Local factors drive leaf breakdown in tropical streams

Abstract

Plants of riparian forests provide abundant dead leaves for freshwater stream ecosystems which support detritus-based food webs. The increased replacement from natural riparian forests to Eucalyptus plantations, an exotic species distributed throughout the neotropic landscapes, alters leaf breakdown as a key ecosystem process. We evaluate the breakdown of native and exotic leaf species with distinct physical and chemical characteristics (traits) in two different tropical reference condition streams located in Cerrado and Atlantic Forest biomes. We tested the hypothesis that regardless of the leaves’ origin (native or non-native species), leaf litter with higher nutrients and less recalcitrant compounds has higher decay rates. Eucalyptus camaldulensis leaf breakdown was faster than the native species Miconia chartacea in both streams. Leaf breakdown was driven by local characteristics (context dependent) and the macrodecomposer community, with more intensity to the litter's intrinsic physical and chemical quality. The higher leaf breakdown of E. camaldulensis was evidenced in the Atlantic Forest stream, that with the most increased water flow, further accelerating the leaf breakdown. Our findings indicate that due to the innate physical and chemical characteristics of E. camaldulensis, its decomposition occurs at a faster rate compared to native tropical species, as evidenced by the stream flows.