| In recent years, with the rapidly economic growth, China has become one of the top three nitrogen deposition concentration areas in the world. Soil organic carbon pool plays an important role in the global carbon cycle, the increase of N deposition will affect the stability of soil carbon. Analysis of the effects of soil carbon input and output in alpine wetland by static chamber gas chromatography, effect of nitrogen addition on soil carbon mineralization in Alpine peatland by incubation experiments. Four different levels of nitrogen fertilizer application were designed as control (0 kg N·hm-2·a-1, CK), low nitrogen (10 kg N·hm-2·a-1, LN), medium nitrogen (20 kg N·hm-2·a-1, MN) and high nitrogen (80 kg N·hm-2·a-1, HN), each containing 0-5 cm and 5-15 cm soil depth. Each treatment comprised four replicate plots of 3 x 3 m on the wetland floor. The investigation interpreted the short-term effect of increasing N deposition on SOC stability in alpine wetland from microbial community structure and functional aspects, further more, provided a reference for evaluated the soil C contribution to global climate change. The results obtained showed as the following:Nitrogen addition significantly promoted the above ground biomass and litter decomposition rate. The average biomass under different nitrogen treatments were significantly higher than control treatment 76.21%,56.67% and 35.93%, respectively; HN, MN and LN treatment of litter decomposition rates were significantly higher than CK 115.96%,90.64% and 66.60%, respectively. At 20℃ incubation temperature, the soil mineralization rate under HN and MN were significantly higher than that in control treatment 165.79% and 168.42%, carbon mineralization rate under LN was 68.42% higher than that of control, but not significant. Nitrogen addition significantly promoted the emissions of CO2, CH4. Under the HN, MN and LN treatment, the mean soil CO2 emission were significantly higher 34%,80.96% and 26.72% than that of the CK; the average soil CH4 emission was significantly higher 117.65%,123.53% and 62.75% than that of CK. Nitrogen addition has a significant effect on the soil carbon sink. The soil carbon sink under LN, MN and HN were significantly higher than the control treatment of 45.67%,34.73% and 118.55%.The richness of the soil bacteria, archaea and microbial community diversity were significantly affected by the nitrogen addition. Bacterial richness increased significantly with the increase of N application rate; archaea abundance under the LN treatment significantly high 34.36% than that of CK, however, archaea richness under HN treatment was significantly lower 61.35% than that of control treatment. Litter residual rate and Actinobacteria showed significant negative correlation, and with Nitrospirae was significant positive correlation; soil CO2 emission and Proteobacteria and Actinobacteria had a significant positive correlation, the CH4 flux and Archaea, Verrucomicrobia and Planctomycetes showed significant positive correlation.Soil urease and nitrate reductase activity increased with the increase of N application rate, and promoting effect of HN treatment on enzyme activity was the most significant, soil β-glucosaccharase and polyphenol oxidase activity under MN treatment were promoted the most significant effect, however, effect of soil catalase activity on nitrogen addition is not significant. Litter residual rate was a significant positive correlation with soil nitrate reductase and polyphenol oxidase activity; soil CO2 emission and soil urease and catalase activity were significant or extremely significant positive correlation, between soil CH4 emission and β-glucosaccharase, nitrate reductase and catalase activity showed a significant positive correlation.In a word, nitrogen addition promoted the carbon input and carbon output in the alpine peatland, and the soil dynamics under the nitrogen addition was active. Above all, the overall performance for the promotion of nitrogen to promote carbon sequestration. |
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