Pub Date : 2026-02-12DOI: 10.1016/j.soilbio.2026.110125
Fangbin Hou, Leonardo Hinojosa, Boris Jansen, Elly Morriën, Franciska T. de Vries
{"title":"Plant species specific effects of root exudates on the formation and destabilization of soil organic matter","authors":"Fangbin Hou, Leonardo Hinojosa, Boris Jansen, Elly Morriën, Franciska T. de Vries","doi":"10.1016/j.soilbio.2026.110125","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110125","url":null,"abstract":"","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"47 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160812","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}
Pub Date : 2026-02-09DOI: 10.1016/j.soilbio.2026.110122
Peng He, Jianing Wang, Xuewei Wang, Tengfei Ma, Ning Ling
Soil organic carbon (SOC) dynamics is strongly influenced by plant residue inputs, yet the microbial mechanisms—particularly the identity, activity, and temporal dynamics of microbial communities assimilating shoot-versus root-derived carbon (C)—remain poorly understood. This study employed DNA-based stable isotope probing (DNA-SIP) combined with amplicon sequencing to trace the incorporation of 13C-labeled shoot and root residues from alfalfa into soil microbial communities across a time series of 1, 7, 14, 30, and 48 days. We identified distinct bacterial and fungal taxa actively involved in residue decomposition and classified their temporal response strategies as rapid, intermediate, or delayed based on peak activity. Shoot and root residues differed in elemental stoichiometry, which contributed to divergent bacterial and fungal responses during residue-derived C assimilation. Fungal community composition was more strongly influenced by residue type than bacterial communities. Bacterial assembly was predominantly stochastic, with rapid responders (e.g., Lysobacter and Streptomyces), exhibiting conserved functional potentials in nitrogen (N) assimilation and phosphorus (P) cycling, dominating both residue types. In contrast, fungal communities were governed primarily by deterministic processes and exhibited distinct residue-specific metabolic strategies: shoot C assimilation was driven by rapid, often pathogenic taxa (e.g., Fusarium), whereas root C assimilation favored intermediate and delayed saprotrophic and symbiotic fungi (e.g., Orbilia and Cochlonema). These findings suggest that shoot and root residue quality (e.g., elemental stoichiometry) selects for distinct successional strategies and functional traits in microbial decomposers, offering a mechanistic basis for predicting residue-specific contributions to soil C and nutrient cycling.
{"title":"Distinct successional strategies and assembly dynamics of soil microbial community utilizing carbon derived from plant shoot versus root residues","authors":"Peng He, Jianing Wang, Xuewei Wang, Tengfei Ma, Ning Ling","doi":"10.1016/j.soilbio.2026.110122","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110122","url":null,"abstract":"Soil organic carbon (SOC) dynamics is strongly influenced by plant residue inputs, yet the microbial mechanisms—particularly the identity, activity, and temporal dynamics of microbial communities assimilating shoot-versus root-derived carbon (C)—remain poorly understood. This study employed DNA-based stable isotope probing (DNA-SIP) combined with amplicon sequencing to trace the incorporation of <ce:sup loc=\"post\">13</ce:sup>C-labeled shoot and root residues from alfalfa into soil microbial communities across a time series of 1, 7, 14, 30, and 48 days. We identified distinct bacterial and fungal taxa actively involved in residue decomposition and classified their temporal response strategies as rapid, intermediate, or delayed based on peak activity. Shoot and root residues differed in elemental stoichiometry, which contributed to divergent bacterial and fungal responses during residue-derived C assimilation. Fungal community composition was more strongly influenced by residue type than bacterial communities. Bacterial assembly was predominantly stochastic, with rapid responders (e.g., <ce:italic>Lysobacter</ce:italic> and <ce:italic>Streptomyces</ce:italic>), exhibiting conserved functional potentials in nitrogen (N) assimilation and phosphorus (P) cycling, dominating both residue types. In contrast, fungal communities were governed primarily by deterministic processes and exhibited distinct residue-specific metabolic strategies: shoot C assimilation was driven by rapid, often pathogenic taxa (e.g., <ce:italic>Fusarium</ce:italic>), whereas root C assimilation favored intermediate and delayed saprotrophic and symbiotic fungi (e.g., <ce:italic>Orbilia</ce:italic> and <ce:italic>Cochlonema</ce:italic>). These findings suggest that shoot and root residue quality (e.g., elemental stoichiometry) selects for distinct successional strategies and functional traits in microbial decomposers, offering a mechanistic basis for predicting residue-specific contributions to soil C and nutrient cycling.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"46 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146670","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}
