I had put five tires down at the east end of one of my rose strips, not the one parallel to the road. I put the tires there to prevent my neighbor from running over my roses with his four-wheeler. Then I decided to dump compost in the bottom, then potting soil when I was ready to plant.
Some animal dug down to the compost. I don't guess I should have put the compost directly into something I was going to plant. I should have mulched it first. I didn't think it would matter, but animals are not great respecters of plants.