The Oak Savanna is a transition zone between the big woods to the east and prairies to the west. Fire would rip across the prairie and into a wooded area. At this interface, scattered groves of bur oaks became the dominant vegetation because their corky bark gives them the ability to withstand fire.
As a result of limited competition for sun, the oaks were majestic with wide canopies and wide low branches. Under the dappled shade of these trees, a special combination of prairie and forest groundlayer plants and animals coexist.
Less then 0.01% of Oak Savanna is left in Minnesota due to settling and lack of fire.
The Oak Savanna at Saint John's Abbey Arboretum was used for grazing cattle, which kept invading tree growth minimal, but damaged the ground layer vegetation.
The ground layer vegetation has been planted to native prairie grasses and forbs.