Establishment of the evergreen broad-leaved tree species Castanopsis cuspidata in an abandoned secondary forest in western Japan

Recently, populations of Castanopsis cuspidata have often expanded into secondary forests in western Japan. To determine the establishment processes of this species, we analyzed its spatial distribution in a secondary forest dominated by Quercus variabilis and Quercus serrata that is located adjacent to a stand dominated by C. cuspidata. Saplings, defined as a parts per thousand yen30 cm stem length (SL) and < 5 cm diameter at breast height (DBH), were abundant and their size distribution was inversely J-shaped, indicating continuous recruitment. Although seedlings (SL < 30 cm) and small saplings (30 a parts per thousand currency sign SL < 50 cm) of C. cuspidata were aggregated near flowering trees of this species, some were found a parts per thousand yen40 m from the nearest adults, suggesting that there is animal-aided dispersal of acorns. The distribution of larger-sized individuals (a parts per thousand yen100 cm SL) of C. cuspidata was unrelated to distance from the nearest flowering C. cuspidata or dominant Quercus species (a parts per thousand yen5 cm DBH), but was associated with dead Pinus densiflora trees, which were abundant at the site. Thus, the establishment of C. cuspidata in this forest is controlled mainly by two factors, viz. patterns of acorn dispersal by animals, and forest disturbance regime (i.e., deaths of pine trees).