THE THEORY AND PRACTICE OF WORKING PLANS 



11 



It is obvious that where the constant c is approximately 

 .5 the error in finding nv by the formula method is least, since 



ri 

 2 ^ 



It is also obvious that finding c and using it in the formula 

 is more correct than applying a general reducing factor such as 

 found in the case of Douglas fir above. 



To further illustrate the workings of c the average value of 

 c has been found by and applied to the white pine yields as given 

 in table 6, Bulletin 13, U. S. Dept. of Agriculture, new series, 

 for site quality II, i.e., medium site quality. The values by 

 formula, with and without use of c and by summation of yield 

 table are also given. 



AVERAGE VALUE OF CONSTANT c IN WHITE PINE, SITE QUALITY II 

 Based on Table 6, U. S. Dept. Agric. Bull. 13, N. S. 



Rotation (Years). 



40. 



50- 



60. 



70. 



80. 



90. 

 100. 

 no. 

 120. 



130. 



140. 



Average. 



227 

 280 



330 

 368 



399 

 426 



449 

 465 

 484 

 506 

 549 



nv =n(a -\-b 



nv =c Xr Xi. 



Difference 



betw. Last 



Two 



Columns. 



Feet, Board Measure, per Acre. 



11.750 

 18,300 

 23,450 

 28,050 

 3 2 ,000 

 35450 

 38,500 

 41,600 

 44,050 

 45,750 

 47,050 



5,337- 

 10,280 



15,525 

 20,764 

 25,588 

 30,239 

 34,610 

 38,745 

 42,654 

 46,280 

 51,604 



5,334-5 

 10,248 



15,477 

 20,644 



25,536 

 30,203 



34,573 

 38,771 

 42,650 

 46,299 

 51,660 



3 

 32 

 48 

 120 

 52 

 36 

 37 

 26 



4 

 19 

 56 



39-4 



Note. — Values over one hundred years from prolonged curves. 



The value of Flury's constant in finding the normal growing 



stock is evident since, as Flury says,* " the normal growing 



* Grosse und Aufbau des Normalvorrates im Hochvvalde, Mitteilungen der 

 Schweiz. Centralanstalt fiir das forstliche Versuchswesen, XI, i, 1914, pp. 97-148. 



