Plant and Soil 106, 171-177 (1988) © Kluwer Academic Publishers
PLSO 7373 Nutrient relations in coppiced black cottonwood and red alder
M.A. RADWAN and D.S. DeBELL
Forestry Sciences Laboratory, Pacific Northwest Research Station, USDA, Forest Service, Olympia,
WA 98502, USA
Received 6 May 1987. Revised September 1987
About This File:
.This file was created by scanning the printed publication.
i Misscans identified by the software have been corrected; )
hoyvever, some mistakes may remain.
Key words: .
..
Alnus rubra, efficiency of nutrient utilization, essential elements, nutrient concentration,
nutrient content, Populus trichocarpa
Abstract
Two-year-old coppice of black cottonwood and red alder, grown in pure culture and in mixture, were
compared using terminal twigs and leafless shoots harvested in the winter. Terminal twigs were taken with
buds intact; they were about 15 cm long. Leafless shoot samples included all above-ground components. In
pure culture, dry weights of the leafless shoots per plant were similar for the two species. In mixture with
alder, however, weight of the cottonwood plants was enhanced and that of alder was reduced, but neither
response was statistically significant. Nutrient concentration, content per plant, and utilization varied by the
plant tissues analyzed, cultural treatment (pure vs. mixed), and species. In general, nutrient concentrations
were higher in the terminal twigs than in the leafless shoots of both species. Cultural treatment did not
significantly affect nutrient concentration in cottonwood twigs or in the leafless shoots of either species.
Concentrations of N and Fe were significantly higher and those of Mn were lower in twigs of mixed alder
than in twigs of pure alder. Twigs of cottonwood were significantly higher than those of alder in concentra­
tion of P and Zn, and lower in N, Mn, and Cu. Compared with alder, cottonwood leafless shoots were
significantly higher in concentration of Ca, but lower in N, S, Cu, and Mn. With few exceptions, nutrient
content was highest in the shoots of the large plants of mixed cottonwood, intermediate in medium-sized
pure cottonwood and pure alder, and lowest in the small mixed alder. Cottonwood was significantly more
efficient than alder in use of N, S, and Cu, and less efficient in use of Ca. Some of the differences between
cultural treatments and species may be associated directly or indirectly with the N2-fixing ability of red alder.
Mixed culture of the two species appears promising because of the increased growth of cottonwood. Planted
separately in pure culture, the choice between cottonwood and alder may be determined, in part, by the
nutritional status of the soil where plantations are established.
Introduction
(DeBell, 1975). These species are known for their
high yield when grown separately. Also, because of
alder's ability to fix atmospheric nitrogen, biomass
production might be substantially increased when
cottonwood and alder are grown in mixture (Tar­
rant and Trappe, 1971).
In 1973, a comprehensive study to evaluate cop­
pice biomass production of cottonwood and red
alder, in pure and mixed plantings, was established
along the Columbia River in southwest Washing­
ton, USA. During the lO-year study, there were
five harvests of the leafless, above-ground bio­
There is much interest in intensive culture of
hardwood coppice on short rotations. The suc­
cessive crops produced by such regimes can dra­
matically increase production of biomass for en­
ergy, and fiber for the pulp and paper industry.
In the Pacific Northwest of the United States,
two native hardwood species, black cottonwood
(Populus trichocarpa Torr. & Gray) and red alder
(Alnus rubra Bong.), have been identified as par­
ticularly suitable for intensive coppice management
171
'
172
Radwan and DeBell
mass - an initial, noncoppice harvest in 1975,
followed by four coppice harvests at 2-year inter­
vals. The yield of the first coppice harvest was much
greater from the mixed plantings than from pure
alder or cottonwood (DeBell and Radwan, 1979).
