764
Growth and foliar nutrient response to fertiHzation and precommercial thinning in a
coastal western red cedar stand
CONSTANCE A. HARRINGTON I
USDA Forest Service, Southern Forest Experiment Station, P.O. Box 3516, Monticello, AR 71655, U.S.A.
AND CHARLES A. WIERMAN Boise Cascade Corporation, P. O. Box 50, Boise, ID 83728, U.S.A.
Received February 2, 1989
Accepted November 30, 1989
HARRINGTON, C. A., and WIERMAN, C. A.
1990.
Growth and foliar nutrient response to fertilization and
precommercial thinning in a coastal western red cedar stand. Can. J. For. Res. 20: 764-773.
Seven silvicultural treatments were applied to a young (15- to 20-year-old), naturally regenerated western red cedar
(Thuja plicata Donn ex D. Don) stand growing on a poor-quality site in western Washington. The treatments were
as follows: unthinned, unfertilized (untreated); unthinned, fertilized with ammonium nitrate, dicalcium phosphate,
and potassium sulfate; thinned, unfertilized; thinned, fertilized with urea; thinned, fertilized with ammonium nitrate;
thinned, fertilized with ammonium nitrate and dicalcium phosphate; and thinned, fertilized with ammonium nitrate,
dicalcium phosphate, and potassium sulfate. Elemental application rates were 300 kg nitrogen, 100 kg phosphorus,
129 kg calcium, 100 kg potassium, and 41 kg sulfur per hectare. Growth and foliar nutrient concentrations were monitored
for 5 years. Five-year height growth and diameter growth of the 20 tallest trees per 0.08-ha measurement plot were
both substantially greater in all thinned or fertilized treatments than in the unthinned, unfertilized treatment. The three
best treatments for height growth (the treatments containing ammonium nitrate and dicalcium phosphate) had 65070
more growth than the unthinned, unfertilized treatment. The two best treatments for diameter growth (thinned, fertilized
with ammonium nitrate and dicalcium phosphate) had 106070 more growth than the unthinned, unfertilized treatment.
The effects of thinning alone were small compared with the effects of fertilization alone or fertilization combined with
thinning. Initial foliar nitrogen concentrations showed that the site was nitrogen deficient, and both nitrogen sources,
urea and ammonium nitrate, increased growth. The addition of dicalcium phosphate resulted in significantly greater
incremental growth above that attributed to nitrogen alone, but the further addition of potassium sulfate did not increase
growth significantly. Increases in foliar nitrogen and phosphorus associated with fertilization were still evident 5 years
after treatment. All sizes of trees responded to treatment, and growth of the total stand followed the same trends as
for the 20 tallest trees per plot. Basal area growth on an absolute basis was best in the unthinned, fertilized treatment
(more than twice that of the unthinned, unfertilized treatment) and on a percent basis was best in the thinned treatment
fertilized with ammonium nitrate, dicalcium phosphate, and potassium sulfate.
HARRINGTON, C. A., et WIERMAN, C. A. 1990. Growth and foliar nutrient response to fertilization and precommercial
thinning in a coastal western red cedar stand. Can. J. For. Res. 20 : 764-773.
Sept traitements sylvicoles ont ete effectues dans un jeune peuplement (15-20 ans), originant de regeneration naturelle,
de Cectre de I'ouest (Thuja plicata Donn ex D. Don) croissant sur une station pauvre dans l'ouest de l'etat de Washington.
Les traitements etaient : non eclairci, non fertilise (non traite); non eclairci, fertilise avec du nitrate d'ammonium, du
phosphate dicalcique et du sulfate de potassium; eclairci, non fertilise; eclairci, fertilise avec de I'uree; ec1airci, fertilise
avec du nitrate d'ammonium; eclairci, fertilise avec du nitrate d'ammonium et du phosphate dicalcique; et eclairci,
fertilise avec du nitrate d'ammonium, du phosphate dicalcique et du sulfate de potassium. Les taux d'application ont
ete de 300 kg azote, 100 kg phosphore, 129
calcium, 100 kg potassium et 41 kg sulfure a I'hectare. La croissance
et les concentrations foHaires en elements nutritifs ont ete suivies pendant 5 ans. Les croissances en hauteur et en diametre
apres 5 ans sur les 20 arbres les plus hauts par parcelle de 0,08 ha etaient substantiellement plus fortes dans tous les
traitements d'ec1aircis ou fertilises lorsque compares aux traitements sans eclaircis, non fertilises. Les trois meilleurs
traitements pour la croissance en hauteur (les traitements contenant Ie nitrate d'ammonium et Ie phosphate dicalcique)
ont eu une croissance de 65070 superieure au traitement non eclairci et non fertilise. Les deux meilleurs traitements pour
I'accroissement en diametre (eclairci, fertilise avec Ie nitrate d'ammonium et Ie phosphate dicaIcique) ont eu une croissance
de 106% superieure au traitement non eclairci, non fertilise. Les effets de l'eclaircie seule ont ete faibles lorsque com­
pares a la fertilisation seule ou la fertilisation combinee avec I'eclaircie. Les concentrations initiales foliaires en azote
ont montre que la station etait deficiente en cet element et que les deux sources d'azote, I'uree et Ie nitrate d'ammonium,
ont augmente la croissance. L'ajout de phosphate dicalcique a augmente significativement la croissance lorsque com­
pare a l'ajout d'azote seul mais I'addition supplementaire de sulfate de potassium n'a pas augmente significativement
la croissance. Les accroissements en azote et phosphore foliaire associes avec la fertilisation etaient encore evidents
5 ans apres Ie traitement. Les arbres de toutes les dimensions ont reagi au traitement, et la croissance globale du peuplement
a suivi les memes tendances que les 20 arbres les plus hauts par parcelle. La croissance en surface terriere sur une base
absolue etait la plus elevee pour Ie traitement non eclairci, fertilise (plus du double que Ie traitement non eclairci et
non fertilise) et sur une base de pourcentage, Ie traitement eclairci, fertilise avec Ie nitrate d'ammonium, Ie phosphate
dicalcique et Ie sulfate de potassium, etait Ie meilleur.
[Traduit par la revue]
I
present address: USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Avenue SW, Olympia,
WA 98502, U.S.A.
