Events - 25/04/2018
Newsletter no. 3
|Close your eyes and imagine a Spanish beach, the dazzling sun, a splashing sea… “¡vaya, vaya! Aquí no hay playa!” In fact, Spain almost didn’t have the sun that week when 12 TRUSTEE early stage researchers (ESRs) and trainees from Spanish National Research Council (CSIS), Max Planck Institute for Biogeochemistry and University of Extremadura gathered again to study a pasture tree-grass ecosystem (‘dehesa’) of Majadas. What ESRs learnt this time – read here.|
The venue of the first TRUSTEE Summer school was located in Navalmoral de la Mata nearby the field site next to the town of Majadas de Tiétar . The school took a very hands-on approach thus only the first day was devoted to lectures on: retrieval of plant traits with empirical and physical models (Pablo Zarco-Tejada); overview of the target ecosystem: tree-grass pasture ecosystem in Majadas, ‘dehesa’ (Gerardo Moreno); SpecLab projects and expertise (Pilar Martín); calculation of net ecosystem exchange (NEE) (Mirco Migliavacca); projects of Max Planck institute in Majadas study site (Javier Pacheco-Labrador); fluxes and meteorological measurements (Arnaud Carrara); field work planning (Pilar Martín); safety in the field (Mirco Migliavacca) and TRUSTEE project (Marco Celesti).
The rest of the days – practice, practice and practice. These were divided between 2 field days and 2 days of practical sessions and data analysis. During the first day of field activities, different topics were studied: a gas-exchange chamber (Oscar Pérez-Priego) coupled with radiance measurements with a FloxBox (Javier Pacheco-Labrador); grass reflectance measurements with ASD spectroradiometer in a collar and across a 25*25 m plot (Pilar Martín); goniometer and characterization of bidirectional reflectance distribution function (BRDF) (Marco Celesti); grass sampling for biochemical and biophysical analysis (Rosario González and Lara Vilar del Hoyo); an eddy-covariance tower and lysimeter (Arnaud Carrara).
Field measurements (day 2): drone flights with a spectrometer over the crown of a tree: nadir and off-nadir measurements; CO2-response curve measurements with a LICOR-6400 instrument (David Martini); leaf area index measurements with a LAI-2200 instrument (José Ramon Melendo and Javier Becerra); SPAD measurements of chlorophyll content (Rosario González); leaf measurements in an ASD leaf clip (Javier Pacheco-Labrador).
(Calculation of fluxes and sun induced fluorescence)
The overall objective was to retrieve and analyze CO2 fluxes and Sun Induced Fluorescence (SIF) obtained from field instrumentation. This involved correcting and optimizing a best fit regression function using the raw CO2 data obtained from gas chambers. Using this, key parameters were extracted to model the response of gross primary productivity (GPP) to light conditions. Along with this, SIF was retrieve using FloxBox data where GPP was subsequently modelled using hyperspectral data and a partial least squares regression (PLSR) approach.
(1D and 3D models for retrieval of biophysical parameters from canopy and leaf optical data)
This project foucused on the parametrization and sensitivity analysis of a coupled 1D-3D radiative transfer model. The PROSAIL model was used to simulate grass spectra, while the 3D FLIGHT model was used to simulate tree spectra. PROSAIL was inverted to calculate biophysical parameters such as leaf area index (LAI) and Equivalent Water Thickness (Cw) and was validated against field measurements. Subsequently, simulated spectra from FLIGHT was compared to Compact Airborne Spectrographic Imager (CASI) reflectance using statistical techniques.
(Angular dependence of reflectance response modelling with the SCOPE model)
Project 3 involved acquiring the theoretical and practical basis for simulating multi-angular spectral data using the SCOPE radiative transfer model. Simulations were ran to understand the effects of various plant traits on reflectance factors and SIF Bidirectional Reflectance Distribution Function (BRDF).
(Leaf to canopy hyperspectral imaging: analysis of vegetation indices and PLSR performance for airborne (CASI) and proximal (ASD) data)
The main theme of this project was to explore the use of high resolution airborne spectral data to characterize field-scale biophysical variables. As such, leaf traits were upscaled to the canopy scale using empirical PLSR modeling approach. Principal component analysis ( PCA) and other statistical methods were used to reduce noise in spectral data and various vegetation indices were subsequently computed based on hyperspectral data. Biophysical and biochemical variables were predicted based on these indices and a model efficiency/correlation analysis was performed.
The last day of the week was a beautiful one! A guided tour to the Monfragüe national park took place, where the amazing views and the local fauna taught everyone involved more about the traditional ecosystem in Extremadura. In Majadas del Tiétar, Mirco Migliavacca and Pilar Martín narrated to the locals about the work being done in the area and for which purpose it is being used. After this, a huge meal was shared with the ESRs, teachers and locals in a very friendly environment.
Next training course will be held in Milan, Italy, during next September. The ESRs will have to present their work to all the actors involved in the project, so this could be a nice opportunity to get a deep knowledge of their work if you are interested, aren’t you?
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