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• referents areas, Data will be collected in August or early September.. <br />B.6.2. General sampling vrocedure <br />The general sampling procedure described in B.4,2. x111 be folloxed in the <br />measurement of cover, productivity and botanical composition. <br />8.6.9. Plot size <br />For measurement of cover, xe propose to use the minimal area (16 square feet) <br />as a plot size. Hoxever, to obtain maximum accuracy of estimates, the plot <br />x111 be divided into 16 individual subplots, xhich x111 be located <br />contiguously within a 2 by 8-foot plot. For each subplot, xe x111 record <br />the totA.l cover of perennial herbaceous species (cover to be estimated im <br />its most absolute attribute rather than by the technique of total plant <br />spread), and the percentage composition contributed by prairie sandreed, <br />• xestern/thickspike xheatgrasa, xestern ragxeed, sandhill mutely, sand dropeeed, <br />and needleandthread, xhich are the dominant and sub-dominant species (see <br />Table 2). To measure the standing-crop biomass (productivity), xe rill clip <br />the perennial herbaceous species on plots one-fourth the minimal area <br />(2 by 2 feet) and retain the herbage for drying and xeigfiing. <br />8.6.4. Sample size <br />As for sandsage density.. xe x111 cover the area tq be mined according to <br />the general sampling procedure, and shall obtain a minimum of 15 plots per <br />subsite. <br />B.6.5. Statistical calculations <br />For these measures, the statistics n, x and Sx2 x111 enter a group <br />comparison T test with similar values from a reference area. If the tyro <br />samples to be compared are equal itt size, the group comparison T test <br />• involves the calculation of t by the equation <br />t - a n(n-1) / sx2 . <br />9 <br />