关键词: 表土结皮, 黄土, 红壤, 黑土, 紫色土

Abstract:

Soil surface crust attracted great attention because of its effects on plant growth and output, and further infiltration and runoff production and sediment yield. Soil surface crust formation is the product of soil and rainfall. The sensitivity of soil crust formation depends on soil properties and rainfall characteristics; however, it is difficult to evaluate the sensitivity of soil surface crust formation because key factors of soil crust formation are still unclear. In addition, many types of soils, especially loess soil, purple soil, red soil and black soil with different physical and chemical properties are distributed spatially in serious soil and water loss regions of China, such as the Loess Plateau region and Sichuan. However, soil crust sensitivities of these regions are short of report. Based on experiment results under simulated rainfalls and conclusions of other researchers, the paper considered that fine particles, aggregate stability and high rainfall intensity are three key factors affecting soil crust formation. Among them, fine particles, especially silt particles provide material for soil crust formation. Whereas, soil particles are commonly in the pattern of aggregates, so aggregates stability decides the rate and degree of soil crust development. In addition, rainfalls with high intensity disrupt the aggregates by its impact energy and change the balance condition of soil; so, rainfalls decide whether soil surface crust develops or not. Analyzing the soil properties and rainfall characteristics, soil crust sensitivities of the above-mentioned regions are concluded. In the Loess Plateau region, silt particles are predominant, and aggregate stability is weak, whereas, rainstorms are frequent; therefore, it is sensitive for loess soil to form soil surface crust. In purple soil region, the content of silt and clay particles is more than 50%, and aggregate stability is weak due to the higher content of rock chipping; consequently, it is prone to form soil surface crust under rainfalls with high rainfall intensity. In red soil region, it is difficult to form soil surface crust except soils developed from granite and shale due to high sand particles or stable aggregates. In black soil region, it is impossible to form soil surface crust on typical black soils with aggregate content of more than 50%. However, soil crust can develop on non-typical black soils.

Key words: soil surface crust, loess soil, red soil, black soil, purple soil