多露石石漠化区岩面流对岩-土界面土壤的冲蚀效应

Erosion Effect of Rock Surface Flow on Soil at Rock-soil Interface in Rocky Desertification Area

岩面流在基岩出露的喀斯特石漠化区普遍存在,其容易受岩面形状影响以汇聚或分散的方式对岩—土界面处土壤进行冲刷侵蚀,这是喀斯特石漠化区土壤侵蚀/漏失发生的重要物理过程。为分析不同岩面形状下岩面流对岩—土界面土壤颗粒分布的影响,揭示岩面流对岩—土界面土壤的冲蚀效应,选择具有典型石漠化特征的休耕地(1年岩面流冲刷作用),在其中选取3种典型岩面形状(平直型、外凸型和内凹型岩面)为研究对象,采用激光粒度仪分析法,分析距岩—土界面不同水平距离(0~2,2~4,4~6,6~8,8~10,20 cm)及不同土层(0—10,10—20 cm)处土壤的颗粒分布特征。结果表明:(1)不同岩面形状下岩面流对岩—土界面处土壤的冲蚀影响依次为内凹型>平直型>外凸型;内凹型岩—土界面处土壤中黏粒含量最低,外凸型岩—土界面处土壤中黏粒含量最高;(2)岩面流对岩—土界面土壤冲蚀作用主要集中在距岩—土界面水平距离0~2 cm范围内,在其范围内内凹型岩—土界面土壤的砂粒含量均显著高于外凸型和平直型,而在距岩—土界面其他水平距离处土壤颗粒分布情况无显著性差异;(3)在岩面流影响下岩—土界面土壤颗粒分形维数均值排序依次为外凸型>平直型>内凹型,与土壤中黏粒含量呈正比,砂粒含量呈反比。研究结果可为深入认识基岩出露石漠化区土壤侵蚀/地下漏失发生过程提供科学参考。

Rock surface flow is ubiquitous in karst rocky desertification area exposed to bedrock,and it is easily affected by the shape of rock surface to scour soil at the rock-soil interface in the way of aggregation or dispersion,which is an important physical process of soil erosion/leakage in the karst rocky desertification area.In order to analyze the effect of rock surface flow on the soil particle distribution at rock-soil interface under different rock surface shapes,and reveal the erosion effect of rock surface flow on the soil at rock-soil interface,the fallow farmland(1-year erosion of rock surface flow)with typical rocky desertification characteristics was selected in this study,in which three typical rock surface shapes(flat,convex and concave)as the research objects.The distribution characteristics of soil particles at different horizontal distances(0~2,2~4,4~6,6~8,8~10,20 cm)and different soil layers(0—10,10—20 cm)from rock-soil interface were analyzed by laser particle size analyzer.The results showed that:(1)The influence of rock surface flow on soil erosion under different rock surface shapes is in the order:concave>flat>convex.The clay content of soil at the concave rock-soil interface was the lowest,and that at the convex rock-soil interface was the highest.(2)The erosion effect of rock surface flow on the soil at the rock-soil interface was mainly concentrated in the horizontal distance of 0~2 cm from the rock-soil interface.Within the range,the sand content of the soil at the concave rock-soil interface was significantly higher than that of the convex and straight type,while there was no significant difference in the distribution of soil particles at other horizontal distances from the rock-soil interface.(3)Under the influence of rock surface flow,the average fractal dimension of soil particles at rock-soil interface was in the order of convex type>flat type>concave type,which was proportional to the content of clay in soil and inversely proportional to the sand content.The results could provide scientific reference for further understanding the occurrence process of soil erosion/underground leakage in bedrock exposed rocky desertification areas.