Biogeochemistry最新文献

{"title":"Can coarse woody material account for the nitrogen imbalance at Hubbard Brook Experimental Forest, New Hampshire, USA?","authors":"Andrew Ouimette,&nbsp;Jack Hastings,&nbsp;Tony D’Amato,&nbsp;John J. Battles,&nbsp;Mark Ducey,&nbsp;Jane R. Foster,&nbsp;Colin Fuss,&nbsp;Christine Goodale,&nbsp;Chris Johnson,&nbsp;Ashley Lang,&nbsp;Scott V. Ollinger","doi":"10.1007/s10533-026-01314-2","DOIUrl":"10.1007/s10533-026-01314-2","url":null,"abstract":"<div><p>The decay of coarse woody litter serves a potentially important role in forest nitrogen cycling. The carbon-rich, nitrogen-poor chemistry of wood allows it to immobilize, store, and in later stages of decomposition, supply nitrogen to forest ecosystems. The decay of woody litter happens over decadal time scales, making direct observations of its importance to nitrogen cycling challenging. Modeling woody litter decay can provide insights into its role in nitrogen cycling but is complex because it is influenced by microbial stoichiometric demands, wood chemistry, time spent as standing versus downed wood, input rates from mortality and disturbances, decay rates, and whether these processes are dynamic over time. One ecosystem where these uncertainties are particularly relevant is the Hubbard Brook Experimental Forest in New Hampshire, USA, where long-term monitoring of a reference watershed has revealed a persistent imbalance between nitrogen inputs and losses. Microbial immobilization of nitrogen in decaying wood has been proposed as an unaccounted-for nitrogen sink. To test whether coarse dead wood contributes to this imbalance, we modeled nitrogen and carbon dynamics during decay and the processes influencing their cycling. We found that 1) Nitrogen dynamics in dead wood likely do not account for a substantial fraction of the nitrogen imbalance observed at Hubbard Brook, and 2) Low microbial carbon-use efficiency for wood decay (&lt; 0.10) was most consistent with observed data and had a large influence on the capacity of wood to immobilize nitrogen and the fate of wood-derived carbon.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01314-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diverse microbial communities show uniform respiration response to nitrogen addition in simulated early-stage leaf litter decomposition experiments","authors":"Renée Z. Wang,&nbsp;Michaeline B. N. Albright,&nbsp;Dennis Suazo,&nbsp;La Verne Gallegos-Graves,&nbsp;Thomas Yoshida,&nbsp;John Dunbar,&nbsp;Marie E. Kroeger","doi":"10.1007/s10533-026-01322-2","DOIUrl":"10.1007/s10533-026-01322-2","url":null,"abstract":"<div><p>Plant litter decomposition by microbes plays a major role in soil CO₂ and dissolved organic carbon (DOC) production. Adding reactive nitrogen species is predicted to affect these fluxes, but it’s unclear to what extent since both microbial community composition and abiotic soil and litter chemistry will influence outcomes. We therefore sought to understand broad geochemical trends across diverse microbial assemblages during the initial stages of litter decomposition by incubating 10 diverse soil communities in identical geochemical conditions – sterile sand and leaf litter with water, inorganic nitrogen (ammonium nitrate), organic nitrogen (urea), or both – in the dark for 48 days at 25 °C. The headspace was regularly purged with ambient air, and we measured CO₂ production, microbial biomass C:N, bacterial and fungal community composition, DOC and dissolved total nitrogen (DTN) concentrations, respiratory quotients (RQ), and carbon use efficiency (CUE). Overall, we find across all communities and treatments that most grass litter carbon (~ 30%) is aerobically respired as CO₂ while some (~ 6%) is consumed as DOC and less than 1% becomes biomass. Compared to the water control, nitrogen treatment – particularly organic nitrogen – increases CO₂ production and DOC consumption by roughly 10% and 1% respectively, but CUE, RQ, and biomass C:N are unchanged. By constraining the litter and chemical composition of our incubations, we show reactive nitrogen addition enhances rather than alters existing microbial pathways of CO₂ production during the early stages of leaf litter decomposition.