Soil Biology & Biochemistry最新文献

{"title":"Bacterial tyrosinases as extracellular sources of quinone-based electron shuttles in soil","authors":"Felix Panis ,&nbsp;Markus Kleber ,&nbsp;Annette Rompel","doi":"10.1016/j.soilbio.2025.109903","DOIUrl":"10.1016/j.soilbio.2025.109903","url":null,"abstract":"<div><div>Extracellular electron transfer in soils provides microorganisms with a powerful tool to obtain energy for the sustenance of life processes under oxygen scarcity. Electron shuttles provided by natural organic matter (NOM) are widely considered the ubiquitous mediators that carry electrons from the cell to an acceptor that is particulate or physically distant. Specifically, quinone moieties associated with NOM are seen as the rechargeable molecular entities that make this process possible. For more than 3 decades, the hypothetical, abiotic recondensation of organic residues into polymeric macromolecules called humic substances has served as an explanation for the presence of quinone moieties in soils. As this so-called ‘humification’ model has been superseded, an alternative explanation for the origin of quinoid electron shuttles in natural systems is called for. Here we present a literature survey to show that prokaryotic microorganisms are capable of excreting tyrosinases, an enzyme class with the ability to synthesize soluble and mobile orthoquinones in extracellular soil environments. We argue that this mechanism represents a key pathway for microorganisms to keep their immediate environment stocked with electron shuttles featuring electrochemical specifications tailored to their individual needs.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"210 ","pages":"Article 109903"},"PeriodicalIF":9.8,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144568954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of different soil erosion levels on gross N transformation processes and gaseous N losses: An incubation study","authors":"Julia Schoof ,&nbsp;Maire Holz ,&nbsp;Tobias Rütting ,&nbsp;Reinhard Well ,&nbsp;Caroline Buchen-Tschiskale","doi":"10.1016/j.soilbio.2025.109905","DOIUrl":"10.1016/j.soilbio.2025.109905","url":null,"abstract":"<div><div>Erosion is a key driver of topsoil removal in agriculture, resulting in nutrient losses and leaving truncated soil profiles on shoulder slopes, where subsoil material can be incorporated into topsoil by the plough, changing soil properties and, thus, altering biogeochemical cycling and associated nitrogen (N) losses. To date, the effects of topsoil erosion on N cycling have rarely been investigated. We conducted a short-term mesocosm experiment, integrating ¹⁵N tracing techniques to quantify N transformation processes, focusing on N availability and N losses in three artificially eroded agricultural topsoils. Nitrogen transformation pathways were simulated using the numerical model <em>Ntrace</em>, considering N uptake by maize (<em>Zea mays</em> L.) at early development stages. The ¹⁵N label also allows the quantification of nitrous oxide (N₂O) and dinitrogen (N₂) losses by applying the ¹⁵N gas flux method (¹⁵NGF).</div><div>Erosion induced topsoil dilution significantly reduced gross N turnover and consequently N₂O and N₂ emissions in both treatments with and without plants. The oxidation of ammonium (NH₄⁺) to nitrate (NO₃⁻) was by far the dominating N pathway across all investigated topsoils, followed by N_org mineralization &gt; NH₄⁺ immobilization. However, more than 90 % of total N₂O losses derived from the NO₃⁻ pool, with coupled nitrification-denitrification assumed to be the dominant process at water contents of ∼40 % water-filled pore space (WFPS). Although maize more than doubled N₂O + N₂ emissions in some treatments, the overall effect of topsoil dilution on gaseous N losses was considerably greater, independent of maize presence. Our study contributes to a more comprehensive understanding of N cycling in erosion-affected agricultural soils, which is essential for enhancing N fertilizer use efficiencies and reducing N pollution.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109905"},"PeriodicalIF":9.