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For purpose of establishing the range of spedes density within the Reference Area, the 75% range of • <br />variation would be established as: <br />z(x)e <br />inhere: <br />z = the number of standard deviations (both ways firm the mean) encompassing <br />75% of the normal distribution (= L15; see Rohlf and Sokal 1969, Table P) <br />s = sandazd deviation (n-1) <br />The standazd is the point at which the centra175% of the distribution of overall spedes density in the <br />Reference Areas begins. Mathematically this would be: <br />Mean Reference Areas species density (no. of spedes per 100 sq.m.) - 1.15 s <br />In words, we aze selecting as the standazd the midpoint (in terms of probability distribution) of the <br />lower half of the range of variation of the Reference Areas. <br />Note that this test addresses total species density, not just native spedes density (see Alternative Test <br />D below). (Noxious weeds will be omitted in conformance with other existing requirements). The <br />point of addressing total spedes density, including annualjbiennial species and introduced spedes, is <br />that the total spedes density is azguably a strong indication of the existence of niche spaces that could <br />eventually be occupied by the native forb and woody plant spedes that exist in the Reference Areas. <br />The "best" (in the agricultural sense) stands of grass might not qualify because they would have <br />crowded out the `weeds" (which, in the agricultural sense, means most of the spedes that we aze <br />interested in here). At the other end of the spectrum, protection from accepting an actual `weed <br />patch" is assured by requirements limiting the partidpation of noxious weeds in cover and production <br />standazds. <br />The final step for this assessment would be aone-sample t-test comparirtg the reclaimed azea species <br />density mean against the Reference Areas standard number (described above). <br />CJ <br />• <br />TR-.50 <br />52 <br />Revised 07105 <br />