I sure know a lot of people study and swear by them in the South and a lot of theory's are they are caused by nature and deadfalls. I work with a group of foresters and they are skeptical as the tree would have to be several hundred years old to fall into that category and by then they are of great size and few species will live that long. We have trouble finding civil war bullets and shells that have survived in wood and that war was not that long ago. Most we find are in dead cedars and extinct chestnuts. I do know of some of the oak species reach 500 years old but are very large. Also lots of times muscadine will wrap a young tree and bend it down. This is seen on oaks a lot cause they grow so slow in the beginning competing for sunlight.
I have seen the patterns carved and the shapes made. I know in the 1800's people would try all sorts of goofy things with trees in making circles by grafting and so forth.
Remember a renewable(hardwood) forest that is select cut can be cut every 30 years for timber so that gives you an idea of size and rate of growth.This does not apply to loblolly pines and tulip populars though.They can be harvested sooner especially on a north face.
Good topic. Look forward to your pictures.
TnMtns