A preliminary study on the effects of pyroclastic fall deposit on the forest ecosystem in southwestern hokkaido, japan

In southwestern Hokkaido, volcanic activities were high during historical times. For examination of their effects on forest ecosystem, we conducted preliminary survey using a dendroecological technique. Tree-ring samples were collected mainly in the southern part of the Ishikari Lowland where some layers of pyroclastic fall were found. The number of tree-rings was counted and tree-ring widths were measured. As a result, we could distinguish from the 1739 tree ring measurements the effect of eruption with its subsequent Ta-a volcanic deposition. This proves that the effect on tree growth changed in proportion to distance from the origin of the pyroclastic fall