Abstract: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.