Causal relationship between leaf litter beetle communities and regeneration patterns of vegetation in the Atlantic rainforest of Southern Brazil (Mata Atlântica)

Abstract

Old growth forests in the Atlantic rainforest of Southern Brazil are increasingly replaced by secondary forests. Effects on arthropods are assumed to be particularly important as they provide the bulk of biodiversity and play an integral role for ecosystem processes and services. During forest regeneration vegetation structure, leaf litter composition and microclimatic conditions were found to strongly affect leaf litter beetle communities. This study aimed at highlighting the question whether there is evidence that restoration actions to support the regeneration of old-growth forest vegetation structure can enhance the re-establishment of old-growth forest leaf litter beetle communities in secondary forests in the Mata Atlântica. A conceptual model structure representing a causal effect chain was built and checked against observational data for vegetation and leaf litter beetles from different regeneration stages using structural and microclimatic variables. By the results in this study the hypothesis of an ecological causal effect chain was clearly supported. There was reasonable evidence that during the regeneration process varying vegetation composition results in varying structural characteristics inside the vegetation stand and the associated leaf litter. The changed structural parameters proved to alter the microclimatic conditions within the leaf-litter and subsequently the differences in microclimatic conditions showed a significant influence on the leaf litter beetle community within the forest regeneration sites. These results have important implications for arthropod species conservation as they show that the probability of conserving or re-establishing old growth leaf litter beetle communities can be increased by maintaining and restoring suitable vegetation, structure and microclimatic conditions.