352 FORESTRY IN NEW ENGLAND 



trees which form the typical forest growth on old fields. Pure 

 stands of either species and mixtures of the two are all found, 

 but pure stands are more common than mixtures. Gray birch 

 is a species which requires a bare soil for a seed-bed, while red 

 cedar can start well under more adverse conditions, even in a 

 thick sod. This difference in the habits of the two species ex- 



Fig. 130. — On the flat is a stand of the best quality swamp hardwoods. Soft maple, 

 tulip tree, yellow birch, black birch, and elm are the principal species. A thinning is 

 needed. 



plains why pure stands now of one species and then of the other 

 are met with on old fields. The gray birch seizes possession of 

 those fields which were abandoned after having some other crop 

 than grass, while on abandoned pasture or meadow opportunity 

 was given the cedar to form pure stands. A fire running over a 

 pasture or meadow might result in exposing mineral soil and 

 creating a seed-bed favorable for gray birch. 



