Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance

Authors

Ken W. Krauss, U.S. Geological SurveyFollow
Guerry O. Holm Jr.
Brian C. Perez
David E. McWhorter
Nicole Cormier, U.S. Geological Survey
Rebecca F. Moss, USGS Wetland and Aquatic Research Center
Darren J. Johnson, USGS Wetland and Aquatic Research Center
Scott C. Neubauer, Virginia Commonwealth University
Richard C. Raynie, Louisiana Coastal Protection and Restoration Authority

Document Type

Article

Date of this Version

2016

Citation

Krauss, K. W., G. O. Holm Jr, B. C. Perez, D. E. McWhorter, N. Cormier, R. F. Moss, D. J. Johnson, S. C. Neubauer, and R. C. Raynie (2016), Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance, J. Geophys. Res. Biogeosci., 121, 1503–1521, doi:10.1002/ 2015JG003224.

Comments

U.S. government work.

Abstract

Coastal marshes take up atmospheric CO₂ while emitting CO₂, CH₄, and N₂O. This ability to sequester carbon (C) is much greater for wetlands on a per area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEE_c) of CO₂ and CH₄ using eddy covariance (EC) in comparison with fluxes of CO₂, CH₄, and N₂O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g Cm^-2 yr^-1 was lost through NEE_c from the brackish marsh. Of this, 11 g Cm^-2 yr^-1 resulted from net CH₄ emissions and the remaining 171 g Cm^-2 yr^-1 resulted from net CO₂ emissions. In contrast, -290 g Cm² yr^-1 was taken up through NEEc by the freshwater marsh, with 47 g ^Cm-2 yr^-1 emitted as CH4 and -337 g Cm^-2 yr^-1 taken up as CO₂. From chambers, we discovered that neither site had large fluxes of N₂O. Sustained-flux greenhouse gas accounting metrics indicated that both marshes had a positive (warming) radiative balance, with the brackish marsh having a substantially greater warming effect than the freshwater marsh. That net respiratory emissions of CO₂ and CH₄ as estimated through chamber techniques were 2–4 times different from emissions estimated through EC requires additional understanding of the artifacts created by different spatial and temporal sampling footprints between techniques.