SUCCESSIONS IN BOGS 35 



open the vegetation the greater the tendency to vary and the 

 greater the number of species of secondary importance. The 

 association is found in a variety of physiographic situations. Its 

 characteristic principal species are Cornus stolonifera, C. pani- 

 culata, C. amomum, Rosa Carolina and several willows (Salix 

 cordata, S. nigra, S. discolor). Seasonal aspects are prominent. 

 The last two associations contain members more southern in 

 distribution than northern. The association which follows more 

 directly is not the bog forest but the Acer-Ulmus association. 

 The presence of an undergrowth which belongs to the southern 

 deciduous forest center indicates conditions favorable to a rapid 

 final establishment of deciduous trees. 



D. The bog forest associations 



The replacement of a bog shrub association may occur without 

 the intervention of any factors other than the appearance of the 

 invading forest species. Two well-marked types of bog forest 

 associations are easily distinguished. 



1. Larix laricina association. Tamarack bogs of various 

 stages in development are found in Ohio. There are localities 

 with the association of conifers just developing at the margin 

 of bog heaths and shrubs; in others the conifers have completely 

 covered the filled-in peat basin ("muskeags"), and are now dis- 

 appearing as an association. Scattered individuals of Pinus 

 strobus, Tsuga canadensis and Betula lutea are present, with shrubs 

 derived mainly from the Alnus-Rhus association. Rhododendron 

 viscosum is found in several localities. Taxus canadensis, Medeola 

 virginiana, Clintonia borealis, Dalibarda repens and Lycopodium 

 sp. occur apparently only in northeastern localities. 



2. Thuja occidentalis association. This type of conifer dom- 

 inance in bogs is well exemplified in a bog about thirty-five miles 

 west of Columbus (Ohio Naturalist, 9:193-199. 1910). The 

 vegetation in open stands is now found varying in the direction 

 to the deciduous forest. With arbor vitae are found Acerrubrum, 

 Liriodendron tulipifera, Fraxinus nigra, Juglans cinerea, Platanus 

 occidentalis and Prunus serotina. The undergrowth is mainly 

 that of the Alnus-Rhus association. 



