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JUNE JULY AUG SEPT. 



Figui'e 12. — The ether extractive content of Douglas- fir needles 

 during the 1969 fire season. 



Energy Content 



The energy content of fir needles showed the most increase during the fire season, 

 amounting to about 700 B.t,u./lb. in 1968 and 500 B.t.u./lb. in 1969 (figs. 13 and 14). 

 Pine gained 400 and 200 B.t.u./lb. respectively (figs. 15 and 16). Pine showed a de- 

 crease during both years up to August and then an increase; fir generally gained during 

 the summer. Most of this gain in fir was due to an increase in extractive content in 

 1969, while no similar trend occurred in 1968. (H^iff = difference between total energy 

 content, ^x.ot' ^^"^ energy content of the extracted needles, Hgj;-;; . ) The extractives 

 from Douglas-fir and ponderosa pine average about 16,000 B.t.u./lb. with a range of 

 14,000 to 20,000 B.t.u./lb. The increase in energy content of the fir in 1968 was 

 due mainly to the energy change in the extracted needles. These data were not subjected 

 to statistical analysis because the extensive time involved in calorimeter runs resulted 

 in a limited amount of data. Generally speaking, these data show that fir gains in 

 energy during the fire season, while pine decreases from May to August and then gains 

 again. The change in fir is due to the change in extractive content and energy content 

 of the extracted needles. The change in pine is apparently caused by a change in 

 energy content of the extractives themselves, which implies a compositional change. 



11 



