Investigating the effects of herbaceous root systems on the soil detachment process at the species level

Abstract

Plant root growth significantly affect soil detachment process, whereas the mechanism of how roots affect the soil detachment process by overland flow at species level is not fully understood. This study was conducted to investigate the soil detachment rate responds to plant-induce soil properties and root traits at species level. Two typical herbaceous plants, Bothriochloa ischcemum (Linn.). Keng (BI; fibrous root system) and Artemisia vestita Wall. ex Bess (AG; tap root system), from the Loess Plateau were studies for one year under six planted densities of 5 plants m−2, 10 plants m−2, 15 plants m−2, 20 plants m−2, 25 plants m−2, and 30 plants m−2. In total, 24 steel tanks were planted, and two plots were used as bare soil controls. Their soil detachment rates were tested under a constant overland flow (1.5 l s−1) on a 26.2 % slope. The results showed that soil detachment rate under the six planted densities ranged from 0.034 kg m2 s−1 to 0.112 kg m2 s−1 for BI and was ranged from 0.053 kg m2 s−1 to 0.132 kg m2 s−1 for AG, which all greatly reduced soil detachment rate and were 68.17 % to 92.33 % and 69.20 % to 87.27 % less than that of the control. In general, BI was more effective in reducing soil detachment rate than AG, achieving a mean soil detachment rate that was 23.75 % lower. With increasing plant density, soil detachment rate decreased as a power function. The overland flow hydraulic characteristics, soil properties and root traits influenced by plant density were positively or negatively correlated with soil detachment rate. Specifically, soil detachment rate decreased with velocity, bulk density, root length density, and increased with shear stress and Darcy–Weisbach friction factor as power or exponential functions. On this basis, the soil detachment rate (Dr) can be satisfactorily estimated by overland flow velocity (v), soil bulk density (BD) and root length density (RLD) as a power function (Dr = 63.03v0.174 × BD−20.712 × RLD−0.233R2 = 0.65; NSE = 0.60; p < 0.01).