Effects of different types of undecomposed surface litter on the sediment transport capacity

Plant litter cover affects the sediment transport capacity of overland flow, which, in turn, influences the prediction of the soil erosion. In previous studies, researchers focused on the differences in the hydraulic variables and soil erosion for different types of litter incorporated in the soil or present on the surface. The quantitative relationship between the litter morphology and sediment transport capacity on no-till systems with litter covered surfaces has not been examined yet. Therefore, in this study, the effects of different types of litter on the hydraulic variables and sediment transport capacity were examined, along with the quantitative relationships among the three aspects. To this end, one discharge magnitude (2.632 x 10(-3) m(2) s(-1)), two slope gradients (8.8% and 26.8%), and five types of undecomposed surface litter (Populus simonii, Robinia pseudoacacia, 114)pophae rhamnoides, Pinus tabuliformis, and Bothriochloa ischaemum) were considered to conduct experiments in a steel flume bed. The coverage of each type of litter ranged from 0% to 70%. The results showed that the flow regime, hydraulic variables and sediment transport capacity were affected by the types of litter. The length, width-to-length ratio and roundness of the individual litter leaves could suitably reflect the impact of the litter morphology on the sediment transport capacity, as indicated by the high Pearson correlation coefficients (> 0.5). Long and narrow litter with a small roundness more notably reduced the sediment transport capacity than short and wide litter with a large roundness. The litter morphology did not influence the relationships between the sediment transport capacity and hydraulic variables. In particular, the hydraulic variables such as the unit stream power, flow velocity combined with slope gradient, and stream power combined with flow depth could accurately predict the sediment transport capacity (R-2 > 0.94), and the characteristic variables of the litter morphology and cover were not required to be considered in the prediction equation. The presented findings can be used to develop a simple algorithm to predict the sediment transport capacity of litter covered surfaces.

Automated summary

This study examined the effects of different types of plant litter on hydraulic variables and sediment transport capacity, as well as the quantitative relationships among them. The results showed that the morphology of individual litter leaves can impact sediment transport capacity, while the relationships between sediment transport capacity and hydraulic variables were not influenced by litter morphology. The findings can be used to develop a simple algorithm for predicting sediment transport capacity on litter-covered surfaces.