Search Results (133)

Morphology is an important characteristic of the hydraulic and gravitational processes driving gully erosion. In this study, field scouring experiments were conducted on five experimental plots using terrestrial laser scanning to study gully erosion processes. The erosion and deposition on a gully slope were quantified using the M3C2 algorithm. The results show that the proportion of sediment yield of the gully slope in the whole slope–gully system ranged from 81.5% to 99.7% for different flow discharges (25, 40, 55, 70, and 85 L/min). Compared with low flow discharges (25 and 40 L/min), the gully slope presented more intense gully head retreat and higher erosion intensity under relatively high discharges (55, 70, and 85 L/min). Alcove expansion processes were characterized by horizontal and vertical cycles. Vertical dynamic changes were dominated by the co-evolution of collapses of the gully head and the deepening of the alcove. Horizontal development mainly manifested as a widening of the alcove caused by the hydraulic erosion of the gully wall. The roughness of the gully slope increased gradually with the increase in scour times and then tended towards stability. These results provide a reference for understanding the processes and mechanisms of gully erosion. Full article

Gravity erosion is one of the main physical processes of soil erosion and sediment sources in catchments, and its spatiotemporal patterns and driving mechanisms are seriously understudied, mainly due to the the great difficulties in monitoring and quantifying. This study obtained gravity erosion amounts by runoff scouring experiments on the field slope of the hilly–gully region of the Chinese Loess Plateau. The terrain point cloud before and after gravity erosion was obtained based on the TLS, SfM and the fusion of single-scan TLS and SfM, and then the gravity erosion was estimated by four terrain change detection algorithms (DoD, C2C, C2M and M3C2). Results showed that the M3C2 algorithm plus fused data had the highest quantization accuracy among all the algorithms and data sources, with a relative error of 14.71%. The fused data combined with M3C2 algorithm performed much better than other algorithms and data sources for the different gravity erosion magnitudes (mean relative error < 17.00%). The DoD algorithm plus TLS data were preferable for collapse areas, while the M3C2 algorithm plus TLS was suitable for the alcove area. This study provides a useful reference for the monitor and quantitative research of gravity erosion in complex topographic areas. Full article

Evapotranspiration (ET) is an important part of agricultural water consumption, yet little is known about nocturnal evapotranspiration (ETN) patterns. An eddy covariance system was used to observe ET over five consecutive years (2020–2024) during the growing season in a dry farming area of the Loess Plateau. Daytime and nocturnal evapotranspiration were partitioned using the photosynthetically active radiation threshold to reveal the changing characteristics of ETN at multiple time scales and its control variables. The results showed the following: (1) In contrast to the non-significant trend in ETN on the diurnal and daily scales, monthly ETN dynamics exhibited two peak fluctuations during the growing season. (2) The contribution of ETN to ET exhibited seasonal characteristics, being relatively low in summer, with interannual variations ranging from 10.9% to 14.3% and an annual average of 12.8%. (3) The half-hourly ETN, determined by machine learning methods, was driven by a combination of factors. The main driving factors were the difference between surface temperature and air temperature (Ts-Ta) and net radiation (Rn), which have almost equivalent contributions. Regression analysis results suggested that Ta was the main factor influencing ETN/ET at the monthly scale. This study focuses on the nighttime water loss process in dry farming fields in Northwest China, and the results provide a basis for rational allocation and efficient utilization of agricultural water resources in arid regions. Full article

The Pécel loess–paleosol profile is a 25.72-metre-high well-preserved sequence in the northern part of Hungary. It was sampled every 4 cm for the purpose of sedimentological analysis and every 12 cm for the purpose of mollusc investigation, which are relatively high resolutions in loess investigation. Twenty samples were radiocarbon-dated from the L1 layer (top 8 m of the sequence). Subsequently, an age–depth model was constructed, from which an accumulation rate was calculated. Based on these radiocarbon and previous magnetic susceptibility data, the Pécel’s L1 layer is correlated with the Chinese Loess Plateau’s L1 layer and the MIS 2–4 stages. The malacological examinations show that the temperature was basically warm during the development, and there was open vegetation except on the S2, S1 and L1S1 paleosol layers, where significant forest expansion was shown. With the magnetic susceptibility and the malacological data, it is possible to track the changes in the conditions through the Chinese Loess Plateau’s timeline. Full article

