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Title: EFFECTS OF ELEVATED ATMOSPHERIC CO2 ON BIOMASS AND CARBON ACCUMULATION IN A MODEL REGENERATING LONGLEAF PINE COMMUNITY

Author
item Runion, George
item DAVIS, MICHEAL - UNIV. SOUTH. MISS.
item PRITCHARD, SETH - COLLEGE OF CHARLESTON
item Prior, Stephen - Steve
item MITCHELL, ROBERT - JOSEPH W. JONES, ECO.RES.
item Torbert, Henry - Allen
item Rogers Jr, Hugo
item DUTE, ROLAND - AUBURN UNIVERSITY

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2005
Publication Date: 7/1/2006
Citation: Runion, G.B., Davis, M.A., Pritchard, S.G., Prior, S.A., Mitchell, R.J., Torbert III, H.A., Rogers Jr, H.H., Dute, R.R. 2006. Effects of elevated atmospheric co2 on biomass and carbon accumulation in a model regenerating longleaf pine community. Journal of Environmental Quality. 35:1478-1486.

Interpretive Summary: Examining how the rise in global atmospheric CO2 impacts the structure and function of forest ecosystems is important due to their economic and ecological value. This is particularly true for Longleaf pine savannahs which once occupied 37.2 million ha of the southeastern United States; however, timber harvesting, fire suppression, and conversion of forests to farmland has reduced the land area of this system to 4% of its original range. A model regenerating Longleaf pine community exposed to two levels of atmospheric CO2 (ambient or elevated) was monitored for soil CO2 losses. Our results suggest that soil CO2 losses were higher under elevated atmospheric CO2, but this forest systems could still be a net sink for atmospheric CO2 due to more biomass being added.

Technical Abstract: Plant species vary in response to atmospheric CO2-enrichment and differences in physiology, structure, and symbiotic relationships do not always reliably predict species responses, especially when grown in communities. Experiments examining effects of CO2-enrichment on plant communities are critical to further our understanding of ecosystem response to global climate change. A model regenerating longleaf pine ecosystem was exposed to two CO2 regimes (ambient, 365 'mol/mol and elevated, 720 'mol/mol) for three years using open-topped chambers. Total above- and belowground biomass was 70% and 49% greater, respectively, in CO2-enriched chambers; carbon (C) content followed a similar response pattern, resulting in a significant increase of 13.8 Mg C per ha under elevated CO2. Responses of individual species, however, varied. Longleaf pine (Pinus palustris) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta), rattlebox (Crotalaria rotundifolia), and butterfly weed (Asclepias tuberosa) exhibited negative above- and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta) did not differ significantly between CO2 treatments; C content again followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure; 88% of total biomass in CO2-enriched plots was allocated to longleaf pine with only 8% allocated to wiregrass, rattlebox, and butterfly weed. In comparison, ambient CO2 plots allocated 76% of total biomass to longleaf pine but had 19% allocated to wiregrass, rattlebox, and butterfly weed. Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well as atmospheric CO2 continues to rise. Despite variable species responses, the system gained 11.4 Mg C per ha under high CO2 suggesting that this ecosystem should be a sink for atmospheric CO2.