Ecological restoration increases conservation of taxonomic and functional beta diversity of woody plants in a tropical fragmented landscape

Ecological restoration can re-establish plant species populations, enhance forested habitats extension, improve landscape connectivity, and enable biodiversity persistence within a landscape. However, the potential benefits of ecological restoration on beta diversity have never been explored. Here we use field data to investigate, for the first time, if restoration plantings enhance the taxonomic and functional plant beta diversity in a fragmented landscape of the threatened Atlantic forest. Woody species were evaluated for 320 plots established in 18 forest fragments and 14 restoration plantings within a sugarcane production landscape with low forest cover, in southeastern Brazil. Diversity metrics were assessed using the multiple incidence-data version of Hill numbers and were compared among three sets of study sites: fragments, restoration plantings and the two combined. Fragments showed higher levels of alpha diversity and proportional abundance of non-pioneer and animal-dispersed species than restoration plantings. Exotic, pioneer and non-zoochoric species were more abundant in restoration plantings, an expected result considering sites still be in the early or mid-successional stages of development. Taxonomic and functional beta diversity of trees was greatest when both areas were combined. For regenerating plants, however, beta diversity results varied according to species incidence-based frequencies. Although restoration plantings do not result in full recovery of alpha diversity, they can all together complement diversity of forest fragments at the landscape level. The findings indicate two key ecological implications for biodiversity conservation: the critical importance of forest fragments as biodiversity repositories and the positive effect of restoration efforts on landscape-scale diversity in degraded regions. These novel results highlight the importance of species selection for restoration initiatives toward species and functional attributes recognized as significantly reduced or locally rare. Overall, forest fragments and restoration plantings can act synergistically to promote recovery of plant diversity in heavily deforested agricultural landscapes.