528 



THE COMMUNITY 



cordingly affected by the biomass of the 

 primary consumers. 



Juday reported that, excluding the fishes, 

 the ratio of the plant biomass to the ani- 

 mal biomass was 7.3 to 7.5 for the soft- 

 water lakes, and 12.1 to 22.2 for the hard- 

 water lakes. In other words (p. 133) "the 

 soft water lakes were approximately two to 

 three times as efficient in converting their 

 plant material into animals as the hard 

 water lakes." This conclusion should have 

 future value in biomass studies, since it 



brings out the corollary that, as between 

 communities, higher biomass does not nec- 

 essarily imply higher biotic efficiency. 



In preceding pages the major commu- 

 nity has been defined (Chap. 25), and its 

 structure (Chap. 26) and metabohsm 

 (Chap. 27) have been examined. The fol- 

 lowing chapter carries the analysis a step 

 further. That is, we shall be concerned 

 with the periodic disposition of matter and 

 energy within and across the boundaries of 

 communities. 



28. COMMUNITY ORGANIZATION: PERIODISM 



In general terms, the major phenomena of 

 the earth are cychc. There are geological 

 rhythms in erosion and in deposition (Wan- 

 less, 1938). Study of the annual growth 

 rings of trees discloses evidence of cycles 

 of climate over the last few thousand 

 years (Huntington, 1914; Douglass, 1928); 

 the evidence from varves is even better 

 for late Pleistocene and early post- 

 Pleistocene (Antevs, 1925). There is a 

 rather confusing body of evidence relating 

 to the positive or negative correlation of 

 sun spot cycles (pp. 85-87) to a variety 

 of earthly events, such as annual precipita- 

 tion, bird migration (Clements and Shel- 

 ford, 1939), and various other activities 

 (Pearse, 1939). There are well-defined 

 cycles in climate, environmental factors (p. 

 87), and in population phenomena (p. 

 366). Communities have extensive and 

 complex seasonal rhythms, lunar and tidal 

 rhythms, and many periodicities associated 

 with the cycle of day and night. Within 

 communities, there are almost countless 

 periodicities of the constituent plants and 

 animals, at the organismal level, that are 

 results of both environmental and physio- 

 logical rhythms. 



In the present chapter we are concerned 

 with periodic community responses. Such 

 concern is both intracommunity and inter- 

 community in scope. 



We are now in a better position to exam- 

 ine certain activities of the interdepend- 

 ent species populations at the level of the 

 relatively independent major community. 

 Such temporal activities may be discussed 

 conveniently in terms of (1) seasonal, (2) 

 lunar, and (3) diel or daily phenomena. 



SEASONAL ASPECTS OF THE 

 COMMUNITY 



The majority of communities have a 

 rhythmic, seasonal sequence of changes in 

 at least some parts of their structure. This 

 sequence is generally coordinated with, 

 and in large part induced by, the rhythmic 

 seasonal sequence of change in the dura- 

 tion, or intensity, or quahty of certain basic 

 physical influences, such as fight, tempera- 

 ture, and precipitation operating differen- 

 tially over latitude and altitude (see pp. 

 89,93,207). 



Changes of seasonal character in the ani- 

 mate portion of the commtmity reflect the 

 operation of one or more of the following 

 phenomena (Fig. 177): (1) direct action 

 by one or more of the basic physical in- 

 fluences upon organisms (b); (2) direct 

 action of the secondary physical influences 

 —for example, density or rate of evapora- 

 tion, induced by action of the basic physi- 

 cal factors, upon organisms (d); (3) direct 

 action of the basic physical influences upon 

 the inanimate medium of the community 

 (a); (4) direct action of the secondary 

 physical influences upon the inanimate 

 medium of the community (e). Such 

 direct and indirect induction of community 

 activity upon a seasonal framework may 

 be augmented or reenforced by (5) the 

 endogenous rhythms of seasonal activity in 

 certain of the component species popula- 

 tions of certain communities. 



Our information of this fifth category of 

 activity is less precise since such endoge- 

 nous patterns are more or less in step with 

 the seasonal march of the operating influ- 



