Unraveling the paradox of soil erosion and conservation: Insights from China.

Analyzing the drivers of soil conservation (SC) service is crucial for ecosystem restoration. However, previous studies often overlook the relationship between soil erosion and SC. In this study, we applied the revised universal soil loss equation (RUSLE) model to analyze the spatiotemporal trends and driving forces of SC service across China from 1990 to 2019. The results indicate that both soil erosion and SC service have exhibited overall increasing trends over the past 30 years. The average SC amount increased 21.3 % from 1990s to 2010s. The average total SC amount and capacity were 229.95 billion t a-1 and 242.91 t ha-1 a-1, respectively. Spatial analysis reveals significant regional variability, with 26.6 % of the land area experiencing fluctuations in SC, these regions contribute to 87.5 % of the total SC amount in the country. We developed a classification system with six patterns to assess the impacts of climate change and human activities on SC. Patterns dominated by climate change exhibit consistent trends in soil erosion and SC service, whereas those dominated by human activities show opposite trends. When climate change and human activities interact, the relationship becomes more complex. Climate change has the most significant influence on SC alterations, affecting 77.1 % of areas with SC changes, while human activities also play a notable role. Although regions primarily impacted by human activities account for only 1.8 % of the total area, they represent 45,200 km2. The remaining 21.1 % of areas are influenced by both climate change and human activities, highlighting the importance of human activities in 22.9 % of areas with SC changes. These findings underscore the synergistic effects of climate change and human activities on SC in China, providing a foundation for future research and the development of targeted SC strategies.

Mapping and quantifying medium-term soil loss rates in mountain olive groves using unmanned aerial vehicle technology.

Olive groves are one of the main agroecosystems in the Mediterranean region, but water erosion, aggravated by inappropriate soil management, is compromising the environmental sustainability of these crops. National and international public organisations, including the European Union via its Common Agricultural Policy, have acknowledged the problem and recognise the need to quantify the effects of this process. However, the variability of currently available short-term soil erosion measurements, together with limited understanding of the underlying processes, mean there is considerable uncertainty about the long-term effects of soil erosion. This paper presents an innovative procedure called SERHOLIVE4.0 designed to measure and model long-term soil erosion rates in olive groves, by means of structure-from-motion (SfM) techniques by which image information is obtained from unmanned aerial vehicles (UAVs). For the present study, the procedure was evaluated in mountain olive groves, where the erosion rate was calculated from historical surface reconstructions. Overall, this approach was found to be practical and effective. The method includes the following steps: [1] measure the current relief using UAV technology; [2] reconstruct the historical relief from field measurements; [3] calculate soil truncation (h) and obtain a soil erosion rate map; [4] determine the erosive dynamics of the slope and establish the relation between tree truncation, slope and mounds. The method we describe presents the following advantages:•it quantifies soil losses by reference to existing tree mounds;•it is straightforward to apply;•its application enhances the calibration of erosion models.

Impacts of different slash disposals on soil and water erosion of high-intensity management Eucalyptus grandis × urophylla plantation.

Background: The slash disposal-burning forest-in high-intensity management Eucalyptus grandis × urophylla plantation has accelerated soil degradation. Statement of the problem: Slash disposals is a contributing factor, but its specific role in the correlation between rainfall-runoff and soil erosion remains elusive. Objectives: his study investigated the characteristics of rainfall-runoff and soil erosion resistance in different methods of slash disposals in plantation. Methods: Three methods of slash disposal, namely burning forest (BF), moving away (MA), and spreading evenly (SE), were established. A field simulation experiment of rainfall was conducted, and path analysis was used. Results: The findings revealed that the water holding, infiltrating properties and the time the rainfall-runoff generated of SE were increased by approximately 10∼20 %, 100 %, and 80 %, respectively, compared with BF and MA. Water loss, soil loss and nutrient loss were significantly reduced by 62.23 % and 61.56 %, 69.06 % and 49.55 %, and 58.8 % and 65.42 % in SE and BF compared to MA. Path analysis suggested that different from BF and MA, the correlation between soil water properties and rainfall-runoff factors in SE was weakened, simultaneously considering the result that SE had the lower proportions of silt for sediment component (75.31 %), it stabilized the soil structure. Conclusions and prospect: Consequently, SE mitigated the erosion force by reducing rainfall-runoff and enhancing the anti-erosion of soil through improved water properties, making it a viable slash disposal. This work provides a detailed description of the soil erosion characteristics of plantation, including water, soil, and nutrient losses caused by rainfall-runoff, as well as the soil anti-erosion due to different slash disposals. These findings offer valuable insights for the management of high-intensity Eucalyptus grandis × urophylla plantations.

