58 Forest Mensuration 



1. The cubic increment percentage of the total bole coincides with the 

 cubic increment percentage of the merchantable bole; 



2. The merchantable bole does not increase in length during the period 

 of observation. 



PARAGRAPH XC. 



CONSTRUCTION OF VOLUME TABLES. 



Volume tables are "tree yield tables" from which the volume of a tree 

 of given species, given age, given diameter breast high or stump high, 

 given height, given merchantable bole, given position (suppressed, dom- 

 inant, etc., or isolated, crowded, etc.), given locality and so on can be 

 readily read. The units of volume are cubic feet, board feet, standards, 

 cords, etc., according to the requirements of the case. 



Obviously, volume tables give, or should give, the volumes of average 

 trees ; they may give, in addition, the maximum and minimum volume 

 possible in a tree of stated description. 



Volume tables are constructed either on the basis of hundreds (thou- 

 sands) of measurements taken from trees actually felled in the woods 

 (possibly also sawn at a saw mill, to ascertain the grades) or on the 

 basis of a smaller number of complete section analyses. 



The rapidity of volume growth of a species and the development of its 

 form height depend on many local factors notably on climate, soil, sylvi- 

 cultural systems at hand, influence of fires, fungi, insects, etc. 



Owing to the multitude of local factors influencing the volumes and 

 the changes of volumes, local volume tables alone are entitled to a place 

 in exact mensuration. 



Volume tables for second growth are more reliable than volume tables 

 for first growth. 



Circular 445 of Bureau of Forestry defines volume table as "a tabular 

 statement of the volume of trees in board feet or other units upon the 

 basis of their diameter breast high, their diameter breast high and height, 

 their age, or their age and height." 



The method of construction of volume tables is either .mathematical or 

 graphical. 



i. Mathematical method. 



The volumes ascertained for trees of a given diameter (breast high or 

 stump high with or without bark), a given merchantable length or total 

 length, a given age or a given quality or locality are added up. 



The sum total of these volumes divided by the number of trees forming 

 it yields the average volume of the tree of stated description. 



These averages are shown, for the various diameters, lengths, ages and 

 localities, in tabular form. 



The volumes corresponding with such diameters, lengths, ages and lo- 

 calities, for which sample trees were not cut and measured, are found by 

 arithmetic interpolation. 



