Search Results (421)

The trade-offs and synergies among ecosystem services can provide clues for understanding the mechanisms of regional ecological evolution. Previous studies have mainly concentrated on administrative divisions to characterize ecosystem services trade-offs and synergies within specific regions. However, ambiguity persists regarding the spatial diversity and scale dependency of regional ecosystem services, along with the degree to which human activity and climatic variation influence the relationships of multiscale ecosystem services. This study focuses on the Yangtze River Delta Urban Agglomeration in China. Based on grid, county-level, and city-level scales, it analyzes five ecosystem services, namely habitat quality, carbon storage, food production, soil conservation, and water yield, from 2000 to 2020. By using correlation analysis and spatial autocorrelation methods, this study explores the intensity of the trade-offs and synergies among ecosystem services and their spatial patterns. Then, combined with the Optimal Parameters-based Geographical Detector, it identifies the dominant driving factors, quantifies their degree of contribution, and reveals the multiscale differentiation of ecosystem service relationships and their causes. The results show that the five ecosystem services all exhibit significant spatiotemporal heterogeneity. At the grid scale, there is a trade-off relationship between food production and the other four services, while a strong synergistic effect exists among the remaining four services. At the county scale, the synergistic association between habitat quality and carbon storage is the most significant, with the highest contributions from the average annual precipitation and average annual temperature (q-values 0.893 and 0.782, respectively). At the prefecture-level city scale, the intensity of the ecosystem services trade-offs and synergies shows an increasing trend, and the impact of interactions between socio-ecological elements is significantly higher than that at the grid and county scales. This research provides an evidence-based foundation for decision makers to devise suitable strategies that support the coordinated advancement of ecology and the economy across various spatial scales. It is crucial for promoting precise ecosystem regulation and the sustainability of the Yangtze River Delta Urban Agglomeration in China. Full article

Pile foundations are widely used to support offshore wind turbines. While the p-y curve method is adopted for analysis of pile–soil interactions in popular design specifications, including the American Petroleum Institute (API), its accuracy remains unassessed systematically and quantitatively. This study established a database by collecting 491 sets of pile p-y curves from multiple offshore wind turbine projects. The database was used to statistically evaluate the accuracy of the API p-y curve method for cohesionless soils. The model accuracy is represented by a model factor defined as the ratio of measured to predicted values of soil resistance around the pile. The results showed that accuracy assessment using the field data is significantly different from that using the laboratory model test data. On average, the API p-y curve method overestimates the true soil resistance in the field by about 30%, but underestimates that in the laboratory by about 8%. The dispersions in prediction accuracy of both cases are high. Correction terms are introduced to calibrate the current API p-y curves. The calibrated API methods were shown to be accurate in general and medium dispersive in prediction accuracy. Last, the model factors for the current and calibrated API methods were demonstrated to be lognormal random variables. Full article

As one of the mooring foundation types for floating wind turbine platforms, research on the anchor pullout bearing characteristics of mooring pile foundations remains insufficient, and the underlying mechanism of anchor pullout bearing capacity needs further investigation and clarification. This paper conducts a numerical study on the bearing characteristics of mooring pile foundations under tensile anchoring forces with loading angles ranging from 0° to 90° and loading point depths of 0.2L, 0.4L, 0.6L, and 0.8L (where L is the pile length). The research findings indicate that the anchor pullout bearing capacity decreases as the loading angle increases from 0° to 90°, and exhibits a trend of first increasing and then decreasing with the increase in loading point depth. For rigid pile-anchors, the maximum anchor pullout bearing capacity occurs at a loading point depth of 0.6–0.8L, while for flexible piles, it appears at 0.4–0.6L. Both the bending moment and shear force of the pile shaft show abrupt changes at the loading point, where their maximum values also occur. This implies that the structural design at the loading point of the mooring pile foundation requires reinforcement. Meanwhile, the bending moment and shear force of the pile shaft gradually decrease with the increase in the loading angle, which is attributed to the gradual reduction of the horizontal load component. The axial force of the pile shaft also undergoes an abrupt change at the loading point, presenting characteristics where the upper section of the pile is under compression, the lower section is in tension, and both the pile top and pile tip are subjected to zero axial force. The depth of the loading point significantly influences the movement mode of the pile shaft. Shallow loading (0.2–0.4L) induces clockwise rotation, and the soil pressure around the pile is concentrated in the counterclockwise direction (90–270°). In the case of deep loading, counterclockwise rotation or pure translation of the pile shaft results in a more uniform stress distribution in the surrounding foundation soil, with the maximum soil pressure concentrated near the loading point. Full article

