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Restoration Ecology of Coastal Riparian
Areas: An Applied Approach
Adaptive Cope Team 1
INTRODUCTION
Riparian areas of the Oregon Coast Range are largely
dominated by red alder (Alnus rubra) following historic logging
or fire distmbance. Conifers are often excluded from these sites
due to the competitive nature of the alder.
Latge woody debris from conifeo; is an important component
in the stream ecosystem, affecting flows of water, nutrients and
fisheries habitat. Downed conifers have a long life once they
fall to the forest floor. Alder by contrast is short-lived both as
an upright tree and as a downed log.
In order to provide a continuous source of conifer debris over
time, conifers must be established within the present
alder-dominated site.
.
Astoria
t
Underplanting
Study Sltas
Newport
OBJECTIVES
Eugene
Determine which treatment or combination of treatments
results in:
• Highest conifer swvival by species
• Highest conifer seedling growth by species
*
METHODS
Six alder-dominated riparian sites throughout the Oregon
Coast Range (Figure 1) were subjected to overstory and
understory treatments, and seedlings of four conifer species were
planted under the alder canopies. At each site, three overstory
treatment plots (0.2 ha) were established: a control, partial
overstory removal, and total overstory removal (Figure 2). Each
overstory treatment contains an understory control and complete
understory removal plots. Four conifer species (western
redcedar, western hemlock, Douglas-fir, and grand fir) were
underplanted at 2m X 2m spacing, with every other seedling
tubed against browsers. Seedling height and diameter has been
monitored at the end of each growing season
1
Gold
Beach
Figure 1. - Study sites for riparian underplanting project in
coastal Oregon.
College of Forestry, Oregon State University, Newport, Oregon.
297
treatments than in the control, but height growth in the total and
partial overstory treatments were not significantly different from
each other. Mean height growth of western hemlock was
significantly (p<.05) higher than all other species. Douglas-fir
height growth was not different than grand fIT, but was
significantly (p<.05) greater than western redcedar.
BLOCK (SITE)
Overatory Treatment-Control
SUMMARY
Treatment
Treatment
COntrol
Total Removal
OF OF WH WAC
Though the results of this experiment are preliminaIy, some
early trends are i~enti:fied. With partial or no overstory removal,
understory manipulation is important to the swvival of all
species with the exception of western redcedar. With total
overstory removal, understory manipulation appears important
to Douglas-fIT swvival in particular.
Total or partial overstory manipulation resulted in greater
seedling height growth. Western hemlock outperfonned all other
species over all treatments f9r height growth. Tubed seedlings
grew taller than non-tubed seedlings.
OF OF WH WRC
Ovarstary Treetmant·PartIaI Removal
UnderItory
Understory
Treatment
Treatment
Control
Total Removal
DF GF WH WRC
UndemoIy
understory
Traetmant
Traatment
Control
Total Removal
OF GF WH WRC
CONCLUSIONS
OF GF WH WRC
This study is beginning to answer questions concerning the
establishment of conifer seedlings in riparian areas when light
is the limiting resource. The results presented here represent
initial response to treatments in the flfSt two years. The study
will be monitored for a total of six years. This applied research
project compliments many fundamental riparian research
projects administered by the COPE program, including studies
of vegetation dynamics, hydrology, and fisheries and wildlife
research.
OF GF WH WRC
This research is cooperatively funded by:
Figure 2. - Experimental design for underplanting study, showing
the overstory, understory. and species treatments at each
site (block). Underplanted conifers were DF=Douglas fir,
GF=grand fir. WH=western hemlock. WRC=western
redcedar.
RESULTS
• Oregon State University
• Coastal Oregon Productivity
Enhancement
• (COPE) Program
• Other State and Federal
Agencies
• The Forest Industry
• County Governments
• Oregon Small Woodlands
Association
Swvival by species over all sites and treatments was quite
variable, but some overall trends are apparent after two years
(Figure 3). Western redcedar had high swvival on most sites
relative to the other species, however some decline in swvival
was seen by the end of the second year. With partial or no
overstory removal, understory manipulation appears to be a key
factor in SUIVival of all species except western redcedar.
Height growth increment for seedlings was significantly
affected by the overstory treatment (p<.Ol), species (p<.OOOl),
and tubing effects (p<.OOOl). Mean height growth was
significantly (p<.05) higher in both the total and partial overstory
298
Percent Survival
100~-----------------------------------------------------
804-------+-~------------r-+--
80
40
20
o
Douglas-fir
w. hemlock
grand fir
w. redcedar
Traa1m8ntS
•
§
Over none Under none
Over part Under total
HIII1 Over none Under total
mB
Over total Under none
I§§I Over part Under none
~
Over total Under total
Figure 3. - Survival of seedlings at the end of two years in all combinations of treatments. Treatments legend describes the combination
of treatments as Over none Under none = Overstory removal none, Understory removal none, etc.
299