The parentheses contain levels of significance from a two-tailed t-test of differences 

 between the bulk densities for intermediates and dominants. Branches of the sample 

 grand fir intermediates appeared normal in length but were more spindly and sparsely 

 distributed than for dominants. Hence, crown volume of intermediates was large rela- 

 tive to weight, resulting in low bulk densities. Surprisingly, bulk densities of 

 intermediates and dominants for ponderosa pine were not significantly different. 

 Apparently, both crown weight and volume are reduced for intermediate ponderosa pine, 

 resulting in little change in bulk densities. This seems likely to hold true for other 

 species as wel 1 . 



Moisture Content 



Moisture contents were intensively sampled to determine ovehdry crown weights. 

 Thus, reliable moisture estimates of foliage and branchwood at top, middle, and bottom 

 live crown positions were obtained. Coefficients of variation computed for each species 

 using individual tree moistures averaged 16 percent for foliage and 18 percent for 

 branchwood. Evaluation of differences in moisture content among species and of seasonal 

 variation in moisture content was confounded by uncontrolled sources of variation and 

 thus was not attempted. 



At the same crown positions, foliage moisture was consistently greater than 

 branchwood moisture by an average of 24 percentage points (table 10) . Moisture contents 

 of both foliage and branchwood were highest in the top sections and decreased downward 

 through the crown. Perhaps the upper sections of tree crowns contain a larger propor- 

 tion of young growth that is characterized by low dry matter content and high percentage 

 moisture content than the lower sections of crowns. Or perhaps growing tips, distrib- 

 uted more densely in the upper sections, exercise priority in the distribution of water 

 in response to internal water deficits (Kramer and Kozlowski 1960) . In either case, 

 higher moisture contents are maintained in the upper croivn. The moisture content of 

 entire live crowns averaged 102 percent for dominants and 86 percent for intermediates. 

 Thus, simply doubling ovendry weights of crown material should result in reasonable 

 estimates of fresh green weights. 



Although the data clearly indicate that the moisture content of dominants is 

 greater than intermediates, conclusions are tenuous because influences such as date and 

 site confound the data for this comparison. Differences in moistures between crown 

 sections of intermediates are much less than for dominants. In fact, foliage moistures 

 of intermediates appear uniform throughout the crown. 



The variation in moistures between foliage and branchwood and by crown position 

 points out the need to select samples wisely when studying tree crown moisture contents 

 in order to avoid bias. 



This study has provided equations based on about 500 sample trees for predicting 

 weights of foliage, live and dead branchwood, and small tree boles. Relationships be- 

 tween tree crown biomass and d.b.h., tree height, crown length, crown ratio, and crown 

 class were evaluated in selecting the most precise and useful equations. Tree crown 

 bulk densities were also determined. This information provides a basis for appraising 

 fire behavior potential of tree cutting activities in advance of cutting. Numerous 

 other applications from predicting tree crown biomass are also possible. 



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