Search Results (7,084)

To evaluate the ameliorative effects of different green manure crops on continuously cropped protected pepper soil and to identify suitable green manure species for plateau-protected cultivation systems, a one-factor randomized complete block design was conducted with five treatments: common vetch (L1), pea (L2), hairy vetch (L3), radish (L4), and a control without green manure (CK). Soil physicochemical properties, enzyme activities, and microbial community composition were determined at the full-bloom stage before green manure incorporation. Compared with CK, L1 reduced soil pH from 8.63 to 8.34 and decreased total salt content by 45.5%, increased alkali-hydrolyzable nitrogen by 40.93%, and significantly enhanced catalase activity. L3 increased available phosphorus by 23.72% and urease and sucrase activities by 71.32% and 56.31%, respectively, while significantly affecting fungal β-diversity and community composition. Community composition analysis showed that L3 increased the relative abundances of the bacterial genus Rhizobium and the fungal genus Rhizophagus, while reducing the relative abundance of Ascomycota and several potentially pathogen-associated fungal taxa. Redundancy analysis and Mantel tests indicated that bacterial community composition was mainly associated with soil total salt content, alkaline phosphatase, and available phosphorus, whereas fungal community composition was more closely related to urease and alkaline phosphatase. Random forest analysis and partial least squares path modeling further suggested that sucrase, urease, and catalase were important factors closely associated with changes in the soil quality index (SQI). Overall, common vetch performed better in reducing soil salinity, increasing alkali-hydrolyzable nitrogen, and improving the soil quality index and may therefore be considered a suitable green manure species for improving continuously cropped protected pepper soil on the Qinghai Plateau. Hairy vetch showed advantages in increasing available phosphorus and regulating fungal community composition, indicating its potential suitability for protected soils with limited phosphorus availability. Full article

Saline-affected soils exhibit poor mechanical properties and are prone to durability degradation under environmental disturbances, severely hindering infrastructure development in saline-affected regions. This study adopted a synergistic consolidation treatment for sulfate-salinized soils using a guar gum (GG) and Portland cement composite system, formulating 25 mix designs with GG content ranging from 0% to 2% and cement content from 0% to 12%. The unconfined compressive strength (UCS), dry–wet cycle durability, and repeated load fatigue performance of the stabilized soils were systematically tested. Combined with microstructural characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and CT scanning, the evolution patterns of the solidified soil’s mechanical properties and the macro-micro interaction mechanisms were revealed. Results indicate that cement is the primary strength source in cement-stabilized soil: at a cement dosage of 12%, the UCS reaches 2.53 MPa, a 41-fold increase compared to the native soil. A significant synergistic strengthening effect exists between cement and GG at the optimal GG dosage of 0.5%–1.0%, with the optimal mixture ratio being 6%–9% cement blended with 0.5%–1.0% GG. With this optimized ratio, the stabilized soil shows a strength retention rate of 87.2% after 10 dry–wet cycles, and its fatigue life extends to 1986 cycles (a 42.6% increase compared to pure cement-stabilized specimens). Microstructural analysis suggests that the stabilization process is fundamentally governed by interfacial micro-coating mechanisms. The reaction between cement aluminates and soil sulfates generates abundant ettringite, which is hypothesized to form a rigid skeletal framework. Simultaneously, GG forms a hydrogel network that acts as a dense, protective organic–inorganic micro-coating on the surface of soil aggregates and cement phases. This interfacial encapsulation optimizes the pore structure, reducing porosity to 1.43% and fundamentally blocking inward water infiltration pathways at the aggregate interface. However, excessive GG (>1.5%) coats cement particles, hinders hydration reactions and induces structural defects, ultimately leading to performance degradation. This study elucidates the macro-micro coupled mechanism of GG-cement composite consolidation for saline–alkali soils, providing theoretical foundations and technical solutions for saline–alkali soil consolidation engineering. Full article

