Early Stages in Bog Succession 



George B. Rigg 

 University of Washington, Seattle 



Introduction 



It is well known that sphagnum bogs result from the abundant growth 

 of Sphagnum in undrained places. The bog, of course, develops grad- 

 ually, and it requires the lapse of a considerable period of time before 

 the stage of physiographic succession is reached in which the surface is com- 

 posed of the living moss underlaid with the products of various stages of its 

 decay, supporting a bog association of xerophytic shrubs. 



The climate and the topography of the Puget Sound country are well 

 suited for the development of sphagnum bogs. In a region which has 

 been at least twice covered with the debris of the advance and retreat of 

 glaciers, naturally there are many depressions which are entirely un- 

 drained or whose drainage is at best very poor. The abundant winter 

 rainfall, the lack of low winter temperatures and the high atmospheric 

 humidity due to rain and fog are conditions favorable to the luxuriant 

 growth of Sphagnum. 



Naturally we should expect that in a region where Sphagnum bogs 

 are so abundant as in the Puget Sound country there would be seen 

 many instances of bogs in various stages of development. Such instances 

 have been frequently observed by the writer. Cases have been seen in 

 which a habitat is on its way toward development into a typical bog but 

 has not yet arrived at that stage because not sufficient time has elapsed. 

 In other cases one of the conditions is present, but no bog is developing 

 because of the absence of the other condition. There are plenty of un- 

 drained habitats, but they do not become bogs unless Sphagnum grows in 

 them to such an extent that the substratum, except at the surface, is 

 composed of the products of various stages of the decay of vegetable mat- 

 ter (largely Sphagnum) in the absence of an adequate supply of oxygen. 

 Likewise the moss is abundant in many places where its growth is not 

 resulting in Sphagnum bogs because there is too much opportunity for 

 drainage. 



(195) 