Extreme rainstorms are difficult to predict and often result in catchment-scale rainfall flooding, leading to substantial economic losses globally. Enhancing the numerical computational efficiency of flood models is essential for improving flood forecasting capabilities. This study presents an integrated hydrological–hydrodynamic model accelerated using GPU (Graphics Processing Unit) technology to perform high-efficiency and high-precision rainfall flood simulations at the catchment scale. The model couples hydrological and hydrodynamic processes by solving the fully two-dimensional shallow water equations (2D SWEs), incorporating GPU-accelerated parallel computing. The model achieves accelerated rainstorm flooding simulations through its implementation on GPUs with parallel computing technology, significantly enhancing its computational efficiency and maintaining its numerical stability. Validations are conducted using an idealized V-shaped catchment and an experimental benchmark, followed by application to a small catchment on the Chinese Loess Plateau. The computational experiments reveal a strong positive correlation between grid cell numbers and GPU acceleration efficiency. The results also demonstrate that the proposed model offers better computational accuracy and acceleration performance than the single-GPU model. This GPU-accelerated hydrological–hydrodynamic modeling framework enables rapid, high-fidelity rainfall flood simulations and provides critical support for timely and effective flood emergency decision making. Full article

The Loess Plateau (LP), the cradle of Chinese civilization, has a long history of agricultural activities closely linked to ecological changes. This study addresses a fundamental question: what was the maximum sustainable cropland area threshold for the LP prior to modern soil and water conservation measures? To answer this, we analyzed the historical data to investigate changes in the cropland area and their ecological impacts over the past 4000 years, with the specific aim of examining the long-term interactions between land exploitation and the ecosystem that defined sustainable thresholds. Three key stages of cropland area development were identified: slow growth (2000–500 BC), a fluctuating phase (500 BC–1000 AD), and rapid expansion (1000–2000 AD). During the slow-growth and rapid-expansion stages, the cropland areas were estimated at 34.9 ± 23.4 and 117.9 ± 34.1 thousand km², with growth rates of 2.9 and 8.7 thousand km²/100 years, respectively, while the fluctuating period stabilized at 62.1 ± 18.1 thousand km². Population growth was the primary driver of cropland expansion (56.9%), followed by agricultural technology and policy adjustments (27%) and climate change (16.1%). Particularly over the past 1000 years, climate deterioration and a population surge due to the abolition of the poll tax accelerated cropland expansion, resulting in deforestation, intensified soil erosion specific to the LP, and frequent flooding of the lower Yellow River (YR). In contrast, during the fluctuating period, rapid social development did not lead to major ecological issues, suggesting that moderate cropland expansion can balance social development and ecological sustainability. Based on the historical conditions, without modern soil and water conservation measures, this study determined that the upper limit of the cropland area during the fluctuating period (80.2 thousand km²) is the maximum sustainable cropland area for the LP, establishing a scientific basis to guide future land-use strategies. Especially in the face of population pressure and climate deterioration, developing agriculture and adjusting policies to increase grain production will be essential to balance the ecological risks and maintenance of food security while remaining within this threshold. These findings offer insights into the agricultural history and ecological management of the LP and can serve as a reference for similar studies of other regions. Full article

Vegetation dynamics and their underlying driving mechanisms have emerged as a prominent research focus in ecological studies of the Chinese Loess Plateau (CLP). Current investigations, however, employ simplified methodologies in analyzing the influencing factors, limiting their capacity to comprehensively elucidate the intricate and multidimensional mechanisms that govern vegetation transformations. Utilizing fractional vegetation cover (FVC) datasets spanning 2000 to 2021, this research applies both XGBoost-SHAP and Geodetector approaches for comparative analysis of the driving factors and precise quantification of climatic change (CC) and human activity (HA). The results indicate that: (1) The CLP has experienced an annual FVC increase of 0.62%, with 95.1% of the region demonstrating statistically significant vegetation improvement. (2) Precipitation and land use emerge as the primary determinants of FVC spatial distribution, with their interactive effects substantially exceeding the impacts of individual factors. (3) While both XGBoost-SHAP and Geodetector methodologies consistently identify the primary driving factors, notable discrepancies exist in their assessment of temperature’s relative importance, revealing complementary dimensions of ecological complexity captured by different analytical paradigms. (4) Approximately 94.3% of FVC variations are jointly influenced by HA and CC, with anthropogenic factors predominating at a contribution of 67%. Land use modifications, particularly transitions among cropland, grassland, and forests, constitute the principal mechanism of human influence on vegetation patterns. This investigation enhances the understanding of vegetation responses under combined natural and anthropogenic pressures, offering valuable insights for ecological rehabilitation and sustainable development strategies on the CLP. Full article

