Plant species determine tidal wetland methane response to sea level rise.

Mueller, Peter; Mozdzer, Thomas J; Langley, J Adam; Aoki, Lillian R; Noyce, Genevieve L; Megonigal, J Patrick · Nat Commun · 2020

basic_science · Level V

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Abstract

Blue carbon (C) ecosystems are among the most effective C sinks of the biosphere, but methane (CH<sub>4</sub>) emissions can offset their climate cooling effect. Drivers of CH<sub>4</sub> emissions from blue C ecosystems and effects of global change are poorly understood. Here we test for the effects of sea level rise (SLR) and its interactions with elevated atmospheric CO<sub>2</sub>, eutrophication, and plant community composition on CH<sub>4</sub> emissions from an estuarine tidal wetland. Changes in CH<sub>4</sub> emissions with SLR are primarily mediated by shifts in plant community composition and associated plant traits that determine both the direction and magnitude of SLR effects on CH<sub>4</sub> emissions. We furthermore show strong stimulation of CH<sub>4</sub> emissions by elevated atmospheric CO<sub>2</sub>, whereas effects of eutrophication are not significant. Overall, our findings demonstrate a high sensitivity of CH<sub>4</sub> emissions to global change with important implications for modeling greenhouse-gas dynamics of blue C ecosystems.

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