Determination of bole weight and specific gravity .- -Pie -shaped segments of the disks 

 were split along the 20th ring from the cambium to separate the 20-year increment from the 

 entire segment. After soaking the segments to regain lost moisture, their volumes were ob- 

 tained by water displacement; then the segments were dried in several steps to an ovendry 

 condition and weighed. From these data the total volume and increment volume were computed 

 in cubic feet by siimming the Smalian formula for volume of a parabolic frustum for each log. 

 The volume of the section from a stump height of 1 foot to breast-height point was computed as 

 (0.03)(dia. inside bark at b.h.) and assumed to have a specific gravity equal to that of the 

 breast -height section. 



The weight of each bole was computed by multiplying each end-area in the volume summa- 

 tion by its corresponding specific gravity, then multiplying the total by 62.4 pounds per cubic 

 foot . The bole specific gravity was obtained as an intermediate step by dividing the above total 

 by the total volume. Analogous calculations were used to determine the specific gravity of the 

 outer 20-year increment. 



VARIATION IN SPECIFIC GRAVITY AS A FUNCTION OF HEIGHT 



The way in which specific gravity of a given annual increment changes with height must be 

 considered in deriving formulas to convert breast-height data to total-tree estimates. Much 

 has been written concerning variation in specific gravity (Goggans 1961). However, three 

 papers provide special insight into the causes and nature of the variation of specific gravity 

 with height. 



1. Larson's (1960) investigations showed that the transition from large diameter to 

 small diameter cells was related to the cessation of terminal elongation, and that the 

 vertical extent and magnitude of the change in tracheid development depended upon the 

 Intensity of the apical stimulus. This theory suggests that variations in tracheid development 

 should be related to distance from apical meristem, rather than to height above the ground 

 level. Although cell diameter is only one factor affecting specific gravity, the correlation of 

 secondary wall thickening with cell diameter permits a similar argument to be applied to 

 specific gravity. 



2. The strength of this approach is demonstrated by data cited by Richardson (1961). 

 Of the three sequence types described by Duff and Nolan (1953), the type I or oblique 

 sequence showed the best concordance of data from various portions of the tree bole . In 

 this sequence, a single annual increment is traced from the apex to the base. Points are 

 identified by the number of Internodes from the apex at the time of deposition . For Corsican 

 pine, Richardson reported that gravity decreased to a minimum at about the fifth intemode 

 from the apex, then increased to about the 20th, and subsequently leveled off. 



3. Smith and Wilsie (1961), studying the effect of summer water deficits on tracheid 

 development in the oblique series in loblolly pine, found that the slope of the linear regres- 

 sion of specific gravity on internodes from the apex was closely related to the moisture 

 stress during the year of formation. 



These three papers Indicate that: 



1 . Factors such as crown development and vigor may affect the trend of upper tree 

 specific gravity by supplying additional sources of auxin from elongating laterals . 



4 



