A test of species-area theory on a high disturbance area of the Gothic earthflow

Abstract

The species-area relationship (SAR) is a widely used concept in ecology, yet there is much controversy over its form. It has traditionally been assumed either to have a simple universal power-law form, S = cAz, or to be idiosyncratic, varying from habitat to habitat, taxa to taxa, and spatial scale to spatial scale. Recently, a non-power-law, yet universal, form of the SAR has been derived from the maximum entropy principle. It has been shown to predict well the shapes of SARs across habitats, taxa, and spatial scales, and to allow estimation of species richness at biome scale from small plot data. All prior tests of this new theory have been conducted in relatively undisturbed habitats. This study tests the theory in a highly disturbed habitat on the Gothic Earthflow. While the theoretical prediction, based on 1 m2 data, for species richness in the entire 256 m2 plot was 37% lower than the measured richness, the slope values from the disturbed plot fell within the cluster of values taken from various undisturbed sites, and all followed the predicted curve fairly closely. The underestimate of large-scale species richness may result from statistically dynamic SAR slopes during the early stages of succession on a disturbed site. Further studies along successional gradients are needed to understand better the degree to which maximum entropy theory can be applied to disturbed habitats.