Studies On Urban Plant Community Located At Chongming Island Of Shanghai

A lot of attentions have been paying on the ecosystem rehabilitation and reconstruction of urban,and the theories and techniques have been developing as well.Based on the local climate conditions,soil conditions,plant communities, economics,urban development,culture and so on,it is very significant to rehabilitate and reconstruct the urban ecosystem with the ecological principles and techniques. Chongming island,the bridge for promoting the economy developing of Yangtze River delta,is the third largest island in our country and the largest estuarine alluvial island, and is the only National Ecological Demonstration Area in Shanghai else.It is worth of studying how to use local plant resources cleverly,how to reconstruct a more stable urban plant communities and how to avoid making mistakes during rehabilitating and reconstructing the urban ecosystem.With data from 107 plots of plant communities existed at Chongming island,a research program has been carried into community tree species components,community types,spatial structure,the rate of evergreen tree species to deciduous tree species,the composition of arbor species and shrub species,the rate of indigenous tree species to exotic tree species,plant life forms,community physiognomy,richness of arbor species layer and shrub species layer for a community,the community diversity,both characteristics and quality of artificial plant communities and so on,the results show that phanerophyte species are dominant,i.e.shrub species are widely used.Deciduous tree species with the characteristics of small foliage type,coriaceous,non-entire margin, simple leaf are the main component of a community and determine a community physiognomy of Chongming Island.The tree species planted in Chongming Island are not reasonable because of both the biological habit and ecological characteristics of tree species being not taken into account while building a community,which is very simple for construction,low for diversity,low abundance for seasonal sceneries,lacking individuality for different function communities. Species associations of the artificial plant community in Chongming Island have been analyzed by means of the species association analysis.18 species pairs show a positive association in the foundation,which 9 species pairs are obviously positive association,9—11(Ailanthus altissima cv.Hongye—Weigela florida),12—19(Buxus sinicaaa—Gardenia jasminoides),4—16(Magnolia grandiflora—Acer palmatum cv. Atropurpureua),3—8(Trachycarpus fortunei—Ligustrum lucidum),1—19(Cinnamomum camphora—Gardenia jasminoides),3—17(Trachycarpus fortunei—Pittosporum tobira),2—7(Metasequoia glyptostroboides—Ginkgo biloba),4—10(Magnolia grandiflora—Magnolia denudata),5—10(Cedrus deodara—Magnolia denudata).9 species pairs are some positive association,1—11(Cinnamomum camphora—Weigela florida),11—20(Weigela florida—Cercis chinensis),10—17(Magnolia denudata.—Pittosporum tobira),5—12(Cedrus deodara—Buxus sinica),12—17(Buxus sinica—Pittosporum tobira),9—18(Ailanthus altissima cv.Hongye—Kerria japonica), 2—8(Metasequoia glyptostroboides—Ligustrum lucidum),3—12(Trachycarpus fortunei—Buxus sincai),7—20(Ginkgo biloba—Cercis chinensis).Because the growth vigor for tree species with positive association are good,so it should be an example for the ecosystem rehabilitation and reconstruction in Chongming Island,i.e.the biological habit and ecological characteristics of tree species should be bound with site conditions,plant species should be allocated reasonable and avoid allocating plant species with negative association in the same community.According to our research made,some suggestions have been proposed,some techniques have been discussed and close to nature Plant Community Landscape models have been made as well for the ecosystem rehabilitation and reconstruction in Chongming Island.