Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Abrupt Thaw in a Finnish Palsa: Potential CH4 Production Driven by Vegetation Adaptation in the Transition From Permafrost to Post-Thaw Soils","authors":"M. R. Baysinger,&nbsp;M. Laurent,&nbsp;M. Verdonen,&nbsp;J. Reif,&nbsp;T. Kumpula,&nbsp;S. Liebner,&nbsp;C. C. Treat","doi":"10.1029/2025JG008847","DOIUrl":"10.1029/2025JG008847","url":null,"abstract":"<p>Permafrost peatlands store substantial amounts of carbon, though persistence of this soil carbon is unknown in a rapidly warming Arctic. To investigate potential carbon production from soils at different stages of permafrost degradation, we incubated soils from a palsa mire in northern Fennoscandia. Three soil horizons from four thaw stages were included within the transect, beginning with intact permafrost and ending in an established post-thaw wetland. Samples were incubated anaerobically for a year at different temperatures (4°C, 20°C) with the aim of investigating drivers of carbon degradation rates. Additional subsamples from the intact palsa were incubated under aerobic conditions, or inoculated with thermokarst pond water to further explore thaw processes on soil. Total CO₂ and CH₄ produced ranged from 9,910 ± 626 (from the surface peat of the established post-thaw wetland, at 20°C) to 1,921 ± 126 μg C g⁻¹ DW (from the intermediate thaw stage of the palsa permafrost, incubated at 20°C). The CH₄ temperature sensitivity was markedly higher in permafrost soils, with <i>Q</i>₁₀<i>s</i> more than four times larger than that of the active layer (active layer average: 1.7 ± 1.6, permafrost average: 8.4 ± 5). Methanogenesis generally increased with thaw, but the largest increase of cumulative methane production was between the wetland thaw stages (from 633 to 2,880 μg CH₄-C g⁻¹ DW), where graminoids colonized the post-thaw environment. This uptick in CH₄ production 30+ years after post-thaw wetland establishment implies that increases in CH₄ production are largely due to vegetation inputs rather than thawed permafrost carbon contributions.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008847","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021984","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":"High-Resolution Satellite Data Improve Insights Into Landscape Fires and Their Drivers in Southeastern Africa","authors":"V. Fernández-García,&nbsp;L. N. Phelps,&nbsp;T. Strydom,&nbsp;P. J. Muando,&nbsp;J. Ranaivonasy,&nbsp;C. E. R. Lehmann,&nbsp;C. A. Kull","doi":"10.1029/2024JG008635","DOIUrl":"10.1029/2024JG008635","url":null,"abstract":"<p>High-resolution time series of burned area derived from Sentinel-2 can advance understanding of the determinants and dynamics of fire by incorporating small fires previously excluded from regional analyses. Here, we assessed the drivers of fire frequency, size, and seasonality across Southeastern Africa comparing fine (Sentinel-2 MSI) and moderate (MODIS) resolution data. Twenty-six predictors of ignition patterns, fuel load, flammability, and fire spread were incorporated into machine learning models to evaluate their predictive capacity, relative importance, and directional relationships with fire regime attributes. We found large differences between fine- and moderate-resolution estimates of fire frequency, size, and to a lesser extent seasonality. Models using Sentinel-2 showed better predictive performance than those using MODIS with <i>R</i>² values of 0.24 and 0.13, respectively, for fire frequency when validated in regions outside the training areas. However, the shapes of the relationship curves between fire regime attributes and predictors were generally consistent between sensors. High fire frequency was positively associated with fuel load and environmental seasonality, whereas low fire frequency was associated with interannual stability in land cover, livestock density, and human population. Fire sizes were generally small at both the high and low extremes of the precipitation and vegetation productivity gradient, as well as in highly transformed areas. The fraction of fire outside of the fire season was higher in low seasonality environments and under strong human influence. We demonstrate the general applicability of existing theory of fire dynamics derived via moderate-resolution fire data to fine-resolution data, while providing more nuanced insights into fire drivers.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008635","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145012630","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":"Island Size Modulates the Effects of Multiple Global Change Factors on Greenhouse Gas Emissions and Microbial Communities","authors":"Jawad Ali Shah,&nbsp;Hans J. De Boeck,&nbsp;Chunyu Yue,&nbsp;Sajid Ali,&nbsp;Jianping Wu","doi":"10.1029/2025JG009017","DOIUrl":"10.1029/2025JG009017","url":null,"abstract":"<p>Islands are the most vulnerable ecosystems to climate change, yet our understanding of how island soil reacts to multiple global change factors (GCFs) remains limited. This study investigated the impact of warming (W), drought (D), nitrogen addition (N), warming + drought (WD), warming + N addition (WN), N addition + drought (ND), and warming + N addition + drought (WND) on greenhouse