Printed in Canada J lmprimc
au
Canada
HARRINGTON AND WIERMAN
Introduction
Western red cedar (Thuja plicata Donn ex D. Don) is an
important component of old-growth stands in western
Canada and the United States. The species has wide eco­
logical amplitude, especially in relation to soil nutrition
(Weetman et al. 1988), and occurs in pure and mixed stands
throughout the region. In relation to its common tree
associates, Douglas-fir (Pseudotsuga menziesii (Mirb. )
Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.),
and Sitka spruce (Picea sitchensis (Bong.) Carr.), western
red cedar has generally been neglected in the regeneration
and management of young-growth stands in the region, in
part because of the lack of information on the species.
Western red cedar has probably been planted and managed
more in Britain (Aldhous and Low 1974; O'Carroll 1967),
where it is an exotic species, than in North America, where
it is native. However, North American interest in the biol­
ogy and silviculture of western red cedar has been increas­
ing (cf. Imper and Zobel 1983; Minore 1983; Nystrom et al.
1984; Radwan and Harrington 1986), and a symposium on
the species was recently held (Smith 1988). Very little infor­
mation is available on the performance of the species under
management. The 5-year response of a western red cedar
stand on a poor-quality coastal site to precommercial
thinning and several fertilization treatments is summarized
in this report. An earlier report (Harrington and Wierman
1985) presented 2-year growth for the total stand and 3-year
growth for the 20 tallest trees per plot.
Materials and methods
The study area and study establishment procedures are outlined
in detail in Harrington and Wierman (1985) and are only described
briefly here. The study area,located 10 km from the Pacific Coast
in Clallam County,Washington (48°8'N,124°38'W),has a mild
and wet climate with annual precipitation averaging 2700 mm.
Elevation is approximately 100 m; the area has little relief, with
maximum slopes less than 10010. The soil series is Kydaka,a member
of the medial, acid, mesic Typic Humaquepts (Soil Survey Staff
1975). The closest equivalent in the Canadian system of soil
classification would be the Humic Gleysols with Mor humus
(Agriculture Canada Expert Committee on Soil Survey 1987). The
Kydaka series is a moderately deep,poorly drained,silty clay loam.
Surface mineral soil on the study area has a pH of 4.6. The 50-year
site index for western red cedar on the study area is about 20 m
(Kurucz 1978).
In 1980,the stand was predominantly western red cedar saplings.
Other tree species present were western hemlock, Pacific yew
(Taxus brevijolia NutL), Pacific silver fir (Abies amabilis Doug!.
ex Forbes), Sitka spruce, red alder (Alnus rubra Bong.). and
cascara (Rhamnus purshiana DC.). Salal (Gaultheria shallon
Pursh) and red and blue huckleberry (Vaccinium parvijolium
Smith, V. ovalijolium Smith) were the most common shrubs.
The overstory of the previous stand, consisting primarily of
western red cedar 0.5 to 4 m in diameter, was clear-cut in 1961.
Two salvage sales have been held in the area since the original log­
ging,but large amounts of both sound and rotten woody debris
remain on the site. The majority of the young-growth stand prob­
ably regenerated from seed that germinated following logging; in
1980,these trees were 15 to 20 years old and 5 to 6 m tall. Some
advanced and delayed reproduction was also present,resulting in
a substantial range in tree size. Stocking averaged 5900 stems per
hectare but was variable; low stocking was generally associated with
large stumps and woody debris or was found in areas of poorer
than average drainage.
Twenty-eight permanent plots were established, each with a
30 x 50 m treatment area and a 20 x 40 m interior measurement
765
plot. Seven treatments were replicated in four blocks, and treat­
ment assignment was random within each block. The treatments
were as follows: (i) unthinned,unfertilized (untreated) (UT -UF);
(ii) unthinned, fertilized with ammonium nitrate, dicalcium
phosphate,and potassium sulfate (UT -NPK); (iii) thinned, unfer­
tilized (T -UF); (tv) thinned, fertilized with urea (T -Ur);
(v) thinned,fertilized with ammonium nitrate (T-N); (vi) thinned,
fertilized with ammonium nitrate and dicalcium phosphate (T-NP);
and (vii) thinned, fertilized with ammonium nitrate, dicalcium
phosphate,and potassium sulfate (T-NPK). The plots were blocked
to account for variability in soil drainage. In the thinned plots,
the western red cedar crop trees were spaced at approximately
3 x 3 m (1100 trees per hectare or 88 trees per measurement plot).
The biggest trees with the best form were selected as crop trees
rather than attempting to achieve exact spacing. The thinning was
done by hand during October 1980; thinning slash was left on the
site. Elemental rates of fertilizer application were 300 kg N . ha 1
(urea or ammonium nitrate), 100 kg p. ha -1 and 129 kg Ca· ha 1
(dicalcium phosphate), and 100 kg K· ha 1 and 41 kg S· ha I
(potassium sulfate). Fertilizers were cross applied by hand between
March 26 and April 3, 1981. Weather conditions during and
immediately following fertilization were cool and wet.
All trees 1.3 m or taller were tagged and measured for total height
and diameter at breast height (1.3 m). Trees shorter than 1.3 m
were tagged and measured for height on thinned plots,but not on
unthinned plots because of their excessive number and suppressed
crown position. All tagged trees were remeasured for height and
diameter following the second and fifth growing seasons since treat­
menL The 20 tallest trees per plot were remeasured for height and
diameter after the first,second,third,and fifth growing seasons.
Dormant-season foliage samples were collected from to upper
crown class trees in each plot 1,2,3,and 5 years after treatment.
Current-year foliage from the upper third of the tree crown was
analyzed for total N (Kjeldahl procedure in Jackson 1958) and for
P,K,S,and Ca (wet ash procedure in Horwitz 1980) by the Plant
and Soil Analytical Laboratory at the University of Idaho.
Height growth and diameter growth of the 20 tallest trees per
plot were analyzed for the total 5-year period using analysis of
covariance; initial height or diameter was used as the covariate.
Trees that sustained top damage during the experiment were not
included in the analysis of height growth. Specific treatment
contrasts were tested as listed in Table 1. The trees in the total stand
were divided into three initial height classes: height class 1
trees
:;:;3.0 m,height class 2 = trees >3.0 m and <4.5 m, and height
class 3 = trees ;:::4.5 m. To test for treatment responses in the
height classes, 5-year height and diameter growth were analyzed
using a split plot design. The silvicultural treatments were the whole
plot treatments, and the height classes were the split plot treatments.
