Tuesday, August 7, 2007

PS 38-199: Ecological interactions between plants and animals: Implications for the conservation and restoration of an Atlantic forest island

Marina Fleury1, Leslie Calderón2, Kaizer J. F. Alves2, Mauro Galetti2, Ricardo R. Rodrigues3, Marco Aurélio Pizo4, and Hilton Thadeu Z. Couto5. (1) Laboratory of Forest Ecology and Restoration, LERF/ESALQ/USP & Laboratory of Biodiversity and Conservation LaBiC/UNESP, (2) Laboratory of Biodiversity and Conservation LaBiC/UNESP, (3) Laboratory of Forest Ecology and Restoration, LERF/ESALQ/USP, (4) Universidade Vale dos Sinos, UNISINOS, (5) Laboratory of Quantitative Methods, ESALQ/USP

Island ecosystems are considered the most sensible to anthropogenic influences. Most Brazilian coastal islands have suffered changes on their species composition.Nowadays the Anchieta Island is a protected park, but was hardly deforested and suffered an introduction of mammals, some of which are overpopulated now.Since fauna plays a key role in vegetal community, the loss or change on animal-plant interactions affects the structure and composition of species.We are analyzing the possible limiting factors on natural regeneration process of tree successional stages of Anchieta Island: old fields (OF), early secondary (ESF) and old growth forests (OGF), evaluating the role of avifauna on seed dispersal, seed rain, seedbank, seed dispersal, seed predation and herbivore, as well as soil fertility. We registered great activity and abundance of frugivorous birds, varying according to the habitats (OF=ESF>OGF).Seed rain has been composed predominantly by anemocorics species (91%; ESF=OGF>OF). The seed predation in the dry season was more intense in the OGF than ESF and OF, with 97.5% of plots visited by seed predators.Our data is pointing to the absence of viable seedbank on OF, probably due to severe runoff. The mortality of saplings on the Island was 61.3%, being higher on the unfenced treatment for all tested species and in all habitats, showing a strong negative effect of vertebrate herbivores on plants.To isolate the effects of the physical damage we used artificial seedlings, registering higher rate on ESF (32.5%) than other habitats (OF=14%;OGF=19.5%) by an intense litter deposition on this site (17.5%). The treading was similar among habitats, suggesting that vertebrates are using the whole Island, probably due to overabundance. So, we are detecting distinct bottlenecks acting simultaneously in the natural regeneration process in all successional stages of the Island. Considering each step in the forest regeneration will help to define more effective and affordable restoration procedures.