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@ARTICLE{Krmer:1041486,
      author       = {Krämer, Julie and Siegmann, Bastian and Castro, Antony
                      Oswaldo and Muller, Onno and Pude, Ralf and Döring, Thomas
                      and Rascher, Uwe},
      title        = {{D}ownscaling the full-spectrum solar-induced fluorescence
                      emission signal of a mixed crop canopy to the photosystem
                      level using the hybrid approach},
      journal      = {Remote sensing of environment},
      volume       = {324},
      issn         = {0034-4257},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2025-02272},
      pages        = {114739 -},
      year         = {2025},
      abstract     = {Remote sensing of hyperspectral vegetation reflectance and
                      solar-induced chlorophyll fluorescence (SIF) isessential for
                      evaluating crop functionality and photosynthetic
                      performance. While primarily applied in monocultures,these
                      tools show promise in diverse cropping systems, enhancing
                      ecological intensification. Plant-plantinteractions in such
                      systems can influence key physiological processes, such as
                      photosynthesis, making SIF avaluable tool for evaluating how
                      crop diversity affects photosynthetic function and
                      productivity. However,detecting SIF in diverse stands
                      remains challenging due to uncertainties in light
                      re-absorption and scattering. Toaddress these challenges, we
                      propose a hybrid model inversion framework that combines
                      canopy observationswith physical modeling to derive leaf
                      biochemical, canopy structural variables, and SIF spectra at
                      leaf andphotosystem levels. This approach employs a machine
                      learning retrieval algorithm (MLRA), trained on
                      syntheticspectra from radiative transfer model (RTM)
                      simulations, to quantify re-absorption and scattering
                      effects. Usingthe SpecFit retrieval algorithm, the temporal
                      evolution of full-spectrum SIF at the canopy level can be
                      derived. Todownscale SIF to the photosystem level and
                      retrieve its quantum yield, we corrected the canopy SIF
                      spectrum forre-absorption and scattering effects calculated
                      from TOC reflectance. Spectral measurements were gathered
                      fromfield experiments conducted over three years, covering
                      various growth stages of cereal and legume monocropsand
                      their mixture. Our method accurately predicts important leaf
                      biochemical and canopy structural variables,such as leaf
                      area (LAI, R2 = 0.75) and leaf chlorophyll content (LCC, R2
                      = 0.91), and shows a general highretrieval performance for
                      light absorption (fAPARChl, R2 = 0.99 for the internal model
                      validation). We confirmedthe reliability of our method in
                      modeling re-absorption and scattering processes by comparing
                      canopy SIFdownscaled to the leaf level with independent
                      leaf-level SIF measurements. While the results show a
                      goodprediction accuracy in terms of fluorescence magnitude
                      at the leaf level, we did not find a strong agreement
                      ofcorresponding leaf and canopy measurements at the single
                      plot level.},
      cin          = {IBG-2},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001471626900001},
      doi          = {10.1016/j.rse.2025.114739},
      url          = {https://juser.fz-juelich.de/record/1041486},
}