Erosion Area Research Articles

Effect of bridge height on airflow and aeolian sand flux near surface along the Qinghai-Tibet Railway, China

In this work, we studied the near-surface flow field structure of railway bridges with different heights through field investigation and wind tunnel simulation experiments. Meanwhile, we simulated the distribution of sand accumulation around a bridge via CFD software based on the sand accumulation around the Basuoqu bridge in the Cuona Lake section of the Qinghai–Tibet Railway. Results show that the sand around this railway bridge is mainly from the lake sediment on the west side of the railway and the weathered detritus on the east side. The height of the railway bridge in the sandy area affects the distribution of the near-surface flow field and the variation in speed on both sides of the bridge. The wind speed trough on both sides of the 6 m high bridge is higher, and the horizontal distance between the wind speed trough and the bridge section is 1.5 times that of the 3 m high bridge. Wind speed attenuates in a certain range on the windward and leeward sides of the bridge, forming an aeolian area; under the beam body, it is affected by the narrow tube effect, forming a wind erosion area. The height of the bridge determines its sand transport capacity. Under certain wind conditions, the overhead area at the bottom of the 3 m high bridge and its two sides do not have the sand transport capacity, so sand accumulates easily. Nevertheless, the sand accumulation phenomenon gradually disappears with the increase in bridge clearance height. The objectives of this study are to reveal the formation mechanism of sand damage for railway bridges, provide theoretical support for the scientific design of railway bridges in sandy areas, and formulate reasonable railway sand prevention measures to ensure the safety of railway running, which have certain theoretical significance and practical value.

MODERN PROCESSES IN THE BEADED CHANNELS OF STEPPE RIVERS OF THE KHOPER-BUZULUK PLAIN

Beaded-shaped channels (or chain-of-ponds), characterized by alternating lake-like extensions and narrow runs, are widespread on small rivers of the steppe zone of Russia. Extensions of channels - beads (pools or ponds), with a depth of up to 5-6 m, are of great importance for cattle breeding, providing a watering place during the dry periods of the year, when the flow of small rivers stops. However, the mechanisms of their specific channel shape formation are still debatable: it is explained by uneven siltation of channels, formation of whirlpools, groundwater discharge, karst processes or relict thermokarst. The aim of the study was to assess the role of water flow in the formation and support of the beaded shape of river channels. The tasks were to reveal the hydrological regime of the Kardail and Kupava rivers, determine the hydrodynamics of the flow in beads and runs, describe the characteristics of erosion and accumulation processes and the sediment transport, as well as to identify relict elements of the channel and floodplain structure that do not correspond to modern water state. Water flow of the studied rivers shows a long-term decrease in snowmelt flood, as evidenced by the rare flooding of the high-level floodplain, low rates of bank dynamics, and the discrepancy between the size of meanders and the width of the channel. The annual sediment load of the studied beaded rivers is low, estimated at 6,05 t/km2 in 2023. The reason is a low supply of sediments from the catchment area and low rates of erosion of channel bed and banks built of clay and silt. The present-day dynamics of water flow do not help the deepening and expansion of the beads. The flow reaches maximum speed (up to 1-1,3 m/s) in channel runs, while in channel extensions flow speeds drop to 0-0,3 m/s, supporting the sediment accumulation, despite the presence of whirlpools. A significant part of channel extensions is located on sites of former pools of the ancient meandering channel, inherited by the modern watercourse. On the former riffles the channel narrowed and a low-level floodplain was formed. Deep channel extensions were preserved due to the low sediment load and its fine composition, which prevents its rapid settling from the suspension. The results of the study suggest possible contribution of other factors to the formation of original deep pools, including the cryogenic ones.

