Semi-Desert Grassland
Global Name:
Intermountain Semi-Desert Grassland
No photos are currently available
Global Rank :
G3?
State Rank :
S3?
(see reason below)
External Links
State Rank Reason
These arid grasslands are very limited in extent. They have likely decreased in condition due to grazing and invasive species, and they will likely continue to be threatened by these activities and impacts. However, the overall condition and extent of these habitats are poorly documented leading to uncertainty in their rank.
General Description
This National Vegetation Classification Group is a minor grassland type in Montana, occurring in the relatively high elevation basins, valley bottoms and the lower foothills of the Bighorn/Wyoming Basin, and potentially in extreme southwest MT (Beaverhead County) and also near Gardiner in southern Park County. These arid grasslands are composed of drought-tolerant perennial bunchgrasses such as Needlegrasses (Stipa spp.), Blue Grama (Bouteloua gracilis ), Sand Dropseed (Sporobolus cryptandrus ), Sandberg’s Bluegrass (Poa secunda ), and Bluebunch Wheatgrass (Elymus spicatus ). Scattered shrubs and subshrubs, such as Wyoming Big Sagebrush (Artemisia tridentata ssp wyomingensis, Saltbush (Atriplex spp.), Broom Snakeweed (Gutierrezia sarothrae ), and Winterfat (Krascheninnikovia lanata ) are often present. These grasslands are only marginally different from those of G273 Rocky Mountain Low Elevation - Dry Grassland as they overlap extensively in species’ composition. However, they generally occur in more arid sites and are more limited in geographic distribution in the state. Substrates are often well-drained sandy or loam soils derived from sedimentary parent materials but are quite variable and may include fine-textured soils derived from igneous and metamorphic rocks. This group does not have a similar Ecological System representative in Montana. The most similar communities include some of the driest communities within the Rocky Mountain Lower Montane, Foothill, and Valley Grassland Ecological System.
Diagnostic Characteristics
Semi-arid to Arid Grasslands; Intermountain Region Typical Dominants: Indian Ricegrass (Oryzopsis hymenoides ), Blue Grama (Bouteloua gracilis ), Needle-and-Thread (Stipa comata ), Sandberg’s Bluegrass (Poa secunda ), and Bluebunch Wheatgrass (Elymus spicatus )
Similar Systems
Range
This grassland group is a minor type in MT, occurring in valley bottoms and lower foothills of the Bighorn/Wyoming Basin, and potentially in extreme southwest MT (Beaverhead County) and also near Gardiner in southern Park County. In Montana, G311 occurs or potentially occurs in Level IV Ecoregions: 17m (Dry Mid-elevation Sedimentary Mountains of the Middle Rockies), 18b (Bighorn Basin), 43v (Pryor-Bighorn Foothills of the Northwestern Great Plains); and 17aa (Dry Intermontane Sagebrush Valleys). In Montana, G311 occurs or potentially occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins; southern part of 46 - Northern and Central Rocky Mountain Foothills and 44B - Central Rocky Mountain Valleys.
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
Large Patch
Environment
These arid grasslands occur in the relatively high-elevations basins, valley bottoms and foothills of southern Montana from 4,500-6,500 feet in elevation. They occur on flat to gently sloping terrain and on steep slopes primarily on warmer, southerly slopes. This group experiences cold temperate conditions with hot summers and cold winters. Annual precipitation is usually from 8-15 inches. A significant portion of the precipitation falls in the summer months during convective storms with the remainder falling during the winter and early spring months. Soils supporting this group vary from shallow to deep, and from sandy to finer-textured loams. They are generally well-drained soils derived from sedimentary parent materials, commonly sandstones and shales but are quite variable and may include fine-textured soils derived from igneous and metamorphic rocks. Some occurrences have a high cover of cryptogams on the soil surface, which tends to increase the stability of the soils during torrential summer rains and heavy windstorms (Kleiner and Harper 1972).
