Yes over time the oceans have come and gone as evidenced by the limestone and shale at the surface or buried under so much of Earth. And the woody plants are in a constant battle with the grasses and other shorter plants. It might take many burns to greatly reduce your loblolly and hardwoods. My old friend Leo Kirsch, who was a friend of the Komareks and had set or observed a lot of prairie fires, estimated it would take 20 burns to get buckbrush (Symphoricarpos) back to its original location in the hydrological profile and it is only a shrub. I wonder what the native herbivores were in the prairie Blackbelt? They devour many woody plants, especially those that sprout after fires. Up here, the Aspen Parkland expanded 500 miles into the prairies after the buffalo and elk were killed off and the number of prairie fires was reduced.

There are lots of interesting and fascinating accounts of the effects of fire and grazing on prairies in what is now Kansas in Wm. Least Heat-Moon's 1991 book PrairyErth: a deep map. ISBN 0-395-48602-5