Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Exploring the Influence of Temperature on brGDGT Distributions in Chilean Lakes and Soils: A Comparative Analysis of In Situ Measured and Modeled Temperature Data","authors":"Molly D. O’Beirne,&nbsp;Jamie R. Vornlocher,&nbsp;Laura Lopera-Congote,&nbsp;Emeka E. Emordi,&nbsp;Godspower Ubit,&nbsp;Sergio Contreras,&nbsp;A. Araneda,&nbsp;E. Tejos,&nbsp;J. Moscoso,&nbsp;Josef P. Werne","doi":"10.1029/2024JG008506","DOIUrl":"https://doi.org/10.1029/2024JG008506","url":null,"abstract":"<p>Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane-spanning lipids that change in response to temperature variations. Their adaptability to temperature and widespread presence in sedimentary archives make brGDGTs a valuable tool for reconstructing past temperatures. However, the models used to relate brGDGT distributions to temperature vary widely (e.g., global vs. regional vs. site-specific, differing subsets of brGDGTs, and brGDGT-based indices), leading to inconsistencies in their application and inaccurate temperature predictions in some locations. Using previously published lacustrine and soil brGDGT distributions, we determined whether the type of temperature data used for model calibration (i.e., in situ vs. modeled air temperatures) influences the degree to which temperature relates to brGDGT distributions and therefore the fidelity with which brGDGT-based indices (i.e., MBT′_5ME) may predict temperature. Accounting for differences in the number of samples among lake surface sediment and soil sample data sets, we find that the impact of temperature on brGDGT distribution significantly varies depending on both the temperature and sample data set used, with the most pronounced effects observed in lake surface sediment samples. Similarly, the MBT′_5ME index shows varied correlations with temperature across different temperature and sample data sets. These findings suggest that other factors influence brGDGT distributions to a greater degree than temperature in some locations and that these effects are obscured when samples are combined into global data sets. This insight helps to explain why global brGDGT-based calibration models may not accurately predict temperatures at specific locations and underscores the need for targeted (e.g., cluster-based, regional, or site-specific) temperature calibration models.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008506","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144558136","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 Organic Carbon Stocks of German Salt Marshes: A Comparative Study Along Low- and High-Energy Coastlines","authors":"Ella L. Logemann,&nbsp;Clarisse Goesele,&nbsp;Kai Jensen,&nbsp;Peter Mueller","doi":"10.1029/2025JG008797","DOIUrl":"https://doi.org/10.1029/2025JG008797","url":null,"abstract":"<p>Blue carbon ecosystems, such as salt marshes, store comparably large amounts of organic carbon in their soils and function more effectively as carbon sinks than most other terrestrial ecosystems. Here we provide the first comprehensive study, quantifying soil organic carbon (SOC) stocks in grazed and non-grazed German salt marshes. In Germany, salt marshes are found along the low-energy, microtidal coastline of the Baltic Sea as organogenic ecosystems and along the high-energy, mesotidal coastlines of the North Sea as minerogenic ecosystems. One-meter soil cores were taken across 14 sites covering three distinct salt marsh types: Baltic Sea, North Sea mainland, and North Sea island. Baltic salt marshes held on average the greatest SOC stocks with 221 ± 56.3 (mean ± SE) Mg SOC/ha followed by North Sea mainland salt marshes with 187 ± 24.9 Mg SOC/ha and North Sea island salt marshes with 78 ± 9 Mg SOC/ha. Our findings indicate that livestock grazing resulted in a 1.5-fold increase in SOC density. The microtidal Baltic salt marshes store more SOC in their topsoil than mesotidal North Sea salt marshes, most likely due to the higher sediment deposition rates in North Sea mainland salt marshes causing SOC dilution through mineral inputs. We conclude greater aeration in high-marsh soils might counterbalance SOC accumulation under proceeding succession. Positive livestock grazing effects were relatively consistent within North Sea salt marshes, likely caused by trampling-induced changes in soil biogeochemistry. By contrast, grazing had variable effects on SOC in Baltic Sea salt marshes, with belowground plant productivity identified as the primary driver.