54 



Forest Mensuration 



Breymann, however, neglects: 



1. The change of form figure, during the period of observation; 



2. A number of small factors which ought to be embraced in the 

 formula. 



For stopping height growth or for \ = , the term given for P can 

 be easily reduced to the term given by Schneider for the sectional area 

 increment percentage. 



PARAGRAPH LXXXVII. 



FACTORS INFLUENCING THE CUBIC VOLUME INCREMENT. 



The culmination of the current annual volume increment takes place at 

 a later year than the culmination of the sectional area increment at breast 

 height. Naturally so, because with increasing age of a tree, its root sys- 

 tem as well as the branch system, the feeders of the body, show contin- 

 uous increase. 



Big and long branches, of course, require a great deal of wood fibre 

 to increase and maintain their own strength, like levers increased in 

 length. Hence, from a certain size of branch on, all wood fibre produced 

 by the branch is used up within the branch itself, for its own purposes, 

 instead of being added as increment to the merchantable bole. 



After Dr. Metzger, the crown of a tree yields the maximum of bole 

 increment if its crown diameter is, and if the number of trees per acre 

 are: 



From the theoretical standpoint it seems wise, consequently, to force 

 the lower branches of a tree to die, with the help of proper tension and 

 friction within the leaf canopy, when they exceed a length of 8.25, 7.35, 

 6.35, 4.65 and 4.15 feet respectively (the halves of the diameters). 



Metzger's investigations are interesting, but his conclusions seem to be 

 too sweeping. 



P. P. Pelton recommends the lopping of branches in order to shorten 

 the length of the branch-levers. 



The average annual volume increment of dominant and sound trees 



