Source of mysterious 'fairy circles' found - Live Science

But now, the most detailed monitoring effort ever shows that fairy circles are engineered by the grasses themselves.

21 in the Journal of Ecology, reveals how harsh, dry conditions in Australia, punctuated by occasional heavy rainstorms, create a hostile crust of clay that makes up the barren part of the fairy circles.

It's a self-fulfilling cycle: Where there are no plants, weathering from rain and sun makes the soil ever more inhospitable, while areas where grass has managed to grow become a safe haven, where the vegetation cover lowers the soil temperature by up to 77 degrees Fahrenheit (25 degrees Celsius), traps water and allows new seedlings to take root.

This is key to the formation of the fairy-circle patterns, Getzin said, because if there were more grass species around, they would take advantage of different ecological niches and likely cover the barren spots.

It only takes a couple of hard rains to create this crust, Getzin said.

However, Getzin said, this runoff also creates the potential for plants to survive in gaps between the barren zones.

Getzin and his team once measured the top centimeter of the barren crust at 167 F (75 C), well into egg-frying territory.

The cooler soil temperature makes it possible for seeds to germinate and seedlings to grow, Getzin said.

— Mystical fairy circles grace barren desert.

The different soils mean that the mechanisms for the formation of the circles must be different, Getzin said, but they are still almost certainly forced by the limits on water in the arid environment.

"How else can, in Namibia, perfectly circular grass rings form if it is not the competition of the grasses?" Getzin said