rotting

I have a 31' DBH black walnut in my woods that I discovered a hole leading to the center about 2 feet above the ground and 6-8'' of the center rotted away. There are several other black walnuts in this part of the woods but this is the biggest (not by much) and I like the campground look of this...

Greetings - my first post. I have a large Black Oak about twenty feet from my house. Ten years ago I had to put in an emergency drainage tank near the tree and it probably damaged the roots. Although two arborists have told me the tree is dying and needs to come down, I would like an objective...

I attached a few pictures for reference, but the bark on the lower trunk is starting to rot and separate/fall off. There seems to be a dark stain behind part of the section that is coming off and also a small section of the wood (left side of dark spot) is starting to rot some on the surface...