Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Limited Headwater CO2 Emissions Relative to Downstream C Fluxes: Insights From a Tracer-Enabled Reactive Transport Model","authors":"William J. Larsen,&nbsp;Mark A. Torres,&nbsp;Evan J. Ramos,&nbsp;Sebastian Muñoz,&nbsp;Yi Hou,&nbsp;Tao Sun,&nbsp;Daniel E. Ibarra,&nbsp;Miriam Gammerman,&nbsp;Jonah Bernstein-Schalet,&nbsp;Kly D. Suquino,&nbsp;Preston Cosslett Kemeny","doi":"10.1029/2024JG008592","DOIUrl":"https://doi.org/10.1029/2024JG008592","url":null,"abstract":"<p>Some fraction of the total carbon (C) transported by rivers can enter the atmosphere as CO₂ via gas evasion as water transits from source to sink. Quantifying this evaded portion can be challenging due to the need to constrain chemical and physical parameters along an entire stream network using a limited number of point measurements. To address this challenge, we employed an tracer-enabled (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>δ</mi>\u0000 <mn>13</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${delta }^{13}$</annotation>\u0000 </semantics></math>C and ²²²Rn) reactive transport model to simulate CO₂ evasion along an entire stream network in the Little Deschutes River in the Eastern Cascades, Oregon, USA. We sampled the river network in distinct lanscape regimes and measured potential C sources including soil gas, groundwater springs, and wetland waters. Using these data, we first evaluated the reactive transport model using empirical gas transfer scaling relationships and measured groundwater chemistry. We then employed a Monte-Carlo optimization using riverine observations of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>pCO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{pCO}}_{2}$</annotation>\u0000 </semantics></math>, <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>δ</mi>\u0000 <mn>13</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${delta }^{13}$</annotation>\u0000 </semantics></math>C and ²²²Rn, which yielded more accurate estimates of CO₂ evasion by improving estimates of spatially-averaged groundwater pCO₂ and generating a site-specific gas transfer scaling relationship. Our results demonstrate that riparian wetlands contribute to 19% of the computed CO₂ evasion flux. Lastly, we find that CO₂ evasion only accounts for 12% of the total riverine C flux, with the remaining fraction contributed by advective flux of DIC (50%) and DOC (38%) through the watershed outlet.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145224254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Challenges in Detecting High-Arctic Shrub Expansion From Optical Remote Sensing: Implications for Albedo and Climate Forcing","authors":"Florent Domine,&nbsp;Maria Belke-Brea,&nbsp;Arthur Bayle,&nbsp;Ghislain Picard,&nbsp;Esther Lévesque,&nbsp;Christophe Kinnard","doi":"10.1029/2024JG008593","DOIUrl":"https://doi.org/10.1029/2024JG008593","url":null,"abstract":"<p>Climate change-induced shrub expansion in the Arctic feeds back on climate by reducing surface albedo. Vegetation dynamics are typically monitored by tracking the evolution of vegetation indices, such as normalized difference vegetation index (NDVI), derived from satellite imagery in processes known as greening or browning. However, detecting changes in vegetation type requires sufficient spectral variation. Here, we measured the spectral albedos (346–2,400 nm) of assemblages of prostrate vegetation and of the only erect shrub species <i>Salix richardsonii</i> on Bylot Island in the eastern Canadian high-Arctic to assess spectral differences among common vegetation types. The broadband albedo of <i>S. richardsonii</i> (0.132 ± 0.009) was lower than that of prostrate vegetation (0.166 ± 0.008). However, NDVI values showed no significant difference (0.598 ± 0.074 vs. 0.561 ± 0.021). Satellite remote sensing using NDVI with spatial resolutions from 0.5 to 30 m using Pléiades, Sentinel-2 and Landsat-8 failed to detect differences in reflectance and NDVI between prostrate vegetation and <i>S. richardsonii</i>. These findings suggest that long-term NDVI trend analysis may be insufficient to capture the structural vegetation shift in these climate-sensitive areas. Failure to detect erect shrub expansion in the high-Arctic may therefore omit a climate change effect which produces a surface albedo decrease of 0.03 and a local summer solar forcing of 5.8 W m⁻².