Impact of Prescribed Fire, Timber Removal, and the Seed Bank on Understory Plant Diversity and Canopy Cover in an Oak-Pine Barrens, Central Wisconsin, USA

Abstract

Oak-pine barrens are globally imperiled and support many endangered and threatened species. In central Wisconsin, these ecosystems have been designated as high priority for restoration by the Wisconsin Department of Natural Resources, but information regarding site potential for restoration and the most effective management approaches is lacking. In 1994, after seven decades of fire suppression, management was initiated at Quincy Bluff, a 1900-ha area with extensive oak-pine barrens. In the summer of 2010, we inventoried the area to assess the impact of prescribed fire, timber removal, and the seed bank on understory plant diversity and canopy cover. Species richness and ground layer cover in 2010 were lowest in management units treated with prescribed fire alone and were 50–150% greater in units with substantial reduction in canopy cover and basal area, secondary to timber removal and a tornado event. The cover of species designated as barrens indicator species declined in all units. Seed bank analysis demonstrated low species richness and produced few germinants of restoration value, including barrens indicator species. Despite 16 years of management, further degradation of the herbaceous understory and seed bank has occurred. These results suggest that within seven decades the resiliency of this system has been exceeded, and future management will need to address low propagule availability in order to recover understory diversity consistent with historical accounts of barrens communities.