Subsequently, we evaluated nutrient relations of
the species on terminal twigs collected at the other
three coppice harvests, and on representative sam­
ples of the whole, leafless, above-ground biomass
collected in 1979 and 1983. In the present investiga­
tion, we used plant material obtained in the latter
two harvests to assess selected biomass and nutri­
tional differences between the two species in pure
and mixed cultures. These comparisons would ass­
ist in the selection of species and cultural method
for production of coppice biomass for energy.
Materials and methods
consisted of five rows of nine trees each. Rows were
1.2 m apart, and trees within rows were spaced at
0.6 m. Alder seedlings and cottonwood cuttings
were planted in March 1973. Containerized alder
seedlings were 15-25 cm tall and about 6 mo old.
Cottonwood cuttings were 60 cm long and planted
to a 40-cm depth. Both species were from a local
source, near Vancouver, Washington. Weeds in the
plots were hoed and mowed during the first two
growing seasons. Coppice growth was established
by cutting all plots 15 cm above the ground in
January 1975. Two-year coppice (i.e., sprout
growth) was harvested in winter after the 1976
growing season (1977 harvest), 1978 (1979 harvest),
1980 (1981 harvest), and 1982 (1983 harvest). All
cutting was done at about the same height as the
first cut in 1975.
The 1979 and 1983 harvests are the only ones
considered in this study. Also, all work was con­
fined to the 21 interior plants in each plot.
Study area
The study site is located on Lady Island in the
lower Columbia River near Camas, Washington.
The area is flat with an elevation of about 5 m..
Average annual precipitation is 120 cm, which
occurs as rain during the winter. Soil is Sauvie silt
loam (Fluventic haplaquoll) - an alluvial soil com­
mon to the flood plain of the lower Columbia River
valley. Native vegetation includes black cotton­
wood, willow (Salix spp.), teasel (Dipsacus spp.),
nettle ( Urtica spp.), Canada thistle (Cirsium arvense
(L.) Scop.), and several other herbaceous species.
Red alder does not occur naturally on the island
but is very common in the general area.
Plot establishment and maintenance
Trees in the immediate vicinity of the study site
were removed several years before the study was
started. In 1972, the area was rototilled, and de­
veloping vegetation was controlled with an her­
bicide. Plots were established in early 1973. Plots
were 6 x 6 m and were separated by 2-m-wide
unplanted strips. Treatments were pure cotton­
wood, pure red alder, and a mixture of cottonwood
and alder planted alternately within rows. There
were two replications of each treatment, and treat­
ments were assigned to the plots at random. Plots
Yield
Harvesting was done by cutting all coppice, leaf­
less shoots of the plants on each plot during the
winter. For each harvest, representative subsam­
pIes of the fresh material of each species were dried
to constant weight at 65°C, and yield was cal­
culated on dry-weight basis. Dry weight per plant
was also calculated from the yield and the number
of plants harvested per plot.
Sampling and chemical analysis
Representative samples of terminal twigs and of
the whole above-ground, leafless shoots were taken
from the harvested material, and samples of each
harvest were separated by species and plot. Twigs
were taken with buds intact; they were about 15 cm
long, and there were about 10 twigs per sample.
The "whole-plant" samples represented all above­
ground components (i.e., twigs, branches, stems) as
proportionately as possible, and samples ranged
from 200 to 400 g each. All samples were transpor­
ted to the laboratory in a portable cooler.
Samples were dried to constant weight at 65°C,
ground to 40 mesh in a stainless-steel mill, and
stored in closed containers at - 15°C until analysis.
Nutrient relations in cottonwood and alder
Chemical analyses were carried out as follows: total
N (including nitrate) by the micro-Kjeldahl
procedure (Bremner and Mulvaney, 1982); P by the
molybdenum blue technique (Chapman and Pratt,
1961); S by a turbidimetric method (Butters and
Chenery, 1959); and K, Ca, Mg, Fe, Mn, and Cu by
standard atomic absorption technique (Perkin­
Elmer Corporation, 1976).
Concentrations (i.e., % or ppm) and content
(i.e., g or mg/plant) of each nutrient determined in
the twigs and in the leafless shoots were calculated.
