In this study,the contents of photosynthetic pigments (chlorophyll and carotenoid) and non-structural carbohydrates (NSC;soluble sugars and starches) of the current-year leaves were investigated in young and adult trees of Sabina przewalskii along altitude nearby the timberline of Qilian Mountains.The results demonstrated that:(1)Total chlorophyll contents firstly increased,and then decreased,finally increased again in young trees,while it firstly decreased,and then increased in adult trees,but the lowest values occurred at 3 120 m in both trees.However,the highest value of carotenoid appeared at 2 980 m in young trees,whereas it was at 3 320 m in adult trees.(2)NSC content showed the similar trend to total chlorophyll contents,moreover,the lowest values also occurred at 3 120 m in both trees;but NSC contents of the young trees were higher than that of the adult ones at the corresponding altitude.These suggested that the photosynthetic capacity of S.przewalskii might not decrease with the increasing altitude,and NSC supplied adequately at the higher altitude,which also indicated that the timberline of Qilian Mountains would have the potential to be pushed up to the higher altitude with the global climate changes.