The continued increase in global temperatures is widely expected to influence soil greenhouse gas emissions (GHG) in grazed grassland ecosystems. This study was conducted to quantify the effects of experimental warming and simulated grazing on greenhouse gas emissions in a northern temperate grassland, a system susceptible to climatic fluctuations, during two consecutive growing seasons in 2006 and 2007. Soil greenhouse gas emissions including N2O, CO2 and CH4 were studied. Soil nitrous oxide (N2O) emission at the soil surface increased due to warming, changing the system from an N2O sink to a source in 2006. However, in the following year (2007), the effects of warming on the above-mentioned N fluxes differed with or without defoliation. Soil CO2 and CH4 effluxes showed transient and weak responses to defoliation and warming in both years. In addition, soil respiration was temporarily influenced by a warming x defoliation interaction early in the study, with a 45% decrease in defoliated plots and a 146% increase in non-defoliated plots due to warming. The transient and weak responses of soil N2O, CO2 and CH4 emissions suggest that this temperate grassland may be able to acclimatize fast from warming for the short-term.
Warming; Defoliation; Greenhouse gas emissions; Grasslands;