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The sample t statistic (t al.) to be compared with the weighted tabular t comparison statistic (ti) was then calculated <br />as follows: <br />0 teal.=(rl-35)/V 5x1—x2 _ <br />where: <br />and: <br />sal --x2 = sZp (nl + n2) / nan2 <br />S2 = [(n, -1) 921 + (n2 - 1) s22 ] / (n, + n2 - 2) <br />Where: Subscript 1 = premine vegetation type parameters <br />Subscript 2 = corresponding reference area parameters <br />Calculation of Diversity Indices <br />Diversity indices (II) were calculated for each species and vegetation type sampled during the 1984 sampling <br />period. The Sannon-Weiner Index as presented by Shannon et al. (1973) and again by Pielou (1975) and <br />recommended by the OSM (Larson 1980) was the methodology employed for the indices presented with this study. <br />Calculation of these indices occurred as follows: <br />H=-1:Pilog Pi <br />where: Pi = N, / N <br />Ni = individual cover value for species (i) <br />N = total vegetation cover for all species combined <br />! Description of Veeetation Communities <br />0 <br />Saeebrush <br />The sagebrush vegetation type historically dominated Twentymile Park prior to the conversion of the land to <br />agriculture. It was found on moderate slopes, gently rolling hills, upland benches, and bottomland ten -aces; and on <br />all aspects. Currently it is found along the toe of the foothills surrounding the park and on areas within the park <br />which are unsuitable for agriculture. At the time of vegetation sampling, the sagebrush vegetation type occupied <br />roughly 17.5 percent of the proposed permit area (defined at that time, and used as the basis for all vegetation <br />community composition calculations, as 22,247 acres), or approximately 2,250 acres. Limited disturbances to this <br />vegetation type, i.e. construction of the EMD Borehole and Rock -Dust Tank„ have occurred. <br />As identified on Table 24, Vegetation -Soils Correlation, and Table 25, Characteristics of Soils Underlying the <br />Sagebrush Vegetation Type, several soils are found below the sagebrush community. These soils are always well - <br />drained, usually deep, and were developed from shale and sandstone parent materials. The permeability of these <br />soils is usually very slow; however, it ranges to moderate and moderately -rapid, on occasion. The available water <br />capacity ranges from very -low to high, with no clear trends discernible, and the land capability subclass of these <br />soils is most often VIe (see land use discussion under 2.04.3 for further information regarding land capability <br />subclasses). <br />As identified on Table 26, Sagebrush Vegetation Type, the shrub stratum is dominated by low sagebrush with 10.73 <br />percent ground cover and 57.37 g/m2 production, mountain big sagebrush with 6.73 percent ground cover and 25.45 <br />TR05-51 2.04-54 12/07/05 <br />