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Simulated NH4+-N Deposition Inhibits CH4 Uptake and Promotes N2O Emission in the Meadow Steppe of Inner Mongolia, China

LIU, Xingren, ZHANG, Qingwen, LI, Shenggong, ZHANG, Leiming, REN, Jianqiang
Pedosphere 2017 v.27 no.2 pp. 306-317
ammonium nitrogen, ammonium sulfate, chromatography, cold, diurnal variation, field experimentation, greenhouse gas emissions, growing season, meadows, methane, methane production, nitrogen, nitrous oxide, soil temperature, soil water, steppes, China
Few studies are conducted to quantify the effects of enhanced N deposition on soil nitrous oxide (N2O) emission and methane (CH4) uptake in the meadow steppe of Inner Mongolia, China. A two-year field experiment was conducted to assess the effects of nitrogen (N) deposition rates (0, 10, and 20 kg N ha−1 year−1 as (NH4)2SO4) on soil N2O and CH4 fluxes. The seasonal and diurnal variations of soil N2O and CH4 fluxes were determined using the static chamber-gas chromatography method during the two growing seasons of 2008 and 2009. Soil temperature, moisture and mineral N (NH4+-N and NO3−-N) concentration were simultaneously measured. Results showed that low level of (NH4)2SO4 (10 kg N ha−1 year−1) did not significantly affect soil CH4 and N2O fluxes and other variables. High level of (NH4)2SO4 (20 kg N ha−1 year−1) significantly increased soil NO3−-N concentration by 24.1% to 35.6%, decreased soil CH4 uptake by an average of 20.1%, and significantly promoted soil N2O emission by an average of 98.2%. Soil N2O emission responded more strongly to the added N compared to CH4 uptake. However, soil CH4 fluxes were mainly driven by soil moisture, followed by soil NO3−-N concentration. Soil N2O fluxes were mainly driven by soil temperature, followed by soil moisture. Soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission. These results suggest that the changes of availability of inorganic N induced by the increased N deposition in soil may affect the CH4 and N2O fluxes in the cold semi-arid meadow steppe over the short term.