Intermountain Shadscale - Saltbush Shrubland
Global Name:
Intermountain Shadscale - Saltbush Scrub
Global Rank:
G4G5
State Rank:
S3S4
(see reason below)
External Links
State Rank Reason
This relatively restricted rangeland habitat occupies a small extent in MT. Trends are largely unknown though the habitat has likely experienced declines in condition and much less so in extent. Invasive species and grazing practices are the primary threats, though potential impacts are likely slight.
General Description
This National Vegetation Classification Group is dominated or co-dominated by an open canopy of short, arid-land shrubs, particularly Shadscale (Atriplex confertifolia) or Budsage (Artemisia spinescens) with the former being the most prevalent species. Common shrubby associates at these sites include fourwing saltbush (Atriplex canescens), Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis), Winterfat (Krascheninnikovia lanata), Green Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa), and Broom Snakeweed (Gutierrezia sarothrae). In Montana they are found primarily within the Bighorn Basin in south-central Montana. Sites may also occur near Gardiner and in the Great Plains though these sites with Shadscale as a common component are generally included in G566 - Great Plains Sparsely-Vegetated Badlands. Soils at these sites are generally alkaline or saline, shallow to moderately deep, and typical of an arid climate with little precipitation. These poorly developed soils are mostly Entisols. Elevations of 4,000 5,500 feet are common in the Bighorn Basin and Gardiner areas and sites potentially occur at lower elevations in parts of the Great Plains. Sites occupy flats as well as moderate to steep slopes, breaklands and erodible badlands.
The group may also occur within the Great Plains Region on localized areas often associated with badlands or breakland topography throughout the eastern half of the state, though generally the shadscale in these areas are part of other communities and/or are not dominant or widespread enough to form mappable communities.
This group is equivalent to the Mixed Salt Desert Scrub Ecological System.
Diagnostic Characteristics
Xeromorphic Low and Dwarf-shrubs; Salt Desert Scrub; Lowlands, Alluvial flats, Plains, Badlands Topography; Alkaline, Saline Sites; Silt or Clay Soil Textures; Bighorn Basin
Typical Dominants: Shadscale (Atriplex confertifolia), Four-wing Saltbush (Atriplex canescens), Budsage (Artemisia spinescens)
Similar Systems
Range
This arid shrubland occurs in the Bighorn Basin in south-central Montana in Carbon County on alkaline and saline soils. It may also occur within the Great Plains Region on localized areas often associated with badlands or breakland topography in the eastern half of the state, though generally the shadscale in these areas are part of other communities and/or are not dominant or widespread enough to form mappable communities.
In Montana, G300 occurs in Level IV Ecoregions: 18b (Bighorn basin)
In Montana, G300 occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins
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 are arid or semi-arid sites with warm to hot summers and cold winters. In Montana, annual precipitation is generally about 12 inches or less. Precipitation usually occurs in the spring after snowmelt, as intermittent spring rains, and sometimes during late summer or fall. Soils are shallow to moderately deep, poorly developed, typical of an arid climate with little precipitation. They are often alkaline or saline, poorly developed Entisols. Elevations of 4,000 5,500 feet are common in the Bighorn Basin and Gardiner areas and sites potentially occur at lower elevations in parts of the Great Plains. Sites occupy flats as well as moderate to steep slopes, breaklands and erodible badlands.
Vegetation
These communities are dominated or co-dominated by an open canopy of short shrubs, particularly Shadscale (Atriplex confertifolia) or Budsage (Artemisia spinescens) with the former being the most prevalent species. Common shrubby associates at these sites include fourwing saltbush (Atriplex canescens), Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis), Winterfat (Krascheninnikovia lanata), Green Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa), and Broom Snakeweed (Gutierrezia sarothrae). Spiny hopsage (Grayia spinosa), a Species of Concern also occurs within these communities. Prickly pear (Opuntia polyacantha) may be present at some sites. Graminoids dominate the sparse, or sometimes moderately dense, herbaceous understory. Species present depends on habitat, the alkalinity/salinity of site and past land use, and may include Indian ricegrass (Oryzopsis hymenoides), Blue Grama (Bouteloua gracilis), Western Wheatgrass (Pascopyrum smithii), Sandberg’s Bluegrass (Poa secunda), Alkali Sacaton (Sporobolus airoides), needle and thread (Stipa comata), Bluebunch Wheatgrass (Elymus spicatus) and Inland Saltgrass (Distichlis spicata). Forb cover is generally very low. Annual, native species are common especially on recently disturbed sites and include species such as Nuttall’s povertyweed (Monolepis nuttalliana) and halophytic annuals such as Western Glasswort (Salicornia rubra) and Seepweed or Sea-blite (Suaeda species). Perennial forbs at these sites include Fringed Sage (Artemisia frigida), and Scarlet Globemallow (Sphaeralcea coccinea). Exotic annuals such as Russian Thistle (Salsola tragus) and Cheatgrass (Bromus tectorum) are frequently found in this group.
In Montana, this group is represented by 1 Alliance with 3 Associations within the National Vegetation Classification. Minor patches of A0869 - Atriplex canescens Scrub Alliance may also occur in the Bighorn Basin or near Gardiner.
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.4 M093 Intermountain Saltbush Scrub
TT5.a1.Na.4.b G300 Intermountain Shadscale - Saltbush Scrub
A0870 Atriplex confertifolia Scrub Alliance
CEGL001293 Atriplex confertifolia Wyoming Basins Shrubland
CEGL001300 Atriplex confertifolia / Ericameria nauseosa Shrubland
CEGL001452 Picrothamnus desertorum Shrubland
*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
Species of the salt-desert shrub complex have different degrees of tolerance to salinity and aridity, so they tend to sort themselves out along a moisture/salinity gradient (West 1982). The harsh environmental conditions of these habitats slow down community dynamics. The same species or species similar in stature or appearance often succeed each other after disturbances. Fire frequency was historically very low in these habitats. Heavy sheep grazing practices can significantly impact vigor and cover of the principal shrub species, leading to an increase of annual bromes (Bromus species) and other exotic annual forbs. Sites invaded with exotic annuals are changing the dynamics of this group by increasing fire potential, severity and spread.
Management
Historically, fire was rare in this group due to the characteristic sparse, plant cover. Excessive grazing can result in the demise of the most common perennial grasses in these habitats and lead to an abundance cheatgrass and other invasive annuals. Off-road vehicle travel can detrimentally impact some sites.
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 Community
Vascular Plants
Mammals
Birds
Reptiles
- Diagnostic, Dominant, or Codominant Plant Species for this Community
Vascular Plants
- Other Native Species Commonly Associated with this Community
Vascular Plants
Original Concept Authors
K.A. Schulz 2015
Montana Version Authors
S. Mincemoyer, T. Luna and L. Vance
Version Date
12/5/2024
References
- Web Search Engines for Articles on "Intermountain Shadscale - Saltbush Scrub"
