Résumé
Coexistence mechanisms are the key to understanding the relationship between species richness and community productivity. Model plant communities were used to examine two general kinds of coexistence mechanisms, with and without reproductive and competitive trade-offs. Model parameters (e.g., numbers of species, recruitment limitations, and degree of heterogeneity) were varied to create different levels of species richness in the model community. The different coexistence mechanisms seem to result in different diversity-productivity patterns, suggesting a lack of a generalized relationship between species richness and productivity. Within-site and across-site aspects of such a relationship are discussed. The possibility of a relationship between species richness and productivity for other coexistence mechanisms not explicitly studied here is considered.