Resumen de Mystery fairy rings hint at their source
Deep in the Australian outback, grass-ringed circles of bare earth stretch for several hundred square kilometers across the red soil. This is the first time these "fairy circles" have been spotted outside the Namibian desert, where they have evaded explanation for decades. The discovery could help resolve the long-standing mystery of how they form. "It shows that the fairy circles of Namibia do not exist on their own," says Stephan Getzin at the Helmholtz Center for Environmental Research in Leipzig, Germany. Getzin's team found few ant or termite nests within, or near, the circles and no correlation between rings and locations of the nests that did exist. But they did find that the hard-clay soil crust within the circles was almost impermeable to rainfall--all the water pouring into this area flowed towards the periphery where the thirsty plants await. More water around the circle edges means more biomass and roots, and that leads to the soil becoming looser. Looser soil allows more water to penetrate and feed the vegetation, creating a feedback loop supporting the plants at the edge of the circle. The dominant grasses of the Triodia genus found close to the fairy circles in Australia also form other typical drought patterns such as stripes, labyrinths or spots with individual plants surrounded by bare earth. This provides strong evidence that the fairy circles also arise due to competition for water, Getzin says.
