Methane and nitrous oxide fluxes from four tundra ecotopes in Ny-Ålesund of the High Arctic.

During the summers of 2008 and 2009, net methane (CH₄) and nitrous oxide (N₂O) fluxes were investigated from 4 tundra ecotopes: normal lowland tundra (LT), bird sanctuary tundra (BT), the tundra in an abandoned coal mine (CT) and the tundra in scientific bases (ST) in Ny-Ålesund of the High Arctic. Tundra soils in CT (184.5 ± 40.0 μg CH4/(m²·hr)) and ST (367.6 ± 92.3μg CH4/(m²·hr)) showed high CH4 emissions due to the effects of human activities, whereas high CH4 uptake or low emission occurred in the soils of LT and BT. The lowland tundra soils (mean, -4.4-4.3μg N₂O/(m²·hr)) were weak N₂O sources and even sinks. Bird activity increased N₂O emissions from BT with the mean flux of 7.9μgN2O/(m(2)·hr). The mean N₂O fluxes from CT (45.4 ± 10.2 μg N₂O/(m²·hr)) and ST (78.8 ± 18.5μg N₂O/(m²·hr)) were one order of magnitude higher than those from LT and BT, indicating that human activities significantly increased N₂O emissions from tundra soils. Soil total carbon and water regime were important factors affecting CH₄ fluxes from tundra soils. The N₂O fluxes showed a significant positive correlation with ammonia nitrogen (NH₄(+)-N) contents (r=0.66, p<0.001) at all the observation sites, indicating that ammonia nitrogen (NH₄(+)-N) content acted as a strong predictor for N₂O emissions from tundra soils. The CH4 and N₂O fluxes did not correspond to the temperature variations of soil at 0-15 cm depths. Overall our results implied that human activities might have greater effects on soil CH₄ and N₂O emissions than current climate warming in Ny-Ålesund, High Arctic.