European broadleaved forests are severely fragmented due to a long history of human activity. Nowadays, forest patches occur in a matrix of human modified habitats and forest is expanding through natural regeneration in former agricultural land. The composition of communities in regenerated forest may differ from primary forests and their potential contribution for biodiversity at the landscape level still needs better understanding. We approached this question through the comparison of plant diversity patterns in fragmented oak forest in a mountain landscape under ongoing farmland abandonment and in continuous forest (NW Portugal). In particular, we analyzed floristic composition and species-area relationships. We also tested the performance of the countryside species-area relationship model, which accounts for a differential use of habitats by different species groups, to explain diversity in the multi-habitat context.

Results/Conclusions

Plant communities in continuous forest were mostly composed by forest species (80%), while communities in fragmented forest presented a higher percentage of non-forest species (44%). Results species-area analysis suggest that plant communities in forest patches in multi-habitat landscapes are characterized by higher alfa diversity and lower beta diversity than communities in continuous forest. The countryside model had a better fit than the classic species-area relationship model both when explaining the diversity of particular species groups, such as forest species, as well as when explaining total species richness. These results stress the relevance of accounting for species habitat affinity when studying diversity patterns in multi-habitat landscapes. Overall, results suggested that although fragmentation has driven changes in the floristic composition of forest patches, regenerating forests still maintain a distinct composition from other habitats in the landscape, supporting several exclusive species, thus providing an important contribute for species diversity in the landscape.