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RULE 2 PERMITS
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<br /> visually estimated to average 31 percent, which is about one-half of the normal expectancy. The aspen
<br /> canopy cover at over half of the sample points was substantially reduced due to the recent die-off of
<br /> mature trees,most likely due to the recent drought(Table 2.04.10-42).
<br /> The average ground cover in the aspen community reference area was 72.05 percent with 0.0 percent
<br /> rock, 19.1 percent litter, and 8.85 percent bare ground exposure. Dominant plant species and their ground
<br /> cover percentage included: mountain brome with 16.35 percent, blue wildrye with 15.2 percent,
<br /> bluegrass with 5.35 percent, creepingroot violet (Viola rydbergii) with 5.15 percent, povertyweed (Iva
<br /> axillaris) with 4.35 percent and nettleleaf giant hyssop with 3.6 percent. Of the total plant cover, 97
<br /> percent (70.05 percent average cover) was due to perennial plants (excluding noxious weeds). Annual
<br /> species contributed 2.8 percent and noxious weeds contributed 0.0 percent of the composition. Nine
<br /> perennial species contributed at least 3 percent relative cover or composition (3 percent is the typical
<br /> lower limit for plant diversity bond release evaluations), with three of those species being grasses, four
<br /> forbs, and two shrubs(Table 2.04.10-39).
<br /> The average herbaceous production within the aspen reference area was 1,110 pounds per acre, oven-dry
<br /> weight, with 98 percent (1,092 pounds per acre) due to perennials (grasses contributing 759 pounds per
<br /> acre and forbs providing 332 pounds per acre) and 2 percent due to annuals (all forbs). Noxious weeds
<br /> were not found in or near the reference area(Table 2.04.10-43).
<br /> Woody plant density in the aspen reference area was 2,710 plants per acre with dominance by
<br /> chokecherry (1,263 plants per acre) and mountain snowberry (549 plants per acre). The shrub lifeform
<br /> accounts for 77 percent(2,088 plants per acre), sub-trees account for 8 percent(220 plants per acre), and
<br /> trees account for 15 percent(402 per acre)of the total(Table 2.04.10-44).
<br /> The density of aspen averaged 172 trees per acre using the PCQ method(again the difference between the
<br /> two values was due to aspen recruitment — trees smaller than 5 feet that were not recorded in the PCQ
<br /> measurements). The canopy cover in the reference area was visually estimated to average 32 percent
<br /> (Table 2.04.10-45).
<br /> The comparison of the calculated t-statistic (t*) for the aspen community baseline study area and the
<br /> aspen reference area with the respective tabular t values indicates that in each case t* is less than t. So, it
<br /> can be concluded that the total vegetation ground cover and production for the aspen community baseline
<br /> study area is comparable(equal)to the values obtained from the aspen reference area(Table 2.04.10-38).
<br /> Bottomland-As indicated on Map 4,the bottomland community baseline study area occupies 603.4 acres
<br /> and occurs in the relatively flat alluvial/colluvial deposits within drainages, or the concave basins of the
<br /> drainage headwaters. It is an aggregate of vegetation subtypes (wetland, riparian bottom, sagebrush,
<br /> grassland, and occasionally mountain shrub at elevation). The wetland and riparian bottom subtypes are
<br /> restricted to this physiographic location, whereas the sagebrush, mountain shrub,and grassland types have
<br /> "invaded"from surrounding uplands to take advantage of the more mesic conditions. It generally exhibits
<br /> deep to very deep soils with somewhat elevated moisture levels that result from side-slope outwash,
<br /> varying amounts of lateral subirrigation from stream flow, flood flows, and from occasional seeps and
<br /> springs. Vegetation within the bottomland community grows with elevated density and productivity in
<br /> comparison to the adjacent uplands due to greater amount of water availability. The bottomland reference
<br /> site is located along Wilson Creek just external to the northeast portion of the study area and occupies
<br /> 32.3 acres. This reference area was selected because of its easy access, low probability of future
<br /> disturbance,and the representative mix of sagebrush and grassland sub-types within its boundaries.
<br /> Five sub-types of the Rottomland community were identified (Wetland, Mountain Shrub= Sagebrush,
<br /> Riparian Bottom, and Grassland)during the field vegetation verification studies and are described below.
<br /> Collom—Rule 2,Page 49 Revision Date: 12/20/19
<br /> Revision No.: TR-135
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