Also, nutrient utilization in production of the cop­
pice shoots (i.e., kg dry shoot/g nutrient) were also
estimated from the yield and nutrient content.
Statistical analysis
Differences among treatments in the various
variables studied were examined by split-plot
analysis, with species or cultural treatment (pure vs.
mixed) as main plots and harvest date as subplots.
Three comparisons were made among the whole­
plot treatments: pure vs. mixed cottonwood, pure
vs. mixed alder, and pure cottonwood vs. pure
alder. Differences were considered significant at
p < 0.05. In addition, for each variable deter­
mined, data were averaged for the two plots (re­
plications) and two harvests of each treatment, and
standard error of the mean (SE) was calculated as
usual (Snedecor, 1961).
Results and discussion
Some of the variables studied were significantly
affected by harvest date; in general, nutrient con­
centrations were higher and efficiencies of nutrient
utilization were lower in 1983 than in 1979. The
cultural treatment by harvest date interaction,
however, was rarely significant. The following
presentation and discussion, therefore, are limited
to averages of the two harvests; standard errors are
provided to indicate variation among replications.
Weight of plants
In pure culture, dry weights of the 2-year-old
coppice leafless shoots per plant were similar for
173
the two species (alder, 1.30 ± 0.18 kg/plant; cot­
tonwood, 1.30 ± 0.12). Weights, however, varied
greatly, but not significantly, when plants were
grown in mixture. Thus, cottonwood plants grown
in mixture (2.03 ± 0.30 kg/plant) were 56% larger
than those grown in pure plantings; conversely, size
of alder plants (0.62 ± 0.21 kg/plant) were sub­
stantially smaller (52%) in the mixed culture. In all
mixed plots, cottonwood was clearly the superior
competitor. The species is known to produce more
sprouts than red alder, and its growth is believed to
benefit from the nitrogen added to the soil by the
associated alder (DeBell and Radwan, 1979; Har­
rington and DeBell, 1984).
Nutrient concentrations in terminal twigs
As expected, to al N in the twigs was consistently
and significantly higher in alder than in cotton­
wood (Table 1), reflecting N2-fixation by alder.
Also, as reported earlier (DeBell and Radwan,
1979), N was slightly, but not significantly, higher
in twigs of cottonwood growing in mixture with
alder than in twigs from pure plantings. This gain
was probably caused by increased soil N
(> 50 ppm) in the mixed plots from N2-fixation by
alder (DeBell and Radwan, 1984).
Cottonwood and alder also differed in con­
centrations of nutrients other than N. Thus, com­
pared with alder, cottonwood twigs were signifi­
cantly higher in P and Zn, but lower in Mn and Cu.
Differences in Mn may be caused in part by in­
creased soil acidity associated with presence of
alder in this study (pH: alder, 5.86; cottonwood,
6.01) and earlier studies (DeBell et al. 1983).
Nutrient concentrations of cottonwood twigs
were not significantly affected by cultural treat­
ment. Similarly, concentrations of most nutrients
in alder twigs were not significantly affected; excep­
tions were N and' Fe, which were higher in mixed
alder, and Mn, which was higher in pure alder.
