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Addressing Challenges in Simulating Inter–Annual Variability of Gross Primary Production

De, Ranit ; Bao, Shanning ; Koirala, Sujan ; Brenning, Alexander ; Reichstein, Markus ; Tagesson, Torbern LU ; Liddell, Michael ; Ibrom, Andreas ; Wolf, Sebastian and Šigut, Ladislav , et al. (2025) In Journal of Advances in Modeling Earth Systems 17(5).
Abstract

A long-standing challenge in studying the global carbon cycle has been understanding the factors controlling inter–annual variation (IAV) of carbon fluxes, and improving their representations in existing biogeochemical models. Here, we compared an optimality-based model and a semi-empirical light use efficiency model to understand how current models can be improved to simulate IAV of gross primary production (GPP). Both models simulated hourly GPP and were parameterized for (a) each site–year, (b) each site with an additional constraint on IAV ((Formula presented.)), (c) each site, (d) each plant–functional type, and (e) globally. This was followed by forward runs using calibrated parameters, and model evaluations using Nash–Sutcliffe... (More)

A long-standing challenge in studying the global carbon cycle has been understanding the factors controlling inter–annual variation (IAV) of carbon fluxes, and improving their representations in existing biogeochemical models. Here, we compared an optimality-based model and a semi-empirical light use efficiency model to understand how current models can be improved to simulate IAV of gross primary production (GPP). Both models simulated hourly GPP and were parameterized for (a) each site–year, (b) each site with an additional constraint on IAV ((Formula presented.)), (c) each site, (d) each plant–functional type, and (e) globally. This was followed by forward runs using calibrated parameters, and model evaluations using Nash–Sutcliffe efficiency (NSE) as a model-fitness measure at different temporal scales across 198 eddy-covariance sites representing diverse climate–vegetation types. Both models simulated hourly GPP better (median normalized NSE: 0.83 and 0.85) than annual GPP (median normalized NSE: 0.54 and 0.63) for most sites. Specifically, the optimality-based model substantially improved from NSE of −1.39 to 0.92 when drought stress was explicitly included. Most of the variability in model performances was due to model types and parameterization strategies. The semi-empirical model produced statistically better hourly simulations than the optimality-based model, and site–year parameterization yielded better annual model performance. Annual model performance did not improve even when parameterized using (Formula presented.). Furthermore, both models underestimated the peaks of diurnal GPP, suggesting that improving predictions of peaks could produce better annual model performance. Our findings reveal current modeling deficiencies in representing IAV of carbon fluxes and guide improvements in further model development.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
carbon flux, eddy covariance, gross primary production, inter–annual variability, light use efficiency, optimality-based model
in
Journal of Advances in Modeling Earth Systems
volume
17
issue
5
article number
e2024MS004697
publisher
Wiley-Blackwell
external identifiers
  • scopus:105004169903
ISSN
1942-2466
DOI
10.1029/2024MS004697
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 The Author(s). Journal of Advances in Modeling Earth Systems published by Wiley Periodicals LLC on behalf of American Geophysical Union.
id
d00b8f02-9465-4737-8e6e-4171c78e5d36
date added to LUP
2025-08-06 12:50:12
date last changed
2025-08-08 14:30:30
@article{d00b8f02-9465-4737-8e6e-4171c78e5d36,
  abstract     = {{<p>A long-standing challenge in studying the global carbon cycle has been understanding the factors controlling inter–annual variation (IAV) of carbon fluxes, and improving their representations in existing biogeochemical models. Here, we compared an optimality-based model and a semi-empirical light use efficiency model to understand how current models can be improved to simulate IAV of gross primary production (GPP). Both models simulated hourly GPP and were parameterized for (a) each site–year, (b) each site with an additional constraint on IAV ((Formula presented.)), (c) each site, (d) each plant–functional type, and (e) globally. This was followed by forward runs using calibrated parameters, and model evaluations using Nash–Sutcliffe efficiency (NSE) as a model-fitness measure at different temporal scales across 198 eddy-covariance sites representing diverse climate–vegetation types. Both models simulated hourly GPP better (median normalized NSE: 0.83 and 0.85) than annual GPP (median normalized NSE: 0.54 and 0.63) for most sites. Specifically, the optimality-based model substantially improved from NSE of −1.39 to 0.92 when drought stress was explicitly included. Most of the variability in model performances was due to model types and parameterization strategies. The semi-empirical model produced statistically better hourly simulations than the optimality-based model, and site–year parameterization yielded better annual model performance. Annual model performance did not improve even when parameterized using (Formula presented.). Furthermore, both models underestimated the peaks of diurnal GPP, suggesting that improving predictions of peaks could produce better annual model performance. Our findings reveal current modeling deficiencies in representing IAV of carbon fluxes and guide improvements in further model development.</p>}},
  author       = {{De, Ranit and Bao, Shanning and Koirala, Sujan and Brenning, Alexander and Reichstein, Markus and Tagesson, Torbern and Liddell, Michael and Ibrom, Andreas and Wolf, Sebastian and Šigut, Ladislav and Hörtnagl, Lukas and Woodgate, William and Korkiakoski, Mika and Merbold, Lutz and Black, T. Andrew and Roland, Marilyn and Klosterhalfen, Anne and Blanken, Peter D. and Knox, Sara and Sabbatini, Simone and Gielen, Bert and Montagnani, Leonardo and Fensholt, Rasmus and Wohlfahrt, Georg and Desai, Ankur R. and Paul-Limoges, Eugénie and Galvagno, Marta and Hammerle, Albin and Jocher, Georg and Reverter, Borja Ruiz and Holl, David and Chen, Jiquan and Vitale, Luca and Arain, M. Altaf and Carvalhais, Nuno}},
  issn         = {{1942-2466}},
  keywords     = {{carbon flux; eddy covariance; gross primary production; inter–annual variability; light use efficiency; optimality-based model}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Journal of Advances in Modeling Earth Systems}},
  title        = {{Addressing Challenges in Simulating Inter–Annual Variability of Gross Primary Production}},
  url          = {{http://dx.doi.org/10.1029/2024MS004697}},
  doi          = {{10.1029/2024MS004697}},
  volume       = {{17}},
  year         = {{2025}},
}