Forest understorey herbs are an under-studied component of subtropical mountain forest biodiversity, yet they include several genera of high medicinal and economic value. The rhizomes of Polygonatum (Liliaceae) are a prominent example, but the forest-ecological controls on their bioactive composition in wild populations—particularly for co-occurring congeners—remain poorly resolved. We sampled 92 wild plants of Polygonatum cyrtonema and P. filipes along four altitudinal transects (330–1730 m) in a subtropical mountain forest reserve in southeastern China, quantifying total polysaccharide, three flavonoid monomers (rutin, quercetin, and methylophiopogonanone B), and two LC–MS class signals (ΣFlavonoid, ΣSaponin), together with 13 topographic, edaphic, and biotic predictors. The two species displayed the following distinct rhizome chemical phenotypes: P. cyrtonema tended toward higher ΣSaponin; P. filipes toward higher ΣFlavonoid. The clearest pattern was a robust species × altitude interaction for total polysaccharide (p = 0.002), with the two species following opposite altitudinal trajectories. In multivariate forward-selected redundancy analysis, canopy closure and species identity emerged as the only retained environmental predictors, identifying forest light environment as the strongest single environmental correlate of rhizome chemical variation. Species-specific bivariate analyses further revealed contrasting driver hierarchies as follows: P. cyrtonema chemistry tracked topography, whereas P. filipes chemistry tracked rhizosphere soil enzymes and chemistry; only soil temperature and urease activity were shared across species. These results argue that altitude is not a uniform predictor of rhizome chemistry in wild Polygonatum, and support species-specific, canopy-aware management of medicinal forest understorey herbs in subtropical mountain forests. Full article

To address the dilemma of ‘non-grain use of cultivated land’ and support China’s requisition–compensation balance policy, this study developed a multi-dimensional assessment framework integrating the production, ecological, and economic dimensions (3D evaluation model), using Shenyang City as a case study to demonstrate the framework’s operational application and policy relevance. Based on 34,704 Third National Land Survey (TNLS) parcels (27,408.39 ha), we applied the constraint factor assessment method and entropy-weighted composite index model. The results show that non-cultivated agricultural land (NCAL) is generally marginally suitable (citywide average score: 2.50/4), with highly suitable areas accounting for only 4.04% (1106.30 ha). These areas exhibit a triangular spatial pattern distributed across northeastern Faku County, central Sujiatun District, and southern Xinmin City. Sensitivity tests using equal weights and ±20% dimension-weight perturbations confirm that high-suitability area remains limited (3.37–5.63% under entropy-weight scenarios; 8.54% under equal weights). Primary limiting factors include severe organic matter deficiency (average 19 g/kg), shallow soil depth, unfavorable pH, land requiring engineering restoration (94%), and punctiform heavy metal contamination (7.53% of plots, 2065.05 ha as spatially excluded areas). Consequently, we propose a five-tier sequential restoration framework: (1) near-term priority recultivation of highly suitable areas; (2) mid-term topsoil reconstruction for moderately suitable areas; (3) medium-to-long-term topsoil stripping and thickening for low-suitability areas; (4) long-term soil amelioration and slope-to-terrace conversion for marginally suitable areas; and (5) strict prohibition of restoration in unsuitable areas. This study establishes a spatially explicit decision-making system integrating “evaluation–classification–sequencing”, and distinguishes technical suitability from economic, institutional, and policy feasibility, providing a decision-support framework for scientifically implementing the cultivated land requisition–compensation balance policy. Future empirical studies using post-restoration monitoring data are needed to test its predictive accuracy against observed restoration outcomes. Full article

