Study On Photosynthetic Characteristics And Ecological Function Of Common Ornamental Tree Species In Tianjin

Photosynthetic characteristics and ecological functions of 19 species of ornamental tree species under natural growth conditions were studied.The net photosynthetic rate and transpiration rate were measured by CIRAS-2.The ecological environmental benefits such as carbon sequestration and oxygen release,cooling and humidifying,and water use efficiency of ornamental tree species in Tianjin were systematically studied.To provide theoretical basis for planning and allocation of tree species and construction of ecological gardens in Tianjin,the main analysis results are as follows:1.The changes of net photosynthetic rate and transpiration rate of the tested tree species showed unimodal and bimodal curves,both of which were mainly unimodal.In the seasonal variation of photosynthetic rate,most of the tested tree species showed the highest in summer and lowest in spring,and the highest in summer,followed by spring and autumn.2.The tested tree species showed different carbon sequestration and oxygen release ability,and different tree species of the same tree species showed different performance in different periods and the same period.Clustering analysis was divided into three types: The stronger ability of the tree species are Cercis chinensis Bunge,Crataegus pinnatifida,Fraxinus chinensis Roxb.,Sophora japonica Linn.,Ailanthus altissima（Mill.）Swingle,Begonia evansiana,Forsythia suspensa,Weigela florida（Bunge）A.DC.,Prunus davidiana Franch.General ability of the tree species are Amygdalus triloba,Lonicera maackii（Rupr.）Maxim.,Cerasus sp.,Prunus Cerasifera Ehrhar f.atropurpurea（Jacq.）Rehd.,Ligustrum × vicaryi Hort,Ulmus pumila cv.jinye.;the poor ability of the tree species have Platanus acerifolia,Syringaoblata Lindl,Aureus locustae,Magnolia denudata Desr.3.Total annual solid-carbon oxygen released from large to small trees were Cercis chinensis Bunge,Fraxinus chinensis Roxb.Crataegus pinnatifida,Sophora japonica Linn.,Ailanthus altissima（Mill.）Swingle,Begonia evansiana,Forsythia suspensa,Weigela florida（Bunge）A.DC.,Prunus davidiana Franch.,Amygdalus triloba,Cerasus sp.,Prunus Cerasifera Ehrhar f.atropurpurea（Jacq.）Rehd.,Ligustrum × vicaryi Hort,Ulmus pumila cv.jinye.,Syringaoblata Lindl,Platanus acerifolia,Aureus locustae,Magnolia denudata Desr.4.The tested tree species showed different ability of cooling and humidifying,and the same tree species showed different performances in different periods and same period.The cluster analysis is divided into three categories:The stronger ability of the tree species are Prunus davidiana Franch.,Weigela florida（Bunge）A.DC.,Fraxinus chinensis Roxb.,Cercis chinensis Bunge,Begonia evansiana,Ulmus pumila cv.jinye.,Amygdalus triloba,Ligustrum ×vicaryi Hort,Platanus acerifolia,Crataegus pinnatifida.General ability of the tree species are Ailanthus altissima（Mill.）Swingle,Prunus Cerasifera Ehrhar f.atropurpurea（Jacq.）Rehd.,Aureus locustae,Cerasus sp.,Sophora japonica Linn.,Lonicera maackii（Rupr.）Maxim,Syringaoblata Lindl,Forsythia suspensa.the poor ability of the tree species have Magnolia denudata Desr.5.The overall performance of the water utilization rate of the tested tree species,it can be divided into three categories by cluster analysis: one species is Sophora japonica Linn.,Lonicera maackii（Rupr.）Maxim.the other species are Crataegus pinnatifida,Ailanthus altissima（Mill.）Swingle,Magnolia denudata Desr.,Fraxinus chinensis Roxb.,Cercis chinensis Bunge,Forsythia suspensa,Prunus Cerasifera Ehrhar f.atropurpurea（Jacq.）Rehd.the others are Begonia evansiana,Syringaoblata Lindl,Cerasus sp.,Weigela florida（Bunge）A.DC.,Amygdalus triloba,Ulmus pumila cv.jinye.,Prunus davidiana Franch.,Aureus locustae,Ligustrum × vicaryi Hort,Platanus acerifolia.