我国水土流失典型区土壤表土结皮敏感性

表土结皮是降雨与土壤共同作用下的产物,某一土壤是否结皮、结皮的敏感程度如何,取决于该土壤的性质及所处地区的降雨情况。我国广泛分布着多种理化性质迥异的土壤,尤其是黄土、紫色土、红壤和黑土分布在我国水土流失严重的区域。但是,土壤发育表土结皮的敏感性很少见报道。本文通过分析模拟降雨试验结果及前人研究结论,提出了影响表土结皮发育敏感性的3个关键因素,并基于此对我国四大水土流失典型区土壤表土结皮的敏感性进行了分析。研究表明:细颗粒,尤其是粉粒是表土结皮发育的物质基础;团聚体稳定性是表土结皮发育快慢及程度的决定因素;高强度降雨是表土结皮发育的必要条件。黄土高原地区土壤极易发育表土结皮,四川紫色土区土壤发育表土结皮的概率大,南方红壤区除花岗岩、页岩外其他母岩上发育的土壤很难发育表土结皮,东北典型黑土不发育表土结皮,而非典型黑土易发育表土结皮。

Study on sensitivity of soil surface crust formation in typical regions with serious soil and water loss, China

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.