N2O fluxes and the coupling with CO2 fluxes in agroecosystems

Nitrous oxide (N2O) is a powerful greenhouse gas but its global emissions from natural ecosystems and agroecosystems are uncertain. N2O is a product of both nitrification and denitrification processes in soil and largely controlled by N availability, temperature, moisture, redox potential, pH, and other conditions. Atmospheric N deposition, fertilization, and other human activities are significantly increasing N2O emissions. Studying the coupling of N2O and CO2 fluxes provide new insight to understand belowground carbon and nitrogen cycling. We measured N2O and CO2 fluxes simultaneously in an agricultural site in Massachusetts in 2011 with an eddy covariance system. We further developed an integrated chamber system to measure in situ CO2 and N2O fluxes. This system consists of recently developed laser-based gas analyzers with the new cavity ringdown spectroscopy technique to measure CO2 and N2O. These analyzers were connected to a closed chamber system that enables flux measurement within a five-minute cycle. To develop a model to simulate N2O and CO2 fluxes, we conducted a soil incubation experiment in the laboratory. Soil samples were incubated at the combination of temperatures of 10°C, 20°C and 30°C and water contents of 10%, 20%, and 30%. We will then develop a model to simulate CO2 and N2O fluxes as a function of C stock, N stock, soil temperature, and soil water content.