| Urbanization is the most important aspect of land use and land cover change globally and dramatically altered the ecosystem process and function. Urban ecology has become the hot spot of ecology research. Although, tree growth and carbon storage research in urban area received more and more attention from academy, there is a little knowledge about the influence of urban habitat to tree growth. At present, there are mainly two opposite opinion:the first one thought that the majority of urban grounds became harden, the compact soil limited root grows, hindered water percolation, the habitat became fragmentized extremely, and received indirect and the direct interferences frequently of human activity, the plant growth has been suppressed. The second was that labor management, applies fertilizer, the deinsectization and the trim, the tropical island effect and the relatively low ozone density and so on, may make the urban vegetation grow fast, raise the speed of trees carbon storage. However, the affecting factor in land use type was not explicit, there were still very few researches in the study of different land use type in urban scope, therefore, the study on tree growth and carbon storage of different land use types in urban area is very important.This paper selected the famous historical city Hangzhou, which with the fastest urbanization speed among southeast coast cities, as study case. Two representative species of Cinnamomum camphora and Platanus acerifolia were choosen. We surveyed DBH, height, plants distance and crown of880trees in field investigation, measured the ring winth increament of353trees of recent10years, estimated carbon storage and carbon uptake rate of different species in different land use type.1. The growth rates of Cinnamomum camphora increase with crown in either the government, commercial and residential area (r2=0.53, n=80, P<0.05). Crown is the most important factor in analysising C.camphora’s growth. While, there is no significant relatingship between growth rate and crown in different landscape of P. acerifolia (r2=0.05, n=120, P>0.05), So heterogeneity of urban land cover should be accouted when studying the P. acerifolia’s growth rate across a gradient of urbanization.2. The correlation analysis indicate that the growth rate of C. camphora has a liner positive correlation with age (r2=0.36, n=80, P<0.05). While the correlation between the growth rate of P. acerifolia and age in different land use types are different, which is a negative correlation in government agencies (r2=0.49, n=17, P<0.05), a positive correlation in residential area (r2=0.44, n=17, P<0.05), and no correlation in commercial area (r2=0.03, n=21, P>0.05).3. Carbon sequestration rates of C. camphora in Government land (6kg a-1), Commercial area (5kg a-1), Residential area (4kg a-1), are greater than which in evergreen broadleaf forest (about2.2kg a-1).The Carbon sequestration rate of P. acerifolia in government land is10.27kg a-1and10.18kg a-1in commercial area, and in residential area (15kg a-1), it is much higher, because young trees get fast carbon sequestration rate.4. The carbon fixation of C.camphora in government land, residential area and commercial area is about82.02kg C tree-1,34.01kg C tree-1and33.59kg C tree-1, respecitvely. While, the carbon fixation of P. acerifolia is much higher than C. camphora. In Government land it is111.78kg C tree-1, campare to Commercial area101.49kg C tree-1and Residential area94kg C tree-15. With the intensive expansion of urbanization in recent years, urban trees in Hangzhou were frequently turned over. Carbon storage of street trees is relatively small, as the urban greening trees are relatively young. While the carbon sequestration rates of young trees are higher than those of old ages, therefore, in the future, urban greening should not only increase the area and proportion, but also pay more attention to protect the existing green space. |
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