To investigate the spatial variability of root additional cohesion on loess slope, this paper takes
monospecific stands of Robinia pseudoacacia and Platycladus orientalis grown on slopes in the semiarid
Loess Plateau of northern China as case study. Root distribution could be described by root area ratio
(RAR). Root tensile strength was determined with laboratory mechanical tests. Finally, spatial
variability of root additional cohesion was analyzed. The results showed that biomechanical characteristics
of R. pseudoacacia roots were significantly different from P. orientalis roots. RAR and root additional
cohesion were significantly different among species, slope locations and depth. The analyses of R.
pseudoacacia and P. orientalis root spatial heterogeneity indicated that root reinforcement was not evenly
distributed along slope in the Loess Plateau, which could provide a basic theory of afforestation mode in
spatial distribution and hence control soil erosion and shallow landslide.