Many tree beds in the west village have been planted with cabbages (Brassica oleracea), a hardy, decorative plant, that is not bothered by frost. People tend to prefer the purple variety, as shown below. I'm not sure if dogs have any preference, but I'm guessing the tenders of this tree bed are hoping that dogs do not like purple. Dog droppings can create pollution for trees, as well as unpleasant surprises for pedestrians, so any way to encourage people to curb their dogs is a good. Tree pit grates are a tried and true solution for keeping dogs away from most of the tree pit. Probably a little creative signage as shown below also helps.
White cabbages can also be beautiful, and evocative of the snow that is to come.
Tree pits where plants have been removed, can still display the colors of the season by collecting fallen leaves.