Study On Soil Carbon Stock And Its Spatial Distribution, Physical And Chemical Properties In Shanghai's Urban Green-belt

Urban greenspace system, as one of the most important components of urban compound system, will certainly play an increasingly important role in urban system. Greenspace soil is the basis of the whole greenspace system, which not only provides growth medium for the green plants, but also plays vital role in participating regional carbon cycle and the sustainable development of city. Putting the management of carbon melting into urbanization process is inevitable and crucial to the sustainable development of city. Researching the soil physical and chemical properties of greenspace, exploring the soil carbon pool reserves and its spatial distribution and its dynamic changes has a major and realistic significance because it can help to explore the bearing capacity of the urban soil carbon pool and to respond the city tropical island effect and climatic change.Satellite imgges of Shanghai within the external circle highway were interpreted and by RS (remote sense) and GIS (geography information system),green space data was accessed. The whole greenspace was collected from park green spaces, road green belts, residential areas, green space affiliated to units, coast green space, and green space used as production within the external circle highway of Shanghai City. Based on the community structure, a system of 8 vegetation community types consists of evergreen broad-leaved forest, deciduous broadleaved forest, evergreen coniferous forest, deciduous needle-leaf forest, evergreen shrub forest, deciduous shrub forest, bamboo grove and grass was determined. Sampling points was confirmed by using Fan-shaped Grid Method (FGM) of landscape pattern, and vegetation community types were investigated. Soil samples were determined in the laboratory. Spatial data of large-scale and soil samples'data of small-scale was integrated in this research. Based on these, soil carbon storage of Shanghai urban greenspace and its distributed pattern as well the soil physical and chemical properties of greenspace were obtained. The following conclusion was drawn through the research: 1. Statistical area of urban greenspace of Shanghai was 13910.83hm². The areas ofgreen space affiliated to units was bigger than other green space, which approximately composes the total 2/5, and the rank of other green space about areas was: residential areas(3422.35 hm²)>park green space(1846.22 hm²)>road green belts(1616.82 hm²)>green space used as production(1061.94)>coast green space(335.66 hm²). The average soil carbon density and its carbon pool reserves of the research region from 0-30cm were 25.807 kg·m^-2 and 3589968.57t, and the average soil carbon density and its carbon pool reserves of the research region from 30-60cm were 28.129 kg·m^-2 and 3106810.18t. Both soil carbon density and carbon pool reserves decreased as the soil depth.2. The tendency distribution of soil carbon density in Shanghai urban greenspace was :The soil carbon density was higher in easten Baoshan District, northern Nanhui District, most of Yangpu District and Pudong New Area, Huangpu District and Luwan District, and the value of change was 28.42-61.99 kg·m^-2. The others were located between the two. The soil carbon density was lower in Zhabei District,Hongkou District,Changning District and Putuo District, whose value was 8.33-18.75 kg·m^-2. The tendency distribution of soil organ carbon was: The content was higher in northern Baoshan District, southeast, Pudong New Area, Nanhui District, whose value was 22.11-35.87g·kg^-1. And the content of other space of Pudong New Area, Huangpu District and Luwan District was a little lower, whose vaule was 14.28-22.11 g·kg^-1. The palces of Shanghai were obliously lower, whose value was 5.05-14.28 g·kg^-1.Overall, the soil carbon density and soil organ content of central business district was lower than other places.3. From the vertical direction, soil carbon density presents obviously decreasing progressively tendency as the depth of soil increased. The average soil carbon density of equal-space in 0-60cm was 31.980 kg·m^-2, 23.084 kg·m^-2, 18.710 kg·m^-2, 16.035 kg·m^-2, 14.423 kg·m^-2 and 12.449 kg·m^-2.And soil carbon density from the same soil depth but different vegetation community also presented the same similar change.4. Results showed that average soil bulk density above 30cm was 1.57 g·cm-3, and average soil organic carbon (SOC) above 30cm was 15.52 g·kg^-1, average total nitrogen (TN) was 3.78 g·kg^-1, and average total phosphorus (TP) was 1.13g·kg^-1.The study results above show that poor soil quality, especially the situation of low soil fertility was one of the major constraints which can impact the health of greenspace vegetation. Therefore, improving soil fertility, heighten soil quality and increasing the greenspace area can effectively enhance soil carbon density especially the central business district, and then increase the soil carbon reserve of the whole urban greenspace. Besides, the increase of carbon pools can make greenspace soil absorb CO2 and other greenhouse gases well. Dealing with this research well may effectively steengthen the "Urban Carbon Management" and upgrade the living environment and urban sustainable development of Shanghai City.