COMMUNITY ORGANIZATION: PERIODISM 



533 



each community. This investigation in- 

 cluded a study of seasonal succession in an 

 elm-sugar maple forest during 1925-1926. 

 Later, Jones (1946) added to data 

 gathered on this forest between 1933 

 and 1938. Table 48 contrasts the seasonal 



of habitat niches which age relatively rapid- 

 ly—for example, cattle dropping in the 

 prairie communities (Mohr, 1943), and 

 many soft fungi (Park, 1931a) in forest 

 communities. Figure 180 illustrates such a 

 rapid seasonal succession in the populations 



Table 48. Seasonal Succession in an Elm-Sugar Maple Forest Community in Central Illinois 



pictures of the same community obtained 

 by these two reports. 



Seasonal periodicity is illustrated by a 

 seasonal diagram of a red oak-sugar maple- 

 elm forest (Fig. 179). This diagram 

 of the seasonal fluctuation of species popu- 

 lations is typical of the majority of com- 

 munities, in so far as the general concept 

 is concerned. Naturally there are ex- 

 ceptional circumstances or variations to be 

 expected. In most communities certain 

 species are dominant as to abundance in 

 one year, and the following year occupy a 

 less important statistical position. Again, 

 unusual severity of weather will retard the 

 seasonal succession. Injury to the com- 

 munity may impair or wholly alter the suc- 

 cessional sequence. Furthermore, many 

 small forms, such as diatoms, regularly have 

 two or more maxima of reproduction within 

 a single growing period; such species 

 usually have brief life cycles. 



Within a given community each well- 

 defined type of habitat may undergo 

 seasonal succession. At times this sequence 

 is diflBcult to analyze, as the seasonal 

 sequence may be progressively modified by 

 the serai or ecological succession taking 

 place simultaneously. This is especially true 



of a soft fungus (Hydnum septentrionale) . 

 In this graph, on two successive years, the 



Apr. 12 MQy2 June2 Apr 25 MQy23 June 14 



1927 1928 



Fig. ISO. Seasonal periodicity of the beetle 

 populations in a fungus (Htjdnum septentrion- 

 ale) with respect to individuals and species. 

 (After O. Park.) 



species and individuals were recorded for 

 two separate specimens of fungi. In each 

 case, both number of mycetocolous species 



