Study On The Characteristics Of Greenbelt Community Structure In Shanghai Based On A 1 Hm~2 Plot

In this study,a 1hm2 permanent plot was established in the green belt of Shanghai,and the plant community was selected as the research object.We analyzed the community composition,The areal-types,horizontal structure,Vertical structure,population structure,community density characteristics and sample diversity index.The results from this study not only provide the theory basis for restoration,but also provides reference for the follow-up construction and renovation practice of green belt around the city.It also provides scientific basis for urban plantation ecosystem under the background of urbanization.The main conclusions are as follows:(1)The flora of vascular plant in the study area consisted of 128 species varieties,58 families and 108 genera.In arbor layer plants,there are 13 species,belong to 2 genera and 13 species;There are 25 species in shrub plants,35 genera and 38 species;There are 38 families in herbaceous plants,belong to 78 species varieties,72 genera.Herbaceous plants are the most species,accounting for 60.9%of the total species,of which mainly on.perennial herb.the proportion of shrub species is 29.69%.There are only 13 species in arbor trees,plants with deciduous tree species dominant,a total of 9 species.(2)Viewed From the composition of the genus,Compositae,Rosaceae,Gramineae and Leguminosae are the dominant species of the green belt in Shanghai,followed by Labiatae,Euphorbiaceae,Liliaceae,Sangke,Cruciferae and Polygonaceae.From the subordinate point of view,the northern and temperate tropics of the seed plants are mainly distributed in East Asia,East Asia and North America,and the distribution of the old world temperate and tropical Asia.(3)The green belt plots in Shanghai are characterized by obvious patchy artificial afforestation in the horizontal distribution.In addition to the small area of Robinia pseudoacacia and camphor,almost all species of pure forest are arranged in line.Most of the communities have only one canopy,lack of obvious shrub layer,or shrub layer for the small trees to update the seedlings,the sample to the " single-layer"community-based,"multi-layer" community less proportion.(4)The average height of the trees in the plot is 12.46m,which is mainly the average height>10m trees,accounting for 62.09%of the total.In general,mainly small and medium diameter trees,the average diameter is 12.21cm.From the distribution of tree species at different DBH levels,the number of trees on the 6cm-16cm diameter interval was the highest,accounting for 78.57%of all the individuals.Breast diameter of the largest for camphor,followed by complex feather leaves Koelreut,Sophora japonica,Robinia pseudoacacia and Metasequoia glyptostroboides.(5)By analyzing the relationship between the population density of the main communities and their DBH,crown width,tree height and growth potential,and the effect of community density on the diversity of understory plants,it was concluded that the population density was negatively correlated with the tree factors(P<0.05).The developmental status of herbaceous plants and the density of grasses were also closely related.With the increase of community density,the DBH,crown width and tree height of trees decreased and the growth potential was worse.When the community density was too high,the diversity of plant species decreased accordingly.(6)It is found that the richness index(S),the diversity index Shannon-Wiener,the Pielou index and the simpson index showed a basically consistent trend as the whole species richness and diversity index calculated from the survey data of the plot community.Herb layer>shrub layer>tree layer.(7)The vegetation types of the plot are divided into four vegetation types,mainly composed of evergreen broad-leaved forest and deciduous broad-leaved forest.The diversity trend of species diversity and diversity index of different community types were herbaceous layer>shrub layer>tree layer.Among them,the species richness index in the tree layer was deciduous broad-leaved forest>evergreen broad-leaved forest>evergreen and deciduous broad-leaved mixed forest>deciduous coniferous forest,and the diversity trend of other diversity indices was deciduous broad-leaved forest>Green and deciduous broad-leaved mixed forest>evergreen broad-leaved forest>deciduous coniferous forest.The diversity indices of shrub layer and herb layer were evergreen broad-leaved forest>deciduous broad-leaved forest>deciduous coniferous forest>evergreen and deciduous broad-leaved mixed forest.