The treatment by height class interactions were significant,so spe­
cific treatment contrasts were specified for each height class. Basal
area growth for the 5-year period was analyzed using analysis of
variance with specific treatment contrasts specified. Nutrient con­
centrations were analyzed using a split plot in time design. All but
one element exhibited a significant treatment by time interaction.
To interpret the interactions,the trend lines for changes in foliar
concentrations over time were examined graphically for each
element.
Results
Twenty tallest t rees per plot
Five-year height growth of the 20 tallest trees per plot dif­
fered significantly by treatment (Table 1, P < 0.01) and was
least in the unthinned, unfertilized treatment (Fig. 1). The
best treatments increased 5-year height growth 65007 over the
untreated plots. Annual height growth in the unthinned,
unfertilized treatment declined from the 1st to the 2nd year,
then leveled off at about 0.3 m· year I. Annual height
-
growth of thinned, unfertilized plots was equal to that of the
unthinned, unfertilized treatment for the first 2 years; how­
CAN.
766
J. FOR. RES. VOL. 20, 1990
TABLE 1. Summary of analyses of 5-year height and diameter growth of the 20 tallest
trees per plot
5-year diam. growth
5-year height growth
F
P >F
SS
F
P >F
5.00
lO.88
<0.01
47.07
17.87
<0.01
1
3
6
0.21
0.39
4.52
4.76
2.83
16.41
0.04
0.07
<0.01
2.93
4.19
42.75
1l.l3
5.31
27.05
<0.01
0.01
<0.01
1
1
1
1
1
1
17
27
0.23
0.33
0.23
<0.01
0.09
<0.01
0.78
5.78
5.06
7.27
4.96
0.02
2.05
0.04
0.04
0.02
0.04
0.88
0.17
0.85
2.32
5.01
1.39
0.09
0.03
2.47
4.48 51.55 8.82
19.04
5.28
0.35
l.l3
9.40
0.01
<0.01
0.03
0.56
0.30
0.01
Source of variation
df
SS
Model
Covariate (initial
height or diam.)
Block
Treatment
Contrasts*
T-UF vs. UT-UF
T-N vs. T-UF
T-NP vs. T-N
T-NPK vs. T-NP
T-Ur vs. T-N
T-NPK vs. UT-NPK
Error
Corrected total
lO
NOTE: Type III sum of squares are presented for the covariate, block, and treatment components of the model.
*T -UF, thinned, unfertilized; UT-UF, unthinned, unfertilized (untreated); T-N, thinned, fertilized with
ammonium nitrate; T-NP, thinned, fertilized with ammonium nitrate and dicalcium phosphate; T-NPK, thinned,
fertilized with ammonium nitrate, dicalcium phosphate, and potassium sulfate; T-Ur, thinned, fertilized with
urea; UT-NPK, unthinned, fertilized with ammonium nitrate, dicalcium phosphate, and potassium sulfate.
3
7
S
2
:r:
:r:
0
a:
c.!J
0
a:
c.!J
2
a:
lJ.J
flJ.J
f:r:
c.!J LU
2
lJ.J
0
«
:r:
>
lJ.J
>
:s
6
5
4
3
2
:s
:J 2
:J
2
:J
u
:J
U
0
-0
/
-0
/
*-
",/
-0' ",/
'"/
",/-#
"'/
*-
FIG. 1. Cumulative annual height growth of the 20 tallest trees
per plot, by treatment. ., 1981 growth; I:;l, 1982 growth; 1:1, 1983
growth; b:'l, 1984-1985 growth. Treatment codes are as follows:
UT -UF, unthinned, unfertilized; UT-NPK, unthinned, fertilized
with ammonium nitrate, dicalcium phosphate, and potassium
sulfate; T-UF, thinned, unfertilized; T-Ur, thinned, fertilized with
urea; T-N, thinned, fertilized with ammonium nitrate; T-NP,
thinned, fertilized with ammonium nitrate and dicalcium
phosphate; T-NPK, thinned, fertilized with ammonium nitrate,
dicalcium phosphate, and potassium sulfate.
ever, in years 3 to 5, height growth was about 0.1 m·year-I
greater in the thinned than in the unthinned, unfertilized
treatment. Over the 5-year period, height growth in the
thinned, unfertilized treatment was significantly greater than
in the unthinned, unfertilized treatment (p
0.04).
The fertilized treatments had substantially better 5-year
height growth than the corresponding unfertilized treat­
ments. Differences among treatments in height growth were
generally greatest the 2nd and 3rd years following treatment.
=
0
FIG. 2. Cumulative annual diameter growth of the 20 tallest
trees per plot, by treatment. ., 1981 growth; r;;J, 1982 growth;
i!:l, 1983 growth; cs, 1984-1985 growth. Treatment codes are as
given in Fig. 1.
The thinned, ammonium nitrate treatment had significantly
greater 5-year height growth than the thinned, unfertilized
treatment (p
0.02). Annual height growth in the urea
treatment was relatively low the 1st year (compared with the
ammonium nitrate treatment), but exhibited a substantial
increase between the 1st and 2nd years. Over the 5-year
period the urea treatment had slightly greater 5-year height
growth than the ammonium nitrate treatment (Fig. 1), but
the difference was not statistically significant (p
0.17).
The thinned, ammonium nitrate plus dicalcium phosphate
treatment had significantly better 5-year height growth than
the thinned, ammonium nitrate treatment; thus the addi­
tion of dicalcium phosphate apparently increased height
growth. The additional inclusion of potassium sulfate, how­
=
=
HARRINGTON AND WIERMAN
767
TABLE 2. Summary of analysis of 5-year height and diameter growth of the total stand by initial height class
5-year height growth
5-year diam. growth
Source of variation
df
SS
F
P >F
SS
F
Model
Block (Bl.)
Treatment (Tr.)
Error 1 (Tr. x Bl.)
