Search Results (272)

Most existing studies on anthropogenic N and P inputs in the Yangtze River Basin focus on the middle-lower main stem and large lake regions, while long-term fine-scale assessments of small and medium plateau tributaries in the upper reaches remain limited. This study was based on the Net Anthropogenic Nitrogen and Phosphorus Input (NANI) & (NAPI) models to systematically quantify total anthropogenic N/P inputs and their sources, and to characterize spatiotemporal dynamics. The random forest model was employed to disentangle and quantify key driving factors; additionally, the multiple linear regression (MLR) model was employed to construct prediction equations, and key-factor scenarios were set to predict N and P input evolution trends under reduced fertilizer application and population change. Results indicate that: (1) from 2009 to 2023, the mean annual NANI and NAPI in the study area were (8741.97 ± 1715.37) kg·km⁻²·yr⁻¹ and (2016.01 ± 610.68) kg·km⁻²·yr⁻¹, respectively, exhibiting an overall “first increase, then decrease” trend. Their spatial distribution patterns were highly coupled. The spatial distribution was highly heterogeneous, with high values concentrated in the central dam regions and low values in mountainous areas. (2) Across all sub-basins, food and feed N input and fertilizer application were the primary sources of NANI, accounting for 50.87% and 43.94% of the total on average, respectively, while food and feed P input and fertilizer application dominated NAPI with average shares of 31.31% and 68.69%. (3) Population size, fertilizer application intensity, and livestock/poultry breeding volume were the primary drivers of regional NANI and NAPI. (4) Scenario prediction results show that fertilizer reduction significantly reduces N and P inputs, whereas population growth does not directly elevate N and P loads. Overall, N and P inputs in the Longchuan River Basin are dominated by human activities, with spatiotemporal variations closely linked to agricultural activity intensity and population distribution. These findings provide scientific support for targeted precise zonal N/P control in the Longchuan River Basin, and also offer a reference for non-point source pollution control research and management policy-making in similar plateau basins of the upper Yangtze River. Full article

Eutrophication in shallow plain lakes is highly dynamic and often characterized by short-term trophic fluctuations that are difficult to resolve using annual or single-sensor satellite observations. The Eastern Plain Lake Zone (EPL) of China contains numerous shallow lakes and reservoirs embedded in densely populated and intensively cultivated lowland catchments, making it a representative region for high-frequency eutrophication monitoring. Here, we developed a monthly Trophic State Index (TSI) monitoring framework for lakes and reservoirs in the EPL using Harmonized Landsat–Sentinel (HLS) observations. The XGBoost model using combined spectral features achieved the best validation performance (R² = 0.90, RMSE = 5.23), and provided the highest trophic-state classification accuracy, with an overall accuracy of 0.73 and a Kappa coefficient of 0.66. Lakes showed substantially higher trophic levels than reservoirs, with mean TSI values of 57.32 ± 6.89 and 45.00 ± 9.22, respectively. Temporally, significantly decreasing and increasing TSI trends accounted for about 15% and 5%, respectively. Natural lake TSI reflects integrated climatic, anthropogenic, and hydro-morphological influences, whereas reservoir TSI variability may be more closely associated with hydrological regulation and morphometric conditions. Our results show that HLS observations provide a robust basis for monthly eutrophication monitoring in optically complex shallow lake regions. The EPL-focused framework highlights the value of virtual satellite constellations for detecting short-term trophic deterioration and supporting region-specific lake and reservoir management. Full article

