Volume of needles was calculated by summing the following formula over all tree 



species : 



(V b P b cp)/pn 

 Needle volume, cm. 3 



Volume of branchwood 0-1 cm. in diameter, cm. 3 



Density of branchwood 0-1 cm. in diameter, g./cm. 3 



Needle weight (g.) per gram branchwood 0-1 cm. in diameter 



Proportion of foliage attached to slash 



Density of needles, g./cm. 3 . 



This formula determines the amount of needle volume per unit of branchwood volume. 

 The planar intersect method furnished values of branchwood volume for use in the 

 formula. Weight of needles per gram of branchwood was estimated by stripping needles 

 from samples of branchwood (under 1 centimeter in diameter) and weighing the needle and 

 branch components. The proportion of foliage attached to branches was ocularly esti- 

 mated by species as the percent of total possible needles assuming no needle-fall had 

 occurred. A mercury pycnometer was used to obtain the density values. 



Surface area of branchwood was calculated from: 



.238 nd 



2 



where S = Surface area, cm. . 



Surface area of needles was determined by species from the product of needle 

 volume and needle surface area-to-volume ratio - 



RESULTS AND DISCUSSION 



Density of foliage must be known prior to calculation of fuel volume and surface 

 area. Density of foliage for all species averaged 0.55 gram per cubic centimeter. 

 Density of branchwood, determined from particles in the 0-1 size class for all species, 

 averaged 0.50 gram per cubic centimeter. The proportion of foliage attached to branches 

 averaged 9 percent for old slash and 38 percent for new slash. Other fuel characteris- 

 tics required for the calculations are in table 2. 



Volume and Surface Area 



Fuel volume was concentrated in the lower portions of the slash. About 68 percent 

 of the total volume was below the average mid-depth of the slash (figure 2). Generally, 

 there seemed to be only minor differences in volume between the small- and large-size 

 material and between the old and new slash sampled at various heights above ground 

 (table 3). These results indicate that the small-size material is distributed verti- 

 cally in about the same proportions as all slash material. However, volume of old 

 slash in the first 20 centimeters above ground comprised 52 percent of the total volume, 

 which is noticeably greater than the 34 percent for new slash. The large proportion of 

 old slash volume in the first 20 centimeters above ground was due to the presence of 

 material over 1 centimeter in diameter. 



b J. K. Brown. Ratios of surface area to volume for common fire fuels. Forest 

 Sci. 16(1): 101-105. 1970. 



Vn = 



where Vn = 



4 



