Oscar Pérez-Priego

Publications (11) View all

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  Available from: Oscar Pérez-Priego

  Article: Detection of Water Stress in Orchard Trees with a High-Resolution Spectrometer through Chlorophyll Fluorescence in-filling of the O2-A band

  O. Pérez-Priego, P. J. Zarco-Tejada, J. R. Miller, G. Sepulcre-Cantó, E. Fereres
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  ABSTRACT: A high spectral resolution spectrometer with 0.065-nm full-width half-maximum was used for collecting spectral measurements in an orchard field under three water stress treatments. The study was part of the FluorMOD project funded by the European Space Agency to develop a leaf-canopy reflectance model to simulate the effects of fluorescence. Water deficit protocols generated a gradient in solar-induced chlorophyll fluorescence emission and tree physiological measures. Diurnal steady-state chlorophyll fluorescence was measured from leaves in the field between June and November 2004 using the PAM-2100 fluorometer to study the effects of water stress on chlorophyll fluorescence. Spectral measurements of downwelling irradiance and upwelling crown radiance were conducted with the narrow-band spectrometer, enabling the canopy reflectance to be obtained at subnanometer spectral resolution and permitting the evaluation of the fluorescence in-filling effects on reflectance in trees under water stress conditions. Diurnal and seasonal measurements showed consistently lower steady-state fluorescence (Ft) and quantum yield F Fm in water-stressed trees, yielding mean values of Ft = 038 (well-irrigated) and Ft = 0 21 (water-stressed trees). The agreement between Ft and water potential showed that steady-state fluorescence could be used to detect differences in water stress levels, with determination coefficients ranging between 2 = 048 and 2 = 081 for individual dates. Analysis in the 680–770-nm range showed that the chlorophyll fluorescence in-filling in the O2-A band at 760 nm is sensitive to diurnal variations of fluorescence and water stress, yielding 2 = 0 76 (well-watered treatment), 2 = 0 89 (intermediate stress treatment), and 2 = 07 (extreme stress treatment), demonstrating the close relationships between Ft and in-filling at the crown level. This work was supported in part by the Consejo Superior de Investigaciones Científicas under the CSIC-PIF Program, in part by the European Space Agency (ESA), and in part by the Spanish Ministry of Science and Technology (MCyT) for the projects PIF-200440-F035, ESA-ESTEC Contract 16365/02/NL/FF (FluorMOD), and AGL2003-01468, respectively. The work of P. J. Zarco-Tejada was supported by the Ramón y Cajal (MCyT) and Averroes (JA) programs. The work of J. R. Miller was supported by the Natural Sciences and Engineering Research Council of Canada. Peer reviewed
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  Available from: Oscar Pérez-Priego

  Article: Chlorophyll Fluorescence Detection with a High-Spectral Resolution Spectrometer through in-filling of the O2-A band as function of Water Stress in Olive Trees

  P. J. Zarco-Tejada, O. Pérez-Priego, G. Sepulcre-Cantó, J. R. Miller, E. Fereres
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  ABSTRACT: 2nd International Workshop on Remote Sensing of Vegetation Fluorescence, 17-19 Nov. 2004, Montreal, Canada A high spectral resolution spectrometer of 0.065 nm FWHM in the 680-770 nm range was used for collecting spectral measurements in an orchard of olive trees in Spain under 3 different water stress treatments. The measurements were conducted as part of validation efforts for the FluorMOD project funded by the European Space Agency (ESA) to advance the science of vegetation fluorescence simulation. Diurnal steadystate chlorophyll fluorescence was measured from leaves in the field during summer 2004 using the PAM-2100 fluorometer to study the effects of water stress on chlorophyll fluorescence. Water potential, photosynthesis, and stomatal conductance on trees were also measured in a weekly basis to track the effects of water stress on the tree status and functioning. Infrared Apogee sensors were placed on top of the trees for diurnal thermal data collection, studying the effects of water stress on the tree temperature as an indicator of stress. The Ocean Optics HR-2000 spectrometer was used to measure irradiance and radiance spectra from above tree crowns under different stress conditions. The spectral measurements of irradiance with a cosine corrector and crown radiance with bare fibre were acquired from a pole 7 m in height to collect nadir radiance from the top of tree crowns. Analysis in the red edge covering the 680-770 nm range enabled the study of the chlorophyll fluorescence in-filling in the O2-A band at 760 nm. Results of the spectral analysis and simulation using the FluorMOD radiative transfer model demonstrate that water stress effects on steady-state fluorescence are detectable at the tree level in the O2-A band from reflectance spectra due to the in-filling effects. The development of the FluorMODgui interface has been carried out in the frame of the ESA-project Development of a Vegetation Fluorescence Canopy Model, ESTEC contract no. 16365/02/NL/FF. Within the same project, the leaf and canopy fluorescence models FluorMODleaf and FluorSAIL were developed and provided by R. Pedrós and S. Jacquemoud of LED, University of Paris, I. Moya, Y. Goulas and J. Louis of LURE, University of Paris-South, and Wout Verhoef, National Aerospace Laboratory NLR. Peer reviewed
• Article: Water Stress and Chlorosis Detection in Crop Canopies with AHS Thermal Imagery and CASI and ROSIS Hyperspectral Sensors: Implications on Yield

