Drought stress detection with a coupled AgroC-SCOPE model

2020 ◽  
Author(s):  
Simon De Cannière ◽  
Michael Herbst ◽  
François Jonard
Keyword(s):  
Chlorophyll Fluorescence ◽  
Drought Stress ◽  
Growth Models ◽  
Photosynthetic Apparatus ◽  
Carbon Fluxes ◽  
Crop Growth ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Close Link ◽  
Scope Model

<p>Photosynthesis is the cornerstone of all life on earth. Light energy, captured by chlorophyll, fuels photosynthesis. As an excess of absorbed light leads to harmful products, the excess light is either dissipated as heat or it is re-emitted in the atmosphere. The latter pathway results in a weak, but very specific spectral signal, right from the heart of the photosynthetic apparatus, called chlorophyll fluorescence. Recent advancements in spectrometry have allowed the retrieval of fluorescence with remote sensing. Given its close link to photosynthesis, it has the potential of informing crop growth models. The aim of this study is to estimate the stress parameter of the crop growth model AgroC by incorporating remotely-sensed sun-induced chlorophyll fluorescence (SIF) data. The radiative transfer model SCOPE converts the leaf-level fluorescence obtained from AgroC to canopy-scale SIF. In case of a stress, the SIF at 760 nm decreases, while the SIF at 687 nm shows a more complex relationship to stress. Comparing the modelled canopy-scale and observed SIF provides information on the plant water stress status, allowing a more precise estimate of the photosynthetic activity. Downstream, this leads to a better estimation of the plant growth, as well as a better estimation of the carbon and water fluxes. A field campaign is conducted over a sugar beet field in Merzenhausen, Germany, in which the fluorescence was measured alongside the water and carbon fluxes. As the fluorescence provides an additional constraint on the photosynthesis, the AgroC-SCOPE model is expected to provide significantly better estimates of the carbon fluxes compared to the AgroC model. The results of the coupled AgroC-SCOPE model will be presented at this meeting. This study provides information on the link between drought stress and fluorescence. An approach similar to the one proposed in this study will allow detecting drought stress at the regional to global scale with FLEX data.</p>

scholarly journals FLiES-SIF ver. 1.0: Three-dimensional radiative transfer model for estimating solar induced fluorescence

2020 ◽  
Author(s):  
Yuma Sakai ◽  
Hideki Kobayashi ◽  
Tomomichi Kato
Keyword(s):  
Sensitivity Analysis ◽  
Chlorophyll Fluorescence ◽  
Radiative Transfer ◽  
Three Dimensional ◽  
Radiative Transfer Model ◽  
Model Description ◽  
Transfer Model ◽  
Plant Canopy ◽  
Parallel Layer ◽  
Leaf Level

Abstract. Global terrestrial ecosystems control the atmospheric CO2 concentration through gross primary production (GPP) and ecosystem respiration processes. Chlorophyll fluorescence is one of the energy release pathways of excess incident lights in the photosynthetic process. Over the last ten years, extensive studies have been revealed that canopy scale sun-induced chlorophyll fluorescence (SIF), which potentially provides a direct pathway to link leaf level photosynthesis to global GPP, can be observed from satellites. SIF is used to infer photosynthetic capacity of plant canopy, however, it is not clear how the leaf-level SIF emission contributes to the top of canopy directional SIF. Plant canopy radiative transfer models are the useful tools to understand the causality of directional canopy SIF. One dimensional (1-D) plane parallel layer models (e.g. the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model) have been widely used and are useful to understand the general mechanisms behind the temporal and seasonal variations in SIF. However, due to the lack of complexity of the actual canopy structures, three dimensional models (3-D) have a potential to delineate the realistic directional canopy SIFs. Forest Light Environmental Simulator for SIF (FLiES-SIF) version 1.0 is the 3-D Monte Carlo plant canopy radiative transfer model to understand the biological and physical mechanisms behind the SIF emission from complex forest canopies. In this model description paper, we focused on the model formulation and simulation schemes, and showed some sensitivity analysis against several major variables such as view angle and leaf area index (LAI). The simulation results show that SIF increases with LAI then saturated at LAI > 2–4 depending on the spectral wavelength. The sensitivity analysis also shows that simulated SIF radiation may decrease with LAI at higher LAI domain (LAI > 5). These phenomena are seen in certain sun and view angle conditions. This type of non-linear and non-monotonic SIF behavior to LAI is also related to spatial forest structure patterns. FLiES-SIF version 1.0 can be used to quantify the canopy SIF in various view angles including the contribution of multiple scattering which is the important component in the near infrared domain. The potential use of the model is to standardize the satellite SIF by correcting the bi-directional effect. This step will contribute to the improvement of the GPP estimation accuracy through SIF.

