COUPLING GREENHOUSE GAS EMISSIONS TO SOIL O2 DYNAMICS AT THE AQUATIC-TERRESTRIAL INTERFACE

Soil oxygen (O₂) regulates many biogeochemical processes including biogenic greenhouse gas (GHG) production (e.g. nitrous oxide-N₂O, carbon dioxide-CO₂, and methane-CH₄); yet, due to the scarcity of direct field measurements, few data exists describing the relative abiotic and biotic controls on soil O₂. In-situ near-continuous monitoring of soil O₂ at 10 cm depth from an extensive soil sensor network in a restored wetland in SW Ohio highlights three distinct patterns in soil O₂ dynamics. Patterns include: 1) periodic depletion of O₂ in surface soils influenced by increased soil moisture and biological demand, 2) rapid increase in soil O₂ at a threshold level of soil moisture during soil drainage, and 3) the diurnal fluctuation of soil O₂ during periods of low soil moisture. We explore subsurface GHG concentrations and surface GHG flux to understand how these biotic and abiotic controls on soil O₂ impact soil GHG production and rapid gas exchange across the soil-surface boundary. Our study of soils across an aquatic-terrestrial interface suggests that improving representation of soil O₂ in coupled soil physical-biogeochemical models requires calibration/validation with in-situ near-continuous O₂ monitoring data.