper foliar cover to < 30% with 

little or no surface disturbance. Grazing management must plan for increasing herbaceous 

production and allow for litter accumulation to improve organic matter inputs to stabilize soil 

surface.
January 2013 Page 99

Restoration Pathway - R3B

Management and restoration practices planned must decrease juniper foliar cover to < 15% with 

little or no surface disturbance. Grazing management must plan for increasing herbaceous 

production and allow for litter accumulation to improve organic matter inputs to stabilize soil 

surface.

Ecological Site Interpretations

Animal Community:

Habitat for Wildlife: 

This ecological site provides habitat which supports a resident animal community that is 

characterized by mule deer, bobcat, coyote, blacktailed jackrabbit, desert cottontail, Stephen’s 

woodrat, rock squirrel, pinyon mouse, scrub jay, blacktailed rattlesnake, and red spotted toad. The 

woody vegetation provides nesting opportunities for many bird species.

Plant Diet Preferences by Animal Kind: Months

Animal Kind: Mature Cow Cattle 

Common Name Scientific Name Plant Part J F M A M J J A S O N D

Indian ricegrass Achnatherum hymenoides Entire plant P P P P P P P P P P P P

big bluestem Andropogon gerardii Entire plant

sand bluestem Andropogon hallii Entire plant

sideoats grama Bouteloua curtipendula Entire plant P P P P P P P P P P P P

prairie sandreed Calamovilfa longifolia Entire plant

sunflower Helianthus annuus Entire plant U U U U U D D D U U U U

needleandthread Hesperostipa comata Entire plant D D P P P D D D D D D D

New Mexico feathergrass Hesperostipa neomexicana Entire plant D D P P P D D D D D D D

little bluestem Schizachyrium scoparium Entire plant D D D P P P P D D D D D

Indiangrass (yellow) Sorghastrum nutans Entire plant

Animal Kind: Mature Deer 

Common Name Scientific Name Plant Part J F M A M J J A S O N D

Indian ricegrass Achnatherum hymenoides Entire plant U U P P P U U U D D D U

Bigelow's sagebrush Artemisia bigelovii Leaves

sand sagebrush Artemisia filifolia Leaves

sideoats grama Bouteloua curtipendula Entire plant P P P P P P P P P P P P

black grama Bouteloua eriopoda Entire plant P P P P P P P P P P P P

wild buckwheat Eriogonum Entire plant U U D D D D D D U U U U

sunflower Helianthus annuus Entire plant U U U U U D D D U U U U

oak spp. Quercus Leaves

skunkbush sumac Rhus trilobata Leaves P P P D D D D D D P P P

Animal Kind: Mature Goats 

Common Name Scientific Name Plant Part J F M A M J J A S O N D

Indian ricegrass Achnatherum hymenoides Entire plant U U P P P U U U D D D U

Bigelow's sagebrush Artemisia bigelovii Leaves

sand sagebrush Artemisia filifolia Leaves

sideoats grama Bouteloua curtipendula Entire plant P P P P P P P P P P P P

black grama Bouteloua eriopoda Entire plant P P P D D D D D D D P P

wild buckwheat Eriogonum Entire plant U U D D D D D D U U U U

sunflower Helianthus annuus Entire plant U U U U U D D D U U U U
January 2013 Page 100

oak spp. Quercus Leaves

skunkbush sumac Rhus trilobata Leaves P P P D D D D D D P P P

Animal Kind: Mature Sheep 

Common Name Scientific Name Plant Part J F M A M J J A S O N D

Indian ricegrass Achnatherum hymenoides Entire plant P P P P P D D D D D D P

Bigelow's sagebrush Artemisia bigelovii Leaves

sideoats grama Bouteloua curtipendula Entire plant P P P P P P P P P P P P

black grama Bouteloua eriopoda Entire plant P P P D D D D D D D P P

wild buckwheat Eriogonum Entire plant U U D D D D D D U U U U

sunflower Helianthus annuus Entire plant U U U U U D D D U U U U

oak spp. Quercus Leaves

skunkbush sumac Rhus trilobata Leaves P P P D D D D D D P P P

Legend: P = Preferred; U = Undesirable; D = Desirable

Hydrology Functions:

Soils were originally assigned to hydrologic soil groups based on measured rainfall, runoff, and 

infiltrometer data (Musgrave 1955). Since the initial work was done to establish these groupings, 

assignment of soils to hydrologic soil groups has been based on the judgment of soil scientists. 

