喀斯特地区不同降雨和植被覆盖的坡面产流产沙特征

目的]分析不同降雨类型下的径流和产沙量特征,及其在不同植被覆盖类型和植被覆盖度下的响应,为喀斯特地区黄壤坡面在不同降雨和植被覆盖条件下的产流和产沙量动态特征研究提供理论基础。方法]以贵州省黔南州龙里县羊鸡冲小流域2014—2018年径流小区实测数据为基础,基于均值分类的方法,将研究区降雨类型划分为4类,对各指标进行相关性分析、回归模型模拟以及指数函数分析。结果]不同降雨对研究区产流产沙的影响程度不同,不同植被覆盖类型下降雨特征对产流产沙的影响存在明显的差异。总体上A型降雨(极强雨强,极大降雨量、中等降雨历时的低频次降雨事件)更容易造成侵蚀性危害,该条件下坡面产流和产沙量之间显著相关,并且经果林表现出极好的水土保持效果;B型降雨(强雨强,中等降雨量、短降雨历时的高频次降雨事件)为该地区主要降雨类型;在4种降雨条件下,混交林的水土保持效果优于其他植被覆盖类型。产沙量与雨强、径流深正相关,和植被覆盖度负相关,对产沙量的影响为:径流深平均雨强植被覆盖度。当植被覆盖度到达80%左右,其削减径流以及减沙的效果处于稳定的状态。结论]在降雨一定的前提下,植被是影响坡面产沙量的关键因子。对于喀斯特地区黄壤坡面而言,增加地表覆盖度是减少产沙量的基础,也是防治水土流失的一项重要举措。

Characteristics of Runoff Sediment Yield on Slopes Under Different Rainfall and Vegetation Cover in Karst Areas

Objective] Analysis of the characteristics of runoff and sediment yield under different rainfall patterns, and its responses under different vegetation cover types and vegetation coverage was conducted to provide a theoretical basis for studying the dynamic characteristics of runoff and sediment yield of yellow soil slopes in karst areas.Methods] Based on field measurements from 2014-2018 in Yangjichong watershed (Longli County, Qiannan Prefecture, Guizhou Province), and based on the K-means classification method, the rainfall types in the study area were divided into four categories, and the correlation analysis, regression model, and exponential function analysis of each indicator were carried out.Results] Different rainfall types had diverse effects on sediment yield in the study area, and significant differences existed between rainfall characteristics on sediment yield under different vegetation cover types. The A-type rainfall pattern (low-frequency rainfall events with extremely high intensity, extremely high amounts and medium duration) was more likely to cause erosion. There was significant correlation between runoff yield and sediment yield on slopes, soil and water conservation effect in an economic fruit forest. The B-type rainfall (high-frequency rainfall events with high intensity, medium amounts and short duration) was the main rainfall type in this region. Among the four rainfall types, the soil and water conservation effect of mixed forest was the best, compared with other vegetation cover types. Sediment yield was positively correlated with rainfall intensity and runoff depth, and negatively correlated with vegetation coverage. The sediment yield was strongly influenced by runoff depth, followed by average rainfall intensity and vegetation coverage. When vegetation coverage reached about 80%, the reduction effect on runoff and sediment was stable.Conclusion] Under certain rainfall, vegetation is the key factor affecting slope sediment yield. For a slope of yellow soil in karst areas, increasing surface coverage is not only the basis for reducing sediment yield, but also an important measure to prevent soil erosion.