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{"title":"Microbial-microhabitat interactions drive shrub and herb diversity along an altitudinal gradient in a mountainous birch secondary forest","authors":"Yuhang Wu ,&nbsp;Longfei Hao ,&nbsp;Tingyan Liu ,&nbsp;Pengwu Zhao ,&nbsp;Yanhong He ,&nbsp;Ruijun Zhang ,&nbsp;Jinwei Guo","doi":"10.1016/j.catena.2026.109797","DOIUrl":"10.1016/j.catena.2026.109797","url":null,"abstract":"<div><div>Mountain ecosystems are highly sensitive to climate change, and vegetation-soil-microbe interactions are essential for their ecological functioning. This study was carried out in a <em>Betula platyphylla</em> secondary forest in the Han Mountain National Nature Reserve, Inner Mongolia, with the main goal of unraveling the moisture-driven “microbe-nutrient-vegetation” cascade mechanism along an altitudinal gradient. Sampling was conducted along an altitudinal gradient: low (1225 ± 50 m), middle (1375 ± 50 m), and high (1525 ± 50 m) zones. This study used a metagenomic approach to identify microbial communities. By integrating soil microenvironment properties, microbial functional traits, nutrient availability, and understory plant diversity, we used multivariate statistics and Partial Least Squares Path Modeling (PLS-PM) to unravel the moisture-driven “microbe-nutrient-vegetation” cascade mechanism. (1) Soil water content significantly decreased with altitude, triggering a microbial shift from low-altitude copiotrophic bacteria (e.g., Proteobacteria and Actinobacteria) to high-altitude stress-tolerant fungi (e.g., <em>Cortinarius</em> and <em>Mortierella</em>). With increasing elevation along the altitudinal gradient, microbial metabolic limitation shifted, with phosphorus limitation weakening (vector angle decreased by 2.81 %) and carbon limitation strengthening (vector length increased by 11.32 %). (2) Moisture-regulated nutrient dynamics through microbial traits: Higher moisture at low altitudes enhanced bacterial diversity and carbon/nitrogen accumulation (e.g., dissolved organic carbon (DOC) and available nitrogen (AN)), whereas moisture deficit at high altitudes favored fungi associated with the P cycle (microbial biomass phosphorus (MBP) accumulation). Mid-altitude showed complementary microbial nutrient use, resulting in a peak in available phosphorus (AP) content. (3) Shrub diversity peaked at low altitudes (Chao1 = 6.01) and was mainly promoted by bacteria associated with the C/N cycle. Herb diversity exhibited a mid-altitude bulge (Chao1 = 20.19) and was strongly associated with fungal-driven phosphorus availability (AP contribution rate = 30.1 %). (4) The PLS-PM model (goodness of fit = 0.78) verified that soil water content (total effect β = 0.80) indirectly influenced vegetation diversity by regulating microbial community structure (β = −0.98) and nutrient availability (β = 0.89), forming a core “moisture → microbe → nutrient” cascade pathway. This study elucidates the mechanistic pathways linking moisture, microbes, nutrients, and plants along elevational gradients, deepens our mechanistic understanding of how future climate change may affect soil microbial diversity, and provides a theoretical foundation for developing forward-looking strategies to conserve vegetation diversity.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109797"},"PeriodicalIF":5.7,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923198","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":"Long-term reclamation shifts microbial necromass and its contribution to soil organic matter in two coastal marshes","authors":"Wei Xu ,&nbsp;Qiang Li ,&nbsp;Wenbei Du ,&nbsp;Shufeng Chen ,&nbsp;Xi Yang ,&nbsp;Yuntao Shang ,&nbsp;Fang Wang ,&nbsp;Anna Gunina ,&nbsp;Yidong Wang","doi":"10.1016/j.catena.2026.109796","DOIUrl":"10.1016/j.catena.2026.109796","url":null,"abstract":"<div><div>Reclamation of coastal wetlands decreases soil organic matter (SOM) and changes its composition; however, it remains unclear how reclamation affects microbial necromass and its contribution to SOM. We investigated this question at two coastal marshes (Qilihai, seasonally waterlogged; Beidagang, permanently waterlogged) and adjacent reclaimed farmlands (approximately 60 years old) on the coast of Bohai Bay, China. Particulate (POM) and