8 BULLETIN 285, U. S. DEPARTMENT OF AGRICULTURE. 



REGIONAL VARIATIONS. 



The eastern part of the northern hardwood forest is characterized 

 by the abundance and importance of red spruce and balsam fir. 

 These extend south from Canada along the mountains of New 

 England, the Adirondacks, and the southern Appalachians, at 

 increasing elevations. The relatively pure spruce and fir forests 

 occupy higher altitudes than the hardwood forest, but the two are 

 freely intermixed through a broad but not definitely marked altitudinal 

 zone. Though red spruce is the most common spruce associate of 

 the hardwoods, white spruce is sometimes the more abundant 

 locally. The spruce is largely replaced in the Alleghenies by hemlock ; 

 and here cucumber (Magnolia acuminata Linn.) and yellow poplar, 

 prominent members of the southern hardwood forest, appear in 

 small quantities among the northern hardwoods. 



Like the spruce type, the transitory burned-land type of aspen and 

 paper -birch, is more abundant and of greater perfection in northern 

 New England than in the Lake States. Farther south it becomes 

 less important; paper birch drops out in northern Pennsylvania, and 

 the type loses its identity more and more through the inclusion of 

 other species. 



Of the characteristic northern hardwoods, sugar maple is probably 

 the most abundant in the northeastern States at large. Yellow birch, 

 however, is the most abundant in northern New England. It grows 

 in forests of widely different composition, and shares to some extent 

 the habits of paper birch, appearing on burns in small, pure, even- 

 aged stands (PL X, fig. 1, and PL VII, fig. 2) or in mixed stands with 

 paper birch and aspen, to which it adds an element of permanence. 

 Spruce, maple, and beech, which thrive in the light shade cast by 

 such stands, outlive the paper birch and aspen, and will eventually 

 gain the ascendancy. In the old-growth forests, therefore, yellow 

 birch is found in a great variety of mixtures with spruce, fir, beech, 

 sugar and red maples, white pine, and hemlock, with scattered indi- 

 viduals or groups of other species, notably paper birch and aspen. 

 The old-growth hardwoods in this region are usually very defective, 

 the beech especially. The red maple is usually abundant only as a 

 subordinate growth of little value. 



Ash occurs sparsely in New England at low to moderate elevations. 

 Black birch and black cherry become locally abundant in the moun- 

 tains of southern Vermont and New Hampshire, the Adirondacks, 

 Catskills, and farther south. The northern hardwood forest con- 

 tinues south at gradually increasing altitudes along the southern 

 Appalachian Mountains, becoming more and more restricted to 

 northerly slopes and cool valleys. This region properly belongs to 

 the transition zone between the northern and southern hardwood 



