Topography, drainage capability, and legacy of drought differentiate tropical ecosystem response to and recovery from major hurricanes

Abstract

High-carbon sequestrations of tropical montane forests and coastal mangroves have been greatly disturbed by intensified extreme climate events such as alternating hurricanes and droughts. However, few studies of the hurricane impact have taken into consideration the legacy of past climate events and analyzed the heterogeneity of hurricane impacts between montane forests and coastal mangroves. Here, we studied the impact of Hurricanes Irma and Maria in 2017 on coastal mangroves and upland forests in Puerto Rico after a severe drought during 2015–2016. We investigated the island-wide immediate impact on greenness using fused vegetation index from Sentinel-2 and Landsat-8, and the impact on and the recovery of 62 homogeneous vegetation patches by deriving an impact index and one-year recovery ratio (RR). A linear mixed-effect model was applied to explore roles of hurricane wind, rainfall, topography, and biological components in the impact and the recovery. Island-wide, the immediate impact is highly spatial-heterogeneous. Although most of the island was browned, a green-up strip in the dry south showed benefits from the hurricane rain which relieved the prior drought stress. Coastal mangroves experienced the greatest impact and slowest recovery with relative recovery of 0.44 compared to recovery greater than 0.70 for upland forests, and evergreen forests sustained significantly more damage than deciduous forests. The recovery of evergreen forests was on average 11 days earlier and faster than that of mangroves. Mangrove recovery was mostly limited by inundation-related factors such as elevation, slope, and drainage capacity. While higher elevation relates to slower recovery for upland forests, it favors mangrove recovery. Particularly, mangrove recovery is facilitated by river presence, explaining 65% variation in RR. The differentiated response, recovery, and underlying mechanisms highlighted a complicated array of external forces, geophysical/ biological modulators, and legacy of past climate events in determining and understanding hurricanes’ impact on tropical ecosystems.