Oct. 29,1917 
Fungus Fairy Rings 
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The effect of Calvatia cyathiformis and the other fungi which do not 
produce a bare zone is the temporary stimulation of the natural vegetation. 
This influence seldom covers a zone more than a meter wide. The 
effect on the short grasses is to thicken the sod during years of ample 
moisture supply (PI. 27, B.). 
Agaricus tabularis kills out the vegetation and initiates a succession 
(fig. 15) not essentially different from that occurring on abandoned 
tilled land (Shantz, 1911) or on abandoned roads (Shantz, 1917). The 
original vegetation is often entirely killed. On the inner part of the 
area of bare ground 
weeds develop to form 
the first stage in the 
succession. In this 
area, which lies above 
the dense mycelium, 
the weeds which start 
growth during the 
spring rainy season are 
usually killed by 
drouth while still very 
small. 1 This area of 
stunted annuals (fig. 
15) constitutes the first 
or early-weed stage in 
the succession and con¬ 
sists chiefly of the an¬ 
nuals which are ordinarily abundant in the native sod, such as Plantago 
purshii R. and S., Festuca octoflora Walt., Hedeoma hispida Pursh., Le- 
pidium ramosissimum A. Nels. 
During a normal year these plants dry off about the middle of June 
and the area remains bare for the remainder of the season. Just inside 
this zone and not sharply separated from it is the inner stimulated zone. 
This zone is in the second or late weed stage and is dominated by a 
luxuriant growth of the plants listed in the first stage and the following 
more characteristic ruderals: Ckenopodium incanum (S. Wats.) Heller, 
Lappula occidentale (S. Wats.) Greene, Crypianthe crassisepala (T. and G.) 
Greene, Amaranthus blitoides (Wats.). 
Following the late-weed stage several of the stages clearly recognized 
on abandoned roads or cultivated fields can be distinguished. 
The third, or short-lived grass, stage is marked by Schedonnardus 
panniculatus (Nutt.) Trel., alone or with Malvastrum coccineum (Pursh.) 
Gray, and Sitanion hystrix (Nutt.) Smith. 
1 If deep-rooted perennials such as Artemisia frigida, Gutierrezia sarothrae, etc., occur in this zone, they 
occasionally continue to grow, due to a supply of available soil moisture in the deeper layers erf the soil. 
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Fig. 15.—A sketch of the stages in the succession leading to the reestab¬ 
lishment of the short grass following its destruction by Agaricus 
tabularis. 