Sedimentary characteristics of ion-adsorption rare earth elements and assessment of their resource reuse potential due to soil and water erosion in western Fujian.

With severe soil and water erosion, the crucial ion-adsorption rare earth elements (REEs) have attracted much global attention. REEs play a vital role in tracing material sources and exploring sedimentary characteristics due to their unique and stable geochemistry properties. In the present work, three representational possible redeposition areas in western Fujian were selected as the study areas. The geochemical characteristics of REEs in the sediments of the study areas were evaluated to elucidate that REEs are the products of soil and water erosion and to assess their redeposition characteristics. In the research results, the properties of the parent rocks shown in the samples, together with the negative correlation between the content of REEs in the samples and altitude as well as the relief degree on the land surface (RDLS), fully indicate that the sediments in the study areas are the products of migration caused by soil erosion and redeposition in the downstream areas. At the same time, according to the widely applicable standard of rare earth resources exploitation, that is the boundary grade of ion-adsorption rare earth ore in southern China (∑REE = 500 mg·kg-1), we found that the content of REEs in the study areas was close to or exceeded this standard, and the maximum ∑REE of Guozhai Reservoir (869.11 mg·kg-1) was much larger than this standard. Therefore, the redeposited rare earth in Changting Country has high reuse potential under the current scarce resources.

Stability analysis of roadbed under flood scouring.

Soil roadbed along the river suffers from water erosion at the bottom and collapse at the top under flood scouring, which leads to the suspension of upper pavement slab. In order to ensure the safety of soil roadbed along the river, this study explored the development mechanism of soil roadbed damage by flood in actual cases, and proposed the evolution process of instability under roadbed scouring. The stability law of roadbed along the river under flood scouring was analyzed, and the stability safety factor was corrected to analyze the sensitivity of water depth, flow rate, river bending angle and stability safety factor K in working conditions. The sensitivity of width and height of soil roadbed after flood scouring to water depth, flow velocity, river bending angle was investigated. Moreover, numerical simulation was carried out to determine the displacement nephogram and maximum shear stress nephogram of soil roadbed along the river under the conditions of road surface and roadbed load, vehicle loading or constant change of water depth. By comparing the above theories and engineering cases, the water damage mechanism of soil roadbed along the river was further verified.

A GIS-based modified PAP/RAC model and Caesium-137 approach for water erosion assessment in the Raouz catchment, Morocco.

Water erosion poses a significant environmental threat in the Mediterranean region, with pronounced impacts observed throughout Morocco. It impairs soil quality and disrupts both sediment transport and water availability. Contributing factors range from natural (climate, topography, and geology) to anthropogenic (land use, vegetation cover, and management). This study introduces an improved Priority Actions Program/Regional Activity Centre (PAP/RAC) model, enriched with GIS and the Caesium-137 (137Cs) technique, to investigate erosion within Morocco's Raouz basin. Enhanced with additional variables including soil types, slope length, rainfall erosion potential, slope orientation, soil moisture, and land surface temperature, the model transcends the classical approach, promoting granularity and precision in predictions. In addition to the comprehensive model, the 137Cs method, which discerns long-term soil erosion and redistribution, provides a dual-faceted validation, bolstering the robustness of this project's erosion risk evaluation. This study's outcomes underscore the gravity of the erosion hazard with significant soil depletion rates ranging from 8.1 to 20 t ha-1 yr-1, demonstrating the model's alignment with empirical data, affirming its utility. The modified PAP/RAC model concurs with the 137Cs data, demonstrating its usefulness for water erosion assessment and management in similar areas.

