Montana Field Guide

This vegetation type is characterized by low shrubs (<20 inches tall), primarily either Black Sagebrush (Artemisia nova) or Low Sagebrush (Artemisia arbuscula) often with a significant component of perennial grasses. Areas dominated by Fringed Sage (Artemisia frigida) are also included within this group. Shrub cover is mostly sparse or open, generally ranging between 10 and 30%, occasionally higher. It occurs in southwest and south-central Montana on sites that are gently to moderately sloping, particularly on dry, windswept hills and ridges, predominantly on southerly aspects. This is a minor type in Montana occurring as small to large patches. Typical sites are gently rolling hills and long, gently sloping pediments and fans. These sites are very windy and have shallow, often rocky soils. Rock and gravel cover much of the unvegetated ground surface. Soils are typically shallow, silts or clays, and derived from limestone or shale parent materials. The distinguishing feature of this system is a short-shrub stratum in which dwarf-shrubs (<20 inches tall) contribute at least two-thirds of the woody canopy. Black Sage (Artemisia nova) is the more common dominant in this system. In southwestern Montana, Low Sage (Artemisia arbuscula) may be the dominant, often found on restrictive clay soils that inhibit root depth and create a perched water table. Big Sagebrush (primarily Artemisia tridentata ssp. wyomingensis) may be present within this community. Generally, this type is characterized as steppe vegetation, occurring in areas where precipitation and soil conditions are limiting tree growth. In Montana, this type often grades into or is adjacent to Limber Pine communities.

This Group is equivalent to the Low Sagebrush Shrubland Ecological System.

Arid, Shrub-Steppe; Open, Low Shrub Community; Rocky or Gravelly Sites with Shallow, Calcareous, Clay or Silty Soils; Windswept Benches, Ridges, Gentle Slopes, and Alluvial Fans.

Typical Dominants: Black Sage (Artemisia nova); Low Sage (Artemisia arbuscula); Fringed Sage (Artemisia frigida)

This type occurs in southwest and southcentral Montana. At the northern end of its range, it occurs in the Elkhorn Mountains south of Helena and northeast of Roundup in Musselshell County. It is most abundant in portions of Beaverhead, Madison and Carbon Counties. In Carbon County it is common and widespread on portions of the eastern flank of the Beartooth range on outwash fans and lower slopes, and along the southerly-facing flank of the Pryor Mountains. Black sage dominated types occur throughout the range of the type in MT while Low Sage is primarily limited to Beaverhead County and surrounding areas.

In Montana, G308 occurs within these Level III Ecoregions: 17 (Middle Rockies) and 18 (Wyoming Basin)

In Montana, G308 occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins, 43B - Central Rocky Mountains, 44B - Central Rocky Mountain Valleys, the southern portion of 46 - Northern and Central Rocky Mountain Foothills

Small Patch and Large Patch

This type occupies arid sites that are mostly gently to moderately sloping, especially on dry, windswept hills and ridges and on southerly-facing slopes. Sites range in elevation from 3,500 feet (1070 meters) in Musselshell County and 4,000 feet in Carbon County up to 9,000 feet (2,740 meters) in southern Beaverhead County. Black Sage dominated communities range from the lowest elevations up to about 7,500 feet. Whereas Low Sage dominated types occur primarily above 6,000 feet. Soils are shallow, gravelly, often derived from limestone or shale and high in calcium carbonate. Sites are often characterized by a subsurface that is impermeable or has bedrock near the surface (Wambolt and Frisina 2002). Soils are usually silts or clays. Exposed rock, gravel and bare soil are common in this type. Though slopes are usually gentle, they have been documented to occur on slopes as steep as 37% (Mueggler and Stewart 1980).

The low shrubs Black Sage or Low Sage are dominant and the characteristic species of the type. Overall shrub cover is generally between 10-30% in this type. Grass cover is often higher than shrub cover with a range of 20-75% while forb cover is often much less than grass cover but varies widely from 2-60% cover (Mueggler and Stewart 1980). Other shrubs are usually very limited in these communities with Big Sagebrush (Artemisia tridentata) the only species that may occasionally occupy up to about 10% cover. Areas dominated by the dwarf-shrub, Fringed Sage (Artemisia frigida) are also included within this group, though such areas are usually very limited in extent. Other shrubs and dwarf-shrubs that routinely occur in these communities, although with very sparse cover, include Green Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa), Winterfat (Krascheninnikovia lanata), Broom Snakeweed (Gutierrezia sarothrae), Plains Pricklypear (Opuntia polyacantha), and Gray Horsebrush (Tetradymia canescens).

Grasses are often important components of the community with Bluebunch Wheatgrass (Elymus spicatus), Prairie Junegrass (Koeleria macrantha), and Idaho Fescue (Festuca idahoensis) typically the most common components. Other species that are often present though at very low coverages include Sandberg’s Bluegrass (Poa secunda), Needle-and-Thread (Stipa comata), and Indian Ricegrass (Oryzopsis hymenoides). The sedge Carex duriuscula is often present as well.

The forb component of these communities may be diverse but is mostly limited to low-growing and cushion species. Forb diversity will be most obvious in the first half of the growing season but will appear much more depauperate later in the season as conditions dry and the species whither. Common components include Antennaria species (A. rosea and A. umbrinella), Fleabanes (Erigeron sp.), Hood’s Phlox (Phlox hoodii), and Flax (Linum lewisii). Dozens of other species are often found within these habitats.

Adjacent habitats may support grasslands, woodlands or other upland shrub communities. These may form abrupt or gradual transitions depending upon landscape position, topographical features and soil conditions. Adjacent types will often occur on sites with deeper soils and/or more available moisture. Typical Low or Black Sagebrush habitat is generally drier and rockier than that of Big Sagebrush and other adjacent communities. Woodland communities adjacent to Low and Black Sagebrush include Foothills Limber Pine - Juniper Woodland, Montane - Subalpine Limber Pine Woodland, and Dry Douglas-fir Forest & Woodland. Grassland and shrubland types that grade into or occur adjacent to Low - Black Sagebrush communities include Rocky Mountain Low Elevation - Dry Grassland, Montane - Subalpine Dry Grassland, Rabbitbrush - Arid Steppe and Shrubland, Basin & Wyoming Big (Threetip) Sagebrush Shrubland, Mountain Big Sagebrush Shrubland.

Within MT, this Group is represented by four Alliances and nine Associations within the National vegetation Classification. These likely encompass most, if not all, of the community diversity present in this type.

This community usually occurs in a patchy mosaic with other woodland, sagebrush and grassland communities. Low and Black Sagebrush shrublands generally occur on the driest, most windswept sites with the shallowest soils relative to shrublands dominated by other sagebrush species. Low and Black Sagebrush are easily killed by fire and the plants do not resprout (Wright et al, 1979). Heavy grazing pressure will also lead to a decrease in perennial grasses and potentially to an increase in cheatgrass. Sites invaded by cheatgrass may have altered dynamics including increased fire potential, severity and spread.

Excessive grazing may result in a decrease in perennial grass cover and an increase in less palatable forbs and shrubs. It may also contribute to the invasion of and/or increase in cheatgrass.

Information on restoration considerations of these communities is lacking at this time.

K.A. Schulz 2015

12/5/2024