Study On Emission Of Methane In Grassland-sheep Ecosystem In Typical Steppe

Methane (CH4) is one of the main greenhouse gases (GHGs), the increasing of what affected global climate change. In typical steppe ecosystem, animal released CH4and grassland soil was reported to be a sink for CH4. To evaluate the contribution of sheep to greenhouse gas emissions in typical grassland ecosystem, experiment was designed in2010-2012. In this study, relying on the experimental platform of the Guyuan State Key Monitoring and Research Station of Grassland Ecosystem (China), the effect of grazing, dung, urine and environment factor on the of grassland CH4fluxes were studied, and the CH4emissions from enteric fermentation of sheep from grazing grassland and winter sheepfolds were measured using IPCC "Tier2". Results are as follows:CH4flux of typical grassland soil at8:00am-18:00pm was monitored using ICOS-CH4analyzer in2012. Typical grassland soil was net CH4sink at8:00am-18:00pm. There was most CH4uptake at the end of September.A significantly positive correlation (P<0.05) was found between soil temperature and CH4uptake, and a negative correlation (P<0.01) was found between soil moisture and CH4uptake in SG1, SG2and UG. But no significantly correlation (P<0.05) was found between soil environment factor and CH4fluxes in SG3, SG4and SG5. Moderately grazing stocking grassland has high CH4uptake (2.91kg/hm2in201land3.84kg/hm2in2012). CH4uptake in heavy grazing stocking typical grassland was40-49%of that in moderately grazing stocking treatment.Excretion of urine and dung onto typical steppe grassland from grazing sheep can cause short increases in CH4emission. The flux of CH4from excreta patches peaked within the first4hours after excretion. At constant soil moisture fresh dung mainly impacted CH4emissions. However, both of these occurred within a limited time scope (0.5-8h), after which there were no more distinctions between excreta patches and control grassland. It appears that the impacts of sheep excreta in a grassland system are transient, and therefore its global warming potential is short-term.During feeding experiment in winter, ewe expressed more enteric methane emissions than lamb. Group E3produced the most enteric methane emission. There were no significant differences in methane emissions in the three group lamb. Enteric methane emissions were not significantly different in the sheep in different grazing treatment. Sheep grazing from August to September produced more enteric methane emissions per DM I. Sheep fed in winter produced more methane than grazing in summer.