THE THEORY AND PRACTICE OF WORKING PLANS 3 



tion is, therefore, it should never be used as the sole criterion 

 of regulating the cut. This may be shown diagrammatically 

 as on page 2. 



The Increment 



Increment (syn. accretion, growth) may be defined as the 

 increase in diameter, sectional area, height, volume, quality or 

 value of a tree or a stand. 



Three principal kinds of increment are distinguished: 



Volume increment is the increase in volume of a tree or 

 stand. 



Quality increment is the increase in value per unit of volume 

 due to its augmented intrinsic worth. 



Price increment is the increment in the sale value of forest 

 products independent of quality increment, due to market con- 

 ditions. 



Increment is further differentiated as current annual incre- 

 ment = the increment for a specific year (abbreviation " C.A.I."). 

 Periodic increment = the increment during a specified period of 

 years; mean annual increment = th.e total increment divided 

 by the age (abbreviation "M.A.I."); periodic annual incre- 

 ment = the increment for a specified period of years divided by 

 the number of years in the period, usually used in lieu of the 

 current increment. 



The determination of the increment is the province of forest 

 mensuration; without trespassing on this subject, so admirably 

 covered in Mr. Graves' textbook,* it is worth while to consider 

 the matter solely in its relation to forest organization. 



Not every method of regulating the cut requires the deter- 

 mination of the volume increment; e.g., the Method of Von Man- 

 tel or the Methode de Masson. Again, it is possible to regulate 

 the cut by increment alone (Swiss Method). But most methods 

 of regulating the cut require a determination of the increment. 



The normal increment is the increment of stands fully stocked 



* " Forest Mensuration," Henry Solon Graves. John Wiley & Sons New 

 York, 1906. 



