Do canopy herbivores mechanically facilitate subsequent litter decomposition in soil? A pilot study from a Neotropical cloud forest

There is increasing evidence that the above- and belowground components of ecosystems influence one another, thereby controlling key processes such as organic matter decomposition. The aim of this study was to test the hypothesis that leaf herbivory in forest canopies could facilitate subsequent leaf litter decomposition in soils, through changes in leaf quality (i. e., litter palatability) or geometric form (i. e., increased availability of leaf edges made by herbivore damages). In a 9-month field experiment in an Ecuadorian tropical cloud forest, we compared the decomposition rates of entire leaves (EL) and 15 %-damaged leaves (DL) of Ficuscuatrecasana showing similar initial leaf chemistry. We found that DL decomposed significantly faster than EL in early stages of decomposition (i. e., between 0 and 38 days). A parallel experiment using cellulose discs on which we simulated different degrees of damages revealed, however, that geometry per se (i. e., increased edge availability) did not influence decomposition rates. We discuss these contrasting results and propose that higher edge availability in damaged leaves may promote the access of microbes and/or macro-detritivores to leaf tissues thereby enhancing the initial stages of leaf decomposition.