Forest Ecology and Management,
Management, 30 (1990) 327-340
Elsevier
Elsevier Science
Science Publishers
Publishers B.V.,
B.V., Amsterdam
Amsterdam - - Printed
Printed in
in The
The Netherlands
Netherlands
327
327
Relative
R e l a t i v e Importance
I m p o r t a n c e of
of Water
Water and
and Nutrients
N u t r i e n t s on
on the
the
Growth
Pacific
G r o w t h of
of Coast
Coast Douglas
D o u g l a s Fir
Fir in
in the
the P
acific
Northwest
Northwest
GESSEL 1, R.E. MILLER22 and D.w.
D.W. COLE!
COLE 1
S.P. GESSEL',
IColiege
Seattle, WA 98195
ICollege of Forest Resources, University of Washington,
Washington, Seattle,
98195 (U.S.A.)
(U.S.A.)
2USDA Forest Service, Pacific Northwest Research
Research Station, Olympia, WA 98502
98502 (U.S.A.)
(Accepted
(Accepted 66 January 1989)
1989 )
ABSTRACT
ABSTRACT
Gessel,
S.P., Miller,
water and
Gessel, S.P.,
Miller, R.E.
R.E. and
and Cole,
Cole, D.W.,
D.W., 1990.
1990. Relative
Relative importance
importance of
of water
and nutrients
nutrients on
on the
the
growth
Douglas fir
For. Ecol. Manage., 30:
-340.
growth of
of coast
coast Douglas
fir in
in the
the Pacific
Pacific Northwest.
Northwest. For.
30: 327
327-340.
The
Douglas-fir region
America is
characterized by
The Douglas-fir
region in
in northwestern
northwestern North
North America
is characterized
by abundant
abundant moisture
moisture
supply
significant differences
supply during
during winter, extended
extended dry
dry periods during
during the
the growing-season
growing-season and
and significant
differences
availability. Many soils have low fertility and native tree species
species respond to nitrogen
in water availability.
fertilization, especially Pseudotsuga menziesii (Mirb.) Franco
Franco (coast
(coast Douglas
Douglas fir)
fir).. Although
Although ir­
irfertilization,
rigation
the
rigation of
of commercial
commercial forests
forests in
in this
this region
region is
is currently
currently impractical,
impractical, questions
questions arising
arising about
about the
relative
relative importance of
of water and
and nutrients were examined using
using long-term
long-term growth
growth data
data from
from three
studies.
At
At Pack
Pack Forest, fertilization
fertilization without irrigation doubled
doubled growth
growth rates,
rates, and
and no
no positive growth
growth
responses were measured from irrigation. Short-term (5 years) irrigation with sewage effluent
containing
containing many
many nutrients
nutrients resulted
resulted in
in aa six-fold
six-fold increase
increase in
in biomass production for
for poplar and
three-fold for
Douglas fir
compared to
to irrigation
irrigation with
with equal
volumes of
of river
water.
three-fold
for Douglas
fir as
as compared
equal volumes
river water.
65-year-old stands in
Volume growth in
in 12- to 65-year-old
in southwestern Oregon
Oregon was increased by fertiliza­
fertilizathe location; annual gain averaged 2.73
2.73 m3
m 3 ha -I
-1 for 5-12 years. Response
tion at about 70% of the
was not
not related
related to
to annual
annual precipitation, which ranged
ranged from
from 81 to 279 em,
cm, nor
nor other
other moisture­
moisturerelated
related variables. Absolute
Absolute and
and relative
relative volume response
response showed
showed highest
highest correlation
correlation with soil
soil car­
carbon : nitrogen ratio.
bon:
Compared
be a
Compared with
with nutrition,
nutrition, moisture
moisture does
does not
not seem
seem to
to be
a major
major limiting
limiting factor
factor for
for growth
growth in
in
the Pacific northwest.
the Douglas-fir region of the
INTRODUCTION
The
relative importance
water and
and nutrients
nutrients to
to tree
tree growth
growth and
and forest
forest
The relative
importance of water
productivity is
is a favorite
favorite discussion
discussion topic
topic of forest
forest scientists
scientists and
and practitioners.
practitioners.
productivity
To most
most observers
observers in
in the
the Pacific
northwest, moist
moist climate
climate and
and large
large tree
tree size
size
To
Pacific northwest,
emphasize the
the role
role of water. Research
has confirmed, however, that
that elements
elements
emphasize
Research has
essential for general
general plant
plant growth
growth are
are also
also needed
needed by
by Douglas
to prevent
prevent
essential
Douglas fir to
0378-1127/90/$03.50
0378-1127/90/$03.50
© 1990
1990 Elsevier Science Publishers B.V.
©
328
328
S.P.
ET AL.
S.P. GESSEL
GESSEL ET
AL.
growth reductions
reductions and
and that
that some
some elements
elements may
may be
be deficient
deficient in
in northwestern
northwestern
growth
soils (Gessel
(Gessel et
et al.,
aI., 1950).
1950). Although
Although some
some researchers
researchers (e.g., E
Emmingham
and
soils
m m i n g h a m and
Waring, 1977; Grier
Grier and
and Running, 1977)
1977) consider
consider water
water to
to play
play the
the more
more imim­
Waring,
portant role, the
the opinion
opinion is
is academic
academic to
to practicing
practicing foresters
foresters whose
whose goal
goal is
is to
to
portant
ensure
adequate
amounts
of
both
water
and
nutrients
to
capture
full
growth
ensure adequate amounts of both water and nutrients to capture full growth
potential of sites.
potential
Foresters'
ability to
to improve
improve water
water regimes
regimes is
is more
more limited
limited than
than to
to improve
improve
Foresters' ability
nutrient regimes. In
In most
most natural
natural forests
forests and
and plantations,
plantations, the
the availability
availability of
nutrient
water is
is determined
determined by
by climate,
climate, topography, and
and soils
soils of the
the area.
area. Controlling
water
vegetation and
and stand
stand density
density are
are supplemental
supplemental management
management opop­
competing vegetation
tions. Cost
Cost of water
water and
and its
its allocation
allocation to
to other
other uses
uses essentially
essentially eliminate
eliminate its
its use
use
tions.
in
commercial
forests,
other
than
for
nurseries
and
seed
orchards.
In
contrast,
in commercial forests, other than for nurseries and seed orchards. In contrast,
cost-effective operational
operational programs
programs to
to improve
improve nutrient
nutrient regimes
regimes have
have been
been dede­
cost-effective
for many
many forest
forest areas
areas throughout
throughout the
the world.
veloped for
This paper
paper will
will examine
examine the
the relative
relative importance
importance of water
water and
and nutrients
nutrients to
to
This
growth of
of Douglas
Douglas fir
fir in
in the
the Pacific
Pacific northwest
northwest by
by using
using results
results from
from several
several
growth
irrigation and
and fertilizer
fertilizer trials.
trials.
irrigation
Research in
in forest
forest tree
tree nutrition
nutrition and
and fertilization
fertilization in
in the
the Pacific
Pacific northwest
northwest
Research
began in
in the
the early
early 1950s. Results
Results up
up to
to 1979
1979 are
are reported
reported by
by Gessel
Gessel et
et al. ((1979)
began
1979 )
and
and more
more recently
recently by
by Gessel
Gessel and
and Atkinson
Atkinson (1984).
