Biogeochemistry最新文献

{"title":"Decoupling of dissolved organic carbon (DOC) and dissolved black carbon (DBC) in a temperate fluvial network","authors":"Adrian M. Bass,&nbsp;Chao Gu","doi":"10.1007/s10533-024-01172-w","DOIUrl":"10.1007/s10533-024-01172-w","url":null,"abstract":"<div><p>Black carbon (BC) is a significant component of the global carbon cycle both in terrestrial and aquatic systems. Dissolved black carbon (DBC) is a significant portion of the total dissolved organic carbon (DOC) pool and represents a major flux of recalcitrant carbon to the coastal and deep oceans. Dissolved black carbon can originate from multiple sources related to its relative biogeochemical reactivity with the dynamics of highly recalcitrant DBC integral to long-term sequestration. Thus, understanding how the more recalcitrant fractions of DBC varies in diverse catchments is critical and currently underexplored. We used hydrogen pyrolysis to isolate the fraction of DBC with aromatic clusters above 7 rings, representing the more stable components. Here we report the dynamics of DBC_HyPy over a hydrological year in a temperate catchment, with a long history of coal mining extraction. Quarterly measurements of DBC were undertaken from two main channel and four tributary sites. Hydrogen pyrolysis derived DBC comprised a significant percentage of the total DOC flux (3.2% to 28.3%) and included significant spatial variability. Unlike other studies examining more reactive DBC fractions, bulk DOC concentrations and DBC_HyPy were poorly correlated when considered over an annual scale. Rather, DBC_HyPy was correlated with indicators of groundwater such as dissolved inorganic carbon and conductivity. Data suggest a consistent source of DBC_HyPy not subject to the same mobilisation drivers as DOC, which shows substantial seasonality. Rather, our data shows a potentially consistent supply of stable DBC originating from the coal mining-influenced groundwater. Petrogenic sources of DBC have been poorly constrained to date, the data presented here suggests in some catchments it may be significant and yield catchment scale DOC-DBC decoupling. The dynamics of DBC have implications for carbon fluxes, pollution transport and water quality/treatment requirements. These preliminary findings suggest potentially complex drivers in spatially heterogeneous catchments, contrasting with previous work finding tight DOC-DBC mobilisation dynamics.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 10","pages":"1269 - 1279"},"PeriodicalIF":3.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01172-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142007583","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":"Phosphorus inactivation mitigates the effect of warm winters in a temperate shallow lake (Mielenko Lake, Poland)","authors":"Renata Augustyniak-Tunowska,&nbsp;Rafał Karczmarczyk,&nbsp;Jolanta Grochowska,&nbsp;Michał Łopata,&nbsp;Agnieszka Napiórkowska-Krzebietke,&nbsp;Miquel Lürling","doi":"10.1007/s10533-024-01173-9","DOIUrl":"10.1007/s10533-024-01173-9","url":null,"abstract":"<div><p>Direct and indirect anthropopressure on water ecosystems is the serious problem throughout the world.. In the Northern Hemisphere, an increase in average air temperatures is observed, which implies the occurrence of a shorter period of snow and ice cover during the winter season. The winter 2019/2020 was unusual, because that was the first time in the record, that a complete lack of permanent ice cover was observed on numerous lakes in Poland. Such unusual conditions could influence lake functioning. Hence we analyzed the chemistry of the water–sediment interface (near-bottom and interstitial water and sediment) in the shallow, eutrophic Mielenko Lake (area 7.9 ha, max depth 1.9 m) in 2013 and 2019–2022 period to assess the influence of prolonged water circulation on the bottom zone. Mielenko Lake was subjected to a phosphorus inactivation procedure using Al and Fe salts (PAX 18, PIX 111) in 2020 and 2021. Our research revealed that unusually prolonged winter circulation caused a significant decrease in organic matter content in bottom sediment in 2020, as well as a decrease in NaOH-nrP fraction and TP amounts. That effect was short-term and it did not significantly influence the NaOH-rP fraction amounts. The released P was probably built in macrophytes biomass during vegetation season, because P inactivation has been limiting phytoplankton proliferation, and it favored shifting to a clearwater state with macrophytes domination. This was confirmed by decreasing in phytoplankton biomass, and a massive expansion of the macrophytes range noted in the second year of restoration. Our study shows, that P inactivation could mitigate the negative effects of warm winters in shallow lakes.