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

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ERO Resources • The western wheatgrass vegetation type occurs on upland knolls and ridges as an inclusion in the big sagebrush-wheatgrass type and on upland valleys and side slopes as a major type. The distribution of these grasslands is controlled by soil type and differentially, by surface disturbance including grazing and wildfire. Total affected acreage for this type is 10.3 acres (Table 5). The wheatgrass type occurs on shallow, clayey soils and on moderately deep, loamy soils (Table 4). Where these sites have been disturbed the wheatgrass has either declined or disappeared. Depending on the nature and extent of disturbance the species that typically invade or replace western wheatgrass sites correspond to a complex comprised of soil type and disturbance. Gordon saltbush invades sites that are high in clay. In the majority of these sites the A horizon has been truncated leaving the clayey 8 layer or decomposed shale parent materials exposed. Annual forbs, principally African mustard and • peppergrass, invade disturbed sites overlying clay soil, but not subject to extreme erosion. Cheatgrass invades western wheatgrass areas overlying deeper and more coarse-textured soils. Cheatgrass indicates an original disturbance that does not persist to any high degree in a perennial manner (Daubenmire 1942). Instead, the cheatgrass remains as an obvious marker • of the past disturbance. Ground cover values for the western wheatgrass stands sampled are summarized in Figure 4 and Table 6. The mean values for affected stands sampled are litter - 31.2%, rock - 0.2%, soil - 57.2% and woody species - 1.3%. The herb layer is well developed, within degrees of disturbance with a mean cover value of 13.1%. The two most important grasses in this type are western wheatgrass and cheatgrass with mean values of 4.1% and 7.9%. II.F-40