OOS 16-3 - Plant species diversity, functional diversity and phylogenetic diversity at natural edges in eastern Europe

Background/Question/Methods
Forest edges have intrigued ecologists for a long time. Edges are usually believed to possess higher species richness than the interiors of the adjacent communities, a phenomenon often referred to as ’edge effect.’ However, this pattern may not be valid across all types of forest edges, as edge species richness may depend on certain edge characteristics, including age and dynamics. The overwhelming majority of earlier studies has focused on anthropogenic forest edges (e.g., edges towards agricultural fields). In Eastern Europe, much of the natural vegetation is a mosaic of forest and grassland patches and, consequently, (near-)natural edges cover a considerable proportion of the landscape. This work was conducted in the forest-grassland mosaics of the Kiskunság Sand Ridge (Hungary). We established 25 m² plots in forest interiors, north-facing forest edges, south-facing forest edges, and grassland interiors. In each plot, the percentage cover of all vascular plant species was visually estimated in spring and summer. Our aim was to compare the four habitats according to the following indices: (1) species richness, (2) the number of species with special conservation importance (protected, endemic, and red-listed species), (3) functional diversity based on eight plant traits, and (4) phylogenetic diversity.

Results/Conclusions
We found that species richness was the highest at forest-edges, especially at north-facing ones. Forest interiors proved to have the lowest species richness, while grasslands were intermediate. In contrast, the number of species with special conservation importance was the highest in grassland interiors and the lowest in forest interiors, while it was intermediate in edges. Functional and phylogenetic diversity were equally high in forest interiors and edges and significantly lower in grasslands. Regarding most characteristics studied, moderate differences were revealed between north-facing and south-facing edges. Our results confirm the expectation that forest edges are more species rich than habitat interiors. Our study, however, also emphasises that other metrics should also be considered, as species richness alone is not informative of ecological or conservation importance: habitats that are poor in species may contain a large number of protected, endemic or red-listed species and/or have high functional or phylogenetic diversity. We conclude that in the forest-grassland mosaics of the study region, each habitat deserves conservation attention, that is, the total complexity of the mosaic ecosystem should be preserved.