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Section 779.19 (a) Continued. • Diversity Species diversity as determined from the transects was found to vary widely from one range site to the next and from one year to the next. The lowest values were obatined in 1976 for aspen and big sagebrush. This is explained, however, by the late September sampling date after many forbs were dead and shrub leaves had fallen. If the 1976 data is discarded, the average diversity by range site results in a ranking from highest to lowest of: aspen- 27 species; big sagebrush and mountain shrub-25 species; silver sagebrush-meadow-21 species; meadow-13 species; low sagebrush-9 species; treated big sagebrush-8 species and pastureland~7 species. These data indicate that range sites treated by man to control brush and promote grass growth are floristically simpler than their undisturbed counterparts. Comparison of Table 43, Comparison of Species Diversity by Year Sampled in Range Transects, with Table • 41, Comparison of Available Cover and Production Data on Energy Mines No. 1 and 2, demonstrates that species diversity is not correlated with plant production. The pastureland range site with only 7 species ranked lowest in diversity and second to the highest in forage production. The meadow site with only 13 species produced more forage than range sites having twice the species diversity. Yearly variations between different range sites might be explained by climatic conditions or differences in sampling locations. Plant species diversity indicates that a highly beneficial postmining plant community can be established based upon a relatively simple seed mixture. As can be observed in Section 780.18 the diversity in the seed mixture exceeds the average diversity of all existing range sites. Such a diverse mixture will maximize the potential reestablishment of an ecologically stable and productive postmining plant community. • 779-130