关键词: 土地沙化, 恶性循环, 权图影响结构模型, 系统协调优化

Abstract: In this study, the natural conditions and natural resources of Yanchi County, NingXia Hui autonomous Region and the relation between the social-economic development and environment have been analyzed. With the application of weighted digraph and pulse processes, the author has studied this county's social-economic and environmental system quantitatively. By forcasting and comparing the states and behaviour of the system after it has empted a variety of development strategies, the author suggests some measures and development strategies for the coordinative development and optimum Tuning of the system.In accordance with native conditions and circumstances, seven models are established. Model 1 is built according to the traditional development pattern. ?The results of the predictions show that the traditional development pattern not only deteriorates the social-economic status of the county steadily, but also destroys the natural environment seriously due to desertification. To counter the factors which lead to noxious cycle of the system, the author takes several relevant improvement measures and adjusts development strategies for improving the state of the system.In order to find out the sensitive adjusting and controlling factors so as to optimize the whole system and coordinate the development, the author adjusts different development strategies from the viewpoints of population, animal husbandry, farming, forestry, rural living energy, sideline, and build models 2-6. By comparing the results of the predictions of the five models, on one hand the sensitive adjusting and controlling factor, namely mal hasbandry, is obtained and on the other hand the interacting and promoting relation among different adjusting strategies is analyzed. Thereafter, model 7 is built for the optimum running of the whole system.The conclusions of this paper show that weighed digraph and pulse processes are suitable tool for modelling complex systems like social-economic and environmental system. The adjusting and controlling strategies given by this paper are constructive for the coordinative development of social-economic and environmental system in Yanchi county.

Key words: desertification, noxious cycle, weighted digraph and pulse processes, coordination and optimization of system.