Vegetation biomass change of the Bosoh Peninsula: Impacted by the volcano fumes from the Miyakejima

Since the 2001 eruption, the volcanic fumes from the Oyama of Miyakejima Island, located approximately 200 km southwest from the mainland of Japan, have affected the vegetation health and biomass of the Tokyo metropolitan area. In this study, we evaluated the potential for measuring/mapping relative forest damage/recovery in forests in the Bosoh Peninsula, Chiba Prefecture, Japan, using LANDSAT Enhanced Thematic Mapper data and ASTER Level-1B data. The simple ratio which is derived from the near-infrared and red reflective response was found to correlate well with ground-based measurements of forest damage caused by continuous SO₂ contained in the volcanic fumes. Accumulated data by the synchronized field campaign observation of the Japanese cedar field spectra and by satellite analysis indicates the following interesting features: (1) regional differences of SO₂ levels in the forestal area can be estimated by the simple spectrum ratio of the near-infrared and red bands of multispectral satellite data; (2) time-series images using the simple ratios indicated the location of still damaged and recovered forests between the 2001 eruption and 2003; (3) if the vegetations under study are homogeneous single-species with a similar leaf area index and a similar age, the simple ratio was useful to evaluate vegetation damage or recovery among individual forests throughout many of the forests in the Bosoh Peninsula; (4) the damage level of the Tokyo Bay side was found to be consistently higher than the Pacific Ocean side of the peninsula. This obvious difference is likely caused, not only by SO₂ from Miyakejima Island, but also by long term and chronic discharged gas from heavy industrial complexes.