2009-03-27_REPORT - C1981019 (7)

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2.5 Reference Areas 2.5.1 Mountain Shrub Reference Area The Mountain Shrub Reference Area is comprised of approximately 18 acres of gently to moderately sloping vegetation that has a predominately northwesterly aspect (mesic) and easterly aspect (xeric) (see Plate 1). The Mountain Shrub Reference Area was expanded in 2005 to include the east- facing slope of the ridge to provide representation from the xeric subtype of the Mountain Shrub community. The purpose of this inclusion is to provide a better representation of the distribution of Mountain Shrub communities located on and around Colowyo properties. The xeric exposure tends to exhibit more elevated herbaceous parameters given a modest reduction in the overstory. This reference area is located on the undisturbed ridge immediately west of thE! West Pit Area (see Map 1). A total of 35 plant taxa were observed in this reference area (see Table AB-1). Current annual herbaceous production across the area averaged 584.6 pounds per acre in 2008 with perennial grasses the dominant category (see Table 1). Ground cover in the Mountain Shrub Reference Area (Table AB-2) consisted of 63.0% live vegetation, 0.5% rock, 31.3% litter, and bare soil exposure of 5.2%. Perennial cover across the unit averaged 55.1% with annual and biennial cover averaging 7.8% and noxious weed cover with 0.1%. Dominant taxa were big sagebrush, mountain snowberry, cheatgrass, bluegrass (Poa agasizensis), and Letterman's needlegrass (St/pa iettermanii), with 12.3%, 6.6%, 6.2%, 4.9%, and 4.7% average cover, respectively. With regard to diversity, the Mountain Shrub Reference Area exhibited 6 perennial grasses and 1 perennial forb with between 3% and 50% relative cover. 2.5.2 Sagebrush Reference Area The Sagebrush Reference Area is comprised of approximately 4.7 acres of gently to moderately sloping vegetation that has a predominately northerly aspect (see Plate 2). This reference area is located on a gently sloping ridge north of the Administration / Facilities Area (see Map 1). A total of 30 plant taxa were observed in this reference area (see Table AB-].). Current annual herbaceous production across the area averaged 608.2 pounds per acre in 2008 with perennial grasses and annual grasses the dominant categories (see Table 1). Ground cover in the Sagebrush Reference Area (Table AB-2) consisted of 57.9% live vegetation, 2.4% rock, 25.6% litter, and bare soil exposure of 14.2%. Perennial cover across the unit averaged 34.7% with annual and biennial cover averaging 22.8% and noxious weed cover with 0.1%. Dominant taxa were cheatgrass, big sagebrush, Japanese brome, prairie junegrass (Koeieria macrantha), and western wheatgrass, with 14.1%, 9.6%, 8.0%, 4.9%, and 4.3% Rio Tinto Energy America/Colowyo Mine Page 26 Revegetation Monitoring - 2008