THE CLIMAX. 107 



concerned. The latter determine the dominants that can be present in the 

 region, and the reaction decides the relative sequence of these and the selection 

 of one or more as the final dominant, that is, as the adult organism. 



Kinds of climaxes. — The climatic formation is the real cUmax of the suc- 

 cessional development. As has been seen, various agents may interpose to 

 prevent complete development. The result is to produce apparent climaxes 

 of greater or less duration. These -depend absolutely upon the continuation 

 or recurrence of the action which inhibits further development. They dis- 

 appear as soon as the causative force is withdrawn, and the course of succession 

 resumed in consequence. Such apparent climaxes are always subordinate to 

 the normal developmental or climatic climax, and may accordingly be dis- 

 tinguished as subclimaxes. The application of this term is based upon the 

 two-fold meaning of the prefix sub, of which the original meaning is beneath 

 or under, and the transferred meaning somewhat or rather. The subcUmax is 

 always below or before the climax proper in point of time, and actually beneath 

 it in such coseres as those of peat bogs. Likewise it is subordinate develop- 

 mentally, though in dominance and persistence it may resemble a true climax 

 very closely. In addition to subclimaxes, which are constituted by some stage 

 antecedent to the climatic formation, there may be distinguished potential 

 climaxes which are often subsequent. A potential climax is the actual climax 

 of an adjacent region. It is called potential because it will replace the cUmax of 

 the region concerned whenever its climate is changed. The potential climax 

 of plains grassland is scrub if the rainfall is increased; it is desert if the tem- 

 perature is increased. As is later shown at length, potential climaxes stand 

 in a zonal relation to a particular formation, and this relation is that of the 

 sequence of successional stages. 



Subclimaxes. — ^Various causes produce subclimaxes. Such are (1) soil, (2) 

 reaction, (3) competition, (4) migration barriers, and (5) man. In spite of the 

 greatest difference in their action, they agree in preventing development by 

 handicapping or destroying some stage, usually a climax one. Apart from 

 plant reactions, such an influence is probably exerted by the soil only when 

 it contains an excess of salt. In the Great Basin the climatic formation is 

 that of the sagebrush (Artemisia tridentata), but vast alkaline stretches will 

 long be covered by Sarcobatus and Atriplex. As a consequence of their reac- 

 tion these wiU jdeld theoretically to Artemisia in the course of time, and this 

 seems to be actually taking place at the margins of the alkaline area. In the 

 present state of our knowledge, however, it is impossible to be certain that 

 this can ever occur in the heart of the region without a change of climate. 

 Reactions which retard succession instead of promoting it are few, but they 

 are of great importance. There seem to be but two of these, that of Sphagnum 

 in accumulating water, and that of moor and heath in producing acids or other 

 harmful substances. These reactions, together with the consequent produc- 

 tion of heath sand and "ortstein, " appear to enable moor and heath to persist 

 for a long time over vast areas. There is, however, some warrant for thinking 

 that these subclimaxes are due wholly or partly to the action of man. 



The exact r61e of competition is more difficult to ascertain, but there can 

 be Uttle doubt that it is important and sometimes controlling in maintaining 

 a grassland subclimax. This is said to be true of the Ceylon patanas by 

 Pearson, and it is also confirmed by evidence from the prairies and from moun- 

 tain meadows. A subclimax due to barriers to immigration occurs whenever 



