Edges as ecological filters: Asymmetrical orientation-specific arthropod activity across forest boundaries

Edge formation through moderate retention forestry creates transitional zones that shape environmental gradients and influence arthropod behavior. We examined fine-scale movement dynamics of ground-dwelling arthropods, quantified as orientation-specific activity along and across hard forest edges, in temperate lowland forests of Central Europe. The study focused on buffer-zone stands transitioning toward oak dominance. Drift-fence pitfall traps were placed across retention clearcuts, ecotones, and forest interiors, between April and October 2023. In total, 8643 individuals from 188 species were recorded and classified into five functional groups: predators, herbivores, omnivores, saproxylics, and detritivores. Arthropod activity varied among habitats, with along-edge orientation consistently exceeding across-edge orientation. This pattern is consistent with microclimatic gradients and behavioral orientation cues. Seasonal trends included elevated detritivore activity in the "along" orientation within ecotones during spring, suggesting corridor-like use of transitional habitats, and reduced across-orientation activity of omnivores in forest interiors during summer, consistent with seasonal changes in habitat use. Saproxylics were most active in the "along" orientation within forest interiors during autumn, reflecting their specialization for canopy-closed forests. Ordination analysis and species-level response models identified distinct movement dynamics among functional groups. Detritivores oriented along edges, whereas omnivores were associated with across-oriented activity, particularly outside ecotones. These findings highlight forest edge structure as a key ecological boundary shaping orientation-specific arthropod activity and provide a functional context for interpreting behavioral responses to edge environments. Incorporating functional group responses into retention forestry can support the development of more connected and resilient forest landscapes.