In order to discuss the variation of the ecosystem respiration,soil respiration and carbon sink strength under grazing gradient,the biomasses in alpine weeds meadow lying to the north slope of Qilian mountain were observed from May,2010 to December,2011.Meanwhile the respiration of ecosystem and soil were tested by the static chamber.Results showed that(1)the respiration of ecosystem and soil had an exponential relationship with 5cm soil temperature significantly(P ＜ 0.01).The QloValues of ecosystem respiration under light,moderate and heavy grazing were 4.28,4.16 and 4.43 and the Q10 values of soil respiration were 3.33,3.24 and 3.44,respectively.(2) Ecosystem respiration and soil respiration were higher in summer and lower in winter,carbon released from ecosystem respiration were 854.64,909.79 and 811.70g·m-2·y-1 and released from soil respiration were 564.24,606.92and 534.56g·m ·y respectively under light,moderate and heavy grazing; there was no significant difference of the carbon released between different grazing intensity.(3)Total net primary productivity which was 766.65,707.75 and 570.36gC· m-2· y-1,carbon sink which was 351.93,261.68 and 177.46gC · m-2· Y-1 respectively under light,moderate and heavy grazing both reduced with grazing pressure.The alpine weedy meadow was a carbon sink whether under light grazing or heavy grazing,and carbon sequestration potential was huge.The results provide a basis for understanding the characteristics of carbon cycle of alpine weedy meadow in Qinghai-Tibetan plateau.%于2010年5月-2011年12月在祁连山北坡夏季牧场的高寒杂草类草甸进行生物量监测,并利用密闭箱-气相色谱法进行土壤呼吸观测,以探讨不同牧压梯度下生态系统呼吸、土壤呼吸及碳汇强度的变化.结果表明,(1)生态系统和土壤呼吸速率与5cm日均地温具有极显著的指数关系(P＜0.01),轻牧、中牧和重牧条件下生态系统呼吸对温度的敏感性系数(Q10)分别为4.28、4.16和4.43,土壤呼吸的Q10分别为3.33、3.24和3.44;(2)生态系统呼吸和土壤呼吸均表现出冬季低,夏季高.轻牧、中牧和重牧梯度下生态系统年呼吸碳量分别为854.64、909.79和811.70g·m-2·a-1,而土壤呼吸碳量分别为564.24、606.92和534.56g·m-2·a-1.各牧压梯度下生态系统和土壤的年总释放碳量均无显著差异;(3)随着放牧强度增大,净初级生产碳量(分别为766.65、707.75和570.36g·m-2·a-1)和生态系统碳汇能力(分别为351.93、261.68和177.46g·m-2·a-1)逐渐减弱,但均表现为强碳汇区.研究结果可为了解青藏高原高寒杂草类草甸碳循环特征提供依据.
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