Specific answer: Probably dozens, certainly not thousands. The ground is mostly clay under top soil (forest floor), rocks are rare, and it's fairly damp right now.
Thanks all for replies/ideas/techniques. I'm helping a neighbor create a dirt trail back to his clearing. It looks like there had been a trail there within the last century. Most of the trees there are no more than 3-4 inches in diameter and most are much smaller. In addition to that project, there are several overgrown trails in my woods that I'd like to re-open, just on general principles.
Question: What is meant by "brush grubber"? I see two types when I Google the term. One is like a chain with teeth and the other is like a big pliers with teeth that grip tighter when you pull. I have a medium-size grubber of the later type but it just seems to slip up the tree trunk after the tree bends when I pull with the tractor.
My stump bucket pushes into the ground just fine until it hits a big root and it stops. It seems that I'd need to dig a pretty big hole to get the stump out with the stump bucket. So I plan to put a box blade on the back to smooth over the resulting hole before I get serious with that bucket.
I enjoy learning from the shared experience of the TBN group, so thanks again..