Community Composition Structure Of Green Space And Its Carbon Storage Function In An "Urban-to-rural" Gradient

Accelerated urbanization has affected the landscape pattern of cities, the change of landscape pattern will also affect the composition and structure of urban ecosystem. So, quantitative study between landscape pattern and function of urban ecosystem to become the core issues of landscape ecosystem in urban. In addition, terrestrial ecosystem carbon cycle research has been the hot issues of global ecosystem, while the urban ecosystem as one type of terrestrial ecosystems is an important source of carbon, it is important for us to study ecosystem carbon cycle in urban. Urban green space as an important part in urban, we still know too little of it’s function of carbon storage. This paper takes a Shanghai typical "urban-to-rural" transect as study area, with the field survey of species, geographic information systems and mathematical statistical methods, focuses on the spatial differentiation of carbon storage in "urban-to-rural" under the background of urbanization. The main conclusions of this paper are as the following:(1)Based on the multiple linear regression analysis, urban, suburban and country were defined, the results showed that:the gradient of "urban-to-rural" showed spatial differentiation. This kind of spatial differentiation, the history of development in Shanghai and functions of each regions is consistent, which can provide a scientific basis for urban planning and management.(2) The composition and structure of species in urban, suburban and country within study area showed some differences:a total of50families74generas90species of trees and shrubs. The number of species and the proportion of trees and shrubs in urban, suburban and rural regions have significant differences. Cinnamomum camphora has an absolute advantage in urban, suburban and rural regions, Metasequoia glyptostroboides ranked second. The species similarity of the top10shrubs higher than trees. The proportion of evergreen and deciduous life form is almost equal in urban, suburban and rural regions. Four species diversity indexes Richness(S),Evenness(E),Simpson(D) and Shannon-Wiener(H) trends in each region are urban>suburban>rural, which shows that the differences of species diversity is result of human activities.(3)The carbon density of urban, suburban and country are different, which same as the different types of green space. The total carbon storage in study area is 4,475,410.7Mg C(trees+shrubs),carbon density is71.Mg C/hm2.The carbon density trends in different regions are urban<suburban<rural, the carbon density trends in different green space types are nursery>public park>residential green space>attached green space>street trees. The distribution of carbon storage along the transect is, the high carbon areas in Pudong and center is more dispersed than Minhang and Fengxian.(4)Based on principal component analysis, the results showed that:structure factors(DBH,HEIGHT,CROWN,CLE) have greater impact on carbon storage than composition(S,E,H,D).DBH,HEIGHT and CROWN are the dominant factors for carbon storage in structure factors. E is the dominant factors for carbon storage in composition factors.