Soil microbial carbon (C) use efficiency (CUE) is a critical parameter in C cycling process, but its relationship with aboveground plant communities remains largely unexplored. This study examines how vegetation composition and functional diversity influence microbial CUEST assessed by enzyme stoichiometry-based approach in soils across four subtropical plantation types. We hypothesized that: (i) the effects of overstorey tree and understorey plant diversity on CUEST are shaped by multiple community- and ecosystem-level functional dimensions: dispersions, means, variances, skewness, and kurtosis; and (ii) CUEST is influenced by resource limitations (mainly C and phosphorus, P) in soil. While soil microorganisms in all four plantations were co-limited by C and P, plantations with higher plant diversity have much lower C and P limitations compared to those with lower plant diversity. Across all plantations, plant community attributes, functional traits, and physico-chemical and microbial soil properties affect CUEST variation. Specifically, greater functional diversity in overstorey trees and understorey plants effectively reduces microbial C and P limitations and increases CUEST. The community-weighted contents of leaf nitrogen (N) and P affected CUEST variation more compared to other measures. These findings indicate that plant community composition and functions are critical to regulate CUEST and resource limitations. The results highlight that maintaining a functionally diverse overstorey and understorey vegetation is crucial to increasing soil C accumulation in soils of subtropical forest plantations.
{"title":"Functional trait diversity in overstorey and understorey increases microbial carbon use efficiency in a subtropical forest plantation soil","authors":"Renping Wan, Junxi Hu, Huan Xiao, Zhe Li, Jingnan Xu, Bo He, Lanlan Song, Lifeng Wang, Jian Peng, Xiaoyan Yu, Xiaolin Li, Lihua Tu, Yang Liu, Dongyu Cao, Xinglei Cui, Xinhua He, Congde Huang, Shixing Zhou, Yakov Kuzyakov","doi":"10.1016/j.soilbio.2026.110119","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110119","url":null,"abstract":"Soil microbial carbon (C) use efficiency (CUE) is a critical parameter in C cycling process, but its relationship with aboveground plant communities remains largely unexplored. This study examines how vegetation composition and functional diversity influence microbial CUE<sub>ST</sub> assessed by enzyme stoichiometry-based approach in soils across four subtropical plantation types. We hypothesized that: (i) the effects of overstorey tree and understorey plant diversity on CUE<sub>ST</sub> are shaped by multiple community- and ecosystem-level functional dimensions: dispersions, means, variances, skewness, and kurtosis; and (ii) CUE<sub>ST</sub> is influenced by resource limitations (mainly C and phosphorus, P) in soil. While soil microorganisms in all four plantations were co-limited by C and P, plantations with higher plant diversity have much lower C and P limitations compared to those with lower plant diversity. Across all plantations, plant community attributes, functional traits, and physico-chemical and microbial soil properties affect CUE<sub>ST</sub> variation. Specifically, greater functional diversity in overstorey trees and understorey plants effectively reduces microbial C and P limitations and increases CUE<sub>ST</sub>. The community-weighted contents of leaf nitrogen (N) and P affected CUE<sub>ST</sub> variation more compared to other measures. These findings indicate that plant community composition and functions are critical to regulate CUE<sub>ST</sub> and resource limitations. The results highlight that maintaining a functionally diverse overstorey and understorey vegetation is crucial to increasing soil C accumulation in soils of subtropical forest plantations.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"94 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138616","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}
Pub Date : 2026-02-09DOI: 10.1016/j.soilbio.2026.110121
Laura T. Rea, Clifford Adamchak, Jacqueline R. Gerson, Magdalena A. Franchois, Hans Røy, Eve-Lyn S. Hinckley
