ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

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Different i nvesti gators have used several systems to categorize the arthropods
in the forest floor and forest soil. In the following discussion, I will refer to
those invertebrqtes that inhabit and move about in the forest litter as forest
floor macrofauna, (surface arthropods) and to those that are generally smaller,
less mobile, and occupy the humus and forest soil, as forest soil mesofauna.
Forest Floor Mqcrofauna
Many studies have been made throughout the United States concerning the impact
of harvesting, residue management, and fire on forest floor macrofauna. Some of
these studies were concerned with the effects of mqcrofauna on direct seeding.
Though not designed to determine effects of residue and fire management, results of
these studies could have implications in the management of residues and prescribed
fire; the studies will be reviewed here.
RESEARCH IN THE NORTHERN ROCKY MOUNTAINS
In the northern Rocky Mountains three studies in the past 10 years haye focused
on the effects of forest residue and prescribed fire management or wildfire on
forest floor macrofauna (Fell in and Kennedy 1912; Clayton 1975; and Fell in 1980b).
These three studies were preceded by, and related to, several studies involving
forest floor macrofauna and direct seeding and planting.
Tn the northern Rockies, most evidence that insects are involved in direct or
indirect seeding efforts has been circumstantial (Kennedy and Fell in 1969). Wahl enberg
(1925) surnmqrized the results of ast direct-seedlng projects in the northern
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Rocky Mountain region and qttri buted t e death of an undetermined number of western
white pine seed]i>ngs to cutworm larvae. Haig (19361, and Haig and others (1941)
noted that soi 1 insects, chiefly cutworm (Noctuidae=Phal aenidae) 1 arvae, were one
of the most impoytqnt direct agents of conifer seedling mortality in the western
white pine type in northern Idaho. Schopmeyer (19391, and Schopmeyer and Helmers
(1947), determined thqt either cutting or clipping were the major kinds of injury
to direct-seeded western white pine during the first growing season. They observed
several foms of cutting in both screened spots and unscreened sp~ts; they speculated
that "cutworms, grasshoppers, and other insects may have had a part" in causing the
damage.
Fell in and Kennedy (1 972) studied the abundance of some arthrop~ds inhabiting
the forest floor in three clearcut areas that were prescribed burned in 1960, 1961,
and 1962, in north-central Idaho. Generally, they found more arthropods present
and more tax4 represented an the older burns, and attributed this greater relative
abundance of individual s to movement from adjacent unburned forests, and re opul ation
from ZU~Y~YOP~ wlthin the burned areas. The most abundant arthropod in soir samples
on the oldest burn was the carabid, Amara erratica (Sturm). A projection based on
swnple dqta from the 1960 burn indicatedthere could have been up to 100 cqrabids
per squsre yard (0.836m2) of soil surface. Because of the abundance of this carabid
--and its seed-eating behavior-and because of one or more species of grasshoppers
and cutworms, Kennedy and Fellin (1969) recommended that direct seeding of western
white pine and perhaps other conifers be done the first or sec~nd season after
prescribed burning.