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Soil erosion has been recognized as a critical environmental issue worldwide. While previous studies have primarily focused on watershed-scale soil erosion vulnerability from a natural factor perspective, there is a notable gap in understanding the intricate interplay between natural and socioeconomic factors, especially in the context of spatial heterogeneity and nonlinear impacts of human-land interactions. To address this, our study evaluates the soil erosion vulnerability at a provincial scale, taking Hubei Province as a case study to explore the combined effects of natural and socio-economic factors. We developed an evaluation index system based on 15 indicators of soil erosion vulnerability: exposure, sensitivity, and adaptability. In addition, the combination weighting method was applied to determine index weights, and the spatial interaction was analyzed using spatial autocorrelation, geographical temporally weighted regression and geographical detector. The results showed an overall decreasing soil erosion intensity in Hubei Province during 2000 and 2020. The soil erosion vulnerability increased before 2000 and then. The areas with high soil erosion vulnerability were mainly confined in the central and southern regions of Hubei Province (Xiantao, Tianmen, Qianjiang and Ezhou) with obvious spatial aggregation that intensified over time. Natural factors (habitat quality index) had negative impacts on soil erosion vulnerability, whereas socioeconomic factors (population density) showed substantial spatial variability in their influences. There was a positive correlation between soil erosion vulnerability and erosion intensity, with the correlation coefficients ranging from -0.41 and 0.93. The increase of slope was found to enhance the positive correlation between soil erosion vulnerability and intensity. [ABSTRACT FROM AUTHOR]

Soil erosion is a crucial geo-environmental hazard worldwide that affects water quality and agriculture, decreases reservoir storage capacity due to sedimentation, and increases the danger of flooding and landslides. Thus, this study uses geospatial modeling to produce soil erosion susceptibility maps (SESM) for the Hangu region, Khyber Pakhtunkhwa (KPK), Pakistan. The Hangu region, located in the Kohat Plateau of KPK, Pakistan, is particularly susceptible to soil erosion due to its unique geomorphological and climatic characteristics. Moreover, the Hangu region is characterized by a combination of steep slopes, variable rainfall patterns, diverse land use, and distinct soil types, all of which contribute to the complexity and severity of soil erosion processes. These factors necessitate a detailed and region-specific study to develop effective soil conservation strategies. In this research, we detected and mapped 1013 soil erosion points and prepared 12 predisposing factors (elevation, aspect, slope, Normalized Differentiate Vegetation Index (NDVI), drainage network, curvature, Land Use Land Cover (LULC), rainfall, lithology, contour, soil texture, and road network) of soil erosion using GIS platform. Additionally, GIS-based statistical models like the weight of evidence (WOE) and frequency ratio (FR) were applied to produce the SESM for the study area. The SESM was reclassified into four classes, i.e., low, medium, high, and very high zone. The results of WOE for SESM show that 16.39%, 33.02%, 29.27%, and 21.30% of areas are covered by low, medium, high, and very high zones, respectively. In contrast, the FR results revealed that 16.50%, 24.33%, 35.55%, and 23.59% of the areas are occupied by low, medium, high, and very high classes. Furthermore, the reliability of applied models was evaluated using the Area Under Curve (AUC) technique. The validation results utilizing the area under curve showed that the success rate curve (SRC) and predicted rate curve (PRC) for WOE are 82% and 86%, respectively, while SRC and PRC for FR are 85% and 96%, respectively. The validation results revealed that the FR model performance is better and more reliable than the WOE. [ABSTRACT FROM AUTHOR]

Collapsing erosion is a unique phenomenon commonly observed on the granite residue hillslopes in the tropical and subtropical regions of southern China, characterized by its abrupt occurrence and significant erosion volumes. However, the impacts of soil crust conditions on the erosion of colluvial deposits with granite residual soils have only been studied to a limited extent. To address this issue, this study investigates the impacts of three soil crust conditions (i.e., without crust, 10-minute crust, and 20-minute crust) on gully morphology, rainfall infiltration, and runoff and sediment yield during slope erosion of colluvial deposits with granite residues (classified as Acrisols) in Yudu County, Ganzhou City, Jiangxi Province, China, using simulated rainfall tests and photographic methods. The results showed that as the strength of the soil crust increased, the capacity of moisture infiltration and the width and depth of the gully as well as the sediment concentration and yield ratio decreased; at the same time, the runoff ratio increased. The sediment yield in the without-crust test was found to be 1.24 and 1.43 times higher than that observed in the 10-minute crust and 20-minute crust tests, respectively. These results indicate that soil crusts can effectively prevent slope erosion and moisture infiltration, while providing valuable insights for the management of soil erosion in natural environments. [ABSTRACT FROM AUTHOR]

The China Loess Plateau is subjected to severe soil erosion triggered by intense rainfall, resulting in significant harm and losses to both human society and the natural surroundings. In this study, a novel technique for managing loess erosion is introduced, which involves the utilization of a combined polymer SH and ryegrass. A comprehensive series of tests were undertaken, including rainfall erosion tests, disintegration experiments, and scanning electron microscopy examinations, to assess the accumulative sediment yield (ASY), disintegration ratio, and microstructural features of both untreated and treated loess samples. The results showed a significant reduction in ASY with increased dry density of untreated loess. Furthermore, the combined technique effectively controlled erosion, limiting ASY to 266.2 g/cm2 in 60 minutes. This was approximately one-sixth, one-ninth, and one-fifteenth of the ASY in SH-treated loess (L-SH), ryegrass-treated loess (L-R), and untreated loess, respectively. It resisted disintegration better than ryegrass alone but slightly less than SH. This improvement was due to the combined effect of SH and ryegrass, which reduced raindrop impact, improved loess microstructure, and boosted ryegrass growth. The innovative technique holds the potential to be applied as a field-scale technique in the Loess Plateau region of China. [ABSTRACT FROM AUTHOR]

Soil erosion has resulted in removal of the topsoils containing fine soil particles and plant nutrients, causing decrease in soil fertility in the Hindu Kush, Karakoram and Himalaya (HKH) region. The existing production of cereal crop grains has been reduced to one third of the potential crop grains production owing to land degradation and poor farming practices. It is necessary to assess risk of soil loss and identify appropriate controlling measures to address issues of low agriculture productivity and water insecurity in the region. In the present study, severity of soil loss was predicted using Revised Universal Loss Equation (RUSLE) and ecological measures were identified for sustainable mountain agriculture in the HKH region of Upper Indus Basin, Pakistan. Overall 62.6% area was found to have very low risk of soil loss, i.e., <5 t/(ha·yr), 15.8% area low risk, i.e., 5–25 t/(ha·yr) and 7.5% area moderate risk, i.e., 25–50 t/(ha·yr) in the region. The risk was high, i.e., 50–100 t/(ha·yr) and very high, i.e., >100 t/(ha·yr) in about 6.8% and 7.4% areas respectively. The mean rate of soil loss was about 41.9 t/(ha·yr) in the Hindu Kush, 31.1 t/(ha·yr) in the Himalayas, 18.8 t/(ha·yr) in the Karakoram and overall 29.7 t/(ha·yr) in the three HKH ranges. As such no considerable measures have been adopted by the communities for restoration of the degraded areas except raising fruit/farm trees and supporting limited social forestry for their livelihoods. The slopes cleared for cultivation and susceptible to erosion may be stabilized through sowing/planting of multi-purpose plant species and formation of proper bench terraces. The conservation of forest ecosystem and pastures at higher elevations would help in reducing overland water flow, risk of flash flood hazard and minimizing sediment loads in the downstream. It is essential to adopt site-specific resource conservation techniques and restore possible ecosystem health for sustainable agriculture and economic development in the region in future. [ABSTRACT FROM AUTHOR]

Land dissection density (LDD) provides morphological evidence regarding prior intense soil erosion and quantifies the distribution of land dissections. A comprehensive understanding of the potential factors influencing the spatial pattern and value of the LDD is vital in geological disasters, soil erosion, and other related domains. Land dissection phenomena in China affects large areas with different morphological, pedological, and climatic characteristics. Prior studies have focused on the potential factors influencing the LDD at a watershed scale. However, these results are insufficient to reflect the status quo of dissection development and its primary influencing factors on a national scale. LDD's spatial patterns and the dominant factors at a regional scale in millions of square kilometers remain to be ascertained. This study used the geomorphon-based method and the geographical detector model to quantify the spatial pattern of LDD over China and identify the dominant factors affecting this pattern in China's six first-order geomorphological regions (GR1∼GR6). The results yield the following findings: (1) LDD in China ranges from 0∼4.55 km/km2, which is larger in central and eastern regions than in other regions of China; (2) dominant factors and their dominant risk subcategories vary with each geomorphological region's primary internal and external forces; (3) the influence of natural factors is more significant on the large regional scale in millions of square kilometers compared to anthropogenic factors; relief degree of land surface (RDLS) is dominant in GR1, GR2, and GR5; the slope is dominant in GR6, soil type is dominant in GR3 and GR4, and lithology plays a critical role in the dominant interactions of GR3, GR4, and GR6; (4) the interactions between factors on LDD's spatial pattern have a more significant effect than individual factors. [ABSTRACT FROM AUTHOR]

