沟壁侧面蒸发与黄土高原环境旱化关系初探

 为定量研究沟壁侧面蒸发对加速黄土高原环境旱化的作用,在侵蚀强烈的水蚀风蚀交错带选择典型冲沟,分别在沟岸地（邻近沟缘的沟间地部分）距冲沟沟缘20、100、200、300、400、500、600cm处布设中子管,研究沟岸地土壤水分的垂直分布及其动态变化。结果表明:土壤水分在距沟缘500cm范围内随距离增加而增加,证明了沟壁侧面蒸发作用的客观存在;对距沟缘不同距离0～300cm土层土壤储水量动态变化的研究表明:降雨发生时,不同距离各点的储水增量并无显著差异,但距沟缘20 cm处土壤水分损失最快,而500 cm土壤水分损失最慢,证明了沟壁侧面蒸发通过加速土壤水分蒸发加速黄土高原环境旱化的客观事实。沟岸地土壤储水量与距沟缘距离幂函数关系的确定为定量化研究沟壁侧面蒸发加速黄土高原环境旱化程度奠定了初步基础。

Relationship between side evaporation of gully cliff and environment aridization in Loess Plateau

The intensive soil erosion in the Loess Plateau leads to a distinct increment of ground drape due to the formation of numerous erosion gullies, increases the loss of soil moisture by evaporation, and finally speeds up the environment aridization in the Loess Plateau. To testify this viewpoint, an experiment was conducted at a typical gully bank in the water-wind erosion crisscross region in the north China. Neutron tubes were installed at the bank region of a gully with different distances of 20 cm, 100 cm, 200 cm, 300 cm, 400 cm, .500 cm and 600 cm apart from the gully margin. Soll moisture distribution and dynamic variation of the soil water storage were monitored. The results showed that soil moisture increased with distance from the gully margin in the range of 0 to .500 cm, which proved the external existence of side evaporation at gully cliff. The increments of soil water storage in the layer from 0 to 300 cm at different distances from the gully margin had no significant difference when rainfull occurred, however, the closer the site to the gully margin, the faster soil moisture loss through evaporation. The change of soil moisture loss implied that the side evaporation of gully cliff speeded up the environment aridization in the Loess Plateau. The confirmation of power function relationship between soil water storage and distance apart from the gully margin presented a preliminary base for the quantificatinnal study of side evaporation of gully cliff on accelerating environment aridization in the Loess Plateau.