Burled Beech

At Warren Woods in Berrien County, Michigan, I ran into this unusual beech tree while exploring off-trail. Its exaggerated lower portion is covered with all manner of burls or catheads, and even the little sprouts of trees emerging from the roots are stunted and knobby. Does anyone know what would cause this? It is hollow, and I was hoping to find a thriving colony of trolls living inside, or better yet, elves baking cookies. Or, since Notre Dame isn't far away, maybe a leprechaun dressed in green and whistling the ND fight song, waiting to give away a pot of gold. No such luck!