Vegetation
These arid grasslands are dominated by cool and warm-season, perennial bunchgrasses with cover that is sparse to moderately dense. Cool season grasses include Indian Ricegrass (Oryzopsis hymenoides ), Needle-and-Thread (Stipa comata ), Nelson’s Needlegrass (Stipa nelsonii ), Sandberg’s Bluegrass (Poa secunda ) and Bluebunch Wheatgrass (Elymus spicatus ). Common warm season grasses include Blue Grama (Bouteloua gracilis ), Sand Dropseed (Sporobolus cryptandrus ) and Purple Three-awn Grass (Aristida purpurea ). Scattered shrubs and dwarf-shrubs often are present, especially Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis ), Saltbush (Atriplex spp.), Broom Snakeweed (Gutierrezia sarothrae ), and Winterfat (Krascheninnikovia lanata ). Forb cover is generally sparse but can be relatively diverse. Common forbs are Gaura coccinea , Arrowleaf Balsamroot (Balsamorhiza sagittata ), Hymenopappus filifolius , Machaeranthera canescens , Sphaeralcea coccinea , Lappula occidentalis , Lithophragma glabrum , Lupinus pusillus , Opuntia polyacantha , Plantago patagonica , Pediomelum argophyllum , Artemisia campestris , Artemisia dracunculus , Artemisia ludoviciana , and species of Antennaria, Astragalus, Cryptantha, Eriogonum, Gilia, and Lappula. Cryptogams are abundant at some sites. Exotic species such as Bromus tectorum , Draba verna , Lactuca serriola , Salsola tragus , Kochia scoparia , Poa pratensis , Sisymbrium altissimum , and Tragopogon dubius are often present. In Montana, this group is represented by 3 Alliances and 4 Associations within the National Vegetation Classification. These likely cover most, if not all, the range in vegetation communities present within this group 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.c G311 Intermountain Semi-Desert Grassland
A1262 Achnatherum hymenoides - Pseudoroegneria spicata - Muhlenbergia pungens Grassland Alliance
CEGL001666 Pseudoroegneria spicata - Cushion Plants Grassland
CEGL001674 Pseudoroegneria spicata - Achnatherum hymenoides Grassland
A1270 Hesperostipa comata Grassland Alliance
CEGL001703 Hesperostipa comata - Achnatherum hymenoides Grassland
A3977 Sporobolus cryptandrus - Aristida purpurea var. longiseta - Poa secunda Sandy Stream Terrace Grassland Alliance
CEGL001514 Sporobolus cryptandrus Shrub Grassland
*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.
Management
Improperly managed livestock grazing may increase soil erosion, decrease cover of palatable plant species in these arid grasslands and increase weedy species (USDA 1937). Annual bromes are problematic weeds in these arid grassland settings, resulting in abundant fine fuels when cured that carry fire and increase the frequency of fires (FEIS 1998).
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:
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);
Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
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.
Species of Concern Associated with this CommunityVascular Plants
Mammals
Birds
Reptiles
Amphibians
Diagnostic, Dominant, or Codominant Plant Species for this CommunityVascular Plants
Original Concept Authors
M.E. Hall and M.S. Reid 2015
Montana Version Authors
S. Mincemoyer
Version Date
12/4/2024
References
Literature Cited AboveLegend: View Online Publication Fire Effects Information System (FEIS). 1998. USDA Forest Service. Kleiner, E. F., and K. T. Harper. 1972. Environment and community organization in grasslands of Canyonlands National Park. Ecology 53(2):299-309. USFS [U.S. Forest Service]. 1937. Range plant handbook. Dover Publications Inc., New York. 816 pp.
Additional ReferencesLegend: View Online Publication Do you know of a citation we're missing? Mueggler, W. F. and W. L. Stewart. 1980. Grassland and shrubland habitat types of western Montana. USDA Forest Service Gen. Tech. Rep. INT-66, Intermountain Forest and Range Exp. Sta., Ogden, Utah. 154 pp. Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.
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