TYPES OF CHANGES 

 Replacement Change 



Replacement change within a community is the loss of individ- 

 uals which have died from other than catastrophic causes such 

 as a forest fire, and the growth in their place of individuals which 

 are usually of the same community. There are two types of re- 

 placement change, noncyclic and cyclic; they are operative within 

 the other types of changes to be discussed, and they are not in 

 opposition to them. 



Noncyclic replacement may be considered as a normal replace- 

 ment. When an individual of a given species dies, it will usually 

 be replaced by an individual of a species which is a member of 

 the respective community, but not necessarily of the same species. 

 The death of the chestnut tree (Castanea dentata) has been gradual 

 in the deciduous forest of the Great Smoky Mountains,^^! 

 with swamp chestnut oak {Quercus prinus), red oak (Q. rubra), and 

 red maple {Acer rubrum) as the most common replacement species 

 growing in the openings. 



This kind of change is on an individual basis. It need not be 

 on a one-to-one basis, but certainly over a period of time it will 

 tend to develop on this basis. It is rather obvious that, if a large 

 dominant plant such as a mature tree dies, initially seedlings of 

 several species will appear, but in due time a single dominant 

 will survive, and the rate of replacement is dependent upon the 

 life-spans of the respective species. There usually is neither a per- 

 ceptible nor a significant change in composition or abundance of 

 the dominant and characteristic species within a climax or a 

 long-persisting stand, therefore a continuation of this process 

 throughout the stand results in no significant change in its 

 physiognomic character; however, in the case of the chestnut the 

 floristic change is very significant. It is logical to assume that re- 

 placement change is operative within any community which 

 persists for a time in excess of the life-spans of the dominant and 

 characteristic species. 



A cyclic replacement change is significantly different from the 

 one previously discussed. A phasic cycle is a series of vegetation 



142 • DyxKamics of Commmazmities 



