Visual Assessment Of Urban Tree Injury Risk

Urban green spaces provide a variety of Ecosystem Service(ES)functions such as biodiversity conservation,air and water purification,carbon sequestration and oxygen release,temperature regulation,waste treatment,and public health and well-being,but improperly constructed urban green spaces can also generate negative urban ecosystem services such as pollen allergy and disease vector growth.While urban trees are widely valued for providing a large number of beneficial ecosystem services,the potential of urban trees to generate tree risks that can lead to human casualties and other hazards is often overlooked.Tree risk is the potential for serious consequences from falling branches,falling trees,etc.,resulting from structural damage or mechanical integrity damage caused by disease,insects,drought,high winds,etc.To reduce tree risk,significant resources are required for the planting and maintenance of urban trees.Effective control of tree risks has become an urgent issue for quality improvement and high-quality development of urban green spaces.The assessment dimensions of current studies are mostly focused on trees themselves,and less consideration is given to the possibility of injury to urban people.In this study,based on the theoretical basis of visualization and diagnosis(VTA)and risk assessment index(RAC),we constructed the IUTIR(Injury Risk Index for Urban Trees),which includes three dimensions of risk severity,risk potential and injury potential,and completed the assessment of tree injury risk in Zhongshan Park,Wuhan.Spatial autocorrelation was used to analyze the relationship between tree risk,injury potential and injury risk,and to propose strategies to cope with the injury risk of urban trees in Zhongshan Park,Wuhan.The main research findings are as follows:(1)Based on the theoretical basis of visual diagnosis method,risk evaluation index method and Tomao comprehensive index,three dimensions of indicators were selected:(i)risk severity: tree height,crown width,root instability,abnormal trunk tilt,tree internal decay,tree internal decay,V-clamped trunk,tree abnormal cracks,vain and indeterminate branches and dangerous dead branches;(ii)risk possibility: frequency of tree damagesymptoms;(iii)Injury potential: geographical location of damaged trees,number of active people.(2)Individual risk analysis of tree species for damaged trees revealed that most of the tree species in Zhongshan Park had low individual risk,while the individual risk of tree species for two-bulb pendula,acacia,maple poplar,structural tree,balsam fir,sycamore,ginkgo and park tree were the highest,with individual risk of tree species of 5.03,3.36,2.44,1.42,1.15,1.14,1.03 and 1.03,respectively,which depends to a large extent on the volume of the trees and the frequency of tree damage is high.The reason for this is that the damaged trees are mostly fast-growing species with large crowns and low wind permeability,shallow root systems,fast-growing branches and brittle branches,especially next to the water bodies in the park,whose roads are narrower,and trees are prone to conflict with buildings,which aggravates the deflected crowns of trees.(3)Through spatial autocorrelation analysis of the seven indices in the tree injury risk assessment model,it was found that the spatial distribution all showed obvious aggregation characteristics and positive correlation(p<0.001,z>1.96),and the linear relationship was consistent,with most of them falling within the first quadrant(high-high aggregation type)and the third quadrant(low-low aggregation).The local spatial layout of the park showed negative correlations and was mostly concentrated in the northern and southern parts of the park.The main causal factors are two: first,the northern part of the park is an ecological playground area with more artificial buildings and crowd activities,which easily causes artificial damage to trees;second,the southern part of the park is a landscaped area with a larger water area and tree density,which is prone to natural damage.(4)The corresponding urban tree injury risk management strategies are proposed from three perspectives:(i)risk object-based(tree)management strategies: propose site planning and design policies and tree correction strategies for different damage symptoms;(ii)risk target-based(crowd)management strategies: strengthen safety education and management of visitors,educate visitors about tree risks,reasonably(ii)risk-based target(crowd)management strategy: strengthen safety education and management,educate visitors about tree risks,and reasonably adopt incentives andpenalties through announcements,in-kind funds,etc.;(iii)intelligent garden control strategy: establish a comprehensive database of trees to build a dynamic management and adjustment mechanism of "implementation-monitoring-evaluation-maintenance".This study,for the first time,takes into account the possibility of injury to people,proposes an assessment method for urban tree injury risk,conducts tree injury risk assessment in Zhongshan Park,reveals the spatial distribution characteristics of tree risk,injury potential,and injury risk in Zhongshan Park,explores the coupling and differentiation of its spatial distribution,and distills feasible suggestions for urban tree injury risk control,which is useful for urban tree risk assessment,improving It is of great theoretical and practical significance for urban tree risk assessment,improving ecosystem services and maintaining human well-being.