Is the Arctic home to fairies, the meeting place for leprechauns or the resting place for passing trolls?
Two hundred years ago, many would have answered yes upon seeing a fairy ring in the tundra. A fairy ring is a circle of brownish grass surrounded by a circle of lush bright green grass. When conditions are right toadstools sprout up from this ring. In England, it was believed that these rings were tiny paths beaten by fairies as they joined hands and danced together and that toadstools grew around these rings so that the fairies could sit and rest their tired feet after a long night of dancing. Other mythological characters such as leprechauns and trolls, which were believed to consort with fairies, were also implicated in the construction and use of fairy rings.
How are fairy rings really formed? A spore lands on the ground and germinates. The mycelium, which grows underground, spreads outwards in a circle. As it grows, it secretes enzymes to break down organic matter in the soil into soluble nutrients. At first, the grass takes advantage of these nutrients so that a ring of lush grass appears, but then the fungus absorbs the nutrients, starving the grass, and leaving a ring of dead grass on the inside edge of the growing mycelium. Periodically, mushrooms spring up just behind the outer edge of the mycelium. Rings are formed when the mycelium in the centre dies, nutrients are returned to the soil, and the grass re-grows. Rings can grow up to 20 cm/yr and reach more than 10 m in diameter. One fairy ring in France is more than 600 m in diameter and more than 700 years old! Fairy rings in the Arctic are not so large, but do occur in relatively moist areas where grasses and sedges are dense. Various species of basidiomycetes, including those in the genus Marasmius, are responsible for arctic fairy rings.