Preprints
https://doi.org/10.5194/bg-2021-338
https://doi.org/10.5194/bg-2021-338
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05 Jan 2022
05 Jan 2022
Status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil

Niel Verbrigghe1, Niki I. W. Leblans1,2, Bjarni D. Sigurdsson3, Sara Vicca1, Chao Fang1,4,5, Lucia Fuchslueger1,6, Jennifer L. Soong1,7, James T. Weedon8, Christopher Poeplau9, Cristina Ariza-Carricondo1, Michael Bahn10, Bertrand Guenet11, Per Gundersen12, Gunnhildur E. G. Gunnarsdóttir13, Thomas Kätterer14, Zhanfeng Liu15, Marja Maljanen16, Sara Marañón-Jiménez17,18, Kathiravan Meeran10, Edda S. Oddsdóttir19, Ivika Ostonen20, Josep Peñuelas17,18, Andreas Richter6,21, Jordi Sardans17,18, Páll Sigurðsson3, Margaret S. Torn22, Peter M. Van Bodegom23, Erik Verbruggen1, Tom W. N. Walker24, Håkan Wallander25, and Ivan A. Janssens1 Niel Verbrigghe et al.
  • 1Research Group Plants and Ecosystems, University of Antwerp, Antwerp, Belgium
  • 2Climate Impacts Research Centre, Umeå University, Umeå, Sweden
  • 3Agricultural University of Iceland, Hvanneyri, Borgarnes, Iceland
  • 4Institute of Ecology, School of Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing, China
  • 5State Key Laboratory of Grassland Agro-ecosystems, Institute of Arid Agroecology, School of Life Sciences, Lanzhou University, Lanzhou, China
  • 6Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
  • 7Soil and Crop Sciences Department, Colorado State University, Fort Collins, Colorado, USA
  • 8Systems Ecology, Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
  • 9Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany
  • 10Department of Ecology, University of Innsbruck, Innsbruck, Austria
  • 11Laboratoire de Géologie, École normale supérieure/CNRS, PSL Research University, Paris, France
  • 12Department of Geosciences and Natural Resource Management, University of Copenhagen, Frederiksberg C, Denmark
  • 13Soil Conservation Service of Iceland, Gunnarsholt, Hella, Iceland
  • 14Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
  • 15Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems & CAS Engineering Laboratory for Vegetation Ecosystem Restoration on Islands and Coastal Zones, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
  • 16Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
  • 17CREAF, Cerdanyola del Vallès, Barcelona, Catalonia, Spain
  • 18CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Barcelona, Spain
  • 19Icelandic Forest Research, Mógilsá, Reykjavík, Iceland
  • 20Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia
  • 21International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria
  • 22Climate and Ecosystem Sciences Division, Berkeley Lab, Berkeley, CA, USA
  • 23Environmental Biology Department, Institute of Environmental Sciences, CML, Leiden University, Leiden, The Netherlands
  • 24Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
  • 25MEMEG, Department of Biology, Lund University, Lund, Sweden

Abstract. Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the cli- mate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein, 2016; Shi et al., 2018). Using natural geothermal soil warming gradients of up to +6.4 °C in subarctic grasslands (Sigurdsson et al., 2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (−2.8 ton ha−1 °C−1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (> 50 years) warming revealed that all SOC loss occurred within the first five years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon-climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions, and that SOC losses only occurred in topsoil (0–10 cm). SOC stocks in subsoil (10–30 cm), where plant roots were absent, remained unaltered, even after > 50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

Niel Verbrigghe et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-338', Emma Sayer, 01 Feb 2022
    • AC1: 'Reply on RC1', Niel Verbrigghe, 23 Mar 2022
  • RC2: 'Comment on bg-2021-338', Anonymous Referee #2, 02 Feb 2022
    • AC2: 'Reply on RC2', Niel Verbrigghe, 23 Mar 2022
  • RC3: 'Comment on bg-2021-338', Anonymous Referee #3, 02 Mar 2022
    • AC3: 'Reply on RC3', Niel Verbrigghe, 23 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-338', Emma Sayer, 01 Feb 2022
    • AC1: 'Reply on RC1', Niel Verbrigghe, 23 Mar 2022
  • RC2: 'Comment on bg-2021-338', Anonymous Referee #2, 02 Feb 2022
    • AC2: 'Reply on RC2', Niel Verbrigghe, 23 Mar 2022
  • RC3: 'Comment on bg-2021-338', Anonymous Referee #3, 02 Mar 2022
    • AC3: 'Reply on RC3', Niel Verbrigghe, 23 Mar 2022

Niel Verbrigghe et al.

Data sets

Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil Niel Verbrigghe; Niki I. W. Leblans; Bjarni D. Sigurdsson; Sara Vicca; Chao Fang; Lucia Fuchslueger; Jennifer L. Soong; James T. Weedon; Christopher Poeplau; Cristina Ariza-Carricondo; Michael Bahn; Bertrand Guenet; Per Gundersen; Gunnhildur E. Gunnarsdóttir; Thomas Kätterer; Zhanfeng Liu; Marja Maljanen; Sara Marañón-Jiménez; Kathiravan Meeran; Edda S. Oddsdóttir; Ivika Ostonen; Josep Peũelas; Andreas Richter; Jordi Sardans; Páll Sigurðsson; Peter M. Van Bodegom; Erik Verbruggen; Tom W. N. Walker; Håkan Wallander; Ivan A. Janssens https://doi.org/10.5281/zenodo.4745479

Niel Verbrigghe et al.

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Latest update: 29 Jun 2022
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Co-editor-in-chief
The authors adopted a new and attractive approach, based on the use of thermal springs appearing at different times, to study the short-term and long-term (> 50 years) effect of warming on the soil C stock under subarctic grasslands. This new approach allows to take a new look at the question of a positive feedback between temperature and soils that can amplify global warming. Indeed, most studies on this subject are based on warming experiments conducted over the short term (some years) or on questionable correlative approaches where the temperature co-varies with many other factors (e.g., study of soil C stocks along latitudinal temperature gradients). Their study challenges the current dominant view on the effect of warming on the dynamics of SOM. Indeed, results suggest that soil C losses in the subarctic grasslands studied cease after 5 years of warming. These observations corroborate those obtained in the rare ecosystem warming experiments maintained beyond 10 years. In addition, results suggest that the C stocks present in the deep soil horizons, where plant roots are not or hardly present, are not affected by warming. These unexpected discoveries, together with other recent observations, show the glaring lack of knowledge on the fundamental mechanisms of the effect of temperature on catalytic processes, which seriously compromises our ability to predict the soil-climate feedback.
Short summary
In a subarctic grassland on a geothermal warming gradient, we found large reductions in topsoil carbon stocks, with carbon stocks linearly declining with warming intensity. Most importantly, however, we observed that soil carbon stocks stabilized within 5 years of warming and remained unaffected by warming thereafter, even after > 50 years of warming. Moreover, in contrast to the large topsoil carbon losses, subsoil carbon stocks remained unaffected, even after > 50-years of soil warming.
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