tree well

noun2

1. •
   A hole or depression in the snow around the base of a tree caused by the tree's canopy preventing the accumulation of snow.

   • Steer clear of the tree wells. They can be really deep and dangerous. — 2013
2. •
   A structure designed to protect the base and roots of a tree, typically used in an urban setting.

   • Flat surface tree wells create a cleaner architectural effect where trees appear to grow directly out of the pavement. — 2007