基于RUSLE模型的土壤侵蚀影响因素定量评估:以陕北洛河流域为例

Quantitative Analysis on Influencing Factors of Soil Erosion Using RUSLE:a Case Study of the Luohe Basin in Northern Shanxi Province

为了定量区分土壤侵蚀过程中退耕还林还草实施与降雨的作用,采用日降水、土壤类型、MODIS NDVI及DEM数据和修正通用土壤侵蚀方程(RUSLE),研究了陕北洛河流域退耕还林还草工程实施和降雨对土壤侵蚀的影响,结果表明:(1)2000-2014年陕北洛河流域植被覆盖呈改善趋势,其中>25°区域植被NDVI平均值高于<25°区域,但改善速率低于<25°区域。当不考虑降雨因素变化时,<25°和>25°区域年平均土壤侵蚀模数均呈显著的减少趋势,表明>25°区域的植被覆盖改善,确实能够起到减少土壤侵蚀的作用。(2)2000-2014年陕北洛河流域总体上年降水量、年侵蚀性降雨量、年降雨侵蚀力和年平均土壤侵蚀模数均呈增加过程,且具有较强的同步性,相关性也较强。2009年之后,情况发生变化,尽管仍保持同步关系,但相对较小的年降水量却产生了相对较大的年侵蚀性降雨量,反映出流域内降水日数减少,降水强度增大的情况,与已有研究一致。(3)降雨是流域土壤侵蚀的主导和控制因子,对土壤侵蚀的正向作用占74%,而植被覆盖仅为辅助因子,起次要作用,对土壤侵蚀的负向作用占26%。研究认为需要加强黄土高原气候变化背景下流域土壤侵蚀研究。

This paper is dedicated to quantitative analysis of the impact of＂the project of returning grain plots to forestry and grassland＂and of the rainfall on soil erosion with a case study of Luohe River basin in northern Shanxi Province on the basis of the data of daily precipitation, soil type, and the data of MODIS NDVI and DEM by using the revised universal soil loss equation（RUSE）. The results of the analysis showed that vegetation coverage tended to improve, and average vegetation NDVI in the areas of slope 〉25° was higher than that of slope 〉25°, but the improvement rate is lower; soil erosion in the areas of slope 〈25° and slope 〉25° tended to decline（when the change of rainfall was not taken into consideration）, reflecting soil erosion reduction owing to the improved vegetation in the area of slope 〉25°. The period of 2000-2014 saw the increasing process concerning the annual rainfall, annual erosive rainfall, annual rainfall erosivity and the annual mean soil erosion amount with a strong synchronization and correlation at the same time; however, the circumstances changed after 2009：though the synchronization still maintained, a relatively small annual rainfall have led to a relatively large annual erosive rainfall, reflecting the decrease of the number of rainfall days, and the increase of rainfall intensity, which was consistent with existing outcome of the research. Rainfall was a dominant and controlling factor that played a leading role with a positive effect accounting for ca 74% on soil erosion, while vegetation coverage was a co-factor that played a secondary role with a negative effect accounting for ca 26% on soil erosion. In conclusion, as the influence of climate change on soil erosion is crucial to the Luohe River basin, it needs to strengthen the research on soil erosion in loess plateau area under condition of the climate change.