(1984). A
A Regional
Regional Forest
Forest FertilFertil­
Cooperative initiated
initiated in
in 1969
1969 has
has amassed
amassed 18 years
years of fertilizer
fertilizer rere­
ization
ization Cooperative
sponse data
data over
over aa wide
wide range
range of
of soils
soils and
and sites
sites (Peterson
(Peterson and
and Heath,
Heath, 1986).
1986).
sponse
These
data indicate
indicate that
that nitrogen
nitrogen (N)
is generally
generally deficient
deficient in
in northwest
northwest forfor­
These data
(N) is
ests and
and that
that its
its application
application can
can provide
provide volume
volume responses
responses of
of 60-70%
60-70% for
for 8-10
8-10
ests
no
years. Re-application
Re-application will continue response. Some stands, however, show no
response to
to N
and may
may be
be deficient in
in other
other elements.
response
N and
The
of water
water to
to tree
tree growth
growth and
and water/nutrient
water/nutrient interactions
interactions have
have
The importance
importance of
been addressed by
by several
several researchers. Brubaker
Brubaker (1980)
(1980) concluded from
from increincre­
been
ment cores
cores that
that water
water stress
stress during the
the warm
warm season
season was
was the
the primary
primary factor
factor
ment
tree growth in
in the
the Pacific
the imim­
limiting tree
Pacific northwest. Brix
Brix (1979)
(1979) recognized the
portance of nutrient/moisture
nutrient/moisture inter-relationships
inter-relationships to
to growth
growth of Douglas
but
portance
Douglas fir but
there was
was little
little information on
on the
the subject. Brix
and Mitchell
Mitchell (1986)
concluded there
Brix and
(1986)
measured
period in
in thinned
thinned and
and
and tree
tree water-potentials
water-potentials in
measured soil
soil and
in aa 10-year
10-year period
fertilized
on Vancouver
and concluded
concluded that
that thinning
thinning
fertilized Douglas-fir
Douglas-fir stands
stands on
Vancouver island,
island, and
initially
increased soil
water-potential during
during the
the dry
dry July
period,
initially increased
soil water-potential
July-September
-September period,
while fertilization
fertilization had
effect on
on soil
water-potential despite
despite up
up to
to 60%
60%
while
had little
little effect
soil water-potential
increases
growth.
increases in
in growth.
Woodman
irrigation on
on fertile
Woodman (1971,
(1971, 1973)
1973) investigated
investigated forest
forest irrigation
fertile soils
soils (site
(site
index
western Washington,.
preliminary results
results have
been reported
index II)
II) in
in western
Washington,. Only
Only preliminary
have been
reported
for
these field
and efforts to
to acquire
acquire recent
recent information
unsuccess­
for these
field trials, and
information were unsuccessful.
Woodman
(1971)
stated
that
irrigation
reduced
water
stress
during the
the
ful. Woodman (1971) stated that irrigation reduced water stress during
summer
of 1970
that radial
of dominant
dominant and
and co-dominant
summer of
1970 and
and that
radial growth
growth of
co-dominant Douglas
Douglas
fir
trees was increased
that the
the combined
fir trees
increased by 20%
20%.. Woodman
Woodman (1973)
(1973) observed
observed that
combined
IMPORTANCE
IMPORTANCE OF
OF WATER
WATER AND
AND NUTRIENTS
NUTRIENTS ON
ON GROWTH
GROWTH OF
OF DOUGLAS
DOUGLAS FIR
FIR
329
329
and irrigation
irrigation treatment produced greatest growth durdur­
thinning, fertilization, and
ing 1972.
1972. Results
Results for
for irrigation
irrigation alone
alone were
were variable
variable and
and inconclusive.
inconclusive.
ing
For
plants, Viets
For agricultural plants,
Viets (1962)
(1962) reported growth improvement after
without additional
as improved
efficiency'. Turner
fertilization without
additional water as
improved 'water-use
'water-use efficiency'.
Turner
and Lambert (1987)
(1987) found improved water-use efficiency
efficiency after fertilization of
and
Pinus radiata D. Don
Don (radiata pine)
Pinus
pine) on
on nutritionally poor soils in
in Australia.
STUDY
STUDY AREAS
AREAS
Although
the Pacific
northwest generally
generally includes
includes the
the states
states of
of Washington
Although the
Pacific northwest
Washington
and
British Columbia, our results
and Oregon and
and much
much of the
the province of British
results origiorigi­
nated from
from Washington
and Oregon,
west of
of the
the Cascade
range. Some
Some general
general
nated
Washington and
Oregon, west
Cascade range.
the region will be
be enumerated in
in this
this section, but
but specific details
details
features of the
and soil of each study area
area can
can be
be found in
in the
the appropriate
appropriate sections.
for climate and
sections.
Precipitation
in westside forests range
range from an
an abnormal
abnormal low of 300 mm
mm at
at
Precipitation in
Sequim, W
A to
to aa high
high of
of 4000
4000 mm
mm in
in the
the Olympic
Mountains. Much
Much of
of this
this
Sequim,
WA
Olympic Mountains.
in winter, but
but substantial
substantial amounts
amounts occur in
in autumn
autumn and
and
precipitation falls in
spring. Summers are
are characterized by relatively light precipitation or rain-free
spring.
that last
last 30
in the
the southsouth­
periods that
30 or more days. Summer drought is accentuated in
ern
ern part
part of the
the region. Elevational and
and orographic effects modify patterns
patterns of
that water supply to
to the
the soil varies greatly from area
area to
to area.
area.
local rainfall so that
also differ in
in their
their moisture-holding capacity and
and this
this further accentuates
Soils also
differences in
in available
available water
water for
for forests.
forests.
differences
THE STUDIES
STUDIES
We
data from the
the following studies
studies to
to examine water/nutrient
water/nutrient interinter­
We used data
actions in
in tree
tree growth in
in the
the Pacific
actions
Pacific northwest:
1)
trials and
and an
an irrigation/fertilization trial
trial at
at Pack
1 ) long-term fertilizer trials
Pack Forest;
Forest;
studies using sewage effluent and
and river water at
at Pack
and
22)) irrigation studies
Pack Forest;
Forest; and
3
)
nitrogen
fertilization
trials
in
Douglas-fir
stands
sampling
a
wide
range
of
3)
trials in
stands
total annual
annual precipitation
precipitation and
and soil water-holding capacities in
in southwestern
total
Oregon.
Oregon.
Pack Forest studies
Pack
studies
Pack
km south
south of Seattle, WA at
at the
the base
base of the
the Cascade
Pack Forest
Forest is located 100 km
Range. Elevation
at the
the study areas
areas ranges from 250 to
to 260 m. The
Elevation at
The climate is
a maritime type with the
(annual avthe following characteristics: temperature (annual
av­
erage)) max.
max. 15.6°C,
min. 5.8
5.8°C;
and precipitation
precipitation (monthly
(monthly average
average)) 100
100 mm
mm
erage
15.6 ° C, min.
° C; and
(October to
to March 680 mm, April to
to September 320 mm
mm).
and August are
are
). July
July and
the
Winter
the driest months
months and
and frequently may have only aa few mm
mm of rain. Winter
are relatively mild, and
and severe frosts
frosts occur only occasionally;
temperatures are
S.P.
S.P. GESSEL
GESSEL ET
ET AL.
AL.
