| Soil erosion and soil degenerated by erosion is a main environmental problem in the world. Soil erosion in the loess plateau, is great environmental problem at present, and soil erosion monitoring is of great significance for stipulateing the countermeasures against soil erosion. With Project of the 2nd World Bank Loan of Soil and Water Conservation to Loess Plateau began in 1998 in Qingcheng of GanSU, after 6 years, we have made great progress in the fields of helping the peasants in the area to shake off poverty , improving the environment, and checking sediments for the Yellow River. The paper calculated soil erosion situation of before and after the project execution quantificationally, based on the principles of landscape ecology and soil and water conservation, by field investigation, Remote Sensing (RS) and Geographic Information System, combined with the universal soil loss equation. It was concluded three conclusions: the area of soil erosion, the modulus of soil erosion and the information of spatial distribution of soil erosion. Using landscape pattern software Fragstat3.3, on the landscape scale and the patch type, we study the characteristics of landscape pattern changes in 6 years. we apply the model of CA-Markov with the integration of advantages of the model of Markov and CA for simulation and prediction of soil erosion situation and information of space distribution in 2010, the result shows that the model of CA-Markov can make full use of the outstanding merits of the model of Markov and CA and make well simulation and prediction for the change of soil erosion, the result proves credible. The major research conclusion of this paper as follows:(1) During the 6 years of the secondary World Bank Loan Loess Plateaurehabil Itation Project in Qingcheng, the average of erosion modulus decreased from 78.77 t/hm~2·a before operation to 70.58 t/hm~2·a after operation. The area of soil erosion and the amount of soil erosion have been respectively reduced by 525.87hm2 and 341050t/a, in which the total and the extent in the acutely eroded and the extremely eroded areas decreased significantly; the results are evidently effective from the practical proof. The biggest amount of soil erosion is in the slope of between 25°and 35°, accounted for about 42.51% of the total erosion amount, erosion modulus is 101.68 t/hm~2·a, which belongs to extremely eroded area; the slope of betweenl5°～25°is the second, soil erosion amount accounted for about 31.69%, erosion modulus is 61.49 t/hm~2·a, which belongs to intensively eroded area. The results show that Soil loss on the land where slope is over 15°, is the key factor for the soil erosion control. Farmland (the main type is sloping farmland) in 2004 not only had higher erosion modulus, but also the soil erosion area accounted for 58.09% of the total erosion area, so the farmland is also the key.(2) A view of grid spatial data in 1998 and 2004, the landscape is fragmentized very much in the whole research area. From landscape level, the average patch size in 1998 and 2004 is respectively 0.35 hm~2 and 0.36 hm~2, the area in 2004 is more than 1998. From the patch type class level, all is less to 0.7 hm~2; except the largest patch index of no evident erosion landscape is greater than 5, others are less than 0.1. The largest patch index(dominance)of no evident erosion landscape is 5.26 and in 1998 and 5.58 in 2004, which is more than other types, is the main body in the study area. Landscape fragmentation index of serious area of soil increase, landscape isolation was descended, area distribution is becoming more and more centralized from disperse, while fractal dimension become smaller, the simplification trend of the cropland patch shape increases, the condition of soil erosion improved.(3) The model of CA-Markov well develop the advantage of temporal dynamics of Markov and the advantage of spatial prediction of CA, can well do in predicting the change of soil erosion, and the result is reliable. The forecasting results show that the character of spatial pattern of soil erosion was no significant changes in 2010, and basically maintained the character in 2004, the condition of soil erosion improved.Soil loss amount is the comprehensive results of multifactors, such as precipitation, terrain, vegetation, artificial methods, etc. Terrain and precipitation were thought to be definite values in the short time scale. Soil erosion is mainly affected by vegetation and human activity, but these factors can be got by RS, which ensure the scientific feature and the reliability of the method.The calculated result in the study area shows, the slope of above 25°should be returned to forestland or grassland from slopeland, while the slope between 15°～25°should be improved into terrace from slopeland. At the same time, the farming measures of soil and water conservation can be widely used, such as rotation for soil conservation, etc.It is very important to establish reasonable measures of soil and water conservation and estimate the soil erosion quantitatively, dynamic Monitoring of soil erosion by the universal soil loss equation, combined with GIS and RS techniques. It is hoped that a scientific judgment can be made for the effect of soil and water conservation after the project, and also could provide a scientific basis for working out measures of synthesizing management about soil erosion in the study area.
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