232 CLIMAX AND SERE 



indicated bj^ the course of succession, owing to the fact that the vari- 

 ous seres all qpnverge toward the climax. Since numerous examples 

 of these are to be found in each stage of development, their compara- 

 tive study furnishes evidence of the first importance. This is par- 

 ticularly true of subseres, in which the regeneration of the climax may 

 take place within a lifetime, or even less. Fire, grazing, clearing, 

 draining, and cultivation all provide universal opportunity for such 

 seres, the later stages of which are practically conclusive as to the 

 composition of the climax. 



The convergence diagram above is concerned with primary seres. 

 It is compiled from "Animal Communities in Temperate America" 

 (Shelford, 1913). The serai stages and substages are given in terras 

 of one or more plants and one animal; five stages are recognized in 

 each case though they are not of equal rank. Beginning in the upper 

 right-hand corner with the sand sere, the cottonwood comes in on sand 

 areas very early and is accompanied by the W'hite tiger beetle which 

 disappears at about the time the cottonwood docs. The jack or 

 banksian pine appears as seedlings in the shade of the old cotton- 

 woods and is accompanied by the tiger beetle Cicindela formosa gen- 

 erosa. Later black oak seedlings come up among the declining pines. 

 The ant lion Cryptoleon nebulosum becomes a characteristic animal 

 with its funnels near the black oak. Later white oaks appear among 

 the black oaks, and together with them the oak plant bug, Hyaliodes 

 vitripennis. Later come red oaks, and still later beech and maple. 



The clay bank occurs where erosion causes slumping of clay. There 

 is usually seepage, and progress is very rapid owing to abundant seeds 

 of trees and plants which occur above on the upland. Sweet clover 

 crowds out the tiger beetle of the bare ground, and the shadbush, cot- 

 tonwood, and sweet clover wdth associated animals really constitute 

 one associes; they are separated in the diagram in the order of estab- 

 lishment. 



The hydroseral stages are shown below the climax and are to be 

 read upward. Here again the stages do not constitute associes but 

 represent associated plants and animals. The shallow pond series rep- 

 resents five associes. The white oak referred to is the swamp oak. The 

 sere of the deep tamarack lake or pond as diagrammed is composed 

 of associes. All these stages are quite readily found southeast of 

 Lake Michigan. The beech maple climax is to be found on at least 

 a dozen different types of soil including dune sand. 



Convergence is usually traceable without great difficulty even when 

 not all the organisms are known. The investigator is most likely to be 

 misled by postclimaxes toward which all communities in the area 



