Manual Soil Resmoothing After Wild Boar Rooting Enables Resuming Mowing Management in Hay Meadows Without Hindering Vegetation Recovery

Wild boar (Sus scrofa) is a widespread megaherbivore that can intensively disturb large areas of its habitat both in its native and non-native ranges, when populations reach high densities. The main problem is its rooting habit, which entails intensive disturbance of the topsoil and herbaceous layer. The extent of concomitant habitat degradation varies across ecoregions; some ecosystems are rather resilient, although the damages are long-lasting in others. In mown meadows, a secondary problem is the inability to resume mowing due to the uneven soil surface of rooted patches. This can lead to both economic loss and a loss of management-dependent biodiversity. We assessed the short-term effects of rooting on vegetation cover and composition in central European permanent hay meadows and tested the utility of manual soil surface resmoothing to enable the continuation of mowing. We found that rooting increased bare soil surface but vegetation recovery occurred within a year. Similarly, high resilience was found for species composition. We could not detect any difference between rooted and intact grassland patches after 1 yr. This short-term perturbation of the composition could be associated with a temporary decrease in grassland specialist species and an increase in ruderal and pioneer species. Soil surface resmoothing was an additional disturbance, but vegetation cover returned to the level of intact grasslands within a year. Vegetation composition needed a slightly longer time (2 yr) to recover than that without resmoothing. We thus recommend the application of manual resmoothing in hay meadows with high short-term resilience to rooting, but a risk of long-term degradation (e.g., shrub encroachment) if mowing is not resumed. In hay meadows with lower resilience (because of, e.g., steep slopes), resmoothing should be applied with caution and may be supplemented with seeding to support the recovery of the vegetation and prevent soil erosion.