Search Results (49)

Eukaryotic algae are an important component of the soil microbial community. However, there is limited knowledge about the seasonal variations in the structure of soil algal communities and the correlations between different algal groups and soil environmental factors. Based on gene sequencing of the 18S rRNA V4 region, the changes in the community structure of eukaryotic algae in three different types of soil (sandy soil, forest soil and grassland soil along urban inland lake (Wuhan, China) coast) across four seasons were analyzed, and the correlations between the major taxonomic groups and environmental factors were examined. The annotated algae were ranked by abundance as follows: Chlorophyta, Bacillariophyta, Charophyta, Cryptista, Rhodophyta, Haptophyta and Glaucophyta. The top seven genera in terms of richness were: Chlamydomonas, Tetracystis, Chlorella, Chlorococcum, Coelastrum, Bracteacoccus and Desmodesmus. All soil samples tended to be neutral to alkaline. Environmental drivers for different groups were also explored. In terms of correlation, the environmental factors most related to Chlorophyta were total nitrogen, total phosphorus, and pH. Total nitrogen and water content were most related to Bacillariophyta and Charophyta. The seasonal differences in soil eukaryotic algal communities are more pronounced than the differences between soil types. Chlorophyta and Bacillariophyta are the two most abundant groups in different seasons and soil types. There is a significant difference in community composition between winter and other seasons. Full article

The shrinking of glaciers is drastically transforming headwater catchments, exposing new land surfaces and forming new water bodies, characterized by marked environmental gradients and the activation of potential geochemical hazards. The aim of this study was to characterize and compare the geochemical patterns of soil and water in areas deglaciated between 1970/1984 and 2025 within the Llaca and Gueshgue valleys of the Cordillera Blanca, Peru. Systematic soil and water sampling was conducted, and data were analyzed using descriptive statistics and multivariate techniques. The analyses revealed a clear and statistically significant geochemical differentiation between the two areas (p ≤ 0.05). Gueshgue was identified as a system in transition, exhibiting geochemical signatures of acid rock drainage (ARD), with loamy soils rich in Fe and Al, and acidic waters featuring high redox potential and elevated concentrations of SO₄²⁻, EC, Co, Cu, Mn and Mg. In contrast, Llaca exhibited greater stability, with neutral waters and sandy soils dominated by silicate weathering signatures (SiO₂) and trace elements (Al, Li, Ba, K, and Ti). These findings indicate that the impact of glacier retreat on proglacial ecosystems is heterogeneous; identifying these geochemical patterns is fundamental to establishing baseline monitoring and guiding the sustainable management of these climate-change-sensitive ecosystems. Full article

Plant diversity is a key indicator of ecosystem structure, function, and restoration status, yet its rapid assessment remains challenging in sandy ecosystems where vegetation is sparse, spatially heterogeneous, and strongly affected by exposed soil backgrounds. In such environments, conventional greenness-based spectral indices may not adequately capture species-level variation because plant communities are controlled not only by photosynthetic biomass but also by soil moisture, micro-topography, and dune-related habitat heterogeneity. This study evaluated the potential of Sentinel-2-derived spectral indices for estimating plant α-diversity in the Hunshandak Sandland, northern China. Based on field observations from 888 plots collected during 2017–2024, four α-diversity metrics—species richness, Shannon–Wiener index, Simpson index, and Pielou evenness index—were calculated and compared with 21 spectral indices using correlation analysis, partial least squares regression (PLSR), and random forest (RF) models. The results showed that model performance varied substantially among diversity metrics. Species richness was estimated with the highest accuracy, whereas Shannon–Wiener, Simpson, and Pielou indices showed weaker predictability, indicating that remotely sensed spectral indices were more sensitive to species number than to abundance distribution and evenness. Moisture- and soil-background-sensitive indices, including the Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), Bare Soil Index (BSI/BRI), and Chlorophyll Absorption Ratio Index (CARI), showed relatively stable relationships with plant diversity across different vegetation gradients. Although the overall explanatory power was moderate rather than high, the results demonstrate the practical value of Sentinel-2 spectral indices for regional screening of plant diversity patterns in sandy ecosystems. This study provides empirical evidence for biodiversity monitoring and ecological restoration assessment in semi-arid sandy landscapes and highlights the need to integrate environmental covariates, multi-source remote sensing, and phenological information in future studies. Full article

