title: Elevated carbon dioxide is predicted to promote coexistence among competing species in a trait-based model.
abstract: Differential species responses to atmospheric CO 2 concentration (Ca) could lead to quantitative changes in competition among species and community composition, with flow-on effects for ecosystem function. However, there has been little theoretical analysis of how elevated Ca (eC a) will affect plant competition, or how composition of plant communities might change. Such theoretical analysis is needed for developing testable hypotheses to frame experimental research. Here, we investigated theoretically how plant competition might change under eC a by implementing two alternative competition theories, resource use theory and resource capture theory, in a plant carbon and nitrogen cycling model. The model makes several novel predictions for the impact of eC a on plant community composition. Using resource use theory, the model predicts that eC a is unlikely to change species dominance in competition, but is likely to increase coexistence among species. Using resource capture theory, the model predicts that eC a may increase community evenness. Collectively, both theories suggest that eC a will favor coexistence and hence that species diversity should increase with eC a. Our theoretical analysis leads to a novel hypothesis for the impact of eC a on plant community composition. This hypothesis has potential to help guide the design and interpretation of eC a experiments.
authors.affiliation: Division of Earth and Environmental Sciences Los Alamos National Laboratory Los Alamos New Mexico USA ; Department of Civil and Environmental Engineering University of California Irvine California USA ; Department of Biological Sciences Faculty of Science Macquarie University North Ryde NSW 2109 Australia.
authors.forename: Ashehad A
authors.initials: AA
authors.lastname: Ali
authors.affiliation: Department of Biological Sciences Faculty of Science Macquarie University North Ryde NSW 2109 Australia ; Hawkesbury Institute for the Environment University of Western Sydney Locked Bag 1797 Penrith NSW 2751 Australia.
authors.forename: Belinda E
authors.initials: BE
authors.lastname: Medlyn
authors.affiliation: Department of Biological Sciences Faculty of Science Macquarie University North Ryde NSW 2109 Australia ; UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive 1919 route de Mende 34090 Montepellier France ; UMR 7205 Muséum National d'Histoire Naturelle CP50 45 rue Buffon 75005 Paris France.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Aubier
authors.affiliation: Hawkesbury Institute for the Environment University of Western Sydney Locked Bag 1797 Penrith NSW 2751 Australia.
authors.forename: Kristine Y
authors.initials: KY
authors.lastname: Crous
authors.affiliation: Hawkesbury Institute for the Environment University of Western Sydney Locked Bag 1797 Penrith NSW 2751 Australia ; Department of Forest Resources University of Minnesota St. Paul Minnesota USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Reich
keywords: Elevated CO2; plant competition; species diversity; species traits