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The Shannon-Weiner index is used to communicate and compare species <br />diversity for t1~e mixed brush type/aspen subtype and upland sagebrush <br />co*.mnuiities on affected and wntrol areas. This index is based on t'~e <br />Shannon-Weiner function from the field of information theory (Margalef, <br />~~ 1957; MacArthur and MacArthur, 1961; Lloyd and C~elardi, 1964; Pielou, <br />1966). As a diversity index for canrnuLity analysis, the function <br />describes the average degree of uncertainty of predicting the species of <br />a given individual picked at random fran the com rnuiity. This unce~~ainty <br />and the index increase both as the number of species increases and as <br />the individuals are distributed more and rmre equitably among species <br />already present. The general formula for this index is as follaas: <br />H = - E pi loge pi <br />where pi = decimal fraction of total indLviduals belonging to the i~ <br />species (in this case, percent basal mver is used to express pi). <br />This index may vary from a value of 0 for habitats containing a si-:gle <br />species (e.g., an alfalfa field) to values of 4 or 5 for communities <br />containing many species, each with a smtzll number of individuals. The <br />application of this foxmula to basal cover data to provide estimates of <br />species diversity is illustrated by the following example: <br />~ Basal _ p.loa p. <br />Life Form Species Cover i 'e-i <br />Gass ~robolus cryptandrus 3.9 0.36 <br />Forb Lappula texana 1.5 0.31 <br />Salsola kali 0.6 0.19 <br />Sisymbrium altissimum 0.6 0.19 <br />Sphaeralcea coccinea 1.1 0.26 <br />Sub-shrub Gutierrezia sarothrae 0.8 0.22 <br /> 8.5 1.52 <br />Shannon-[Feiner Index = 1.52 <br /> <br />-17- <br />