Abstract
Four transformation methods from the Braun-Blanquet cover-abundance scale to percentage cover were examined for the calculation of diversity index (H') and evenness index (J'). Percentage cover data of species were collected in fifty stands of various herbaceous plant communities. A newly proposed transformation method, based on the arrangement of cover values in accordance with the geometric progression in each cover-abundance class, is most effective for the estimation of H' and J'. Transformation to geometric mean of class limits is useful for calculation in both diversity and similarity indices. Transformation methods to mean cover (arithmetic mean of class limits) and the arrangement in accordance with the arithmetic progression in each class perform poorly in calculation of H' and J' because of over estimation of cover values in low cover-abundance classes. The difference of performance among the transformation methods seemed to be caused by the geometric nature of the community structure of the stands. Transformation methods are recommended to be selected in connection with the community structure of the subject stands.
