An understanding of the energy levels is essential to the quantitative study of 

 combustion in wildland fuels and the definition of such fundamental variables as fuel 

 energy, fire intensity, combustion rate, and heat yield. Byram (Davis 1959) emphasized 

 this point by stating that, "The energy which maintains the chain reaction of combustion 

 is the heat of corabustion--a quantity which can be measured for any particular fuel." 



Heat content values have been reported for a wide variety of wood fuels , but 

 energy studies of lesser vegetation have probably received most attention from ecol- 

 ogists interested in the application of caloric values to the energy relationships of 

 ecosystems (Long 1934; Golley 1961; Bliss 1962). Golley (1961) concluded that prior 

 to making intensive measurements of energy flow the heat contents must be determined 

 under the specific conditions of a particular study because of variability of plant 

 material. His examination of more than 600 records of plants indicated that significant 

 differences in heat content exist between plant parts, between vegetation collected in 

 different months, and between vegetation growing in different ecological communities. 

 Bliss (1962) found that heat content values for the anatomical parts of evergreen shrubs 

 exceeded those for deciduous shrubs in nearly all cases; however, a significant differ- 

 ence was not established. Amiot (1959) found that the heat of combustion of litter 

 samples differed considerably by forest type; the more coniferous trees the stand 

 contained, the higher was the heat of combustion of its litter. Variations in heat 

 content by needle age, elevation, and season of year were determined for five coniferous 

 species at the Priest River Experimental Forest in Idaho during 1962 and 1963 prior to 

 this current study (table 1) . Hough (1969) recently determined the energy values of 

 some forest fuels from the southern United States. 



Table l.--B'eat content (B.t.n./lb.J of coniferous needles, stratified by needle 

 age and elevation, collected at Priest River Exueriviental Forest 

 in Idaho, itovernber 1962 and June 1953 



Species 



November 



1963 



June 



1963 













Ponderosa pine 



:,30o ft. 



2,620 ft. 



2,300 ft. 



2,620 ft. 













New 



8,268±3 



8,691±S 



8,419±51 



8,486+12 



1 year 



S,598±12 



8,73S±4 



8,706±28 



8,885+10 



2 year 



1-- 



S,639±22 



8 572+83 



S,S62±28 



5 year 









S, 806116 



Dead ground 



8,747±21 



S,S56±23 



8,677±11 



8,627+15 



Western uhite pine 



2,240 ft. 



2,500 ft. 



2,240 ft. 



2,500 ft. 



NeK 



8,687±9 



8,676±11 



8,325+10 



S,402±2'2 



1 year 



S,799±4 



S,67S±23 



S,743±19 



8 ,553133 



2 year 





S,752±15 



S, 803120 



8, 568141 



5 year 









8.593117 



Dead ground 









and/or tree 



S,752±15 



S,678±15 



S,S40±14.2 



8,446+19 



Lodgepole pine 



2,300 ft. 



5,040 ft. 



2.300 ft. 



5,040 ft. 



New 



S, 709x11 



S , S55±5 



8,48614 



8,544110 



1 year 





S,972±2S 



8,71218 



8,927118 



2 year 



8,962+11 



9,057+12 



8.799114 



8,963+34 



3 year 





9,113±1S 



S.S46+1S 



9,037134 



4 year 





9,186±27 





9,083+10 



Dead ground 



8,S61±9 









Grand fir 



2,240 ft. 



3,900 ft. 



2,240 ft. 



3,900 ft. 



Current 



8,394±11 



8,793+16 



8,612+11 



8.510128 



Western larch 



2,300 ft. 



3,900 ft. 



2.240 ft. 



3,900 ft. 



Current 



S,01S±27 



S,0S2±2- 



7,961+7 



",90419 



Dash indicates no needles collected in that age group. 



'^R. W. Mutch. Caloric content in coniferous needles, (Unpublished office report 

 USDA Forest Serv. , on file at Intermountain Forest and Range Exp. Sta. , Northern Forest 

 Fire Lab., Missoula, Mont.). 1963. 



2 



