Prairies are kept free of trees and shrubs by prairie fires. The fire kills a woody plant not by burning it but by boiling the water in the vascular system near the surface of the thin bark. This oak seedling would be killed or at least knocked back by a fire. It might sprout back from the root. If there is no fire for a number of years, maybe 5 to 10, the tree sapling will develop a corky bark about an inch thick thick enough to insulate the the tiny water carrying tubes just below its surface from the fire and the tree will continue to thrive.