Polycyclic aromatic hydrocarbons (PAHs) are persistent and toxic pollutants that accumulate in urban soils, reducing microbial diversity and compromising ecosystem functioning. Developing effective bioremediation strategies requires identifying native degraders and understanding their ecological dynamics under pollutant pressure. Here, we investigated fungal and bacterial communities from PAH-contaminated soil subjected to three consecutive enrichment steps using phenanthrene, fluoranthene, benzo(a)pyrene, benzo(g,h,i)perylene, and their mixture as the sole carbon sources. High-throughput sequencing of ITS2 and V3-V4 amplicons revealed a decline in alpha diversity and a strong restructuring of both communities during the enrichment. Distance-based redundancy analysis showed that contaminant type and enrichment progression jointly shaped community composition, selecting for stress-tolerant taxa. Culturomics yielded 102 fungal isolates, representing 19 taxa, predominantly within Ascomycota. The most represented taxa were Galactomyces pseudocandidus (19 strains), Fusarium oxysporum (five), Stilbella aciculosa and Exophiala attenuata (four each) and Fusarium solani (three). Approximately one-third of isolates harbored associated bacteria, mainly Stenotrophomonas, Bosea and Chitinophaga species. Functional assays identified biosurfactant-producing strains, while microplate screening highlighted Fusarium solani, Galactomyces pseudocandidus and Trametes versicolor as capable of growing under PAH-selective conditions. Overall, our results demonstrate that PAH-contaminated soils host fungal taxa able to persist under pollutant pressure together with recurrent fungi-associated bacteria of potential ecological relevance for bioremediation. Full article

Waste lubricating oils (WLOs) represent a major stream of hazardous petroleum-based residues, with global generation exceeding 24 million tons annually. Improper disposal of WLOs poses risks to soil, water, and air quality, while their chemical composition makes them a potential secondary resource within circular economy frameworks. This review summarizes conventional, advanced, and emerging technologies reported for the recycling and valorization of WLOs into high-value petrochemicals and carbon-based materials. Established processes such as acid–clay treatment, solvent extraction, and vacuum distillation are discussed together with more recent approaches, including catalytic upgrading, hydrotreatment, membrane separation, and thermochemical conversion methods such as pyrolysis and catalytic cracking. Reported data on process performance, environmental considerations, techno-economic indicators, and life cycle assessment outcomes are comparatively analyzed to outline current trends, technical challenges, and future development directions in WLO recycling. Particular attention is given to thermochemical pathways capable of generating carbonaceous materials, including carbon black, porous carbons, and functional carbon nanostructures with potential applications in adsorption, catalysis, electrochemical systems, and tribological formulations. Hybrid and integrated process configurations described in the literature are highlighted for their potential to improve recovery efficiency, enhance product quality, and reduce environmental burdens. In addition, recent life cycle assessment (LCA) and techno-economic analysis (TEA) studies are reviewed to provide insight into the environmental and economic implications of advanced re-refining systems. Overall, the reviewed literature indicates that WLO recycling represents not only an important element of sustainable lubricant management but also a promising waste-to-carbon strategy for the production of value-added carbon-based materials and petrochemical products. Full article

Soil organic carbon (SOC) plays a critical role in climate regulation, soil fertility, and ecosystem resilience, making its accurate spatial quantification essential for sustainable land management and greenhouse gas (GHG) reporting. However, mapping SOC in heterogeneous agroforestry systems remains challenging due to vegetation cover and landscape complexity. In this study, we develop and evaluate a hybrid bare soil modelling- Digital Soil Mapping supported by ML framework to generate high-resolution soil properties predictions in Mediterranean agroforestry systems (Extremadura, Spain). A dual modelling approach was implemented, combining (i) Bare Soil modelling using Sentinel-2 multi-temporal reflectance composites and (ii) Digital Soil Mapping (DSM) supported by environmental covariates (climate, terrain, vegetation) following the SCORPAN framework. Machine learning models, namely Quantile Regression Forests (QRF) and Extreme Gradient Boosting (XGBoost), were applied and optimised using automated hyperparameter tuning (FLAML). A total of 107 LUCAS topsoil samples and 36 complementary points from the Forest ICP Level I were used for calibration and validation, with a 70/30 train–test split. Results show that Sentinel-2-based modelling can effectively capture SOC spatial variability in bare soil conditions, while DSM improves predictions in vegetated areas. Model performance reached R² values up to 0.76 (QRF, pH) and RMSE as low as 0.03 (XGBoost, N), with uncertainty quantified using the Prediction Interval Ratio (PIR) and performance further supported by RPIQ values up to 3.15. However, prediction accuracy remains sensitive to vegetation structure and sample density. The proposed framework provides a scalable and uncertainty-aware approach for SOC mapping, supporting Tier-3 GHG inventories and emerging Monitoring, Reporting, and Verification (MRV) systems. The results highlight the importance of integrating multi-source datasets and hybrid modelling strategies for reliable SOC estimation in complex landscapes. Full article

