Articles | Volume 20, issue 19
https://doi.org/10.5194/bg-20-4087-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-20-4087-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
06 Oct 2023
Research article |
| 06 Oct 2023
| 06 Oct 2023
A modeling approach to investigate drivers, variability and uncertainties in O2 fluxes and O2 : CO2 exchange ratios in a temperate forest
Bioclimatology, University of Göttingen, 37077 Göttingen, Germany
Anne Klosterhalfen
Bioclimatology, University of Göttingen, 37077 Göttingen, Germany
Fernando Moyano
Bioclimatology, University of Göttingen, 37077 Göttingen, Germany
Matthias Cuntz
Université de Lorraine, AgroParisTech, INRAE, UMR Silva, 54000
Nancy, France
Andrew C. Manning
Centre for Ocean and Atmospheric Sciences, School of Environmental
Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
Alexander Knohl
Bioclimatology, University of Göttingen, 37077 Göttingen, Germany
Centre of Biodiversity and Sustainable Land Use (CBL), University of
Göttingen, 37073 Göttingen, Germany
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EGUsphere, https://doi.org/10.5194/egusphere-2026-4223, https://doi.org/10.5194/egusphere-2026-4223, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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Land surface models (LSMs) are essential tools to analyze future climate change. Here we pushed state-of-the-art LSMs out of their comfort zone revealing hidden connections between processes encoded into the models. The LSMs reacted differently due to complex, sometimes counter-intuitive interactions of different water fluxes. We identified surface runoff and soil evaporation as the two main reasons behind model differences, which should be improved by using more mechanistic descriptions.
Ida Bagus Mandhara Brasika, Pierre Friedlingstein, Stephen Sitch, Michael O'Sullivan, Maria Carolina Duran-Rojas, Emma W. Littleton, Toby R. Marthews, Timothy Hill, Wei Li, Yidi Xu, Jiaxin Zhou, Xiangzhong Luo, Ruiying Zhao, Yuanchao Fan, Dedy Sukmara, Timer Manurung, Masayuki Kondo, Alexander Knohl, Tejaswini Jaajpera, and Lisma Safitri
EGUsphere, https://doi.org/10.5194/egusphere-2026-3689, https://doi.org/10.5194/egusphere-2026-3689, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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Oil palm is a major crop in Indonesia, but climate models often treat it as generic cropland. We developed a new way to represent oil palm in the Joint UK Land Environment Simulator. This improved how the model captures carbon stored and released by oil-palm plantations. The work helps estimate emissions from land-use change more realistically, supporting better understanding of tropical agriculture, deforestation and climate impacts.
John D. Marshall, Maren Dubbert, Teresa E. Gimeno, Ruth-Kristina Magh, Kathrin Kühnhammer, David Dubbert, Paul Koeniger, Matthias Cuntz, and Matthias Beyer
Hydrol. Earth Syst. Sci., 30, 4757–4770, https://doi.org/10.5194/hess-30-4757-2026, https://doi.org/10.5194/hess-30-4757-2026, 2026
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Water transport in forest soils occurs both vertically and horizontally. We added a stable isotope label to a small forest plot and monitored its passage vertically into the soil and horizontally into stems of surrounding trees. The labelled water was detected in the upper layers of the soil and in trees up to 6.7 m away, but was mostly taken up by one tree adjacent to the plot. These results affect how we think about summing over individual trees to describe the water economy of a whole forest.
Emmal Safi, Joe Pitt, Grant Forster, Chris Rennick, Simon O’Doherty, Dickon Young, Kanokrat Charoenpornpukdee, Nick Garrard, Dafina Kikaj, Andrew Manning, Gerard Spain, Damien Martin, Morgan Lopez, Michel Ramonet, and Kieran Stanely
EGUsphere, https://doi.org/10.5194/egusphere-2026-1802, https://doi.org/10.5194/egusphere-2026-1802, 2026
This preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).
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We compared whole and synthetic-air reference materials (RMs) for investigating offsets in greenhouse gas measurements so data from different sites/networks can be trusted when combined. By sending whole and synthetic-air (RMs) to six sites and measuring under routine field conditions, we found whole-air gives the most precise results, especially for carbon dioxide and nitrous oxide. Synthetic-air worked fairly well for methane but synthetic-air RMs needs lower uncertainty before wide use.
