Global Biogeochemical Cycles最新文献

{"title":"A Carbon Source in a Carbon Sink: Carbon Dioxide and Methane Dynamics in Open-Water Peatland Pools","authors":"Pierre Taillardat,&nbsp;Annika Linkhorst,&nbsp;Charles P. Deblois,&nbsp;Antonin Prijac,&nbsp;Laure Gandois,&nbsp;Alain Tremblay,&nbsp;Michelle Garneau","doi":"10.1029/2023GB007909","DOIUrl":"https://doi.org/10.1029/2023GB007909","url":null,"abstract":"<p>Peatlands store organic carbon available for decomposition and transfer to neighboring water bodies, which can ultimately generate carbon dioxide (CO₂) and methane (CH₄) emissions. The objective of this study was to clarify the biogeochemical functioning of open-water peatland pools and their influence on carbon budgets at the ecosystem and global scale. Continuously operated automated equipment and monthly manual measurements were used to describe the CO₂ and CH₄ dynamics in boreal ombrotrophic peatland pools and porewater (Québec, Canada) over the growing seasons 2019 and 2020. The peat porewater stable carbon isotope ratios (δ¹³C) for both CO₂ (median δ¹³C-CO₂: −3.8‰) and CH₄ (median δ¹³C-CH₄: −64.30‰) suggested that hydrogenotrophic methanogenesis was the predominant degradation pathway in peat. Open-water pools were supersaturated in CO₂ and CH₄ and received most of these dissolved carbon greenhouse gases (C-GHG) from peat porewater input. Throughout the growing season, higher CO₂ concentrations and fluxes in pools were measured when the water table was low—suggesting a steady release of CO₂ from deep peat porewater. Higher CH₄ ebullition and diffusion occurred in August when bottom water and peat temperatures were the highest. While this study demonstrates that peatland pools are chimneys of CO₂ and CH₄ stored in peat, it also shows that the C-GHG concentrations and flux rates in peat pools are comparable to other aquatic systems of the same size. Although peatlands are often considered uniform entities, our study highlights their biogeochemical heterogeneity, which, if considered, substantially influences their net carbon balance with the atmosphere.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007909","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140556228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unraveling Environmental Forces Shaping Surface Sediment Geochemical “Isodrapes” in the East Asian Marginal Seas","authors":"Sarah Paradis,&nbsp;Markus Diesing,&nbsp;Hannah Gies,&nbsp;Negar Haghipour,&nbsp;Lena Narman,&nbsp;Clayton Magill,&nbsp;Thomas Wagner,&nbsp;Valier V. Galy,&nbsp;Pengfei Hou,&nbsp;Meixun Zhao,&nbsp;Jung-Hyun Kim,&nbsp;Kyung-Hoon Shin,&nbsp;Baozhi Lin,&nbsp;Zhifei Liu,&nbsp;Martin G. Wiesner,&nbsp;Karl Stattegger,&nbsp;Jianfang Chen,&nbsp;Jingjing Zhang,&nbsp;Timothy I. Eglinton","doi":"10.1029/2023GB007839","DOIUrl":"https://doi.org/10.1029/2023GB007839","url":null,"abstract":"<p>As major sites of carbon burial and remineralization, continental margins are key components of the global carbon cycle. However, heterogeneous sources of organic matter (OM) and depositional environments lead to complex spatial patterns in sedimentary organic carbon (OC) content and composition. To better constrain the processes that control OM cycling, we focus on the East Asian marginal seas as a model system, where we compiled extensive data on the OC content, bulk isotopic composition (δ¹³C and Δ¹⁴C), total nitrogen, and mineral surface area of surficial sediments from previous studies and new measurements. We developed a spatial machine learning modeling framework to predict the spatial distribution of these parameters and identify regions where sediments with similar geochemical signatures drape the seafloor (i.e., <i>“isodrapes”</i>). We demonstrate that both provenance (44%–77%) and hydrodynamic processes (22%–53%) govern the fate of OM in