Species Composition And Origin Of Spontaneous Plants Established On Masonry Wall In Urban Chongqing

City masonry wall is a unique landscape of the mountain city.It serves as remnant seminatural habitats that are less frequently disturbed by human activities in urban ecosystems.Masonry wall also plays an important role in maintaining city biodiversity.With the accelerating urbanization rates and biodiversity loss rates,study of the species composition,characteristics and origins of masonry wall plants has many benefits on the understanding and protecting of masonry wall landscapes.It is also of great significance for the conservation of urban biodiversity,especially for the conservation of urban native species and spontaneous species.The results of this study are also of higher value for providing suggestions on species screening and configuration for near-natural vertical afforestation and vertical landscape construction.Chongqing is a representative mountainous city in Southwest China,and this study selected 289 masonry walls in Chongqing metropolitan areas to invesitigate to species composition as well as life-forms of masonry wall plant communities.Also,dispersal method,reproductive strategies and growth characteristics were examined.The species composition of masonry wall plants was further compared among different urban and rural areas,and cities of different climate zones.Main results of this study are as follows:(1)The study recorded 221 masonry wall species belonging to 175 genera of 80 families on masonry walls in Chongqing.Compositae(24 species)and Gramineae(18 species)were the most abundant families.For the life and growth forms,herbage and small growth form were the dominant types,repectively.The dominant species was Ficus virens for trees,Buddleja officinalis and Mallotus repandus for shrubs,Pteris vittata,Sinosenecio oldhamianus,Cyrtomium fortunei,Youngia japonica,Microlepia pseudostrigosa for herbs.(2)The propagule dispersal modes of masonry wall were mainly anemochory(39 species)and bird dispersal(38 species),accounting for 17.81% and 17.35% respectively.The propagule type of masonry wall plant was mainly capsule(119 species)and achene(60 species),accounting for 53.85% and 27.15% respectively.The main reproductive modes of masonry wall plants were seed reproduction(124 species)and facultative vegetable reproduction(88 species),and most of pernenial herbs were facultative reproduction,accounting for 55.71% and 40.18% respectively.(3)The Jaccard index of plant species composition between masonry wall and surrounding ground plant communities was low(0.27 ± 0.01).The plants relying on bird dispersal was 0.40 ± 0.01,had a higher similarity between masonry wall and surrounding ground coummunities than the plants that relying on anemochory,autochorous and uncertain dispersal mode(P < 0.05).(4)Masonry wall plant communities were dominated by native plant(179 species),accounting for 81.00%,and dominated by spontaneous plant(169 species),accounting for 76.47%.29 species were only suitable to grow on masonry walls.It suggested that masonry wall was playing the role as “sanctuary” in conserving native plants in urban areas.(5)The spring investigation revealed 140 masonry wall species in urban regions of Chongqing,84 species in suburb regions of Chongqing.The Jaccard index of plant species composition between urban and suburb regions masonry wall was low(0.38),and the species composition had a difference too.The native species and spontaneous species in suburb masonry wall plants account for 92.85% and 90.71% respectively,both were higher than the urban masonry wall plants.Under the screening effect of masonry wall habitat,the species composition of masonry wall plants in urban and suburb regions had common features.The dominant species were mainly native plants.The dominant species of trees and shrubs were mainly relying on bird dispersal,and the dominant herbaceous species were mainly relying on anemochory.(6)The geographical characteristic,species composition and life forms of masonry wall tree in Chongqing,Hong Kong,and Nanjing were related to the local climates and urban greening communities.Nanjing city masonry walls are located in the northern subtropical zone;tree species composition showed the nature of the temperate zone,and the ratio of evergreen to deciduous species was 0.21,with Broussonetia papyrifera being the dominant species.Hong Kong city masonry walls are located in the southern subtropical zone.Tree species composition showed strong tropical properties,and the ratio of evergreen to deciduous species was 1.54,with Ficus microcarpa being the dominant species.Chongqing city masonry walls are in the central subtropical zone,and the ratio of evergreen to deciduous species was 0.41,with Ficus virens being the dominant species.