THE DECIDUOUS FOREST CLIMAX. 



209 



Cooper (1913 : 227) gives the following summary of the xerosere on Isle 

 Royale, and illustrates the convergence into the final climax by means of a 

 diagram (fig. 6) : 



Climax Forest 

 .(Abies, Setula, Picea canadensis) 



Xerophytio 

 Forest 

 (Pinusbanltsiana 



Picea mariana) 



Tall Shrubs 



(AInus crispa 



CornuBStolonifera, 



Salix ipp.) 



Bog Forest 

 (Lartx 



Cn>ui«]) 



/ 



Bog Forest 



(Larix 

 Picea mariana) 



t 



Ledum Sphagnum 



t 



Bog Shrub Sphagnum 

 (Chamaedaphne 

 Andromeda) 



Bog Shrubs 



(Chamaedaphne 



Andromeda 



AInus incana) 



Swamp Forest 

 (Thuja 



Larix 

 Fraxinua nigra) 



t 



Shrubs 



(Myrlca 

 AInus incana) 



t 



Grasses 



(Calamagrostis 

 canadensis) 



Crustose Lichens Crevice Herbs 

 Grimmia (Potentilla 



tridantata) 



Rock Surface 



Crevice 



Turf Mat 

 (Scirpus 

 caespitosus) 



Rock Pool 



Low Shrubs 



(Rubus idaeus 



Diervilla 



Physocarpus) 



t 



Scattered Herbs 



Subsuccession Subsuccession Subsuccession 



Rock Shore Succession 



Beach Succession Bog Succession 



Delta Swamp Succession 



Xerarch Successions 



Hydrarch Successions 



Primary Successions 



Fia. 6. — Diagram of development of climax forest on Isle Royale. After Cooper. 



"THE XERARCH SUCCESSIONS. 



"Every part of Isle Royale has at some point of its subaerial history been 

 shore. 



"The present coast of the island is made up of rock shores and beaches, the 

 former being much the more extensive. Each type possesses its characteristic 

 series of successional stages, the rock shore succession and the beach succession, 

 both resulting finally in the establishment of the climax forest. 



"With regard to area vegetated through its instrumentality, the rock shore 

 succession is by far the most important of all the successions of Isle Royale. 



"The full series of the rock shore succession includes in its early stages three 

 subsuccessions which later unite into a single series. 



"The rock surface subsuccession advances through crustose lichen and foliose 

 lichen stages to a condition in which the large cladonias are the most important 

 element. The process of invasion along this line alone is very slow. 



"The pioneers of the crevice subsiuxession are certain herbs, notably Poten- 

 tilla tridmtala, whose principal r61e is the formation of humus. Trailing 