Height class (HC)
Error 2 (Tr. x HC)
Contrasts*
Height class 1
T-UF vs. UT-UF
T-N,T-Ur,T-NP,T-NPK vs. T-UF
UT-NPK vs. UT-UF
Height class 2
T-UF vs. UT-UF
T-N,T-Ur,T-NP,T-NPK vs. T-UF
UT-NPK vs. UT-UF
Height class 3
T-UF vs. UT-UF
T-N,T-Ur,T-NP,T-NPK vs. T-UF
UT-NPK vs. UT-UF
Error 3
Corrected total
41
3
28.62
1.14
18.39
2.73
5.50
0.85
34.38
18.79
150.97
7.48
135.53
3.47
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
222.51
8.10
112.79
19.18
79.78
2.65
50.86
25.32
176.18
9.99
373.82
2.07
<0.01
<0.01 <0.01 <0.01
<0.01
0.04
1.23
1.46
2.13
60.58
72.13
105.04
<0.01
<0.01
<0.01
3.58
5.83
2.51
33.54
54.68
23.48
<0.01
<0.01
<0.01
0.57
2.08
2.56
28.05
102.69
126.12
<0.01
<0.01
<0.01
3.72
11.02
34.85
103.29
57.72
<0.01
<0.01
<0.01
0.45
1.00
2.78
0.85
29.47
22.15
49.02
36.83
<0.01
<0.01
<0.01
5.00
10.41
11.37
4.48
226.99
46.88
97.59
106.60
<0.01
<0.01
<0.01
NOTE: Height class I = trees < 3.0 m, height class
·See Table I for definitions of the treatments.
2
6
18
2
12
1
1
1
42
83
=
trees
ever, did not significantly increase height growth. Although
there were minor differences in annual height growth
between the thinned and unthinned treatments amended with
ammonium nitrate, dicalcium phosphate, and potassium
sulfate, 5-year growth was the same (p
0.85).
The silvicultural treatments caused greater increases in
diameter growth of the 20 tallest trees per plot than they
did in height growth (Fig. 2). The best two treatments had
106070 more 5-year diameter growth than the unthinned,
unfertilized treatment. Diameter growth in the unthinned,
unfertilized treatment was consistently the lowest each year
and did not vary much from year to year. Thinning signifi­
cantly increased diameter growth (Table 1, P = 0.01), but
thinning alone resulted in small gains compared with thin­
ning plus fertilization or with fertilization without thinning
(Fig. 2). The thinned, ammonium nitrate treatment had sig­
nificantly greater 5-year diameter growth than the thinned,
unfertilized treatment (p < 0.01). In relation to the four
thinned, fertilized treatments, the unthinned, fertilized treat­
ment had comparable diameter growth the first 3 years but
less diameter growth during the last 2-year period.
Diameter growth of the thinned, fertilized treatments
peaked the 3rd year after treatment, with the best treatments
having annual growth rates almost three times greater than
in the unthinned, unfertilized treatment. Although diameter
growth in all fertilized treatments declined from year 3 to
years 4 and 5, annual growth rates in fertilized plots were
still substantially higher than those in nonfertilized plots.
Plots receiving urea had slightly greater annual diameter
growth each year than those receiving ammonium nitrate;
however, 5-year diameter growth did not differ significantly
0.30). The treat­
between the two N fertilizer sources (p
ment with dicalcium phosphate plus ammonium nitrate had
greater diameter growth each period than the treatment with
only ammonium nitrate, and the 14% increase in 5-year
=
=
3.0-4.5
m, height class
3
=
trees
6.16
;;,;4.5
P>F
m.
diameter growth from adding dicalcium phosphate was
0.03). The thinned treatment
statistically significant (p
containing potassium sulfate in addition to the other fer­
tilizers had greater 5-year diameter growth than the corre­
sponding treatment without potassium sulfate; however, the
0.56). In
difference was not statistically significant (p
contrast with the nonsignificant difference in height growth
between the unthinned fertilized treatment and the corre­
sponding thinned treatment, diameter growth was signifi­
cantly greater in the thinned, fertilized treatment
(p
0.01).
=
=
=
Total stand
The 5-year height and diameter growth of the total stand
followed the same trends as discussed for the 20 tallest trees
per plot. The poorest growth was always in the unthinned,
unfertilized treatment, followed by the thinned, unfertilized
treatment. The effects of treatment, height class, and the
treatment by height class interaction were all significant
(Table 2). For all three height classes the specified contrasts,
thinned versus unthinned (no fertilizer), fertilized versus
unfertilized (both thinned), and fertilized versus unfertilized
(unthinned), were all significant for both height and
diameter growth. Absolute growth increases were greatest
for the largest trees, but the percent increase in growth was
greatest for the trees in the smallest size class.
Basal area growth differed significantly by treatment
(Table 3). The unthinned, fertilized treatment had substan­
tially more basal area at the end of the 5-year treatment
period than any other treatment (Fig. 3). In addition,
periodic basal area growth in the unthinned, fertilized treat­
ment increased more than any other treatment from the first
period (1981 to 1982) to the second (1983 to 1985); thus,
it may continue to diverge from the other treatments for
several years. Five-year basal area growth in the unthinned,
CAN. J. FOR. RES. VOL 20, 1990
768
TABLE
3. Summary of analysis of basal area growth (based on the total stand)
Source of variation
df
Model
Block
Treatment
Contrasts*
T-UF vs. UT-UF
T-N,T-Ur,T-NP,T-NPK vs. T-UF
T-N,T-Ur,T-NP,T-NPK vs. UT-UF
T-NPK vs. UT-NPK
Error
Corrected total
'See Table
I for
P>F
F
SS
9
145.66
9.73
3
6
8.64
137.01
1.73
<0.01
0.21
13.73
<0.01
1
3.29
14.09
1.98
8.47
1.28
37.76
0.18
0.01
1
1
1
18
27
2.13
62.78
29.93
175.58
0.27
<0.01
definitions of the treatments.
fertilized treatment was significantly greater than growth in
< 0.01). The
the corresponding thinned treatment (p
unthinned, unfertilized treatment had greater initial basal
area than any of the thinned treatments; however, the
unthinned, unfertilized treatment had about the same basal
area growth in 1981 and 1982 and lower basal area growth
from 1983 to 1985 than the thinned, fertilized treatments.
