Impacts of grass planting density and components on overland flow hydraulics and soil loss

Abstract

Although abundant studies have confirmed the positive effect of vegetation on runoff and soil erosion reduction, few studies have clarified the effects of planting density and its components (aboveground parts and roots) on slope runoff and soil erosion mechanisms. A series of field experimental plots were constructed on two slopes (3 , 6 ), including a bare land plot as the control, three grassed plots with three grass (Agropyron cristatum) planting densities of 20 cm  20 cm, 15 cm  15 cm, and 10 cm  10 cm, and a plot without aboveground parts, to examine runoff and soil erosion process under simulated overland flow of 4, 8, 12, and 16 L min À1 . The runoff regime was transformed from supercritical-turbulent flow to subcritical-laminar flow with increasing planting density. Grass significantly reduced the runoff rate (RR), velocity (V), shear stress (τ), stream power (ω), and soil loss rate (SLR), with average reductions of 38.6%, 56.6%, 76.5%, 87.6%, and 61.9%, respectively. The aboveground parts contributed 74.1% and 75.1% of the total reduction in RR and V, respectively, while the grass roots contributed to 84.9%, 89.7%, 84.9%, and 69.7% of the reductions in Reynolds number, τ, ω, and SLR, respectively. RR, V, τ, ω, and SLR were significantly affected by slope, inflow discharge, root density, and the ratio of grass stem area to plot area. The runoff-sediment relationship changed from positively exponential function to linear and power functions with the planting density increased. Grass significantly weakened the sensitivity of soil erosion by reducing soil erodibility and improving critical hydrodynamic triggering soil erosion. This study improved the understanding of grass controlling soil and water loss, and the plants with well-developed roots and planting space of 10-15 cm are preferred to provide a scientific reference for revegetation strategy.

Exploring the relationship between soil erosion and hydraulic parameters on slopes with clipped herbaceous vegetation through Bayesian network modeling

“…However, considering other factors beyond flow depth, such as soil composition, vegetation structure, or slope characteristics (Li et al, 2019; Pan, Ma, Wainwright, & Shangguan, 2016b; Xiao et al, 2017), may reveal their potential to overshadow the effects of clipping intensity. For instance, Fu et al (2022) suggested that the roots were the main contributor to the reduction in overland flow shear capacity, accounting for 89.7% of the total reduction. The presence of litter cover in grasslands creates a stable near‐surface layer, which is disrupted when aboveground components are removed through clipping treatments, resulting in a sparse density of stem elements.…”

Exploring Applicability of Different Ecological Protection Measures for Soil and Water Loss Control of Highway Slope in the Permafrost Area: A Case Study of Qinghai-Tibet Highway in China

“…In addition, some research results have shown that soil erodibility is closely related to environmental factors (soil physical and chemical characteristics, vegetation cover and root characteristics, cover type, topography, and geomorphology) [ 23 , 24 , 25 , 26 ]. First, the enhancement of soil anti-erodibility is mainly attributed to the improvement in soil structure, soil shear strength, and soil aggregate stability [ 27 , 28 , 29 ]. Bulk density (BD) and soil texture, among others, have significant effects on aggregate soil stability, infiltration, and soil shear strength [ 18 ].…”

The contribution rate of stem‐leaf and root of alfalfa (Medicago sativa L.) to sediment and runoff reduction

“…Since 1999, in response to soil erosion control and ecological restoration, the “Grain for Green” project has been implemented on the Loess Plateau, which has considerably improved the vegetation cover and ecological environment (Cao et al, 2020; Wu et al, 2019; Zhang et al, 2021). Ground cover comprising grass, shrubs, trees, and crops is closely related to the reduction in soil erosion (Fu et al, 2023; Kervrodan et al, 2020; Liu, Liu, et al, 2020). Herbaceous plants have a higher level of efficacy in reducing soil erosion than shrubs and trees (De Baets et al, 2007; Duan et al, 2019; Lin et al, 2019).…”

“…The primary anti‐erosion mechanism of herbaceous plants is predominantly achieved by the increase in aboveground vegetation biomass and root density (Cao et al, 2015; Casermeiro et al, 2004; De Baets et al, 2007). Given the difference in the anti‐erosion ability between the aboveground canopy and the root system of herbaceous plants, the contribution rate of different grass components to soil loss reduction may be different (Fu et al, 2023; Li & Pan, 2018; Ma et al, 2013; Pan et al, 2010). Aboveground grass vegetation components have been found to be more effective in reducing the overland flow rate and velocity (Li & Pan, 2018; Ma et al, 2013).…”