Aims Decades of empirical work have demonstrated how dominant plant species and nitrogen fertilization can influence the structure and function of plant communities. More recent studies have examined the interplay between these factors, but few such studies use an explicit trait-based framework. In this study, we use an explicit traitbased approach to identify potential mechanisms for communitylevel responses and to test ecological niche theory. Methods We experimentally manipulated plant communities (control, -dominant species, -random biomass) and nitrogen (N) inputs (control, +organic N, +inorganic N) in a fully factorial design. We predicted that traits related to plants' ability to take up different forms of soil N would differ between dominant and subordinate species, resulting in interactive effects of dominant species loss and N fertilization on plant community structure and function. The study took place in a montane meadow in the Rocky Mountains, Colorado, USA. Important Findings After four years, the plant community in removal plots converged toward a species composition whose leaf and root functional traits resembled those of the previously removed dominant species. Ecosystem productivity generally increased with N addition: soil carbon efflux was ~50% greater when either form of N was added, while inorganic N addition increased aboveground biomass production by ~60% relative to controls. The increase in production was mediated by increased average height, leaf mass:area ratio and leaf dry matter content in plant communities to which we added inorganic N. Contrary to our predictions, there were no interactive effects of N fertilization and dominant species loss on plant community structure or ecosystem function. The plant community composition in this study exhibited resistance to soil N addition and, given the functional convergence we observed, was resilient to species loss. Together, our results indicate that the ability of species to compensate functionally for species loss confers resilience and maintains diversity in montane meadow communities.
Bibliographical noteFunding Information:
We thank L. Moorhead and M. Rúa for helpful suggestions on drafts of this manuscript, the staff of the Rocky Mountain Biological Laboratory (RMBL) for their support, and the organizations that funded this research: the Department of Ecology and Evolutionary Biology, University of Tennessee (Q.D.R., J.A.H.), the RMBL Dr Jean Langenheim Fellowship (Q.D.R.), the RMBL Dr Lee R. G. Snyder Memorial Fellowship (J.A.H.), and the Fran Hunter Fellowship (J.A.H.). N.J.S. and A.T.C. thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate. Data accessibility. Data associated with this manuscript are freely available and are archived at https://doi.org/10.6084/m9.figshare.4719199.v1. Conflict of interest statement. None declared.
- dominant species
- functional trait
- removal experiment