You look closer at the tree. A section of its gnarled, ancient bark has been cut away to form a circle, into which two teardrop shapes have been carved. One is cut directly into the wood, whereas the other is formed of the bark itself, the area around it having been hollowed out so that the teardrop stands in relief. You get the impression that one symbolizes light, the other dark.
The two teardrops are arranged vertically and do not seem to relate to either of the two paths—at least, not as far as you can tell.