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Montana Field Guide

Montana Field Guides

Intermountain Semi-Desert Steppe and Shrubland
Global Name: Intermountain Semi-Desert Steppe & Shrubland

No photos are currently available

Global Rank: G4G5
State Rank: S4?

(see reason below)

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State Rank Reason
The overall abundance and range of this habitat is uncertain. Some decreases in condition and possibly extent are likely to have occurred. Conversely, this habitat may have increased in some areas as it may increase with certain types of disturbance and it may be more tolerant of disturbance than some other rangeland types. Threats to the habitat, beyond invasive species and grazing are likely negligible.
 

General Description
This National Vegetation Classification Group is composed of semi-arid, low shrublands and shrub steppe. In Montana, it is a minor type occurring primarily in the Bighorn Basin and surrounding areas near the Pryor and Bighorn Mtns, and in the Intermountain valleys in the southwestern portion of the state. It occurs on a variety of sites and disturbance regimes and is characterized by an open to moderately dense woody layer composed of woody species such as Green Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa) and Winterfat (Krascheninnikovia lanata). Shrub canopy ranges from 10-60% cover with an herbaceous layer that is usually sparse but ranging from essentially absent to dense. Native perennial grasses are usually present and introduced annual and perennial grasses may be common at some sites. This group otherwise occurs throughout the semi-arid western U.S., including areas in the western Great Plains. Sites generally occur on alluvial fans and flats. They may be poorly drained and intermittently flooded with a shallow or perched water table often within 1 m depth (West 1983e).

This group does not have a similar Ecological System but encompasses some of the types found in the Big Sagebrush Shrubland Ecological System.

Diagnostic Characteristics
Arid Shrubland and Steppe; Intermountain Region; Shrub Cover >10%

Typical Dominants: Yellow Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa), Winterfat (Krascheninnikovia lanata)

Similar Systems

Range
In Montana, this is a minor type likely restricted to the Bighorn Basin and surrounding areas near the Pryor and Bighorn Mtns, and in the Intermountain valleys in the southwestern portion of the state. Winterfat communities within this group are likely limited to the Bighorn Basin.

In Montana, G310 occurs in Level IV Ecoregions: 18b (Bighorn Basin), 43v (Pryor-Bighorn Foothills) and 17aa (Dry Intermontane Sagebrush Valleys).

In Montana, G310 occurs or potentially occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins, 44B - Central Rocky Mountain Valleys, and 46 - Northern and Central Rocky Mountain Foothills

Density and Distribution
Based on 2025 land cover layer. Grid on map is based on USGS 7.5 minute quadrangle map boundaries.



Mapped Distribution by County
Big Horn, Carbon
Based on 2025 land cover layer.

Spatial Pattern
Small Patch

Environment
Sites generally occur on alluvial fans and flats. They may be poorly drained and intermittently flooded with a shallow or perched water table often within 1 m depth (West 1983e). Soils may be shallow to deep, and are generally calcareous, fine-textured (clays to silt-loams), derived from alluvium. Soils may be alkaline and moderately saline (West 1983). The climate is continental, generally hot in the summer and cold in winter with large annual and diurnal temperature variations. Annual precipitation is generally less than 16 inches with high inter-annual variation. Much of the precipitation falls as snow with minimal precipitation during the growing season.

Vegetation
This group occurs as open shrub, dwarf-shrub, or shrub-steppe communities. Dominants are usually Green Rabbitbrush (Chrysothamnus viscidiflorus) Rubber Rabbitbrush (Ericameria nauseosa) and Winterfat (Krascheninnikovia lanata). Shrub canopy ranges from 10-60% cover with an herbaceous layer usually sparse but ranging from essentially absent to dense. The Prickly Pear Cacti Opuntia fragilis and Opuntia polyacantha may be present. Characteristic herbaceous species include grasses such as Indian Ricegrass (Oryzopsis hymenoides), Purple Threeawn (Aristida purpurea), Needle-and-Thread (Stipa comata), Bluebunch Wheatgrass (Elymus spicatus) and Sandberg’s Bluegrass (Poa secunda) and forbs such as Achillea millefolium, Astragalus purshii, Calochortus macrocarpus, Erigeron spp., Phlox hoodii, and Sphaeralcea coccinea. Introduced grasses such as Smooth Brome (Bromus inermis), Crested Wheatgrass (Agropyron cristatum) and Kentucky Bluegrass may be common at some sites. Exotic annuals such as Cheatgrass (Bromus tectorum) or Russian-thistle (Salsola tragus) may be abundant depending on precipitation and disturbance.

In Montana, this group is represented by 6 Associations grouped into 2 Alliances within the National Vegetation Classification. The Ericameria nauseosa Alliance (A3196) may also occur in the state.

