COMMUNITY ORGANIZATION: PERIODISM 



531 



ing of species of plants at certain times of 

 the year. Nichols (1923, p. 14) changed 

 the term to aspection. Aspection is equiva- 

 lent to seasonal succession, if both botani- 

 cal and zoological events are used. Such a 

 general view was later espoused by Bek- 

 lemischev (1931) under the term "annual 

 cycles," and as aspection by Carpenter 

 (1938, p. 27), and Clements and Shelford 

 (1939), and as either aspection or seasonal 

 succession by Park, Allee, and Shelford 

 (1939, p. 18). 



Another term closely associated with 

 seasonal succession is phenology. Phenol- 

 ogy, a word already well established, was 

 used by Shelford (1929, p. 4) to embrace 

 the study of correlation between periodic 

 phenomena— for example, the flowering of 

 certain plants and the arrival of migratory 

 birds and mammals. Later the Ecological 

 Society of America (Committee on Nomen- 

 clature, 1935) defined phenology as that 

 science that deals with the time of appear- 

 ance of characteristic periodic events in the 

 life cycles of organisms under natural condi- 

 tions, especially those events influenced by 

 temperature, latitude, and altitude, among 

 other influences in the physical environment. 



One of the comprehensive phenological 

 analyses is that of Leopold and Jones 

 (1947) for Sauk and Dane counties, Wis- 

 consin. They analyzed 328 seasonal events, 

 including blooming of forest, grassland, and 

 sand area herbaceous strata, weeds, and 

 marsh plants, fruiting of shrub and tree 

 strata, and the dates of emergence from 

 hibernation of local mammals and the 

 migration data of a variety of birds. The 

 period analyzed was the decade 1935 to 

 1945, for two localities some thirty miles 

 apart. It was found that the year-to- 

 year variability of phenological events, as 

 compared with their own averages, tends 

 to be greatest in earlv spring, and decreases 

 progressively through Mav. 



Certain plants showed little variability in 

 date of first blooming, and appeared to be 

 governed more by length of daylight than 

 by current weather. Thus white clover, with 

 a standard deviation of 2.4 davs, was the 

 least variable of the plants studied. 



Similarly, certain birds showed little vari- 

 ability in arrival date of the vernal migra- 

 tion. For example, the rose-breasted gros- 

 beak had a standard deviation of 3.1 days, 

 and the upland plover of 3.2 days. 



Leopold and Jones noted that bird migra- 

 tion responded more quickly to temperature 

 changes than did the blooming of plants. 



Correlation of stages in the life history 

 of organisms with regular changes in the 

 basic and secondary physical influences of 

 the environment is usually direct with most 

 plant constituents of a community, and 

 either direct or indirect for animal con- 

 stituents. An example of this sensitive rela- 

 tionship is found in the marine littoral 

 portion of the north temperate Atlantic 

 Ocean. Here (Russell and Yonge, 1928, p. 

 51) occurs a series of species of periwinkles 

 that apparently have a critical stage of their 

 life history directly correlated with the 

 nature of their immediate habitat. The 

 species of periwinkle that live nearest to the 

 low- water tide mark hatch out in an 

 early larval stage as swimmers; the species 

 nearest the center of the intertidal zone ap- 

 pears in a later swimming stage; the species 

 living near the high-water mark has young 

 that are essentially like the adult in be- 

 havior, and can crawl over exposed rocks at 

 once. In this example, tidal rhythm is used 

 in the analysis. 



The annual cycle of events within a com- 

 munity may be divided into a series of 

 seasonal periods, each period characterized 

 by certain more or less specific seasonal 

 (phenological) phenomena. The periods of 

 the vear defined, in whole or in part, bv 

 Smith (1928), Shackleford (1929), Bird 

 (1930), Davidson (1932), Carpenter 

 (1938), Davis (1945), Rice (1946), Jones 

 (1946), and others, are: prevernal, vernal, 

 aestival (estiva!), serotinal, autumnal, and 

 hibernal (hiemal). The first two periods 

 correspond roughly to the spring, the next 

 two to the summer, and the last two to the 

 autumn and winter, respectivelv. 



It must be remembered that latitude and 

 altitude are obviouslv of primary im- 

 portance in the seasonal periodicity of any 

 community. In the county of Teresopolis. 

 Rio de Taneiro, Brazil, the annual cycles of 

 periodicitv in flowering and fruiting of trees 

 and life history events of certain mos- 

 quitoes, birds, and mammals (Davis, 1945) 

 suggest the following division of the vear: 

 prevernal (August and September), vernal 

 (October and November), aestival (Decem- 

 ber and January), serotinal (February and 

 March), autumnal (April and May), and 



