Oak forest decline and effects of two invasive shrubs in the Midwest Driftless Area: current status and implications for the future

Oak forests throughout the world are in a state of decline due to lack of oak seedling recruitment to larger size classes. Much of this recruitment decline has been attributed to changes in ecosystem disturbance regimes that have led to increased competition from other species. The Midwest Driftless Area forests in the United States are currently dominated by large oak trees of three species: Quercus alba L., Q. macrocarpa Mich., and Q. rubra L. These oak forests currently provide habitat for a large variety of flora and fauna, recreational opportunities for people, and an important timber resource. We examined the current status of forest composition and structure of Midwest Driftless Area oak forests. We were specifically interested in understanding how two invasive shrubs, Lonicera tartarica L. and Rhamnus cathartica L., might contribute to the decline of oak recruitment. We found that the recruitment of oak species is poor in comparison to other canopy tree species, including Acer saccharum Marsh. and Tilia americana L., and that the majority of saplings are of non-oak species. Our results revealed