330
330
snow cover is
is infrequent. Douglas
shows net
net photosynthesis
photosynthesis during the
the winwin­
snow
Douglas fir shows
ter months.
months. Radial
Radial growth
April and may
may continue
Ocgrowth begins
begins by
by 15 April
continue into
into late
late Oc­
break for height
height and
and lateral
lateral elongation
elongation occurs
occurs in
in mid-May,
with
tober. Bud
Bud break
mid-May, with
new bud
bud formation
by early
early July.
Soil moisture
is low
low in
in late
late August
and early
early
new
formation by
July. Soil
moisture is
August and
September,
but aa second
second bud-break
bud-break occasionally
occasionally occurs
occurs on
on young
young trees
trees in
in late
late
September, but
summer.
The studies
studies reported here took
took place
place on
on soils
soils formed from glacial
glacial outwash
outwash
The
deposited during
during the
the Vashon
Vashon Ice
Age about
about 12
000 years
years ago.
ago. This
This gravelly
gravelly
deposited
Ice Age
12 000
material
can be
be 15
deep; soils
soils formed
formed on
on it
it are
are in
in the
the Everett
series of
of the
the
material can
15 m
m deep;
Everett series
Inceptisol
and specifically
specifically classified
classified as
as loamy-skeletal
loamy-skeletal mixed
Inceptisol Order
Order and
mixed mesic,
mesic,
Dystric
and chemical
chemical characterischaracteris­
Dystric Xerachrept
Xerachrept (Anonymous,
(Anonymous, 1979).
1979). Physical
Physical and
tics of
of the
the Everett
series are
are given
given in
in Table
Table 1.
tics
Everett series
1.
Long-term fertilizer trials. Several
Several fertilizer trials
trials were established during the
the
Long-term
1950s at
at Pack
to examine
examine different
different rates
rates of
of nitrogen
nitrogen in
in combination
combination
1950s
Pack Forest
Forest to
with other
other elements.
elements. Plots
in area and
and had treated
treated buffer areas.
with
Plots were 0.04 ha in
Some plots
plots were
were thinned;
thinned; all
all were
were in
in the
the previously
previously described
described Everett
series
Some
Everett series
and were
were in
in pure
pure stands
stands of
of site-index-IV
site-index-IV Douglas
fir (34
at 100
100 years).
years). Ni­
and
Douglas fir
(34 m
m at
Nitrogen was
was reapplied
reapplied periodically
periodically so
so that
that all
all fertilized
fertilized plots
plots received
received at
at least
least
trogen
ha -I.
all trees
trees and
and heights
heights of an
an adequate
adequate sample
sample were
1200 kg ha1. Diameters
Diameters of all
measured
every 3
years through
through 1986.
measured every
3 years
1986.
Growth
information for
for three
three unfertilized
unfertilized and
and six
six fertilized
fertilized plots
plots is
is given
given in
in
Growth information
Table 2. Total
Total growth
growth periods
periods range
range from 28 to
to 35
initial volvol­
Table
35 years. Although
Although initial
umes differed
differed somewhat,
somewhat, the
the long-term
long-term growth
growth has
has aa consistent
consistent pattern;
pattern; concon­
umes
trol
m 3 ha-1
15.7 m3
m3
trol plots
plots averaged
averaged 7.6
7.6 m3
ha-I year-1
yeacl and
and fertilized plots
plots averaged
averaged 15.7
TABLE
T A B L E 11
Physical
chemical characteristics
Physical and
and chemical
c h a r a c t e r i s t i c s of
of Everett
E v e r e t t gravelly
gravelly loamy
loamy sand
sand
Soil
Soil Horizon
Horizon
Physical
P h y s i c a l (%)
(%)
> 2-mm
2 - m m fraction
fraction
>
<
< 2-mm
2 - m m fraction
fraction
Sand
Sand
Silt
Silt
Clay
Clay
Chemical
C h e m i c a l (( <
< 2-mm
2 - m m fraction)
fraction)
pH
pH
C E C (cmol(
(cmol( +
+ )kg-1)
)kg - 1 )
CRC
A m m o n i u m (cmol(
(emol ( +
+ )kg-1)
) kg - 1)
Ammonium
Nitrate +
+ nitrite
nitrite (cmol(
(emol ( - )kg-1)
)kg- i )
Nitrate
A
A
B
B
C
C
83
83
83
83
96
96
11
11
6
6
13
13
4
4
4
1
1
Pi.O
5.0
22.0
22.0
0.11
0.11
0.07
0.07
4.8
4.8
14.0
14.0
0.04
0.04
0.01
0.01
4.8
4.8
9.0
9.0
0.03
0.03
0.02
0.02
331
331
IMPORTANCE
IMPORTANCE OF
OF WATER
WATER AND
AND NUTRIENTS
NUTRIENTS ON
ON GROWTH
GROWTH OF
OF DOUGLAS
DOUGLAS FIR
FIR
TABLE
T
A B L E 22
volume (m3
(m 3 ha-1)
ha-1) and
and growth
growth increment
increment (Incr.,
m a ha-1
ha-~ year-I)
year -1) on
on fertilized
fertilized and
and un­
un(lncr., m3
Average volume
fertilized
plots at
Forest
fertilized plots
at Pack
Pack Forest
Treatmene
Treatment 1
C
C
C
C
F
F
F
F
F
F
F
F
C
C
FT
FT
FT
FT
Plot
Plot
no.
flO.
18
1S
F-41
F
-41
IN
1N
F-42
F-42
F-43
F-43
F-12
F-12
28
2S
2N
2N
T-26
T-26
Years
Years
35
35
32
35
35
32
32
32
32
28
28
35
35
35
35
33
33
Volume
Volume
Initial
Initial
Final
Final
Incr.
Incr.
(% ))
157.5
157.5
106.4
106.4
166.9
166.9
85.8
85.8
117.6
117.6
145.4
145.4
126.4
126.4
129.9
129.9
197.4
197.4
389.2
389.2
391.7
391.7
656.3
656.3
588.8
588.8
678.9
678.9
602.5
602.5
382.4
382.4
656.7
656.7
730.5
730.5
231.7
231.7
285.3
285.3
499.3
499.3
503.0
503.0
561.3
561.3
457.1
457.1
257.4
257.4
519.8
533.1
533.1
6.6
6.6
8.9
14.0
14.0
15.7
15.7
17.5
17.5
16.3
16.3
7.3
7.3
14.8
14.8
16.1
16.1
IC,
1C, Control
Control (Untreated)
(Untreated);; F,
F, Fertilized;
Fertilized; T,
T, Thinned.
Thinned.
ha-1
Average long-term growth
fertilization
ha -1 year-1.
year-I. Average
growth was
was at
at least
least doubled by
by fertilization
with no
no additional
additional water
water supply. Current
are almost
almost two-fold
with
Current live volumes are
greater on
on fertilized plots; potential
potential merchantable-yield differences are
are even
even
greater
greater because
because trees
trees in
in fertilized plots
plots have
have larger
larger diameters. Clearly,
im­
greater
Clearly, improved nitrogen supply at
at this
this location enabled
enabled trees
trees to
to make
make more
more efficient
use
use of water
water available
available in
in these
these soils
soils with
with poor
poor moisture
moisture storage.