Aluminum (Al) toxicity in acidic soils severely limits the productivity of Chinese fir (Cunninghamia lanceolata) plantations. Despite being a crucial timber species in southern China, the regulatory mechanisms underlying phenolic accumulation and Al tolerance pathways under Al stress in Chinese fir remain unidentified. In this study, 5-month-old Chinese fir seedlings were treated with an exogenous phenolic synthesis inhibitor (AIP) and precursor (MJ) to establish the following groups: CK, AIP, MJ, Al, Al+AIP, and Al+MJ. Physiological and biochemical indicator analyses, transcriptome analysis, and protein interaction network predictions were conducted. The findings revealed that phenolic compounds enhance Al tolerance in Chinese fir through two mechanisms: (1) regulation of active oxygen homeostasis (elevating SOD and POD activities, promoting AsA and GSH accumulation, and augmenting total antioxidant capacity); and (2) modulation of cell wall characteristics (increasing pectin content and pectinase activity, and facilitating Al sequestration in the cell wall). Moreover, MJ was found to synergistically enhance these processes, while AIP impeded them. Genes associated with antioxidant enzymes, secondary metabolite synthesis, and cell wall modification were implicated in the regulatory mechanisms. This study provides a theoretical foundation for elucidating the adaptation of Chinese fir to Al toxicity in acidic soil environments, offers insights for enhancing Chinese fir productivity in acidic soils, and presents a novel target for breeding trees with stress resistance. Full article

In recent years, the increasing complexity of shield tunneling environments has made it critical to control the deformation of adjacent excavation structures and surrounding soils. This study employs numerical simulation using MIDAS GTS/NX to comprehensively analyze the spatial interaction factors between shield tunnels and wall-pile-anchor-supported foundation pits. Structural parameters of the retaining system and tunneling conditions are also evaluated to identify the key factors influencing construction-induced deformation. The results show that the maximum settlement of the adjacent retaining wall occurs when the tunnel burial depth reaches 1.4L, where L is the height of the diaphragm wall. In addition, when the horizontal distance between the tunnel and the excavation is less than 0.75D (D being the tunnel diameter), significant settlement deformation is observed in the nearby support structures. A linear correlation is also identified between the variation in tunnel crown settlement and the excavation depth of the overlying pit during tunnel undercrossing. Furthermore, sensitivity analysis indicates that increasing the embedment depth of the diaphragm wall effectively reduces horizontal displacement at the wall base. Increasing the wall thickness decreases displacement in the upper section of the wall. Similarly, increasing pile diameter and anchor length and diameter, while reducing the inclination angle of anchors, are all effective in minimizing the lateral displacement of the support structure. Full article