Exploring the physiological information of Sun-induced chlorophyll fluorescence through radiative transfer model inversion

2018 ◽  
Vol 215 ◽  
pp. 97-108 ◽  
Author(s):  
Marco Celesti ◽  
Christiaan van der Tol ◽  
Sergio Cogliati ◽  
Cinzia Panigada ◽  
Peiqi Yang ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Radiative Transfer ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Model Inversion ◽  
Physiological Information

scholarly journals RADIOMETRIC CHARACTERIZATION OF A MARSH SITE AT THE ARGENTINIAN PAMPAS IN THE CONTEXT OF HYPERNETS PROJECT (A NEW AUTONOMOUS HYPERSPECTRAL RADIOMETER)

2020 ◽  
Vol IV-3/W2-2020 ◽  
pp. 95-100
Author(s):  
E. Piegari ◽  
J. I. Gossn ◽  
Á. Juárez ◽  
V. Barraza ◽  
G. González Trilla ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Low Cost ◽  
Photosynthetic Apparatus ◽  
Test Site ◽  
Coastal Marsh ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Coastal Habitat

Abstract. In the context of HYPERNETS project, which is developing a relatively low cost hyperspectral radiometer (and associated pointing system and embedded calibration device for automated measurement of water and land bidirectional reflectance), the tidal coastal marsh in the Mar Chiquita (Argentina) lagoon is being characterized as a test site for validation of radiometric variables. High quality in situ measurements will be available at all spectral bands at this site (and other sites over land and water around the world) for the validation of the surface reflectance data issued from all earth observation missions. This site, dominanted by Sporobolus densiflorus vegetation, is a coastal habitat that provides ecosystem services essential to people and the environment. There is evidence that growth and photosynthetic apparatus of S. densiflorus is negatively affected by the herbicide glyphosate, which is extensively used in the Argentinian agricultural production. As a way to monitor this risk, in this work a theoretical study was performed to establish if it is possible to estimate the chlorophyll content (Ca+b in S. densiflorus), which concentrations are known to be affected by the herbicide, using hyperspectral reflectance. Signatures recorded in situ plus other parameters obtained from a biochemical characterization of the plant were used to obtain a simulated reflectance with the radiative transfer model PROSAIL. Then, a BaseLine Residual approach, based on close band triplets, was proposed to retrieve Ca+b. As a result, we found that it is possible to distinguish between two levels of Ca+b.

scholarly journals Global monitoring of terrestrial chlorophyll fluorescence from moderate-spectral-resolution near-infrared satellite measurements: methodology, simulations, and application to GOME-2

2013 ◽  
Vol 6 (10) ◽  
pp. 2803-2823 ◽  
Author(s):  
J. Joiner ◽  
L. Guanter ◽  
R. Lindstrot ◽  
M. Voigt ◽  
A. P. Vasilkov ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Spectral Resolution ◽  
Hyperspectral Data ◽  
Radiative Transfer Model ◽  
High Signal ◽  
Transfer Model ◽  
Good Precision ◽  
Atmospheric Absorption ◽  
Red Fluorescence ◽  
Global Coverage