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008797","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144558135","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":"Spatial and Temporal Shifts in Dissolved Organic Matter Character Across a Burned Stream Network","authors":"K. A. Wampler,&nbsp;K. D. Bladon,&nbsp;A. N. Myers-Pigg,&nbsp;J. A. Roebuck Jr.","doi":"10.1029/2024JG008687","DOIUrl":"https://doi.org/10.1029/2024JG008687","url":null,"abstract":"<p>Increasing wildfire activity can impact the global carbon cycle, aquatic ecosystem health, and drinking water treatment through alterations in aquatic dissolved organic matter (DOM) composition. However, uncertainty remains about the spatial and temporal variability in wildfire effects on DOM composition. We sought to improve understanding of how burn severity affects stream DOM and how weather, hydrology, and landscape factors contribute to variability in post-fire DOM responses across space and time. Following a large 2020 wildfire in Oregon, USA, we collected water samples to quantify dissolved organic carbon and DOM optical properties at 129 stream sites across the fire-affected stream network. Sampling was repeated across seasonal hydrologic conditions to capture variation in hydrologic pathways and organic matter sources. We developed a PARAFAC model using excitation-emission matrices (EEMs) and used spatial stream network (SSN) models to determine how DOM composition changed across the stream network with burn severity. The greatest shifts in DOM composition were observed during the dry and wetting seasons, with an increase in aromatic DOM at higher burn severities. In contrast, an increase in protein-like DOM was observed during the wet season at higher burn severities. Drainage area, 31-day and 1-day antecedent precipitation, and baseflow index impacted the relationship between DOM composition and burn severity, which could partially explain the variability in post-fire DOM responses. Our study contributes a mechanistic understanding of how wildfire impacts DOM sources and composition, which is critical to predicting wildfire effects on aquatic biogeochemical cycling and preserving ecosystem health and source water quality.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008687","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144520203","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":"Biome-Specific Responses of GOSIF Gross Primary Productivity to Wildfires in South America","authors":"Xingli Gu,&nbsp;Lei Zhou,&nbsp;Qin'ou Liang,&nbsp;Enxiang Xu,&nbsp;Yonggang Chi","doi":"10.1029/2025JG008986","DOIUrl":"https://doi.org/10.1029/2025JG008986","url":null,"abstract":"<p>The frequency and severity of wildfire events have increased significantly due to global warming, further disturbing the terrestrial ecosystem carbon cycle. Observations over the past several decades have shown that wildfires cause a dramatic decline in vegetation productivity. However, the biome-specific responses of gross primary productivity (GPP) to wildfires remain uncleared. Here, structural equation modeling was employed to analyze the mechanisms underlying wildfires on GPP using moderate resolution imaging spectroradiometer (MODIS) satellite data along with climatic and vegetation information in South America over a 20-year period from 2001 to 2020. We observed the biome-specific responses in GPP to wildfires among vegetation types. In forest ecosystems, increased burning severity led to substantial reductions in GPP directly, whereas in savanna ecosystems, wildfires indirectly regulated GPP by altering soil moisture. In grasslands, burned area rather than wildfire severity dominated the decrease in GPP. These findings emphasize the crucial role of vegetation types in exploring the effects of wildfires on the terrestrial ecosystem carbon cycle.