21 



VOLUME OP BARK. 



Western yellow pine is generally thick-barked, though the thick- 

 ness varies with individual trees. Accurate computations on 189 

 trees in the Black Hills and 94 trees in California show very con- 

 sistent results in the volume of bark. As in all trees, the percentage 

 of bark in relation to the total stem volume decreases as the volume 

 of the tree increases, or, in other words, the increase in the bark 

 volume does not keep pace with the increase in stem volume. This 

 differ ence in ratio is less marked in thin-barked species. a 



In relation to diameter, the percentage of bark for the Black Hills 

 is much less than for California, partly due to the larger volume of the 

 Black Hills trees. However, in the cubic feet of bark for the same 

 diameter and height in both regions the difference is less marked. 



Table 19. — Amount of bark of western yellow pine in per cent of total stem volume. 



Diam- 



Volume of bark. 



eter 











breast- 



Black 



Califor- 



high. 



Hills. 



nia. 



Inches. 



Per cent. 



Per cent. 



8 



17 





10 



16 





12 



16 



24 



14 



15 



22 



16 



14 



21 



18 



13 



20 



20 



13 



19 



22 



12 



18 



24 



12 



17 



26 





16 



28 





15 



30 





14 



34 





13 



40-44 





13 





The portion necessarily deducted from Tables 17 and 18 for unmer- 

 chantable material in top and stump will vary with the height of 

 stump and with the diameter to which the top is utilized as well as 

 with the size of the tree. The proportion of material that is lost is 

 larger in small than in mature trees. For cordwood calculations 

 the limb wood more than offsets the loss in top and stump. For 

 saw-timber calculations cubic measure is seldom used. The unmer- 

 chantable part, allowing from 1-foot to 18-inch stumps and 8 to 10 

 inch tops, would vary from about 25 per cent in 12-inch trees to 15 

 per cent in 18-inch trees and 10 per cent in 24-inch trees for the Black 

 Hills. For California it would be a little higher because of the longer 

 tops. The amount to be deducted should be determined on the 

 ground where the stump height and the closeness of utilization are 

 known. 



In case a deduction for both bark and "top and stump" is desired 

 the top and stump should first be deducted and from the remainder a 



o See Circular 126, Forest Tables, Lodg 



le Pine. 



[Cir. 127] 



