Current knowledge about root morphology and its impacts on soil erosion is limited and, therefore, detailed analyses of root
system in controlling soil erosion are needed. In order to determine the effects of root system on soil erosion quantitatively, root investigation and stratified runoff scouring were conducted in field. The
distribution of
vertical root biomass on three sites decreased with the increase of soil depth in a similar manner. Most roots were concentrated in surface soil, and decreased to less than 0.2 kg·m~ -3 in soil below the depth of 40 cm. There was no significant difference in root biomass on the same soil depth from different points. Results from stratified runoff scouring on different soil depths in the field indicated that, on the surface soil layer, the existence of root could effectively improve soil resistance to runoff erosion, and its effect on sediment yield was dominant. While in deeper soil, sediment yield increased with the decrease of root distribution, and was more related to slope gradient, runoff discharge and soil properties. In addition, with the progress of runoff scouring, the form of soil erosion changed from sheet erosion to rill erosion. Investigation of the root distribution patterns revealed that the vertical sediment yield was closely related to root distribution characteristics. Further analysis of the root distribution pattern and the vertical sediment yield allowed establishment of a quantitative relationship between root biomass and vertical sediment yield.