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144503275","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":"Inferring Plant Acclimation and Improving Model Generalizability With Differentiable Physics-Informed Machine Learning of Photosynthesis","authors":"Doaa Aboelyazeed,&nbsp;Chonggang Xu,&nbsp;Lianhong Gu,&nbsp;Xiangzhong Luo,&nbsp;Jiangtao Liu,&nbsp;Kathryn Lawson,&nbsp;Chaopeng Shen","doi":"10.1029/2024JG008552","DOIUrl":"https://doi.org/10.1029/2024JG008552","url":null,"abstract":"<p>Net photosynthesis (<i>A</i>_<i>N</i>) is a key component of the global carbon cycle influencing climate feedback over decadal scales. Although plant acclimation to environmental changes can modify <i>A</i>_<i>N</i>, traditional vegetation models in Earth system models (ESMs) often rely on plant functional type (PFT)-specific parameterizations or simplified acclimation assumptions limiting generalizability across time, space, and PFTs. In this study, we developed a differentiable photosynthesis model to learn the environmental dependencies of<i>V</i>_{<i>c</i>,max25} (maximum carboxylation rate at 25°C, representing photosynthetic capacity), as this genre of hybrid physics-informed machine learning can seamlessly train neural networks and process-based equations together. Compared to PFT-specific parameterization of <i>V</i>_{<i>c</i>,max25}, learning the environment dependencies of key photosynthetic parameters improved model spatiotemporal generalizability. Applying environmental acclimation to <i>V</i>_{<i>c</i>,max25} led to substantial variations in global mean <i>A</i>_<i>N</i> indicating the need to address acclimation in ESMs. The model effectively captured multivariate observations (<i>V</i>_{<i>c</i>,max25}, <i>A</i>_<i>N</i>, and stomatal conductance (<i>g</i>_<i>s</i>)) simultaneously with multivariate constraints, improving generalization across space and PFTs. It also learned sensible acclimation relationships of <i>V</i>_{<i>c,</i>max25} to different environmental conditions. The model explained more than 54%, 57%, and 62% of the variance of <i>A</i>_<i>N</i>, <i>g</i>_<i>s</i>, and <i>V</i>_{<i>c</i>,max25}, respectively, presenting a first global-scale spatial test benchmark of <i>A</i>_<i>N</i> and <i>g</i>_<i>s</i>. These results highlight the potential for differentiable modeling to enhance process-based modules in ESMs and effectively leverage information from large, multivariate data sets.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008552","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144492814","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":"The Importance of Inland Water CO2, CH4, and N2O for Summertime Greenhouse Gas Exchange With the Atmosphere in Arctic Tundra Lowlands","authors":"Melanie Martyn Rosco,&nbsp;Joshua F. Dean,&nbsp;Alberto V. Borges,&nbsp;Ove H. Meisel,&nbsp;Richard van Logtestijn,&nbsp;Geert Hensgens,&nbsp;Sergei Karsanaev,&nbsp;Trofim Maximov,&nbsp;James T. Weedon,&nbsp;Rien Aerts,&nbsp;Jorien E. Vonk,&nbsp;A. Johannes Dolman","doi":"10.1029/2024JG008334","DOIUrl":"https://doi.org/10.1029/2024JG008334","url":null,"abstract":"<p>Inland waters in Arctic landscapes act as conduits of terrestrial organic material, transporting and processing organic material into the greenhouse gases (GHGs) carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), and subsequently exchanging these gases with the atmosphere. To assess the role of inland water emissions in the Arctic GHG budget, it is necessary to quantify their emissions in relation to the terrestrial sink capacity. We present measurements of dissolved CO₂, CH₄, and N₂O from lake, pond, and low-order fluvial systems across two summers (2016–2017) in the Arctic Siberian Indigirka River tundra lowlands. During May–July 2017, the region experienced large-scale flooding, of which we captured the tail end. Using remote sensing images to upscale inland water emissions to an area of approximately 18 km², we calculated combined carbon (C) emissions, CO₂-C, and diffusive CH₄-C under nonflood and flooded scenarios. These ranged from 7.03 ± 1.30 Mg C d⁻¹ (nonflood; mean ± SD) to 9.63 ± 1.24 Mg C d⁻¹ (flooded). Integrating these values into the total C landscape exchange offset the terrestrial C sink by ∼9–∼13%. When N₂O emissions were calculated as CO₂ equivalents, these emissions were negligible relative to CO₂ and CH₄. Our study shows that in the northeast Siberian Arctic tundra, summertime CO₂ and CH₄ emissions from inland waters are a potentially important component of landscape C exchange with the atmosphere, offsetting the terrestrial sink capacity, and this may be an important consideration for constraining future Arctic responses to climate warming.