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144566012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microplastics in agricultural soils: The role of soil texture in modulating oxygen diffusivity and soil respiration","authors":"Jonathan Nuñez ,&nbsp;Joaquín Jiménez-Martínez ,&nbsp;Andrea Carminati ,&nbsp;Denise M. Mitrano","doi":"10.1016/j.soilbio.2025.109906","DOIUrl":"10.1016/j.soilbio.2025.109906","url":null,"abstract":"<div><div>The presence of microplastics (MPs) in soils impacts nutrient cycling and soil respiration. However, the mechanisms underpinning the direction and magnitude of these effects on soil are uncertain. We hypothesized that the presence of MPs affects pore connectivity, leading to changes in oxygen (O₂) diffusivity and soil respiration. Furthermore, we anticipated that the magnitude of the effects would be dependent on both soil texture and MPs morphology. 1 % (w/w) PET MPs fibers (500 μm length) and fragments (125–250 μm) were spiked into rhizotrons filled with either clay or sandy loam soils. O₂ diffusivity differences were determined in microcosm using an oxygen-free chamber. The O₂ concentration in the soil was also measured in optimal conditions for respiration. O₂ diffusivity and concentration were measured using optode imaging. Respiration was estimated from cumulative CO₂ and changes in the size of the water-extractable carbon pool. Adding MPs decreased O₂ concentration in the sandy loam soil (167.4 ± 6.1 mg L⁻¹ air), with a greater reduction observed for fragments (15 %) compared to fibers (12 %). Soil respiration decreased by 40 % in both fragment and fiber treatments in alignment with the reduction in oxygen concentration. Conversely, in the clay soil, the addition of fibers and fragments resulted in a 13 and 7 % increase in O₂ concentration compared to the control (177.9 ± 3.8 mg L⁻¹ air). Both changes in oxygen concentration and diffusivity, show a similar response to MPs for the two soils. These findings indicate that the effects of MPs on soil respiration are likely driven by changes in O₂ dynamics. However, the MPs' impact on O₂ dynamics depends on soil particle size distribution. Future research should consider MP size, morphology, and soil particle distribution interactions to assess MPs' impacts on soil functions.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109906"},"PeriodicalIF":9.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144566078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Land-use driven changes in elemental stoichiometry decouple the positive soil biodiversity-stability relationship","authors":"Xiaoxu Qi ,&nbsp;Zhengkun Hu ,&nbsp;Xianping Li ,&nbsp;Dingyi Wang ,&nbsp;Cheng Xu ,&nbsp;Feng Hu ,&nbsp;Xiaoyun Chen ,&nbsp;Manqiang Liu","doi":"10.1016/j.soilbio.2025.109907","DOIUrl":"10.1016/j.soilbio.2025.109907","url":null,"abstract":"<div><div>Land-use intensification often reduces aboveground biodiversity and ecosystem stability, but its effects on belowground biodiversity across multiple trophic levels and spatial scales, as well as their links to ecosystem stability, remain poorly understood. In this study, we conducted a field survey to assess the α-, β-, and γ-diversity of soil biota (bacteria, fungi, and nematodes) and estimated the temporal ecosystem stability using normalized difference vegetation index (NDVI) along a land-use intensity (forests, orchards, croplands) across 44 sites in subtropical regions. Agricultural land conversion significantly reduced α-, β-, and γ-diversity of soil biota across trophic levels, with higher trophic levels (e.g., microbivorous and omnivorous-predaceous nematodes) more affected than lower ones (e.g., microbes). Soil biodiversity, defined as the average diversity of all soil biota groups, was positively related to the temporal stability of plant productivity, with the higher trophic levels playing a greater role at all scales. However, land-use intensification decoupled the positive relationships between soil biodiversity and the temporal stability at both local and regional scales. Further analyses revealed that changes in soil elemental stoichiometry, particularly the carbon to phosphorus ratio, were a predominant driver of soil biodiversity loss at both local and regional scales, as well as its relationship with the temporal stability. These findings highlight the importance of elemental stoichiometry in shaping biodiversity-stability relationships and provide insights into the impacts of land-use intensification on soil communities and ecosystem resilience.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109907"},"PeriodicalIF":9.