316 GEORGE E. NICHOLS 



of certain edaphic limiting factors is in turn modified by cli- 

 matic factors. In a Sphagnum bog, for example, the Sphagnum 

 tends to grow upward above the original water level, and in cool 

 humid regions like coastal New Brunswick and Nova Scotia 

 (see Ganong, 12) raised bogs may thus be developed; but in 

 less humid regions the evaporating power of the air represents 

 a limiting factor which, in varying degree, inhibits this upward 

 growth of the moss. 



The fact seems clear, then, as has already been suggested, that 

 the climax of a successional series in any edaphic unit area is 

 controlled largely by the influence of some limiting factor, and 

 it therefore follows that the nature of the climax association may 

 varj' with the nature of the soil or of the topography. The 

 term edaphic climax association may be defined as: tl.e most 

 mesophytic association which is capable of development in any 

 given edaphic unit area through the progressive reaction of the 

 various habitat factors. In a favorable situation, the habitat 

 climax association coincides with the regional climax associa- 

 tion-type. 



The term edaphic climax association may be used either (1) 

 in point of time, with reference to a specific successional series, 

 i.e., with reference to the series of associations which follow one 

 another in a given edaphic unit area; or, (2) in point of spatial 

 relations, with reference -to the group of associations which 

 comprise an association-complex (see the following section), 

 where these are genetically related. Used in the latter sense, 

 it suggests the successional relationship which exists between 

 the various associations of the complex. One can refer to such 

 edaphic climax associations as these in terms of the physiographic 

 unit area concerned: thus, trap cliff climax, rock ravine climax, 

 bog climax, salt marsh climax. 



One of the most forcible illustrations of the edaphic climax 

 concept with which the writer is familiar is afforded by the 

 New Jersey pine-barrens (see Taylor, 23; Harshberger, 14). 

 This well-known phytogeographic area is situated in the 

 midst of a region whose climate is capable of supporting a 

 highly mesophytic forest. The portion of the coastal plain 