  P. J. Zarco-Tejada, G. Sepulcre-Cantó, O. Pérez-Priego, J A Sobrino, J. C. Jiménez-Muñoz, A. Berjón, P. Martín, R. González
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  ABSTRACT: Poster presentado en el Congreso Airborne Imaging Spectroscopy Workshop, Bruges, Belgium, 7/10/2005 Methods for water stress and chlorosis detection in crops are presented using the Airborne Hyperspectral Scanner (AHS), Compact Airborne Spectrographic Imager (CASI) and the Reflective Optics System Imaging Spectrometer (ROSIS) airborne sensors. The AHS sensor was used to acquire images of 2-m spatial resolution in the visible, near infrared and thermal spectral regions over an olive orchard in southern Spain to study the spatial variability of water stress and the potential for detecting water deficit conditions at the tree level. ROSIS and CASI sensors were flown at 1 m spatial resolution over 24 vineyard fields with a gradient of nutrient deficiencies, comprising 103 study areas of 10x10 m in size. The AHS sensor was equipped with 20 channels of 20 nm bandwidth for visible and near infrared, 1 channel of 200 nm bandwidth and 42 channels of 13 nm bandwidth for mid infrared, 7 channels of 300 nm bandwidth for short-wave infrared and 10 channels of 400 nm for long-wave infrared. AHS aircraft flights at 7:30, 9:30 and 12:00 GTM in July 2004 were scheduled to study the spatial and temporal variation of the orchard tree temperature as a function of the diurnal variation of water stress. Water and bare soil temperatures were measured simultaneously with airborne sensor flights to calibrate the thermal AHS imagery, acquiring atmospheric optical thickness at the time of image collection. Imagery was processed applying geometric, radiometric and atmospheric correction, obtaining surface temperature with Split-Window algorithms from 17 AHS thermal infrared channels. Water potential, photosynthesis, and stomatal conductance were measured in the field under 3 different water stress treatments weekly from July until November 2004 to track the effects of water stress on the tree status and functioning. Yield data on each olive tree and vineyard 10x10 m study site were measured, including indicators of yield quality. Results obtained between different indicators of yield and quality with i) crown temperature as function of water deficit in olive trees, and ii) chlorosis detection in vineyards as function of nutrient deficiencies will be presented. This methodology shows potential for mapping the spatial variability of water stress and nutrient deficiencies in precision agriculture, enabling the connection with yield reduction as function of stress detection. Peer reviewed
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  Available from: Oscar Pérez-Priego

  Article: Assessing Canopy PRI for Water Stress detection with Diurnal Airborne Imagery

