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Activiities of ASTER Working Groups |
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Forestry and Forest Products Research Institute
Yoshio Awaya |
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Environmental disruptions such as an increase in carbon dioxide and nitrogen oxides in the atmosphere, oceanic pollution, and forest destruction caused by the extension of human activities, have resulted in various crucial phenomina on a global scale, such as global warming, the frequent occurrence of anomalous weather, ozone layer destruction, and the enlargement of desertification.
It is presumed that global warming may increase forest fires, disease and insect injury on a global scale. Recent news on mountain fires and forest blight on a large scale is considered to be actual evidence for this presumption. It is predicted that warming will spread more rapidly than plants can change their habitats. A large number of species may die out. This will disturb an ecological balance greatly. In this context, it has become a critical social issue to grasp the current situation of forests in large regions and to monitor the occurrence of forest blight and mountain fires by means of remote sensing technology.
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A large number of high-resolution optical sensors have been launched since the first launch of MSS by LANDSAT 1 in 1972. Many scientists have poited out the importance of visible and near-infrared rays in identifying vegetation by using data acquired from these optical sensors. Most optical sensors are provided with channels for red and near-infrared rays. The effectiveness of normalized vegetation index ( NDVI ) derived from data obtained by using these channels are examined in details. Only LANDSAT TM and JERS OPS of the existing satellite sensors can observe short-wave infrared rays. ASTER is equipped with the channels for red, near-infrared, and short-wave infrared rays and thus expcted to be useful as a powerful tool for analyzing the conditions of forests.
Fig.1shows the distribution of the blight of birch sparse forests as obtained from analyzing changes in NDVI. The NDVIs were calculated from LANDSAT MSS data. This map refers to a transition zone from the subarctic forest zone to the tundra zone ( lat. ca. 69ﾟ40' N. and long.ca.26ﾟ50' E.). Red color on this map probably indicates areas where dead trees predominate and yellow color indicates areas where forests has undergone moderate damage and remains little recovered.
This map agrees well with the results of the areal investigation, carried in 1973, on forest damge. In this area extensive blight caused by the larvae of a moth has occurred repeatedly at intervals of several ten years. Moth larvae are a leaf-eating insect Therefore, birches can normally survive as far as damage is not so serious. However, birches tend to die if cold weather continues for years and an outbreak of moths occurs. This area experienced an outbreak of moths in 1967-68. Fig.1 shows its after-effect. As described above, high-resolution satellite data serve as a powerful means to grasp the real conditions of forest blight. |
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Fig 1. Damage of birch sparse forests in Northern Finland
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| (This map probably indicates the death of birches in a period of 1972-1987 ) |
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Aged trees tend to blight and die. This tendency seems to grow in the forests of the frigid zone. The blight of pine trees, oaks, Japanese larches, and others has observed in Japan, which is situated in the temprate zone. Data from ASTER equipped with channels for red, near-infrared, and short-wave infrared rays are useful for the classification of forests and the mapping of extensive blight, and for the long-term monitoring of forests in combination with past TM data. |
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( Eco/Oceanography and Limnology WG )
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