Effects Of Nitrogen Addition On The Compositions And Decomposition Of Soil Organic Carbon In Tiantong Schima Superba Forest

Following Europe and the United States, China has become the world’s third-largest nitrogen deposition area. The sharp increase of nitrogen deposition will affect the productivity and stability of forest soil organic carbon. A nitrogen fertilization (NO (0 kg N·ha-1·yr-1), LN (0 kg N·ha-1·yr-1), HN (0 kg N·ha-1·yr-1)) was conducted in Tiantong Schima Superba forest. Combining with the soil incubation under 25℃ and 15℃ respectively, the effect of nitrogen addition on the component, decomposition and temperature sensitivity of soil organic carbon pool was examined.The results are as followings:(1) Low nitrogen fertilization had on significant effect on total organic carbon concentration and total organic carbon concentration was significantly increased under high nitrogen fertilization. Dissolved organic carbon concentration was significantly increased under low and high nitrogen fertilization. Microbial biomass carbon was significantly increased under low nitrogen fertilization, and high nitrogen fertilization had on significant effect on microbial biomass carbon.(2) With the period of incubation (103 days), in the first stage, nitrogen fertilization decreased the organic carbon decomposition rate, after that had on significantly effect. Nitrogen fertilization decreased the organic carbon cumulative decomposition amount, low and high nitrogen fertilization decreased 8.68% and 9.62% than control under 25℃, decreased 5.08% and 7.59% than control under 15℃.(3) Sensitivity between 1.94 and 2.66 under control, between 1.76 and 2.51 under low nitrogen, between 1.89 and 2.44 under high nitrogen. Nitrogen fertilization had on significant effect on soil temperature sensitivity.(4) Nitrogen fertilization make active carbon decomposition rate and resistant carbon decomposition rate decreased under 25℃, increased under 15℃ respectively.