Experiment on the Hydrodynamic Characteristics of Plunging Flows in Bedrock Canyon Bends

AbstractBedrock river incision drives the evolution of the Earth's landscape and is influenced by river hydraulic power. However, the relationship between plunging flows and the curvature of bedrock canyons is poorly understood, which encouraged us to explore how the bend's curvature and undulating beds affect plunging flows. A generalized physical model was built to investigate the hydrodynamic characteristics of plunging flows in a constant curvature flume with plain and undulating beds. Our experimental findings demonstrated that plunging flows were related to secondary circulation, topography, and width‐to‐depth ratios. Plunging flows occurred when secondary circulation reached its peak, and as secondary circulation vanished, the intensity of plunging flows decreased. The undulating bed topography in the bedrock bends suppressed secondary circulation and the development of plunging flows. Bed topography may be a dominant factor in plunging flows in bedrock bends. The potential erosion area in bedrock bends was related to the intensity of plunging flows, which caused velocity inversion to increase the shear stress near the bed. With higher discharges and undulating beds, the intensity of the transverse shear stress of the riverbed near the center was greater. The potential erosion area in bedrock bends was concentrated at the center of the cross‐section around the bend apex upstream. Our experimental results can improve incision models in terms of the distribution of shear stress and flow structure in bedrock bends.

Assessing soil erosion through the implementation of the RUSLE model and geospatial technology in the Isser watershed, northern Algeria

ABSTRACT Soil erosion, triggered by rainfall and runoff, poses a significant challenge for Mediterranean countries, leading to sedimentation in dam reservoirs, decreased storage capacities, and reduced agricultural fertility. Among various erosion estimation models, the RUSLE equation stands out for its consistency and minimal data requirements. The present study aims to utilize geographic information systems (GIS) software to quantify and map soil loss in the Isser watershed in northern Algeria employing the RUSLE model to strategically plan development measures and prioritize actions to safeguard high-risk erosion areas. Implementing the RUSLE-GIS approach involves integrating multiple datasets, including precipitation, soil erodibility, topography, vegetation cover, and anti-erosion practices. By combining these factors, a comprehensive map depicting erosion rates is generated. The findings categorize potential soil erosion into six groups, ranging from very low to extremely high. They indicate that 61.5% of the Isser Basin faces erosion, varying from moderate to very high (>20 t ha−1 year−1). In addition, 25% of the total surface experiences erosion levels classified as high to very high (>50 t ha−1 year−1). This underscores the urgent need for anti-erosive measures. These measures aim to safeguard the basin's soils, extend the lifespan of existing dam reservoirs (Koudiet Acerdoune and Beni Amran), and preserve their water potential.

Evaluation of sand subgrade seepage erosion caused by buried pipeline leakage

Leakage from buried pipelines can lead to an increase in the water content of the subgrade soils and a rise in the water table, leading to soil loosening, erosion and ultimately the formation of hidden voids and roadway collapses. This study presents a discrete-element method and validates its accuracy by utilising cavity data from model experiments. It investigates the mechanism of seepage erosion resulting from pipe leakage and analyses the development of the soil arch effect. Furthermore, it discusses the influence of sand void ratio and particle size on sand seepage erosion. The results indicate that the erosion area is primarily affected by the void ratio and particle size. In comparison to soil particles ranging from 0.1 to 5 mm and from 2 to 5 mm, those with sizes between 0.1 mm and 2 mm generate areas of erosion and loosening that are approximately 40% larger. The proposed model offers a precise analysis of the developmental process and the extent of seepage erosion, thereby contributing to the prediction of potential road cavity areas based on dynamic changes in key factors such as subgrade soil type and groundwater level.

