2021-09-03_PERMIT FILE - C1981019A (8)

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RULE 2 PERMITS In the juniper scrub reference area, average ground cover was 31.4 percent, with 14.1 percent rock, 24 percent litter, and 30.6 percent bare ground exposure. Dominant plant species and their ground cover percentage included: Griffith's wheatgrass (5.8 percent), Wyoming big sagebrush (5.0 percent), thrifty goldenweed(Stenotus armeriodes)(2.8 percent),and cheatgrass(2.4 percent). Of the total plant cover, 85 percent (26.65 percent average cover) was due to perennial plants (excluding noxious weeds). Annual species contributed 15.1 percent and noxious weeds contributed 0.0 percent of the composition. Seven perennial species contributed at least 3 percent relative cover or composition (3 percent is the typical lower limit for plant diversity bond release evaluations), with three of those species being grasses, one forb,and three shrubs(Table 2.04.10-56). The average herbaceous production within the juniper scrub reference area was 182 pounds per acre, oven-dry weight, with 89 percent (162 pounds per acre) due to perennials (grasses contributing 117 pounds per acre, forbs contributing 40 pounds per acre, and sub-shrubs contributing 5 pounds per acre) and 11 percent (20 pounds per acre) due to annuals (grasses contributing 6 pounds per acre and forbs contributing 14 pounds per acre). Noxious weeds were not found in any of the sampling quadrats in the reference area(Table 2.04.10-59). Woody plant density in the juniper scrub reference area was 2,373 plants per acre with dominance by Wyoming big sagebrush (1,572 plants per acre) and low rabbitbrush (335 plants per acre). The shrub lifeform accounts for 94 percent (2,233 plants per acre) and trees account for 6 percent(140 per acre) of the total (Table 2.04.10-60). The comparison of the calculated t-statistic (t•*) for the juniper scrub community baseline study area and the juniper scrub 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 juniper scrub community baseline study area is comparable (equal) to the values obtained from the juniper scrub reference area(Table 2.04.10-38). Mountain Shrub- The mountain shrub community baseline study area occupies 5,017.9 acres and occurs primarily at higher elevations of relatively flat uplands and steep southern facing slopes (as the xeric sub- type), and steep northern facing slopes (as the mesic sub-type) (Map 4). The mountain shrub reference area site is located on the ridgeline east of Wilson Creek and includes the mountain shrub reference area used for the Colowyo Mine, occupying 22.9 acres. The boundaries of the established Colowyo reference area were expanded to include the southeast facing slope of the ridge, thus accounting for the extensive xeric sub-type encountered in the study area. A total of 102 plant species were observed within the mountain shrub community baseline study area while the reference area exhibited 36 taxa. No sensitive species were observed in this area. Noxious weeds observed were Canada thistle and houndstongue(Table 2.04.10-34). The average cover within the mountain shrub baseline study area was 66.15 percent, with 1.7 percent rock, 23.0 percent litter, and 9.2 percent bare ground exposure. Dominant plant species and their ground cover percentage included: mountain snowberry(17.9 percent), bluegrass (8.5 percent), and Gambel oak (Quercus gambelii) (4.9 percent). Of the total plant cover 88 percent (58.2 percent average cover) was comprised of perennial plants (excluding noxious weeds). Annual species contributed 12 percent and noxious weeds contributed 0.3 percent of the composition. Seven perennial species contributed at least 3 percent relative cover or composition (3 percent is the typical lower limit for plant diversity bond release evaluations),with one of those species being a grass, one forb, and five shrubs(Table 2.04.10-61). The average herbaceous production within the mountain shrub community baseline study area was determined to be 927 pounds per acre, oven-dry weight, with 88 percent (820 pounds per acre) due to Collom—Rule 2, Page 54 Revision Date: 12/20/19 Revision No.: TR-135