Desertification In The Transition Zone Between Mowusu Sandy Land And Loess Hill Region

Desertification is an ecologically inverse land succession due to changes in climate and human activities in arid and semi-arid zones. The U. N statistics in 1994 showed that the desertified area around the world is about 36,000,000 km2. In China it is about 2,622,000km2 every year the desertification causes a direct loss of 54 billion Yuan. So it is an important problem facing the social and economic development west china, and holding back the sustainable development of the whole country. On the basis of theories of landscape ecology. Regional geography and historic geography, this paper, taking the transition zone between Maowusu sandy land and bess hill and gullies as the study area, systematically analyzed the environment, processes and controlling approaches of desertification using methods of historical literature analysis, field survey, remote sensing(RS) and GIS, and Quatemary stratum analysis. The main results are as follows: 1. Expand the concept of desertification. Using the theories and methods of landscape ecology and regional sustainable development. The paper analyzed the variability and sucession of landscape ecosystems and past researches on desertification and the relative concepts. With the consideration of requirements of the eco-environment construction and regional sustainable development. The author put forwarad that the desertification is an inverse succession of land type and ecosystem due to changes in natural ecological conditions(including climate, vegetation and land surface) and human activities in arid, semi-arid and humid areas affected by the drought. 2. Put forward the zoning method of the transition between Maowusu sandy land and bess hills and gullies. Using the methods of field survey, satellite image interpretation and comparison of historic literature, and according to the theories and methods of spatial patterns of landscape ecology, geographical differentiation and geographical zoning and mapping, the paper defined the transition zone between Maowusu sandy land and bess hills and gullies. This area not only has the characteristics of inverse succession of landscape ecosystems but also is characterized by the intensive water erosion and wind erosion. Meanwhile, it bears the characteristics of long-term human disturbances on ecologically fragile areas, and provides the possibility and examples of eco-environment restoration. Therefore, it is an idea area to desertification research. 3. Initially brought forward a plan to divide the stages of desertification Based on the analysis of the temporary and spatial processes of desertification over large range (including environmental geology, Quaternary geology, pabeogeography and historic geography), impact of human activities on the originally fragile environment and main aspects and related processes of desertification resulted from the human disturbances, the paper divided the desertification process into 3 stages according to the degree of human impact:geobogical desertification, natural desertification (complete natural desertification and man-induced natural desertification), accelerating desertification. 4. Initilly put forward and analyzed the concept of interface runoff soil erosion of sand-bess: based on on-the-tpot observations of rainstorm-induced erosion and analysis of the erosion mechanism, the thesis put forward the concept of interface runoff soil erosion of sand-bess. This is a very special and localized erosion type and process, which is one of the main sources of coarse sand in five. The paper did preliminary researches on the formation...