ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Seed Loss After Dispersal
From the time tree seed reaches the ground in the fall until it germinates the
foll owing spring, many factors (chiefly rodents, birds, invertebrates and diseases)
reduce the number of seed potentially capable of germination. The number of viable
seeds was estimated from seed traps. Seed loss during winter was estimated from 6-
square-foot (0.5 m2) samples of duff and soil taken from surfaces about 10 feet (3 m)
from selected seed traps. These samples were taken in May 1475 at 16 points within
each cutting method and within the control (uncut) areas,
The difference between the number of filled seed found in the seed traps and
those found at the surface represents an estimate of seed loss.
Seedling Establishment
Seed1 ing establishment is influenced not only by the number of seeds that
germinate but by a broad range of biological and phys ical factors affectieg surv
particularly during the first year fol lowing germinat ion.
Establishment of natural regeneration was studied on permanent circular milacre
plots (43.56 ft2, or 4.05 m2, in surface area) within each subblock; the locations of
these plots were chosen to reflect the conditions of the treatment areas in which
they were installed. The center of each plot was located 23 feet (7 m). from each
permanent point at the lower right corner (looking uphill 1 of the 53.82 ft2 (5 m2)
vegetation quadrants. Measurements were made in the summers of 1978 and 1979. In
1979, the sample size was doubled by establishing temporary points 50 feet (15.24 m)
downhill from each permanent point. Seed-seedling ratios were estimated using the
seed trap closest to each natural regeneration plot.
Seeded Plots
In order to identify the probable causes of seedling mortality, plots were
established on each of the seedbed and residue subblocks within all cutting blocks
(fig. 3). Two and four plots were seeded on each of the burned and unburned sub-
block, respectively. These plots were sown with 200 seeds of each of the following
species: western larch, Douglas-fir, Engelmann spruce, subalpine fir, and lodgepol e
pine ( Pinus contorta Doug1 . ex Loua. ) . A1 1 plots were sown from mid- to late-October
for 5 consecutive years (1974 - 1978), except those that were unburned in 1974 on
subunits 1 and 2 of the shelterwood cutting (block 11), shown in fig. 3.
These plots were located and marked as soon as possible after the treatments
were completed--in the fa1 7 of 1974 on unburned seedbeds and in the fa1 1 of 1975 on
burned seedbeds,
The seeds used in this study were collected near the Coram Experimental Forest
in the fall of 1974, in an area of the same habitat type, elevational zone and
aspect as the study area. Extraction and cleaning was done at the Coeur dlA]ene
nursery; chemical repellent coating was not used, so that field germination would be
as similar to that of naturally dispersed seed as possible.