A large number of loose piles formed by mountain hazards are highly susceptible to hydraulic erosion under rainfall conditions. The use of ecological substrate materials for erosion control and ecological restoration of gravel soil slopes has become a current research hotspot and the study difficulty. The post-earthquake slump accumulation gravel soil in Jiuzhaigou was selected as the research object, and the self-developed modified glutinous rice-based material was used to reinforce the gravel soil. The variable slope flume erosion test and rainfall simulation test were carried out to study the water erosion resistance of the material reconstructed soil under the influence of runoff erosion and raindrop splash erosion. The results show that: As the material content reached 12.5%, the reconstructed soil did not disintegrate after 24 hours of immersion, the internal friction angle was increased by 42.26%, and the cohesion was increased by 235.5%, which played a significant reinforcement effect. In the process of slope erosion, the soil rill erodibility parameter Kr was only 3‰ of the gravel soil control group, the critical shear force τ increased by 272%, and the soil erosion resistance was significantly improved. In the process of rainfall and rainfall on the slope, the runoff intensity of the reconstructed soil was stable, and the ability to resist runoff erosion and raindrop splash erosion was enhanced. The maximum value of soil loss rate on different slope slopes is 0.02–0.10 g·m−2s−1, which is significantly lower than that of the control group and has better erosion reduction effect. [ABSTRACT FROM AUTHOR]

Internal erosion is one of the important factors causing geological disasters. The microstructure of soil can change with seepage erosion, resulting in changes in the hydraulic and mechanical properties of the soil. The evolution of seepage erosion is investigated with X-ray computed tomography (CT) in this study. The change in macropore structure characteristics during the seepage erosion test is quantified and the influence of seepage erosion on soil deformation is analyzed. Moreover, a pore network model (PNM) is established for the specimens and the evolution of the connected pore size characteristics is assessed. The results show that the macropore structure is significantly affected by seepage erosion, especially in terms of the porosity and pore geometry characteristics. The changes in macropore structure characteristics are most obvious in the lower part of the specimen. The influence of seepage erosion on the pore size distribution (PSD) and soil deformation is heterogeneous and closely dependent on the spatial location of the soil. Moreover, seepage erosion enhances macropore connectivity and has a directional impact on macropore orientation. These findings can provide a reference for the theoretical modeling and numerical simulation of the seepage erosion and improve the understanding of the seepage erosion evolution in engineering practice. [ABSTRACT FROM AUTHOR]

Rainfall erosivity is an indicator of rainfall potential to cause soil erosion. The Melamchi extreme flood occurred on June-15 and recurred on July-31, 2021 in Nepal. During these flooding events, a large volume of sediments were eroded, transported and deposited due to the high rainfall erosivity of the basin. In this study, the temporal and the spatial distribution of rainfall erosivity within the Melamchi River Basin was estimated and further linked to sediment discharge and concentration at various sites along the river segments. The daily rainfall data for the event year 2021 of the entire basin were used. Validation was performed by post-flooding grain size sampling. The result showed that rainfall and rainfall erosivity exhibit pronounced intensity within the Melamchi River basin, particularly at Sermathang and Tarkeghang, both located in the middle section of the basin. The average annual rainfall in the Melamchi region was 3140.39 mm with an average annual erosivity of 18302.06 (MJ mm)/(ha h yr). The average daily erosivity of the basin was 358.67 (MJ mm)/(ha h) during the first event and 1241 (MJ mm)/(ha h) for the second event. In the upper section of sampling, the sediment size ranged from 0.1 mm to >8 mm and was poorly graded. However, the lower region had smaller sediment ranging from 0.075 mm to >4.75 mm and also well graded. The smaller size (<1 mm) sediment passing was much higher in the Chanaute (78%) and Melamchi (66.5%) river segments but the larger size (>100 mm) sediments were passed relatively higher from the Kiwil (8.20%) and Ambathan (8.39%) river segments. During pre-monsoon and monsoon seasons, the highest sediment concentration was found to be 563.8 g/L and 344.3 g/L in Bhimtar and the lowest was 238.5 g/L and 132.1 g/L at the Ambathan, respectively. The sediment concentration during the pre-monsoon was found to be higher than the sediment concentration during the monsoon season in the Melamchi River. The more erosive regions in the basin were associated with the presence of highly fractured rock, weathered rocks and a thrust (weak) zone. The higher rainfall erosivity at upstream and the higher sediment concentration at downstream during flooding events have coincided well in the basin. Thus, the estimation of rainfall erosivity at the catchment scale and its influences on sediment concentration in the river are crucial for erosion control measures during flooding times in the Himalaya. [ABSTRACT FROM AUTHOR]

To improve the soil and water stability of expansive soil slopes and reduce the probability of slope failure, novel protection systems based on polymer waterproof coatings (PWC) were used in this study. Herein, three groups of expansive soil slope model tests were designed to investigate the effects of polyester nonwovens and PWC (P-PWC) composite protection system, three-dimensional vegetation network and PWC (T-PWC) composite protection system, and non-protection on the soil and water behavior in the slopes under precipitation–evaporation cycles. The results showed that the moisture change of P-PWC and T-PWC composite protected slopes was significantly smaller than that of bare slope, which reduced the sensitivity of slope moisture to environmental changes and improved its stability. The soil temperature of the slope protected by the P-PWC and T-PWC systems at a depth of 70 cm increased by 5.6°C and 2.7°C, respectively. Using PWC composite protection systems exhibited better thermal storage performance, which could increase the utilization of shallow geothermal resources. Moreover, the maximum average crack widths of the bare slopes were 7.89 and 3.17 times those of the P-PWC and T-PWC protected slopes, respectively, and the maximum average crack depths were 6.87 and 3 times those of the P-PWC and T-PWC protected slopes, separately. The P-PWC protection system weakened the influence of hydro–thermal coupling on the slopes, inhibited the development of cracks on the slopes, and reduced the soil erosion. The maximum soil erosion of slopes protected by P-PWC and T-PWC systems was 332 and 164 times lower than that of bare slope, respectively. The P-PWC and T-PWC protection systems achieved excellent "anti-seepage and moisture retention" and anti-erosion effects, thus improving the soil and water stability of slopes. These findings can provide important guiding reference for controlling rainwater infiltration and soil erosion in expansive soil slope projects. [ABSTRACT FROM AUTHOR]

Soil erosion control based on county scale Soil and Water Conservation Regionalization (SWCR) is an essential component of China's ecological civilization construction. In SWCR, the quantitative analysis of the spatial heterogeneity and driving factors of soil erosion among different regions is still lacking. It is of great significance for soil erosion control to deeply examine the factors contributing to soil erosion (natural, land use, and socioeconomic factors) and their interaction at the county and regional levels. This study focused on a highly cultivated area, Hechuan District of Chongqing in the Sichuan Basin. The district (with 30 townships) was divided into four soil and water conservation regions (I-IV) using principal component and hierarchical cluster analysis. The driving factors of soil erosion were identified using the geographical detector model. The results showed that i) the high cultivation rate was a prominent factor of soil erosion, and the sloping farmland accounted for 78.4% of the soil erosion in the study area; ii) land use factors demonstrated the highest explanatory power in soil erosion, and the average interaction of land use factors explained 60.1% of soil erosion in the study area; iii) the interaction between natural factors, socioeconomic factors, and land use factors greatly contributes to regional soil erosion through nonlinear-enhancement of double-factor enhancement. This study highlights the importance of giving special attention to the effects of land use factors on soil erosion at the county scale, particularly in mountainous and hilly areas with extensive sloping farmland and a high cultivation rate. [ABSTRACT FROM AUTHOR]

Soil erosion is a prominent environmental problem in karst regions. Exploring the spatiotemporal variability of soil erosion and the factors that influence soil erosion is of great significance for regional soil erosion prevention and control. However, the mechanisms influencing the characteristic features of the karst basins, such as bedrock exposure and lithology, still need to be further explored. This study used GIS technology, the Revised Universal Soil Loss Equation model, Getis-Ord Gi*, and partial least squares regression (PLSR) to identify the dominant factors influencing soil erosion and the spatiotemporal variability of soil erosion in 31 sub-basins of the Dabang River Basin (DRB), a typical karst area of Southwest China, from 2010 to 2020. The results indicated that soil erosion in the DRB from 2010 to 2020 was generally decreasing, the mean soil erosion in the DRB in 2010, 2015 and 2020 was 18.46, 16.51 and 15.29 t ha−1 a−1, respectively. During the study period, the area of slight erosion increased by 26.39% (706.54 km2), while severe erosion enlarged by 26.36 km2. Spatially, the DRB was primarily affected by medium and slight soil erosion. The hot spot areas of soil erosion (key control areas) were mainly concentrated in the central and southern parts of the basin, decreasing each year, and the area of soil erosion hot pots has decreased from 43.22% to 20.60%. PLSR decoupling results show that elevation, bedrock exposure, land use type, interbedded limestone and clastic rock, and vegetation coverage were identified as the key variables affecting soil erosion, explaining 52.8% of soil erosion variability, with a high value of the Variable Importance on Projection (VIP) more than 1. These results can be used as a reference for comprehensive control of soil erosion and water loss in the basin. [ABSTRACT FROM AUTHOR]

