LAUSR

ABSTRACT In rural Japan, various types of forest and grassland once used for agroforestry have now been abandoned because of socioeconomic changes associated with the decline in forestry, falling birth rate and aging population. The biodiversity of such secondary forests and grasslands, which had been maintained by routine management, is now in crisis. Among them, Kunugi (Quercus acutissima) forests in Kyushu island were exceptionally maintained by its management with clear-cut every 15–20 years to produce bed logs for shiitake mushroom cultivation. Some of these Kunugi forests have been planted in abandoned cultivated fields and grasslands. To clarify the effect of clear-cutting on the conservation of herbaceous vegetation on the forest floor, the floor vegetation of Kunugi forests in Kumamoto Prefecture with various land-use histories was surveyed before and after clear-cutting. Detrended correspondence analysis showed that some plots that originated from grassland characterized by the dominance of Pleioblastus argenteostriatus before clear-cutting became dominated by Miscanthus sinensis after clear-cutting. After clear-cutting, species of grassland origin emerged and the biodiversity increased. The management of Kunugi forests has facilitated the survival of grassland species such as Solidago virgaurea subsp. asiatica, Eupatorium laciniatum, Adenophora triphylla var. japonica, Desmodium podocarpum subsp. podocarpum, Vincetoxicum amplexicaule and Sanguisorba officinalis. Therefore, the large-scale mosaic landscape of Kunugi patches of various ages within a 15–20-year clear-cutting cycle may have contributed to the maintenance of regional biodiversity.