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 10","pages":"1243 - 1267"},"PeriodicalIF":3.9,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01173-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142007584","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":"Factors influencing seasonal chemistry patterns in Virginia mountain streams","authors":"Ami L. Riscassi,&nbsp;Todd M. Scanlon,&nbsp;James N. Galloway","doi":"10.1007/s10533-024-01163-x","DOIUrl":"10.1007/s10533-024-01163-x","url":null,"abstract":"<div><p>The relative influence of seasonal patterns in hydrological flow and seasonal differences in biological and geochemical activity on stream chemistry patterns is difficult to discern because they covary; temperate systems are characterized by lower mean flow in the summer (i.e. corresponding to deeper flow paths, elevated temperature, and biological activity), and higher mean flow in the winter (i.e. corresponding to shallower flow paths, depressed temperature, and biological dormancy). Using 2018 data, when seasonal stream flow conditions reversed, and two prior conventional water years, the relationship between monthly acid-relevant analyte concentrations and streamflow were compared within and between winter and summer to provide insight into controls on characteristic seasonal chemistry patterns at two mid-Appalachian sites with distinct geology (weatherable mafic and weather resistant siliciclastic). Acid neutralizing capacity (ANC) increased (1) with lower flow, in both seasons and (2) in summer, for all flow conditions. The compounding impacts resulted in a doubling of concentration from typical winter with high flow to summer with low flow at both sites. Base cation patterns tracked ANC at the mafic site, resulting in an ~ 60% increase of from winter with high flow to summer with low flow; distinctions between summer and winter contributed more to the seasonal pattern (72%) than changes in flow. Sulfate increased at the mafic site (1) with higher flow, in both seasons and (2) in winter, for all flow conditions, resulting in an ~ 50% increase from summer with low flow to winter with high flow; distinctions between winter and summer conditions and flow contributed similarly (40–60%) to the typical seasonal chemical pattern. The biogeochemical mechanism driving differences in stream chemistry between summer and winter for the same flow conditions is likely increased rates of natural acidification from elevated soil respiration in summer, resulting in greater bedrock weathering and sulfate adsorption. Findings highlight the significance and consistency of growing vs dormant season variations in temperature and biological activity in driving intra-annual patterns of stream solutes. This data set informs parameterization of hydro-biogeochemical models of stream chemistry in a changing climate at a biologically relevant, seasonal, timescale.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 10","pages":"1175 - 1201"},"PeriodicalIF":3.9,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01163-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141899763","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":"Long-term warming in a temperate forest accelerates soil organic matter decomposition despite increased plant-derived inputs","authors":"Atzín X. San Román,&nbsp;Nivetha Srikanthan,&nbsp;Andreia A. Hamid,&nbsp;Thomas J. Muratore,&nbsp;Melissa A. Knorr,&nbsp;Serita D. Frey,&nbsp;Myrna J. Simpson","doi":"10.1007/s10533-024-01165-9","DOIUrl":"10.1007/s10533-024-01165-9","url":null,"abstract":"<div><p>Climate change may alter soil microbial communities and soil organic matter (SOM) composition. Soil carbon (C) cycling takes place over multiple time scales; therefore, long-term studies are essential to better understand the factors influencing C storage and help predict responses to climate change. To investigate this further, soils that were heated by 5 °C above ambient soil temperatures for 18 years were collected from the Barre Woods Soil Warming Study at the Harvard Forest Long-term Ecological Research site. This site consists of large 30 × 30 m plots (control or heated) where entire root systems are exposed to sustained warming conditions. Measurements included soil C and nitrogen concentrations, microbial biomass, and SOM chemistry using gas chromatography–mass spectrometry and solid-state ¹³C nuclear magnetic resonance spectroscopy. These complementary techniques provide a holistic overview of all SOM components and a comprehensive understanding of SOM composition at the molecular-level. Our results showed that soil C concentrations were not significantly altered with warming; however, various molecular-level alterations to SOM chemistry were observed. We found evidence for both enhanced SOM decomposition and increased above-ground plant inputs with long-term warming. We also noted shifts in microbial community composition while microbial biomass remained largely unchanged. These findings suggest that prolonged warming induced increased availability of preferred substrates, leading to shifts in the microbial community and SOM biogeochemistry. The observed increase in gram-positive bacteria indicated changes in substrate availability as gram-positive bacteria are often associated with the decomposition of complex organic matter, while gram-negative bacteria preferentially break down simpler organic compounds altering SOM composition over time. Our results also highlight that additional plant inputs do not effectively offset chronic warming-induced SOM decomposition in temperate forests.