In article ,
Bob Hobden wrote:

It was first noticed at RBG Kew that after the Great Storm of 87 when some
old trees were torn out of the ground and luckily dropped back into the hole
that instead of dying their health and growth improved markedly in the
following years. That gave the Kew scientists the clue they needed that
ground compaction was an important part of tree health.

I am pretty certain that the soil there is at least largely clay.
In my garden, it is 60% sand and 22% clay, and I can witness that
woody plant roots have no trouble with ordinarily compacted soil.
The original question was about raising the level, but that might
have similar properties, to a greater or lesser degree.


Regards,
Nick Maclaren.