Differential species responses to atmospheric CO₂ 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 (eCₐ) 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 eCₐ 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 eCₐ on plant community composition. Using resource use theory, the model predicts that eCₐ is unlikely to change species dominance in competition, but is likely to increase coexistence among species. Using resource capture theory, the model predicts that eCₐ may increase community evenness. Collectively, both theories suggest that eCₐ will favor coexistence and hence that species diversity should increase with eCₐ. Our theoretical analysis leads to a novel hypothesis for the impact of eCₐ on plant community composition. This hypothesis has potential to help guide the design and interpretation of eCₐ experiments.
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- elevated CO₂
- plant competition
- species diversity
- species traits