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United States Department of Agriculture

Agricultural Research Service

Title: Relating Canopy Hyperspectral Reflectance and Fluorescence Indices to Carbon Related Parameters

Authors
item Middleton, E - NASA GSFC
item Corp, L - SSAI
item Entcheva-Campbell, P - UNIV OF MD
item DAUGHTRY, CRAIG

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 23, 2006
Publication Date: N/A

Technical Abstract: The relative success for monitoring physiological or stand properties related to carbon (C) assimilation using narrow band spectral reflectance and fluorescence indices was evaluated at leaf and canopy levels for mature corn crops (Zea mays L.) and tree saplings of three deciduous species. These were red maple (Acer rubrum L.), tulip poplar (Liriodendron tulipifera L.), and sweet gum (Liquidambar styraciflua L.). The corn crops and tree plantation were arranged in plots, each receiving a controlled nitrogen (N) fertilization regime at one of four dosages in experiments conducted from 2001 to 2005 at the USDA facility in Beltsville, MD, USA. Leaf reflectance spectra were obtained in conjunction with leaf level photosynthesis, fluorescence, and chemistry (chlorophyll and carotenoid content per leaf area; percent C and N by dry mass). Whole plant canopy spectra were supported by yield, dry weight and leaf area index data. The spectra were acquired using a spectroradiometer (ASD-FR FieldSpec Pro, Analytical Spectral Devices, Inc., Boulder, CO, USA), either coupled with a hemisphere for leaf optical properties or to measure nadir radiances 1 m above plant canopies within a 22o field of view. In situ photosynthesis and chlorophyll fluorescence (ChlF) parameters were determined simultaneously with a photosynthetic system (Li-Cor 6400, Lincoln, Nebraska, USA) fitted with a fluorimeter under controlled conditions (temperature, irradiance, carbon dioxide, and humidity). In the laboratory, actively induced fluorescence emission spectra were obtained for both adaxial and abaxial leaf surfaces. Canopy-level steady state ChlF emissions were extracted from the apparent canopy reflectance spectra at 688 and 760 nm using the Fraunhofer Line Depth (FLD) principal. These fall within/near the two stable red and far-red chlorophyll ChlF peaks (centered at 685"10 nm and 735"5 nm). Methods have been developed elsewhere to extract steady state solar induced fluorescence (SIF) from apparent reflectance of vegetation canopies/landscapes using the FLD principal. These data sets were used to parameterize the newly available Fluorescence Model, FluorMOD (Verhoef, W., 2005, 2nd International Workshop on Remote Sensing of Vegetation Fluorescence), a coupled radiative transfer and fluorescence model to estimate canopy ChlF based on an extension of the SAIL Model (Verhoef, 1994). Both fluorescence and reflectance indices were successful in discriminating foliar constituents (e.g., pigment ratios, C/N ratios) but only ChlF indices were correlated with corn yields. In addition, the red/far-red SIF canopy ratio successfully tracked a leaf-level steady state fluorescence ratio (Fs/Chl, r = 0.92) over two corn crops. The relationships between canopy and leaf reflectance and fluorescence indices are presented, as are the FluorMOD simulations. Keywords: Hyperspectral reflectance, fluorescence, carbon, FluorMOD.

Last Modified: 9/10/2014
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