FOREST MANAGEMENT. 313 



The separation of -the age classes (allotting to each age class separate 

 areas) facilitates logging and transportation; it increases, on the other 

 hand, the dangers threatening the forests. 



If a proper gradation of age classes exists in a forest it does not neces- 

 sarily follow that the age classes are properly grouped and arranged in 

 " cutting series." By " proper cutting series " is understood a number of 

 adjoining age classes, sloping roof-like from the older to the younger, toward 

 the windward side. If the cutting series are improper, then sacrifices must 

 be made, hypermature wood must be left, and immature wood must be 

 cut unless the mistake originally at hand is allowed to be perpetuated. 

 In the latter case, the losses of the future are apt to be greater than the 

 sacrifices voluntarily made with a view to the establishment of proper 

 cutting series. Cutting series must be isolated. one from the other, if need 

 be, by " severance cuttings." 



Normal Growing vStock, 



The normal growing stock is at hand where the age gradation of the 

 various woods composing the forest and their respective volumes are nor- 

 mal. A forest, however, might have the normal volume without hav- 

 ing the normal age gradation, when a deficiency of one age class is offset 

 by a surplus in another age class. The normal growing stock, during 

 summer, has the volume 



r 2 X i 

 2 



wherein r represents the rotation, and i the average annual increment of 

 a mature age class. 



Illustration: A spruce forest covers 2,000 acres. The rotation is 100 

 years. The mature wood, 100 years old, contains normally 120 cords per 

 acre. Under these conditions, the area of an age class is twenty acres; the 

 average annual increment of the mature age class is twenty-four cords; 

 and the normal growing stock is 



100 X 100 X 24 



-= 120,000 cords. 

 2 



The volume of poles and trees predestined to be cut and removed prior to 



