Soil Greenhouse Gas Emissions across a Riparian-Upland Transect: How Will Soils Respond to Anticipated Changes in Rainfall Magnitude and Frequency?

Abstract:

Current global climate models predict climate change caused by anthropogenic greenhouse gas emissions will result in altered precipitation regimes by the end of the 21^st century. Although there is still uncertainty regarding how mean annual rainfall will change in the mid-Atlantic region of the U.S., it is predicted that there will be larger rainfall events followed by extended dry periods. How this will affect greenhouse gas emissions across the landscape remains unclear. Here, we investigate the response of CO₂, CH₄, and N₂O emissions from soil cores taken from a riparian-upland transect in southwest Virginia to changes in simulated rainfall magnitude and frequency. A preliminary experiment was conducted in early spring 2014 using soil cores collected in a riparian wetland in Virginia Tech’s StREAM Lab. These cores were divided into three different treatment groups. Each group received the same total amount of water, but the magnitude and frequency of the application of water was altered to simulate a single large storm event, three medium storm events, or seven small storm events. Concentrations of CO₂, CH₄, and N₂O in the chamber headspace were measured with a cavity ring-down spectrometer and used to calculate fluxes from the soil cores. Our preliminary results suggest that larger storm events result in greater temporary suppression of CO₂ emissions, and higher temporal resolution is needed to fully characterize the response of N₂O emissions to storm events. In late summer 2014, additional soil cores will be taken from three different zones along a riparian-upland transect, divided into treatment groups, and subjected to a refined version of the previously mentioned experimental procedures. Additionally, the soil from the three different zones will be characterized with chemical and physical methods. Statistical analyses will be performed to compare the effects of the different treatments and to determine the controls on the response of the soil cores. These results will provide insight into possible feedback loops that may exist between soil greenhouse gas emissions and altered precipitation regimes resulting from climate change.