What was the purpose of SoyFLEX II

The overall objectives of the campaign activities are to acquire and process high quality hyperspectral datasets of fluorescence in conjunction with extended correlative data and perform initial analyses of data quality and generate first estimates of fluorescence.

• Complement the measurements from the soybean mutants from 2015. The data from 2015 look very promising, however not all components were acquired successfully. These missing elements should be recorded this year.
• Provide feedback for existing state of the art fluorescence models. The dataset shall be utilized in the framework of this activity to test and evaluate different modelling approaches that simulate and retrieve top-of-canopy fluorescence
• Understand if fluorescence enables the detection of differences in canopy gas exchange of different crop species and at different times of the day.
• Provide a concise and complete set of experimental data to better understand the mixing of the fluorescence signal within the canopy (from the leaf to the top-of-canopy signal)
• Establish a data analysis routine that allows to calculate two peak fluorescence maps as well as totally integrated fluorescence emission from HyPlant data from a larger set of flight lines
• Complete the time series of Seelhausen und Bily Kriz measurements by continuing the measurement concept from the years 2012-2015.

What was the outcome of SoyFLEX II

The SoyFLEX II experiment was a repetition of an experiment that took place during the 2015 Campaign in Germany. In this experiment, two different varieties of soybean were planted: the standard ‘wild type’ variety named Eiko and the ‘MinnGold’ variety, which shows a greatly reduced amount of leaf chlorophyll content while having the same leaf area index and a similar growth. Thus, the two varieties mainly differ in leaf level chlorophyll content. In this study those two varieties were investigated to show how leaf chlorophyll content, canopy architecture, and photosynthetic efficiency affect top-of-canopy reflectance based vegetation reflectance and sun-induced fluorescence measurements. The dataset on leaf and canopy level was used as input for SCOPE modelling to better parameterize the reabsorption and escape probability of fluorescence in natural canopies and to identify the main parameters that influence canopy fluorescence emission.

When measuring the sun-induced fluorescence emission spectra on fully developed, sun exposed leaves located in the top layer of the canopy we observed that, Eiko present the same fluorescence emission as MinnGold for the red fluorescence peak at 680 nm. For the far-red fluorescence emission peak at 760 nm Eiko shows higher values than MinnGold. Those results are in line with the observation from the SoyFLEX experiment in 2015 [RD-4] and support results from the literature. Changes in the red fluorescence peak (F680) are associated with the plant photochemistry and the far-red fluorescence peak (F760) is related to the chlorophyll content and structural parameters.

However, top of canopy (TOC) sun-induced fluorescence values measured at ground and from the HyPlant airborne sensor show lower red fluorescence values (F687) for Eiko than for MinnGold, but a higher far-red fluorescence peak (F760) in Eiko than in MinnGold. The difference between leaf and TOC measurements may be due to the re-absorption of the fluorescence emitted within a leaf and in the canopy. Fluorescence that is emitted at 680 nm is greatly reabsorb by leaf pigments. Additionally, leaf fluorescence emitted at 680 nm at the bottom of the canopy is re-absorb by a leaf located in the upper-canopy.

Comparing the difference between leaf and canopy measurements we could conclude that the lower red fluorescence (F680) canopy values in Eiko are due to higher canopy re-absorption. By eliminating leaf and canopy re-absorption in SCOPE we could accurately recalculate the fluorescence emission at chloroplast level of both varieties despite their greatly different canopy structure.

Thus by using the experimental set-up of the two soybean varieties we could greatly contribute to our scientific understanding how (1) the fluorescence signal that is emitted at the chloroplast level is re-absorbed within the leaf and by the different canopy layers before reaching the sensor and (2). proved that sun-induced fluorescence can be used as a good indicator of plant photochemistry, once the effects due to reabsorption at leaf and canopy level are taken into account.

Download the FLEX-EU 2016 Final Report

Data Citation Users, who, in their research, use ESA Earth Observation data that have been assigned a Digital Object Identifier (DOI), are asked to use it when citing the data source in their publications:

Digital Object Identifier: https://doi.org/10.5270/ESA-24b3118 SoyFLEX II 2016

The campaign data is available online via FTPS upon submission of a data access request. An active EO Sign In account is required to submit the request.

The data can be downloaded via an FTP client (e.g., FileZilla or WinSCP) using the option "Implicit FTP over TLS".

For further information about the EO Sign In Service you can visit TellUs

Should you need support please contact EOHelp