2019-01-17_PERMIT FILE - C1981008A (2)

Home Browse Search

grasses (including sedges and rushes) are dominant by far (64% cover, 89% relative cover), and desirable perennial forbs (primarily Alsike clover) are next (4.5% cover, 6.2% relative cover). Undesirable species together comprise total cover of 3.3% and relative cover of 4.6%. These include shrubs (gumweed), a few weedy annual forb species, and the noxious weed field bindweed; each of these life forms contributes 1.5% or less total cover. Mean total production measured in June 2007 at 44 plots was 2,677 lb/acre for all vegetation, and 2,513 lb/acre for desirable vegetation. Perennial grasses (including sedges and rushes) contribute most of the production, at 2,4361b/acre (97% of desirable production and 91% of total production). Forbs made up most of the remaining plant production, with a minor contribution from shrubs (gumweed) and the noxious weed species field bindweed. The reference area pasture is in good ecological condition. Soil erosion is minimal; there are no significant gullies or rills, and very little bare ground. Desirable plant species composition is diverse, which provides a robust vegetation stand able to resist some variability in irrigation water application or grazing regimes. Some drier areas tend to be dominated by weedy annual forbs, gunweed, and occasionally cheatgrass, but these areas make up only a small fraction of the reference area, and are typical of flood -irrigated pastures in the Nucla area. The reference area vegetation is representative of the pre -mine irrigated pasture type in the permit area. Irrigated pastures in the permit area were originally mostly dominated by native sagebrush shrublands or pinyon juniper woodlands. When converted to irrigated pasture, trees and shrubs were typically removed mechanically or by flooding, and plant species desired for livestock forage were seeded including perennial grasses and forbs such as alfalfa and clover. These irrigated pastures are intended primarily to provide winter forage for livestock, and secondarily to provide cut hay. Uneven application of flood -applied water is typical because of variable terrain, and wet areas soon become dominated by wetland grasses and (orbs, and sometimes Russian - olive or emergent wetland plants such as cattail or bulrushes. Weedy annual forbs and cheatgrass typically become established on drier sites, and many become dominant in disturbed areas. The species composition and ecological condition of pre -mine irrigated pastures in the permit area varies widely depending on irrigation water availability and management history. A comparison of the 2007 vegetation data in the reference area with pre -mine studies conducted by Peabody Coal Company in 1987 and New Horizon in 1999 (in Attachment 2.05.4(2)(e)-5) and Attachment 2.05.4(2)(e)-2) shows that the reference area vegetation is similar to pre -mine vegetation in the irrigated pasture type. The 1987 total vegetation cover was 71.8% and dominated by perennial graminoids, mostly seeded pasture grasses with Kentucky bluegrass the most dominant, all similar to the 2007 reference area measurements. See Table 2.05.4(2)(e)-2. Mean herbaceous production was measured at 2,823 lb/acre, similar to the 2007 reference area mean. Page 19 May 2016 (TR -75)