Evaluation And Optimization Of The Three-dimensional Greening Landscape On Urban Roads Of Changsha City

With the acceleration of urban modernization construction,in order to maximize the green coverage rate,three-dimensional greening has attracted extensive attention due to its advantages of small land occupation,quick effect and high green coverage.The three-dimensional greening of urban roads can not only effectively improve the road ecological environment.Greening and beautifying the road landscape will make the urban space more comfortable and beautiful.In the beginning of 2017,Changsha City launched the second round of "Three Years of Greening" in the city.As one of the key construction projects,the three-dimensional greening of urban roads has been further developed.Based on the research on three-dimensional greening related theories on urban roads,this paper conducts field research on the tlhree-dimensional greening of the main roads in the Second Ring Road of Changsha City,and records the current status of plant landscapes,from plant species composition,application frequency,ornamental characteristics,application forms and planting.Analyze the way and other aspects.Using the analytic hierarchy process,the three-dimensional greening vine plants and plant landscapes of urban roads in Changsha City were comprehensively evaluated,and the problems in the status quo of three-dimensional greening were summarized,and the optimization and upgrading strategies were proposed to optimize the design.It can also provide references to the related road three-dimensional greening work.The main research contents and results are as follows:(1)The main application forms of urban road three-dimensional greening are as wall greening,slope greening,scaffolding greening,fencing greening,bridge greening,flower bed greening and column greening,and planting methods have adhesion type,drape type,flower box type,embedded type,chip planting type,shaping dressing type.(2)Taking the three-dimensional greening of 16 roads in Changsha as the survey object,80 samples were selected for investigation,and 83 species of common plants were obtained,belonging to 42 families.There are 7 species of arbor,23 species of shrubs,15 species of woody liana,35 species of herbs and 3 species of bamboo,among which 25 species of vines;only 13 species of common plants with higher frequency of application.In terms of ornamental characteristics,the flower-viewing plants are the main ones which account for a maximum of 49.40%.(3)The three-dimensional greening landscape types of urban roads in Changsha include overpasses,pedestrian bridges,underground passages,bus stops,canalized islands,green belts and roadside green belts.The best effect of the three-dimensional green landscape is Lushan Road,followed by Furong Road.The application form frequency is higher for scaffolding greening and bridge greening;The planting method is higher in climbing frequency and hanging type.(4)The selected analytic hierarchy method takes vine plants as an example to consider the three aspects of ornamental value,ecological adaptability and economic benefits,and constructs a three-dimensional green plant species selection evaluation model for urban roads,and comprehensively evaluates 25 vine plants to obtain Changsha City.The three-dimensional greening of urban roads lacks level I specie,there are 8 species in Level Ⅱ plants,5 species in Level Ⅲ,5 species in Level Ⅳ,6 species in Level V levels,1 species in Level VI,and no plants in Level VII.The top 5 overall scores are:Parthenocissus tricnspidata,Parthenocissu thomsoni,Parthenocissus semicordata,Campsis grandiflora and Mucuna sempevirens.(5)Using the analytic hierarchy process to establish a three-dimensional greening plant landscape evaluation model from the four aspects of functional value,social benefit,ornamental characteristics and ecological quality,and comprehensively evaluate the selected 30 plant landscape units to obtain the three-dimensional urban road in Changsha.The overall situation of greening plant landscapes is general,most of them are intermediate levels.The overall quality sequence of the landscape is the channelized island>bus stop>pedestrian bridge>underground passage>overpass>roadside green belt>vehicles dividing green belt.The optimal three-dimensional greening configuration mode is "Hanging down and climbing".(6)Summarize the main problems existing in the three-dimensional greening of urban roads in Changsha.Based on actual conditions and landscape construction principles.It proposes to enrich the plant species,especially the vine plants,to promote the plant configuration mode of "hanging down",to control the application of seasonal flowers and to accelerate the integration of three-dimensional greening into the urban road green space system,and to optimize the design accordingly.