ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

MANAGEMENT IMPLICATIONS
The combined effects of residue management practices and harvesting systems in
coniferous forests not only directly influence forest floor macrofauna, but a1 so
indirectly by modifying the environment in which these qnd other important forest
insects live. The difficulties of analyzing treatment effect have been surmarized by
Huhta (1971) as follows:
Catastrophes in an ecosystem, such as deforestation or burning,
alter nearly every environmental factor, biotic or abiotic,
interacting in such a complex way that it is very difficult to
distinguish the factors which principally account for the
changes in the animal communities. To discover the primary
causes of the changes in the population densities of the dif-
ferent species or of the successional trends of the whole
community, accurate information would have to be acquired about
the habits and responses of each component species to each
factor at the different stages of their life cycles, together
with detailed long-term microclimatic records not only in the
habitat in general, but a1 so separately in the particular
microhabitat of each species.
Such detailed studies were beyond the scope of the investigation reported in this
paper.
Intense removal of fiber, especially in clearcuts, seems to significantly
reduce the populations of some taxa, particularly two and three seasons after har-
vesting and residue removal, but we cannot now predict the complete significance of
this reduction because so many groups are involved, and we have only determined the
taxa involved to groups at the family level or above. Groups involved are those
responsible for the mechanical degradation of residues and for providing entry
courts for decay micro-organi sms. Other groups are phytophagous, feeding on seeds
and other plant tissues and others are very effective predators. Further compl i-
cating the complete interpretation of the treatment imp1 ications is a general lack
of information on food chains, interorganism relationships and the biology and
ecology of the species involved. Other investigators have reported that 100 percent
tree removal and residue util ization ul tirnately leads to impoverishment of sites
(Moore and Norris 1974). In Europe, some stands with a history of repeated removal
of litter from clearcuts have been observed to be either chronically infested with
forest pests or predisposed to recurrent mass infestations (Francke-Grosmann 1963).
Some investigators have reported that the most important factor Snfluencing
succession of fauna in clearcut areas is whether the felling residues are left on
the site or removed (Huhta and others 1967).
Prescribed burning of residues, particularly in clearcuts, also severely impacts
many groups of forest floor fauna by directly killing the organisms as well as
removing the residues and forest litter required by these insects for f~od and
she1 ter, In other coniferous forests "burning over" of resfdues is very destructive
to all groups of forest floor arthrop~ds because of the heat produced and the bulk
of some populations may be destroyed (Huhta and others 1967). Some anfmals, depending
on litter for food, have become "extinct" in burned over areas once litter remaining
after burning had decomposed (Huhta and others 1967). Other investigators rep~rt
that with the exception of mesofaunal species and spiders, population reductions do