Given the challenges posed by high groundwater levels, thick sand layers, and strong permeability in water-rich sandy strata, cut-off walls often fail to fully isolate the hydraulic connection between the inside and outside of a foundation pit. As a result, dewatering inside the pit—especially from confined aquifers—can cause significant external groundwater drawdown and subsequent ground settlement. Using a deep excavation conducted in Xiamen as a case study, this study developed a two-dimensional hydro-mechanical coupled finite element model to systematically investigate the effects of various dewatering scenarios and soil permeability coefficients on surface settlement around the pit, and to reveal settlement patterns induced by dewatering and excavation in such strata. Field monitoring data were incorporated to validate the numerical model, ensuring accuracy and reliability. Key findings include the following: (1) Dewatering contributes to over 76% of the total settlement at each stage, with confined drawdown being the dominant factor, implying that dewatering optimization should take priority over controlling excavation rate. (2) Under confined dewatering, the settlement influence zone extends beyond 80 m, far exceeding the extension caused by excavation alone; thus, monitoring and protection ranges must be adjusted dynamically. (3) The horizontal permeability of sand shows a nonlinear positive correlation with settlement, and this sensitivity grows with depth, highlighting the need for accurate permeability determination and stricter controls in deep excavations within water-rich sand layers. From an engineering perspective, these findings underscore the importance of prioritizing confined aquifer dewatering management, dynamically expanding settlement monitoring zones, and rigorously characterizing permeability profiles to mitigate excessive ground settlement and protect adjacent infrastructure. Full article

This study aimed to evaluate the leaching of nutrients and pathogens following the surface application of pH-modified slurry on sandy soil. Three slurry pH modification strategies—mineral and biological acidification (pH 5) and alkalinization (pH 9.5)—were tested using mineral acids or bases, paper-industry by-products, or combinations of additives. We hypothesized that: (i) acidification increases nitrogen (N) and phosphorus (P) leaching through nutrient solubilization, and (ii) effective sanitization reduces the risk of pathogen leaching. A 24-day column leaching experiment was conducted with slurry applied at 240 kg N ha⁻¹ and four weekly irrigation events. Results indicated that nitrate (NO₃⁻) leaching accounted for less than 15% of the total nitrogen applied; however, acidified slurry significantly increased ammonium (NH₄⁺) leaching by 72%. The combination of H₂SO₄ with sucrose reduced NH₄⁺ and NO₃⁻ leaching, although P leaching exceeded 35% of the total P applied. Sulphur (S) concentrations in leachates ranged from 42.3 to 112.8 mg S kg⁻¹ soil, particularly in treatments involving H₂SO₄ or SO₄²⁻—rich additives such as spent acid. Faecal coliform leaching declined throughout the study, with acidified slurry consistently maintaining levels below the threshold for irrigation water (<100 MPN/100 mL). Regarding nutrient leaching, pH-modified slurry may present a higher risk of N, P and S leaching compared to untreated slurry, which could also be interpreted as an increase in plant nutrient availability. Full article

Thermal conductivity is a key input parameter in geotechnical and shallow geothermal engineering, directly influencing the design, efficiency, and long-term performance of ground heat exchangers, energy piles, and ground-source heat pump systems. Reliable parameterisation of this property in sandy soils remains challenging due to nonlinear interactions between water content, bulk density, and soil structure. This study develops a machine-learning-based workflow for robust parameterisation of thermal conductivity in quartz-rich sands using a large, internally consistent laboratory dataset comprising 1716 samples, including 1455 moist measurements used for modelling, obtained from nationwide site investigations. Air-dry specimens were identified as laboratory-induced drying states and excluded to restrict the analysis to hydro-mechanical conditions representative of typical shallow subsurface environments. Several regression algorithms representing different modelling strategies were evaluated within a unified and reproducible framework and benchmarked against selected classical empirical formulations. Model performance was assessed using standard accuracy metrics together with diagnostics describing the functional stability of predicted thermal-conductivity surfaces. The results reveal a systematic trade-off between predictive accuracy and functional consistency, indicating that models optimised for accuracy may produce functionally unstable and less suitable parameterisations for engineering applications. Accuracy-optimised models frequently produce locally irregular parameter fields, whereas more strongly regularised models yield smoother and physically more coherent response surfaces. The proposed workflow supports reliable thermal-property parameterisation for geotechnical design and shallow geothermal modelling. Full article

