THE EFFECTS OF A TYPHOON ON JAPANESE WARM TEMPERATE RAIN-FORESTS

A powerful typhoon (Typhoon No. 13) affected stands of primary warm te mperate rainforest in Yakushima, southern Japan, in 1993. Censuses in three sites 1-5 months after the typhoon showed low levels of mortalit y resulting from the typhoon (0.4-3.0% of stems). Stems killed by the typhoon were generally larger than surviving stems. Among surviving st ems there were generally low levels of damage (e.g. 0.5-1.3% of surviv ing stems lost crowns) and not all damage was widespread (e.g. defolia tion was apparent only in one of three sites). The sizes of uprooted s tems, stems that lost crowns and relatively undamaged stems were not d ifferent. Different species appeared to be damaged in different ways a t different sites. Damage was most evident in higher altitude seaward sites but gap formation was more frequent in lower altitude sites near valley floors. After the typhoon the resultant gap area occupied 9.4% of one site and 8.6% of another, which is greater than that before th e typhoon. Fresh sprouts were found on 17.35% of 2161 stems after the typhoon, including many apparently undamaged stems as well as those th at were damaged. Species which sprouted most frequently were those tha t regenerate by seed least frequently in these forests; these species may maintain their relative abundance in part by sprouting. Most tree species in these forests may be relatively resistant to typhoons and t here may be more opportunities for their regeneration following gap fo rmation caused by the typhoon.