Clarifying the trade-offs and synergies between land use and ecosystem services in major water source river basins is enhancing regional land resource distribution and safeguarding water-related ecological environments. The Danjiangkou Reservoir Basin—the water source area of the South-to-North Water Diversion Project—land use change characteristics from 2012 to 2022 were focused on in this study. Five categories of ecosystem services, represented by six land use-related indicators, were selected for analysis. The InVEST model was utilized to conduct a quantitative assessment of their spatial and temporal variations. This study investigates the spatial variations of ecosystem services, analyzes their trade-offs and synergies, and explores the impacts of land use changes on the supply and interactions of these services. The findings reveal that cultivated land was served as the dominant source of land use conversion. Specifically, the largest areas of cultivated land conversion were to forest land (240.91 km²), followed by water bodies (144.65 km²) and construction land (38.43 km²). The selected ecosystem services exhibited distinct temporal and spatial variation: water yield, total carbon storage, and habitat quality showed upward trends, whereas total nitrogen output, total phosphorus output, and soil erosion demonstrated declining trends. Overall, the synergy and trade-off relationships among the six ecosystem service indicators weakened; however, the degree of improvement in trade-offs exceeded the decline in synergies. The integration of land use change, ecosystem service functions, and trade-off/synergy relationships into a unified analytical framework facilitates a robust theoretical foundation for basin-scale ecological management. This approach offers a scientific foundation for spatial optimization, ecological redline delineation, and resource allocation within the basin. Full article

Ensuring the safe landing of deep-sea mining vehicles (DSMVs) on soft seabed sediments is critical for the stability and operational reliability of subsea mineral extraction. However, deep-sea sediments, particularly in polymetallic nodule regions, are characterized by low shear strength, high compressibility, and rate-dependent behavior, posing significant challenges for full-scale experimental investigation and predictive modeling. To address these limitations, this study develops a high-fidelity finite element simulation framework based on the Coupled Eulerian–Lagrangian (CEL) method to model the landing and penetration process of full-scale DSMVs under various geotechnical conditions. To overcome the high computational cost of FEM simulations, a data-driven surrogate model using the random forest algorithm is constructed to predict the normalized penetration depth based on key soil and operational parameters. The proposed hybrid FEM–ML approach enables efficient multiparameter analysis and provides actionable insights into the complex soil–structure interactions involved in DSMV landings. This methodology offers a practical foundation for engineering design, safety assessment, and descent planning in deep-sea mining operations. Full article

Designing deep foundations in densely urbanized areas presents significant challenges due to complex soil conditions, high groundwater levels, and the proximity of sensitive infrastructure. This study addresses these challenges through the development and numerical analysis of a combined pile–raft foundation (CPRF) system for a 75 m tall hotel tower in Frankfurt am Main, Germany. The construction site is characterized by heterogeneous soil layers and is located adjacent to a historic quay wall and bridge abutments, necessitating strict deformation control and robust structural performance. A comprehensive three-dimensional finite element model was developed using P_LAXIS 3D to simulate staged construction and soil–structure interaction (SSI). The CPRF system comprises a 2 m thick triangular raft and 34 large-diameter bored piles (1.5 m in diameter, 40–45 m in length), designed to achieve a load-sharing ratio of 0.89. The raft contributes significantly to the overall bearing capacity, reducing bending moments and settlement. The predicted settlement of the high-rise structure remains within 45 mm, while displacement of adjacent heritage structures does not exceed critical thresholds (≤30 mm), ensuring compliance with serviceability criteria. The study provides validated stiffness parameters for superstructure design and demonstrates the effectiveness of CPRF systems in mitigating geotechnical risks in historically sensitive urban environments. By integrating advanced numerical modeling with staged construction simulation and heritage preservation criteria, the research contributes to the evolving practice of performance-based foundation design. The findings support the broader applicability of CPRFs in infrastructure-dense settings and offer a methodological framework for future projects involving complex SSI and cultural heritage constraints. Full article

