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

Abstract

Neubauer, Scott C.; and Raynie, Richard C., "Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance" (2016 Abstract Coastal marshes take up atmospheric CO 2 while emitting CO 2 , CH 4 , and N 2 O. 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 CO 2 and CH 4 using eddy covariance (EC) in comparison with fluxes of CO 2 , CH 4 , and N 2 O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g C m À2 yr À1 was lost through NEE c from the brackish marsh. Of this, 11 g C m À2 yr À1 resulted from net CH 4 emissions and the remaining 171 g C m À2 yr À1 resulted from net CO 2 emissions. In contrast, À290 g C m 2 yr À1 was taken up through NEE c by the freshwater marsh, with 47 g C m À2 yr À1 emitted as CH 4 and À337 g C m À2 yr À1 taken up as CO 2 . From chambers, we discovered that neither site had large fluxes of N 2 O. 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 CO 2 and CH 4 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.

Direct and Indirect Effects of Tides on Ecosystem‐Scale CO2 Exchange in a Brackish Tidal Marsh in Northern California

“…Annual uptake at the marsh was lower than NEE reported for a freshwater marsh in Louisiana (−337 g C m −2 yr −1 ; Krauss et al, ), a New England salt marsh (−336 to −256 g C m −2 yr −1 ; Forbrich & Giblin, ), and a para grass‐dominated subtropical marsh in Taiwan (−376 g C m −2 yr −1 ; Lee et al, ), on par with a restored salt marsh in New Jersey (−213 g C m −2 yr −1 ; Artigas et al, ), and greater than uptake at a reed‐dominated marsh in Taiwan (−53 g C m −2 yr −1 ; Lee et al, ) and growing season uptake measured at a salt marsh in Virginia (−130 g C m −2 ; Kathilankal et al, ). While tidal marshes, including our site, are typically net sinks of atmospheric CO 2 , a brackish marsh in Louisiana was observed to be a net CO 2 source, emitting 171 g C m −2 yr −1 (Krauss et al, ), and NEE at an urban tidal marsh in the Hudson‐Raritan estuary ranged from −310 g C m −2 yr −1 to 984 g C m −2 yr −1 (Schäfer et al, ), highlighting the potential for large interannual variability in NEE in tidal wetlands. While this study focused on the subannual dynamics of NEE caused by tidal activity, future work will focus on interannual variability in carbon fluxes at the marsh, which can be driven by climatic, hydrological, and anthropogenic influences.…”

Relationships Between Salinity and Short-Term Soil Carbon Accumulation Rates from Marsh Types Across a Landscape in the Mississippi River Delta

“…Furthermore, if these marshes transition to more saline marshes due to climate change, or towards fresh marshes due to large scale restoration actions, the short-term global carbon pool may change. Balancing the greenhouse gas emissions from each of these four marsh types with the short-term carbon accumulation rates may provide a comprehensive understanding of the role of these marshes in overall carbon sequestration (Poffenbarger et al 2011;Holm et al 2016;Krauss et al 2016). For example, fresh marshes may accumulate a large amount of carbon, but they produce methane gas during anaeraboic metabolism, which has a global warming potential that is 25 times greater than carbon dioxide (Whiting and Chanton 2001).…”

A Biogeochemical Compromise: The High Methane Cost of Sequestering Carbon in Restored Wetlands

“…Interpolations based on seasonal measurements, where necessary, are detailed in Petrescu et al (2015). More information can be found in the supporting information and existing literature (Chamberlain, Groffman, et al, 2017;Chu et al, 2015;Desai et al, 2015;Flanagan & Syed, 2011;Friborg et al, 2000Friborg et al, , 2003Herbst et al, 2013;Holm et al, 2016;Jammet et al, 2017;Krauss et al, 2016;Lee et al, 2016;Long et al, 2010;Mastepanov et al, 2008;Olson et al, 2013;Parmentier et al, 2011;Pugh et al, 2017;Rinne et al, 2007;Runkle et al, 2013;Sachs et al, 2010Sachs et al, , 2008Shurpali et al, 1993Shurpali et al, , 1995Tiemeyer, 2013;Y. Zhang et al, 2012;Zona et al, 2009).…”