Synthesis of soybean soluble polysaccharide-based eco-friendly emulsions for soil erosion prevention and control.

This paper introduces the synthesis of an environmentally friendly emulsion that can be used as a soil anti-water erosion material. SSPS-g-P(BA-co-MMA-co-AA) emulsions were prepared using free radical copolymerization with soybean soluble polysaccharide (SSPS), acrylic acid (AA), butyl acrylate (BA), and methyl methacrylate (MMA). The structure, thermal stability, and morphology were characterized using FT-IR,TG,SEM, and particle diameter analysis. The resistance to water erosion, compressive strength and water retention of emulsion-treated loess/laterite was studied and germination tests were conducted. The results demonstrated that the duration of washout resistance of loess with 0.50 wt% emulsion exceeded 99 h, and the water erosion rate was 56.0 % after 72 h, while the water erosion rate of pure loess is 100.0 % after 4 min;the duration of washout resistance of laterite with 0.50 wt% emulsion exceeded 2 h, which was 8 times longer than pure laterite;The compressive strengths of 0.5 wt% emulsion-treated loess/laterite were 3.5 Mpa and 5.8 MPa, respectively, which were 7 and 9 times higher than that of pure soil. The plant seeds germinated normally half a month after planting. These findings suggest that emulsions can be used to control soil erosion without affecting the germination of plant seeds.

Selective uneven enrichment of soil organic carbon among different-sized sediments under a rain-induced overland flow: 13C stable isotope evidence.

Soil organic carbon (SOC) enrichment varies among sediments of different sizes during rain-induced overland flow erosion. This selective transport of SOC is complex in conjunction with the exposure of labile and stable organic carbon (OC), accompanied by heterogeneous aggregate disintegration under raindrop effects. Utilizing the variations in δ13C values of SOC fractions, we traced this selective transport, linking it to aggregate-wrapped SOC changes during erosion. A modified soil pan facilitated the simultaneous monitoring of splash and sheet erosion via artificially simulated rainfall, with control over the intensity and slope. Aggregate composition, SOC distribution, and δ13C values in the erosion samples were analyzed. The results indicated that distinct sorting existed within the aggregate fragments. Along with SOC variation among different sediment sizes, the proportions of clay and fine silt within sediment aggregates increased as a function of slope and rainfall intensity, whereas particulate OC within aggregates decreased. The SOC enrichment ratios (ERocs) and δ13C values in splash-eroded sediments were positively correlated with those in sheet-eroded sediments. The ERocs in splash-eroded sediments were lower than those in sheet-eroded sediments, but δ13C values were the opposite. Moreover, δ13C values of SOC enriched in sediment particles of all sizes from aggregate stripping were lower than those of the original soil. This indicates that raindrop hits promote heavy C loss during sheet erosion, which is different for mineral-associated and particulate OC. As the slope and rainfall intensity increased, δ13C values for all sediment sizes decreased over the course of erosion. Interestingly, the highest δ13C values were observed under a rainfall intensity of 60 mm h-1, whereas the highest SOC concentrations were noted on a 5° slope. These observations suggest divergent mechanisms affect δ13C values and SOC concentrations in eroded sediments. All these results verified that selective sorting existed for the light SOC fraction. Finally, the internal selective transport of one SOC fraction may explain the enhanced mineralization and reaggregation capacity of the deposited sediments.

A review of the characteristics of rainfall simulators in soil erosion research studies.

