Plant species traits and capacity for resource reduction predict yield and abundance under competition in nitrogen-limited grassland

1. The objective of this study is to test whether plant traits that are predicted by resource-competition theory to lead to competitive dominance are correlated with competitive response and abundance in a nitrogen-limited grassland. We collected species trait and soil nutrient data on non-leguminous perennial prairie plant species in replicated monoculture plots established for this purpose. 2. The soil nitrate concentration of 13 species grown in long-term (5-year) monocultures (a measure of R*) was correlated with their relative yield (a measure of competitive response) and with their abundance in competition. The trait best correlated with a species' relative yield was root length density (RLD), and the trait best correlated with abundance in competition was biomass : N ratio. 3. The traits that best predicted nitrate R* were the biomass : N ratio and allocation to fine roots, where species with higher biomass : N and allocation to fine roots had lower R*. Easily measured species traits may therefore be useful proxy measures for R*. 4. The dominance of species with lower nitrate R* levels and higher RLD and biomass : N in monoculture is qualitatively consistent with the prediction of resource-competition theory that the species most efficient at acquiring, retaining and using the major limiting resource will be the best competitors. Additional mechanisms are needed to explain how these species coexist.