mineral-associated organic matter (MAOM) pools were separated by ultrasonic dispersion from 0 to 15 and 15–30 cm soil depth. Reclamation decreased the concentrations of soil organic carbon (SOC) (20–96 %) and microbial necromass carbon (MNC) (3.4–93 %) in bulk soil and fractions (except for Beidagang's subsoil), especially for the topsoil. Despite site-specific variations in SOC dynamics, MNC contributions to bulk SOC pools showed minimal change at both locations. The ratio of fungal necromass carbon (FNC) to SOC increased in the POM (+121 %) of the Qilihai topsoil, while it decreased in the POM (−62 %) of the Beidagang subsoil. At the Qilihai, the MNC decreased with lipids in bulk soil and the MAOM, while increased with SOC, total nitrogen (TN), N-containing compounds and short-range ordered mineral Fe (Fe_SRO) in bulk. In contrast, at the Beidagang, the MNC increased with SOC, TN and Fe_SRO, decreased with phenolic and N-containing compounds in bulk soil and the two fractions. Thus, wetland reclamation reduced the pools of SOC and MNC, and different waterlogging conditions induced divergent shifts in the components of MNC and its contribution to SOC.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109796"},"PeriodicalIF":5.7,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923182","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 pH and latitude as a major predictor of C:N:P stoichiometry in Germany","authors":"Pegah Khosravani ,&nbsp;Ndiye Michael Kebonye ,&nbsp;Ruhollah Taghizadeh-Mehrjardi ,&nbsp;Hadi Shokati ,&nbsp;Ling Hu ,&nbsp;Thomas Scholten","doi":"10.1016/j.catena.2025.109785","DOIUrl":"10.1016/j.catena.2025.109785","url":null,"abstract":"<div><div>Soil stoichiometry governs nutrient cycling to ensure optimal ecosystem functionality. Although the soil carbon‑nitrogen‑phosphorus (C:N:P) stoichiometry and ecosystem functioning are closely related, much less is known about how environmental predictors regulate the spatial distribution of these ratios in temperate regions. Specifically, the statistical relationships of soil properties (such as soil pH and clay content), climate variables (like precipitation and temperature), and topographic features (i.e., slope and aspect) on C:N:P stoichiometric patterns at regional scales remain poorly understood. In our study, we combined Cubist machine learning for spatial predictions with state-of-the-art statistical approaches—generalized additive models and structural equation modeling—to disentangle the quantitative relationships between environmental predictors and soil C:N, C:P, and N:P ratios across Germany. The relative importance analysis of environmental predictors shows that soil pH is the major predictor of stoichiometric ratios, acting through its fundamental control on nutrient availability. Higher soil pH corresponded to lower stoichiometric ratios and vice versa. Latitude emerged as another important predictor due to its effect on temperature, which plays a crucial role in these ratios, such that increasing latitude corresponds to lower ratios. As expected, wall-to-wall spatial distribution maps of the stoichiometric ratios showed varying patterns due to different environmental predictor influences. These findings enhance our understanding of environmental-stoichiometric interactions and offer valuable insights needed for sustainable soil management in temperate regions.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109785"},"PeriodicalIF":5.7,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923169","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":"Asynchronous responses of particulate and mineral-associated organic carbon to environment driven by aridity reshaped soil organic carbon stability of Qinghai-Xizang Plateau","authors":"Yubin Wang ,&nbsp;Deng Ao ,&nbsp;Baorong Wang ,&nbsp;Yang Hu ,&nbsp;Bicheng Zhang ,&nbsp;Haolin Zhang ,&nbsp;Wei Guo ,&nbsp;Sisay Mekonnen ,&nbsp;Can Xu ,&nbsp;Shaoshan An","doi":"10.1016/j.catena.2025.109780","DOIUrl":"10.1016/j.catena.2025.109780","url":null,"abstract":"<div><div>Global climate change is altering temperature and precipitation patterns, which profoundly affect soil organic carbon (SOC) dynamics, especially in sensitive high-elevation ecosystems of the Qinghai-Xizang Plateau (QXP). SOC consists mainly