Agricultural and Forest Meteorology最新文献

{"title":"Revealing future changes in China’s forest fire under climate change","authors":"Guanglei Li ,&nbsp;Jiaying Hai ,&nbsp;Jiazheng Qiu ,&nbsp;Danni Zhang ,&nbsp;Chang Ge ,&nbsp;Hongliang Wang ,&nbsp;Jiansheng Wu","doi":"10.1016/j.agrformet.2025.110609","DOIUrl":"10.1016/j.agrformet.2025.110609","url":null,"abstract":"<div><div>Forest fires, driven by global change, have become an increasingly severe concern for the future. To mitigate this uncertainty, understanding the projected response patterns of forest fires under climate change can provide valuable insights, especially in regions like China, where forest fires are prone to occur and highly sensitive to climate variations. This study used the Random Forest algorithm to develop predictive models for occurrence probability, intensity levels, and burned area of forest fires in China. These models were applied to future climate simulations under SSP1–2.6, SSP2–4.5, and SSP5–8.5 scenarios, providing predictions for the mid-term (2041–2060) and long-term (2081–2100) periods with a comparative analysis against the baseline period (2001–2020) to assess relative changes. Results show that, by the end of the century, 60 % to 70 % of forested areas in China are projected to face increased fire risk, with the average percentage increase not exceeding 20 %, and most low-risk areas remaining at low risk. Nevertheless, the transition to moderate or high fire risk is particularly significant in the long term under SSP5–8.5, with hotspots such as the Greater Khingan Mountains, central and southeastern hilly regions, and the gorges of the western Yunnan Plateau. While fire intensity in most fire-prone areas is projected to remain at medium-to-low levels, localized intensification is possible in southwestern China. The increase in burned areas is projected to be widespread, covering 63 % to 64 % of fire-prone areas, with the greatest growth occurring in the mid-term and under SSP5–8.5. Compared to the southern regions, northeastern China shows a smaller proportion of areas experiencing increased burned areas but a larger total increase, indicating more concentrated fires in specific areas. These findings reveal the distinct future trajectories of different forest fire characteristics with regional variability in China, offering critical information for their comprehensive consideration and integration into forward-looking, scientifically robust national fire prevention planning.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110609"},"PeriodicalIF":5.6,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144108023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Age-dependent moisture response of conifers near their cold range limit","authors":"Jan Tumajer ,&nbsp;Grudd Håkan ,&nbsp;Jernej Jevšenak ,&nbsp;Andreas J. Kirchhefer ,&nbsp;Francesco Marotta ,&nbsp;Jiří Mašek ,&nbsp;Kiara Maria Nowatzki ,&nbsp;Nikolaus Obojes ,&nbsp;Markus Stoffel ,&nbsp;Václav Treml ,&nbsp;Jelena Lange","doi":"10.1016/j.agrformet.2025.110634","DOIUrl":"10.1016/j.agrformet.2025.110634","url":null,"abstract":"<div><div>Growth dynamics of cold subarctic and subalpine forests are primarily sensitive to temperature, but growth responses may vary across regions or shift over tree ontogeny. Systematic assessments of spatial, interspecific, and demographic variation in temperature and moisture limitation of tree growth at cold distribution margins are essential for enhancing our understanding of how these ecosystems will evolve under climate regimes. To address this gap, we built a network of 22 tree-ring width chronologies from cold forests covering two regions (Fennoscandia, European Alps), three species (<em>Pinus sylvestris, Pinus cembra, Larix decidua</em>), and two age cohorts (45–100 and &gt;150 years). We combined daily climate-growth correlations with the process-based Vaganov-Shashkin growth model to identify differences in critical growth factors between species and age cohorts. In addition, we assessed the coincidence of unusually wide and narrow tree rings with years of specific climatic anomalies. Although growing season temperature was the dominant growth-limiting factor, seasonal effects of water balance on tree growth were considerably large and varied systematically between regions, species, and particularly age cohorts. The growth of young <em>P. sylvestris</em> in Fennoscandia responded negatively to water balance and narrow rings coincided with wet years. In contrast, the growth of young <em>P. cembra</em> in the Alps was drought-limited. Old trees of all species and both age cohorts of L. <em>decidua</em> in the Alps showed limited sensitivity to water balance. The patterns of climate-growth responses in cohort chronologies based on tree age at the year of coring were similar to ontogenetic shifts of climate-growth responses if chronologies were based on the cambial age of individual rings. Our results stress the need to account for interspecific and demographic differences in sensitivity to climate in large-scale studies of cold forest ecosystems.