Assessing the importance of riparian zones conservation for leaf decomposition in streams

Because of changes in riparian zones and water properties, human disturbances in terrestrial ecosystems can affect the decomposition of organic matter and invertebrate assemblages in forest streams. The aim of this study was to evaluate how changes in the riparian zones influenced leaf breakdown rates and colonization by invertebrate shredders. Leaves of Miconia chartacea were incubated in four streams of the same watershed that presented different conservation levels in the riparian zones. Leaf breakdown rates were higher in the presence of shredders and in the most preserved stream. In terms of abundance and biomass, shredders differed among streams, and the importance of these organisms on leaf decomposition decreased in altered streams. These results suggest the conservation level in the riparian zones influenced leaf decomposition mediated by shredders, and the observed decrease in breakdown rates was probably due to the high sensitivity of shredders to changes in the availability of food resources and habitat.