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008334","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144367517","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 Total Suspended Solids on Photomineralization of Dissolved Organic Matter in the Peace-Athabasca Delta, Canada","authors":"W. Dolan,&nbsp;T. M. Pavelsky,&nbsp;J. Davis,&nbsp;N. LaFramboise,&nbsp;C. A. Polik,&nbsp;R. M. Cory","doi":"10.1029/2024JG008620","DOIUrl":"https://doi.org/10.1029/2024JG008620","url":null,"abstract":"&lt;p&gt;Northern deltas receive chromophoric dissolved organic matter (CDOM) from their watersheds, which can be oxidized to carbon dioxide upon absorption of sunlight (i.e., photomineralized). These deltas also receive total suspended solids (TSS), which may shade sunlight absorption by CDOM, thus limiting photomineralization. To quantify this interaction for the first time, we measured photomineralization rates at 11 sites in the Peace-Athabasca Delta (PAD), Canada. We sampled waters during a July 2022 field campaign for TSS concentration, CDOM concentration (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;CDOM&lt;/mtext&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${a}_{text{CDOM},lambda }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;), total downwelling sunlight attenuation coefficients (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;K&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;d&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mtext&gt;tot&lt;/mtext&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${K}_{d,text{tot},lambda }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;), and light attenuation coefficients due to CDOM (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;K&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;d&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mtext&gt;CDOM&lt;/mtext&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${K}_{d,text{CDOM},lambda }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;). TSS ranged from &lt;1 to 112 mg/L with an average of 19 ± 34 mg/L (mean ± one standard deviation), an order of magnitude lower than TSS reported in rivers entering the PAD earlier in the open water season. &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;CDOM&lt;/mtext&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${a}_{text{CDOM},lambda }$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; at 305 nm (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;CDOM&lt;/mtext&gt;\u0000 ","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144367390","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":"Methane Dynamics in Braided River Sections of the Free-Flowing Vjosa River, Albania","authors":"Barbara Jechsmayr,&nbsp;Edurne Estévez Cano,&nbsp;Gabriel Singer","doi":"10.1029/2025JG008856","DOIUrl":"https://doi.org/10.1029/2025JG008856","url":null,"abstract":"<p>Greenhouse gas emissions give rivers an important role in the global carbon cycle. Since methane (CH₄) has a higher warming potential than carbon dioxide, it is essential to understand how, where, and when CH₄ is produced and emitted. We investigated spatiotemporal variations of CH₄ concentration and outgassing fluxes in free-flowing braided river sections of the Vjosa River and their relation to seasonal discharge shifts, which drive fine sediment deposition, hyporheic isolation, and surface drying. Localized sampling in the hyporheic zone allowed the investigation of potential dependencies of CH₄ concentration on the availability of oxygen, alternative electron acceptors, and organic matter (OM). Compared to other river systems, we found very low CH₄ concentrations (from 1.7 to 1,167.3 nmol L⁻¹) and emission fluxes (from −0.03 to 0.21 mmol m⁻² d⁻¹). Hyporheic CH₄ concentrations diverged between campaigns, depths, and habitats differing in surface water availability. Surface drying led to decreased or even negative CH₄ fluxes. Dissolved OM best explained CH₄ occurrence, yet large uncertainties remained, and patterns along depth, across habitats and campaigns were not always as expected from simplified redox gradients. Our results indicate the importance of small-scale habitat heterogeneity in the hyporheic zone driven by sediment composition and fine sediment deposition. This likely affects the availability of oxygen, other electron acceptors, and OM, that define the habitat suitability for CH₄ production. In spatiotemporally dynamic braided rivers, exchange processes between hyporheic zone, surface water, and atmosphere must be considered simultaneously in order to mechanistically decipher final greenhouse gas emissions to the atmosphere.