Ya, relationship is a challenging concept, implies something reciprocal. But it's still the best word I can come up with to describe what happens when you climb a challenging tree in the forest. When you're standing on the ground looking up at it there's a lot you can figure out and understand about the tree. Everything changes during the climb, you REALLY get to know the tree, every aspect of the form and structure is revealed, how it moves in the wind, what it sounds like etc. etc, how it makes you feel (extreme fear, no fear, something in between). After you're back on the ground and look up you're seeing it through completely different eyes. I guess that understanding is what I think of as "relationship". It's same for many things that people have "relationships" with that are considered inanimate: cars, guns, tools, mountains, boots, you name it. Trees are not inanimate of course so they lend themselves even more to a feeling of relationship once you get to know one. Climbing is not the only way to get there but it certainly moves the process along.
-AJ