Plinthite is a major pedogenic feature in the Kamuli catena, posing significant challenges for agricultural land use. This study investigates the morphological expression and mineralogical insights into plinthite within the soil-landscape of Kamuli District. Soil characterization involved detailed field morphological descriptions along the Kamuli catena followed by laboratory characterization of major soil properties. Plinthite mineralogy was determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Morphology of plinthic soils varied along the catena with summit pedons exhibiting shallow plinthic horizons and backslope pedons showing comparatively deeper occurrences. The lowlands underlain by alluvium of the Holocene lacked plinthite. Mineralogical analysis of ten plinthite samples identified two distinct assemblages. Group 1 (quartz, kaolinite, hematite, goethite, manganite) represents a highly weathered endmember associated with stable summits. Group 2 (muscovite, kaolinite, hematite, goethite, manganite), with elevated K, Mg, Na, and Ca in SEM-EDS, indicating they are recent compared to Group 1. This elemental composition directly reflects the signature of the parent material preserved within Group 2 samples. Plinthite in the Kamuli catena is a relict feature, whose formation is tied to past drainage regimes. Its multi-stage history is recorded in the two mineralogical groups separated by hundreds of thousands of years of landscape evolution. Group 1 represents plinthite from the deeply weathered African Surface. Group 2 is later formed on the substrate exposed by stripping along the Victoria Nile. Full article

To reveal the differences in stratum response among different environmental sections and the influences of key construction parameters on deep soil deformation during river-crossing double-line shield tunneling, the paper takes the East Genshan Road River-Crossing Tunnel as the engineering case, and systematically investigates the stratum responses of the onshore and riverbed sections as well as the effects of construction parameters via field monitoring, measured construction parameter data and three-dimensional finite element simulation based on ABAQUS. The simulation results suggest that, compared with the onshore section, the riverbed section may present larger cumulative displacement, more intense deep soil response and a wider influence range of transverse settlement under the investigated high-water-pressure and saturated soft-soil conditions. These differences are more reasonably interpreted as the combined effects of burial depth, stratum composition, mechanical properties, hydraulic boundary conditions, surface boundary constraints and overburden conditions. Among these factors, the high-water-pressure and saturated soft-soil environment may contribute to the enhanced disturbance diffusion and cumulative deformation response observed in the riverbed section. The longitudinal displacement evolution of the riverbed section presents obvious stratified transmission characteristics, and its transverse settlement trough shows a typical double-peak W-shaped distribution with larger peak values, wider trough profile and slower far-field attenuation. The single-factor parametric analysis suggests that, within the investigated parameter ranges, cutterhead torque produced the largest absolute settlement variation, followed by total shield thrust and tunneling speed. The results of this study can provide a reference basis for settlement control and construction parameter optimization of river-crossing double-line shield tunneling in high-water-pressure and saturated soft soil strata. Full article

To evaluate the effects of saline water on the yield and quality of tomatoes, a late fruit-setting stage irrigation experiment was conducted in a greenhouse using two cultivars: medium-fruited, tasty Strawberry tomato (fresh-eating) and large-fruited Maofen tomato (fresh/processing). For this, plants were grown in pots containing substrate, and five irrigation water electrical conductivity (EC) levels (1.0 as control, 2.6, 4.2, 5.8, and 7.4 dS m⁻¹) were applied for each cultivar, resulting in a 2 × 5 factorial design with 10 treatments in total. Then, tomato growth, fruit ion composition, and quality attributes were evaluated. The results showed that 1.0–7.4 dS m⁻¹ saline water had no significant impact on the plant height, stem diameter, single-fruit weight, or total yield of either cultivar. However, Strawberry tomato’s marketable yield decreased by 23.5% at 7.4 dS m⁻¹. The yield per plant of Maofen tomato was 2.7 times that of Strawberry tomato. Fruit Na⁺ content increased with EC for both cultivars; Maofen tomato had higher Na⁺ and a lower K⁺/Na⁺ ratio, with greater ion content responses to salinity. Regression analysis revealed distinctly nonlinear responses in key yield, ion, and quality parameters across the salinity gradient. The fruit comprehensive quality score (CQS) rose with EC, and Strawberry tomato’s average CQS increase (109%) was significantly higher than Maofen tomato’s. In conclusion, saline irrigation initiated when the fourth-cluster fruits attained 60% of the final harvested diameter, at EC ≤ 5.8 dS m⁻¹ for Strawberry tomato and ≤7.4 dS m⁻¹ for Maofen tomato, improved fruit quality without compromising yield. Strawberry tomato is recommended for quality-oriented production, whereas Maofen tomato is better suited for yield-oriented production, providing scientific support for saline water utilization in greenhouse soil-less cultivation. Full article