  L. Suárez, P. J. Zarco-Tejada, G. Sepulcre-Cantó, O. Pérez-Priego, J. R. Miller, J. C. Jiménez-Muñoz, J A Sobrino
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  ABSTRACT: Soil Moisture Experiments 2004 (SMEX04) Special Issue A series of diurnal airborne campaigns were conducted over an orchard field to assess the canopy Photochemical Reflectance Index (PRI) as an indicator of water stress. Airborne campaigns over two years were conducted with the Airborne Hyperspectral Scanner (AHS) over an orchard field to investigate changes in PRI, in the Transformed Chlorophyll Absorption in Reflectance Index (TCARI) normalized by the Optimized Soil-Adjusted Vegetation Index (OSAVI) (TCARI/OSAVI), and in the Normalized Difference Vegetation Index (NDVI) as function of field-measured physiological indicators of water stress, such as stomatal conductance, stem water potential, steady-state fluorescence, and crown temperature. The AHS sensor was flown at three times on each 2004 and 2005 years, collecting 2 m spatial resolution imagery in 80 spectral bands in the 0.43–12.5 μm spectral range. Indices PRI, TCARI/OSAVI, and NDVI were calculated from reflectance bands, and thermal bands were assessed for the retrieval of land surface temperature, separating pure crowns from shadows and sunlit soil pixels. The Photochemical Reflectance Index, originally developed for xanthophyll cycle pigment change detection was calculated to assess its relationship with water stress at a canopy level, and more important, to assess canopy structural and viewing geometry effects for water stress detection in diurnal airborne experiments. The FLIGHT 3D canopy reflectance model was used to simulate the bi-directional reflectance changes as function of the viewing geometry, background and canopy structure. This manuscript demonstrates that the airborne-level PRI index is sensitive to the de-epoxidation of the xanthophyll pigment cycle caused by water stress levels, but affected diurnally by the confounding effects of BRDF. Among the three vegetation indices calculated, only airborne PRI demonstrated sensitivity to diurnal changes in physiological indicators of water stress, such as canopy temperature minus air temperature (Tc–Ta), stomatal conductance (G), and stem water potential (ψ) measured in the field at the time of each image acquisition. No relationships were found from the diurnal experiments between NDVI and TCARI/OSAVI with the tree-measured physiological measures. FLIGHT model simulations of PRI demonstrated that PRI is highly affected by the canopy structure and background. Financial support from the Spanish Ministry of Science and Education (MEC) for the projects AGL2003-01468 and AGL2005-04049 are gratefully acknowledged, as well as the support of grant from INIA (RTA02-070), European Union 6th Framework Programme (INCO-CT-654 2004-509087), and MEC CONSOLIDER-RIDECO (CSD2006-00067). Peer reviewed
• Article: Detection of water stress in orchard trees with a high-resolution spectrometer through Chlorophyll fluorescence in-filling of the O-2-A band

  John R. Miller, Óscar Pérez-Priego, Pablo J. Zarco-Tejada, Elías Fereres Castiel, Guadalupe Sepulcre-Cantó
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  ABSTRACT: A high spectral resolution spectrometer with 0.065-nm full-width half-maximum was used for collecting spectral measurements in an orchard field under three water stress treatments. The study was part of the FluorMOD project funded by the European Space Agency to develop a leaf-canopy reflectance model to simulate the effects of fluorescence. Water deficit protocols generated a gradient in solar-induced Chlorophyll fluorescence emission and tree physiological measures. Diurnal steady-state Chlorophyll fluorescence was measured from leaves in the field between June and November 2004 using the PAM-2100 fluorometer to study the effects of water stress on Chlorophyll fluorescence. Spectral measurements of downwelling irradiance and upwelling crown radiance were conducted with the narrow-band spectrometer, enabling the canopy reflectance to be obtained at sulmanometer spectral resolution and permitting the evaluation of the fluorescence in-filling effects on reflectance in trees under water stress conditions. Diurnal and seasonal measurements showed consistently lower steady-state fluorescence (Ft) and quantum yield Delta F/Fm' in water-stressed trees, yielding mean values of Ft = 0.38 (well-irrigated) and Ft = 0.21 (water-stressed trees). The agreement between Ft and water potential showed that steady-state fluorescence could be used to detect differences in water stress levels, with determination coefficients ranging between r(2) = 0.48 and r(2) = 0.81 for individual dates. Analysis in the 680-770-nm range showed that the Chlorophyll fluorescence in-filling in the O-2-A band at 760 urn is sensitive to diurnal variations of fluorescence and water stress, yielding r(2) = 0.76 (well-watered treatment), r(2) = 0.89 (intermediate stress treatment), and T 2 = 0.7 (extreme stress treatment), demonstrating the close relationships between Ft and in-filling at the crown level.
  Ieee Transactions on Geoscience and Remote Sensing 43 (12), 2860-2869 (2005).