PARENT SESSION
Poster Session #11: Elevated CO₂.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Effects of elevated CO₂ and future climate on mechanisms of species coexistence in plant communities.

PETERSON, ANDREW¹, GRIFFIN, KEVIN¹, ¹

ABSTRACT- An important issue in global change biology is the development of a mechanistic understanding of how increasing levels of CO₂ and predicted changes in interannual climate variability will affect species coexistence in terrestrial plant communities. Regional-scale climate models predict an increase in the frequency of above normal temperature events due to increasing CO₂ and other greenhouse gases in the atmosphere. Such changes in the frequency distribution of temperature fluctuations has significant implications for species coexistence because many important life-history traits of plants are nonlinear functions of temperature. Depending on the shape of these nonlinearities, the long-term average value of these traits can be very sensitive to relatively small changes in the frequency distribution of temperature fluctuations. It has been known for some time that interspecific differences in the nonlinear response of life-history traits to environmental fluctuations are important regulators of species coexistence. We present original data and a new analysis of a previously published data set showing that elevated CO₂ changes the shape of the nonlinear response of certain life-history traits to temperature for four herbaceous species. A simple competition model incorporating these effects of elevated CO₂ shows reversals in species dominance under some future climate scenarios. This research illustrates a mechanistic framework for understanding how elevated CO₂ and climate change may alter competitive interactions and species composition in terrestrial plant communities.

KEY WORDS: climate change, CO₂, competition, nonlinearities