模拟降雨条件下林木裸露根系分布方式对坡面土壤侵蚀的影响

为探究喀斯特地区林木根系分布方式对坡面土壤侵蚀的影响,采用人工模拟降雨方法,研究林木根系3类分布方式：根系横坡方向局部裸露（横向）、根系顺坡方向局部裸露（顺向）、根系垂直坡面（垂直）的土壤侵蚀特征。降雨强度为75 mm/h,降雨历时为90 min,坡度为25°。结果表明：（1）降雨过程中,横向和垂直生长根系影响土壤入渗,壤中流和地下径流产流时间表现为顺向>横向>垂直;顺向坡面地表径流初始产流时间比横向和垂直坡面略有提前,但差异不显著（p>0.05）;（2）横向、顺向及垂直坡面地表径流总量大小表现为顺向>垂直>横向,壤中流与地下径流产流速率在降雨过程中缓慢增加,降雨停止后急剧减小;（3）林木根系3类分布方式坡面间的地表减沙效益表现为横向>垂直>顺向。综上所述,顺向坡面的汇流作用促使地表产流产沙增加,垂直坡面增加土壤降雨入渗并减少侵蚀,横向坡面对坡面径流泥沙的拦蓄作用最为明显。研究结果对认识喀斯特石漠化坡地土壤侵蚀机理和水土流失防治措施提供了参考。

Effects of Distribution Patterns of Tree Bare Roots on Slope Soil Erosion Under Simulated Rainfall

In order to explore the effects of tree root distribution pattern on slope soil erosion in karst area under rainfall conditions, using artificial rainfall simulation methods, soil erosion characteristics of three types of tree root distribution were studied. And the three tree root distribution patterns were partial bare surface in the direction of root transverse slope (Horizontal), partial bare surface of root along slope (Oblique) and unexposed surface of root vertical slope (Vertical). The rainfall intensity was 75 mm/h, the rainfall duration was 90 min, and the slope was 25°. The results showed that:(1) During rainfall, roots of trees growing horizontally and vertically both affected soil infiltration. The generation time of mid-soil flow and underground runoff followed the order of Oblique>Horizontal>Vertica. The initial runoff generation time of surface runoff on Oblique slope was slightly earlier than that on Horizontal and Vertical slope, but the difference was not significant (p>0.05). (2) The total amount of surface runoff on Horizontal, Oblique and Vertical slopes followed the order of Oblique>Vertical>Horizontal. The flow velocity rate of the mid-soil flow and underground runoff increased slowly in the process of rainfall and decreased sharply after rainfall stopped. (3) The surface sediment reduction benefits of three types of forest root distribution patterns followed the order of Horizontal>Vertical>Oblique. In conclusion, the confluence effect of Oblique slope promoted the increasing of surface runoff and sediment yield, while the Vertical slope increased soil rainfall infiltration and reduced erosion, and the Horizontal slope had the most obvious effect on the retention of runoff and sediment on the slope. The results could provide a reference for understanding soil erosion mechanism and soil erosion control measures of karst rocky desertification slope land.