In addition, 5-year basal area growth did not differ between
the thinned, fertilized treatments and the unthinned, unfer­
tilized treatment (p
0.27). The four thinned, fertilized
treatments exhibited similar basal area growth rates; these
treatments should soon have equal or greater total basal area
than the unthinned, unfertilized treatment. The thinned,
unfertilized treatment had the least basal area growth for
both periods. However, basal area growth from 1983 to 1985
in the thinned, unfertilized treatment was almost as great
as growth in the unthinned, unfertilized treatment, which
had much greater initial basal area. For the 5-year period,
there was no significant difference in basal area growth
between the thinned, unfertilized treatment and the
0.18).
unthinned, unfertilized treatment (p
=
Nutrient concentrations
Nutrient concentrations differed by treatment and over
time (Table 4; Fig. 4), and for all elements except S, the
treatment by time interaction was highly significant.
Nitrogen concentrations in the unthinned, unfertilized
treatment ranged over time from 0.9 to L 1 0/0. All silvi­
cultural treatments resulted in higher N concentrations in
current-year foliage than did the unthinned, unfertilized
treatment (Fig. 4). For most treatments, the maximum
values occurred the 1st year after treatment. Thinning alone
resulted in consistently higher N concentrations than in the
unthinned, unfertilized treatment. Although the magnitude
of the foliar response decreased over time, all treatments
containing N exhibited elevated levels of N at all measure­
ment dates. The urea treatment clearly produced the highest
foliar N concentrations.
Phosphorus concentrations initially ranged from 0.12 to
0.14% in the treatments that did not include P fertilizer.
Phosphorus levels were increased substantially by P fertil­
ization, with the maximum values of 0.25 to 0.28% attained
2 years after treatment (Fig. 4). The separation between the
treatments receiving P and those not receiving P was still
evident after 5 years. Although the differences were not
large, during the first 2 years, P concentrations in the urea
treatment were slightly lower than in the other treatments.
16
14
12
10
6
4
2
o ����-=�-=���
-0' ,,/
.-K
()+ .-K
L
'V
_"
'V
.l /
"-
..:5;' -0f-.../
,,
"
/
/
-,
-
,
FIG. 3. Cumulative basal area of the total stand, by treatment.
Values for 1980 represent basal areas after thinning but before
growth has occurred.
, 1980; 0, 1981-1982 growth; E:J,
1983-1985 growth. Treatment codes are as given in Fig. 1.
Foliar K levels in all treatments ranged from 0.45 to
0.72%. Trees in treatments that included potassium sulfate
(UT -NPK, T -NPK in Fig. 4) had the highest initial levels
of K and fairly high levels at all measurements. Foliar K
also increased in 1982 and 1983 in the thinned, unfertilized
treatment. Trees on plots in the two treatments receiving
K had high K concentrations, and their growth rates were
among the fastest growing treatments. When all treatments
were considered, however, K concentrations were not related
to relative growth rates nor did treatments separate into
distinct groups, those receiving K and those not receiving
K, based on growth rates.
Foliar concentrations of S ranged from 0.08 to 0.15%.
Although the differences were larger in some years than in
others, all the fertilized treatments, including those not
applying S, had consistently higher concentrations of S than
the unthinned, unfertilized treatment at all dates (Fig. 4).
Sulfur concentrations in all treatments were highest in 1982
or 1983.
Concentrations of foliar Ca ranged from 0.55 to 1.03070.
The three treatments that included Ca (UT-NPK, T -NP,
and T -NPK in Fig. 4) had the highest Ca levels initially;
however, these treatments exhibited dramatic declines in
HARRINGTON AND WIERMAN
769
their relative positions in terms of foliar concentrations.
Calcium concentrations were most consistent over time in
the unthinned, unfertilized treatment.
-N-..:::t --000<"1000
cicicicicicici
V V VVV
'fl<"1 0 '<:1"0 NI.O
Discussion
This young western red cedar stand growing on a poor
quality site responded to silvicultural treatments. Although
there were major differences among treatments, thinning
alone, fertilization alone, and thinning plus fertilization all
resulted in greater height and diameter growth rates for the
20 tallest trees per plot than in the unthinned, unfertilized
treatment. The results of this study were similar to those
with other northern conifers (e.g., Gessel et al. 1979;
Weetman et al. 1987). Northern coniferous forests gener­
ally have thick organic layers and low mineral cycling rates
as a consequence of their low temperatures and acid soils
(Weetman et al. 1987), When soil moisture deficits are not
the major limitation to growth, silvicultural treatments that
increase nutrient availability usually result in increased tree
growth.
Thinning without fertilization resulted in small but sig­
nificant increases in growth. When compared with the
unthinned, unfertilized treatment, 5-year growth of the
20 tallest trees per plot in the thinned treatment was
increased 240/0 for height growth and 34% for diameter
growth. After 5 years, total basal area was lower in the
thinned, unfertilized treatment than in the unthinned, unfer­
tilized treatment, but the higher growth rates exhibited by
the thinned treatment plots imply that the thinned treatment
may catch up over time. Western red cedar responded to
thinning slowly in trials in Britain (Aldhous and Low 1974);
therefore, it may be necessary to wait longer with western
red cedar than with other species to judge the efficacy of
thinning in increasing or maintaining growth. In addition,
thinning will concentrate growth on fewer stems in thinned
than in unthinned plots,
The thinned, unfertilized treatment had consistently
higher foliar concentrations of N and K and in some years,
higher concentrations of S than the unthinned, unfertilized
treatment. These increases in nutrient concentrations could
reflect both decreases in competition for relatively small
pools of available nutrients and increases in available
nutrient pools as a result of increased nutrient cycling rates
or more substrate available for decomposition (i.e., the thin­
ning slash) (Ingestad et al. 1981; Miller et al. 1976). In addi­
tion, crop tree root systems may have expanded following
thinning, thus potentially increasing the nutrients available
per tree.
Foliar nutrient concentrations in the unthinned, unfer­
tilized treatment were similar to those reported for other
young, unmanaged coastal western red cedar stands (Radwan
and Harrington 1986). Based on deficiency levels for
greenhouse-grown seedlings (Walker et al. 1955), trees in the
unthinned, unfertilized treatment were deficient in N, defi­
cient or close to deficient in P, K, and S, and above defi­
ciency levels for Ca. The applicability of their deficiency
levels to older trees has not been established, however, and
may need modification. For example, Walker et al. (1955)
reported 1.5% to be the cutoff level for foliar N. Based on
that level, trees in all treatments in this study except the urea
treatment and most of the stands sampled by Radwan and
c:.:---:
\O("t1-n--
f/l
f/l
o:
m
S;!