of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), each responding differently to environmental changes. However, previous studies in high-elevation ecosystems has often overlooked how these two SOC pools react asynchronously to varying conditions, limiting our understanding of SOC stability and carbon cycling under climate change. This study examines how POC and MAOC vary along aridity gradients on the QXP and assess their implications for SOC stability and carbon sequestration. Soil samples were collected from 220 sites at two depths (0–20 cm and 20–40 cm), across arid, semi-arid, semi-humid, and humid regions. SOC increased roughly 5 times from arid to humid regions (about 13.18 g·kg⁻¹ and 69.22 g·kg⁻¹), and SOC stability was only 0.57 in semi-arid region and lower than other regions. Crucially, POC and MAOC responded asynchronously to environmental factors. NDVI and climate variables drove rapid POC gains in semi-arid regions, whereas in semi-humid and humid regions rising vegetation cover triggered steep MAOC accumulation. These findings highlight that SOC pools respond differently to aridity: labile POC tracks moisture-driven vegetation increases in transitional semi-arid and semi-humid regions, while stable MAOC accumulates faster under wetter conditions. Our study reveals the critical role of asynchronous responses between POC and MAOC in controlling SOC content and stability on the QXP, with implications for predicting C-cycle feedbacks under climate change.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109780"},"PeriodicalIF":5.7,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923170","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":"Measures of pyrogenic carbon in native forest and plantations of northern Australia","authors":"Freddy Jontara Hutapea ,&nbsp;Liubov Volkova ,&nbsp;Daniel S. Mendham ,&nbsp;Michael I. Bird ,&nbsp;Senani Karunaratne ,&nbsp;Jacqueline R. England ,&nbsp;Michael Brand ,&nbsp;Christopher J. Weston","doi":"10.1016/j.catena.2025.109784","DOIUrl":"10.1016/j.catena.2025.109784","url":null,"abstract":"<div><div>Pyrogenic carbon (PyC) is a highly stable fraction of soil organic carbon that plays an important role in the global carbon budget and biogeochemical processes. However, the stocks and dynamics of PyC in soils remain insufficiently characterized, largely due to longstanding challenges in obtaining accurate and reliable assessments. On Melville Island, northern Australia, fire is a common land management tool likely to influence both soil total organic carbon (TOC) and PyC. This study compared PyC to 50 cm depth and TOC to 100 cm depth in soils under three land uses (native <em>Eucalyptus</em> forests, <em>Eucalyptus pellita</em> plantations and <em>Acacia mangium</em> plantations) with differing recent fire frequencies. This study also compared the performance of nitric acid‑hydrogen peroxide digestion (PyC_KMD) and mid-infrared spectroscopy (PyC_MIRS) in estimating PyC, using hydrogen pyrolysis (PyC_Hypy) as the reference technique. The results showed strong evidence that TOC stocks (0–10 cm soil) were lower under <em>E. pellita</em> plantation (18 Mg ha⁻¹) than either <em>A. mangium</em> plantations or native forests (each about 25 Mg ha⁻¹) (<em>p</em> &lt; 0.01), and in all cases declined with increasing soil depth. PyC_hypy stock was distributed relatively evenly to 50 cm depth in each land use, at about 4–5 Mg ha⁻¹ per 10 cm depth interval. Although native forests were subject to prescribed burns approximately every two years (compared with fire exclusion over 15+ years in the plantations), the ratio of PyC_hypy to TOC (PyC_hypy/TOC) under native forests was lower than under <em>A. mangium</em> and <em>E. pellita</em>, suggesting that repeated fire events may lead to re-combustion of PyC. PyC_hypy/TOC increased with increasing soil depth, strongly suggesting the preferential translocation of PyC into deeper soil layers relative to TOC in the sandy and highly porous soils of Melville Island.</div><div>Among the three methods used to estimate PyC, PyC_KMD was not well correlated with PyC_Hypy, while PyC_MIRS, based on the available calibration database, explained 23 % of the variation in PyC_Hypy. Compared to direct measurements by Hypy, MIRS tended to underestimate PyC in soil with TOC less than 45 g kg⁻¹ and overestimate PyC in soil with TOC greater than 45 g kg⁻¹. Expanded calibration datasets are required to improve the performance of MIRS for estimating PyC in the sandy forest soils of tropical Australia.