The Effects of Thirteen Years of Annual Prescribed Burning on a Quercus Ellipsoidalis Community in Minnesota

A Quercus ellipsoidalis community in central Minnesota has been prescribed burned annually since 1965 in an attempt to restore the area to its presettlement oak savanna structure and composition. By 1979 density and basal area of the overstory were significantly lower in the burned area than in an adjacent unburned area but were still higher than estimated savanna values because of the persistence of stems @>25 cm diameter at breast height (dbh). A tall—shrub/small—tree layer was totally lacking in the burned area but averaged 19% cover in the unburned area. Understory richness was significantly higher in the burned area than in the unburned area. Most of the species that showed a significant difference between the two areas peaked in the burned area; this was especially true for grasses and forbs. These results indicate that annual prescribed burning is gradually restoring the area to savanna but that the restoration is not yet complete. Complete restoration may not be possible with annual burning because such burning seems to have little effect on large—tree (@>25 cm dbh) mortality.