Irrigation/Fertilization
When initial
initial experiments
experiments at
at Pack
demon­
Irrigation~Fertilization trial.
trial. When
Pack Forest
Forest demon-
strated large
large responses
responses to
to nitrogen, we became
became interested in
in the
the relative
relative imim­
strated
portance of water
water and
and essential
essential elements for improving stand
stand growth. An
ex­
portance
An exwas established
established in
in 1958 to
to test
test the
the interaction
interaction of additional
additional nitrogen
nitrogen
periment was
or additional
additional water, with
with and
and without
without thinning. A
site was
was selected with
with
or
A level site
stand of Douglas
on averageaverage­
aa uniform, moderately stocked, 30-year-old
30-year-old stand
Douglas fir on
quality soil. Water
irrigation was
was pumped from an
an abandoned
which
quality
Water for irrigation
abandoned clay-pit which
the rainy
rainy season.
accumulated runoff during the
The experimental
experimental design had
had three
three replicated blocks, each
each with
with eight 0.040. 04­
The
ha plots
plots without
without buffers. The
The eight
treatments were: control
control (C);
thinning
ha
eight treatments
(C); thinning
( T ); fertilization
(F); irrigation
( I ); thinning
( TF ); thinning
(T);
fertilization (F);
irrigation (I);
thinning and
and fertilization
fertilization (TF);
thinning
and irrigation
irrigation (TO;
fertilization and
and irrigation
irrigation (FI);
and thinning, fertilizafertiliza­
and
(TI); fertilization
(FI); and
and irrigation
irrigation (TFI).
and fertilization
fertilization were
were completed early
early in
in
tion
(TFI). Thinning and
tion and
the first
first growing-season. Elemental
Elemental additions
additions (kg
ha -1
the
(kg ha
-1 )) were: nitrogen, 224;
and copper, iron, zinc, man­
potassium, 224; magnesium, 45; phosphorus, 100; and
manganese (combined total)
total) 45. The
The irrigation
irrigation period was
was July
to mid-September
ganese
July to
moisture levels were
were monitored by
by tensiometers. Irrigation
for 4 years. Soil moisture
Irrigation
332
332
S.P. GESSEL
ET AL.
GESSEL ET
water averaged
averaged about
about 300
300 mm
mm per
per summer
summer period
period over
over the
the 44 years,
years, or
or 23
23 mm
mm
water
week -1 . Irrigation
Irrigation was
was discontinued
discontinued after
after four
four growing-seasons
growing-seasons because
because finanfinan­
week-1.
cial support
support was
was lacking.
lacking.
cial
Diameter of
of all
all trees
trees and
and height
height of
of about
about 14
14 dominant
dominant or
or codominant
codominant trees
trees
Diameter
per treatment
treatment were
were measured
measured annually
annually through
through 1965
1965 and
and thereafter
thereafter at
at 5-year
5-year
per
intervals through
through 1986.
1986. Initial
Initial volumes
volumes and
and absolute
absolute and
and relative
relative volume
volume growth
growth
intervals
are summarized
summarized for two
two 3-year
3-year periods
periods after
after establishment
establishment (Table
(Table 3).
3). In
In unun­
are
thinned plots,
plots, the
the controls
controls averaged
averaged 13-22
13-22%
more initial
initial volume
volume than
than did
did plots
plots
thinned
% more
of other
other treatments.
treatments. In
In thinned
thinned plots,
plots, controls
controls averaged
averaged 14-33%
14 -33% more.
more. ConCon­
of
sequently, covariance
covariance analysis
analysis was
was used
used to
to adjust
adjust for
for these
these initial
initial volume
volume difdif­
sequently,
ferences
ferences within
within unthinned
unthinned and
and thinned
thinned conditions
conditions and
and thus
thus isolate
isolate the
the effects
effects
TABLE
T A B L E 33
Average gross volume (m
(m33 h
ha
(PAl; m3
yearby treattreat­
Average
a -- 1)
1) and periodic annual increment
increment (PAl;
m 3 hha
a --I1 year
- I)
1) by
ment
two 3-year
periods, the
the thinning
thinning (T),
(T), fertilizing
(F), and
and irrigation
irrigation (I)
(I) trials
trials at
at Pack
Pack
ment for
for two
3-year periods,
fertilizing (F),
Forest
Forest
Treatment
Treatment
Average adjusted,
adjusted, gross
gross annual
annual growth
Average
growth
Volume
Volume
(begin)
(begin)
Absolute g
growth
Absolute
rowth
Unthinned
Unthinned
147.5
C
C
147.5
F
F
122.9
122.9
II
115.0
115.0
F
128.1
FII
128.1
Thinned
Thinned
T
104.0
T
104.0
FT
76.1
FT
76.1
IT
IT
89.7
89.7
FIT
69.6
FIT
69.6
Period 11
Period
Period 22
(3
years)
(3 years)
(3 years)
years)
(3
Period 11 +
+2
Period
2
(6 years)
years)
(6
Period 2/1
2/1
15.3
15.3
15.5
15.5
15.9
15.9
17.1
17.1
18.4
18.4
25.1
25.1
22.9
22.9
23.9
23.9
16.9
16.9
20.3
20.3
19.4
19.4
20.5
20.5
1.20
1.20
1.62
1.62
1.44
1.44
1.40
1.40
11.8
11.8
14.9
14.9
12.1
12.1
14.5
14.5
17.5
17.5
21.6
21.6
20.2
20.2
21.5
21.5
14.7
14.7
18.2
18.2
16.1
16.1
18.0
18.0
1.48
1.48
1.45
1.45
1.67
1.67
1.48
1.48
Relative
R e l a t i v e growth
g r o w t h (control
( c o n t r o l = 100%)
100%)
Unthinned
Unthinned
C
100
C
100
100
100
101
F
F
83
101
83
104
II
78
78
104
F
112
87
FII
87
112
Thinned
Thinned
100
T
T
100
100
100
126
73
FT
FT
73
126
103
IT
86
103
IT
86
123
FIT
FIT
67
123
67
=
100
100
136
136
124
124
130
130
100
100
120
120
115
115
121
121
100
100
135
135
120
120
117
117
100
100
123
123
115
115
123
123
100
100
124
124
110
110
122
122
100
100
98
98
113
113
100
100
Average
Average growth
growth for
for each
each treatment
treatment in
in unthinned
unthinned and
and thinned
thinned conditions
conditions was
was adjusted
adjusted by
by covari­
covariance
ance for
for initial
initial differences
differences in
in stand
stand volumes.
volumes.
333
IMPORTANCE OF
OF WATER
WATER AND
AND NUTRIENTS
NUTRIENTS ON
ON GROWTH
GROWTH OF
OF DOUGLAS
DOUGLAS FIR
FIR
IMPORTANCE
of fertilization
fertilization and
and irrigation.
irrigation. A
significant regression
regression relation
relation between
between growth
growth
of
A significant
and initial
initial volume
volume (P
0.10) existed
existed in
in both
both unthinned
unthinned and
and thinned
thinned condicondi­
and
(P < 0.10)
tions.
tions. Although adjusted means
means among the
the treatments showed large differdiffer­
ences, none
none were
were statistically
statistically significant
significant in
in the
the first,
first, second,
second, or
or the
the combined
combined
ences,
6-year period
period of
of observation.
observation. This
This lack
lack of
of significance
significance indicates
indicates that
that non-treatnon-treat­
6-year
ment sources of variation
variation masked the
the apparent
apparent strong effects of individual and
and
ment
combined treatments.
treatments.
combined
Wastewater studies
studies
Plots
were established
established on
on the
the previously
previously described
described Everett
soil as
as follows:
follows: an
an
Plots were
Everett soil
area kept
kept vegetation-free;
vegetation-free; an
an area
area planted
planted with
with Douglas-fir
and an
an
area
Douglas-fir seedlings;
seedlings; and
planted with
with Lombardy-poplar
cuttings. Plantings
in April
and
area planted
Lombardy-poplar cuttings.