Soil erosion and the subsequent sedimentation are serious environmental problems. Improper land management coupled with intense rainfall has complicated the problem in the Ethiopian highlands. Consequently, soil loss costs a profound amount of the national GDP and deters land productivity. Quantifying soil loss and prioritizing areas for conservation is imperative for proper planning and resource management. Therefore, this study aimed at estimating the mean annual soil loss rate of Gilgel Abay watershed which has critical implications on Lake Tana and Abbay River (Upper Blue Nile River), using RUSLE and morphometric analysis methods. Datasets including rainfall, soil, Digital Elevation Model and land use/land cover were used to generate important parameters required for the soil loss estimation. Data collected through field observation, consultation with experts and document analysis were used for validation purposes. The results of the study reveal that the watershed experienced an average soil loss rate of 39.8 t ha−1 yr−1. Subsequently, nearly 25% (37,038 ha) of the watershed is threatened by moderate to very severe soil loss. Among the four sub watersheds, sub watershed 3 (S3) and sub watershed 4 (S4), which consist of about 65% (105,000 ha) of the total area of the study watershed, experienced an annual soil loss rate of over 30 t ha−1 yr−1. The amount of soil loss that the study watershed has experienced is above the soil loss tolerance level of Ethiopia (2–18 t ha−1 yr−1) and the tropical region (10 t ha−1 yr−1). Similarly, the results of morphometric analysis showed that the studied watershed has S-shaped hypsometric curve, an indication for maturity stage of landscape development. The studied watershed is also characterized by a non-circular shaped drainage with rugged and dissected topography that contributes to high flash flood, peak discharge and incidence of soil loss. The result of both models signified that S3 and S4 are highly susceptible to soil erosion. Therefore, these two sub watersheds need priority for soil and water conservation (SWC) measures. Furthermore, the study demonstrated the importance of the integration of different models in the identification of soil erosion prone areas and prioritization for the proper implementation of SWC measures. [ABSTRACT FROM AUTHOR]

Benggang is a special type of soil erosion, which widely distributes in the granite residual soil area of southern China. Owing to the influence of local climate and topography, shallow cracks having different morphological characteristics are easily formed on the slope surface. These shallow cracks damage the surface structure of the slope and accelerate water infiltration, making it easier to cause severe soil and water loss. However, the mechanism of Benggang process is still unclear, especially for slopes with different shallow crack characteristics. In this study, granite residual soil was collected from Benngang erosion area in Yudu County, Jiangxi Province, southern China. Three experimental treatments with slope surface crack rates of 0%, 5.23%, and 11.70% were performed. Simultaneous monitoring of moisture content and soil temperature in the slope were carried out during rainfall, and the characteristics of preferential flow were monitored with different crack rates. Morphological development and evolution process of Benggang with different crack rates were studied. Results show that high surface crack rate of the shallow surface on the slope accelerated the development of shallow gully erosion, leading to premature occurrence of gully erosion. As the shallow crack rate increased from 0% to 5.23% and 11.70%, the width-depth ratio of the rills at the slope bottom increased from 0.69 to 1.02 and 1.16, respectively. At the same time, a correlation between moisture and temperature data was observed for the process of water-heat coupled migration. The upper soil temperature of slope decreased quickly due to preferential flow. The simultaneous monitoring of soil moisture and temperature can effectively track preferential flow and indicate the water movement. Temperature data was a more sensitive indicator of the seepage paths of preferential flow compared to moisture data. [ABSTRACT FROM AUTHOR]

Soil erosion is a major issue in Loess Plateau, China, and quantitative analyses of sediment sources are crucial for soil erosion control. In this study, a combination of flood couplet analysis and composite fingerprint identification was used for historical reconstructions of soil erosion in sediment source areas in Loess Plateau. Each flood couplet was constructed based on sediment 137Cs activity, and past soil erosion was calculated using soil bulk density and storage capacity curves. The contribution rates of the sediment sources were calculated using the fingerprinting method, and the amount of erosion in the sediment source areas was estimated. The best fingerprint combination (Cr, Ni, V, and TOC) enabled a 97.2% recognition of sediment sources from 29 flood events (1956–1990) in the Loess Plateau. The contribution rates of gullies, farmland, grassland, and shrubland were 44.89%, 26.38%, 10.49%, and 18.24%, respectively. These four land use types contributed 1,227, 751, 512, and 279 tons of sediments, respectively. Re-vegetation decreased soil erosion (1966–1983), whereas deforestation increased soil erosion (1956–1965 and 1984–1990). Rational soil and water conservation measures on slopes and check dam construction in gullies are therefore suggested to mitigate erosion. [ABSTRACT FROM AUTHOR]

Extreme rainfall events on a slope under ridge tillage systems cause concentrated stream soil loss. To analyse the critical thresholds for different stages of water erosion process of ridge systems, simulated rainfall-erosion experiments for the contour wide ridge (CWR), contour narrow ridge (CNR), longitudinal wide ridge (LWR), and longitudinal narrow ridge (LNR) were conducted under four rainfall intensities, with slope gradients of 3° and 5°. For the runoff event, the runoff depth order was LNR > LWR > CWR > CNR; the soil loss order was CNR > LNR > CWR > LWR. The product of slope factor (S) and rainfall erosivity (R) or runoff depth (D), can be adopted as critical thresholds for different stages of runoff and soil erosion process. For the longitudinal ridge systems, R values were provided for LWR and LNR and were the beginning of sheet flow, whereas the product of rainfall erosivity and slope factor (RS) values were provided for LWR and LNR as the beginning of the accelerated concentrated flow. For the contour ridge systems, R values were provided for CWR and CNR as critical thresholds for the beginning of overflow. The product of runoff depth and slope factor (DS) values were 9.98 and 7.73 mm for CWR and CNR, respectively, and were critical thresholds for the beginning of ridge failure; the DS values were 18.45 and 12.75 mm for CWR and CNR, respectively, and were critical thresholds for the beginning of the formation of ephemeral gully erosion. The critical thresholds can distinguish different stages of soil erosion process modelling. [ABSTRACT FROM AUTHOR]

Grass recovery is often implemented in the loess area of China to control erosion. However, the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear. Taking the typical forage species (Coreopsis) in semiarid areas as subject, this study quantified the effects of canopies and roots on controlling slope runoff and erosion. A series of field experiments were conducted in a loess hilly region of China. Field plots (5 m length, 2 m width, 25° slope gradient) constructed with three ground covers (bare soil; Coreopsis with intact grass; only roots of Coreopsis), were applied with simultaneous simulated rainfall (60 mm h−1) and upslope inflow (10, 30, 50, 70, 90 L min−1). The results showed that compared with bare soil, intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average, and decreased soil erodibility parameter by 66.3%. As inflow rate increased, the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min−1 and 35.11 to 121.96 g m−2 min−1, respectively. Canopies relatively contributed 66.7% to lowering flow velocity, turbulence, weakening erosive force and increasing hydraulic resistance. Roots played a predominant role in reducing soil loss and enhancing soil anti-erodibility, with relative contributions of 78.8% and 73.8%. Furthermore, the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most. These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes, especially under large inflow rates and at upper slope sections. We suggest protecting Coreopsis with intact grass at upper slope sections, while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections, with roots reserved. [ABSTRACT FROM AUTHOR]

In this study, two adjacent gauged catchments on the Chinese Loess Plateau were selected, in which one catchment was afforested and one was restored with natural vegetation in 1954. The distributions of soil erosion rates were estimated between 2010 and 2020 with a high spatial resolution of 2 m in the paired catchments based on the Revised Universal Soil Loss Equation model (RUSLE) and Geographic Information Systems (GIS). The results showed that the simulated soil erosion rates in 2010–2020 averaged 12.58 and 8.56 t ha−1 a−1 for the grassland and forestland catchment, respectively. Moreover, areas with high soil erosion rates (> 80 t ha−1 a−1) were mainly distributed in the topography with steep slope gradients (>45°). Comparisons between simulated soil erosion rates and observed annual sediment loads indicated that the simulation results of the grassland catchment were lower than the observed values, while it was reversed in the forestland catchment. We conclude that the RUSLE model cannot simulate the gravity erosion induced by extreme rainfall events. For the forestland catchment, insufficient streamflow and dense vegetation coverage are crucial factors resulting in hindering the movement of sediments. [ABSTRACT FROM AUTHOR]

One of the most common types of soil degradation is water erosion. It reduces soil quality at the erosion site and may cause sedimentation issues at the deposition site. This phenomenon is estimated using a variety of models. The Revised Universal Soil Loss Equation (RUSLE) model is the most often used, due to its consistence and low data requirement. It is useful for estimating annual soil loss at the watershed scale. To investigate the relationship between soil erosion and sediment deposition, the combined RUSLE and Sediment Delivery Ratio (SDR) models are used. The Wadi El Hachem watershed is a coastal and mountainous Mediterranean basin with rugged topography and high degree of climatic aggressiveness. Both of these characteristics can have an immediate effect on soil erosion and sediment yield. This research includes estimating the Average Annual Soil Loss (A) and Sediment Yield (SY) in the Wadi El Hachem watershed, mapping different RUSLE factors as well as A and SY, and studying the influence of rainfall erosivity (R) on A and SY in dry and rainy years. The A results vary from 0 to 410 t·ha−1·yr−1 with an annual average of 52 t·ha−1·yr−1. The Renfro's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, coefficient of variation, and Nash-Sutcliffe efficiency (NSE) values of 0.38%, 0.02, 0.07%, and 1.00, respectively. The average SY throughout the whole watershed is around 27 t·ha−1·yr−1. The SY map for the entire Wadi El Hachem watershed revealed that sediment production zones are mainly concentrated in the Northeast of the basin, at the basin's outlet, and in the tributaries of the dam. The simulation results of soil loss and sediment yield in dry and rainy years revealed that R is one of the main factors affecting soil erosion and sediment deposition in the Wadi El Hachem watershed. The mean difference in R factor between dry year and rainy year is 671 MJ·mm·ha−1·h−1·yr−1. As a result of this fluctuation, the soil loss and sediment yield have increased by 15 and 8 t·ha−1·yr−1, respectively. The results of this research can be used to provide scientific and technical support for conservation and management strategies of the Wadi El Hachem watershed. [ABSTRACT FROM AUTHOR]

