Effects of Elevated Atmospheric Carbon Dioxide on Biomass and Carbon Accumulation in a Model Regenerating Longleaf Pine Community

Plant species vary in response to atmospheric CO 2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO 2 Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO 2 , a model regenerating longleaf pine community composed of five species was exposed to two CO 2 regimes (ambient, 365 μmol mol −1 and elevated, 720 μmol mol −1 ) for 3 yr. Total above‐ and belowground biomass was 70 and 49% greater, respectively, in CO 2 –enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha −1 under elevated CO 2 Responses of individual species, however, varied. Longleaf pine ( Pinus palustris Mill.) was primarily responsible for the positive response to CO 2 enrichment. Wiregrass ( Aristida stricta Michx.), rattlebox ( Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed ( Asclepias tuberosa L.) exhibited negative above‐ and belowground biomass responses to elevated CO 2 , while sand post oak ( Quercus margaretta Ashe) did not differ significantly between CO 2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO 2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO 2 –enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO 2 plots, but only 8% under high CO 2 Therefore, while longleaf pine may perform well in a high CO 2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO 2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science.