INITIAL UNDERSTORY RESPONSE TO GAP-BASED REGENERATION METHODS FOR MATURE UPLAND OAK FORESTS

Problems with oak regeneration, and concerns by environmental and conservation organizations, are driving interest in longer rotations and in reproduction methods that retain the overstory for an extended time period. Clearcutting and shelterwood regeneration methods are providing mixed results for oak seedling development and recruitment due to the increased abundance of shade tolerant midstory species. The irregular group shelterwood (Femelschlag) system has been used in Central Europe to address these issues, and may provide the basis for a gap-based system in the Central Hardwood Forest Region. This study examines the two-year effects of a gap-based regeneration method featuring 60m diameter gaps (0.72 ac), and associated midstory removal 30m into the surrounding forest matrix, on natural oak and competitor tree species reproduction as well as on planted white oak seedlings (Quercus alba L.). In addition to seedling growth and survival, the study also characterizes the spatial patterning of light transmittance from gap centers into the forest matrix beyond gap margins. Results from this study can serve as a basis for oak management addressing recruitment issues and providing a regeneration method compatible with a range of forest ownership objectives