Rainfall simulators are widely employed in soil erosion studies, and it is common for these simulators to be customized to address specific research questions. Nevertheless, there are certain characteristics that rainfall simulators should fulfill in the context of soil erosion studies. Rainfall simulators should simulate natural precipitation as accurately as possible. It is essential to monitor the size spectrum of generated raindrops, their maximum or terminal velocity, the uniformity of the surface distribution of rain, the kinetic energy and the overall intensity of the rain. This review aims to outline the characteristics and the corresponding measurement methods for rainfall simulators in soil erosion research. Electronic instruments like distrometers are considered more suitable for precise and comprehensive measurements than traditional instroments or literature based derivatives. By adhering to these characteristics, researchers can ensure the reliability and accuracy of their findings. Consequently, this overview serves as a valuable resource for researchers seeking to employ rainfall simulators in their investigations of soil erosion.

Estimation of annual soil CO2 efflux under the erosion and deposition conditions by measuring and modeling its respiration rate in southern China.

Soil respiration (Rs) is a crucial ecological process of carbon (C) cycling in the terrestrial ecosystems, and soil erosion has a significant impact on its C budget and balance. However, the variations of Rs rate and their CO2 efflux induced by erosion are currently poorly understood. To this end, four landscape positions (top, up, middle and toe) with different erosional and depositional characteristics were selected on a typical eroded slope in southern China to conduct field experiments, aiming to explore the effects of erosion and deposition on Rs among various sites. From March 2021 to February 2022, the in-situ Rs were measured using an automated soil respiration system, together with soil temperature at 5 cm depth (Ts5) and water content at 10 cm depth (SWC10). We initially constructed various Rs models across a one-year period, based on its relationships with Ts5 and SWC10. Subsequently, the seasonal changes of Rs at different erosional sites were simulated by the optimum models, and their annual CO2 fluxes were further estimated. The results showed that Rs rates at all sites displayed a bimodal seasonal pattern, with the highest values in May and August. And the measured Rs of the eroding and depositional sites were 0.05-7.71 and 1.47-13.03 µmol m-2 s-1, respectively. Also, remarkably higher Ts5 and SWC10 were observed in depositional sites versus the eroding sites (P < 0.05). Additionally, Rs rates at all sites were positively correlated with SOC and Ts5, but negatively correlated with SWC10. Herein, Rs models to single- and double-variable were established at different positions, and we found that the fitted R2 and AIC differed on various sites, primarily in erosional and depositional sites. Furthermore, through the best-fitting models (higher R2 and lowest AIC) we screened, the average Rs values of 3.03 and 4.46 µmol m-2 s-1 were quantitatively estimated for the eroding and depositional sites, respectively. Finally, it could be further assessed that the mean annual soil CO2-C efflux of eroded site (1104.14 g m-2) was significantly lower than that of depositional site (1629.46 g m-2). These findings highlighted the effect of erosion and deposition on Rs, which will facilitate a better understanding of C cycling in terrestrial ecosystems.

Spatial assessment of soil erosion by water using RUSLE model, remote sensing and GIS: a case study of Mellegue Watershed, Algeria-Tunisia.

