A Study On Health Assessment Of Sophora Japonica Street Trees In Beijing Urban Core Area

In order to understand the health status of Sophora japonica street trees in Beijing,explore the health assessment method suitable for Sophora japonica street trees and provide a reference for the fine management of the landscaping trees in Beijing,in this study,the growth,health and management status of Sophora japonica street trees in the urban core area of Beijing were investigated and analyzed.We selected appropriate morphological indexes of crown,trunk and root to build the health assessment index system of Sophora japonica street trees and divided the tree health level using factor analysis and cluster analysis.And the physiological and nutrient indexes of the trees leaves with different health levels were measured.The condition and the changes at the end of growing season of physiology and nutrient of trees with different health status were analyzed to explore the relationship between the morphological health and internal physiology and nutrients of street trees.The results showed:(1)The diameter of Sophora japonica street trees in Beijing urban core area were mainly of medium and large diameter,with an average diameter of 31.0cm,and the overall age were large.The tree height was mainly from 8 to 15 m,with an average value of 11.2m.The diameter and tree height structure varied from street to street.The average crown width was 9.3m and the average crown length was 8.4m.The overall management and protection measures of the Sophora japonica street trees in the urban core area were good.But pruning methods also need to be further standardized.In addition,there were many trees with potential traffic hazards.And root exposure was more common.Some of the street trees were greatly affected by nearby buildings.(2)In Beijing urban core area,the healthy,sub-healthy and unhealthy trees of the Sophora japonica street trees accounted for 45.9 percent,40.1 percent and 14.0 percent,respectively.The health condition of trees varied greatly between streets.The health condition of the trees on the west side of the road was slightly better than that on the east side,while the south and north side were very similar.The crown condition was an important factor to reflect the health of the Sophora japonica street trees.(3)There was a significant positive correlation between specific leaf area(SLA)and tree health score,therefore,SLA can better reflect the morphological health status of the Sophora japonica street trees.Other physiological and nutrient indexes had little significant correlation with tree health scores.At the end of the growing season,the relative chlorophyll content of Sophora japonica street trees decreased gradually.The leaf water content and specific leaf area changed little.N content showed a trend of gradual decrease by about 20%.Although the change trend of P content and K content were not obvious,they also decreased by about 20% and 30% respectively.