Agricultural sulfur (S) inputs are a primary source of anthropogenic S to the environment, often stimulating microbial sulfate reduction (MSR) in downstream environments and driving multiple ecosystem consequences. Because it is assumed that bulk oxygenated soils do not support reduction processes, MSR is typically only studied in saturated environments like downstream wetlands. Here, we investigated MSR activity and its spatial distribution within soil profiles experiencing different hydrologic conditions (dry, moist, saturated) across Napa Valley, California, USA, where elemental S is added to vineyards as a fungicide. Using a combination of 35S-sulfate radioisotope tracer methods and silver film imaging, we observed the highest sulfate reduction rates (SRRs) (22.10 ± 61.02 nmol cm-3 soil day-1) in small microsites during moist conditions, and lower SRRs (0.90 ± 2.05 nmol cm-3 soil day-1) in diffuse zones during saturated conditions. Our findings suggest that MSR activity within upland soils shifts between microsites with high SRRs during moist conditions, and diffuse zones with lower SRRs during saturated conditions. Remarkably, we also found evidence that microsites with MSR persisted during dry conditions, further challenging the conventional view that MSR is restricted to bulk anoxic environments. Our findings highlight the potential for upland soils to be important areas of S transformations within the human-altered S cycle.
{"title":"Microsites Support Microbial Sulfate Reduction in Upland Soils","authors":"Laura T. Rea, Clifford Adamchak, Jacqueline R. Gerson, Magdalena A. Franchois, Hans Røy, Eve-Lyn S. Hinckley","doi":"10.1016/j.soilbio.2026.110121","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110121","url":null,"abstract":"Agricultural sulfur (S) inputs are a primary source of anthropogenic S to the environment, often stimulating microbial sulfate reduction (MSR) in downstream environments and driving multiple ecosystem consequences. Because it is assumed that bulk oxygenated soils do not support reduction processes, MSR is typically only studied in saturated environments like downstream wetlands. Here, we investigated MSR activity and its spatial distribution within soil profiles experiencing different hydrologic conditions (dry, moist, saturated) across Napa Valley, California, USA, where elemental S is added to vineyards as a fungicide. Using a combination of <sup>35</sup>S-sulfate radioisotope tracer methods and silver film imaging, we observed the highest sulfate reduction rates (SRRs) (22.10 ± 61.02 nmol cm<sup>-3</sup> soil day<sup>-1</sup>) in small microsites during moist conditions, and lower SRRs (0.90 ± 2.05 nmol cm<sup>-3</sup> soil day<sup>-1</sup>) in diffuse zones during saturated conditions. Our findings suggest that MSR activity within upland soils shifts between microsites with high SRRs during moist conditions, and diffuse zones with lower SRRs during saturated conditions. Remarkably, we also found evidence that microsites with MSR persisted during dry conditions, further challenging the conventional view that MSR is restricted to bulk anoxic environments. Our findings highlight the potential for upland soils to be important areas of S transformations within the human-altered S cycle.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"58 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138617","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}
Numerous models have been developed to simulate nitrous oxide (N2O) emissions from agricultural soils, yet accurately capturing the spatial and temporal variability of soil N2O fluxes remains a challenge. To better estimate soil N2O emissions, we developed a statistical model based on the Gaussian function, with parameters that vary according to edaphic properties. A global database of N2O emissions from agricultural soils, derived from laboratory incubation experiments, was established to parameterize, calibrate and validate the developed model. Simulations demonstrated that incorporating multiple edaphic properties, including soil moisture, mineral nitrogen contents, carbon to nitrogen ratio, silt content, bulk density and soil depth, enabled reliable prediction of N2O emissions from sieved soils. However, the initially parameterized model significantly overestimated emissions from intact soils. To address this, soil structure correction factors, quantified by bulk soil properties, were introduced into the model. Incorporating these structure corrections enabled the model to successfully predict N2O emissions from intact soils, highlighting the importance of accounting for soil structure in models. The improved model was then employed to simulate N2O emissions from different field sites with contrasting agricultural treatments, after further taking into account temperature effects. It effectively captured the temporal dynamics of N2O fluxes, including the timing and magnitude of N2O emission peaks, particularly under optimal N additions and long-term tillage. Overall, this soil-specific model provides a robust tool to predict the large spatiotemporal variations in N2O fluxes across different soils under various environmental settings, which is critical for reducing uncertainty in large-scale estimates.