;
Ncicici""':ciciciN
-N--t0<"10<"1000
cicicicicicici
V V VV
r-'fl<"I r- 1.0 r-Q\
0_<""'4_0\00\0
0)
-=
.g
.5
o
0.
"';v)
<"I
"":
f/l
f/l
---M-_M
000 ...... 000
cicicicicicici
VVV VV
N ...... Q\ooQ\ooO
<"I<"I'fl'<:l"Q\NO
triO\""':NtriN
f/l
f/l
O'\MOO\oV- OO- O
000-0'<:1"00 ...... 0
cicicicicicicici""':
-M-N--0000000
cicicicicicici
v
V VVV
VJ
::::
...
o
..c::
0'"
o
..c::
p..
I.O- N<"1N<"I<"I
r-<"I'<:I"-ooor-
....M
.: ..tN
<"I
f/l
f/l
Q\
N
..t..:i
OO-O'\-\o-N-O'\
N O- OOOOON
cicicicicicicicici
V
-N--0000000
cicicicicicici
V VVV V
r-<"I00 1.0 r- 1.0 N
r-'fl'fl00-00
-
f/l
f/l
MciM
N
r-
M
3
NN
M
;;:;
..:iciNciMcioo..:i
CAN. J. FOR. RES. VOL. 20, 1990
770
1.8
.
1.6
z
w
(!J
0
0:
1.4
z
1.2 - - - -....
t:
_
0
1.0
.
N,
-
LEGEI\JD
UT- UF
6.- --6.
UT - NPK
- - -.
T- UF
+ - . T- Ur
........ T - N
'Y--'Y
T- NP
A-A T- NPK
0-0
-, .
. !:-:
t
_u"._
-"
.
.
....
.
,
o
_
_
_
_
_
.........
--
1
.
'
0
0.8
0.8
0.7
:::> US
UJ
«
!0
a.. :$I
0
0.6
0.5
'
.
0.4
1.1
:::> U
0.9
...J
«
() 0.7
0.5 +---+-----1
1984
1985 1983
1982
1981
FlO. 4. Concentrations of nitrogen, phosphorus. potassium, sulfur, and calcium in dormant season foliage by treatment and year.
Foliage was not collected in 1984, Treatment codes are as given in Fig. L
Harrington (1986) and by Imper and Zobel (1983) would
be considered N deficient.
Fertilization alone dramatically increased growth. Height
growth of the 20 tallest trees per plot was about the same
as growth in the best thinned and fertilized treatments
(650/0 greater than untreated), and diameter growth was 79%
greater than in the unthinned, unfertilized treatment. When
compared with the thinned and fertilized treatments, how­
ever, diameter growth rates of the 20 tallest trees per plot
in the unthinned, fertilized treatment were always less than
growth rates in thinned, fertilized treatments with the highest
growth rates. In addition, the relative rank of the unthinned,
fertilized treatment in terms of diameter growth rates has
decreased over time in relation to the fertilized treatments
with lower stand densities. Foliar concentrations of N and
P in the unthinned, fertilized treatment decreased more
between the last two measurement periods than those in the
corresponding thinned treatments. This more rapid decrease
in foliar nutrient concentrations may indicate more rapid
depletion of available nutrients in the unthinned plots.
The excellent response to fertilizer in the unthinned stand
was somewhat unexpected given the high densities present.
HARRINGTON AND WIERMAN
The high shade tolerance of western red cedar (Minore 1979)
may enable it to expand leaf area (and consequently increase
growth) under low light conditions if nutrition is adequate.
Fertilization without thinning was clearly the best treatment
in terms of 5-year basal area growth. In addition, the
relatively good growth of crop trees in this treatment and
the potential for producing trees of better form or quality
(assuming that higher stand densities will increase natural
branch pruning) indicate this type of treatment may warrant
consideration when sawlog production is the management
objective.
Both urea and ammonium nitrate substantially increased
height and diameter growth. Based on foliar N concentra­
tions and changes in periodic growth rates, it appears that
the growth response to urea may last longer than the
response to ammonium nitrate. The somewhat larger and
possibly longer response to urea may be due to greater reten­
tion (and later turnover) of urea than ammonium nitrate
in the forest floor and surface soil (Knowles 1975). Given
the poor soil drainage in the study area, most fine roots were
probably concentrated in these surface layers. First-year
height growth was less with urea than with ammonium
nitrate; this could have resulted from an initial immobiliza­
tion of urea. In western hemlock stands, urea fertilization
has been reported to increase mortality of mycorrhizal roots
(Gill and Lavender 1983a) and to decrease foliar concen­
trations of P, Ca, Mg, Mn, Fe, AI, and B (Gill and Lavender
1983b), If urea application initially caused root mortality
in the present study, it could provide an alternative explana­
tion for why 1st-year height growth was less in the urea treat­
ment than in the ammonium nitrate treatment. In addition,
Ist- and 2nd-year P concentrations were lowest in the urea
treatment, a trend that that would be expected if mycorrhizal
roots were damaged. However, based on the higher foliar
N concentrations in the urea treatment, we can infer that
at least sometime prior to the collection of foliage after the
first growing season, more N was available for uptake or
other factors promoted more N uptake in the urea treatment
than in the ammonium nitrate treatment. Since the soil in
the study area is poorly drained, it is unlikely that signifi­
cant amounts of nitrate were rapidly leached from the site
(Wollum and Davey 1975); however, nitrate may have been
leached from the primary rooting zone, thus making it effec­
tively less available. The poorly drained soil conditions
would also have favored nitrate losses due to denitrifica­
tion (Hauck 1968).
Urea is the most common N fertilizer used in forests in
the United States. Urea is frequently selected because its
higher N concentration generally results in lower costs per
unit of N applied than with other N sources. Ammonium
nitrate was selected as the primary N source in this study
because we thought the large amounts of organic matter pres­
ent on the site indicated a high potential for N immobiliza­
tion, which would reduce the N available for uptake. In this
experiment, though, immobilization may have increased N
conservation. Research has indicated that the relative
efficacy of these two N sources is related to soil character­
istics, species of tree, and weather conditions during and
following application (cf. Dangerfield and Brix 1979).
