16 



resulting number. Such a form factor is admittedly an ar- 

 bitrary ratio being dependent upon the basal area of all trees 

 in the stand and the average height of the dominant trees 

 only. Its use is simplified, however, in that the cubic foot 

 volume of the stand may be calculated directly by the for- 

 mula V = BHF in which V = volume of stand in cubic feet, 

 B = breast-high basal area, H = average height of dominant 

 tree and F = forest form factor, the average height of the 

 dominant tree being less variable than the average height of 

 all trees. It will be noted that the first two form factors in 

 Table II are high, but the ratio falls rapidly. This is ex- 

 plained by the fact that trees other than dominants are 

 growing into the lower diameter limits of the table and, other 

 things being equal, the form factor is higher the more nearly 

 the average height upon which it is based approaches the 

 average height of all the trees in the stand. Later in the life 

 of the stand the form factor is much more constant. Table 

 IV in which the diameter limit is the same closely resembles 

 Table II, while reference to Table III will show that with a 

 high minimum diameter limit the period during which the 

 form factor decreases is greatly prolonged. This is explained 

 by the fact that suppressed and intermediate trees (i.e., trees 

 with less than the average height of the dominants) are grow- 

 ing into the lower diameter limit of the table for a longer 

 period. 



Increment. Properly included in yield tables but easily 

 derivable from data given, increments are omitted in order 

 that the tables may not prove cumbersome. 



Table III gives the normal yield in board feet and addi- 

 tional cords, cubic feet and cords of better second growth 

 stands. It differs from Table II in that the lower diameter 

 limit is seven instead of two inches and board foot volumes 

 are included. It is based on the same plots as Table II the 

 trees between two and seven inches being omitted in the 

 computations. Methods of construction were the same as 

 for Table II. 



