Plant Landscape Of Street Trees And Green Belts In Downtown Of Chongqing Evaluation And Optimization

The plant landscape of the street tree green belt bears the role of a city’s gateway image,and its overall quality has a significant impact on the appearance of the city,the ecological environment and other aspects.However,the existing landscape construction lacks relevant theoretical guidance.There are problems such as single tree species selection,unreasonable evergreen and deciduous leaves ratio,similar plant landscapes,lack of maintenance management,and so on.At present,there are few researches on plant landscape evaluation of street tree green belts.This paper selects 47 roads in the central city of Chongqing,a total of 54 survey samples as the research objects,which are divided into two parts: site survey and landscape evaluation.First,use the field investigation method to investigate the tree species composition structure,growth and characteristics,landscape configuration,management and protection,planting standardization and plant landscape satisfaction of the street tree green belt plant landscape,and make a summary.Secondly,on the basis of the first half of the research and cognition,using the analytic hierarchy process,combined with a large number of road plant landscape evaluation related literature content analysis and expert opinion consultation,construct a street tree green belt plant landscape evaluation system,and evaluate 54 survey objects..Finally,based on the survey and evaluation results,optimization strategies are proposed for the plant landscape of street tree green belts of different types of roads,aiming to provide some ideas for the construction and optimization of the plant landscape of street tree green belts in the future.The main findings are as follows:(1)According to the survey and statistics,there are 84 species of plants used in the sample,belonging to 50 families and 73 genera.Among them,there are 31 species,32 species,and 21 species of trees,shrubs,and herbs;In terms of a single sample,about35.19% of the samples have no more than 3 species of plants,and some samples even have only one plant,and 62.96% of the samples use yellow pueraria,ficus microphylla,plant species richness Low,the species selection is too concentrated.The evergreen deciduous leaf ratio of woody plants is about 2.71:1,and the evergreen plants account for too much,which is not conducive to winter lighting,and the seasonal changes are not rich enough.The ratio of native soil to exotic plants is 4.25:1,and native tree species are fully used,with obvious zonality characteristics.The types of flowers and foliage plants are abundant,while fruits and other types are scarce,and the winter landscape is sluggish.(2)The vertical level of the plant landscape is not rich enough and lacks the transition and connection between the levels.The single-and double-layer structure reaches 55.17%;the plane planting form is mainly tree-pond,accounting for about46.30%.In terms of growth,the phenomenon of sidewalk trees with partial crowns,exposed roots,litter,and substandard height under the branches is more serious.In terms of different road levels,the application frequency of the multi-layer structure of trees,shrubs and grass,the tree belt type and the combined type are main roads>secondary trunk roads> branch roads,and the phenomenon of poor growth is represented by branch roads> secondary trunk roads> main roads.(3)The quality of plant landscape management and maintenance and planting standardization need to be improved.In terms of management and maintenance,in addition to the high degree of application of white trunks,tree pond mulching,pruning and cutting stems,other measures are insufficiently applied,and maintenance costs are included in labor costs.It accounts for a large proportion;in terms of planting norms,there are problems such as small plant spacing and substandard planting pond widths,which become more serious as the road level decreases.Citizens generally believe that the current effect of the plant landscape of the street tree green belt is average,and there are problems such as too many evergreen trees,monotonous landscape configuration and neglect of management.(2)The vertical level of the plant landscape is not rich enough and lack of transition and connection between levels.The single-and double-layer structure reaches55.17%;the plane planting form is mainly tree pond type,accounting for about 46.30%.In terms of growth,the phenomenon of sidewalk trees with partial crowns,exposed roots,litter,and substandard height under the branches is more serious.In terms of different road types,the application frequency of arbor-shrub-grass multilayer structure,tree belt type and combined type gradually decreases with the decrease of road grade,while the phenomenon of poor growth gradually increases.(3)The quality of plant landscape management and maintenance and planting standardization need to be improved.In terms of management and maintenance,in addition to the high degree of application of white trunks,tree pond mulching,pruning and cutting stems,other measures are insufficiently applied,and maintenance costs are included in labor costs.It accounts for a large proportion;in terms of planting norms,there are problems such as small plant spacing and substandard planting pond widths,which become more serious as the road level decreases.Citizens generally believe that the current effect of the plant landscape of the street tree green belt is average,and there are problems such as too many evergreen trees,monotonous landscape configuration and neglect of management.(4)Starting from the three aspects of landscape,ecology and economic applicability,there are 11 evaluation indexes,including 6 quantitative indexes and 5qualitative indexes,and the principle of analytic hierarchy process is used to construct a plant landscape evaluation system model for street trees and green belts.The top 4weighted factors in the index layer are,in order,the diversity of ornamental characteristics,the growth potential of plants,the coordination of the environment,and the safety of the landscape.They are the key factors to improve the comprehensive quality of the plant landscape of the street tree green belt.After evaluating the plant landscapes of 54 survey samples,there are 6 “excellent” grades,17 “good” grades,18 “fair” grades,11 “poor” grades,and “extremely poor” grades.There are 2 "bad" ones.The overall level is medium level,and there is still a lot of room for improvement;from the perspective of different road levels,the effect of the landscape quality of the street trees and green belts is represented by the main road> secondary trunk road> branch road.(5)Comprehensive investigation and evaluation results propose optimization strategies for plant landscapes as follows: optimize the ratio of evergreen and deciduous leaves,and take care of all life forms;enrich plant species and excavate excellent native plants;pay attention to the creation of ornamental characteristics and seasonal landscapes;enrich vertical directions Levels,choose suitable collocation forms;increase the application of herbaceous ground cover plants and integrate them into flower borders and grass borders;attach importance to management and maintenance and establish long-term maintenance mechanisms;establish and improve Chongqing’s local street tree plant landscape construction specifications;pay attention to the original landscape Improve the quality of the greening of poor roads;learn from excellent cases at home and abroad to create characteristic and high-quality landscape streets.