This study introduces an innovative deflection-controlled design method (DCM) for evaluating the bearing capacity of offshore mono-bucket foundations (MBFs) in clay, integrating advanced numerical simulations using FLAC3D with the modified cam clay (MCC) soil model. Departing from conventional ultimate bearing capacity approaches, the proposed method prioritizes serviceability limits by constraining foundation deflections to ensure optimal structural performance and turbine efficiency. A systematic investigation revealed that the MBF performance is predominantly governed by eccentricity ratios and soil–structure interaction, with vertical loads exhibiting a minimal impact in a serviceability limit state. Key findings include the following: (1) the rotation center (RC) stabilizes at approximately 0.8 times the skirt length (L) under loading; (2) thin, deep MBFs (aspect ratio > 1.0) exhibit up to a 30% higher bearing capacity compared to wide, shallow configurations; (3) increasing eccentricity ratios (ε = 0.31–1.54) enhance the moment capacity but reduce the allowable horizontal force by 15–20%; (4) compressive vertical loads (υ = −0.30) slightly reduce the normalized bending moments (ω) by 5–10% at low eccentricities (ε < 0.5). The numerical framework was rigorously validated against centrifuge test data, demonstrating high accuracy (error < 3%) in predicting foundation behavior. By bridging geotechnical mechanics with practical engineering requirements, this study provides a robust and efficient design framework for MBFs, offering significant improvements in reliability and cost-effectiveness for offshore wind turbine applications. The proposed DCM successfully guided the design of an MBF in southeastern China, demonstrating its efficacy for use with homogeneous clay. Full article

Efficient irrigation management is essential for optimizing yield and quality in specialty crops like hot peppers (Capsicum chinense), particularly under controlled greenhouse environments. This study employed a novel sensor-based system integrating soil moisture and sap flux monitoring to evaluate water use dynamics in Capsicum chinense, a species for which such applications have not been widely reported. Three cultivars—Habanero, Helios, and Lantern—were grown under three volumetric soil moisture contents: low (15%), medium (18%), and high (21%). Water uptake was measured at leaf (transpiration, stomatal conductance) and plant levels (sap flux via heat balance sensors). Photosynthesis, fruit yield, and capsaicinoid concentrations were assessed. Compared to high irrigation, medium and low irrigation increased photosynthesis by 16.6% and 22.2%, respectively, whereas high irrigation favored greater sap flux and vegetative growth. Helios exhibited an approximately 8.5% higher sap flux as compared to Habanero and about 10% higher as compared to Lantern. Helios produced over 30% higher fruits than Habanero and Lantern under high irrigation. Habanero recorded the highest pungency, with a capsaicinoid level of 187,292 SHU—exceeding Lantern and Helios by 56% and 76%, respectively. Similarly, nordihydrocapsaicin and dihydrocapsaicin accumulation were more cultivar-dependent than irrigation-dependent. No significant interaction between cultivar and irrigation was observed, indicating genotype-driven water use strategies. Our study contributes to precision horticulture by integrating soil moisture and sap flux sensors to reveal cultivar-specific water use strategies in Capsicum chinense, thereby demonstrating the potential of an integrated sensor-based irrigation system for efficient irrigation management under increasing water scarcity in protected environments. As a preliminary greenhouse study aimed at maintaining consistent irrigation throughout the growing season across three volumetric soil moisture levels, these findings provide a foundation for subsequent validation and exploration under diverse soil moisture conditions including variations in stress duration, stress frequency, and stress application at different phenological stages. Full article

