Large difference of inhibitive effect of nitrogen deposition on soil methane oxidation between plantations with N‐fixing tree species and non‐N‐fixing tree species

The responses of soil methane (CH4) net fluxes to nitrogen (N) addition in a N‐fixing tree species (Acacia auriculiformis(AA)) and a non‐N‐fixing tree species (Eucalyptus citriodora(EU)) plantation were studied in southern China. Treatments were conducted at each plantation with three N levels (0, 50, and 100 kg N ha−1yr−1for control, medium‐N, and high‐N treatment, respectively, abbreviated as C, MN, and HN). From August 2010 to July 2011, CH4flux was measured biweekly using a static chamber and gas chromatography technique. The soils of both sites acted as sink of atmospheric CH4. The CH4uptake rate in control of theAAsite (36.3 ± 3.2μg CH4‐C m−2h−1) was greater than that of theEUplantation (29.9 ± 0.9μg CH4‐C m−2h−1). In theAAplantation, the averaged rates of CH4uptake for the MN (28.6 ± 2.3μg CH4‐C m−2h−1) and HN treatment (23.8 ± 2.8μg CH4‐C m−2h−1) were decreased by 21% and 35%, respectively, compared to the control. However, there was no change of soil CH4uptake between N‐treated plots and the controls in theEUsite. Our results indicated that there might be large difference of inhibitive effect of N deposition on soil CH4oxidation between theAAandEUplantations. The projected increase of N deposition would weaken the capability of N‐fixing tree species plantations for atmospheric CH4sink in tropical and subtropical regions.