Study On Vegetation Restoration Of Cutting Slopes In The Karst Area Of Southeast Chongqing

Southeast Chongqing is located in the hinterland of the Wuling Mountains,with many mountains and few flat land.It belongs to a typical Karst landform area and is characterized by fragile ecology and relatively prominent soil erosion problems.With the rapid development of regional transportation,there is a large demand and quantity for highway construction,and the excavation rate is high during the road traffic construction process,resulting in a large number of cutting slopes.In the process of highway construction,once excavation is damaged,it will further worsen ecological problems,and it is urgent to study vegetation restoration measures.This article takes the vegetation restoration of road cutting slopes as the starting point,and combines the needs of road traffic functions,landscape aesthetics,and other factors.After extensive on-site research,slope types and habitats are studied.Using the Analytic Hierarchy Process(AHP)to screen the types of slope vegetation,configure plants for different types of slopes,and attempt to propose systematic design strategies,providing ideas and references for vegetation restoration of karst highway cutting slopes in southeastern Chongqing.The research results are as following:(1)The representative G65 and G5515 expressways in the southeast region of Chongqing,the Chongqing Southeast section of the S3 Chongqing Hunan double line,and the Chongqing Southeast section of the S26 Youyan Expressway were chosen as the research objects.Randomly investigate 214 cutting slopes distributed over 700 kilometers of the above road sections.The cutting slopes can be divided into 6 types: steep rocky slopes,gentle soil slopes,rock-soil slopes,retaining wall slopes,mortar slopes,and frame beam slopes.Among them,the sum of the number of steep rocky slopes and rock-soil slopes is 94,accounting for the largest proportion.At the same time,through field research on the habitats of 214 cutting slopes in the karst area of southeastern Chongqing,combined with laboratory soil testing and local meteorological data analysis,the overall climate characteristics of the slopes in southeastern Chongqing and the corresponding habitat characteristics of six different types of slopes were summarized.(2)Through a survey of common plant species on slopes and slopes of over 700 kilometers of highways in southeastern Chongqing,a total of 86 species of slope plants belonging to 84 genera and 46 families were identified and recorded.The main species are Fabaceae,Poaceae and Rosaceae,accounting for 29% of the species.On this basis,the importance value formula screening and Analytic Hierarchy Process are used to construct a vegetation selection system for slope vegetation restoration from four aspects:resistance,protection,landscape,and economy.A comprehensive selection of 38 common plant species suitable for the Kaster cutting slope in southeastern Chongqing was conducted,and the descending order of optimization scores is as follows.Trees:Koelreuteria bipinnata,Robinia pseudoacacia,Broussonetia papyrifera,Cupressus funebris,Pinus massoniana,Liriodendron chinense,Liquidambar formosana,Cinnamomum camphora.Shrubs: ndigofera bungeana,Vitex negundo,Pyracantha fortuneana,Rhus chinensis var.roxburghii,Lespedeza thunbergii subsp.Formosa,Buddleja davidii,Nandina domestica,Rosa cymose,Coriaria nepalensis,Rosa roxburghii,Rosa chinensis,Jasminum mesnyi,Bougainvillea spectabilis.Vines:Parthenocissus tricuspidata,Biancaea decapetala,Akebia trifoliata,Ficus sarmentosavar.impressa,Mucuna sempervirens,Lonicera japonica,Ficus tikoua,Argyreia pierreana.Grass native vegetation types: Saccharum arundinaceum,Miscanthus floridulus,Chrysanthemum indicum,Senecio scandens,Dicranopteris pedate,Medicago sativa,Cortaderia selloana ’Variegata’,Festuca elata,Lolium perenne.At the same time,the cases with good greening effect found in the process of on-site research are selected,and their greening plant species selection and configuration structure are summarized and analyzed,and the corresponding typical cases of six types of slopes are proposed for vegetation restoration configuration.(3)Based on the above theoretical research combined with on-site investigation and analysis,a vegetation restoration strategy for the kast cutting slope in southeastern Chongqing is proposed from four aspects: habitat transformation,selection of vegetation restoration types,configuration form,and conservation management.Strategies of habitat transformation include adding planting slots,improving soil,storing and discharging facilities,pulling climbing nets,planting bag technology,and building planting platforms;Plant selection is based on the characteristics of six different types of habitats: steep rock slopes,gentle soil slopes,rock-soil slopes,retaining wall slopes,mortar slopes,and frame beam slopes.Suitable trees,shrubs,grass,and vines are selected for vegetation configuration according to local conditions;Conservation management includes supporting measures such as fertilization,irrigation,replanting,and pruning.From slope vegetation restoration strategy throughout the entire process of habitat transformation,plant selection and plant arrangement and conservation management.(4)The above slope vegetation restoration strategy,slope research vegetation types,configuration structure,and experience of typical successful cases are applied to the practice of slope restoration of calamus cover wildcat road graben in Youyang County.By analyzing the site climate,soil and specific slope morphology,different habitat modification and vegetation design and construction plans were formulated for different types of slopes,and put into construction and maintenance practice,which was again verified and achieved a more satisfactory vegetation restoration effect.