ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

One of the most efficient methods of harvesting mature or overmature lodgepole
pine and regenerating the new forest is clearcutting, followed by the disposal
of logging residue, and then by natural or artificial seeding, or planting.
Most commercial lodgepole pine forests earmarked for timber production do not
respond well to partial cutting. One reason is the intolerance of young lodge-
pole pine to shade; another is damage of new forest growth by dwarf mistletoe
infection from remaining overstory trees.
In clearcut forests, the soil and vegetative characteristics that influence
the hydrologic stability of the forest floor can be altered drastically,
especially if logging residue is piled and burned. One immediate effect of
this treatment is the baring of soil surfaces between windrows of residue, there-
by making these surfaces vulnerable to the impacts of water erosion.
Results of a recent study on eight harvest units and four unlogged units
of a larch/Douglas fir forest in western Montana show that tractor logging
produces changes in soil and vegetative characteristics that improve the hydro-
logy and soil stability of the forest floor. The study also shows that
broadcast burning of the logging residue exerted effects on these soil and
vegetative characteri sti cs that are detrimental for runoff and erosion control .
However, the moderate degree of runoff and soil erosion hazard and its brief
duration indicates that this treatment is probably not permanently damaging to
these watersheds (Packer and W i 11 iams, 1976).
The extent to which these conclusions apply where lodgepole pine forests
on similar (gently sloping) terrain are clearcut and the logging residue is
either piled and burned, broadcast burned, chipped and respread on site, or
chipped and hauled away, is not known and needs investigation. This paper
describes the immediate, two-year and four-year effects of these residue
disposal treatments on lodgepole pine forest watersheds in western Wyoming.
STUDY AREA AND METHODS
In the summer and autumn of 1971 , four 20-acre tracts of lodgepole pine in
the Union Pass area of the Bridger-Teton National Forest were clearcut. Each of
these tracts was divided into four 5-acre blocks and different logging residue
disposal treatments were applied. On two of the tracts half of the logging
residue was disposed of by dozer-piling into windrows that were burned. The
other half of the residue was broadcast-burned. Logging residue on the other two
tracts was chipped. The chips were respread uniformly on the forest floor on
half of the blocks in these two tracts and removed completely from the other half.
Although the harvesting of timber from these tracts was completed in the fall
of 1971, the windrowed residue was not burned until the fall of 1972 and the
broadcast residue was not burned until the summer of 1973. The chips were spread
on the blocks designated for that treatment in early summer of 1973. Lodgepole
pine planting and seeding was completed by July 1973.
Three sets of 60 rainfall-simulating infil trometer plots were established
on the study areas, one set each in 1973, 1975, and 1977. Within each set of
plots, 48 were located on the four clearcut tracts and 12 in adjacent unlogged
forest. Twelve of the 48 plots on the clearcut tracts were located on each tract,
three on each of the four blocks comprising each tract. This study design
facilitated evaluation of the effects of the different logging residue disposal
treatments on soil and vegetal characteristics, overland flow and soil stability