</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008593","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146717","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":"Bald Cypress (Taxodium distichum) Knees Are Methane Sources Controlled by Geomorphology, Climate, and Hydrologic Extremes","authors":"Skylar K. Ross,&nbsp;Niklas Klauss,&nbsp;Marissa Miles,&nbsp;Kabi Raj Khatiwada,&nbsp;Bassil El Masri,&nbsp;Benjamin R. K. Runkle,&nbsp;Gary E. Stinchcomb,&nbsp;Jessica B. Moon","doi":"10.1029/2025JG008996","DOIUrl":"https://doi.org/10.1029/2025JG008996","url":null,"abstract":"<p>While woody root structures, such as bald cypress (<i>Taxodium distichum</i>) “knees,” can act as conduits of methane (CH₄), little has been done to explain variation from this flux pathway. We captured spatial (i.e., across knee surface, within sites, between sites) and temporal dynamics of CH₄ from knees, and built empirical models to predict the contribution of knees to net CH₄ fluxes. Knee and soil CH₄ fluxes were measured across seasons within the lower Mississippi Alluvial Valley in a main channel (semi-permanently flooded), side channel (seasonally flooded), and a reservoir edge (artificially flooded). Knees were a net source of CH₄ across all seasons, even during periods of soil CH₄ uptake. During periods of high knee CH₄ efflux, fluxes varied across the knee surface, decreasing with height from the ground. Knee CH₄ fluxes at the main and side channels decreased during a severe drought and increased ∼ ten-fold in summer and two-fold in winter following flooding events. At the reservoir edge, knee fluxes differed between the controlled draw up and draw down at the same water level, likely due to differences in temperature and oxygen availability. Knee CH₄ fluxes were positively correlated with water level (measured from subsurface wells, above ∼−70 cm in the soil profile) and subsurface temperature, but the strength of the relationships differed across geomorphic positions. Cypress knees appear to be an important contributor to wetland CH₄ efflux and accounting for the density of knees is needed to upscale their fluxes and better understand their ecosystem contribution.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial Resuscitation and Growth Rates in Deep Permafrost: Lipid Stable Isotope Probing Results From the Permafrost Research Tunnel in Fox, Alaska","authors":"T. A. Caro,&nbsp;J. M. McFarlin,&nbsp;A. E. Maloney,&nbsp;S. D. Jech,&nbsp;A. J. Barker,&nbsp;T. A. Douglas,&nbsp;R. A. Barbato,&nbsp;S. H. Kopf","doi":"10.1029/2025JG008759","DOIUrl":"10.1029/2025JG008759","url":null,"abstract":"<p>Permafrost is at increasing risk of thaw as cold regions in the Northern Hemisphere continue to warm. The lability of organic carbon in permafrost post-taw largely depends on the rate at which microorganisms resuscitate and proliferate after many years in freezing, dark, anaerobic conditions. Moreover, the bulk of the Earth's permafrost exists at deep subsurface horizons, far below the active layer, that have been isolated for hundreds, thousands, or millions of years. However, the resuscitation and growth rates of microorganisms in deep permafrost remain unknown. To quantify these rates, we conducted lipid stable isotope probing (lipid-SIP) on permafrost cores of late-pleistocene age from four locations within the Permafrost Research Tunnel near Fairbanks, Alaska. We compare rates of microbial growth, marker gene sequences, and greenhouse gas (CO₂, CH₄) emissions across cores held anaerobically at ambient (−4°C) and elevated temperatures (4°C, 12°C). In deep, ancient permafrost, microbial growth is exceedingly slow, often undetectable, within the first month following thaw, indicating a notable lag period, where only 0.001%–0.01% of cells turn over per day. This suggests a “slow reawakening” that could provide some buffer between anomalous warmth and C degradation if permafrost refreezes seasonally but remains anaerobic. However, within 6 months, microbial communities undergo dramatic restructuring and become distinct from both the ancient and overlying surface communities. These results have critical implications for predictions of microbial biogeochemical contributions in a warming arctic, especially as thaw proceeds into deeper and more ancient permafrost horizons.