Abstract:

【Objective】The aim of this study is to provide some references for the rule of soil erosion and the control of soil loss in Yimeng Mountainous area by analysing the dynamic change relationship of soil erosion intensity distribution relevant to slope gradient, soil types, rainfall, vegetation cover and land use.【Method】Supported by the technology of GIS＆RS, data of slope gradient, soil erodibility and data of annual rainfall erosivity, vegetation cover, land use and soil erosion intensity in different years (1986, 1995 and 2005) in the study area were acquired from Landsat TM image, relief map, soil map and meteorological information. Then, the hilly and mountain region of the study area was divided into 122 subbasins in which the soil erosion intensity index (SEI), average slope (AS), soil erodibility index (KI), average annual rainfall erosivity (AR), average vegetation fraction (AVF) and land use structure characteristic index (SI) were used to study the dynamic change relationship between soil erosion intensity distribution and the above factors at subbasin scale by the method of statistical analysis. 【Result】The investigation showed that with the increase of vegetation cover, the change of land use structure tended to be favorable for controlling soil erosion, the soil erosion intensity in the hilly and mountain region in the years of 1986, 1995 and 2005 presented a obvious decline. The effect of soil factors on the distribution of soil erosion intensity of the three years was not significant. The annual rainfall erosivity significantly influenced the distribution of erosion intensity in 2005 with a lower contribution rate (CR), which was 5.35%. Slope was the most critical factor affecting the distribution of erosion intensity, but the CR fell from 92.82% in 1986 to 84.23% in 2005. Vegetation cover only effected in 1986 with a CR of 7.18%, while the effect of land use which is closely related to human activities had been gradually enhanced, and the CR reached 15.77% in 2005. 【Conclusion】 When the space difference in distribution of annual rainfall erosivity increased, rainfall will be a factor which significantly influence the distribution of erosion intensity. Affected by human activity, land use exhibited its noteworthy factor on the erosion distribution after the restoration of vegetation. It is suggested that adjustment and optimization of land use structure should still be made in this area for the control of soil erosion.

Key words: Yimeng mountainous, soil erosion intensity, controlling factor, spatial distribution, dynamic change