A Field Platform for Continuous Measurement of Canopy Fluorescence

Abstract

International audienceThis paper presents a field platform for continuous measurement of fluorescence at the canopy level. It consists of a 21-m-high crane equipped for fluorescence measurements. The crane is installed in the middle of the fields dedicated to agricultural research. Thanks to a jib of 24 m and a railway of 100 m distance, fluorescence measurements can be performed at nadir viewing over various field crops. The platform is dedicated to the development and test of future passive or active airborne and space-borne vegetation sensors. A new fully automatic instrument, called TriFLEX, has been installed at the end of the jib. TriFLEX is designed for passive measurement of fluorescence in the oxygen A and B absorption bands. It is based on three spectrometers and allows for continuous measurements with a repetition rate of about 1 Hz. The data products are the radiances of the target, the fluorescence flux at 687 and 760 nm, and several vegetation indexes, including the photochemical reflectance index and the normalized difference vegetation index. A new algorithm for fluorescence retrieval from spectral bands measurement is described. It improves upon the well-known Fraunhofer line discriminator method applied to passive fluorescence measurement by taking into account the spectral shape of fluorescence and the reflectance of vegetation. A measurement campaign of 38 days has been carried out in summer 2008 over a sorghum field. The evolution of the signals showed that the crop was suffering from stress due to lack of water. After several rainy days, a reversion of the water stress was observed

Gross Primary Production of a Wheat Canopy Relates Stronger to Far Red Than to Red Solar-Induced Chlorophyll Fluorescence

“…The site is equipped with a movable crane, which can translate between two contiguous field plots of 100 × 200 m 2 and 60 × 150 m 2 . Additional information on the site and instrumental equipment can be found in [32]. The two plots were sowed with winter wheat (Triticum turgidum durum, …”

“…Hence, RSIF would be a preferential choice to assess physiologically-induced ChlF variations, and the detection of both peaks would provide complementary information on photosystem I (PSI) and PSII emissions [31]. In this study, we used the field platform for continuous measurements of fluorescence [32] located in Avignon, France to investigate both diurnal and seasonal dynamics of RSIF and FRSIF over a wheat crop during a complete vegetative cycle. SIF was continuously measured and retrieved from the O 2 -B (SIF687) and O 2 -A (SIF760) bands.…”

Ground-Based Optical Measurements at European Flux Sites: A Review of Methods, Instruments and Current Controversies

“…The reason for the small number of people using hyperspectral systems in unattended settings is that hyperspectral spectroradiometers are not necessarily designed with this in mind, and therefore adapting them to be weather proof, motorized and with data storage connections is not trivial. Technological advances in recent times by those mentioned above will pave the way for a larger scientific deployment of these instruments across other sites, because the results obtained are already showing good relationships with EC fluxes [9,10,20,33,40].…”

Remote sensing-based estimation of gross primary production in a subalpine grassland

“…Currently, several research groups have developed different automatic devices to collect canopy spectral properties (Leuning et al, 2006;Hilker et al, 2007;Nakaji et al, 2007Nakaji et al, , 2008Daumard et al, 2010;Hilker et al, 2010;Ide et al, 2010;Balzarolo et al, 2011;Meroni et al, 2011) for the purpose of gaining new insights into the quantification and monitoring of plant photosynthesis on a temporal scale. Such devices are generally operated automatically for long periods in the sampling area of flux towers.…”