Trophic Interactions and Plant Species Richness along a Productivity Gradient

We analyzed the interactive effects of trophic structure and disturbance on species diversity of plant communities along a productivity gradient by merging the intermediate disturbance hypothesis with a simple three-trophic-level predator-prey model. In two-trophic-level systems, i.e. without carnivores, the model produces a unimodal, hump-shaped pattern of species richness, which is consistent with patterns predicted from other models. If carnivores are included, trophic cascades produce a bimodal pattern of species richness over the productivity gradient. We have found no appropriate data sets in the literature with which to assess the validity of our model. We thus offer the model as an alternative hypothesis to be tested regarding plant species richness in productivity gradients, and as a reminder of the importance of trophic structure for patterns and processes in plant communities.