Preprints
https://doi.org/10.5194/egusphere-2024-3788
https://doi.org/10.5194/egusphere-2024-3788
16 Dec 2024
 | 16 Dec 2024

Drivers of soil organic carbon from temperate to alpine forests: a model-based analysis of the Swiss forest soil inventory with Yasso20

Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn

Abstract. Predicting soil organic carbon (SOC) stocks and its dynamics in forest ecosystems is crucial for assessing forest C balance, but the relative importance of key controls – litter inputs, climate, and soil properties – remains uncertain. Here, we linked SOC stocks at 556 old-growth Swiss forest sites from 350 to 2000 m a.s.l. to a comprehensive set of environmental variables, encompassing climate (mean annual precipitation, MAP: 700–2100 mm, mean annual temperature, MAT: 0–12 °C), soil properties, and forest types. In addition, we compared measured SOC stocks with stocks simulated by the Yasso20-model that is widely used for reporting SOC stock changes. Since Yasso20 is driven solely by litter inputs and climate, deviations between modelled and measured stocks can reveal the significance of additional factors such as organo-mineral interactions that we hypothesized to be crucial for SOC stocks.

Total SOC stocks exhibited distinct regional patterns, with the highest values in the Southern Alps, where soils are rich in Fe and Al oxides and receive high MAP. On average, total SOC stocks simulated by Yasso20 aligned well with measured SOC stocks (13.7 vs 13.2 kg C m-2). However, the model did not capture regional SOC variability, underestimating SOC stocks by up to 7 kg C m-2 in the Southern Alps. The underestimation was primarily explained by soil mineral properties with their influence depending on soil pH. In soils with pH ≤ 5, exchangeable Fe had the strongest effect on Yasso20 deviations from measured stocks, while in soils with pH > 5, exchangeable Ca had the strongest effect on model deviations. Beyond Fe and Ca, MAP emerged as an important driver of total SOC stocks, with SOC stocks increasing with MAP. At higher elevation, this coincided with low MAT and a high share of conifers. While Yasso20 accounted for MAT, Yasso20 underestimated SOC stocks for MAP > 1400 mm.

Overall, our results indicate that mineral-driven SOC stabilization and climate are the primary drivers of Yasso20 deviations from measured SOC stocks. Incorporating mineral-driven SOM stabilization and coupling to a soil water model can improve the modeling of SOC stocks. However, further studies are needed to verify how C stabilization mechanisms and soil moisture can be included in model-based estimates of SOC stock changes, which is the primary application of Yasso in greenhouse gas inventories.

Competing interests: One of the (co-)authors is a member of the editorial board of Biogeosciences.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Journal article(s) based on this preprint

25 Aug 2025
Drivers of soil organic carbon from temperate to alpine forests: a model-based analysis of the Swiss forest soil inventory with Yasso20
Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn
Biogeosciences, 22, 4107–4122, https://doi.org/10.5194/bg-22-4107-2025,https://doi.org/10.5194/bg-22-4107-2025, 2025
Short summary
Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3788', Anonymous Referee #1, 07 Feb 2025
    • AC1: 'Reply on RC1', Claudia Guidi, 14 Mar 2025
  • RC2: 'Comment on egusphere-2024-3788', Anonymous Referee #2, 15 Feb 2025
    • AC2: 'Reply on RC2', Claudia Guidi, 14 Mar 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3788', Anonymous Referee #1, 07 Feb 2025
    • AC1: 'Reply on RC1', Claudia Guidi, 14 Mar 2025
  • RC2: 'Comment on egusphere-2024-3788', Anonymous Referee #2, 15 Feb 2025
    • AC2: 'Reply on RC2', Claudia Guidi, 14 Mar 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Reconsider after major revisions (25 Mar 2025) by Bertrand Guenet
AR by Claudia Guidi on behalf of the Authors (04 Apr 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (11 Apr 2025) by Bertrand Guenet
RR by Anonymous Referee #2 (05 May 2025)
RR by Anonymous Referee #1 (21 May 2025)
ED: Publish subject to minor revisions (review by editor) (22 May 2025) by Bertrand Guenet
AR by Claudia Guidi on behalf of the Authors (28 May 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (30 May 2025) by Bertrand Guenet
AR by Claudia Guidi on behalf of the Authors (07 Jun 2025)

Journal article(s) based on this preprint

25 Aug 2025
Drivers of soil organic carbon from temperate to alpine forests: a model-based analysis of the Swiss forest soil inventory with Yasso20
Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn
Biogeosciences, 22, 4107–4122, https://doi.org/10.5194/bg-22-4107-2025,https://doi.org/10.5194/bg-22-4107-2025, 2025
Short summary
Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn
Claudia Guidi, Sia Gosheva-Oney, Markus Didion, Roman Flury, Lorenz Walthert, Stephan Zimmermann, Brian J. Oney, Pascal A. Niklaus, Esther Thürig, Toni Viskari, Jari Liski, and Frank Hagedorn

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
Predicting soil organic carbon (SOC) stocks in forests is crucial for assessing C balance, yet drivers of SOC stocks remain uncertain at large scales. Across a broad environmental gradient in Switzerland, we compared measured SOC stocks with those modelled by Yasso20, commonly used for GHG budgets. Our results show that soil mineral properties and climate are main controls of SOC stocks, indicating that better accounting of these processes will advance accuracy of SOC stock predictions.
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