Effects Of Simulated Atmospheric Nitrogen Deposition On The Exchange Fluxes Of Greenhouse Gases In The Temperate Forest Soil

Now, China has become one of the most serious regions under nitrogen deposition followed by Europe and America. The bulk deposition of nitrogen will continue to increase due to the economy in the following years. Nitrogen deposition can lead to changes in nitrogen status of forest soils, and then alter the key processes of carbon cycle and accumulation, in addition, the fluxes of greenhouse gases(CO2, CH4and N2O). The field experiment was conducted to clarify how the effects of four nitrogen levels and three nitrogen forms on the effects of emission fluxes of greenhouse gases and the content of carbon and nitrogen in the temperate forest. The coupling relationship between soil carbon and nitrogen have also been analysed and the responsing mechanism of nitrogen deposition to the planted forest have also been explored. The main conclusions are as follows:1) Nitrogen deposition had positive effect on CO2emission. Cumulative CO2emission reached the significant level in medium nitrigen and high nitrogen treatment. The positive effects caused by mixed nitrogen were larger than that caused by nitrate nitrogen and ammonium nitrogen on CO2emission. CO2emission showed a significant positive exponential relationship with soil temperature, and the Q10values, representative of temperaturesensitivity of respiration, was similar between all of the treatments. Whereas CO2emission were positively linear with soil moisture, and the dependence of CO2emission on soil moisture increased significantly in nitrogen treatments.2) The absorption action of different nitrogen forms were distinct. Nitrate nitrigen treatment had positive effect in a short term and ammonium nitrogen had the opposite effect. In addition, CH4fluxes showed a correlated relationship with soil temperature and moisture, however, such relationship had been masked to somewhat degree by nitrogen deposition.3) Nitrogen deposition increase N2O emissions significantly and the largest emission appeared in high nitrogen treatment which followed by emissions appeared in medium nitrigen treatment. The differences were not significant between mixed nitrogen and ammonium nitrogen, but were significant between any of them and nitrate nitrogen. In the entire year, N2O fluxes showed a significant correlated relationship with soil moisture.4) Nitrogen deposition had no significant impacts on soil carbon organic and total nitrogen content. Nitrogen fertilization significantly increased NO3--N and NH4+-N content on the top of the soil. Soil organic carbon showed a positive correlation with soil total N in all nitrogen level treatments. Meanwhile, soil CO2fluxes and N2O fluxes reached the significant or highly significant level by N fertilization, and soil CO2emission rates and CH4uptake rates, N2O emission rates and CH4uptake rates both showed a positive correlation.