The Change Of Urban Green Space And Its Impact On Eco-environmental Effects

The rapid urbanization leads to a series of eco-environmental problems, such as air pollution, urban heat island, water deterioration and decrease of biological diversity. This affects influence directly the state of regional ecological security and sustainable development. As the background of urban ecosystem, urban green space is a suitable way to balance the relationship between rapid urbanization and the eco-environmental problems. Landscape ecology that studies pattern, process and function offers a comprehensive way to solve these complicated ecological problems. Recently, multi-discipline researches on quantifying the pattern of urban green space and the following eco-environmental effects have become hot topics of urban ecological studies. As the most rapid urbanization area in China, Shanghai area’s landscape pattern and environment experience a tremendous change. This dissertation takes Shanghai city as the case study area, analyzing the change rules of urban green space and the following eco-environmental effects based on the theories and methods of landscape ecology, remote sensing, geographic information system technology, spatial analysis as well as statistics analysis. Main methods and conclusions in this dissertation are as follows:(1) Based on the1997,2000,2005and2008image data, basic data and sample plot survey, the dissertation integrates remote sensing and GIS-based spatial information technology to analyze urban green space composition and its spatial-temporal change processes. The result of the case study in Shanghai shows that urban green space has decreased from2031.2km2to1364.7km2during1997to2008and the proportion of crop land in the rural area has declined more than50%. Compared with the complex change process in the rural area, the chang in central urban area green space shows an upward trend. Total vegetation coverage has decreased significantly, the area of full and high coverage has dropped heavily, while the medium coverage, the low coverage and the no vegetation have increased. A survey of111field plots in Shanghai shows that the urban green space in central area are dominated over by deciduous broad-leaved forest and evergreen broad-leaved forest, consisted of155species,117genera and76families, where the frequency of Camphor and Magnolia grandiflora is more than30%. Old parks, compared with recently established parks, have greater average height, average diameter at breast height, average canopy density and species diversity. There are only a few trees in the green space of residential area where the species is not diversified but there are more trees and more diversified species in the old residential area than in the new one. The street tree survey shows that Sycamore and Camphor have a high proportion, but the street trees have a trend of diversification recently.(2) Based on the classification map of urban green space, the dissertation integrates the landscape index, gradient analysis, spatial statistics to quantitative analyze the configuration of green landscape and its change rules. The gradient spatial analysis of urban green space in responses to the urbanization gives a deeper understanding of the pattern and process and supplies a background for the function study. The results show that the landscape pattern of urban green space changes along with the development of urbanization, the urban green space in the rural area present more fragmental along with the sprawl of urbanization, especial in Pudong, Nanhui and Songjiang area. The number of urban green space in central area shows little increase, but more fragmental and complex which was influenced by human beings. The complex change process of urban green space and non-green space makes the rural area possess higher landscape diversity than the central area.(3) The dissertation integrates CITYgreen software to analyze the ecological benefits of urban green space. Based on the regional ecosystem analysis method and analysis of the framework and calculation principles of CITYgreen model in assessing the benefits of urban green space in air pollution removal, carbon storage and sequestration and stormwater runoff, an approach is figured out to obtain appropriate parameters of this model to calculate the ecological benefits of different urban land use types in the study area of Shanghai. The results indicate that the ecological value of air pollution removal, carbon storage and sequestration and stormwater runoff of study area drops from1.62billion RMB to1.42billion RMB in total from1997to2008. The ecological benefits of rural areas are more than those in the proper of Shanghai. However, the ecological benefits of the most parts of rural area decrease from1997to2008in study area while it increase in parts of the proper area, Pudong district and Nanhui district. Based on the scenario model of CITYgreen, the forecasting results show that the benefits of urban green space in2020will almost double than that in2008.(4) According to temporal analysis on inter-annual variations of land surface temperature (LST), the thermal environmental effects performance from centralized to decentralized, sprawls along with the extension axis and major traffic lines showing a irregular form, and there are significant LSTs gradients from the city proper to surrounding rural areas. The thermal environmental effects are improved a lot in the city proper area while in the rural area they become worse. The land surface temperature of different landscape types are in the order of building landscape> crop landscape> urban green space landscape> water landscape. Furthermore, the overall relations between thermal environmental effects pattern and landscape index as well as biophysical features and population density are quantitatively explored. The patch density, euclidian area-weighted mean nearest neighbor distance, normalized difference impervious surface index and population density have a positive relationship with LST while the vegetation cover and total area of green space show a negative correlation with LST.Above on, based on the theories and methods of landscape ecology and environmental science, integrate a variety of quantitative analysis method, this dissertation qualitativly analyzes the change of urban green space and the following eco-environmental effects. The dissertation establishes a comprehensive method to evaluate the urban eco-environmental effects of urban green space and presents a quantitative method systemizing urban green space pattern and function at multi-level. Based on the analysis of composition, change process and function of urban green space at different gradient scale (level) in the study area, the dissertation also provides fundamental data for urban green space planning and construction in Shanghai, and thus inspire to similar studies.