The magnitude of net soil nitrous oxide (N2O) production from a snow‐covered catchment in a northern temperate forest was investigated. There was considerable net soil N2O‐N production and consumption through the snowpack, ranging from −6.6 to 26.2 g‐N ha−1 d−1. There was no difference in net N2O production among topographic positions despite significant variation in soil moisture, reduction‐oxidation conditions, and pore water dissolved organic carbon and nitrate. Soil temperatures did not vary among topographic positions, suggesting that temperatures at or above the freezing point allow N2O production to proceed under the snowpack. Redox conditions were lower at wetland positions compared to lowlands and uplands, suggesting that the biogeochemical pathway of N2O production varies with topography. Over the entire nongrowing season, 1.5 kg of N2O‐N was exported to the atmosphere from the 6.33 ha catchment, representing 31% of the growing season N2O‐N production. These results suggest that winter is an active time for gaseous N production in these forests and that N2O production under the snowpack represents an often unmonitored flux of N from catchments.

Most forest nitrogen budgets are imbalanced, with nitrogen inputs exceeding nitrogen outputs. The denitrification products nitrous oxide (NO) and dinitrogen (N) represent often-unmeasured fluxes that may close the gap between explained nitrogen inputs and outputs. Gaseous NO and N effluxes, dissolved NO flux, and traditionally measured dissolved nitrogen species (i.e., nitrate, ammonium, and dissolved organic nitrogen) were estimated to account for the annual nitrogen output along hillslope gradients from two catchments in a temperate forest. Adding NO and N effluxes to catchment nitrogen output not only reduced the discrepancy between nitrogen inputs and outputs (9.9 kg ha yr and 6.5 or 6.3 kg ha yr, respectively), but also between nitrogen outputs from two catchments with different topographies (6.5 kg ha yr for the catchment with a large wetland, 6.3 kg ha yr for the catchment with a very small wetland). Dissolved NO comprised a very small portion of the annual nitrogen outputs. Nitrogen inputs exceeded nitrogen outputs throughout the year except during spring runoff, and also during autumn storms in the catchment with the large wetland. Failing to account for denitrification products, especially during summer rainfall events, may lead to underestimation of annual nitrogen losses.