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