Emergy Analysis And Model Building Of Agro-ecosystem

Agriculture is the foundation of national economic development. Agricultural sustainable development is an important part of the social-economic sustainable development and an key historical task of building new socialist countryside in our country.On the basis of the review of the agro-ecosystem researches, this dissertation applys the emergy analysis theory and input-output theory to analyse the input and output situation of the agro-ecosystem in Kaifeng City, to study the intrinsic relationships within the system inner elements consisted of the system and that one between them and the extral environment of the sestem, and reveals the factors and characteristics influencing the system succession. Then, relyed on the above research, the agricultural ecological model of Kaifeng City is built up, as a result, the foundation of the reasonable use of agricultural resources and the City's agro-ecosystem sustainable development is established.The dissertation is divided into six chapters:Chapter one reviews the agro-ecosystem research progress. This part focused on the research present about the input and output, the emergy analysis, the sustainable development evaluation, and the ecological service functions of agro-ecosystem are emphersized to analyze. The deficiencies and the development trends in research are discussed also.Chapter two explains the method of agro-ecosystem research. This part firstly explines the emergy analysis theory including the basic concepts of emergy theory, the major emergy indexes system and the process of emergy analysis. Sencondly, the main contents of the research is intruduced including the region choice, the study contents, and the methods to get the necessary data and so on.Chapter three analyzes and evaluates the emergy of Kaifeng agro-ecosystem from two aspects. First, the total emergy input-output structure and major emergy index system of Kaifeng agro-ecosystem are analyzed and evaluated in a opinion of macro approach. Sceond, emergy input-output structure of Kaifeng agro-ecosystem in level of rural household is analyzed in micro approach opinion, and reveals the regional difference of ecosystem emergy input and output. Based on above analyses, the emergy input-output model of Kaifeng ecosystem is formed.The conclusion drawn from the analyses is that the agro-ecosystem structure of Kaifeng city is relatively good, but still needs to be futher optimized. More detailed conclusions are as follows: (1) Total emergy input of agro-ecosystem grow slowly, in which the proportion of artificial auxiliary emergy input is larger than that of renewable environmental resources. Among unrenewable industrial emergy input, the emergy input of chemical fertilizer accounts for a significant proportion, which indicates that traditional inorganic fertilizer is still playing an important role. (2) Total emergy output of the agro-ecosystem has been in the development trend that first increase and then decrease and then increase again, in which farming and stockbreeding emergy output have higher proportion, meanwhile, fishery and forestry emergy output have lower proportion. (3) The net emergy yield rate of Kaifeng agro-ecosystem has been high but grows slowly and has varies significantly, which shows that the economic emergy input is in a low level. Environmental loading ratio has been going down, which indicates that Kaifeng agro-ecosystem has little environmental stress in production, and that more emergy output can be achieved when artificial auxiliary emergy input increases. (4) The agro-ecosystem has low production dominance and high stability indexes. The change indicates that the production units of the agro-ecosystem have the inclination towards balance, and that problems exist in the interactions between subsystems, in system automatic control and in the feedback mechanism. In the future, the agricultural ecosystem restructuring should be continued and strengthened, and more attention should be paid to the scientific nature of the restructuring. (5) Whether analyzed from the aspect of rural households'input-output structure, or analyzed from the the majar emergy idexes system, the regional difference of Kaifeng rural households'emergy input and output is significant. (6) On the basis of emergy analysis, by using Cobb-Douglas production function model , the production function model of agro-ecosystem for Kaifeng city is built, and it fit well with the actual input and output of kaifeng agro-ecosystem.In chapter four, the succession of Kaifeng agro-ecosystem is analyzed. The focus is the impacts and their characteristics on the system by the changes in land use, environment condition and rural households'investing behaviors. The analysis results indicate that Kaifeng agro-ecosystem succession has the characteristics of anterograde(positive direction), and that the leading factors which influence Kaifeng agro-ecosystem succession are agricultural production technology conditions and human activities, etc.The building of ecological model for Kaifeng is discussed in chapter five. Principles to build agricultural ecological model are analyzed emphatically, main current agricultural ecological patterns in Kaifeng are analyzed and evaluated also. Based on that, an ecological agriculture model for Kaifeng is built, and measures to construct ecological agriculture in Kaifeng city are put forward.In chapter six, the conclusions of the dissertation are drawn from all the analysis above, issues need further study are brought forward.