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• DISCUSSION <br />Vegetation Type Moisture Relatlonshlps <br />Distribution of the eight natural vegetation types across the landscape in the Yoast Baseline <br />and Supplemental study areas was strongly related to soils and aspect-controlled moisture <br />conditions. Western Wheatgrass /Alkali Sagebrush ecosystems were tied directly to clay- <br />rich shallow soils derived from shales on convex sites, usually along ridges. Steep Mountain <br />Brush ecosystems were associated with sharply convex topography on soils derived from <br />sandstones. Sagebrush ecosystems were found on usually deep soils of loamy texture; <br />similar loamy soils on north- and south-facing aspects were likely to support Mountain <br />Brush and Sagebrush ecosystems, respectively. Mountain Brush ecosystems that occurred <br />on south- or west-facing slopes probably had a shallower and/or rockier soil than <br />Sagebrush ecosystems on similar exposures. Aspen ecosystems are found on sites similar to <br />sites on which the most moist Mountain Brush ecosystems are found. In both, the surface <br />horizons are deep and dark. The Aspen areas overall have deeper soils and more stored <br />groundwater, however. The Alkali Meadow and Alkali Sagebrush/ Greasewood types occur <br />on alluviaVcolluvial materials below slopes occupied by the Alkali Sagebrush/ Western <br />• Wheatgrass type in which alkalinity is high and soil texture is clayey. <br />It was clear that mountain snowberry had a relatively wide ecological amplitude compared to <br />other shrubs in the area (see Figures 1,3,10, and 14). Mesic Drainage vegetation was <br />highly variable, depending on microsite conditions, flood history, and geomorphic status <br />(eg. recent terrace material, long-stable channel banks, recently cut channel banks). <br />Grassy Creek Riparian <br />The riparian zone of the section of Grassy Creek within the study area was examined. <br />Through this reach, Grassy Creek flows within a flood channel approximately 30 to 50 feet <br />wide, incised approximately 10 feet deep into the older floodplain (see Figure 9a). In some <br />areas the creek active flows are contained within a two to three foot wide channel (see <br />Figure 6b), while in other areas, flow is diffuse through wetlands across the bottom of the <br />flood channel (Figures 9a,b,c). Some of these wetlands were typical sedge/rush fens with a <br />dominance of beaked sedge (Figures 9a,b). Other areas, slightly less wet, were dominated <br />by redtop (Figure 9b). A few wetland areas were dominated by broadleaf cattail (Tvnha <br />latifolia, Figure 9c). In all cases, willows (Salix bebbiana and S. monticola) were common <br />• along the edge of the channel bottom. Occasional senescent thinleaf alder (Alnus tenuifolia) <br />was also found (Figure 9a). At the western end of the study area reach of Grassy Creek, <br />21 <br />