National Vegetation Classification

Download the complete NVC hierarchy for Montana

TT5 B05 Desert and Semi-desert
TT5.a S61 Cool Semi-desert
TT5.a1 F121 Cool Desert and Semi-desert Shrub-Steppe
TT5.a1.Na D040 Western North American Cool Semi-Desert Scrub and Grassland
TT5.a1.Na.1 M171 Great Basin-Intermountain Dry Shrubland and Grassland
TT5.a1.Na.1.d G310 Intermountain Semi-Desert Steppe and Shrubland
A3195 Chrysothamnus viscidiflorus Steppe and Shrubland Alliance
CEGL002799 Chrysothamnus viscidiflorus / Hesperostipa comata Shrubland
CEGL002933 Chrysothamnus viscidiflorus / Poa pratensis Ruderal Shrub Grassland
CEGL005590 Chrysothamnus viscidiflorus / Agropyron cristatum Ruderal Shrubland
CEGL005591 Chrysothamnus viscidiflorus / Bromus tectorum Ruderal Shrubland
CEGL005593 Chrysothamnus viscidiflorus / Poa secunda - Bromus tectorum Ruderal Shrubland
A3196 Ericameria nauseosa Steppe and Shrubland Alliance
CEGL001330 Ericameria nauseosa / Pseudoroegneria spicata Shrubland
A3202 Krascheninnikovia lanata Steppe and Dwarf-shrubland Alliance
CEGL001325 Krascheninnikovia lanata / Phlox spp. Dwarf-shrubland
View more information on the NVC standard in Montana
*Disclaimer: Some Alliances and Associations are considered provisional. Some require further documentation to verify their occurrence in the state and some may be modified or deleted in future revisions after collection of additional data and information.

Dynamic Processes
Information on processes within these communities is lacking at this time.

Management
Information on management of these communities is lacking at this time.

Restoration Considerations
Information on Restoration Considerations of these communities is lacking at this time.

Species Associated with this Community
  • How Lists Were Created and Suggested Uses and Limitations
    Animal Species Associations
    Please note that while all vertebrate species have been systematically associated with vegetation communities, only a handful of invertebrate species have been associated with vegetation communities and invertebrates lists for each vegetation community should be regarded as incomplete. Animal species associations with natural vegetation communities that they regularly breed or overwinter in or migrate through were made by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Werner et al. 2004, Adams 2003, and Foresman 2012);
    2. Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
    4. Calculating the percentage of observations associated with each vegetation community relative to the percent of Montana covered by each vegetation community to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use. Species that only overwinter in Montana were only evaluated for overwintering habitat use. Species that only migrate through Montana were only evaluated for migratory habitat use. In general, species are listed as associated with a vegetation community if it contains structural characteristics known to be used by the species. However, species are not listed as associated with a vegetation community if we found no support in the literature for the species’ use of structural characteristics of the community even if point observations were associated with it. If you have any questions or comments on animal species associations with vegetation communities, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Plant Species Associations
    Please note that while diagnostic, dominant, or codominant vascular plant species for a vegetation community have been systematically assigned to those communities and vascular plant Species of Concern were systematically evaluated for their associations with vegetation communities, the majority of Montana’s vascular plant species have not been evaluated for their associations with vegetation communities and no attempt has been made to associate non-vascular plants, fungi, or lichens with vegetation communities. Plant species associations with natural vegetation communities were made in a manner similar to that described above for animals, but with review of Lesica et al. (2022) and specimen collection data from the Consortium of Pacific Northwest Herbaria. If you have any questions or comments on plant species associations with vegetation communities, please contact the Montana Natural Heritage Program's Program Botanist.

    Suggested Uses and Limitations
    Species associations with vegetation communities should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning. These potential lists of species should not be used in place of documented occurrences of species or predicted habitat suitability models (this information can be requested at: https://mtnhp.mt.gov/requests/), or systematic surveys for species and onsite evaluations of habitat by trained biologists. Users of this information should be aware that the land cover data used to generate species associations is based on satellite imagery from 2016 and was only intended to be used at broader landscape scales. Land cover mapping accuracy is particularly problematic when the vegetation communities occur as small patches or where the land cover types have been altered over the past decade. Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections). Finally, although a species may be associated with a particular vegetation community within its known geographic range, portions of that vegetation community may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
    • Consortium of Pacific Northwest Herbaria. https://www.pnwherbaria.org/ Last accessed May 30, 2025.
    • Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
    • Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
    • Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
    • Lesica P., M. Lavin, and P.F. Stickney. 2022. Manual of vascular plants, 2nd Edition. Brit Press. 779 p.
    • Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.

Original Concept Authors
M.E. Hall, M.S. Reid, K.A. Schulz 2015

Montana Version Authors
S. Mincemoyer

Version Date
12/5/2024


References
  • Literature Cited AboveLegend:   View Online Publication
    • West, N. E. 1983e. Southeastern Utah galleta-threeawn shrub steppe. Pages 413-421 in: N. E. West, editor. Temperate deserts and semi-deserts. Ecosystems of the World, Volume 5. Elsevier Publishing Company, Amsterdam.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.
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Citation for data on this website:
Intermountain Semi-Desert Steppe and Shrubland.  Montana Field Guide.  Retrieved on , from