Impact of Precipitation Intensity and Riparian Geomorphic Characteristics on Greenhouse Gas Emissions at the Soil-Atmosphere Interface in a Water-Limited Riparian Zone

As concentrations of greenhouse gases (GHG: N2O, CO2, CH4) continue to increase in the earth’s atmosphere, there is a need to further quantify the contribution of natural systems to atmospheric GHG concentrations. Within this context, characterizing GHG contributions of riparian zones following storms events is especially important. This study documents soil GHG effluxes in a North Carolina riparian zone in the days following both a natural 2.5-cm precipitation event, and that same event associated with the addition of 8.7 cm artificial rainwater in select static chambers. No significant differences in CO2, CH4, and N2O fluxes in response to increased moisture were observed between a depression, a sand bar, and an upland forested area. However, in this water-limited riparian zone, less negative CH4 fluxes (i.e., methane oxidation decreased) and higher CO2 fluxes (i.e., aerobic respiration increased) were observed following precipitation. A short-term burst in N2O emission was observed in the hours after precipitation occurred, but elevated N2O emissions did not persist long enough to turn the site from the N2O sink to a N2O source in the 3 days following the beginning of the experiment. Our results are in contrast with riparian GHG studies in wetter environments and illustrate the importance of water limitation in regulating riparian soil response to precipitation with respect to GHG emissions. More studies should be conducted in water-limited environments (e.g., US southeast/southwest) before management strategies commonly applied in wetter environments (e.g., US Northeast/Midwest) are applied in these regions.