2010-12-17_REVISION - C1981019 (106)

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RULE 2 PER MITS contributing 37 pounds per acre). Noxious weeds were not found in any of the sampling quadrants in the sagebrush reference area (Table 2.04.10 -69). Woody plant density in the sagebrush reference area was 3,275 woody plants per acre with dominance by mountain big sagebrush (1,679 plants per acre) and low rabbitbrush (1,541 plants per acre). The shrub lifeform accounts for 100 percent of the total (Table 2.04.10 -70). The comparison of the calculated t- statistic (t *) for the sagebrush community baseline study area and the sagebrush reference area with the respective tabular t values indicates that in each case t* is less than t. So, it can be concluded that the total vegetation ground cover and production for the sagebrush community baseline study area is comparable (equal) to the values obtained from the sagebrush reference area (Table 2.04.10 -38). Minor Vegetation Communities and Other Designations Improved Pasture - As indicated on Map 4C, a single developed field of improved pasture (23.5 acres) occurs in the southeastern portion of the study area where a relatively flat bench of shrubland /forest was cleared and planted primarily to smooth brome (Bromus inermis) and thickspike wheatgrass (Agropyron dasystachyum). A reference area for improved pasture (11.1 acres) was established along lower Morgan Creek northwest and external to the study area boundary (Map 4C). This reference area was selected because of its elevation, ease of access, low probability for future disturbance, and representation of early mine reclamation (1970 - 1990) at the existing Colowyo operation. Mine revegetation from this period typically included "improved" varieties or genotypes of both introduced and native species that exhibit better germination, larger growth form, and /or have more efficient nutrient uptake. A total of 12 plant species were observed within the reference area. No sensitive species were observed. Two noxious weed species were observed, Canada thistle and whitetop (Table 2.04.10 -34). The average vegetation cover within the reference area was 74.0 percent, with 0.0 percent rock, 19.6 percent litter, and 6.5 percent bare ground exposure. Dominant species and their ground cover percentage included: smooth brome (57.1 percent), crested wheatgrass (Agropyron cristatum) (8.4 percent), and povertyweed (3.2 percent). Of the total plant cover 99 percent (73.5 percent average cover) was due to perennial plants (excluding noxious weeds). Annual species contributed 0.6 percent and noxious weeds contributed 0.1 percent of the composition. Four perennial species contributed at least 3 percent relative cover or composition (3 percent is the typical lower limit for plant diversity bond release evaluations), three of those species being grasses and one forb (Table 2.04.10 -71). The average herbaceous production within the improved pasture reference area was 1,476 pounds per acre, oven -dry weight, with 99 percent (1,472 pounds per acre) due to perennial species (grasses contributing 1,453 pounds per acre and forbs contributing 18 pounds per acre), and less than 1 percent due to annuals (grasses contributing 3 pounds per acre and fortis contributing 0 pounds per acre). The remaining 0.1 percent (1.3 pounds per acre) was comprised of noxious weeds (Table 2.04.10 -72). Woody plant density in the improved pasture reference area was 6.7 woody plants per acre with dominance by rubber rabbitbrush (4 plants per acre). Shrubs accounted for 100 percent of the total woody plant density (Table 2.04.10 -73). Sage Grouse Target Habitat Reference Area - As indicated on Map 4C, the Sage Grouse reference area occupies 79.5 acres and is located on flat upland between Collom, and Morgan Creeks, in an area that has Collom - Rule 2, Page 69 Revision Date: 1/23/09 Revision No.: PR -03