62 FORKST VALUATTON 



2. Expenses incurred to produce the stand or grow it to the 

 age of 45 years : 



Cost of planting prolonged, c (i.op m ), 



or 8 (i.02 4 "') $ 19.40 



Current yearly expenses e with intere'st. 



e(iQp m i =E( m _ o where E= _e_ 

 i. op i .op 



'y\l 

 and yearly rent of land with interest, 



rent ' ""- Si(i.op--i), 



i. op i 



simplifying (E-fS>c) (i.op i) or 



(25 + 5) (i.02 45 i) $ 43. 13 



Thinning at age of 20 years, cost with interest. 



Ta(i.op'"- a ) = 3(i-02 25 ) 4-92 



Total expenses per acre $ 67.45 



3. Income per acre obtained from the stand during the 45 

 years, 



Thinning at 30 (just paid expense) $ o 



Thinning at 40, $10 with interest for five years 11.04 



Total income $11.04 



4. Net cost per acre: 



$67.45 $11. 04 = $56.41 



and cost value of the stand of 80 acres, $4,5.12. 



5. This calculation is usually expressed in a formula as fol- 

 lows : 



m Gc c(i.op in )-f- (Sc + E) (i.op 111 i>^(Ta(i.op m -- a )+Tb etc.) 



when Ta is made at a loss or is a negative quantity, Ta, is de- 

 ducted from costs as ( Ta) as in the sample case above. 



In the formula Gc means : the cost value of one acre of the 

 growing stock, m years old. 



6. The above case fully illustrates the usual calculation. If 

 natural reproduction replaces planting, c may be zero. Similarly, 

 if there are expenses of clearing the land, as on a burn, of cultivat- 

 ing the plantation, of filling fail places, etc., these expenses are 

 charged and prolonged exactly as planting, c. 



