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occasionally Rocky Mountain maple (Ater glabrum) achieved the size and growth form of a tree. <br />Dominance was shared with the shrubs (27.5 percent of total vegetation cover), native perennial <br />(orbs (23.2 percent of total vegetation cover), and the native perennial grasses (11.8 percent of <br />total vegetation cover). These last three growth forms, especially the native perennial (orbs, <br />contributed most of the diversity found in this vegetation type. Introduced forts and grasses <br />comprised only a small part of cover; the combined cover of introduced species was less than 1 <br />percent of total vegetation cover. Total cover of native annual and biennial forts was also less than <br />1 percent of total vegetation cover. <br />Quaking aspen dominated this vegetation type with 35.8 percent cover (Table A1). All shrubs <br />combined accounted for 27.5 percent cover. Taller shrubs such as serviceberry (Amelanchier <br />alnifolia) with 11.3 percent cover, chokecherry (Padus virp'ni~ ana ssp, melanocaroa) with 5.6 <br />percent cover, and Gambel's oak (Ouercus gambeliil with 1.8 percent cover, frequently occurred in <br />the understory along with a mix of shorter shrubs dominated by mountain snowberry <br />(Sy~phoricarpos rotundifoliusl with 7.4 percent cover. The combination of perennial native <br />grasses and (orbs contributed 35.0 percent cover, The dominant grasses and grass-like species <br />were blue wildrye (Eymus glaucus) with 5.6 percent cover, elk sedge (Carex Qeyeri) with 3.2 <br />• percent cover, and Agassiz bluegrass (Poa agassizensisl with 1.5 percent cover. The dominant <br />(orbs that contributed between 1 and 4 percent cover were Astoria violet (Viola praemorsal, <br />white-flowered peavine (Lathyrus leucanthusl, American vetch (Vicia americanal, nettle-leaf <br />giant hyssop (Agastache urticifolial, spreading aniseroot (Osmorhiza depaupQrata), ballhead <br />valerian (Valerians c8pitata ssp. acutiloba) and Engelmann aster (Eucephalus enyelmanniil. The <br />most common introduced species was hound's tongue (Cvnoclossum officinale) with 0.2 percent <br />cover and 53.3 percent frequency. <br />Species Composition -Supplemental Area <br />In the Supplemental Study Area, the all-layer relative cover by quaking aspen is less than the <br />Baseline Area (27.9 percent of total vegetation cover (Table 81) vs. 35.8 percent of total <br />vegetation cover (Table A1), and likewise the all-layer cover by tall shrubs is less (20.4 percent <br />of total vegetation cover vs. 27.5 percent of total vegetation cover), as is cover by native perennial <br />(orbs (19.2 percent of total vegetation cover vs. 23.2 percent of total vegetation cover). However, <br />the Supplemental Area has far greater cover by native perennial graminoids (28.6 percent of total <br />vegetation cover vs. 11.8 percent of total vegetation cover), almost entirely due to the greater <br />abundance of Agassiz bluegrass (21.0 percent of total vegetation cover vs. 1.5 percent of total <br />vegetation cover). <br />7 <br />