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The reference areas will be used to determine weighted averages for comparison with the revegetated areas • <br />as allowed for in 4.15.7(4)(b). Weighted average values will be developed for cover and production as more <br />fully described in the following sections. Weighting will be as follows. Baseline studies determined that 83 <br />percent of the premine undisturbed vegetation was mixed brush/aspen, while 17 percent included upland <br />sagebrush. Therefore, weighted values will be determined by multiplying .83 times fhe appropriate mountain <br />brush reference area parameter value and adding that value to the product of .17 times the appropriate <br />sagebrush reference area parameter value. <br />Cover. For all reclaimed areas, successful revegetation for cover will be based on the canopy cover of Irving <br />herbaceous vegetation (4.15.8(3)(a)(i) and (b)). The herbaceous cover in reclaimed areas is higher than in <br />premine areas due to the applied current reclamation technologies and the early successional status of the <br />reclaimed communties. This resuks in revegetated areas dominated by herbaceous spades regardless of <br />the number of shrubs present. However, in the interim, herbaceous vegetation is practicable for the <br />postmining land uses and desirable for erosion control as successional patterns establish in the reclaimed <br />communities. Redente and others (1984) in a study of succession on disturbed sites in northwest Colorado, <br />found that seeded areas were dominated by grasses five years later, no matter what the composition of the <br />original mix was. • <br />Cover data will be collected from the reclaimed bond release area and the sagebrush and mountain brush <br />reference areas during the same period. The herbaceous cover component determined from sampling in <br />the reclaimed and reference areas will be used for the comparison. The herbaceous cover value from the <br />mountain brush reference area will be multiplied by .83 while the herbaceous cover value from [he <br />sagebrush reference area will be multiplied by .17. The two products will be added to determine the <br />weighted cover value. The resulting weighted value will be multiplied by a factor of two in order to determine <br />the actual value to be used in the success comparison. As discussed in the revegetation success section of <br />Seneca II-W Permit C-82-057 (Tab 22), this is a practical approach for development of a cover standard. It <br />solves the problem of a cover standard derived from only the herbaceous component of a woody dominated <br />reference area which is too low, or a cover standard derived from combined herbaceous and woody <br />vegetation from the same reference area which is unreasonably high. <br />The calculated cover standard will be compared to the mean herbaceous cover value for the revegetated <br />areas. For vegetative cover, the revegetated area shall be considered acceptable if it is not less than 90 • <br />7332 Revised 0115/93 <br />