gas (GHG) emissions and microbial communities in various subtropical island soils. The results showed that ecological stochasticity of multiple GCFs was strongly regulated by the island area. Drought and the combination of WD significantly reduced dissolved organic carbon and NO₃⁻-N concentrations in terrestrial and island soils. Moreover, the amount of soil microbial phospholipid fatty acids in terrestrial land was significantly increased by interactive treatments (<i>P</i> &lt; 0.05). The cumulative CO₂ emissions of WN and W significantly increased by 64.2% and 51.8%, respectively, whereas D reduced it by 49.2% in terrestrial soil relative to the control treatment (CK). In large islands, drought led to an increase in CO₂ emissions by 90% (<i>P</i> &lt; 0.05). In the medium and small islands, warming and the combination of WN led to higher CO₂ emissions. Regarding N₂O, the terrestrial site acted as a sink (except for WN), whereas islands were N₂O sources. Island size directly affected various GHG emissions, while indirect effects modulated these fluxes through soil properties and microbial communities. Collectively, this study empirically demonstrate that concurrent global changes can lead to directional alterations of soil properties, GHG emissions, and microbial communities in island soils.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998798","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":"Diverse Cooccurring Metabolisms Support Sulfur and Methane Cycling in Wetland Surficial Sediments","authors":"Emily K. Bechtold,&nbsp;Danhui Xin,&nbsp;Maricia Pacheco,&nbsp;Brandy M. Toner,&nbsp;William A. Arnold,&nbsp;Yu-Ping Chin,&nbsp;Michael J. Wilkins","doi":"10.1029/2024JG008478","DOIUrl":"10.1029/2024JG008478","url":null,"abstract":"<p>The Prairie Pothole Region (PPR) of North America contains millions of small depressional wetlands with some of the highest methane (CH₄) fluxes ever reported in terrestrial ecosystems. In saturated soils, two conventional paradigms are (a) methanogenesis is the final step in the redox ladder, occurring only after more thermodynamically favorable electron acceptors (e.g., sulfate) are reduced, and (b) CH₄ is primarily produced by acetoclastic and hydrogenotrophic pathways. However, previous work in PPR wetlands observed co-occurrence of sulfate-reduction and methanogenesis and the presence of diverse methanogenic substrates (i.e., methanol, DMS). This study investigated how methylotrophic methanogenesis—in addition to acetoclastic and hydrogenotrophic methanogenesis—significantly contributes to CH₄ flux in surface sediments and thus allows for the co-occurrence of competing redox processes in PPR sediments. We addressed this aim through field studies in two distinct high CH₄ emitting wetlands in the PPR complex, which coupled microbial community compositional and functional inferences with depth-resolved electrochemistry measurements in surficial wetland sediments. This study revealed methylotrophic methanogens as the dominant group of methanogens in the presence of abundant organic sulfate esters, which are likely used for sulfate reduction. Resulting high sulfide concentrations likely caused sulfide toxicity in hydrogenotrophic and acetoclastic methanogens. Additionally, the use of non-competitive substrates by many methylotrophic methanogens allows these metabolisms to bypass thermodynamic constraints and can explain co-existence patterns of sulfate-reduction and methanogenesis. This study demonstrates that the current models of methanogenesis in wetland ecosystems insufficiently represent carbon cycling in some of the highest CH₄ emitting environments.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008478","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144998779","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":"Role of Aquatic Plants in Carbon Dioxide Exchange Between the Littoral Zone of a Eutrophic MidLatitude Lake and the Atmosphere","authors":"R. Okunishi,&nbsp;H. Iwata,&nbsp;Y. Ochiai,&nbsp;M. Yamada,&nbsp;H.-D. Park","doi":"10.1029/2025JG009029","DOIUrl":"10.1029/2025JG009029","url":null,"abstract":"<p>Inland water is a crucial component of the land-atmosphere carbon exchange. The role of aquatic plants in carbon dioxide (CO₂) exchange has been understudied, and few studies have considered their influence on diel variation. This study analyzed 2 years of eddy covariance CO₂ flux data obtained in the littoral zone of a eutrophic midlatitude lake with differing aquatic plant cover. In the summer of 2022, when floating-leaved plants were abundant, marked CO₂ uptake was observed during the day, whereas in the summer of 2020, with minimal floating-leaved plant cover, daytime uptake was less pronounced. When averaged, the maximum CO₂ uptake occurred in the afternoon in the summer of 2020, when CO₂ exchange at the air-water interface likely dominated the total exchange, and uptake was enhanced due to a high gas transfer velocity and presumably low dissolved CO₂ concentrations in the afternoon. By contrast, CO₂ uptake reached a maximum around noon in the summer of 2022, in phase with solar radiation. The leaves of plants protruded into the air, and direct uptake, due to the leaf photosynthesis, likely caused the cooccurrence of the peak CO₂ uptake and solar radiation. The estimated annual CO₂ exchange was 14 ± 7 gC m⁻² in 2020 and −170 ± 4 gC m⁻² in 2022. This study found that the abundance of aquatic plants determined the diel environmental dependence of the summer CO₂ exchange in the littoral zone of a midlatitude lake, as well as the magnitude and direction of the annual CO₂ exchange.