Large-scale land consolidation projects (LCPs) have been carried out on the Loess Plateau to increase the area of agriculture land. The newly created land is prone to soil erosion under the effects of water and gravity. Taking a typical high-filling body (HFB) formed by LCPs in Yan'an, China as the subject, this study comprehensively investigated the types and causes of soil erosion with multiple methods of field investigation, on-site monitoring and laboratory tests. Results showed that the HFB presented a composite pattern of soil erosion with multiple types mainly including underground erosion, mixed water-gravity erosion, seepage erosion, and scouring erosion. The type of erosion varied spatially in different parts of the HFB depending on the dominant factors, mainly including the groundwater state, rainfall, runoff, gravity action, topography, and soil erodibility. The underground erosion mainly occurred at the positions with higher groundwater level and larger hydraulic gradient, while scouring erosion mainly occurred at the positions with extensive interactions of surface runoff, channel slope gradient and soil properties. And near the leading edge of the top of the slope, a band of mixed water-gravity erosion occurred owing to the effects of water and gravity. In addition, nearly saturated soils at the toe of HFB displayed groundwater exfiltration and slope-face slumping. Based on our findings on the causes and variation of soil erosion for the HFB, we proposed the following erosion prevention and control measures to protect the LCPs on the Loess Plateau: to construct drainage ditches and blind ditches to form a complete drainage system, plant alfalfa on the top platform to increase rainfall interception and reduce surface runoff, set seepage ditches and plant deep-rooted plants at the toe of the slope to improve slope toe stability, monitor groundwater level and slope deformation to learn the erosion dynamics and slope stability, and optimize the geometry of HFB such as the slope gradient and slope steps to reduce soil erosion. [ABSTRACT FROM AUTHOR]

Nitrogen deposition will alleviate the nitrogen limitation in terrestrial ecosystems and greatly affect vegetation growth, thereby soil erosion. It is important to clarify the effects of nitrogen addition to the plant roots and soil properties on the soil erosion process. A nitrogen addition experiment was conducted in the grassland dominated by Bothriochloa ischaemum (Linn.) Keng (BI), which has received 0, 2.5, 5, and 10 g N m−2 yr−1 (N0, N2.5, N5 and N10, respectively) for three consecutive years. Then, a total of 150 undisturbed soil samples were collected (including bare soil control) and subjected to flowing water to test their soil detachment capacities under six shear stress levels (10.2 Pa to 29.9 Pa). Three-year nitrogen addition increased the soil bulk density, soil cohesion and nitrate nitrogen while decreasing the saturated hydraulic conductivity, soil water-stable aggregates, soil organic carbon, total nitrogen and ammonium nitrogen. The root mass density and root diameter decreased with nitrogen addition. And the root length, surface area and volume density of the N0 and N5 treatments were larger than those of the other treatments, while the plant roots were significantly inhibited by N10. Additionally, the soil detachment capacity (Dc) and rill erodibility (Kr) of the N0 and N5 treatments were significantly less than those of the N2.5 and N10 treatments, of which the Dc (0.020 kg m−2 s−1) of the N0 treatment was 69.0%, 24.3% and 66.8% less than that of the N2.5, N5 and N10 treatments, respectively. The Kr of the N0 treatment was 0.0012 s m−1, which was 72.1%, 25.0% and 70.0% less than that of the others. This study implies that an increase in nitrogen addition likely exacerbates soil erosion in the early (approximately 2.5 g N m−2 yr−1) and late phases (more than 10 g N m−2 yr−1). However, when the nitrogen addition rate is approximately 5 g m−2 yr−1, soil erosion may be inhibited because of the responses of the plant roots and soil to nitrogen addition. [ABSTRACT FROM AUTHOR]

Benggang erosion is caused by a special type of gully erosion in southern China that seriously endangers the local ecology and environment. In this study, typical Benggang collapsing-wall soils were used as the study area to investigate the effects of different initial moisture contents and dicranopteris linearis root weight densities, as well as their interactions on disintegration in orthogonal test method. The results showed that the rate of soil disintegration decreased as a linear function of the initial moisture content. The soil disintegration rate tended to rise and then fall as the root weight density increased, reflecting an optimum root weight density of 0.75–1.00 g/100 cm3. The incorporation of dicranopteris linearis roots was most effective for soil consolidation in the shallow layers of soil. In addition, the disintegration rate of the collapsing-wall soils increases as the soil layer deepened. The dicranopteris linearis root system and initial moisture content had an interactive effect that was more pronounced in deeper soils. However, the combined effect of these processes was always dominated by the initial moisture content. Moderate initial soil moisture content (0.20–0.24 g/g) and the addition of a high root density in dicranopteris linearis (0.75–1.00 g/100 cm3) were the optimal combinations that reduced the disintegration rate. In conclusion, maintaining a suitable natural moisture content in collapsing-wall soils and taking measures that use plants to consolidate soil can effectively prevent and control the occurrence of Benggang erosion. The results of this study provided further insight into the factors that influence soil disintegration and offered a scientific basis for soil erosion management in the southern China. [ABSTRACT FROM AUTHOR]

Monitoring and evaluating the evolution of rocky desertification timely and studying the characteristics of soil erosion under different rainfall patterns are of great scientific significance for regional soil and water conservation, rocky desertification control and ecological environment construction. Four periods of remote sensing image data from 2005 to 2020 were selected to study the evolution characteristics of rocky desertification and its impact on soil erosion in the controlled boundary area of Shibantang hydrological station of Yeji River Watershed, Guizhou Province, China. According to the 408 erosive rainfall events, the soil erosion under different rainfall patterns in the watershed was analyzed. The results showed that: erosive rainfall events in the study area were mainly pattern A, accounting for 57.4% of the total rainfall events; the second was pattern B, accounting for 28.9% of the total rainfall events; the rainfall pattern of C occurred occasionally. Among them, pattern A was the main rainfall pattern leading to soil and water loss and had the largest contribution rate to soil erosion in the watershed. From 2005 to 2020, the area of rocky desertification showed a decreasing trend, accounting for 72.2% from 87.9%. Spatially, rocky desertification has mainly concentrated in the middle south of the watershed since 2010, while the rocky desertification mainly concentrated in the middle and north before 2010. The effects of different grades of rocky desertification on soil erosion were different, and the soil erosion modulus in areas with the medium, severe and extremely severe rocky desertification was generally small. The soil erosion modulus estimated by the RUSLE (Revised Universal Soil Loss Equation) model was still much higher than that calculated by the data measured by the hydrological monitoring station. Therefore, the application of the RUSLE model in karst area needs to be further modified. These results can provide reference for rocky desertification control, soil erosion control and fragile ecosystem restoration in karst area. [ABSTRACT FROM AUTHOR]

Accurately calculating detachment capacity is the most fundamental issue when establishing a soil erosion process model. Colluvial deposits of Benggang are typical soil-gravel mixtures, whereas the understanding of the soil detachment of colluvial deposits is limited. This work investigated the effects of the gravel contents on the soil detachment capacity of colluvial deposits and its hydrodynamic mechanism. The colluvial sample was collected in Anxi County, Fujian Province, Southeast China, and a small-sample scouring test was used. The slope steepness ranged from 18% to 84%, unit discharge ranged from 0.56×10−3 to 2.22×10−3 m2 s−1, and gravel content ranged from 0% to 70%. The results indicated that the gravel content is the primary factor that influences the detachment capacity, followed by the discharge and then the slope. The detachment capacity trend with the gravel content varied over different slopes and discharges. Stream power represents the best hydrodynamic parameter for modelling the detachment capacity of colluvial deposits and can be used to establish a fitting equation for the colluvium together with the mean weight diameter (MWD) (Nash-Sutcliffe efficiency (NSE)=0.96). As the gravel content increased, the soil erodibility parameters increased several folds, in some cases more than 10 folds, mainly because the soil shear strength decreased gradually. Meanwhile, as the gravel content increased, the gravel specific surface area increased, the obstruction of gravel to runoff increased, and the energy needed for runoff to overcome gravel obstruction increased, leading to 2–3 folds higher critical shear stress of runoff for soil-gravel mixtures compared with pure soil. In summary, gravel can influence the detachment capacity by changing the soil properties, and the gravel content also affects the relationship between soil detachment capacity and the hydrodynamic parameters. These findings deepen the understanding of the influence of gravel on soil erosion and provide a basis for establishing a soil erosion process model in colluvial deposits. [ABSTRACT FROM AUTHOR]

