Chlorophyll fluorescence effects on vegetation apparent reflectance: I. Leaf-level measurements and model simulation

Citation
Pj. Zarco-tejada et al., Chlorophyll fluorescence effects on vegetation apparent reflectance: I. Leaf-level measurements and model simulation, REMOT SEN E, 74(3), 2000, pp. 582-595
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
REMOTE SENSING OF ENVIRONMENT
ISSN journal
0034-4257 → ACNP
Volume
74
Issue
3
Year of publication
2000
Pages
582 - 595
Database
ISI
SICI code
0034-4257(200012)74:3<582:CFEOVA>2.0.ZU;2-1
Abstract
Results from a series of laboratory measurements of spectral reflectance an d transmittance of individual leaves and from a modeling study are presente d which demonstrate that effects of natural chlorophyll fluorescence (CF) a re observable in the red edge spectral region. Measurements have been made with a Li-Cor Model 1800 integrating sphere apparatus coupled to an Ocean O ptics Model ST1000 fiber spectrometer in which the same leaves are illumina ted alternately with and without fluorescence-exciting radiation in order t o separate the fluorescence emission component from the reflectance spectru m. The resulting difference spectrum is shown experimentally to be consiste nt with a fluorescence signature imposed on the inherent leaf reflectance s ignature. A study of the diurnal change in leaf reflectance spectra, combin ed with fluorescence measurements with the PAM-20000 Fluorometer, show that the difference spectra are consistent with observed diurnal changes in ste ady-state fluorescence. In addition, the time decay in the difference signa ture from repetitive leaf spectral reflectance measurements is seen to be c onsistent with the time decay of the leaf fluorescence signal (Kautsky effe ct) of dark-adapted leaves. The expected effects of chlorophyll fluorescenc e emission on the apparent spectral reflectance from a single leaf are also simulated theoretically using the doubling radiative transfer method. Thes e modeling results demonstrate that the laboratory observations of a differ ence spectrum with broad peak at about 750 nm and a much smaller peak near 690 nm are in agreement with theory. Model simulation shows that chlorophyl l pigment and fluorescence each affect indices that are being used in optic al remote sensing to characterize pigment levels and stress in vegetation c anopies. Implications for high spectral resolution remote sensing of forest canopies are presented in a companion paper. (C) 2000 Elsevier Science Inc .