this margin. Hydrodynamic processes can either promote the degradation of OM in mobile mud-belts or preserve it in stable mud-deposits. The distinct isotopic composition of OC sources from marine productivity and individual rivers regulates the age and reactivity of OM deposited on the sea-floor. The East Asian marginal seas can be separated into three main <i>isodrapes</i>: hydrodynamically energetic shelves with coarser-grained sediment depleted in OC, OM-enriched mud deposits, and a deep basin with fine-grained sediments and aged OC affected by long oxygen exposure times and petrogenic input from rivers. This study confirms that both hydrodynamic processes and provenance should be accounted for to understand the fate of OC in continental margins.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007839","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The African Regional Greenhouse Gases Budget (2010–2019)","authors":"Yolandi Ernst,&nbsp;Sally Archibald,&nbsp;Heiko Balzter,&nbsp;Frederic Chevallier,&nbsp;Philippe Ciais,&nbsp;Carlos Gonzalez Fischer,&nbsp;Benjamin Gaubert,&nbsp;Thomas Higginbottom,&nbsp;Steven Higgins,&nbsp;Shakirudeen Lawal,&nbsp;Fabrice Lacroix,&nbsp;Ronny Lauerwald,&nbsp;Mauro Lourenco,&nbsp;Carola Martens,&nbsp;Anteneh G. Mengistu,&nbsp;Lutz Merbold,&nbsp;Edward Mitchard,&nbsp;Mthokozisi Moyo,&nbsp;Hannah Nguyen,&nbsp;Michael O’Sullivan,&nbsp;Pedro Rodríguez-Veiga,&nbsp;Thais Rosan,&nbsp;Judith Rosentreter,&nbsp;Casey Ryan,&nbsp;Simon Scheiter,&nbsp;Stephen Sitch,&nbsp;Nicola Stevens,&nbsp;Torbern Tagesson,&nbsp;Hanqin Tian,&nbsp;Mengjia Wang,&nbsp;Joel S. Woon,&nbsp;Bo Zheng,&nbsp;Yong Zhou,&nbsp;Robert J. Scholes","doi":"10.1029/2023GB008016","DOIUrl":"https://doi.org/10.1029/2023GB008016","url":null,"abstract":"<p>As part of the REgional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project, we developed a comprehensive African Greenhouse gases (GHG) budget covering 2000 to 2019 (RECCAP1 and RECCAP2 time periods), and assessed uncertainties and trends over time. We compared bottom-up process-based models, data-driven remotely sensed products, and national GHG inventories with top-down atmospheric inversions, accounting also for lateral fluxes. We incorporated emission estimates derived from novel methodologies for termites, herbivores, and fire, which are particularly important in Africa. We further constrained global woody biomass change products with high-quality regional observations. During the RECCAP2 period, Africa's carbon sink capacity is decreasing, with net ecosystem exchange switching from a small sink of −0.61 ± 0.58 PgC yr⁻¹ in RECCAP1 to a small source in RECCAP2 at 0.16 (−0.52/1.36) PgC yr⁻¹. Net CO₂ emissions estimated from bottom-up approaches were 1.6 (−0.9/5.8) PgCO₂ yr⁻¹, net CH₄ were 77 (56.4/93.9) TgCH₄ yr⁻¹ and net N₂O were 2.9 (1.4/4.9) TgN₂O yr⁻¹. Top-down atmospheric inversions showed similar trends. Land Use Change emissions increased, representing one of the largest contributions at 1.7 (0.8/2.7) PgCO₂eq yr⁻¹ to the African GHG budget and almost similar to emissions from fossil fuels at 1.74 (1.53/1.96) PgCO₂eq yr⁻¹, which also increased from RECCAP1. Additionally, wildfire emissions decreased, while fuelwood burning increased. For most component fluxes, uncertainty is large, highlighting the need for increased efforts to address Africa-specific data gaps. However, for RECCAP2, we improved our overall understanding of many of the important components of the African GHG budget that will assist to inform climate policy and action.