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B,4,5. Statistical calculations <br />Ye have prepared a form (Table 1) that will be used as a record of all <br />measurements. This form includes all values needed for assessing sampling <br />precision and for calculating success standards and group-comparison T testa. <br />Values for sandsage density rill be used tq establish a success standard <br />according to the xeighted-average procedure of k,15.7(4)(b). <br />B, S. Species Diversity <br />B.S.1. Introduction <br />The matter of species diversity, its data base, and its application as a <br />success standard, is not defined explicitly in the regulations. Preliminary <br />drafts proposed the calculation of a diversity index from cover or biomass <br />data, but indexes are difficult to interpret and apply as a success standard, <br />• Consequently, we propose to handle species diversity in its oldest, most <br />objective form--the number of perennial herbaceous species per minimal area. <br />To d0 60, we must define the "minimal area" to be used as a plot size (see <br />Section B.5,3,). Because this attribute is relatively constant over time, <br />xe propose to establish the success standard for species diversity directly <br />from the area to be mined. <br />B. 5.2. General sampling procedure <br />The procedure for sampling species diversity is identical to that for <br />sandsage density as described in Section B.4.2. <br />B.5.3. Plot size <br />Species-area curves have been applied to ecological sampling for many years. <br />They w.;re first used by Ehropean ecologists to determine the "minimal area" <br />constituting a stand. More recently they have been used to establish an <br />. appropriate plot size for sampling. The species-azea curve is especially <br />r suited to the determination of an appropriate plot size that may be used <br />4 <br />