Capacity of Forests and Grasslands to Achieve Carbon Neutrality in China

Forests and grasslands play an important role in carbon cycling. They not only absorb CO2 from the air through vegetation biomass and soil carbon sinks, but also reduce and control the horizontal transport of soil carbon (i.e., reinforcing soil carbon storage via soil conservation), thus avoiding erosion-induced CO2 emissions. In this study, vegetation biomass and soil carbon sinks, soil carbon reinforcement and reduced carbon emissions via soil conservation by forests and grasslands were quantified on the scale of the whole of China. The analysis was based on the distribution of biomass and the soil carbon pool and soil erosion rates derived from national surveys, as well as carbon density values from field surveys and literature. In 2021, forests and grasslands in China generated 394.18 Mt C/year (y) of steady-state carbon sinks through vertical biomass and soil absorption. The biomass carbon sinks of grasslands, and those of leaves, twigs, flowers and fruits of the forests, were not taken into account when quantifying the stable biomass sink, because they can become net producers of CO2 due to seasonal withering and carryover, or they can form soil organic carbon as potential soil carbon sinks. The amount of horizontal soil carbon reinforcement in China’s forests and grasslands in 2021 was 20.31 Mt C/y, which was positively correlated with the reduction in the water erosion area; consequently, vertical emissions of approximately 14.89–29.78 Mt of CO2 into the atmosphere were avoided. Overall, in 2021, China’s forests and grasslands absorbed atmospheric CO2 and reduced emissions by 1.46–1.47 Gt CO2/y, equivalent to approximately 13% of China’s annual fossil CO2 emissions. This study demonstrates the fact that the adoption of forest and grassland measures sequesters carbon in soil and biota and reduces the risks of CO2 emissions by both vertical and horizontal paths, which is important for achieving carbon neutrality and mitigating climate change.

Simulation of Elbow Erosion of Gas–Liquid–Solid Three-Phase Shale Gas Gathering Pipeline Based on CFD-DEM

Shale gas gathering pipelines often contain liquid water and solid sand in the early stage of production, which leads to the failure of pipeline components easily under the action of gas–liquid–solid three phases. A computational fluid dynamics (CFD) model based on the fluid volume method (VOF) and discrete element method (DEM) was established to study the flow law of gas–liquid–solid three-phase flow in the elbow of shale gas gathering pipeline and the erosion law of the inner surface of the elbow was studied by coupling the Oka erosion prediction model. By comparing the experimental results of erosion damage of the elbow, it is found that the model established can well predict the erosion characteristics and erosion amount under the action of three phases. Combined with the field pipeline parameters and operating conditions, the paper further simulates the elbow erosion behavior under relevant working conditions. The results show that the particles rotate clockwise from the outer wall of the pipe through the bottom of the pipe when passing through the elbow under the action of gas and water phases. When the gas velocity increases, the particles at the elbow mainly gather at the bottom of the elbow and the wall of the outer arch. When the water content increases gradually, the particles gathered on the outer arch wall of the elbow move along the outer arch wall of the elbow and face the inner arch surface gradually, and the erosion area is mainly concentrated on the outer arch wall of the elbow and the outlet horizontal pipe. Under the condition of the liquid phase, the movement characteristics of the water phase and particles in the elbow of the gas gathering pipeline and the erosion characteristics of the pipeline surface are obviously different from those under the condition of the gas–solid two-phase. The model and simulation results established in this paper provide a reference for the erosion damage protection of shale gas gathering pipeline elbow.

Failure analysis and numerical simulation of the regulating valve with particle erosion and cavitation erosion in the black-water treatment system

The black-water regulating valve is very easy to be damaged due to the erosion of the key components, such as valve spool and valve seat. This work presents the failure analysis of the spool and seat of regulating valve in the black-water treatment system. Scanning electron microscopy and X-ray energy-dispersive spectrometer were used to detect the morphology and chemical compositions of failure valve samples. The computational fluid dynamics method was also adopted to simulate the medium flow characteristics in black-water regulating valve. The results show that most erosion areas of the valve occur at the spool-seat throttle zone. The erosion profile is mainly manifested in plastic deformation pits, cutting abrasions, furrows, pinhole pits and impact pits. The particles and cavitation bubbles move toward the throttle zone driven by black-water medium, causing particles impact and bubbles collapse. The particle flow velocity in the throttle zone of the valve is between 50 and 175 m/s, while the maximum velocity can reach 175 m/s. The valve suffered severe particle erosion and cavitation erosion under the particle impact and bubble collapse, finally resulting in its failure.

