108 THE THEORY AND PRACTICE OF WORKING PLANS 



z and zi in figuring cc, the cut would be 41,084 board feet. The 

 cut would be distributed among the different size classes as 

 dictated by silvicultural and market conditions. 



(c) Value and Application. — The method's chief advantage 

 is that an exact account of what is done can be kept, and of 

 the effect produced by the operations carried on, so as to modify 

 future proceedings to suit the object in view. The short 

 period between surveys allows checking, and lessens the chance 

 of overestimating. However, forest management in America 

 is seldom intensive enough to apply the method since it involves 

 too much time and expense by requiring such frequent re- 

 measurements of the whole forest. 



14. BY AREA AND VOLUME.— BASED ON AGE CLASSES. DIRECT 

 METHOD (HUFNAGL *). 



(a) Description of Method. — If the volume and the area 

 of the oldest stands which, presumably, will be cut in the next 

 ten or twenty years is known the average volume per acre 



equals -. This volume multiplied by the allowed annual cut 

 a 



in area equals the allowed annual cut in volume. 



(b) Example. — Referring to example of method No. i above: 

 Variation I. Area not reduced. Annual cutting area equals 

 166 acres. The volume of the oldest stands to be cut in the 

 next twenty years (oldest age class) equals 140,000 M. feet board 

 measure, their area is 3500 acres. 



Then the average volume per acre = - = 4oM. feet board 



a 



measure. 



The volume of the annual cut = 4oM.Xi66 = 664oM. feet 

 board measure. 



Variation II. Area Reduced. Using the figures given in 

 the example of Variation II, ^Method No. i above: Annual 



* Hufnagl, " Praktische Forsteinrichtung," is the source of this and the sub- 

 sequent method (No. 15). 



