Oxygen (O2) availability and diffusivity in wetlands are controlling
factors for the production and consumption of both carbon dioxide (CO2)
and methane (CH4) in the subsoil and thereby potential emission of these
greenhouse gases to the atmosphere. To examine the linkage between highresolution spatiotemporal trends in O2 availability and CH4/CO2 dynamics
in situ, we compare high-resolution subsurface O2 concentrations, weekly
measurements of subsurface CH4/CO2 concentrations and near continuous
flux measurements of CO2 and CH4. Detailed 2-D distributions of O2
concentrations and depth-profiles of CO2 and CH4 were measured in the
laboratory during flooding of soil columns using a combination of planar O2
optodes and membrane inlet mass spectrometry. Microsensors were used to assess apparent diffusivity under both field and laboratory conditions. Gas concentration profiles were analyzed with a diffusion-reaction model for quantifying production/consumption profiles of O2, CO2, and CH4. In drained conditions, O2 consumption exceeded CO2 production, indicating CO2
dissolution in the remaining water-filled pockets. CH4 emissions were negligible when the oxic zone was >40 cm and CH4 was presumably consumed below the depth of detectable O2. In flooded conditions, O2 was transported by other mechanisms than simple diffusion in the aqueous phase. This work demonstrates the importance of changes in near-surface apparent diffusivity, microscale O2 dynamics, as well as gas transport via aerenchymous plants tissue on soil gas dynamics and greenhouse gas emissions following marked changes in water level.