434 FAGER [CHAP. 19 



reached its maximum, a further increase in order can occur by an increase in 

 the numbers and kinds of organisms which utilize various waste products that 

 still contain available energy. The community tends toward a steady state 

 where the entropy change for the system as a whole is a minimum: a situation 

 where the rate of decrease in entropy, resulting from the import and internal 

 production of complex organic materials, approximately balances the rate of 

 entropy increase resulting from irreversible processes. 



Concurrent with an increase in order, there develops an increase in com- 

 plexity. This is usually described in terms of numbers and kinds of organisms 

 present, their distribution and their interactions. Bertalanffy (1950) has shown 

 that, in a steady-state open system, the ratio of concentrations (numbers/unit 

 measure) of different components (organisms) depends only on the system 

 constants (kind and intensity of interactions). Therefore, as long as the constants 

 do not change, the composition remains the same. He has shown that such a 

 system is self-regulatory in the sense that it reacts against a disturbance of 

 the steady state in a manner which offsets the effects of the disturbance. In 

 the case of an individual organism, this reaction may overshoot the mark 

 and lead to a series of physiologic oscillations around the steady-state position. 

 In the case of a community, as Bray (1958) points out, the movement is one- 

 sided for a community cannot overshoot ; what is seen is the steady state and 

 various less-ordered stages leading up to it. 



Patten (1959) has developed a general theory of ecosystem dynamics — with 

 appropriate modifications it can be applied to a smaller community — on the 

 basis of modern information theory. In this context he has formally defined 

 efficiency and the conditions for succession, steady state and senescence of 

 communities. He concludes that Odum and Pinkerton's (1955) theory that 

 open systems in the steady state tend to operate at low efficiencies which are 

 optimum for maximum output of power is theoretically incorrect and is not 

 supported by the evidence which has been cited. He re-emphasizes the perhaps 

 obvious but worth repeating fact that the standing-crop biomass is not directly 

 related to either gross or net productivity and is only "a relatively static side 

 issue to the main stream of energy flow". As Patten admits, one of the major 

 problems preventing the use of information theory in the study of community 

 dynamics is that of measurement. It is, therefore, necessary to continue using 

 energy flow. However, as entropy units can be directly converted to "bits", 

 energy flow can be converted to information if the assumption is made that the 

 rate of entropy increase is closely approximated by the rate of energy release 

 in respiration. He applies this relation to four studies of the energy flow in 

 freshwater habitats. This is an interesting mental exercise but does not seem 

 to provide much more understanding of the situation than the original papers. 



In considering biological phenomena, it is evident that the community 

 stands far up in a hierarchy based on organization. The general theory of 

 organization suggests that there is always an interplay of action-reaction 

 between the higher and lower levels of organization, the higher ones depending 

 for their existence upon the continuance of the lower and the lower being 