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110634"},"PeriodicalIF":5.6,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144115712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Historical trends and future projections of compound cloudy-rainy events during the global winter wheat harvest phase","authors":"Xuan Gao ,&nbsp;Jinwei Dong ,&nbsp;Sha Zhou ,&nbsp;Fulu Tao ,&nbsp;Dongsheng Zhao ,&nbsp;Xi Zhang ,&nbsp;Qiang Zhang ,&nbsp;Ziwei Chen ,&nbsp;Quansheng Ge","doi":"10.1016/j.agrformet.2025.110637","DOIUrl":"10.1016/j.agrformet.2025.110637","url":null,"abstract":"<div><div>Compound cloudy-rainy events (CCREs), characterized by prolonged rainfall and extensive cloud cover, when occurring during the harvest phase, could adversely affect the drying, harvesting, and transportation of mature grains, and even lead to grain mold and sprouting. However, existing studies have focused more on the growth phases, while trends in CCREs during the harvest phase have been largely undocumented. Here we investigated the spatial-temporal variations of CCREs during the harvest phase of winter wheat globally for the historical (1985–2022) and future (2015–2074) periods. Our results reveal a significant decrease in CCREs during the winter wheat harvest phase on a global scale across the two periods. Spatially, reduced cloudy-rainy days cover about 60 % of the winter wheat-producing area. Additionally, the trend patterns of CCREs exhibit considerable spatial heterogeneity. Specifically, pronounced increases are primarily located in eastern North America, western Europe, and eastern Asia, where agricultural mechanization levels are higher. Meanwhile, the asynchronous trends between cloudy days and rainy days lead to spatial variability in the underlying causes of the observed increases in CCREs across these regions. Overall, the results of this study provide novel insights into agricultural climate mitigation and adaptation for global food security.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110637"},"PeriodicalIF":5.6,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soil moisture thresholds at progressive mortality stages of larch plantations in the northwest China","authors":"Yanfang Wan ,&nbsp;Pengtao Yu ,&nbsp;Yushi Bai ,&nbsp;Yanhui Wang ,&nbsp;Jiamei Li ,&nbsp;Yipeng Yu ,&nbsp;Zebin Liu ,&nbsp;Xiao Wang ,&nbsp;Lihong Xu","doi":"10.1016/j.agrformet.2025.110638","DOIUrl":"10.1016/j.agrformet.2025.110638","url":null,"abstract":"<div><div>Increasing drought stress due to climate warming has triggered various negative impacts on plantations in dryland areas, including growth reduction, crown dieback, and even tree mortality, with unavoidable consequences for forest ecosystems. However, how drought stress progressively led to the damage process from growth reduction to mortality for mature trees remains largely unclear, especially its varying soil moisture thresholds. Here we selected mature trees in larch (<em>Larix principis-rupprechtii</em>) plantations in the dryland areas of northwest China, and monitored the progressive tree responses in an extreme summer drought event in 2021, including transpiration, radial growth, leaf area index, discoloration, defoliation, crown dieback and tree mortality. The results showed strong responses of larch trees to summer drought, such as large stem shrinkage, dramatic decrease in transpiration and leaf area index, and obvious discoloration, defoliation, crown dieback and tree mortality at some sites. The intensity of tree responses mainly depended on soil moisture rather than meteorological factors and there were strong relationships between tree responses and relative soil water content (RSW) of 0–60 cm layers. Based on the trees responded to RSW, five soil drought stress levels or progressive mortality stages and their corresponding RSW thresholds were determined as following: no detectable hydraulic limitations (RSW&gt;0.7, Level I), persistent stem shrinkage and onset of transpiration reduction (0.45&lt;RSW≤0.7, Level II), onset of slight discoloration and defoliation (0.35&lt;RSW≤0.45, Level III), onset of crown dieback and tree mortality (0.25&lt;RSW≤0.35, Level IV), and severe defoliation, crown dieback and tree mortality (RSW≤0.25, Level V). This study showed that the trees responded to climatic drought were strongly regulated by soil moisture and thus were strongly site-specific. These findings will help to evaluate the degree and spatio-temporal distribution of tree damage and mortality in plantations under increasing climatic drought, particularly in dryland areas.