Search Results (1,743)

Efficient nitrogen (N) management in perennial fruit orchards is constrained by species-specific differences in N demand and fruit N removal, which can result in distinct soil N uptake patterns even under similar fertilization regimes. This study assessed whether apple (Malus domestica Borkh.) and sweet cherry (Prunus avium L.) orchards differ in soil mineral nitrogen (Nmin) composition by analyzing nitrate (NO₃⁻) and ammonium (NH₄⁺) stocks in topsoil (0–20 cm). Soil samples were collected in spring from a long-term orchard experiment over two consecutive years and from a commercial orchard on two sampling dates in Germany. In apple orchards, Nmin was dominated by NO₃⁻ (83%), whereas cherry orchards showed a more balanced composition (42% NO₃⁻ and 58% NH₄⁺). These patterns were consistent across years, sites, fertilization types (mineral or organic), and key soil properties, including total organic carbon and total nitrogen, but were not explained by these factors. The elevated NH₄⁺ proportion in cherry soils suggests a species-associated pattern in soil N dynamics. Overall, the results highlight species-associated differences in soil Nmin composition between apple and sweet cherry orchards. Accounting for tree species differences may therefore improve N management and enhance N use efficiency in apple and sweet cherry production. Full article

Eutrophication remains a persistent water-quality problem in shallow lakes, where external inputs interact with internal loading and biogeochemical cycling. Although floating treatment wetlands (FTWs) are increasingly promoted as nature-based solutions for water remediation, their field-scale interpretation in hydrologically complex eutrophic lakes remains challenging. This study examined the spatial organization of water quality during the operation of a floating-island system in a eutrophic urban lake affected by polluted tributary inflow. The study was not designed to quantify isolated FTW removal efficiency, but to evaluate spatial water quality organization during FTW operation under real-use field conditions. Water quality was monitored over two growing seasons across six functionally defined zones, and spatial and temporal patterns were analyzed using descriptive statistics and linear mixed-effects models. The results showed parameter-specific spatial structuring rather than a uniform treatment response. The clearest inlet-lake contrasts were observed for electrical conductivity (EC), suspended matter (SM), and nitrate nitrogen (NO₃-N), whereas biochemical oxygen demand (BOD₅), ammonium nitrogen (NH₄-N), and total organic carbon (TOC) showed lower values at the inlet and higher values in downstream zones. Dissolved oxygen (DO), oxygen saturation (SO), chemical oxygen demand (COD), nitrite nitrogen (NO_2-N), and orthophosphate phosphorus (PO₄-P) showed moderate or non-robust zonal effects. These findings indicate that FTWs in shallow eutrophic lakes should be evaluated through functional zoning and parameter-specific interpretation rather than as isolated units with uniform removal responses. Full article

The role of mangrove root exudates in mediating the nitrogen cycle, particularly under high dissolved inorganic nitrogen (DIN) input, in coastal ecosystems remains unclear. This research investigated variation in the root exudates, and nitrogen transformation and output, in constructed mangrove wetlands planted with Kandelia obovata under high, moderate, and low nitrogen-input levels (PCWs-H, PCWs-M, and PCWs-L, respectively). PCWs-H promoted increased root density and biomass accumulation, enhancing soil nitrogen sequestration, whereas PCWs-L induced greater specific root length, specific root surface area, and number of root tips. These changes directly influenced denitrification efficiency. Hydroxymethoxyphenylcarboxylic acid-O-sulfate and Arg-Ser released in root exudates under PCWs-H might act as potential denitrification inhibitors, thereby suppressing denitrifiers and impairing dissolved nitrogen purification. Elevated nitrogen loading predominantly limited denitrification, resulting in relative NO₃⁻-N removal rates of PCWs-H < PCWs-M < PCWs-L (p < 0.05). Compared with PCWs-H and PCWs-L, the enhanced soil organic nitrogen storage under PCWs-M was associated with flavonoids in root exudates. Metagenomic analysis showed that denitrification was the dominant nitrogen removal pathway. Nitrogen loading influenced the effects of root exudates on the microbial community. Under PCWs-H, triterpenoids promoted norBC and nirK/S abundance but depressed amoABC abundance. Sterols and flavonoids in exudates under PCWs-L depressed nosZ abundance, instead activating dissimilatory nitrate reduction to ammonium. Compared with PCWs-H and PCWs-L, N₂O emissions were minimal under PCWs-M. This study revealed that mangrove root exudates mediate the nitrogen cycle in mangrove wetlands, providing a theoretical basis for local authorities to manage DIN inputs and mitigate N₂O emissions. Full article