Soil erosion is an important global phenomenon that can cause many impacts, like morphometry and hydrology alteration, land degradation and landslides. Moreover, soil loss has a significant effect on agricultural production by removing the most valuable and productive top soil's profile, leading to a reduction in yields, which requires a high production budget. The detrimental impact of soil erosion has reached alarming levels due to the exacerbation of global warming and drought, particularly in the arid climates prevalent in Tunisia and Algeria and other regions of North Africa. The influence of these environmental factors has been especially evident in the catchment of Mellegue, where profound vegetation loss and drastic changes in land use and cover, including the expansion of urban areas and altered agricultural practices, have played a significant role in accelerating water-induced soil loss between 2002 and 2018. The ramifications of these developments on the fragile ecosystems of the region cannot be overlooked. Accordingly, this study aimed to compare soil losses between 2002 and 2018 in the catchment of Mellegue, which is a large cross-border basin commonly shared by Tunisian-Algerian countries. The assessment and mapping of soil erosion risk were carried out by employing the Revised Universal Soil Loss Equation (RUSLE). This widely recognised equation provided valuable insights into the potential for erosion. Additionally, changes in land use and land cover during the same period were thoroughly analysed to identify any factors that may have contributed to the observed risk. By integrating these various elements, a comprehensive understanding of soil erosion dynamics was achieved, facilitating informed decision-making for effective land management and conservation efforts. It requires diverse factors that are integrated into the erosion process, such as topography, soil erodibility, rainfall erosivity, anti-erosion cultivation practice and vegetation cover. The computation of the various equation factors was applied in a GIS environment, using ArcGIS desktop 10.4. The results show that the catchment has undergone significant soil water erosion where it exhibits the appearance of approximately 14,000 new areas vulnerable to erosion by water in 2018 compared to 2002. Average erosion risk has also increased from 1.58 t/ha/year in 2002 to 1.78 in 2018, leading to an increase in total estimated soil loss of 54,000 t/ha in 2018 compared to around 25,500 t/ha in 2002. Maps of erosion risk show that highly eroded areas are more frequent downstream of the basin. These maps can be helpful for decision-makers to make better sustainable management plans and for land use preservation.

Study on Low-Temperature Performance Decay of Composite-Modified Porous Asphalt Mixture under Medium- and High-Temperature Water Erosion.

This paper studies the decay law of low-temperature crack resistance performance of rubber powder basalt fiber composite-modified porous asphalt concrete (CM-PAC) under medium- and high-temperature water erosion. Firstly, the prepared Marshall specimens were subjected to water erosion treatment at different temperatures of 20 °C, 40 °C, and 60 °C for 0-15 days. Then, the processed specimens were subjected to low-temperature splitting tests, and acoustic emission data during the splitting test process were collected using an acoustic emission device. It can be seen that the low-temperature splitting strength and low-temperature splitting stiffness modulus of CM-PAC gradually decrease with the increase in water erosion time. The maximum reduction rates of the two compared to the control group reached 72.63% and 91.60%, respectively. The low-temperature splitting failure strain gradually increases. Under the same erosion time, the higher the temperature of water, the more significant the amplitude of changes in the above parameters. In addition, it is shown that as the water erosion time increases, the first stage of loading on the specimen gradually shortens, and the second and third stages gradually advance. As the water temperature increases and the water erosion time prolongs, the acoustic emission energy released by the CM-PAC specimen during the splitting process slightly decreases. The application of acoustic emission technology in the splitting process can clarify the changes in the failure pattern of CM-PAC specimens during the entire loading stage, which can better reveal the impact of medium- to high-temperature water on the performance degradation of CM-PAC.

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Understanding the effects of upslope runoff and soil pipe collapse on slope water erosion can provide scien-tific basis for preventing Mollisol degradation caused by soil erosion. We conducted an experiment to investigate the effects of upslope inflow rate and soil pipe collapse on slope water erosion and to quantify the contribution of soil pipe erosion to slope soil erosion. The experiment included three inflow rates (30, 40, and 50 L·min-1) and three near-surface soil hydrological conditions (without soil pipe: NP; with soil pipe but no pipe flow: PF0; with pipe flow: PF1). The results showed that: 1) Slope soil erosion increased with increasing inflow rates; when the inflow rate increased from 30 L·min-1 to 40 and 50 L·min-1, slope soil erosion increased by 100.0%-111.5% and 214.8%-289.2%, respectively. 2) The soil pipe occurrence and pipe flow formation aggravated the slope water erosion process. At inflow rates of 30, 40, and 50 L·min-1, slope soil loss under the PF0 and PF1 treatments were 1.4-1.6 times and 1.7-2.1 times of that under the NP treatment. The contribution of soil pipe erosion to slope soil loss was 26.7%-37.6% under the PF0 treatment and 40.5%-51.9% under the PF1 treatment. 3) Soil pipe collapse intensified the rill erosion process. Compared with the NP treatment at 30, 40, and 50 L·min-1 inflow rate, rill erosion amounts under the PF0 and PF1 treatments increased by 38.1%-66.0% and by 93.7%-128.4%, respectively. Our results suggested that increasing upslope inflow rate resulted in higher surface runoff velocity, which promoted runoff detachment and transport capacity, and then aggrandized the amount of slope soil erosion. Moreover, soil pipe collapse exacerbated rill erosion process. When the soil pipe collapsed, all surface runoff was converted to soil pipe flow, which accelerated flow velocity and slope soil erosion process, and then increased the amount of slope soil erosion.

