CHAPTER Y. 



DETERMINATION OF THE ROTATION OR AGE OF 

 EXPLOIT ABILITY. 



The first thing to determine in organising a forest is the age- 

 of exploitability or the rotation to adopt. On this depends not only 

 the size and sum total of the timber produced but also the quantity 

 to be removed in the annual exploitations. 



A Rotation properly so called is applicable only to a canopied 

 collection of trees. As regards solitary trees or the individuals of a 

 canopied collection of trees considered singly, the age at which they 

 become exploitable, varies from tree to tree according to the special 

 growth and surroundings of each ; for them, therefore, what we 

 ■would have to determine is not the age at which they would become 

 severally exploitable, but simply the condition or the size of the 

 exploitable individual taken generally. 



SECTION L 



Age at which Quantitative Exploitability is realized. 



The end of Quantitative Exploitability is of course the produc- 

 tion of the largest amount of material. Here we are concerned not 

 ■with the total quantity of produce accumulated at any time in a 

 forest but with the quantity obtainable within a given time, in 

 othar words, the average sum of production of the soil. This, we 

 have alretidy shown, does not exist lor individual trees but only for 

 a canopitd collection of trees considered as an organic whole. 

 Hence if it wei'e possible to watch the progressive development of 

 such a collection of trees from the very moment that it came into 

 existence, the question of finding out the mean annual production 

 would be simple enough. For in that case, to ascertain the mean 

 auQual production at any time we would have only to measure the 



