ARS | Publication request: Soil respiration, CH4, and N2O fluxes in a semi-arid grassland affected by elevated CO2, warming, and water availability

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2008
Publication Date: October 5, 2008
Citation: Dijkstra, F.A., Morgan, J.A., Follett, R.F. 2008. Soil respiration, CH4, and N2O fluxes in a semi-arid grassland affected by elevated CO2, warming, and water availability. In: Joint annual meetings of the Geological Society of America, American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, and Gulf Coast Asso. of Geological Studies. October 2008. CDROM.

Technical Abstract: As the global climate changes, information on how those changes will affect the land-atmosphere exchange of greenhouse gases is needed to understand and predict future exchanges. While considerable research has been done on the effects of single climate factors, almost no work has been done evaluating how multiple climate factors affect greenhouse gas exchanges. We studied the effects of a factorial combination of two CO2 (present ambient [385 ppm], and elevated [600 ppm] CO2), and two temperature (present ambient, and elevated temperature [1.5/3.0 ºC warmer day/night]) regimes on soil respiration, CH4, and N2O fluxes during the growing season of 2007 in a semi-arid grassland, Wyoming, USA (Prairie Heating And CO2 Enrichment, PHACE). Because biological activity in this system is highly constrained by water availability, we also studied the effects of water additions (4 additions of 20 mm each during the growing season) in separate plots. Water addition plots helped determine the extent to which CO2 and warming effects on trace gas fluxes were due to indirect effects on soil water. Flux rates were determined by monitoring temporal changes in gas concentrations in static chambers placed over the grassland. Elevated CO2 significantly increased soil respiration (by 22%) and warming significantly reduced CH4 consumption (by 23%). Water additions marginally increased soil respiration, and had no effect on CH4 consumption. CO2 and warming treatment effects on trace gas fluxes remained significant after correcting for their effects on soil moisture. These results indicate that mechanisms other than soil moisture were largely responsible for the elevated CO2 and warming effects on soil respiration and CH4 consumption. We observed no significant treatment effects on N2O and no significant CO2*warming interactions. Our results highlight the need for a more mechanistic understanding of greenhouse gas exchange responses to climate change. [GRACEnet Publication]