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• juniper communities in sandy clay and clay soils derived from shales of the Wasatch and Green <br />River Formations, and frequently in the presence of Astragalus duchesnensis. The elevation <br />range within which this species is found is 4,700 to 6,800 feet which is just within the lower limits <br />of the elevation range of the Study Area. The plant communities (and elevations) of occurrence of <br />this species are suggestive of an affinity for drier and warmer conditions, likely with less plant <br />competition. Substrate differences between Wasatch and Green River materials compared to <br />Mesa Verde group and Lewis Shale materials have been discussed above. <br />Stemless buckwheat (Eriogonum acaule) is found in northwestern Moffat County in Colorado and <br />in Wyoming on barren hillsides in fine particle soils at elevations ranging from 5,680 to 6,820 feet. <br />For some of the same reasons listed for Debris milkvetch, stemless buckwheat is not known in <br />Routt County and unlikely to occur in the study area. Specimens at the University of Colorado <br />Herbarium give the habitat as "fine buff - colored soils of barrens" and "silty soil of barren hillsides." <br />The collection localities are in the same area as Astragalus jejunus and exhibit the same general <br />geology (Wasatch and Browns Park Formations of Tertiary Age). <br />Ephedra buckwheat (Eriogonum ephedroides) is found in Rio Blanco County in Colorado and in <br />Utah on sparsely vegetated slopes consisting of the white shales of the Green River Formation <br />• and soils derived from them. The elevational range within which this species is found is 5,600 to <br />6,030 feet, lower than the elevation range of the Study Area. The difference in the depositional <br />environment of Green River Formation materials versus Mesa Verde Group materials has been <br />discussed above. This plant occurs at Raven Ridge on oil shale, west of Rangely, where it has <br />been documented growing with Penstemon grahamii and Bolophyta ligulata. There is no <br />possibility of this being in the Study Area. <br />Woodside buckwheat (Eriogonum tumulosum) is found in Utah and Colorado in Moffat County in <br />mixed desert shrub and pinyon - juniper woodlands mainly on rocky outcrops and sedimentary <br />gravels or clays. The elevation range for this species is 5,800 to 6,300 feet, well below that of the <br />Study Area suggesting affinities for warmer and drier conditions. <br />Utah gentian (Gentianella tortuosa) is found in south Nevada, Utah and Colorado in Rio Blanco <br />County on barren shale knolls and slopes of the Green River Formation which is characterized by <br />marlstone, sandstone and oil shale. Known localities are usually rocky windswept summits on oil <br />shale and often in conjunction with the presence of Thalictrum heliophilum. This species is found <br />at elevations of 8,500 to 10,800 feet, much higher than the elevation range of the Study Area. In <br />• 29 <br />