Soil Water Repellency: A Key Factor in Post-fire Erosion
Soil Water Repellency: A Key Factor in Post-fire Erosion
复制标题
土壤防水性：火后侵蚀的关键因素
DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
L. Macdonald
中科院分区：
文献类型：
--
作者：
S. Doerr;R. Shakesby;L. Macdonald
土壤斥水性（疏水性）阻止水润湿或渗透干燥的土壤。这种情况在各种植被类型和气候下，特别是在森林火灾后都有记录。拒水性是土地管理者，水文学家和土壤科学家相当感兴趣的，因为（i）它可以在燃烧过程中被诱导，增强或破坏，（ii）它的存在会导致渗透率显着降低。这种渗透的减少通常被认为是森林火灾后经常在一系列尺度上观察到的径流和侵蚀增加的主要原因。本章的目的是提供一个基本的了解土壤斥水性，其测量，燃烧对土壤斥水性的影响，以及它在不同尺度的径流和侵蚀过程中的相对重要性。人们普遍认为，拒水性是由土壤颗粒表面存在的具有疏水性质的有机化合物引起的。在燃烧过程中，凋落物和表土中的这些物质会挥发并在土壤中凝结，从而引起或加强防水性。然而，在非常热的火灾中，这些化合物会被破坏，土壤会被破坏。在大多数情况下，火会增加排斥性，这往往局限于土壤的顶部几厘米或几分米，而且往往在空间、时间和程度上具有高度可变的性质。它通常在干燥条件下最明显，在长时间潮湿条件下减少或不存在。然而，减少或消除土壤斥水性所需的润湿的持续时间和量随土壤类型、烧伤严重程度和润湿前土壤斥水性的持久性而变化。燃烧还引起土壤和植被的一系列其他变化，这些变化在引起火灾后径流和侵蚀增加方面可能同样重要，甚至可能更重要。这些因素使得评估火灾后水文学和侵蚀过程中防水性的作用具有挑战性。这是特别如此，在较大的尺度上，由于所涉及的许多因素的高空间变异性和难以表征的反作用的土壤斑块，灰，生物扰动，土壤裂缝，烧毁树根，在减少地表径流所产生的强烈防水补丁。迄今为止的研究表明，拒水性可以强烈影响火灾后的径流和侵蚀过程，可以增强或减少拒水性在烧毁景观的相对影响的因素已经相当好地建立。然而，量化和预测火灾后侵蚀过程中拒水性的相对贡献作用仍然是一个重大挑战，特别是在更大的尺度上。需要更多的操作实验和更详细的监测，以提供一个更好的知识基础的程度上的影响，土壤水的排斥径流和侵蚀的领域在不同尺度的自然降雨事件。
Soil water repellency (hydrophobicity) prohibits water from wetting or infiltrating dry soil. This condition has been documented under a wide range of vegetation types and climates and particularly following forest fires. Water repellency is of considerable interest to land managers, hydrologists and soil scientists because (i) it can be induced, enhanced or destroyed during burning and (ii) its presence can cause a marked reduction in infiltration rate. This reduction in infiltration is commonly presumed to be the primary cause of the increases in runoff and erosion that are often observed at a range of scales following forest fires. The goal of this chapter is to provide a basic understanding of soil water repellency, its measurement, the effects of burning on soil water repellency, and its relative importance in runoff and erosion processes at different scales. It is widely accepted that water repellency is caused by the presence of organic compounds with hydrophobic properties on soil particle surfaces. During burning such substances in the litter and topsoil can be volatized and condensed in the soil, inducing or intensifying water repellency. During very hot fires, however, these compounds can be destroyed and soils are rendered wettable. In most cases fire increases repellency, which tends to be confined to the top few centimeters or decimeters of the soil, and often of highly variable nature spatially, temporally and in its degree. It is typically most pronounced under dry conditions and reduced or absent following prolonged wet conditions. The duration and amount of wetting needed to reduce or eliminate soil water repellency, however, varies with soil type, burn severity, and the persistence of soil water repellency prior to wetting. Burning induces also a series of other changes to soils and the vegetative cover that may be just as, or possibly even more, important in causing the observed increases in runoff and erosion following fire. These factors make it challenging to assess the role of water repellency in post-fire hydrology and erosion processes. This is particularly so at larger scales due to the high spatial variability of many factors involved and the difficulty in characterizing the counteracting role of wettable soil patches, ash, bioturbation, soil cracks, and burnt-out tree roots in reducing the surface runoff engendered by strongly water repellent patches. Research to date has demonstrated that water repellency can strongly affect post-fire runoff and erosion processes and the factors that can enhance or reduce the relative impact of water repellency in burnt landscapes have been reasonably well established. Quantifying and predicting the relative contribution role of water repellency in post-fire erosion processes, however, remains a major challenge particularly at larger scales. Additional manipulative experiments and more detailed monitoring are needed to provide a better knowledge base on the extent of the impact of soil water repellency on runoff and erosion in the field under natural rainfall events at different scales.