Julia Kelly, Tim Schacherl, Lars Eklundh, Hongxiao Jin, Anne Klosterhalfen, Alexander Knohl, and Natascha Kljun
EGUsphere, https://doi.org/10.5194/egusphere-2026-1822, https://doi.org/10.5194/egusphere-2026-1822, 2026
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It is vital to monitor drought-related reductions in forest productivity over large areas. We tested the ability of 12 satellite variables to capture negative drought impacts on forest productivity across 18 European forest sites. Surface temperature worked best across all forest sites and droughts. After drought, forest productivity recovered faster than some commonly-used satellite variables, meaning use of these variables may underestimate forests’ resilience to drought.
Biplob Dey, Toke Due Sjøgren, Peeyush Khare, Georgios I. Gkatzelis, Yizhen Wu, Sindhu Vasireddy, Martin Schultz, Alexander Knohl, Riikka Rinnan, Thorsten Hohaus, and Eva Y. Pfannerstill
Biogeosciences, 23, 1423–1457, https://doi.org/10.5194/bg-23-1423-2026, https://doi.org/10.5194/bg-23-1423-2026, 2026
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Trees release reactive gases that affect air quality and climate. We studied how these emissions from European beech and English oak change under realistic scenarios of combined and single heat and ozone stress. Heat increased emissions, while ozone reduced most of them. When stressors were combined, the effects were complex and varied by species. Machine learning identified key stress-related compounds. Our findings show that future tree stress may alter air quality and climate interactions.
Beatriz P. Cazorla, Ana Meijide, Javier Cabello, Julio Peñas, Javier Martínez-López, Rodrigo Vargas, Leonardo Montagnani, Alexander Knohl, Lukas Siebicke, Benimiano Gioli, Jiří Dušek, Ladislav Šigut, Andreas Ibrom, Georg Wohlfahrt, Eugénie Paul-Limoges, Kathrin Fuchs, Antonio Manco, Marian Pavelka, Lutz Merbold, Lukas Hörtnagl, Pierpaolo Duce, Ignacio Goded, Kim Pilegaard, and Domingo Alcaraz-Segura
Biogeosciences, 23, 1223–1243, https://doi.org/10.5194/bg-23-1223-2026, https://doi.org/10.5194/bg-23-1223-2026, 2026
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We assess whether satellite-derived Ecosystem Functional Types (EFTs) reflect spatial heterogeneity in carbon fluxes across Europe. Using Eddy Covariance data from 50 sites, we show that EFTs capture distinct Net Ecosystem Exchange dynamics and perform slightly better than Plant Functional Types (PFTs). EFTs offer a scalable, annually updatable approach to monitor ecosystem functioning and its interannual variability.
José Ángel Callejas-Rodelas, Justus van Ramshorst, Alexander Knohl, Lukas Siebicke, Dietmar Fellert, Marek Peksa, Dirk Böttger, and Christian Markwitz
Earth Syst. Sci. Data, 18, 845–874, https://doi.org/10.5194/essd-18-845-2026, https://doi.org/10.5194/essd-18-845-2026, 2026
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A dataset expanding around seventy eight site-years was compiled, harmonized and presented. The dataset consisted in eddy covariance and meteorological measurements over four pairs of agroforestry and open cropland systems, and one pair of agroforestry and open grassland system. This is the first ever dataset compiling this type of data over temperate agroforestry systems.
Tanguy Postic, François de Coligny, Isabelle Chuine, Louis Devresse, Daniel Berveiller, Hervé Cochard, Matthias Cuntz, Nicolas Delpierre, Émilie Joetzjer, Jean-Marc Limousin, Jean-Marc Ourcival, François Pimont, Julien Ruffault, Guillaume Simioni, Nicolas K. Martin-StPaul, and Xavier Morin
Geosci. Model Dev., 18, 7603–7679, https://doi.org/10.5194/gmd-18-7603-2025, https://doi.org/10.5194/gmd-18-7603-2025, 2025
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PHOREAU is a forest dynamic model that links plant traits with water use, growth, and climate responses to explore how species diversity affects productivity and resilience. Validated across European forests, PHOREAU simulates how tree communities function under drought and warming. Our findings support the use of trait-based modeling to guide forest adaptation strategies under future climate scenarios.
