Il] MAIN HABITATS, SUCCESSIONS, AND CLIMAXES 33I 



climatic climax '. Similarly the biotically engendered disclimaxes 

 may be termed ' biotic climaxes ', and those due to topographic 

 features 'physiographic climaxes '. However, with removal of such 

 a ' master factor ' as burning or grazing, the succession usually re- 

 turns gradually to the autogenic main sere — at all events approxi- 

 mately. And then there are instances in which an apparent climax 

 constitutes in reality a preclimax in that its dominant or co-dominants 

 are replaceable by one stage of others more advanced in life-form 

 or competition-impress. This is really only a final type of sereclimax, 

 or community arrested and held at some relatively early stage, and 

 comprising the other form of subclimax with serai relationships 

 simpler than the disclimax. Again by some authorities the term 

 preclimax is used for one type of what we have here called sub- 

 climax, namely that developing under locally unfavourable con- 

 ditions. Finally there is the post climax, of vegetation more advanced 

 than that of surrounding climax tracts, due to locally more favourable 

 conditions obtaining in its limited area. This should be distin- 

 guished from the relict community or fragment of a community 

 that has survived some important change, whether this was toward? 

 the improvement or detriment of the general environment. 



Whether or not we believe in the ' monoclimax ' hypothesis of a 

 full regional climatic climax as not only the highest type which can 

 exist in a given climate but also as the one which will ultimately 

 develop more or less throughout the land area of that climate, the 

 concept has its attractions and adherents. It appears, however, that 

 soil (including water) and other conditions often prevent locally 

 such ' regional ' development more or less permanently, and certainly 

 no observer can wait to the end of the geological age and consequent 

 termination of such an ' experiment '. Even if a general regional 

 climatic climax were developed, who is to say that, for example, 

 subsequent leaching or other effects might not lead to differential 

 retrogression. Consequently it seems best to admit the likelihood, 

 in any one region, of several different climax communities as repre- 

 senting what may then be termed a ' polyclimax '. Even examples 

 of the components of such a regional mosaic themselves frequently 

 vary from spot to spot as well as with time, for example as indi- 

 ^ iduals in the dominant layer come and go and all manner of very 

 local fragmentarv seres are engendered ; indeed such variations can 

 be so endless and perplexing that some ecologists, as has already 

 been stated, doubt the validity of the very concept of climax, let 

 alone its regional expression. 



