| Our country has become after Europe, North America’s third-largest nitrogen deposition area. In the next few decades, nitrogen deposition quantity along with the development of the economy will continue to increase. Nitrogen deposition will change the forest soil physical and chemical properties and nitrogen supply, which affect the carbon cycle and cumulative process of soil and soil of greenhouse gases(CO2, CH4, N2O) exchange flux. Study the influence of different level of nitrogen input on forest soil, will help us to evaluate forest soil’s contribution to the global climate change.Four treatment groups were established in Lesser Khingan Mountains Liangshui experimental field in May 2008, from low to high respectively by:control(CK,0kg N?hm-2),low nitrogen(LN,30 kg N?hm-2),moderate nitrogen(MN,60 kg N?hm-2)and high nitrogen(HN,120 kg N?hm-2), respectively. Through investigating physical and chemical properties of the soil, greenhouse gas fluxes and herbal diversity, the results are as follows:(1) The simulated nitrogen deposition has significant effects on greenhouse gas flux change. CH4 gas emission flux is greater than the absorption fluxes, the different concentration changes with the seasons, N0 concentration, N1 concentration, N2 concentration are in the October 1 at the upper end of CH4 emission fluxes and N3 concentration on October 1, opposite to absorb maximum flux, concentration and other significant difference;CO2 gas flux are emission flux and the concentration of the seasons change law basic same, maximum flux of CO2 gas emissions are generated in August, the minimum value produced in October, flux of CO2 gas emissions with the seasons change significant difference; N2 O under N0, concentration of N2 gas flux for absorption of flux, and the concentration of N2 absorption of flux is greater than the concentration of N0, N1, N3 concentrations gas N2 O flux for emission flux, concentration of N3 emission flux is greater than the concentration of N1, the significant difference between the various concentration, gas N2 O flux has no regular change with season.(2) Under the simulated nitrogen deposition greenhouse gas flux in the same concentration of different season significantly difference(P < 0.05), in the same season greenhouse gas flux under different concentrations of no significant difference(P > 0.05). N2 O and CH4 gas flux, there is no correlation between CO2 gas flux; CH4 and CO2 gas flux gas flux both significant linear positive correlation(P < 0.05).(3) The simulated nitrogen deposition has significant effects on soil physical and chemical properties, nitrogen to the soil p H value increased with the increase of nitrogen concentration; Soil total nitrogen increased with the concentration of nitrogen deposition and soil total nitrogen at the same time with the seasons change is more obvious; Soil organic carbon under different concentration have significant changes, organic carbon has the remarkable difference with the seasons change.(4) There were significant correlation between soil temperature and flux of greenhouse gases, and significant difference between different concentrations. CH4 gas flux in N0 concentrations and soil under 5 cm soil temperature were positively correlated(P < 0.05); CO2 emission flux in various concentrations are associated with soil temperature(P < 0.05), including nitrogen sample concentration is characterized by significant correlation(P < 0.01); Gas N2 O flux in N0 concentration and surface temperature has significant correlation(P < 0.01), and the soil under 5 cm soil temperature correlation(P < 0.05). Greenhouse gas flux and soil moisture, soil p H, soil organic carbon, and there is no significant correlation between total carbon in soil.(5) The simulated nitrogen deposition on herb diversity affect significantly, herb plant growth condition. In terms of herb community diversity, nitrogen deposition on the spring without a significant impact on herbaceous community diversity; Has obvious effects in summer and autumn season two, nitrogen deposition accelerated the plant life cycle is complete. Plant growth condition, high nitrogen deposition on plant have a significant impact, plant plant height increased with the increase of the concentration of nitrogen deposition.(6)Greenhouse gases under simulated nitrogen deposition has some correlations with herb diversity, the study found that CH4, N2 O flux and the species richness, Simpson index, shannon index does not exist. CO2 gas flux, shannon index, Simpson index does not exist correlation, CO2 gas flux and the species richness index(S) were extremely significant positive correlation(r = 0.847, P < 0.01).
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