Effects of rodent gnawing on the survival of current-year seedlings of Quercus crispula

Emergence, survival and mortality patterns of current-year oak (Quercus crispula Blume) seedlings were investigated for 4 consecutive years in a secondary oak forest in Hokkaido, northern Japan. Despite the emergence of a considerable number of oak seedlings in the years following masting, few current-year seedlings survived until the end of the growing season. Almost all of the seedlings died from damage to their stems caused by the gnawing of rodents. Rodent gnawing on transplanted oak seedlings was also observed in the year following masting but not in the year following a bad crop year. Cuttings of dwarf bamboo, Sasa, did not reduce the seedling mortality caused by gnawing. However, transplanted oak seedlings were gnawed more quickly when they were placed on the forest floor with a thicker Sasa covering. All rodents trapped in the vicinity of the study area were Apodemus speciosus Temminck. These results suggest that rodents strongly influence the recruitment of oak trees not only through the predation and dispersal of acorns but also through gnawing seedlings.