Salt dust storms are a distinct and highly hazardous type of dust storm in arid and semi-arid regions. Salt crusts commonly develop on the surfaces of desiccated lake beds, and variations in their structure and properties directly influence dust release. To investigate how wetting–drying alternation affects the erodibility of sodium sulfate salt crusts with varying salt contents, four crust types with 0%, 1%, 3%, and 5% sodium sulfate were prepared under controlled laboratory conditions. A combination of wind-tunnel tests, direct shear tests, and surface morphology observations was employed to evaluate changes in mechanical properties and wind-erosion responses before and after wetting–drying treatment. The results showed that wetting–drying alternation induced pronounced cracking, salt crystallization, and the formation of a loose surface layer in salt-bearing crusts, with structural damage severity increasing with salt content. In contrast, the physical crust without added salt exhibited minimal surface deterioration. Direct shear tests revealed that after wetting–drying, the internal friction angle of salt-bearing crusts first decreased and then increased with salt content, while cohesion declined markedly; the 5% salt crust showed a 32.4% reduction in cohesion, indicating substantial structural degradation. Wind-tunnel tests further demonstrated that wind-erosion intensity increased significantly after wetting–drying treatment across all salt contents, with the largest relative increase observed in the 1% salt crust. Wind-erosion intensity also scaled approximately as a power function of salt content. These findings demonstrate that wetting–drying alternation is a critical trigger for the degradation of sodium sulfate salt crusts and for enhancing their erodibility. Post wetting–drying, salt crusts may evolve into highly erodible surfaces, becoming major potential sources of salt dust storms. This study provides a theoretical foundation for understanding salt dust release from desiccated lake beds and for improving early warning of ecological hazards in arid regions. Full article

Seasonal hydrological variation can reorganize fluorescent dissolved organic matter (FDOM) in floodplain lakes; yet, its expression in Poyang Lake remains uncertain. We assessed campaign differences in FDOM composition by comparing 32 excitation–emission matrices from 16 fixed sites sampled during the dry and wet periods of 2024 using parallel factor analysis (PARAFAC), fluorescence indices, paired tests with Benjamini–Hochberg correction, and principal component analysis. Rank 4 fitted better and resolved two humic-like and two protein-like regions, although incomplete validation limited component-specific interpretation. In the wet period, C2 and combined humic-like maximum fluorescence intensity (Fmax) decreased (q = 0.00836), whereas bulk total organic carbon (TOC) and total Fmax did not differ. Mean protein-like contribution rose from 25.0% to 37.5% (q = 0.00322); the biological index increased, the humification index decreased, and the fluorescence index was unchanged. The first two principal components explained 78.11% of the variance, and an exact paired multivariate test detected an overall period difference (p = 3.05 × 10⁻⁵). No component–environment correlation survived correction or differed between periods. FDOM composition therefore underwent a campaign-specific reorganization without a corresponding change in bulk carbon, but the two-campaign design and incomplete validation preclude causal or source-specific inference. Full article

The Lacul fără nume landslide dam in the Vrancea Mountains (Romania) represents a unique example of a dynamic landslide dam system characterized by recurrent damming–breaching cycles. Through the combined use of remote sensing, field investigations, and historical reconstruction, eight such cycles were documented over a period of 49 years. To the best of current knowledge, this is one of the few documented landslide dams reported in the scientific literature that exhibits frequent damming–breaching episodes involving repeated dam failure, renewed slope instability, and subsequent re-damming with renewed lake impoundment over comparatively short timescales. The observed persistence and spatial extent of the associated lake are highly variable, ranging from 12 days to almost 10 years and from 23,920 m² to 82,610 m², respectively. Antecedent precipitation was frequently elevated prior to lake state transitions, but a seasonally constrained Monte Carlo analysis showed no significant departure from the climatic background, while numerous intense rainfall periods occurred without documented transitions. Similarly, no systematic temporal association was identified between recurrent lake state transitions and regional seismicity, although the initial dam formation coincided with the 1977 Mw 7.4 Vrancea earthquake. These findings suggest that precipitation conditions and seismicity alone cannot explain the recurrent damming and drainage, which likely result from interactions between hydrometeorological forcing, geomorphic processes, and human influences. Taken together, the results and the proposed conceptual model demonstrate that debris-flow-generated landslide dams can evolve into persistent and dynamic geomorphic systems capable of posing recurring hazards over multiple decades. Full article

