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[Display omitted] • Distribution of vegetation avoided erosion in China increased by 12.89% in 1990–2020. • Greening of the surface has significantly prevented soil and water loss. • Spatial distribution roughly conforms to the division of the Hu Huanyong line. • Surface greening promotes a increase in vegetation avoided erosion efficiency. Global surface greening is very important to slow down regional warming, promote ecological balance and sustainable development, and China has made a significant contribution to this in the past 30 years, and effectively alleviated environmental problems such as land degradation, water shortage and air pollution by rapidly increasing vegetation coverage. Previous studies have shown that vegetation plays a positive role in alleviating soil erosion, but there is no quantitative description of runoff erosion and sediment transport under vegetation evolution with long time series and high resolution in China area. In this study, we use the RUSLE model and multi-source satellite remote sensing data to simulate overland soil erosion in China from 1990 to 2020 and analyze both the temporal and spatial variation of vegetation avoided erosion (VAE) and its correlation with multiple driving factors, such as Gross Primary Production (GPP). The results show that: 1)The distribution has increased by 12.89 % from 1990 to 2020, which is significant, and indicates that greening of the surface has significantly prevented soil and water loss;2)The spatial correlation strength of VAE-GPP in China is roughly in line with the division of the Hu Huanyong line (Hu-line), which is the result of the combined effect of vegetation distribution and human activities;3)The efficiency of VAE was significantly improved, especially the forest, accounting for about 76.50 % of the total, which was twice the sum of the other types. The research conclusion is of great significance to soil erosion prevention and control, soil ecological improvement, vegetation dynamic planning and regional sustainable development. [ABSTRACT FROM AUTHOR]

Abstract: Efficient intervention to control soil erosion in rural tropical landscapes requires accurate models for predicting the spatial location and intensity of degradation. The Universal Soil Loss Equation (USLE) has commonly been applied for spatial erosion risk assessment in the tropics, but has rarely been validated using ground observations of soil degradation. As with any empirical model, application in new regions requires calibration before results are used for decision support. We evaluated USLE effectiveness for predicting erosion in a small watershed in western Kenya based on 420 georeferenced ground observations of ordinal erosion class (three categories) systematically collected from throughout the basin. Relativized model factors were parameterized using standard remote assessment methods based on interpolated spatial data layers. Inference of degradation status at cultivated sites was estimated by calibration to near infrared diffuse reflectance spectra obtained from sampled soils; diagnostic models based on spectra produced validation accuracies of 78% for three categories. Association between USLE predicted risk and observed erosion, estimated using mixed effects logistic regression to control for within-site variability, correctly classified only 38% of sites into three degradation classes and model sensitivity for delineating regions of severe degradation was only 28%. Graphical modeling was used to identify those USLE risk factors that were conditionally associated with observed degradation, and an ordinal logistic regression model, employing only these factors was developed. This alternative model, which allowed statistical flexibility in estimating effect direction and strength, correctly predicted ordinal degradation class at 54% of field sites, with 55% sensitivity for the severe degradation class. This result suggests a critical need for efficient ground-based sampling schemes to be used in conjunction with flexible statistical models based on USLE factors for future investments in erosion risk assessment in the tropics. [Copyright &y& Elsevier]

