The Role of Hydrologic Connectivity on Leaf Litter Processing in the Paraná River Floodplain

POI DE NEIFF, A.; NEIFF, J. J.; CASCO, S. L.; GALASSI, M. E. & FRANCESCHINI M. C.

Cuiabá, Brasil.

Conferencia; 8th INTECOL International Wetlands Conference; 2008

We analyzed leaf decomposition rate and invertebrate colonization of leaf litter in three riverine wetlands with different inundation regimes. Replicate bags of nine types of litter, ranging in lignin content from 1.04 to 25.71%, were incubated in a natural floodplain of 8 km wide, yielding a total of 165 litterbags. For each wetland we calculated the quotient between the number of flooded days and isolated days. The coefficient of variation of physicochemical parameters was used as index of habitat heterogeneity. Leaf litter decomposition rate (expressed as percent remaining dry weight) was significantly faster in the site with strong hydrologic connection compared to the sites with weak connectivity. The highest number of invertebrates per g remaining litter was registered in the more connected wetland. After 30 days of incubation, the nitrogen content of water explains the variability in decomposition rate and invertebrate abundance. Differences in the invertebrate composition were more pronounced across wetlands than across leaf litter types within a wetland. Despite the high number of species associated with leaf decomposition in the floodplain wetlands (82 taxa), few taxa dominated the invertebrate assemblage. Many of these invertebrates may not be directly involved in shredding leaf litter, and collectors dominate the invertebrate assemblages at the study sites. The position of the wetland in the drainage network influenced the composition of the riparian vegetation, its leaf decomposition rate and invertebrate assemblages. Our study indicated that different inundation regime maintain high heterogeneity en leaf litter processing at the studied floodplain.