Taxonomic and functional beta diversity of woody communities along Amazon forest succession: The relative importance of stand age, soil properties and spatial factor

Abstract

Predicting how multiple drivers shape beta diversity across tropical forest is one of the most important issues in ecology. However, the relative importance of drivers to the spatial and temporal dissimilarities in woody species composition (beta diversity) along Amazon forest succession remains poorly studied. In this study, we assessed how stand age (factor related to habitat filtering and succession), soil properties (factors related to resource availability and environmental filtering) and forest patches distance (spatial factor related to dispersal limitation) affect the taxonomic and functional beta diversity along an Amazon forest succession. Taxonomic and functional beta diversity indices were quantified based on abundance-based metrics and trait-based approach using functional traits related to plant dispersion and growth. Overall, taxonomic and functional beta diversity was consistently higher in initial successional stage among plots and sites; however, old-growth forest presented the lowest functional beta diversity. We observed differences in beta diversity components among successional stages and old-growth forest. The beta diversity components showed a clear higher pattern in the different second-growth forests than in the old-growth forest. Soil fertility and stand age explained most of the variation in taxonomic and functional turnover and beta diversity. This pattern probably is an outcome of the patches within a continuous old-growth forest as main seed sources for the colonization and establishment of tree species. We observed that functional beta diversity was lower than taxonomic beta diversity; therefore we presumed that there is higher functional redundancy in old-growth forests, compared to taxonomic beta diversity. However, despite the lower functional beta diversity and higher functional redundancy in old-growth forest, probably shade-tolerant species have different functions than second-growth forests that re-growing after shifting cultivation. We argue that an old-growth forest has lower functional diversity than second-growth forests but, it is probably induced by a high turnover of second-growth forests.