Accurately assessing the spatiotemporal dynamics and influencing factors of ecosystem stability in arid desert regions (ADR) is crucial for ecological conservation and the achievement of high-quality regional development. However, existing assessment frameworks generally fail to adapt to the extremely fragile ecological conditions of ADR. Therefore, the Alxa Desert, a typical region, was selected as the research region, and an ecosystem stability assessment framework tailored to regional characteristics (perturbation–resilience–function) was constructed. Perturbation represents external pressure, resilience reflects the capacity for recovery and adaptation, and function serves as the supporting foundation. The three dimensions are dynamically coupled and jointly determine the stability status of the ecosystem in the Alxa Desert. Methodologically, this study innovatively introduces the Cloud Model–Analytic Hierarchy Process (CM-AHP) to calculate indicator weights, which more effectively addressed the widespread fuzziness and uncertainty inherent in ecosystem assessments compared to traditional methods. In addition, spatial autocorrelation methods was applied to reveal the spatial and temporal evolution characteristics of ecosystem stability from 2000 to 2020. Furthermore, the optimal parameters geographical detector model (OPGDM) was applied to analyze the effects of natural and human factors on the spatial differentiation of ecosystem stability in Alxa Desert. In addition, the Markov–FLUS model was employed to simulate the future trends of ecosystem stability over the next two decades. The results indicate that ecosystem stability in Alxa Desert from 2000 to 2020 was primarily characterized by vulnerable and moderate levels, with the area classified as extremely vulnerable decreasing significantly by 10% relative to its extent in 2000. Spatially, higher stability was observed in oasis regions and southeastern mountainous regions, while lower stability was concentrated in the desert hinterlands. Overall, ecosystem stability shifted from vulnerable toward moderate levels, reflecting a trend of gradual improvement. From 2000 to 2020, the Moran’s I varied between 0.78 and 0.81, showing strong spatial clustering. Surfce Soil moisture content (SSMC), Soil organic carbon (SOC), and enhanced vegetation index (EVI) were the primary factors influencing the spatial differentiation of ecosystem stability in Alxa Desert. The interaction between these factors further enhanced their explanatory power. Future forecasting results indicate that ecosystem stability will further improve by 2030 and 2040, particularly in the northern and southern areas of Alxa Left Banner and Alxa Right Banner. The findings can offer a theoretical foundation for future ecological conservation and environmental management in ADR. Full article

The plant microbiome plays a role in pathogen defense, but its role in different resistant varieties and ecological niches remains unclear. This study used 16S rRNA and ITS sequencing to investigate microbial communities and interactions in disease-resistant (PT) and susceptible (Bourbon) coffee varieties of five ecological niches: leaves, fruits, roots, rhizosphere soil, and non-rhizosphere soil. We found that the microbial communities differed significantly between the two varieties. The resistant variety was enriched in beneficial bacteria from the Actinobacteriota phylum and a stable, modular microbial network dominated by saprotrophic fungi. In contrast, the susceptible variety had a higher abundance of opportunistic pathogens and stress-indicator fungi, including Neurospora spp., which were more prominent in the rhizosphere and non-rhizosphere soils. These networks were fragile and dominated by pathotrophic fungi, reflecting ecological imbalance. Our findings show that plant disease resistance is influenced not only by host genetics but also by co-evolutionary interactions with the microbiome. These insights provide a foundation for developing targeted biocontrol strategies to manage plant-associated microbial communities. Full article

Accidental surface surcharge will generate additional load in the stratum, which then leads to unfavorable impacts on the underlying shield tunnel. This paper proposes a probabilistic analysis method to address this problem. In this framework, an improved soil–tunnel interaction model considering the nonlinearity of the subgrade is established at first, and the Newton–Raphson iterative solution algorithm is employed to acquire tunnel responses. Then, the random field models of the initial stiffness and the ultimate reaction of the subgrade are constructed to realize the spatial variability of soil properties. Finally, with the aid of the Monte Carlo Simulation method, the probabilistic analyses on tunnel responses are performed by combining the improved soil–tunnel interaction model and the random field model of subgrade parameters. The applicability and the superiority of the improved soil–tunnel interaction model are validated by a historical case from Shanghai Metro Line 9. The results prove that the traditional linear foundation model will overestimate the bearing capacity of the subgrade, thereby leading to overly optimistic assessments of surcharge-induced tunnel responses. This shortcoming could be addressed by the improved nonlinear soil–tunnel interaction model. The influences of spatial variability of soil properties on tunnel responses are nonnegligible. The stronger the uncertainties of subgrade parameters, in terms of the initial stiffness and the ultimate reaction concerned in this work, the higher the failure risk of the shield tunnel subjected to the surcharge. The failure modes of the tunnel subjected to the surcharge are controlled by the longitudinal curvature radius of the tunnel within the current assessment criteria, which means if this evaluation indicator can be restricted within the allowable value, then the opening of the circumferential joint and the longitudinal settlement can also meet the requirements. Compared with the influences of the uncertainty of the subgrade ultimate reaction, the spatial variability of the subgrade initial stiffness has greater influences on tunnel failure risk under the same conditions. An increase in the range of surcharge will raise the risk of tunnel failure, while the influence of tunnel burial depth is just the opposite. Full article