The literature about concentration of mineral
nutrients in twigs or shoots of plants contains no
information on black cottonwood and only very
little on red alder (Radwan and Crouch, 1974). In
general, however, our data for both species are
within the ranges of concentrations reported for
twigs of other hardwoods, including some Alnus
174
Radwan and DeBell
Table 1. Nutrient concentrations in terminal twigs of black cottonwood and red alder in pure and mixed plantings*
Nutrient
element
Species/culture
Cottonwood/
Red alder/
Cottonwood/
Red alder/
pure
pure
mixed
mixed
per Cent
1.49 ± 0.06
1.41 ± 0.03
1.29 ± 0.05
Ca
1.05 ± 0,02
0.90 ± 0.07
K
p
0.84 ± 0.10
0.45 ± 0.03
0.80 ± 0.06
0.52 ± 0.04
0.10 ± 0.00
0.11 ± 0.01
0.11 ± 0.01
N
1.21 ± 0.08
0.22 ± 0.01
0.19 ± 0.01
S
0.11 ± 0.01
Mg
0.15 ± 0.01
0.15 ± 0.01
ppm
Cu
Fe
Zn
Mn
12 ± 1
78 ± 14
107 ± 8
20 ± 2
1.03 ± 0.06
0.22 ± 0.01
0.16 ± 0.01
10 ± 1
18 ± 1
72 ± 10
86 ± 11
62 ± 7
102 ± 4
22 ± 2
105 ± 15
0.86 ± 0.06
0.21 ± 0.01
0.14 ± 0.01
20 ± 1
112 ± 15
58 ± 7
78 ± 5
* Values are averages of four samples each ± SE.
and Populus spp. (Blackman et al. 1979; Grigal et
al. 1979; Kubota et al. 1970; Langille and Maclean
1976).
Nutrient concentrations in coppice shoots
All nutrients determined occurred in much lower
concentrations in the shoots (Table 2) than in the
terminal twigs (Table 1). This was expected because
of the dilution of nutrients in the shoots by the
much higher proportion of structural materials,
such as cellulose and lignin.
In pure culture, differences between the two spe-
cies were similar to those shown by the twig data
for N, Cu, and Mn. In addition, Ca concentration
was significantly higher in cottonwood than in
alder. In contrast with concentrations in the twigs,
P and Zn did not differ significantly by species, and
cultural treatment had no significant effect on any
nutrients in the shoots of either species.
Nutrient content of coppice shoots
Unlike concentrations, contents (i.e., weights) of
nutrients reflect differences in nutrient accumula­
tion by plants. As expected, trends of the differen-
Table 2. Nutrient concentrations in 2-year-old coppice leafe
l ss shoots from pure and mixed plantings of black cottonwood and red
alder*
Nutrient
element
Species/culture
Cottonwood/
Red alder/
Cottonwood/
Red alder/
pure
pure
mixed
mixed
0.38 ± 0.05
per cent
N
0.34 ± 0.03
0.68 ± 0.02
Ca
0.41 ± 0.03
0.26 ± 0.04
K
0.37 ± 0,02
0.39 ± 0.03
0.38 ± 0,02
0.39 ± 0.01
0.74 ± 0.02
0.25 ± 0,03
0.40 ± 0.02
ppm
P
756 ± 57
S
227 ± 25
Mg
601 ± 47
Cu
Fe
6 ± 0
66 ± 12
Zn
58 ± 4
Mn
10 ± 2
* Values are averages of four samples each ± SE.
805 ± 60
552 ± 52
542 ± 40
10 ± 1
51 ± 5
781 ± 70
323 ± 10
554 ± 63
6 ± 1
59 ± 2
929 ± 60
620 ± 33
549 ± 34
9 ± 1
57 ± 10
43 ± 10
61 ± 2
40 ± 7
34 ± 2
14 ± 4
27 ± 3
Nutrient relations in cottonwood and alder
alder. Of all the differences between species and
cultural treatments, however, the only statistically
significant difference was in the higher N content of
the mixed vs. pure cottonwood. For all other com­
parisons, variation between replications in both
concentration and weight was greater than differen­
ces between treatments.
ces within and among species in the nutrients varied
greatly by the method in which the results were
expressed (i.e., concentration vs. content). Some
differences changed little, whereas others were even
reversed (Table 2, Fig. 1). Thus, differences bet­
ween pure cottonwood and pure alder in N and
most other nutrients were relatively the same
whether results were expressed in terms of con­
centration (e.g., 0.34 vs. 0.68% N) or content per
plant (e.g., 4.5 vs. 8.8 g N). On the other hand,
regardless of differences in concentration, contents
of all nutrients were higher in mixed cottonwood
than in pure cottonwood or mixed alder, reflecting
the much larger cottonwood plants in mixed cul­
ture. Similarly, contents of all nutrients determined
were higher in pure alder than in mixed alder (e.g.,
1.1 vs. 0.6 g P/plant). Again, this was caused mainly
by the smaller size of plants in the mixed culture.
