Bcnjiiioii and Slallard: climax formations .177 



qnence, Sphaynuui ir.akcs little or no growth, Bctula, Populus and 

 sometimes Ulinus appear in the places left vacant by windthrows. 

 Coruus si ol oil if era, Sali.v discolor and farther northward, Alniis 

 iiicana, often come in also, but these are later replaced by the trees 

 named above. As the swamp fills up a Populiis-Betula associes be- 

 comes established, to be succeeded finally by the climax Acer-Tilia 

 forest, as the process of falling is carried still further. 



A Larix or Larix-Picea swamp, if drained and not disturbed 

 by clearing or burning, gradually fills up, thereby reducing the wa- 

 ter-content of the soil. With the draining away of the water and 

 filling up by washing in of soil along the edges. Sphagnum disap- 

 pears. As the filling proceeds, Larix dies out, Populus, Betida, 

 Uhiiiis and occasional individuals of Abies and Fraxinns nigra tak- 

 ing their places. In that part of the region bordering on the climax 

 pine forest, Picea, Abies, Bctula and Fraxinns are the usual domi- 

 nants following Larix as the swamp becomes filled up. These, as 

 filling proceeds, are replaced by Acer, Tilia and other trees of the 

 climax forest. As the result of drainage not complicated by the 

 introduction of other factors, the normal succession from the Larix- 

 Picea associes to the climax Acer-Tilia forest takes place. 



The results of the study of succession in Minnesota are essen- 

 tially in accord with the findings of Cowles (1901), Whitford 

 (1901), Transeau (1903), Coulter (1904), Howe (1910), and 

 others who have made a study of swamps and climax forests in 

 Michigan, Ohio, and eastward to Vermont. 



Cooper (1910) has concluded that on Isle Royale the climax for- 

 est is an association of Abies, Picea and Betnla, and he regards this 

 as the climax vegetation of parts of northern Minnesota and north 

 and east into Canada. As concerns Minnesota at least, this does 

 not appear to be the case. The Abies-Picea-B etula stage is rather 

 to be regarded as an associes which may in places persist indef- 

 initely as a subclimax. It seems probable that such is the case on 

 Isle Royale. Where these trees are dominant in Minnesota, the 

 islands or parts of the mainland are low, and the water-content of 

 the soil too high to permit the invasion and establishment of Pinus. 

 With the building up of the soil or as a result of any other change 

 which would decrease the water-content of the soil, Abies, Picea 

 and Betnla would undoubtedly be succeeded by the Pinus association. 



