Impoundment increases methane emissions in Phragmites ‐invaded coastal wetlands

作者：Rebecca Sanders‐DeMott, Meagan J. Eagle, Kevin D. Kroeger, Faming Wang, Thomas W. Brooks, Jennifer A. O'Keefe Suttles, Sydney K. Nick, Adrian G. Mann, Jianwu Tang · 发表于：Global Change Biology · 年份：2022 · DOI：10.1111/gcb.16217 · 被引用次数：49 · 研究领域：Coastal wetland ecosystem dynamics、Peatlands and Wetlands Ecology、Marine and coastal ecosystems

Abstract Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH 4 ) emissions due to regular inundation with sulfate‐rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites , that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50‐fold increase in CH 4 emissions, but effects on carbon dioxide (CO 2 ) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water‐table depth or salinity during the growing season and was a strong CO 2 sink of −352 g CO 2 ‐C m −2 year −1 offset by CH 4 emission of 11.4 g CH 4 ‐C m −2 year −1 . Growing season CH 4 flux was driven primarily by temperature. Methane flux exhibited a diurnal ...