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 9","pages":"1159 - 1174"},"PeriodicalIF":3.9,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01165-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141791119","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":"Four decades of changing dissolved organic matter quality and stoichiometry in a Swedish forest stream","authors":"Chris D. Evans,&nbsp;Sara Jutterström,&nbsp;Johanna Stadmark,&nbsp;Mike Peacock,&nbsp;Martyn Futter,&nbsp;Dolly Kothawala,&nbsp;Don Monteith,&nbsp;Filip Moldan","doi":"10.1007/s10533-024-01166-8","DOIUrl":"10.1007/s10533-024-01166-8","url":null,"abstract":"<div><p>Dissolved organic matter (DOM) concentrations have risen by a factor of two or more across much of Europe and North America during recent decades. These increases have affected the carbon cycle, light regime, drinking water treatability, and the energy and nutrient budgets of lakes and streams. However, while trends in DOM quantity are well characterised, information on how/whether qualitative properties of DOM have changed are scarce. Here, we describe over 40 years of monitoring data from a forested headwater stream in the Gårdsjön experimental catchment, southwest Sweden, which provides a unique record of biogeochemical change, including optical and stoichiometric DOM quality metrics, spanning the entire period of recovery from acidification. For the period 1980–2020 we find a 71% reduction in decadal mean sulphate concentrations, and a similar reduction in inorganic aluminium concentrations, alongside a 64% increase in dissolved organic carbon (DOC) concentrations. Over the same period, colour (absorbance at 420 nm) increased almost twice as much as DOC, whereas dissolved organic nitrogen (DON) increased by only one third as much. These results demonstrate a shift in stream water composition, with DOM becoming dominated by highly coloured, complex, nitrogen-poor compounds. This material is likely more resistant to biological degradation, but more susceptible to photochemical degradation. Changes in DOM stoichiometry could lead to intensified nitrogen and/or phosphorus limitation in surface waters, while increased colour/DOC ratios could intensify light-limitation of primary production beyond that expected from DOC increases alone. We observed increases in organic matter associated metals (iron 117%, organically complexed aluminium 85%) that exceeded the increase in DOC, consistent with their increased mobilisation by more aromatic organic matter. All observed changes are consistent with recovery from acidification being the primary driver of change, implying that past acidification, and ongoing recovery, have profoundly affected terrestrial and aquatic biogeochemistry, ecology and the carbon cycle.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 9","pages":"1139 - 1157"},"PeriodicalIF":3.9,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01166-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141768616","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":"Reduced accrual of mineral-associated organic matter after two years of enhanced rock weathering in cropland soils, though no net losses of soil organic carbon","authors":"Noah W. Sokol,&nbsp;Jaeeun Sohng,&nbsp;Kimber Moreland,&nbsp;Eric Slessarev,&nbsp;Heath Goertzen,&nbsp;Radomir Schmidt,&nbsp;Sandipan Samaddar,&nbsp;Iris Holzer,&nbsp;Maya Almaraz,&nbsp;Emily Geoghegan,&nbsp;Benjamin Houlton,&nbsp;Isabel Montañez,&nbsp;Jennifer Pett-Ridge,&nbsp;Kate Scow","doi":"10.1007/s10533-024-01160-0","DOIUrl":"10.1007/s10533-024-01160-0","url":null,"abstract":"<div><p>Enhanced rock weathering (ERW), the application of crushed silicate rock to soil, can remove atmospheric carbon dioxide by converting it to (bi) carbonate ions or solid carbonate minerals. However, few studies have empirically evaluated ERW in field settings. A critical question remains as to whether additions of crushed rock might positively or negatively affect soil organic matter (SOM)—Earth’s largest terrestrial organic carbon (C) pool and a massive reservoir of organic nitrogen (N). Here, in three irrigated cropland field trials in California, USA, we investigated the effect of crushed meta-basalt rock additions on different pools of soil organic carbon and nitrogen (i.e., mineral-associated organic matter, MAOM, and particulate