Urban underground construction in water-rich sandy strata produces large quantities of high-fluidity pipe-jacking spoil whose high water content, residual conditioning agents and heavy metal contaminants make conventional dewatering and landfilling increasingly unsustainable under carbon peaking and neutrality targets. This study explores a low-carbon route that converts such spoil into CO₂ foamed concrete through a coupled alkali activation–CO₂ foaming process. Ground granulated blast furnace slag and fly ash are used as geopolymer precursors, while a CO₂-based aqueous foam is introduced as both a pore-forming phase and carbon source. Single-factor tests and an L16(4⁴) orthogonal design are conducted to quantify the effects of CO₂ concentration, foam volume fraction, geopolymer dosage and alkali activator content on fluidity, setting time and compressive strength. Scanning electron microscopy (SEM) is employed to examine pore structure, gel morphology, carbonate precipitation and the interfacial transition zone around spoil particles. The results identify an optimum mix window (CO₂ 60–80%, foam 70–80%, geopolymer ≈ 20% and alkali activator ≈ 10% of solids) that delivers a fluidity above 210 mm, 28-day strength exceeding 3.0 MPa and a uniform closed-pore network. A multi-scale mechanism is proposed in which physical foaming, chemical carbonation and spoil particle immobilization act synergistically to form a dense gas–solid–soil composite suitable for in situ backfilling. Full article

To elucidate the effects of different plantation types on understory vegetation and soil properties in the Mu Us Sandy Land, this study investigated five plantation types: Pinus sylvestris var. mongolica Litv. pure forest, P. sylvestris var. mongolica-Salix psammophila C. Wang and Ch. Y. Yang mixed forest, Salix matsudana Koidz. pure forest, Amorpha fruticosa L. pure forest, and A. fruticosa-S. psammophila mixed forest, using bare sandy land as a control. Through quadrat survey and stratified soil sampling, we assessed the understory plant diversity, soil characteristics, and their interrelationships. The results showed the following: (1) A total of 11 understory plant species, belonging to 11 genera and five families, were recorded, predominantly shrubs from Asteraceae and Fabaceae, and perennial herbs. The S. matsudana pure forest exhibited the highest understory plant diversity, with Shannon and Margalef indices (1.72 and 1.87, respectively) significantly higher than other stands. (2) Soil nutrients varied significantly with forest type. The mixed forest of A. fruticosa and S. psammophila notably improved the contents of soil total nitrogen and organic matter, whereas the soil total phosphorus content was generally low in all stands. (3) Spearman correlation analysis revealed the differential responses of diversity indices to soil factors: the Simpson dominance index was significantly negatively correlated with 10~20 cm soil water content (SWC) (r = −0.9, p < 0.05), and significantly positively correlated with 20~40 cm total phosphorus (TP) (r = 0.9, p < 0.05), with no significant correlations with other soil factors (TN, TK, OM, pH); the Shannon diversity index was highly significantly negatively correlated with 0~10 cm SWC (r = −0.97, p < 0.01), and no significant correlations with other soil factors (TN, TK, TP, OM, pH); the Pielou evenness index was significantly positively correlated with 0~10 cm pH (r = 0.9, p < 0.05) and positively correlated with 20~40 cm pH (r = 0.8) (not statistically significant); by contrast, the Margalef richness index showed no significant correlations with all measured soil physicochemical factors. This study demonstrates that S. matsudana pure forest is more conducive to the development of understory plant diversity, and that soil factors exert a stronger regulatory effect on community structure (evenness and dominance) than on species richness in this arid sandy ecosystem. Full article

Real-time monitoring and early warning of foundation pits are critical for geotechnical safety. However, the rainfall-induced hydro-mechanical coupling effects on water-rich sandy excavations remain poorly understood. The impact of rainstorms on excavation stability demands urgent investigation. This study examines the response of a deep excavation at Beijing Daxing Airport during the “31.7” extreme rainfall event using a multi-sensor monitoring network and numerical simulations. Results reveal that excavation-induced displacement features a neutral point at 0.4–0.6H (H = slope height), with retaining pile displacements reaching 0.14%H_e (H_e = excavation depth). Extreme rainfall events elevate the groundwater table, triggering a rise in pore-water pressure within the soil mass. This process can induce excessive displacement in the excavation, posing a substantial threat to its overall stability. It is recommended to set the critical groundwater rise threshold for Beijing at 15% of the slope height (H) and to provide a 20% axial load-bearing safety margin for support systems in rainfall-prone areas. The safety threshold established in this study will serve as a scientific basis for early warning systems of excavation safety during extreme weather events. Full article