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110638"},"PeriodicalIF":5.6,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantification and comparison of prediction uncertainty associated with different practices of crop modeling","authors":"Yujing Gao ,&nbsp;Daniel Wallach ,&nbsp;Baojing Gu ,&nbsp;Liang Tang ,&nbsp;Tao Lin ,&nbsp;Xini Chang ,&nbsp;Toshi Hasegawa ,&nbsp;Senthold Asseng ,&nbsp;Tamer Kahveci ,&nbsp;Gerrit Hoogenboom","doi":"10.1016/j.agrformet.2025.110633","DOIUrl":"10.1016/j.agrformet.2025.110633","url":null,"abstract":"<div><div>Crop models are widely used as decision support tools in agriculture and natural resource management. However, the current practices in crop modeling and evaluation vary significantly, making it challenging to compare uncertainties across different models and studies. This study aims to quantify and compare the uncertainties associated with four different crop modeling practices using a standardized evaluation framework. The four modeling practices are: 1) using a single model, considering only model bias for uncertainty; 2) using a single model, accounting for both model bias and parameter uncertainty; 3) employing a multi-model ensemble to account for model bias, parameter uncertainty, and structural uncertainties; and 4) using a multi-model ensemble to consider uncertainties induced by model bias, parameters, structures, and inputs. We developed a framework that integrates Markov Chain Monte Carlo (MCMC) and Bayesian Model Averaging (BMA) to consistently quantify prediction uncertainty across these practices. The framework was applied to an Asian rice dataset. The results revealed that common model evaluation approach (Practice 1) tends to underestimate the uncertainty of model predictions. Relying on a single process-based model presents a substantial risk in critical decision-making situations. In contrast, the BMA ensemble predictor (<em>e-BMA</em>) demonstrated higher reliability, making it a preferable choice for future decision support. Our Bayesian framework provides a more robust and adaptable approach for project-specific decision-making, with promising applications in digital agriculture.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110633"},"PeriodicalIF":5.6,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of forest canopy structure on temperature buffering in young planted forests with varied tree species compositions revealed by terrestrial laser scanning","authors":"Mengxi Wang ,&nbsp;Haben Blondeel ,&nbsp;Loïc Gillerot ,&nbsp;Hans Verbeeck ,&nbsp;Frieke Van Coillie ,&nbsp;Félicien Meunier ,&nbsp;Shengmin Zhang ,&nbsp;Pieter De Frenne ,&nbsp;Kris Verheyen ,&nbsp;Kim Calders","doi":"10.1016/j.agrformet.2025.110640","DOIUrl":"10.1016/j.agrformet.2025.110640","url":null,"abstract":"<div><div>Forest structure mediates below-canopy temperatures, creating unique microclimates for forest organisms. However, the understanding of how intricate forest canopy structure affect below-canopy air temperatures remains incomplete, especially in early-stage planted forests. Additionally, conventional forest structure metrics lack detailed structural information. We used 156 Terrestrial Laser Scanning single scans from 39 plots in a tree diversity experiment located at Zedelgem, Belgium, to explore how tree diversity and canopy structure affect below-canopy temperature. Five site-adapted species were planted, with plots varying in tree species richness from monocultures to four-species mixtures across twenty composition levels. Vertical plant profiles were derived from four scan locations per plot, allowing for the calculation of four variables to describe various aspects of forest canopy structure: foliage height diversity, total plant area index, canopy height, and canopy openness. Our findings showed that below-canopy temperature buffering was stronger in summer than in winter, with pine proportion dominating the buffering effect. Although canopy structure explained a small portion of the variance, it showed notable buffering potential, with summer cooling associated with low canopy openness and winter warming linked to high foliage height diversity and low canopy openness. Moreover, the community weighted mean specific leaf area, as an indirect proxy for transpiration potential, demonstrated strong summer cooling. Our findings suggest that local forest management strategies focused on temperature buffering should consider increasing pine proportions, as they enhance the buffering capacity in early forest development. As the forest matures, the advantages of a more diverse and denser canopy may become more apparent.