ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Pissodes strobi Peck, In a thinned red-pine, Pinus resinosa Ait., plantation in
Ontario, stumps attacked by fungi appeared to be unsuitable or unattractive to
insects, preventing the encroachment of bark- and wood-feeders (Martin 1965). Brown
rots and carbonizing decays that attack cellulose seem to restrict insect activity,
in contrast to white rots that do not seem to do so (Kimmey and Furniss 1943).
Earlier in this Symposium, Dr. Mike Larsen discussed the relative significance of
brown and white rots in the forest ecosystem. Some insect species parasitized by
fungi ref1 ect other cases of apparent antagonism (Roberts 1973).
Many insect and disease relationships in the forest ecosystem are very benefi-
cial in that they contribute directly to the carbon and nutrient recycling process
in dead plant residues and to the development of forest soil organic layers. Other
Snsect-disease relationships are responsible for mortality and retarding growth in
forest stands, An integrated insect-disease approach is often needed to fully
understand the total forest pest impact (Wickman and Scharpf 1972). An excellent
example of this concerns the need to very carefully consider the impact of dwarf
mistletoe when contemplating partial cutting of lodgepole pine, Pinus contorta var
latifolia Engelm., stands to manage the mountain pine beetle, Dendroctonus ponderosae
.-D. Cole 1978).
INSECTS CREATE RESIDUES AND PREDISPOSE FORESTS TO FIRE
Insects and diseases kill forest trees and create dead plant bodies or residue.
This material may decay, thus contributing to the recycling process by creating a
reservoir both for nitrogen fixation as well as for pest inoculum. Or, these large
accumulations of residues (fuels) may burn violently (fig. 21, consuming all or most
of the residue as well as killing any living trees left in the insect or disease
centers. Such wildfires affect the immediate recycling of nutrients as well as the
removal of the pest inocul urn; however, wi 1 dfi res a1 so increase genetic turnover
because the survival potential of individuals with possible insect and/or disease
resistant genotypes is negated by their increased probability of being burned. An
ecosystem with these insect-disease-fire interactions may preserve endemic insect
and disease activity, perhaps as a means of shortening the turnover time for availa-
bl e genes in 1 ong-1 ived trees.
Figure 2.--In August of 2961, a Zightning ignited wi2d;Fire roared through
28,000 acres of jack-strawed ZodgepoZe pine residue, The trees had
been kiZZed by the mountain pine beetle be-tween 5926 and 1938 on the
Bitterroot and adjacent Na-tConaZ Forests in western Montana.