a LOW DENSITY 
NO 
t=) 
=) 
oO 
a 
3 
(s) 
HIGH DENSITY ———> 
CROWN WEIGHT PER CORD (POUNDS DRY WEIGHT) 
LMS GN NAW Ba nino es LO 
DBH (INCHES) 
FicurE 3. — Crown weight per cord on good sites 
at different densities. Equations for each den- 
sity condition are as follows (Lc.cd. = log of 
crown weight per cord; D = d.b.h. ** = highly 
significant regression ): 
A. Low-density condition: 
Le.cd. = 4.2436 -- .1358D**, r2 = .57 
B. High-density condition: 
Le.cd. = 4.0013 -- .1293D**, r?2 = .78 
the quantity of crown weight produced per 
cord can be estimated, knowing the average 
d.b.h. of harvested trees and the relative stand 
density. If stand density falls between the 
high and low standards, interpolation of 
crown weight will improve the results. This 
method is more accurate if the harvested 
trees are of a uniform diameter. 
Crown weight per cord varies consider- 
ably with different stand densities and aver- 
age diameters. The following tabulation shows 
the weight (in pounds) of tree crowns to be 
expected from cutting one cord of wood on 
a good site under different density condi- 
tions: 
DBH Class (inches) 
Density 4 6 8 
Low 5,012 2,684 1,436 
High 3,049 1,681 927 
Weight of the overstory for larger cord- 
wood volumes may be obtained by multiply- 
ing number of cords times crown weight in 
proper diameter and density classes in the 
tabulation above. 
An explanation of the variables used for 
regression analysis in figure 3 may be of 
interest. Diameter (d.b.h.) was measured on 
each sample tree. Crown weight per cord was 
obtained by first determining the cordwood 
volume in each sample tree, next calculating 
the number of trees per cord (1.0 divided by 
cordwood volume per sample tree), then mul- 
tiplying this value times the crown weight per 
tree. Volume for each sample tree was de- 
termined from a cordwood volume table 
based on a 3-inch merchantable top.? 
The weight of needles per crown ex- 
pressed as a percent of total crown weight 
with 95-percent confidence intervals is shown 
below for each of four stand conditions: 
Percent of crown weight 
Stand condition in needles 
Confidence 
Site Density Mean level 
Good High 51 47-55 
Low 42 34-50 
High and low 46 39-53 
Poor High 43 38-48 
Low 38 33-43 
High and low 41 36-46 
Good and poor High andlow 43 40-46 
In good-site, high-density stands, approx- 
imately 50 percent of the crown weight is in 
needles. Poor-site, low-density stands may 
have only 38 percent of their crown weight in 
needles. A representative estimate for all sites 
and densities would be approximately 43 per- 
cent of crown weight in needles, the remain- 
ing 57 percent being in branchwood and top, 
excluding the stem of the tree. 
Fire behavior is dependent upon the in- 
teraction of many factors. The primary in- 
2 Gevorkiantz, S. R., and Olsen, L. P. Composite 
volume tables for timber and their application 
in the Lake States. U.S. Dept. Agr. Tech. Bul. 
1104, 51 pp., illus. 1955. 