Plantings were in
April 1975
1975 and
the study
study terminated
terminated in
in October
after the
the fifth
fifth growing-season,
growing-season, but
but biobio­
the
October 1979
1979 after
mass
mass was measured for 4 years.
Within each
each vegetative
vegetative type,
type, one
one subplot
subplot received
received Seattle
Seattle sewage
sewage wastewater
wastewater
Within
and
one
received
an
equal
amount
of
water
from
a
nearby
river.
About
4 0-50
and one received an equal amount of water from a nearby river. About 40-50
mm
mm of wastewater or river water was applied weekly in
in an
an 8-h period using
sprinklers. Except
times when
when the
the pumping equipment
irrigation sprinklers.
Except for a few times
the sprinkler system froze, all plots
plots were irrigated on
on this
this
malfunctioned or the
weekly schedule
schedule for
for aa total
total of
of 5
5 years
years from
from September
September 1974
through August
weekly
1974 through
August
1979.
1979.
Wastewater
about 550 kg N
year -11 or aa 5-year total
total
Wastewater irrigation provided about
N hha
a --11yearabout 2286
2286 kg N
ha-1
with river water provided 7 kg
of about
N ha
-1 (Table
(Table 4). Irrigation
Irrigation with
N hha
a --11 yyear
e a r -- 11 or aa total
a --11.. Biomass
Biomass was estimated through
N
total of about 35 kg h
ha
through
destructive sampling
sampling of
of selected
selected trees,
trees, and
and regression
regression equations.
equations.
destructive
Biomass production of Douglas
Douglas fir and
Biomass
and poplar
poplar is given in
in Table
Table 5. A grass
grass
component that
Nuthat existed as
as an
an understory on
on all plots
plots was not
not removed. Nu­
trient cycling
cycling and
and the
the fate
fate of
of applied
applied elements
elements have
have been
been reported
reported elsewhere
elsewhere
trient
(Schiess
and Cole,
trees clearly
clearly had
had greater
greater biobio­
(Schiess and
Cole, 1981).
1981 ). Wastewater-irrigated
Wastewater-irrigated trees
mass
production than
than those
those irrigated
irrigated with
with river
river water.
water. In
trees irrigated
irrigated
mass production
In 1978,
1978, trees
with wastewater
wastewater averaged
averaged 2.4
2.4 m
m tall,
tall, compared
compared to
to 1.
m for
for trees
trees irrigated
irrigated with
with
with
1.77 m
TABLE
4
TABLE4
Amounts (kg ha
-1 y
year-I)
ha-1
e a r - l ) of water, nitrogen, and
and phosphorus applied to irrigated plots (5-year
annual average)
annual
Water
Water
(em)
(cm)
Douglas
Douglas fir
fir
Poplar
Poplar
198
241
Wastewater
Wastewater
R i v e r water
water
River
N
N
P
P
N
N
P
P
362
434
29
31
77
8
2
3
334
334
s.P. GESSEL
GESSELET
ET AL.
AL.
S.P.
TABLE
T A B L E 55
Above-ground
wastewater and
water irrigation,
by species
Above-ground biomass
biomass accumulation
accumulation (t
(t ha
h a -,
- 1)) for
for wastewater
and river
river water
irrigation, by
species
and year
year
and
Wastewater
Wastewater
River
water
River water
Trees
Trees
Grass'
Grass 1
Total
Total
Trees
Trees
Grass 1
Grass'
Total
Total
Poplar
1976
1976
1977
1977
1978
1978
1979
1979
Total
Total
8.5
8.5
28.2
28.2
14.8
14.8
18.4
18.4
69.9
69.9
8.0
8.0
6.0
6.0
10.1
10.1
6.0
6.0
30.1
30.1
16.5
16.5
34.2
34.2
24.9
24.9
24.4
24.4
100.0
100.0
1.0
1.0
1.2
1.2
1.8
1.8
3.4
3.4
7.4
7.4
1.6
1.6
1.2
1.2
2.1
2.1
1.9
1.9
6.8
6.8
2.6
2.6
2.4
2.4
3.9
3.9
5.3
5.3
14.2
14.2
Douglas fir
1976
1976
1977
1977
1978
1978
1979
1979
Total
Total
2.9
2.9
4.4
4.4
14.0
14.0
12.8
12.8
34.1
34.1
8.5
8.5
8.4
8.4
6.7
6.7
3.4
27.0
27.0
11.4
11.4
12.8
12.8
20.7
20.7
16.4
16.4
61.3
61.3
0.9
0.9
1.6
1.6
3.8
3.8
3.6
3.6
9.9
9.9
1.6
1.6
0.8
0.8
3.3
3.3
2.4
2.4
5.9
5.9
2.5
2.5
2.4
2.4
6.0
6.0
4.9
4.9
15.8
15.8
1Grass understory.
understory.
'Grass
river water. The
The corresponding height of unirrigated
unirrigated Douglas
planted nearby
nearby
river
Douglas fir planted
at the
the same
same time
time was
was 1.
at
1.66 m.
Results
that irrigation
with essentially
essentially nutrient-free
nutrient-free river
water did
did
Results show that
irrigation with
river water
little
growth of Douglas
Douglas fir on
Comlittle to
to improve height
height growth
on this
this coarse-textured
coarse-textured soil. Com­
pared to
to river-water
river-water additions, the
the same
same amount
amount of water
water containing N
and P
pared
N and
P
plus other
other elements (Table
4) increased
increased total
total productivity six-fold for
for poplar
poplar
plus
(Table 4)
and three-fold for
for Douglas-fir. When
When understory
understory grass
grass is included in
in the
the propro­
and
the differences are
are retained. The
The two
two species reacted
reacted differdiffer­
ductivity figures, the
ently to
to nutrient
nutrient supply. Douglas
fir outgrew poplar
poplar under
under irrigation
irrigation with
with nunu­
ently
Douglas fir
trient-free water, while
while poplar
poplar far
far exceeded Douglas
fir with
with the
the added nutrient
nutrient
trient-free
Douglas fir
supply.
supply.
Below-ground biomass
biomass accumulation shows the
the same
same relationships
as aboveabove­
relationships as
utrient-rich water
water accelerated production of root
root material
material more
more than
than
ground. N
Nutrient-rich
nutrient-poor water. Poplar
Poplar roots
roots were
were more
more responsive
responsive than
than Douglas
fir to
to
nutrient-poor
Douglas fir
nutrients (Table
6).
nutrients
(Table 6).
