Annual nitrous oxide fluxes from temperate forest soils in the northeastern United States

Nitrous oxide (N 2 O) fluxes were measured from soils in a red pine plantation and a mixed hardwood stand in the northeastern United States. On an annual basis, the pine stand had an efflux of 0.010±0.015 kg N/ha/yr and the hardwood stand had an efflux of 0.017±0.017 kg N/ha/yr. Low net nitrification rates in both stands are suggested as the reason for the low rates of N 2 O emissions. Slight seasonal trends were noted in both stands, with highest efflux rates in early summer and late fall. Both stands showed small but extended periods of uptake during summer and early fall. Diel patterns were not observed in either stand. This study suggests that on a global basis, a lower limit for N 2 O emissions from temperate forests is 0.012 Tg N/yr, contributing less than 1% of the estimated total emissions from terrestrial sources.