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144566013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrate reduction across soils transitioning from coastal forest to wetland are hotspots for denitrification","authors":"Stephanie J. Wilson,&nbsp;J. Patrick Megonigal","doi":"10.1016/j.soilbio.2025.109904","DOIUrl":"10.1016/j.soilbio.2025.109904","url":null,"abstract":"<div><div>Sea level rise drives spatial migration of coastal ecosystems and can lead to the accelerated replacement of coastal forests with tidal wetlands. During this transition, changes in inundation frequency and saltwater intrusion dramatically alter soil biogeochemistry and redox conditions. Soil biogeochemical cycles in steady-state upland and wetland ecosystems are well studied, but pathways and rates in rapidly changing ecosystems are largely unconstrained. We characterized reduction of reactive nitrogen (N) via denitrification and dissimilatory nitrate reduction to ammonia (DNRA) at four sites where coastal forest is undergoing ecosystem state change and becoming wetland throughout the Chesapeake Bay. Sites were chosen to vary in soil characteristics, vegetation, and salinity regime. Soils were incubated with ¹⁵N-labeled nitrate to estimate potential rates of denitrification and DNRA. Denitrification rates ranged from 0.011 to 26 nmol N g⁻¹ hr⁻¹ and DNRA rates ranged from −0.30 to 5.6 nmol N g⁻¹ hr⁻¹. DNRA rates were low with no clear pattern across the sites. Denitrification rates were higher in transition zone soils than in upland soils at three of the four sites (<em>p</em> &lt; 0.05). Rates of denitrification in wetlands were lower than that observed in transition soils when hydrogen sulfide (H₂S) concentrations were high, favoring DNRA, but not where H₂S was low. Rates of denitrification across sites and zones were driven by soil moisture and related to organic matter content. Our data suggest that transition zone soils act as hotspots for N removal due to intermittent inundation and oscillating redox conditions. The N cycling characteristics of soils changing from forest to wetland are unique enough from steady-state upland and wetland ecosystems to address as a distinct ecotone in forecasts of future ecosystem function and N exchange at the coastal terrestrial-aquatic interface.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109904"},"PeriodicalIF":9.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144547572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Harnessing arbuscular mycorrhizal fungal communities for ecological restoration: a conceptual framework","authors":"Wei Fu ,&nbsp;Tianyi Niu ,&nbsp;Songlin Wu ,&nbsp;Zhipeng Hao ,&nbsp;Matthias C. Rillig ,&nbsp;Baodong Chen","doi":"10.1016/j.soilbio.2025.109902","DOIUrl":"10.1016/j.soilbio.2025.109902","url":null,"abstract":"<div><div>Harnessing plant-beneficial microbes, such as arbuscular mycorrhizal (AM) fungi, holds great potential as a nature-based solution for ecological restoration. However, despite relentless efforts to propagate, stimulate, enrich, or engineer AM fungal communities, their effectiveness in restoration practices remains uncertain. To help solve this problem, we propose a conceptual framework that integrates three key components: pre-restoration assessment, strategic inoculation, and establishing an ecological support system (ESS) to enhance and sustain AM fungal functionality. As the core of this framework, the ESS focuses on selecting mycotrophic plants, managing key biotic interactions involving AM fungi and improving the soil environment, so as to promote the co-development of the plant-AM fungi-soil microbiota ternary system. These guidelines are intended to ensure the applicability and sustainability of AM fungal management in restoration practices. We further advocate for conserving soil microbial biodiversity and integrating core microbiomes with AM fungi to ensure the success of ecological restoration efforts.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109902"},"PeriodicalIF":9.