I have ancient Ponderosa pines here on the property. The range is from 12" to well over 38". I lose three or four every ten years or so to Pine Bark beetle. When they rot and fall - I just leave the stump. It will be gone in five years also. Something - coyote, skunk, badger or raccoon - always digs around these rotting stumps. Encourages their demise.
They go after the ants, which begin working the stumps as soon as they start to rot.