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140342987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methane Emissions From the Qinghai-Tibet Plateau Ponds and Lakes: Roles of Ice Thaw and Vegetation Zone","authors":"Yang Li,&nbsp;Genxu Wang,&nbsp;Shouqin Sun,&nbsp;Shan Lin,&nbsp;Peng Huang,&nbsp;Jinwang Xiao,&nbsp;Linmao Guo,&nbsp;Jinlong Li,&nbsp;Chunlin Song","doi":"10.1029/2024GB008106","DOIUrl":"https://doi.org/10.1029/2024GB008106","url":null,"abstract":"<p>Comprehensive seasonal observation is essential for accurately quantifying methane (CH₄) emissions from ponds and lakes in permafrost regions. Although CH₄ emissions during ice thaw are important and highly variable in high-latitude freshwater ponds and lakes (north of ∼50°N), their contribution is seldom included in estimates of aquatic-atmospheric CH₄ exchange across different alpine ecosystems. Here, we characterized annual CH₄ emissions, including emissions during ice thaw, from ponds and lakes across four alpine vegetation zones in the Qinghai-Tibet Plateau (QTP) permafrost region. We observed significant spatial variability in annual CH₄ emission rates (8.44−421.05 mmol m⁻² yr⁻¹), CH₄ emission rates during ice thaw (0.26−144.39 mmol m⁻² yr⁻¹), and the contribution of CH₄ emissions during ice thaw to annual emissions (3−33%) across different vegetation zones. Dissolved oxygen concentration under ice, along with substrate availability and water salinity, played critical roles in influencing CH₄ flux during ice thaw. We estimated annual CH₄ emissions from ponds and lakes in the QTP permafrost region as 0.04 (0.03−0.05) Tg CH₄ yr⁻¹ (median (first quartile−third quartile)), with approximately 20% occurring during ice thaw. Notably, the average areal CH₄ emission rate from ponds and lakes in the QTP permafrost region amounts to only 8% of that from high-latitude waterbodies, primarily due to the dominance of large saline lakes with lower CH₄ emission rates in the alpine permafrost region. Our findings emphasize the significance of incorporating comprehensive seasonal observation of CH₄ emissions across different vegetation zones in better predicting CH₄ emissions from alpine ponds and lakes.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling","authors":"Justine Ramage,&nbsp;McKenzie Kuhn,&nbsp;Anna-Maria Virkkala,&nbsp;Carolina Voigt,&nbsp;Maija E. Marushchak,&nbsp;Ana Bastos,&nbsp;Christina Biasi,&nbsp;Josep G. Canadell,&nbsp;Philippe Ciais,&nbsp;Efrèn López-Blanco,&nbsp;Susan M. Natali,&nbsp;David Olefeldt,&nbsp;Stefano Potter,&nbsp;Benjamin Poulter,&nbsp;Brendan M. Rogers,&nbsp;Edward A. G. Schuur,&nbsp;Claire Treat,&nbsp;Merritt R. Turetsky,&nbsp;Jennifer Watts,&nbsp;Gustaf Hugelius","doi":"10.1029/2023GB007953","DOIUrl":"https://doi.org/10.1029/2023GB007953","url":null,"abstract":"<p>The northern permafrost region has been projected to shift from a net sink to a net source of carbon under global warming. However, estimates of the contemporary net greenhouse gas (GHG) balance and budgets of the permafrost region remain highly uncertain. Here, we construct the first comprehensive bottom-up budgets of CO₂, CH₄, and N₂O across the terrestrial permafrost region using databases of more than 1000 in situ flux measurements and a land cover-based ecosystem flux upscaling approach for the period 2000–2020. Estimates indicate that the permafrost region emitted a mean annual flux of 12 (−606, 661) Tg CO₂–C yr⁻¹, 38 (22, 53) Tg CH₄–C yr⁻¹, and 0.67 (0.07, 1.3) Tg N₂O–N yr⁻¹ to the atmosphere throughout the period. Thus, the region was a net source of CH₄ and N₂O, while the CO₂ balance was near neutral within its large uncertainties. Undisturbed terrestrial ecosystems had a CO₂ sink of −340 (−836, 156) Tg CO₂–C yr⁻¹. Vertical emissions from fire disturbances and inland waters largely offset the sink in vegetated ecosystems. When including lateral fluxes for a complete GHG budget, the permafrost region was a net source of C and N, releasing 144 (−506, 826) Tg C yr⁻¹ and 3 (2, 5) Tg N yr⁻¹. Large uncertainty ranges in these estimates point to a need for further expansion of monitoring networks, continued data synthesis efforts, and better integration of field observations, remote sensing data, and ecosystem models to constrain the contemporary net GHG budgets of the permafrost region and track their future trajectory.