FOREST MANAGEMENT 127 



lower than the latter ; it rises gradually, and culminates later 

 than does the current increment, its maximum being also 

 lower ; the decrease from this point is less fast in the average 

 than in the current yearly increment. The mean annual in- 

 crement reaches its maximum when it is the same as the 

 current annual increment ; previous to that it is lower, subse- 

 quently higher than the latter. 



Besides the quantity increment dealt with above, it is also 

 necessary, for the purposes of forest management and valua- 

 tion, to take into account the quality and price increments. 

 Quality accretion or increment follows from the increase of 

 value per cubic foot, which is associated with increased age 

 and dimensions of the trees in a wood. With additional 

 volume, there is a more than proportionate inci -ase in price 

 per unit of measurement ; hence the need of this factor being 

 duly noted. It has nothing to do with the price of tim- 

 ber in the general tendency of the market, which receives 

 consideration under the term "price increment/' Price 

 increment denotes the change in value (positive or negative) 

 which may be occasioned by economic circumstances, most 

 of them beyond the control of the forester. Thus prices are 

 influenced very greatly by the shortage or superabundance of 

 the supplies of imported timber, and locally by the formation 

 of new roads or railway lines. 



All three forms of increment (volume, quality, and price) 

 may be conveniently expressed as percentages. 



As the sum of these three values (volume, quality, 

 and price increments) represents the actual increase in the 

 value of the forest, it is not difficult, after the three 

 items are known, to ascertain the return on the invested 

 capital. 



The value of a wood is judged from the present worth of 

 its timber contents, T ; that of the land, L ; and a sum must 

 also be named to cover the costs of management, M, which 

 will include working expenses, taxes, wages, and so forth. 

 If the volume, quality, and price percentages be called 

 respectively a, b, and c, then from these variables, which 