Botrytis cinerea is a major phytopathogenic fungus responsible for substantial economic losses in horticultural crops, underscoring the need for sustainable alternatives to synthetic fungicides. This study investigated the influence of physical, chemical and biological culture parameters on the antifungal activity of culture filtrates produced by Trichoderma harzianum BOL-12QD. Culture conditions were sequentially optimised by evaluating light-filter exposure, carbon and nitrogen source composition, potato ecotype selection, co-cultivation with Botrytis cinerea, and volatile-mediated interactions. Antifungal activity was assessed using mycelial growth inhibition assays against Botrytis cinerea. Among the individual factors, violet-filter illumination, a medium containing 5 g L⁻¹ glucose and 250 g L⁻¹ potato extract, the Leke Pek’e potato ecotype, ammonium nitrate as nitrogen source, and co-cultivation with Botrytis cinerea at 10⁴ conidia mL⁻¹ produced the highest inhibitory effects. Sequential integration of these optimised conditions resulted in enhanced antifungal activity, reaching up to 62% inhibition. Volatile organic compounds produced by Trichoderma harzianum BOL-12QD exhibited only minimal antifungal activity under the conditions tested, suggesting that volatile-mediated antagonism plays a limited role in this system. In contrast, culture-dependent modulation of extracellular metabolite profiles was evidenced by comparative ¹H NMR fingerprinting, which revealed condition-specific spectral differences, with the optimised treatment displaying a distinct metabolic signature relative to all other conditions. Cytotoxicity assays in murine peritoneal macrophages showed no significant reduction in cell viability at concentrations up to 200 μg mL⁻¹. In vivo exposure to the optimised culture filtrate (250 mg kg⁻¹ d⁻¹ for 10 days) induced transient treatment-related clinical observations without mortality, indicating a need for further detailed toxicological characterisation. Overall, these findings demonstrate that the antifungal activity of Trichoderma harzianum BOL-12QD is strongly modulated by interacting environmental, nutritional and biological culture parameters. The results support the potential of optimised culture filtrates as a source of bioactive metabolites for biocontrol applications, while highlighting the importance of integrated biochemical and toxicological evaluation. Full article

To elucidate the runoff generation pathways and associated carbon–nitrogen transport characteristics on grass-covered black soil slopes under varying rainfall intensities and slope gradients, a series of simulated rainfall experiments was conducted. Three rainfall intensities (30, 60, and 90 mm·h⁻¹) and four slope gradients (0°, 5°, 10°, and 15°) were investigated. The processes governing surface and subsurface runoff were systematically analyzed, alongside measurements of ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), and total organic carbon (TOC) concentrations and their corresponding fluxes across different flow pathways. At a rainfall intensity of 30 mm·h⁻¹, subsurface runoff preceded surface runoff generation, contributing 55.6% to 79.3% of the total runoff within the initial 60 min. When rainfall intensity increased to 60 and 90 mm·h⁻¹, surface runoff became the dominant pathway across all slope treatments, with the sole exception of the 5° slope. Elevated rainfall intensity substantially increased surface runoff volumes, whereas subsurface runoff exhibited only marginal changes. The influence of slope gradient on runoff pathways was non-monotonic; notably, at moderate to high rainfall intensities, the 5° slope maintained a comparatively higher proportion of subsurface runoff. Ammonium nitrogen was primarily transported via surface runoff, especially under rainfall intensities of 60 and 90 mm·h⁻¹. Nitrate nitrogen was predominantly mobilized through subsurface runoff at 30 mm·h⁻¹, but as rainfall intensity increased, surface runoff gradually assumed dominance. The concentration differences in total organic carbon between surface runoff and subsurface runoff were generally minor; nevertheless, TOC flux was primarily governed by surface runoff. Correlation analyses revealed that ammonium nitrogen export was most closely associated with surface runoff volume, nitrate nitrogen export was jointly influenced by both surface runoff and subsurface runoff, and total organic carbon export exhibited the strongest relationship with total runoff and surface runoff volume. Collectively, these findings demonstrate that rainfall intensity modulates the partitioning between surface and subsurface runoff, thereby profoundly influencing both the pathways and magnitudes of carbon and nitrogen export from grass-covered black soil slopes. Full article

