Effects of elevated carbon dioxide and increased temperature on methane and nitrous oxide fluxes: evidence from field experiments

Climate change could alter terrestrial ecosystems, which are important sources and sinks of the potent green‐house gases (GHGs) nitrous oxide (N 2 O) and methane (CH 4 ), in ways that either stimulate or decrease the magnitude and duration of global warming. Using manipulative field experiments, we assessed how N 2 O and CH 4 soil fluxes responded to a rise in atmospheric carbon dioxide (CO 2 ) concentration and to increased air temperature. Nitrous oxide and CH 4 responses varied greatly among studied ecosystems. Elevated CO 2 often stimulated N 2 O emissions in fertilized systems and CH 4 emissions in wetlands, peatlands, and rice paddy fields; both effects were stronger in clayey soils than in sandy upland soils. Elevated temperature, however, impacted N 2 O and CH 4 emissions inconsistently. Thus, the effects of elevated CO 2 concentrations on N 2 O and CH 4 emissions may further enhance global warming, but it remains unclear whether increased temperature generates positive or negative feedbacks on these GHGs in terrestrial ecosystems.