</div><div>Further work is required to quantify PyC beyond 50 cm deep soil, to track temporal changes in soil PyC across different land uses and fire histories, and to evaluate the performance of different methods in quantifying PyC across diverse soil types.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109784"},"PeriodicalIF":5.7,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923113","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":"Decoupling effects of driving factors on sediment load in the middle reaches of the Yellow River","authors":"Chaohui Ma ,&nbsp;Xiaoxue Guo ,&nbsp;Ruirui Xu ,&nbsp;Peng Gao ,&nbsp;Jiahui Zhou ,&nbsp;Yuxuan Zhang ,&nbsp;Xingmin Mu","doi":"10.1016/j.catena.2025.109733","DOIUrl":"10.1016/j.catena.2025.109733","url":null,"abstract":"<div><div>Extensive soil and water conservation practices have profoundly reshaped sediment transport in the middle reaches of the Yellow River. Scientifically quantifying the driving factors behind these changes is essential for effective watershed management. Previous studies have primarily focused on the direct contributions of climate and human activities to sediment load across the entire watershed, often neglecting runoff-mediated pathways and spatial heterogeneity. This study analyzed the spatiotemporal variation in sediment load across the middle Yellow River and its sub-regions using continuous hydrological records from 1960 to 2020. Partial Least Squares Structural Equation Modeling was applied to elucidate the direct effects of vegetation and climate on sediment load from runoff-mediated indirect effects and to reveal the spatial heterogeneity of driving factors. Results showed a highly significant decline in sediment load (P &lt; 0.01) from 1960 to 2020. Since 2000, Wu–Long region has become the main sediment source. The driving factors of sediment load in the study area exhibited both temporal and spatial variability. Temporally, climate prevailed from 1980 to 1999 (total effect = 0.37), whereas vegetation became dominant from 2000 to 2020 (total effect = −0.33). Spatially, Tou–Wu region was primarily influenced by climate (−0.85 ≤ total effect ≤ −0.52), while vegetation dominated the Wu–Long region (−0.41 ≤ total effect ≤ 0.57). Runoff had a highly significant effect on sediment load variations (P &lt; 0.01). The indirect effects of vegetation through runoff in the Tou–Long and Wu–Long regions (−0.55 to 0.36 and −0.59 to 0.32, respectively) exceeded the direct effects (−0.10 to 0.10 and 0.18 to 0.25), confirming runoff as a key mediating factor. This study reveals spatial heterogeneity of sediment load drivers in the Hekou–Longmen region, providing a scientific basis for precision management and sustainable ecology in the middle Yellow River.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109733"},"PeriodicalIF":5.7,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923112","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 redistribution, weathering and soil organic carbon dynamics in a Mediterranean landscape","authors":"Markus Egli ,&nbsp;Annette den Boer ,&nbsp;Mike C. Rowley ,&nbsp;Dmitry Tikhomirov ,&nbsp;Maziar Mohammadi ,&nbsp;Salvatore Raimondi","doi":"10.1016/j.catena.2025.109781","DOIUrl":"10.1016/j.catena.2025.109781","url":null,"abstract":"<div><div>Due to climate change and intense land use, soils are highly dynamic in Mediterranean regions. Soil redistribution rates (erosion/accumulation) are assumed to be the main factor changing soil evolutional trajectories, weathering and organic carbon dynamics in these landscapes, but their interactions remain poorly understood. Therefore, we investigated soil redistribution rates, weathering state, soil organic carbon dynamics and its chemistry in a Mediterranean area, Corleone, Sicily. Although the soils showed clear signs of degradation and erosion of up to 39 t ha⁻¹ yr⁻¹, as determined by ^239+240Pu tracing, soil erosion measurement and modelling were made challenging by the vertic characteristics of some soils. With decreasing erosion rates, the soils had a