PLANT DIVERSITY AND ECOSYSTEM PRODUCTIVITY - THEORETICAL CONSIDERATIONS

Ecosystem processes are thought to depend on both the number and ident ity of the species present in an ecosystem, but mathematical theory pr edicting this has been lacking, Here we present three simple models of interspecific competitive interactions in communities containing vari ous numbers of randomly chosen species, All three models predict that, on average, productivity increases asymptotically with the original b iodiversity of a community. The two models that address plant nutrient competition also predict that ecosystem nutrient retention increases with biodiversity and that the effects of biodiversity on productivity and nutrient retention increase with interspecific differences in res ource requirements. All three models show that both species identity a nd biodiversity simultaneously influence ecosystem functioning, but th eir relative importance varies greatly among the models. This theory r einforces recent experimental results and shows that effects of biodiv ersity on ecosystem functioning are predicted by well-known ecological processes.