| Desertification has been a main ecological environment question of North part of China in the past 50 years by its wide distribution and rapid expansion, influenced the local social economic sustainable development directly and threatened the ecological security of the economic cycle of Beijing and Tianjin. Dolonnur County of Inner Mongolia Autonomous Region is located in sand source fringe area around Beijing and Tianjin, has a typical ecological vulnerability. Since nearly 100 years, as a result of the population sharp increase, the big area of natural pasture opened up for the farming, and especially from 50's of 20th century, because the one-sided route of "regards grain as the key link" during the periods of "the Great Leap Forward" and "the Great Cultural Revolution", has made Dolonnur County one of the most serious desertification threatened area in the region. Although the present overall situation of desertification had the distinct improvement compared to that on 90's of the last century, but the local area was still expanding. The modem remote sensing technology has the superiority in the land desertification research, like macroscopic, accurate, broad, direct-viewing, tendency and current situation and so on. Therefore, adopts the quick remote sensing monitor method, accurately grasps the distribution and changing tendency of desertification, has the vital significance to the desertification preventing and controlling strategy.Taking the theory of Earth systems science as the direction, the landscape ecology theory and principle as the basic theory, using remote sensing(RS), geographic information system(GIS) technology, aerial photo of 1960, 1975 and TM data of 1987, 1995, 2000, 2005 with different time and spatial resolution were processed, and the land desertification information in 6 periods of time were extracted by the way of human-computer conversation. Among them, the smallest patch is in 10×10 pixels, and interpretation processing error is within three pixels (100×100m). The spatio-temporal characteristics of desertification evolution of the research area in nearly 50 years were discussed by using the method of GIS spatial analysis, overlay function and suitable mathematical model.(1) The spatio-temporal characteristics of desertification evolution of Dolonnur county in nearly 50 years. The results showed that, desertification area in 1960-1995 increased 1106. 2 km~2, and in 1995-2005 reduced 487.71 km~2. It mainly distribute on central region of country and north part region. It indicated that, since the implementation of "the Beijing-Tianjin dust storms sources control project", "the project of withdrawing graze and returning to grassland", "banning herd and confinement feeding project", "eco-migration project", the area of desertification in Dolonnur county reverses quickly, most of the mobile dunes were stabilized and the total area of desertification gradually reduced.(2) The landscape pattern of land change of desertification in Dolonnur county was analyzed through the landscape metrics computation, and the fractal dimension and stability of different desertification land landscape were discussed. In 1960, the area of initial state desertification area was the largest, then for the mild desertification, the serious desertification, the severe desertification, the area of moderate desertification was the smallest. The desertification land in 1975 and 1987, the each land desertification area from large to small are: initial state, mild desertification, serious desertification, the severe desertification land. In 1995, the area of mild desertification land landscape was the largest, was the dominant type of desert landscape. In 2000, moderate desertification area was the largest, then for the mild desertification, the initial state, the severe desertification, area of the severe desertification was the smallest. In 2005, the area of the initial state desertification land landscape was the largest, also was the dominant type of desert landscape. On the whole, the average value of fractal dimension of desertification area in Dolonnur county are between 1.3988-1.5635 in 6 periods of time, which still close to the value of random motion, therefore it had the latent mobile tendency. The stability of the structure of patch mosaic of mild desertification area in Dolonnur county tended to weaken along with the time series increasing, but the stability of the structure of patch mosaic of the severe desertification area in Dolonnur county has gradually improved since 1987, also the stability is relative high.(3) Analysis of driving factors of desertification and cumulative impact of Dolonnur county. We select some natural factors, including average annual temperature, precipitation, evaporation, average wind speed and etc; and some human factors, including total year-end population, GDP, livestock number, the area of plow land, the food yield and etc. The cumulative impact of driving force of desertification was analyzed with sliding average and grey relational analysis. The results showed that the accumulative impact of annual mean temperature came to the maximum in the third year, the accumulative impact of annual mean precipitation was the most significant in the fourth year, the impact of evaporation and wind speed was gradually increased with the time scale and was in most significant in the tenth year; population reached the maximum in the first year; the impact of the area of farmland of desertification gradually decreased in the duration of one to ten years; the impact of desertification of aggregate yields of grain reached to the maximum in the fifth years; the impact of desertification of total number of livestock was the most significant in the second years. From the contribution of the information of principal components, the ratio of the contribution of human factors is 57.29％, the contribution of natural factors is 16.76％. Therefore, and the root cause of land desertification ishuman factors.(4) The analysis of desertification of Dolonnur county. The ecological foot-print of was Dolonnur county calculated by using time serial data from 1986 to 2005. The results indicated that, per capita ecological foot-print of Dolonnur county from 1986 to 2005 had an increasing tendency, 0.699hm~2 in 1986 and 3.505hm~2 in 2005, increased 2.806hm~2. In 1986-1989, it's being discovered from comparing and analyzing per person of ecological foot-print and per person of ecosystem bearing capacity, the Dolonnur County assumed the ecology earnings, but from 1990, it appeared the ecological deficit. It showed that, along with the desertification reverses, the desert transformed into farmland, grassland and forest land, the ecological foot-print assumed increasing year by year.(5) CA simulation of desertification in Dolonnur county. The results showed that, the proportion of the area of desertification in Dolonnur county in recent 10 years compare to 2005 has small increasing tendency and the area will increase from 409.14km~2 in 2005 to 452.71km~2 in 2015. Among them, the proportion of mild desertification will continually grow, but the scope growing will be small. The area of initial state and mild desertification will grow from 159.60km~2 in 2005 to 163.91km~2 in 2010. The area of moderate desertification presents a weak growing tendency, will reach to 89.25km~2 in 2010, and 90.45km~2 in 2015. The severe and serious desertification will assume the tendency which will increase slightly, but the increasing scope will be very small, is only 24.33％, which reflects the desertification control will be more and more difficult. It can be said that, in the stable situation of desertification control policy, the above characteristics have basically reflected changing type of desertification of Dolonnur county in future 10 years.Because the desertification is a complex process of the interaction between nature and the human factors, some of the questions will need to be in thorough research and be perfect. (1)the question of time correspondence with remote sensing image;(2) microscopic and macroscopic unifies, using GIS space expansion model, distribution limited conventional view computation, spatial;(3) quantitative analysis of intrinsic mechanism of the formation and development of desertification;(4)analysis of association effect and feedback mechanism of desertification.
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