{"title":"A soil-specific model to predict N2O emissions from laboratory and field experiments","authors":"Baoxuan Chang, Zhaopei Chu, Xia Zhu-Barker, Xiaotang Ju, Si-Liang Li, Zhifeng Yan, Timothy J. Clough","doi":"10.1016/j.soilbio.2026.110117","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110117","url":null,"abstract":"Numerous models have been developed to simulate nitrous oxide (N<sub>2</sub>O) emissions from agricultural soils, yet accurately capturing the spatial and temporal variability of soil N<sub>2</sub>O fluxes remains a challenge. To better estimate soil N<sub>2</sub>O emissions, we developed a statistical model based on the Gaussian function, with parameters that vary according to edaphic properties. A global database of N<sub>2</sub>O emissions from agricultural soils, derived from laboratory incubation experiments, was established to parameterize, calibrate and validate the developed model. Simulations demonstrated that incorporating multiple edaphic properties, including soil moisture, mineral nitrogen contents, carbon to nitrogen ratio, silt content, bulk density and soil depth, enabled reliable prediction of N<sub>2</sub>O emissions from sieved soils. However, the initially parameterized model significantly overestimated emissions from intact soils. To address this, soil structure correction factors, quantified by bulk soil properties, were introduced into the model. Incorporating these structure corrections enabled the model to successfully predict N<sub>2</sub>O emissions from intact soils, highlighting the importance of accounting for soil structure in models. The improved model was then employed to simulate N<sub>2</sub>O emissions from different field sites with contrasting agricultural treatments, after further taking into account temperature effects. It effectively captured the temporal dynamics of N<sub>2</sub>O fluxes, including the timing and magnitude of N<sub>2</sub>O emission peaks, particularly under optimal N additions and long-term tillage. Overall, this soil-specific model provides a robust tool to predict the large spatiotemporal variations in N<sub>2</sub>O fluxes across different soils under various environmental settings, which is critical for reducing uncertainty in large-scale estimates.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"312 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138615","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}
Pub Date : 2026-02-09DOI: 10.1016/j.soilbio.2026.110124
Martin-Georg Endress, Sergey Blagodatsky
Both active and dormant soil microorganisms spend a substantial fraction of their carbon and energy resources to maintain themselves, yet microbial maintenance metabolism remains inadequately represented in models of soil carbon cycling. The calorespirometric ratio (CR) of heat to CO2 release has been established as a powerful tool to investigate the bioenergetics of microbial growth in soil, but its application to non-growth metabolism has not been systematically explored. Here, we use dynamic modeling to assess how maintenance processes influence the coupling between microbial carbon and energy use as reflected by the CR and how maintenance alters the relationship between the CR and microbial carbon use efficiency (CUE). We find that maintenance metabolism reduces apparent CUE, while its effects on the CR depend on the energy content of the soil organic matter (SOM) or biomass compounds consumed to fuel the maintenance reaction. A compilation of literature data on the CR in different soils reveals highly variable values, indicating that soil microbes utilize a wide range of substrates and metabolic pathways to meet their maintenance demands. In arable soils, we find a close linear relationship between maintenance CR and average SOM energy content, while there is no clear pattern in forest soils. Compiled CR observations after glucose addition display a pronounced drop in CR at the onset of the retardation phase, suggesting a shift towards the use of energy poor substrates. We present a bioenergetic framework to incorporate maintenance metabolism in process-based models of soil microbial carbon use, and our compiled data show how maintenance processes affect the coupling between carbon and energy cycling both in unamended soils as well as after the addition of labile substrates.
