Plant Photosynthetic Characteristics along Slope Gradients in an Alpine Meadow Region on the Eastern Edge of Qinghai-Tibetan Plateau

Photosynthetic characteristics of 59 species (12 families) was determined in an alpine meadow on the Qinghai-Tibetan Plateau of China.We investigated quadrats of plant community at different slope gradients.We also measured the photosynthetic parameters such as net photosynthesis rate (P_n),transpiration rate (T_r),stomatal conductance (G_s) and water use efficiency (WUE) in different plant and functional groups.The results showed that the photosynthetic traits were different among species and functional groups (p<0.05).Various plant species adapted to mountain environment in their own ways.The P_n values of functional groups was in the order of grasses>sedges>legumes>forbs while WUE was in the order of sedges>grasses>legumes>forbs.T_r had no change between functional groups except for grasses.G_s in grasses and sedges were lower than legumes or forbs.Species composition of the plant community had been changed at slope aspect gradients.The south-facing slope was dominated by sedges and grasses but the north-facing slope was dominated by forbs.Relative abundance of legumes was higher at the southwestern and northwestern slope.WUE in sedges and grasses was higher than any other functional groups,in which T_r had little change.Plant species with high photosynthetic efficiency and high water use efficiency are valuable to vegetation protection and restoration.