Adhesion Properties of Recycled High-Viscosity Asphalt-Aggregate Interface under Dynamic Water Erosion.

The drainage of asphalt pavement requires the use of a large amount of high-viscosity-modified asphalt, which faces the service environment under dynamic water erosion. The feasibility of recycling high-viscosity-modified asphalt should be investigated to facilitate sustainable infrastructure construction. This study used ultrasonic equipment to simulate dynamic water erosion test conditions and tested the adhesion performance of different types of recycled high-viscosity asphalt at various environmental temperatures. The adhesion energy index and microstructure of recycled high-viscosity asphalt were analyzed using the contact angle test and AFM test. The results demonstrate that the higher the environmental temperature, the worse the anti-stripping performance of recycled high-viscosity asphalt. From the perspective of adhesion performance indicators, a 6% recycling agent dosage is more conducive to restoring the performance of aged high-viscosity -modified asphalt. The AFM test showed that the microstructure of high-viscosity -modified asphalt represented significant changes with an increase in the recycling agent content, and the change in the adhesion force of recycled high-viscosity -modified asphalt was consistent with the results of macroscopic adhesion performance tests. This study illustrates the applicability of implementing regeneration technology for the recycling of aged drainage asphalt pavement.

Soil erosion assessment in the Amazon basin in the last 60 years of deforestation.

Anthropic activities in the Amazon basin have been compromising the environmental sustainability of this complex biome. The main economic activities depend on the deforestation of the rainforest for pasture cattle ranching and agriculture. This study analyzes soil erosion to understand how deforestation has impacted the Amazon basin in this context, using three land-use temporal maps (1960, 1990, 2019) through the revised universal soil loss equation (RUSLE). Our results point to a significant influence of deforestation due to the expansion of agricultural and livestock activities on soil erosion rates in the Amazon Basin. The average soil erosion rate has increased by more than 600% between 1960 and 2019, ranging from 0.015 Mg ha-1 year-1 to 0.117 Mg ha-1 year-1. During this period, deforestation of the Amazon rainforest was approximately 7% (411,857 km2), clearly the leading cause of this increase in soil erosion, especially between 1990 and 2019. The south and southeast regions are the most impacted by increasing soil erosion, in which deforestation was accelerated for expanding agriculture and livestock activities, mainly in the sub-basins of the Madeira, Solimões, Xingu, and Tapajós that present soil erosion increases of 390%, 350%, 280%, and 240%, respectively. The sub-basins with the highest sediment delivery rate (SDR) are under the influence of the Andes, highlighting Solimões (27%), Madeira (13%), and Negro (6%) due to the increase in the soil erosion rate increase in these sub-basins.

Soil erodibility for water and wind erosion and its relationship to vegetation and soil properties in China's drylands.

