| Urbanization is the development trend of human civilization. Chinese urbanization has entered into a phase of high-speed development since the reform and opening-up. With concentration of population and fast development of industry and transportation, urbanization often brings negative impacts to regional eco-environment, such as increasing pollutant emissions, decline in environmental quality and forest, farmland and water coverage. The composition and spatial structure of landform coverage is considerably changed, challenging the maintainence of biological diversity. Therefore, research on the evolution of landscape pattern during the process of urbanization has scientific significance, and will serve as a guide on urban development and planning.This paper begins with the discussion on the development course and basic theories of landscape ecology and urban landscape ecology, and proceeds to review the important development direction of urban landscape ecology. Based on the basic theories and research content, the methods and basic data are defined.The main contributions of this dissertation are as follows.1The urban expansion and landscape pattern succession. This section takes Changsha and its central city as the study area. The study begins with the establishment of landscape geo-database of the past three decades. The process of urban expansion is studied by analyzing the change of landscape pattern indices. The land use transferences trends are analyzed to identify the direction of urban space expansion. The study finds out that the urbanization of Changsha occupied farmlands and woodlands. Due to the single-core urban expansion mode in Changsha, a typical cyclic city structure was formed in the central city, and the landscape pattern indices also showed a corresponding gradient trend. The central city of Changsha was expanding eastward in recent years. With the integration of Changsha, Zhuzhou and Xiangtan City, and the development process of Hexi Pilot Area, the central city of Changsha moved in the south and west direction on the expansion trend. The urbanization process led to landscape fragmentation, but at the same time, the central city of Changsha gradually formed a pattern system which is dominated by urban landscape of high connectivity and contagion.2The spatiotemporal changes of landscape pattern in response to urbanization. This section takes the Hexi Pilot Area of Changsha as an example. In the process of urbanization, human activities in urban regions usually have influence on landscape patterns and landscape spatial patterns have profound impact on ecological systems. The landscape diversity index was often used to describe landscape spatial patterns. The correlation between different landscape metrics has been discussed in this section. The results show that:First, the study area to promote rapid urbanization process, urban built-up areas for nearly20years expanded3times, the main erosion of urbanization were forest and farmland landscapes. Second, in the early process of urbanization, landscape diversity index increased rapidly, a serious landscape fragmentation and ecological systems are strongly influenced by urbanization, and landscape diversity index decreased later, the formation of simple urban landscape. Third, the landscape diversity index and the Percentage of Landscape (urban) index follow quadratic function relation, the landscape diversity index between Largest Patch Index and Contagion index showed significant negative correlation.3The scaling issues of landscape pattern analysis. Based on the methods of wavelet analysis and geo-statistics analysis, this section analyzes the impact of landscape pattern by the characteristic scale and identifies the characteristic scale of the landscape system of Changsha City. The landscape pattern indices show six types of different features when the range and grain change. Therefore selecting the appropriate scales (the range and grain) on the landscape pattern analysis is very important. The farmland and woodland of the study area show a characteristic scale of120m, and the urban shows multiple characteristic scales of120m,3840m and7680m. The characteristic scales which are identified by wavelet analysis is basically the same as the geostatistical methods.4Identifying ecological corridors using shortest path algorithm based on raster data. Ecological corridor, which plays an important role in biodiversity protection, is defined as a stretch of nature mosaic that facilitates the migration of animals. Many GIS software packages use raster cost surface to identify the path of least resistance between source and destination. Limitation of those methods is that only a single path can be identified. However, ecological corridors should be more complicate and more redundant. Many alternative paths with relatively less cost might exist in fact, for animals may not choose the optimum path when moving between different habitats. In this paper, a new approach based on Spatial Analyst Tools of ArcGIS using raster data is proposed to identify the redundant routes. Firstly, the resistance cost surface moving from source to adjacent raster is defined. Secondly, the accumulated least-cost raster from both source and destination habitat to any other raster on the cost surface is evaluated. Two accumulated least-cost rasters are added by raster calculation module. The value of the added raster is the accumulated least-cost which passes the current raster. Thirdly, the corridor is obtained by extracting the added raster with a certain value. Corridors of six simulated landscape patterns with different spatial autocorrelation are used to assessment this procedure. The results show that the corridors obtained by the procedure not only include the optimum path, but also contains some sub-optimum paths. The corridor is redundant and fit for describing the migration behavior of animals. Lastly, the identification of the ecological corridors in West Bank Pilot Planning Area of Changsha is used as an example. The results show that eleven key habitats existed in study area. Corridors of twenty adjacent habitat pairs are analyzed. The results show that all the corridors are of certain width and some of the corridors have furcation or even bypath. However, there are some bottlenecks in some corridors, which become the key zone for the ecological restoration.5The construction and optimization of regional landscape security pattern based on the connectivity. This paper builds the regional landscape security pattern, which regards urban region of Changsha as the research object. It extracts respectively five components of the ecological security pattern, which includes source, buffer, corridor, radiation and node, and it clears the key areas which need ecological protection in research region. At the same time, the research shows that, because of the characteristic shape of Changsha-the distance from the east to the west is longer than the south to the north, the ecological barriers from the south to the north should be jointly constructed with surrounding cities, especially, the areas of city fusion of Changsha-Zhuzhou-Xiangtan urban agglomeration in the southern, and it needs to refer to the green heart planning of Changsha-Zhuzhou-Xiangtan to leave a ecological conservation belt between cites to ensure regional ecological security.The basic ideas of the paper includes three points; firstly, this paper reviews and analyzes the regional urban development and expansion, and discusses the inner link between city expansion and regional landscape pattern evolution, and makes topic discussion on the scale problems which make an influence on study conclusion. Then, it makes researches on the extraction and recognition methods of ecological corridor, and makes tests on corridor identification method by using simulation landscape, and makes empirical research on the corridor recognition of Big Hexi pilot area. Finally, previous theories and methods are used in practice to construct the landscape security pattern system of Changsha, which provides support and advice for urban planning. |
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