Windstorms create heterogeneous patches of early successional habitat distributed within a matrix of older forest. These storms create large tree tip-up mounds which form unique microhabitats that are relatively free of competitors. In addition, these elevated habitats may be quite favorable because they receive higher light, attract avian seed dispersers, and serve as a refuge from large ungulates. We tested the hypothesis that distinct plant communities would rapidly form on these mounds compared to adjacent randomly selected control plots located off the mounds. We tested our hypothesis in two mature northern hardwood forests in the Upper Peninsula of Michigan where windstorms created an array of mounds. Mounds were surveyed 3-4 years after each storm event. We visually estimated plant cover for all species and recorded reproductive status for a subset of these species.
Results/Conclusions
Entirely distinct plant communities formed on tip-up mounds; mounds also had significantly higher total plant cover and diversity. In addition, nut and berry producing species (e.g. elderberry, red raspberry, pin cherry) were found nearly exclusively on tip-up mounds while ferns dominated the adjacent control plots on the forest floor. These dominant nut and berry producing species are preferred forage of white-tail deer suggesting that the mounds were an important browsing refuge. In addition, these species are bird dispersed, suggesting that these mounds may be attractive sites to perch for avian frugivores. Overall, mounds represent unique microsites with bare soil, few competitors, and a refuge from browsers. From a landscape perspective, tip-up mounds provide highly localized and distinct habitats that promote diversity and coexistence by enhancing the abundance of species that are uncommon forest-wide.