HURRICANE IMPACTS TO TROPICAL AND TEMPERATE FOREST LANDSCAPES

Hurricanes represent an important natural disturbance process to tropi cal and temperate forests in many coastal areas of the world. The comp lex patterns of damage created in forests by hurricane winds result fr om the interaction of meteorological, physiographic, and biotic factor s on a range of spatial scales. To improve our understanding of these factors and of the role of catastrophic hurricane wind as a disturbanc e process, we take an integrative approach. A simple meteorological mo del (HURRECON) utilizes meteorological data to reconstruct wind condit ions at specific sites and regional gradients in wind speed and direct ion during a hurricane. A simple topographic exposure model (EXPOS) ut ilizes wind direction predicted by HURRECON and a digital elevation ma p to estimate landscape-level exposure to the strongest winds. Actual damage to forest stands is assessed through analysis of remotely sense d, historical, and field data. These techniques were used to evaluate the characteristics and impacts of two important hurricanes: Hurricane Hugo (1989) in Puerto Rico and the 1938 New England Hurricane, storms of comparable magnitude in regions that differ greatly in climate, ve getation, physiography, and disturbance regimes. In both cases pattern s of damage on a regional scale were found to agree with the predicted distribution of peak wind gust velocities. On a landscape scale there was also good agreement between patterns of forest damage and predict ed exposure in the Luquillo Experimental Forest in Puerto Rico and the town of Petersham, Massachusetts. At the Harvard and Pisgah Forests i n central New England the average orientation of wind-thrown trees was very close to the predicted peak wind direction, while at Luquillo th ere was also good agreement, with some apparent modification of wind d irection by the mountainous terrain. At Harvard Forest there was evide nce that trees more susceptible to windthrow were felled earlier in th e storm. This approach may be used to study the effects of topography on wind direction and the relation of forest damage to wind speed and duration; to establish broad-scale gradients of hurricane frequency, i ntensity, and wind direction for particular regions; and to determine landscape-level exposure to long-term hurricane disturbance at particu lar sites.