higher amount of oxalate-extractable Fe stocks, more crystalline Fe, a lower (Ca + K)/Ti ratio (as a weathering indicator) or a higher CIA value. The organic C stocks ranged from 7 to 25 kg m⁻² (average of 14 kg m⁻²). A major part of organic carbon was stored in the large aggregate fraction (≥63 μm). Soil organic carbon dynamics and quality were strongly linked to the soil redistribution rates. Erosion removed the strongly weathered part of the soil and left behind a younger and fresher soil matrix with a low org. C content, but an organic carbon fraction that was enriched in aliphatic chains and lignin-like compounds having a less mature status. The investigated soils had in general an optimal composition for stabilising and sequestering organic matter, even highly eroded and shallow soils still contained a considerable amount of org. C, which is untypical for Mediterranean areas.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109781"},"PeriodicalIF":5.7,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923114","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":"Diversity, composition, networks, and assembly processes of soil microbial communities across slope positions in a karst peak cluster depression","authors":"Chengfu Zhang ,&nbsp;Limin Zhang ,&nbsp;Yang Cao ,&nbsp;Sunjian Zhang ,&nbsp;Maohui Tian ,&nbsp;Yan Sun ,&nbsp;Wenting Zhang ,&nbsp;Weici Su ,&nbsp;Weiquan Zhao ,&nbsp;Guandi He ,&nbsp;Tengbing He","doi":"10.1016/j.catena.2025.109778","DOIUrl":"10.1016/j.catena.2025.109778","url":null,"abstract":"<div><div>Soil microbial communities regulate ecological and biogeochemical processes. Existing studies have mostly focused on how slope position influences microbial diversity or composition, ignoring its impact on microbial networks and community assembly processes. We investigate how slope position (bottom, lower, middle, upper, and top) affects soil microbial diversity, composition, network structures, and assembly mechanisms in a karst peak cluster depression. We report significant decreases in bacterial alpha diversity from the bottom to the top, and for Sobs, Chao 1, and Shannon diversity indices to decrease by 19.09 %, 17.21 %, and 8.85 %, respectively. Fungal diversity remains stable at each of the five slope positions. Beta diversity reveals distinct bacterial and fungal community structures at different slope positions. The relative abundances of Proteobacteria and Verrucomicrobiota are greater at top slope position, and those of Chloroflexi, Myxococcota, Gemmatimonadota, and Glomeromycota are lower. These shifts in microbial community structure are mostly driven by variations in soil physicochemical properties and plant diversity. Bacterial networks are more complex and stable at middle, upper, and top slope positions than at bottom and lower slope positions; similar trends are apparent in fungal network complexity and vulnerability. Fungal networks are most robust at bottom slope positions, and most naturally connected in the lower slope. Deterministic processes, predominantly heterogeneous selection, dominate bacterial community assembly, while stochastic processes, specifically dispersal limitation, affect fungal community structure. Our results suggest that slope position affects the structure, network complexity and stability, and assembly processes of soil bacterial and fungal communities in the karst peak cluster depression. These findings demonstrate spatial variation in soil bacterial and fungal communities along slope positions, and that the potential exists to leverage microbial communities in ecological restoration.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109778"},"PeriodicalIF":5.7,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923115","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":"Stabilization of organic matter in topsoils under different tundra vegetation in Central Spitsbergen (high Arctic)","authors":"Anna Bartos ,&nbsp;Łukasz Musielok ,&nbsp;Wojciech Szymański","doi":"10.1016/j.catena.2025.109772","DOIUrl":"10.1016/j.catena.2025.109772","url":null,"abstract":"<div><div>Soil organic matter (SOM) stability in Arctic soils is a key factor influencing carbon sequestration and greenhouse gas emissions, particularly in the context of climate change. Despite numerous studies