Linking landscape indexes to ecological processes is the key topic of landscape ecology. However, traditional landscape metrics based on the Patch-Mosaic Model have no ecological significance. In this study, the runoff-sediment landscape index coupling land use, topography, soil, and vegetation factors was constructed to link landscape patterns to runoff and sediment. In the study area, the runoffsediment landscape index at the class scale showed an increasing trend from 0.10 in 1995 to 0.26 in 2015. Cropland had a higher runoff-sediment landscape index compared to grassland or forestland. At the landscape scale, the runoff-sediment landscape index showed a decreasing trend since 1995; furthermore, it decreased by 36.24% in 2015 compared with the index in 1990. The runoff-sediment landscape index had higher correlations with runoff and sediment compared with traditional landscape metrics. Redundancy analysis showed that the runoffsediment landscape index had a higher contribution to runoff and sediment compared to traditional landscape metrics, explaining 90.1% of the variability. The soil erosion risk assessed by the runoff-sediment landscape index showed an increasing trend upstream of the Dali River watershed. More attention should be paid to this area in future vegetation restoration attempts, as exploring the impact of landscape pattern changes on ecological processes, especially hydrological processes, plays an important role in comprehensive watershed management. [ABSTRACT FROM AUTHOR]

Extensive landslides were triggered by the Wenchuan earthquake (in China) on 12 May 2008, causing a tremendous amount of loose material suspended on the hillslopes, likely to be eroded and transported by rain. It is of great significance to study the long-term variation of the quantity and spatiotemporal distribution of loose deposits after a great earthquake in order to understand the restoration process, to assess the risk of future soil erosion, including geological hazards, and to further develop ecological governance strategy. In this study, information about the multi-temporal loose deposits on the ranges of the Baisha River Basin, an alpine valley near the epicenter, was extracted by object-oriented remote sensing interpretation, and analysis on their spatiotemporal variation showed that the earthquake in 2008 resulted in loose deposits covering an additional area of 81.09 km2, with a volume estimated at 0.357 billion m3. Within five years after the earthquake, the vegetation had recovered rapidly, and the extent of the deposits was significantly less. From 5 to 13 years after the earthquake, the vegetation continued to recover but at a slower rate and a decreasing trend in newly formed deposits was evident. The total area, volume and quantity of the loose deposits gradually stabilized. The geometric mean center of the loose deposits gradually moved back towards the upstream area after the earthquake and, by 2021, the mean center was about 4 km away from its pre-earthquake position. Taking the mean center of the loose deposits in 2008 as the center, the deposits in the downstream area shrank significantly after the earthquake, but collapses and landslides of deposits persisted in the upstream area to the west-southwest, west-northwest and north-northwest from the mean center, indicating future source areas of new loose deposits in the basin. [ABSTRACT FROM AUTHOR]

Process interactions on catenas have supported grazing adapted ecosystems and sustained biodiversity values in the source zone of the Yellow River in western China for millennia. In recent decades, anthropogenic disturbance and climate change have threatened the integrity of these systems, impacting upon environmental values and their capacity to sustain local livelihoods. Collaborations between local experts and a team of international researchers during a workshop and field excursion to this area in July 2019 developed a cross-disciplinary, process-based model of alpine meadow catenas. This paper relates the contemporary health of these grassland-wetland systems to their 'best achievable state' under prevailing boundary conditions, differentiating stages of degradation and recovery in relation to climate and land use changes. Recovery is underway for alpine meadow catenas at Maqin. Reduced land use pressures (stocking rates) and longer growing seasons have enhanced grassland-wetland conditions. However, recovery prospects are limited for local areas of extremely degraded grasslands (heitutan), as breached abiotic thresholds have resulted in soil and nutrient loss and reduced capacity for water retention. While lagomorphs and rodents act as ecosystem engineers when alpine meadows are in a healthy state, irruptions locally increase the proportion of bare ground and inhibit recovery potential. Management options that support recovery of alpine meadows are presented for differing stages of degradation. [ABSTRACT FROM AUTHOR]

The impacts of vegetation restoration on the soil erosion have been widely elucidated in the semi-arid regions. However, the magnitude of soil erosion on abandoned sloping farmland still remained unclear and their responses to vegetation succession were rarely addressed. The main objective of this study is to determine the magnitude of soil erosion along vegetation succession and explore the impact of vegetation succession on soil erosion from abandoned sloping farmland. Field observations were employed to monitor the rainfall, runoff, and soil erosion of seven sloping farmland plots with different abandoned ages and bare land from 2015 to 2019. The results indicated that the annual runoff depth and soil erosion modulus of vegetation types were in the range of 0.46 to 5.49 mm·a−1 and 1.3 to 24.5 t·km−2·a−1, respectively. The vegetation effectively reduced the annual surface runoff and soil erosion with reduction of 73.8% to 97.8% and 98.0% to 99.9% as opposed to bare land. However, there were no significant differences in runoff and soil erosion for different vegetation types along succession. The largest event of vegetation types contributed to 38.7%–44.1% of the annual runoff and 42.5%–66.3% of the annual soil erosion, respectively. Vegetation restoration considerably alleviated the contribution of largest erosive event to annual soil erosion. The relationships between soil erosion, runoff and rainfall factors could be fitted well by linear functions, and the performances of regression models in predicting runoff were more satisfactory compared to predicting soil erosion. The Artemisia gmelinii (Agm) + Stipa bungeana (Sb) optimized the trade-off between sediment reduction and runoff maintenance, which should be selected as the suitable vegetation types to achieve the sustainability of socio-ecological systems. [ABSTRACT FROM AUTHOR]

This study highlights the influence of freezing-thawing processes on soil erosion in an alpine mine restoration area. Accordingly, a series of simulation experiments were conducted to investigate runoff, sediment, and nutrient losses, and potential influencing factors under freeze-thaw (FT) conditions. Three FT treatments (i.e., 0, 3, and 5 FT cycles), and two soil moisture contents (SMCs; i.e., 10% and 20% SMC on a gravimetric basis) were assessed. The runoff, sediment yield, ammonia nitrogen (AN), nitrate nitrogen (NN), total phosphorus (TP), and dissolved phosphorus (DP) losses from runoff were characterized under different rainfall durations. The fitting results indicated that the runoff rate and sediment rate, AN, NN, TP, and DP concentrations in runoff could be described by exponential functions. FT action increased the total runoff volume and sediment yield by 14.6%–26.0% and 8.8%–35.2%, respectively. The runoff rate and sediment rate increased rapidly with the increment of FT cycles before stabilizing. At 20% SMC, the total runoff volume and sediment yield were significantly higher than those at 10% SMC. The loss curves of AN and NN concentrations varied due to differences in their chemical properties. FT action and high SMC promoted AN and NN losses, whereas the FT cycles had little effect. FT action increased TP and DP losses by 60.2%–220.1% and 48.4%–129.8%, respectively, compared to cases with no FT action; the highest TP and DP losses were recorded at 20% SMC. This study provides a deep understanding of freezing-thawing mechanisms in the soils of alpine mine restoration areas and the influencing factors of these mechanisms on soil erosion, thereby supporting the development of erosion prevention and control measures in alpine mine restoration areas. [ABSTRACT FROM AUTHOR]

Internal erosion occurs when fine particles escape from the soil driven by seepage flow, which is considered to be the crucial factor causing the failure of earth structures filled with gravelly soil. The objective of this paper is to suggest an appropriate method to assess internal erosion potential of gravelly soil. By analyzing the sensitivity of soil material to internal erosion, the variable (Dc15/df85)max and the content of coarse particles (Pc) are selected as the evaluation indexes (Dc15 and df85 are the diameters of 15% mass passing in the coarse component and 85% mass passing in the fine component, respectively). A series of gravelly soils with different particle size distributions are tested for internal erosion by the self-made permeameter. Based on the test results, an evaluation method for the internal erosion of gravelly soil is proposed. Gravelly soil is prone to internal erosion when 60% ≤ Pc < 95% and (Dc15/df85)max > 9.5. The proposed method shows good accuracy in evaluating the internal erosion of 36 soil samples from other studies, which confirms the reliability of the method. The proposed method makes it possible to accurately assess internal erosion of gravelly soil, and an alternative method is provided for engineers to determine whether there is a risk of internal erosion in earth structures consisting of gravelly soil. [ABSTRACT FROM AUTHOR]