José Ángel Callejas-Rodelas, Alexander Knohl, Ivan Mammarella, Timo Vesala, Olli Peltola, and Christian Markwitz
Biogeosciences, 22, 4507–4529, https://doi.org/10.5194/bg-22-4507-2025, https://doi.org/10.5194/bg-22-4507-2025, 2025
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The spatial variability of CO2 and water vapour exchanges with the atmosphere was quantified above an agroforestry system and further compared to a monocropping system using a total of four eddy covariance stations. The variability of fluxes within the agroforestry site was found to be as large as the variability between agroforestry and monocropping site, induced by the heterogeneity of the site, which highlights the need for replicated measurements above such ecosystems.
Gabriel Destouet, Nikola Besic, Emilie Joetzjer, and Matthias Cuntz
Atmos. Meas. Tech., 18, 3193–3215, https://doi.org/10.5194/amt-18-3193-2025, https://doi.org/10.5194/amt-18-3193-2025, 2025
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Over the past two decades, global flux tower networks have provided valuable insights into ecosystem functioning. However, the standard eddy-covariance method used for processing flux data has limitations, leading to data loss and limited resolution due to fixed time steps. This paper introduces a new method using wavelet analysis to increase temporal resolution and improve data retention. Applied at the Hesse forest flux tower in France, this approach provides high-resolution flux estimates, enhancing the accuracy of flux measurements.
Thorge Wintz, Alexander Röll, Gustavo Brant Paterno, Florian Ellsäßer, Delphine Clara Zemp, Hendrayanto, Bambang Irawan, Alexander Knohl, Holger Kreft, and Dirk Hölscher
EGUsphere, https://doi.org/10.5194/egusphere-2025-2596, https://doi.org/10.5194/egusphere-2025-2596, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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We investigated how the size and diversity of tree patches in Indonesian oil palm landscapes influence the movement of water to the atmosphere and local cooling. Our study shows that larger tree patches increase cooling mainly by supporting greater plant diversity and more complex vegetation structure. These findings suggest that expanding and diversifying tree patches can help manage microclimate and water cycling in agricultural areas.
Gab Abramowitz, Anna Ukkola, Sanaa Hobeichi, Jon Cranko Page, Mathew Lipson, Martin G. De Kauwe, Samuel Green, Claire Brenner, Jonathan Frame, Grey Nearing, Martyn Clark, Martin Best, Peter Anthoni, Gabriele Arduini, Souhail Boussetta, Silvia Caldararu, Kyeungwoo Cho, Matthias Cuntz, David Fairbairn, Craig R. Ferguson, Hyungjun Kim, Yeonjoo Kim, Jürgen Knauer, David Lawrence, Xiangzhong Luo, Sergey Malyshev, Tomoko Nitta, Jerome Ogee, Keith Oleson, Catherine Ottlé, Phillipe Peylin, Patricia de Rosnay, Heather Rumbold, Bob Su, Nicolas Vuichard, Anthony P. Walker, Xiaoni Wang-Faivre, Yunfei Wang, and Yijian Zeng
Biogeosciences, 21, 5517–5538, https://doi.org/10.5194/bg-21-5517-2024, https://doi.org/10.5194/bg-21-5517-2024, 2024
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This paper evaluates land models – computer-based models that simulate ecosystem dynamics; land carbon, water, and energy cycles; and the role of land in the climate system. It uses machine learning and AI approaches to show that, despite the complexity of land models, they do not perform nearly as well as they could given the amount of information they are provided with about the prediction problem.
