humus mixture, and also removes much unwanted vegetation that can suppress 

 newly established birch seedlings. 



Productivity of even-aged stands is increased considerably and rotations are 

 shortened by periodic thinnings (see "Fuelwood," below). Stocking guides, 

 based on mean stand diameter and basal area per acre, coupled with stand 

 prescriptions, are used to determine when and how much to thin and when to 

 make the final harvest cutting (Leak et al. 1970; and Solomon and Leak 1969). 

 Basal area, the area in cross section at breast height of a single tree or of 

 all the trees in a stand, is usually expressed in square feet. 



Natural Enemies 



Northern hardwoods have several natural enemies. One of these is beech bark 

 disease caused by beech scale insect infestation, which may be followed by 

 infection by the parasitic bark fungus Nectria coccinea var. faginata . This 

 is a lethal disease and is the chief obstacle to producing high quality beech 

 logs. 



Birch dieback is an unidentified disease that destroyed thousands of square 

 miles of yellow and paper birch in the New England States and Eastern Canada 

 during the 1930s and 1940s. Dieback has caused the virtual disappearance of 

 birches in some areas (Hepting 1971). Although the disease has subsided in 

 recent years, a recurrence is possible. A similar condition, postlogging 

 decadence, often develops in birches excessively exposed by heavy partial 

 cutting. 



The saddled prominent caterpillar has defoliated large areas of northern 

 hardwood stands in the characterization area in recent years. Most hardwoods 

 can withstand 2 to 3 years of moderate defoliation and still recover 

 (Houseweart and Dixon 1977) but severe defoliation can kill trees in one 

 season. 



Most fungi that cause decay in living trees are found only in heartwood. A 

 number of such organisms cause cull in birch but some grow outward from 

 heartwood into sapwood and cambium. These decay fungi cause trunk cankers. 

 Several wood-rotting fungi are possible causes of cankers on birches. Among 

 them is Poria obliqua . Birch is also susceptible to several fungi that are 

 known to be canker-producing, especially Nectria galligena . A number of 

 canker diseases also occur on the various species of maple. The most common 

 ones are caused by Nectria strummela , and Eutypelaa parasitica . 



WHITE PINE-HEMLOCK-HARDWOOD TYPE 



Habitat Conditions 



This forest type is composed chiefly of eastern white pine, eastern hemlock, 

 beech, sugar maple, red maple, yellow birch, white ash, paper birch, red 

 spruce, and northern red oak. White pine was the species most eagerly sought 

 by loggers in the original forests of the coastal zone and economically is 

 still the most important forest species. 



19-17 



10-80 



