ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

While providing a desirable environment both for forest regeneration, and for
many forest animals, fires also influence other forest flora and fauna, and fire
variabil ity makes general izations concerning flre effects difficult (Lyon and
others 1978). However, fires not only affect the flora and fauna within deteriora-
ting residues, but also the habitat of the fauna that utilize the forest floor and
the upper layers of mineral soil by altering the environment and food supply on and
in the ground. Generally, invertebrates, often "undesirables," decrease in number
following a burn (Reichert and Reeder 19721, usually because the animals or their
eggs are killed by flame or heat, and their food supply and she1 ter are diminished.
The effects of fire on invertebrate populations may be transitory or long lasting,
as well as selective and varying among species; in some cases burning also destroys
natural predators of pest species. Analyzing the effect of residue management and
prescribed fire on forest floor and soil invertebrates is compl icated by the fact
that we still do not always know which are our friends and which are our enemies.
Most of the organisms that 1 ive in forest residues, the forest floor, and
forest soil, are decidedly beneficial. The species and groups involved include not
only natural enemies of pests, but also organisms that decompose residues. The
series of events in the decomposition and fragmentation of residues is initiated by
several species of beetles that loosen the bark on the resfdues as well as introduce
wood-decaying fungi. As described by Mi tchel 1 and Sartwel 1 (1 9741.3
"This is followed by a progression of other arthropods, each contributing
to the fragmentation of the material (Wickman 1965; Elton
1966). Following bark beetles are wood borers such as ambrosia
beet1 es (Scolytidae), fl at-and round- headed borers (Buprestidae and
Cerambycidae) , term1 tes (.Isoptera), horntai 1 s (Siricidae) , carpenter
bees (Apidae)., and carpenter ants (~ormicidae) . These insects bore
holes deep into the wo~d and a1 so introduce wood-destroying fungi
(Boyce 1923, Shea and Johnson 1962, Wright and others 1956, Wright
and Hqrvey 1967, Kimey and Furniss 19431."
Although decomposition itself is largely a microbial process, fragmentation of the
material is largely an arthropod process. This fragmentation may increase the area
of residues exposed to microblal activity by up to 15 times compared to unfrag-
mented residues ( WStkamp lgJl)-. Moreover, the fecal material produced by these
species of arthropod "fragmenters" encourages the growth of decomposing microbes,
particularly bacteria (Crossley 19701.
Following the arthropod "fragmenters" , forest floor and forest soil mesofauna
(intermediate-sized organisms) are the next arthro od group in the decomposition
process; most are vqrious species of mites and Col r embola wtth a wide variety of
feeding habits. Mqny are saprophytes that feed on bacteria, fungal hypae, or
other living plsnts or animals. Although they do not directly contribute to chemical
decomposition of 1 itter nor to the turnover of plant nutrients, they play a mafor
role in the rocess by breaking organic tissue Snto smaller pieces. The smaller
these partic ! es become, the more susceptible they are to action by other organisms,
such as bacteria, and fungi, involved directly In the decomposition process (Metz
and Farrier 1971 1.
"Harmful" forest floor or forest soil fauna can ~nly
be categorized as such
insofar as they act or feed in a way that is in competition with, or counter to,
what man wants out of the resource. For the most part, harmful insects include
those that feed on seeds, seedlings, or sprouts of desirable coniferous and broad
1 eaf species.