天然降雨下川中丘陵区不同年限植物篱水土保持效用

通过对遂宁水土保持试验站内不同坡度(10°和15°)植物篱小区及对应对照小区为期7年的水土流失定位观测,探究了天然降雨条件下香根草植物篱和新银合欢植物篱在其生长年限增长过程中对紫色土坡耕地水土流失的影响。结果表明:(1)当植物篱开始发挥其水土保持作用时,减流率(年均)达10.5%～20.0%,减沙率(年均)达53.5%～54.5%,减流作用随年限增长波动较大,减沙作用逐渐趋稳;(2)10°香根草植物篱水土保持效果最优,其减流和减沙作用均在生长年限为1年时开始发挥,10°新银合欢植物篱次之,其减沙作用较减流作用提前约1年凸显,15°香根草植物篱最弱,其布设小区多数次降雨减流率均明显低于10°植物篱小区;(3)总体上植物篱能够降低坡度对坡耕地水土流失的加剧作用,其中径流流失减少28.9%,泥沙流失减少11.3%,并削弱降雨量与径流泥沙的相关程度;(4)平均径流系数和降雨引发泥沙量随植物篱年限增长逐渐趋稳,其中10°小区香根草植物篱和新银合欢植物篱对特大暴雨(12 h降水总量140.0 mm)和大暴雨(12 h降水总量为70～140 mm)下产生的径流系数消减明显,达15.0%～34.4%,各植物篱对所有降雨等级平均单位降雨所产生泥沙量均有明显消减作用,达34.1%～48.5%。

Study on Soil and Water Conservation Effects of Vetiveria zizanioides and Leucaena leucocephala Hedgerows with Different Planting Years in Central Hill Region of Sichuan Basin

By analyzing the soil and water loss monitoring observation data (2010-2016) of the Suining Soil and Water Conservation Experimental Station, this article studied the effects of Vetiveria zizanioides and Leucaena leucocephala hedgerows with different planting years which were layout in purple sloping farmland under natural rainfall conditions. The results showed that:(1) During the study period, when the hedgerows began to play its soil and water conservation role, the average annual runoff reduction rate reached 10.5%~20.0%, and the average annual sediment reduction rate reached 53.5%~54.5%. The reduction rates of hedgerows on average annual runoff fluctuated in different planting years, but its effect on reducing sediment gradually stabilized. (2) The Vetiveria zizanioides hedgerow (10°) showed the best influence on soil and water conservation, giving its reduction effects on runoff and sediment in its first planting year. Leucaena leucocephala hedgerows (10°) gave the inferior effectiveness on soil and water conservation, which sediment-reducing effect was one-year earlier than the runoff-reducing effect. The effects of Vetiveria zizanioides hedgerows (15°) were the worst, showing the lower runoff reduction rates than others. (3) In general, hedgerows could weaken the effects of slope gradients on soil and water loss on sloping farmland, in which runoff loss was decreased by 28.9%, sediment loss by 11.3%, and could also weaken the correlation between rainfall and runoff and sediment. (4) The runoff coefficient and sediment loss caused by the rainfall in hedgerow plots gradually stabilized with the increasing planting years. Torrential rain (12 hours precipitation over 140.0 mm) caused the highest runoff coefficient, followed by heavy rain (12 hours precipitation between 70~140 mm), the runoff coefficient caused by torrential rain and heavy rain were reduced by 15.0%~34.4% in the Vetiveria zizanioides hedgerow (10°) and Leucaena leucocephala hedgerow (10°) plots. The average sediment loss per millimeter of rainfall,was decreased by 34.1%~48.5% in hedgerow plots.