Studies examining the relationship between species richness and the productivity of ecological communities have taken one of two opposite viewpoints, either viewing productivity as a primary driver of richness, or richness as a driver of productivity.  Recently, verbal and graphical hypotheses have been proposed that attempt to merge these perspectives by clarifying the causal pathways that link resource supply, species richness, resource use and biomass production.   In this talk, we present mathematical models that formalize how these pathways can operate simultaneously in a single ecological system.  Our models combine a metacommunity framework in which dispersal and disturbance determine regional dynamics with classic consumer-resource theory that governs local species interactions.  Using these models, we show that the mechanisms by which resource supply influences species richness are inherently linked to the mechanisms by which species richness controls resource use and biomass production in competitive communities.  Our models also show that resource supply can affect species richness and richness can affect productivity simultaneously at a single spatial scale.  Finally, our models reproduce scale-dependent associations between species richness and community biomass that have been reported elsewhere.