on carbon stocks in the Arctic, a significant knowledge gap remains regarding the mechanisms of SOM stabilization and their impact on the quantity and quality of SOM across different tundra vegetation types. The main aim of this study was to determine SOM characteristics in surface horizons of permafrost-affected soils covered with different tundra vegetation types (pioneer tundra, arctic meadow, moss tundra, and heath tundra) in the central part of Spitsbergen (Svalbard). Physical fractionation was used to separate SOM into POM (particulate organic matter) and MAOM (mineral-associated organic matter) fractions, while particle-size fractionation was applied to evaluate SOM distribution and composition in sand, silt, and clay fractions. The results indicate that in topsoils under heath tundra POM fractions dominate the carbon and nitrogen pools, whereas in pioneer tundra topsoils, the majority of the carbon and nitrogen are stored in MAOM fractions. Moreover, a substantial proportion of SOM is occluded within macro- and microaggregates. Furthermore, the results obtained from FTIR analysis revealed substantial differences in the chemical properties of individual soil fractions, both concerning the degree of occlusion in aggregates and across particle size fractions. This study provides clear evidence that tundra vegetation types significantly influence both the spatial distribution and chemical composition of SOM in the topsoils of central Spitsbergen.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109772"},"PeriodicalIF":5.7,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923167","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":"Hydrothermal stress influences the spatial distribution pattern of soil organic carbon and its stock in Xinjiang","authors":"Yunhao Li ,&nbsp;Mingjie Shi ,&nbsp;Ping'an Jiang ,&nbsp;Jinzhi Gu ,&nbsp;Jia Guo ,&nbsp;Jiahao Zhao ,&nbsp;Gongxin Wang ,&nbsp;Yanmin Fan ,&nbsp;Hongqi Wu","doi":"10.1016/j.catena.2025.109789","DOIUrl":"10.1016/j.catena.2025.109789","url":null,"abstract":"<div><div>Soil organic carbon (SOC) is a critical component of the terrestrial ecosystem carbon cycle. Its spatial distribution and formation mechanisms are essential for understanding carbon sink functions and informing management strategies in arid regions. However, current research has mainly focused on local areas, lacking systematic analyses of large-scale SOC spatial distribution and its driving mechanisms in arid zones-particularly the interactions between hydrothermal stress and other environmental factors. To address this gap, this study focuses on Xinjiang, a typical arid region in China. Based on 2757 measured soil samples, we integrated remote sensing imagery and multi-source environmental covariates to construct a Random Forest (RF) model for spatial prediction of SOC content. We further innovatively combined SHapley Additive exPlanations (SHAP analysis) and piecewise Structural Equation Modeling (pSEM) to analyze the dominant factors and response mechanisms controlling SOC in arid regions. The results of this innovative study are: (1) the Random Forest model achieved reliable prediction with an R² of 0.67, revealing that SOC spatial distribution exhibits a geomorphic gradient pattern of high levels in mountains (over 15 g kg⁻¹), moderate levels in oases, and low levels in deserts (below 5 g kg⁻¹), primarily controlled by hydrothermal conditions, with a total estimated stock of 3.19 Pg C for the top 30 cm; (2) evapotranspiration (ET) and soil moisture (SM) are the most important positive drivers of SOC, while soil temperature (ST) and vapor pressure deficit (VPD) exert significant negative effects; and (3) human activities regulate local hydrothermal stress through irrigation, but SOC stability is highly dependent on management practices. This study reveals the coupled pathways of hydrothermal stress mechanisms and human regulation in SOC formation, providing a theoretical basis and methodological support for carbon stock assessment and precision management in arid regions.</div></div>","PeriodicalId":9801,"journal":{"name":"Catena","volume":"264 ","pages":"Article 109789"},"PeriodicalIF":5.7,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145882974","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}