fairy ring
n.— «Evidence of logging is best visualized by the way redwoods grow in rings, sometimes referred to as “fairy rings.” These are caused by the resprouts that grow around a stump. You can get a sense of how big the original tree was by measuring the inside of the fairy ring.» —“Redwood’s amazing biology makes them survivors” by Joe Rigney Santa Cruz Sentinel (California) July 22, 2004. (source: Double-Tongued Dictionary)