Fairy circles of Namibia

wolram

http://science.uniserve.edu.au/schoo...irycircle.html

I site i stumbled across, and just wondered if an explanation has been found.

wolram

http://en.wikipedia.org/wiki/Allelopathy

One of the most famous cases of purported allelopathy is in desert shrubs. Salvia leucophylla was one of the most widely known early examples because it was on the cover of the journal Science in 1964[2] Bare zones around the shrubs were hypothesized to be caused by volatile terpenes emitted by the shrubs. However, like many allelopathy studies, it was based on artificial lab experiments and unwarranted extrapolations to natural ecosystems. In 1970, Science published a study where caging the shrubs to exclude rodents and birds allowed grass to grow in the bare zones.[3] A detailed history of this interesting story can be found in Halsey 2004.[4]

Bystander

Diffuse knapweed is absolute death on grasses --- just try letting it go for a while in a lawn.