THE NORTHERN HARDWOODS REGION 273 



species with their Hght shade reproduction of sugar maple and 

 often of hemlock and spruce, if seed trees are present, soon 

 takes place. Finally with the maturity of the paper birch and 

 poplar the sugar maple comes into control, though usually 

 the yellow birch in the stand persists with the maple. The 

 reversion from the birch and poplar type to the original hard- 

 wood type is then complete. The sugar maple and hemlock 

 play a part identical in principle with that played by spruce and 

 balsam in the spruce region. There it will be remembered the 

 birch and poplar type was slowly reproduced to spruce and 

 balsam and finally reverted to one of the original and permanent 

 types. In the northern hardwoods region, sugar maple and, to 

 a limited extent, hemlock accomplish the same end. The birch 

 and poplar type is even-aged in form. 



4. Old-Field Hardwoods. — This type occurs on lands once 

 used for agriculture and now abandoned. It is important since 

 there are large areas in the aggregate of land formerly cultivated. 



The composition is of mixed hardwoods, particularly hard 

 maple, yellow and paper birch and white ash. Oftentimes pure 

 stands of maple or birch are seen, and the species do not differ 

 materially from those in the hardwood type, except for the 

 absence of the heavy-seeded beech, whose seed is not easily 

 scattered over the open fields. The proportion of white ash is 

 often greater than in the hardwood type. The stands of old- 

 field hardwoods are all young or middle-aged, for two reasons; 

 first, because most of the so-called abandoned farm land was 

 abandoned within the last fifty years, and second, because 

 stands of this type, as they pass middle-age resemble more and 

 more the original hardwood type, and often cannot be distin- 

 guished from it. They are more even-aged in form than a re- 

 peatedly culled stand of the hardwood type, but this distinction 

 may not serve to separate them from stands of the hardwood 

 type which have been heavily cut. Indeed, an old field may seed 

 up very irregularly and present from the beginning the appear- 

 ance of an uneven-aged stand. In most cases there is little if 

 any practical advantage in keeping the two types separate except 



