Laserfiche WebLink
• mountain brush forest, pasture and mesic drainages. The elevation range of the Study Area is <br />—6,700 feet to —7,600 feet. <br />Some of the species listed in Table 23 are most effectively found in the early season, and their <br />presence could not be determined definitively in a study that began in July. An early season floral <br />inventory will be required in 2009 to assess these species and fill in the early season flora <br />missing from the Study Area species list. <br />EVALUATION OF INDIVIDUAL SPECIES <br />Debris milkvetch (Astragalus detritalis) is found in Moffat and Rio Blanco Counties in <br />northwestern Colorado and in Duchesne and Uintah Counties in Utah. This species occurs on <br />rocky sandy -clay to sandy -loam soils as well as on alluvial terraces with cobbles in pinyon - juniper <br />and mixed desert shrub communities between 5,400 to 7,200 feet. These vegetation types reflect <br />lower and drier conditions than are present in the Sage Creek Underground project area. <br />Substrates in the area of Debris milkvetch's known occurrence are derived from the Eocene -age <br />Wasatch, Green River and Uinta formations. The marlstones, oil shales, claystones, shales, <br />• sandstones and siltstones there are of lacustrine origin often reflecting the high salt content of <br />large interior - draining lakes. These sediments are thought to have been associated with <br />freshwater or at most brackish lagoon and deltaic deposits. The absence of Debris milkvetch <br />outside the bounds of the lacustrine sediments is likely why no occurrences in Routt County are <br />known. These differ substantially from the older late Cretaceous sediments that predominate in <br />the Study Area. <br />Duchesne milkvetch (Astragalus duchesnensis) likewise is found in Moffat and Rio Blanco <br />Counties in northwestern Colorado and in Duchesne and Uintah Counties in Utah in pinyon - <br />juniper woodlands and desert shrub communities. The elevational range within which this species <br />is found is 4,600 to 6,400 feet, lower than the elevation range of the Study Area. For some of the <br />same reasons listed for Debris milkvetch, Duchesne milkvetch is not known in Routt County and <br />unlikely to occur in the study area. <br />Starveling milkvetch (Astragalus jejunus) is found in northwestern Moffat County (peripheral in <br />Colorado) and in southwest Wyoming, northern Utah, southeast Idaho and Nevada (disjunct) on <br />dry hilltops, gullied bluffs, and barren ridges or river terraces. It is also found on tuff, shale, <br />sandstone or clays. The elevational range within which this species is found is 5,500 to 7,500 <br />• 27 <br />