The Effect Of Nitrogen Fertilization And Litter Input On Soil Nitrogen Mineralization Of Cinnamomum Camphora Plantation In Subtropical Aera

With the rapid development of global industry and agriculture, a large number of reactive nitrogen has been inputting to the forest ecosystems. As an important part of biogeochemical cycles, the response mechanism of forest soil nitrogen conversion process to exogenous nitrogen input is concerned widely.A continuous investigation of soil nitrogen availability and nitrogen mineralization was carried out from July2010to April2011in Cinnamomum camphora community by using resin-core method in Hunan Botanical Garden. In order to reveal the effects of different carbon and nitrogen input on soil nitrogen mineralization, some treatments were executed to the trees investigated including carbon input and nitrogen input, a. Fertilizing soil with different concentration of gradient nitrogen (LN:5g·m-2、MN:15g·m-2、HN:30g·m-2). b. Litter exclusion to control carbon input, c. Litter redouble to add carbon input. The results showed that:(1) Available nitrogen content was significantly different in different seasons in Cinnamomum camphora community. Available nitrogen content declined to the bottom at April and climbed to the top at October. Ammonia was the main part of available nitrogen, which was69.6%～96.4%of Cinnamomum camphora community.(2) Seasonal differences in the net soil nitrogen mineralization rate were significant. Available soil nitrogen net accumulation at October and April, and the net nitrogen mineralization value was positive. Available net soil nitrogen consumption at January and July, the net nitrogen mineralization value was negative. Nitrogen mineralization showed a net accumulation in all over the year except. Annual amount of net nitrogen mineralization was valued as66.06kgN·hm-2(0-15cm soil layer)(3) After nitrogen fertilizing, the nitrogen mineralization increased with fertilizing concentration at January, April and July. The declining trend appeared at the high nitrogen concentration fertilizing at October, but still higher than control treatment, which indicated that nitrogen fertilizer can improve soil nitrogen mineralization rate. It also showed that fertilization treatment improved the soil ammonium nitrogen content and ammonification rate significantly but not to nitrate nitrogen. (4) Litter redouble and exclusion treatments significantly improved ammonium and available nitrogen concentration and the litter redouble was higher than litter exclusion, there was no significant effect on nitrate nitrogen of two treatments.(5) At different fertilization levels, litter redouble and litter exclusion treatments both improved soil nitrate nitrogen content, and he litter redouble was higher than exclusion; The two treatments had no significant effect on soil ammonium nitrogen but had significant effect on available soil nitrogen.