Assignments are made based on comparison of the characteristics of unclassified soil profiles with 

profiles of soils already placed into hydrologic soil groups. Most of the groupings are based on the 

premise that soils found within a climatic region that are similar in depth to a restrictive layer or 

water table, transmission rate of water, texture, structure, and degree of swelling when saturated, will 

have similar runoff responses. Four (4) Hydrologic Soil Groups are recognized (A-D). For specific 

definitions of each hydrologic soil group see the National Engineering Handbook, Chapter 7, Part 

630 Hydrology, or visit: http://policy.nrcs.usda.gov/OpenNonWebContent.aspx?content=22526.wba 

The hydrologic soil groups are based on the following factors:

• intake and transmission of water under the conditions of maximum yearly wetness 

(thoroughly wet)

• soil not frozen

• bare soil surface

• maximum swelling of expansive clays 

The slope of the soil surface is not considered when assigning hydrologic soil groups. In its simplest 

form, hydrologic soil group is determined by the water transmitting soil layer with the lowest 

saturated hydraulic conductivity and depth to any layer that is more or less water impermeable (such 

as a fragipan or duripan) or depth to a water table (if present). 

The runoff curve numbers are determined by field investigations using hydrologic cover conditions 

and hydrologic soil groups.

Hydrologic Interpretations

Soil Series Hydrologic Group

Flugle B

Mespun A

Otero B
January 2013 Page 101

Palma B

Trail A

Recreational Uses:

This ecological site offers fair to good potential for hiking, horseback riding, nature observation, 

photography, camping and picnicking. Hunting for mule deer is fair and trapping for fur-bearing 

animals is good.

Wood Products:

This ecological site has a potential for wood products that are limited to fuelwood and fencing 

material. Although this is a limited potential, it may well be very economical. If this ecological site 

transitions to the juniper state or the eroded state as much as six to ten cords of fuelwood per acre 

may be harvested. Harvesting should be selective and done by hand cutting. 

Other Products:

Grazing:

This ecological site is suitable for grazing by all kinds and classes of livestock during all seasons of 

the year. Because of the ecological site’s potential to produce woody plants, it is very suited to 

browsing animals. Desirable forage plants are big bluestem, little bluestem, Indiangrass, sideoats 

grama, black grama, and New Mexico feathergrass, 

Supporting Information

Associated Sites:

Site Name Site ID Site Narrative

Sand Hills 13-16” P.Z. 045CY099 Sand Hills ecological site will occur adjacent to and in 

association with Deep Sand Savanna ecological site. 

Sand Hills may occur as small to large islands 

scattered throughout the Deep Sand Savanna sites. 

Deep Sand Savanna sites will have greater production.

Loamy Sand 13-16” P.Z. 045CY092 Loamy Sand ecological sites typically occur at a lower 

position on the landscape. 

Similar Sites:

Site Name Site ID Site Narrative

Deep Sand 12-16” P.Z. 045CY900 Deep Sand ecological site is very similar to the Deep 

Sand Savanna ecological site in plant community 

composition with production generally greater on 

Deep Sand Savanna sites. Deep Sand slopes may range 

from 1 to 8 % with the Deep Sand Savanna sites 

ranging from 1 to 5% and slightly undulating.
January 2013 Page 102

Inventory Data References:

Inventory data is based upon medium-intensity and high-intensity sampling of locations representing 

the ecological site concept. Other information incorporated into the ESD is from long-term 

observation of well-managed ranges, range inventory data, scientific studies, and numerous 

historical accounts of vegetation present at time of settlement. Several years of clipping data and 

numerous old range inventories have been reviewed (old New Mexico NRCS - Area 8 dated 

06/18/75, and old Texas NRCS Area 21 dated 03/21/79). Photos by Joe Bob Quail.

