Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

Bibliographic data

Multivolume work

Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [WP-4 INTERPRETATION AND MODELLING]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: LEAF REFLECTANCE A STOCHASTIC MODEL FOR ANALYSING THE BLUE SHIFT. W. Lüdeker, K. P. Günther

Document type:: Multivolume work

Structure type:: Chapter

3 RESULTS Some results of the model simulations are presented in figure 2 to 4. All parameters needed for the cal culations are taken from the literature, but in some cases not all optical, geometrical or physilogical pa rameters were found so that some estimates had to be made. In our first approach the influence of the pigment concentration on the reflectance spectra was analy zed. According to our model the pigments are not homogeneously distributed in the leaf but are enclo sed in small particles , the chloroplasts (Morel and Bricaud 1981). Thus the pigment concentration can be calculated by two independent methods. First, assu ming a constant number of chloroplasts per unit volume in the leaf, the total pigment concentration of the leaf is given by multipying this number with the internal pigment concentration of the chloro plasts. By reducing the internal pigment concentra tion of the chloroplasts means that the leaf and the chloroplasts become more transparent On the other hand, assuming a constant internal pigmentation of the chloroplasts the leaf becomes more transparent by reducing the number of chloroplasts per unit volume. In this case the optical properties of the chloroplasts are unchanged. Running the stochastic model with both versions for calculating the total pigment concentration it was shown that the reflectance spectrum in the visible part is influenced only slightly at the order of less than 0.5% over the whole spectrum. In general, hig her local pigment concentrations in the chloroplasts induce reduced absorption combined with higher re flectance. This so called sieve-effect becomes re markable only in the absorption bands of chlorophyll a by increasing the linewidth. Additional the sieve- effect flattens the absorption spectrum of the leaf and thus flattens the reflectance spectrum too. Based on this result, the dependence of the reflec tance spectra on the pigment concentration is analy zed by reducing the number of chloroplasts per unit volume only. In figure 2 three reflectance spectra are shown demonstrating the influence of pigment reduction. Due to the decrease of the the pigment concentration a reduced absorption is seen by an increase of the reflection assocoated with a blue shift of the red edge. The increase of the calculated reflectance at e.g. 680 nm is about 6%, when the pigment concentration decreases to about 1/16 of the initial concentration which was about 3 mg/cm 3 of chlorophyll a and b. The shift of the red edge is typical nm, when the leaf color changes from fully green leaves (3 mg/cm 3 ) to light-green leaves (about 0.2 mg/cm 3 ). This result is in very good agreement with the experimental results of Buschmann and Lichtenthaler (1988) for cherry-laurel leaves, having comparable pigmentation. Also in the green spectral range at about 560 nm a quite good agreement between the modele reflec tance spectra and the experimental data of Bu schmann and Lichtenthaler (1988) is seen. The incre ase of the reflectance at 560 nm by decreasing the pigment concentration at an equal amount is nearly identical for the measured and modeled data. The model shows an increase of the reflectance from 9% for fully green leaves to 25% for light green leaves while the experimental data for cherry-laurel leaves increase from 10% to 26%. For all calculations a difference between the mo delled reflectance spectra and the measured data is seen in the near-infrared region. In this spectral range the internal cell structure and thus the scat tering coefficient determines the reflectance spec tra, because pigment and water absorption is negli gible. On the other hand the water content of the leaf determines the arrangement and the optical cross section of the cells indirectly and thus the scattering coefficient. In our approach, presented in this paper, the scattering coefficient is held con stant. leading to constant reflectance in the near-in frared region. Based on the good agreement of the calculated re flectance spectra with the data found in the litera ture, the seasonal cycle of the reflectance features of oak leaves was calculated. The annual variation of different leaf pigments as chlorophyll a and b, lu tein, violaxanthin, neoxanthin and anthocyanin is gi ven by Sanger (1971) , while the specific spectral ab sorption coefficients for these pigments are found in Lichtenthaler (1987b) and Thimann and Edmondson (1949). Figure 2: Reflectance spectra of the model leaf depending on the pigment concentration. All other leaf parameter are held constant. I: maximum concentration c 0 2: reduced concentration c Q / 4 3: reduced concentration c Q / 16 478

Access restriction

Copyright

fullscreen: Proceedings of the Symposium on Global and Environmental Monitoring (Part 1)

Multivolume work

Volume

Chapter

Chapter

Table of contents

Cite and reuse

Volume

Chapter

Image

Image fragment

Citation links

Citation recommendation