Benefit of the snout: wild boar rooting disturbance has downstream impacts on species diversity in local vascular plant communities

Changes in land-use, climate and legislations, have shifted ungulate ranges throughout Europe. Ungulates can strongly impact local vegetation structure and composition, creating effects that can cascade throughout the ecosystem. Wild boar (Sus scrofa) may be particularly impactful as their feeding, nesting and rooting activities reduce plant cover and change local soil conditions. Quantifying these impacts is becoming increasingly important as wild boar continue to recolonize throughout Europe. In a comparative analysis, we investigated the short-term plant community response to wild boar rooting in a recently recolonised, boreal ecosystem. We explored how vascular plant species richness, diversity and the composition of species traits varied along a gradient of disturbance intensity over a 5-year period. We found higher overall vascular plant species richness and diversity with increasing rooting intensity. Plots with high-rooting intensity had, on average, 27 % more species diversity than plots in low-rooting intensity. Rooting intensity was also linked to a number of traits fundamental to interactions across trophic levels, including insect pollination, and nectar production. Importantly, we demonstrated that the ecological effects of rooting disturbance varied with forest stand age. In young forests, species richness was 61 % higher in high-intensity rooting plots than low-intensity rooting plot, however the effect reduced with stand age. This suggests that rooting and environmental conditions could have diverging impacts on different plants species. In a managed boreal forest, rooting by wild boar has the potential to alter local plant community composition, thereby shifting the local ecosystem, and potentially contributing to broader ecological community change.