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 3","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01322-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mobilized dissolved organic matter provides niche space for prokaryotes in the deep subterranean estuary of a sandy beach","authors":"Grace A. Abarike,&nbsp;Simone Brick,&nbsp;Julius Degenhardt,&nbsp;Anja Reckhardt,&nbsp;Rena Meyer,&nbsp;Bert Engelen,&nbsp;Jutta Niggemann","doi":"10.1007/s10533-026-01315-1","DOIUrl":"10.1007/s10533-026-01315-1","url":null,"abstract":"<div><p>A fraction of organic carbon in beach sands is mobilizable as dissolved organic matter (DOM). The molecular composition of this mobilizable DOM and its relation to microbial metabolism is central for biogeochemical processes in beach ecosystems, yet, still poorly understood. To identify these DOM-microbe interactions, we analyzed two continuous 24-m-long sediment cores from the high-energy beach of Spiekeroog Island, Germany. The beach is characterized by a deep subterranean estuary (STE), where sediments are flushed by fresh, saline and brackish water. Even though beach sands are generally low in organic carbon, we found that concentrations of mobilizable DOM from sediments were approximately 16 times higher than the <i>in-situ</i> groundwater concentrations. Ultrahigh-resolution mass spectrometry revealed that the mobilized DOM was enriched in labile compounds, providing a potential source of bioavailable carbon for microbial communities. Cluster analyses identified distinct groups of DOM compounds that correlated with specific prokaryotic taxa and demonstrated that DOM composition influences microbial community differentiation revealed by 16S rRNA gene sequence clustering. Aerobic taxa, including <i>Pseudomonadota</i> and <i>Nitrososphaeria</i>, dominated oxic and redox transition zones and were primarily associated with labile, nitrogen-rich DOM clusters. In contrast, anaerobic taxa such as <i>Chloroflexota</i> and <i>Bathyarchaeia</i>, found in deeper sediments, correlated with more recalcitrant DOM compounds. These findings suggest that mobilized DOM contributes to niche differentiation and thus plays a role in shaping microbial community structures in STE sediments. Variations in DOM composition and redox conditions appear to create distinct ecological niches, enabling different prokaryotic taxa to thrive according to their metabolic capacities and substrate preferences.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01315-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soil heterotrophic respiration after irrigation retirement is differentially influenced by moisture and substrate availability over time","authors":"Violeta Mendoza-Martinez,&nbsp;Veronica Acosta-Martinez,&nbsp;Agustin Núñez,&nbsp;Kelly Wrighton,&nbsp;Meagan E. Schipanski","doi":"10.1007/s10533-026-01312-4","DOIUrl":"10.1007/s10533-026-01312-4","url":null,"abstract":"<div><p>Water limitations are forcing producers to transition large areas of currently irrigated farmland into dryland agriculture across the Western U.S. with unclear effects on global soil carbon (C) dynamics. An experiment established in 2017 in a no-till, maize system in Colorado suggested that soil heterotrophic respiration (R_h) following irrigation retirement was co-regulated by water and available C. We continued R_h measurements in 2021–2022 along with monthly soil samplings to explore the interactive effects of soil moisture and available C on microbial community composition and activity. Plant C inputs, available soil water, bacteria, fungi, and protozoa fatty acid methyl ester (FAME) biomarkers, enzyme activity, and R_h decreased after irrigation retirement, while actinobacteria abundance was not affected. Non-irrigated plots accumulated higher concentrations of dissolved organic carbon (DOC) and, in the absence of new C inputs, R_h from older SOC pools did not differ by irrigation treatment, suggesting limited microbial access to available C under low moisture. Short-term R_h variation was primarily moisture-driven, whereas cumulative residue inputs explained longer-term differences. Overall, microbial activity under irrigation retirement was co-limited by water and substrate availability. Management strategies that enhance soil moisture retention and maintain residue inputs are essential to sustain soil C cycling and resilience.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01312-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrate sources and transformation pathways in salt-affected agricultural ditches: biogeochemical responses along contrasting salinity gradients","authors":"Shenhao Qu,&nbsp;Dongli She,&nbsp;Yongchun Pan,&nbsp;Alimu Abulaiti,&nbsp;Peng Chen,&nbsp;Zhenqi Shi,&nbsp;Lei Hu,&nbsp;Yongqiu Xia","doi":"10.1007/s10533-026-01318-y","DOIUrl":"10.1007/s10533-026-01318-y","url":null,"abstract":"<div><p>Agricultural nitrate pollution, largely associated with high-intensity fertilizer application and untreated or insufficiently treated waste inputs, has become a major driver of water quality degradation worldwide. Agricultural ditches, as key recipients of surface runoff and lateral seepage, function as both transport conduits and biogeochemical hotspots for nitrogen transformation. In salt-affected ditches, high nitrogen inputs and