2010-12-17_REVISION - C1981019 (106)

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RULE 2 PERMITS (48.7 percent average cover) was comprised of perennial plants (excluding noxious weeds). Annual species contributed 12 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 four of those species being grasses, one forb, and two shrubs (Table 2.04.10 -66). The average herbaceous production within the sagebrush community baseline study area was determined to be 774 pounds per acre, oven -dry weight, with 90 percent (694 pounds per acre) due to perennials (grasses contributing 506 pounds per acre, forbs contributing 149 pounds per acre, and sub - shrubs contributing 40 pounds per acre) and 10 percent (77 pounds per acre) due to annuals (grasses contributing 49 pounds per acre and forbs contributing 28 pounds per acre). The remaining 0.4 percent (3.3 pounds per acre) was due to noxious weeds (Table 2.04.10 -67). Woody plant density was 4,156 woody plants per acre with dominance by mountain big sagebrush (2,378 plants per acre), mountain snowberry (740 plants per acre), and low rabbitbrush (589 plants per acre). The shrub lifeform accounts for 99 percent (4,152 plants per acre) and trees account for 1 percent (3.2 plants per acre) of the total (Table 2.04.10 -68). The xeric sub -type within this community is generally found on the steeper slopes (thin soils) with southerly aspects intergrading with xeric mountain brush and juniper scrub. The mesic sub -type is found on the relatively flat uplands (deeper soils) intergrading with xeric mountain shrub, as well intergrading with mesic mountain shrub on the steeper slopes with northerly aspects. The xeric sub -type exhibits lower total vegetation cover (57 percent vs. 43 percent), lower vegetation cover in each of the lifeforms, and higher cover attributed to bare ground and rock when compared with the mesic sub -type. The mesic sub -type is dominated by mountain big sagebrush while Wyoming big sagebrush tends to dominate the xeric sites. Western wheatgrass and several bluegrass species are most numerous in the mesic sites and Griffith's wheatgrass is dominant in the xeric sub -type. A majority of the sagebrush community found within the study area is mature, dense, and decadent. Land managers (Colowyo) have made several attempts to reduce the density of sagebrush and create pockets of grassland and young stands of sagebrush. Evidence of sagebrush chaining over approximately 60 acres was observed, and it appears that over the past ten to fifteen years prescribed burns in large areas of sagebrush have occurred. At higher elevations, most of these burn areas contain young, healthy sagebrush. At lower elevations and more xeric sites, the return of sagebrush to dominance appears to be much slower. Seral shrub species such as snakeweed and low rabbitbrush as well as grasses still dominate. In the sagebrush reference area, average cover was 51.0 percent, with 0.7 percent rock, 32.8 percent litter, and 15.6 percent bare ground exposure. Dominant plant species and their ground cover percentage included: Japanese brome (9.8 percent), mountain big sagebrush (8.7 percent), western wheatgrass (8.2 percent), Sandberg bluegrass (7.7 percent), and snakeweed (Guttierezia sarothrae) (4.6 percent). Of the total plant cover, 75 percent (38.3 percent average cover) was due to perennial plants (excluding noxious weeds). Annual species contributed 25 percent and noxious weeds 0 percent of the composition. Six 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 and three shrubs (Table 2.04.10 -66). The average herbaceous production within the sagebrush reference area was 907 pounds per acre, oven - dry weight, with 82 percent (741 pounds per acre) due to perennials (grasses contributing 494 pounds per acre, forbs contributing 87 pounds per acre, and sub - shrubs contributing 160 pounds per acre) and 18 percent (167 pounds per acre) due to annuals (grasses contributing 130 pounds per acre and forbs Collom — Rule 2, Page 68 Revision Date: 1/23/09 Revision No.: PR -03