Living plants and plant roots can reduce runoff and soil erosion.Using a rain simulator,a series of soil erosion experiments were conducted to study the influence of living roots and canopies of ryegrasees (Lolium perenne L.) during the growing season on sediment yields and runoff of a silt loam soil.The results indicated that during the growing season, decrements in runoff and sediment yields increased with time.Sediment yields (r~2=0.999) and decrements in runoff (r~2=0.946) were closely related to the root surface area density.The contributions of roots and canopies of ryegrasees to the reductions in runoff and sediment yields were different.Canopies usually contributed more to the runoff decrement than the roots,whereas roots contributed up to 96% of the decrease in sediment yields in the late stage of the growing season. Living plants and plant roots can reduce runoff and soil erosion. Using a rain simulator, a series of soil erosion experiments were conducted to study the influence of living roots and canopies of ryegrasees (Lolium perenne L.) during the growing season on sediment yield and runoff of a silt loam soil.The results indicated that during the growing season, decrements in runoff and sediment yields increased with time. Sediment yields (r ~ 2 = 0.999) and decrements in runoff (r ~ 2 = 0.946) were closely related to the root surface area density. These contributions of roots and canopies of ryegrasees to the reductions in runoff and sediment yields of different. Canopies usually contributed more to the runoff decrement than the roots in the late stage of the growing season.