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1• <br />2.8 Reference Areas <br />2.8.1 Mountain Shrub Reference Area <br />The Mountain Shrub Reference Area is comprised of approximately 18 acres of gently to <br />moderately sloping vegetation that has a predominately northwesterly aspect (mesic) and easterly aspect <br />(xeric) (see Plate 1). The Mountain Shrub Reference Area was expanded in 2005 to include the east- <br />facing slope of the ridge to provide representation from the xeric subtype of Mountain Shrub. The <br />purpose of this inclusion is to provide a better representation of the distribution of Mountain Shrub <br />communities located on and around Colowyo properties. The xeric exposure tends to exhibit more <br />elevated herbaceous parameters given a modest reduction in the overstory. This reference area is <br />located on a ridge west of the West Pit Area (see Map 1). <br />A total of 19 plant taxa were observed in this reference area (see Table AB-1). Current annual <br />herbaceous production across the area averaged 346 pounds per acre in 2006 with perennial grasses the <br />dominant category (see Table 1). Ground cover in the Mountain Shrub Reference Area (Table 17) <br />consisted of 39.9% live vegetation, 0.9% rock, 48.9% litter, and bare soil exposure of 10.2%. Perennial <br />cover across the unit averaged 39.99'o with annual and biennial cover averaging 0.1%. Dominant taxa <br />were bluegrass (Poa agasizensis), Wyoming big sagebrush, slender wheatgrass, Letterman needlegrass <br />(Sripa /e[termanii), and mountain snowberry (Sympharigrpos oreophi/usj with 11.7%, 5.2%, 5.0%, <br />4.5%, and 4.5% average cover, respectively. With regard to diversity, the Mountain Shrub Reference <br />Area exhibited 5 perennial grasses and no perennial fortis with between 3% and 50% relative cover. <br />2.8.2 Sagebrush Reference Area <br />The Sagebrush Reference Area is comprised of approximately 4.7 acres of gently to moderately <br />sloping vegetation that has a predominately northerly aspect (see Plate 2). This reference area is <br />located on a gently sloping ridge north of the Administration /Facilities Area (see Map 1). A total of 25 <br />plant taxa were observed in this reference area (see Table AB-1). Current annual herbaceous production <br />across the area averaged 272 pounds per acre in 2006 with perennial grasses the dominant category <br />(see Table 1). Ground cover in the Sagebrush Reference Area (Table 17) consisted of 32.6% live <br />vegetation, 1.9% rock, 45.8% litter, and bare soil exposure of 19.7%. Perennial cover across the unit <br />averaged 30.1% with annual and biennial cover averaging 2.5%. Dominant taxa were Wyoming big <br />sagebrush, prairie junegrass (Koe%da macrantha), western wheatgrass, and bluegrass with 7.9%, 4.1%, <br />3.4%, and 2,9% average cover, respectively. With regard to diversity, the Sagebrush Reference Area <br />exhibited 5 perennial grasses and 1 perennial forb with between 3% and 50% relative cover. <br />Rlo Tinto Energy America / Colowyo Mine Page 59 Revegetatian Monitoring - 2006 <br />