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007953","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relationships Between Plankton Size Spectra, Net Primary Production, and the Biological Carbon Pump","authors":"Michael R. Stukel,&nbsp;Moira Décima,&nbsp;Thomas B. Kelly,&nbsp;Michael R. Landry,&nbsp;Scott D. Nodder,&nbsp;Mark D. Ohman,&nbsp;Karen E. Selph,&nbsp;Natalia Yingling","doi":"10.1029/2023GB007994","DOIUrl":"https://doi.org/10.1029/2023GB007994","url":null,"abstract":"<p>Photosynthesis in the surface ocean and subsequent export of a fraction of this fixed carbon leads to carbon dioxide sequestration in the deep ocean. Ecological relationships among plankton functional groups and theoretical relationships between particle size and sinking rate suggest that carbon export from the euphotic zone is more efficient when communities are dominated by large organisms. However, this hypothesis has never been tested against measured size spectra spanning the &gt;5 orders of magnitude found in plankton communities. Using data from five ocean regions (California Current Ecosystem, North Pacific subtropical gyre, Costa Rica Dome, Gulf of Mexico, and Southern Ocean subtropical front), we quantified carbon-based plankton size spectra from heterotrophic bacteria to metazoan zooplankton (size class cutoffs varied slightly between regions) and their relationship to net primary production and sinking particle flux. Slopes of the normalized biomass size spectra (NBSS) varied from −1.6 to −1.2 (median slope of −1.4 equates to large 1–10 mm organisms having a biomass equal to only 7.6% of the biomass in small 1–10 μm organisms). Net primary production was positively correlated with the NBSS slope, with a particularly strong relationship in the microbial portion of the size spectra. While organic carbon export co-varied with NBSS slope, we found only weak evidence that export efficiency is related to plankton community size spectra. Multi-variate statistical analysis suggested that properties of the NBSS added no explanatory power over chlorophyll, primary production, and temperature. Rather, the results suggest that both plankton size spectra and carbon export increase with increasing system productivity.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140333213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrogen Cycling Feedback on Carbon Dynamics Leads to Greater CH4 Emissions and Weaker Cooling Effect of Northern Peatlands","authors":"Bailu Zhao,&nbsp;Qianlai Zhuang","doi":"10.1029/2023GB007978","DOIUrl":"https://doi.org/10.1029/2023GB007978","url":null,"abstract":"<p>Northern peatlands have been a carbon sink since their initiation. This has been simulated by existing process-based models. However, most of these models are limited by lacking sufficient processes of the N cycle in peatlands. Here, we use a peatland biogeochemistry model incorporated with N-related processes of fixation, deposition, gas emission, loss through water flow, net mineralization, plant uptake and litterfall to project the role of the peatlands in future radiative forcing (RF). Simulations from 15-ka BP to 2100 are conducted driven by CMIP5 climate forcing data of IPSL-CM5A-LR and bcc-csm1-1, including warming scenarios of RCP 2.6, RCP 4.5 and RCP 8.5. During the Holocene, northern peatlands have an increasing cooling effect with RF up to −0.57 W m⁻². By 1990, these peatlands accumulate 408 Pg C and 7.8 Pg N. Under warming, increasing mineral N content enhances plant net primary productivity; the cooling effect persists. However, RF increases by 0.1–0.5 W m⁻² during the 21st century, mainly due to the stimulated CH₄ emissions. Northern peatlands could switch from a C sink to a source when the annual temperature exceeds −2.2 to −0.5°C. This study highlights that the improved N cycle causes higher CO₂-C sink capacity in northern peatlands. However, it also causes a significant increase in CH₄ emissions, which weakens the cooling effect of northern peatlands in future climate.