18 sampling areas of size 5 m×5 m were selected

of which 15 sampling areas were composed of Ostryopsis davidiana Decaisne vegetation community only.Soil shear strengths at the depths of 20

40

60

80

and 100 cm in the 18 plots were measured.3 bare lands of size 5 m×5 m were selected and soil compaction and the ratio of sectional root area were measured as well.The effect of soil shear strength in bare land was then removed from the soil sample in Ostryopsis davidiana Decaisne vegetation community.By calculation

the ratio of sectional root area was 1.014% and the corresponding shear strength was the maximum value of 0.134 6 kN/m2.Analyses indicated that the increased value of soil shear strength in the Ostryopsis davidiana Decaisne vegetation community rood system was positively correlated to the ratio of sectional root area.