Montana Field Guide

These arid shrublands 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). 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.

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)

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

Large Patch

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.

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 system.

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.

Species of the salt-desert shrub complex have different degrees of tolerance to salinity and aridity, and so tend to sort themselves out along a moisture/salinity gradient (West 1982). The harsh environmental conditions of these systems 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 this system. 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 system by increasing fire potential, severity and spread.

Historically, fire was rare in this system due to the characteristic sparse, plant cover. Excessive grazing can result in the demise of the most common perennial grasses in this system and lead to an abundance cheatgrass and other invasive annuals. Off-road vehicle travel can detrimentally impact some sites.

K.A. Schulz 2015

S. Mincemoyer, T. Luna and L. Vance

12/5/2024