Oak savanna woodlands were once a dominant ecotone throughout the upper Midwest. These ecosystems represented a transitional zone between prairie communities to the west that eventually graded into Big Woods forest. Most of the oak savanna landscapes of most of the Midwest were extensively homesteaded and farmed during the middle 1800s and few intact savanna landscapes remain today. Given the current interest in preserving, maintaining, and restoring these systems, it is imperative that the natural factors that have shaped these areas are investigated. This research investigates the potential of developing reference conditions in a relatively intact oak savanna in the Sherburne National Wildlife Refuge, Minnesota. This research provides a context for current management activities centered on maintaining and restoring oak savanna ecosystems.