Rainfall partitioning, a crucial process in shaping the local hydrological cycle, governs canopy interception and subsequent soil water recharge. While canopy structure and meteorological conditions fundamentally regulate this process, the role of plant self-organization and its interactions with meteorological drivers (non-precipitation variables in particular) remain underexplored. To address this gap, we investigated rainfall partitioning components, including the amount, intensity, efficiency, and temporal dynamics of throughfall and stemflow, in clumped and scattered Vitex negundo L. var. heterophylla (Franch.) Rehder shrubs in the Yangjuangou catchment of the Chinese Loess Plateau during the 2021–2022 rainy seasons. Despite comparable net precipitation (clumped: 83.5% vs. scattered: 84.2% of incident rains), divergent rainfall partitioning strategies emerged. Clumped V. negundo exhibited greater stemflow (8.6% vs. 5.2%), characterized by enhanced intensity, efficiency, and favorable temporal dynamics. Conversely, scattered shrubs favored throughfall generation (79.0% vs. 74.9%). Consistent with previous research, rainfall amount was recognized as the primary control on partitioning rains. Furthermore, our integrated analysis, combining machine learning with variance decomposition, highlighted the critical roles of antecedent canopy wetness (4 h pre-event leaf wetness) and wind speed thresholds (e.g., low wind vs. gust) in regulating partitioning efficiency and temporal dynamics. These findings advance the mechanistic understanding of the interplay between plant self-organization and hydrological processes, demonstrating how morphological adaptations in V. negundo optimize water harvesting in semi-arid ecosystems. This addressed the need to incorporate dynamic interplays between plant structure (specifically, self-organized patterns) and meteorological factors (particularly non-precipitation variables) into ecohydrological models, especially for improved predictions in water-limited regions. Full article

Wetting-induced soil deformation significantly impacts land stability and management on the Chinese Loess Plateau. This study analyzed silt soils from the Late Pleistocene (1 m depth) and Middle Pleistocene (25 m depth) to investigate compression and collapsible deformation during wetting. The compression in both soils progressed through three stages: slow deformation under low pressure, accelerated deformation under moderate pressure, and decelerated deformation under high pressure. Wetting intensified the compression in the 1 m sample but reduced it in the 25 m sample, with the deformation becoming more sensitive to the initial water content under higher pressures. Collapse tests showed contrasting behaviors: the 1 m sample exhibited collapsibility, while the 25 m sample displayed expansiveness (a negative collapsibility coefficient). Microstructural analysis revealed that the 1 m sample with abundant macropores and overhead structures had a lower structural stability than the 25 sample with more stable, rounded micropores. The wetting-induced deformation was governed by the balance between clay mineral expansion and structural collapse, with collapsibility prevailing when collapse dominated and expansiveness prevailing when expansion was predominant. These findings provide valuable insights into soil–water interactions and support improved land use and management strategies in the loess region. Full article