Nitrogen (N) fertilization is a fundamental agronomic practice that governs crop productivity, yet its effects on the molecular composition and chemical stability of soil organic carbon (SOC) remain poorly understood, especially in cereal–legume intercropping systems. Traditional studies have focused on total SOC stocks rather than molecular-level changes, and the mechanistic pathway linking N addition to SOC functional group transformation remains unclear. This study addressed these critical gaps by investigating how graded N addition (0, 180, 270, and 360 kg N ha⁻¹) reshapes SOC chemistry in a subtropical soybean–maize intercropping system. Soil physicochemical properties, inorganic N pools, N-transformation enzyme activities (urease, nitrate reductase, and glutaminase), microbial biomass indices, labile organic carbon fractions (particulate, mineral-associated, and dissolved organic carbon), and SOC functional groups characterized by Fourier transform infrared (FTIR) spectroscopy were quantified across a two-year field experiment (2024–2025). Results showed that increasing N rates significantly elevated nitrate nitrogen (NO₃⁻-N) accumulation while depressing soil pH. Nitrogen-transformation enzymes, especially nitrate reductase and glutaminase, responded strongly and positively to the N gradient. Microbial biomass carbon (MBC) and nitrogen (MBN) increased with moderate N input but exhibited saturation or decline at 360 kg N ha⁻¹, accompanied by reduced microbial carbon use efficiency (CUE) and a lower MBC/MBN ratio. Among labile carbon fractions, dissolved organic carbon (DOC) was the most responsive pool, increasing markedly with N addition and correlating strongly with NO₃⁻-N. FTIR analysis revealed that N addition shifted SOC functional group composition toward chemically recalcitrant structures: the relative abundances of aromatic C=C and carbonyl C=O groups increased significantly, whereas labile C–O groups declined. Random forest modelling identified C=C, NO₃⁻-N, and DOC as the three most influential predictors of SOC chemical composition. Structural equation modelling (SEM) demonstrated a sequential mechanistic pathway: N fertilization increased NO₃⁻-N, which stimulated glutaminase activity and enhanced DOC, ultimately promoting C=C/C=O stabilization and explaining 91.3% of the variance in SOC aromaticity. These findings reveal that N addition does not merely augment SOC quantity but fundamentally transforms its molecular architecture toward greater chemical stability through a nitrate-mediated, enzyme–labile carbon coupling mechanism. This study provides a novel spectroscopic–mechanistic framework for understanding carbon–nitrogen interactions in intercropping agroecosystems and informs precision N management strategies aimed at simultaneous crop production and long-term soil carbon sequestration. Full article

The application of urea in agricultural practices leads to carbon dioxide (CO₂) emissions through hydrolysis. Urea, when applied to soil, reacts with water and undergoes hydrolysis, releasing ammonia (NH₃) and CO₂. This reaction is facilitated by soil enzymes such as urease. The released NH₃ can further undergo nitrification, producing nitrate (NO₃⁻) and nitrous oxide (N₂O). While CO₂ from urea hydrolysis is relatively small compared to other sources, cumulative emissions from agricultural activities contribute significantly to climate change and agriculture’s carbon footprint. A straightforward calculation model (CO₂ = A × 0.73) was employed to approximate CO₂ emissions in various countries based on annual urea usage. In this model, China led emissions with 40,483 Gg yr⁻¹, followed by India (26,031 Gg yr⁻¹) and the USA (12,032 Gg yr⁻¹). Out of total annual emissions (94,763 Gg), China contributed 43%, India 27%, the USA 13%, the EU 8%, Pakistan 5%, and Indonesia 4%. China’s CO₂ emissions from urea were 16% higher than India, 30% higher than the USA, 35% higher than the EU, 38% higher than Pakistan, and 39% higher than Indonesia. As expected from the deterministic IPCC formula (CO₂ = Urea × 0.73), the relationship between urea consumption and CO₂ emissions is linear with a slope of 0.73. Linear regression shows that for every 1000-ton increase in urea consumption, CO₂ emissions increase by 730 tons (0.73 Gg) (R² = 0.99, p < 0.001). Pakistan’s urea consumption grew at an average annual rate of 2.2% from 2015 to 2023, with corresponding CO₂ emissions increasing from 4015 to 4788 Gg yr⁻¹ (total increase of 20% over eight years). Optimizing fertilizer application rates, timing, and methods to enhance nutrient uptake efficiency, along with sustainable agricultural practices (organic matter management, conservation tillage, and precision agriculture), can help mitigate environmental impacts. This study emphasizes implementing sustainable agricultural practices and integrated nutrient management to minimize CO₂ emissions from urea application, enabling agricultural systems to contribute to climate change mitigation and reduced carbon footprints. Full article