Soil fungi are key drivers of terrestrial ecosystem functioning, contributing to organic matter decomposition, nutrient cycling, and plant–microorganism interactions. Despite their importance, the global distribution and structural biases of public sequence records for soil fungi remain incompletely characterized. In this study, we analyzed soil-associated fungal DNA sequences retrieved from the NCBI GenBank database using a custom R-based bioinformatics pipeline. Following filtering and metadata standardization, 544,554 filtered sequence records were obtained. The taxonomic composition of the dataset consisted primarily of Ascomycota (69.62%), followed by Basidiomycota, Glomeromycota, and Mucoromycota, with Trichoderma, Penicillium, and Aspergillus representing the most frequent genera. The geographic distribution revealed strong sampling bias, with China and the United States accounting for over one-third of all records. Ecological metadata indicated that rhizospheric and forest soils were the most common sources of the deposited sequences. At the same time, gene marker analyses confirmed the widespread use of the ITS region as the primary fungal barcode. Sequence diversity analyses revealed continental variation, with Europe and Asia showing higher medians, while the ordination highlighted clustering of sequence profiles, particularly among records from extreme environments. This study demonstrates the potential of public sequence databases for large-scale biodiversity assessments while highlighting the influence of sampling bias and the limitations of metadata. Full article

Medicinal plants are rich sources of bioactive secondary metabolites, yet their long-term effects on the rhizosphere (RS) microbial communities remain poorly understood, particularly with respect to microbial selection and functional potential. This study evaluated the number of selected groups of microorganisms culturable in vitro in the RS and bulk soil (BS) within 10-year monocultures of 11 medicinal plant species, and as a targeted case study, we performed shotgun metagenomic profiling for Allium ursinum. The abundance of microorganisms differed markedly among plant species, indicating species-specific RS selection. Azotobacter spp. showed the strongest variation: they were not detected in the RS of Allium ursinum, Thymus vulgaris, and Carum carvi, whereas higher counts were observed under Artemisia dracunculus (135.1 × 10² CFU g⁻¹ DM), Melissa officinalis (67.1 × 10² CFU g⁻¹ DM) and Calendula officinalis (38.8× 10² CFU g⁻¹ DM). Azotobacter spp. may serve as a sensitive candidate indicator of RS imbalance. Metagenomic analysis of the A. ursinum-associated soil revealed fine-scale taxonomic restructuring, while major functional categories remained broadly similar between the RS and BS. The novelty of this study lies in the development of the Integrated Microbiological Health Soil Index (IMHSI) and the proposal of a Nitrogen Enrichment Index (NEI) as exploratory composite metrics that integrate selected functional microbial groups. Full article

