Tree Density and Fire Scarring in Minnesota Oak Savanna: Implications for Restoration
Mickley, James Gilbert
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Due to fire suppression subsequent to European settlement, Midwestern oak savanna has become one of the rarest ecosystems in North America, with only 0.02% of the original range surviving today. Because of the necessity of fire in perpetuating this ecosystem, restoration and management is difficult, especially because little is known about original conditions and fire dynamics of oak savanna. To address these uncertainties, fire scarring was studied at one of the longest-managed remnants of oak savanna at the Cedar Creek Natural History Area in Central Minnesota, which has been burned periodically since 1964. Fire scars lead to a lower life expectancy, therefore high levels of scarring can indicate the beginnings of a shift towards prairie or oak scrub. Both contact and non-contact scarring are prevalent in oak savanna at Cedar Creek, with scarring on as much as 800/0 of trees over 10 cm DBH. Contact scarring is more prevalent in areas with higher tree densities prior to the start of the bum program. Noncontact scarring is usually present only in smaller diameter classes, but with improper burning techniques, it may also affect larger trees. Both contact and non-contact scarring can be controlled by more careful management, leading to more successful restoration and preservation of oak savanna.