The steeply sloping agricultural highlands in Korea have severe soil erosion. Estimation of both soil erosion and sedimentation in these highlands is necessary to make plans for soil-conservation measures, but it is not feasible using existing soil-erosion models. This study measured the site-specific concentrations of 137Cs and 210Pbex on both a highland slope (33% slope) and a reference site (undisturbed flat area) to estimate soil erosion and redistribution. The use of the fallout radionuclide (FRN) method was evaluated to see if it is a suitable method for characterizing soil erosion. Results were compared with those obtained with the Universal Soil Loss Equation (USLE), which is an empirical model that estimates annual soil erosion. The average concentrations of 137Cs and 210Pbex at the reference site were 11.57±0.24 Bq kg−1 and 59.74±4.2 Bq kg−1, respectively. Concentrations of 137Cs and 210Pbex in the experimental slope were 16.4% and 10.8%, respectively, of those at the reference site. Radionuclide inventories were lower at the upper point of the slope than those at the basal point of the slope. Concentrations of 137Cs and 210Pbex were significantly correlated with available phosphorus, organic matter, CEC, and exchangeable cations. Estimation of soil redistribution rate using 137Cs and 210Pbex showed site-specific variations at different points along the slope, and respective ranges were −17.46∼−207.51 and 1.55∼−581.38 Mg ha−1 yr−1, which indicated that more erosion was assessed by 210Pbex than by 137Cs. Redistribution analysis showed that soil erosion occurred along the entire slope, except for the bottom point of the slope where 1.55 Mg ha−1 yr−1 of sediment accumulated. The USLE provided a single value of the average annual soil loss in the entire slope, which was either 166 or 398 Mg ha−1 yr−1, depending on the soil erodibility factor (soil series factor and calculated factor from soil sample analysis) used in the model. We conclude that the FRN method using 137Cs and 210Pbex radionuclides can be used to assess soil erosion and redistribution in steeply sloping agricultural highlands. Verification of soil-erosion values using the FRN method and soil-erosion models has been controversial, but it merits further study at many locations with different soils, topography, and management practices. [ABSTRACT FROM AUTHOR]

Vegetation coverage recovery after the Wenchuan earthquake has important implications for preventing post-seismic geohazards and soil erosion. However, spatiotemporal changes in vegetation coverage recovery and its driving factors have not been sufficiently studied in the quake-hit areas. This paper aims to analyze vegetation coverage recovery and its driving factors in the quake-hit areas using monadic linear regression, coefficient of variation, and geographical detector. First, we used Moderateresolution Imaging Spectroradiometer (MODIS) data to calculate the vegetation coverage from 2008 to 2018 in the quake-hit areas. Second, we assessed the trend and stability of vegetation recovery in the quake-hit areas based on vegetation coverage. Finally, combined with topography, climate, soil type, vegetation type, and human activities in the quake-hit areas, the driving factors affecting vegetation coverage recovery were analyzed. The results showed that the vegetation coverage level in the quake-hit areas recovered about 90% of that before the earthquake. Vegetation coverage recovery was mainly improved in a stepwise manner: increasing and then stabilizing, then increasing and stabilizing again. Elevation, soil type, and road density were the main factors affecting vegetation coverage recovery, and the interaction among all factors positively strengthened their impacts on vegetation coverage recovery. In addition, the results also revealed the categories that were conducive to vegetation coverage recovery among the same environmental factors and can provide a scientific reference for vegetation coverage recovery in the quake-hit areas. [ABSTRACT FROM AUTHOR]

Biocrusts affect soil detachment through above-ground (top crust's surface covering) and below-ground (sub-crust's binding and bonding, B&B) effects, which might vary with biocrust development or coverage. However, these effects in humid climates are still unclear. This study was conducted to apportion and quantify the surface covering and B&B effects of moss biocrusts with five coverage levels (1%–20%, 20%–40%, 40%–60%, 60%–80%, and 80%–100%) on soil detachment by overland flow in a subtropical humid climate. Two treatments with one being intact moss crusts and one removing the above-ground moss tissues were designed for each coverage level, and bare soil was used as the baseline. The results indicated that soil detachment capacity (Dc) and rill erodibility (Kr) decreased with biocrust coverage. After removing the above-ground moss tissues, the impeding effect of biocrusts on soil detachment weakened, but still increasing soil erosion resistance relative to bare soil. For intact crust, Dc was reduced by 50%–95% compared with bare soil, wherein 36%–55% and 14%–40% were attributed to the surface covering and B&B, respectively. The top crust contributed more than sub-crust to the soil detachment reduction, which were related to but not linear with biocrust coverage. When biocrust coverage reached mid-to-higher level (40%–100%), both top crust and sub-crust steadily contributed to soil detachment reduction with 60% and 40%, respectively. The findings advance a better understanding of the influencing mechanism of biocrusts on soil erosion in humid climates and highlight the importance of saving biocrusts as ecosystem functions. [ABSTRACT FROM AUTHOR]

The gully is the most dynamic and changeable landform unit on the Loess Plateau, and the characteristics of gully landforms are key indicators of gully evolution. Different gully profiles are connected and combined through runoff nodes. Thus, it is necessary to cluster gully profiles into a gully profile combination (GPC) to reveal the spatial variation in gully landforms throughout the Loess Plateau. First, the gradient and gully evolution index (GEI) of two sample areas in Changwu and Suide in Shaanxi Province, China are calculated and analysed based on GPC. Then, the gradient and GEI are calculated by using 90-m-resolution digital elevation model (DEM) data for the severe soil erosion area with the basin as the research unit. On this basis, the spatial variation in the development degree is analysed with Getis-Ord Gi*. The results show that the degree of gully undercutting decreases from southeast to northwest under the influence of rainfall. Due to the soil properties, the loess in the northwest is more prone to collapse, resulting in the decrease of GEI from northwest to southeast. The development degree of gullies is closely related to rivers. The strong erosive capacity of rivers leads to greater differences in gullies within the basin. At the same time, the skewness and kurtosis of the gully index in the basin are correlated; when the distribution of the gully index in the basin is less normal, the distribution of the gully index is more concentrated. These results reveal the spatial variation characteristics of the Loess Plateau based on GPC. [ABSTRACT FROM AUTHOR]

Abrupt changes in land use/land cover have often characterized Andean rural landscapes. This is particularly notorious in the Paute River watershed in southern Ecuador. We seek to show how, under tenets of the global economy, rural mountain landscapes suffer constant modifications due to the agricultural practices of dwellers and migrants. Erosion of arable slopes takes center stage in analyzing vulnerability due to the high erodibility factor found in this watershed. By using remote sensing and GIS applications, we analyzed the potential erodibility with intersections of rural development constraining of ecosystem services, including the production of water, food, and cultural values in the Paute River watershed. We found six sources of migratory flows and analyzed topographic and elevation effects in potential erodibility indexes of agroecological options to ameliorate the environmental stress. We identified factors associated with migration trends observed in the area and assessed vulnerability issues of resource management that could prevent deforestation, soil erosion, and acculturation amidst the pressures of development in the region. We conclude that sustainable development options can be implemented with a watershed management approach oriented to diminish emigration. This approach shall be integrative, inclusive, and respectful of the rich biocultural diversity heritage conservation of southern Ecuador. [ABSTRACT FROM AUTHOR]

Strong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation. [ABSTRACT FROM AUTHOR]

Soil conservation practices can greatly affect the soil erosion process, but limited information is available about its influence on the particle size distribution (PSD) of eroded sediment, especially under natural rainfall. In this study, the runoff, sediment yields, and effective/ultimate PSD were measured under two conventional tillage practices, downhill ridge tillage (DT) and plat tillage (PT) and three soil conservation practices, contour ridge tillage (CT), mulching with downhill ridge tillage (MDT), and mulching with contour ridge tillage (MCT) during 21 natural rainfall events in the lower Jinsha River. The results showed that (1) soil conservation practices had a significant effect on soil erosion. The conventional tillage of DT caused highest runoff depth (0.58 to 29.13 mm) and sediment yield (0.01 to 3.19 t hm−2). Compared with DT, the annual runoff depths and sediment yields of CT, MDT and MCT decreased by 12.24%–49.75% and 40.79%–88.30%, respectively. (2) Soil conservation practices can reduce the decomposition of aggregates in sediments. The ratios of effective and ultimate particle size (E/U) of silt-and sand-sized particles of DT and PT plots were close to 1, indicating that they were transported as primary particles, however, values lower/greater than 1 subject to CT, MDT and MCT plots indicated they were transported as aggregates. The ratios of E/U of clay-sized particles were all less than 1 independently of tillage practices. (3) The sediments of soil conservation practices were more selective than those of conventional tillage practices. For CT, MDT and MCT plots, the average enrichment ratios (ERs) of clay, silt and sand were 1.99, 1.93 and 0.42, respectively, with enrichment of clay and silt and depletion of sand in sediments. However, the compositions of the eroded sediments of DT and PT plots were similar to that of the original soil. These findings support the use of both effective and ultimate particle size distributions for studying the size selectivity of eroded sediment, and provide a scientific basis for revealing the erosion mechanism in the purple soil area of China. [ABSTRACT FROM AUTHOR]