Nutrient uptake and accumulation, therefore,
were influenced primarily by plant size which was
determined by species and cultural treatment.
Generally, with few exceptions, nutrient accumula­
tion was highest in the large plants of mixed cotton­
wood, intermediate in medium-sized pure cotton­
wood and alder, and lowest in the small mixed
Nutrient utilization
Efficiency in use of nutrients by the two species is
expressed in amount of dry leafless shoot biomass
'
produced over a 2-year period per gram nutrient.
We limited our data to the above-ground woody
biomass because leaves and roots are not usually
harvested and used in energy production.
As with nutrient concentration and content, the
data show that utilization varied by nutrient, cul­
tural treatment, and species (Fig. 2). The species
also differed in the order in which the macronu­
trients were used (i.e., amount of nutrient/g dry
shoot), as follows: N
K
Ca > P > Mg > S
for cottonwood, and N > K > Ca > P > S >
Mg for alder. For both species, efficiency in use of
=
=
10
9
1 30
o co
Pure
tonwood
8
lliI
7
c
co
g
,0. e
"...
c
G)
'C
...
::I
C
if
5
I
T
::
Pure
red alder
Mixed
cottonwood
Mixed
red alder
Standard error
(n ;:4)
at
1
0
1 20
1 10
...
c
co
1 00
"
90
0.
"...
c
. IQ)
i:
...
::I
C
tn
3
E
': .:,:,
2
::
N
Ca
K
P
S
175
Mg
Cu
Fe
Zn
Fig, 1, Nutrient content of black cottonwood and red alder 2-year-old coppice leafless shoots.
Mn
Radwan and DeBell
176
180
·3500
..
c
G)
'C
....
3000
2500
o Pure
Iill Pure
::::I
m
....... ....
0
0
.c
II)
..
"
m
cottonwood
....
c
Q)
'C
....
::::I
C
red alder
Mixed cottonwood
c
2000
1500
ll;
1 60
I
Mixed red alder
T
Standard error
(n =4)
en 0
0
.c
In
..
"
1000
"
W
})},t{
Wj
1 40
1 20
:i'
m
'.
"
"
"
"
1 00
'
0
'
0
0'
'
0
80
::
u'
,,'
:
g
60
0
,
g:
m
,,'
40
",
",
",
<>,
0,
0,
500
g!
20
0:
gl
,,'
01:
0
N
Ca
K
P
S
Mg
0
",
I
I
Cu
W
l1i::
.
m
"
"
:!:
:
,,'
,,'
Fe
Zn
"Ii
iff
Mn
Fig. 2. Nutrient utilization in production of 2-year-old coppice leafless shoots of black cottonwood and red alder,
nutrients was essentially not affected by cultural
treatment. The only significant effect of cultural
treatment was in use of S by alder; pure alder was
more efficient than mixed alder.
Both alder and cottonw.�,)Qd did not vary signifi­
cantly in their utilization of P, K, Mg, Fe, Zn, and
Mn, In contrast, compared with alder, cottonwood
used N, S, and Cu more efficiently, but Ca less
efficiently, The lower efficiency of utilization of N
by alder is not surprising, Alder seems to fix much
more N than, is needed for its own growth, and it
incorporates much N in its tissues.
Efficiency of utilization of N, P, K, Ca, and Mg
for trees of three different geographic sources of
eastern cottonwood (Populus deltaides Bartr, ex
Marsh,) has been reported (Blackman et ai, 1979).
These values, which were calculated for whole 11year-old trees, are generally higher than our data
for 2-year-old leafless coppice. There are no data in
the literature for alder.
