EXECUTIVE SUMMARY

Elizabeth Forsyth

Patterns of Typhoon Damage in Two Subtropical Forests

Bachelors of Science with Honors

May 2006

Cyclonic wind events, typhoons or hurricanes, impact a large proportion of the forests of the world at varying frequencies. There is little known about the influence of frequent typhoons on forest structure and even less about the processes through which they impact trees. The impact of typhoons on forest structure in Fushan Experimental Forest in northeastern Taiwan, which is impacted by an average of 1.4 typhoons a year, was compared with the forest structure of Lien-Hua-Chiuh (LHC), a forest in western Taiwan with less frequent typhoon impact (0.94/yr). DBH and height were recorded for 100 canopy trees in each forest, and the impact of two 2005 typhoons (Typhoon Haitang and Typhoon Matsa) on tree structure was analyzed in each forest. The average tree height in LHC was 12.9m versus 10.2m in Fushan. The canopy in LHC was less uniform than in Fushan. At Fushan 0.01% of the trees were damaged by typhoon Matsa and 0.02% by typhoon Haitang, with the most common type of damage being bole break, followed by uprooting. Short (<10.2m) diseased or damaged trees were more likely to be felled by the typhoons than short healthy trees. Species composition and topography were weakly correlated with damage rates and patterns.