Study On The Relationship Between Land Use And Soil And Water Loss In Xiangxi Watershed

With the development of the economy and society, land use condition changed and has affected the soil erosion process. Applied the"3S"technology to the soil loss fast investigate can help the government to hold the soil loss actuality in time and exactly. Through the study on the relationships between land use and soil loss variation, exploring the couple mechanism of the land use and soil loss variation, analyzing the soil loss development trend and rule, has the very important theory and practical meaning to learn the soil loss variation disciplinarian and soil and water conservation, at the same time, it can be support definitude the train of thoughts of soil and water conservation and expedite the ecosystem construction.Changjiang River is the longest and largest basin in China. But, its soil erosion problem is very serious due to the dual effects of natural and artificial factors, according to investigation, soil erosion is mainly distributing in the up-stream of the Changjiang River. Taken Xiangxi River watershed of three gorges region as research object, using 3S technology, landscape ecology, gray system theory, and Mann-Kendall order trend analysis method, research on the coupling relation between dynamic change of land use and the spatial-temporal change process of soil and water loss was implemented, and the conclusions were as following:(1) The technique approach and method for distilling regional soil erosion intensity and its factors were put forward. On the basic of 3-S technology, and by human-machine alternation and combined with half automatic interpretation of computer, and by biology biomass index combined with field indication calibration, and spatial analysis of soil erosion intensity, the effective extraction of land use type, vegetation cover index, soil erosion intensity could be realized, and the accuracy of field check amounted to 89.1%.(2) Evaluation method system on dynamic change of land use situation was established. By analysis of spatial dynamic degree, calculation of Markov diversion model, and landscape pattern analysis, the dynamic change of land use situation could be systematically evaluated. The research showed that, from 1988 to 1999, mutual diversion existed among different land use types, in which, the diversion from farmland to woodland, grassland and horticulture, and the diversion from grassland to woodland and farmland were dominating; steep slope field was changed to woodland, grassland, and garden plot with the area of 100.73 km2, 65.18 km2, and 48.44 km2 respectively; the fragment index of landscape for different land use types was increasing, and its structure became complex from simple; the figure spot density of landscape increased from 1.73 to 16.19, the diversity index decreased from 1.69 to 1.56.(3) The evaluation method system for spatio-temporal change process of soil erosion was established. By analysis of change velocity of soil erosion intensity, analysis of spatial barycenter diversion, analysis of fractal characteristic and its stability of spatial structure, spatio-temporal change process of soil erosion intensity could be analyzed effectively. The research showed that, the annual change ratio of erosion intensity class was ranked as tiny, intense, tempestuously, moderate, and light; the change of average figure spot barycenter of each soil erosion intensity class at longitude was bigger than that at latitude; except tiny erosion, the figure spots of other erosion intensity class had the increasing trend, which showed that each erosion class developed toward tiny erosion, and the situation of soil and water loss was becoming better.(4) The coupling relation between land use type and soil erosion intense was initially clarified. Research showed that different soil erosion types had different soil erosion ratio; the soil erosion ratio of horticulture, farmland, forest, grass land and bush land, was bigger, while that of residential area, traffic land, and water area was small; the dimension effect of average figure index and figure spots of landscape pattern on soil erosion structure was most, however, that of average figure area was small.(5) The driving factors and its quantitative analysis method for soil and water loss were initially discussed. Which showed that the 5-year average of the runoff and sandiness in Gaolanhe small watershed, the branch of Xiangxi River, took on a decline trend since the end of 1980; and that the contribution rate of artificial action to the sediment transfer in Xiangxi River watershed was 53.8%, and that of natural factors was 46.2%, therefore, the main reasons that aroused the sandiness transfer change of Xiangxi River watershed were artificial factors.