Reliability of glenoid measurements performed using Multiplanar Reconstruction (MPR) of Magnetic Resonance (MRI) in patients with shoulder instability

PurposeMeasurement of glenoid bone loss in the shoulder instability can be assessed by CT or MRI multiplanar imaging and is crucial for pre-operative planning. The aim of this study is to determine the intra and interobserver reliability of glenoid deficiency measurement using MRI multiplanar reconstruction with 2D assessment in the sagittal plane (MPR MRI).MethodsWe reviewed MRI images of 80 patients with anterior shoulder instability with Osirix software using MPR. Six observers with basic experience measured the glenoid, erosion edge length, and bone loss twice, with at least one-week interval between measurements. We calculated reliability and repeatability using the intra-class correlation coefficient (ICC) and minimal detectable change with 95% confidence (MDC95%).ResultsIntra and Inter-observer ICC and MDC95% for glenoid width and height were excellent (ICC 0,89-0,96). For erosion edge length and area of the glenoid were acceptable/good (ICC 0,61-0,89). Bone loss and Pico Index were associated with acceptable/good ICC (0,63 -0,86)) but poor MDC95% (45 - 84 %). Intra-observer reliability improved with time, while inter-observer remained unchanged.ConclusionThe MPR MRI measurement of the anterior glenoid lesion is very good tool for linear parameters. This method is not valid for Pico index measurement, as the area of bone loss is variable. The pace of learning is individual, therefore complex calculations based on MPR MRI are not resistant to low experience as opposed to true 3D CT

Comparison of Oil Extraction and Density Extraction Method to Extract Microplastics for Typical Agricultural Soils in China

Microplastic pollution in agricultural soil threatens soil quality and human health which has attracted extensive attention worldwide. However, there is no uniform standard for microplastic extraction methods and the identification of microplastic component in different typical agricultural soils. In this study, an artificial simulation adding experiment was used in eight typical agricultural soil samples in China. The aim of the study was to use different methods for extraction, comparing the extraction rates of four microplastics and their influence on polymer identification using ATR- FTIR. The two separate methods were oil extraction (water + oil and saturated NaCl solution + oil), and density method (saturated NaCl solution). The four types of microplastics include polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyethylene (PE). We found that the oil extraction method effectively extracted four types of microplastics in agricultural soils, which varied from 83.33% to 100.00%. However, the extraction rate of PET under the oil extraction method and PP under the density method from Southern laterite area was lower than other soils. The presence of iron and aluminum ions influenced the extraction rates of microplastics in the Southwest laterite area. With the increase in microplastic density, the extraction rates of the density method decrease. The oil extraction methods with the cleaning of residual oil were recommended for the higher density microplastics. The density method was recommended for the lighter microplastics in agricultural soils. However, these two extraction methods were not ideal to extract the microplastics from the Southern laterite area and the appropriate extraction methods for laterite need to be further studied in the future. Our results can provide technical support for the extraction treatment and scientific microplastic pollution control of typical agricultural soils with different erosion areas.

Detection of mainland Kedah’s shoreline changes (2013-2020); a case study

Abstract Shoreline erosion and accretion are natural processes that involve the gradual change in the shape and position of coastlines due to the movement of water, sediment, and geological factors. These processes have significant implications for coastal environments, ecosystems, and human activities. Therefore, it is essential to frequently assess the shoreline changes for effective coastal management, sustainable development, and safeguarding valuable ecosystems. In the present study, shoreline condition along mainland Kedah (109 km) was investigated through remote sensing and geographical information system (GIS) techniques. The assessment was performed over the period of 7 years (2013 and 2020) by analysing the satellite images captured by Landsat-8 satellite Operational Land Imager (OLI) at 15 m resolution. Preprocessing was established by performing image geometric correction and registration. Next, the Support Vector Machines (SVMs) toolbox was used for image classification to define the water and non-water fields. Later, the shoreline was extracted from the classified images and overlaid in a geodetic base in ArcGIS software to detect shoreline changes. The results showed that the majority of mainland Kedah’s shoreline did not experience extensive erosion or accretion at which 54% of the shoreline (58.8 km) was found to be stable. Erosion was observed at 6 locations with a total length of 10.1 km (9% of the total shoreline length) which was mainly concentrated in the non-protected areas. On the other hand, shoreline accretion was observed at 19 locations with a total length of 40.1 km (37% of the total length). It is worth highlighting that the erosion areas were concentrated in the southern part of the coastline, while the accretion areas were distributed between the middle part and the north side of mainland Kedah’s shoreline.

