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Downscaling of solar-induced chlorophyll fluorescence from canopy level to photosystem level using a random forest model


Liu, X and Guanter, L and Liu, L and Damm, A and Malenovsky, Z and Rascher, U and Peng, D and Du, S and Gastellu-Etchegorry, J-P, Downscaling of solar-induced chlorophyll fluorescence from canopy level to photosystem level using a random forest model, Remote Sensing of Environment, 231 Article 110772. ISSN 0034-4257 (2019) [Refereed Article]

Copyright Statement

Copyright 2018 Elsevier Inc.

DOI: doi:10.1016/j.rse.2018.05.035


Solar-induced chlorophyll fluorescence (SIF), an electromagnetic signal that can potentially indicate vegetation photosynthetic activity, can be retrieved from ground-based, airborne and satellite measurements. However, due to the scattering and re-absorption effects inside the leaves and canopy, SIF measured at the canopy level is only a small part of the total SIF emission at the photosystem level. Therefore, a downscaling mechanism of SIF from the canopy level to the photosystem level is important for better understanding the relationship between SIF and the vegetation gross primary production (GPP). In this study, firstly, we analyzed the canopy scattering effects using a simple parameterization model based on the spectral invariant theory. The probability for SIF photons to escape from the canopy was found to be related to the anisotropic spectral reflectance, canopy interception of the upward solar radiation, and leaf absorption. An empirical approach based on a Random Forest (RF) regression algorithm was applied to downscale SIF constrained by the red, red-edge and far-red anisotropic reflectance. The RF was trained using simulations conducted with the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model. The performance of the SIF downscaling method was evaluated with SCOPE and Discrete Anisotropic Radiative Transfer (DART) model simulations, ground measurements and airborne data. Results show that estimated SIF at the photosystem level matches well with simulated reference data, and the relationship between SIF and photosynthetically active radiation absorbed by chlorophyll is improved by SIF downscaling. This finding in combination with other evaluation criteria suggests the downscaling of canopy SIF as an efficient strategy to normalize species dependent effects of canopy structure and varying solar-view geometries. Based on our results for the SIF-APAR relationship, we expect that such normalization approaches can be helpful to improve estimates of photosynthesis using remote sensing measurements of SIF.

Item Details

Item Type:Refereed Article
Keywords:solar-induced chlorophyll fluorescence, downscaling, canopy level, photosystem level, spectral invariant theory, Random Forest regression
Research Division:Engineering
Research Group:Geomatic engineering
Research Field:Photogrammetry and remote sensing
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Assessment and management of Antarctic and Southern Ocean ecosystems
UTAS Author:Malenovsky, Z (Dr Zbynek Malenovsky)
ID Code:127578
Year Published:2019 (online first 2018)
Funding Support:Australian Research Council (FT160100477)
Web of Science® Times Cited:93
Deposited By:Geography and Spatial Science
Deposited On:2018-08-03
Last Modified:2019-09-06

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