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Introduced perennial grass <br />timothy (Phleum oratensel <br />Shrubs • <br />mountain snowberry (Sym~horicarpos rotundifoliusl <br />These species clearly tolerate a wide variety of ecological conditions and, interestingly, are, <br />with the fortunate exception of hound's tongue, all species that volunteer out of native <br />topsoil in reclaimed areas. <br />The number of species which were found to be associated with only one of the vegetation <br />types (Tables A23 and B30) ranged in 1990 from 9 in the Improved Pasture to 21 in the <br />Sagebrush vegetation type, and in 1992 from none in the Improved pasture-Upland to as <br />high as 12 in the Mountain Brush type and 17 in the Aspen type. Some unique associations <br />of note are: box-elder and river hawthorns were observed only in the Mesic Drainage <br />vegetation type; red clover and alfalfa were observed only in the Improved pasture; and <br />birchleaf mountain mahogany and bitterbrush were observed only in the Mountain Brush. <br />For most of the native species that occurred in only one vegetation type, this reflects an <br />actual narrow ecological amplitude. For introduced species, occurrence in one type may <br />indicate narrow ecological amplitude or it may relate to uncommon occurrence of conditions • <br />of disturbance and seed distribution necessary to allow it to establish. <br />Threatened and Endangered Plants and Communities <br />The Colorado Natural Heritage Inventory database was checked (Mount Harris, Hayden, <br />Dunckley, and Hayden Gulch quadrangles) for the known occurrence of any threatened or <br />endangered plants or plant communities in or near the study areas. No known occurrences <br />of state-listed plants of special concern (see CMLRB 1988) were shown on these maps. One <br />community of special concern, the Acer nequndo - Populus ancustifolia / Cornus stolonifera <br />(Swida sericeal community was mapped on the Mount Harris and Hayden quadrangle maps in <br />the vicinity of the Yampa River, well north of the Yoast study area. The information present <br />in CNPS (1989) was checked to assess the likely occurrence of rare plants in western Routt <br />County; none were indicated. Finally all plants observed were checked against the Cobrado <br />Natural Heritage Inventory list of Plant Species of Special Concern (CNHI 1987); none of <br />the plants listed were included on that list. <br />• <br />30 <br />