Responses to canopy loss and debris deposition in a tropical forest ecosystem: Synthesis from an experimental manipulation simulating effects of hurricane disturbance
Hurricanes, cyclones, or typhoons are intense and broad-scale disturbances that affect many island and coastal ecosystems throughout the world. We summarize the findings of the articles that compose this special issue of Forest Ecology and Management, which focuses on a manipulative experiment (the Canopy Trimming Experiment, CTE) that simulates two key aspects of hurricane effects in a wet tropical forest. Although previous studies of tropical and subtropical forests have documented changes resulting from hurricanes, it is not clear which of the two simultaneously occurring direct effects of hurricanes—canopy openness or debris deposition—most influence responses. In the Luquillo Experimental Forest (LEF) of Puerto Rico, a multi-disciplinary team of scientists used replicated factorial manipulations to determine the independent and interactive effects of canopy openness and debris deposition on structural and functional characteristics of the forest. The majority of responses were primarily driven by canopy openness rather than by debris deposition. Canopy openness resulted in significant increases in densities of and compositional changes in woody plants, ferns, and some litter arthropods, and significant decreases in coqui frog abundances, leaf decomposition, and litterfall. Debris deposition significantly increased tree basal area and microbial diversity on leaf litter, but these increases were relatively small and ephemeral. Several interactive effects of canopy openness and debris addition emerged, including those involving understory herbivory, canopy arthropod structure, terrestrial gastropod abundances and composition, and soil solution chemistry. Arguably, hurricanes are the most important natural disturbance that affect the LEF, and most characteristics that were measured in the CTE showed evidence of resistance or resilience. By identifying the causal factors affecting secondary successional trajectories of diverse taxa ranging from microbes to vertebrates, biogeochemical attributes, microclimatic characteristics, and measures of ecosystem processes following hurricane disturbance, we better understand tropical forest dynamics resulting from past hurricanes and are better able to predict mechanisms of change related to future hurricanes.