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' (Agropyron desertorum), Kentucky bluegrass (Poa pratensis), and alfalfa (Medicago <br />saliva) along with a number of introduced weedy species at varying densities (Hayes <br />Environmental Services, Inc., 1995). <br />The "Bare" cover designation includes rock slides, steep-walled cliffs, and the Deep <br />Creek slump and other areas where small slumps have and are occurring. <br />Riparian Zones <br />' Riparian zones occur along project area drainages and are characterized by comparatively <br />narrow vegetation communities requiring wetter soil hydrologic conditions than the <br />surrounding uplands. The boundaries of riparian zones are limited in width by the steep <br />topography associated with drainage systems. These zones may or may not include a <br />recognized wetland component. A variety of tree species are usually associated with the <br />riparian zones of the project area and, where occurring, the shrub component is denser <br />than in the surrounding uplands due to soil moisture conditions. Recent studies in the <br />semiarid west comparing riparian areas with adjacent uplands showed that riparian zones <br />support up to 400 percent more plant biomass, up to 200 percent more species richness, <br />I and contribute to large increases in density and species richness for birds when compared <br />with upland areas (Clary and Medin, 1998). <br />' Shrubs such as Gambel oak (Quercus gambelii), snowberry (Symphoricarpos <br />oreophilus), serviceberry (Amelanchier alnifolia), chokecherry (Prunus virginiana), and <br />red-osier dogwood occur on drier sideslopes. In more moist situations a few narrow-leaf <br />cottonwood are present. A spruce/fir community is common to riparian zones of higher <br />elevations along Deep Creek. This community is characterized by Englemann spruce <br />(Picea englemannii) and Colorado blue spruce (Picea pungens). Understory shrub <br />components are similar to those of lower elevations, though species such as Woods rose <br />(Rosa woodsii) and thinleaf alder (Alnus incana tenuifolia) are somewhat more <br />prevalent. Aspen becomes a co-dominant tree species as elevation increases and is the <br />f dominant species in wetter zones of the higher elevations.