Ebullition dominates methane fluxes from the water surface across different ecohydrological patches in a temperate freshwater marsh at the end of the growing season

• Published in: The Science of the total environment Vol. 767; no. C; p. 144498
• Main Authors: Villa, Jorge A., Ju, Yang, Yazbeck, Theresia, Waldo, Sarah, Wrighton, Kelly C., Bohrer, Gil
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2021; Elsevier
• Subjects: Bubbling; Diffusion; Greenhouse gas flux; Patch dynamics; Spatial heterogeneity; Bubbling; Spatial heterogeneity; Patch dynamics; Diffusion; Greenhouse gas flux
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.144498

Measurements of the spatial heterogeneity of methane fluxes in wetlands are critical to better understand and predict methane emissions at the ecosystem scale. However, the within-wetland spatial heterogeneity of fluxes is rarely assessed. Here, we use a spatially balanced rapid chamber-based survey of methane at different ecohydrological patches within a temperate freshwater marsh. We measured fluxes exclusively from the water surface without including vegetation. We further used the data from chamber measurements to partition diffusive and ebullitive fluxes. Three ecohydrological patches were distinguishable in the marsh, defined by the type and presence/absence of vegetation. These patches were emergent vegetation, floating-leaved, and open water. Net methane fluxes from the water surface (diffusion plus ebullition) in emergent vegetation patches were larger than in the floating-leaved vegetation and open water patches (p < 0.05). Diffusive fluxes, representing a sizable smaller fraction of net fluxes, were larger in vegetated than in unvegetated patches (p < 0.05), while ebullitive fluxes mirrored the magnitude and differences observed in the net fluxes. Moreover, pooled net and ebullitive fluxes across patches (but not diffusive fluxes) were negatively correlated with water levels, the primary variable affecting patch distribution. Altogether, our results indicate that the differences among ecohydrological patches are driven by ebullition, ultimately highlighting challenges faced by scientists and practitioners in the field and modelers seeking to improve the predictability and resolution of wetland biogeochemical models. [Display omitted] •We used a spatially balanced survey to measure methane fluxes in a temperate marsh.•Diffusive fluxes were similar in vegetated patches and different than in open water.•Net methane fluxes and ebullition were larger in patches with emergent vegetation.•Net and ebullitive fluxes across patches were negatively correlated with water levels.