ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

INTRODUCTION
In the early days, the main concern of foresters was how to get the logs out of
the forest. As time went on, they realized the importance of achieving good spacing
and species composition for maximum growth of reproduction, Today, added to these
si 1 vicul tural concerns, is a growing realization of the importance of protecting the
site for future rotations and sustained yields. In the southeast, intensive harvest
for pulp wood is a reality. In the Rocky F~lountains, we are beginning to think about
greater efficiency in the use of energy and resources with each rotation. We are
asking questions like, "How much fiber can we remove from a site before we damage the
ability of a soil to support a comparable forest in the same rotation time?", or
"How frequently can we burn and at what temperatures before irreparable damage is
done?"
Questions like these have been the stimulus of qy research over the past seven
years, This paper will summarize the high1 ights of that research and provide what
answers we have. It is not intended as a survey of the recent literature, but rather
takes some newly formed theories and develops these into useful manaqcrial tools
through the use of extensive field and laboratory measurements.
Three main studies form the basis of this report:
1. Studies of the effects of different intensities of fire on nutrient cycling
on soil derived from quartzitic arqillite at the Lubrecht Experimental Forest near
b?issoula i n western Montana, and nitrient retention by forest soils.
2. Studies of the influence of clearcutting, she1 terwood and group se 1 ect
cutting with 4 levels of slash disposal on andeptic cryoboralfs on the Coram
Experimental Forest near Glacier National Park.
3. The impact of fire and logging on nutrient cycling and soil deteriorat
the Lubrecht Experimental Forest.
A1 1 three areas are covered by ~ouglas-fir and western 1 arch.
THE INFLUENCE OF FIRE ON NUTRIENT CYCLING
ion
ion at
This study began as a simple exploration of the changes in soil chemistry wrought
by different fuel loadings and different burn intensi ties at different times of year.
The forest is at 1,464 m elevation on coarse textured, shallow quartzi tic argill i tes
with low cation exchange capabilities 2.4 - 9 meq/l00 g. The habitat type (Pfister et
-
a1 . 1977) is a north slope maturing PSME/VACA (~seudotsu~a
menziesii/vaccinium
caespitosum) type with relatively steep topography (35-42%), heavy snowfall (1.5 m or
5 feet), and moderate precipitation (466 mm, 18.3 inches). The forest had been undis-
turbed for 70 years (previous logging) and had 2-11 kg/m2 of old rotten residual
fuels.