Habitat heterogeneity as a key to high conservation value in forest-grassland mosaics

Forest-grassland mosaics are widespread features at the interface between tree- and grass-dominated ecosystems. However, the importance of habitat heterogeneity in these mosaics is not fully appreciated, and the contribution of individual woody and herbaceous habitats to the overall conservation value of the mosaic is unclear. We distinguished six main habitats in the forest-grassland mosaics of the Kiskunsag Sand Ridge (Hungary) and compared the species composition, species richness, Shannon diversity, naturalness, selected structural features, environmental variables, and the number of protected, endemic, red-listed and specialist species of the plant communities. Each habitat had species that were absent or rare elsewhere. Grasslands had the highest conservation importance in most respects. North-facing forest edges had the highest species richness, while south facing edges were primarily important for tree recruitment. Among the forest habitats, small forest patches were the most valuable, while large and medium forest patches had the lowest conservation importance. We showed that the current single-habitat focus of both research and conservation in the studied forest-grassland mosaics is not justified. Instead, an integrated view of the entire mosaic is necessary. Management practices and restoration projects should promote habitat heterogeneity, e.g., by assisting tree and shrub establishment and survival in grasslands. The legislative background should recognize the existence of fine-scale forest-grassland mosaics, which are neither grasslands nor forests, but a mixture.