Date of Award
The United States Forest Service is conducting an oak savanna restoration using thinning and prescribed burning in the Manistee National Forest in Michigan to provide habitat for Karner blue butterflies (Lycaeides melissa samuelis). Since this is a federally endangered species, alternatives to spraying pesticides to control exotic invasive defoliators, such as European gypsy moths (Lymantria dispar), are necessary. Although gypsy moths are invasive to North America, there are several predators, such as whitefooted mice (Peromyscus leucopus), other small mammals, invertebrates, and parasitoids, keeping gypsy moth populations low. This study investigated whether the interaction between the small mammal community and gypsy moths in July was affected by the type of mechanical forest thinning method (i.e., bulldozer, masticator, shear cutter) used during an oak savanna restoration at two sites (Pines Point and Hayes Road) over two years (2010-2011). Relative abundance was measured for small mammals and gypsy moth pupae were placed and monitored at two study sites to determine predation rates in July 2010 and 2011. Furthermore, Pines Point was used to investigate the impacts of thinning and burning on small mammal communities over four years (2008-2011) in the fall. The study at Hayes Road focused on the small mammal community response to thinning alone in August over two years (2010-2011). Overall, mean predation rates were higher in thinned (26%-62%) than control plots (14%-47%). Small mammal relative abundance also tended to be higher in thinned than control plots in all months at both sites. Since there were no significant differences in predation rates among vi treatments nor any detrimental impacts to the small mammal community, it is recommended that the treatment found to benefit the Karner blue butterflies the most be implemented. The combination of thinning and burning were particularly beneficial to the small mammal community overall and promoted oak savanna species to immigrate into the restored area. More generally, it is recommended that levels of gypsy moth predation rates and small mammal communities be analyzed on a site specific level for longer periods of time to determine if ecosystems can be restored and gypsy moth predation increased simultaneously.
Larsen, Angela Lynn, "Effects of Oak Savanna Restoration and Thinning on Gypsy Moth Predation Rates and Small Mammal Communities" (2012). Masters Theses. 23.