Wetland ecosystems in large lake basins play a critical role in maintaining regional water security and ecological balance. Despite their importance, the long-term spatiotemporal dynamics of basin wetlands and their effects on lake water quality under intensive human disturbance remain elusive. This study leveraged multi-source satellite archives from 1986 to 2025 to construct a framework for extracting and classifying potential wetlands in the Chaohu Lake basin, Anhui province, China, and examined its evolution and its relationship with water quality. The resulting wetland maps are highly reliable, with overall accuracy ranging from 81.63% to 94.22% and precision approaching 99%, effectively addressing spectral confusion and boundary instability caused by hydrological fluctuations. In total, the basin contains approximately 2139.9 km² of potential wetlands (16%), which are spatially concentrated along the lake and river corridors. Over the 36-year period, wetlands underwent distinct phases of “relative stability—rapid decline—Emerging recovery,” with shrinkage primarily in the west and relative stability in the east, while ponds and paddy fields experienced the most frequent conversions. In recent years (2010–2025), changes in the water environment of Lake Chaohu showed strong spatiotemporal consistency with wetland dynamics. As partial wetland recovery emerged after 2015, concentrations of total nitrogen (TN), total phosphorus (TP), and chlorophyll-a (Chla) declined and stabilized, and the area affected by cyanobacterial blooms decreased by 46%, suggesting a potential role of wetland recovery in improving water quality and mitigating non-point-source pollution. This study provides a comprehensive characterization of wetland dynamics and their influence on water quality, offering valuable data and guidance for wetland conservation, ecological restoration, and integrated lake management in the Chaohu Lake Basin. Full article

The Hetao Irrigation District in arid northwestern China presents a significant challenge in balancing agricultural intensification and water conservation, particularly in its terminal lake, Wuliangsu Lake. This study examined how changes in Land Use/Land Cover (LULC) and cropping structures influenced the lake’s water quality. By using remote sensing data for LULC classification and agricultural statistics for crop composition, we analyzed the spatio-temporal variation in LULC and cropping structure in the irrigation district and quantified the associated agricultural non-point source pollution loads (total nitrogen, total phosphorus, and chemical oxygen demand) entering the lake. A calibrated Environmental Fluid Dynamics Code model was applied to evaluate water quality responses to cropping structure optimization. Our findings revealed significant shifts in LULC and cropping structure during the study period, driven by agricultural intensification, ecological restoration policies, urbanization, market forces, and national food security strategies. Concurrently, agricultural non-point source pollution loads into the lake showed a steady declining trend from 2018 to 2023, with total nitrogen (TN) decreasing by 15%, total phosphorus (TP) by 16.9%, and chemical oxygen demand (COD) by 19.4%. Model simulations demonstrated that optimizing the cropping structure, specifically by reducing the area of high-fertilizer crops (sunflower) and expanding low-fertilizer crops (spring wheat) and forage crops for ecological purposes, could further improve lake water quality. Under the intensive adjustment scenario, the inflow loads of TN, TP, and COD decreased by 10%, 11.7%, and 10.9%, respectively, while the corresponding in-lake concentrations decreased by 22.1%, 19.8%, and 18.7%, respectively. TP exhibited the highest sensitivity to such adjustments. By linking cropping structure adjustments with hydrodynamic-water quality modeling, this study provides a quantitative framework for assessing water quality responses in arid irrigated systems, offering a scientific basis for balancing agricultural production and water ecosystem protection in the Hetao district and similar regions. Full article

The Southern Jiangsu hills region is located within the Yangtze River Delta Ecological Barrier. Soil erosion poses a threat to the development of commercial forests and the water quality of Lake Taihu, making it urgent to quantify the mechanisms by which vegetation and rainfall regulate slope erosion. This study established five standard runoff plots in Zhangzhu, Yixing, and continuously monitored runoff and soil loss from 2022 to 2023. By combining Random Forest modeling, partial least squares structural equation modeling (PLS-SEM), and moderation effect analysis, the study assessed the contributions of various driving factors under different rainfall types. The results indicate that the peach orchard (PEA + GRA) is an optimal ecological model, achieving runoff and sediment reduction rates of over 54.09% and 70.19%, respectively. Rainfall is the dominant factor driving runoff (r = 0.75), while the maximum 30 min rainfall intensity (I₃₀) is the dominant factor driving soil loss (r = 0.82). Furthermore, during low- to moderate-intensity rainfall events, vegetation attributes primarily govern hydrological responses; however, during extreme Type III rainstorms (24 h rainfall exceeding 50 mm), rainfall volume becomes the decisive factor. Moderation analysis further reveals that vegetation height and cover exert significant moderating effects on the initial transition phase from rainfall to runoff. These findings provide evidence-based guidance for optimal soil and water conservation strategy selection in subtropical hilly landscapes. Full article