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008856","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331885","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":"Diffuse Fertilization or Lack Thereof: A Multisite Synthesis of Water and Carbon Fluxes","authors":"E. Schwartz,&nbsp;G. Keppel-Aleks,&nbsp;A. L. Steiner","doi":"10.1029/2025JG008757","DOIUrl":"https://doi.org/10.1029/2025JG008757","url":null,"abstract":"<p>Aerosols or clouds in the atmosphere scatter incoming shortwave radiation and increase diffuse radiation. At the Earth's surface, diffuse radiation can penetrate deeper into vertically complex vegetation. Leaf photosynthesis and transpiration can be coupled through stomatal conductance and are thought to increase together at low diffuse fractions (K_d) until an optimal point, after which diffuse enhancement decreases. Because ground-based measurements of diffuse radiation are sparse, prior studies have used atmospheric proxies to determine K_d. With eddy covariance observations from the National Ecological Observatory Network (NEON) and evapotranspiration (ET) retrievals from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS), we quantify the relationship between K_d, ET, and net ecosystem exchange (NEE) across 5 years, 32 sites, and 6 plant functional types (PFTs). At most NEON sites (26 out of 32), ET decreases with increasing K_d without an optimal point or diffuse enhancement. Moisture-dominant NEON sites experience less enhancement of ET under diffuse conditions compared to radiation-dominant sites. Cloud contamination limits the availability of ECOSTRESS ET data and prevents quantification of the K_d-ET relationship on broader spatial scales. Although the optimal points in the K_d-NEE relationship are variable across NEON sites, a majority show diffuse enhancement of NEE (19 out of 32), predominantly in forest and shrub/scrub PFTs. Most NEON sites also show an enhancement in the net carbon-water ratio (NEE/ET; 25 out of 32). We partially attribute differences in NEON results from prior studies to differences between ground-based observations and modeled products of diffuse radiation.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008757","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331884","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":"The Thermal Reactivity and Molecular Diversity of Particulate Organic Carbon in the Amazon River Mainstem","authors":"Sarah Z. Rosengard,&nbsp;Jose Mauro S. Moura,&nbsp;Robert G. M. Spencer,&nbsp;Carl Johnson,&nbsp;Ann McNichol,&nbsp;Brenna Boehman,&nbsp;Valier Galy","doi":"10.1029/2024JG008660","DOIUrl":"https://doi.org/10.1029/2024JG008660","url":null,"abstract":"<p>The Amazon River mobilizes one of the largest fluxes of particulate organic carbon (POC) from land to coastal ocean sediments, playing an important role in the long-term sequestration of biospheric organic carbon in the ocean. Ramped oxidation (RPO) analyses of suspended sediments collected from the Amazon River mainstem, Solimões River, Madeira River, and Tapajós River presented an opportunity to parse riverine POC by thermal reactivity, extract the activation energy distributions of specific biomolecular pools in these samples, and characterize the molecular diversity of POC across the floodplain. The thermal reactivity data imply that POC from the Amazon River basin spans a wide but relatively homogenous activation energy range across samples, suggesting that the degradation history of the organic carbon comprising riverine suspended particles is relatively constant across depths within the mainstem and different tributary locations. Coupling activation energy distributions to stable and radiocarbon isotopic analyses shows that ca. 85% of mainstem POC derives from a range of partially degraded terrestrial sources, likely organic matter from mineral soil horizons, and that a similar range of soil sources influences the biomolecular diversity in tributary samples. In agreement with earlier assessments, ca. 10% of the riverine POC flux is fresh vegetation and up to 5% of it is petrogenic organic matter. Expanded RPO analyses of samples across the Amazon river-to-ocean continuum would provide an opportunity to track the fate of these different organic matter pools downstream that is uniquely different from, but complementary to, past compound-specific and bulk analyses of riverine POC.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 6","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008660","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315290","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}