Agency/State Correlation:

This ecological site has been correlated with the following states and/or agencies: Forest Service 

Southwest Region, BLM New Mexico, New Mexico/Texas NRCS.

Type Locality:

State: NM

County: Lincoln

Socorro

Torrance

Other References:

Data collection for this ecological site was done in conjunction with the progressive soil surveys 

within the Pecos-Canadian Plains and Valleys 70 Major Land Resource Area of New Mexico. This 

ecological site has been mapped and correlated with soils in the following soil surveys: Chaves, De 

Baca, Guadalupe, Lincoln, Sna Miguel, Santa Fe, Torrance.

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Rangeland Health Reference Sheet:

Reference Sheet

Author(s)/participant(s): Identify one or more authors

Contact for lead author: Identify the state and/or MLRA contact

Date: 3/12/2012 MLRA: 045C 

Ecological Site: Deep Sand Savanna 13-16 P.Z. Artemisia filifolia/Andropogon halliiSchizachyrium scoparium, (sand sagebrush/sand bluestem-little bluestem)

045CY999 This must be verified based on soils and climate and plant indicator species (see 

Ecological Site Description). Current plant community cannot be used solely to identify the 

ecological site. 

Composition (indicators 10 and 12) based on: X Annual Production, Foliar 

Cover, Biomass 

Indicators. For each indicator, describe the potential for the site. Where possible, (1) use numbers, 

(2) include expected range of values for above- and below-average years for each community and 

natural disturbance regimes within the reference state, when appropriate and (3) cite data. Continue 

descriptions on separate sheet. 

1. Number and extent of rills: None on slopes less than 5%, and increasing only slightly beyond 

that range. After wildfires, extended drought, high-intensity summer thunderstorms, or 

combinations of these disturbances, rills may double in number. Healing should be rapid 

(within one year) after such an event. 

2. Presence of water flow patterns: Water flow patterns may be few, but where present flow 

patterns are short and not connected. Flow patterns should only be present following intense 

storm events. Numerous obstructions can alter flow paths. Flow pattern length and numbers 

may double after wildfires, extended drought or combinations of these disturbances. 

3. Number and height of erosional pedestals or terracettes: No pedestals or terracettes caused 

by water should occur on this site at reference condition. Wind caused pedestals are rare and 

only would be on the site after wildfires, extended drought or combinations of these 

disturbances. Slightly more pedestals would be expected where steeper sites deliver additional 

water from off-site after high-intensity summer thunderstorms. These would show signs of 

healing within 1 year after severe storm event. 

4. Bare ground from Ecological Site Description or other studies (rock, litter, standing dead, 

lichen, moss, plant canopy are not bare ground): Expect 35 – 40% bare ground (less than 2
January 2013 Page 107

feet in diameter) in the intervals between natural disturbance events. Bare ground would be 

expected to increase to 60% the first year following wildfire and then decrease to pre fire levels 

within 2 to 5 years. 

5. Number of gullies and erosion associated with gullies: Drainages where present are 

stabilized with native vegetation and should show no signs of active erosion. 

6. Extent of wind scoured, blowouts and/or depositional areas: Wind erosion is minimal to 

nonexistent. Significant wind erosion would only be present following wildfire, extended 

drought or combinations of these disturbances. Wind scour, blowouts and/or depositional areas 

should be rare and only associated with disturbances (e.g. small mammal burrows, resting 

areas). 

7. Amount of litter movement (describe size and distance expected to travel): Litter should be 

evenly distributed across site. Litter movement consists primarily of redistribution of fine litter 

(herbaceous plant material) in flow patterns for distances of not more than 1 meter. Litter 

movement over 5 feet may occur after wildfires, extended drought or combinations of these 

disturbances. Amounts and size of material moved may increase after high-intensity summer 

thunderstorms. 

8. Soil surface (top few mm) resistance to erosion (stability values are averages - most sites 

will show a range of values): Stability class rating at 3.5 to 4.5 in interspaces at soil surface. 

Under plant shrub or grass plant canopy values will be 4 to 5. Values should be at the high 

range for fine textured soils. Soils with a surface layer of very coarse sand to fine gravel have 

stability values that range from 3.0 – 4.0.