Drought is a key climatic driver of grassland degradation; however, the coupling mechanisms between drought-triggering thresholds and ecosystem resilience under different hydroclimatic conditions, as well as their spatial heterogeneity, remain insufficiently understood. Here, we investigated Central Asian grasslands by integrating Copula-based joint probability analysis, drought-triggering threshold identification, and quantitative assessment of vegetation resilience. We systematically revealed spatial patterns of leaf area index (LAI) loss probability, as well as gradient-dependent transitions in the coupling between triggering thresholds and resilience across aridity gradients. Results showed that the probability of LAI loss (LAI ≤ 40th percentile) increased from 36.35% under mild drought to 39.99% under extreme drought, while more severe losses (LAI ≤ 10th percentile) increased from 11.16% to 12.62%. For a given drought intensity, more severe vegetation loss required substantially stronger water deficit conditions. Triggering thresholds increased along the aridity gradient, with the eastern Kazakhstan and western Xinjiang regions showing the highest drought sensitivity. Vegetation resilience also exhibited pronounced spatial differentiation, with the Balkhash Lake region, southern Inner Mongolia, and Gansu showing the lowest resilience and longest recovery times, whereas humid regions exhibited significantly higher resilience. Most importantly, the relationship between triggering thresholds and resilience shifted systematically across aridity gradients, changing from a significant negative correlation in semi-arid regions (synergy pattern) to a positive correlation in humid regions (trade-off pattern), with transition points at AI = 0.45–0.46. This indicated that hydroclimatic conditions fundamentally regulated the coupling between drought resistance strategies and recovery capacity. This study provides a robust scientific basis for accurately assessing drought vulnerability and developing differentiated adaptation strategies for grassland ecosystems under climate gradients. Full article

Non-grain production of cultivated land has increasingly affected regional food security and the stability of agricultural ecosystems. In traditional rice-producing regions, changes associated with non-rice cultivation, fallow land, rice-fishery integrated farming, and intensive agricultural management are reshaping the spatial structure of paddy landscapes. To identify the long-term spatiotemporal evolution of paddy systems, this study investigated Northern Jiangxi, China, using Landsat surface reflectance imagery from 2000, 2005, 2010, 2015, and 2020 on the Google Earth Engine (GEE) platform. The Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI) were used to construct a phenology-based Flooding Frequency (FF) indicator. Based on the annual frequency with which pixels satisfied the condition LSWI > EVI, cultivated land was classified into three categories: non-flooded cropland, standard rice paddy, and high-frequency flooded cropland. In this study, non-flooded cropland was used as an indicator of potential non-rice cultivation rather than as direct evidence of confirmed non-grain production. Landscape metrics, transition matrices, gravity center migration, standard deviation ellipses, and geographically weighted regression (GWR) were then used to examine paddy landscape dynamics, fragmentation patterns, and county-level spatial associations with socioeconomic factors. The results suggest that the paddy system in Northern Jiangxi experienced marked stage-based fluctuations between 2000 and 2020. Standard rice paddy recovered during 2005–2010, whereas non-flooded cropland expanded considerably during 2010–2015, accompanied by intensified paddy landscape fragmentation. Non-flooded cropland was mainly distributed around urban fringes, transport corridors, and some hilly margins. Standard rice paddy was concentrated in traditional grain-producing areas, including the Poyang Lake Plain and the Gan-Fu Plain. High-frequency flooded cropland was primarily located in low-lying lake areas, where its dynamics were likely associated with rice-fishery integrated farming, continuous irrigation, and hydrological fluctuations. Landscape metrics showed that the largest patch index and mean patch size of standard rice paddy declined after 2010, indicating reduced spatial continuity of core paddy fields. The GWR analysis provided auxiliary evidence that total population, per capita gross domestic product (GDP), and urbanization rate were spatially associated with changes in non-flooded cropland at the county level; however, the results should be interpreted as exploratory associations rather than causal mechanisms. Overall, paddy landscape change in Northern Jiangxi was expressed not only through changes in cultivated land area, but also through the reorganization of paddy function, spatial continuity, and land-use intensity. Future cropland protection should therefore move beyond area-based control toward integrated management of quantity, quality, function, and spatial configuration. Future research should further verify these findings using dynamic cropland boundaries, higher-resolution imagery, and more detailed socioeconomic data. Full article

