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The concept of equitability (or evenness) is further modified by the concept of <br />homogeneity. McIntosh (1967) stated that~the species within a stand are homogen- <br />eously distributed when the probability of occurrence is the same throughout the <br />stand. His definition of homogeneity is as follows: <br />"...homogeneity in [he second sense is a statement of similarity of <br />species canposition of a group of communities, stands, or samples of <br />ensembles of organisms." <br />Measurements of diversity by homogeneity indices however are not considered <br />sound ecologically by some researchers (McIntosh, 1967; Peet, 1974) since it is <br />necessary to know the total number of species in the sampling universe. This is <br />not believed to be realistically obtainable. <br />Alternatively, some researchers have turned to another index, heterogeneity. <br />Heterogeneity is defined by Peet (1974) as being the relative concentration of <br />dominance or the functional number of species in a community and which carbines <br />• the richness of species with their evenness of distribution. <br />In the measurement of diversity by heterogeneity indices, either of two differing <br />theories of measurement are applied. The first and most popular, [he "informa- <br />tion theory" is explained by Pielou (1966): <br />"... i[ is equated with the amount of uncertainty that exists regarding <br />the species of an individual selected at random from a population. The <br />more species there are and the more nearly even their distribution, the <br />greater the diversity... since information content is a measure of uncer- <br />tainty, it is a reasonable measure of heterogeneity." <br />Unfortunately, there is no agreement however that diversity and uncertainty may <br />be equated. Further, the Shannon-Wiener (Weaver) formula by which the index is <br />commonly calculated is believed to hold some bias (Peet, 1974). <br />• 3-61 <br />