salinity can interact to enhance nitrate accumulation and mobility, thereby increasing the potential for downstream transport. To bridge this knowledge gap, we investigated two representative saline agricultural ditches located in northwestern China, a region characterized by an arid climate and saline–alkaline soils. We employed stable isotope analysis (δ¹⁵N-NO₃^– and δ¹⁸O-NO₃^–) combined with a Bayesian stable isotope mixing model (MixSIAR) to identify nitrate sources and transformation pathways. Results showed that manure and sewage (M&amp;S) and chemical fertilizer (CF) were the dominant contributors, accounting for 42.6% and 42.1%, respectively, in the first ditch and 43.8% and 36.0% in the fifth ditch. Soil nitrogen (SN) contributed relatively less (15.3% and 20.2%, respectively). The results of both nitrate isotope analysis and chloride ion tracing revealed that the nitrate in the ditches originated primarily from agricultural activities and anthropogenic discharge. Interestingly, the nitrate transformation pathways differed notably between the two ditches, which is primarily driven by variations in nitrogen substrate availability and salinity levels. Hydrochemical and isotopic patterns suggest reduced nitrate removal potential under higher salinity, consistent with constraints on microbial nitrate reduction. These findings highlight the pivotal role of salinity in influencing nitrogen cycling and underscore the need for integrated management strategies that simultaneously address nutrient inputs and control salinity. Effective mitigation measures should prioritize seasonal fertilizer management and manure handling improvement, especially during winter irrigation periods when residual nutrients are mobilized. In addition, adaptive drainage strategies are needed to maintain nitrate removal efficiency under increasing salinity stress. This study provides isotope-based constraints to support science-based policymaking and adaptive water governance under salinization pressure.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01318-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Composition, release and controls of sediment phosphorus in estuaries near shrimp aquaculture areas","authors":"Bo Yang,&nbsp;Jie Xu,&nbsp;Bin Yang,&nbsp;Xinzhuang Wang,&nbsp;Zhiming Ning,&nbsp;Qin Li,&nbsp;Lei Xie,&nbsp;Dongliang Lu,&nbsp;Jiaodi Zhou,&nbsp;Haifang Huang,&nbsp;Zhenjun Kang","doi":"10.1007/s10533-026-01316-0","DOIUrl":"10.1007/s10533-026-01316-0","url":null,"abstract":"<div><p>Chemical sequential extraction and high-resolution diffusive gradients in thin-film (DGT) techniques were employed to study the mobilization behavior and underlying mechanisms of phosphorus (P) in estuarine sediments. This study focused on two contrasting subtropical estuaries in the Maowei Sea, northern Beibu Gulf: the Maoling River Estuary (MLRE, dominated by natural processes) and the Qin River Estuary (QRE, influenced by coastal shrimp pond effluent). Sediment samples were collected in December 2020 (winter) and July 2021 (summer). Overall, the contents of inorganic P, organic P (OP), and DGT-labile P in core sediments of the QRE were significantly higher than those in the MLRE. Notably, the average concentration of DGT-labile P in the QRE sediments (7.82 ± 4.94 µmol L⁻¹) was approximately 4.6 times greater than that in the MLRE sediments (1.69 ± 0.96 µmol L⁻¹). During the investigation, the QRE sediments consistently acted as a net source of P to the overlying water. In contrast, the MLRE sediments functioned as a source of P in winter but transitioned to a weak sink in summer. Sedimentary P release was driven by dissimilatory sulfate reduction and dissimilatory Fe (III) reduction, regulated mainly by the content and speciation of sedimentary P and sedimentary organic matter (SOM). In the MLRE, where sedimentary P and SOM contents were relatively low, P release was governed by the migration and transformation of multiple P forms, including exchangeable P (Ex-P), Fe-bound P (Fe–P), OP and authigenic apatite P (Ca–P). In comparison, due to shrimp pond effluent inputs, the QRE exhibited higher sedimentary P and SOM contents, and P release was primarily controlled by Fe–P mobilization. These results highlight that coastal shrimp aquaculture can supply substantial amounts of high-quality SOM and P to estuarine sediments, significantly altering sedimentary P cycling.