Study Area
This study was conducted in east-central Minnesota at the Cedar Creek Ecosystem Science Reserve (CCESR) (Latitude: 45.401, Longitude -93.201) located in the Anoka Sandplain, a glacial outwash area with coarse-textured soil low in organic matter and total nitrogen (Grigal et al. 1974). Maintained by fire, prairie and oak savanna were dominant upland vegetation types in the Anoka Sandplain prior to European settlement (Wovcha et al. 1995). The oak savanna/woodlands at CCESR are characterized by low tree diversity. They are dominated by two species of oaks, Quercus macrocarpa Michx and Quercusellipsoidalis E. J. Hill, accompanied by varying abundances of a small number of mesophytic species, depending on the burn frequency (Peterson and Reich 2001). In 1964 a program of prescribed burns (ranging from controls to annual burns) was initiated at CCESR to restore and maintain oak savanna and to study the effects of fire on vegetation (Irving 1970).