Influence of wild boar (Sus scrofa L.) on vegetation development in the Meerdaal forest

The wild boar is a native ungulate species for Flanders, however due to overhunting and a reduction of forested area in the last centuries wild boar disappeared. After several decades of absence, wild boar officially reappeared in Flanders (Limburg) in 2006. Since then, a strong increase in both numbers and distribution has occurred, similar quick expansions are reported in many other countries. Due to these recent increases, the management and monitoring of wild boar has become an issue of global conservation concern. Wild boars are true ecosystem engineers, they can vastly influence species abundances, richness and ecosystem dynamics. Especially their typical rooting behavior can create ecosystem level effects. Studies on the impacts of wild boar on fauna and flora suggest density-dependent effects, this is in line with the intermediate disturbance hypothesis. However, the environmental effects of wild boar are controversial, assessing impacts on natural systems is not straightforward. Wild boar can especially play an important role on forest ecosystems. They are probably the most important natural modifiers of plant communities. At the moment there are limited numbers of good quantitative studies on the impacts of wild boar on forest biodiversity. Therefore, there is need for additional research. The most suitable ecosystem component for wild boars in temperate forests is the understory vegetation. This component is also a very important part of the forest overall biodiversity, accounting for up to 80% of plant species. Our aim is to contribute knowledge on the impacts of wild boar rooting in temperate forest. Our goals can be divided in two parts: 1) Non-temporal part: examining the relation between specific habitat parameters, plant functional traits and plant species and wild boar rooting intensity 2) Temporal part: Examining the impacts of wild boar recolonization and different levels of rooting intensity on understory vegetation development. For two strict forest reserve in the Meerdaal forest, detailed vegetation relevés, soil and dendrometric data from three snapshots with different levels of wild boar density are available. For the last survey also detailed estimations of wild boar rooting distribution is available. Our results suggest that wild boar prefer the forest stands with richer soils and plant communities. The presence of ancient woodland species seems to play an important role. Further, we can conclude that at the moment wild boar density is not high enough to delineate impacts, either positive or negative, exerted by wild boar. Our results are in line with a suggested shift towards a more mesic lowland oak and beech forest observed for these forest reserves, without current impact of wild boar.