Livestock manure management remains a significant environmental challenge due to nutrient losses that may contribute to soil and water contamination. This study investigated nitrogen and phosphorus transformations, as well as organic matter stabilisation, in poultry manure subjected to microbial inoculation under controlled laboratory conditions (EI) and long-term field storage (EII). In the laboratory experiment, chicken and turkey manure were treated with denitrifying bacteria, conditioning bacteria, or their combination. The results indicate treatment-dependent differences in ammonium accumulation and nitrate formation in leachates, with the combined microbial inoculum suggesting reduced nutrient mobility compared with the untreated controls. In the field experiment, temporal changes in nitrogen fractions revealed an initial phase of intensive mineralisation, followed by gradual stabilisation of nitrogen forms. Phosphorus concentrations (total phosphorus—P_tot and orthophosphate—PO₄³⁻) decreased over time, suggesting reduced potential for leaching, although the underlying mechanisms likely include immobilisation and redistribution within the manure matrix. Differences in nutrient dynamics between chicken and turkey manure were observed. A humification stabilisation index (HSI) was applied to describe changes in organic matter quality during manure storage, indicating progressive transformation towards more stable forms. However, due to the limited replication and the lack of continuous monitoring of key process parameters, the results should be interpreted as indicative rather than conclusive. Overall, the study suggests that microbial inoculation may influence nutrient transformations and support manure stabilisation processes, highlighting its potential as a complementary strategy in environmentally oriented manure management strategies. Full article

Soil extracellular enzymes serve as critical drivers in the cycling of nutrients within ecosystems, and their stoichiometry can effectively reveal the metabolic resource limitations of soil microorganisms. However, extracellular enzyme activities, microbial metabolic characteristics, and their influencing factors in different grassland types in the Qilian Mountains have rarely been studied. This study focuses on alpine meadows (TJs), swampy meadows (HBs), and temperate desert grasslands (DLHs) in the Qilian Mountains. Extracellular enzyme activity and stoichiometric characteristics in the 0–30 cm soil layer were analyzed to explore the limiting factors on microbial metabolism and clarify the main driving factors affecting nutrient limitation. Compared with swampy meadows and temperate desert grasslands, alpine meadows exhibited greater extracellular enzyme activity, as revealed by the results. Statistical analysis revealed that enzyme activity exhibited a significant positive correlation with nitrate nitrogen (NO₃⁻-N), total phosphorus (TP), total potassium (TK), available potassium (AK), and dissolved organic carbon (DOC), while showing a significant negative correlation with soil moisture content (SWC) (p < 0.05). Vector analysis of soil enzymes showed that soil microorganisms in the three grassland types are limited by carbon (C) and phosphorus (P). Among them, DLH microorganisms are highly restricted by carbon, while HB microorganisms are highly restricted by phosphorus. Random forest results showed that total phosphorus (TP), available potassium (AK), nitrogen-to-phosphorus ratio (N: P), nitrate nitrogen (NO₃⁻-N), and readily oxidizable carbon (ROC) contribute significantly to vector length, while total potassium (TK), soil organic carbon (SOC), particulate organic carbon (POC), bulk density (BD), and carbon–nitrogen ratio (C: N) contribute significantly to vector angle. A partial least squares path model (PLS-PM) revealed that although microbial metabolic limitation is influenced by specific soil factors, the comprehensive effect of soil physicochemical properties is the dominant factor regulating microbial carbon and phosphorus limitation. This study provides valuable data and insights that elucidate the metabolic characteristics of soil microorganisms across different grassland types in the Qilian Mountains, thereby improving the mechanistic understanding of soil nutrient cycling and supporting evidence-based strategies for the sustainable management and conservation of these fragile ecosystems. Full article

Decontaminated sandy soils in Fukushima are characterized by low fertility and high nitrogen (N) loss, requiring effective nutrient management strategies. This study evaluated the effects of rice husk biochar on N dynamics, focusing on ammonium (NH₄⁺) retention, nitrification, and plant N availability, using column, incubation, and pot experiments with decontaminated Fukushima soil. A significant interaction between biochar application and time indicated that biochar-applied soils showed different patterns in NH₄⁺ and nitrate leaching over the experimental period. Incubation results showed that biochar reduced net nitrification rates (−18.1%) and tended to reduce the abundance of ammonia-oxidizing bacteria DNA. These effects may be attributed to the porous structure and adsorption properties of biochar. In the pot experiment, co-application of biochar with organic amendments (manure and kudzu) reduced plant N uptake by 9.6% and 9.0%, respectively, compared with their sole application. This indicates a trade-off between N retention and plant availability, particularly during the initial stage after biochar application. These findings highlight the importance of carefully balancing N retention and availability when applying biochar and organic amendments in low-fertility soils. Full article

