Soil crusting on sandy soils and its influence on wind erosion
Soil crusting on sandy soils and its influence on wind erosion
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DOI：
10.1016/s0341-8162(02)00201-1
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发表时间：
2003-08
期刊：
影响因子：
6.2
通讯作者：
J. Rajot;S. Alfaro;L. Gomes;A. Gaudichet
中科院分区：
文献类型：
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作者：
J. Rajot;S. Alfaro;L. Gomes;A. Gaudichet
在降雨的情况下，大多数土壤的表面都会形成一层硬壳。对于粘土含量足够丰富的土壤（粘土含量>5%），众所周知，物理结皮是造成可用于风蚀的颗粒供应限制的原因。桑迪土壤很容易结皮和风蚀。事实上，即使在轻微的风化之后，结构性的“筛壳”也会在桑迪土壤上形成。这种结皮在表层表现为松散的砂层，覆盖在细颗粒集中的薄层上。本研究的主要目的是确定这种结皮的形成是否限制了（1）夹带到跃移中的沙粒和（2）吸收到垂直风蚀通量中的细颗粒（直径<20 μm的颗粒悬浮在大气中）的可用性。为此，从1998年2月至6月，在尼日尔，1公顷（100×100 m）的桑迪土壤（桑迪沙生土壤）上裸露出所有的凋落物和植被覆盖物，以增加风蚀。水平和垂直的风蚀通量的测量进行了对这一地区的结壳后，出现在雨季开始的第一场雨事件。实验结果的分析表明，尽管可用于跳跃的松散粗颗粒的量显著减少，但由于结壳，这种颗粒的供应没有限制。同样地，虽然在第一次降雨后，自由砂层中细颗粒（<20 μm）的含量下降到1.5%，但在结皮形成后，细颗粒的垂直通量不受供应限制。因此，似乎与在细颗粒含量较高的土壤上形成的其他类型的结皮不同，筛分结皮不能保护农业土壤免受风蚀。
Under rainfall, a crust forms at the surface of most soils. For soils rich enough in clay (clay content >5%), it is well known that a physical crust is responsible for a supply limitation of particles available for wind erosion. Sandy soils are very prone to crusting as well as to wind erosion. Indeed, structural ‘sieving’ crusts develop on sandy soils even after light rainfalls. This kind of crust shows a loose sand layer at the surface overlying a thin layer where fine particles are concentrated. The main objectives of this study were to determine whether such a crust formation limits the availability of (1) sand grains for entrainment into saltation and (2) fine particles for uptake into a vertical wind erosion flux (suspension in atmosphere of particles <20 μm diameter). For this, 1 ha (100×100 m) of sandy soil (sandy psammentic Haplustalf) was bared of all litter and vegetation cover to enhance wind erosion from February to June 1998 in Niger. Measurements of horizontal and vertical wind erosion fluxes were performed on this area before and after crusting that appeared immediately after the first rain event at the onset of the rainy season. Analysis of the experimental results show that in spite of an important reduction in the amount of loose coarse grains available for saltation, there is no supply limitation in such grains due to crusting. In the same manner, it is shown that although the fine-particle (<20 μm) content in the free sand layer drops to 1.5% after the first rain event, the vertical flux of fine particles is not supply limited after crust formation. Thus, it appears that unlike other types of crusts that form on soils with higher contents in fine particles, sieving crusts do not protect agricultural soils from wind erosion.