Abstract
The aim of this study is to examine the relationship between the spatial pattern of the dieback of Castanopsis sieboldii and topography on the Mt Mihara-yama of Hachijo-jima Island in 2010, in order to clarify the probability of the tree mortality and to control the bark beetle (Platypus quercivorus). Results of our vegetation surveys show that the dieback of Castanopsis sieboldii was found between 200–400 m on the southwest slope of Mt. Mihara-yama. The general liner model (GLM) analysis indicated that the total amount of radiation, altitude, and slope aspect were significant, and also, the probabilities of the dieback of Castanopsis sieboldii were higher on the ridge of the southwest-facing slope. In 2010, the period of no rainfall was lasted during 20 days of July, and furthermore, the total rainfall in August was 40% less than the normal value. The summer dry condition in 2010 could trigger the dieback of Castanopsis sieboldii because the mycorrhizal fungus carried by the bark beetle should affect the tree water relations. Consequently, the dieback of Castanopsis sieboldii caused by the bark beetle in 2010 was mainly occurred on the drier ridges of the southwest-facing slopes of Mt. Mihara-yama.
