(Taken from the Final Sweet Grass Hills Amendment and Environmental Impact Statement, April 1996)
Below is a summary of the habitat/community types identified in or peripheral to the Sweet Grass Hills prepared by Western Technology and Engineering, Inc. (1989). Most of the area designated as an ACEC consists of coniferous forest and scree vegetation/community types.
Several types potentially occur in the prairie surrounding the Sweet Grass Hills. However, most of the flat, arid prairie surrounding the Sweet Grass Hills has been altered by agriculture. Little native prairie, probably formerly dominated by western wheatgrass, needleandthread and blue gramma, now remains.
Absence of fescue species differentiates the prairie grassland from foothills, montane, and subalpine grasslands. Dominant species include wheatgrasses (primarily western in association with thickspike and bluebunch), needlegrass (primarily needleandthread with some green needlegrass), blue gramma and dryland sedges (threadleaf and needleleaf).
This type is dominant in the Buttes immediately above prairie grassland. Fescues dominate most stands. Pristine sites are dominated by rough fescue. Idaho fescue is present in each stand, but composition is low. Perennial forbs contribute 4 to 10 percent composition by weight. Needleandthread increases with grazing and rough fescue decreases dramatically.
As in the foothills grassland zone, rough fescue is the dominant species over most of the montane grassland. Potential habitat types within this zone include rough fescue/Idaho fescue, rough fescue/bluebunch wheatgrass, and Idaho fescue/bluebunch wheatgrass.
The rough fescue/bluebunch wheatgrass and Idaho fescue/bluebunch wheatgrass types are more limited than the rough fescue/Idaho fescue type in the Sweet Grass Hills.
The subalpine grassland is limited to relatively small areas above timberline on the summits of Mount Royal and West Butte. Rough fescue is dominant in some stands, but community stature and associated species composition indicate dissimilarities with montane grassland. Two types are rough fescue/shrubby cinquefoil and sedge meadow. Idaho fescue and shrubby cinquefoil are dominant on the top of Mount Royal.
Relative cover of shrubby cinquefoil in some areas warrants separation from grassland types. Rough fescue, usually the dominant grass, identifies the shrubby cinquefoil/rough fescue habitat type. Idaho fescue is dominant in other stands, implying a shrubby cinquefoil/Idaho fescue type. Since shrubby cinquefoil generally increases with grazing, this type may be a grazing induced seral community in the Sweet Grass Hills.
Swales, upland drainages and other snow accumulation areas support a low shrub type dominated by western snowberry and rose. Understory species are similar to the adjacent grasslands with higher abundance of mesic-site species. Kentucky bluegrass has generally invaded these stands.
Limber pine is present as a codominant or subdominant in the Douglas-fir series, and forms pure stands on dry ridges east of Mt. Brown. Limber pine stands are frequently open, appearing as a woodland or savannah. Idaho fescue is the dominant understory species.
Douglas-fir occurs as dense forests on north facing aspects at lower elevations and as a savannah on drier south-facing slopes. It is a seral component of higher elevation forest in the spruce or subalpine fir series. Douglas-fir types described for the Bear's Paw Mountains and the Little Rocky Mountains that may be present in the Sweet Grass Hills include Douglas-fir/western snowberry, Douglas-fir/serviceberry, Douglas-fir/kinnininnick, Douglas-fir/Oregon grape, Douglas-fir/Canada violet, Douglas-fir/twinflower and Douglas-fir/bunchberry dogwood.
Lodgepole is extensive at mid to upper elevations on cool, mesic slopes. It is likely seral, related to fire history. Types that may be present include lodgepole pine/twinflower, lodgepole pine/mixed shrub, lodgepole pine/huckleberry species, and lodgepole pine/common juniper.
Spruce is found on East Butte at mid to upper elevations. Potential types include spruce/twinflower, spruce/common juniper and spruce/matted clematis on limestone substrates.
Subalpine fir/common juniper and subalpine/twinflower may be found in the Sweet Grass Hills. Other possible subalpine fir types include subalpine fir/grouse whortleberry, and subalpine fir-whitebark pine at the highest elevations.
The BLM contracted the Montana Riparian/Wetland Association to conduct a wetland inventory of public lands in the Sweet Grass Hills in 1989 and 1990. The following creeks were inventoried; Pratt, Iron, Breed, Little Joe, Corral, Deer, Dohrs, Sage, Tootsie, and Government. Status of the health and function condition of these areas is shown in Table 3.1.
TABLE 3.1
STATUS OF RIPARIAN-WETLAND AREAS
IN THE
SWEET GRASS HILLS STUDY AREA
Pratt Creek
Iron Creek
Functioning At Risk
Little Joe Creek
Corral Creek
Functioning At Risk
Dohr's Creek
Sage Creek
Functioning At Risk
Tootsie Creek
Government Creek
*Status definitions are in the Glossary of the Final EIS.
Aspen occurs as groves surrounded by grassland and as woodland in coniferous forest. Understory is dense and diverse. Possible types include aspen/sweetroot in the groves and aspen/twinflower or aspen/western snowberry in the coniferous forests.
Most rocky slopes are poorly vegetated and can be designated technically as scree, talus or rock outcrop. Scattered trees occur on some rocky slopes and may be designated as limber pine/scree, spruce/scree or lodgepole pine/scree depending on tree species dominance.
There are currently no plant taxa in the Sweet Grass Hills that are listed as threatened or endangered under the Endangered Species Act of 1973.
The Montana Natural Heritage Program has been involved with several sensitive species studies in the Sweet Grass Hills. There are a number of plant communities in excellent condition which are rare or at the extremes of their ranges in the state and in need of further study. On-site surveys for sensitive plants would be needed for environmental assessments on specific actions.
The Montana Natural Heritage Program has an element occurrence record for the following sensitive plant species in the Sweet Grass Hills:
Twiggy Halimolobos (Halimolobos virgata) - A sparse population was found in the East Butte area about two miles NE of Mount Brown.
Long Sheath Waterweed (Elodea longivaginata) - This is an aquatic species in an oil and gas field 4.5 miles north of Whitlash.
Heart-Leaved Buttercup (Ranunculus cardiophyllus) - This was originally found on private land near West Butte but was not relocated in subsequent field surveys on public land.