抄録
Forest structure and annual ring growth studies were conducted in study plots at different elevations within the forest on the western slopes of Rishiri Island. The results of the survey showed that mixed forests of coniferous trees and broadleaved trees were expanding in the 200 m and 400 m elevation zones, consisting of old Ezo spruce (Picea jezoensis) and around 100 years old Sakhalin fir (Abies sachalinensis) and broad-leaved trees. On the other hand, the 600 m plot was a Erman’s birch (Betula ermanii Cham) forest, consisting of broadleaved trees of different ages. The upper layers of the mixed forests below 400 m elevation were destroyed for some reason about 100 years ago, and the present forest is composed of trees that have grown since then. It was considered unlikely that the cause of the destruction of the upper layer was human-induced deforestation, but more likely to have been caused by natural disasters such as typhoon damage.
