Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Quantifying Dust Nutrient Mobility Through an Alpine Watershed","authors":"Jeffrey R. Nielson,&nbsp;Janice Brahney","doi":"10.1029/2024JG008175","DOIUrl":"https://doi.org/10.1029/2024JG008175","url":null,"abstract":"<p>Dust has the potential to play a significant role in the nutrient dynamics of alpine watersheds with important ecological implications. However, little is known about how dust nutrients circulate through the environment and which watershed characteristics facilitate dust impacts on water quality. This study explored the contribution of dust-deposited nutrients, focusing on a high-elevation Long Term Ecological Research site, where dust samples have been continuously collected since 2017. We incorporated observed dust nutrient compositions, including fractions of inorganic and organic nitrogen and phosphorus, into a popular hydrological model, the Soil and Water Assessment Tool, and ran simulations for 2019–2021. By comparing simulations with and without dust nutrient inputs, we estimated the impact of dust-deposited nutrients on individual watershed processes. Results revealed a significant contribution of dust-deposited nutrients, particularly soluble reactive phosphorus (SRP), to several nutrient cycling and transport pathways. Notably, dust contributed up to 19.3% of the SRP load in annual streamflow (increasing monthly streamflow concentration by up to 10.9 μg <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>L</mi>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{L}}^{-1}$</annotation>\u0000 </semantics></math> ). Spatial analysis of model estimates demonstrated a relationship between topography, soil type, and the cycling and transport of dust nutrients. The largest dust nutrient contributions were found in catchment areas with lower slope and less hydric soils, where other natural mobilization processes may be limited. This comparative modeling approach stresses the importance of including dust nutrients in watershed models, especially in oligotrophic systems, and has potential to validate these findings elsewhere and identify how watershed characteristics may either mollify or accentuate the impacts of dust deposition on mountain freshwater systems.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143119424","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":"Effects of Hot Versus Dry Vapor Pressure Deficit on Ecosystem Carbon and Water Fluxes","authors":"Miriam R. Johnston,&nbsp;Mallory L. Barnes,&nbsp;Yakir Preisler,&nbsp;William K. Smith,&nbsp;Joel A. Biederman,&nbsp;Russell L. Scott,&nbsp;A. Park Williams,&nbsp;Matthew P. Dannenberg","doi":"10.1029/2024JG008146","DOIUrl":"https://doi.org/10.1029/2024JG008146","url":null,"abstract":"<p>Vapor pressure deficit (VPD) has increased and will likely continue increasing, with wide-ranging effects on ecosystems. Future VPD increases will largely be driven by warming, yet most experiments examining VPD effects on plants have done so by changing humidity. Here, we used meteorological data and carbon and water fluxes measured at 26 climatically-diverse eddy covariance sites to quantify the extent to which VPD has been driven by variation in air temperature versus humidity. We fit generalized additive models (GAMs) at each site to quantify effects of hotter (and wetter) and cooler (and drier) versus typical VPD on ecosystem-scale fluxes of carbon and water. We found that VPD has occurred under diverse combinations of temperature and humidity: &gt;50% of a site's daytime growing season temperature range and &gt;35% of its relative humidity range have often combined to define a particular VPD. We found moderate evidence that hotter versus drier VPD of the same magnitude differentially affect gross primary productivity (GPP), net ecosystem productivity (NEP), and latent heat flux (LE): Selected GPP and NEP GAMs at about half of sites and LE GAMs at about a third of sites included a VPD-temperature interaction. The magnitude of the interaction varied, but was generally 29%–57% of the effect attributable solely to VPD. The direction of the interaction also varied, but hot VPD was commonly associated with higher carbon fluxes. These effects were not strongly modified by soil moisture. Overall, results emphasize the relevance of VPD-temperature interactions at a critical time of rapid VPD increase.