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Abstract Methane (CH4) dynamics in wetlands are spatially variable and difficult to estimate at ecosystem scales. Patches with different plant functional types (PFT) represent discrete units within wetlands that may help characterize patterns in CH4variability. We investigate dissolved porewater CH4concentrations, a representation of net CH4production and potential source of atmospheric flux, in five wetland patches characterized by a dominant PFT or lack of plants. Using soil, porewater, and plant variables we hypothesized to influence CH4, we used three modeling approaches—Classification and regression tree, AIC model selection, and Structural Equation Modeling—to identify direct and indirect influences on porewater CH4dynamics. Across all three models, dissolved porewater CO2concentration was the dominant driver of CH4concentrations, partly through the influence of PFT patches. Plants in each patch type likely had variable influence on CH4via root exudates (a substrate for methanogens), capacity to transport gas (both O2from and CH4to the atmosphere), and plant litter quality which impacted soil respiration and production of CO2in the porewater. We attribute the importance of CO2to the dominant methanogenic pathway we identified, which uses CO2as a terminal electron acceptor. We propose a mechanistic relationship between PFT patches and porewater CH4dynamics which, when combined with sources of CH4loss including methanotrophy, oxidation, or plant‐mediated transport, can provide patch‐scale estimates of CH4flux. Combining these estimates with the distribution of PFTs can improve ecosystem CH4flux estimates in heterogenous wetlands and improve global CH4budgets.
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Diel Greenhouse Gas Emissions Demonstrate a Strong Response to Vegetation Patch Types in a Freshwater Wetland
Abstract Wetland methane (CH4) fluxes are highly variable over spatial and temporal scales due to variations in CH4production, oxidation, and transport. While some aspects of temporal variability in CH4fluxes are well documented, diel variability is poorly constrained, and studies report conflicting findings, making it difficult to generalize. Topographic, geochemical, hydroclimatic, and vegetative variability can result in characteristically different “patches” that likely influence differences in diel patterns. We investigated diel patterns of CH4fluxes from a large seasonal‐mineral soil wetland in Maryland (USA) across three functionally unique patches: two with vegetation (emergent and submerged aquatic vegetation) and one without (open water) during the summer of 2021. To explore the relationships between vegetation, environmental conditions, and flux patterns, we also measured physiochemical variables (air and water temperature, pH, relative humidity, PAR, dissolved oxygen, and water depth). To our knowledge, this is the first study comparing diel variability using chambers across such distinct vegetation patch types. We found that diel patterns were strongly linked to patch types: CH4fluxes from the emergent vegetation did not display a consistent diel pattern, while fluxes from the submerged vegetation and no vegetation patches frequently peaked at 13:00 and 05:00, respectively. These differences could be a direct result of vegetation impact on production, oxidation, and/or transport of CH4or on conditions covarying with patch type. This study contributes to the growing understanding of how CH4fluxes vary spatially over diel cycles and emphasizes the importance of considering spatially varying diel patterns when estimating fluxes.
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- Award ID(s):
- 1856560
- PAR ID:
- 10673440
- Publisher / Repository:
- Publisher
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 129
- Issue:
- 11
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JG008193
