Slightly off topic, but in the UK we call rings of fungus "fairy rings" (https://en.wikipedia.org/wiki/Fairy_ring).

Myself and others have witnessed these at native orchid sites and one pattern is that orchids don't grow within the ring; it seems the expanding ring consumes nutrients within, eating outwardly as it expands. This in itself is interesting because typically terrestrial orchids have a heavy symbiotic relationship with fungi. There are interesting physical similarities I can see here; a robustness on the perimeter due to higher nitrogen availability, and more barrenness within the interior.