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Proceedings, XXth congress

bul 2004
jp. 66-
- 14772
r. Volker
for the
hout the
ary data,
/e would
titute for
ware and
ially Mr.
Sun-Hwa Kim' and Kyu-Sung Lee
Department of Geoinformatic Engineering, Inha University, Incheon, S. KOREA
22032128 @inhavision.inha.ac.kr

KEY WORDS: Remote Sensing, Ecology, Forestry, Accuracy, Quality, Algorithm
MODIS LAI product has been increasingly important for analyzing the process and productivity of terrestrial ecosystems at global
scale. This study was aimed to assess the quality of global MODIS LAI product for applications in regional and even in local scales.
To examine the quality of MODIS LAI data, we produced a reference LAI map that was derived by relating the ground-measured
LAI to Landsat ETM+ reflectance over the forest of the Kyongan watershed in central Korean peninsula. After the reference LAI
map was rescaled at 1 km spatial resolution, it was compared with the MODIS LAI product that was generated about the same time
with the reference data. From the comparison between the MODIS LAI and the reference LAI, it was found that MODIS LAI values
were slightly higher at the forestland than the reference map and they were generally lower in grasslands and croplands. Specially,
MODIS LAI pixels estimated by the backup algorithm by using NDVI were obviously under-estimated comparing with the reference
LAI value. The MODIS LAI pixels that were attenuated by cloud cover also showed large difference from the reference LAI value.
The discrepancy between the MODIS LAI and the reference LAI can be also caused by the misclassification of MODIS land cover
product that is one of the input variable to create MODIS LAI The quality of MODIS LAI product was largely dependent on the
estimation algorithm, cloud cover, and the accuracy of MODIS land cover product. e
Although it has been relatively new since we are able to get
MODIS LAI product, the estimation algorithm development
started since the early 1990's. After launching the EOS terra
satellite in 1999, the Moderate Resolution Imaging
Spectrometer (MODIS) has begun to deliver 1km global scale
LAI products. EOS program progressed the validation of
MODIS products with production of MODIS data. After 2003,
the papers about validation of provisional MODIS products
were began to introduce. Main products of validation were
MODIS land cover and LAI products. The cases of validation
of MODIS LAI product have two parts, which are the
validation of LAI Radiative Transfer algorithm itself and the
accuracy of LAI product by using empirical methods (Tian et
al., 2002; Cohen et al., 2003). Since MODIS LAI product was
primarily designed at global and continental scales, the
validation of various geographic areas must be continued in
local or global scale. The validity of MODIS global LAI
product is being analyzed at several sites over the world, but it
is rare to find any studies of analyzing at temperate forest in
northeast Asia.
Leaf Area Index (LAI) has been an important parameter that is
directly related to the photosynthesis, evapotranspiration, and
the productivity of plant ecosystem (Bonan, 1993).
Measurement of LAI in the field is very difficult, and requires a
great amount of time and efforts (Gower et al., 1999). The
mapping of LAI in large geographic area may be impossible
when we rely on the field measurement. To solve this problem,
there have been continuing efforts to develop methodologies to
estimate LAI using remote sensor data (Turner et al., 1999).
The normalized difference vegetation index (NDVI) was the
most commonly used, however, showed the saturation
phenomenon in high LAI value (Chen and Cihlar, 1996;
Carlson and Reley, 1997). Although empirical modeling is
relatively easy and useful method for relating field measured

Corresponding author
LAI to remote sensor data, several factors have certain
influence empirical model (Cohen et al., 2003). The vegetation
type, canopy structure, background, atmospheric conditions,
and topographic conditions were affects the empirical model
(Tian et al., 2000; Panferov et al., 2001).
In this study, we are attempted to determine the validity of
MODIS global LAI product at temperate forest in northeast
Asia. Terrestrial ecosystem in this region is vulnerable to
several factors of environmental perturbations. MODIS LAI
product can be an invaluable source of information for
analyzing the status and activity of vegetation at regional and
local scale.
Study area
The study area, the Kyongan Watershed, is located near the
Seoul metropolitan area in central Korean peninsula. The study
area covered about 1,070km? area and 6796 of them is forest.
Two third of the forest is natural forest of mixed deciduous
species, in which the dominant species are oaks (Quercus
mongolica) mixed with natural pine species. The remaining one
third of the forest is coniferous plantation stands of Korea pine
(Pinus karaiensis), Pitch pine (Pinus rigida), and Larch (Larix
leptolepis). Except for a few plantation forest stands, most
forests have very dense canopy closure over 80% and average
tree age ranges from 20 to 50 years. The study area has been an
experimental watershed for many years to study local-scale
runoff and water quality monitoring, in which site-specific LAI
estimate can be a variable of interest for the hydrological
studies (Lee et al., 2003).