Spatial heterogeneity of soil detachment capacity by overland flow at a hillslope with ephemeral gullies on the Loess Plateau

Zhang

et al. 2018

Hydrological Processes

Water erosion on hillslopes is a worldwide environmental problem, which is a rainfall‐induced process, especially extreme rainfall. The great intensity of extreme rainfall strongly enhances the power of overland flow to detach soil and transport sediment. Plant litter is one of the most important constituents of ecosystems that often covers the soil surface and can be incorporated into topsoil. However, little attention has been paid to its effect on flow hydraulics owing to the veiled nature. This study aimed to examine the effects of incorporated litter on the hydraulic properties under extreme rainfall condition. To reach this goal, six litter rates of 0, 0.05, 0.10, 0.20, 0.35, and 0.50 kg m−2 and four litter types collected from deciduous trees, coniferous trees, shrubs, and herbs were incorporated into topsoil. Then, simulated rainfall experiments were performed on five slope gradients (5°, 10°, 15°, 20°, and 25°) with an extreme rainfall intensity of 80 mm h−1. The results showed that Froude number and flow velocity of the overland flow decreased, whereas flow resistance increased exponentially with litter incorporation rate. Litter type had an influence on flow hydraulics, which can mainly be attributed to the variations in surface coverage of the exposed litter and the litter morphology. Flow velocity and Darcy–Weisbach coefficient increased markedly with slope gradient. However, the variation of slope gradient did not modify the relationships between flow hydraulics and incorporated litter rate. The random roughness, resulting from heterogeneous erosion due to the uneven protection of surface exposed litter, increased linearly with litter incorporated rate. As rainfall proceeded, flow hydraulics varied with incorporated litter rate and slope gradient complicatedly due to the increases in flow rate and coverage of the exposed litter and the modification of soil surface roughness.

Section: Methodsmentioning

confidence: 99%

Hydraulics of overland flow influenced by litter incorporation under extreme rainfall

Zhang

et al. 2018

Hydrological Processes

“…Plant litter was strongly associated with soil resistance to flowing water erosion on the restored lands (Wilson et al, 2008;Li et al, 2015;Sun et al, 2016). The LD of restored lands was greater than that of slope farmland (Table II).…”

Section: Near Soil Surface Characteristics Under Different Restoratiomentioning

confidence: 99%

“…BSC thickness is defined as the total thickness of the BSCs and the soil layer adhered to by BSCs Wang et al, 2017aWang et al, , 2017b. The detailed measuring procedures can be found in previous studies Li et al, 2015). The detailed procedures for BSC thickness measurement can be found in the previous studies of Wang et al (2017aWang et al ( , 2017b.…”

Section: Soil Sampling and Near Soil Surface Characteristics Measuremmentioning

confidence: 99%

“…It could be well simulated with BSC thickness or RD as an exponential or linear function on the Loess Plateau. Li et al (2015) and Sun et al (2016) showed that rill erodibility was negatively related to plant litter density (LD) incorporated within the topsoil layer. Wang et al (2013b) reported that the steady infiltration rate was significantly negatively correlated with BSC thickness, BD, and Cl, and it was positively related to RD.…”

Section: Introductionmentioning

confidence: 99%

“…More than 2 Mha of steep croplands have been converted to forest-land, shrub-land, and grass-land by artificial planting or natural succession at the end of 2012 on the Loess Plateau (Chang et al, 2011). Li et al (2015) revealed that the incorporated LD within the top 5 cm soil layer ranged from 0.07 to 1.08 kg m -2 in a forest-land covered by black locust restored for 20 years on the Loess Plateau. Zhao et al (2014) found that the mean coverage of BSCs can increase to 60% to 70% in the most restored lands on the Loess Plateau.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Soil erodibility as impacted by vegetation restoration strategies on the Loess Plateau of China

Earth Surf Processes Landf

Zhang

et al. 2018

Self Cite

Near soil surface characteristics change significantly with vegetation restoration, and thus, restoration strategies likely affect soil erodibility. However, few studies have been conducted to quantify the effects of vegetation restoration strategies on soil erodibility in regions experiencing rapid vegetation restoration. This study was conducted to evaluate the effects of vegetation restoration strategies on soil erodibility, reflected by soil cohesion (Coh), penetration resistance (PR), saturated conductivity (Ks), number of drop impacts (NDI), mean weight diameter of soil aggregates (MWD), and soil erodibility K factor on the Loess Plateau. One slope farmland and five 25‐year‐restored lands covered by old world bluestem, korshinsk peashrub, shrub sophora, sea‐buckthorn, and black locust were selected as test sites. The old world bluestem was restored via natural succession, while the other four lands were restored by artificial planting. A comprehensive soil erodibility index (CSEI) was produced by a weighted summation method to quantify the effects of vegetation restoration strategies on soil erodibility completely. The results showed that Coh, Ks, NDI, and MWD of the five restored lands were greater than those of the slope farmland. However, the PR and K of the five restored lands were less than those of the slope farmland. CSEI varied greatly under different restoration strategies, from 1 to 0.214. Compared with the control, these indices decreased on average by 68.2%, 78.6%, 72.7%, 75.8%, and 62.8% for old world bluestem, korshinsk peashrub, shrub sophora, sea‐buckthorn, and black locust, respectively. The variation in soil erodibility was significantly influenced by biological crust thickness, bulk density, organic matter content, plant litter density, and root mass density. Shrub‐lands via artificial planting, especially korshinsk peashrub, were considered the most effective restoration strategies to reduce soil erodibility on the Loess Plateau. The results are helpful for selecting vegetation restoration strategies and asking their benefits in controlling soil erosion. © 2018 John Wiley & Sons, Ltd.

Earth Surf Processes Landf

Assessment of soil factors controlling ephemeral gully erosion on agricultural fields

Barrio

Campo‐Bescós

Giménez

et al. 2018

The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion. Copyright © 2018 John Wiley & Sons, Ltd.