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145129283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phylogeny, Functional Types, and Environment Drive Different Leaf C:N:P Stoichiometric Patterns of Alpine Shrubs in Xizang, China","authors":"Xinru Zhang,&nbsp;Guangshuai Cui,&nbsp;Zhenjun Zuo,&nbsp;Wei Shen,&nbsp;Xinsheng Liu,&nbsp;Zhong Wang,&nbsp;Lin Zhang","doi":"10.1029/2025JG009102","DOIUrl":"10.1029/2025JG009102","url":null,"abstract":"<p>Concentrations of leaf carbon (C), nitrogen (N), phosphorus (P), and their stoichiometric ratios are essential for understanding plant nutrient uptake strategies and ecosystem functions such as primary productivity and nutrient cycling. Climate and soil factors and plant genetics all pose important impacts on the variation of leaf C:N:P stoichiometry. However, which factor determines the geographic variation of leaf C:N:P stoichiometry in alpine shrubs remains unclear. In this study, we analyzed 218 samples composed of 24 shrub species from 80 shrubland sites in Xizang to explore the geographic variations of leaf C:N:P stoichiometry in response to changes in climate, soil properties, phylogeny, and shrub functional types The stoichiometric ratios of leaf C:N:P exhibit significant geographical variation particularly along longitudinal and altitudinal gradients. However, the primary drivers of these variations differed among elements. Phylogeny accounted for the majority of the variation in leaf N content (62.02%), whereas leaf C content and the C:N ratio were primarily influenced by shrub functional types (63.96% and 57.78%, respectively). In contrast, leaf P content and the C:P ratio were predominantly regulated by environmental factors (64% and 60%, respectively). Among the environmental variables, soil pH emerged as the primary driver of leaf C:N:P stoichiometric variation, exerting a greater impact than climatic factors and soil nutrient content. This study highlights the critical roles of phylogeny, shrub functional types, and environmental factors in shaping the geographical patterns of elemental composition and stoichiometric traits, contributing to a deeper understanding of plant adaptive strategies and trait evolution under diverse environmental conditions.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145111120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking Microbial Communities and Molecular Transformations of Dissolved Organic Matter to the Fate of Nitrogen in Karst Aquifers","authors":"Ruixuan Gai,&nbsp;Jing Bao,&nbsp;Wei Xiu,&nbsp;Fang Guo,&nbsp;Qiang Li,&nbsp;Qiang Zhang","doi":"10.1029/2025JG008961","DOIUrl":"10.1029/2025JG008961","url":null,"abstract":"<p>Understanding the biogeochemical processes governing carbon and nitrogen cycling in karst aquifers is critical. However, the specific pathways through which dissolved organic matter (DOM) influences nitrogen cycling under varying degrees of aquifer confinement remain poorly understood. This study addresses this knowledge gap by analyzing geochemical characteristics, DOM compositions, and microbial communities in three types of aquifer media, karst fissure media (KFM), karst conduit media (KCM), and karst window groundwater (KWG), at the Zengpiyan karst site in southern China, using carbon isotopes, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and amplicon sequencing. Results indicated that longer hydraulic residence time in KFM was associated with enhanced denitrification, whereas shorter residence in KCM/KWG favored nitrification. DOM was dominated by terrestrial lignin-like molecular formulas (55.92%), but residence time shaped molecular composition and biodegradation: KFM showed lower nominal oxidation state of carbon (NOSC_wa, −0.60 ± 0.37) yet a higher end-member index (I_bio, 0.37 ± 0.05), reflecting microbial preferential consumption of labile, high NOSC fractions, leaving recalcitrant lignin-like molecular formulas. Core taxa <i>Comamonas</i> and an unclassified Comamonadaceae genus were associated with lignin-like molecular formulas degradation and denitrification, while <i>Nitrospira</i> contributed to nitrification via lignin-like molecular formula-derived intermediates. Together they formed a “lignin-like molecular formulas degradation, ammonification, nitrification” cascade, with 53.82% of DOM degradation reactions involving nitrogen loss through CHON transformations. Overall, extended residence time in karst aquifers enables sequential degradation of recalcitrant lignin-like molecular formulas under low NOSC conditions via synergistic interactions between microbes, refining conceptual models of C-N coupling in hydrologically heterogeneous karst systems.