9. Soil surface structure and SOM content (include type and strength of structure, and Ahorizon color and thickness): The average Soil Organic Matter (SOM) 1 to 3%. Structure of 

the soils surface horizon is weak granular. Soil surface is stable and evidence of movement is 

very slight.

10. Effect on plant community composition (relative proportion of different functional 

groups) and spatial distribution on infiltration and runoff: Grasses should be uniformly 

distributed and runoff from sites is generally low. Surface runoff is slow and available water 

holding capacity is low. Diverse grass, forb, shrub functional/structural groups and diverse root 

structure/patterns reduces raindrop impact slows overland flow providing increased time for 

infiltration to occur. Extended drought reduces short and mid bunchgrasses causing decreased 

infiltration and increased runoff. This condition will self-correct in 2 to 5 years following 

disturbance unless a threshold has been crossed. 

11. Presence and thickness of compaction layer (usually none; describe soil profile features 

which may be mistaken for compaction on this site): No compaction layer should be present.

There are no soil profile features in the top 9 inches of the soil profile that would be mistaken 

for a management induced soil compaction layer. 
January 2013 Page 108

12. Functional/Structural Groups (list in order of descending dominance by above-ground 

weight using symbols: >>, >, = to indicate much greater than, greater than, and equal to) 

with dominants and sub-dominants and "others" on separate lines:

Dominants: Warm season tall bunchgrasses >> Warm season mid bunchgrass = evergreen 

shrub Subdominants: Warm season mid bunchgrasses > Minor component: evergreen trees > 

forbs = deciduous shrubs. 

13. Amount of plant mortality and decadence (include which functional groups are expected 

to show mortality or decadence): Plant mortality is typically minimal. Expect short/mid 

bunchgrasses mortality/decadence during or following drought. Most of the perennial plants in 

this community are long lived. Extended droughts would tend to cause relatively high 

mortality in short lived species such as bristlegrass. Shrub mortality would be limited to severe 

droughts. The combination of wildfires and extended droughts would cause even more 

mortality for several years following the fire than either disturbance functioning by itself would 

cause. 

14. Average percent litter cover ( %) and depth ( inches): The reference community phase 

averages 10% - 20% litter cover evenly distributed with a litter depth of 1/2 inch. After 

wildfires, extended drought, or combinations of these disturbances, litter cover and depth 

decreases to none immediately after the disturbance (e.g., fire) and dependent on climate and 

plant production increases to post-disturbance levels in one to five growing seasons. 

15. Expected annual production (this is TOTAL above-ground production, not just forage 

production): Unfavorable Production 635 lbs/ac; Normal Production 1015 lbs/ac; Favorable 

Production 1700 lbs/ac. 

16. Potential invasive (including noxious) species (native and non-native). List Species which 

BOTH characterize degraded states and have the potential to become a dominant or codominant species on the ecological site if their future establishment and growth is not 

actively controlled by management interventions. Species that become dominant for only 

one to several years (e.g., short-term response to drought or wildfire) are not invasive 

plants. Note that unlike other indicator, we are describing what is NOT expected in the 

reference state for the ecological site: Juniper, pinyon and oak are the greatest threat to 

dominate this site in the long term after disturbance (primarily following wildfire exclusion but 

also includes high human or herbivore impacts and extended drought). Pinyon and juniper and 

oak are most likely to retain dominance if allowed to alter natural fire regime. 

17. Perennial plant reproductive capability: All plant species should be capable of reproduction 

depending on water regime. All plants should be vigorous, healthy and reproductive depending 

on disturbance (e.g., drought). Plants should have numerous seed heads, vegetative tillers etc. 

The only limitations are weather-related effects, wildfire, and natural disease that may 

temporarily reduce reproductive capability. 

Reference Sheet Approval:

Approval Date

State Range Specialist 7/15/2012
January 2013 Page 109

Site Description Approval:

Authorship:

Author(s) Date

___________________ 24 July 2012

Site Approval:

Name Date Agency Affiliation 

___________________ 24 July 2012 Forest Service

___________________ 24 July 2012 Natural Resources Conservation Service

___________________ 24 July 2012 Bureau of Land Management