2008-07-25_PERMIT FILE - C1981010A (2)

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each percentage point on Figure 2.3-1 and using the intersection of the bisected angle results in a fair condition rating. Condition, by itself, will not allow a range manager [o properly evaluate grazing use. In addition to condition, a determination of available animal unit months (AUM) per range site are required. Available AUM's were determined based on 1980 sampling data for production of current annual growth (CAG) of herbaceous vegeta- tion. Cook (1970) defined an AUM as a cow-calf unit with a consumption of 804 lbs of forage per month. Shrub production (CAG) was not evaluated in terms of available AUM's. The general assumptions were made that shrubs which occur across the mine site are preferentially not grazed by livestock because of low palatability and because during the seasons of livestock use (i.e. spring and summer) adequate and more desirable herbaceous vegetation is available. Further, the shrubs are generally inaccessible due [o stand density and shrub height. The analyses also assume that if [he composition of perennial herbaceous species changes, i[ will do so slowly and cannot be accurately evaluated from one year to • [he next. Therefore, [here is no value in measuring composition to determine condition more frequently than every other year. Table 2.3-23 lists each vegeta- tion type, total acres available for grazing in 1980 and available AUM's. In all range sites, pounds of available forage refers only [o herbaceous vegeta- tion since much of [he CAG from mature stands of serviceberry, oak, etc., are generally unavailable and/or are selected against by browsing sheep and so was no[ sampled in 1980. Appendix D shows all calculations for figuring AUM's. Results and Discussions: Based on 1979 and 1980 field data, the big sagebrush-grass vegetation type (range site C) is in fair condition. IC should be reemphasized that condition is based on the potential for use by sheep. The areas would generally be rated lower overall for cattle, but higher for wildlife use. The mountain shrub community was divided into two range sites on the north and east aspects and areas above • 2-118