|Abstract or Summary
- Stocking levels and height growth rates of noble fir and
associated species were measured on 51 clearcut study areas within
the Pacific silver fir zone of the Oregon and Washington Cascades.
Clearcut study areas were approximately 20 years old and had either
planted noble fir or natural regeneration of noble fir from a seed
source adjacent to the clearcut. Study areas occupied a variety of
slope aspects, Inclinations and elevations. Clearcut study areas
were grouped by ecological types (groups of environmentally similar
plant associations) and the regeneration method used to reforest the
Stocking levels were generally high on 1/400 hectare plots
(1/162 acre). The average percent stocking (the ratio of
unstocked versus stocked plots) for naturally regenerated clearcuts
ranged from 71.6 percent on cool-dry sites to 93.3 percent for the
cool-moist ecological types. Planted clearcuts had less variation,
with the average percent stocking ranging from 78.3 to 89.0 pecent
on cool-dry and cool-moist ecological types, respectively.
The stocking density on the Pacific silver fir zone clearcuts
sampled was very high, ranging from 528 to 13,696 trees per hectare. The mean density for all the clearcuts surveyed was 3962
trees per hectare (1604 trees per acre).
The relative stocking by individual tree species was clearly
dominated by noble fir. The relative composition (the proportion of
each species sampled on a clearcut) for noble fir was 44.6 percent
on naturally regenerated clearcuts compared with 39.2 percent for
planted clearcuts. Other species ranged from less than 1 to 21
percent relative composition.
In comparisons with Douglas-fir, noble fir stocking was
significantly greater on naturally regenerated clearcuts at the
south and north extremes of its natural range, the Willamette and
Mount Baker-Snoqualmie National Forests, respectively. The
difference in composition for noble fir and Douglas-fir was
significant on planted clearcuts only on the Gifford Pinchot
Mean height growth for the trees sampled varied little among
tree species and ecological types. Only western hemlock was
significantly less than the other species, and then, only at
locations north of the Columbia River. Noble fir, Douglas-fir and
Pacific silver fir were nearly equal in height growth on all
ecological types for all National Forests. There was however a
trend for height growth to be more on low elevation, warm ecological
types and less on the high elevation, cool-dry ecological types.
The use of broadcast burning for site preparation caused Pacific
silver fir to have lower densities and relative composition than on
clearcuts that had not been broadcast burned. The use of broadcast
burning on severe upper-slope clearcuts, where advance regeneration
Pacific silver fir is present, should probably be restricted.
On clearcuts where adjacent forested stands contain substantial densities of mature noble fir or where noble fir has been planted,
noble fir is able to survive and grow well (greater than 23
centimeters per year) on Pacific silver fir zone clearcuts of the
Oregon and Washington Cascades.
Implications based on the results of this study are that plant
associations may not be good predictors of regeneration stocking and
growth of noble fir and other upper-slope species over large areas.
Predictions may be possible on a more local basis.