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differences in straw derived hydrophilic and hydrophobic carbon incorporation into soil microbial necromass","authors":"Jun Zhang ,&nbsp;Fenghua Zhang ,&nbsp;Lei Yang","doi":"10.1016/j.soilbio.2025.109901","DOIUrl":"10.1016/j.soilbio.2025.109901","url":null,"abstract":"<div><div>Microorganisms are important modulators for transformation and allocation of straw-derived carbon into soil organic carbon (SOC). However, little is known about how straw-derived dissolved organic matter (DOM) is converted into microbial necromass carbon in soil. To address this, hydrophilic (Hi-DOM) and hydrophobic (Ho-DOM) carbon fractions were extracted from cotton straw and added to soil with a 10-year history of straw incorporation for a 45-day mineralization incubation. CO₂ emissions and ¹³C enrichment after addition of ¹³C-labeled Hi-and Ho-DOM into soil were analyzed, and the differences between the utilization of Hi-and Ho-DOM by microorganisms, as well as their incorporation into amino sugars were also determined. The results revealed that during the initial incubation phase (0.25–5 days), the mineralization rate of Hi-DOM was 1.1–2.7 times faster than that of Ho-DOM. Furthermore, cumulative CO₂ production gradually increased during the incubation, and by the end of the experiment, Hi-DOM yielded 1.4 times more CO₂ than Ho-DOM. Moreover, both Hi-DOM and Ho-DOM exhibited a positive priming effect. Similarly, the ¹³C content derived from Hi-DOM (0.48 mg g⁻¹) was noticeably higher than that from Ho-DOM (0.41 mg g⁻¹) in SOC. Residual ¹³C from Hi-DOM and Ho-DOM accounted for 20.1 % and 35.6 % of the total added carbon, respectively, indicating the dependence of microbial C uptake on substrate quality. Higher ¹³C-GlcN and ¹³C-MurN levels were witnessed in Ho-DOM and Hi-DOM-treated soils, respectively. Furthermore, Hi-DOM-treated soil exhibited higher bacterial necromass ¹³C and total microbial necromass ¹³C than Ho-DOM-treated soil, suggesting a fungal preference for complex compounds while bacteria preferred the utilization of simpler substrates for amino sugar formation. Furthermore, Hi-DOM exhibited prolonged and faster soil activity, as evidenced by significantly increased Hi-DOM-sourced ¹³C enrichment percentages in the amino sugar pool by the end of incubation. In conclusion, the distinct properties of straw-derived DOM can alter the intensity and magnitude of its conversion into microbial necromass carbon. Combined with the differential contributions of newly formed microbial residues to the SOC pool, this study enhances predictions of how straw carbon incorporation influences microbial carbon storage capacity and SOC sequestration potential.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109901"},"PeriodicalIF":9.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144533907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploiter no more: root metabolites driving denitrification inhibition from diverse plants","authors":"Jincheng Li ,&nbsp;Roland Bol ,&nbsp;Davey L. Jones ,&nbsp;David R. Chadwick ,&nbsp;Xiaotang Ju ,&nbsp;Chuihua Kong ,&nbsp;Yunting Fang ,&nbsp;Di Wu","doi":"10.1016/j.soilbio.2025.109898","DOIUrl":"10.1016/j.soilbio.2025.109898","url":null,"abstract":"<div><div>Soil denitrifiers can profoundly benefit from plant root activities by utilizing the released labile carbon (C) in root exudates, though the plants may not receive direct benefits in return. However, the role of root metabolites in promoting or suppressing denitrification remains poorly understood across a wide range of plant species. Additionally, the underlying mechanisms driving these effects are still elusive. We used an optimized hydroponic-based approach to collect root metabolites in hydroponic solution from 100 plant species. We then assessed their differential effects on soil denitrification potential, microbial activity and the abundance of denitrification genes. Out of the 100 plant species tested, the root metabolites of 21 exhibited biological denitrification inhibition (BDI), while 51 stimulated denitrification under conditions of sufficient C supply. Some of the collected BDI root solutions inhibited soil denitrifying activity within the heterotrophic community and reduced the abundance of key denitrification genes, including <em>nirK</em>, <em>nirS</em> and <em>nosZ</em>. Several potential BDI-related secondary metabolites, such as flavonoids, were identified using untargeted LC–MS metabolomics. Our findings suggest that the inhibition of denitrification through root metabolites may be a widespread strategy among plant species, offering new insights for developing effective strategies to mitigate plant-mediated N losses in the rhizosphere.