Wizard,
forgot to mention in my email to you, that when I park out east of you and past the U.S. Forestries parking lot and even some times at the their parking lot, I to have had dirt bike tracks very very close to my truck as well. It doesn't happen all the time, but it does happen.
I have no idea who it is and there's never any damage that I am aware of either. I know for a fact though, that there is always off-road vehicles out there who enter the area off of Power Line Road. Mike's out there as well at various times as well.