Forest Mensuration 21 



The timber form factor, based on cubic measure of a tree, rises with 

 increasing age and increasing height up to a certain point (for Yellow 

 Pine at 3 poles), provided that the term timber includes all stuff over 

 3 inches in diameter. The timber form factor is a function more of 

 the diameter than of the height. Timber form factors of Yellow Pine 

 are: 



Trees I pole high 07 



Trees 2 poles high 36 



Trees 3 poles high 48 



Trees 4 poles high 46 



Trees 7 poles high 45 



The timber form factor in shade bearers is a little higher than that 

 in light demanders (within an age limit of 150 years, for trees in close 

 stand). 



The bole form factor can be found, in fact, only for species forming 

 a straight bole free from large branches (hence especially for conifers). 

 The bole form factors, to begin with, are large; with increasing height, 

 they decrease gradually to a par with the timber form factors e. g., for 

 Yellow Pine: 



1 pole high 70 3 poles high 49 



2 poles high 55 4 poles high 47 



7 poles high 45 



European common form factors are collected by thousands of measure- 

 ments taken in a large variety of localities. It must be remembered that 

 a form factor read from a table is never applicable to an individual tree, 

 and is only applicable to an average tree amongst thousands. 



For trees less than 120 years old, the branch wood (stuff less than 3 

 inches in diameter) comprises from 15% to 28% of the entire tree vol- 

 ume; this figure, in the case of broadleaved species, rises from 25% up 

 to 33%. For trees as now logged in America, the branchwood percentage 

 is naturally very much smaller. 



The tree form factor equals stump plus bole plus branches 



ideal cylinder 



The timber form factor equals aH stuflF having over 3" diameter 



ideal cylinder 



The bole form factor equals bole from ground to tip 

 ideal cylinder 



By form height is meant the product of height (total height of tree) 

 times form factor, or else that much of the height of the ideal cylinder 

 which the tree volume, poured into the ideal cylinder, would fill. Since 

 the form factor on the whole decreases with increasing height, the form 

 height is a fairly constant quantity ; at least for trees of merchantable 

 size. Hence the helps and hints given in Paragraph XXVII (to quickly 

 find the volume of standing trees from mere diameter-measurement) may 



