Study On The Effect Of Grazing On Greenhouse Gas Emissions In Grassland Soil

The grassland soil is considered as sources or sinks of atmosphere greenhouse gas and plays an important role in the process of global warning process.Soil greenhouse gas emissions are affected by soil properties,climatic conditions and grazing conditions on grassland.In this study,the effects of stocking rates and grazing systems(rotational grazing)on soil greenhouse gas emissions were observed from a foothills fescue prairie and a dry mixedgrass prairie,respectively.Moreover,we also preliminarily researched on the effects of dung and urine patch and livestock trampling on soil greenhouse gas emissions.The main results are as follows:1.Continuous grazing increased the sources capability of soil CO2 and N2O,and weakened the sink capability of soil CH4.However,there were no obvious regularities for seasonal and annual changes of soil greenhouse gas emissions among the different stocking rates from a foothills fescue prairie.2.The rotational grazing with low stocking rate contributed to decrease soil CO2 and N2O emission,and increase soil CH4 uptake on a dry mixedgrass prairie.The sand loamy soil had relatively high CO2 emission and low CH4 uptake compared with the loam sandy soil,but there was no significant difference for N2O emission between of them on a dry mixedgrass prairie.3.There was a higher emission capability of soil CO2 and N2O from a foothills fescue prairie than a dry mixedgrass prairie,but there was no significant difference for soil CH4 uptake between of them.4.Dung and urine patch potentially increased the soil greenhouse gas emissions on grassland.The emission capabilities of soil Co2 and CH4 were higer in dung patch than in urine patch,and the emission capability of soil N2o in urine patch beyond higer than in dung patch.However,the emission capability of greenhouse gases was not sustainable in dung and urine patch.The N2o emission lasted the longest,but the CH4 emission lasted the shortest in dung and urine patch.5.There will be a threshold level for effect of livestock trampling on the soil greenhouse gas emissions on grassland.Livestock trampling caused the decreasing of soil CO2 emission and CH4 uptake and the increasing of soil N2O emission when the trampling extent exceeded a threshold level.