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@ARTICLE{Gerhards:852605,
      author       = {Gerhards, Max and Schlerf, Martin and Rascher, Uwe and
                      Udelhoven, Thomas and Juszczak, Radoslaw and Alberti,
                      Giorgio and Miglietta, Franco and Inoue, Yoshio},
      title        = {{A}nalysis of {A}irborne {O}ptical and {T}hermal {I}magery
                      for {D}etection of {W}ater {S}tress {S}ymptoms},
      journal      = {Remote sensing},
      volume       = {10},
      number       = {7},
      issn         = {2072-4292},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2018-05509},
      pages        = {1139 -},
      year         = {2018},
      abstract     = {High-resolution airborne thermal infrared (TIR) together
                      with sun-induced fluorescence (SIF) and hyperspectral
                      optical images (visible, near- and shortwave infrared;
                      VNIR/SWIR) were jointly acquired over an experimental site.
                      The objective of this study was to evaluate the potential of
                      these state-of-the-art remote sensing techniques for
                      detecting symptoms similar to those occurring during water
                      stress (hereinafter referred to as ‘water stress
                      symptoms’) at airborne level. Flights with two camera
                      systems (Telops Hyper-Cam LW, Specim HyPlant) took place
                      during 11th and 12th June 2014 in Latisana, Italy over a
                      commercial grass (Festuca arundinacea and Poa pratense) farm
                      with plots that were treated with an anti-transpirant agent
                      (Vapor Gard®; VG) and a highly reflective powder (kaolin;
                      KA). Both agents affect energy balance of the vegetation by
                      reducing transpiration and thus reducing latent heat
                      dissipation (VG) and by increasing albedo, i.e., decreasing
                      energy absorption (KA). Concurrent in situ meteorological
                      data from an on-site weather station, surface temperature
                      and chamber flux measurements were obtained. Image data were
                      processed to orthorectified maps of TIR indices (surface
                      temperature (Ts), Crop Water Stress Index (CWSI)), SIF
                      indices (F687, F780) and VNIR/SWIR indices (photochemical
                      reflectance index (PRI), normalised difference vegetation
                      index (NDVI), moisture stress index (MSI), etc.). A linear
                      mixed effects model that respects the nested structure of
                      the experimental setup was employed to analyse treatment
                      effects on the remote sensing parameters. Airborne Ts were
                      in good agreement (∆T < 0.35 K) compared to in situ Ts
                      measurements. Maps and boxplots of TIR-based indices show
                      diurnal changes: Ts was lowest in the early morning,
                      increased by 6 K up to late morning as a consequence of
                      increasing net radiation and air temperature (Tair) and
                      remained stable towards noon due to the compensatory cooling
                      effect of increased plant transpiration; this was also
                      confirmed by the chamber measurements. In the early morning,
                      VG treated plots revealed significantly higher Ts compared
                      to control (CR) plots (p = 0.01), while SIF indices showed
                      no significant difference (p = 1.00) at any of the
                      overpasses. A comparative assessment of the spectral domains
                      regarding their capabilities for water stress detection was
                      limited due to: (i) synchronously overpasses of the two
                      airborne sensors were not feasible, and (ii) instead of a
                      real water stress occurrence only water stress symptoms were
                      simulated by the chemical agents. Nevertheless, the results
                      of the study show that the polymer di-1-p-menthene had an
                      anti-transpiring effect on the plant while photosynthetic
                      efficiency of light reactions remained unaffected. VNIR/SWIR
                      indices as well as SIF indices were highly sensitive to KA,
                      because of an overall increase in spectral reflectance and
                      thus a reduced absorbed energy. On the contrary, the TIR
                      domain was highly sensitive to subtle changes in the
                      temperature regime as induced by VG and KA, whereas
                      VNIR/SWIR and SIF domain were less affected by VG treatment.
                      The benefit of a multi-sensor approach is not only to
                      provide useful information about actual plant status but
                      also on the causes of biophysical, physiological and
                      photochemical changes},
      cin          = {IBG-2},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {582 - Plant Science (POF3-582)},
      pid          = {G:(DE-HGF)POF3-582},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000440332500162},
      doi          = {10.3390/rs10071139},
      url          = {https://juser.fz-juelich.de/record/852605},
}