The Hydraulic Architecture Characteristics For The Major Tree Species In The Eastern Mountain Region Of Northeast China

Under the background of global climate change,increasing drought may lead to mass death of trees in different climatic regions.The study on the response of xylem hydraulic structure and embolic vulnerability to water stress has become a hotspot.In this study,seven common tree species in the eastern mountainous regions of northeastern China,Ulmus japonica,Quercus mongolica,Juglans mandshurica,Betula platyphylla,Acer mono,Larix gmelinii,Pinus koraiensis were chosen as the research objects.HPFM and pressure chamber were used to measure the branchlet water potential and hydraulic structure parameters of twigs,further establishing a vulnerability curve.The main characteristics of branchlet water potential,hydraulic structure parameters and xylem embolic vulnerability were studied,and the relationship between them and architecture parameters was explored in order to establish the anti-embolism index of xylem structure.By observing the intra-species differences in the hydraulic structures of the main tree species during the growth process,it was found that there were significant seasonal changes,and the inter-species differences were related to the phenological rhythm of tree species growth.The changes in hydraulic structure parameters of different tree species are affected by the water potential of the branchlets,maintaining the normal water transport during the growing season of the trees,both of which reflect the water transport strategies of the trees.The mean value of the water supply efficiency during growing season from May to September followed the pattern:ring-porous species>diffuse-porous species>non-porous species.The daily variation range of branchlet water potential and hydraulic structure parameters of tree species reflect the degree of embolization,indicating the embolism vulnerability in different degrees.By comparing the correlation coefficients among the three parameters,the daily variation range of stem specific conductivity and P50 were the most suitable for describing the embolism vulnerability of tree species.From May to September,the mean value of daily variation range of stem specific conductivity in the growing season were as follows:U.japonica>J.mandshurica>B.platyphylla>Q.mongolica>A.mono>P.koraiensis>L.Gmelinii.,and the highest daily variation range in June-July of growing season.According to the P50 mean value of different wood property species,the embolism vulnerability is in the order of ring-porous species>semi-ring porous species>diffuse-porous species>non-porous species.Two indexes above the level of branchlet can indicate the antithrombotic ability of trees.The daily variation range of stem specific conductivity and P50 was positively correlated with the diameter of vessel(tracheid)whereas negatively correlated with other structural parameters of xylem.The water transport efficiency and embolism vulnerability of each tree species are derived from the interaction between xylem anatomical structural parameters.