{"title":"Bioenergetics of microbial maintenance metabolism in soil","authors":"Martin-Georg Endress, Sergey Blagodatsky","doi":"10.1016/j.soilbio.2026.110124","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110124","url":null,"abstract":"Both active and dormant soil microorganisms spend a substantial fraction of their carbon and energy resources to maintain themselves, yet microbial maintenance metabolism remains inadequately represented in models of soil carbon cycling. The calorespirometric ratio (CR) of heat to CO<ce:inf loc=\"post\">2</ce:inf> release has been established as a powerful tool to investigate the bioenergetics of microbial growth in soil, but its application to non-growth metabolism has not been systematically explored. Here, we use dynamic modeling to assess how maintenance processes influence the coupling between microbial carbon and energy use as reflected by the CR and how maintenance alters the relationship between the CR and microbial carbon use efficiency (CUE). We find that maintenance metabolism reduces apparent CUE, while its effects on the CR depend on the energy content of the soil organic matter (SOM) or biomass compounds consumed to fuel the maintenance reaction. A compilation of literature data on the CR in different soils reveals highly variable values, indicating that soil microbes utilize a wide range of substrates and metabolic pathways to meet their maintenance demands. In arable soils, we find a close linear relationship between maintenance CR and average SOM energy content, while there is no clear pattern in forest soils. Compiled CR observations after glucose addition display a pronounced drop in CR at the onset of the retardation phase, suggesting a shift towards the use of energy poor substrates. We present a bioenergetic framework to incorporate maintenance metabolism in process-based models of soil microbial carbon use, and our compiled data show how maintenance processes affect the coupling between carbon and energy cycling both in unamended soils as well as after the addition of labile substrates.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"39 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146669","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}
Humin, defined as the residual fraction of soil organic matter remaining after alkaline extraction, has been recognized as the predominant and most stable form of organic matter in mineral soils for centuries. Consequently, it is imperative to reconsider this at the modern instrumental level, as the current evidence about its composition is primarily influenced by the analytical methods applied. Here, humin was recovered from the <20 μm organo-mineral μm fraction of forest and grassland topsoils after exhaustive sequential extractions. On average, humin accounted for ∼36 % of the total organic carbon (C) in the organo-mineral complex in grassland soils, and for >50 % in forest soils. Obtained humins were then investigated by 13C-NMR, Pyrolysis-GC-MS, THM-GC-MS, acid hydrolysis followed by monosaccharide detection and quantification, and thermal analyses (DTG and DSC). The studied humins consisted of a broad mixture of C types, including alkyl C (∼34 %) and O-alkyl C (∼30 %), while they were remarkably poor in carboxyl C, which may explain their insolubility in alkali solutions. Overall, humins from forest soils seemed more microbially transformed than those from grassland soils. In particular, carbohydrates were mainly of microbial origin, lipids preserved the features of their original precursors (suberin, epicuticular waxes), whereas the degree of preservation of lignins was unclear. Carbon recalcitrance, measured by acid hydrolysis, was higher in forest humins (40 %) than in grassland humins (34 %). At the same time, humins from forests showed a lower thermal stability than those from grasslands, but were characterized by a higher energy density. Contrary to views that propose a humin composition predominantly aromatic, alkyl or poly-alkyl in nature, our study showed that humins are highly chemodiverse, containing a wide range of organic compounds, none of them being predominant. Their degree of microbial reworking varied with vegetation type and, thus, with corresponding plant inputs; on a larger scale, it probably varies with climate and parent material, a hypothesis to verify in future research.