Background: This study aims to measure Greenhouse Gas (GHG) emission fluxes at the soil–air and water–air interfaces in urban wetlands on the Qinghai–Tibet Plateau and identify the primary controlling factors. The objective is to elucidate the key drivers of carbon and nitrogen processes at different interface levels in wetlands within high-altitude urban settings, thereby providing a scientific basis for accurately estimating their contribution to greenhouse gas emissions. Results: In the wetlands of Xining City, with the exception of soil pH, bulk density, and moisture content (which showed no significant change over time), all other soil physicochemical properties differed significantly among the three wetlands and among the sampling periods (p < 0.05). Soil moisture content was less affected by variations across different wetlands and over time, and differences in soil physicochemical properties among different wetlands were small (p > 0.05). Significant differences were observed in the spatiotemporal variations in the physicochemical properties of water bodies in Xining’s wetlands (p < 0.05), although water pH and total organic carbon (TOC) were less affected by the interaction between different wetlands and time periods. There were no significant differences in the bulk density and moisture content of wetland sediments in Xining over time (p > 0.05), while all other physicochemical indicators of sediments showed significant differences (p < 0.05). The physicochemical properties of sediments were influenced by both different wetland types and different time periods. GHG fluxes at the water–air interface in Xining wetlands were greater than those at the soil–air interface; overall, GHG emissions from both interfaces acted as “sources.” Seasonal variations in wetland GHG emissions were pronounced, with emission peaks occurring from June to August. The study found that the primary soil factor influencing GHG emissions at the soil–air interface was total phosphorus (TP), while the primary sediment factors affecting emissions at the water–air interface were TP and nitrate nitrogen (NO₃⁻-N), and the primary water factor was TOC. The interannual cumulative emissions from both interfaces in the wetland totaled 705.88 g·m⁻². GHG emissions from the soil–air and water–air interfaces contributed 47.88% and 52.12%, respectively, to the global warming potential (GWP) of the wetland, while methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) contributed 32.55%, 62.33%, and 5.12%, respectively, to the GWP. Conclusions: Investigating the GHG emission patterns in Xining’s wetlands and identifying the primary factors influencing these emissions provides a scientific basis for the protection and restoration of these wetlands. This is of great significance for safeguarding the ecological security of Xining’s wetlands as well as the overall ecological security of high-altitude wetlands. Full article

Compost offers high potential for sustainable agriculture, but its agronomic outcomes vary. This critical review combines qualitative evidence with literature-derived quantitative benchmarks for compost maturity, salinity, nutrient loading, application-rate classes and monitoring triggers. Evidence demonstrates that mature, stable composts consistently improve soil health, including aggregation, water-holding capacity, soil organic carbon (SOC), and nutrient availability while boosting crop yield and establishment. These high-quality composts are characterized by low phytotoxicity, moderate C:N ratios, acceptable EC levels, and pathogen compliance. However, benefits are not universal. Immature or poorly stabilized compost poses risks of phytotoxicity, ammonia toxicity, and nitrogen immobilization. Excessive application rates are associated with nutrient imbalances, increased salinity, nitrate leaching, phosphorus runoff, greenhouse-gas trade-offs, and cumulative contaminant loading. To enhance the precision of rate recommendations, this review categorizes applications into four distinct tiers: starter or maintenance (2–5 Mg dry matter ha⁻¹), common agronomic (5–20 Mg ha⁻¹), rehabilitation (20–35 Mg ha⁻¹), and high-risk (>35 Mg ha⁻¹). It posits that the final application rate must be dictated by the most limiting factors, such as crop nitrogen requirements, soil-test phosphorus levels, salinity tolerance, contaminant thresholds, hydrologic risk, or specific management objectives. In conclusion, while manure-based composts enhance short-term fertility, they introduce significant risks of phosphorus accumulation and salinity compared to green-waste alternatives. This review, therefore, redefines compost not as a generic organic amendment, but as a quality-controlled, rate-sensitive input essential for precision nutrient management. Full article

