Figure 2.

Graphs of the SAR and the spatial persistence parameter for each of five tropical forests. (a) Log-log graph of the observed species-area data. Each plot encompasses a total area A₀ = 50 ha. We measure the mean species diversity, S_i, found in disjoint patches obtained by repeated bisections of A₀. The log-log species-area data are concave down for all five plots. The SAR is approximated loosely by the power law, z = 0.25, whose slope is indicated by the trapezoid (red). (b) The persistence parameter, a_i = S_i/S_i−1, provides a sensitive tool for analyzing SARs and testing self-similarity. Self-similarity would predict constant a ≃ 2^−0.25 ≃ 0.84, shown in red. All five persistence curves are seen to depart from the power-law model over the entire range of areas.