110 Forestry Quarterly 



These values for c express at the same time the general relative 

 increment conditions of the five species, the most rapid, pine and 

 spruce, having the highest, the slower correspondingly lower 

 values. The slower the development the longer time does it take 

 to bring the constant c to the value .5 ; before that time the theo- 

 retical formula gives too high, after that too low a normal stock. 

 The rotations at which the formula becomes correct, if based 

 on timberwood, lie for pine between 90 and 100, for spruce between 

 90 and 120, for beech between 120 and 140, for fir the same, for 

 oak at 160 years. 



There is then a certain lawfulness expressed in these figures, 

 which brings to expression the specific character of the species. 

 Even widely separated geographical regions and methods of man- 

 agement exhibit a considerable parallelism in the constants, which 

 is of significance in regulatory work. 



The trend of the curves for the constants are particularly instruc- 

 tive in comparing the progress of normal stock changes from decade 

 to decade. This is dependent on the specific progress of increment 

 of the species and not on the form of bole or more or less taper. 

 The rapidly growing but early declining pine has reached the value 

 for c=.5 in fifty years, while the slow fir has not reached it in 

 140 years. 



In a brief discussion, the author points out that the addition 

 of yield tables with periodic instead of annual data is itself 

 incorrect, but he shows that the error of various methods of addi- 

 tion is not large except for pine, in which owing to the rapid early 

 development the early accumulation of stock influences the result 

 more decidedly, and the error may for some positions exceed even 

 10 per cent. 



The author then investigates the distribution of the normal 

 stock over age and diameter classes, or the participation of these 

 in building up the stock. A tabulation and graphic illustration 

 gives for different species and sites for rotations of 100 and 120 

 years the percentic contribution of each ten-year ageclass to total 

 and to timberwood stock. It shows that the ageclasses 61-100 

 and 61-120 furnish 70-80, and 80-90 per cent, respectively, 

 accentuating the importance of ascertaining more carefully the 

 stock condition of these ageclasses. The regularity of the per- 

 centic stock distribution in the same species according to different 

 yield tables gives confidence in the lawfulness of this participation 



