New vegetation indices for remote measurement of chlorophylls based on leaf directional reflectance spectra
Year: 2001
Authors: Maccioni A., Agati G., Mazzinghi P.
Autors Affiliation: Istituto di Elettronica Quantistica, Consiglio Nazionale delle Ricerche (IEQ-CNR), Via Panciatichi 56/30, 50125 Firenze, Italy;
Istituto Nazionale di Ottica Applicata, Largo E. Fermi 6, 50125 Firenze, Italy
Abstract: Directional reflectance (R) spectra from 380 to 780 nm for nadir illuminated leaves of four different plants (croton, Codiaeum variegatum; spotted eleagnus, Eleagnus pungens Maculata; Japanese pittosporum. Pittosporum tobira and Benjamin fig, Ficus benjamina Starlight) were acquired at a viewing angle of 30 degrees from the nadir direction. Chlorophyll-a and -b content of leaves covered a range of 1-60 and 0.5-21 mug/cm(2), respectively. In contrast with previous results from hemispherical reflectance measurements, directional reflectance data does not correlate well with chlorophyll concentration. This is mainly due to the external reflectance (R-R) at the leaf epidermis, caused by the mismatch of the refractive index at the air-epidermis and epidermis-inner layer boundary. The external reflectance can be identified with the blue flat reflectance between 380 and 480 nm. The inner reflectance (R-1), obtained by subtracting the external reflectance from the measured spectra, was found to be linearly related to the logarithm of the chlorophyll content. Good fitting of the log (Ch1) versus R-1(lambda) curves were obtained for R-1 in the green band (around 550 nm) and close to the inflection point in the red edge (around 700 nm). The coefficient of determination, r, of curve fitting improved (up to 0.97) when the normalised inner reflectance NR1(lambda) = R-1(lambda)/R-1(lambda (0)), with lambda (0) greater than or equal to 750 nm, was used instead of the absolute reflectance. The best indices for Ch1, Ch1-a and Ch1-b determination were R-542(1)/R-750(1), R-706(1)/R-750(1) and R-556(1)/R-750(1), respectively. However, since the content of Chi-a relative to Ch1-b was almost constant for the plants investigated, the two last indices must be further validated on leaves with a high variability in the Ch1-a:Ch1-b ratio. The error in the determination of chlorophyll content was found to be of the order of 10%. This value was lower than those obtained by applying the vegetation indices previously suggested. Therefore, the normalised inner reflectance in the green and in the red edge represents a more suitable index for the chlorophyll determination than those up to now used. (C) 2001 Elsevier Science BY. All rights reserved.
Journal/Review: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY
Volume: 61 (1-2) Pages from: 52 to: 61
More Information: This research was supported by the Agenzia Spaziale Italiana (ASI) under the ARS-99-15 and ARS-98-59 projects: Modelli di riflettanza bidirezionale di vegetazione.KeyWords: Chlorophyll; Leaf directional reflectance; Leaf reflectance spectra; Remote sensing of chlorophyll; Chlorophyll a; Chlorophyll b, analytical error; Concentration (parameters); Controlled study; Correlation function; Nonhuman; Plant leaf; Priority journal; Reflectometry; Vegetation, Angiosperms; Chlorophyll; Croton; Ficus; Mass Spectrometry; Plant Leaves, Codiaeum variegatum; Croton; Eleagnus; Ficus benjamina; Pittosporum; Pittosporum tobiraDOI: 10.1016/S1011-1344(01)00145-2ImpactFactor: 1.251Citations: 189data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-11-10References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here
