Effects of Oak Woodland Restoration Treatments on Sapling Survival and Tree Recruitment of Oaks in an Upland Mesic Oak-dominated Forest

摘要

Oak-dominated (Quercus spp.) woodlands, defined here as mixed woody and diverse herbaceous plant communities with > 70% tree canopy containing few nonoaks (see also Taft 1997), comprise a small fraction of the area in North America occupied prior to fire suppression. Historically, frequent low intensity fires maintained oakdominated forests, woodlands, and savannas across the Midwest and interior South of the United States (Anderson and Bowles 1999, Fralish et al. 1999, Heikens 1999, Brewer 2001, Van Lear 2004, Ruffner and Groninger 2006). Fire exclusion in the 20~(th) century enabled firesensitive hardwoods to colonize previously fire-maintained oak woodlands (Hart et al. 2008, Nowacki and Abrams 2008). These tree species produced a more closed canopy (> 90%) than the historically open, sparse canopies of oak woodlands and savannas (Bowles and McBride 1998), leading to widespread oak regeneration failure and losses of groundcover plant diversity (Abrams 1992, Bowles and McBride 1998). These diverse oak communities are rare ecosystems (Anderson and Bowles 1999) and are thought to occupy less'than 0.02% of the area in North America they occupied before fire exclusion (Nuzzo 1986).