Regeneration of a temperate deciduous forest in Sasa grassland was investigated focusing on vegetation structure and population growth in a series of beech (Fagus crenata) forest-oak (Quercus mongolica var. grosseserrata) forest-Sasa grassland near the top of Mt. Jippo, southwestern Japan. Beech forest on the mountain slope and Sasa grassland on the summit might have been present for at least about 330 years. A temperate deciduous forest might have been, however, present on the summit before. In the oak forest, some trends were observed along the transect from the forest toward the Sasa grassland : the height of canopy trees became shorter, the DBH distribution changed from a bell type to an L-shape, and stand age estimated by annual rings became younger. These findings suggested that the oak forest might have developed as a secondary forest, and that disturbance perhaps due to logging occurred more than 85 years previously. It seems that the Sasa grassland enlarged after disturbance of the former forest edge, followed by regeneration of the ecotone community dominated by oak. In the Sasa grassland, radial growth in the early stage of young isolated oak tree trunks was comparatively slow, suggesting suppression by Sasa foliage. It was concluded that the presence of Sasa was the main factor suppressing the establishment and growth of tree seedlings, and that in addition, strong wind had an adverse effect on the growth of individuals such as saplings higher than the Sasa foliage. Therefore, Sasa grassland shows little tendency to change to forest.
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