三峡库区等高植物篱的控蚀效益及其机制

 水土流失是影响长江中上游地区社会、经济持续发展的关键限制因素。等高植物篱农作措施具有很好的控制土壤侵蚀功效,但还缺乏较为系统的定量研究。根据1993年在三峡库区典型流域建设的5个植物篱小区,对径流、土壤侵蚀的多年连续观测数据分析,结果表明:4种试验植物篱均有很好的水土保持效果,从植物篱栽植的第4年起,水土效益呈现出较为稳定的态势。同对照相比,植物篱小区土壤侵蚀量下降18·4%～70·0%,径流下降幅度为17·2%～70·8%。马桑、黄荆较香根草、新银合欢有着更为突出的控制侵蚀效果,但不同植物篱之间水土保持效益的差异没有达到统计显著水平。植物篱小区内,局部的径流流速变化是导致侵蚀产沙变化的根本原因,即在植物篱条带的上坡位置,径流流速下降,而在条带的下坡位置,径流流速增加。经过流速的一减一增,使得在小区出口的径流流速及径流量同对照小区相当的情况下,条带上坡位置由于流速下降,径流携沙能力下降,而导致泥沙侵蚀本身的减少和已经侵蚀泥沙的淤积,并最终使侵蚀量大幅下降。

Mechanism and effect of different contour hedgerow types on runoff and sediment erosion in Three Gorges Reservoir Area

Five hedgerow-experimental-plots was established in 1993, data of　runoff and soil loss under simulation rainfall and natural rainfall in each plot from 1994—1997 was collected to understand the benefits and mechanism of hedgerow to conserve water and soil. The results indicated that: Every plant hedgerow chosen has a big effect of conserving runoff and soil from 1994 to 1997. Soil loss reduction was 18.4%-70.0% (the average reduction was 29.7% in 1994 and 60.8% in 1997)and runoff reduction range from 17.2% to 70.8% (the average reduction was 33.7% in 1994 and 44.7% in 1997). And also Loriaria sinica and Vitex negundo played a more significant role in reducing runoff and soil erosion than Vetiveria zizanioides did, but the difference didn't reach to the statistical significant level different. The variations of runoff velocity in the hedgerow plot led essentially to the difference of soil losses. The runoff velocity in the upper slope of hedgerow strip decreased as the result of its obstruction and increased in the lower slope of hedgerow strip. Therefore, soil losses decreased greatly because of reduction runoff velocity and runoff amount　between hedgerow's.