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Ecosystems (2010) 13: 286–301 DOI: 10.1007/s10021-010-9317-6 Ó 2010 Springer Science+Business Media, LLC

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
´ Barbara A. Richardson,1,2* Michael J. Richardson,1,2 Grizelle Gonzalez,3 4,5 6 Aaron B. Shiels, and Diane S.Srivastava
165 Braid Road, Edinburgh EH10 6JE, UK; 2Luquillo LTER, Institute for Tropical Ecosystem Studies, University of Puerto Rico at Rıo Piedras, P.O. Box 70377, San Juan, Puerto Rico 00936-8377, USA; 3International Institute of Tropical Forestry, USDA Forest Service, ´ ´ Jardın Botanico Sur, 1201 Calle Ceiba, San Juan, Puerto Rico 00926-1119, USA; 4Institute for Tropical Ecosystem Studies,University ´ of Puerto Rico at Rıo Piedras, P.O. Box 70377, San Juan, Puerto Rico 00936-8377, USA; 5University of Hawai‘i at Manoa, 3190 Maile Way, Honolulu, Hawaii 96822, USA; 6Department of Zoology and Biodiversity Research Centre, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
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ABSTRACT
Hurricanes cause canopy removal and deposition of pulsesof litter to the forest floor. A Canopy Trimming Experiment (CTE) was designed to decouple these two factors, and to investigate the separate abiotic and biotic consequences of hurricane-type damage and monitor recovery processes. As part of this experiment, effects on forest floor invertebrate communities were studied using litterbags. Canopy opening resulted in increased throughfall, soil moistureand light levels, but decreased litter moisture. Of these, only throughfall and soil moisture had returned to control levels 9 months after trimming. Canopy opening was the major determinant of adverse changes in forest floor invertebrate litter communities, by reducing diversity and biomass, irrespective of debris deposition, which played a secondary role. Plots subjected to the most disturbance,with canopy removed and debris added, had the lowest diversity and biomass. These two parameters were higher than control levels when debris was added to plots with an intact canopy, demonstrating that increased nutrient potential or habitat complexity can have a beneficial effect, but only if the abiotic conditions are suitable. Animal abundance remained similar over all treatments, becauseindividual taxa responded differently to canopy trimming. Mites, Collembola, and Psocoptera, all microbiovores feeding mainly on fungal hyphae and spores, responded positively, with higher abundance in trimmed plots, whereas all other taxa, particularly predators and larger detritivores, declined in relative abundance. Litterbag mesh size and litter type had only minor effects

Received 29 August2009; accepted 25 January 2010; published online 13 February 2010 Author Contributions: BAR and MJR identified invertebrates, analyzed and interpreted data, and wrote the paper. GG designed the litterbag experiment, managed the field component and invertebrate extractions, and helped analyze and interpret data. ABS managed the planning and organization of the canopy trimming and environmental measures.DSS analyzed and interpreted data. All authors edited the paper. *Corresponding author; e-mail: barichardson@clara.co.uk

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Invertebrate Response to Canopy Trimming on communities, and canopy trimming and debris deposition explained most variation between sites. Effects of trimming on diversity, biomass, and abundance of some invertebrate taxa were still seen when observations finished andcanopy closure was complete at 19 months. This suggests that disturbance has a long-lasting effect on litter communities

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and may, therefore, delay detrital processing, depending on the severity of canopy damage and rate of regrowth. Key words: canopy gaps; community composition; forest manipulation; fungi; litterbags; relative abundance.

INTRODUCTION
Tropical hurricanes, typhoons...