Effects of nitrogen and phosphorus additions on CH4 flux in wet meadow of Qinghai-Tibet Plateau

Methane (CH4) is a critical greenhouse gas, and wetlands are the largest natural emitters of CH4. Owing to global climate change and the intensification of anthropogenic activities, the input of exogenous nutrients such as nitrogen (N) and phosphorus (P) into wetland ecosystems has increased, which may significantly affect nutrient cycling and CH4 fluxes from wetlands. However, the environmental and microbial effects of the addition of N and P on CH4 emissions from alpine wetlands have not been thoroughly examined. We conducted a two-year field experiment with N and P addition to examine its impact on CH4 emissions from wetlands on the Qinghai-Tibet Plateau (QTP). The treatments comprised a blank control (CK), N addition (15 kg N ha-1 yr-1, N15), P addition (15 kg P ha-1 yr-1, P15), and NP coaddition (15 kg NP ha-1 yr-1, N15P15). We measured CH4 flux, soil environmental factors, and microbial community structure for each treatment plot. The results showed that the CH4 emissions of N and P addition were higher than CK. Specifically, the CH4 fluxes of N15, P15, and N15P15 treatments were 0.46 mg CH4 m-2 h-1, 4.83 mg CH4 m-2 h-1, and 0.95 mg CH4 m-2 h-1 higher than the CK. Additionally, the CH4 fluxes of N15P15 treatments was 3.88 mg CH4 m-2 h-1 lower than the P15 and 0.49 mg CH4 m-2 h-1 higher than the N15. This finding indicated that the CH4 flux in the alpine wetland soil was more sensitive to the addition of P. N and P addition increased not only soil organic carbon content (P < 0.05) but also the relative abundance of Chloroflexi and Actinobacteria in the soil, which may be the main reason for the promotion of CH4 emissions. Therefore, our results indicate that N and P addition can change the microbial abundance and community structure of wetland soil, and the distribution of soil carbon, promote CH4 emissions, and ultimately affect the carbon sink function of wetland ecosystems.