COMMUNITY ORGANIZATION: PERIODISM 



535 



succession of forest beetles, referred to in 

 the preceding figure, with the seasonal suc- 

 cession of carabid beetles in the beach drift. 

 The correlation between these two 

 figures suggests a direct relationship be- 



Jon. Feb. Mar. Apr. Moy June July Aug. Sept. Oct. Nov Dec. 



Fig. 181. Seasonal periodicity of beetles in 

 the forest communities bordering Uie south- 

 em end of Lake Michigan, and the seasonal 

 .Tiarch in air temperature, relative humidity, 

 and radiant energy. (Graph shows percentage 

 Df species active, based on data from April, 

 1922, to December, 1928; mean monthly air 

 temperature in degrees F; mean monthly rel- 

 ative humidity in percentage; radiant energy 

 in gram-calories/sq. cm. /sec. ) (After O. Park.) 



jjJ Mor Apr. May June July Aug. Sept. Oct. 



TIME IN MONTHS 



Fig. 182. Correlation of (A) seasonal pe- 

 riodicity of active species of beetles for the 

 forest communities bordering the southern end 

 of Lake Michigan with (B) seasonal periodic- 

 ity of active species of Carabidae in the 

 beach drift of Lake Michigan. (After O. Park.) 



tween the phenology of inland forest and 

 meadow communities, and the seasonal 

 periodicity of the Lake Michigan beach 

 drift. 



In dramatic contrast with periods of 

 relative activity and abundance is the 

 winter or hibernal season. This is a time 



of relative inactivity and scarcity, in so far 

 as the whole community is concerned. The 

 hght is at its lowest average intensity, but 

 in deciduous forests the lower strata of the 

 communities are relatively brighter as a 

 consequence of the defoliation of the 

 canopy (O. Park, 1931), whereas the bank- 

 ing of snow upon the evergreen canopy of 

 coniferous communities reinforces the rela- 

 tive dimness below (Fig. 183). The tem- 

 perature is correspondingly low, the bare 

 branches of deciduous trees ofi^er much less 

 protection from winds, the forest and 

 prairie floors are often blanketed by snow, 

 and the smaller lakes, ponds, and streams 

 may have the upper strata or the entire 

 vertical system of strata frozen. 



In such temperate communities the total 

 activity is at its lowest ebb. The most 

 obvious activities are those concerned with 

 the search for food by the relatively few 

 species of resident, homoiothermal animals 

 that remain active. These usually are the 

 winter bird population (Chapman, 1918; 

 Sanborn, 1922; Eifert, 1941'), and certain 

 mammals (Hamilton 1939, 1943). This 

 state of relative inactivity deserves thought- 

 ful attention. The activities of winter 

 residents serve to accentuate the contrast, 

 in the same community, between the 

 warmth, noise, and verdure of summer, and 

 the cold, stillness, and frozen whiteness of 

 winter. 



At the level of integration under ex- 

 amination, namely, the major community 

 at the level of survival, the rhythmic winter 

 inactivity of the mafority of the interde- 

 pendent species populations alternated with 

 their summer activity, corresponds to the 

 diel periodicity of the majority of in- 

 dividuals. Thus we are concerned with the 

 life of populations, rather than with the life 

 of individual organisms. This long-term 

 view of the communitv in seasonal balance 

 is related philosophicallv to the view of the 

 communitv in diel balance, to be discussed 

 presently. 



° Regional lists of wintering bird populations 

 throughout the United States may be found 

 annually in Audubon Field Notes, published 

 by the National Audubon Society (formerly 

 published as the Season, a supplement in the 

 Audubon Magazine). Additional information on 

 bird populations, relating to fall and spring 

 migration and the breeding season, is also 

 included. 



