A Canopy Trimming Experiment in Puerto Rico: the response of litter invertebrate communities to canopy loss and debris deposition in a tropical forest subject to hurricanes
Insects and other invertebrates in leaf litter are important components in decomposition, nutrient cycling, and food webs. As part of larger study to look at the effects of hurricane disturbance on tropical forests, Forest Service scientists and Long Term Ecological Research collaborators installed a canopy trimming experiment (CTE) in El Yunque National Forest. The experiment was designed to decouple the two main effects of hurricanes-canopy removal and deposition of litter to the forest floor-and to investigate the separate abiotic and biotic consequences of hurricane-type damage and monitor recovery processes.
Canopy opening resulted in increased throughfall, soil moisture and light levels, but decreased litter moisture. It was also reduced diversity and biomass of invertebrate litter communities, irrespective of debris deposition, which played a secondary role. Plots subjected to the most disturbance, with canopy removed and debris added, had the lowest invertebrate diversity and biomass. Individual taxa responded differently to canopy trimming. Invertebrates such as mites, springtails, and bark lice that feed mainly on fungal hyphae and spores became more abundant in trimmed plots, whereas all other taxa, particularly predators and larger detritivores, declined in relative abundance. Effects of trimming on diversity, biomass, and abundance of some invertebrate taxa were still seen when the forest canopy completely closed at 19 months. This suggests that hurricane disturbances have a long-lasting effect on litter communities and may, therefore, delay detrital processing, depending on the severity of canopy damage and rate of regrowth.