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling Attenuation of Nitrogen Loads Delivered to Coastal Bays From Ecological Restoration of Cultivated Wetlands","authors":"Adrian R. H. Wiegman,&nbsp;Casey D. Kennedy,&nbsp;Christopher Neill,&nbsp;Rachel W. Jakuba,&nbsp;Molly K. Welsh,&nbsp;David Millar,&nbsp;Anthony Buda","doi":"10.1029/2025JG008742","DOIUrl":"10.1029/2025JG008742","url":null,"abstract":"<p>Nitrogen (N) pollution is a major threat to coastal ecosystems, worsened by the loss or degradation of natural wetlands, which historically acted as N sinks. In the glacial outwash plain of Southeastern Massachusetts, N pollution primarily from human waste and turf fertilizer has caused coastal eutrophication. Social and economic factors have driven ecological restoration efforts on wetlands previously modified for cranberry farming. These restoration projects offer a chance to enhance ecosystem N attenuation, but the extent and spatial distribution of watershed N loads through these farms remain poorly understood. To address this gap, we adapted a U.S. Geological Survey (USGS) groundwater model to identify wetland contributing areas and model potential N load reduction from the retirement and restoration of 984 cranberry farms. Using modeled contributing areas and data and assumptions about attenuation rates, we estimated N load reductions for farm retirement and restoration scenarios in 24 embayments. For restoration of all farms, median N load reductions were less than 3% in nine embayments, 3%–10% in seven embayments, and 10%–30% in eight embayments. Attenuation was limited by the contributing area intercepted by cranberry farms, ranging from 1% to 75% of watershed areas. Our model serves as a screening tool to identify farms with high potential to reduce watershed N loads, but more field monitoring is needed to refine N attenuation estimates in former cranberry wetlands. This work highlights the critical linkage between wetlands, development patterns, and ecosystem health, emphasizing the need for sustainable resource management approaches.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008742","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101654","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":"Tracking Long-Term Trends in Sockeye Salmon (Oncorhynchus nerka) Population Dynamics Using Sterol and Stanol Biomarkers in Lake Sediments","authors":"D. Dagodzo,&nbsp;D. C. Eickmeyer,&nbsp;L. E. Kimpe,&nbsp;D. T. Selbie,&nbsp;J. P. Smol,&nbsp;J. M. Blais","doi":"10.1029/2025JG008903","DOIUrl":"10.1029/2025JG008903","url":null,"abstract":"<p>We analyzed biomarkers, including sterols, stanols, and δ¹⁵N, in sediment cores from lakes with well-documented sockeye salmon return histories. Our goal was to improve estimates of past changes in salmon escapement, that is, the population that return to their freshwater nursery lakes, inferred using sediment biogeochemical markers. Cholesterol, the predominant sterol in adult sockeye salmon muscle tissue, displayed a strong positive relationship with escapement (<i>R</i>² = 0.8, <i>p</i> = 0.001, and <i>F</i>_1,8 = 28.3). Sediment concentrations of the plant-derived sitosterol and algal-derived fucosterol, absent in salmon muscle tissue also related positively with salmon escapement, suggesting that salmon-derived nutrients from decomposing fish promote the production of these lipids by primary producers in the lakes. We developed a novel salmon sterol index (SSI_a) from values in surface sediments of the nine Alaskan lakes [(cholesterol + coprostanone + epicoprostanol + desmosterol)/(cholesterol + coprostanone + epicoprostanol + desmosterol + fucosterol + sitosterol + stigmastanol)] that was strongly related with salmon return density (pseudo <i>R</i>² = 0.86 and RMSE = 0.071). This index also tracked historical sockeye escapement patterns and δ¹⁵N values in ²¹⁰Pb-dated lake sediment cores from Frazer, Karluk, Red, and Kinaskan lakes that span more than a century of salmon population history, suggesting that the index has potential as a proxy for tracking historical salmon populations, particularly when used in combination with independent biomarkers of salmon-derived nutrient inputs. SSI_a and the other salmon sterol indices we developed show promise for improving and extending long-term sockeye salmon population estimates using lake sediment records, which will help inform salmon conservation and management efforts.