CHOICE OF ROTATION 113 



this the total net income gees to $1967 at 120 years but the average 

 per year begins to decrease. 



The table also indicates that the owner receives highest average 

 rental per acre from his land if he cuts it at eighty years or thirty 

 years before highest average yearly income occurs. 



In this calculation for Greatest Net Income per acre and year, 

 the assumption is that we normally have a forest and not merely 

 bare land; that this forest is reasonably regular so that a yearly 

 income is produced. If then Rotation is eighty years, for instance, 

 we could take an eighty-acre sample of this forest and get from this 

 eighty acres each year : 



One acre of ripe timber. 



Several acres of thinnings (these are made about every ten 

 years in good forests abroad) and we would have as expenses: 



One acre to plant and 



Eighty acres to protect, pay taxes on, etc. 



Putting this in a formula we have : 



Yr -f Ta -!- Tb, etc. C re 

 Average Net Income per acre = 



where Yr Stumpage Value or net Yield of one acre of ripe tim- 

 ber, here eighty years old. 



Ta = Value of Thinnings made when the stand is a years 

 old, etc. 



C = Cost of planting one acre, 

 re = Value of taxes, protection, administration, etc., i. e., 



of yearly expenses for r acres. 

 Using the above table we have : 



12 12 84 



Average Net Income per acre on eighty year rotation 



80 



d. Rotation for Highest Rent per Acre of Land. 



This is also called "'Financial Rotation'' and may also be called 

 "Rotation for highest Rate of Interest on Capital." The assumption 

 here is that bare land is the real capital and that by using it to raise 

 timber this land is made to pay a rental, and the object is, in using 

 this Rotation, to secure best net rental per acre. The calculation, 

 :then, starts out with an acre of bare land and inquires into the 



