Changes in decomposition rate and litterfall in riparian zones with different basal area of exotic Eucalyptus in south-eastern Brazil

Exotic species in riparian environments can influence the quantity and quality of litterfall in the ecological system. The objective of this study was to evaluate the influence of Eucalyptus leaves on litterfall and terrestrial and aquatic leaf decomposition in a riparian forest in São Paulo state, Brazil. Three riparian zones were evaluated, and they were designated as areas of low (L), medium (M) and high (H) Eucalyptus basal area, respectively. Each riparian area was evaluated by surveying its structure and floristic composition. The amount of litterfall was evaluated over one year, and leaves were collected in terrestrial and vertical collectors. We evaluated the rates of aquatic and terrestrial decomposition of Eucalyptus and native leaves within litterbags. In general, area H had lower species richness, a higher edge effect and high Eucalyptus litterfall. Area L had higher species diversity (H′, Shannon– Wiener index), higher Pielou’s equitability index (J′), and smaller amounts of Eucalyptus litterfall. Eucalyptus leaves had higher extractive and lignin content compared with that of native trees. Eucalyptus leaves had a lower decomposition rate, except for the aquatic environment in area M. Our results show that the presence of Eucalyptus in riparian zones can increase litterfall and reduce the rate of leaf decomposition, but more studies are needed to evaluate any changes in ecosystem function from Eucalyptus presence.