Table 4 . --Percent of total fuel volume and surface area 

 comprising the slash, by diameter classes 



Diameter : 

 size class : 



Volume 



: Surface 



area 



Old slash 



: New slash 



: Old slash : 



New slash 



Cm. 



Percent 



Percent 



Percent 



Percent 



0-1 



1 . 



3 . 8 



49.0 



79.4 



1 7 



1-5 



4.4 



7.3 



1 D . u 



o . Z 



3-10 



9.3 



11.7 



11.6 



4.7 



10+ 



85.3 



77.2 



24.4 



7.7 





100.0 



100.0 



100.0 



100.0 



A practical fuel sampling technique is suggested by the observation that most of 

 the slash volume (77 and 85 percent, table 4) was from material over 10 centimeters 

 in diameter. If estimates of slash volume are desired, line intersect sampling of 

 material over 10 centimeters in diameter probably would provide adequate fuel volume 

 estimates. Aerial photographs might provide an effective, relatively inexpensive for- 

 mat for sampling with the line intersect method. 



Loading 



Loadings for the eight blocks examined are shown in the following tabulation: 



Degree of 

 loading 



Highest 



Lowest 



Average 



All material 



(kg./m. 2 ) ( tons /acre ) 



47.3 

 5.1 

 26.5 



211 

 23 

 118 



0-1 cm. -size class 

 (kg./m. 2 ) (tons /acre) 

 5.5 



1.24 

 19 

 .57 



2.6 



Bulk Density 



Bulk density, a measure of tjie porosity of a fuel complex, decreased from the 

 ground up through the slash (figure 3). In the lower 20 centimeters of old slash, bulk 

 density was quite high, averaging 0.10 gram per cubic centimeter. This was due to a 

 large volume of material over 1 centimeter in diameter lying close to the ground. 

 Average bulk densities for the entire depth of slash were as follows: 



Slash age All material Q-l cm. -size class 



(g./cm.^) (g./cm. 3 ) 



Old 0.053 0.00054 



New .030 .00104 



The bulk density of old slash is almost twice that of new slash. This indicates 

 that aging of slash permits compaction even within a few months. In a study of slash 

 from nine conifer species, Fahnestock and Dieterich-^/ found that slash depth was reduced 

 by 20 percent in 1 year and 45 percent within 5 years. Bulk density also would be 

 correspondingly reduced, although to a lesser extent than depth because loading would 

 decrease due to decay, at least over a 5-year period. 



7 G. R. Fahnestock and J. H. Dieterich. Logging slash flammability after five years. 

 USDA Forest Serv. , Intermountain Forest $ Range Exp. Sta. Res. Pap. 70, 15 p., illus. 

 1962. 



7 



