Abstract
The impact of the Towada-Chuseri Tephra fall (7 cm thick; To-Cu; ~6000 cal yr BP) on vegetation was investigated by the pollen analysis of core samples obtained from Tashiro Mire (560–575 m a.s.l.), Aomori Prefecture, Japan. The results indicate that a stable Fagus-Quercus forest had been established before the tephra fall. Just after the tephra fall, Quercus subgen. Lepidobalanus percentages increased abruptly by more than 80%. Other tree pollens uniformally decreased, especially Fagus, which showed a significant decrease from 30% to 2.6%. Lepidobalanus subsequently showed a gradual decline beginning 1.7 cm above the tephra, whereas other trees showed gradual increases. At 8.9 cm above the tephra (150–250 years after the tephra fall), the arboreal pollen composition reached a stable state with a similar composition to that before the tephra fall. Contrasting responses of Fagus and Lepidobalanus after the tephra fall shows their tolerances for its impact. The non-arboreal pollen composition, mainly originating from mire vegetation, also changed appreciably after the tephra fall and did not returned to the initial state, indicating that the mire condition was seriously altered.
