我国荒漠化发生机理与防治对策

“荒漠化”是当今全球关注的一个重大的社会、经济和环境问题。《公约》为全球防治荒漠化的联合行动提供了一种全新的方式。本文运用生物控制理论中正负反馈回路的自我调节和自我加强作用分析了荒漠化过程的内在机制;用耗散结构理论分析了系统实现良性循环的途径,并提出我国防治荒漠化应遵循的4个原则：1)调节农林牧水工复合生态系统的结构和功能;2)实行“生态系统管理”,促进系统内的良性循环;3)传统知识与现代科学技术相结合;4)完善政策措施和加强科学管理。

MECHANISM OF DESERTIFICATION AND SUSTAINABLE STRATEGIES TO COMBAT DESERTIFICATION IN CHINA

The study of the desertification is a young discipline composed of interaction and compromise of multi-disciplines. It is characterized by the remarkable trend of progress of the research on desertification from microscope to macroscopic scales,namely the research on desertification is in progress from ecosystem, landscape, region to earth. The desertification combating is a complex engineering which is being gradually infiltrated between the new technologies and disciplines and it needs active coordination and hard efforts through multidisciplinary combination and inter-ministerial partnership. According to the definition of desetrification of the UN Convention to Combat Desertification, the geographic scope (range from 0.05 to 0.65) at the risk tO cause desertification in China is mainly located in the arid, send-arid and dry sub-humid areas occupying 3.317 million km², which covers 34.6% of the total land territory of China. The desertification affected lands are mainly distributed in the Northwest the west part of the Northeast and the most part of the North China and the total area of the desertification affected lands is approximately 2.622 million km² occupying 27.3%of the total land territory of China. China has made great achievements for combatting desertification. However, in general speaking, desertification is in progress in China.In light of the National integrated Survey of Desertification Affected Lands, degraded lands caused by desertization process alone develops in an average annual rate of 2 460km² since 1970 s. Climatic variation and human activity are the two major impact factors in the processes of desertification. Human activity arouses and accelerates desertification processes. The mechanism causing desertification contains the following three aspects:the feedback function between the human productive system and its environment; the impact of global change on the processes of desertification; and the acceleration of desertification is the process and state of the dissipative structure. According to the action and effect the human productive system can be divided into positive feedback mechanism and negative feedback mechanism. The former is a self-enhancement function and the latter is a self-regulation one. When the negative feedback loop is stronger than the positive feedback one, the system will be in a stable state. On the contrary, the system will be in a state of unlimited "growth" or "decline", and the density of desertification will be increased and the affected area of desertification will be enlarged. In the study, the feedback loop mechanism is adopted to analysis the crop cultivation, animal husbandry and forestry through the intertransformations between "stable" and "growth" of the whole system which caused by the self-regulation system. The optimum solution to combat desertification is to transform traditional extensive management into intensive farming and grazing system management, to develop and utilize rationally natural resources and finally restore the degraded ecology and rehabilitate the desertification affected lands. Climatic variation is also an interactive mechanism that should not be ignored. By analyzing the GCM model established on the basis of the meteorological data of more than 30 running years from 700 meteorological stations in China, it is predicted thatup to 2030 year, the total area of arid areas will be enlarged 2 211 km² per year and the area of humid area will be reduced 3 023. 5 km² per year when the CO2 was doubled and the air temperature increased 1.5～4℃. The dissipative structure is aimed to extend the research target into open system with material and energy exchange. It is engaged to study how the macroscopic system can be transformed into ordered state from the disordered stato. Water and thermal resources in arid zones are very Unbalanced. Serious wind and water erosions and unsaturation of biology, salt accumulation in soil will cause the system to develop in a more disordered state, and the "entropy" value will be increased and desertificat