Uso combinado del LIDAR y medidas hiperspectrales para la teledetección de la fluorescencia y el perfil vertical del dosel

Revista oficial de la Asociación Española de Teledetección[EN] We report the development of a new LIDAR system (LASVEG) for airborne remote sensing of chlorophyll fluorescence (ChlF) and vertical profile of canopies. By combining laser-induced fluorescence (LIF), sun-induced fluorescence (SIF) and canopy height distribution, the new instrument will allow the simultaneous assessment of gross primary production (GPP), photosynthesis efficiency and above ground carbon stocks. Technical issues of the fluorescence LIDAR development are discussed and expected performances are presented.[ES] Se presenta el desarrollo de un nuevo sistema LIDAR (LASVEG) para la teledetección aerotransportada de la fluorescencia de la clorofila (ChlF) y el perfil vertical del dosel. Mediante la combinación de la fluorescencia inducida por láser (LIF), la fluorescencia inducida por el sol (SIF) y la distribución de la altura del dosel, el nuevo instrumento permitirá la evaluación simultánea de la producción primaria bruta (GPP), la eficiencia de la fotosíntesis y las reservas de carbono por encima del nivel del suelo. Se discuten cuestiones técnicas del desarrollo del LIDAR fluorescencia y se presentan las prestaciones previstasThis instrument is developed in the framework of the CALSIF project with the support of the French national agency ANR and the French space agency CNES.Ounis, A.; Bach, J.; Mahjoub, A.; Daumard, F.; Moya, I.; Goulas, Y. (2016). Combined use of LIDAR and hyperspectral measurements for remote sensing of fluorescence and vertical profile of canopies. Revista de Teledetección. (Special Issue):87-94. doi:10.4995/raet.2015.3982.SWORD8794Special Issu

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence

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

This paper reviews the currently available optical sensors, their limitations and opportunities for deployment at Eddy Covariance (EC) sites in Europe. This review is based on the results obtained from an online survey designed and disseminated by the Co-cooperation in Science and Technology (COST) Action ESO903—“Spectral Sampling Tools for Vegetation Biophysical Parameters and Flux Measurements in Europe” that provided a complete view on spectral sampling activities carried out within the different research teams in European countries. The results have highlighted that a wide variety of optical sensors are in use at flux sites across Europe, and responses further demonstrated that users were not always fully aware of the key issues underpinning repeatability and the reproducibility of their spectral measurements. The key findings of this survey point towards the need for greater awareness of the need for standardisation and development of a common protocol of optical sampling at the European EC sites

Interpreting seasonal changes in the carbon balance of southern Amazonia using measurements of XCO2 and chlorophyll fluorescence from GOSAT

Amazon forests exert a major influence on the global carbon cycle, but quantifying the impact is complicated by diverse landscapes and sparse data. Here we examine seasonal carbon balance in southern Amazonia using new measurements of column-averaged dry air mole fraction of CO2 (XCO2) and solar induced chlorophyll fluorescence (SIF) from the Greenhouse Gases Observing Satellite (GOSAT) from July 2009 to December 2010. SIF, which reflects gross primary production (GPP), is used to disentangle the photosynthetic component of land-atmosphere carbon exchange. We find that tropical transitional forests in southern Amazonia exhibit a pattern of low XCO2 during the wet season and high XCO2 in the dry season that is robust to retrieval methodology and with seasonal amplitude double that of cerrado ecosystems to the east (4 ppm versus 2 ppm), including enhanced dilution of 2.5 ppm in the wet season. Concomitant measurements of SIF, which are inversely correlated with XCO2 in southern Amazonia (r =0.53, p<0.001), indicate that the enhanced variability is driven by seasonal changes in GPP due to coupling of strong vertical mixing with seasonal changes in underlying carbon exchange. This finding is supported by forward simulations of the Goddard Chemistry Transport Model (GEOS-Chem) which show that local carbon uptake in the wet season and loss in the dry season due to emissions by ecosystem respiration and biomass burning produces best agreement with observed XCO2. We conclude that GOSAT provides critical measurements of carbon exchange in southern Amazonia, but more samples are needed to examine moist Amazon forests farther north. Citation: Parazoo, N. C., et al. (2013), Interpreting seasonal changes in the carbon balance of southern Amazonia using measurements of XCO2 and chlorophyll fluorescence from GOSAT

A new airborne lidar for remote sensing of canony fluorescence and vertical profil

We report the development of a new lidar system for airborne remote sensing of chlorophyll fluorescence (Ch1F) and vertical profile of canopies. By combining laser induced fluorescence (LIF), sun-induced fluorescence (SIF) and canopy height distribution, the new instrument will allow the simultaneous assessment of gross primary production (GPP), photosynthesis efficiency and above ground carbon stocks. Technical issues of the lidar development are discussed and expected performances are presented

Effect of canopy structure on sun-induced chlorophyll fluorescence

International audienceWe investigated the impact of canopy structure on chlorophyll fluorescence properties. For this purpose, we developed SpectroFLEX, an instrument for quantitative measurements of canopy fluorescence in O 2A and O 2B atmospheric absorption bands. The fluorescence emission of a natural grass canopy was compared with the leaf level fluorescence spectrum acquired simultaneously. It was found that the red-to-far-red fluorescence ratio decreased by a factor of two from the leaf to the canopy level. In addition, this ratio decreased under high light conditions. FluoSAIL simulations were conducted to study the impact of canopy density and geometry on this decrease. This effect has been attributed to a preferential re-absorption of red fluorescence emission during radiative transfer within the canopy compared to far-red emission. © 2012 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)

Monitoring the diurnal time course of vegetation dynamics with geostationary observations : the gflex project

International audienceGiven the present state of the art, remote sensing of vegetation fluorescence from space can be considered as feasible on a technical point of view. However, many unresolved questions remain about its interpretation and its use as a physiological indicator. Low sun synchronous orbiting satellites are not adapted to capture the highly dynamical variations of vegetation fluorescence under environmental constraints because of their long repeat cycles. However, high frequency observations can be reached by geostationary platforms. We present and discuss here the GFLEX project. Its objective is the use of a multispectral imaging system to assess photosynthesis dynamics as a function of irradiation by observing chlorophyll fluorescence and the photochemical reflectance index from a geostationary orbit. The possibility to merge GFLEX and OCAPI, an ocean colour geostationary project for marine applications is also discussed

Intergenerational wealth mobility in France : 19th and 20th century

This paper examines intergenerational wealth mobility between fathers and children in France between 1848 and 1960. Considering wealth mobility in the long run requires taking into account not only positional mobility (that is, how families move within a given distribution of wealth), but also structural mobility induced by changes in the distribution of wealth. Such changes are related to two structural phenomena: in the nineteenth century, the rising number of individuals leaving no estate at death and, after World War I, the decline in the number of the very rich who could live off their wealth. The paper studies the movements between these groups and estimates the intergenerational elasticity of wealth, taking into account the persistence at the bottom and at the top

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