Vegetation of Northern Cape Breton. 341 



b. ASSOCIATION-COMPLEXES DUE TO FIRE 



Fire, like cultivation, destroys the original vegetation and 

 causes the institution of new successional series. According to 

 the completeness of the devastation, particularly as it afifects the 

 humus layer with its subterranean plant organs and its micro- 

 organisms, broadly speaking, two lines of succession may be dis- 

 tinguished : one where the humus has escaped serious injury, 

 the other where the humus has been destroyed. Between these 

 there of course are intermediate possibilities. 



Humus little injured. — Let it be assumed that previous to the 

 conflagration a burned area has supported a forest of the climax 

 type. Aside from the annihilation of much of the antecedent 

 vegetation, the most obvious immediate effect of fire is the 

 removal of the forest cover and the consequent increased illumi- 

 nation of the forest floor. The revegetation of such an area is 

 destined to be accomplished partly through the agency of plants 

 which in various ways have survived the fire, partly through the 

 invasion of plants from other sources. Almost the first after- 

 effect of the fire is seen in the rapid spread of certain herbaceous 

 species which were only sparingly represented in the original 

 forest, but which are able to flourish in the new environment. 

 Cornus canadensis perhaps nowhere develops more luxuriantly 

 than in burned areas, while Linnaea borealis americana and 

 Maiantliemnm canadense also thrive here. Of the shrubs and 

 small trees in the burned forest, Corylus rosfrata, Acer spicatum 

 and Vihurnuni cassinoides frequently survive. The local 

 herbaceous element in the flora may predominate for a longer 

 or shorter period, but it is soon augmented by an extraneous 

 element in which the following species are usually conspicuous : 

 Ly CO podium clavatum and Gaultheria procumbens; Solidago 

 bicolor and S. macropliylla; Pteris aquilina and the "fire-weeds," 

 Epilobium angiistifolium and Anaphalis margaritacca, which fre- 

 quently form a rank growth; and Rubus idaeits canadensis, 

 which within a few years may produce an almost impenetrable 

 tangle over the entire area. 



In the reestablishment of forests in burned areas of this sort, 

 the paper birch, as elsewhere in the northwoods. is everywhere 

 the conspicuous pioneer. This tree, it will be recalled, is spar- 

 ingly represented in the regional climax forest. After a burn it 

 reproduces rapidly, partly by means of coppice shoots from 



