fairy rings

[Keithfungi]

Hi Scott:
Well, you certainly have raised an interesting question. Two things to bear in
 mind:
1. The mycelium producing the fruiting bodies (mushrooms) is dikaryotic or
 diploid. It is not the product of a single spore, but rather of two spores.
 And it probably still lives inside the area of the ring (and maybe a goodly
 ways outside). 
2. Fruiting (producing mushrooms) tales a lot of things going right to make it
 happen: rught nutrients, right temp, etc. Maybe outside the ring the soil is
 too "rich" and inside it is too poor due to the growth of the ring mycelium. 
Of course, not much has been done with rings in nature. So you can probably
 come up with all sorts of interesting hypotheses. 
Any one else have any ideas?
Keith Klein
Mankato State University