Role of above- and belowground traits in the functional structure and species dominance of tropical fern communities in response to edge effects

Recent investigations have revealed the coordination and trade-offs between above- and belowground traits in structuring functional strategies of plant communities, but none of these have addressed ferns, a diverse plant lineage in tropical forests. We investigated terrestrial ferns from the perspective of how below- and aboveground traits are coordinated with functional responses to forest edges, which represent a significant part of the world's forest cover. Specifically, we examined differences in functional strategies between forest edges and forest interior as well as traits associated with species dominance. Fern richness and abundance were sampled in 24 edge plots and 44 interior plots within the Brazilian Atlantic Forest. We obtained data for five leaf traits and three rhizome traits. Ferns did not express any functional coordination between above- and belowground traits. At the edge, ferns did not display functional homogenization. In both the interior and at the edge, ferns exhibited multiple trait covariations across a broad spectrum of plant sizes and leaf numbers, associated with rhizome type and the presence of leaf trichomes and stolons. There were no cohesive functional groups of generalists or of exclusive species of forest edges and the forest interior. Fern species dominance was related to the species-specific number of leaves and the presence of stolons. We conclude that below- and aboveground traits did neither respond in conjunction nor as a functional response to edge effects. However, both kinds of traits affected the functional structure and species dominance of fern communities at the edge and in the interior of the forest.