• 173 papers related to ephemeral gully erosion in Web of Science were reviewed. • Critical morphological features of ephemeral gully channel were different worldwide. • Topographic, climate, land management, soil, and hydraulics factors were assessed. • Fifteen methodological approaches employed to quantify gully erosion were evaluated. • Complexity of gully channel development and driving force mechanisms were discussed. Although concern for ephemeral gully (EG) erosion has been growing within the research community, knowledge gaps still need to be identified for a state-of-the-art review. This review is based on an extensive search of published literature in the Web of Science database that specifically addressed EG erosion. This review included 173 papers published in 56 scientific journals over the last 30 years. The results indicated that the main EG erosion topics were related to gully erosion processes, factors, methodology, models, and the detrimental effects of EGs. The definition of EG was identical worldwide. There is an urgency to define critical morphological values under different conditions for identifying EG channel locations in fields in order to map and model their development quickly and accurately. Topographic factors have been much more studied than other contributing factors, including climate, land management, soil, and hydraulics. Fifteen different methodological approaches or technologies, which were categorized into four kinds of methods, including field monitoring, modelling, simulation experiments, and review, have been employed to assess and quantify EG erosion. The average soil erosion rate of EGs in 36 publications increased and decreased with increase of slope and catchment areas, respectively, and the number of EGs linearly increased with catchment area. The complexity of the development of EG channels and the driving force mechanisms should also be studied intentionally, e.g., the quantification of soil detachment and sediment transport mechanisms for both surface and subsurface flow during different sub-processes, including gully head advance, sidewall collapse and bed incision. It was concluded that the interactive effects of different contributing factors on EG erosion across various spatio-temporal scales should be further researched. The comprehensive utilization or application of new methods and technologies, e.g., automatic monitoring technologies, artificial intelligence, machine learning algorithms, would be helpful to improve study efficiency and accuracy. The scientific basis of prediction models still needs further development and refinement. This review provides recommendations and suggestions to improve knowledge, prediction, and control of EG erosion. [ABSTRACT FROM AUTHOR]

• Spatio-temporal variations of effective sediment sizes were investigated on field plots. • Sediment size was more susceptible to erosional degradation under low intensity rainfall. • Erosional degradation impact exhibited a unimodal variation with soil structure stability. • Rainfall intensity, pH and bulk density contributed jointly to sediment size (p < 0.001). • This study facilitated an understanding of sediment transport mechanisms on eroded lands. Land degradation by erosion alters soil properties to a varying extent and definitely influences the subsequent soil erosion. However, little is known about the impact of erosion-induced land degradation on the erosion process from the aspect of sediment size characteristics, which may not only indicate aggregate breakdown and sediment transport mechanism, but also influence sediment deposition. Here, the effective sediment size distribution (undispersed) and its dynamics during sheet erosion on different eroded lands (non, moderately and very-severely eroded) were studied under field rainfall simulation on five types of soils (Calcic Luvisols, Ferric Luvisols, Plinthic Alisols, Plinthic Acrisols and Acric Ferralsols) formed separately on loess deposits, quaternary red clays and basalt from temperate to tropical climate. The rainfalls at the intensities of 45 and 90 mm h−1 were simulated on pre-wetted bare fallow plots (3 × 0.8 m2, 10° slope). The effect of erosion degree on the effective sediment size showed a unimodal trend from temperate Luvisols to tropic Ferralsols, coupled with the influence of rainfall intensity to a varying extent. Under the low-intensity rainfall, except for Ferralsol, the moderate erosion degree increased the sediment size by −49% to 72% relative to non-eroded lands, in contrast to a decrease of 6–64% for the very-severe erosion degree. The high-intensity rainfall was shown to lessen the erosion degree effect for Luvisols, magnify it for Alisol, and change it to positive for Acrisol. Sediment transport was dominated by suspension-saltation of <0.10 mm size fraction for Luvisols regardless of erosion degree due to the weak soil structure, and shifted from both rolling (0.5–2 mm) and suspension-saltation on the non/moderately eroded lands to only suspension-saltation on the very-severely eroded lands for the other soil types. Rainfall intensity, pH and bulk density contributed jointly to sediment size (Adj-R2 = 0.76, p < 0.001), and exchangeable sodium showed a positive effect on its temporal variation (Adj-R2 = 0.36, p < 0.001). The varying effects of land degradation by erosion on sediment size and transport mechanism at the soil pedon and regional scales merit consideration in land management and rehabilitation as well as erosion modeling. [ABSTRACT FROM AUTHOR]