2013-04-10_PERMIT FILE - C1981019A (4)

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RULE 2 PERMITS The density of larger aspen averaged 139 trees per acre using the point- center - quarter (PCQ) method (the difference between the two values was due to aspen recruitment — trees smaller than 5 feet that were not recorded in the PCQ measurements). The canopy cover in the aspen community baseline study area was visually estimated to average 31 percent, which is about one -half of the normal expectancy. The aspen canopy cover at over half' of the sample points was substantially reduced due to the recent die -off of mature trees, most likely due to the recent drought (Table 2.04.10 -42). The average ground cover in the aspen community reference area was 72.05 percent with 0.0 percent rock, 19.1 percent litter, and 8.85 percent bare ground exposure. Dominant plant species and their ground cover percentage included: mountain brome with 16.35 percent, blue wildrye with 15.2 percent, bluegrass with 5.35 percent, creepingroot violet (Viola rydbergii) with 5.15 percent, povertyweed (Iva axillaris) with 4.35 percent and nettleleaf giant hyssop with 3.6 percent. Of the total plant cover, 97 percent (70.05 percent average cover) was due to perennial plants (excluding noxious weeds). Annual species contributed 2.8 percent and noxious weeds contributed 0.0 percent of the composition. Nine 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, four forbs, and two shrubs (Table 2.04.10 -39). The average herbaceous production within the aspen reference area was 1,110 pounds per acre, oven -dry weight, with 98 percent (1,092 pounds per acre) due to perennials (grasses contributing 759 pounds per acre and forbs providing 332 pounds per acre) and 2 percent due to annuals (all forbs). Noxious weeds were not found in or near the reference area (Table 2.04.10 -43). Woody plant density in the aspen reference area was 2,710 plants per acre with dominance by chokecherry (1,263 plants per acre) and mountain snowberry (549 plants per acre). The shrub lifeform accounts for 77 percent (2,088 plants per acre), sub -trees account for 8 percent (220 plants per acre), and trees account for 15 percent (402 per acre) of the total (Table 2.04.10 -44). The density of aspen averaged 172 trees per acre using the PCQ method (again the difference between the two values was due to aspen recruitment — trees smaller than 5 feet that were not recorded in the PCQ measurements). The canopy cover in the reference area was visually estimated to average 32 percent (Table 2.04.10 -45). The comparison of the calculated t- statistic (t *) for the aspen community baseline study area and the aspen 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 aspen community baseline study area is comparable (equal) to the values obtained from the aspen reference area (Table 2.04.10 -38). Bottomland - As indicated on Map 4C, the bottomland community baseline study area occupies 603.4 acres and occurs in the relatively flat alluvial /colluvial deposits within drainages, or the concave basins of the drainage headwaters. It is an aggregate of vegetation subtypes (wetland, riparian bottom, sagebrush, grassland, and occasionally mountain shrub at elevation). The wetland and riparian bottom subtypes are restricted to this physiographic location, whereas the sagebrush, mountain shrub, and grassland types have "invaded" from surrounding uplands to take advantage of the more mesic conditions. It generally exhibits deep to very deep soils with somewhat elevated moisture levels that result from side -slope outwash, varying amounts of lateral subirrigation from stream flow, flood flows, and from occasional seeps and springs. Vegetation within the bottomland community grows with elevated density and productivity in comparison to the adjacent uplands due to greater amount of water availability. The bottomland reference site is located along Wilson Creek just external to the northeast portion of the study area and occupies 32.3 acres. This reference area was selected because of its easy access, low probability of future disturbance, and the representative mix of sagebrush and grassland sub -types within its boundaries. Collom — Rule 2, Page 62 Revision Date: 9/28/11 Revision No.: PR -03