Linking Subsurface Biogeochemical Nitrogen Cycling to Surface Fluxes

Soil biogeochemical processes produce greenhouse gases which can have significant environmental impacts when exchanged with the atmosphere. The magnitude of surface fluxes is driven by vertical concentration gradients, thus understanding drivers of below-ground N2O and NO production and consumption pathways is critical to atmospheric greenhouse gas mitigation strategies. We present subsurface gas composition and surface flux measurements in laboratory soil mesocosms to understand how depth-dependent soil processes impact surface fluxes. Diffusive gas probes are buried at three depths in three mesocosms of Northeastern agricultural soil and the columns are capped for surface flux measurements. We measure N2O (14N15NO, 15N14NO, 14N14NO, N218O), NO, CO2 (12CO2, 13CO2), and O2 coupled with soil moisture and temperature measurements using a Tunable Infrared Laser Direct Absorption Spectrometer (TILDAS). Isotopically resolved maps of trace gases in response to 15N-labled N2O and NO dosing under a range of conditions provides insight into the impact of soil moisture and oxygen content on subsurface transport, abiotic transformations and biological processes impacting surface fluxes.