Soil erosion is currently a major contributor to the degradation of global soil resources. The characteristics of sediment size distribution affect soil erosion processes. However, few studies have quantitatively explored soil erosion processes and sediment size distributions on natural hillslopes for different land uses, especially in the Chinese Mollisol region. The objective of this study was to investigate the impacts of land uses (corn, fallow, buffer strip and bare hillslopes) under 5° and 10° slope gradients on total runoff, runoff rates, soil losses, sediment concentration processes, and sediment size distributions. Natural runoff plots (20 m long and 5 m wide) were subjected to inflow scour experiments (1 L min−1 m−2, lasting 40 min). The results showed that the total runoff varied from 2.62 to 6.40 L m−2 and from 8.36 to 20.39 L m−2 on hillslopes at 5° and 10°, respectively. The changes in runoff rates versus run time exhibited gradual increasing trends at 5°, but exhibited initial rapidly increasing trends and then relatively stable trends at 10°. Fallow hillslopes produced the lowest soil losses, which were 45.34%–45.92%, 2.74%–6.72% and 1.68%–3.44% for the corn, buffer strip and bare hillslopes, respectively. Most sediment concentrations were very small and stabilized between 0.5–2.0 g L−1 on the fallow hillslopes and 1.5–3.0 g L−1 on the corn hillslopes at 5°, but the changing trends in sediment concentration versus run time for the four land uses generally decreased at 10°. Furthermore, it was demonstrated that the proportion of sediment <0.25 mm was the largest in comparison with the other sediment size fractions, and <0.25 mm soil particles and aggregates played a dominant role in soil aggregate loss under different land uses. Thus, protecting these precious soil particles and aggregates by applying proper soil conservation measures especially for the relatively gentle hillslopes was particularly important. Additionally, the fallow hillslope with greater soil and water conservation capacities was very suitable for the Mollisol hillslopes. [ABSTRACT FROM AUTHOR]

To quantify the impacts of native vegetation on the spatial and temporal variations in hydraulic properties of bank gully concentrated flows, a series of in situ flume experiments in the bank gully were performed at the Yuanmou Gully Erosion and Collapse Experimental Station in the dry-hot valley region of the Jinsha River, Southwest China. This experiment involved upstream catchment areas with one- and two-year native grass (Heteropogon contortus) and bare land drained to bare gully headcuts, i.e., Gullies 1, 2 and 3. In Gully 4, Heteropogon contortus and Agave sisalana were planted in the upstream catchment area and gully bed, respectively. Among these experiments, the sediment concentration in runoff in Gully 3 was the highest and that in Gully 2 was the lowest, clearly indicating that the sediment concentration in runoff obviously decreased and the deposition of sediment obviously increased as the vegetation cover increased. The concentrated flows were turbulent in response to the flow discharge. The concentrated flows in the gully zones with native grass and bare land were sub- and supercritical, respectively. The flow rate and shear stress in Gully 3 upstream catchment area were highest among the four upstream catchment areas, while the flow rate and shear stress in the gully bed of Gully 4 were lowest among the four gully beds, indicating that native grass notably decreased the bank gully flow rate and shear stress. The Darcy-Weisbach friction factor (resistance f) and flow energy consumption in the gully bed of Gully 4 were notably higher than those in the other three gully beds, clearly indicating that native grass increased the bank gully surface resistance and flow energy consumption. The Reynolds number (Re), flow rate, shear stress, resistance f, and flow energy consumption in the gully beds and upstream areas increased over time, while the sediment concentration in runoff and Froude number (Fr) decreased. Overall, increasing vegetation cover in upstream catchment areas and downstream gully beds of the bank gully is essential for gully erosion mitigation. [ABSTRACT FROM AUTHOR]

Accurate assessment of soil erosion is an important prerequisite for controlling soil erosion. The engineering-control (E) and tillage (T) factors are the keys for Chinese Soil Loss Equation (CSLE) to accurately evaluate water erosion in China. Besides, the E and T factors can reflect the water and soil conservation effects of engineering-control and tillage practices. But in the current full coverage of soil erosion surveys in China (such as soil erosion dynamic monitoring), for the same practice, the E or T factors are assigned the same value across the country. We selected 469 E and T factors data based on runoff plots from 73 publications, and they came from six soil and water conservation regions. Correlation analysis, regression analysis, and nonparametric tests were used to determine the comparability of the data, and it was proved that the runoff plots dimensions are consistent with the local topography. The results of one-way ANOVA and nonparametric tests for E and T factors in different regions showed that the engineering-control practices have good soil and water conservation effects and weaken the regional differences of other environmental factors, so there were no significant differences in E factors between different regions. However, there were significant differences in T factors between different regions, and the geodetector was applied to explore the intrinsic driving force of the spatial distribution of T factors. The results of the geodetector showed that the dominant driving forces of the spatial distribution of different types of tillage practices were not completely the same. When using CSLE to calculate water erosion, the E factor of the same practice can be used uniformly throughout the country, and the T factor needs to be considered and selected according to regional differences. At the same time, when choosing tillage practices in each water and soil conservation region, practices with better sediment reduction benefits should also be selected according to the regional environmental conditions. [ABSTRACT FROM AUTHOR]

Raindrop size, rainfall intensity and runoff discharge affect the detachment and transportation of soil particles. Among these three factors, the rainfall intensity seems to be more important because it can change other two factors. Storm patterns can be determined by changing the rainfall intensity during the storm. Therefore, the objective of this research is to test the influence of storm pattern on runoff, soil erosion and sediment concentration on a rangeland soil slope under field rainfall simulation. Four storm rainfall intensity patterns were selected for examining the effects of variations in storm event characteristics on soil erosion processes. The selected storm patterns were: I (45, 55 and 70 mm h−1); II (45, 70 and 55 mm h−1); III: (70, 55 and 45 mm h−1); and IV (55, 45 and 70 mm h−1). The last pattern is a new one instead of the uniform pattern which has been sufficiently studied in previous researches. The experiments were conducted in field plots (in Kojour watershed, Mazandaran Province, Iran) with an area of one square meter and an constant slope gradient of 18%, surrounded by galvanised sheets. Following the non-uniform prioritization of the storm patterns for the studied variables, time to runoff (I>II>IV>III), runoff volume (III>IV>II>I), sediment concentration (IV>III>I>II) and soil erosion (III>IV>II>I)), it can be generally inferred that each pattern has specific effect on soil erosion processes during a storm. The results of the general linear model (GLM) test indicated that the effects of storm pattern on time to runoff, total runoff volume, runoff coefficient and soil erosion were significant at a level of 99%. The Duncan test showed that the storm patterns can be divided into three groups of III, IV; II; I (for time to runoff), I, II; IV, III (for runoff coefficient), and I; II; IV, III (for runoff volume and soil erosion). [ABSTRACT FROM AUTHOR]

Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau. Based on the data of check-dams from 1950 to 2014, our study roundly analyzed the regional distribution, function and the problems of check-dams on the Loess Plateau. A total of 17,094 check-dams with a storage capacity of over 100,000 m3 and an average density of 0.027 counts km−2 were installed on the Loess Plateau. Check-dams' densities varied greatly in the Qinghai Province, Gansu Province, Ningxia Hui Autonomous Region, Inner Mongolia Autonomous Region, Shaanxi Province, Shanxi Province and Henan Province. The highest density of check-dams reached 0.088 counts km−2 in Shaanxi Province, whereas the lowest density of check-dams was only 0.005 counts km−2 in Qinghai Province. However, after decades of operation, 3025 large check-dams and 2257 medium check dams are dangerous and have security risks, which are seriously threatening downstream safety. The dangerous rate of check-dams is high. Specifically, the check-dams in Shanxi and Qinghai Province have the highest dangerous rates, with both exceeding 53%. Therefore, there is an urgent need for carrying out reinforcement of the dangerous check-dams. The results are helpful to policymakers to extend and develop check-dams. [ABSTRACT FROM AUTHOR]

Gully erosion is a worldwide problem of land degradation and water quality, and it is also frequent in Brazil. Typically, anthropic influence is the major driver of gully evolution. To study and monitor gullies it is necessary to use specific instruments and methods to obtain accurate information. The objective of this study was to use Terrestrial Laser Scanning (TLS) to create digital elevation model (DEM) accurately and define morphometric variables that characterize gullies in a mountainous relief. Two different interpolations were evaluated using the Topogrid and GridSurfaceCreate algorithms to elaborate DEM. Topographic profile for gullies was used to assess modeling quality. The DEM of the Gully 1 (G1) from the Topogrid algorithm estimated soil loss of 49%, whereas the GridSurfaceCreate algorithm estimated a soil loss of 97%, in a period of 1 year. The estimated soil loss for the Gully 2 (G2) was 14% from the Topogrid, and 8% from the GridSurfaceCreate algorithm. The GridSurfaceCreate algorithm underestimated the volume to area ratio for G2 due to a failure on interpolating a region of low point representativity. The Topogrid algorithm represented better the terrain irregularities, as observed through the topographic profiles traced in three regions of G1 and G2. Statistical analysis showed that the GridSurfaceCreate algorithm presented lower accuracy in estimating elevations. The underestimation trend of this algorithm was also observed in G2. The gullies showed considerable soil losses, which may reduce the areas suitable for agricultural activities, and silting up of water courses. The Topogrid algorithm presented satisfactory results, denoting great potential to produce morphometric data of gullies. [ABSTRACT FROM AUTHOR]