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008146","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143119035","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 Machine Learning Approach for Filling Long Gaps in Eddy Covariance Time Series Data in a Tropical Dry Forest","authors":"Mohammed Abdaki,&nbsp;Arturo Sanchez-Azofeifa,&nbsp;Hendrik F. Hamann","doi":"10.1029/2024JG008375","DOIUrl":"https://doi.org/10.1029/2024JG008375","url":null,"abstract":"<p>Long-term eddy covariance (EC) data are crucial for understanding the impact of global change on ecosystem functions. However, EC data often contain long gaps, particularly in tropical dry forests (TDF) due to seasonality and El Niño-Southern Oscillation (ENSO) phases. These factors create high variability, complex dependencies, and dynamic flux footprints. No current gap-filling method adequately addresses long gaps in TDFs. This study introduces a novel framework for addressing this issue by (a) defining gap sizes by their relative percentages, (b) training, tuning, and evaluating two machine learning (ML) models: MissForest for short gaps and Prophet for intermediate and long gaps, and (c) predicting half-hourly EC data from 2013 to 2022 for six EC variables, where actual gap data sets ranged from 26.6% to 28.4%, at TDF in Costa Rica. Results indicate that MissForest excelled at filling short gaps (≤5%, <i>R</i>² = 0.76 and Nash-Sutcliffe efficiency (NSE) = 0.71), while Prophet performed exceptionally well for gaps between 5% and 10% (<i>R</i>² = 0.72 and NSE = 0.67). However, both models struggled with gaps between 10% and 13%. Validation showed <i>R</i>² values of 0.79, 0.88, and 0.77 for CO₂ flux, sensible heat flux, and latent heat flux, respectively, with corresponding NSE values of 0.78, 0.86, and 0.72, and normalized root mean squared error (NRMSE) around 2E-4. Additionally, to validate our results, we applied our approach at three EC sites with different ecological conditions, demonstrating robust performance. This study presents a reliable ML approach for imputing long gaps in EC data, which can be applied to sites with strong variability.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143118659","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":"Role of Micrometeorological Memory in Modulating Sub-Daily Scale Variability of Net Ecosystem Exchange","authors":"Akash Verma,&nbsp;Leena Khadke,&nbsp;Elizabeth Eldhose,&nbsp;Subimal Ghosh","doi":"10.1029/2024JG008356","DOIUrl":"https://doi.org/10.1029/2024JG008356","url":null,"abstract":"<p>Net Ecosystem Exchange (NEE) is crucial for understanding the carbon balance in ecosystems, indicating whether they act as carbon sinks or sources. While the impact of hydrometeorological factors on NEE at daily and monthly scales has been well-researched, the significance of sub-daily variability and the influence of memory in micrometeorological variables remain understudied. This study addresses this gap by analyzing the temporal dynamics of NEE using half-hourly data from 29 FLUXNET sites over at least 6 years. We found that sub-daily variability of NEE contributes 10%–55% of 13-day NEE variability, depending on seasonal cycles and biome characteristics. Using an information theory based transfer entropy (TE) approach, we identified the causal drivers of NEE variability at sub-daily scales within a 6-hr memory. Our results show that the memory of micrometeorological variables significantly impacts NEE, surpassing their instantaneous effects. Temperature (TA), vapor pressure deficit (VPD), and soil water content (SWC_Mean) consistently affect NEE within this 6-hr memory, whereas the influence of sensible heat (H) and incoming shortwave radiation (SW_IN) diminishes at higher lags. While the magnitude of average TE from micrometeorological variables to NEE exhibits notable seasonal variations, the temporal structure of how information is transferred does not significantly differ across seasons, as reflected by the shape of TE values over various time lags. SWC_Mean, VPD, and TA impact NEE jointly, while H and SW_IN have overlapping effects. Additionally, precipitation influences NEE indirectly through SWC_Mean. Our findings highlight the importance of accounting for high-frequency NEE variability and its underlying drivers when investigating the ecohydrological interactions, shedding light on the role of memory in carbon-water interactions.