Evaluation And Application Of Leaf Scorch Resistance Of Landscape Tree Species In Chongqing

Global warming,extreme high temperature days in Chongqing continued to increase,and the phenomenon of sunburn injury of plants is aggravated.Plant sunburn damage not only affects the urban landscape benefits,but also leads to plant growth damage and even death,and reduces the ecological benefits of urban Greenland system.As one of the "four furnaces",landscape plants in Chongqing area face more severe challenges of sunburn at high temperature.Therefore,this thesis studies the anti-burning ability of landscape tree species in Chongqing,and provides a theoretical basis for the construction of anti-leaf scorch evaluation system of landscape tree species was provided.Based on the results of filed survey and literature review,eight tree species with high survival rate were selected as the research object.From July to August 2021,the experiment of light simulated leaf scorch resistance was carried out.The experimental subjects included Acer palmatum,A.buergerianum,A.mono,A.palmatum‘Atropurpureum’,Osmanthus fragrans var.thunbergii,Osmanthus fragrans ’Latifolius’,Cinnamomum camphora and Ginkgo biloba.In this thesis,the experimental research method is used to explore the anti-leaf scorch ability of landscape tree species from the time dimension.The experiment is divided into long-term and short-term light simulation experiments.Under the same light environment,the anti-leaf scorch injury index,grade and net photosynthetic rate(Pn),transpiration rate(Tr)and other 9 morphological and physiological indexes of the leaves of the experimental tree species were determined.The experimental data were analyzed by variance analysis,cluster analysis and factor analysis.The comprehensive evaluation of the anti-leaf scorch resistance of the experimental tree species was carried out,and the optimization model of the anti-leaf scorch plants in Chongqing under extreme high temperature weather was explored.The findings of this study are as follows:(1)Through the survey of landscape tree species in Chongqing,The types of green spaces with the largest number of trees affected by sunburn are parks,followed by streets,and squares.The sunburn resistance of different tree species in each green space was obvious,and the anti-sunburn performance of Acer palmatum,Ginkgo biloba and Osmanthus fragrans ‘Latifolius’ in each green space was poor,but Cinnamomum camphora,Osmanthus fragrans var.thunbergia showed better anti-sunburn characteristics in each green space.Among the different types of green space,the proportion of sunburn damage of tree species in park green space is the lightest,the green space in the square is lighter,and the street green space is the heaviest,and the different causes of damage are mainly affected by the interaction between light,temperature and humidity,the differences between different tree species and human factors.(2)The experimental results showed that all tree species produced leaf scorch morphological phenotype under different light duration,and the degree of leaf scorch resistance varied among species;deciduous trees were less resistant to leaf scorch than evergreen trees,and the physiological and morphological performance of plant resistance to leaf scorch differed significantly under different time-length light simulations.In the long-time light simulation,Ginkgo biloba,A.palmatum,and Cinnamomum camphora were highly adapted,A.buergerianum,A.mono,and Osmanthus fragrans var.thunbergii were less adapted to light,and A.palmatum‘Atropurpureum’ and Osmanthus fragrans ’Latifolius’ were the least adapted to light;in the short-time light simulation,A.palmatum ‘Atropurpureum’,Osmanthus fragrans’ Latifolius’,Ginkgo biloba,and A.buergerianum were more adapted to light,and A.mono,Osmanthus fragrans var.thunbergii,A.palmatum,and Cinnamomum camphora were less adapted,were lower.(3)Based on the experimental results,we evaluated the leaf scorch resistance of the eight experimental landscape tree species by combining the overall leaf scorch resistance scores.The leaf scorch resistance evaluation was divided into 3 levels: the strongest ones were A.buergerianum,Cinnamomum camphora and Osmanthus fragrans var.thunbergii;the weaker ones were Ginkgo biloba,A.mono,and A.palmatum;the weakest ones were A.palmatum ‘Atropurpureum’,Osmanthus fragrans ’Latifolius’.According to the comprehensive evaluation of leaf scorch resistance,we will explore the practice of optimizing the configuration of landscape tree species under extreme high temperature,and select the tree species with strong leaf scorch resistance and high temperature tolerance to enhance the resilience of landscape plant communities and ecosystem.The challenge of plant adaptation to urban habitat change is severe,and research on leaf scorch-resistant landscape plants can facilitate the development of plant configuration form optimization and maintenance management,and promote the scientific and rational planning of landscape tree species selection practice under extreme weather.