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008903","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101879","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":"A Neural Network-Based Estimate of the Seasonal to Inter-Annual Variability of the Lake Superior Carbon Cycle","authors":"Daniel E. Sandborn,&nbsp;Elizabeth C. Minor,&nbsp;Jay A. Austin","doi":"10.1029/2024JG008610","DOIUrl":"10.1029/2024JG008610","url":null,"abstract":"&lt;p&gt;Lake Superior emits and absorbs CO&lt;sub&gt;2&lt;/sub&gt; with significant seasonal and interannual variability, which complicates efforts to constrain its carbon cycle. While it regains atmospheric CO&lt;sub&gt;2&lt;/sub&gt; equilibrium on sub-annual scales, resulting in a sustained rise in observed &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; over the last two decades, significant gaps in observation have prevented examination of variability in its carbon cycle on smaller temporal or spatial scales. We developed a reconstruction of daily mean Lake Superior surface water &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; lake-air flux with a spatial resolution of 0.02° &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;×&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${times} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 0.02° in order to infer trends and drivers of carbon cycling in Lake Superior on seasonal to interannual scales. A feed-forward neural network was trained and tested on underway &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; measurements spanning ice-free seasons of 2019–2023, yielding a spatially-comprehensive product describing inorganic carbon dynamics over a five-year period. Lake Superior alternated between net annual CO&lt;sub&gt;2&lt;/sub&gt; influx and efflux, with values ranging from &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.30&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.06&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;Tg&lt;/mtext&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mtext&gt;yr&lt;/mtext&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${-}0.30pm 0.06,{text{Tg},mathrm{C},text{yr}}^{-1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (influx) to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;0.06&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.06&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;Tg&lt;/mtext&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mi&gt;C&lt;/mi&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mtext&gt;yr&lt;/mtext&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $0.06pm 0.06,{text{Tg},mathrm{C},text{yr}}^{-1}$&lt;/an","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008610","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101865","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":"Year-Round δ13C-CH4 Reveals Seasonal Transition in Methane-Related Processes in a Boreal Mire","authors":"Xuefei Li,&nbsp;Janne Rinne,&nbsp;Eeva-Stiina Tuittila,&nbsp;Timo Vesala","doi":"10.1029/2025JG008922","DOIUrl":"10.1029/2025JG008922","url":null,"abstract":"<p>While boreal mires are known to be a significant natural source of methane (CH₄), the seasonality of the related processes and their controls are still poorly understood. Here we aim to characterize CH₄ production, oxidation and transport, and their drivers in a boreal mire using year-round continuous measurements of stable carbon isotope composition (δ¹³C-CH₄) in dissolved and emitted CH₄. We found reversed vertical profiles of δ¹³C-CH₄ in the summer (higher values at surface) and in the winter (higher values at bottom). The ¹³C enriched emitted CH₄, as compared to pore water CH₄, indicated methane oxidation at the peat-snow interface by sphagnum mosses in the winter. The observed hysteretic δ¹³C-CH₄ - pCH₄ relation indicated the importance of substrate availability for methane production in addition to soil temperature, and their time-lagged seasonal cycles. Our data also demonstrated the dominance of plant-mediated transport in the summer, the dominance of diffusion through peat and moss matrix (with associated microbial methane oxidation) in the winter and a transition in the spring and autumn. In general, the measured δ¹³C values of emitted CH₄ at this and other northern mires are considerably lower than the values used in atmospheric inversion models. Our comprehensive data set provided invaluable insight into wetland δ¹³C-CH₄, the dynamic interplay of multiple processes related to CH₄ emission in boreal mires, especially in the rarely studied winter, spring, and autumn, the incorporation of which into Earth System Models will allow more accurate prediction of wetland responses to ongoing climate change.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008922","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101876","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}