That's the bark of an old Long Leaf. It is the thickness of the bark and its grass stage that protect it from forest fire and allows it to survive when so many of the other species are killed.
Back before all the forest fires were put out by well-meaning citizens, this quality was what generated so many acres of Long Leaf Pine in the South.
It's not just the cutting down of the Long Leaf that can be blamed for the lack of Long Leaf forests. It's also the lack of fire and the need for a fast growing timber tree to support human needs.