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01316-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147559620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"No indications for a priming effect on soil organic carbon mineralization in a temperate river system","authors":"Man Zhao,&nbsp;Gerard Govers,&nbsp;Liesbet Jacobs,&nbsp;Steven Bouillon","doi":"10.1007/s10533-026-01317-z","DOIUrl":"10.1007/s10533-026-01317-z","url":null,"abstract":"<div><p>Globally, rivers are vital conduits transporting and processing terrestrial carbon, and are generally considered to act as source of carbon dioxide (CO₂) towards the atmosphere. A large amount of soil organic carbon (SOC) is transferred from the land surface to river systems each year, where it mixes and interacts with the autochthonous carbon pool (i.e., produced in-stream via photosynthesis). The latter has been suggested to be more labile and to potentially affect—positively or negatively—the mineralization rate of the more recalcitrant SOC, a mechanism referred to as the priming effect (PE). Here, we performed series of short-term (7 days) incubation experiments to investigate whether the addition of (¹³C-labelled) algal carbon (C) affected SOC mineralization in an aquatic environment, under different nutrient (nitrogen, N; phosphorus, P) conditions. Dissolved oxygen (DO) was continuously measured using a fiber-optic sensor. The concentrations and stable isotope composition of particulate organic carbon (POC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC) were measured to help to distinguish the sources of the mineralized C. Overall, algal C mineralized much more rapidly compared to SOC, but its presence had only weak and insignificant effects on SOC mineralization. Overall, under our experimental conditions, our results do not indicate that phytoplankton-derived organic carbon substantially affects SOC mineralization rates in aquatic systems.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01317-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of fire on dissolved carbon and greenhouse gas production rates and their temperature sensitivity in subalpine wetlands","authors":"Pranjal Dwivedi,&nbsp;Holly K. Roth,&nbsp;Sean Fettrow,&nbsp;Charles C. Rhoades,&nbsp;Thomas Borch,&nbsp;Céline Pallud","doi":"10.1007/s10533-026-01307-1","DOIUrl":"10.1007/s10533-026-01307-1","url":null,"abstract":"<div><p>Wetlands comprise only 5–8% of land surface but hold 20–30% of estimated soil carbon globally. However, wetlands are also significant sources of greenhouse gases such as methane (CH₄) and nitrous oxide (N₂O). Disturbances such as wildfires can alter the balance between carbon storage and greenhouse gas production in wetland systems; therefore, it is crucial to understand wetland response and recovery after wildfires. While wildfires are known to significantly impact ecosystem function through changes in soil properties, nutrient cycling, and hydrology, subalpine wetlands remain understudied, with the exception of organic matter-rich peatlands. Though temperature fluctuations regulate microbial processes, it is unclear how seasonal temperature patterns influence wildfire effects. We investigated these interactions in burned subalpine wetland soils in the Medicine Bow National Forest, Wyoming, USA, 1 year after the 2020 Mullen fire. We measured potential rates of carbon dioxide (CO₂), CH₄, N₂O, and DOC production using slurry experiments and flow-through experiments with soil collected from two depths (0–2 and 15–17 cm). Both experiments were conducted at local minimum, mean, and maximum July air temperatures (9, 18, and 27 °C). In situ porewater measurements showed that burned wetland areas had higher dissolved organic carbon (84–105 mg/L vs. 65 mg/L), sulfate (2.8–3.3 mg/L vs. 1.4 mg/L), and nitrate concentrations (1.3–1.9 mg/L vs. 0.5 mg/L) compared to unburned wetland areas, particularly in shallow depths (0–12 cm). Slurry experiments revealed approximately 1.3 times higher potential CO₂ production rates and fivefold higher N₂O production rates, but 2.9 times lower CH₄ production rates in burned compared to unburned wetland soils. Flow-through reactor experiments corroborated these findings, showing higher DOC (2–4 ×), Fe(II) (1.5–2 ×), and DIC (1.3–1.8 ×) potential production rates but lower CH₄ production rates (0.4–0.8 ×) in burned wetland soils. The suppression of methanogenesis and enhancement of Fe(III) reduction in these soils suggest altered redox conditions, potentially resulting from changes in organic matter composition, soil exposure, and hydrology following fire. Temperature sensitivity analysis revealed higher Q₁₀ values for Fe(II) production in burned wetland soils (1.60–2.90 vs. 1.57), indicating that fires enhance the temperature response of Fe(III) reduction pathways. These findings provide insights into post-fire biogeochemistry of sensitive subalpine wetland systems, with implications for the global carbon cycle and drinking water quality.