216 THE NORMAL AGE CLASSES. 



this. The area of the age classes under the several methods 

 of treatment is now as follows : 



a. Ckar Cutting in High Forest. 

 The area of each age class, in a normal state, is : 



A A 



C = n x c = n X -, or C = n x - 



r r+ s 



according as to whether each clearing is at once re-stocked, or 

 allowed to lie fallow for s years. 



Example ; 



Let area A = 1050 acres 

 Rotation r = 100 years 

 s = 5 

 n = 20 

 then: 



, ,. A 1050 1A 

 Annual age gradation = = -\?\ = 10 acres ; 



and the age-classes : 



Blanks c x s 10x5 =50 acres. 



d ( 1 20 years old woods) = cx n = 10x20= 200 



C u (21 40 )=== 200 



C /77 (41 60 )=== 200 



C /F (61 80 )=== 200 



C v (81100 )=== 200 



.4 = 1050 acres. 



b. /Shelter-wood Compartment System. 



As already explained, under this system the old crop is 

 gradually led over into a young wood in the course of a 

 number of years, which has been indicated by m. There is 

 always an area under regeneration, which contains a certain 

 number of old trees and young growth, and this may be called 

 the regeneration class = C v ; it wanders gradually through the 

 whole forest, until, at the beginning of the second rotation, it 

 is found in the original position. As regeneration sometimes 



