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

^a USDA-ARS National Soil Dynamics Laboratory, 411 South Donahue Drive, Auburn, AL 36832
^b Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS 39406-5018
^c Department of Biological Sciences, College of Charleston, Charleston, SC 29401
^d Joseph W. Jones Ecological Research Center, Newton, GA 31770
^e Department of Biological Sciences, Auburn University, Auburn University, AL 36849

^* Corresponding author (gbrunion{at}ars.usda.gov)

Received for publication April 30, 2005. Plant species vary in response to atmospheric CO₂ 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 CO₂. 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 CO₂, a model regenerating longleaf pine community composed of five species was exposed to two CO₂ 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 CO₂–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 CO₂. Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO₂ 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 CO₂, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO₂ treatments. As with pine, C content followed patterns similar to biomass. Elevated CO₂ resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO₂–enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO₂ plots, but only 8% under high CO₂. Therefore, while longleaf pine may perform well in a high CO₂ world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO₂ 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.