降雨过程中红壤表土结构变化与侵蚀产沙关系

通过人工模拟降雨和表土微形态观测,研究了发育于泥质页岩、第四纪红粘土和花岗岩3种母质的红壤在降雨侵蚀过程中表土土壤结构的变化及其对侵蚀的影响。结果表明:降雨过程中,泥质页岩红壤极易形成土壤结皮,增加径流,响应结皮的形成,径流速率和含沙量较高,且迅速达到最大值,随后径流稳定而含沙量持续下降。第四纪红粘土红壤团聚体稳定,较难形成结皮,且结皮易被破坏,导致侵蚀过程中产流产沙量较低,均随降雨时间的延长而呈缓慢上升趋势。花岗岩红壤基本上不能产生结皮,粗化现象严重,因此产流量和产沙量也较低;由于土壤团聚体稳定性差以及径流的选择性运移,泥质页岩红壤和花岗岩红壤侵蚀泥沙中细颗粒(<0.02mm)含量远高于土壤中该粒径颗粒。而第四纪红壤侵蚀泥沙中粗颗粒较多,以多级团聚体的团聚体为主。

Relationship between Top Soil Structure Changes and Erosion Process of Red Soil under Simulated Rainfall

Top soil structure changes and their effects on erosion were studied under simulated rainfall in red soils derived from shale, Quaternary clay and granite. The results showed as followed: Soil crust developed easily in the red soil derived from shale, which accelerated runoff generation and made runoff velocity and sediment content rise to peak value quickly; while in the soil derived from Quaternary clay, because of high aggregate stability, crust developed more difficultly and was easy broken down. Companied with the crust formation and breakdown, the runoff velocity and sediment content rose slowly and fluctuated in a small range. Crust did not found in the soil derived from granite, on which surface sandy layer appeared during erosion process. The sediment size distribution depended on aggregate stability and runoff transportation. The percent of fine particles (<0.02 mm) in sediment were higher than that in soils in the soils derived from shale and granite. And the sediment of soil derived from Quaternary red clay contain much more coarser component which were compound aggregates.