The Characteristices And Influencing Factors Of Soil Greenhouse Gases Emissions From Typical Cropland And Forest In Hilly Areas Of The Central Sichuan Basin

Soil is the main source or sink of greenhouse gases (such as CO2, CH4, N2O). The conversion of land use would influence soil micro-environment and microbial physiological and biochemical processes, and thus significantly affect greenhouse gas fluxes from soils. In this study, the static chamber-gas chromatographic techniques were used to measure the soil CO2, CH4, N2O emissions from three typical croplands(GD1, GD2and GD3) and forests(LD1, LD2and LD3) at Yanting Agro-ecological Experimental Station of purple soil, Chinese Academy of Sciences, from October in2012to August in2013. Meanwhile, soil temperature, moisture(WFPS) and soluble carbon (DOC) have been conducted to analyze the effects of them on soil greenhouse gas emissions. Finally, we assessed global warm potentials (GWP) of soil CO2, CH4, N2O emission from cropland and forest. The main results were as follows:1. In the observation period, soil temperature, soil moisture (WFPS) and dissolved organic carbon of three croplands (they had the same cropping systems, farming systems and fertilizing) had no significant differences. Soil moisture of the three forests had no significant differences. Besides, cropland to forest conversion was more earlier, soil moisture was more and more lower. At the same time, soil dissolved organic carbon content was more and more higher.2. In the observation period, the CO2, CH4and N2O emission fluxes of three croplands (GD1, GD2and GD3) in wheat and maize season had no significant differences. However, the greenhouse gas cumulative emissions of three forests had significant differences:LD3>LD2>LD1, indicating that cropland to forest conversion was more earlier, greenhouse gas cumulative emissions was more and more greater. That is, the gloable warming potential was more greater.3. In the cropland, soil temperature had significant effects on CO2and CH4emission, but it had no significant effects on N2O emission. Meanwhile, there was no significant relationship between soil moisture and CO2, CH4and N2O emission flux. Soil DOC contet had significant effects on CO2and N2O emissions, but it had no significant effects on CH4emission. In the forest, soil temperature correlated significantly to CO2emission flux, but there was no significant relationship between soil temperature and CH4and N2O emission flux. Soil temperature correlated significantly to three gases. Besides, soil DOC contet correlated significantly to CO2and CH4emission flux, but there was no significant relationship between DOC contet and N2O emission flux.4. Comparisons of LD3> GD3-N through LD3and GD3-N soil system integrated warming potential of greenhouse gases (GWP). After returning farmland to forests, integrated warming potential of greenhouse gases decreased, indicating that the farmland into forest can reduce the warming effect, is beneficial to the environment.In conclusion, under the influence of soil temperature, moisture (WFPS) and soluble carbon (DOC), cropland to forest conversion can effectively reduce soil N2O emissions so as to significantly reduce the comprehensive effects of greenhouse gases on global warming.