Regional Landscape Ecological Risk Assessment Of City Watershed Based On Landscape Pattern

In the process of urbanization, most of all, the region which was experienced rapid urbanization processing, due to the human activities interfere is involved strongly, which breaking the intrinsic landscape pattern composition of the ecosystem, leading to the changes of processes in the natural ecological and the loss of biodiversity, and affecting the regional ecological safety. Therefore, it is becoming a concern to a number of researchers by how to express the level of the ecological system risk in rapid urbanization quantitatively, and effective and reasonable assessment.The paper use the Qingshui stream which in the main city of Chongqing as an example, combined with the principle and approach of landscape ecology, drawing on the theories and methods of ecological risk assessment which come from domestic and foreign, using ERDAS9.2 image processing software and the remote sensing image data of Qingshui stream in 1988, 1998, 2007 to obtain the watershed landscape pattern change information of three period. According to characteristics of landscape pattern, we can build the landscape ecological risk index based on landscape pattern to regard as the indicators of landscape ecological risk assessment, and use the spatial analysis methods of ARCGIS9.2 to variable space-based of the risk index, which can revealed the spatial distribution grades and its change of the ecological risk in Qingshui stream, then we proposed the strategies and comprehensive control measures of watershed ecological risk management for the corresponding risk areas.The results showed that: In the process of rapid urbanization, the landscape pattern has changed greatly in Qingshui stream. Farmland, forest, water and other natural or semi-natural landscapes was changed to the cultural landscape as urban construction land promptly, which mainly register as farmland, forest reducing numerous, urban construction land increase, especially since Chongqing became a municipality, urban construction land has been growth more rapidly.Landscape diversity index was a gradual declined, in the context of the sustainable land-use change, the landscape heterogeneity was diminishing, a large number of farmland and forest was converted to urban construction land. Landscape dominance index gradually increased, the forest land being replaced by construction land gradually, while the landscape evenness index gradually decreased.Ecological Risk spatial class distribution of Qingshui stream has a certain regularity, the value of the landscape ecological risk increased gradually from Gele mountain to its east and west sides, from the built-up areas of the watershed northeast such as Shapingba, Xiaolongkan, increased to the watershed southwest, the size of the risk value distribution is showed banded structure, the risk value of the central watershed is high, Gele mountain and the built-up areas of the watershed northeast is low.Finally, the paper combine with the actual situation in the Qingshui stream, we proposed the strategies and comprehensive control measures of watershed ecological risk management in order to make the Qingshui stream to restore the ecosystem which harmony between man and the natural, and to improve the urban landscape, providing valuable reference to Qingshui stream of its ecological environment protection study and the layout of industrial economy.