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110640"},"PeriodicalIF":5.6,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature-driven shifts in spatiotemporal stability of climate-growth responses of Douglas-fir (Pseudotsuga menziesii) from the southern Baltic Sea region","authors":"Marcin Klisz ,&nbsp;Radosław Puchałka ,&nbsp;Mariusz Gławenda ,&nbsp;Marcin Koprowski ,&nbsp;Roberts Matisons ,&nbsp;Sandra Metslaid ,&nbsp;Aleksei Potapov ,&nbsp;Tobias Scharnweber ,&nbsp;Eric Andreas Thurm ,&nbsp;Rita Verbylaite ,&nbsp;Adomas Vitas ,&nbsp;Martin Wilmking ,&nbsp;Jernej Jevšenak","doi":"10.1016/j.agrformet.2025.110628","DOIUrl":"10.1016/j.agrformet.2025.110628","url":null,"abstract":"<div><div>The southern Baltic region spans a significant part of the European continent with its forests under significant pressure due to climate changes. The implications of these changes are crucial for both native and non-native tree species. Under future climate scenarios, most native conifer populations might lose their climatic optima in the region. In contrast, for non-native Douglas-fir (<em>Pseudotsuga menziesii</em> (Mirb.) Franco), climatic conditions are expected to become optimal in the Baltic Sea region. Therefore, understanding the acclimatisation trajectory of Douglas-fir over the last century is essential to assess its potential to supplement retreating species and reduce pressure on local habitats. To study the region-wide acclimatisation in the secondary distribution, we established a network of 27 Douglas-fir tree-ring chronologies along the south Baltic Sea. We determined the spatio-temporal stability of the climate signal in tree rings and the potential coastal effect on the plasticity of the growth response. We found a region-wide trend of climate-growth relationships, with a dominant effect of the early-growth season temperatures being more pronounced for mature than young stands. Sites with higher mean annual temperatures exhibit a stronger positive temperature–growth correlation, demonstrating the sensitivity of Douglas-fir to climate warming. Douglas-fir could serve as a more heat-tolerant alternative to the declining European species of the Pinaceae family and contribute to the preservation of functionally comparable coniferous forest communities. However, forest practitioners should be aware that Douglas-fir may alter habitat conditions affecting microclimate and influencing species diversity.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110628"},"PeriodicalIF":5.6,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A combined effect of heat and drought limits the growth of Central European silver fir","authors":"Peter Marcis ,&nbsp;Jaroslav Vido ,&nbsp;Daniel Kurjak ,&nbsp;Adriana Lestianska ,&nbsp;Dominik Poltak ,&nbsp;Jergus Rybar ,&nbsp;Michal Bosela","doi":"10.1016/j.agrformet.2025.110610","DOIUrl":"10.1016/j.agrformet.2025.110610","url":null,"abstract":"<div><div>Prolonging drought periods and more extreme heatwaves limit tree species adaptation to environmental changes. Silver fir (<em>Abies alba</em>, Mill.) has been considered one of the species suitable for forest ecosystem adaptation and mitigation strategies in future climate conditions. Here, we present a dendroecological study of the joint effects of droughts and heatwaves on the radial growth of silver fir. We sampled tree-ring width series of 105 dominant individuals collected between 2016 and 2019 across the region of Western Carpathians on the elevational gradient of 200 – 1480 m a.s.l. The results suggest a rapid growth decline (∼1.00 cm².year^-1) of dominant individuals since the mid-1990s compared to the growth release during the 1980′s. A combined approach of absolute and relative temperature thresholds for heatwave quantification revealed a more frequent combination of severe heatwaves and droughts after 2000, especially in the lower and middle parts of the elevation gradient. Furthermore, we found an increasingly negative joint effect of drought and heatwaves on the growth of silver fir. We revealed statistically significant (<em>p</em> &lt; 0.05) growth reduction (&gt;25 %) during years with the joint effect of severe droughts and severe heatwaves on both the upper and lower edges of silver fir’s vertical distribution. Individuals growing at higher elevations experienced a significant growth reduction at a lower absolute temperature threshold (∼30 °C) compared to individuals growing in the lower parts of the Western Carpathians, where this reduction occurred at a higher absolute temperature threshold (∼35 °C). Our findings reveal heatwaves as an important ecological factor that should be considered in future dendroecological studies.