Montana Field Guide

In Montana, this open, low shrubland and shrub-steppe group 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.

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

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

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

Small Patch

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 1983e). 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.

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.

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

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

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

M.E. Hall, M.S. Reid, K.A. Schulz 2015

S. Mincemoyer

12/5/2024