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009029","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929514","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":"Evapotranspiration Sensitivity to Environmental Variability Provides a Window Into Subsurface Processes in the Soil-Plant-Atmosphere Continuum","authors":"Christopher L. Kibler,&nbsp;Gregory R. Quetin,&nbsp;Anna T. Trugman","doi":"10.1029/2025JG009097","DOIUrl":"10.1029/2025JG009097","url":null,"abstract":"<p>Evapotranspiration (ET) is co-regulated by subsurface water availability, atmospheric demand for water, and radiation. Spatial differences in the limiting factors on ET that emerge along the soil-plant-atmosphere continuum result in distinct ecohydrological regimes with differing sensitivities to atmospheric and subsurface drivers. However, different components of the soil-plant-atmosphere continuum are not equally well understood. Deep subsurface water access is particularly difficult to measure and model, but can sustain ET under drought conditions when shallow soil moisture appears to be acutely limiting. Here, we exploited this principle to identify ecosystems that rely on deep subsurface water availability. We first used a plant hydraulic model to determine the expected ET behavior for plants with deep water access. We then examined 19 flux towers and found that responsiveness of ET to atmospheric conditions during dry periods was indicative of some ecosystems with deep water access. We used the divergent sensitivities of ET to vapor pressure deficit, radiation, and shallow soil moisture to identify distinct ecohydrological regimes in gridded data covering the continental U.S. We diagnosed deep water usage in ecosystems where ET remained sensitive to atmospheric conditions despite being insensitive to shallow soil moisture variability. Further, we found that drought stress, plant hydraulic traits, and ecosystem biophysical variables mediated the sensitivity of ET to aboveground and belowground conditions.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144923756","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":"Genome-Resolved Metagenomic Insights Into Aquifer Microbiome Adaptations Following Two Decades of Neutral In Situ Leaching","authors":"Guoxi Lian,&nbsp;Tianjing Zhang,&nbsp;Yifu An,&nbsp;Huiying Xu,&nbsp;Juan Sun,&nbsp;Ran Yin,&nbsp;Zhenyao Shen,&nbsp;Huaming Guo,&nbsp;Till L. V. Bornemann,&nbsp;Alexander J. Probst,&nbsp;Wei Xiu","doi":"10.1029/2024JG008587","DOIUrl":"10.1029/2024JG008587","url":null,"abstract":"<p>Neutral in situ leaching (ISL) is a prominent technique for extracting uranium (U) from sandstone-type U deposits. However, the intricate biogeochemical processes and associated microbial communities in environments subjected to prolonged neutral <i>in situ</i> U leaching remain insufficiently understood. Here, capitalizing on groundwater samples collected from an area subjected to two decades of ISL (Undergoing-ISL) and a background aquifer (Non-ISL) at the Qianjiadian U mining site (the first CO₂ + O₂ ISL site located in the Songliao Basin of northern China), we investigate the responses of aquifer microbiomes to CO₂ + O₂ ISL using genome-resolved metagenomics, resulting in a total of 315 medium- and high-quality bacterial metagenome-assembled genomes (MAGs) and 5 archeal genomes. Seven putative keystone MAGs were identified based on their high connection degree and low betweenness centrality within the co-occurrence network of reconstructed MAGs, notably highlighting the prevalence of microorganisms involved in sulfur, ammonium, and Fe(II) oxidation, which are integral to facilitating U(IV) oxidation during CO₂ + O₂ ISL. In particular, sulfur-oxidizing bacteria and Fe(II)-oxidizing bacteria (<i>Rhodoferax</i> spp. and <i>SHZL01</i> spp.) played a key role in U mobilization during long-term neutral ISL. These findings enhance our understanding of subsurface microbial ecology and hold significant implications for bioremediation strategies and groundwater management in regions affected by mining.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144918835","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":"Midday Depression of Photosynthesis in Spartina alterniflora in a Virginia Salt Marsh","authors":"H. M. Mast,&nbsp;X. Yang","doi":"10.1029/2024JG008338","DOIUrl":"10.1029/2024JG008338","url":null,"abstract":"<p>Salt marshes sequester a disproportionately large amount of carbon dioxide (CO₂) from the atmosphere through high rates of photosynthesis and carbon burial. Climate change could potentially alter this carbon sink, particularly the response of vegetation to environmental stressors that can decrease photosynthesis. Midday depression of gross primary production (GPP), characterized by a decline in photosynthesis during midday, has been documented in multiple ecosystems as a response to drought, high temperatures, and other