Jacob A. Nelson, Sophia Walther, Fabian Gans, Basil Kraft, Ulrich Weber, Kimberly Novick, Nina Buchmann, Mirco Migliavacca, Georg Wohlfahrt, Ladislav Šigut, Andreas Ibrom, Dario Papale, Mathias Göckede, Gregory Duveiller, Alexander Knohl, Lukas Hörtnagl, Russell L. Scott, Jiří Dušek, Weijie Zhang, Zayd Mahmoud Hamdi, Markus Reichstein, Sergio Aranda-Barranco, Jonas Ardö, Maarten Op de Beeck, Dave Billesbach, David Bowling, Rosvel Bracho, Christian Brümmer, Gustau Camps-Valls, Shiping Chen, Jamie Rose Cleverly, Ankur Desai, Gang Dong, Tarek S. El-Madany, Eugenie Susanne Euskirchen, Iris Feigenwinter, Marta Galvagno, Giacomo A. Gerosa, Bert Gielen, Ignacio Goded, Sarah Goslee, Christopher Michael Gough, Bernard Heinesch, Kazuhito Ichii, Marcin Antoni Jackowicz-Korczynski, Anne Klosterhalfen, Sara Knox, Hideki Kobayashi, Kukka-Maaria Kohonen, Mika Korkiakoski, Ivan Mammarella, Mana Gharun, Riccardo Marzuoli, Roser Matamala, Stefan Metzger, Leonardo Montagnani, Giacomo Nicolini, Thomas O'Halloran, Jean-Marc Ourcival, Matthias Peichl, Elise Pendall, Borja Ruiz Reverter, Marilyn Roland, Simone Sabbatini, Torsten Sachs, Marius Schmidt, Christopher R. Schwalm, Ankit Shekhar, Richard Silberstein, Maria Lucia Silveira, Donatella Spano, Torbern Tagesson, Gianluca Tramontana, Carlo Trotta, Fabio Turco, Timo Vesala, Caroline Vincke, Domenico Vitale, Enrique R. Vivoni, Yi Wang, William Woodgate, Enrico A. Yepez, Junhui Zhang, Donatella Zona, and Martin Jung
Biogeosciences, 21, 5079–5115, https://doi.org/10.5194/bg-21-5079-2024, https://doi.org/10.5194/bg-21-5079-2024, 2024
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The movement of water, carbon, and energy from the Earth's surface to the atmosphere, or flux, is an important process to understand because it impacts our lives. Here, we outline a method called FLUXCOM-X to estimate global water and CO2 fluxes based on direct measurements from sites around the world. We go on to demonstrate how these new estimates of net CO2 uptake/loss, gross CO2 uptake, total water evaporation, and transpiration from plants compare to previous and independent estimates.
Justus G. V. van Ramshorst, Alexander Knohl, José Ángel Callejas-Rodelas, Robert Clement, Timothy C. Hill, Lukas Siebicke, and Christian Markwitz
Atmos. Meas. Tech., 17, 6047–6071, https://doi.org/10.5194/amt-17-6047-2024, https://doi.org/10.5194/amt-17-6047-2024, 2024
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In this work we present experimental field results of a lower-cost eddy covariance (LC-EC) system, which can measure the ecosystem exchange of carbon dioxide and water vapour with the atmosphere. During three field campaigns on a grassland and agroforestry grassland, we compared the LC-EC with a conventional eddy covariance (CON-EC) system. Our results show that LC-EC has the potential to measure EC fluxes at only approximately 25 % of the cost of a CON-EC system.
Christian Rödenbeck, Karina E. Adcock, Markus Eritt, Maksym Gachkivskyi, Christoph Gerbig, Samuel Hammer, Armin Jordan, Ralph F. Keeling, Ingeborg Levin, Fabian Maier, Andrew C. Manning, Heiko Moossen, Saqr Munassar, Penelope A. Pickers, Michael Rothe, Yasunori Tohjima, and Sönke Zaehle
Atmos. Chem. Phys., 23, 15767–15782, https://doi.org/10.5194/acp-23-15767-2023, https://doi.org/10.5194/acp-23-15767-2023, 2023
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The carbon dioxide content of the Earth atmosphere is increasing due to human emissions from burning of fossil fuels, causing global climate change. The strength of the fossil-fuel emissions is estimated by inventories based on energy data, but independent validation of these inventories has been recommended by the Intergovernmental Panel on Climate Change. Here we investigate the potential to validate inventories based on measurements of small changes in the atmospheric oxygen content.
Karina E. Adcock, Penelope A. Pickers, Andrew C. Manning, Grant L. Forster, Leigh S. Fleming, Thomas Barningham, Philip A. Wilson, Elena A. Kozlova, Marica Hewitt, Alex J. Etchells, and Andy J. Macdonald
Earth Syst. Sci. Data, 15, 5183–5206, https://doi.org/10.5194/essd-15-5183-2023, https://doi.org/10.5194/essd-15-5183-2023, 2023
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We present a 12-year time series of continuous atmospheric measurements of O2 and CO2 at the Weybourne Atmospheric Observatory in the United Kingdom. These measurements are combined into the term atmospheric potential oxygen (APO), a tracer that is not influenced by land biosphere processes. The datasets show a long-term increasing trend in CO2 and decreasing trends in O2 and APO between 2010 and 2021.