organic matter, POM), active microbial biomass, and microbial community composition. After 2 years of crushed rock additions, MAOM stocks were lower in the upper surface soil (0–10 cm) of plots with crushed rock compared to unamended control plots. At the 2 sites where baseline pre-treatment data were available, neither total SOC nor SON decreased over the 2 years of study in plots with crushed rock or unamended control plots. However, the accrual rate of MAOM-C and MAOM-N at 0–10 cm was lower in plots with crushed rock vs. unamended controls. Before ERW is deployed at large scales, our results suggest that field trials should assess the effects of crushed rock on SOM pools, especially over multi-year time scales and in different environmental contexts, to accurately assess changes in net C and understand the mechanisms driving interactions between ERW and SOM cycling.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 8","pages":"989 - 1005"},"PeriodicalIF":3.9,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01160-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141755349","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":"Biotic regulation of nitrogen gas emissions in temperate agriculture","authors":"Maya Almaraz,&nbsp;Rebecca Ryals,&nbsp;Peter Groffman,&nbsp;Stephen Porder","doi":"10.1007/s10533-024-01157-9","DOIUrl":"10.1007/s10533-024-01157-9","url":null,"abstract":"<div><p>It is generally assumed that fertilizer addition is the prime driver of nitrogen (N) gas loss from modern cropping systems. This assumption has its basis in observations of nitrous oxide (N₂O, an important greenhouse gas) emissions, and is contrary to theory from unmanaged ecosystems, where N losses are controlled by plant physiological influence on the soil environment. However, dinitrogen (N₂) emissions are likely a major N loss pathway in both managed and unmanaged ecosystems, but these emissions are very difficult to measure. We directly measured N₂ and N₂O emissions from two temperate agricultural systems over the course of the growing season to test when total N gas losses are highest. We hypothesized that N₂ emissions mirror those of N₂O, with the largest flux immediately after fertilization, early in the growing season. Instead, we found that N₂ emissions were highest at the end of the growing season, and were most strongly correlated with soil moisture, which increased after plant senescence. Dinitrogen emissions were an order of magnitude larger than N₂O. Thus, while N₂O emissions were highest following fertilization, overall N gas loss was greatest at the end of the growing season. These data suggest that total N gas losses are high and have different temporal patterns from N₂O fluxes. Understanding the magnitude and controls over these losses are important for understanding and managing the N cycle of temperate agricultural systems.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 9","pages":"1079 - 1087"},"PeriodicalIF":3.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01157-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141597610","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":"Does montane meadow restoration influence the mineral association and stability of soil carbon?","authors":"Seren H. Bagcilar,&nbsp;Cody C. Reed,&nbsp;Simon R. Poulson,&nbsp;Paul S. J. Verburg,&nbsp;Benjamin W. Sullivan","doi":"10.1007/s10533-024-01162-y","DOIUrl":"10.1007/s10533-024-01162-y","url":null,"abstract":"<div><p>Soil carbon (C) stability is an important consideration for management that aims to increase long-term C storage. The fraction of soil C allocated to physico-chemically protected mineral-associated organic matter (MAOM) is a common soil C stability benchmark. However, the reality of soil C persistence is more complex than MAOM content alone—particularly in ecosystems such as meadows with high rates of belowground C inputs that can stimulate MAOM decomposition. Here, we combined three metrics of soil C persistence to characterize soil C stability across a meadow restoration chronosequence averaging belowground C gains of 330 g C m⁻² y⁻¹ for ~20 y. The metrics were: (1) the fraction of soil C in MAOM and particulate organic matter (POM), (2) the susceptibility of soil C to decomposition under varying temperatures, and (3) the utilization of MAOM-C by microbes. Two metrics suggested soil C stability may increase following montane meadow restoration. As soil C concentration increased with restoration, C storage in MAOM, but not POM, increased (metric 1). The susceptibility of MAOM-C to decomposition (microbial respiration relative to MAOM-C) decreased with increasing soil C concentration across temperatures (metric 2). Stable isotope results could not definitively determine the source of carbon dioxide efflux (metric 3) but generate hypotheses for future research to address. We posit that C sequestered following montane meadow restoration could be stable, with implications for regional C storage objectives. Further, our data point toward complex mineral-associated C dynamics including the potential importance of plant inputs for MAOM formation in meadow soils.