River embankments mitigate the loss of grassland biodiversity in agricultural landscapes

Agricultural intensification has resulted in severe declines in the extent and diversity of seminatural habitats in Europe, whereas the extent of secondary habitats has increased considerably. River embankments have become one of the most extensive and widespread secondary habitats in former floodplains. We compared the diversity patterns of secondary dry and wet grasslands on river embankments with those of seminatural dry and wet grasslands in a Hungarian agricultural landscape using the following community descriptors: (a) species diversity, (b) phylogenetic diversity and (c) functional diversity. We also performed trait-based analyses to evaluate the ecosystem services provided by these secondary grasslands. Both grassland types of the embankments showed significantly higher Shannon diversity compared with their seminatural counterparts. The cover of generalist species (i.e., cosmopolitan species, weeds and nonindigenous plant species) was high in the secondary grasslands. We found significant differences in phylogenetic diversity between the secondary and seminatural grasslands: secondary grasslands showed significantly lower mean nearest taxon distances than the seminatural grasslands. Functional diversity did not differ between the secondary and seminatural grasslands according to the Rao's quadratic entropy. However, we found higher community-weighted means of specific leaf area, plant height and flowering period in the secondary grasslands, which are related to important ecosystem services (via biomass production and pollination). Well-planned management actions and restoration activities could help further improve the ecological function and conservation value of secondary grasslands on river embankments, contributing to the maintenance of species diversity and sustaining the functionality of ecosystems in agricultural landscapes.