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143118171","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":"Assessing Simulations of Forest Hurricane Disturbance and Recovery in Puerto Rico by ELM-FATES Using Field Measurements","authors":"Mingjie Shi,&nbsp;Michael Keller,&nbsp;Barbara Bomfim,&nbsp;Lara Kueppers,&nbsp;Charlie Koven,&nbsp;Jessica Needham,&nbsp;Tamara Heartsill-Scalley,&nbsp;L. Ruby Leung","doi":"10.1029/2024JG008350","DOIUrl":"https://doi.org/10.1029/2024JG008350","url":null,"abstract":"<p>In the past three decades, Puerto Rico (PR) experienced five hurricanes that met or exceeded category three, and they caused severe forest structural damage and elevated tree mortality. To improve our mechanistic understanding of hurricane impacts on tropical forests and assess hurricane-affected forest dynamics in Earth system models, we use in situ forest measurements at the Bisley Experimental Watersheds in Northeast PR to evaluate the Functionally Assembled Terrestrial Ecosystem Simulator coupled with the Energy Exascale Earth System Model Land Model (ELM-FATES). The observations show that before Hurricane Hugo, 77.3% of the aboveground biomass (AGB) is from the shade-tolerant plant function type (PFT). The Hugo-induced mortality rates are over ∼50%, and they induce a ∼39% AGB reduction, which recovers to a level like the pre-Hugo condition in 2014, following a second, lower intensity hurricane, Georges. We perform numerical experiments that simulate damage from Hugo and Georges on the forests, including defoliation, sapwood and structural biomass damage, and hurricane-induced mortality. ELM-FATES can reasonably represent coexistence between the two PFTs–light-demanding and shade-tolerant–for both the pre-Hugo and post-Hugo conditions. The model represents a reasonable size distribution of mid-and large-sized trees although it underestimates AGB, likely due to the overestimated nonhurricane mortality. ELM-FATES temporarily stimulated leaf biomass and diameter increment after Georges, an effect that should be tested with observations of future hurricane defoliation events. This research indicates that addressing model-data mismatches in tree mortality and understory dynamics are essential to simulation of more extreme hurricane effects under climate change.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008350","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117799","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":"Biogeochemistry of Riverine Organic Matter Inputs to the Patagonian Fjords and Implications for Fjord Organic Carbon Budgets","authors":"Sebastien Bertrand","doi":"10.1029/2024JG008531","DOIUrl":"https://doi.org/10.1029/2024JG008531","url":null,"abstract":"<p>Fjords are increasingly recognized as hotspots for organic carbon (OC) burial. The OC buried in fjords is of both marine and terrestrial origin, with a predominance of terrestrial OC in fjords worldwide. The proportions of marine and terrestrial OC in fjords are traditionally calculated using end-member modeling based on <i>δ</i>¹³C and/or N/C. However, characterizing the terrestrial end-member remains a challenge, with authors inconsistently using measurements obtained on land plants, soils, and/or river sediments. Here, we analyzed the TOC, <i>δ</i>¹³C, and N/C composition of soil samples, suspended river sediments, and bulk and grain-size fractions of river sediments from the main rivers discharging into the Patagonian fjords (44–48°S), to identify the processes that affect the biogeochemistry of the terrestrial organic matter reaching fjords via rivers. Radiocarbon measurements indicate that Patagonian rivers contain 0.18% petrogenic OC and variable concentrations of biospheric OC. Despite soil <i>δ</i>¹³C significantly decreasing with precipitation, <i>δ</i>¹³C in river sediments remains relatively stable around −27‰. In contrast, N/C in river sediments is highly variable, mostly due to a high contribution of petrogenic nitrogen in glacier-fed rivers. Furthermore, N/C varies significantly with sediment grain size, making it virtually impossible to define a fixed N/C value to represent the terrestrial end-member. By comparison, grain size has a limited influence on <i>δ</i>¹³C. Overall, our results support the use of riverine <i>δ</i>¹³C to define terrestrial OC in mixing models, regardless of the presence of glaciers in the watershed, and they suggest that the fraction of terrestrial OC buried in fjord sediments may have been underestimated.