8 - Predicting Responses of Tropical Plant Communities to Elevated CO2: Lessons from Experiments with Model Ecosystems

Abstract

This chapter attempts to synthesize the current understanding of how, and through which mechanisms, tropical plant communities are likely to respond to rising atmospheric CO2. Studies with tropical plants indicate that responses of individually grown plants to elevated CO2 do not scale well (with consistent predictability) to those obtained when individuals are grown under competitive conditions. Predictions of dramatic increases in biomass accumulation and leaf area production at the level of the community, especially in naturally nutrient-limited systems, are consistently contradicted by evidence from model and in situ communities. Sufficient evidence now exists to state that the speed and the extent to which shifts occur under elevated CO2 are linked to the age of the plants and to the availability of other growth-limiting resources, especially nutrients. In nature, innumerable positive and negative feedbacks occurring at all levels of system complexity influence the structure and composition of plant communities. This leads to the prediction that elevated atmospheric CO2 concentrations will lead to changes in species dominance in tropical plant communities, just as it will in other geographic regions.