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• <br />STEEP MOUNTAIN BRUSH VEGETATION <br />(Photographs 71 -72) <br />In the Steep Mountain Brush areas the underlying slopes are 2 to 3(h):1(v) or steeper. These <br />steep sites often correspond with the presence of underlying resistant geologic material, usually <br />sandstone. Primarily occurring on south- to west - facing slopes, the cover (compared to Mountain <br />Brush) is much more open with relatively little development of Gambel's oak; when oak is present <br />it is usually dwarfed in stature. Soils on these sites are shallow and the vegetation reflects this <br />lack of soil moisture. Total top layer vegetation cover is less than 50 %. By far the most extensive <br />lifeform is shrubs, nearly all this cover is provided by Gambel's oak, Saskatoon serviceberry, <br />mountain snowberry and big sagebrush, in order of decreasing abundance. Mountain mahogany <br />(Cercocarpus montanus) and bitterbrush (Purshia tridentata) are locally abundant. Native <br />perennial graminoids are the next most abundant lifeform, the bulk of which is bluebunch <br />wheatgrass, sun sedge, and Agassiz bluegrass. Native perennial forbs account for less that 10% <br />of vegetation cover, primarily comprised of arrowleaf balsamroot (Balsamorhiza sagitata), few - <br />flowered goldenrod (Solidago velutina), and American vetch. Introduced annual grasses, <br />• Japanese brome, and cheatgrass account for less than 5% of vegetation cover. <br />WESTERN WHEATGRASS / ALKALI SAGEBRUSH <br />(Photograph 40) <br />Dominance in this type is held by native perennial cool season grasses. By far the bulk of this <br />cover is provided by western wheatgrass, but Letterman needlegrass (Achnatherum lettermanh), <br />oniongrass, slender wheatgrass, and Agassiz bluegrass are all locally abundant in the type. <br />Mountain brome and Junegrass also occur with rather high frequency, though they provide little <br />cover. Early in the year and in wet years native perennial forbs provide substantial cover. Mules <br />ears (Wyethia amplexicaulis), arrowleaf balsamroot, one - flower woodsunflower (Helianthella <br />uniflora), American milkvetch (Vicia americana) and timber milkvetch (Astragalus miser) are often <br />extensive components of the ground cover. Western yarrow, bracted aster, showy goldeneye <br />(Heliomeris multiflora), longleaf phlox (Phlox longifolia), and Pacific aster are often important <br />contributors to cover also. Tapertip onion (Allium acuminatum), fringed thistle (Cirsium <br />centaurae), Nuttall larkspur (Delphinium nuttallianum), and lambstongue groundsel (Senecio <br />integerrimus) are also commonly encountered. Native shrubs are variably abundant, but when <br />present, most often alkali sagebrush (Seriphidium arbusculum ssp. longilobum) is most abundant. <br />• 21 <br />