Studies On Desertification Assessment & Monitoring--Taking Yanchi As Example

As the global environment degradation, more and more attention is paid to desertification worldwide. After half century disputing and even there still some debating, the definition on desertification in the United Nations Convention to Combat Desertification in Countries Experiencing Serious Drought and/or Desertification, Particularly in Africa were accepted by most of people worldwide, namely, "desertification" means land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities.In this paper, through methods of theory with typical studies the author point out the guidelines for choice the desertification assessment system. Under guidance of integrated, dominant and practical, the indicators used for desertification assessment should be rational in science, use small sample, measurable with minimized error, sensitive and easily got with less cost and broadly used, integrated and without harm to ecosystem. While in practical desertification assessment, one should base on the research scale, monitoring & assessment method, technical measures and outlay investment to select climate factors, soil factors, topography factors, vegetation factors, hydrological factors and some social economic factors whivh including human factors.As development of computer science and for monitoring methods, 3S (GIS, GPS, RS) supported desertification monitoring method will be one of the most advanced and abroadly used methods in future. By images computer interpreting, artificial interpreting and images computer screen drawing methods will be the most used and popularized.Taking Yanchi County as case studies, by data collection & analysts with typical investigation data, and by using R2V digital method, Arc View GIS softare and the mathematical methods of Markov Chain model and Fuzzy Pattern Recognition, desertification pattern and trend were studied. The results show that in past 40 years, desertification has been seriously in Yanchi County. Desertified land has takes 89.04% in its north part and mean yearly increased rate was 4.03%. The main causes of desertification in Yanchi County are frangible ecological condition (rich erosive sandy soil materials, drought weather condition, strong wind in winter & early spring, thin plant covering) with global change (temperature increasing, rain fall reducing with seasonable drought) combined with un-rational human activities. Over-speeded population increment is the basic cause of desertification. It leads over grazing, over cultivation, un-rational Chinese medicine and fuel wood collection. Mis-management & small control investment speed up the desertification. For desertification combating in future, much attention should be paid to change idea (family planning & sustainable development), taking advantage of project of "Reversion of Farmland to Forest" and other policies, enhance management (massive propagation and strictly implementation of Desertification Law) and increase investment in desertification control. First, animal stock should be reduced as population control policy. Some pastureland should be enclosed & protected. Rotation grazing should be adopted. Second, over-cultivation should be stopped. Combined with Yan-Huan-Ding Water Transportation Project, immigration should well be organized to avoid over-cultivation. Third, massive propagation and strictly implementation law should stop un-rational Chinese medicine and fuel wood collection activities.At last some problems opinions on desertification as assessment baseline, time and space scale, indicators, drought and its effect to plant are discussed. And the regulation for desertification fixed monitoring should be made in near future.