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109898"},"PeriodicalIF":9.8,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disentangling the contribution of mycorrhizal fungi to soil organic carbon storage","authors":"Xin Guan ,&nbsp;Jiang Jiang ,&nbsp;Aimée T. Classen ,&nbsp;Sami Ullah ,&nbsp;Gangsheng Wang","doi":"10.1016/j.soilbio.2025.109900","DOIUrl":"10.1016/j.soilbio.2025.109900","url":null,"abstract":"<div><div>Ectomycorrhizal fungi (ECM) play a fundamental role in plant-soil carbon and nitrogen cycling in forest ecosystems, yet their influence on soil organic carbon (SOC) sequestration remains underexplored, particularly in process-based models. Here, we develop a Mycorrhizal fungi-mediated Microbial-ENzyme Decomposition (Myc-MEND) model to explore ECM effects on plant carbon fixation and nitrogen uptake. The model was calibrated with biomass of foliage, wood, and roots, and annual net primary productivity from forests in eastern NC, USA. Our findings show that ECM enhance plant nitrogen availability, increasing plant productivity but not directly promoting SOC sequestration. We find that the increased nitrogen provided by ECM to plants decreased plant C:N ratio and led to a 17 % increase in plant photosynthate. This increase in plant quality and quantity increased SOC storage up to 20 %. However, these increases also stimulated saprotrophic microbial activity and extracellular enzyme production, resulting in a 14 % decline in SOC, particularly a 19 % reduction in the particulate organic carbon pool. The most influential pathway for SOC stability was the stabilization of recalcitrant mycorrhizal mycelium necromass, which accounts for 36 % of mineral-associated organic carbon (MOC) storage and 31 % of overall SOC accumulation. Although mycorrhizal colonization led to a net 14 % decrease in total SOC storage, it contributed to a 10 % increase in MOC, highlighting its role in enhancing MOC formation. Our simulations demonstrated that ECM influence the microbial carbon pump by lowering plant C:N ratios, reducing microbial carbon use efficiency, and altering plant-soil carbon fluxes. Overall, our results underscore the critical role of ECM in regulating microbial carbon pump mechanisms and their indirect contributions to SOC persistence via MOC formation. By bridging empirical observations and theoretical modeling, this study lays the groundwork for integrating mycorrhizae processes into future research aimed at predicting ecosystem carbon fluxes and assessing their climate change mitigation potential.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109900"},"PeriodicalIF":9.8,"publicationDate":"2025-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144516239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soil nitrogen availability increases the abundance of nitrogen-fixing plants in subtropical forests","authors":"Xibin Sun ,&nbsp;Scott X. Chang ,&nbsp;Matthew D. Petrie ,&nbsp;Yixue Hong ,&nbsp;Meimei Li ,&nbsp;Zilong Ma ,&nbsp;Heng Huang ,&nbsp;Zhenchuan Wang ,&nbsp;Chengjin Chu ,&nbsp;Fuchen Luan ,&nbsp;Hao Chen","doi":"10.1016/j.soilbio.2025.109894","DOIUrl":"10.1016/j.soilbio.2025.109894","url":null,"abstract":"<div><div>The energy consumption theory suggests that the abundance of nitrogen-fixing plants (N-fixers) should decrease with increasing soil N availability. However, this theory fails to explain why there are more abundant N-fixers in N-rich tropical regions compared to N-limited temperate regions, which is known as the “N paradox.” We investigated changes in N-fixer abundance as soil N availability increased along two mountainous elevational gradients with different lithologies (granite vs. slate soil parent material) in subtropical forests located in Guangdong Province, China. Bayesian regression analysis revealed that soil N availability was the main factor influencing changes in N-fixer abundance across sites with different elevations in each study location. Despite comprising less than 2 % of total tree abundance across sites, N-fixers were more abundant in high-N slate forests than in low-N granite forests, and their abundance increased at higher elevation sites that had greater soil N availability in both locations. We attribute this pattern to N-fixers enhancing their competitiveness in high soil N forest locations by down-regulating symbiotic N fixation rates, accumulating N in leaves, and improving soil phosphorus acquisition. Our findings provide a case study explanation for the “N paradox,” and can help to improve predictions of changes to N-fixer abundance under increasing atmospheric N deposition.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"209 ","pages":"Article 109894"},"PeriodicalIF":9.8,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144488763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}