Research On Spontaneous Vegetation In The Urban Riparian Zone Of The Grand Canal (Hangzhou Section) With Its Surrounding Water System

Urban riparian zone is an essential natural element for the sustainable development of cities.However,its plant landscape is facing problems,such as lack of regional characteristics,low ecological benefits,and landscape homogeneity.Spontaneous vegetation(SV)have brought new opportunities and ways to solve them through its advantages.The Beijing-Hangzhou Grand Canal is not only a living cultural heritage,but also a flowing ecosystem.This study takes the Hangzhou section of the BeijingHangzhou Grand Canal and its surrounding water system as the research site to explore the application of SV in the urban riparian zone.The main research conclusions are as follows:(1)A total of 201 species of SV were recorded in 74 families,169 genera in the investigation area;3074 spontaneous trees(ST)in 21 families,30 genera and 33 species with height(H)≥ 1.5m were also recorded.The survey results confirmed the ability of urban riparian habitats to support the occurrence,colonization,and growth of SV.The potential of SV in protecting and promoting urban biodiversity,creating near-natural plant communities are also pointed out.(2)The dominant families of SV in the investigation area were Gramineae,Compositae and Moraceae,the dominant species were mainly tree seedlings and invasive herbaceous plants;The habitat types of SV can be divided into three types which differs in dominant species,community composition and diversity characteristics,including artificial soil revetment,hard revetment and semi-natural green space.The source of those differences significantly correlated to the growth location,riparian profile type and maintenance intensity.(3)The diameter at breast height of ST in the investigation area is concentrated in 10-30cm;6 ST have higher average diameter at breast height than the overall,18.41 cm,which have the potential to be used as large trees in garden green space,including Paulownia fortune,Melia azedarach,Pterocarya stenoptera,Ulmus parvifolia,Celtis sinensis,Broussonetia papyrifera;Under the influence of different habitat factors,ST also showed differences in species composition,size and diversity characteristics,reflecting the diversities of growth rate,growth ability and adaptability to habitats from ST,and also pointed out the influence of conservation managers’ preferences.The construction of urban riparian plant landscape should meet ecological benefits and landscape functions.Based on a fully understanding of various characteristics of SV in different regions,landscape architects should take the natural conditions and functional requirements as the guide,select species that can adapt to the habitat conditions,meet the site needs,and display regional characteristics.It’s also necessary to explore modes and methods for building communities that are low-cost,low-maintenance,high-efficiency stable co-constructing using SV and cultivated plants.Besides,adopting differentiated maintenance management is the key to achieve sustainable development of plant landscapes.