Effect of La2Sn2O7 content on the anti-arc erosion capability of Ag-Ni-La2Sn2O7 composites

La2Sn2O7 has high melting point and excellent thermal stability, which improves the wettability between matrix and reinforcement. In this study, La2Sn2O7 powder was synthesized by chemical coprecipitation method, and Ag-Ni-La2Sn2O7 composites were prepared by vacuum hot-pressing sintering. The effect of La2Sn2O7 content on the arc erosion behavior of Ag-Ni-La2Sn2O7 composites was studied. The Ag-Ni-La2Sn2O7 (85:12:3) composite has the lowest arc energy and the highest breakdown strength. With the increase of La2Sn2O7 content, the defects on the cathode surface decrease and the erosion areas become flat. After arc erosion, the samples generate Ag2O, NiO, La2O3 and SnO2. In this study, the mechanism of La2Sn2O7 to improve the anti-arc erosion capability of composites is mainly enhancing the viscosity of the molten pool by the ``pinning'' action, consuming energy by the decomposition of La2Sn2O7, and the promotion of arc movement.

Endoscopic diagnosis and treatment of lichen planus of the esophagus

Purpose of the study: to attract the attention of endoscopists and doctors of other specialties to the problem of diagnosis and treatment of lichen planus of the esophagus. Materials and methods. From January 2010 to December 2023, lichen planus was the cause of dysphagia in 7 of 17 patients with unexplained cicatricial strictures of the esophagus. Our own experience and literature data on endoscopic semiotics and treatment of lichen planus of the esophagus are presented. Results of the study. Lichen planus is most often localized in the upper third of the esophagus and is accompanied by a narrowing of the esophageal lumen. The mucosa is hyperemic, dull, with areas of epithelial detachment, erosions, and fibrin deposits. All 7 patients had grade 2-3 esophageal strictures with isolated esophageal involvement (3) or oral involvement (4). Morphological changes were nonspecific: ulcerations, granulation tissue and fibrosis of the underlying layers, atrophy and thinning of the epidermis, acanthosis. Only in 2 cases apoptotic Civatte bodies were detected in the suprabasal layer, which is a characteristic feature of lichen planus of the esophagus. All patients underwent courses of endoscopic bougienage, supplemented by intramural injections of triamcinolone. This manipulations led to stabilization of the esophageal lumen at 10-15 mm without a tendency to restenosis. Conclusion. Further experience is needed to determine optimal treatment strategies, but it is critical to pay particular attention to symptom assessment in patients with skin disorders and odynophagia or dysphagia. These actions will facilitate an earlier diagnosis of lichen planus of the esophagus and increase the effectiveness of endoscopic treatment.

Modeling and Locating the Wind Erosion at the Dry Bottom of the Aral Sea Based on an InSAR Temporal Decorrelation Decomposition Model