Abstract. Globally mapped terrestrial chlorophyll fluorescence retrievals are of high interest because they can provide information on the functional status of vegetation including light-use efficiency and global primary productivity that can be used for global carbon cycle modeling and agricultural applications. Previous satellite retrievals of fluorescence have relied solely upon the filling-in of solar Fraunhofer lines that are not significantly affected by atmospheric absorption. Although these measurements provide near-global coverage on a monthly basis, they suffer from relatively low precision and sparse spatial sampling. Here, we describe a new methodology to retrieve global far-red fluorescence information; we use hyperspectral data with a simplified radiative transfer model to disentangle the spectral signatures of three basic components: atmospheric absorption, surface reflectance, and fluorescence radiance. An empirically based principal component analysis approach is employed, primarily using cloudy data over ocean, to model and solve for the atmospheric absorption. Through detailed simulations, we demonstrate the feasibility of the approach and show that moderate-spectral-resolution measurements with a relatively high signal-to-noise ratio can be used to retrieve far-red fluorescence information with good precision and accuracy. The method is then applied to data from the Global Ozone Monitoring Instrument 2 (GOME-2). The GOME-2 fluorescence retrievals display similar spatial structure as compared with those from a simpler technique applied to the Greenhouse gases Observing SATellite (GOSAT). GOME-2 enables global mapping of far-red fluorescence with higher precision over smaller spatial and temporal scales than is possible with GOSAT. Near-global coverage is provided within a few days. We are able to show clearly for the first time physically plausible variations in fluorescence over the course of a single month at a spatial resolution of 0.5° × 0.5°. We also show some significant differences between fluorescence and coincident normalized difference vegetation indices (NDVI) retrievals.

scholarly journals FLiES-SIF version 1.0: three-dimensional radiative transfer model for estimating solar induced fluorescence

2020 ◽  
Vol 13 (9) ◽  
pp. 4041-4066
Author(s):  
Yuma Sakai ◽  
Hideki Kobayashi ◽  
Tomomichi Kato
Keyword(s):  
Sensitivity Analysis ◽  
Chlorophyll Fluorescence ◽  
Radiative Transfer ◽  
Three Dimensional ◽  
Radiative Transfer Model ◽  
Model Description ◽  
Transfer Model ◽  
Plant Canopy ◽  
Parallel Layer ◽  
Leaf Level

Abstract. Global terrestrial ecosystems control the atmospheric CO2 concentration through gross primary production (GPP) and ecosystem respiration processes. Chlorophyll fluorescence is one of the energy release pathways of excess incident light in the photosynthetic process. Over the last 10 years, extensive studies have revealed that canopy-scale Sun-induced chlorophyll fluorescence (SIF), which potentially provides a direct pathway to link leaf-level photosynthesis to global GPP, can be observed from satellites. SIF is used to infer photosynthetic capacity of plant canopy; however, it is not clear how the leaf-level SIF emission contributes to the top-of-canopy directional SIF. Plant canopy radiative transfer models are useful tools to understand the mechanism of anisotropic light interactions such as scattering and absorption in plant canopies. One-dimensional (1-D) plane-parallel layer models (e.g., the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model) have been widely used and are useful to understand the general mechanisms behind the temporal and seasonal variations in SIF. However, a 1-D model does not explain the complexity of the actual canopy structures. Three-dimensional models (3-D) have a potential to delineate the realistic directional canopy SIFs. Forest Light Environmental Simulator for SIF (FLiES-SIF) version 1.0 is a 3-D Monte Carlo plant canopy radiative transfer model to understand the biological and physical mechanisms behind the SIF emission from complex forest canopies. The FLiES-SIF model is coupled with leaf-level fluorescence and a physiology module so that users are able to simulate how the changes in environmental and leaf traits as well as canopy structure affect the observed SIF at the top of the canopy. The FLiES-SIF model was designed as three-dimensional model, yet the entire modules are computationally efficient: FLiES-SIF can be easily run by moderate-level personal computers with lower memory demands and public software. In this model description paper, we focused on the model formulation and simulation schemes, and showed some sensitivity analysis against several major variables such as view angle and leaf area index (LAI). The simulation results show that SIF increases with LAI then saturated at LAI>2–4 depending on the spectral wavelength. The sensitivity analysis also shows that simulated SIF radiation may decrease with LAI at a higher LAI domain (LAI>5). These phenomena are seen in certain Sun and view angle conditions. This type of nonlinear and nonmonotonic SIF behavior towards LAI is also related to spatial forest structure patterns. FLiES-SIF version 1.0 can be used to quantify the canopy SIF in various view angles including the contribution of multiple scattering which is the important component in the near-infrared domain. The potential use of the model is to standardize the satellite SIF by correcting the bidirectional effect. This step will contribute to the improvement of the GPP estimation accuracy through SIF.

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