Two other
other irrigation
studies with
with sewage effluent or
or sludge in
in the
the same
same area
area
Two
irrigation studies
similar results. A
stand on
on Ev­
of Pack
Pack Forest
Forest showed similar
A 36-year-old Douglas-fir
Douglas-fir stand
Everett soil irrigated
irrigated for
for 2 years
years with
with river
river water
water or
or aa sludge suspension showed
erett
no growth
growth increase
increase with
with river
river water
water (Stednick, 1979),
while irrigation
irrigation with
with
no
1979), while
increased growth. Schiess
Schiess and
and Cole
similar
sludge suspension increased
Cole (1981)
(1981) applied similar
treatments to
to aa nearby
nearby 50-year-old
50-year-old Douglas-fir
plots irrigated
irrigated with
with
treatments
Douglas-fir stand. On
On plots
they measured
measured aa 112%
increase in
in 4-year
4-year basal-area
basal-area growth
growth
sewage effluent, they
112% increase
335
335
IMPORTANCE
DOUGLAS FIR
IMPORTANCEOF
OF WATER
WATERAND
AND NUTRIENTS
NUTRIENTS ON
ON GROWTH
GROWTHOF
OF DOUGLAS
FIR
TABLE
T A B L E 66
Biomass (t
(t ha
h a -- I)
~) in
in 1979
1979 after
after wastewater
wastewater and
a n d river-water
river-water irrigation,
irrigation, by
by component
c o m p o n e n t and
and species
species
Biomass
Douglas
Douglas fir
fir
Poplar
Poplar
Wastewater
Wastewater
River water
water
River
Wastewater
Wastewater
River
River water
water
Steml
Stem I
Foliage
Foliage
Sub-total
Sub-total
Roots
Roots
41.20
41.20
4.80
4.80
46.00
46.00
24.70
24.70
5.86
5.86
1.07
1.07
6.93
6.93
5.20
5.20
20.70
20.70
8.00
8.00
28.70
28.70
7.40
7.40
6.40
6.40
2.90
2.90
9.30
9.30
2.00
2.00
Total
Total
%
% Stem
Stem
% Roots
Roots
%
70.70
70.70
58
58
35
35
12.13
12.13
48
48
43
43
36.10
36.10
57
57
20
20
11.30
11.30
57
57
18
18
IStem includes
includes branches.
1Stem
branches.
(compared
with growth
growth in
in the
the 6 years
years before
before irrigation).
with river
river
(compared with
irrigation). Irrigation
Irrigation with
water showed aa 44%
4 4 % increase
increase over the
the previous 6 years'
years' growth.
water
Relations
Relations in southwestern Oregon
Oregon
Climatic
patterns in
in southwestern
southwestern Oregon
are similar
similar to
to the
the rest
rest of the
the Doug­
Climatic patterns
Oregon are
Douglas-fir
las- fir region, but
but less
less rainfall
rainfall and
and greater
greater evaporative
evaporative stress
stress make
make the
the area
area
drier. Although water
water availability
availability generally is considered the
the most
most important
important
drier.
fertilizer trials
trials have
have proven
proven that
that N
availability
growth-limiting factor, local fertilizer
N availability
also constrains
constrains growth
growth of Douglas fir.
fir. Of
fertilizer trials,
trials, the
the percentage
percentage
also
Of 114
114 fertilizer
that
N is similar
(60-70%);
that showed response
response to
to N
similar to
to the
the broader
broader regional average
average (60-70%
);
moreover,
site index,
similar average
gains in
in gross
gross cubic
cubic volume
moreover, for aa given site
index, similar
average gains
from fertilization
( Miller
fertilization of both
both thinned
thinned and
and unthinned stands
stands were
were reported
reported (Miller
et
1988a).
et al.,
aI., 1986, 1988a).
No
tests of irrigation
irrigation are
are available
available to
to compare
compare the
the relative
relative importance
importance of
No tests
water and
and nutrients
nutrients to
to forest
forest growth
growth in
in southwestern
southwestern Oregon.
Measures to
to
water
Oregon. Measures
moisture (weed control and
and mulching with
with plastic
plastic or
or paper), howhow­
conserve moisture
invariably increase
increase seedling survival
survival and
and growth.
growth. Recent
research to
to prepre­
ever, invariably
Recent research
growth and
and response
response to
to N
fertilization in
in southwestern
southwestern Oregon
dict
N fertilization
Oregon
dict volume growth
data for
for 64 locations (Miller
et al.,
aI., 1988b). Through
Through linear
linear correlacorrela­
provided data
(Miller et
tion and
and multiple-regression analyses, independent variables
variables for describing
tion
moisture and
and N
status at
at these
these trials
trials were
were related
related to
to dependent variables
variables such
such
moisture
N status
as
N fertilization.
as site
site index, growth
growth of unfertilized stands, and
and response
response to
to N
These
Douglas-fir stands
These trials
trials were
were selected from
from aa total
total of 114 trials
trials in
in Douglas-fir
stands after
after
pre-set standards
standards of site
site uniformity among the
the plots
plots at
at individual 10meeting pre-set
locations. Response
Response to
N ha-1
to an
an application
application of 224 kg N
ha -1 at
at each
each location
location was
was
calculated by
by comparing
comparing growth
growth on
on fertilized
fertilized plots
plots to
to growth
growth on
on unfertilized
unfertilized
calculated
336
336
S.P.
ET AL.
AL.
S.P. GESSEL
GESSELET
response at
at each
each location were adjusted
adjusted for initial
initial differdiffer­
plots. Estimates
Estimates of response
in relative
relative density among the
the plots
plots (Curtis, 1982).
ences in
1982 ).
Variables
used to
to characterize
characterize moisture
moisture and
and nutrient
nutrient conditions at
at these
these 64
Variables used
locations
are described in
in Table
correlations among these
these indepenindepen­
locations are
Table 7. Linear
Linear correlations
dent variables
variables reveal that
that many
many are
are significantly correlated (Table
dent
(Table 8). For
For
site index (SI)
with increasing precipitation
precipitation (p),
example, site
(sI) increases with
(p), effective
depth (ds),
available moisture-holding capacity Wc),
min­
soil depth
(d~), available
(0c), anaerobically min2), total
total N
and organic matter
matter ((OM,
OM, OM2).
eralized N
N (Nmin,
(Nmi,, Nmin
Nmi, 2),
N (N,
(N, N2),
N2), and
OM2).
Conversely, s1
SI decreases with
with increasing elevation (He)
nega­
(He) which itself is negawith variables
variables describing soil depth, N, and
and OM.
These data
data
tively correlated with
OM. These
indicate that
that site
site index, aa measure
measure of site
site productivity, is influenced by both
both
indicate
moisture and
and N
status in southwestern Oregon.
moisture
N status
Growth
stands was directly correlated with
with site
site index
index (and
Growth of unfertilized stands
(and
its determinant
determinant factors
factors of moisture
moisture and
and nitrogen
nitrogen status)
status) and
and with
with stand
stand relarela­
its
measure of stocking and
and tree
tree size; Table
Table 8). These
These high
high
tive density (C>r;
tive
(Jr; aa measure
correlations are
are expected because
because of the
the mathematical
mathematical relationship
relationship between
between
correlations
and tree
tree height, numbers, and
and size. Surprisingly, volume growth
growth
volume growth and
was
significantly
correlated
with
all
variables
indicating
soil-N
status,
but
not
was
with all variables
soil-N status, but not
as indicators of soil-moisture
soil-moisture status.
status. Like fertilizer trials,
with p,
with
p, C>n
Jr, ds,
d~, or Bc
Oc as
TABLE
TABLE 77
Description
Description and
and statistics
statistics for
for the
the independent
independent variables at
at 64
64 locations
locations in
in southwestern
southwestern Oregon
Oregon
Variable
Variable
Average
Average
cv
Moisture
M o i s t u r e indicators
indicators
Precipitation
year - 11))
Precipitation (p; mm
mm yearSolar
Solar radiation
radiation ratio
ratio ((Q:)
Q:)
Elevation
Elevation (He;
(He; m)
m)
Effective
Effective soil
soil depth
depth (d.;
{ds; em)
cm)
Available
Available water-holding
water-holding capacity
capacity (8e;
(0¢; mm)
mm )
1676
1676
1.52
1.52
623
623
107
107
174
174
31
31
7
7
47
47
31
31
43
43
N u t r i e n t indicators
i n d i c a t o r s ((O-15-cm
0 - 1 5 - c m depth)
depth)
Nutrient
Mineralizable
Mineralizable N'
N i (Nmin;
{Nmin; p.p.m.)
