Scale Dependency in the Species-Area Relationship of Plant Communities

The species-area relationship (SAR) is one of the most frequently described patterns in biodiversity; however, it is seldom applied in conservation practice. Awareness of some shortcomings such as scale dependency is the basis for a better understanding of biodiversity patterns and a way to cope with artifacts occurring in empirical data. We demonstrate effects of scale dependency within plant communities deriving from different scale ranges, extreme values and curve intersections on empirical data of forest and grassland communities and propose to reduce the effect of scale dependence and artifacts of the SAR within plant communities by using limited scale ranges. Due to scale dependence, an appropriate limited scale range should be chosen, depending on vegetation type and realized scale range of the considered data set. Species-area curves based on the standard Whittaker plots for plant communities could act as references to assess species richness of the large pool of vegetation records of different sizes and provide a tool for ranking species diversity for grassland and forest communities, where vegetation records differ considerably in plot size.