Chlorophyll Fluorescence Effects on Vegetation Apparent Reflectance: II. Laboratory and Airborne Canopy-Level Measurements with Hyperspectral Data

Relationships found between Compact Airborne Specfluorescence: the curvature index R6832/(R675·R691) and trographic Imager (CASI) hyperspectral canopy reflecthe R685/R655 ratio calculated from the canopy reflectance measurements at laboratory and field levels with tance are related to leaf-measured Ft, Fm9 and DF/Fm9 PAM-2000 chlorophyll fluorescence data are presented. steady-state features, and are in agreement with theoretiThis is a continuation of the paper where relationships cal simulations using the leaf Fluorescence-Reflectanceat the leaf level between leaf reflectance and chlorophyll Transmittance model. To test these findings in a field fluorescence were found and demonstrated to be consissetting, airborne field hyperspectral CASI data of 2-m tent with theory using the Fluorescence-Reflectancespatial resolution, 7.5-nm spectral resolution, and 72 Transmittance (FRT) model. Experiments using the hypchannels was used, collected in deployments over 12 sites erspectral CASI sensor in the laboratory to observe a of Acer saccharum M. in the Algoma Region, Ontario canopy of maple seedlings are performed as an interme(Canada) in 1997 and 1998. A field sampling campaign diate step to demonstrate the link between the results at was carried out for biochemical contents of leaf chloroleaf-level and the CASI field canopy levels. Scene obserphyll and carotenoids, chlorophyll fluorescence, and leaf vations of the seedlings utilizing a long-pass blocking filreflectance and transmittance. Leaf-level relationships ter showed that apparent canopy reflectance in the laboobtained between optical indices and physiological indiratory is affected by changes in fluorescence emissions. A cators were scaled up to canopy level through canopy relaboratory experiment on seedlings subjected to diurnally flectance models using input model parameters related to induced change shows the strong link between CASI canthe canopy structure and viewing geometry at the time opy reflectance optical indices in the 680–690-nm region of data acquisition. Results show that scaled-up optical and Fv/Fm dark-adapted chlorophyll fluorescence. indices in the 680–690-nm region are related to Fv/Fm Stressed and healthy maple seedlings are used to demonchlorophyll fluorescence measured in the 20320-m study strate the use of optical indices calculated from the 680– sites. Consistency between leaf, laboratory, and field can690-nm spectral region to track changes in steady-state opy hyperspectral data is shown in this and the previous paper, demonstrating the effect of fluorescence on observations of apparent vegetation reflectance. Elsevier * Centre for Research in Earth and Space Science (CRESS), York Science Inc., 2000 University, Toronto, Canada † Department of Physics and Astronomy, York University, Toronto, Canada ‡ Ontario Forest Research Institute, Ontario Ministry of Natural INTRODUCTION Resources, Sault Ste. Marie, Ontario, Canada