|Davis, Micheal - AUBURN UNIVERSITY|
|Mitchell, Robert - JONES ECOLOGICAL RES.CTR.|
|Rogers Jr, Hugo|
Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2001
Publication Date: August 1, 2001
Citation: Pritchard, S.G., Davis, M.A., Mitchell, R.J., Prior, S.A., Boykin, D.L., Rogers, H.H., and Runion, G.B. 2001. Root dynamics in an artificially constructed regenerating longleaf pine ecosystem are affected by atmospheric CO2 enrichment. Environmental and Experimental Botany 46:55-69. Interpretive Summary: There is little information about how rising global atmospheric CO2 concentrations will affect competitive relationships between economically and ecologically important tree species. A better understanding of these processes will contribute to better management of longleaf pine forests. We have shown that if the current rise in atmospheric CO2 continues, the roots of longleaf pine might grow much larger than the roots of several other species including sand post oak. This suggests that longleaf pine will be a better competitor in the future. This information contributes to knowledge about how longleaf pine forests, economically and ecologically important plant systems of the southeastern U. S. will function in a higher CO2 world.
Technical Abstract: Different responses to elevated CO2 exhibited by different plant functional types may alter competition for above- and belowground resources. Because C allocation to roots is often favored over C allocation to shoots in plants grown with CO2 enrichment, belowground function of forest ecosystems may change significantly. We established an outdoor facility to examine the effects of elevated CO2 on root dynamics in artificially constructed communities of five early successional forest species: (1) Pinus palustris Mill.; (2) wiregrass, Aristida stricta Michx.; (3) Quercus margaretta; (4) Crotalaria rotundifolia Walt. ex Gemel; (5) Asclepias tuberosa L.. These are common in early successional longleaf pine savannahs throughout the southeast. A combination of minirhizotrons and soil coring was used to examine rooting dynamics. CO2-enriched plots exhibited 35% higher standing root crop length, 37% greater root length production per day, and 47% greater root length mortality per day. These variables, however, were enhanced by CO2 enrichment only at the 10-30 cm depth. Relative root turnover (flux/standing crop) was unchanged by elevated CO2. Sixteen months after planting, root biomass of pine was 62% higher in elevated compared to ambient CO2 plots. Conversely, the combined biomass of rattlebox, wiregrass, and butterfly weed combined was 28% greater in ambient compared to high CO2 plots. There was no difference in root biomass of oaks after 16 months of exposure to elevated CO2. Using root and shoot biomass as a metric, longleaf pine realized the greatest and most consistent benefit from exposure to elevated CO2.