128-2 Grassland Precipitation and N Deposition Drive Soil Greenhouse Gas Fluxes.
N2O production was more than twice as high in the increased nitrogen treatment relative to the control. The rate of CH4 production and consumption was low and highly variable throughout the year. However, in late March the added N plots consumed more CH4 than the ambient plots, which on average released methane; also, the reduced water treatment increased net CH4 consumption. We found that soil respiration (CO2 release) declined on average by >33% in the reduced precipitation treatments. The increased precipitation plots showed first increased and subsequently decreased respiration across the rainy season relative to control. Soil respiration did not respond to N treatments.
Overall, the addition of nitrogen stimulated both the release of N2O and the consumption of CH4 in this grassland. In terms of GHG forcing, these opposing effects result in no net increase in climate warming potential. The decreased water treatment caused increased methane consumption and decreased CO2 release. The impact of drought in this grassland is therefore to decrease the overall GHG release to the atmosphere. Further molecular research is underway to understand the microbial community responses associated with the observed changes in gas fluxes.