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Published July 16, 2020 | Published + Supplemental Material
Journal Article Open

Wide discrepancies in the magnitude and direction of modeled solar-induced chlorophyll fluorescence in response to light conditions

Abstract

Recent successes in passive remote sensing of far-red solar-induced chlorophyll fluorescence (SIF) have spurred the development and integration of canopy-level fluorescence models in global terrestrial biosphere models (TBMs) for climate and carbon cycle research. The interaction of fluorescence with photochemistry at the leaf and canopy scales provides opportunities to diagnose and constrain model simulations of photosynthesis and related processes, through direct comparison to and assimilation of tower, airborne, and satellite data. TBMs describe key processes related to the absorption of sunlight, leaf-level fluorescence emission, scattering, and reabsorption throughout the canopy. Here, we analyze simulations from an ensemble of process-based TBM–SIF models (SiB3 – Simple Biosphere Model, SiB4, CLM4.5 – Community Land Model, CLM5.0, BETHY – Biosphere Energy Transfer Hydrology, ORCHIDEE – Organizing Carbon and Hydrology In Dynamic Ecosystems, and BEPS – Boreal Ecosystems Productivity Simulator) and the SCOPE (Soil Canopy Observation Photosynthesis Energy) canopy radiation and vegetation model at a subalpine evergreen needleleaf forest near Niwot Ridge, Colorado. These models are forced with local meteorology and analyzed against tower-based continuous far-red SIF and gross-primary-productivity-partitioned (GPP) eddy covariance data at diurnal and synoptic scales during the growing season (July–August 2017). Our primary objective is to summarize the site-level state of the art in TBM–SIF modeling over a relatively short time period (summer) when light, canopy structure, and pigments are similar, setting the stage for regional- to global-scale analyses. We find that these models are generally well constrained in simulating photosynthetic yield but show strongly divergent patterns in the simulation of absorbed photosynthetic active radiation (PAR), absolute GPP and fluorescence, quantum yields, and light response at the leaf and canopy scales. This study highlights the need for mechanistic modeling of nonphotochemical quenching in stressed and unstressed environments and improved the representation of light absorption (APAR), distribution of light across sunlit and shaded leaves, and radiative transfer from the leaf to the canopy scale.

Additional Information

© Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 24 Dec 2019 – Discussion started: 03 Feb 2020 – Revised: 11 May 2020 – Accepted: 08 Jun 2020 – Published: 16 Jul 2020. The US-NR1 AmeriFlux site is supported by the US DOE Office of Science through the AmeriFlux Management Project (AMP) at Lawrence Berkeley National Laboratory (award no. 7094866). BMR was supported by the NASA CMS project (award no. NNX16AP33G) and the US Department of Energy's Office of Science Terrestrial Ecosystem Science program (award nos. DE-SC0010624 and DE-SC0010625). CESM (CLM4.5 and CLM5.0) is sponsored by the National Science Foundation and the US Department of Energy. ORCHIDEE is supported by CNES TOSCA under the FluOR and ECOFLUO projects. ITB was supported by NASA (contract no. 80NSSC18K1312). We would like to thank the W. M. Keck Institute for Space Studies and internal funds from the Jet Propulsion Laboratory for support of the field measurements at Niwot Ridge (https://www.kiss.caltech.edu/techdev/photosynthesis/photosynthesis.html, last access: 6 January 2020). A portion of this research was carried out through the OCO-2 project at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research has been supported by the NASA (grant no. 18-TE18-0062). Author contributions. NP, TM, and IB designed the research. NP, TM, AN, BR, CB, FM, IB, YZ, BQ, MS, and DB performed the research. AN, BR, CB, FM, IB, YZ, BQ, MS, and NM contributed model simulations. TM, DB, SP, PB, JS, KG, and CF contributed observational data. NP, TM, AN, and BR analyzed data. NP, TM, AN, BR, CB, IB, YZ, NM, DB, and CF wrote the paper. Data availability. All observational data (APAR, SIF, GPP, and relative SIF) are provided as hourly time series. The data can be found at https://data.caltech.edu/records/1231. The data are saved as a .csv file. The supplement related to this article is available online at: https://doi.org/10.5194/bg-17-3733-2020-supplement. The authors declare that they have no conflict of interest. Review statement. This paper was edited by Christopher Still and reviewed by Christiaan van der Tol and Georg Wohlfahrt.

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Additional details

Created:
August 19, 2023
Modified:
October 20, 2023