Soil detachment caused by flowing water erosion in six typical herbaceous plant root systems on the Loess Plateau, China

The effects of herbaceous plant root systems on soil erosion differ due to differences among plant species and root types. Six typical herbaceous plants that commonly appear during vegetation succession on the Loess Plateau were selected to detect the effects of plant root traits on the soil detachment at a species level. In total, 180 undisturbed soil samples were collected, and their soil detachment capacities were tested by overland flow by six specific combinations of slope (3) and flow discharge (4). Soil detachment capacity was estimated effectively using shear stress, bulk density, and root surface area density [R2 = 0.78; Nash–Sutcliffe efficiency (NSE) = 0.63]. The results showed that mean values of soil detachment capacity were ranged from 0.09 to 1.17 kg m−2 s−1. Pioneer species of Artemisia capillaris and Leymus secalinus had a high soil detachment capacity and were 6.32–12.57 times greater than that of late succession species. The mean soil detachment capacity of plant with tap root system (Artemisia argyi, A. capillaris, and A. vestita) was 1.23 times greater than that of other plants with fibrous root systems (Bothriochloa ischcemum, L. secalinus, and Stipa bungeana). Soil detachment capacity decreased with soil bulk density as a power function (p < 0.01) and decreased with root traits of root length density, root surface area density, root area ratio, and root mass density as exponential functions (p < 0.01). Thus the effects of plant roots on soil erosion differed among herbaceous species were well reflected by the root surface area density.