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110610"},"PeriodicalIF":5.6,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144088656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The sequence of physiological stress thresholds responses to drought in a temperate mixed forest","authors":"Rui Zhang ,&nbsp;Chuankuan Wang ,&nbsp;Ruibing Duan ,&nbsp;Lele Wang ,&nbsp;Ying Jin","doi":"10.1016/j.agrformet.2025.110635","DOIUrl":"10.1016/j.agrformet.2025.110635","url":null,"abstract":"<div><div>Predicting the influence of worldwide drought on forests remains constrained by lacking of mechanistic understanding of trait interactions in defining physiological dysfunction under water stress, particularly with respect to the interaction between plant stomatal regulation and hydraulics. In this study, we investigated key stomatal and hydraulic traits of leaves and stems for 17 temperate woody species in northeastern China. We found that the stomatal closure point (the water potential at 88 % loss of maximum stomatal conductance) was positively correlated with the water potentials at leaf turgor loss, stem hydraulic conductivity, and 50 % loss of stem hydraulic conductivity. The 50 % loss of leaf hydraulic conductance of all studied species occurred before 50 % stem embolism, in agreement with the vulnerability segmentation hypothesis. Almost all studied tree species reached complete stomatal closure before 50 % stem embolism, but after the 50 % loss of leaf hydraulic conductance. Collectively, the observed sequence of water potential for key physiological dysfunctions not only facilitates carbon assimilation for as long as possible, but also helps to avoid substantial loss of the hydraulic function in woody stems with high construction costs. The interactions between stomatal regulation and multiple hydraulic traits may scale up to influence the water use of whole plants.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110635"},"PeriodicalIF":5.6,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144088921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isotopic disequilibrium of the retro-diffusive CO2 efflux affects photosynthetic C18OO discrimination and the estimation of mesophyll conductance","authors":"Sui Min Huang ,&nbsp;Jérôme Ogée ,&nbsp;Xiao Ying Gong ,&nbsp;Wei Ting Ma ,&nbsp;Lei Li ,&nbsp;Xuming Wang ,&nbsp;Hans Schnyder ,&nbsp;Rudi Schäufele","doi":"10.1016/j.agrformet.2025.110636","DOIUrl":"10.1016/j.agrformet.2025.110636","url":null,"abstract":"<div><div>Photosynthetic C¹⁸OO fractionation (Δ¹⁸O) has been used to estimate mesophyll conductance (<em>g</em>_m) in C₃ and C₄ species. However, this requires knowledge of the degree of isotopic equilibration (θ_r) between leaf water and the CO₂ molecules penetrating the leaf interior and re-escaping without being assimilated (<em>F</em>_retro). Here, we re-examine the theory of Δ¹⁸O-<em>g</em>_m estimation and its sensitivity to changes in the ¹⁸O composition (δ¹⁸O) of CO₂ on young and old leaves of six C₃ species. Our results showed that, when full isotopic equilibrium was assumed, <em>g</em>_m values were sensitive to the δ¹⁸O of the CO₂ sources. Utilizing a new isotopic mass balance model that distinguishes metabolic (<em>R</em>_t) and purely diffusive (<em>F</em>_retro) CO₂ fluxes, we found that the gross H₂O-equilibrated efflux (θ_r<em>F</em>_retro+<em>R</em>_t) represented 157±12 % (mean±SE) of net CO₂ assimilation, and was positively correlated to stomatal conductance, implying a limitation imposed by stomata. Furthermore, leaf water was not completely in equilibrium with <em>F</em>_retro (θ_r&lt;1) or the CO₂ pool at the site of hydration (θ&lt;1), which led to errors in estimated <em>g</em>_m. Our results have broad implications for the interpretation of Δ¹⁸O in terms of mesophyll conductance, and highlight the necessity of considering the isotopic disequilibrium of the retro-diffusive CO₂ efflux.</div></div>","PeriodicalId":50839,"journal":{"name":"Agricultural and Forest Meteorology","volume":"371 ","pages":"Article 110636"},"PeriodicalIF":5.6,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144088920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}