Further research is necessary to determine the optimum N
fertilizer for coastal western red cedar stands.
After 5 years, the treatment with the poorest growth had
the highest foliar Ca oncentration and the treatment with
771
the best growth had the lowest Ca concentration. This may
imply that Ca is low at this site but is not limiting growth.
This may also imply that the high Ca concentrations usually
found in western red cedar foliage (Imper and Zobel 1983;
Radwan and Harrington 1986) indicate luxury consumption.
Radwan and Harrington (1986) reported that foliar concen­
trations of all macronutrients except Ca were positively cor­
related with height growth of western red cedar over a range
of sites; they suggested that western red cedar may accu­
mulate Ca in excess of its nutrient needs. Certainly the foliar
concentrations associated with deficiency symptoms in seed­
lings (0.1 to 0.2070, Walker et al. 1955), are substantially
lower than Ca concentrations observed in this or other
studies (Gessel et al. 1951; Imper and Zobel 1983; Radwan
and Harrington 1986). Based on the available evidence, we
conclude that the growth responses associated with dicalcium
phosphate were primarily due to increased P, rather than
Ca, uptake. Phosphorus was not completely limiting growth,
however, as evidenced by the good growth response to N
alone and by our inability to separate growth-response
groups based on P concentrations.
In this and other studies (Snowden and Waring 1985),
dicalcium phosphate has increased foliar P levels and tree
growth. Dicalcium phosphate was selected to be the P source
in this experiment primarily to avoid possible soil acidifica­
tion associated with other more commonly used P fertilizers
(Tisdale and Nelson 1975), Since soil pH was low on this
site (4.6) we felt we could best see response to P using a
source unlikely to lower soil pH and possibly make other
elements less available.
The addition of potassium sulfate did not significantly
increase 5-year growth, however, both height and diameter
growth were generally best in the treatment containing
potassium sulfate. Future research studies might include a
similar treatment to more thoroughly assess response to these
elements. Trees in treatments that included potassium sulfate
had the highest concentrations of foliar K and S in the first
2 years, indicating that the fertilizer source used was effec­
tive in increasing foliar levels of both elements. Foliar con­
centrations of K and S in all treatments were in the defi­
ciency range established for seedlings (Walker et al. 1955),
but were comparable to foliar values in other coastal western
red cedar stands (Imper and Zobel 1983; Radwan and
Harrington 1986). Relative growth rates of the treatments
were not well correlated with foliar concentrations of K or S
(Harrington and Wierman 1985).
Both the magnitude and the duration of the growth
responses should encourage forest managers interested in
growing western red cedar. The cost effectiveness of the
various treatments cannot be assessed until we know how
long the different treatment responses will last. Thinning
responses should last for many years. Response to N fertil­
ization is generally short-lived; however, response of
Douglas-fir to N fertilization on a very N-deficient site
persisted after 15 years (Miller and Tarrant 1983). Certainly
the response to N in the present study was still present in
years 4 to 5. Response to P fertilization on some sites in the
southeastern United States and Australia has lasted for many
years (Fisher and Garbett 1980; Gentle et al. 1986; Hunter
et al. 1985; Pritchett 1976). The magnitude of the incremen­
tal response to P on our study site was small compared with
the response to N alone, but the incremental response was
evident in all measurement periods.
CAN. J. FOR. RES. VOL 20. 1990
772
This study, taken in conjunction with previous work on
seedlings (Walker et al. 1955; Zasoski and Bledsoe 1980),
and on older trees in British Columbia (Weetman et aI. 1988)
and in Britain (Aldhous and Low 1974; O'Carroll 1967),
clearly demonstrates that western red cedar will respond to
thinning and fertilization. The specific results from this study
are most applicable to western red cedar stands similar to
the study area in age, stocking, and soil properties. To pre­
dict responses to silvicultural treatments in other types of
stands, additional studies need to be established over a range
of stand and site conditions. Future work is also needed to
explore a wider range of treatments and to assess treatment
effects on both stand growth and wood quality.
Acknowledgements
We thank ITT Rayonier Inc. for assistance in conduct­
ing the study. We also thank O.F. Weetman, 1.S. Shum­
way, D.S. DeBell, and two anonymous reviewers for helpful
suggestions in improving the manuscript.
AGRICULTURE CANADA EXPERT COMMITTEE ON SOIL SURVEY.
1987. The Canadian system of soil classification. 2nd ed. Agric.
Can. Publ. No. 1646.
ALDHOUS, J.R., and Low, A.J. 1974. The potential of western
hemlock,western red cedar,grand fir and noble fir in Britain.
Her Majesty's Stationery Office, London. For. Comm. Bull.
No. 49.
DANGERFIELD, J., and BRIX, H. 1979. Comparative effects of
ammonium nitrate and urea fertilizers on tree growth and soil
processes. In Proceedings of the Forest Fertilization Conference,
25-27 Sept. 1979, Alderbrook Inn, Union, WA. Edited by
S.P. Gessel,R.M. Kenady, and W.A. Atkinson. University of
Washington, College of Forest Resources, Institute of Forest
Resources, Seattle. Contrib. No. 40. pp. 133-139.
FISHER, R.F.,and GARBETT, W.S. 1980. Response of semimature
HUNTER, I.R., GRAHAM, J.D., GALLAGHER, S.S.,and CALVERT,
K.T. 1985. Long-term foliar phosphorus response of Pinus
radiata to superphosphate fertilizer. N.Z. J. For. Sci. 15: 89-100.
IMPER, D. K., and ZOBEL, D.B. 1983. Soils and foliar nutrient
analysis of Chamaecyparis lawsoniana and Thuja plicata in
southwestern Oregon. Can. J. For. Res. 13: 1219-1227.
INGESTAD, T., ARONSSON, A., and AGREN, G.I. 1981. Nutrient
flux density model of mineral nutrition in conifer ecosystems.
Stud. For. Suec. 160: 61-71.
JACKSON, M.L. 1958. Soil chemical analysis. Prentiss-Hall, Inc.,
Englewood Cliffs, NJ.
KNOWLES, R. 1975. Interpretation of recent
15
N studies of
nitrogen in forest systems. In Forest soils and forest land manage­
ment. Edited by B. Bernier and C.H. Winget. For. Soils For.
Land Manage. Proc. North Am. For. Soils Conf. 4th 1973
(1975). pp. 53-65.
