Forest Diversity and Structure Surrounding Vernal Pools in Pictured Rocks National Lakeshore, Michigan, USA

Abstract

Vernal pools have been identified as unique contributors to forest biodiversity, with habitat management guidelines commonly recommending concentric zones of varying conservation intensity. However, little is known about the associated edaphic and forest structure characteristics associated with vernal pools. At Pictured Rocks National Lakeshore (Michigan, USA), we measured a stratified-random sample of 18 of 51 vernal pools to investigate soil pH, down dead wood, tree stocking, species richness, species evenness, species diversity, and species importance values within and across these zones. Within the pool zone, live tree basal area and live tree density was significantly lower and down dead wood volume was significantly higher than either the buffer or matrix zones. Nested-ANOVA and NMDS ordination indicated that importance values of under-represented species increased closer to the vernal pool. Tree diversity and richness were positively correlated with vernal pool area. These findings suggest the buffer zone serves as a transition zone between vernal pools and the surrounding forest, complementing the proposed guideline goals of reducing impacts of forest management. Vernal pools are unique forested wetlands and may provide an opportunity to maintain and enhance ecosystem complexity and resiliency.