| Under the circumstance of global environment change, the increase of nitrogen deposition will change plants composition in forest community, while the change of plants composition will change the amount and composition of forest litters. The above change leads to the change of the amount and composition of forest litters, soil microorganisms and soil animal community, and the fluctuation of the soil organic carbon. The forest soil carbon circulation is affected accordingly. This thesis studies the cryptomeria in Shixiazi Forest Farm, Yucheng District, Ya’an City, Southwest Sichuan Province, researching the influence of nitrogen deposition and litters composition change on the soil organic carbon and activated carbon in the cryptomeria forest. The nitrogen additions are Blank(0g·m-2·a-1), Low Nitrogen(5g·m-2·a-1), Medium Nitrogen(10g·m-2·a-1), and High Nitrogen (15g·m-2·a-1). The forest litters are cryptomeria, Chinese fir-cryptomeria (1:1), and phoebe nanmu-cryptomeria (1:1). In the research, CK, LN, MN, HN, SL, NL, LNSL, MNLS, HNSL, LNNL, MNNL and HNNL respectively represent Blank+cryptomeria, Low Nitrogen, Medium Nitrogen, High Nitrogen, Chinese fir-cryptomeria, phoebe nanmu-cryptomeria, Low Nitrogen+Chinese fir-cryptomeria, Medium Nitrogen+Chinese fir-cryptomeria, High Nitrogen+Chinese fir-cryptomeria,Low Nitrogen+phoebe nanmu-cryptomeria, Medium Nitrogen+phoebe nanmu-cryptomeria and High Nitrogen+phoebe nanmu-cryptomeria. The results show that:(1) Within one year of the research, different nitrogen deposition levels significantly increased the content of soil organic carbon (p<0.05) in cryptomeria forest. When it was90d, the content increased when the nitrogen deposition amount increased. Then the content of soil organic carbon was the highest in the soil with MN. There was no big difference between the soil with LN and the soil with HN. The change of litters composition significantly increased the content of soil organic carbon (p<0.05), in the order of CK<SL<NL. The combine of Nitrogen deposition and litters composition treatment also increased the content of soil organic carbon in cryptomeria forest, without obvious variation law between the treatments.(2) Within one year of the research, low nitrogen treatment significantly increased the number of soil microorganism and carbon content (p<0.05) in cryptomeria forest. Before270d, medium nitrogen and high nitrogen treatment significantly increased the number of soil microorganism and carbon content (p<0.05). The change of litters composition significantly increased the number of soil microorganism and carbon content (p<0.05) in cryptomeria forest, in the order of CK<SL<NL. Under the treatment of Nitrogen deposition and litters composition combined, HNSL treatment significantly increased the number of soil microorganism and carbon content (p<0.05), while other treatments didn’t have obvious change law.(3) Within one year of the test, different nitrogen deposition levels significantly increased the content of soil dissolved organic carbon (p<0.05) on the whole in cryptomeria forest. When it was90d, the content increased when the nitrogen deposition amount increased. Then the content of soil dissolved organic carbon was the highest in the soil with MN. There was no obvious difference in LN and HN. The change of litters composition increased the content of soil dissolved organic carbon (p<0.05), in the order of CK<SL<NL. The combine of Nitrogen deposition and litters composition treatment also increased the content of soil dissolved organic carbon in cryptomeria forest, but only MNSL and HNSL treatments were significantly different with CK.(4) In a year of the experiment, different nitrogen deposition levels averagely increased the content of soil easy oxidizable organic carbon in cryptomeria forest. MN treatment reached the significant level(p<0.05) compared to the CK; LN was below the significant level; HN treatment reached the significant level(p<0.05) for the first270days. The change of litters composition obviously increased the content of soil easy oxidizable organic carbon (p<0.05), there was no significant difference between SL and NL treatments. The combine of Nitrogen deposition and litters composition treatments overall increased the content of soil easy oxidizable organic carbon in cryptomeria forest, but only HNSL and LNNL treatments were significantly different with CK(p<0.05). |
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