Hurricane Georges Accelerated Litterfall Fluxes of a 26 yr-old Novel Secondary Forest in Puerto Rico

Abstract

Defoliation and fallen debris are common visible effects of hurricanes and are accompanied by invisible effects such as altered element fluxes, changes in element concentration of plant parts, and variability of processes (Lugo 2008). While ecologists are increasingly documenting visible effects of hurricanes and other disturbances (Everham and Brokaw 1996, Lugo 2008, Turton 2008) less work has been conducted on the invisible effects of hurricanes, which center on the functional attributes of forests. One such functional attribute with both visible and invisible components is litterfall and associated mass and element fluxes. Examples of studies of tropical forests where litterfall mass and element fluxes were monitored before and after a hurricane include work in Puerto Rico (Lodge et al. 1991, Frangi and Lugo 1991, Scatena et al. 1996, Beard et al. 2005, Van Bloem et al. 2005), Hawaii (Herbert et al. 1999), and Mexico (Whigham et al. 1991). These studies cover a range of climates (dry, moist, and wet) and focused on mature native vegetation. To avoid repetitive citations to these papers, we will refer to them by country when the information cited is supported by all of them. The expansion of human populations and changes in land cover due to deforestation, use, and land abandonment, cause increases in the cover of tropical secondary forests (Brown and Lugo 1990) and there is a need to learn about their functioning and resilience (Lugo and Helmer 2004, Chazdon 2008, Lugo 2009). We had an opportunity to contribute to this research need when Hurricane Georges passed over a study area (Fig. 1) where we were monitoring litterfall and element fluxes of a secondary forest with a novel composition of introduced and native tree species (below). The hurricane moved at 24 km/h over Puerto Rico between 21 and 22 September 1998 as a Category 3 hurricane in the Saffir Simpson scale with maximum sustained winds of 184 km/h and occasional gusts of 240 km/h. We addressed two questions: How resilient to hurricane winds are the fluxes of litterfall mass and chemical elements in a young secondary forest and how do resilience and fluxes in this forest type compare with those of mature forest vegetation in dry, moist, and wet climates? The comparison with mature forests sheds light on the effects of age in forest response to hurricane winds. Moreover, since our study forest had a mixed composition of