Canopy height and its spatial heterogeneity predominantly determine damages to tropical forests by major hurricanes, with a mitigating legacy effect of drought

The severity of damage to tropical forests by hurricanes is determined by the interplay between disturbance strength and resistance of forests. While major hurricanes often follow a warming period with severe drought, there has been no quantitative assessment of the legacy of drought on responses of tropical forests to major hurricanes. We aim to derive factors that determine landscape spatial distribution of canopy damages by hurricanes and to investigate how drought will affect forest responses to major hurricanes. We used canopy height data from two LiDAR campaigns in Puerto Rico before and after Hurricane Maria in September 2017 after severe drought in 2014–2016 to analyze canopy damage during the hurricane. Spatial error models were applied to canopy height reduction in wet, moist, and dry forest zones on pre-hurricane canopy properties, hurricane forcing, geomorphology, and rainfall deficit during the drought. Pre-hurricane canopy properties dominated over the other variables in determining the spatial variation of canopy height reduction. Drought affected forest response to the hurricane in different ways: The rainfall deficit during the drought cut off the canopy height reduction of wet forest but elevated that of dry forest. Pooling the data from all three zones, drought alleviated significantly the canopy height reduction, and this alleviation of damage was stronger for forests with taller trees. For island setting under major hurricanes, forest resistance dominates to control landscape spatial distribution of canopy damage. This study suggests that defoliation during pre-hurricane drought may have protected forests from hurricane damage.