Cedar trees and rock piles

Here is a little spot I explored last weekend, in Boxborough. Leaving the road to the north, I crossed a little hill and on the northwestern side there was a wall which I followed, contourwise, west and south. There was a first rock pile:
and as I followed the wall I came to another rock in the same relative position to the wall, with a little juniper bush growing on it.
I thought I detected rocks under the plan growth:
I mention it, not because I understand the similar positioning of these two rock piles, but because I wanted to call attention to the juniper tree which is a kind of cedar. It is not uncommon to find a juniper bush growing in a rock pile at a site were fields have gone back to being woods. It does not follow that these are farming related piles, and I think we know they are not. But I think also that the Juniper may be deliberately planted in/on a rock pile. I wanted to give some examples.
Here is one with a cedar tree, from Stow:
I honestly think this is a deliberate memorial which includes the cedar tree.