THE ABSOLUTE FORM QUOTIENT 529 



Putting as before the d. b. h. = lOO, the values of d^, do, d->, etc., are 

 found in Table I and inserted in the above formula. The Rinicker or 

 absolute form factors for the form classes are then computed. See 

 Table I. 



The form factors do not form an arithmetical series as the form 

 quotients, but increase more rapidly, so that the form factor in each 

 subsequent class is about lo per cent larger than in the preceding one. 



When constructing the volume tables for pine and spruce Professor 

 Jonson uses the breast height form factor. In doing this he reduces 

 the form factor by a method which differs somewhat from the usual 

 one. 



Just as the volume of the stem above breast height is the product 

 of the basal area at breast height, length of stem above breast height 

 and an absolute form factor, so we obtain the total volume of the tree 

 by multiplying the basal area at the stump with the total height and a 

 suitable absolute form factor /o- 



The correct basal area at stump cannot be directly measured on ac- 

 count of the root swelling. We obtain this area, however, by calculat- 

 ing how many per cent the normal stump diameter D^ is larger than 

 diameter at breast height D. This computation is made with the help 

 of the equation for the stem curve. 



If we obtain !)„ = i.op D, then £>o^= i-O/'" ^' and 



Ji,= — - = • I .o/)- = I .Op- B. 



4 4 



The normal stump diameter Dq being known, the absolute form fac- 

 tor for the volume on stump is easily obtained by interpolation in 

 Table I, if we know the new form quotient of the tree. If, for example, 

 the diameter halfway between stump and top is found, with the help 

 of Hoejer's formula, to be 6y.y per cent of d. b. h. and Dq is 103.0 



67.7 

 per cent, then the new form quotient is — ^^^— = 0.657 ^^^ ^^^ abso- 

 lute form factor, f,„ by interpolation = 0.449. 



The total volume of the stem is F = Bo. /?./o or V=B. i.of^-h.fo, 



V 

 the breast-height form factor F = , = i.op^fo- 



A sufficient number of breast-height form factors were computed 

 in each form class and then multiplied witli their respective heights. 

 The "form heights" obtained were then plotted graphically with the 

 heights as the abscissae (figure 2). 



Other not computed form heights and form factors were obtained 

 by interpolation. 