Drylands with fragile socio-ecological systems are vulnerable to soil erosion. China's drylands face the dual threat of water (WAE) and wind erosion (WIE). To mitigate soil erosion in drylands, China has implemented numerous ecological restoration measures. However, whether vegetation and soil have different effects on soil erodibility for water erosion (soil erodibility, K) and wind erosion (soil erodible fraction, EF) in drylands is unclear, hindering decision makers to develop suitable ecological restoration strategies. Here, we conducted a large-scale belt transect survey to explore the spatial variation of K and EF in China's drylands, and examined the linear and nolinear effects of aridity (aridity index), vegetation (fractional vegetation cover and below-ground biomass), and soil properties (bulk density, total nitrogen, and total phosphorus) on K and EF. The results showed in China's drylands that the K ranges from 0.02 to 0.07, with high values recorded in the northern Loess Plateau and the eastern Inner Mongolia Plateau. The EF ranges from 0.26 to 0.98, and shows longitudinal zonation with higher values in the east and lower values in the west. Aridity has a negative linear effect on K and an inverse U-shaped nonlinear effect on EF. Aridity can affect K and EF by suppressing vegetation growth and disrupting soil properties. However, K and EF had different responses to some vegetation and soil variables. K and EF had opposite relationships with soil bulk density, and EF was significantly affected by fractional vegetation cover, while K was not. Overall, the effects of aridity and soil properties on soil erodibility were more pronounced than those from vegetation, whose effect on soil erodibility was limited. This study provides relevant information to support reducing soil water and wind erosion by highlighting the hotspot areas of soil erodibility, relevant for implementing vegetation restoration and soil conservation measures in drylands.

Effects of Wind-Water Erosion and Topographic Factor on Soil Properties in the Loess Hilly Region of China.

Wind and water erosion processes can lead to soil degradation. Topographic factors also affect the variation of soil properties. The effect of topographic factors on soil properties in regions where wind and water erosion simultaneously occur remains complicated. To address this effect, we conducted this study to determine the relationships between the changes in wind-water erosion and soil properties in different topographic contexts. We collected soil samples from conical landforms with different slope characteristics and positions in the wind-water erosion crisscross region of China. We examined the soil 137Cs inventory, soil organic carbon (SOC), total nitrogen (TN), soil particles, soil water content (SWC), and biomass. 137Cs was applied to estimate soil erosion. The results show that the soil erosion rate followed the order of northwest slope > southwest slope > northeast slope > southeast slope. The soil erosion rate on the northwest slope was about 12.06-58.47% higher than on the other. Along the slopes, the soil erosion rate decreased from the upper to the lower regions, and was 65.65% higher at the upper slope than at the lower one. The change in soil erosion rate was closely related to soil properties. The contents of SOC, TN, clay, silt, SWC, and biomass on the northern slopes (northwest and northeast slopes) were lower than those on the southern slopes (southeast and southwest slopes), and they were lower at the upper slope than at the lower one. Redundancy analysis showed that the variation in soil properties was primarily affected by the slope aspect, and less affected by soil erosion, accounting for 56.1% and 30.9%, respectively. The results demonstrate that wind-water erosion accelerates the impact of topographic factors on soil properties under slope conditions. Our research improves our understanding of the mechanisms of soil degradation in gully regions where wind and water erosion simultaneously occur.

Spatiotemporal evolution of soil water erosion in Ningxia grassland based on the RUSLE-TLSD model.

Accurate assessment of grassland soil erosion before and after grazing exclusion and revealing its driving mechanism are the basis of grassland risk management. In this study, the long-term soil erosion in Ningxia grassland was simulated by integrating and calibrating the transport limited sediment delivery (TLSD) function with the revised universal soil loss equation (RUSLE) model. The differential mechanisms of soil loss were explored using the GeoDetector method, and the relative effects of precipitation changes (PC) and human activities (HA) on grassland soil erosion were investigated using double mass curves. The measured sediment discharges from six hydrological stations verified that the RUSLE-TLSD model could reliably simulate water erosion in Ningxia. From 1988 to 2018, the water erosion rate of grassland in Ningxia ranged from 74.98 to 14.98 t⋅ha-1⋅a-1, showing an overall downward trend. July to September is the period with the highest of water erosion. The slope is the dominant factor influencing the spatial distribution of water erosion. After grazing exclusion, the net water erosion rate in Ningxia grassland and sub-regions decreased significantly. The double mass curves results show that human activities were the main driver of net erosion reduction. The focus of water erosion control in Ningxia is to control soil erosion in different terrains and protect grassland with slopes greater than 10°.

