Oak Savanna

What do white-tailed deer, wild turkeys, and the Federally endangered Karner blue butterfly have in common? They all live within the oak savannas of southwest Michigan. Oak savannas are rare and unique ecosystems where locally droughty (dry) environmental conditions result in sparse tree growth. Ample sunlight stimulates a diversity of herbaceous plants that are also adapted to these conditions on a fragile, sand soil. Commonly occurring plants within this ecosystem include little blue stem, coreopsis, and wild lupine.

Oak Savanna

Deer regularly visit savannas in the summer when little blue stem and other warm-season grasses are actively growing. The succulent new growth is much more tasty than cool-season plants that grew in the spring and have since dried. These warm-season grasses also support a rich selection of grasshoppers and other insects. Hen turkeys lead their poults into these savannas to gorge on these protein-rich insects. Adult Karner blues nectar (feed) on a variety of flowering plants, but they must lay their eggs on the lupine. This unique relationship restricts Karners to the oak savanna ecosystem for their survival. In different ways, oak savannas provide for a portion of the habitat needs for each of these species.

Wildfire played an important role in maintaining oak savannas prior to European settlement. Repeated fires helped shape the savannas, cleaning out understory brush and creating their sparsely wooded character. With modern fire suppression programs and capabilities, wildfire is no longer allowed to play its historic role in this ecosystem. In substitution, managers now thin and cull the oak stands. They are also setting fire under controlled conditions to mimic the role of wildfires.

The management objective is to restore both the sparse oak stands and the diversity of plants that struggle to survive in this droughty, fragile landscape. The objective will be achieved if the habitat remains suitable for the continued use by deer, turkeys, and Karner Blues.