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vegetation type, this is not to predict that they may not proceed through further succession <br />toward composition more closely approximating Mountain Brush in time. <br />On the other hand, until 1994, the heavy woody cover of the Mountain Brush Reference Area has <br />shown a tendency to react with delay; reduction in cover percent during drought has been <br />delayed, as has recovery following cessation of drought. The Mountain Brush Reference Area <br />dropped only 9.7 percentage points from 1987 to 1989 (during the worst of the drought), but <br />continued to drop another 2 percentage points in 1990 (as the drought satiated). In 199'1, the <br />Mountain Brush Reference Area cover increased by nearly 8 percent, and in 1992 the total <br />cover decreased by 13 percent. The 1992 decline relates partly to the f.sct that the boundaries <br />of the reference area as sampled for 1992 had been adjusted to reflect the originally identified <br />reference area limits more correctly, and included less of the very heavy oak and serviceberry <br />stands on the steep east-facing slopes; this is responsible for at least some of the decline in <br />cover since experience has shown the dense overhead canopy of these species generally <br />corresponds to higher total plant cover than any other type of vegetatior~ in the area. In 1993, <br />with the same sample area boundaries used in 1992, the total cover increased by 7.3 percent. <br />In 1994, the Mountain Brush Reference Area was subject not only to the severe drought <br />conditions, but was inadvertently affected by herbicide drift as a local rancher attempted to <br />remove shrub cover from nearby grazing areas. Between the drought and herbicide accident, <br />the result was a decrease in cover to 66.8 percent; the previous lowest observed cover in the <br />area since 1987 was 74.9 percent in 1992. What part of this decrease was attributable to <br />drought and what part was due to herbicide effects is not known. In the only reclaimed area <br />measured every year (Wadge Pasture), there was a 16.5 percent drop in cover in 1994, <br />suggesting that the drought effect may be substantial. <br />As has been the case for the previous years' monitoring at the Seneca II Mine, the 1994 cover <br />data reflect a parallel variation in the herbaceous component of vegetation cover between <br />reclaimed and reference areas. Considering the herbaceous cover only, as would be possible <br />under Colorado Division of Minerals and Geology (DMG) regulations, all of the reclaimed areas <br />except the youngest (1992 reclaimed areas) have cover values above an herbaceous cover <br />standard set by either of the reference areas. <br />26 <br />