The dust originating from the extinct lake of the Aral Sea poses a considerable threat to the surrounding communities and ecosystems. The accurate location of these wind erosion areas is an essential prerequisite for controlling sand and dust activity. However, few relevant indicators reported in this current study can accurately describe and measure wind erosion intensity. A novel wind erosion intensity (WEI) of a pixel resolution unit was defined in this paper based on deformation due to the wind erosion in this pixel resolution unit. We also derived the relationship between WEI and soil InSAR temporal decorrelation (ITD). ITD is usually caused by the surface change over time, which is very suitable for describing wind erosion. However, within a pixel resolution unit, the ITD signal usually includes soil and vegetation contributions, and extant studies concerning this issue are considerably limited. Therefore, we proposed an ITD decomposition model (ITDDM) to decompose the ITD signal of a pixel resolution unit. The least-square method (LSM) based on singular value decomposition (SVD) is used to estimate the ITD of soil (SITD) within a pixel resolution unit. We verified the results qualitatively by the landscape photos, which can reflect the actual conditions of the soil. At last, the WEI of the Aral Sea from 23 June 2020, to 5 July 2020 was mapped. The results confirmed that (1) based on the ITDDM model, the SITD can be accurately estimated by the LSM; (2) the Aral Sea is experiencing severe wind erosion; and (3) the middle, northeast, and southeast bare areas of the South Aral Sea are where salt dust storms may occur.

Soil erosion prediction and spatiotemporal heterogeneity in driving effects of precipitation and vegetation on the northern slope of Tianshan Mountain

Soil erosion changes become more unclear in the future due to climate change and increased human activity. However, the spatiotemporal heterogeneity in the driving effects of key factors on soil erosion remains inadequately understood on the northern slope of the Tianshan Mountains (NSTM). In this paper, the spatiotemporal evolution of soil erosion on the NSTM was evaluated in the historical period (2000–2015) by the Revised Universal Soil Loss Equation (RUSLE) model. Subsequently, the FLUS-CMIP6-RUSLE model was employed to predict soil erosion in the future period (2030–2050). Then, the GTWR model was used to dissect the spatiotemporal heterogeneity in the driving effects of precipitation and vegetation. The results indicated that soil erosion on the NSTM fluctuated from 2000 to 2015, increasing by 1.77 t ha −1 yr −1. Soil erosion areas mainly occurred in Changji City, Fukang City, Hutubi County, Mulei County, Qitai County, and Turpan City. The soil erosion modulus in 2030, 2040, and 2050 under different climate scenarios will be 26.56,28.83, and 37.49 t ha −1 yr −1, respectively. The spatial pattern of soil erosion is similar to the historical period. Precipitation was the main factor intensifying soil erosion in the eastern and western counties from 2000 to 2020, while the soil erosion change in central counties was affected by vegetation. In the future, soil erosion change in the counties (i.e., Karamay, Yili, Tacheng, Shihezi, Manas, Qitai, and Mulei) will be driven by precipitation. The vegetation will be the main driver of soil erosion change in central and eastern counties (i.e., Urumqi, Turpan, Fukang City, Jimsar County, and Changji City). This study firstly attempts to explore the spatiotemporal heterogeneity in the driving effects of precipitation and vegetation using Spatial-Temporal Geographically Weighted Regression (GTWR) in urban agglomerations of NSTM. It is meaningful to explore erosion-prone regions and to implement rational soil conservation measures in the study region and similar regions in the world.

An assessment of anticipated future changes in water erosion dynamics under climate and land use change scenarios in South Asia

Water erosion has emerged as a significant global environmental challenge, particularly in South Asia, recognized as one of the regions hardest to hit globally by climate change. This study aims to identify the potential erosion hotspots in South Asia and to assess areas under risk in the future due to climate and land use change scenarios. We utilized the Revised Universal Soil Loss Equation (RUSLE), an empirical erosion model, to estimate erosion for both historical and future periods, considering two distinct Shared Socio-economic Pathways (SSP126 and SSP585). The baseline model predicts a mean water erosion rate of 10.6 t. ha−1. year−1 in South Asia, with more than 30 t. ha−1. year−1 recorded for 6.3 % of the total land area. Notably, Bangladesh and Nepal exhibit significantly higher erosion rates than other South Asian countries. Further, our projection indicates an + 10 % increase in erosion rates during the near future (2021–2040) under SSP585 compared to the historical estimates. A substantial rise of approximately + 31 % and + 39 % in water erosion rates in South Asia is anticipated during the far future periods of 2061–2080 and 2081–2100 under SSP585. At the country level, Bangladesh (+42 %), Bhutan (+108 %), and Nepal (+70 %) are expected to experience substantial increases in erosion rates during the 2081–2100 period, with India projecting a + 38 % increase. Additionally, a significant + 35 % expansion in the spatial extent of high erosion areas (>30 t. ha−1. year−1) is foreseen in 2081–2100 under SSP585. Furthermore, under the low climate change scenario (SSP126), the impact on the erosion rates is minimal, while under SSP585, a substantial increase in erosion rates is anticipated. Regions such as Southern India, the arid and semi-arid areas near the India-Pakistan border, and the Himalayan foothills are identified as hotspots for significant changes in erosion rates. Acknowledging a certain level of uncertainty, our study provides valuable insights into erosion risk areas in South Asia and their plausible future impacts due to climate and land use changes. This information can assist policymakers in South Asian countries in developing national-level strategies for soil conservation and climate resilience.

