THE NORMAL YIELD. 243 



the yield under the system of clear cutting. The material 

 under (2) represents the intermediate yields, which should 

 amount to 32,150 c'. Total yield = 90,810 cubic feet, as 

 before. 



d. Coppice and Coppice with Standards. 



The normal yield of coppice woods is calculated in the same 

 way as for clear cutting in high forest. In this case, the 



A 



annual cutting area is = and the volumetric yield is com- 

 posed of the material standing on that area, plus thinnings in 

 the younger age gradations. 



In coppice with standards, the annual cutting area is the 

 same as in simple coppice. The normal annual yield is 

 composed of : 



(1) The underwood on the oldest age gradation, less those 

 trees which are left to grow into standards. 



(2) The contents of the oldest, R years old, age gradation of 

 the overwood. 



(3) The thinnings amongst the younger age gradations 

 of overwood standing on the annual coupe, and occasionally 

 in the younger underwood gradations. 



Example : 



Taking the data given at p. 238, the yield in overwood is 

 as follows : 



40 trees (mature) 100 years old, each = 50 c' = 2000 



40 80 = 30 c' = 1200 



50 60 = 15 e' = 750 



70 40 = 2 c' - 140 



Total ... - 4090 c' 

 to which the volume of the underwood has to be added. 



The normal annual yield of overwood must also be equal to 

 the annual increment laid on by all the overwood during one 

 year, or 



7= 2-0 x 200 + (15 - 2) x 130 + (30 - 15) x 80 +(50- 30) x 40, 



1= 4090 cubic feet. 



R 2 



