2020-08-10_PERMIT FILE - C1981018A (2)

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ERO Resources j2 � W- . ;[T11FT, Nil11M: tI*GTE The big sagebrush-wheatgrass type is the most conwmn vegetation type on the permit area. This vegetation type occurs on a wide variety of terrain including ridgetops, sideslopes and upland valleys and includes units 10 and 11 on the vegetation map (Table 4 and Maps 9 and 10, Pocket). Pig sagebrush-wheatgrass sites display an internal patchiness within the overall mosaic. The two largest segments of this characteristic are controlled by soils and by past and present land use. Variation in soils alter the density characteristics of the sagebrush overstory and the herb understory. Differences in the intensity of sheep utilization of areas also contribute to the nature of the shrub overstory and herb layer. The patchiness can be described vegetationally by the amount of Colorado wildrye in the herb understory versus western wheatgrass. The shrub canopy in those areas where Colorado wildrye predominates is more closed, whereas the western wheatgrass sites are marked by a more open shrub • layer. Soils underlying the more dense sagebrush areas are primarily coarse. Under the open sagebrush -western wheatgrass sites soil textures tend more toward loamy and are more shallow. Although these units are mapped separately, the dynamics of both are highly interrelated. In addition, both units are the products of a sagebrush-wheatgrass type that predominated on the site prior to overgrazing. As such, a single discussion incorporating both of the subtypes is appropriate to understanding their interrelatedness and to explaining the effects of land use on this type. This type accounts for 132.9 acres of the total affected mine permit area (Table 5). Ground cover values in the big sagebrush-wheatgrass sites sampled are lichens and mosses - 1.7%, litter - 27.4%, rock 1.4%, soil - 57.3% and woody species - 16.1%. In the reference areas these values are lichens and mosses - 1.0%, litter - 30.5%, rock 1.8%, soil - 56.5% and woody • species - 17.3% (Figure 4, Table 6). II.F-34