Leigh S. Fleming, Andrew C. Manning, Penelope A. Pickers, Grant L. Forster, and Alex J. Etchells
Atmos. Meas. Tech., 16, 387–401, https://doi.org/10.5194/amt-16-387-2023, https://doi.org/10.5194/amt-16-387-2023, 2023
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Measurements of atmospheric O2 can help constrain the carbon cycle processes and quantify fossil fuel CO2 emissions; however, measurement of atmospheric O2 is very challenging, and existing analysers are complex systems to build and maintain. We have tested a new O2 analyser (Picarro Inc. G2207-i) in the laboratory and at Weybourne Atmospheric Observatory. We have found that the G2207-i does not perform as well as an existing O2 analyser from Sable Systems Inc.
Kim A. P. Faassen, Linh N. T. Nguyen, Eadin R. Broekema, Bert A. M. Kers, Ivan Mammarella, Timo Vesala, Penelope A. Pickers, Andrew C. Manning, Jordi Vilà-Guerau de Arellano, Harro A. J. Meijer, Wouter Peters, and Ingrid T. Luijkx
Atmos. Chem. Phys., 23, 851–876, https://doi.org/10.5194/acp-23-851-2023, https://doi.org/10.5194/acp-23-851-2023, 2023
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The exchange ratio (ER) between atmospheric O2 and CO2 provides a useful tracer for separately estimating photosynthesis and respiration processes in the forest carbon balance. This is highly relevant to better understand the expected biosphere sink, which determines future atmospheric CO2 levels. We therefore measured O2, CO2, and their ER above a boreal forest in Finland and investigated their diurnal behaviour for a representative day, and we show the most suitable way to determine the ER.
Xin Yu, René Orth, Markus Reichstein, Michael Bahn, Anne Klosterhalfen, Alexander Knohl, Franziska Koebsch, Mirco Migliavacca, Martina Mund, Jacob A. Nelson, Benjamin D. Stocker, Sophia Walther, and Ana Bastos
Biogeosciences, 19, 4315–4329, https://doi.org/10.5194/bg-19-4315-2022, https://doi.org/10.5194/bg-19-4315-2022, 2022
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Identifying drought legacy effects is challenging because they are superimposed on variability driven by climate conditions in the recovery period. We develop a residual-based approach to quantify legacies on gross primary productivity (GPP) from eddy covariance data. The GPP reduction due to legacy effects is comparable to the concurrent effects at two sites in Germany, which reveals the importance of legacy effects. Our novel methodology can be used to quantify drought legacies elsewhere.
Linh N. T. Nguyen, Harro A. J. Meijer, Charlotte van Leeuwen, Bert A. M. Kers, Hubertus A. Scheeren, Anna E. Jones, Neil Brough, Thomas Barningham, Penelope A. Pickers, Andrew C. Manning, and Ingrid T. Luijkx
Earth Syst. Sci. Data, 14, 991–1014, https://doi.org/10.5194/essd-14-991-2022, https://doi.org/10.5194/essd-14-991-2022, 2022
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We present 20-year flask sample records of atmospheric CO2, O2, and APO from the stations Lutjewad (the Netherlands), Mace Head (Ireland), and Halley (Antarctica). Data from Lutjewad and Mace Head show similar long-term trends and seasonal cycles, agreeing with measurements from another station (Weybourne, UK). Measurements from Halley agree partly with those conducted by other institutes. From our 2002–2018 Lutjewad and Mace Head records, we find good agreement for global ocean carbon uptake.
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Short summary
A better understanding of O2 fluxes, their exchange ratios with CO2 and their interrelations with environmental conditions would provide further insights into biogeochemical ecosystem processes. We, therefore, used the multilayer canopy model CANVEG to simulate and analyze the flux exchange for our forest study site for 2012–2016. Based on these simulations, we further successfully tested the application of various micrometeorological methods and the prospects of real O2 flux measurements.
A better understanding of O2 fluxes, their exchange ratios with CO2 and their interrelations...
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