Frequent agricultural irrigation events continuously raise the groundwater table on loess platforms, triggering numerous loess landslides and significantly contributing to soil erosion in the Chinese Loess Plateau. The movement of irrigation water within the surficial loess layer is crucial for comprehending the mechanisms of moisture penetration into thick layers. To investigate the infiltration and evaporation processes of irrigation water, a large undisturbed soil column with a 60 cm inner diameter and 100 cm height was extracted from the surficial loess layer. An irrigation simulation event was executed on the undisturbed soil column and the ponding infiltration and subsequent evaporation processes were systematically monitored. A ruler placed above the soil column recorded the ponding height during irrigation. Moisture probes and tensiometers were installed at five depths to monitor the temporal variations in volumetric water content (VWC) and matric suction. Additionally, an evaporation gauge and an automatic weighing balance measured the potential and actual evaporation. The results revealed that the initially high infiltration rate rapidly decreased to a stable value slightly below the saturated hydraulic conductivity (K_s). A fitted Mezencev model successfully replicated the ponding infiltration process with a high correlation coefficient of 0.995. The monitored VWC of the surficial 15 cm-thick loess approached a saturated state upon the advancing of the wetting front, while the matric suction sharply decreased from an initial high value of 65 kPa to nearly 0 kPa. The monitored evaporation process of the soil column was divided into an initial constant rate stage and a subsequent decreasing rate stage. During the constant rate stage, the actual evaporation closely matched or slightly exceeded the potential evaporation rate. In the decreasing rate stage, the actual evaporation rate fell below the potential evaporation rate. The critical VWC ranged from 26% to 28%, with the corresponding matric suction recovering to approximately 25 kPa as the evaporation process transitioned between stages. The complete evaporation process was effectively modeled using a fitted Rose model with a high correlation coefficient (R² = 0.971). These findings provide valuable insights into predicting water infiltration and evaporation capacities in loess layers, thereby enhancing the understanding of water movement within thick loess deposits and the processes driving soil erosion. Full article

Understanding the dynamics of soil water content (SWC) is essential for effective land management, particularly in regions affected by underground mining. This study investigates the spatial and temporal patterns of SWC and its interaction with topographic and edaphic factors in coal mining and non-coal mining areas of the Chenghe watershed, located in the southeast of the Chinese Loess Plateau, which is divided by a river. Our findings revealed that the capacity to retain moisture in the top layer of coal mining areas is significantly higher (25.21%) compared to non-coal mining areas, although deeper layers exhibit lower SWC, indicating altered moisture dynamics due to underground mining disturbances. Coal mining areas show greater spatial and temporal variability in SWC, suggesting increased sensitivity to moisture fluctuations, which complicates water management practices. Additionally, underground mining activities introduce more intense effects on the relationship between SWC and topographic factors (i.e., GCVR across soil profile of 0–60 cm; slope at depth of 50 cm) or edaphic factors (i.e., soil organic matter and available potassium at depth of 30 cm; pH at depth of 50 cm) compared to non-coal mining areas. This variability is evident in the temporal shifts from positive to negative correlations, particularly in coal mining areas, reflecting modifications in both soil physical and chemical properties resulting from mining activities. In contrast, non-coal mining areas maintain a more stable moisture regime, likely due to preserved natural soil structures and processes. These contrasting findings emphasize the necessity for tailored management strategies in coal mining regions to address the unique challenges posed by altered soil characteristics and water dynamics. Full article

The Chinese Loess Plateau (CLP) is ecologically fragile, and water resources are extremely scarce. Soil thermal conductivity (λ) is a vital parameter for controlling surface heat transfer and is the key to studying the energy exchange and water balance of the soil surface. The objective of this study is to investigate the spatial distribution characteristics of soil thermal conductivity on the Loess Plateau. The research primarily employed soil heat transfer models and the Google Earth Engine (GEE) platform for remote sensing cloud computing, compares and analyzed the suitability of six models (Cambell model, Lu Yili model, Nikoosokhan model, LT model, LP1 model, and LP2 model), and utilized the selected improved model (LT model) to analyze the spatiotemporal characteristics of thermal conductivity on the CLP, examining the impacts of soil particle composition, bulk density, elevation, moisture content, and land use on thermal conductivity. The results show that the LT model is the best in the relevant evaluation indices, with a determination coefficient (R²) of 0.84, root mean square error (RMSE) of 0.18, and relative error (RE) of 0.16. Furthermore, the λ on the CLP shows an overall trend of increasing from northwest to southeast, with a lower λ between May and August and a higher one between September and October. The λ of different land use types is as follows: built-up land > cropland > grassland > forest land > barren. The bulk density (ρ_b) and altitude mainly influence λ in the CLP. The results of this study can provide a theoretical basis for studying hydrothermal variation in the CLP, model application, energy development, and land resource use. Full article

