稳定同位素组成可以用来记录生物和生态系统对环境条件变化的响应，或者作为对环境变化的一种间接的历史记录。项目选取内蒙古荒漠草原具有代表性的区域-达茂旗国家草原保护建设科技综合示范园区，充分考虑影响草原生态系统温室气体排放的各个因子，以混合放牧处理（羊单牧、牛单牧、牛羊混合放牧）作为对草原生态系统的一种干扰，研究草地植物及其根系、土壤有机碳和土壤呼吸的稳定碳同位素组成及变化趋势；放牧牛羊采食牧草、牛羊绒毛、粪便和牛羊呼出CH4的稳定碳同位素组成，以及它们间的相互关系。项目综合考虑土壤呼吸-植被及其根系-家畜食性、呼吸及产品-排泄物这一循环系统，分析影响草原生态系统温室气体δ13C值的相关因子及其变化特征，并追踪温室气体的源与汇，探讨放牧草原生态系统在低碳经济中的作用，预测不同放牧方式对土壤碳封存能力的影响，为发展低碳型草地畜牧业经济模式提供理论和技术支撑。

Stable isotope composition can be used to record the response of biological and ecological systems to changing environmental conditions, or as an indirect historical record of environmental change. The project will select representative desert steppe of Inner Mongolia, national grassland protection and integrated technique demonstration area in Damao banner, and consider relative factors that affect greenhouse gas emissions from grassland ecosystem. The mixed grazing treatment (grazing sheep, grazing cattle and mixed grazing cattle and sheep) is considered as one kind of interference of grassland ecological system. The aims are to analyze changes of stable carbon isotope compositions of plants and their roots, soil organic carbon and soil respiration, and stable carbon isotope compositions of forage, wool, feces and CH4 emission from livestock and the relationships among them. The project considers soil respiration, vegetation and root, livestock production and excrement for analysis of the related factors, which affect δ13C values and their change characteristics of greenhouse gas in grassland ecosystem, and for tracking sources and sinks of greenhouse gas. The project will explore function of the low carbon economy in grazing grassland ecosystem, predict the effects of different grazing model on soil carbon sequestration capacity, and provide theoretical and technical support for the economic model of low carbon type of grassland animal husbandry.