Cup plant biases community nitrogen composition in response to increasing prairie community diversity
High diversity grassland ecosystems such as Midwestern tallgrass prairies often exhibit increased biomass production and nutrient uptake relative to less diverse ecosystems due to complementarity between species and disproportionate influences of highly productive individual species. This positive empirical relationship between biodiversity and ecosystem function is often applied by land managers concerned with reducing nutrient runoff from agricultural landscapes. By comparing responses of the highly productive forb cup plant (Silphium perfoliatum) and less productive neighboring species to increasing diversity in reconstructed prairie plots, this study sought to understand the mechanisms responsible for such positive relationships between species diversity and ecosystem function in an agricultural context. Nitrogen content of aboveground tissue was measured in leaves of cup plant and neighboring species during and after the growing season. Results suggest that cup plant, when planted at high densities, may override the expected positive influence of species diversity on nitrogen removal by restored prairie communities. These findings indicate that complementarity in resource use and biased effects of the focal species operate simultaneously in prairies restored in agricultural environments. The differential response of co-occurring productive and less productive species are potentially important considerations for restoration projects in agricultural contexts.