Total
Total N
N (N;
(N; % ))
Organic matter
matter 22 (OM;%
(OM; % ))
Organic
Carbon:
Carbon : nitrogen
nitrogen ratio
ratio (C:
( C: N)
N)
Mineralizable N'
N 1 (N
(Nmln
h a --11))
min 2;
Mineralizable
2;kg ha
Total
')
Total N
N (N
(N2;
ha --1)
2;tt ha
matter 22 (OM
(OM2;
ha --11))
Organic matter
2;tt ha
50
50
0.15
0.15
7.9
7.9
33.3
33.3
42.0
42.0
1.26
64.7
64.7
56
56
53
53
51
51
36
36
51
51
43
43
31
31
Composite
C o m p o s i t e indicator
indicator
index 3 (SI;
(sl; m at
at age 50)
Site index3
33.6
33.6
18
18
11Anaerobically
Anaerobically mineralized
mineralized N
N (Waring
(Waring and
and Bremner,
Bremner, 1964)
1964)..
22Walkley-Biack
method (Jackson,
(Jackson, 1958).
1958).
Walkley-Black method
aFrom King (1966)
(1966)..
3From
cv
337
337
IMPORTANCE
IMPORTANCEOF
OFWATER
WATERAND
ANDNUTRIENTS
NUTRIENTSON
ON GROWTH
GROWTHOF
OFDOUGLAS
DOUGLASFIR
FIR
TABLE
TABLE S8
Correlation
Correlation coefficients
coefficients (r)
(r) between
between variables associated
associated with
with volume growth
growth (m3
(m 3 ha-I)
ha -~) of
of un­
unand their response to 225 kg N
N ha
ha-1
southwestern
treated Douglas fir stands and
-I at 64 locations in southwestern
Oregon
Oregon
Variable11
Site index
(m)
(m)
Stand
Stand
SI
sI
1
A
Abh
bh I
sIX
SI × Abh
Abh
~r
15,
--0.16
--0.16
---
Untreated
Untreated growth
Response
Absolute
Absolute
Absolute
Relative
Relative (%)
(%)
**
0.56
0.56**
-0.11
--0.11
0.02
0.02
**
0.51
0.51"*
0.04
0.04
-0.12
--0.12
-0.11
-- 0.11
-0.13
--0.13
-0.16
- 0.16
-0.23
--0.23
-0.26
-- 0.26**
**
-0.3S
--0.38**
0.21
0.21
-0.2S
--0.28**
O.lS
0.18
0.16
0.19
0.15
-0.02
--0.02
-0.06
-0.06
- 0.04
-0.04
-0.14
-0.14
0.10
0.13
0.13
-0.12
-0.12
- 0.04
-0.04
-0.11
-0.11
**
0.42
0.42**
**
0.46
0.46**
0.23
**
-0.46
- 0.46**
**
0.41
0.41"*
**
0.53
0.53**
0.26
0.26**
-0.04
- 0.04
- 0.04
-0.04
0.10
0.29
0.29**
-0.06
- 0.06
-0.06
- 0.06
0.16
0.16
-0.20
- 0.20
- 0.20
-0.20
0.01
**
0.48**
0.48
-0.21
- 0.21
-0.21
- 0.21
0.06
0.06
Site
Site
p
p
H
Hee
Q:
d
d~s
e
0cc
Soil test
test
N
Nmin
min
N
N
OM
OM
C:N
C: N
N
Nmin
min22
N
N22
OM
OM22
0.44
0.44
**
-0.57
-0.57**
-O.OS
-0.08
**
0.34
0.34**
0.27
0.27**
**
0.36
0.36**
**
0.36
0.36**
0.28
0.28**
-0.23
- 0.23
**
0.39
0.39**
**
0.41
0.41"*
**
0.37
0.37**
IA
~Abh,
Jr, relative density (Curtis, 1982);
1982); for other abbreviations, see text.
bh, age at breast, height; 15"
**P~<
P.;;0
.05; **
.Ol.
0.05;
**,, P.;;
P~< O0.01.
is ggrowth-limiting
tthis
h i s eevidence
v i d e n c e aalso
l s o ssuggests
u g g e s t s tthat
h a t nnutrient
u t r i e n t sstatus
t a t u s is
r o w t h - l i m i t i n g iin
n ssouth­
outhwestern
w
e s t e r n Oregon.
Oregon.
Yearly
225 kkg
2.73 m
m33 hha
Y e a r l y rresponse
e s p o n s e tto
o 225
g N
N hha
a --11 aaveraged
v e r a g e d 2.73
a --11 (coefficient
( c o e f f i c i e n t ooff vvari­
ariaation=
t i o n = 106%
1 0 6 % )) dduring
u r i n g tthe
h e 55--112
2 yyears
e a r s ooff oobservation;
b s e r v a t i o n ; oobservation
b s e r v a t i o n pperiod
e r i o d aaver­
verso aaverage
was
22 m
m3a hha
aaged
g e d aabout
b o u t 88 yyears,
e a r s , so
v e r a g e ttotal
o t a l ggain
ain w
a s aat
t lleast
e a s t 22
a --1.
1. Both
B o t h aabsolute
bsolute
were
aand
n d ppercentage
e r c e n t a g e ggains
a i n s ffrom
r o m nitrogen
n i t r o g e n ffertilization
e r t i l i z a t i o n (mean
(mean =
= 17.4%,
17.4 %, CV=
c v - - 127)
12 7 ) w
ere
This
is eexpected
ssignificantly
i g n i f i c a n t l y rrelated
e l a t e d tto
o C:N
C : N rratio
a t i o ooff tthe
h e ssurface
u r f a c e ssoil
o i l (Table
( T a b l e 88).
). T
h i s is
xpected
N rratios
bbecause
e c a u s e C:
C:N
a t i o s eexceeding
x c e e d i n g aabout
b o u t 330:
0 : 11 ggenerally
e n e r a l l y iindicate
n d i c a t e ddecreasing
ecreasing N
N
aavailability
v a i l a b i l i t y aand
n d tthus
h u s aan
n iincreasing
n c r e a s i n g nneed
e e d ffor
or N
N ffertilization.
e r t i l i z a t i o n . We
W e eexamined
x a m i n e d rre­
elationships
l a t i o n s h i p s aamong
m o n g vvolume
o l u m e response,
r e s p o n s e , C:
C :N
N rratio
a t i o ooff tthe
h e surface
s u r f a c e soil,
soil, aand
n d Oc
0c ooff tthe
he
within
was:
ssoil
oil w
i t h i n rooting
r o o t i n g ddepth.
e p t h . Our
O u r qquestion
uestion w
a s : ddoes
o e s moisture
m o i s t u r e aavailability
v a i l a b i l i t y llimit
imit
would
rresponse
e s p o n s e tto
o N
N ffertilizer?
e r t i l i z e r ? An
A n aaffirmative
f f i r m a t i v e aanswer
nswer w
o u l d cconfirm
o n f i r m tthe
h e iimportance
mportance
ooff m
o i s t u r e tto
o ggrowth
r o w t h iin
n tthis
h i s aarea.
rea.
moisture
I n tthis
h i s ccovariance
o v a r i a n c e aanalysis,
n a l y s i s , Oc
0c w
a s aa ccontinuous
o n t i n u o u s vvariable
a r i a b l e tthat
h a t rranged
a n g e d ffrom
rom
In
was
338
338
S,P,
S.P. GESSEL
GESSELET
ET AL.