For hydrological parameterization in high-Andean catchments, it is necessary to understand whether near-surface hydro-structural soil properties can provide a surrogate signal of particle-size composition when direct texture information is sparse. This study evaluated the extent to which sand, silt, and clay fractions can be approximated from organic matter ($\mathrm{OM}$), bulk density (${\rho }_b$), and saturated hydraulic conductivity ($K_{\mathrm{sat}}$) in the Zamora Huayco (ZH) and Irquis catchments, southern Ecuador. A harmonized dataset ($n=44$) was analyzed through exploratory statistics, compositional assessment, correlation analysis, PCA, fraction-wise regression, $\mathrm{ILR}$-based modeling, AIC/BIC term reduction, sensitivity analysis excluding $\mathrm{OM}$, nested $\mathrm{LOOCV}$, and bootstrap-based uncertainty intervals. Among LULC classes, samples classified as paramo occupied a distinct high-Andean hydro-edaphic domain, characterized by a differentiated relationship between soil physical properties and hydrological behavior. PCA showed that the dominant covariance structure involved $\mathrm{OM}$, ${\rho }_b$, $K_{\mathrm{sat}}$, and the redistribution between sand and silt. The BIC-reduced $\mathrm{ILR}$ model provided the most balanced formulation, with positive nested $\mathrm{LOOCV}$ performance for sand, silt, and clay ($R_{\mathrm{LOOCV}}^2=0.147$, $0.704$, and $0.124$, respectively) and exact $100\%$ compositional closure after inverse transformation. Silt was the most stable predicted fraction, whereas sand and clay retained larger residual uncertainty, stronger tail departures, and partial compression of the observed variability. The proposed equations provide local hydro-pedotransfer support, although their predictive signal remains dependent on further refinement, uncertainty assessment, and external validation before regional application. Full article

The agricultural and environmental application of Miscanthus × giganteus biomass ash (MBA) as a soil amendment requires a thorough assessment of its properties, nutrient potential, and associated risks. This study characterizes the elemental composition, pH, cation exchange capacity (CEC), and polycyclic aromatic hydrocarbons (PAHs) content of MBA in comparison with other common biomass ashes (crops, wood, and sewage sludge) referred to the international regulatory standards. The ash exhibits a strong alkaline pH (11.03), suggesting potential to improve soil pH in acid soils, but requires careful controlled application to prevent excessive alkalization. The main nutrients detected include K (5.54%), Ca (2.07%), Mg (0.37%), and P (0.86%), indicating its potential as a soil amendment, though long-term use may cause nutrient imbalances. Micronutrients such as Zn (240.67 mg·kg⁻¹), Mn (297 mg·kg⁻¹), and Cu (33.5 mg·kg⁻¹) are found in concentrations suitable for agricultural use, while potentially toxic elements (PTEs), including Cd, Cr, Ni, and Pb, are below detection limits, thereby reducing the risk of pollution. As (8.3 mg·kg⁻¹) and ΣPAHs (1.63 mg·kg⁻¹) remain within safety thresholds, suggesting a low environmental toxicity of MBA. The low Na content (0.12%) indicates a minimal risk of salinity accumulation, distinguishing MBA from high-sodium biomass ashes. Soil alkalization, disruptions in nutrient balance, and element leaching are risks to be considered. Despite these concerns, its composition is in agreement with established safety guidelines, supporting its feasibility for valorization as a sustainable soil amendment and remediation material. To maximize agronomic benefits and mitigate environmental risks, it is important to utilize the ash, considering site conditions and carry out regular monitoring of the soil. Full article

Intensive agricultural practices based on continuous monocropping and prolonged bare-soil fallows have contributed to soil degradation and loss of biological functioning. Replacing fallows with cover crops (CCs) is a promising strategy to restore soil quality, yet their legacy effects on rhizosphere fungal communities remain poorly understood. This study evaluated the legacy effects of Urochloa (syn. Brachiaria) brizantha cover cropping on rhizosphere fungal communities, as well as soil physicochemical and biological properties, in a degraded common bean system. A field experiment with a randomized complete block design included: bare fallow (BM), one (B1) or two (B2) CC cycles before bean, a perennial pasture (PB), and a pristine soil reference (PS). High-throughput sequencing showed that Urochloa-based treatments significantly shifted fungal community composition compared to BM, increasing saprotrophic and beneficial taxa (e.g., Mortierella, Penicillium, Coprinellus) and reducing potential pathogens such as Fusarium. These changes were associated with higher soil organic carbon, aggregate stability, microbial biomass, and enzyme activities, especially in B2 and PB. Indicator taxa identified by LEfSe were linked to organic matter decomposition and nutrient cycling. Multivariate analyses revealed strong associations between fungal community structure and soil properties. Overall, U. brizantha cover cropping induced measurable legacy effects, promoting soil biological recovery even after short-term implementation. Full article