stressors linked to climate change. Yet, midday depression has not been thoroughly investigated in salt marsh ecosystems. Here, we show that the midday depression of GPP in a <i>Spartina alterniflora</i> salt marsh on the Eastern Shore of Virginia was ubiquitous and occurred on 76% of the 283 days studied during the 2019–2022 growing seasons. GPP was estimated from eddy covariance measurements with flux partitioning. Using random forest, we found that the daily maximum tidal height and air temperature were the strongest predictors of midday depression of GPP, with lower high tides and warmer temperatures associated with more severe depression. This result suggests midday depression occurs when GPP decreases in the afternoon in response to salinity and water stress. To our knowledge, this is the first examination of midday depression of photosynthesis in <i>S</i>. <i>alterniflora</i> at the ecosystem scale. Our results highlight the potential of climate change to increase midday depression of photosynthesis and ultimately weaken the salt marsh carbon sink.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008338","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144918848","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":"Increasing Microbial Carbon Use Efficiency With Elevation Depending on Growth and Respiration Differently Between Topsoils and Subsoils","authors":"Gang Huang,&nbsp;Yan-gui Su","doi":"10.1029/2025JG009148","DOIUrl":"10.1029/2025JG009148","url":null,"abstract":"<p>Microbial carbon use efficiency (CUE) is a key regulator of soil carbon sequestration and nutrient cycling. However, how microbial growth, respiration, and CUE respond to elevation gradients—particularly across soil depths—remains unclear. In this study, we quantified microbial CUE, growth, and respiration using the ¹⁸O–H₂O labeling method in both topsoil (0–20 cm) and subsoil (20–40 cm) along an elevation transect in a tropical montane forest. Microbial growth and CUE increased with elevation, while microbial respiration declined in the topsoil but exhibited no consistent pattern in the subsoil. The elevational pattern of microbial CUE was coregulated by growth and respiration in the topsoil, whereas it was predominantly driven by growth in the subsoil. Microbial CUE was negatively correlated with biomass-specific carbon-, nitrogen-, and phosphorus-acquiring enzyme activities, suggesting that lower nutrient acquisition investment facilitates more efficient carbon utilization. Furthermore, CUE was negatively associated with the enzymatic C:P ratio in the topsoil but positively in the subsoil, indicating that enhanced CUE with elevation results from the stronger alleviation of carbon and phosphorus limitations, respectively. Overall, our results reveal that while microbial CUE consistently increases with elevation across soil profiles, its underlying controls differ fundamentally between topsoil and subsoil.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144915310","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":"Drought Response in Three Conifer Species Detected by Sap Flow and Proximal Thermal Remote Sensing","authors":"Daphna Uni,&nbsp;Russell L. Scott,&nbsp;Mostafa Javadian,&nbsp;Joel Biederman,&nbsp;Matthew P. Dannenberg,&nbsp;William K. Smith","doi":"10.1029/2025JG009127","DOIUrl":"10.1029/2025JG009127","url":null,"abstract":"<p>Dryland forests of the southwest United States face a warming and changing hydroclimate, yet our ability to monitor and predict vegetation-drought dynamics over large regions remains limited. Here, we examine drought responses and predictability of sap flow for three species (Douglas fir, ponderosa pine, and southwestern white pine) over two consecutive years. We collected tree-scale sap flow velocity and evaluated its relationship with soil water content (SWC) and vapor pressure deficit (VPD). Next, we identified the soil moisture threshold beyond which sap flow was no longer limited by SWC. We also assessed whether proximal remote sensing of canopy temperature and canopy-to-air temperature difference (ΔT) can capture ecosystem-scale drought response dynamics. Significant sap flow reductions occurred in response to drought periods, but sap flow quickly recovered following large rainfall events. When SWC was below a threshold of ∼7% (cm³/cm³), SWC and sap flow were positively correlated, indicating water-limited conditions, while above this threshold, only VPD and sap flow were positively related, indicating atmospheric demand limited conditions. Species differences were minor, but ponderosa pine sap flow responded most rapidly to soil dehydration. ΔT was significantly correlated with sap flow, but the relationship switched from positive (<i>R</i> = 0.73−0.94) during the pre- and post-monsoon to negative during the monsoon (<i>R</i> = −0.31−0.48). This shift likely reflects a transition from soil moisture supply to atmospheric demand limitation during wetter periods. These findings highlight the potential of combining tree-scale sap flow measurements with thermal remote sensing to enhance understanding of vegetation-drought dynamics in dryland forests.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144915312","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}