The lower Mahanadi basin in eastern India is experiencing significant land and soil transformations that directly influence agricultural sustainability and ecosystem resilience. In this study, we used geospatial techniques to analyze the spatial-temporal variability of soil quality and land cover between 2011 and 2020 in the lower Mahanadi basin. The results revealed that the cropland decreased from 39,493.2 to 37,495.9 km², while forest cover increased from 12,401.2 to 13,822.2 km², enhancing soil organic carbon (>290 g/kg) and improving fertility. Grassland recovered from 4826.3 to 5432.1 km², wastelands declined from 133.3 to 93.2 km², and water bodies expanded from 184.3 to 191.4 km², reflecting positive land–soil interactions. Soil quality was evaluated using the Simple Additive Soil Quality Index (SQI), with core indicators bulk density, organic carbon, and nitrogen, selected to represent physical, chemical, and biological components of soil. These indicators were chosen as they represent the essential physical, chemical, and biological components influencing soil functionality and fertility. The SQI revealed spatial variability in texture, organic carbon, nitrogen, and bulk density at different depths. SQI values indicated high soil quality (SQI > 0.65) in northern and northwestern zones, supported by neutral to slightly alkaline pH (6.2–7.4), nitrogen exceeding 5.29 g/kg, and higher organic carbon stocks (>48.8 t/ha). In contrast, central and southwestern regions recorded low SQI (0.15–0.35) due to compaction (bulk density up to 1.79 g/cm³) and fertility loss. Clay-rich soils (>490 g/kg) enhanced nutrient retention, whereas sandy soils (>320 g/kg) in the south increased leaching risks. Integration of LULC with soil quality confirms forest expansion as a driver of resilience, while agricultural intensification contributed to localized degradation. These findings emphasize the need for depth-specific soil management and integrated land-use planning to ensure food security and ecological sustainability. Full article

A good understanding of the effects of different afforestation measures in alpine sandy land on the physicochemical properties, enzymatic activities, and bacterial community structure of such crusts enables elucidation of the succession patterns of biological soil crusts and provides a theoretical basis for precise optimization of desertification control programs in alpine sandy land. In the present study, four afforestation measures—Salix cheilophila+ Populus simonii (WLYY00), S. cheilophila (WL), P. simonii (YY), and Caragana korshinskii (NT00) plantations—were adopted. The physicochemical properties and enzymatic activities of bare sand, algae crust, and moss crust in the four afforested sites were analyzed using Illumina high-throughput sequencing and PICRUSt2 functional prediction to investigate the bacterial community structure and function. Results indicated the following: (1) Water content, nutrient content, enzymatic activities, and bacterial community richness and diversity increased stepwise with succession from the bare sand stage to algae crust and to moss crust. The enhancement effect of YY on the above indicators and fine particle content was most prominent. (2) The primary environmental factors affecting bacterial community structure in algae and moss crusts were adequate phosphorus and organic matter, respectively, and the correlations between the activities of the four enzymes and the bacterial community structure are also quite close. (3) Functional prediction indicated that metabolism was the main primary function of biological soil crusts at the various sample sites. YY maintained the balance of primary functions and provided precise support for the physiological characteristics and ecological needs of different crust types in the secondary functions. In conclusion, among the four types of afforestation measures with a restoration period of 24 years, YY provided a greater advantage in improving the nutrient content, bacterial community structure, and functional potentials of biological soil crusts. The results of this study can serve as a scientific reference for screening of afforestation measures and protecting and utilizing biological soil crusts during the ecological restoration of alpine sandy lands in the present study area and other regions. Full article

With the continuous expansion of urban rail transit networks, construction safety of connecting passages—as critical weak links in underground structural systems—has become pivotal for project success. Although artificial ground freezing technology effectively addresses adverse geological conditions (e.g., high permeability and weak self-stability), it is influenced by multi-field coupling effects (temperature, stress, and seepage fields), which may trigger chain risks such as freezing pipe fractures and frozen curtain leakage during construction. This study deconstructed the freezing method workflow (‘drilling pipe-laying → active freezing → channel excavation → structural support’) and established a hierarchical evaluation index system incorporating geological characteristics, technological parameters, and environmental impacts by considering sandy soil phase-change features and hydro-thermal coupling effects. For weight calculation, the Analytic Hierarchy Process (AHP) was innovatively applied to balance subjective-objective assignment deviations, revealing that the excavation support stage (weight: 52.94%) and thawing-grouting stage (31.48%) most significantly influenced overall risk. Subsequently, a Bayesian network-based risk assessment model was constructed, with prior probabilities updated in real-time using construction monitoring data. Results indicated an overall construction risk probability of 46.3%, with the excavation stage exhibiting the highest sensitivity index (3.97%), identifying it as the core risk control link. These findings provide a quantitative basis for dynamically identifying construction risks and optimizing mitigation measures, offering substantial practical value for enhancing safety in subway connecting passage construction within water-rich sandy strata. Full article

