We measured CO(2), N(2)O, and CH(4) fluxes between soils and the atmosphere in ambient and N-addition pints at a productive black cherry-sugar maple forest in northwest Pennsylvania to examine the link between N-cycling and trace gas fluxes. Fluxes were estimated using in-situ chambers. Net annual N mineralization was 121.0 kg N ha(-1) yr(-1), and net nitrification was 85.8 kg N ha(-1) yr(-1), or 71% of net mineralization. Carbon dioxide (5.09 Mg C ha(-1) yr(-1)) efflux and CH(4) uptake (8.90 kg C ha(-1) yr(-1)) were among the highest rates reported for temperate deciduous forests. Emissions of N(2)O (0.225 kg N ha(-1) yr(-1)) were within the range of rates reported elsewhere, including locations with lower rates of N-cycling. A short-term study (May-Oct.) showed that N fertilization reduced both CO(2) emissions and CH(4) uptake (CO(2) by 19%; CH(4) by 24%). N(2)O effluxes in fertilized plots were not different from control plots, The relatively high rate of soil respiration corresponded to a high rate of N-cycling; however, N(2)O emissions were not substantially greater than those measured at other locations, suggesting that rapid N-cycling or N additions in temperate forests do not necessarily result in large emissions of N(2)O. Concurrent rapid rates of N-cycling and high rates of CH(4) uptake did not support the hypothesis that N-cycling rates directly control CH(4) uptake. Links between N-cycling and CH(4) oxidation are complex; the influence of N-cycling on flux rates must consider not only the rate of cycling, but also the disposition of N-cycling products, and the factors that influence rates of N dynamics.
