Montana Field Guide

This group is composed of open, dwarf-shrublands mostly of relatively pure stands of Gardner’s saltbush (Atriplex gardneri), and in south-central Montana by Bird's-foot Sage (Artemisia pedatifida). It occurs in the Bighorn Basin in the south-central part of the state across portions of the Great Plains Region. Sites occur on clay or silt soils that are saline and alkaline. Substrates are generally derived from marine shales with sites found on windswept basins, alluvial flats and plains within the Bighorn Basin. Elsewhere, Gardner’s Saltbush is found on gentle slopes, rolling topography and badlands across the plains. Other low shrubs are sometimes present at these sites. The herbaceous layer is typically sparse with perennial forbs infrequent, while perennial grasses and annual forbs may be common at some sites. These communities are similar to G300 - Shadscale - Saltbush Shrubland and G566 - Great Plains Sparsely-Vegetated Badlands but can be distinguished by the dominant species and by total vegetation cover.

This Group is equivalent to the Mat Saltbush Shrubland 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 and Great Plains Region.

Typical Dominants: Gardner’s saltbush (Atriplex gardneri), Bird’s foot Sage (Artemisia pedatifida)

This group occurs in Montana from the Bighorn Basin in the south-central part of the state across portions of the Great Plains Region, with concentrations in Rosebud and Carter Counties and areas bordering the Missouri River from the Breaks to Fort Peck Dam. Extensive areas occur north of the Missouri River between and south of Malta and Glasgow. Communities dominated by Bird’s foot Sage only occur within the Bighorn Basin.

In Montana, G301 occurs in Level III and IV Ecoregions: 18b (Bighorn basin), 42 (Northwestern Glaciated Plains), and 43 (Northwestern Great Plains).

In Montana, G301 occurs or potentially occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins, 52 - Brown Glaciated Plains, 53A - Northern Dark Brown Glaciated Plains, 54 - Rolling Soft Shale Plain, 58A,B,C,D - Northern Rolling High Plains, 60A - Pierre Shale Plains, and 60B - Pierre Shale Plains, Northern Part.

Large Patch

Mat Saltbush shrublands occur on clay or silt soils that are saline and alkaline. In Montana, substrates are generally derived from marine shales with sites found on windswept basins, alluvial flats and plains within the Bighorn Basin. Gardner’s Saltbush is found on gentle slopes, rolling topography and badlands across the plains. Climate is temperate and semi-arid. Summers are generally hot, and freezing temperatures are common in the winter. Mean annual precipitation ranges from about 8-13 inches. Approximately two-thirds of the annual precipitation falls in spring and early summer. Substrates are typically saline, alkaline, fine-textured soils developed from shale or alluvium. Bare soil is common, and infiltration rates are typically low at these sites.

This group is composed of open, dwarf-shrublands mostly of relatively pure stands of Gardner’s saltbush (Atriplex gardneri), and in south-central Montana by Bird's-foot Sagebrush (Artemisia pedatifida). Other shrubs present at these sites, especially in southern Montana include Budsage (Artemisia spinescens), winterfat (Krascheninnikovia lanata), shortspine horsebrush (Tetradymia spinosa), Shadscale saltbush (Atriplex confertifolia) or Fourwing Saltbush (Atriplex canescens) may be present. Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis) can occur in patches on more favorable substrates that are less saline or alkaline. The herbaceous layer is typically sparse. Perennial forbs are infrequent and scattered in the undergrowth. Common species include smooth Woody Aster (Xylorhiza glabriuscula) and Scarlet Globemallow (Sphaeralcea coccinea). Annual species of Atriplex, Povertyweed (Monolepis nuttalliana), Goosefoot (Chenopodium) and Seepweed (Suadea) are frequently present. Perennial grasses have the highest herbaceous cover. Indian Ricegrass (Oryzopsis hymenoides), Blue Grama (Bouteloua gracilis), Bottlebrush Squirrel-tail (Elymus elymoides), Thickspike Wheatgrass (Elymus lanceolatus), Western Wheatgrass (Pascopyrum smithii), Sandberg’s Bluegrass (Poa secunda), or Alkali Sacaton (Sporobolus airoides) are the most common species found at these sites. In less saline areas, there may be inclusions of grasslands dominated by Needle-and-Thread (Stipa comata), Western Wheatgrass, or Bluebunch Wheatgrass (Elymus spicatus). Cheatgrass (Bromus tectorum) or other annual bromes can become abundant, especially in disturbed sites.

In Montana, this group is represented by 5 Associations grouped into 2 Alliances within the National Vegetation Classification, which probably covers the diversity of vegetation types within the state.

The harsh environmental conditions of these sites slow down community dynamics. Following disturbance, the same species or species similar in stature or appearance often succeed each other. Fire frequency was historically very low in these communities. Heavy sheep grazing practices can significantly impact vigor and cover of the principal shrub species, leading to an increase of cheatgrass and other exotic annual forbs. Sites infested with cheatgrass are changing the dynamics of these communities by increasing fire potential, severity and spread.

Heavy grazing pressure can result in the loss of the most common perennial grasses at these sites and lead to an abundance cheatgrass and other annual bromes and forbs.

Gardner’s saltbush has an extensive, highly branched root system and tolerates poor site conditions. It has been used to stabilize soils and to reclaim disturbed sites (Clarke and others 1943; Carlson and others 1984). It was one of only two species to establish on coal mine spoils in Wyoming (Frischknecht and Ferguson 1984).

K.A. Schulz 2019

S. Mincemoyer, T. Luna

12/5/2024