黄土高原典型群落近地表特征对坡面流水动力学特征的影响

Effect of Patterns of Land Surface on the Charateristics of Hydrodynamics of Overland Flow in Typical Herbaceous Communities of Sloping Lands on the Loess Plateau

[目的]阐明植被群落近地表特征对坡面流水动力参数的影响,揭示植被群落近地表特征影响土壤侵蚀过程的作用机制,以期为评估黄土高原草地植被恢复的生态水文效应提供理论指导。[方法]选取黄土高原典型白羊草群落[Bothriochloa ischcemum(Linn.)Keng])和铁杆蒿群落(Artemisia vestita Wall.ex Bess),通过设置不同近地表要素,进行了人工模拟降雨试验(雨强:60 mm/h;降雨历时:60 min)。[结果](1)随植物群落各要素依次减少,流型从缓流变为急流。植被群落覆盖径流流速降低了8.66%~76.79%,径流量减少了-12.45%~49.30%,Darcy-weisbach阻力系数和曼宁糙率系数分别增加了62.55%~4346.92%和33.16%~717.25%。(2)生物土壤结皮对流速降低作用最大,分别较地上部分和根系增加了54.44%~199.32%和225.31%~425.95%;地上部分对Darcy-weisbach阻力系数和曼宁糙率系数增加作用最强,分别较生物土壤结皮和根系增加了175.76%~4676.57%和29.68%~1114.74%。近地表各要素对径流量的影响不一致,白羊草群落地上部分和铁杆蒿群落生物土壤结皮可减少径流量,而其余各要素均可增加径流量。(3)白羊草群落地上部分和根系分别减小流速和增加Darcy-weisbach阻力系数的作用大于铁杆蒿,而生物土壤结皮的作用小于铁杆蒿。白羊草群落地上部分和生物土壤结皮对曼宁糙率系数的增加效应低于铁杆蒿,根系则高于铁杆蒿。白羊草群落地上部分减少径流量作用较铁杆蒿增加了4367.80%;白羊草生物土壤结皮增加产流量的作用较铁杆蒿增加了183.52%。白羊草和铁杆蒿群落的根系均可增加产流量,且白羊草群落增加的作用较铁杆蒿减少了49.77%。[结论]植被地上部分、生物土壤结皮和根系可减小流速、流量;增加Darcy-weisbach阻力系数、曼宁糙率系数,但因植物种类的差异可导致植被群落近地表特征对水动力特征的减少或增加量不同。

[Objective]The influence of near-surface characteristics of vegetation community on the hydrodynamic parameters of overland flow was elucidated,and the mechanism of the influence of near-surface characteristics of vegetation community on soil erosion process was revealed,in order to provide theoretical guidance for the evaluation of eco-hydrological effects of vegetation restoration in grassland on the Loess Plateau.[Method]Herbaceous plant communities of Bothriochloa ischcemum(Linn.)Keng and Artemisia vestita Wall.ex Bess were selected.Artificial simulated rainfall experiments(rainfall intensity:60 mm/h;Rainfall duration:60 min)were conducted in herbaceous plant communities with different near-surface characteristics.[Results](1)With the decrease of plant community elements,the flow pattern changed from slow flow to rapid flow.Runoff velocity decreased by 8.66%~76.79%,runoff decreased by-12.45%~49.30%,and resistance increased by 62.55%~4346.92%and 33.16%~717.25%.(2)Biological soil crust had the greatest effect on the decrease of flow velocity,increasing by 54.44%~199.32%and 225.31%~425.95%,respectively,compared with aboveground part and root system.The aboveground part had the strongest effect on resistance increase,which increased by 175.76%~4676.57%and 29.68%~1114.74%compared with biological soil crust and roots,respectively.The effects of the near-surface factors on the runoff were not consistent.The biological soil crusts of aboveground part of Bothriochloa ischcemum(Linn.)Keng and Artemisia vestita Wall.ex Bess could reduce the runoff,while the other factors could increase the runoff.(3)The effects of overground part and root of Bothriochloa ischcemum(Linn.)Keng on decreasing velocity and increasing Darcy-Weisbach resistance coefficient were greater than those of Artemisia vestita Wall.ex Bess,while the effects of biological soil crusts were less than those of Artemisia vestita Wall.ex Bess.Aboveground part and biological soil crust of Bothriochloa ischcemum(Linn.)Keng on the Manning roughness coefficient increases effect was lower than Artemisia vestita Wall.ex Bess,the effect of root was higher than Artemisia vestita Wall.ex Bess.The decrease of runoff in aboveground part of Bothriochloa ischcemum(Linn.)Keng community increased by 4367.80%compared with Artemisia vestita Wall.ex Bess.The effect of soil crusts on increasing runoff yield was 183.52%higher than that of Artemisia vestita Wall.ex Bess.The root system of both Bothriochloa ischcemum(Linn.)Keng and Artemisia vestita Wall.ex Bess communities could increase runoff yield,and the increasing effect of Bothriochloa ischcemum(Linn.)Keng community was 49.77%less than that of Artemisia vestita Wall.ex Bess.[Conclusion]The aboveground part of vegetation,biological soil crust and root system can reduce the velocity and discharge.The Darcy-weisbach resistance coefficient and Manning roughness coefficient increased,but the decreasing or increasing of near-surface characteristics of vegetation communities on hydrodynamic characteristics was different due to the difference of plant species.