In arid, sandy soils ranging from Angola to South Africa, “fairy rings” of perennial grass species dot the landscape. These rings have inspired ecological and mythological speculation about their origins. Norbert Jürgens of the University of Hamburg in Germany has worked on these rings for years and has determined that they are the result of the sand termite (Psammotermes allocerus).
Termites create these rings after eating the roots of grass. Their chomping results in a bald patch that becomes the ring center. The soil in the center of that patch stays damper than neighbouring areas. The circles’ bull’s eye then sustains both the moisture-loving termites and a belt of grasses around its edge.
I’ve seen rings like these in New Zealand grasslands, though was taught somewhere, sometime, that they were fungus related. I’ll check for termites next time I’m in a field with some of these.
More information here.