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008531","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117234","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":"Atmospheric Dryness Constrains CO2 Uptake During the Peak Growing Season and at Noontime in an Alpine Wetland Ecosystem","authors":"Liqin Hua,&nbsp;Jing Tao,&nbsp;Yahui Qi,&nbsp;Zhuangzhuang Wang,&nbsp;Da Wei,&nbsp;Xiaodan Wang","doi":"10.1029/2024JG008262","DOIUrl":"https://doi.org/10.1029/2024JG008262","url":null,"abstract":"<p>Increase in atmospheric dryness, characterized as vapor pressure deficit (VPD), might constrain terrestrial productivity. Nevertheless, the precise temporal impacts of VPD on the gross primary productivity (GPP) of alpine wetland ecosystems during the growing season remain elusive. The alpine ecosystems of the Tibetan Plateau (TP), where productivity is highly constrained by the cold climate, have experienced pronounced warming of 0.26°C decade⁻¹ with associated increase in VPD. In this study, by examining eddy covariance observations taken in an alpine wetland on the TP over five consecutive years, we characterized when and how VPD variation causes negative impact on ecosystem productivity. The TP alpine wetland functioned as a net CO₂ sink with magnitude of 164.6 ± 22.0 g C m⁻² yr⁻¹. It was found that VPD played a crucial role in the seasonal variation in GPP especially in the peak growing season, that is, it even suppressed the positive effect of temperature on GPP. As temperatures declined in the latter stages of the growing season, the inhibitory effect of VPD on GPP gradually diminished. We further found that the VPD at midday (13:00–14:30) was crucial for inhibition of photosynthesis and midday depression of GPP. Our results emphasize the role of atmospheric dryness during the middle growing season and at midday on GPP, thereby providing new insights into how VPD affects CO₂ uptake in a warming climate.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115107","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":"Multiple Elevation-Dependent Climate Signals From Quantitative Wood Anatomical Measurements of Rocky Mountain Bristlecone Pine","authors":"Julie Edwards,&nbsp;Will L. Tintor,&nbsp;Alexandre F. Nolin,&nbsp;Connie A. Woodhouse,&nbsp;Georg von Arx,&nbsp;Kevin J. Anchukaitis","doi":"10.1029/2024JG008307","DOIUrl":"https://doi.org/10.1029/2024JG008307","url":null,"abstract":"<p>Southwestern North America has experienced significant temperature increases over the last century, leading to intensified droughts that significantly affect montane forests. Although tree-ring data have provided long-term context for this recent drought severity, the varying physiological responses of trees to climate variability make it challenging to disentangle the combined influence of temperature and soil moisture. Here we investigate complex climate-growth relationships in Rocky Mountain bristlecone pine (<i>Pinus aristata</i>) at a low-elevation and a high-elevation site using quantitative wood anatomy (QWA). Significant correlations with climate were found for low-elevation tree-ring width (TRW) and earlywood chronologies, including positive correlations with spring and early summer precipitation and drought indices and negative correlations with spring and early summer maximum temperatures. At high elevations, TRW and earlywood chronologies show positive responses to summer moisture, whereas latewood chronologies correlate positively with August and September maximum temperatures and negatively with August precipitation. We leverage this differing seasonality of moisture and temperature signals and compare the QWA data to known droughts. The earlywood lumen area is found to be highly responsive to drought because of its physiological reliance on water availability for maintaining turgor pressure during cell enlargement. We also observed a decline in temperature sensitivity at the high elevation site, suggesting shifts in the dominance of limiting factors. Integrating QWA with traditional dendrochronology improves interpretations of tree-ring data for use in climate reconstruction, offering detailed insights into tree physiological responses and the mix of environmental and developmental controls on cell growth.