Ephemeral gullies, which are widely developed worldwide and threaten farmlands, have aroused a growing concern. Identifying and mapping gullies are generally considered prerequisites of gully erosion assessment. However, ephemeral gully mapping remains a challenge. In this study, we proposed a flow-directional detection for identifying ephemeral gullies from high-resolution images and digital elevation models (DEMs). Ephemeral gullies exhibit clear linear features in high-resolution images. An edge detection operator was initially used to identify linear features from high-resolution images. Then, according to gully erosion mechanism, the flow-directional detection was designed. Edge images obtained from edge detection and flow directions obtained from DEMs were used to implement the flow-directional detection that detects ephemeral gullies along the flow direction. Results from ten study areas in the Loess Plateau of China showed that ranges of precision, recall, and F-measure are 60.66%–90.47%, 65.74%–94.98%, and 63.10%–91.93%, respectively. The proposed method is flexible and can be used with various images and DEMs. However, analysis of the effect of DEM resolution and accuracy showed that DEM resolution only demonstrates a minor effect on the detection results. Conversely, DEM accuracy influences the detection result and is more important than the DEM resolution. The worse the vertical accuracy of DEM, the lower the performance of the flow-directional detection will be. This work is beneficial to research related to monitoring gully erosion and assessing soil loss. [ABSTRACT FROM AUTHOR]

The karst mountainous area is an ecologically fragile region with prominent human-land contradictions. The resource-environment carrying capacity (RECC) of this region needs to be further clarified. The development of remote sensing (RS) and geographic information system (GIS) provides data sources and processing platform for RECC monitoring. This study analyzed and established the evaluation index system of RECC by considering particularity in the karst mountainous area of Southwest China; processed multisource RS data (Sentinel-2, Aster-DEM and Landsat-8) to extract the spatial distributions of nine key indexes by GIS techniques (information classification, overlay analysis and raster calculation); proposed the methods of index integration and fuzzy comprehensive evaluation of the RECC by GIS; and took a typical area, Guangnan County in Yunnan Province of China, as an experimental area to explore the effectiveness of the indexes and methods. The results showed that: (1) The important indexes affecting the RECC of karst mountainous area are water resources, tourism resources, position resources, geographical environment and soil erosion environment. (2) Data on cultivated land, construction land, minerals, transportation, water conservancy, ecosystem services, topography, soil erosion and rocky desertification can be obtained from RS data. GIS techniques integrate the information into the RECC results. The data extraction and processing methods are feasible on evaluating RECC. (3) The RECC of Guangnan County was in the mid-carrying level in 2018. The mid-carrying and low-carrying levels were the main types, accounting for more than 80.00% of the total study area. The areas with high carrying capacity were mainly distributed in the northern regions of the northwest-southeast line of the county, and other areas have a low carrying capacity comparatively. The coordination between regional resource-environment status and socioeconomic development is the key to improve RECC. This study explores the evaluation index system of RECC in karst mountainous area and the application of multisource RS data and GIS techniques in the comprehensive evaluation. The methods can be applied in related fields to provide suggestions for data/information extraction and integration, and sustainable development. [ABSTRACT FROM AUTHOR]

Soils in the hydro-fluctuation belts of the reservoirs are most highly influenced by the special hydro-conditions and reservoir operation, leading to unique soil erosion process and largely accelerate soil erosion intensity. The present study aimed to estimate soil erosion rate in the hydro-fluctuation belt of the Pubugou Reservoir, Southwest China, based on the framework of Universal Soil Loss Equation (USLE). An attempt has been made to modify the original USLE by including the reservoir water erosivity (W), a new factor into the model. Soil erosion rate from different land use types were quantitatively estimated, using the USLE and the modified USLE respectively. Field observation showed that soil erosion rate in dry farmland, bare land and grassland was 4700, 44600 and 5050 t/km2, respectively. The erosion rate assessed by the modified USLE was closely related to that recorded from the field monitoring data. The findings of this study clearly highlight the importance of inclusion of the W factor to the original USLE model while assessing soil erosion in the reservoir hydro-fluctuation belt. [ABSTRACT FROM AUTHOR]

An understanding of how different land covers affect soil erosion caused by rainfall is necessary in mountainous areas. The land cover usually plays an important role in controlling landslide hazards associated with these terrains. This paper presents the results of a field experiment where several types of land covers were placed on a full-scale embankment as erosion control. An 8 m wide, 21 m long, and 3 m high embankment with a 45° side-slope was built with lateric soil. The soil was compacted under a relative compaction of 70% to simulate a natural soil slope. Two sides of the embankment were divided into six land cover areas, with three different areas of bare soil, and one each of a geosynthetic cementitious composite mat (GCCM), vetiver grass, and a combination of GCCM and vegetation. Soil erosion and moisture levels were monitored for each land cover area during six natural rainfall events encountered over the experimental period. Field results were compared with a numerical simulation and empirical soil loss equation. The results revealed that the GCCM gave the best erosion control immediately after installation, but vetiver grass also exhibited good erosion control six months post-construction. [ABSTRACT FROM AUTHOR]

Both tillage erosion and water erosion are severe erosional forms that occur widely on sloping agricultural land. However, previous studies have rarely considered the process of landform change due to continuous simulation experiments of alternating tillage erosion and water erosion. To identify such changes, we applied a scouring experiment (at a 60 L min−1 water discharge rate based on precipitation data from the local meteorological station and the catchment area in the Yuanmou County, Yunnan Province, China) and a series of simulated tillage experiments where plots were consecutively tilled 5, 10, and 15 times in rotation (representing 5 yr, 10 yr, and 15 yr of tillage) at slope gradients of 5°, 10°, and 20°. Close-range photogrammetry (CRP) employing an unmanned aerial vehicle (UAV) and a real-time kinematic global positioning system (RTK-GPS) was used to measure landform changes, and high-resolution digital elevation models (DEMs) were generated to calculate net soil loss volumes. Additionally, the CRP was determined to be accurate and applicable through the use of erosion pins. The average tillage erosion rates were 69.85, 131.45, and 155.34 t·hm−2·tillage pass−1, and the average water erosion rates were 1892.52, 2961.76, and 4405.93 t·hm−2·h−1 for the 5°, 10°, and 20° sloping farmland plots, respectively. The water erosion rates increased as tillage intensity increased, indicating that tillage erosion accelerates water erosion. Following these intensive tillage treatments, slope gradients gradually decreased, while the trend in slope gradients increased in runoff plots at the conclusion of the scouring experiment. Compared to the original plots (prior to our experiments), interactions between tillage and water erosion caused no obvious change in the landform structure of the runoff plots, while the height of all the runoff plots decreased. Our findings showed that both tillage erosion and water erosion caused a pseudo-steady-state landform evolutionary mechanism and resulted in thin soil layers on cultivated land composed of purple soil in China. [ABSTRACT FROM AUTHOR]

The bank slopes in hydro-fluctuation areas of reservoirs or lakes suffer from severe erosion due to an absence of protection. Waves are one of the important external forces that cause bank erosion and slope failures. However, the processes and quantified impacts of wave-induced erosion on slopes remain unclear under different water level-fluctuation conditions. This paper focuses on the characteristics of wave-induced slope erosion under three conditions: water level dropping (WLD), fixed (WLF) and rising (WLR). A steel tank with glass pane was used to simulate the wave-induced slope erosion in the three treatments. The slope elevation data were collected by using the method of the pin meter for every 15 minutes from the beginning to the end, a total of 5 times during all treatments. These data were processed by using software (SURFER 9.0) to get the slope micro-topography and the erosion volume. Then the temporal and spatial change of slope erosion was analysed according to the erosion amount or erosion rate calculated based on bulk density of slope soil. The results demonstrated that the soil erosion rates for different water level changing treatments are in the following order: WLR>WLD>WLF. For the erosion spatial variation, the middle part of the slope was the major source of sediment in the WLD. The upper part of the slope was the major source of the sediment for the other two treatments. Compared with the standard deviation (SD), the coefficient of variation (CV) based on the SD is more representative of variations in the soil surface roughness (SSR). Furthermore, the good fit between the SSR and soil erosion rate have the potential to be used to predict soil erosion. Above all, the injection angle of the wave determined the rate of erosion to some extent, and the fall-back flow of the wave could also influence the extent of erosion, deposition, and bank morphology. It is vital to choose the appropriate index (SD or CV) in the three water levels to improve the prediction accuracy. This paper could provide scientific knowledge to manage reservoirs or river banks. [ABSTRACT FROM AUTHOR]

Monitoring and analyzing changes in the extent of cultivated land may inform strategic decisions on issues of environmental and food security. The dry cropland area of 12000 km2 in the Three Gorges Reservoir Region (TGRR) of China is essential for feeding the local population of ≈20 million, but is highly prone to soil erosion, leading to the delivery of excessive amounts of sediment and associated pollutants to the Three Gorges Reservoir (TGR), and causing serious eco-environmental consequences. Against this background, this paper used Landsat images and a digital elevation model to analyze the altitudinal distribution of, and dynamic changes in, the area of dry cropland during the period 1990 to 2015. The results suggest that dry cropland was mainly distributed in the elevation range of 200-600 m. The dry cropland area decreased from 12525.37 km2 to 11796.27 km2 during the 25-year study period, including a particularly significant decrease in the rate of decrease from 6.93 km2/yr to 43.99 km2/yr after 2000. The largest decline in the dry cropland area occurred in the elevation range of 600-900 m. The transformations between dry cropland and forest revealed the impact of the TGR operation on the extent of dry cropland. A total of 528.79 km2 of dry cropland with slopes >25° were converted to forest after 2000, whereas a total of 642 km2 of forest was converted to dry cropland during the study period, and these conversions mainly occurred between the elevation of 200–900 m. These spatiotemporal changes in the dry cropland area are likely to raise new issues concerning food security in the TGRR. [ABSTRACT FROM AUTHOR]