{"title":"The ultimate fraction – Chemical characterization of humins from forest vs grassland soils","authors":"Pere Rovira, Beatrice Giannetta, Joeri Kaal, Agustín Merino, César Plaza, Claudio Zaccone","doi":"10.1016/j.soilbio.2026.110118","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110118","url":null,"abstract":"Humin, defined as the residual fraction of soil organic matter remaining after alkaline extraction, has been recognized as the predominant and most stable form of organic matter in mineral soils for centuries. Consequently, it is imperative to reconsider this at the modern instrumental level, as the current evidence about its composition is primarily influenced by the analytical methods applied. Here, humin was recovered from the <20 μm organo-mineral μm fraction of forest and grassland topsoils after exhaustive sequential extractions. On average, humin accounted for ∼36 % of the total organic carbon (C) in the organo-mineral complex in grassland soils, and for >50 % in forest soils. Obtained humins were then investigated by <sup>13</sup>C-NMR, Pyrolysis-GC-MS, THM-GC-MS, acid hydrolysis followed by monosaccharide detection and quantification, and thermal analyses (DTG and DSC). The studied humins consisted of a broad mixture of C types, including alkyl C (∼34 %) and <em>O</em>-alkyl C (∼30 %), while they were remarkably poor in carboxyl C, which may explain their insolubility in alkali solutions. Overall, humins from forest soils seemed more microbially transformed than those from grassland soils. In particular, carbohydrates were mainly of microbial origin, lipids preserved the features of their original precursors (suberin, epicuticular waxes), whereas the degree of preservation of lignins was unclear. Carbon recalcitrance, measured by acid hydrolysis, was higher in forest humins (40 %) than in grassland humins (34 %). At the same time, humins from forests showed a lower thermal stability than those from grasslands, but were characterized by a higher energy density. Contrary to views that propose a humin composition predominantly aromatic, alkyl or poly-alkyl in nature, our study showed that humins are highly chemodiverse, containing a wide range of organic compounds, none of them being predominant. Their degree of microbial reworking varied with vegetation type and, thus, with corresponding plant inputs; on a larger scale, it probably varies with climate and parent material, a hypothesis to verify in future research.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"245 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138618","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}
Pub Date : 2026-02-08DOI: 10.1016/j.soilbio.2026.110120
Mohammad Rahmat Ullah, Steve Kwatcho Kengdo, Derek Peršoh, Ye Tian, Jakob Heinzle, Carolina Urbina Malo, Chupei Shi, Tillmann Lueders, Christian Poll, Wolfgang Wanek, Andreas Schindlbacher, Werner Borken
Long-term soil warming may alter microbial community structure and functioning in forest soils, thereby affecting carbon and nutrient cycling processes. We examined the effects of >14 years of soil warming (+4°C during snow-free seasons) on the fungal biomass marker ergosterol, and on fungal and bacterial communities in a spruce dominated mountain forest in the Austrian Alps. Soil warming decreased ergosterol, and the ergosterol-to-microbial biomass carbon (MBC) ratio at 0-10 and 10-20 cm soil depth, with a stronger decline in ergosterol, indicating a higher sensitivity of fungi than bacteria to long-term warming. Warming also shifted the fungal community at both soil depths, favoring Boletus luridus, an ectomycorrhizal (ECM) fungus, which emerged as the dominant OTU in warmed plots. The dominance of ECM over saprotrophic fungi (SAP) under warming at topsoil likely resulted from increased fine root production and enhanced competition for substrates and nutrients. Bacterial abundance and community composition remained mostly unaffected at both depths, likely due to their greater resilience to elevated temperatures and their high taxonomic diversity. Our findings therefore suggest that long-term warming primarily affects fungal community composition and functional traits, thereby enhancing the contribution of ECM with fine roots to the carbon cycle in the calcareous forest soil.
