造林整地工程对人工幼林系统径流输移的影响

 为探讨造林整地工程对人工幼林系统坡面水沙输移中的作用及程度,从产流、汇流的机制与理论模型出发,对旱区人工幼林系统地表径流调控的关键途径进行了分析。结果表明,在降雨特性、地形、土壤3大影响坡面产流、汇流的因素中,地形因素是人工调控的关键。在当前技术、经济条件下,通过造林整地,改变微集水区坡长、坡度乃至坡形,是最简单而有效的人工调控手段。对20个不同整地方式人工幼林地田间径流小区和未整地空白对照径流小区的观测表明,鱼鳞坑、水平沟、反坡梯田3种造林整地工程,虽可有效地削减径流向系统外部环境的输移,但其调控径流能力远未达到工程设计要求,其地表径流输移的削减率,在39.92%～65.11%之间,削减率与集水坡长成反相关,3种整地方式中,以反坡梯田整地的削减率最大。造林整地径流小区与传统直线型坡面径流小区对比观测,难以揭示整地对微区坡面产流影响的实质;造林整地工程设计中所期望的拦泥蓄水作用,则因忽略了含沙径流入渗、整地对微区地形与产流、产沙的影响等而被大幅削弱。

Influence of Land Preparation for Afforestation on Runoff Producing and Transport from Slopes with Young Planted Trees System

By means of theoretical model and mechanism of producing and conflux of runoff, the key pathway of surface runoff regularity of young planted trees system was studied. The results showed that topography was extremely important among the three factors of rainfall, soil and topography which affected the runoff producing and conflux. The land preparation for afforestation to change micro-basin characteristics such as length, gradient and configuration of surface was a simple and effective measure for controlling surface runoff in the planted trees site of Loess Plateau. But if the land preparation work was designed according to traditional records of runoff plot with straight slope, it could not reach the desired design standard, which can only reduce runoff by 39.92%～51.80%, 52.39%～52.86%, 62.66%～65.11% for fish-scale pits, contour trench, reverse-slope terrace respectively. Compared with traditional runoff plot of straight slope, the runoff records of land-preparation plot can only illustrate the total effect of land preparation in reducing runoff, but can not demonstrate the influence nature of land preparation to runoff producing. It was the neglecting of impact of muddy water infiltration, slope gradient and configuration on surface runoff producing and erosion that weakened the expected functions for reducing erosion and runoff transportation on design.