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007978","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Importance of Riverine Nutrient Supply for the Marine Silica Pump of Arctic Shelves: Evidence From the Laptev Sea","authors":"M. C. F. Debyser,&nbsp;L. Pichevin,&nbsp;R. E. Tuerena,&nbsp;A. Doncila,&nbsp;I. Semiletov,&nbsp;R. S. Ganeshram","doi":"10.1029/2023GB007828","DOIUrl":"https://doi.org/10.1029/2023GB007828","url":null,"abstract":"<p>Arctic shelves receive a large load of nutrients from Arctic rivers, which play a major role in the biogeochemical cycles of the Arctic Ocean. In this study, we present measurements of dissolved silicon isotopes (δ³⁰Si(OH)₄) around the Laptev Sea and surface waters of the Eurasian shelves collected in October 2018 to document terrestrial silicon modifications on shelves and their contribution to the Arctic basin. Nitrogen was found to be depleted in surface waters and the limiting nutrient to primary production in the Laptev Sea, allowing excess silicon export to the central Arctic Ocean. Heavy δ³⁰Si(OH)₄ in the water column was linked to the strong biological removal of DSi on shelves, enabled by vigorous N recycling. From isotopically constrained processes, we estimate that &gt;50% of the silicon from riverine inputs is removed within the Lena River delta and on the Laptev Sea shelf. Extrapolating this to major Siberian rivers, this leads to an export of 2.5 ± 0.8 kmol/s of riverine silicon through the Transpolar Drift. An updated isotopic budget of the Arctic Ocean reproduces the observed δ³⁰Si(OH)₄ signatures out of the Arctic Ocean and underlines the importance of biological processes in modulating silicon export. Given that opal burial fluxes on Artic shelves are controlled by denitrification and N-limitation, these processes are sensitive to ongoing climate change. As a consequence of higher riverine DSi inputs and shelf denitrification responding to productivity, it is inferred that silicon export from the Arctic Ocean could increase in the future, accompanied by lighter δ³⁰Si(OH)₄ signatures.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007828","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing the Atmospheric Mn Cycle and Its Impact on Terrestrial Biogeochemistry","authors":"Louis Lu,&nbsp;Longlei Li,&nbsp;Sagar Rathod,&nbsp;Peter Hess,&nbsp;Carmen Martínez,&nbsp;Nicole Fernandez,&nbsp;Christine Goodale,&nbsp;Janice Thies,&nbsp;Michelle Y. Wong,&nbsp;Maria Grazia Alaimo,&nbsp;Paulo Artaxo,&nbsp;Francisco Barraza,&nbsp;Africa Barreto,&nbsp;David Beddows,&nbsp;Shankarararman Chellam,&nbsp;Ying Chen,&nbsp;Patrick Chuang,&nbsp;David D. Cohen,&nbsp;Gaetano Dongarrà,&nbsp;Cassandra Gaston,&nbsp;Darío Gómez,&nbsp;Yasser Morera-Gómez,&nbsp;Hannele Hakola,&nbsp;Jenny Hand,&nbsp;Roy Harrison,&nbsp;Philip Hopke,&nbsp;Christoph Hueglin,&nbsp;Yuan-Wen Kuang,&nbsp;Katriina Kyllönen,&nbsp;Fabrice Lambert,&nbsp;Willy Maenhaut,&nbsp;Randall Martin,&nbsp;Adina Paytan,&nbsp;Joseph Prospero,&nbsp;Yenny González,&nbsp;Sergio Rodriguez,&nbsp;Patricia Smichowski,&nbsp;Daniela Varrica,&nbsp;Brenna Walsh,&nbsp;Crystal Weagle,&nbsp;Yi-Hua Xiao,&nbsp;Natalie Mahowald","doi":"10.1029/2023GB007967","DOIUrl":"https://doi.org/10.1029/2023GB007967","url":null,"abstract":"<p>The role of manganese (Mn) in ecosystem carbon (C) biogeochemical cycling is gaining increasing attention. While soil Mn is mainly derived