Broadband direction-of-arrival (DOA) estimation using a single acoustic vector sensor (AVS) is an important problem in passive underwater source localization and underwater acoustic signal processing, especially for compact underwater platforms and passive acoustic monitoring applications. However, conventional grid-based sparse Bayesian learning (SBL) may suffer from grid mismatch when the true bearing lies between adjacent predefined grid points. Although a dense grid can reduce this mismatch, it increases computational cost and dictionary coherence. To address this problem, this paper proposes an acoustic-intensity-guided local grid-refinement SBL method, termed AI-LGR-SBL. The pressure and particle-velocity channels are first used to construct acoustic intensity information and detect candidate source regions. The coarse bearing results then guide target-related spectral peak selection during SBL iterations, and local grid refinement is performed only around the selected directions. Simulations involving single-source and two-source scenarios show that AI-LGR-SBL yields sharper spatial spectra and lower estimation errors than conventional grid-based SBL. Compared with basic SBL, AI-LGR-SBL reduces the RMSE by approximately 10% in the low-SNR region and by 4–7% at relatively high SNRs. Compared with globally dense-grid SBL, it reduces the average runtime by approximately 47.3% and 43.6% in the single-source and equal-power two-source scenarios, respectively. Lake-trial data further demonstrate clear bearing–time trajectories and effective sub-grid peak refinement, supporting the feasibility of the proposed method for broadband underwater DOA estimation and passive source localization using a single AVS. Full article

Black soil degradation poses critical threats to agricultural sustainability and global food security, yet systematic frameworks integrating ecological security assessment, driver identification, and forward-looking early warning remain underdeveloped for black soil watersheds. This study develops and implements a comprehensive assessment–interpretation–early warning framework for the Xingkai Lake Basin, a representative black soil region at the China–Russia border. We developed a multivariate ecological security index (MESI) to describe the spatiotemporal dynamics between 2000 and 2023. An XGBoost–SHAP framework was applied to quantify dominant drivers of ecological security spatial heterogeneity and examine synergistic effects among driving factors through geographical detector interaction analysis. A Bayesian network model was subsequently employed to simulate the probability of warning grade occurrence under multiple univariate and multivariate scenarios. Findings revealed the following: (1) Spatial analysis revealed persistent north–south differentiation, with high spatial association zones contracting from 25% to 21% despite strengthened global spatial auto correlation. (2) XGBoost–SHAP driver analysis quantified that land use intensity and landscape fragmentation collectively explained over 75% of spatial heterogeneity in MESI. (3) BN models demonstrated greater sensitivity in simulating no warning and severe warning levels. This study provides scientifically rigorous insights into the sustainable management of ecosystems in black soil river basins and offers a generalizable decision-support framework for conducting ecological safety early warning research in other regions facing similar agricultural pressures. Full article