AL.
11
0
0
'1,0
QJ
>'I
0
..c:
.I:
8
8
=
=
E
QJ
Ul
c
0
o
~x
0.
oi
Ul
QJ
a::
°
,=
=
=
o
%
".,
B
u
6
6
a
u
==
a
o
4
4
D
=
tl
2
2
=
=
=
=
m=
a
a
a
l= a
o
¢=
=
o
=
0
0
a
=
p
=
a
l=
=
=
m
o
a
a
=
a
=
a
=
I:
°==
= a
=
a
J=
I .....
I
I
D
a
@
0
J=
-- 22
=
o
m
- 44
0
200
26o
16o
100
140
140 ,
360
300
400
460
500
500
o
120
120 t
100
~0o4
80
'if:.
QJ
Ul
c
c
0
o
0.
Ul
QJ
t"v"
a::
60
60o
0
40
40-
o
0
0
o
0
0
°o°8
do
-
0
0
0
o
0
0
o
0
20
20.
,, --20
20
o
0
o
0
....
100
16o
v
0
=o
oo ~
~
~o
!'lo
o
o
I o~
I
o
0
0
200
26o
300
35o
46o
400
500
500
AVAILABLE
A V A I L A B L E MOISTURE-HOLDING
M O I S T U R E - H O L D I N G CAPACITY
CAPACITY (mm)
(ram)
Fig.
Fig. 1.
1. Average
Average annual volume response by
by 64
64 Douglas-fir
Douglas-fir stands in southwestern
southwestern Oregon to 224
224
kg
fertilization.
kg N
N ha
ha -1
-1 5
5-12
-12 years after fertilization.
56 to
to 422
422 mm;
mm; it
it was
was derived
derived from
from horizon
horizon depth,
depth, gravel
gravel content,
content, texture
texture of
of
56
<2-mm
parent material.
material. Five
classes of C:N
ratios were asas­
< 2-mm fraction, and parent
Five classes
C : N ratios
0 -25, 25.1-35,
25.1-35, 35.1
45.1-55, 555+.
The analysis
analysis of covariance
covariance of
signed: 0-25,
35.1-45,
5 + . The
-45, 45.1-55,
percentage of response
response showed some
some statistically
statistically significant
that
percentage
significant relationships; that
absolute response
response showed none.
none. For
percentage of response, the
the analysis
analysis is
is
for absolute
For percentage
summarized in
in Table
Table 9.
summarized
This
(a) no
This covariance
covariance analysis
analysis showed: (a)
no significant
significant common
common regression
regression of
response
0¢ (Fig. 1); (b)
(b) no
response over f)c
no significant difference among
among regression
regression coefcoef­
classes; and
and (c)
no significant
significant interaction
interaction between
between f)c
ficients for
for the
the five
five C:
ficients
C: N
N classes;
(c) no
0c
339
339
IMPORTANCE
AND NUTRIENTS
IMPORTANCE OF
OF WATER
WATERAND
NUTRIENTS ON
ON GROWTH
GROWTH OF
OF DOUGLAS
DOUGLASFIR
FIR
TABLE
TABLE 9
9
Summary
S u m m a r y of
of covariance
covariance analysis
analysis
Source of
of variation
Source
variation
DF
DF
Mean
M e a n square
square
F
F
p<
P<
Within +
+ residual
residual
Within
0c (regression)
(regression)
()c
54
54
11
4
4
4
4
1645
1645
2287
2287
2266
2266
2331
2331
-1.39
1.39
1.38
1.38
1.42
1.42
-0.244
0.244
0.254
0.254
0.241
0.241
C: N
C:N
0¢ X C : N
()cXC:N
classes. These
These results
results indicate that
that moisture
moisture availability
availability did not
not limit response
response
to N
analysis of variance, however, showed aa sigsig­
to
N fertilizer. An
An accompanying analysis
nificant
difference
in
average
responses
among
the
observed
C:
N
classes.
nificant difference in average responses among the observed C: N classes.
In
site index
index and
and volume growth
growth of unfertilized stands
stands in
in southsouth­
In conclusion, site
western
Oregon were
western Oregon
were correlated with
with variables
variables indicating both
both site
site moisture
moisture
and nitrogen
nitrogen status.
status. Variables
that correlated
correlated well with
with site
site index
index and
and growth
and
Variables that
correlated well with
with response
response to
to fertilfertil­
of unfertilized stands, however, seldom correlated
no strong
strong evidence that
that response
response to
to fertilizer
fertilizer N
was greater
greater at
at
izer. We
We found no
N was
locations with
with relatively
relatively more
more favorable
favorable moisture
moisture relations
relations or, conversely, that
that
locations
response was
was less at
at sites
sites with
with less
less precipitation, more
more summer or
or total
total solar
solar
response
poorer 8e•
may have
have been
been improved at
at those
those
radiation, or poorer
0c. Water-use
Water-use efficiency may
where response
response to
to fertilizer
fertilizer occurred.
occurred.
locations (ca.
(ca. 70% )) where
The combined results
results from
from these
these studies
studies in
in the
the Pacific
The
Pacific Northwest
Northwest U.S.A.
us to
to conclude that,
that, compared with
with nutrition, moisture
moisture is not
not aa major
major
lead us
factor for the
the growth
growth of Douglas
in the
the region.
region.
limiting factor
Douglas fir in
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
Financial support for the
the wastewater
wastewater component of this
this study
study was
was supplied
Financial
by the
the U.S.
and the
the Municipality of Metropolitan
Metropolitan
by
U.S. Army
Army Corps
Corps of Engineers
Engineers and
Seattle (METRO).
support for the
the southwestern
southwestern Oregon
research
Seattle
(METRO). Financial
Financial support
Oregon research
was provided by
by the
the U.S.
Management
was
U.S. Department
Department of Interior,
Interior, Bureau
Bureau of Land
Land Management
and the
the U.S. Department
through the
the SouthSouth­
and
Department of Agriculture, Forest
Forest Service, through
western Oregon
western
Oregon Forestry
Forestry Intensified Research
Research (FIR)
(FIR) Program.
Program.
REFERENCES
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U.S.D.A. Soil
Anonymous, 1979.
1979. Soil
Soil Survey
Survey of
of Pierce
Pierce County,
County, Washington.
Washington. U.S.D.A.
Soil Conservation
Conservation Serv­
Serv131 pp.
pp.
ice, 131
Brix,
W.A.
Brix, H.,
H., 1979.
1979. Moisture-nutrient
M o i s t u r e - n u t r i e n t interrelationships.
interrelationships. In:
In: S.P.
S.P. Gessel,
Gessel, R.M.
R.M. Kenady
Kenady and
and W.A.
A t k i n s o n (Editors),
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Seattle, WA,
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Atkinson
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on soil
soil and
and tree
tree
Brix,
water stress
stress in
in aa Douglas-fir
Douglas-fir stand.
stand. Can.
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Brubaker,L.B.,
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growth anomalies
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Gessel,
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