Plantation forests cannot support the richness of forest specialist plants in the forest-steppe zone

In forestry, several types of management practices are used, which have significant effects on species richness and composition. A number of studies concerning the effect of management on biodiversity have been conducted in the tropical and temperate forest zones. This topic is less studied in the forest steppe biome, where the reestablishment of plants from the surrounding patches is more limited than in the forest biome. Most studies compare alien plantations with seminatural forests. However, the effects of dominant tree species is mixed with the effect of the site preparation and site history in such comparisons, due to intensive site preparation in case of forest plantations. In this study, we separate the effect of these management elements. We examined the potential of currently used forestry protocol in preserving the plant biodiversity of the forest herb layer in the Pannonian sand forest steppe using 266 forest plots from the Kiskunság sand region in Hungary. The total richness and richness of habitat preference groups (forest specialists, grassland specialists, native weeds, and aliens) were compared in natural and plantation forests of different tree species to explore the effects of dominant tree species and site preparation on the species composition. Factors determining the richness of forest specialists in plantations were analyzed by fitting a regression tree, and the habitat preference of these species was described by their fidelity to the forest types. Our results show that total species richness is less sensitive to management than the richness of some species groups with a specific habitat preference. Forest specialist species can survive almost only in continuous seminatural oak forests, that is, in forests that are continuously present and do not undergo any site preparation. They are completely missing from young plantations, most likely because site preparation completely removes them. Their limited recolonization is possible only in plantations of native trees in landscapes where seminatural oak forests have been continuously present. Even under these conditions, only half of the forest specialist species are able to recolonize in the plantations. Grassland specialists, on the other hand, are present in every forest type but with low richness. Site preparation acts as a colonization window for weeds and aliens. However, while the richness of weeds is the highest in young plantations and decreases in established plantations, probably due to the canopy closing, the richness of aliens is the same in both young and established plantations. Considering our results, the current forestry protocol is hardly suitable for maintaining the plant biodiversity of forests in the forest steppe zone, therefore, management practices should be changed to focus more on the conservation of these endangered habitats.