湄公河流域土壤侵蚀空间特征及其优先治理区确定

湄公河流域拥有丰富的自然生态系统,为沿岸居民提供了食物、交通等众多方面支持,在东南亚地区具有极其重要的地位。土壤侵蚀是该流域主要环境问题,易引发土地退化和河流泥沙淤积。基于气候、土壤、遥感等区域数据产品,使用通用土壤流失方程(USLE,Universal Soil Loss Equation),对湄公河流域土壤侵蚀状况及空间分布特征进行探究,并通过联合信息熵方法,确定该流域土壤侵蚀的主导因素。结果表明,湄公河流域平均土壤侵蚀模数为1.98×10~3 t km~(-2) a~(-1),属轻度侵蚀;流域内近40%区域存在不同强度的土壤侵蚀,侵蚀较严重的地区主要包括11个子流域(M4—M7、M9、T4—T6、T8、T10、T20),是未来土壤侵蚀重点治理区域。土地利用类型、坡度和海拔是该流域土壤侵蚀的主导因素,其中灌丛和裸地/稀疏植被分别为强烈和极强烈侵蚀,土壤侵蚀模数与坡度的关系为随坡度的增加呈先增加后减小的趋势,和土壤侵蚀模数与海拔的关系相同。流域内剧烈程度侵蚀发生区主要特点为:土地利用类型为裸地/稀疏植被和灌木,海拔在500—2000 m,坡度在8—25°。基于优先级理论,对湄公河子流域的优先治理次序进行排序和划分等级,共分为4个等级,达到第一级的共3个子流域。通过以上研究分析以期能为湄公河流域今后的水土保持规划和管理工作提供一定的科学参考依据。

Assessment of soil erosion and prioritization for treatment at the catchment level in the Mekong basin

The Mekong River''s abundant natural ecosystems supports the lives of coastal residents in numerous ways and plays a major role in Southeast Asia. Soil erosion is a major environment problem and can easily lead to land degradation and sedimentation. In this study, we applied the Universal Soil Loss Equation model to explore soil erosion and spatial distribution characteristics of the Mekong River Basin. We also combined the Information Entropy method to explore the dominant factors of soil erosion. The results showed that the average soil loss is 1.98×10³ t km^-2 a^-1. There are different levels of soil erosion in about 40% of the area. Serious erosion mainly comes from elven catchments (M4-M7, M9, T4-T6, T8, T10, and T20). Land cover type, slope, and altitude are dominant factors influencing soil erosion in the basin. Shrub and bare/spare vegetation areas are subject to strong and extreme erosion. The mean soil loss first increases and then decreases with increasing slope, and it is the same with mean soil loss and altitude. The major characteristics of extreme erosion areas are: bare/spare vegetation and shrub, sea level range of 500 m to 2000 m, and slope range of 8 to 25°. Finally, based on the Priority Theory, the priority governance order of the Mekong River Basin was ranked and graded. It was divided into four grades and there are three tributaries belonging to the first grade. Our results could provide a scientific reference for future planning and management of soil and water conservation in the Mekong River Basin.