The Early Responses Of Carbon Dynamics From A Cold-Temperate Coniferous Forest Soil To Simulated Nitrogen Deposition

The forest is the main terrestrial ecosystems, soil carbon dynamics is an important part of one of the carbon cycle in forest ecosystems. With the development of human society, the increase in atmospheric nitrogen deposition induced a series of major environmental problems, a direct threat to human survival and development has become a concern to governments and scientists most major global ecological and environmental sciences. Atmospheric nitrogen deposition input can contribute to the high-latitude forest vegetation growth and ecosystem carbon sequestration, to explain the important one of the ways of the world’s unknown carbon sink. The boreal forest is Earth’s second-largest forest zone, the soil carbon pool composition, conversion of atmospheric nitrogen deposition in response to research the frontier of global change ecology. Depth study of.cold-temperate coniferous forest soil carbon dynamics.in response to simulated nitrogen deposition, and help to improve the carbon cycle and carbon balance of forest ecosystems, and future atmospheric nitrogen deposition increase scenarios boreal forest ecosystem carbon and nitrogen management theory basis. In this study, in Daxinganling cold temperate coniferous forest areas to establish control of atmospheric nitrogen deposition simulation experiment platform. In order to simulate the atmosphere of NH4+and NO3-input and its interaction and reference Daxinanling station the actual atmospheric nitrogen deposition fluxes (8.5kgN hm-2a-1), set up three kinds of nitrogen in NH4Cl, KNO3and NH4NO3and control (Control,0kgN hm-2a-1), low nitrogen (Low-N,10kgN ha-2a-1), nitrogen (Medium-N,20kgN hm-2a-1), high nitrogen (High-N,40kgN ha-2a-1) four levels of nitrogen were simulated atmospheric nitrogen deposition increased by1,2and4times scenario, the boreal forest ecosystem carbon and nitrogen cycling key process changes, each handling three duplication. The use of field monitoring, and other means of stable isotope techniques and indoor physical and chemical analysis, nitrogen form and dose of boreal forest soil organic carbon (DOC, POC, MOC), transformation and Soil CO2flux. The main findings are as follows:1. Nitrogen input effects on dissolved organic carbon from a cold-temperate coniferous forest soilThroughout the growing season, cold-temperate coniferous forest soil DOC and DIC concentrations obvious seasonal variations. Nitrogen inputs tend to increase the organic layer and mineral content of soil DOC. Low nitrogen treatment tend to increase in nitrogen and high nitrogen treatment tends to reduce the organic layer and mineral layer of soil DIC concentrations. KNO3, NH4NO3is and NH4Cl processing, tend to increase the organic layer of soil DOC concentration. Nitrate fertilizer (KNO3and NH4NO3) input tends to increase the mineral layer of soil DOC concentration, ammonium nitrogen (NH4Cl) to enter the opposite. Nitrate fertilizer input tends to increase the organic layer of soil DIC concentrations, ammonium nitrogen fertilizer tend to reduce the organic layer of soil DIC concentrations. The KNO3processing tend to increase the mineral soil DIC concentrations. NH4NO3is and NH4Cl processing, tend to reduce the mineral layer of soil DIC concentrations.2. Nitrogen input effects on Particulate and mineral associated organic carbon from a cold-temperate coniferous forest soilDifferent types of nitrogen and nitrogen levels tend to increase in coarse, fine POC content, low nitrogen and nitrogen tend to increase soil MOC content and high nitrogen tend to reduce soil MOC content, KNO3and NH4Cl treatments conducive to the accumulation of soil MOC, the NH4NO3processing tends to reduce soil MOC content, but the difference was not significant. Soil texture, fine POC and MOC content show distinct seasonal variations.Different nitrogen levels tend to reduce the0-10cm the topsoil δ13CMacro POM the, δ13CMicro-POM and δ13CMOM the value, and sub-surface soil (10～20cm and20～30cm) is just the opposite response to increased nitrogen. Different nitrogen types also tend to reduce the0～10cm surface soil δ13CMacro-POM, δ13CMicro-POM, and δ13CMOM the value, and the inhibitory effect of ammonium nitrogen fertilizer than the nitrate fertilizer is more obvious. Soil δ13C values of the the topsoil Shakespeare surface sensitive, POM, MOM is more sensitive to the response to the increase of nitrogen.3. Nitrogen input effects on CO2efflux from a cold-temperate coniferous forest soilThe pattern of seasonal variation in soil CO2flux by soil temperature and soil moisture control, on the whole with the same single-peak pattern of soil temperature, but high degree of consistency with the changes of soil moisture during the growing season. N addition did not change soil moisture content but significantly reduced soil DIC in the organic layer and increased soil DOC in the organic and mineral soil layers. Short-term nitrogen addition did not increase soil NH4+-N content, but significantly increased soil N03--N content. Atmospheric nitrogen deposition will stimulate CO2emission from cold-temperate coniferous forest soils in the Daxing’anling region in the short term. The soil CO2flux was primarily driven by soil temperature, followed by soil moisture and DIC content.