Influência de espécies exóticas invasoras no componente arbóreo da Floresta Atlântica: avaliação das características funcionais, diversidade filogenética e estrutura da comunidade

Abstract

The biological invasion is pointed out as one of the major causes of extinction os species. However, the mechanisms that drive such impacts are scarce in the studies, and few surveys approach multiple community responses to invasion. Therefore, we aimed to evaluate if Artocarpus heterophyllus and other exotic species would influence in the taxonomic and phylogenetic composition, taxonomic, phylogenetic and fuctional diversity, structural parameters and carbon stock in an Insular tropical forest in Brasil. The study was developed in Ilha Grande, Angra dos Reis, State of Rio de Janeiro in areas with recent anthropic impacts and some with invasion of A. heterophyllus. We quantified the woody indivduals (tree, trellets and shrubs) with diameter at breast height (DBH) ≥ 5cm in 16 plots of 15m radius (706m²), being eight with A. heterophyllus and eight without A. heterophyllus. We found 1.048 individuals in 99 species and 43 families. Six other exotic species were detected in the area, being three this species were also observed in areas without A. heterophyllus. Due to this observation, we also compared areas with exotics (11plots) and without exotics (5 plots) - incluing A. heterophyllus and the other six exotic species. From the total number of species quantified, we collected functional characteristics in individuals of 83 species, covering a minimum of 80% of the coverage value os each plot. These functional characteristics are related to the use of the resources for growth or in a more conservative way by the species. The characteristics measured were: leaf area, specific leaf area, dry mass contente, leaf tickness, leaf area ratio and wood density. We observed higher biomass in areas with A. heterophyllus, variation in taxonomic and phylogenetic compositon in areas with and without A. heterophyllus and with and without exotic (A. heterophyllus + other six exotic) and reduction of phylogenetic diversity (MNTD index and NTI metric) for areas with exotic. In this sense, we observed positive influences (increase of biomass-stock of Carbon and functional equability), negative (alteration of taxonomic and phylogenetic compostion and reduction of phylogenetic diversity) and neutral of A. heterophyllus and other exotic species in community and ecosystem parameters. We emphatize caution in providing management for such species and if it is based on the negative impacts, a risk analysis on how to replace the positive impacts of exotic species in the community should be made.