Sediment and soil organic carbon loss during continuous extreme scouring events on the Loess Plateau

Abstract

AbstractThe frequency of extreme hydrological events highlights the need to establish an empirical model of soil organic carbon (SOC) loss based on hydraulic characteristics. This model would aid in understanding and mitigating excessive SOC loss (SOCL) on the Loess Plateau, where severe erosion occurs. To construct such a model, we established five study plots of similar slope in the Loess Plateau: four experimental vegetation successional communities and one bare land control. An in situ field scouring experiment was carried out to measure and analyze soil erosion, hydraulic parameters, and SOCL. The first scour saw the greatest increase in sediment concentration (0.007 g ml−1) and sediment amount (2.886 kg) and the most significant SOC loss (8.361 g). Further scouring in each plot decreased total SOCL. The factors affecting SOCL included soil erodibility (median particle size, sediment concentration, total sediment loss, SOC concentration, total SOCL) and hydrodynamics (runoff depth, power, velocity, and shear force), which accounted for 93 and 29% of SOCL. Flow velocity, especially 2 m from the bottom of the transition section (L2), was most closely correlated to SOC concentration (0.681; P < .05). Flow velocity affects selective migration of sand in sediment, thus affecting SOC concentration. We based our sediment and SOCL model on observed hydrodynamics, including V2 (flow velocity at L2) in said model. Predicted values supported measured values more precisely (R2 > .98). Our findings and developed model aid in predicting SOCL on slopes during severe erosion events.