FUEL DETERMINATIONS 

 USED IN THE ANALYSIS 



As stated in the text, the fuel complex on 

 the 55,910 acres burned by the Sundance Fire 

 was divided into three levels: ground litter, 

 brush, and crown material. The crown mate- 

 rial consumed was composed of foliage and 

 branches under 1/8-inch diameter based on 

 observations made in .the field. The brush 

 level quantity was field sampled and the maxi- 

 mum size involved in the fire front was set at 

 one-fourth inch. The ground litter was 

 sampled in the field at two locations and 

 visual estimates were made throughout the 

 area. Because of findings in laboratory work 

 on fuel consumption, the quantity of the 

 total litter fuel involved in the front was set at 

 20 percent. 



The crown weights were calculated on the 

 basis of timber inventories made by the 

 U. S. D. A. Forest Service. An assumption 

 that State and private lands contain about the 

 same variety of timber types was made after 

 information received from agencies in Idaho 

 had been reviewed. The number of acres occu- 

 pied by each cover type on Forest Service 

 land, based on the 1961 forest inventory, is 

 as follows: 



Trees 5 inches All Forest 



Cover type 



d.b.h. and above 



lands 





Acres 



Acres 



Larch 



4,924 



5,849 



Alpine fir 



3,636 



3,636 



Spruce 



1,892 



3,508 



Hemlock 



1,077 



1,238 



Douglas- fir 



798 



883 



White pine 



694 



726 



Cedar 



670 



710 



Lodgepole pine 



395 



395 



Ponderosa pine 



170 



170 



Total 



14,256 



17,115 



for the Kaniksu Working Circle were deter- 

 mined by the following d.b.h. classes: 5 to 9 

 inches, 9 to 11 inches, 11 to 15 inches, 15 to 

 19 inches, and over 19 inches. Crown weight 

 per acre was then determined from 

 Fahnestock's study for each d.b.h. class using 

 trees of average d.b.h. to represent each class. 

 The weight of needles was calculated assum- 

 ing 24 percent of the crown weight is foliage. 

 Branches less than one-eighth inch in diameter 

 were assumed to make up 6 percent of the 

 crown foliage. The weight of crown fuel less 

 than one-eighth inch in diameter was calcu- 

 lated as 30 percent of the crown weight. 

 (These percentages were derived by weighting 

 averages by volume for each species present in 

 the Sundance Fire area.) 



Crown weights (ovendry basis) for all 

 species in the area are as follows: 



Timber Foliage plus 



size class Crowns ' Foliage branches < 1/8" 



Inches (Ibs./acre) (Ibs./acre) (Ibs./acre) 



5-9 



4,320 



1,037 



1,296 



9-11 



3,870 



929 



1,161 



11+ 



4,830 



1,333 



1,630 



Total 



13,020 



3,299 



4,087 



A field sample was taken on a 1/10-acre plot 

 near the confluence of Young's Creek and 

 Pack River in a stand of white pine and 

 Douglas-fir appearing typical of timber in that 

 area. All trees were tallied by species and 

 1-inch d.b.h. classes. Crown weights were 

 calculated from relationships between tree 

 d.b.h. and crown weight (4). Dry -weight 

 estimates per acre are as follows: 



A study by Fahnestock (3), relating timber 

 volume to slash weight, provided estimates of 

 the crown fuel. First, average timber volumes 



Species 



White pine 

 Douglas-fir 



Total 



Foliage 

 (Ibs./acre) 

 3,620 

 5,360 



8,980 



Foliage plus 

 branches < 1/8" 



(Ibs./acre) 



3,700 

 6,800 



10,500 



23 



