Dead grass redux
 

Eggs Zachtly wrote:

Unlikely. I've got several large maples (silver and sugar) and
the only surface roots I see are large and woody and would easily
be burried for years if I covered them with an inch or two of
topsoil.

And you'd shorten the trees lifespan, in the process. Those roots
are there, at that depth, for a reason. That's where the water,
nutrients, and more importantly, oxygen is located.

I have seen many species of trees in urban settings that are surrounded
by paving almost up to their trunk and they grow very large and appear
very healthy.

Paving like that is not something I would ever do or recommend, but it's
clear evidence that the idea of adding a few additional inches of
topsoil under trees will have ZERO effect on oxygen availability to the
roots, and a healthy layer of turf grass under a tree will probably do
more for water retention and keeping the soil moist and cool in the
middle of summer vs having bare soil.