It called my attention that in South Finland there are pine trees which apparently are able to grow with their roots barely covered with soil. Some sit directly on hard rock with all their roots visible. I took two photos of this on 2006:
http://pix.hamoid.com/finland2006/nature_is_a_huge_canvas.jp...http://pix.hamoid.com/finland2006/going_back_to_my_roots.jpg
Those trees survive winter winds at -22F (-30C) with very little sunlight, although sometimes winds knock them down making a vertical wall out of the exposed roots.
You are right, if one sees roots it doesn't mean there aren't other roots.
I think the difference is, South Finland was compressed by 1 km of ice during the last ice age, and the ground is pure granite that is blown up using explosives whenever a new building or road is built.
In those places I talk about, the dirt layer is extremely thin or often nonexistent. The photos I linked don't show that, but many trees are clearly sitting on pure red granite rock with just a little bit of dirt and moss surrounding the roots, in the middle of pale rock.
