Windthrow-generated mounds create contrasting regeneration niches for red oak and black cherry in a deer-browsed Carolinian forest

Windstorms are a dominant recurrent natural disturbance type within Carolinian old-growth forests in southwestern Ontario. This study examined how windthrow generated microsites differ from background microsites in soil properties and seedling survival across 84 locations in Hamilton. For each site, soil samples from windthrow generated mound tops and adjacent non-disturbed forest floor were analyzed. Seedlings of red oak (Quercus rubra) and black cherry (Prunus serotina) were planted on mound tops and adjacent ground microsites, and their survival was monitored. Non-disturbed ground microsites had significantly higher soil moisture (p < 0.001) and organic matter (p < 0.001) than disturbed sites, whereas disturbed sites were consistently drier (p < 0.001). Red oak survival was 28% higher on the non-disturbed microsites relative to the disturbed microsites, while black cherry survival was 41% higher on disturbed microsites relative to the non-disturbed ground microsite. Logistic regression analyses reveal that soil moisture was the strongest predictor of seedling survival (p = 0.030), with contrasting responses between the two species (p = 0.019). These results suggest that windthrow generated mounds create distinct environmental conditions that selectively favor unique autecology. As windthrow frequency rises under climate change, mounds could become major mediators of forest canopy composition.