Methane and nitrous oxide fluxes from four tundra ecotopes in Ny-Alesund 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-Alesund of the High Arctic. Tundra soils in CT (184.5 +/- 40.0 mu g CH4/(m(2).hr)) and ST (367.6 +/- 92.3 mu g CH4/(m(2).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, -4.4-4.3 mu g N2O/(m(2).hr)) were weak N2O sources and even sinks. Bird activity increased N2O emissions from BT with the mean flux of 7.9 mu g N2O/(m(2).hr). The mean N2O fluxes from CT (45.4 +/- 10.2 mu g N2O/(m(2).hr)) and ST (78.8 +/- 18.5 mu g N2O/(m(2).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-Alesund, High Arctic. (C) 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.