where S is the number of species, A is the plot area and c a constant. The model is an accurate means of describing the plant species richness of small and intermediate sample sizes (Rosenzweig, 1995; Zhang et al., 2006). The parameter z was fitted on untransformed data by ordinary least-squares regression. The power function described the data extremely well, with the medians of the coef- ficient of determination R2 1⁄4 0.99 for all species and R2 1⁄4 0.97 for the herbaceous understory.