Drought is a global issue that affects agricultural productivity and sustainable development. The application of Bacillus subtilis has significant potential in alleviating drought stress and increasing yield. However, it is not yet clear how Bacillus subtilis affects microbial populations, crop yield, and the biochemical characteristics of rhizosphere soil, as well as the interactions among these factors. In this study, cotton was used as the experimental crop, and different application rates of Bacillus subtilis (0 kg·ha⁻¹ and 45 kg·ha⁻¹ (B)) and drought stress levels (H represents conventional irrigation, 350 mm; L represents 80% of conventional irrigation, 280 mm) were set as three replicates per group. The changes in rhizosphere-soil-related variables, microbial community diversity, enzyme activity, and cotton yield were studied. Compared to the control, the available nitrogen content increased by 19.76–62.40%, and soil moisture increased by 2.48–7.72%. The activities of urease, sucrase, and alkaline phosphatase increased, malondialdehyde content decreased, the Soil Plant Analysis Development (SPAD) value increased, and cotton yield increased by 8.94–9.28%. According to the structural equation model, Bacillus subtilis can increase microbial community diversity and network complexity, improve soil nutrients and enzyme activity, and increase cotton yield. This study’s findings may offer a theoretical foundation for enhancing soil quality and raising agricultural yields in arid regions. Full article

Large-diameter rock-socketed monopiles supporting offshore wind turbines in soft clay strata face significant geotechnical risks from negative skin friction (NFS) induced by construction surcharges. While the effects of NFS on axial drag loads are documented, the critical interaction between horizontal pile loading and NFS development remains poorly understood. This research bridges this gap using a rigorously validated 3D finite element model that simulates the complex coupling of vertical substructure loads (5 MN), horizontal loading, and surcharge-induced consolidation. The model’s accuracy was confirmed through comprehensive verification against field data for both NFS evolution under surcharge and horizontal load–displacement behavior. The initial analysis under representative conditions (10 MN horizontal load, 100 kPa surcharge, 3600 days consolidation) revealed that horizontal loading fundamentally distorts NFS distribution in the upper pile segment (0 to −24 m), transforming smooth profiles into distinct dual-peak morphologies while increasing the maximum NFS magnitude by 57% (from −45.4 kPa to −71.5 kPa) and relocating its position 21 m upward. This redistribution was mechanistically linked to horizontal soil displacement patterns. Crucially, the NFS neutral plane remained invariant at the clay–rock interface (−39 m), demonstrating complete independence from horizontal loading effects. A systematic parametric study evaluated key operational factors: (1) consolidation time progressively increased NFS magnitude throughout the clay layer, evolving from near-linear to dual-peaked distributions in the upper clay (0 to −18 m); NFS stabilized in the upper clay after 720 days while continuing to increase in the lower clay (−18 to −39 m) due to downward surcharge transfer, accompanied by neutral plane deepening (from −36.5 m to −39.5 m) and 84% maximum axial force escalation (12.5 MN to 23 MN); (2) horizontal load magnitude amplified upper clay NFS peaks at −3.2 m and −9.3 m, with the shallow peak magnitude increasing linearly with load intensity, though it neither altered lower clay NFS nor neutral plane position; (3) surcharge magnitude increased overall NFS, but upper clay NFS (0 to −18 m) stabilized beyond 100 kPa, while lower clay NFS continued rising with higher surcharges, and the neutral plane descended progressively (from −38 m to −39.5 m). These findings demonstrate that horizontal loading critically exacerbates peak NFS values and redistributes friction in upper pile segments without influencing the neutral plane, whereas surcharge magnitude and consolidation time govern neutral plane depth, total NFS magnitude, and maximum drag load. This research delivers essential theoretical insights and practical guidelines for predicting NFS-induced drag loads and ensuring the long-term safety of offshore wind foundations in soft clays under complex multi-directional loading scenarios. Full article