218 



THE NORMAL AGE CLASSES. 



The annual coupe is c = — and yl = c x r. 



The number of overwood classes is = — = f, hence- 



t X r 



Area of each age class on each annual couije = * =:^ — =-, 

 ^ Ii tXr t 



200 ^ -200 

 100 5 X 20 



15 

 5 



2 acres. 



As the whole forest consists of r coupes, each overwood 

 class, consisting of /• gradations, contains, in a normal forest, 



- X /• = — units of area, or *^^ = 40 acres. This shows, 

 t t 5 



that, theoretically, the proportion of the age classes is the 



same as in high forest, although the distribution is different. 



Example. — Data as before. 



A = 200 ; R = 100 ; /• = 20, number of overwood classes 

 t = 5. 



Normal annual cutting area r = — 



200 

 20 

 10 



10 acres. 



= z acres. 



On each coupe each age gradation I 



of overwood occupies . . ) ^ ^ 



The area and distribution of the several age classes is as 

 follows : — 



Cotiix' Xo. 20, oldest : 



Underwood = 10 acres = 20 years ol 

 Overwood on 2 ,, =20 ,, , 



2 „ = -iO „ , 



•2 „ = 60 „ , 



2 ,, z= 80 „ 



2 ,, = lOU „ 



Coupe Xo. 1, i/oiiiKjest : 



Underwood = 10 acres = 1 year old. 



Overwood on 2 ,, = 1 ,, ,, 



,, ,, '2 ,, = 21 years ,, 



