The study on biomass estimation in Mongolian Grassland
using satellite data and field measurement data
Hirokazu Yamamoto, Koji Kajiwara, and Yoshiaki Honda
Center for Environmental Remote Sensing, Chiba University.
1-33, Yayoi-cho, Inageku, Chiba, 263-8522, Japan
Tel : +81-43-290-3835 Fax : +81-43-290-3835
E-mail : kath@ceres.cr.chiba-u.ac.jp
Keywords: Biomass Estimation, NOAA AVHRR LAC, Field Measurement Data
Abstract:
It is said that earth environment is affected by changing vegetation biomass. So, it is needed the analysis of physical parameter of vegetation in the wide area by using satellite data, which has middle spatial resolution (approx. 1km
2). In this study, biomass is estimated on a large scale using NOAA AVHRR LAC data received in Mongolia and field measurement data.
As the result, we found that it is able to estimate vegetation biomass without influence of cloud contamination and vegetation growth in case of more than 5 days composite of NOAA AVHRR LAC data. And we could estimate biomass in the wide area until less than 10% error.
1. Introduction
Carbon is one of the most important element on the earth, and it can become with key word of the mechanism of earth fluctuation. Also, it is said that vegetation has the important role of the carbon circulation of biosphere-lithosphere-atmosphere. Therefore, it is needed for environment monitoring to understand plant productivity globally.. Many research have done to the estimation of vegetation amount using satellite data which has characteristics of high frequency and middle spatial resolution such as NOAA AVHRR in recent years.
EOS-AM1(Terra) satellite has launched successfully, and MODIS is expected to the understanding of global dynamics. Japan also has plan of launch satellite, ADEOS-II GLI, ADEOS -III SGLI, but there are no methodology of calibration and validation for the above mentioned middle resolution satellite. We already tried the acquisition of various kinds of ground based data in Mongolian grassland in comparison with the satellite data scale, and we succeeded in estimating the relation between vegetation index and vegetation cover ratio (VCR) obtained by the mobile measurement system (Yamamoto et al.,1997). However, actually, such these data have not been applied to satellite data using the model obtained from field measurement data.
2. Objective
The aim of this study is the following items.
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To construct of biomass estimation model which can be calibrated from the relationship between vegetation index - vegetation cover ratio - biomass using the field experiment data
- To apply the field data to satellite data.
- To evaluate the derived satellite biomass estimation by using meteorological station data in Mongolia.
3. Method
3.1 The Study Area and Data
The study area of field measurement and satellite data is Mongolian grassland. Figure.1 shows the range of this study area of field measurement. Field measurement data we used in this study was acquired in summer from 1995 to 1998(Table.1). NOAA AVHRR LAC data received at Ulaanbaatar in Mongolia was used as satellite data. Table.2 shows acquisition date and time of AVHRR data used in this study.
3.2 Analysis of Field Measurement Data
The mobile measurement system is quick measurement system for acquisition of the various kinds of ground information over a large area such as the scale of satellite data. Sensor height from the ground is approximately 2 m. Optical axis of this system is adjusted to become parallel and being fixed to always measure nadir. Spectrometer measures in the visible and near-infrared region (350nm- 1050nm) with 512 channels. Observation item is spectral reflectance and ground digital image for vegetation cover ratio. In this study, vegetation cover ration is defined as the proportion of the green plant that is viewed in nadir direction from the sensor to ground surface.
The biomass measurement is cutting all the grass (green leaf) inside of 1m
2 area with the hand, and wet grass weight and dry grass weight by using drying machine for 8.5 hours is measured. And this system is also able to acquire nadir ground digital image, spectral information, and grass height. System is designed the same as mobile measurement system. In this study, 58 good biomass measurement points obtained from August 3 to August 9, 1998 in Site.1 were analyzed. And 5 points data had been obtained in August 10, 1998 in Site.2 and 3 points data had been obtained in August 11 in Site.3. Observation items are spectral reflectance, ground images, and biomass(wet and dry grass weight, and grass height). In this study, biomass is defined as the weight of sufficient dried up grass which is green and fresh matter on the ground.
Calculation of vegetation coverage ratio is derived from digital images using RGB pattern method and hue and intensity method (Yamamoto et al.,1997).
Figure.1 The study Area
