Drought Resistance Evaluation And Allocation Optimization Of Native Tree Species In Chongqing

In the context of global warming and the urban heat island effect,the scarcity of urban water resources and the increasing dryness of urban air have seriously affected the growth and development of garden tree species.The native tree species in Chongqing are rich,and there is great potential for development and expansion.However,an in-depth understanding of their ecological habits is still insufficient.Therefore,it is important to explore the excellent drought-resistant tree species among native species to adapt to climate warming and form an ecologically stable and landscape-rich urban greening system.Therefore,based on the survey of tree species application status and chances of survival under drought conditions in the Chongqing city landscape,this study selects native tree species to finish drought resistance experimentsTherefore in this paper,the data,such as species checklist and growth status of native tree species,were collected through field surveys to screen out the commonly used ones in Chongqing gardens.Candidate native tree species with ornamental value,ecological value,and great application potential are also selected to conduct drought resistance experiments.Based on the results of the drought resistance evaluation of Chongqing native tree species and the current situation of plant configuration in different sites,a plant configuration optimization was proposed for the landscape application of Chongqing native tree species under drought habitats.The conclusions of this study are as follows:（1）Through field surveys on four types of urban green spaces,including park green spaces,residential green spaces,campus green spaces,and road green spaces,the data on native tree species checklist,plant status,and drought habitat problems in Chongqing gardens were collected and then organized.Firstly,commonly used native tree species in Chongqing were divided into three groups based on the distribution frequencies:high-frequency species,such as Ginkgo biloba and Cinnamomum camphora;medium-frequency species,such as Albizia julibrissin and Eucommia ulmoides;low-frequency species,such as Camptotheca acuminate and Liriodendron chinense.Secondly,the percentage of drought damage of native tree species in different green spaces was summarized in the following order:road green space>campus green space>residential green space>park green space.The comparative analysis of the damage levels of native tree species in gardens of the same type was finished.Finally,through the influence factor analysis,the drought resistance of tree species is closely related to water factors,inter-species differences,and human factors.（2）Combining the literature review and research results,the commonly used native tree species in Chongqing with good ornamental value,ecological value,and application potential were selected as the test species to implement drought resistance experiments.Twelve physiological indexes（such as leaf relative water content,transpiration rate,net photosynthetic rate,intercellular CO₂concentration,stomatal conductance,instantaneous water use efficiency,and maximum photochemical quantum efficiency under dark adaptation）and two growth indexes（including leaf wilting degree and branchlet growth）were selected as drought resistance indexes to construct a comprehensive evaluation system on drought resistance tree species.The drought resistance of 17 species was ranked as follows:Idesia polycarpa>Poncirus trifoliata>Eucommia ulmoides>Acacia julibrissin>Magnolia officinalis>Toona ciliata>Ginkgo biloba>Emmenopterys henry>Euscaphis japonica>Cinnamomum camphora>Phoebe zhennan>Ormosia hosiei>Liriodendron chinense>Daphniphyllum macropodum>Camptotheca acuminata>Cercidiphyllum japonicum>Davidia involucrata.Through cluster analysis,the test species were summarized into three classes based on the drought resistance:the strongest drought resistance trees include Santalum,Tsuga,Eucommia,Acacia,Thicket,and Redbud;the stronger drought resistance trees include Ginkgo,Fragaria,Wild Crowberry,Balsam fir,and Nanmu;the weaker drought resistance trees include Redbud,Gooseberry,Crossed Lettuce,Pleasant Tree,Lianxiang Tree,and Dove.（3）Based on the results of preliminary investigation and drought resistance evaluation,the ecological characteristics and landscape characteristics of 17 test tree species were analyzed.In this study,the principles of"suitable for the land"and"suitable for the land and suitable for the tree"were adopted to select the test tree species with strong drought resistance in 10 typical plots of 4 types of park green space,residential green space,campus green space and road green space.The multi-layer plant configuration structure was adopted as the optimization strategy,so on strengthen the ecological resilience of Chongqing green space system and promote the sustainable development of urban human settlements.