Climate drivers of litterfall biomass dynamics in three types of forest stands on the Loess Plateau

Litterfall is a link in the energy flow and material cycling of ecosystems, which maintain the primary productivity of forests. However, there is no consensus regarding the factors driving for the litterfall biomass dynamics because of the high spatial–temporal heterogeneity. Herein, we investigated and compared the stand litter biomass, litterfall biomass, including its components in the pure Robinia pseudoacacia forest (RL), pure Platycladus orientalis forest (PL), and mixed forest of Robinia pseudoacacia and Platycladus orientalis (ML) from 2020 to 2022 in the gully erosion area of the Loess Plateau. Correlation and multiple regression analyses were used to study the relationships among the amount of stand litter, litterfall biomass, and seasonal temperature and precipitation. Significant variation was found in the seasonal and annual litterfall biomass of the three types of forest stands. Annual stand litter biomass was in the order PL > RL > ML, whereas the annual litterfall biomass was in the order RL > ML > PL. The seasonal dynamics of litterfall biomass of twigs, leaf and fruits exhibited a ‘unimodal pattern’ with a peak in October. Annual leaf litterfall biomass formed, the main body of litter in all the components, accounting for 57.14–67.05 % of the total litterfall biomass. The correlation and regression analysis results showed that the stand litter biomass was primarily affected by the average temperature. Total litterfall biomass and twigs, leaf, and fruits were significantly affected by the precipitation and the maximum temperature, however, flower litterfall biomass was mainly affected by the average temperature. Overall, our results indicated that temperature plays a key role in the climatic factors affecting forest litterfall processes, while different climatic conditions and biological characteristics probably caused the differences in litterfall biomass. In the long term, temperature will potentially play a leading role in altering carbon storage and nutrient cycling as the climate warms.

High-resolution soil erosion mapping in croplands via Sentinel-2 bare soil imaging and a two-step classification approach

Erosion-induced lateral soil redistribution leads to spatially heterogenous soil composition, which can be captured through the distinctive spectral reflectance of soils under varying levels of erosion influence. This points to the potential of using remotely sensed soil spectra to detect severe erosion and deposition hotspots in exposed croplands and, importantly, further differentiate the intra-class spectral variability of moderate erosion that often occupies the largest proportion. Here, we aim to develop a two-step erosion classification and mapping approach based on multitemporal compositing of Sentinel-2 bare soil images of a typical agricultural region (11,500 km2) of northeast China. A random forest classifier was firstly trained against the ground-truth data derived from very high resolution (VHR) imagery in Google Earth, with an overall accuracy of 91 % that allowed for clear delineation of severe erosion and deposition areas based on their distinct topographic and spectral features particularly in the red and red-edge bands. In the second step, the remaining area of moderate erosion (60.30 %) was further differentiated using Iterative Self-Organizing cluster unsupervised classification to yield a five-class soil erosion map at 10 m spatial resolution. The accuracy of the predicted map was successfully validated by independent Caesium-137 (137Cs) and soil organic carbon observations at catchment and regional scales, as revealed by significant inter-class differences in soil redistribution rates estimated from 137Cs inventory. The severe erosion class had a soil loss rate of 5.5 mm yr−1, suggesting that previous assessments have underestimated erosion severity. The spatial accordance of crop growth with soil erosion intensity, particularly in localized settings, further highlighted the potential of bare soil imaging for mapping the spatiotemporal development of soil erosion and its response to targeted sustainable cropland management efforts.

