Simulated nitrogen deposition reduces CH4 uptake and increases N2O emission from a subtropical plantation forest soil in southern China

To date, few studies are conducted to quantify the effects of reduced ammonium (NH4 +) and oxidized nitrate (NO3 2) on soil CH4 uptake and N2O emission in the subtropical forests. In this study, NH4Cl and NaNO3 fertilizers were applied at three rates: 0, 40 and 120 kg N ha21 yr21. Soil CH4 and N2O fluxes were determined twice a week using the static chamber technique and gas chromatography. Soil temperature and moisture were simultaneously measured. Soil dissolved N concentration in 0–20 cm depth was measured weekly to examine the regulation to soil CH4 and N2O fluxes. Our results showed that one year of N addition did not affect soil temperature, soil moisture, soil total dissolved N (TDN) and NH4 +-N concentrations, but high levels of applied NH4Cl and NaNO3 fertilizers significantly increased soil NO3 2-N concentration by 124 % and 157%, respectively. Nitrogen addition tended to inhibit soil CH4 uptake, but significantly promoted soil N2O emission by 403 % to 762%. Furthermore, NH4 +-N fertilizer application had a stronger inhibition to soil CH4 uptake and