Establishment of a pollard beech forest, "Agariko, " in Mt. Chokai, northern Japan.

Abstract

The establishment of an unique beech forest dominated by pollard type trees in the foothill of Mt. Chokai, northern Japan, was studied by analyzing stand structure, annual rings (both done in 1997), and aerial photographs taken in the past. Most beech (Fagus crenata) individuals had a pollard like form of base with up to more than 11 stems which had sprouted at up to 4 m above the ground. The dbh-class distributions of sprouted stems were similar to those of secondary forests, though those of individual trees (estimated by summed basal area or sprouted stems) suggested the forests to be rather developed ones. Tree ring analyses showed that the stems had sprouted simultaneously several times during the past 50-170 years. The similar patterns were also found among the sprouted stems of same individuals. The aerial photographstaken in 1961 showed that one of these stands had a descrete canopy with sparse crowns, though those in 1986 showed the continuous, and closed canopy. These results suggested that the forest was formed and maintained by an unique logging systems in the past ; some sprouted stems of a individual were logged in late inter with deep snow, with the interval of 2040 years, leaving a few sprouted stems per individual unlogged. Considering the eco-physiology of sprouting, this system seems to have worked to keep large-sized beech individuals alive by making sprouts after logging.