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SPECTRORADIOMETRIC MEASUREMENTS OF TREE SPECIES IN THE CASPIAN 
FORESTS OF IRAN 
M. Abbasi 3 , M.E. Schaepman b , A. Darvishsefat 3 , H.M. Bartholomeus b , M.R. Marvi Mohajer 3 , H. Sobhani 3 
3 Department of Forestry, Faculty of Natural Resource, University of Tehran, Karaj. Iran- 
mozhgan.abasi@gmail.com, adarvish@ut.ac.ir, mohajer@nrf.ut.ac.ir, hsobhan@nrf.ut.ac.ir 
b Centre for Geo-Information, Wageningen University and Research Centre, P.O. Box 47, NL-6700 AA Wageningen, Gelderland, 
The Netherlands- (Michael.Schaepman, Harm.Bartholomeus)@wur.nl 
Commission VII, WG VII\3 
KEY WORDS: Field Spectroradiometry, spectral signatures, vegetation indices, Caspian forest, Illumination, Iran 
ABSTRACT: 
Forest type maps play a significant role in sustainable forest management. For many years aerial photos and satellite data were a 
primary data source supporting forest type mapping. Recent developments in remote sensing provide opportunities to further enhance 
forest type maps by introducing variations of spectral, biochemical and biophysical properties at various scales. A structural sampling 
and collection of the above variables will support an improved interfacing between spatially continuous data, forest type maps and 
finally will support forward and inverse modeling of advanced forest biochemical, -structural, and other relevant variables. 
The main objective of this study is to acquire, process and analyze spectral signatures of main forest tree species of the Caspian forest 
(namely Fagus orientalis, Quercus castaneifolia, Carpinus betulus, Alnus subcordata, and Parrotiapersica) located in the Research 
Forest owned by the University of Tehran on the Northern slopes of the Elburz mountains, Iran. We have sampled 102 spectra each 
of the afore mentioned tree species using leaf ‘pile’ reflectance and branch pile reflectance. We build a comprehensive database of 
leaf optical properties, and other measures such as branch and twig reflectance. Field spectroradiometric measurements (350-2500nm) 
were carried out in the course of summer 2007. Spectral measurements were acquired in altitude gradients between 400-2100m (low, 
mid and high elevation) of the Elburz mountains. All spectral signatures after preprocessing were analyzed physically and 
statistically. We select a set of vegetation indices related to optical properties of the leaves and exploit changes of vegetation 
reflectance signature dependent on illumination conditions (shaded vs. non-shaded leaves) and chlorophyll content. We conclude that 
the Vogelmann index (R740/R720) is more sensitive to chlorophyll content in comparison with the other indices. It shows that 
hornbeam (Carpinus betulus) is significantly different in spectral signatures compared to beech {Fagus orientalis), oak, {Quercus 
castaneifolia) and alder (Alnus subcordata) as well as ironwood {Parrotia persica) with alder and oak being statistically different 
(p<0.0001, a= 0.01). Variability in spectral properties related to tree age and exposition is also assessed. We conclude by presenting 
a comprehensive spectral database of leaf optical properties of the main dominant tree species for further use in the determination of 
photosynthetic and non-photosynthetic fractions, remote determination of dominant species, radiative transfer based on forest 
modeling, and ecosystem change analysis (invasive species, etc.). 
1. INTRODUCTION 
The Caspian forest belongs to the broadleaf deciduous biome, 
which is widely distributed from North America to Europe 
and Asia. These forests receive considerable precipitation, 
between 750 and 2,200 mm per year. The Caspian forest 
contains the most important and significant natural habitats 
for in-situ conservation of biological diversity, including 
those containing threatened species of outstanding universal 
value from the science or conservation point of view of with 
a significant ecological value. 
In recent years contemporary with developing new satellite 
data, numerous studies have been performed to prepare forest 
type maps of the north of Iran by multispectral data, but their 
results did not indicate high overall accuracy (Shataee et al., 
2004; Latifi et al., 2006; Darvishsefat et al., 2003). Because 
of the mountainous and complex micro topography condition 
as well as high diversity in these forests, it needs high 
spectral and spatial resolution for an accurate type map. 
There is a strong optimism that with the arrival of the new 
generation of imaging spectrometers (hyperspectral data), 
significantly higher quality data will be available. 
Spectroradiometry has advantages over conventional 
techniques to map forest type, allowing the non destructive 
sampling of objects and enabling users to gain critical 
information more quickly and cheaply. In recent years many 
researchers have studied the spectral characteristics of species 
and have prepared spectral libraries that are necessary for 
providing reference spectra for a number of procedures in 
remote sensing, e. g. spectral unmixing (Kneubuehler et al., 
1998; Schaepman & Dangel 2000). 
Leaf optical properties are influenced by the species-specific 
structure of the leaf surface and the concentration of 
chlorophyll and other biochemical constituents, water content, 
and leaf structure (Asner, 1998; Jacquemoud & Ustin; 
Stimson et al., 2005). Many optical vegetation indices have 
been investigated related to biochemical compositions in leaf 
and canopy level to investigate the spectral differences 
among the species (Blackburn, 1997; Lovelock & Robinson, 
2002; Maire et al., 2003; Clevers et al., 2005; Malenovsky, et 
al., 2005). 
The scope of this study was to acquire spectral signatures of 
the most important tree species of the Caspian forest namely 
Fagus orientalis, Quercus castaneifolia, Carpinus, betulus, 
Alnus subcordata, and Parrotia persica and to assess the 
spectral reflectance differences among the afore mentioned 
tree species using vegetation indices (Vis) related to 
chlorophyll content. This information is necessary for