This study explores the revival of cotton (Gossypium spp. L.) farming in Italy through sustainable practices, addressing economic and water-related challenges by integrating cultivar selection, arbuscular mycorrhizal fungi (AMF) inoculation, and deficit irrigation under organic farming. Field trials evaluated two widely grown Mediterranean cultivars (Armonia and ST-318) under three irrigation levels (I-100: 100% crop water requirement; I-70: 70%; I-30: 30%) across two Sicilian soil types (sandy loam vs. clay-rich). Under I-100, lint yields reached 0.99 t ha⁻¹, while severe deficit (I-30) yielded only 0.40 t ha⁻¹. However, moderate deficit (I-70) maintained 75–79% of full yields, proving a viable strategy. AMF inoculation significantly enhanced plant height (68.52 cm vs. 65.85 cm), boll number (+22.1%), and seed yield (+12.5%) (p < 0.001). Cultivar responses differed: Armonia performed better under water stress, while ST-318 thrived with full irrigation. Site 1, with higher organic matter, required 31–38% less water and achieved superior irrigation water productivity (1.43 kg m⁻³). Water stress also shortened phenological stages, allowing earlier harvests—important for avoiding autumn rains. These results highlight the potential of combining adaptive irrigation, resilient cultivars, and AMF to restore sustainable cotton production in the Mediterranean, emphasizing the importance of soil-specific management. Full article

Desert plant communities play a vital role in sustaining the stability of arid ecosystems; however, they demonstrate limited resilience to environmental changes. A critical aspect of understanding community assembly mechanisms is determining whether soil texture heterogeneity affects vegetation diversity in arid deserts, especially under conditions of extreme water scarcity and restricted nutrient availability. This study systematically examined the relationships between plant diversity and soil physicochemical properties across four soil texture types—sand, sandy loam, loamy sand, and silty loam—by selecting four representative desert systems in the Hami region of Xinjiang, China. The objective was to elucidate the mechanisms through which soil texture may impact desert plant species diversity. The findings revealed that silty loam exhibited distinct characteristics in comparison to the other three sandy soil types. Despite its higher nutrient content, silty loam demonstrated the lowest vegetation diversity. The Shannon–Wiener index (H′), Simpson dominance index (C), Margalef richness index (D), and Pielou evenness index (Jsw) for silty loam were all lower compared to those for sand, sandy loam, and loamy sand. However, silty loam exhibited higher values in electrical conductivity (EC), urease activity (SUR), and nutrient content, including soil organic matter (SOM), ammonium nitrogen (NH⁴⁺-N), and available potassium (AK), than the other three soil textures. This study underscores the significant regulatory influence of soil texture on plant diversity in arid environments, offering new insights and practical foundations for the conservation and management of desert ecosystems. Full article

Mycorrhizal symbiosis in rice enhances drought adaptation but there are limited studies regarding the frequency and amplitude of mycorrhizae colonization in traditional landraces. This study investigates mycorrhizal colonization frequency (FMS) and intensity (IRS) in 12 rice landraces across three agroecological zones (Tarai, Inner-Tarai, Mid-hill) of Far-West Nepal under drought stress. Field experiments exposed landraces to control, intermittent, and complete drought treatments, with soil properties and root colonization analyzed. Results revealed FMS and IRS variations driven by soil composition and genotype. Mid-hill soils (acidic, high organic matter) showed lower FMS but elevated IRS under drought, while neutral pH in Tarai and silt/clay-rich soils supported higher FMS. Sandy soil in Inner-Tarai also promoted FMS. Drought significantly increased IRS, particularly in Anjana and Sauthiyari (Tarai), Chiudi and Shanti (Inner-Tarai), and Chamade and Jhumke (Mid-hill), which exhibited IRS surges of 171–388%. These landraces demonstrated symbiotic resilience, linking mycorrhizal networks to enhanced nutrient/water uptake. Soil organic matter and nutrient levels amplified IRS responses, underscoring fertility’s role in adaptation. FMS ranged from 50 to 100%, and IRS 1.20–19.74%, with intensity being a stronger drought-tolerance indicator than frequency. The study highlights the conservation urgency for these landraces, as traditional varieties decline due to hybrid adoption. Their drought-inducible mycorrhizal symbiosis offers a sustainable strategy for climate-resilient rice production, emphasizing soil–genotype interactions in agroecological adaptation. Full article