ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

PREFACE
In the early 1970'~~ the Forest Residues Research and Development Program of the
Intermountain Forest and Range Experiment Station began a 5-year study to evaluate
the environmental consequences of the combined effects of silvicultural systems,
harvesting, and residue disposal a1 ternatives in western larch-Douglas-fir stands.
As part of that Program several studies involving a variety of disciplines were
conducted, i ncl uding two entomological studies invol ving two groups of forest insects.
The results of one study are presented in this paper (Fellin 1980b).
The objective of this study was to determine and evaluate the combined effects
of harvesting methods, sil vicul tural prescriptions, and forest residue management,
including prescribed fire on the fauna of the forest floor. This study is restricted
to those soil surface or forest floor arthropods often categorized as macrofauna
(Ah1 gren 1974). This group consists of the larger arthropods--beet1 es ants, centi -
pedes, millipedes, spiders, etc.--usually greater than 10 mn in size lwagner and
others 1977). Fichter (1941) defines soil surface fauna as "populations composed of
those species which travel, for the most part, over the surface of the ground, and
though closely associated with the 1 itter as material for abode, constitute, when
active (not resting, hiding or hibernating), a distinct society."
Reported elsewhere in this proceedings (Fell in 1980~) are the partial results of
the other entomological study that was concerned with the effect of harvesting and
residue management practices on forest sol 1 arthropods such as mites and coll embol a,
intermediate-sized organisms often referred to as mesofauna (Metz and Farrier 1971 ) .
This proceedings also offers a review of some relationshi s of harvesting,
residue management and fire to forest insects and diseases (Fe f l in 1980a). The
review paper summarizes the past and current research concerning the effects of
forest practices on both forest floor macrofauna and forest floor mesofauna.
INTRODUCTION
Sivilcultural practices modify forests by removing all or part of both the
coniferous overstory and the understory. Management of the resul tant residues,
including prescribed fire, modifies the forest floor and forest soil component by
removing or destroying both man-generated residues as well as natural forest residues,
often eliminating or seriously influencing the litter and decomposition layers of the
forest floor. Sil vicul tural and residue management practices a1 so dramatically affect
macro- and micro-meteorological conditions and in turn nearly all flora and fauna,
either by killing some plants and animals or by a1 tering the environment, thus modi-
fying the behavior of organisms.
The ecological consequences of a1 1 types of cuttings--especial ly clearcutting-
are incompletely understood and are the subject of increased attention and debate,
Cl earcutting has been the si 1 vicul tural practice most widely employed in c~niferous
forests of the northern Rocky Mountains.
In managed coniferous forests in the northern Rocky Mountains, studies aye under
way to determine the effects of harvesting and silvicultural practices on the two
most widespread and destructive insect species, the western spruce budworm and the