36 MEASFEKMENT OF STANDING T«EES. 



2. Estimate of Volume hy means of Form Factors, 

 a. DefiniUon and Classification of Form Factors. 



By " form factor " is understood the proportion, which exists 

 between the vohime of a tree and that of a regularly-shaped 

 body of the same base and height as the tree. The 

 form factor means, therefore, a coefficient, with which the 

 volume of the regularly-shaped (geometrical) body must be 

 multiplied in order to obtain the volume of the tree. 



Any regularly-shaped body, the volume of which can easily 

 be calculated by means of a mathematical formula, is suited 

 for the above purpose. In practice, only the cone and cylinder 

 have been employed, and at the present time onh' the latter is 

 used. Let s be the area of the basal section of the tree, h its 

 height, / the form factor and r the volume, then — 



Volume of cj-linder = s X h, 

 Volume of tree = v = s X h X /, 

 and 



r 



Form factor = f = 



s X h 



The volume of the stem of a tree by itself is always smaller 

 than that of the corresponding cylinder ; hence, the form factor 

 for the stem only is always smaller than 1. If the volume of 

 the branches is added, the form factor is sometimes greater 

 than 1, especially during the early youth of the tree. 



Various kinds of form factors are used in forestry, of which 

 the following may be mentioned : — 



(1.) Stem form factors, which refer only to the volume of 



the stem above ground. 

 (2.) Tree form factors, which refer to stem and branches, 



omitting root wood. 

 (3.) Timber form factors, which refer onl}' to the parts of 

 the tree classed as timber, whether they are taken 

 from the stem or branches, omitting all other 

 material. 



