Management and restoration of sand savannas and barrens is an important conservation goal in the eastern U.S. and Canada. However, little information is available comparing historic and modern conditions, and how remnants respond to different restored fire intensities. Our study site was the 197 ha Tefft savanna, an eastern sand savanna remnant in northwest Indiana, which had undergone three decades of fire protection. Data from the U. S. Public Land Survey indicate that in 1833, vegetation was black and white oak barrens, and pin oak savanna, with trees averaging 50 stems/ha and 4 m2/ha basal area. In 1986, unburned black oak and white oak stands averaged > 400 stems/ha, with about 10 m2/ha basal area. To assess the effects of fire in restoring this vegetation, we first compared effects of dormant season high and low intensity fire (measured by scorch height) on woody vegetation among 9 split plots representing black oak, white oak, and pin oak stands. Twenty years later, we compared the same plots, all of which were burned 3 times per decade with low intensity fires.
Results/Conclusions
After initial burns, black oak and white oak stands receiving high intensity fire averaged < 200 stems/ha, and < 5m2/ha basal area, which was significantly lower than with low intensity fire or unburned control. These stands also had lower oak canopy cover with high intensity fire than without fire, but intermediate cover with low intensity fire. Density, cover, and basal area of non-oak tree species that had invaded during absence of fire were much lower than that of oaks, and were not reduced significantly by initial burning. Repeated low intensity burns did not further affect cover or basal area of oaks or non-oaks, but reduced lower size class stem densities and promoted post-fire sprouting in the shrub layer. Over the 20-year period, oak basal area increased due to ingrowth into larger size classes. Time since fire regulated shrub layer structure on a four-year cycle. Density and cover of trees and shrubs returned to pre-burn conditions by the second and fourth growing seasons after fire, respectively, with non-oak tree species exceeding pre-burn cover and density by the fourth season. These results suggest that high intensity fire is more important than repeated low intensity burning in structuring and restoring eastern sand savanna, and that non oak tree species may be resistant to low intensity fire once established.
