Influences of Typhoon Disturbance on a Hardwood Forest of Northeastern Taiwan
Teng-Chiu Lin, Lih-Jih Wang, Yue-Joe Hsia, Fu-Wen Horng, Tzer-Ton Lin, C.B. Liou, Steven P. Hamburg and Hen-Biau King
Typhoon is one of the most catastrophic natural disturbances to the forest ecosystems of Taiwan. The annual occurrence of typhoon averaged 2 events in the NE Taiwan for the last one hundred years. Six typhoons occurred in the summer of 1994 contributing 2270 mm of precipitation as compared to the annual total of 4900 mm. Two typhoons occurred in 1996 contributing 750 mm of precipitation as compared to the annual total of 3800 (?) mm. In contrast, annual precipitation was 3000 and 2850 mm for non-typhoon years in 1993 and 1995, respectively. In 1994, the typhoon storm flow was 974 mm, or 36% of the annual streamflow and the annual total storm flow was 1334 mm. Annual storm flow was only 250 and 330 mm for non-typhoon years 1993 and 1995, respectively. Typhoon storms contributed more than 40% of the annual nutrient input via precipitation for Na+, Cl- and Mg2+ in 1994. Yet, for anthropogenically derived ions (NH4+, NO3- and SO42-) the contribution was less than 15%. For nutrient output the 1994 typhoon storm flow contributed about 40% for NO3- and 22-30% for all other major ions. Canopy leaf area index (LAI) decreased as the results of defoliation and was as much as 66%, associated with 5000 kg/ha litterfall in 1994. The effect of typhoons on the changes of tree species composition was not significant. Four years' monitoring indicated that the recovery of LAI was slow and the LAI fluctuated frequently as struck by unpredictable typhoon events. The damage patterns of forest stands are notably different between those of hurricane and typhoon. Hurricanes have been found to affect forest composition and the regeneration of forest is rapid. The differences might result from the history of disturbance regime and the associated adaptation of forests to the disturbance. It is hypothesized that the frequent typhoon events maintain the dynamics of the disturbance-recovery process of the studied forest ecosystem.