Effects of a Severe Typhoon on Forest Dynamics in a Warm-temperate Evergreen Broad-leaved Forest in Southwestern Japan

The effects of a typhoon on forest dynamics and the response of major tree species were studied in a warm-temperate evergreen broad-leaved forest in southwestern Japan. The strongest typhoon on record (T9313) passed through this region in 1993. Return periods of typhoons over 30 ms−1 in instantaneous wind velocity and T9313 were estimated to be 2.2 and 104.5 years, respectively. Approximately 10% of all stems suffered some damage from T9313 and annual stem mortality rose from 1.3 to 2.7%. The estimated period that the number of stems would fall below 10% of the initial was four years shorter with T9313-class typhoons than without them. Thus, the disturbance by T9313 was not catastrophic at the site although T9313 was an episodic typhoon. The short-term responses of major tree species to T9313 were classified into four types: 1) blunt-response type with little decrease and recruitment of stems in the DBH ≥ 5 cm class (Distylium racemosum), 2) retreat type with larger decrease than recruitment (e.g. Quercus acuta), 3) sharp-response type with a large decrease and much recruitment (e.g. Cinnamomum japonicum), and 4) advance type with less decrease than recruitment (Eurya japonica). Among the four regeneration types classified by previous studies (climax, light-demanding, subcanopy, and few-sapling), the climax and few-sapling types each showed a specific short-term response, the blunt-response and retreat types, respectively, that explains one aspect of the regeneration strategies of each type. On the other hand, the light-demanding or sub-canopy type showed multiple short-term responses, indicating that each regeneration type contains species with various regeneration strategies.