Characteristics of beech mixed forest distributed at low elevations on Mt. Toishi, northern Kyushu, in the upper warm-temperate zone of Japan

The aim of this study was to clarify the structure and regeneration status of mixed beech (Fagus crenata) forest on Mt. Toishi in the Sangun mountain range in northern Kyushu, a relatively low-latitude region in Japan, with emphasis on forests at lower elevations. We focused on a mixed beech forest at a low elevation of Mt. Toishi and compared the forest structure of the target stands, including tree species and size, with the forest structure near the peaks of Mt. Toishi and Mt. Sangun. Deciduous broad-leaf trees were dominant near the peaks, while evergreen broad-leaf trees dominated at lower elevations, whereas the relative dominance of beech trees was not significantly different. Near the peaks, the number of large-diameter beech trees forming the canopy decreased, and small-diameter trees were present. The proportion of small-sized trees was lower in the low-elevation forest area than in the forest area near the peak. Even at lower elevations, juvenile beech trees grew in limited areas on steep slopes along forest roads. These sites suggested that regeneration of beech populations is possible even at low elevation.