Number of forest fragments and understory plants exert opposite effects on multiple facets of bird diversity in eucalypt plantations

Context The increase of areas destined for tree plantations worldwide, combined with a reduction in native habitats, has generated a growing debate about the capacity of these production systems in maintaining biodiversity. Indeed, tree plantations’ landscape context and local vegetation structure can affect biological diversity. Objectives To assess the influence of landscape and local variables on multiple facets of bird diversity in eucalypt plantations distributed in Atlantic Forest landscapes. Methods Using Generalized Additive Models, we assessed the effects of landscape (i.e. forest cover, pasture cover, number of forest fragments and edge density) and local variables (i.e. number of understory plants, native trees, perches, understory layer height and mean diameter at breast height) on bird taxonomic, functional and phylogenetic richness and diversity. Results Only the number of forest fragments and understory plants showed a significant effect on the different facets of bird diversity. Taxonomic and functional diversities, and phylogenetic richness were negatively influenced by the number of forest fragments in the landscape. Conversely, taxonomic richness and diversity, functional diversity, and phylogenetic richness were positively influenced by the number of plants in the understory of the eucalypt plantations. Conclusion To maintain multiple facets of bird diversity in anthropic landscapes, we reinforce the need to avoid fragmenting the existing forest remnants in the landscape and ensure the presence of understory vegetation in eucalypt plantations.