Study On The Composition Of Woody Plants In The Comprehensive Parks In Different Built Times Of Chongqing

Parks are the main concentrated distribution of urban plant communities,which great impact the function of city ecological system.Nowadays,the structure and transformation attract huge attention of researchers from urban ecology.The basal plant community in park is artificial plant community that impacted a lot by human activities.To achieve a better organization and construct the park,it is a necessary to study the park plant community and relevant influencing factors.However,the mainstream research focus on the different green land?park size?urban-rural gradient etc.In order to study the construction and diversity of park plant community,less attention was paid on the diversity and current situation of comprehensive park build on various decades.Hence,this study select 15 comprehensive parks which are established on different generation,and based the history of Chongqing park greening,divide research time into three stages.The research objects are trees and shrubs,by comparing the life form?plant source,index of diversity and Jaccard index,to discuss the construction and diversity of plant community in Chongqing comprehensive park,then to provide the evidence for further construction and organizing of park greening.The results show that(1)there are 103 species of woody plant in selected 15 comprehensive parks,including 59 species of trees and 44 species of shrubs with the dominant Rosaceae family.Belong the woody plant,there are 60 evergreen species,43 deciduous species.The woody plants are also divided into 66 native species and 37 alien species.The parks on all three constructive stages based on evergreen and native species with distinct subtropical zone feature.Below the arbor species,the amount of deciduous trees in the third stage is significantly more than in the previous two stages.Below the shrub species,the number of deciduous groups shows the up trend but not obvious.(2)there is no significant difference of arbor species richness in selected parks within selected sampling size,abundance is much lower than other two stages.While there is no significant difference in richness index and cover index,also the Simpson index and Pielou index in shrub.Whether the arbor or shrub,the Jaccard index in the first stage is significantly higher than in the other two stages,which illustrated the homogenization.There is no evidence show the clear relationship between the construction time and Jaccard index.(3)there is a noticeable change on the advantage arbor species build in different establish time.In early term,mainly are Ficus virens,Sweet osmanthus,Camphor,then change to more Ficus macrocarpa,Janpanes flowering cherry,Champac,Lotus mangnolia and so on.While for the shrub,no obvious changes on advantage species(mainly Rhododendron,Ligustrum lucidum,Pittosporum)? Only the DBH of Ficus virens,Ficus macrocarpa,Camphor over 60 cm,which means these trees are planted in the early stage.The DBH of Sweet osmanthus,Lotus magnolia,Janpanes flowering cherry are less or similar to 15 cm,which means there are planted in recent years.