Print PageLitter arthropods are patchily distributed in tropical forests. The tree template hypothesis posits that tree species, through differences in litter traits such as volume, chemistry and structure can account for this patchiness in arthropod distribution, hence determine the structure of litter communities. The ecosystem size hypothesis provides one possible mechanism allowing trees to act as templates. It states that greater habitat volumes foster arthropods in higher trophic levels by increasing arthropod abundance and diversity in lower levels. In a Panama rainforest we sampled litter arthropod communities under the canopies of 93 individuals from 10 tree species in the early wet season, when litter is deepest; and resampled 25 individuals from 5 species in the late wet season, when litter is mostly decomposed.
Results/Conclusions
Tree species provided arthropods with habitats that differed in litter quantity and quality; but despite some tree species supported differently some arthropods groups, we did not find strong support for the tree template hypothesis. Contrarily, supporting the ecosystem size hypothesis, litter depth, independent of the tree species producing it, explained significantly arthropod composition and deep litter sustained a higher predator:prey ratio. These ratios were lowest in the late wet season when litter was shallowest. We conclude that individual tree species can modify the structure of litter arthropod communities mostly through changes in litter volumes. Our results extend the ecosystem size hypothesis to litter environments and suggest a framework to understand bottom-up vs. top-down forces in structuring litter communities.
