80 THE THEORY AND PRACTICE OF WORKING PLANS 



able trees will give the increment per acre of the young growth 

 below merchantable size." * 



E.g., area of young growth under 12 inches diameter breast 

 high = 6 per cent of total area (1000 acres) or 60 acres. A 

 normally stocked stand of Western yellow pine 12 inches in 

 diameter (about sixty years old) contains 5850 board feet; f 



^—^ = 97.5 board feet = the increment per acre of the young 



growth below merchantable size. There are 60 such acres, 

 hence 97.5X60 = 5850 feet board measure. But the average 

 density of stocking is only .7, so the real increment = 4095. 

 The increment of the merchantable timber has already been 

 figured at 24,500 feet; this + the 4095 increment on unmer- 

 chantable timber = 28,595. Then — ^ = -z ^^^ = 2,001,650 



2 2 



feet board measure. 



rru 1 4- ^ \ • I V — nV o , 3,500,000 — 2,001,650 



The annual cut (y) =t-\ = 28,595+^^-^^ 



r 200 



= 36,087 feet board measure. 



(c) Value and Application. — Dating from a decree of the 



Vienna Hofkammer in 1788 (whence the name " Kameraltaxe "), 



this method has won the cognomen of " Austrian," although 



in Austria it is now used only as a check on other methods 



of determining the cut (see Part Two). Adapted to rather 



primitive conditions, especially to irregular, uneven-aged forests, 



the Austrian formula has grave disadvantages in that it assumes 



both i and nV as constants, whereas in consequence of cutting 



and unforeseen contingencies they are always changing, e.g., 



becoming better by correct cutting, becoming worse by storms, 



windfall, etc. In view of these changing constants the formula 



cannot secure even an approach to normal during the next 



rotation unless the cut is revised at least every ten years. 



* Barrington Moore, ibid. 



t From Tables 10 and 19, Bulletin loi, Forest Service, U. S. Dept. Agri. 

 X E. J. Irish has suggested that r and not r' be used, since the increment of the 

 young growth is included. 



