Photosynthesis and water use characteristics among different habitats and plant functional types in Horqin sandy land

To clarify the plant photosynthesis and water use characteristics among different habitats and different plant functional types,five habitats in Horqin sandy land with decreasing soil fertility were selected to represent inter-dune grassland(IDG),fixed sand dunes(FD),semi-fixed sand dunes(SFD),semi-mobile sand dunes(SMD),and mobile sand dunes(MD).The gas exchange characteristics of 35 species of shrubs and herbages(some species existed in several habitats) were measured across the five habitats.The 35 species were divided into different plant functional types according to their life forms,photosynthetic types and nitrogen-fixation characteristics.The net photosynthetic rate(Pn),water use efficiency(WUE),and intrinsic water use efficiency(WUEi) decreased with decreasing soil N status.In addition,there were no or few differences in Pn among ILD,FD and SFD sites,and between SMD and MD sites.There was no,or few differences in WUE and WUEi between ILD and FD sites,and among SFD,SMD and MD sites.Leaf Pn,WUE and WUEi differed significantly among different plant functional types.Leaf Pn,WUE and WUE were higher in grasses than in herbs and shrubs grasses and shrubs.Leaf Pn,WUE and WUEi were higher in C4 plants than in C3 plants,while there were no significant differences between non-legumes and legumes.Herbaceous plants,especially grasses,should be taken into account more in vegetation recovery in Horqin sandy land.