On the main island in my current world I have at least (playing no map) one mountain that has quite a bit of meadows around the base of it and a very high oak density. It wouldn't surprise me if there's a native oak in the snow there.

Unfortunately, I have no idea where it is anymore, so I have no way to check. :-)

Actually, I'm sure I could find it, but I am coming to the conclusion that no map is (at least in earlier game) best played nomadic.