ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

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Habitat Manipulation
Small mammals have evolved with the communities that they inhabit (Bendell 1974).
Mutual compatibility is a result of this evolution. Disruptions such as fire or
logging may cause serious imbalances (Tevis 1956b): some animal populations may be
eliminated, new species may invade, some species will greatly increase in numbers.
Fires or logging may initiate an early successional stage as a disclimax. This
may be perpetuated by recurrent fire, unusual ly high rodent populations, heavy grazing
by large mammals, or edaphic factors. Special consideration, including a1 ternative
harvesting methods, should be given to situations with this potential.
To reduce impacts on forest regeneration, small mammal control is best imple-
mented by not creating suitable habitat for potentially destructive specie^.^
Consideration should be given to the kind of habitat created by different treatments
and the proximity of logging to potentially colonizing populations. For example,
pocket gophers invade and multiply in clearcuts where they damage and destroy tree
seedlings. Retention of 500-foot wide buffer strips in lodgepole pine forests has
been suggested to a1 leviate this situation. Another a1 ternative for discouraging
pocket gopher populations, is partial cutting to maintain partial shade and minimal
soil disturbance (Barnes 1974).
Golden-mantl ed ground squirrel s are considered a threat to reforestation because
of their seed-eating habits. Historically, in northwestern California, these
squirrels occurred only in open granite outcroppings and avoided the virgin Douglasfir
(~seudotsu~a -baxifoZia) and white fir (~bies concolor) forests. After the
initiation of harvest programs, golden-mantled ground squirrels spread from these
isolated areas through virgin forest into clearcuts 2-1/2 miles distant (Tevis 1956a).
In areas where a1 1 vegetation has been removed by clearcutting and burning, as
much as 100 percent of on-site conifer seeds have been consumed by wildlife
(Tevis 1956~). Halvorson (In Press), Tevis (1956c), and Sullivan (1979) have sug-
gested that leaving some patches of unburned vegetation would provide alternate food
sources and might reduce seed depredation. Unburned patches allow more species of
small mammals to survive the fire, but there is also a wider variety of food remaining
to buffer the effect of seed consumption.
The effectiveness of aerial seeding in northern Montana was improved by delaying
seeding until snow was on the ground. This made the seed unavailable to rodents
until spring when small mammal populations are at a seasonal low. Seed was also
unavailable to birds because it penetrated into the snow. Germination occurred in the
spring after snow me1 t, thereby reducing the time the seed was exposed to
depredation.
If wildlife habitat is a major consideration in forest management, priority
should be given to the creation of a vegetative mosaic of species composition and
vegetative structure. Benefits of a vegetative mosaic include:
a) Variety of food and
b) Edge effects.
2Personal Communication; W i
Office, Missoula, Mont.
9 Personal Communication: G.
cover.
11 iam Beaufai t, USDA Forest Service, Regiona
Wilson.