DISSERTATION RESEARCH: The nexus of observation and modeling of methane emissions from inland water bodies

Ohio State University, The, Columbus OH

Investigators

Abstract

The impacts of climate and wetlands on each other are currently not well understood. While wetland plants consume carbon dioxide from the atmosphere, wetlands also produce methane, a powerful greenhouse gas that influences the global climate. Methane production and its movement within the soils of wetlands results from many simultaneous processes. Microorganisms living in wetland soils where there is no oxygen can produce methane. Methane, being lighter than air, works its way through the soil and can escape into the atmosphere. However, during transport through soils, specialized bacteria can consume methane if the local chemistry is favorable to that process. Additionally, plants can facilitate the movement of methane from soils to the atmosphere. This project will study the transport of methane through wetland vegetation and improve mathematical models of that process. This will be accomplished by developing new measurement techniques that can more accurately predict how much methane is transported through wetland plants. Results from this work will improve our general understanding of how wetlands function with respect to release of methane gas, a potent greenhouse gas important in climate modeling. Plant transport is perhaps the most complex and least understood of the common methane pathways from the soil to the atmosphere. Moreover, wetlands are frequently comprised of a tight mosaic of land cover types. However, few models currently account for the effects of plant heterogeneity within the wetland on the total methane flux. Plants move methane both through their root aeration system, aerenchymous tissue, and through their xylem and stomata. It has been hypothesized that methane dissolved into the pore water at the plant root zone is mobilized by the plant as it transpires. However, the role of stomatally conducted methane is not clear and is almost always ignored by modern methane emission models. In this project, researchers will design and deploy novel chambers to quantify plant-mediated fluxes of methane from wetlands and use those data to parameterize a general model of the process. The study site for chamber deployment will be the Old Woman Creek National Estuary Research Reserve. These activities are part of a comprehensive measurement campaign involving traditional static chambers to measure diffusive fluxes through the water column, pore-water dialysis peepers, which provide a profile of methane concentrations in the soil, and an eddy-covariance tower, which will provide site level measurements of methane flux into the atmosphere. The plant hydrodynamics model, FETCH2, and a wetland methane model will be coupled to simulate the methane emitted through plants.