An aeolian event and a fluvial episode affected Gale crater, Mars, prior to 3.6 billion years ago. Both were short-lived and catastrophic. The same two events also modified the Southern Highlands of the red planet during the same time interval. We show that events in Gale crater were a part of those that modified vast areas of the southern hemisphere of Mars. As such, the patterns documented in Gale crater are consistent with reshaping of large portions of Mars by short-lived catastrophic events by wind and water, although data from other regions are needed to establish this on a planetary scale. The study is based on data collected by the Curiosity rover during the past 14 years. The aeolian event that excavated Gale crater was lithologically controlled. It formed two distinct morphological provinces with two contrasting rock types. One was the cone-shaped ancestral Aeolis Mons, informally known as Mt. Sharp, that consists of sandstone, siltstone, and mudstone. The other was the nearly flat hollowed margin, the ancestral crater floor, that was initially covered by loose pebbles, cobbles, and boulders which were reworked and lithified to a conglomeratic rock unit later. Commonly reported Martian aeolian erosion rates cannot account for the abrasion and transport of 39,000 km³ of sediments out of Gale crater. This conclusion is supported by little modification of Gale crater during the past 3.6 billion years by ordinary winds. Our evaluation indicates that the excavation of Gale crater took place by a powerful aeolian perturbation that resembled a sand-blasting operation. It was short-lived, had extremely high erosion rates, and occurred during a cold and dry climate. The fluvial episode followed the aeolian event. The study of its sedimentary record indicates that it began with intense precipitation-driven great floods that eroded the ancestral Mt. Sharp, carved large canyons on its slope, and reworked gravels of the ancestral crater floor into giant bedforms. Flood waters also formed a deep lake that experienced one rise and one fall of lake-level and had a dynamic storm-driven sedimentation. The fluvial episode was also short-lived and indicates catastrophic actions of water during a warm and wet climate. As such, this study suggests that the extensive reshaping of the red planet during the Late Noachian period, including formation of valley networks, occurrence of hundreds of crater lakes, and excavation of numerous craters, were also due to short-lived, intense, climate-related perturbations by powerful wind and water rather than by ordinary, slow rate, long-duration processes. Another implication of the study is for the mineralogical evolution of Martian sedimentary rocks. It indicates that the Late Noachian period may have been mostly cold and dry, similar to the modern Mars. Its low water/rock ratio and cold temperatures halted chemical weathering that resulted in preservation of highly unstable minerals such as olivine and pyroxene. The fluvial perturbation with its high water/rock ratio was not long and/or warm enough to alter or significantly affect the mineralogy by weathering at the source region, or during the transport, or at the depositional site. Full article

Understanding the coordinated development of production, living, and ecological (P–L–E) functions is critical for sustainable watershed governance in rapidly transforming regions. Using the Chaohu Lake Basin, China, as a case study, this study developed a process–pattern–potential–driver framework for watershed-scale P–L–E coordination analysis from 2000 to 2020. Unlike previous studies that mainly assess coordination levels or map spatial patterns, this framework further identifies subsystem constraints, quantifies coordinated development potential, and determines key factors driving spatial differences. The results show that production and ecological functions remained weakly coordinated, indicating persistent tension between economic growth and ecological protection. In contrast, the relationships between production and living functions and between living and ecological functions improved from strong imbalance to moderate coordination. Spatially, higher coordination levels were concentrated in the southwestern basin. Decoupling analysis further reveals that production activities, especially the energy-intensive secondary industry, were the main constraint on ecological function. In addition, 88.2% of the basin showed an increasing trend in coordinated development potential. Land-use patterns, socioeconomic conditions, and eco-environmental quality were identified as direct drivers, whereas climate change mainly acted indirectly. By linking diagnostic results with spatially differentiated management needs, this study provides a basis for more targeted watershed governance. Full article

Flooding is one of the most common and destructive natural disasters worldwide, and projections indicate that its intensity will increase across various climate regions during this century. South Sudan is particularly vulnerable due to a combination of factors, including hydrological releases from Lake Victoria, local rainfall patterns, and wetland retention dynamics. These factors raise important questions regarding the hydrological connectivity between Lake Victoria and the Nile system. This study examined how upstream hydrological conditions impact flood dynamics in South Sudan’s flood-prone regions, specifically in the states of Jonglei and Unity along the River Nile. To statistically estimate flood propagation lag time from Lake Victoria to the Sudd wetland, we used Cyclone Global Navigation Satellite System (CYGNSS) remote sensing data and water-level altimetry from both Lake Victoria and the River Nile at Mangalla. The analytical methods included moving block bootstrap (MBB) cross-correlation and Gaussian process (GP) modeling. Furthermore, we validated the event-based propagation and inundation patterns using flood event reports from the Displacement Tracking Matrix (DTM). The findings indicate that the statistical propagation signals took approximately 106 days during the wet season (95% confidence interval [CI]: 60–150 days) and 134 days during the dry season (95% CI: 75–195 days) for the downstream water level response to reach the River Nile at Mangalla, and 3–4 weeks to reach the adjacent floodplains downstream. Residual stationarity diagnostics showed augmented Dickey–Fuller (ADF) statistics below −7 across the analyzed propagation pathways, indicating statistically stationary lag-adjusted residual behavior. Consistent temporal correspondence between inferred flood arrival windows and independently reported DTM flood-impact periods provides cautious support for the hydrological plausibility of the estimated propagation structure. Full article