GERMAN FORKS'! MANAGEMENT FOREST REGULATION. 



245 



Sormal yield table for spruce. 

 [Main growth (rxnlnaive of thinnings) per acre.] 



In very regular growths trial areas only are measured. The more usual manner of deter- 

 mining the rate of accretion, however, for purposes of yield calculation, is by felling sample trees 

 of each class, dissecting and measuring the accretions of past periods. 



In modern times the exact measurements are mostly confined to the growths that are utilized 

 during the first or first two periods of twenty years. 



FELLING BUDGET. 



After all these data for each compartment have been booked, and the yield of branchwood 

 and roots for even these are mostly utilized as well as the probable amounts to be taken out in 

 thinnings, have been estimated and recorded, and after the likelihood of decreased accretion 

 in the different compartments has also been determined from measurements and experience, the 

 "felling budget' 1 is determined as a sum of the stock on hand and the amount of annual accretion 

 multiplied by the time, during which it is allowed to grow, i. e., in the average to the middle of 

 the period in which the compartment is placed, divided by the period of rotation. Thus a growth 

 of eighty-five years, which showed a stock on hand of 3,825 cubic feet per acre, and hence had an 

 average accretion hitherto of 3,825-4-85 = 45 cubic feet per year, which is likely to be reduced on 

 account of gradual reduction in stock and other untoward conditions to 30 cubic feet, would yield 

 during the first period 3,825 + 30 x 10 = 4,125 cubic feet. And if the compartment contained 50 acres 

 it should be credited in the working plan in the column for the period I with 4,125 x 50 = 206,250 

 cubic feet. By adding up the amounts of the yield of all the compartments placed in the first 

 period and dividing by 20 (the length of the period) the animal budget which should be felled 

 during the period is found. If, however, it is desired to equalize the fellings more or less through 

 a longer period for instance, the time of rotation then the amounts in all the periods must be 

 summed up, and these sums as nearly as possible equalized by shifting the position of the com- 

 partments from one period into another (necessitating always new calculations of the accretion) 

 until the equalization in the periodic sums is effected. 



Even then, however, before finally determining the annual budget, a calculation is made to 

 see whether the area contains as much timber as it normally should; if more, the budget may be 

 increased; if less, a saving must be made in order to bring up the stock on hand to the normal. 

 If, for instance, we know from the experience tables that our forest should normally yield 50 cubic 

 feet per acre a year in a 100-year rotation, then the normal stock would be 100x50-^-2=2,500 cubic 



