ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

The use of prescribed fire to disrupt normal succession patterns and control
understory vegetation (Martin and others 1977) often has beneficial effects on
forest insects, such as described above, with Ips problems in pine and aspen stands
in the southeast. The use of fire in itself, besides reducing shrubs and herbaceous
plants to increase tree growth (Martin and others 1977), has serious impl ications
for forest insects. Fire exclusion could influence the incidence of parasitism in
some cases by a1 tering the species composition of flowering and frui t-bearing
ground cover which is important as as food source for adult parasitoids, such as
the ichneumonids. In other cases, fire exclusion could infl uence cone-seed or
other "harmful" insects that spend part of their life cycle in the litter (Kickert
and others 1976).
SOME MANAGEMENT IMPLICATIONS
Throughout this paper, I have described some of the interactions and relation-
ships between harvesting, forest residues and fire management, and forest insects
(to a lesser extent, diseases), particularly in the northern Rocky Mountains. 1
also have selected and described some classic, or at least representative, examples
of some of these interactions. I w ill discuss three management impl ications of
these varied interactions: mqnagement of forest residues, fire management, and
si lvicul tural 'practices.
Management of Forest Residues
From the dl SCU ssions above, it is apparent that forest residues constitute a
habitat, substrate, and food for a wide variety of insect species-some "harmful",
and some "beneficial "-as well as for a variety of decay organisms, many symbiotically
associated with one or more insect species. In the northern Rocky Mountains and
el sewhere, there are management impl ications associated with both natural and man-
made residues that involve what we may call "harmful" insects.
NATURALLY CREATED RESIDUES
At least four significant natural factors create residues in the northern
Rockies--insects, windthrow, fire, and diseases. f will discuss the first three,
Residues Created by Insects
Without a doubt, at this time the most serious and far-reaching management
problem attributable to insect-created forest residues concerns the mi 11 ions of
dead lodgepole pine (standing and prone). killed by the mountain pine beetle.