100 



80 







Douglas-fir 



(Pseudotsuga menziesii) 























Green Fire Insect Unknown mortality 



Stand Composition (present) 



Figure 2 — Alive (green) and dead Douglas-fir 

 by cause of mortality. 



Most infestation was by the Douglas-fir beetle. Addi- 

 tional mortality, especially of small diameter trees, 

 was caused by Pseudohylesinus nebulosus LeConte 

 and wood borers. 



These data show that almost one-third of the Dou- 

 glas-fir that were green and considered alive following 

 the 1988 fires died from delayed effects of fire or in- 

 sect infestation. Where mortality is evenly distributed, 

 the fire-killed and green Douglas-fir mosaics appear 

 slightly affected. However, where mortality is con- 

 centrated, drastic altering of the mosaic is apparent. 



On the other hand, lodgepole pine mortality con- 

 sisted of 51.6 percent of the 4,758 sampled trees. This 

 breaks down to 30.5 percent due to fire injury, 17.9 

 percent due to insects, and 3.2 percent to unidentified 

 causes (fig. 3). All trees retaining green foliage after 

 the 1988 fires may be considered survivors of the fires. 



However, even though they still had green foliage, 

 green phloem, and appeared alive, almost two-thirds 

 of the lodgepole that subsequently faded had been com- 

 pletely girdled by light ground fires. Many of these 

 trees' deaths from fire injury were not apparent even 

 3 to 4 years after the fires, and quite often not until 

 the lodgepole were infested by the pine engraver dps 

 pini [Say]) or the twig beetles, Pityophthorous confer- 

 tus Swaine and Pityogenes knecteli Swaine, did rapid 

 fading occur. Of all the lodgepole pine that died from 

 all causes, including fire injury, 44 percent were in- 

 fested by the pine engraver. Mountain pine beetle, 

 Dendroctonus ponderosae Hopkins, infested only 0.8 

 percent of the lodgepole. 



In this data set, and as observed by others (Blackman 

 1931; Hopkins 1905), mountain pine beetle is not 

 strongly attracted to fire-injured trees. In addition 

 to the stress of fire injury, trees had been subjected 

 to drought for several years. These stress factors 

 did not significantly increase nor precipitate an out- 

 break of mountain pine beetles, which again points 

 to uniqueness in terms of lack of response to stress 

 factors that are commonly associated with Douglas- 

 fir beetle and pine engraver infestations. 



Mortality of Engelmann spruce totaled 41 percent 

 of the 439 trees in the sample: 31.9 percent were 

 killed by fire injury, 6.6 by insects, and 2.5 percent 

 died from unidentified factors (fig. 4). Spruce beetle 

 (Dendroctonus rufipennis [Kirby]) killed almost one- 

 half of the spruce killed by insects. Other insects that 

 caused spruce death were Ips pilifrons Swaine and 

 wood borers of families Buprestidae and Cerambyci- 

 dae. The high loss of spruce to fire injury is related 

 to thin bark, which causes them to be easily killed 

 by fire. 



Subalpine fir had 37.3 percent survival of the 134 

 trees in our sample. Most mortality was attributed 



Lodgepole pine 



(Pinus contort a) 



.t—y-) 



Green Fire Insect Unknown mortality 



Stand Composition (present) 



Figure 3 — Alive (green) and dead lodgepole 

 pine by cause of mortality. 



Green 



Fire Insect Unknown mortality 



Stand Composition (present) 



Figure 4 — Alive (green) and dead Engelmann 

 spruce by cause of mortality. 



4 



