Michigan Oak savanna restoration: A comparison of mechanical thinning approaches in the context of prescribed fire and native seeding

Oak savanna systems were once fairly common across the midwestern United States but now occur in isolated patches. The increasing rarity of these ecosystems combined with conservation concerns for savanna-associated species such as the federally endangered Karner blue butterfly have resulted in a growing interest in oak savanna restoration and management. In this study, we explore the effectiveness of several different savanna restoration approaches using an operational-scale restoration experiment established in 2008 and 2009 on the Huron-Manistee National Forest in Lower Michigan. We compared three mechanical thinning approaches (bulldozer, masticator, and shear cutter) in conjunction with prescribed burning and native seed treatments. Our results suggest that among mechanical thinning approaches, the shear cutter was the most effective for promoting management goals of higher herbaceous plant cover, higher wild lupine cover, reduced woody plant cover, and lower invasive species cover. Postestablishment prescribed burning appears to be effective for furthering these management goals by reducing woody plant cover and creating more exposed soil for plant colonization. Seeding treatments further promoted desired cover types, while minimizing undesired cover types. The results presented here highlight some important differences among several common restoration approaches that may prove useful to practitioners interested in oak savanna restoration.