Facilitation and competition on alpine elevation gradients: A global experiment on the organization of plant communities

• Ragan Callaway
• Robin Brooker
• Christopher J. Lortie
• Richard Michalet

Abstract
We propose to organize three meetings, each 7-10 days, in order to analyze data and develop conceptual, empirical, and mathematical models with a working group that has been loosely organized and conducting experiments on interactions in alpine plant communities around the world. Results from one of the nine sites for which data have been collected, the French Alps, and other preliminary analyses indicate that interactions shift from highly competitive in low elevation alpine meadows to highly facilitative in communities ¿l1000m higher and near the physical limits of plant growth. These competitive and facilitative interactions also appear to be coupled with community properties such as biomass, diversity, evenness, and the relative abundance of target species. Furthermore, shifts in species interactions and the intensity of species interactions along elevation gradients appear to correlate with community characteristics and regional climate. We are requesting funds from NCEAS to solve the problems inherent to such a large group of investigators from different parts of the world with a large data set. Funding will allow us to work cohesively as a group on statistical analyses of experimental data, to integrate experimental results with community properties in innovative ways, and to develop empirical and conceptual models for the relationship between climate, biogeography, and plant interactions on gradients.