Regional and local patterns in plant species richness with respect to resource availability

The hump-shaped relationship between plant species richness and productivity is a well-established and important paradigm. While plot-based species richness patterns on local scales have received much attention. little is currently known about species-based patterns on a regional scale. Using Ellenberg's indicator values for 1802 plant species in central Europe, we assess the patterns in regional species richness with respect to light, water, and mineral nutrient availability - three variables that strongly influence productivity. The results of this analysis are compared to those of published studies on smaller scales leading to the following conclusions: 1. On a regional scale in central Europe there is a hump-shaped relationship between soil nutrient supply and plant species richness within a given biome. 2. The peak in species richness for grasslands and wetlands occurs on nutrient-poor soils, while the peak for forests is on nutrient-rich soils. 3. Gradients in plant productivity controlled by different variables (i.e. water, nutrients, or disturbance) have dissimilar effects on plant species richness.