This research was supported by a private gift from Great Dismal Swamp Mitigation Bank in support of basic research, grant 70233 from North Carolina's Water Resource Research Institute, a grant from the NC Department of the Environment and Natural Resources, and a grant to E. S. Bernhardt from the U.S. Department of Energy's Office of Science (BER) through the Coastal Center of the National Institute for Climatic Change Research at Tulane University. J. L. Morse was supported by a U.S. Environmental Protection Agency Science to Achieve Results (STAR) Fellowship (FP916599), and M. Ardón was supported by NSF DBI-085576.
Carbon Dioxide, Greenhouse effect--Environmental aspects--Southeastern United States, Wetlands
Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000–64 800 kg CO2·ha-1· yr-1) comprised 66–100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4·ha-1·yr-1) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O·ha-1·yr-1) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions.
Jennifer L. Morse, Marcelo Ardón, and Emily S. Bernhardt 2012. Greenhouse gas fluxes in southeastern U.S. coastal plain wetlands under contrasting land uses. Ecological Applications 22:264–280. http://dx.doi.org/10.1890/11-0527.1