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01307-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial survivability during repeated extreme dry-wet cycles determines CO2 emissions after rewetting of dried soils in humid temperate forests","authors":"Masataka Nakayama,&nbsp;Yuri Suzuki,&nbsp;Yukiko Abe,&nbsp;Takeshi Taniguchi,&nbsp;Mariko Atarashi-Andoh,&nbsp;Jun Koarashi,&nbsp;Hirohiko Nagano","doi":"10.1007/s10533-026-01310-6","DOIUrl":"10.1007/s10533-026-01310-6","url":null,"abstract":"<div><p>Shifts in precipitation patterns with less frequent rain events accompanied by global warming will trigger soil drying and rewetting, even in humid regions. Because rewetting of dried soil provokes pulse carbon dioxide (CO₂) emissions from soils, the chronic soil dry-wet cycle (DWC) in humid regions may provide positive feedback, contributing to global warming. In this study, we aimed to reveal the effects of repeated DWCs on soil CO₂ emissions, and the factors affecting emissions after rewetting in humid temperate forests. Experimentation included incubation of soils under five sequential DWCs. CO₂ emissions from the soils were measured throughout the incubation period, except during periods of drying. Soil extractable organic carbon (EOC) and microbial biomass carbon (MBC) were also measured at three hours and at five days after the first, third, and fifth rewetting. Rewetting of dried soil significantly increased CO₂ emissions during the first DWC, whereas the size of the pulse CO₂ emissions after rewetting decreased with an increasing number of subsequent cycles. Soil rewetting decreased soil MBC and increased EOC, and the EOC concentration decreased during each subsequent wet period. Based on path analysis, MBC three hours after rewetting was strongly and positively correlated with CO₂ emissions in the following five days in the dry-wet treatment (regression coefficient <i>β</i> = 0.710, <i>p</i> &lt; 0.001). The results suggest that microbial survivability to soil DWCs, rather than sudden labile carbon supply, determines the response of pulse CO₂ emissions from soils after rewetting during repeated soil DWCs in humid regions.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01310-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147441403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drought shifts dissolved organic matter sources from above- to belowground and stress-induced processes in Amazon white-sand forests","authors":"D. Frederik Lange,&nbsp;Carsten Simon,&nbsp;Robert E. Danczak,&nbsp;Simon A. Schroeter,&nbsp;Yago R. Santos,&nbsp;Jonismar S. da Silva,&nbsp;Sávio J. F. Ferreira,&nbsp;Shujiro Komiya,&nbsp;Cléo Q. Dias-Junior,&nbsp;Carlos A. Quesada,&nbsp;Thorsten Schäfer,&nbsp;James C. Stegen,&nbsp;Gerd Gleixner","doi":"10.1007/s10533-026-01308-0","DOIUrl":"10.1007/s10533-026-01308-0","url":null,"abstract":"<div><p>White-sand forests contribute significantly to dissolved organic matter (DOM) production in the central Amazon, forming blackwater rivers that dominate organic matter export from the Amazon basin to the ocean. Despite their importance in controlling DOM export, white-sand forests are understudied, and it remains unclear whether systematic changes in the formation of blackwater DOM occur and how seasonal variations and extremes like El Niño-associated droughts impact them. We collected soil porewater from two central Amazon white-sand forests for 2 years, spanning a wet La Niña year followed by an El Niño drought year. The molecular composition of DOM was analyzed using high-resolution mass spectrometry, and correlation network analysis was employed to identify ecologically meaningful DOM subsets. Using additional chemical characterization, database annotations, correlation with ¹⁴C-age of DOM and climatic variables, and ecological null modeling, we propose five distinct DOM sources: plant litter and throughfall, soil organic matter (SOM) decomposition, root exudation, and two drought response subsets of likely microbial and plant origin. During drought conditions, aboveground plant-derived compounds decreased, while SOM products, root exudates, and drought response compounds increased. These drought responses were qualitatively similar in both years but notably amplified in the drier El Niño year. Drought amplified deterministic control over DOM composition, indicating that DOM reflected directed biological responses and that future droughts are likely to generate similar shifts. Overall, drought substantially altered belowground carbon cycling by shifting DOM sources and inducing stress responses, effects expected to recur and potentially intensify under future climate scenarios.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"169 2","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-026-01308-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147340317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}