Effects of an ongoing oak savanna restoration on small mammals in Lower Michigan

Abstract

Oak (Quercus spp.) savannas have declined drastically in the midwestern United States since European settlement. Oak savanna restoration projects are primarily driven by species closely linked to this habitat type, such as the federally endangered Karner blue butterfly (Lycaeides melissa samuelis). However, it is essential that other species are monitored during restoration. Small mammals, due to their importance in ecosystem function, are particularly useful to study. The United States Forest Service is currently conducting an oak savanna restoration in the Manistee National Forest in Lower Michigan using forest thinning and prescribed burning. To understand management impacts on small mammal communities, we live trapped small mammals in each of the mechanically thinned plots (i.e., bulldozer, masticator, and shear cutter) and control plots in five blocks over six years (2008–2013), as well as measured vegetation variables each year. Initially, we used a permutation multivariate analysis of variance (perMANOVA) to determine if there were treatment and year interactions for both small mammal community assemblages and vegetation variables. We then compared changes in small mammal diversity, relative abundance, and vegetation variables among treatments using exploratory randomized block design analysis of variances (ANOVAs). Canopy cover was significantly lower in bulldozer and shear cutter thinned plots than control plots five years following thinning. We observed significant treatment by year interactions in how the small mammal community responded. A large increase in relative abundance of white-footed mice occurred one year post-thinning in all treatments. Within 1–2years of treatment, thirteen-lined ground squirrels and meadow jumping mice, both open-canopy grassland species became established on thinned plots. The retention of brush piles in bulldozer and shear cutter plots provided important refuge habitat for small mammals following thinning. Restoration efforts were beneficial to the small mammal community overall and promoted grassland species to immigrate into the restored area.