C. Fire – Bark Beetle Interactions
The effects of fire and bark beetles are not independent of each other. Lodgepole trees which survive fire seem very susceptible to bark beetles, perhaps capable of triggering an epidemic. Trees killed by bark beetles quickly become fuel to support more intense fires Fire allows another generation of lodgepole pine, which can eventually support more beetles. In contrast, beetle kill of lodgepole in seral forests opens the canopy and thus accelerates growth of the fir and hemlock and the transition to the more fire-proof fir-hemlock forest. The long term effect of beetles thus may be to decrease chance of fire earlier than otherwise, if the stage of high fuel loads passes without fire.
In many northern Rocky Mountain forests, fire suppression led to abnormally large areas of old lodgepole pine with resulting massive beetle kills, much larger than would have occurred in the primeval condition. At Crater Lake, some seral forests have recently reached the size of susceptibility to beetles; recycling them to new, beetle-proof stands with controlled fire might seem a logical thing to do. However, this appears NOT to be appropriate. Many of these stands were converted from fir-hemlock to lodgepole by fires caused by white man and a return to primeval conditions requires some area of lodgepole forest be allowed to revert to fir-hemlock. Furthermore, controlled burning in lodgepole reduces fuel loads only temporarily, since the overstory is usually killed, producing extremely high ground fuels as the debris falls, and probably requiring a reburn for safety. In the resulting lodgepole stand, fire danger and beetle susceptibility eventually will be high again. Thus, a general program of controlled burning in seral stands is ruled out by (1) the policy to return to primeval forest, which requires conversion of some lodgepole forest to fir-hemlock, and (2) long-range safety considerations, i.e., allowing stands to develop naturally to fir-hemlock and thus reducing the fire danger permanently at no management cost. A present period of widespread beetle kills and the resultant high fire danger appear to be the price of a return toward primeval conditions in several of the seral communities.
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