Rainstorm erosion difference and topographical changes induced by heavy rainfall between afforestation and grassland restoration catchments on the Chinese Loess Plateau

The frequency and intensity of heavy rainfall on the Chinese Loess Plateau (CLP) are increasing due to global climate change, which has caused severe soil erosion. However, precise evaluation of heavy rainfall-induced soil erosion, deposition, and related topographical changes at the catchment scale is lacking, and there is uncertainty as to how effectively trees can inhibit erosion, especially during heavy rainfall. In this study, we selected a pair of catchments with afforestation and natural grassland restoration on the CLP. Precise evaluation of erosion and topographic changes induced by heavy rainfall was conducted based on airborne light detection and ranging (LiDAR) data. In the grassland catchment, the gully bed area increased by 17.6 %, the gully slope and inter-gully land area decreased by 1.4 %, and the length of the gully shoulder line decreased by 4.4 %. Conversely, the forestland catchment experienced a decrease in gully bed area of 8.8 %, an increase in gully slope area of 5.3 %, a decrease in inter-gully land area of 9.9 %, and a decrease in the length of the gully shoulder line of 11.4 %. Following heavy rainfall, both catchments experienced a substantial increase in terrain relief. Soil erosion in the gully slope accounted for >90 % of the total erosion in both catchments, while deposition in the same area contributed to >75 % of the total deposition. The grassland catchment experienced a unit area erosion of 233,908 m3 km−2, which was 4.7 times greater than that of the forestland catchment (49,768 m3 km−2). In both catchments, erosion predominantly transpired in the steep slope region adjacent to the gully shoulder line, accounting for >15 % of the gully slope erosion area. The grassland catchment exhibited a continuous distribution pattern of erosion and deposition, whereas the forestland catchment exhibited a scattered and intertwined distribution pattern. This study is essential for further research on erosion and topographic changes induced by extreme weather events and to determine appropriate measures.

Spatiotemporal Distribution Characteristics and Influencing Factors of Freeze–Thaw Erosion in the Qinghai–Tibet Plateau

Freeze–thaw (FT) erosion intensity may exhibit a future increasing trend with climate warming, humidification, and permafrost degradation in the Qinghai–Tibet Plateau (QTP). The present study provides a reference for the prevention and control of FT erosion in the QTP, as well as for the protection and restoration of the regional ecological environment. FT erosion is the third major type of soil erosion after water and wind erosion. Although FT erosion is one of the major soil erosion types in cold regions, it has been studied relatively little in the past because of the complexity of several influencing factors and the involvement of shallow surface layers at certain depths. The QTP is an important ecological barrier area in China. However, this area is characterized by harsh climatic and fragile environmental conditions, as well as by frequent FT erosion events, making it necessary to conduct research on FT erosion. In this paper, a total of 11 meteorological, vegetation, topographic, geomorphological, and geological factors were selected and assigned analytic hierarchy process (AHP)-based weights to evaluate the FT erosion intensity in the QTP using a comprehensive evaluation index method. In addition, the single effects of the selected influencing factors on the FT erosion intensity were further evaluated in this study. According to the obtained results, the total FT erosion area covered 1.61 × 106 km2, accounting for 61.33% of the total area of the QTP. The moderate and strong FT erosion intensity classes covered 6.19 × 105 km2, accounting for 38.37% of the total FT erosion area in the QTP. The results revealed substantial variations in the spatial distribution of the FT erosion intensity in the QTP. Indeed, the moderate and strong erosion areas were mainly located in the high mountain areas and the hilly part of the Hoh Xil frozen soil region.