Visible and invisible effects of Hurricane Jova in a tropical dry forest ecosystem in western Mexico
There is a growing interest on the potential socio-ecological impacts of hurricanes worldwide. Previous research about hurricane effects on ecosystems has centered on evaluating changes in patterns (visible structural effects: e.g. defoliation, understory light availability, uprooting of trees, avian nesting resources, branch and tree mortality) not in processes (invisible functional effects: primary productivity, water and biogeochemical cycles). Changes in ecosystem processes are poorly understood due to the lack of pre-disturbance data. In recent decades, hurricane impacts on ecosystems have increased particularly along the Mexican Pacific coast where Hurricane Jova landed in October 2011, causing an unprecedented forest disturbance. At the Chamela-Cuixmala LTER site we have a unique dataset that includes up to 30 years of pre-hurricane Jova data for some ecosystem processes. Our objective was to synthesize pre- and post-hurricane data to document the immediate visible and invisible effects of Hurricane Jova on this seasonally dry tropical forest ecosystem in western Mexico.
The visible effects of hurricane Jova (category 2) were remarkable. In the primary forest, there was decreased flowering and fruit production over the first year, and a third of known parrot tree-cavity nest-sites were lost, with a 2-mo delay in the timing of nesting by parrots in the first breeding season after the hurricane. In the secondary forest, abundance of amphibians and reptiles tended to increase probably due to greater light availability in the understory, whereas abundance of insects (lepidopterans) did not change. Hurricane Jova triggered massive forest defoliation and altered ecosystem processes. Litterfall rates of mostly non-senescent leaves and branches increased by three-fold immediately after Jova. This was by far the highest litterfall peak in 30 years of continuous monthly measurements, but dropped quickly to pre-hurricane levels in the following months. At the watershed level, there was a positive balance in dissolved organic carbon and nitrogen fluxes. The quick return to pre-hurricane levels for many processes may indicate that primary tropical dry forest is resilient to low-level hurricane impacts. However, other climatic events such as severe droughts, atypical dry season rains, or a prolonged rainy season, associated with the El Niño-La Niña cycle in the Pacific Ocean, need to be investigated to understand the vulnerability of this ecosystem to infrequent climatic events that may increase with climate change.