FOREST SUCCESSION AND RATE OF GROWTH IN 

 SPHAGNUM BOGS 



By George B. Rigg 

 Professor of Botany, University of Washington 



Field observations on forest succession in some sphagnum bogs of 

 the Puget Sound region have been made by the writer during the ten 

 years of his residence in Seattle. During the summer of 1913, v^hile 

 employed as scientist in kelp investigation in the United States Bureau 

 of Soils, he visited several bogs in the coastal region of Alaska from 

 Cape Spencer to the Shumagin Islands. The bogs here reported do 

 not include any at high elevations and do not include bogs occurring 

 adjacent to salt water. 



The writer has elsewhere^ defined the term "sphagnum bog" as "that 

 stage in the physiographic succession of an area during which its sur- 

 face is entirely devoid of ordinary 'hard' soil, and is composed com- 

 pletely of living sphagnum under which is fibrous brown peat composed 

 mainly or entirely of partially decayed sphagnum." He has also else- 

 where^ ^ described all of the bogs here mentioned except the Maltby 

 bog. This is situated in Snohomish County, Washington, about 1,600 

 meters (i mile) south of the town of Maltby. It has an area of about 

 32 hectares (80 acres). 



I. PUGET SOUND BOGS 



In general, the forest is advancing upon the bogs of the Puget Sound 

 region. This is evidenced by the fact that in nearly all of them trees 

 are found growing in the sphagnum, and also by the fact that seedlings 

 are commonly found, both among these trees and extending farther 

 out into the bog in cases where only a portion of the sphagnum has 

 trees growing on it. 



The forest that is advancing upon these bogs is largely coniferous. 

 The tree that most commonly leads in the invasion is the western hem- 



*"A summary of bog theories." PI. World 19: 310-325, 1916. 



* "The effect of some Puget Sound bog waters on the root hairs of Trades- 

 cantia." Bot. Gaz. 55 : 314-326, 1913. 



'"Notes on the flora of some Alaskan sphagnum bogs." PI. World 17: 167- 

 182, 1914. 



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