| Through the measurement of the mechanical properties and fiber(tracheid)morphological indexes of 22 kinds of street trees in Wenjiang district,Chengdu,the relative strength of each index of the wood properties of these trees was analyzed,and the wind-resistance was comprehensively evaluated by AHP and fuzzy mathematics membership function method.Based on the investigation of the damage after three gales,the actual wind-resistance of the trees was analyzed.The main results are as follows:(1)The mechanical properties of the branches of 22 kinds of street trees in Chengdu were significantly different,and the bending strength and impact toughness of the branches of Photinia × fraseri Dress and Cinnamomum camphora were significantly different.The results show that the bending strength and impact toughness of the trees are positively related to the wind-resistance.(2)There was a significant difference in fiber(tracheid)morphology among 22 kinds of street trees in Chengdu.The results showed that the length,length-width ratio,double wall thickness and wall-cavity ratio of the tree fiber(tracheid)were positively correlated with the wind-resistance,while the width and cavity diameter were negatively correlated with the wind-resistance.(3)According to the index correlation analysis,the correlation coefficient values of bending strength and impact toughness,fiber(tracheid)cavity diameter,fiber(tracheid)wall-cavity ratio are significant,the correlation coefficient values are 0.727,0.814 and-0.642 respectively,the difference is significant,indicating that bending strength and impact toughness,fiber(tracheid)wall-cavity ratio are significantly positive.There is a significant negative correlation between bending strength and fiber(tracheid)cavity diameter.There was no significant correlation between bending strength and fiber(tracheid)length,fiber(tracheid)width,fiber(tracheid)length-width ratio,fiber(tracheid)double wall thickness.(4)By using AHP and fuzzy mathematics membership function method,the wind-resistance of 22 kinds of street trees was evaluated.The comprehensive score was between 0.158 and 0.733,and the wind-resistance of different trees was obviously different.Prunus cerasifera and Photinia × fraseri Dress have better wind-resistance,Bauhinia blakeana and Michelia chapensis are not suitable for street trees.The tree species are divided into three groups by cluster analysis.There are 10 kinds of tree species with wind-resistance grade I,i.e.strong wind-resistance;6 kinds of tree species with wind-resistance grade II,i.e.general wind-resistance;6 kinds of tree species with wind-resistance grade III,III,i.e.weak wind-resistance.(5)Through the analytic hierarchy process(AHP)and comprehensive evaluation method,the wind-damage of 22 kinds of street trees was analyzed.The comprehensive score was between 0.018 and 0.065,the difference was significant,and the wind-damage was significantly different.The damage of Bauhinia blakeana and Elaeocarpus decipiens was obvious,which indicated that their ability of wind-resistance was weak.Through the cluster analysis of the comprehensive score of wind-damage,the tree species are divided into three grades: 8 kinds of wind-damage grade I,with strong wind-resistance;7 kinds of wind-damage grade II,with moderate wind-resistance;7 kinds of wind-damage grade III,with weak wind-resistance.(6)The results of cluster analysis of the total value of the membership function of wind-resistance and the comprehensive score of wind-damage show that the classification results of 17 kinds of tree species are completely consistent,5 kinds of tree species are similar,and there is no completely contradictory classification.It can be seen that the results of cluster analysis are basically the same through the total value of wind-resistance membership function and the comprehensive score of winddamage.The fuzzy membership function method can be used as the evaluation method of wind-resistance of street trees,and the strength of wind-resistance of street trees can be predicted by the wood properties of branches.(7)In this study,the prediction method of wood property index and the comprehensive evaluation method of wind-damage were established respectively.The two comprehensive evaluation methods of wind-resistance were verified by each other and had a high consistency,which provided a certain reference for the selection of wind-resistant tree species in cities. |
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