表土结皮形成影响因素述评  

Summary on influencing factors of soil surface crust or seal

作　　者：刘平[1] 张虎元[1] 王锦芳[2] 严耿升[1] 

机构地区：[1]兰州大学西部灾害与环境力学教育部重点实验室,甘肃兰州73000 [2]兰州大学资源环境学院,甘肃兰州730000

出　　处：《干旱区地理》2009年第5期662-668,共7页Arid Land Geography

基　　金：国家科技部十一五科技支撑项目(2006BAK30B02)

摘　　要：西北干旱半干旱地区,表土结皮普遍发育,其形成受诸多因素影响。土壤质地是影响表土结皮形成的最重要因素。此外,团聚体稳定性、表面粗糙度、矿物质和交换性离子浓度、降雨历时、降雨强度、前期含水量、湿润速度等因素同样对结皮的形成具有重要影响。结皮的形成可以简要归纳为两个主要过程,一是团聚体的分散,二是分散后的粘粒阻塞土壤孔隙。因此团聚体稳定性和粘粒含量是影响表土结皮形成的关键。研究发现,土壤中粘粒含量为20%～30%时,极易形成结皮,当粘粒含量超过40%时,团聚体变得较为稳定,结皮形成受到一定抑制。此外,土壤中如果富含蒙脱石矿物,或者土壤溶液具有较低的交换性钠离子和电解质浓度,则表土结皮易于形成。前期含水量和湿润速度对结皮形成也同样具有重要影响。试验表明,粘粒含量较高的试样在较低的前期含水量情况下更容易形成结皮,因为稳定性较高的团聚体在干燥条件下更容易因迅速湿润而崩解。湿润速度对表土结皮的影响作用随着粘粒含量的增加而增大,但在土壤结构不稳定条件下,其影响作用受到很大限制。影响结皮形成的各因素并不是孤立的,它们之间互相作用、互相影响,这给定量研究和分析结皮形成敏感性带来很大难度,如何对各影响因子的临界值进行确定以及定量研究各影响因子对结皮形成的敏感性将是该领域今后研究的发展方向和有待深入的方面。表土结皮不仅局限于适于植物生长的土壤表部,在西北地区铁路及高等级公路土质边坡表部以及诸多土建筑遗址表层均有发育,这对工程构筑物的正常运营和保存构成诸多不利影响。因此该领域向岩土工程学科方向的发展将是其今后重要研究方向之一。Surface crusting is a common occurrence in many soils worldwide, especially in arid and semiarid soils. The formation of soil surface crust/seal mainly depends on soil permanent properties （ such as soil texture, mineralo- gy, organic and inorganic polymers, composition of exchangeable cations, aggregate stability, antecedent water con- tent and wetting rate）. The objective of this study is to classify these influence factors and review the main research direction in this field. The general sequence of events that leads to crust formation under rainfall conditions can be described as follows ： （i） breakdown of soil aggregates caused by raindrop impact or slaking ; （ii） movement of clay particles and blockage of soil pores. So the aggregate stability and clay content have substantial effects on formation of surface crust/seal. Research shows that soils with 20 - 30 percent clay were the most susceptible to crust forma- tion. With increasing clay content above 40 percent, soil structure became more stable, crust formation was dimin- ished. In addition, smectitic soils, low levels of exchangeable sodium percentage and electrolyte concentration were all beneficial to the formation of soil surface crust/seal. Wetting rate, antecedent moisture content, also significantly affect soil susceptibility to crusting, but this was often neglected by many researchers. Fast wetting of dry soil caused aggregate slaking and crusting whereas high antecedent moisture content decreased aggregate disintegration. Quanti- tative study on the influence of various factors to the surface crust formation is the future research direction in this field although this would be challenging because of the interaction among these factors. In arid and semi - arid are- as in Northwest China, surface crust is also a very common phenomenon on the surface of earthen architecture site and soil slope on both sides of highway and railway. The presence of surface crust has produced the adverse effect on transit operation and conservation of e

关 键 词：表土结皮 交换性钠离子浓度 团聚体 时效性 影响因素 粘土矿物 

分 类 号：S152[农业科学—土壤学]