我国西南山区降雨侵蚀力时空变化趋势研究

Temporal and Spatial Variations of Rainfall Erosivity in Southwest China from 1960 to 2009

降雨是我国西南山区土壤侵蚀的主要动力因素,降雨侵蚀力反映了降雨对土壤侵蚀的潜在能力,研究降雨侵蚀力的时空变化趋势对我国西南山区土壤侵蚀的监测、评估、预报和治理具有重要意义。利用1960—2009年129个气象站逐日降雨量资料,计算出西南山区各气象站逐年降雨侵蚀力。采用趋势系数、气候倾向率和克吕格插值等方法对西南山区降雨侵蚀力50年来的时空变化趋势进行了探讨。结果表明:西南山区降雨侵蚀力空间分布特征与年降水量的空间分布特征一致;西南山区西北部的青藏高原区域降雨侵蚀力年际变化明显,变差系数Cv一般高于0.40;西南山区大部地区降雨侵蚀力呈上升趋势,说明由降雨侵蚀力引起的土壤侵蚀风险在增加,但在成都平原附近降雨侵蚀力在明显下降;降雨侵蚀力变化趋势系数随海拔高度升高而不断增加,在海拔2 500 m以上地区尤为明显,西南山区西北部的高海拔地区海拔高度对降雨侵蚀力增加具有放大效应。

Rainfall is the main driving force of soil erosion in the southwest China. It shows that rainfall eros- ivity has the potential ability causing severe soil loss. So, It is of great significance to soil erosion monitoring, as- sessment, prediction and control by researching on the temporal and spatial variation of rainfall erosivity in south- west China. Based on the daily rainfall amounts of 129 meteorological stations, the rainfall erosivity was calculated in the southwest China. With the method of trend coefficient, climate tendency rate and kriging interpolation, the rainfall erosivity trends were discussed. The result indicated that the spatial distribution of average annual rainfall erosivity is nearly the same as that of average annual precipitation. There is significant temporal difference of rain- fall erosivity in the Qinghai-Tibet Plateau of the northwest of the study area, and the Cv value is higher than 0.40. The rainfall erosivity of most of the study area shows increasing trend during the last 50 years which indicates that the potential ability of the soil loss caused by rainfall increases in southwest China. But, the rainfall erosivity shows decreasing in the area of Chengdu Plain. The coefficients of tendency increase with increasing altitude, and it is particularly evident in areas above an altitude of 2 500 m. The higher altitude enlarges the increasing trend of rain- fall erosivity.