The Impact of the Kikai-Akahoya Explosive Eruption on Vegetation in Southern Kyushu, Japan, Clarified by Phytolith Studies

Abstract

This study aims to clarify the impact of the explosive eruption of Kikai Caldera (7, 300cal BP) on vegetation in southern Kyushu, Japan, based on phytolith studies.
A significant change in phytolith assemblages below and above the Koya pyroclastic flow (K-Ky) elucidated that the hazardous pyroclastic flow had changed vegetation from lucidophyllous forests such as Castanopsis and Lauraceae associated with bamboo grass bush to grassland represented by Miscanthus in southern Osumi and Satsuma Peninsula. The recovery of the lucidophyllous forests in this area was considered to start about 600-900 years after the volcanic event, based on the hiatus between the erupted ages of the tephras, which was estimated as 600-900 years. However, the forest vegetation in these areas was partly in the process of recovery. The damage to lucidophylllous forests in the area northward from the mid part of Kagoshima prefecture, which the K-Ky pyroclastic flow did not reach but which was affected by the intensive Akahoya ash fall (K-Ah) alone, was considered to be relatively small.