2008 Research Highlights
Carbon Fluxes Respond to Drought in Coastal Plain Forests
Full accounting of ecosystem carbon pools and fluxes in coastal plain ecosystems remains less studied compared to upland systems, even though the carbon stocks in these systems may be up to an order of magnitude higher, making them a potentially important component in regional and global carbon cycle.
Scientists working with the Eastern Forest Environmental Threat Assessment Center report carbon pools and CO2 exchange measurements during three hydrologically contrasting years (2005-2007) in a coastal plain loblolly pine plantation in North Carolina. The forest was a strong carbon sink during all three years, according to eddy covariance measurements of CO2 exchange. The inter-annual differences in net ecosystem exchange of CO2 were traced to drought-induced decrease in canopy conductance that correlated better with precipitation deficit than with soil volumetric water content. Differences in gross ecosystem productivity and lower daytime respiration during the drier years (e.g., 2006 and 2007) may have contributed to the observed inter-annual differences in net ecosystem exchange.
Overall, the response of carbon fluxes to contrasting moisture availability was more limited than reported for other (e.g., upland) ecosystems, and the drought effect was mediated by demand (e.g., vapor pressure deficit) rather than supply (e.g., volumetric water content), implying physiological limitations to water transport.
Contact: Steve McNulty, Southern Global Change Program team leader, (919) 515-9489, smcnulty@fs.fed.us
Partners: North Carolina State University, University of Toledo, Weyerhaeuser Company
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Photo by USDA Forest Service Southern Research Station archive
