Effect Of Returning Farmland To Grassland On CO₂ And CH₄ Flux In Soil

The implementation of the project of "returning farmland to grassland" in China has achieved initial success in the past three decades.Now the ecological functions have gradually recovered.The agro pastoral ecotone of Inner Mongolia of this study are located in this area.From the point of view of the source and sink of major greenhouse gas,we discuss the ecological function of "returning farmland to grassland".we observed changes in CO₂ and CH₄ fluxes while with affected environmental factors in soils of corn fields and grassland（selected Artificial grassland and Corn fields）.Analyzed soil temperature and soil moisture on gases fluxes,and evaluate the ecological benefits of "returning farmland to grassland".Using the Culture of undisturbed soil column combined with static opaque chamber-gas chromatography,the main conclusions are as follows:⑴During the entire experiment,the CO₂ flux in both the corn field and the grassland is positive,that is,both uses of the soil are the source of CO₂ emission.The average CO₂ flux of the soil under different rainfall intensities was F（CO₂）50mm>F（CO₂）25mm>F（CO₂）10mm,and the CO₂ flux was positively correlated with soil moisture,（P<0.01）;under different temperatures,the average CO₂ flux of the soil was F（CO₂）20℃>F（CO₂）15℃>F（CO₂）10℃,and the CO₂ flux was positively correlated with the soil temperature,（P<0.01）.⑵The flux of CH₄ in the soils of corn fields and grasslands during the cultivation process is negative,that is,the both utilization mode of soils are the sinks of CH₄.The result of CH₄ absorption flux in rainfall intensities shows that F（CH₄）50mm<F（CH₄）25mm<F（CH₄）10mm.CH₄ absorption flux is inversely proportional to the precipitation intensity;The CH₄ absorption flux under different temperatures shows F（CH₄）10℃<F（CH₄）15℃<F（CH₄）20℃,and the CH₄ flux was highly significantly positively correlated with soil temperature（P<0.01）.（3）The CO₂ emission flux and CH₄ absorption flux in the Corn field soil were greater than that in the grassland.Convert the CH₄ to CO₂ for comprehensive analysis,the total CO₂ emission in the corn field was 1232.0 kg C ha^-1Y^-1,which was higher than the 852.1 kg C ha^-1Y^-1 in the grassland soil.Changing the land from farmland to grassland can reduce the greenhouse gas emissions of the soil.The implementation of the project of returning farmland to grassland has achieved remarkable results in mitigating the greenhouse effect and improving the degraded ecological environment,and is an effective way to realize the sustainable utilization of land resources.