| With the acceleration of global urbanization,urban vegetation is becoming more and more important.The semi-natural vegetation remnant in Chenshan is one of the most representative forests in the Shanghai area.We established a 1 hm2 permanent plot in Chenshan and all free-standing trees with≥ 1cm in diameter at breast height (DBH) in the plot were mapped,tagged and identified to species.We analyzed the community composition,size class structure,and spatial distribution of the Chenshan forest..The results from this study not only provide the theory basis for restoration and conservation of Chenshan’s vegetation community,but also strengthen urban forest biodiversity monitoring network in Shanghai.Main conclusions are as follows:(1) As for community composition,there are 53 species,which belong to 46 genera in 28 families in the plot.These 28 families belong to six areal types and 48 genera belong to 11 areal types.At both the family and genus levels,the Pan-tropic plants are the most abundant type,followed by the North Temperate Zone plants.As for species composition,deciduous trees account for the majority (60.38%) of the forest,followed by evergreen trees. Vertically,there are three clear layers,including canopy layer (T,≥10m),sub-tree layer (U,4m-10m),and shrub layer (S,<4m).(2) Woody plants in Chenshan permanent plot were divided into 11 types of vegetation community.Deciduous broadleaf dominated community accounts for a large proportion.In terms of development stages,Cinnamomum camphora community and the Celtis sinensis community are growing; The Cinnamomum camphora-Robinia pseudoacacia community,Acer buergerianum community,Liquidambar formosana-Celtis sinensis community,Robinia pseudoacacia community,Robinia pseudoacacia+Ligustrum sinense community and Liquidambar formosana community are mature and stable.The Broussonetia papyifera community is in intermittent development.The Ilex chinensis community and Elaeocarpus glabripetalus community are in the declining stage.(3) The diversity of various communities was analyzed at three DBH classes (DBH>10 cm,4 cm<DBH≤10 cm,and 1 cm≤DBH≤4 cm).The DBH>10m class showed the highest diversity of individual difference.The simpson index and Shannon-Wiener index of Cinnamomum camphora community,Liquidambar formosana-Celtis sinensis community,Robinia pseudoacacia community were higher than others.The richness of individuals was higher for the 4 cm<DBH≤10 cm class than that of the DBH>10 cm class.Except for the Elaeocarpus glabripetalus community,the diversity of individual difference for the 1 cm≤DBH≤4 cm class in different community types was high.(4)The distribution pattern of dominant species in scale 0-15 m showed that Cinnamomum camphora, Robinia pseudoacacia,Celt1s sinensis,Ligustrum sinense,Aphananthe aspera,,Acer buergerianum,C.japonicum and Broussonetia papyifera have a clumped distribution on a smaller acale and tend to have random spatial distributions with increasingly enlarged scales.In contrast, Elaeocarpus glabripetalus has a clumped distribution and Ulmus pumila has a random spatial distribution.With increasingly enlarged scales,Liquidambar formosana and Ilex chinensis have random spatial distribution-clumped distribution-random spatial distribution.(5) The regeneration of woody plants in the plot was mainly through seedlings.There were 5937 seedlings in the plot,which belong to 38 species,32 genera,and 22 families..Cinnamomum camphora has the most seedlings,followed by Celtis sinensis and Ligustrum sinense,with each species having over 500 seedlings.There was high biological diversity of seedlings in 11 communities.The correlation analysis between number of seedlings and 14 biological factors and 2 environmental factors showed that there was significant difference in the establishment of seedlings of different height levels in the sampled populations and that the establishment of seedlings appeared to correlate well with biological factors,but not with environmental factors such as crown and elevation. |
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