Plant Community Composition More Predictive than Diversity of Carbon Cycling in Freshwater Wetlands

Changes in the world’s species composition and the loss of biodiversity have prompted a closer investigation of the importance of biodiversity and community composition to ecosystem functioning. However, few studies have explored this relationship outside of controlled experiments. Here, we examined the relationship between plant diversity, primary production, and methane efflux in freshwater wetlands in an across-site field study and assessed the applicability of experimental findings to natural wetlands. Four wetland sites in central Ohio (USA) were divided into two plant communities, one dominated by clonal species and one dominated by non-clonal species. We found that plant diversity was negatively correlated with aboveground biomass in both the clonal and non-clonal communities. Overall, plant community composition was a stronger predictor than diversity of the response variables and in certain instances a stronger predictor than environmental factors such as soil organic matter content, moisture content, and pH. Thus, plant community composition is an important driver of ecosystem functioning in depressional wetlands beyond the well-known environmental factors. Additionally, our work indicates that results from experimental wetland studies of the relationship among diversity, biomass and methane emission are not applicable to the wetland ecosystems included in our study.