Conclusions
Coppice production in pure stands was similar
for cottonwood and alder, Mixed culture of the two
species, however, appears promising because of the
increased growth of cottonwood.
Planted separately in pure culture, the choice
between cottonwood and alder may be determined,
in part, by the nutritional status of the soil where
plantations are established, especially when fer­
tilizer applications are to be minimized, For exam­
ple, cottonwood may be preferred if soil supplies of
S are limiting because of the species' greater effi­
ciency in use of this nutrient. Similarly, alder may
be selected for sites where soil Ca is low, Alder
should also be the preferred species on soils where
N is low because of alder's N2-fixing ability and
despite its lower efficiency in use of N,
Acknowledgements
We thank the U.S. Department of Energy, Bio­
mass Energy Technology Division, Short Rotation
Woody Crops Program for funds which helped
support this research, We also thank personnel of
Crown Zellerbach Corporation for help with esta­
blishing the study and with plant sampling and
harvesting, and to J,W. Hazard, J.M. Kraft, J,E,
Wilcox, and D,W. Johnson, USDA Forest Service,
for their valuable assistance with other phases of
the study,
Nutrient relations in cottonwood and alder
References
177
Grigal D F, Ohmann L F and Moody N R 1979 Nutrient
content of some tall shrubs from northeastern Minnesota.
Blackman B G, Baker J B and Cooper D T 1979 Nutrient use
by three geographic sources of cottonwood. Can. J. For. Res.
9, 532-534.
Bremner J M and Mulvaney C S 1982 Nitrogen-total. In Meth­
ods of soil analysis, part 2, Ed. A L Page. Agronomy 9,
595-624.
Butters B and Chenery E M 1959 A rapid method for the
determination of total sulphur in soils and plants. Analyst. 84,
239-245.
Chapman H D and Pratt P F 1961 Methods of analysis for soils,
plants, and waters. Div. Agric. Sci. Univ. Calif., Berkeley.
DeBell D S 1975 Short-rotation culture of hardwoods in the
Pacific Northwest. Iowa State J. Res. 49, 345-352.
DeBell D S and Radwan M A 1979 Growth and nitrogen
relations of coppiced black cottonwood and red alder in pure
and mixed plantings. Bot. Gaz. 140 (Suppl.), S97-S101.
DeBell D S and Radwan M A 1984 Repeated coppicing of
cottonwood and alder affects soil properties. Agronomy
Abstr. 1984, 258.
DeBell D S, Radwan MA and Kraft J M 1983 Influence of red
alder on chemical properties of a clay loam soil in western
Washington. USDA For. Servo Res. Pap. PNW-313. Pacific
Northwest For. and Range Exp. Stn., Portland, Oreg.
USDA For. Servo Res. Pap. NC-168. North Central For. Exp.
Stn., St. Paul, Minn.
Harrington C A and DeBell D S 1984 Effects of irrigation, pulp
mill sludge, and repeated coppicing on growth and yield of
black cottonwood and red alder. Can. J. For. Res. 14, 844­
849.
Kubota J, Riegar S and Lazar V A 1970 Mineral composition
of herbage browsed by moose in Alaska. J. Wildl. Manage.
34, 565-569.
Langille W M and Maclean K S 1976 Some essential nutrient
elements in forest plants as related to sl?ecies, plant part,
season, and location. Plant and Soil 45, 17-26.
Perkin-Elmer Corporation 1976 Analytical Methods of Atomic
Absorption Spectrophotometry. Perkin-Elmer Corp., Nor­
walk, Conn.
Radwan M A and Crouch G L 1974 Plant characteristics related
to feeding preference by black-tailed deer. J. Wildl. Manage.
38, 32--41.
Snedecor G W 1961 Statistical methods applied to experiments
in agriculture and biology. Iowa State Univ. Press, Ames.
Tarrant R F and Trappe J M 1971 The role of Alnus in improv­
ing the forest environment. Plant and Soil, Special Vol. 335­
348.