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 9","pages":"1089 - 1105"},"PeriodicalIF":3.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01162-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141597748","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 hydrogenation of cholesterol to coprostanol by anaerobic bacteria: evidence from Antarctic lacustrine sediment","authors":"Xin Chen,&nbsp;Jianjun Wang,&nbsp;Jing Jin,&nbsp;Yaguang Nie,&nbsp;Zhangqin Zheng,&nbsp;Yulu Xue,&nbsp;Weidong Kong,&nbsp;Wenhan Cheng,&nbsp;Jifeng Zhang,&nbsp;Lewen Liang,&nbsp;Yi Yang,&nbsp;Steven D. Emslie,&nbsp;Xiaodong Liu","doi":"10.1007/s10533-024-01121-7","DOIUrl":"10.1007/s10533-024-01121-7","url":null,"abstract":"<div><p>Fecal sterols are traditionally ascribed as important biomarkers for animal excrement, and have been widely used to identify the source of organic matter and to reconstruct paleoecological changes in Antarctic terrestrial, aquatic, and marine ecosystems. However, the in situ microbial hydrogenation of cholesterol to coprostanol could have significance as a proxy to infer paleoenvironmental studies in Antarctica, particularly in anoxic sediment. Here, we report that abundant coprostanol, which was traditionally deemed as a biomarker for human sewage contamination, was found in three anoxic sediment profiles (AC2, BI, and CH1), which were strongly influenced by animal excrement at North Victoria Land, western Ross Sea, Antarctica. Our results suggest that the high concentrations of coprostanol in these three sediment profiles were not due to animal excrement, since coprostanol is not present in penguin guano and is a minor component in seal excrement. Coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) ratios suggest that coprostanol in the sediment cores of AC2 and BI was primarily derived from bacterial hydrogenation of cholesterol introduced by penguin guano. Coprostanol in CH1 sediments is related to human sewage due to intensive research activities from 1968 to 2006 in this region. However, the low abundance of coprostanol and the ratios of coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) in a relatively oxidizing sediment core (IIL1) infer that coprostanol was likely contributed by seal settlement. Together with high-throughput sequencing of the 16S rRNA gene, the conversion of cholesterol to coprostanol by anaerobic bacteria (e.g., <i>Eubacterium coprostanoligenes</i>) could occur in anoxic aquatic systems. Our results suggest that the presence of coprostanol in Antarctic lacustrine sediment with anoxic conditions does not necessarily indicate seal activity and human waste as the microbial hydrogenation of cholesterol to coprostanol should also be considered.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 9","pages":"1107 - 1122"},"PeriodicalIF":3.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01121-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141602741","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":"Estimating the global root exudate carbon flux","authors":"Nikhil R. Chari,&nbsp;Shersingh Joseph Tumber-Dávila,&nbsp;Richard P. Phillips,&nbsp;Taryn L. Bauerle,&nbsp;Melanie Brunn,&nbsp;Benjamin D. Hafner,&nbsp;Tamir Klein,&nbsp;Sophie Obersteiner,&nbsp;Michaela K. Reay,&nbsp;Sami Ullah,&nbsp;Benton N. Taylor","doi":"10.1007/s10533-024-01161-z","DOIUrl":"10.1007/s10533-024-01161-z","url":null,"abstract":"<div><p>Root exudation, the export of low-molecular weight organic carbon (C) from living plant roots to soil, influences microbial activity, nutrient availability, and ecosystem feedbacks to climate change, but the magnitude of this C flux at ecosystem and global scales is largely unknown. Here, we synthesize in situ measurements of root exudation rates and couple those to estimates of fine root biomass to estimate global and biome-level root exudate C fluxes. We estimate a global root exudate flux of 13.4 (10.1–20.2) Pg C y⁻¹, or about 9% (7–14%) of global annual gross primary productivity. We did not find differences in root mass-specific exudation rates among biomes, though total exudate fluxes are estimated to be greatest in grasslands owing to their high density of absorptive root biomass. Our synthesis highlights the global importance of root exudates in the terrestrial C cycle and identifies regions where more in situ measurements are needed to improve future estimates of root exudate C fluxes.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 7","pages":"895 - 908"},"PeriodicalIF":3.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01161-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141561241","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}