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e ESPEY, HUSTON BASSOCIATES, INC. C J Species diversity among the reference azea communities is highest for the big sagebrush community with a diversity index of 41.7. Forty-nine species were encountered on fifteen transects. F.quitability or evenness of cover distribu- tion among species is lowest for this reference community with an index of 1.02. This low equitability index reflects the low number of dominant species in this reference community. Species diversity indices for the big sagebrush reference and affected communities aze very similaz. The equitability index is lower for the reference community. This is attributable to the denser and more robust big sagebrush shrub stratum which competes well for available sunlight, reducing the growth of understory species. The similazity index shows a 38.4 percent overlap of cover by species between the big sagebrush reference and affected communities. This low percent overlap is appazently caused by the close proximity of the reference azea to Curtis Creek and its subsequent ripazian habitat. Total vegetation cover was slightly • higher in the affected azea. The reference area has a much higher shrub cover (32.4 percent) than the affected area (15.0 percent). Understory species aze more prevalent in the affected area and th's accounts for the much higher productivity of ,~sl-sue- ~ . - a I --~ the affected area Nl/~;rams per squaze meter)Jas opposed to the reference azea (96.7 grams per squaze mete) (see Table R-11). ----- -- ~~e% r 4.3 MOUNTAIN SHRUB COMMUNTi'Y The mountain shrub reference community is located on a north slope at approximately 7,300 feet neaz the Northern No. 1 (FF-Seam) Mine. The soil of this site is the Owen Creek series, a major soil type of the mountain shrub community. The approximately 2-acre reference community is triangular in shape. The results of the quantitative analysis indicate that with respect to shrub dominants, total shrub cover, and understory grass dominants the reference and affected communities aze similaz. Productivity is somewhat greater in the • K-43