@shanekingsley seems to know lots about trees. My understanding is those raised rings probably do far more harm than good. They don't have enough weight or structure to provide any support to a tree and they bury the transition between roots and trunk which can encourage rot there.I've got these things around a few trees on my lot (actually these are City of Mississauga trees) that my wife doesn't like any longer. She wants to get rid of them but feels the tree will fall out. I believe they're only ornamental and will have zero effect on the tree.
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Thoughts on removal? I assume there's a chance that the roots are within the enclosed area, and that could cause issues.
As for soil, I called a few of the shops recommended here and all of them said the same thing 'No soil deliveries until April', so that's unfortunate as I wanted to get going on this before the house work starts.
Also....aeration BEFORE or AFTER the soil gets here?
If you do remove them, I would consider mulching a circle. Makes it much easier to cut the lawn when you don't need to cut right beside the tree.
I don't know for sure, but I think aeration before soil makes sense. Open up the dense layer you've got. I have the aerator that punches two holes at a time. It takes a while but it's free.