Outwards-Facing Managed Oak Forest Edge Hosts Rich Assemblages of Hymenoptera

Forest edge habitats created by forest management significantly influence species assemblage of hymenopteran communities. In 2021, we carried out research in a managed oak woodland located in Slovakia, utilizing three flight interception traps (FITs) to examine hymenopteran communities. Two of the traps were placed at the forest edge, with one facing the clearing and the other directed towards the closed-stand forest. The third trap was situated 100 meters within the closed-canopy forest. We separately collected subsamples within the forest edge. These subsamples were distinguished as 'ecotone inwards' and 'ecotone outwards' to accurately capture the distinct directional movements of hymenopterans at the forest edge (flying from the closed forest towards the clearing and vice versa). We identified 287 species in 19 families during the sampling period. The species richness, abundance and the phylogenetic diversity were found to be significantly different favouring the ecotone outwards microhabitats. However, we did not confirm higher species richness nor abundance in the forest edge compared to closed forest. The dissimilarity of species differed significantly between inwards- and outwards-facing ecotone and closed-forest stand. The life history traits exhibited the following trends: pollenophagous, herbivorous and nectarivorous species exhibited a positive association with the forest edge. Predatory species were associated more to closed forest. Cavity-nesting and above-substrate nesting species were situated in the ecotone outwards, while non-cavity nesters and below-substrate nesters were found in the ecotone inwards microhabitats. Our results support the creation of small-scale (~0.3 ha) open patches in temperate deciduous forests due to their positive effect on biodiversity of hymenopteran species within the outwards-facing part of the forest edge.