Estimación del factor de cobertura vegetal en la Cuña Boscosa Santafesina utilizando índices espectrales / Estimation of the cover management factor in the usle using spectral indices

Resumen La Cuña Boscosa Santafesina ha sufrido desmontes que causaron fragmentación y deterioro. Los suelos se destinaron a la actividad ganadera y agrícola, con labranza tradicional, favoreciendo procesos de erosión hídrica. La Ecuación Universal de Pérdida de Suelo es ampliamente utilizada para predecir la pérdida de suelo, siendo el factor C (cobertura y manejo), uno de los principales componentes. Para su determinación se pueden utilizar imágenes satelitales, siendo el objetivo de este trabajo obtenerlo para un sitio de la Cuña Boscosa. Para esto, se delimitó una microcuenca con Sistemas de Información Geográfica e información satelital. Se identificaron sectores según el uso del suelo y se obtuvo el factor C utilizando el Índice de Vegetación de Diferencia Normalizada de doce imágenes del período de julio de 2020 a mayo de 2021. Los valores obtenidos también fueron comparados con las precipitaciones diarias de la zona. Como resultado se generaron mapas del factor C para cada fecha y para el valor promedio del período estudiado. Aunque el factor C promedio en sectores de vegetación natural fue similar al del sector cultivado, este último presentó una mayor variación que acompañó al desarrollo de los cultivos. Además, las tierras cultivadas presentaron menor cobertura vegetal en los períodos de mayores precipitaciones, dejando al suelo expuesto al efecto erosivo de la lluvia. Esta metodología es promisoria para cuantificar el factor C durante el ciclo de un cultivo y evaluar su dinamismo espacio-temporal, pero deberá validarse con datos de campo.

Abstract The Cuña Boscosa Santafesina has suffered deforestation that caused fragmentation and deterioration. The soils were used for livestock and agricultural activities with traditional tillage, favouring water erosion processes. The Universal Soil Loss Equation is widely used to predict soil loss, with C factor (cover and management) being one of the main components. For its determination, satellite imagery can be used, being the objective of this paper to obtain it for a site of the Cuña Boscosa. To achieve this, a micro-basin was delimited with Geographic Information Systems and satellite information. Sectors were identified according to the land use and the C factor was obtained using the Normalized Difference Vegetation Index of twelve images from the period July 2020 to May 2021. The values obtained was compared with daily rainfall in the area. As results, C factor maps were generated for each date and for the average value of the period studied. Although the average C factor in sectors of natural vegetation was similar to that of the cultivated sector, the latter presented a greater variation that accompanied the development of the crops. In addition, cultivated land had less vegetal cover in periods of higher rainfall, leaving the ground exposed to the erosive effect of the rain. This methodology is promising for quantifying C factor during a crop cycle and evaluate is spatio-temporal dynamism, but it must be validated with field data.

Improving estimation of water soil erosion by introducing lithological formation for environmental remediation.

Soil erosion is a serious and complex environmental problem worldwide, especially in the centre west of Tunisia. Whereas the construction of hill reservoirs is part of the soil and water conservation strategy, many of these have a siltation problem. Dhkekira is one of the smallest watersheds in central Tunisia whose most lithological formation consists of materials that are quite susceptible to water erosion. Due to the lack of low-scale lithological data, digital IR aerial photos with 2 m spatial resolution were considered. A semi-automatic classification of aerial photos, based on the image's textural indices is developed. The lithologic map extracted from aerial photos was used as input for ANSWERS-2000 water erosion model. Results obtained indicate first, with the semi-automatic classification of the mean and standard deviation of the thumbnail histograms that image output could help to give an idea about the existence of some surface lithological formation. The model applied to Dhkekira watershed showed that the spatial difference in water erosion was not caused only by land cover and slope, but also by lithological formation. The percentage of each lithological formation in sediment yield at the Dhkekira hill reservoir was estimated to be 69% sediment yield from Pleistocene and 19.7% from Lutetian-Priabonian.