Study On Vegetation Under Human Disturbance In Sheshan Area, Shanghai

As the only mountainous area in Shanghai,Sheshan area has the richest vegetable species of Shanghai.It is also the one of the only remnant nature vegetation in Shanghai,which plays a very important part of Shanghai's vegetation.In Sheshan,there are typical zonal vegetation types of Shanghai.However,with the fast economic development in Shanghai,human activities make a great effect on the natural vegetation in Sheshan.From the facts that the typical vegetation is being destroyed and the biological diversity is being reduced,we can see this Last Green Land is suffering the serious threat.What is the status there now? And what is the future of this forest? All the questions are needed to be answered to,which are the first step of the protection.The thesis makes study of the vegetation in ten hills of Sheshan area,Shanghai.In order to fred out the structure,species composition and distribution characteristic of the vegetable community,44 tree communities' cases and 306 herb communities' cases have been investigated by identifying and measuring all trees in quadrants established in the forest.In the further research,analyzed by PC-ORD,44 tree communities are grouped into 3 shrub types and 15 tree types in the way of farthest neighbor.Calculating the species diversity,each group is compared with one another from different community physiognomy.By using "space replacing time" method,seven main tree species' population age structure was analyzed,in order to speculate the dynamic development of the local vegetation in Sheshan.In the aspect of the herb communities, 306 herb communities were divided into 144 spring herb communities and 162 autumn ones. Bray-Curtis cluster and DCA ordination analysis has been used to reflect the relationship between the herb community and environment.Besides,with the compared analysis on vegetable types, species diversity and characteristic,this paper shows the effect of human disturbance to the natural forest.Some mainly results are given as follows:(1)44 plant communities have been investigated and compiled.There are 137 species,60 genus and 123 family plants recorded in this area.Via PC-ORD software,41 tree communities were grouped into 15 types in the method of Cluster analysis,in which there were 12 deciduous broad-leaved forests(DBLF),1 mixed evergreen and deciduous broad-leaved forest(MEDBLF) and 2 evergreen broad-leaved forests(EBLF).Cinnamomum camphora Community which is planted by human beings is the chief evergreen broad-leaved forest.And Castanopsis sclerophylla Community is still remained,which is the typical vegetation in Sheshan.However,the whole Sheshan shows the characteristic of secondary forest which is mainly covered by deciduous broad-leaved forests.(2)This thesis analyses the species diversity of each level and the whole of the tree communities.At the tree layer,the diversity of Sheshan's vegetation is obviously lower than natural forest in other places,which ranked in order of MEDBLF>DBLF>EBLF.The shrub layer's diversity is higher than the tree layer,which ranked in order of EBLF>MEDBLF>DBLF. The herb layer's diversity is obviously higher than both tree and shrub layer,which ranked in order of EBLF>MEDBLF>DBLF.In the aspect of the whole community level,the diversity ranked in order of MEDBLF>DBLF>EBLF,which is the same to the tree level.Strong human disturbance makes that later community's diversity is lower than the previous,which shows the secondary properties of north subtropical zone forest.(3)With "space replacing time" method,seven mainly tree species' population age structure has been analyzed and divided into 4 types,in order to speculate the rule of the local vegetation dynamic development in Sheshan.Unimodal Firmiana simplex and Sporadic Quercus fabric, Robinia pseudoacacia,Castanopsis sclerophylla and Broussonetia papyrifera are not able to be the dominant species in Sheshan,because of the discontinuous and fluctuated upgrade.Inverse-J Cinnamomum camphora and L Celtis sinesis have a lot of regeneration individuals so that there is large possibility that they will be the dominant species.As the Cinnamomum camphora planted by human beings,Sheshan would have been keeping the status of deciduous broad-leaved forest for a long time,without the artificial forest.(4)306 communities have been investigated and 183 species,including 129 natural herbs which are belonging to 42 genus,46 tree,2 bamboo and 6 fern.Compared with the downtown area of Shanghai and Dajinshan Island at the level of life form,ratio of annual herbaceous is decreasing in the order of downtown area,Sheshan and Dajinshan Island,which shows the gradient variation of human disturbance from strong to weak.(5)Using PC-ORD software,144 spring herb communities and 162 autumn herb communities have been grouped into 43 and 36 types with the method of cluster analysis.And each part of types was analyzed by DCA ordination into 12 and 11 groups.We can draw some conclutions as following:a.light,moisture condition and human disturbance plays an important part of the herb communities' distribution.In spring,light is more important and moisture in autumn,b.There is possibility to appear for the herb community with the similar niche in spring. However,they will be distinguished in autumn,c.In spring,the tall herb species which can't endure trampling appear with the ones which can endure trampling in the same environment.But they will disappear from these place in autumn,d.Foreign species with high suitability can be in different habitat.(6)Compared with the vegetation of downtown area of Shanghai,Dajinshan Island and Sheshan area,we can draw the conclusion that Sheshan's natural vegetation is being destroyed by human activities,such as tourism and mining activities.The threat of human beings in Sheshan area is obviously better than downtown area in Shanghai,but the more frequent,the worse it is. Human disturbance would make the vegetation develop into landscaping or in deflected succession way.