is often difficult to interpret correctly, but when such a cycle is 

 analyzed as a whole, the changes satisfy the climax criteria. 



The change from community to community in place, even 

 though phasic, is easily confused with a directional change which 

 would be successional if the change were upgrade, and retro- 

 gressional if the change were downgrade. This change may pro- 

 ceed horizontally in lieu of being exclusively in place. The con- 

 fusion with succession and retrogression arises readily because of 

 the alterations in habitat conditions. The change from one com- 

 munity phase of the cycle to the next one probably operates 

 similarly to a replacement. In fact, during part of the commu- 

 nity-to-community change it may be very difficult to differentiate 

 it from a replacement phasic cycle. Fluctuations within the com- 

 munity cyclic change are expected, and therefore a degree of 

 variation will occur in the habitat, species, and populations. But 

 when the cycle is analyzed as a whole, it will be found that the 

 changes are within circumscribed limits which satisfy the criteria 

 of a climax, in spite of the conspicuous alterations between phases. 



At first it seems that directional changes offer no difficulty in 

 assigning a succession or retrogression, rather than a climax, status 

 to a community; generally, if a directional change is taking place, 

 the community under consideration does not satisfy the criteria 

 of a climax. However, the rate of change from a near-terminal 

 stage to the climax is usually very slow, much slower than be- 

 tween the earlier stages of a successional series; in fact the 

 changes may not be perceptible during the study-span of one 

 person. Furthermore, the near-terminal stage may have many of 

 the attributes of a climax. 



Fluctuations of small magnitude usually cause no difficulty, 

 but fluctuations of relatively great magnitude can easily cause 

 trouble in the applicability of the climax concept. For a particular 

 type of climax community, a certain magnitude of fluctuation 

 change is expected and is within the framework of the steady- 

 state. A fluctuation change of relatively great magnitude in a 

 community may be confused with a phasic cycle replacement 

 change which is not characteristic of the particular community, 

 and intensive study over a long period of time may be required 



l.<^6 • DyxKanmics of Commimimities 