Environmental toxicants may affect the height of children and adolescents. However, studies on the toxicological effects based on extensive internal exposure omics are still lacking. This study aimed to identify key toxicants associated with height and assess the mediating role of sex steroid hormones. To this end 1660 participants aged 6–19 years from subsample A in the National Health and Nutrition Examination Survey (NHANES) were included. Exposome was characterized by 58 toxicants within 12 families. After assessment by the exposome-wide association analysis and mixture models, we identified 17 toxicants inversely associated with height-for-age Z-scores (HAZ), predominantly metals and volatile organic compound (VOC) metabolites. Tin exhibited the strongest inverse association (β = −0.261), followed by lead (β = −0.230). The primary contributors to reduced height included tin, lead, the VOC metabolite 2-ATCA, ethylene oxide, and nitrate. Notably, males and younger children were the more susceptible subgroups. Furthermore, mediation analysis revealed that sex steroid hormones, particularly total testosterone and estradiol, mediated 8% to 37% of the associations. These findings suggest that endocrine-related pathways may link toxicant exposure to impaired linear growth, highlighting the necessity of reducing exposure during childhood. Full article

To elucidate the effects of nitrogen (N) addition on soil carbon (C), N, and phosphorus (P) cycling in high-altitude orchards on the Qinghai–Tibet Plateau, a three-year field experiment was conducted at an altitude of 3000 m with four N application rates (0, 150, 300, and 450 kg N ha⁻¹, designated as CK, N150, N300, and N450, respectively). We determined soil physicochemical properties, 12 soil enzyme activities, and metagenomic characteristics, and further adopted partial least squares path modeling (PLS-PM) for data analysis and mechanism exploration. The results were as follows: (1) The N300 treatment yielded the maximum C-hydrolase activities and soil organic carbon content, with a 40.6% increase in soil organic carbon compared with the CK group. (2) The N450 treatment resulted in a 365.4% increase in soil nitrate content and significantly reduced the soil pH (from 6.32 to 5.86). Such environmental filtering significantly decreased the relative abundance of Nitrospirota and its core denitrification genes, including nosZ and narI. (3) Continuous N input induced secondary soil P limitation, leading to a more than 90% increase in phosphatase activities under the N450 treatment. Pseudomonadota activated soil P sources by enriching the functional potential of the phn gene cluster. Furthermore, the PLS-PM analysis revealed a significant negative statistical association between P-cycling enzymes and N-cycling functional potential (p < 0.01). This statistical linkage supports the observation of divergent metabolic responses among different element cycles. In conclusion, under the specific experimental conditions tested, an optimal N application rate of 300 kg N ha⁻¹ is recommended to balance agricultural productivity and soil ecological health. The microbiome of alpine apple orchards responds to elevated N input through metabolic trade-offs, namely reducing the functional potential for denitrification and enhancing the P recycling system. These findings provide vital molecular evidence to guide fertilizer reduction, optimize nutrient management, and promote the sustainable development of high-altitude agroecosystems. Full article

Wildfires are increasing in frequency and severity across Mediterranean ecosystems. However, the immediate soil biogeochemical responses that determine shortly post-fire resilience remain poorly understood. This study assessed how contrasting fire severity levels influence soil physicochemical, nutrient, and biochemical properties in ecologically relevant vegetation microsites—beneath Quercus ilex L. canopy, Stipa tenacissima L. tussock, and open interspaces—in a Mediterranean holm oak woodland in central Spain. Soils were sampled early after a wildfire and analyzed for organic matter, nutrient pools, water repellency, microbial respiration, nitrogen mineralization, and enzyme activities. Fire severity was the dominant driver of immediate post-fire soil responses. High-severity fire reduced soil organic matter, cation exchange capacity, total C and N, nitrate, microbial respiration, and all measured enzyme activities, with the most pronounced losses occurring beneath Q. ilex canopy. In contrast, ammonium, labile phosphorus, pH and soil water repellency increased under high severity, mainly in this microsite. Low-severity fire generally preserved biological functioning, with values comparable to unburned soils. Microsite identity modulated the magnitude of fire effects, with soils beneath Q. ilex cover microsite showing the greatest sensitivity, and open interspaces the least. The microsite × severity interaction detected for key nutrients and biochemical variables suggests that high-severity fire might destroy the microsite-specific fertility islands that constitute the functional core of Mediterranean woodland soils. These findings should be considered in management strategies prioritizing their monitoring and protection. Full article