两种驱动力作用下植被调控堆积体坡面减水减沙效益

定量分析侵蚀驱动力的变化对于植被调控堆积体坡面水文和产沙过程的影响,对于深刻理解植被防护堆积体侵蚀及其水土保持效益具有重要作用。该研究以陡坡工程堆积体(30°)作为研究对象,采用野外模拟降雨和降雨+上方汇水试验研究苜蓿对工程堆积体侵蚀过程的影响及其减水减沙效益。结果表明:1)两种驱动力下苜蓿对工程堆积体坡面减沙和减流效益分别为57.28%～98.51%和13.17%～83.11%,加入上方汇水后减沙和减流效益分别减少17.01%和68.74%;2)降雨条件下苜蓿对堆积体坡面减流减沙效益随降雨强度增大降低,而加入上方汇水后减沙效益随降雨强度增大而增大,但减流效益减小。显著性差异分析表明降雨强度对裸坡和苜蓿堆积体的径流和产沙均有显著影响(P0.01),且上方汇水的作用大于降雨;3)两种驱动力下裸坡堆积体侵蚀速率总体随产流历时减少,而苜蓿堆积体在降雨条件下侵蚀速率总体增大。加入上方汇水后裸坡及苜蓿堆积体坡面侵蚀和径流随产流历时的波动性显著增强;4)裸坡堆积体在降雨和降雨+上方汇水条件下产流前期的平均侵蚀速率是后期的1.06～2.90倍,苜蓿堆积体在降雨条件下产流前期平均侵蚀速率小于后期。研究成果可为生产建设项目工程堆积体水土流失防治和植被措施布设提供科学指导,具有显著的科学意义和工程实践指导价值。

Benefits of soil and water reduction on spoil heaps by vegetation under two driving forces

Soil erosion on spoil heaps has become an important environmental issue and it causes serious soil erosion, geological disasters and even limits land resources. The influence of grass on soil loss on steep spoil heaps remains elusive. This study aimed to investigate the effects of Artemisia gmelinii on runoff and erosion processes of spoil heaps with silt loam soil. The effects of vegetation on runoff and sediment reduction benefits were quantified. Field rainfall experiment and rainfall with scouring experiment were performed. A series of rainfalls at three rainfall intensities (0.8, 1.2, and 1.8 mm/min) and fixed discharge flow rate (15 L/min) were simulated in four plots (3 m by 2 m, including repeats). The spoil heaps were characteristics with the gravel content of 10% and slope gradient degree of 30. The characteristics and differences of vegetation''s regulation of hydrological and erosion processes of spoil heaps under two driving forces were analyzed. The results showed: 1) Artemisia gmelinii reduced average soil loss rate and runoff rate by 57.28%-98.51% and 13.17%-83.11%, respectively, under the two driving forces, and the benefits of soil reduction and runoff reduction were decreased by 17.01% and 68.74%, respectively after adding the upper catchment flow. The vegetation not only decreased the erosion of the spoil heaps, but also made the erosion process of the spoil heaps smoother. 2) The benefits of soil and water loss reductions were decreased by 4.32%-21.10% with the increase of rainfall intensity for Artemisia gmelinii spoil heaps under rainfall experiment, and it was 26.85%-56.30% for runoff reduction benefits. However, the benefits of soil loss reduction were increased by 45.55%-46.35% and runoff rate reduction was decreased by 54.21%-55.54%, respectively, under rainfall and scouring experiment. Significant difference analysis also showed that rainfall intensity had a significant impact on soil and water yield of bare and Artemisia gmelinii spoil heaps (P<0.01) under the two driving forces, and the effect of discharge flow was significant than rainfall. 3) The soil loss rate was decreased with runoff duration for bare spoil heaps under rainfall and rainfall with scouring experiment, while it was increased for Artemisia gmelinii spoil heaps only under rainfall condition. The fluctuation of erosion and runoff on bare and Artemisia gmelinii spoil heaps was increased significantly with time as the driving force changed from rainfall to rainfall with scouring. The average soil loss rate was increased by 6.63-7.15 times and 4.92-192.81 times for bare soil and Artemisia gmelinii spoil heaps, respectively, when a fixed discharge flow was added. They were 4.96-10.81 times and 6.77-44.04 times for the average runoff rate. The change of driving forces had greater impact on Artemisia gmelinii than bare spoil heaps. 4) The average soil loss rate for bare spoil heaps during the early stage was 1.06-2.90 times that of the later stage under both driving forces, while it was 35.21%-59.30% for Artemisia gmelinii spoil heaps under rainfall condition. However, the stage with serious soil loss changed with rainfall intensity under rainfall and scouring experiment for Artemisia gmelinii spoil heaps. The results can provide guidance for the prevention and control of soil erosion and runoff loss in the spoil heaps of production projects. These results have significant value for guiding engineering practice.