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r1 <br />L~ <br />distributed over a unit area. This measure would have no real meaning in terms <br />of reclamation anyway. Distribution of individuals by species is generally <br />termed "evenness." The suggested index instead describes the other half of <br />diversity known as "richness" or how many species are present in a covununity. <br />The index (H') suggested by Bonham is known as [he Shannon-Weiner Index and is <br />adequately described by Pielou (1966). For each range site that Eollows each <br />(H') as calculated and those species that contribute in total between 70% and 80% <br />of the diversity index are so indicated in the tables and are described below. <br />It should be emphasized [hat little difference exists between the calculated (H') <br />and the associated herbaceous cover or shrub density values. In other words, [he <br />species that provide [he greatest shrub density or herbaceous cover also provide <br />the greatest diversity values. The purpose of diversity is to indicate how many <br />of the species present must be reestablished to produce an ecologically stable <br />community, i.e. approximately 70% diversity (Bonham, 1980). <br />On range site A [he overall herbaceous plant diversity (H') is .9786 and Eor <br />• shrubby species, .7160. (These values are dimensionless.) In range site A, <br />eight herbaceous species comprise 73% of the diversity index (H'), (Table <br />2.3-16). In terms of shrub diversity (H'), 73% of the diversity for shrubs is <br />provided by four species (Table 2.3-17). Since Artemisia tridentata and Prunus <br />virginiana both provide equal diversity i.e. 12.79%, either one may be used in <br />calculating the 73% diversity for shrubs in this range site. <br />In range site B, total herbaceous species diversity (H') is .8434 based on 1980 <br />data; while total shrub diversity (H') is .7432 (Tables 2.3-18 and 2.3-19). <br />Ten plant species provide about 74% of the total herbaceous species diversity <br />(Table 2.3-18) Achilles lanulosa, Agropyron trachycaulum, Balsamorhiza sagittata <br />and Stellaria jamesiana each provide 2.87% of the total herbaceous diversity. <br />Therefore only two of the four species need be included in the total to provide <br />74% of the diversity. <br />Four shrubby species in range site B provide 76% of the shrub diversity (H') <br />. (Table 2.3-19). <br />2-106 <br />