Resilience of tropical dry forest productivity to two hurricanes of different intensity in western Mexico

Tropical dry forests (TDFs) on the Pacific Coast of Mexico experience seasonal droughts and very infrequent direct hurricane disturbance. Over a 4-year period, two hurricanes made landfall in the Chamela-Cuixmala Biosphere Reserve, Hurricane Jova (category 2) in October 2011 and Hurricane Patricia (category 4) in October 2015. Our permanent long-term watershed-scale research program in the reserve provided a unique opportunity to analyze the ecosystem response to these hydrometeorological extreme events. Since 1982, we have been collecting monthly litterfall samples in 120 litter traps across five small contiguous watersheds. A direct instantaneous effect of both hurricanes was a massive deposition of green and senescent leaves, and fine woody debris to the forest floor. Hurricane-month litterfall flux largely exceeded the amount produced in any month of the pre-disturbance period (1982-2010), suggesting low resistance to hurricanes. Post-Jova recovery was fast, a response likely explained by a combination of the unusually high dry-season precipitation and higher than average total annual precipitation, coupled to a large flux of P-enriched litter and the re-sprouting response of many TDF species. Annual litterfall the year following Patricia decreased to half of that during the hurricane year, concomitant with a decrease in annual rainfall 20% below average. Ecosystem resilience seems strongly linked to post-disturbance water availability. Therefore, drought after a hurricane may limit the capacity of tropical dry forests to rapidly recover. The implications of these climate-related disturbances for forest recovery and management are discussed.