rockm

Keep it in the pot--or not. I leave my trees in the pots over the winter. Some remove them. I leave mine in because root start growing before you unover the trees for the spring. This can cause some problems if the roots grow too big to get back into the pot--although if the tree is due for a spring repotting anway, this doesn't make that much difference, as you will be root pruning the plant.

Anyway, Mulch over the pot and the bricks (which are there to provide a drainage field underneath the pot. If you put the pot on top of mulch or the soil, it's likely to become clogged and water will pool at the root zone. That's VERY bad.

You're after a big mass of mulch over the tree's roots. This mass won't really keep the tree "warm" --although it wil probably keep it warmer in the colder months for the most part--it will "lag" temperatures, though. That is, keep temps from swinging too quickly, or reaching extremes. The mass will also keep the roots cooler in the spring, an important thing to prevent premature growth during warm snaps before actual spring arrives.