Relationships between d.b.h. and actual fractions of foliage and branchwood compo- 

 nents follow similar trends among species, probably largely influenced by the mechanical 

 requirements for supporting suspended loads (McMahon 1975) (fig. 12). Foliage and 0- to 

 0.24 -inch branchwood fractions decrease markedly with increasing d.b.h. The 0.25- to 

 0.99-inch branchwood fractions display the greatest variation; however, they generally 

 increase up to 4 to 12 inches then decrease. The 1.00- to 2.99-inch branchwood frac- 

 tions increase steeply throughout the range of sample tree data except for ponderosa 

 pine. Its fraction levels off above a d.b.h. of 20 inches because increasing amounts 

 of branchwood exceed 3 inches in diameter. 



Large fractions of foliage and branchwood components are not necessarily associated 

 with large weights per tree of foliage and branchwood components. The crown weights and 

 component fractions must be viewed together to determine component weights. Generally, 

 the tolerant species support the greatest weights of foliage, an exception being ponder- 

 osa pine which produces nearly as much foliage as Engelmann spruce at comparable tree 

 diameters. Weights of 0- to 0.24-inch branchwood are greatest for the firs and hemlock. 

 Weights of branchwood exceeding 1 inch are considerably greater for ponderosa pine than 

 for other species. 



For the species where dominants and intermediates were both sampled, the fraction 

 of foliage for the dominants was consistently greater than for the intermediates, 

 averaging 3 percentage points more at 2 inches d.b.h. and 16 percentage points more at 

 12 inches d.b.h. Differences in branchwood fractions between dominants and inter- 

 mediates varied by species and d.b.h.; thus, any pattern of differences common to all 

 species was not evident. 



Bolewood Fractions 



Weights of unmerchantable tips and boles of trees 4 inches and less in d.b.h. can 

 be partitioned into 0- to 1-inch, 1- to 3-inch, and 3+-inch diameter size classes using 

 fractions in table 9. Because unmerchantable tip and small tree bole material to 0.25 

 inch in diameter was insignificant, this size class was lumped into the 0- to 1-inch 

 class. The size class fractions are averages of data for all species. They were 

 averaged after finding that variation of the fractions among species and dominants and 

 intermediates was small. 



Table 9 .--Fractions for partitioning weights of unmerchantable tips (for trees 

 5 inches and greater d.b.h.) and small tree boles (4 inches and. less 

 d.h. h. ) into 0- to l-inch^ 1- to 2-inch, and 2+-inch size classes 



Size 



class 



(inch) 



Tips 



Merchantable top diameter, inches 

 3:4:6 



Small tree boles 



D.b.h. , inches 



1 



- 1 



1 - 3 

 3+ 



0. 03 

 .97 







0.01 

 .39 

 .60 



0.003 0.08 0.03 0.01 0.01 



.10 .91 .83 .31 .19 



.90 .01 .14 .68 .80 



24 



