SUCCESSIONS IN BOGS 37 



U. americana, Liriodendron tulipifera, Juglans nigra, Carya cordi- 

 formis. Rhododendron viscosum is still an occasional constitu- 

 ent in the shrub layer beneath the trees. 



Elms, black ash, the tulip tree, and black gum (Nyssa sylva- 

 tica) are frequent members of tamarack bogs in several localities of 

 northeastern Ohio. 



In a few bogs of central Ohio the tulip tree, Magnolia acuminata, 

 Celtis occidentalis, Amelanchier canadensis are found mingling 

 with the northern components. They are typical examples 

 of an incoming forest association, the species of which attain 

 their best development farther south. 



SECONDARY SUCCESSIONS 



The successions due to the intervention of man show that the 

 structure initiated- after fire and clearing consists of pioneers 

 derived to a large extent from the original associations. They 

 re-establish themselves in a much shorter time on soils in which 

 the physical conditions approach those of the bog meadow and 

 bog shrub. Breaking done on peat soil occupied by bog forests 

 or mesophytic forest species will result in the establishment of a 

 vegetation characteristic of mineral soils. The botanical struc- 

 ture is chiefly made up by ruderal invaders, capable of rapid 

 mobility and establishment; the chance for the usual sequence 

 of successions then becomes remote. Fungus diseases are of 

 minor importance in modifying the vegetation cover. Reverse 

 courses of development, retardation, or the hastening in the 

 sequence of successions often occur when for any reason drainage, 

 drought, shrinkage of the peat soil, or excessive precipitation 

 produce variations in the available water. Bogs of that char- 

 acter present a disjointed distribution and a confusing diversity. 



THE RELATION OF VEGETATION TO THE CHEMICAL NATURE OF 



PEAT SOILS 



This problem has been the subject of a long standing dispute. 

 Not all field work is adapted to throw light on this vexed ques- 

 tion. Difficult as is the attempt to establish a correlation between 