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143114819","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":"Landscape Influences on Microclimate and Tree Growth Cessation in a Semi-Arid Montane Forest","authors":"Fin Malone,&nbsp;Zachary H. Hoylman,&nbsp;Jia Hu,&nbsp;Kelsey G. Jencso","doi":"10.1029/2024JG008483","DOIUrl":"https://doi.org/10.1029/2024JG008483","url":null,"abstract":"<p>As climate change impacts the severity and frequency of drought, knowledge of hillslope-to-watershed scale ecohydrology is increasingly necessary to inform appropriate conservation, restoration, and management of forested ecosystems. In mountain environments, spatial patterns of water and energy organize forest productivity at plot, hillslope, and watershed scales. These microclimatic patterns are impacted by gradients in elevation, aspect, and local topographic convergence and divergence. In water-limited ecosystems, such patterns may be first-order drivers of tree growth. However, there is limited field-based research characterizing how seasonal drivers of forest growth may vary across complex terrain. Throughout the growing season, we measured soil moisture, vapor pressure deficit, soil and air temperatures, and radial growth at 27 Douglas-fir (<i>Pseudotsuga menziesii</i>) sites within Lubrecht Experimental Forest, Montana USA. Using these data, we assessed the influences of elevation, aspect, and local topographic position on hillslope-scale microclimates. These seasonal microclimates were then compared to the observed timing of tree growth cessation. Generally, trees located in high elevations, north-facing aspects, and convergent topographic positions were correlated with decreased temperatures, greater soil moisture, and reduced vapor pressure deficits, leading to later growth cessation. However, at the wettest positions, persistently saturated soil moisture conditions contributed to earlier cessation. Our findings highlight the landscape partitioning of forest microclimates and subsequently, their contribution to the spatial organization of growing seasons in semi-arid mountain watersheds. Lastly, we suggest that over longer timescales these seasonal microclimates influence tree growth year after year, contributing to the organization of cumulative forest growth previously observed within the watershed.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008483","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143114293","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":"Source Identification of Organic Carbon in Mountainous Reservoirs Sediments Using Stable Isotopes and n-Alkanes","authors":"Yuan Zhou,&nbsp;Jianfeng Xu,&nbsp;Wei Ye,&nbsp;Kai Wang,&nbsp;Haiming Lu,&nbsp;Xianqiang Tang,&nbsp;Danyang Wang,&nbsp;Deti Xie,&nbsp;Jiupai Ni,&nbsp;Fangxin Chen","doi":"10.1029/2024JG008323","DOIUrl":"https://doi.org/10.1029/2024JG008323","url":null,"abstract":"<p>This study focuses on the sources of organic carbon (OC) in surface sediments of reservoirs in the mountainous regions, as well as their dynamics and contribution mechanisms in the carbon cycle. Spatial variations in organic carbon, n-alkanes, δ¹³C, and δ¹⁵N were analyzed, and a Bayesian isotope mixing model was applied to quantify the relative contributions of different OC sources. The results indicate that the concentration range of organic carbon in sediments is 0.88%–3.72%. The average concentration of long-chain n-alkanes is 3.69 μg/g, accounting for 71.4%, indicating that the main source of organic carbon is allochthonous organic carbon. In addition, the Bayesian mixture model results of carbon and nitrogen isotopes also indicate that allochthonous organic carbon is the main contributor. Specifically, sewage (33.1%), C₃ plants (27.1%), and soil organic carbon (19.9%) were identified as the dominant sources. This research highlights the influence of human activities, such as urbanization and agriculture, on OC dynamics and underscores the role of reservoirs in regulating OC transport. The findings provide critical insights into the mechanisms of OC sequestration in agricultural watersheds and offer valuable guidance for water resource management and ecological protection strategies in mountainous environments.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143113770","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}