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• percent lower in the Permit Area. Native perennial torb and grass and aspen cover was greater in the <br />permit area, while shrub cover was greater in the Expansion Area. The presence of major plant species <br />was similar in both areas. The higher total vegetation cover in the areas sampled in the Permit Area is <br />most likely attributable to reduced grazing pressure in the permit area, and the fact that sampled <br />stands in the Permit Area fell on steep slopes with north and east aspects. Added to the extra moisture <br />these type of sites provide, grazing impacts on such sites are also usually very limited. In addition, the <br />southern two-thirds of the Permit Area has not been grazed by domestic livestock for several years. <br />Western Wheatgrass /Alkali Sagebrush (Figure 2) <br />Within this type, the unifying environmental factor is the presence of very heavy soils that are <br />penetrated very slowly by plant roots as well as air and water. These soils are of variable depth; in <br />the shallowest, intact shale fragments are common in the upper profile, while in the deep soils, <br />weathering has reduced shale parent material to clay at depths well below the surface. On these soils, <br />the bulk of annual wetting probably occurs slowly through the winter as snow melts and water slowly <br />seeps into the solum. After spring passes and stored moisture has been depleted, moisture in the form <br />• of thunder showers typically arrives so intensely that most runs off without penetrating these heavy <br />soils. Soils that occur on these sites include the Aaberg, Waybe, Binco, Buckskin, and Roult series. <br />The most abundant and consistently present species of these sites is western wheatgrass (Agropyron <br />smilhii), whose ability to root through extremely heavy soil is well-known. For example, in the <br />'playas' of the northern Great Plains, closed basins within which weak erosional transport moves clay <br />to ihebottom of the depressions, western wheatgrass forms near-monocultures. Although the <br />topographic conditions on which the Western Wheatgrass /Alkali Sagebrush vegetation type occurs are <br />universally convex, western wheatgrass maintains a strong presence. Occurring along with it are a <br />variety of what amount to spring ephemeral species that grow during spring and are dormant during the <br />summer when the heavy soils become extremely dry and are typically not recharged during summer <br />precipitation. These species include wild onion (Allium acuminatum), Pacific aster (Aster chilensis), <br />timber milkvetch (Astragalus miser), arrowleat balsamroot (Balsamorhiza sagittata), one-flower <br />woodsunflower (Helianthella uniflora), holly-leaf clover (Trifolium gymnoraroon), and mules-ear <br />(Wyethia amnlexicaulisl. The latter can form large monocultures that seem to correlate with <br />north-facing exposure and/or snow-accumulation sites. Another locally conspicuous component of this <br />ecosystem is alkali sagebrush (Artemisia longiloba). This low, early-flowering and tridentate <br />• sagebrush varies from near absence to thorough dominance. It is speculated that both grazing history <br />