The Relationships Between Xylem Hydraulic Characteristics And Biomass Of Robinia Pseudoacacia And Acer Truncatum

In this study,the research objects are two drought resistant species Robinia pseudoacacia and Acer truncatum commonly used in northwest China,they were sown and raised in greenhouses in the NWAFU,water treatments were carried out in different degree when seedling height is about 25 cm,they were divided into normal irrigation group,mild water stress group and severe water stress group.After 5 months growth,the water potential of the three groups was measured by pressure chamber method;Cochard Cavitron centrifuge technique was used to construct the embolism vulnerability curve,and calculate the xylem embolism vulnerability(P12,P₅₀,P₈₈),low pressure liquid flow meter?LPFM?was used to determine the hydraulic conductivity and the degree of xylem embolism recovery;portable photosynthetic apparatus was used to determine the photosynthetic indexes,and calculate the water use efficiency,biomass,ground and underground biomass and total leaf area,in order to explore the variation of xylem hydraulic characteristics and growth of two tree species under different moisture conditions during the growth period,to explore the relationship between xylem hydraulic characteristics and biomass of woody plants,it is beneficial to evaluate the responses of plants to drought stress,and is of great significance for predicting the distribution of trees and selecting tree species for drought resistance under the background of climate change.The main conclusions are as follows:1.The VC curves show that the Robinia is a typical plant of the "R" type species,Acer is a typical "S" type species,Robinia's P12,P₅₀,and P₈₈ are greater than Acer.With the increase of water stress,the P12,P₅₀ and P₈₈ of the two tree species decreased,and the ability of embolism restoration decreased.Effect of soil moisture on the vulnerability of the Robinia embolism is greater than that of Acer,Robinia embolism recovery ability is better than that of acer.2.With the deepening degree of water stress,the photosynthetic physiological indexes?Pn,Tr,Ci,Gs?of Robinia and Acer were significantly decreased,the water use efficiency increased,and the water use efficiency of Robinia response more sensitive to water stress than Acer.3.With the increase of water stress,the biomass of two species were reduced,and the root shoot ratio,stem leaf ratio increased.Different soil moisture conditions have great effect on biomass of Robinia,and Only when the water stress to a certain extent,affected the biomass of Acer.4.The water conductivity and the embolism recovery ability of the two tree species were positively correlated with biomass,and P12,P₅₀ and P₈₈ were negatively correlated with water use efficiency.The correlation between P₅₀ and biomass significantly?R2 = 0.998 and 0.818?,the correlation between P₈₈ and biomass were lower?R2=0.614 and 0.423?,the amount of P12 significantly correlated with biological of Robinia?R2=0.938?,P12 and Acer biomass have a weak correlation?R2=0.423?.These indicated that the tree species with "S" type plants had better ability to endure water stress than the "R" type plants,thus maintaining a considerable amount of biomass.