Human activities and climate change have significantly influenced the water cycle, impacting flood risks and water security. This study centers on the Jing River Basin in the Chinese Loess Plateau, analyzing hydrological patterns and flood progression using the HEC-HMS model under changing conditions. The findings indicate that climate change substantially affects flood predictions, increasing peak flows and volumes by up to 10.9% and 11.1%, respectively. It is essential to recognize that traditional flood models may underestimate the risks posed by these changes, emphasizing the necessity for updated methods incorporating climatic and human factors. Changes in land use, such as the expansion of grasslands and forests, have reduced peak discharges and flood volumes. Consequently, the combined impacts of climate and land use changes have intensified flood frequencies, necessitating updated strategies to manage risks effectively. The dynamics of flooding are significantly impacted by changes in climate and land use, particularly in minor floods that occur frequently, highlighting the influence of climate change on flooding trends. Within the Jing River Basin, hydrological patterns have been shaped by both climatic variations and human activities, leading to an increase in extreme hydrological events and concerns regarding water security. Using the HEC-HMS model, this study examines the hydrology of the Jing River Basin, focusing on the design of storm events and analyzing various flood characteristics under different scenarios. Climate change has resulted in higher peak discharges and volume surges ranging from 6.3% to 10.9%, while shifts in land use, such as decreases in farmland and the expansion of grasslands, have caused declines ranging from 7.2% to 4.7% in peak flows and volumes. The combined effects of climate variation and land utilization have complex implications for flood patterns, with milder to moderate floods showing a more significant impact and shorter return periods facing increased consequences. These findings underscore the interconnected nature of climate change, land use, and flooding dynamics in the Jing River Basin, highlighting the need for comprehensive strategies to address these challenges and ensure sustainable water management in the region. Full article

Chinese pine has been extensively planted in the Loess Plateau, but it faces significant threats from Gansu zokor. Traditional methods for monitoring rodent damage rely on manual surveys to assess damage rates but are time-consuming and often underestimate the actual degree of damage, particularly in mildly affected pines. This study proposes a remote sensing monitoring method that integrates hyperspectral analysis with physiological and biochemical parameter models to enhance the accuracy of rodent damage detection. Using ASD Field Spec 4, we analyzed spectral data from 125 Chinese pine needles, measuring chlorophyll (CHC), carotenoid (CAC), and water content (WAC). Through correlation analysis, we identified sensitive vegetation indices (VIs) and red-edge parameters (REPs) linked to different levels of damage. We report several key results. The 680 nm spectral band is instrumental in monitoring damage, with significant decreases in CHC, CAC, and WAC corresponding to increased damage severity. We identified six VIs and five REPs, which were later predicted using stepwise regression (SR), support vector machine (SVM), and random forest (RF) models. Among all models, the vegetation index-based RF model exhibited the best predictive performance, achieving coefficient of determination (R²) values of 0.988, 0.949, and 0.999 for CHC, CAC, and WAC, with root mean square errors (RMSEs) of 0.115 mg/g, 0.042 mg/g, and 0.007 mg/g, and mean relative errors (MREs) of 8.413%, 9.169%, and 1.678%. This study demonstrates the potential of hyperspectral remote sensing technology for monitoring rodent infestations in Chinese pines, providing a reliable basis for large-scale assessments and effective management strategies for pest control. Full article

Reliable paleoflood proxies can help reconstruct past flood variation patterns. Here, we investigated the grain-size data of a 63 cm core retrieved from Lake Chaonaqiu, western Chinese Loess Plateau, in order to build a long time-series of flood occurrence from sedimentology that extends the period of instrumental data. Our results indicate that three parameters (mean, standard deviation and grain-size ratio of 16–63/2–16 μm) are sensitive to hydrodynamic changes in Lake Chaonaqiu, which are further linked to high-energy inflow associated with high-intensity rainfall or flood events. These three parameters’ variations were well correlated with the precipitation records reconstructed from tree-rings and historical documents in neighboring regions and overlapped with 109 historical flood events from historical documents in counties around the lake for the past 300 years. Therefore, we propose that the grain size in the sediments of Lake Chaonaqiu is a reliable paleoflood proxy. The sensitivity of flood signals to grain size may be related to the precipitation and vegetation cover in the catchment of the lake, which are further linked to the strength of the East Asian summer monsoon. Full article