| The conception of Ecosystem Health emerged at an early age, but it was not until 70s of 20 century that it really drew people's attention and finally was established in 1988. During this period, the environment problems raised by the highly development of Industrialize and the rapid growth of Economy had prominent influence on us human being. In order to improve situation of the Ecosystem, people all over the world began to draw focus on Ecosystem Health research, more and more people appealed to defend the Ecosystem Health. Now days, a lot of scholars has developed deep study on varied ecological fields, such as the ocean, seacoast, swamp, forest, veldt, desert, diggings, cities and so on, all of which, theory of Lake Ecosystem Health is the most profound one. Whereas, it also exists some intractable issues, for example, definition of the Lake Ecosystem Health, selection of the evaluation indices system and evaluation methods, etc.Dongchang Lake is located in the City of Liaocheng, which is the peculiar large City Lake. The lake contributes to city's social and economy development. Recent years, the increase of the tourists influenced Lake Ecosystem at some certain extent. This thesis learns from the study result of those scholars and sets foot on studying the Ecosystem Health of the city lake-Dongchang Lake primary. At the same time, this thesis maps out the evaluation indices system of Ecosystem Health, fixes the evaluation classification criterion and assesses the Ecosystem Health of Dongchang Lake using fuzzy-pattern recognition and RBF ANN model, data came from 2005. The main ideas of this thesis include:1. Map out evaluation indices system of Ecosystem Health, fix the evaluation classification criterion and describe particularly the characters of each scale.The reported documents on evaluation indices overseas mainly laid stress on pure Ecological indices or suggested that we should also consider about the factor of human influence, but none of them were put into effect. This thesis thinks about human, society, economic indices and the Ecological indices of the lake while mapping out the evaluation indices system of Ecosystem Health, sets up an indices evaluation system which has 6 guidelines and 18 indices. It covers factors of environmental influence, economy development, sights, system, structure and condition of the lake. With the principles above, divides the health condition of Ecology into five grades, that is very healthy, healthy, sub-healthy, micro-morbidity, morbidity and describe the characters of each scale, establish classification criterion using proper approach.2. Evaluate the Ecosystem Health condition of Dongchang Lake in the way of fuzzy-pattern recognition and RBF ANN model.In comparatively, this thesis uses fuzzy-pattern recognition and RBF ANN model to evaluate the Ecosystem Health condition. Fuzzy-pattern recognition employs Euclidean Distance and Hamming Distance to evaluate. The result is the condition of the lake belongs to the 2ed level, in accordance with the actuality. The RBF ANN model figures the condition between 3～4 level, that is the condition between sub-healthy and micro-morbidity, unilateral with the reality. Analyzing the result, the main reason is that the training data is insufficient. The application of RBF ANN model needs further study in the future. 3. Work out the calculate programme of fuzzy-pattern recognition and RBF ANN model.In order to make the operation mush easier and make model has wider transplantation, work out the programme using matlab language. It performs in order accompanying with concrete instruction which is easy to understand.4. Considering evaluation results, put forward suggestions and measures to improve the Ecosystem Health of Dongchang Lake.
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