| Abstract |
- The effects of six alternative site preparation
treatments were compared at three different sites in
southcentral Oregon. Treatments included a logged-only
control, ripping, brushblading, disking, chemical, and
chemical followed by disking. Subplots containing
ponderosa pine bareroot (2+0) and containerized (1+0)
and lodgepole pine containerized (1+0) seedlings were
also included in the experiment.
The study involved the remeasurement of the plots
eight growing seasons after establishment. The
treatments were evaluated based on changes in selected
soil chemical and physical properties, the response of
non-conifer vegetation, and the survival and growth of
the planted pines.
Soil samples were analyzed for total N, total S,
total C, and extractable phosphorus. Bulk density was
also determined for each sample. In general, the
brushblade and chemical/disk treatments caused the
greatest reduction in nutrient levels and the greatest
increase in bulk density compared to the control arid
other treatments.
The greatest differences in the amount of non-conifer
vegetation among site preparation treatments
were observed at the low elevation site (East Aspen),
which supported an established shrub community prior to
treatment. Total aboveground biomass of shrubs was
highest on the control plot. Ripping had the second
highest shrub biomass, followed by the disk, brushblade,
chemical, and chemical/disk treatments. Plant
communities at the higher elevation sites (Swede Cabin
and Camp Nine) were primarily composed of grass, sedge,
and forb species with scattered shrubs. In general, the
control and rip plots had the highest canopy coverage of
herbaceous vegetation at these sites, followed by the
brushblade, disk, chemical/disk, and chemical
treatments.
Pine survival was satisfactory for all treatments
except the rip and control plots at East Aspen and Swede
Cabin. Survival was low for all treatments at Camp Nine. The greatest differences in conifer height growth
among site preparation treatments occurred at East
Aspen. At this site, the chemical/disk and chemical
treatments resulted in a substantial increase in height
growth compared to the control. Disking, brushblading,
and ripping also increased height growth, but to a
lesser extent. All of the treatments except ripping
were equally effective at Swede Cabin in increasing
height growth compared to the control. At Camp Nine,
the effect of treatments with respect to height growth
was the same as that at East Aspen, although the
magnitude of the differences was less.
The results of this study indicate the importance
of controlling competing vegetation in order to achieve
maximum survival and early growth of planted pines in
southcentral Oregon.
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