科尔沁沙地不同氮素生境和功能型植物的光合作用与水分利用特性

为了阐明不同生境和不同功能型植物的光合作用与水分利用特征,沿着土壤全氮逐渐降低的梯度,选取了丘间草地(IDG)、固定沙丘(FD)、半固定沙丘(SFD)、半流动沙丘(SMD)和流动沙丘(MD)五个典型的生境,测定了5个生境上共35种植物(有些植物种分布在多个生境)的气体交换特征,并从生活型、光合作用途径和固氮生理特性方面划分植物功能型进行分析。结果表明,随着土壤氮素逐渐降低,各生境植物的净光合速率(P_n)、水分利用效率(WUE)和潜在水分利用效率(WUE_i)均呈降低趋势,但是P_n在IDG、FD和SFD之间,与SMD和MD之间差异均不显著,WUE和WUE_i在IDG和FD之间,以及SFD、SMD和MD之间差异均不显著。禾本科草本的P_n、WUE和WUE_i 均显著高于非禾本科草本和灌木。C₄植物的P_n、WUE和WUE_i均高于C₃植物。P_n、WUE和WUE_i在豆科植物和非豆科植物间差异均不显著。在科尔沁沙地的植被恢复过程中应该重视净光合速率和水分利用效率较高的草本植物,尤其是禾本科草本的作用。

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.