Mechanisms of positive biodiversity-production relationships: insights provided by delta C-13 analysis in experimental Mediterranean grassland plots

We investigated the role of water use in a Mediterranean grassland, in whic h diversity was experimentally manipulated, and a positive relationship was observed between plant species richness and productivity. Soil moisture pa tterns and stable carbon isotope ratios (PC) in leaves indicated greater wa ter use by plants growing in species-rich mixtures compared to monocultures . These results suggest that complementarity or facilitation may be the mec hanism responsible for the positive relationship between plant diversity an d ecosystem processes.