JONSON ABSOLUTE FORM QUOTIENT -^85 



BRIEF OUTLINE OF THE THEORY AND METHOD 



The volume and taper of trees of any given diameter and height 

 is determined entirely by one single factor, that is, the ratio between 

 two diameters on the tree. The diameters chosen as most con- 

 venient for classifying trees according to such ratio are the d. b. h. 

 and a diameter at a point half way between the breast height and 

 the top. This ratio is called the absolute form quotient; the ex- 

 pression of this quotient into decimals is called the form class. There 

 is, therefore, no numerical difference between "form quotient" and 

 "form class." 



The word "absolute" refers to the fact that all trees are treated on 

 the same basis, that is, according to the taper of the trunk above the 

 breast height.'^ 



Two sets of tables are used, one for volume, the other for taper. 

 Each is arranged according to diameter, form class, and height of 

 all trees. 



That is, knowing the diameter, form class, and height of a tree of 

 any species, you can obtain from the tables its volume or taper series. 



Moreover, it does away with extensive stem analysis, being as accu- 

 rate in new regions as in those where conditions are already known. 



This eliminates the necessity of making local volume tables. Once 

 the tree tallies are made and the factors affecting volume, including 

 form class, are secured, the volume tables will give you the volume, 

 and the taper tables, the number of logs of any specified size for the 

 locality in question. 



Determination of the form Quotient 



The form quotient of any type does not vary much even for large 

 regions. There are at least two methods of obtaining the form quo- 

 tient. (1) Direct measurements on trees. The middle diameter is 

 measured on felled trees, or by observations on standing trees from 

 the ground, by means of any suitable instrument.^ One could even 

 use tree climbers to obtain the middle diameter. By choosing fairly 



" This is contrary to the procedure followed by Schiffel, Mass, and others 

 whereby the d. b. h. (whose relati\"e location varies according to the height of 

 the trees) was compared to the diameter half way up the total height of the 

 tree. Thus, for a tree 30 feet high, the d. b. h. lies at 1.5 per cent of the height, 

 but for a tree 100 feet high, it lies only at 4.5 per cent of the height. 



^ Several such instruments have been devised but do not seem to have been 

 used extensivelv in anv countrv. 



