ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Cottontail (~~ZviZagus spp. ) populations may increase in cl earcuts where there
dense tree regeneration or shrubby and herbaceous undergrowth. Windrowing slash
benefits this species (costa and others 1976).
Snowshoe hare (~epus amertkanus) and porcupine (~rethizon dorsatwn) reoccupy
logqed areas after the establishment of shrubs and sap1 ings needed for food and cover.
EFFECTS OF HARVESTING METHODS : CLEARCUT VS. PARTIAL CUT
Clearcuts and partial cuts both result in an increase of light and available
moisture, with the resul tant re1 ease of understory vegetation. The major difference
is that habitat modification in a clearcut is more extreme than in a partial cut.
Extreme habitat modification results in the displacement of some species and unusual
increases in numbers of other species. For example, although tree squirrels are dis-
placed from cl earcuts, ground squirrels and pocket gophers, which prefer open areas
and scarified soil, increase is cl earcuts (Barnes 1974).
The impacts of microtines and deer mice on forest regeneration are-not as siqnifi-
cant on partial cuts as on clearcuts. Generally, habitat changes are less dramatic on
partial cuts than on clearcuts. The results are less pronounced changes in small
mammal populations. Figure 2 shows the small mammal species that may be found after
different harvesting and residue treatments.
EFFECTS OF RESIDUE TREATMENTS
Broadcast Burns
Broadcast burns may result in the nearly complete removal of living vegetat ion
and a scattering of unburned slash. Under the ashes are roots, corms, bulbs, rh i zomes ,
dormant seeds, and spores. Many of these sprout immediately, stimulated by fire 3
increased light, moisture, nutrients, and the lack of competition.
Most burrowing small mammals survive a fire due to the insulation of the soil, if
their burrows are sufficiently ventilated. In a Montana study, subsurface temperatures
at 2 inches were 118°F (48'C) in spite of 500°F (260°C) soil surface temperatures
(Halvorson in press). Howard and others (1959) found subsurface temperatures of
140°F (60°C) to be lethal to caged rodents buried beneath a chapparal fire. In
. unventilated burrows or where the relative humidity was above 50 percent, death
occurred around 1 20°F (49'C) (~awrence 1966).
Species 1 iving above ground may escape by fleeing (Komarek 1969). However, large
and small mammals and birds, are sometimes killed by a hot, fast-moving fire
(Kipp 1941). A burn is reoccupied soon after the ash settles if species habitat
requirements are met (Tevis 1956d). Other animals may remain in adjacent unburned
areas, where as newcomers they are more vulnerable to predation than the resident small
mammals (Metzgar 1967). Where fire has removed a1 l ground cover, deer mice are
usually the only species that will become immediately established in si nificant
numbers. Other species will return as vegetation becomes established. Dimock 1974,
Tevi s lgS6d).
Incompletely burned residue in broadcast burns usually provides a better distri-
bution of cover than concentrated incomplete burning of piled slash. Chipmunks and
golden-mantled ground squirrels benefit from this distribution of slash.
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