from bedrock, atmospheric deposition could be a major source of Mn to surface soils, with implications for soil C cycling. However, quantification of the atmospheric Mn cycle, which comprises emissions from natural (desert dust, sea salts, volcanoes, primary biogenic particles, and wildfires) and anthropogenic sources (e.g., industrialization and land-use change due to agriculture), transport, and deposition, remains uncertain. Here, we use compiled emission data sets for each identified source to model and quantify the atmospheric Mn cycle by combining an atmospheric model and in situ atmospheric concentration measurements. We estimated global emissions of atmospheric Mn in aerosols (&lt;10 μm in aerodynamic diameter) to be 1,400 Gg Mn year⁻¹. Approximately 31% of the emissions come from anthropogenic sources. Deposition of the anthropogenic Mn shortened Mn “pseudo” turnover times in 1-m-thick surface soils (ranging from 1,000 to over 10,000,000 years) by 1–2 orders of magnitude in industrialized regions. Such anthropogenic Mn inputs boosted the Mn-to-N ratio of the atmospheric deposition in non-desert dominated regions (between 5 × 10⁻⁵ and 0.02) across industrialized areas, but that was still lower than soil Mn-to-N ratio by 1–3 orders of magnitude. Correlation analysis revealed a negative relationship between Mn deposition and topsoil C density across temperate and (sub)tropical forests, consisting with atmospheric Mn deposition enhancing carbon respiration as seen in in situ biogeochemical studies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007967","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140310320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Overwinter and Spring Thaw Nitrous Oxide Fluxes in a Northern Prairie Cropland Are Limited but a Significant Proportion of Annual Emissions","authors":"Claudia Wagner-Riddle,&nbsp;Kate A. Congreves,&nbsp;Shannon E. Brown,&nbsp;Warren D. Helgason,&nbsp;Richard E. Farrell","doi":"10.1029/2023GB008051","DOIUrl":"https://doi.org/10.1029/2023GB008051","url":null,"abstract":"<p>Croplands that experience seasonal soil freezing and thawing have been shown to be significant sources of N₂O emissions. Yet, there is a paucity of year-round N₂O emission data for one of the most significant crop production regions that seasonally freeze, the Prairies. Here, we present micrometeorological N₂O fluxes measured over 4 years in Saskatchewan, Canada, to evaluate the magnitude of freeze-thaw N₂O emissions and investigate its driving factors. Significant thaw related emissions occurred in 2 of the 4 years and were associated with relatively higher fall nitrate levels and a more gradual soil thawing period. Overall, fall soil nitrate levels were a strong explanatory variable for the differences in non-growing season (NGS) N₂O emission (<i>r</i>² = 0.485). Measured cumulative N₂O emissions for the NGS were 123–938 g N ha⁻¹ and were much smaller than those obtained at other cold climate sites but amounted to 52% of annual totals on average. The November to April period contributed 30% of the annual total emissions in years without major thaw events, but 70% in years with significant thaws. NGS N₂O emissions were not explained by cumulative freezing degree days unlike most other cold climate sites. We propose that NGS N₂O emissions are more strongly influenced by thaw dynamics during freezing-thawing conditions in dry regions, whereas freezing intensity is the dominant factor for wetter regions. Our results indicate that even for a semi-arid region freeze-thaw is an important source of N₂O emissions and must be considered for more accurate reporting and development of mitigation strategies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 4","pages":""},"PeriodicalIF":5.2,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}