Trees, Shrubs and Conifers: Old tree and root damage by border installation, 1 by Cearbhaill

Cearbhaill wrote:
I am getting ready to put some border/edging around a new bed and am concerned about it affecting the health of a tree that will be enclosed.
The bed surrounds a very old hickory nut tree and I am wondering about any roots near the surface that might be affected by our digging down 4 or 5 inches?

I wouldn't worry so much but this bed is penninsula shaped and the tree in question is on the end. The means that roots on three sides of the tree will be disturbed. The current plan has us within about four feet of the trunk of the tree- is this far enough? Would moving it out to five feet make an appreciable difference or is the entire plan a bad idea? How about trimming the border material down to two or so inches deep?

I do not want to lose this tree!
It is the tree just left of the two cheesey reindeer.