Methane and Nitrous Oxide Emissions from a Temperate Peatland under Simulated Enhanced Nitrogen Deposition

Nitrogen (N) deposition has increased in recent years and is significantly affected by global change and human activities. Wetlands are atmospheric CH 4 and N 2 O sources and may be affected by changes in N deposition. To reveal the effects of increased N deposition on peatland greenhouse gas exchange, we observed the CH 4 and N 2 O emissions from controlled microcosms collected from a temperate peatland in the Xiaoxing’an mountains, Northeast China. We found that the moss biomass did not change, but the total herb biomass increased by 94% and 181% with 5 and 10-times-higher N deposition, respectively. However, there were no significant changes in CH 4 emissions from the microcosms with N addition. The unchanged CH 4 emissions were mainly caused by the opposite effect of increased nitrate and ammonium concentrations on soil CH 4 production and the increased plant biomass on CH 4 emission. We also found that the manipulated microcosms with 5 and 10-times-higher N deposition had 8 and 20-times-higher seasonal average N 2 O emissions than the control microcosms, respectively. The increased N 2 O emissions were mainly caused by short-term (≤7 d) pulse emissions after N addition. The pulse N 2 O emission peaks were up to 1879.7 and 3836.5 μg m −2 h −1 from the microcosms with 5 and 10-times-higher N deposition, respectively. Nitrate and ammonium concentrations increasing in the soil pore water were the reason for the N 2 O emissions enhanced by N addition. Our results indicate that the increase in N deposition had no effects on the CH 4 emissions but increased the N 2 O emissions of the temperate peatland. Moreover, pulse emissions are very important for evaluating the effect of N addition on N 2 O emissions.