{"title":"Long-term soil warming decreases fungal biomass and alters fungal but not bacterial communities in a temperate forest","authors":"Mohammad Rahmat Ullah, Steve Kwatcho Kengdo, Derek Peršoh, Ye Tian, Jakob Heinzle, Carolina Urbina Malo, Chupei Shi, Tillmann Lueders, Christian Poll, Wolfgang Wanek, Andreas Schindlbacher, Werner Borken","doi":"10.1016/j.soilbio.2026.110120","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110120","url":null,"abstract":"Long-term soil warming may alter microbial community structure and functioning in forest soils, thereby affecting carbon and nutrient cycling processes. We examined the effects of >14 years of soil warming (+4°C during snow-free seasons) on the fungal biomass marker ergosterol, and on fungal and bacterial communities in a spruce dominated mountain forest in the Austrian Alps. Soil warming decreased ergosterol, and the ergosterol-to-microbial biomass carbon (MBC) ratio at 0-10 and 10-20 cm soil depth, with a stronger decline in ergosterol, indicating a higher sensitivity of fungi than bacteria to long-term warming. Warming also shifted the fungal community at both soil depths, favoring <em>Boletus luridus</em>, an ectomycorrhizal (ECM) fungus, which emerged as the dominant OTU in warmed plots. The dominance of ECM over saprotrophic fungi (SAP) under warming at topsoil likely resulted from increased fine root production and enhanced competition for substrates and nutrients. Bacterial abundance and community composition remained mostly unaffected at both depths, likely due to their greater resilience to elevated temperatures and their high taxonomic diversity. Our findings therefore suggest that long-term warming primarily affects fungal community composition and functional traits, thereby enhancing the contribution of ECM with fine roots to the carbon cycle in the calcareous forest soil.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"48 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134150","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}
Pub Date : 2026-02-05DOI: 10.1016/j.soilbio.2026.110111
Lijun Hou, Philippe Constant, Joann K. Whalen
Biological high-affinity H2 uptake in soil is the largest global sink for atmospheric H2. Soil pH often influences soil biological activity but the impact of pH on high-affinity H2 oxidizing bacteria (HOB) was not confirmed. We compared the activity and diversity of group 5/1h HOB in agricultural and forest soils across a gradient from pH 4 to pH 8. The potential H2 uptake activity was approximately 2 times higher in agricultural soil than in forest soil across the pH gradient. Both H2 oxidizing activity and HOB community structure were non-responsive to pH adjustment in these soils, and no pH optima was observed. Greater H2 oxidizing activity was associated with higher iron content and lower carbon and nitrogen concentrations in soil. Catabolic repression of HOB was likely triggered when more organic carbon was present, due to the mixotrophic metabolism in the HOB community. A few hhyL genotypes (5%) responded to pH manipulation, but preference for acidic or alkaline pH was not consistent at the HOB taxonomic level. We conclude that pH preference is not an ecological trait that predicts group 5/1h HOB distribution in soil.
{"title":"Diversity and activity of group 5/1h high-affinity H2 oxidizing bacteria is non-responsive to pH","authors":"Lijun Hou, Philippe Constant, Joann K. Whalen","doi":"10.1016/j.soilbio.2026.110111","DOIUrl":"https://doi.org/10.1016/j.soilbio.2026.110111","url":null,"abstract":"Biological high-affinity H<sub>2</sub> uptake in soil is the largest global sink for atmospheric H<sub>2</sub>. Soil pH often influences soil biological activity but the impact of pH on high-affinity H<sub>2</sub> oxidizing bacteria (HOB) was not confirmed. We compared the activity and diversity of group 5/1h HOB in agricultural and forest soils across a gradient from pH 4 to pH 8. The potential H<sub>2</sub> uptake activity was approximately 2 times higher in agricultural soil than in forest soil across the pH gradient. Both H<sub>2</sub> oxidizing activity and HOB community structure were non-responsive to pH adjustment in these soils, and no pH optima was observed. Greater H<sub>2</sub> oxidizing activity was associated with higher iron content and lower carbon and nitrogen concentrations in soil. Catabolic repression of HOB was likely triggered when more organic carbon was present, due to the mixotrophic metabolism in the HOB community. A few <em>hhyL</em> genotypes (5%) responded to pH manipulation, but preference for acidic or alkaline pH was not consistent at the HOB taxonomic level. We conclude that pH preference is not an ecological trait that predicts group 5/1h HOB distribution in soil.","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"91 1","pages":""},"PeriodicalIF":9.7,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134151","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}
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