Dispersal limitation and canopy structure shape the occurrence and abundance of Staphylea pinnata in archaeologically protected forest patches on medieval hillforts

Archaeologically protected forest patches often experience modified management regimes, yet their ecological role within managed forest landscapes remains poorly understood. We investigated the relative importance of canopy structure and landscape connectivity for the occurrence and abundance of the understory shrub European bladdernut Staphylea pinnata , in medieval hillforts embedded in temperate forests of the Outer Western Carpathians (southern Poland). Environmental differentiation between hillforts and adjacent forest stands was assessed using multivariate analyses, while colonization patterns were evaluated in relation to the distance to the nearest natural population. In addition, ordinal regression models were used to identify stand-level drivers of shrub abundance. Hillforts did not differ substantially from surrounding forest stands in terms of ground substrate or topographic conditions, indicating that they do not constitute a distinct habitat type. However, colonized hillforts occupied a narrower range along the stand light index gradient, suggesting structural filtering by canopy conditions. Distance to the nearest natural population showed the clearest directional association with hillfort occupancy, a pattern consistent with a role of propagule pressure and dispersal limitation. Local abundance was positively associated with the stand light index, a stand-level proxy for canopy permeability, suggesting that canopy-related stand structure may influence local population performance. Our results highlight that the persistence of S. pinnata in forested archaeological sites is primarily associated with stand structure and spatial connectivity, rather than with site-specific ground substrate or topographic conditions. These findings emphasize the role of canopy management and landscape continuity in supporting light-responsive understory shrubs within managed temperate forests. At the landscape scale, maintaining and restoring connectivity with nearby source populations may enhance colonization of suitable protected forest patches, thereby contributing to local biodiversity conservation.