KURUCZ, J .F. 1978. Preliminary, polymorphic site index curves
for western redcedar-Thuja plicata Donn.-in coastal British
Columbia. For. Res. Note No. 3. Macmillan Bloedel Ltd.
Vancouver.
MILLER, R.E., and TARRANT, R.F. 1983. Long-term growth
response of Douglas-fir to ammonium nitrate fertilizer. For. Sci.
29: 127-137.
MILLER, R.E., LAVENDER, D.P.,and GRIER, C.C. 1976. Nutrient
cycling in the Douglas-fir type-silvicuItural implications. In
Proceedings, 1975 National Convention, Society of American
Foresters,28 Sept. - Oct. 2, 1975, Washington, DC. Society of
American Foresters, Washington, DC. pp. 359-390.
MINORE, D. 1979. Comparative autecological characteristics of
northwestern tree species-a literature review. USDA For. Servo
Gen. Tech. Rep. PNW-87.
___ 1983. Western red cedar-a literature review. USDA For.
Servo Gen. Tech. Rep. PNW-150.
NYSTROM, M.N., DEBELL, D.S.,and OLIVER, C.D. 1984. Devel­
opment of young growth western redcedar stands. USDA For.
Servo Res. Pap. PNW-324.
O'CARROLL, N. 1967. Early growth of conifers on machine­
cutover peatland. In Proceedings of the 14th IUFRO Congress,
4-9 Sept. 1967, Munich. Vol. 4. sec. 23. Deutscher Verband
slash and loblolly pine plantations to fertilization with nitrogen
and phosphorus. Soil Sci. Soc. Am. J. 44: 850-854.
GENTLE, S.W., HUMPHREYS, F.R. , and LAMBERT, M.J. 1986.
Continuing response of Pinus radiata to phosphatic fertilizers
over two rotations. For. Sci. 32: 822-829.
GESSEL, S.P.,WALKER, R.B., and HADDOCK, P.G. 1951. Prelim­
RADWAN, M.A., and HARRINGTON, C.A. 1986. Foliar chemical
inary report on mineral deficiencies in Douglas-fir and western
red cedar. Soil Sci. Soc. Am. Proc. 15: 364-369.
GESSEL, S.P., KENADY, R.M., and ATKINSON, W.A. (Editors).
concentrations,growth, and site productivity relations in western
red cedar. Can. J. For. Res. 16: 1069-1075.
SMITH, N. (Editor). 1988. Western Red Cedar: Does it have a
1979. Proceedings of the Forest Fertilization Conference,
25-27 Sept. 1979, Alderbrook Inn, Union, WA. University of
Washington, College of Forest Resources, Institute of Forest
Resources, Seattle. Contrib. No. 40.
GILL, R.S.,and LAVENDER, D.P. 1983a. Urea fertilization: effects
on primary root mortality and mycorrhizal development of
Future? Proceedings of the Western Red Cedar Symposium,July
1987, University of British Columbia, Vancouver.
young-growth western hemlock. For. Sci. 29: 751-760.
___ 1983b. Urea fertilization and foliar nutrient composition
of western hemlock (Tsuga heterophylla (Raf.) Sarg.). For. Ecol.
Manage. 6: 333-341.
HARRINGTON, C.A., and WIERMAN, C.A. 1985. Response of a
poor-site western redcedar stand to precommercial thinning and
fertilization. USDA For. Servo Res. Pap. PNW-339.
HAUCK, R.D. 1968. Nitrogen source requirements in different
soil-plant systems. In Symposium on Forest Fertilization­
Theory and Practice, April 1967, Gainesville, FL. Edited by
G.W. Bengtson. Tennessee Valley Authority National Fertilizer
Development Center, Muscle Shoals, AL. pp. 47-57.
HORWITZ, W. (Editor). 1980. Official methods of analyses of the
Association of Official Analytical Chemists. 13th ed. Associa­
tion of Official Analytical Chemists,Washington, DC.
Forstlicher Forschungsanstalten, Freiburg. pp. 471-482.
PRITCHETT, W.L. 1976. Phosphorus in forest soils. Phosphorus
Agric. 67: 27-35.
SNOWDEN, P., and WARING, H.D. 1985. Effects of factorial com­
binations of urea,dicalcium phosphate,gypsum and potassium
chloride on growth and foliage composition of closely spaced
Pinus radiata. Aust. For. Res. 15: 333-352.
SOIL SURVEY S TA FF. 1975. Soil taxonomy. U.S. Dep. Agric.
Agric. Handb. No. 436.
TISDALE, S.L., and NELSON, W.L. 1975. Soil fertility and fer­
tilizers. Macmillan Publishing Co., Inc. New York.
R.B., GESSEL, S.P., and HADDOCK, P.G. 1955.
Greenhouse studies in mineral requirements of conifers: western
red cedar. For. Sci. 1: 51-60.
WALKER,
WEETMAN, G.F., KRAUSE, H.H., KOLLER, E., and VEILLEUX,
J.-M. 1987. Interprovincial forest fertilization trials, 5- and
lO-year results. For. Chron. 63: 184-192.
WEETMAN, G.F.,RADWAN, M.A.,KUMl, J.,and SCHNORBUS, E.
1988. Nutrition and fertilization of western red cedar. In Western
Red Cedar: Does it have a future? Proceedings of the Western
Red Cedar Symposium,July 1987. Edited by N. Smith. Univer­
sity of British Columbia, Vancouver. pp. 47-59.
HARRINGTON AND WIERMAN
WOLLUM, A.G., II, and DAVEY, C.B. 1975. Nitrogen accumula­
tion, transformation and transport in forest soils. In Forest soils
and forest land management. Edited by B. Bernier and
C.H. Winget. For. Soils For. Land Manage. Proc. North Am.
For. Soils Conf. 4th 1973 (1975). pp. 67-106.
773
ZASOSKI, R.J., and BLEDSOE, C.S. 1980. Growth of forest tree
seedlings in sewage sludge amended media. In Program and
Abstracts, 53rd Annual Meeting of the Northwest Scientific Asso­
ciation,27-29 March 1980,University of Idaho, Moscow. North­
west Scientific Association, Pullman, WA. Abstr. 57.
About this file: This file was created by scanning the printed publication. Some mistakes introduced by scanning may remain.