Edge and herbivory effects on leaf litter decomposability in a subtropical dry forest

Abstract

It is increasingly recognized that understanding the functional consequences of landscape change requires knowledge of aboveground and belowground processes and their interactions. For this reason, we provide novel information addressing insect herbivory and edge effects on litter quality and decomposition in fragmented subtropical dry forests in central Argentina. Using litter from Croton lachnostachyus (a common shrub species in the region) in a decomposition bed experiment, we evaluated whether litter quality (carbon and nitrogen content; carbon: nitrogen ratio) and decomposability (percentage of remaining dry weight) differ between litter from forest interiors or edges (origin) and with or without herbivory (damaged/undamaged leaves). We found that edge/interior origin had a strong effect on leaf litter quality (mainly on carbon content), while herbivory was associated with a smaller increase in nitrogen content. Herbivore damage increased leaf litter decomposability, but this effect was related to origin during the initial period of litter incubation. Overall, undamaged leaf litter from the forest edge showed the lowest decomposability, whereas damaged leaf litter decomposed at rates similar to those observed in litter from the forest interior. The interacting edge and herbivory effects on leaf litter quality and decomposability shown in our study are important because of the increasing dominance of forest edges in human-modified landscapes and the profound effect of leaf litter decomposition on nutrient cycling.