182 



THE INCREMENT 



l^ast its maximum, and be falling : hence the former 

 culminates later than the latter. During the inter- 

 mediate period between the two culminations, the 

 mean annual increment is still rising, whereas the 

 cm-rent annual increment is already falling. 

 These points are further illustrated by the adjoining 



diagram (Fig. 43), giving the current annual and mean 



annual increment for Scotch pine. 



Mean 



Annual 



Increment. 



Cuirent 

 Annual 

 Increment. 



AGE, IX YEARS. 

 Fi?. 43. 



(5.) Whenever the object of management consists in the 

 realisation of the greatest return of volume, the rota- 

 tion must coincide with the year, in which the mean 

 annual increment culminates. 

 The following example will illustrate this : — 

 The current annual increment of spruce in the above 

 example culminates at 30 years, the mean annual increment 

 at 70 years. In the course of 210 years there would be seven 

 rotations of 30 years, or three rotations of 70 years. The 



