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r <br />(3) simple to calculate. <br />The most frequently used index of similarity is the Motyka (also called <br />Bray and Curtis) index of similarity (Motyka, Dobrzanski, and Zawadski, 1950). <br />The formula for this index is: <br />ISmo = 2w x 100 <br />a+b <br />where: <br />w = sum of the lesser value for each component pair from <br />areas A and B <br />a = sum of the values for area A <br />b = sum of the values for area B <br />Similarity values as low as 45% (based on species cover) have been used <br />to denote similarity between communities (Steward and Webber, 1981) and simi- <br />larities above 85% (based on species cover) can be assumed to reflect samples <br />from a homogeneous sample location (Bray and Curtis, 1957). <br />Growth-forms Used for Evaluation of Reclamation <br />When the similarity index is used to evaluate reclamation success, the <br />evaluation should be based on 1) the number of growth-forms the reclaimed area <br />has in common with the reference area, and 2) the values of cover and production <br />of each of those growth-forms. Cover and production may be evaluated as separate <br />attributes or they may be converted to relative values and combined into <br />an importance value. Reclamation success should be evaluated at the growth- <br />form level rather than the species level because it provides for flexibility in <br />selection of species to be used in reclamation while retaining the essential <br />structure of the vegetation community disturbed. The use of grass, shrub, and <br />forb species different from those found in an area prior to mining is not <br />