Oak savanna, a transitional ecosystem between open prairie and dense oak forest, was once widespread in Minnesota. Upon European settlement much of the oak savanna was destroyed. Recently, efforts to restore this ecosystem have increased and often include the reintroduction of fire. Though fire is known to serve an important role within oak savannas, there are currently few studies which address fire regimes on timescales longer than the last century. This research presents a paleoecological history of Sherburne National Wildlife Refuge (SNWR) in MN, USA, spanning the last ~8000 years. The objectives of this study were to use charcoal, pollen, and magnetic susceptibility of lake sediments collected from Johnson Slough (JS) within the refuge to evaluate the natural range of variability and disturbance history of the oak savanna within the refuge, assess the success of current restoration strategies, and add to the regional paleoecological history. The mid/late Holocene period of the JS record shows a period of high fire activity from ca. 6500 to 2600 cal year BP, with a shift from prairie to oak savanna occurring over this same period. A (possibly agricultural) disturbance to JS sediments affected the period from ca. 2600 cal year BP to 1963 AD, which includes the time of Euro–American settlement. However, the destruction and subsequent restoration of the oak savanna is evident in a pollen ratio of Quercus:Poaceae, indicating that current restoration efforts have been successful at restoring the oak savanna to within the natural range of variability seen just prior to destruction.
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Acknowledgements This project was funded by the United States Fish and Wildlife Service Cooperative Agreement #30181AJ166. Thank you to Kurt Kipfmueller for making the contact between TH, AB and JDS. Thank you to Mitchell Power and Bryan Shuman, who offered extremely helpful insight to improve this research. We also appreciate the support of everyone at the RED Lab, particularly Shawn Blissett, Jennifer Watt, Vachel Carter, Jesse Morris, and Zachary Lundeen, for the hours they spent at the microscopes discussing this project. We would also like to acknowledge the staff of SNWR, Anne Sittauer, Elizabeth Berkley, and Sally Zodrow, who were extremely helpful in coordinating fieldwork and providing background information on the refuge. Field equipment was rented from LacCore, and an initial core description was performed at their facilities at the University of Minnesota. Edward Cushing provided very useful pollen reference slides. Radiocarbon dates were analyzed by Doug Dvoracek at the Center for Applied Isotope Studies in Atlanta, Georgia, and plutonium analysis was performed by Michael Ketterer at Northern Arizona University.
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- Land management
- Oak savanna
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