中文摘要：

以甘肃玛曲试验站的高寒草甸为研究区域,2014年8月采用LI-8150土壤碳通量观测系统和LED灯模拟饱和光合潜力,观测对照、轻牧、重牧3个放牧梯度下的生态系统潜在净生产力（potential net ecosystem productivity,NEPpot）及生态系统呼吸（ecosystem respiration,Re）。结果表明,1）对照、轻牧、重牧3个处理的NEPpot日变化均呈先升高后降低的变化特征,且不同时间NEPpot大小均呈现出对照〉轻牧〉重牧（P〉0.05）;Re及总初级生产力（potential gross primary productivity,GPPpot）有相似的变化特征;2）8月的NEPpot、Re、GPPpot出现逐旬降低的变化趋势;3）8月底,轻牧、重牧组地上生物量分别比对照组低24.88%、47.69%（P〈0.05）;4）地上生物量对放牧响应的敏感性均大于GPPpot、NEPpot及Re（P〈0.001）,NEPpot、Re、GPPpot与日均温呈正相关（P≤0.001）,与5 cm土壤湿度呈负相关（P〈0.01）。因此,随放牧强度的增加,地上生物量的减少,高寒草甸生态系统NEPpot、Re、GPPpot逐渐降低。

英文摘要：

The aim of this study was to evaluate the effects of grazing on ecosystem respiration and productivity in a meadow grassland on the Qinghai-Tibetan Plateau.We used an LI-8150 Automated Soil CO2 Flux System and a LED light system to simulate maximum photosynthetic active radiation,and measured ecosystem respiration（Re） and potential net ecosystem productivity（NEPpot） under three grazing treatments（no grazing,light,and heavy grazing） in a meadow grassland of Maqu County,Gansu Province,on the Qinghai-Tibetan Plateau in August 2014.The results can be summarized as follows： 1） The diurnal NEPpotpeaked at noon in all three treatments,and increased with decreasing grazing intensity（P〉0.05）.The Re and potential gross primary productivity（GPPpot） showed similar patterns; 2）The NEPpot,Re,and GPPpotdecreased from early to middle to late August under all of the different grazing rates during the study period; 3） The aboveground biomass in the light and heavy grazing treatments was significantly reduced by 24.88% and 47.69%,respectively,as compared with the no-grazing treatment in late August; 4） Aboveground biomass was more sensitive to grazing than were GPPpot,NEPpot,and Re（P〈0.001）.NEPpot,Re,and GPPpotwere significantly positively correlated with average temperature（P〈0.001） and significantly negatively correlated with soil moisture at5 cm depth（P〈0.001）.Consequently,the NEPpot,Re,and GPPpotgradually decreased with increasing grazing intensity and decreasing aboveground biomass.