In order to investigate the variations of root characteristics in terms of anti-bending with changes of root diameter and slope position,a total number of 36 Robinia pseudoacacia L.trees on a steep rocky slope were selected and root samples were collected.Anti-bending forces of the root samples were measured using an electronic universal testing machine.The results show that the relationship between anti-bending capability and slope position was significant.Root anti-bending capability decreased from upper-slope position to the down-slope position.For roots in the upper and the lower slope positions,the relationship between bending strength and root diameter can be described by a power function,and root tolerance of bending increased with root diameter.As for the roots collected in the mid-slope position,there was no significant relationship between bending tolerance and root diameter.Root flexural modulus decreased as root diameter increased,which can also be described by a power function.Flexural modulus decreased from the upper slope to the down slope for roots with diameters greater than 8 mm.Maximum anti-bending forces and fracture deflections of the roots did not differ significantly among the three slope positions.The former decreased from the upper slope towards the down slope,while the latter increased from the upper to down slope.In conclusion,the roots in the upper slope had the strongest bending resistance,which contributed most to the slope stability