Biomass
21 (1990) 11-25
Dry Weight Partitioning Among 36 Open-Pollinated Red
Alder Families
Donal D. Hook,a Dean S. DeBell,b Alan Agerc & Daniel Johnsonb
aClemson University, Forestry Sciences Laboratory, 2730 Savannah Highway, Charles­
ton, South Carolina 29414, USA bpacific Northwest Experiment Station, USDA, Forest Service, Olympia, Washington 98502, USA C
College of Forest Resources, University of Washington, Seattle, Washington 98195, USA (Received 25 August 1988; revised version received 11 January 1989;
accepted 22 March 1989)
ABSTRACT
Six trees of each of 36 red alder (Alnus rubra Bong.) open-pollinated
families were harvested from a genetic test plantation in September of the
second field season and analyzed for growth and dl)' weight partitioning.
Families from elevations greater than 300 m were significantly shorter
than from those below 300 m and tended to be in intermediate or
suppressed positions in the plantation canopy. Families from the most
southerly drainage system, Santiam, were smaller than those from the
more northerly drainages. When low elevation families (those from less
than 300 m; 24 of the 36 families met this criterion) were analyzed
separately, no statistically significant variation was found among the
growth traits. In contrast, significant family variation was found in all of
the dry weight partitioning traits and relative crown class. Family herita­
bility (h2) values for low elevation families varied from 0·00 to 0'39 for
growth traits and from 0·39 to 0·69 for dl)' weight partitioning traits. At
this age and stage of plantation development, there seemed to be more
variation in dl)' weight partitioning than growth of low elevation red alder
families. Family means of the dry partitioning traits varied from as little as
5% to as much as 20% around the population means; hence, it appears
that variation in some partitioning traits is large enough to be of practical
significance in breeding and tree improvement programs.
Key words:
leaf area ratio, leaf weight ratio, stem harvest index, woody
harvest index, specific leaf area, elevation, drainage system, heritability.
Biomass
0 144-4565/90/$03.50
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11
-
© 1990 Elsevier Science Publishers Ltd, England.
12
D. D. Hook et al.
INTRODUCTION Red alder (Alnus rubra Bong.) grows rapidly during early life, fixes
nitrogen symbiotically via actinomycetes in its roots, and grows naturally
over a wide range of soil and site conditions. Because of these charac­
teristics, the species has good potential for use in short rotation planta­
tions for bioenergy in the Pacific Northwest. Information concerning
opportunities for cultural improvement of alder growth is beginning to
accumulate but data on genetic variation and tree improvement are
limited.l Two studies of geographic variation have been conducted. One
greenhouse study indicated no difference in height growth at 20 weeks
among populations collected along a 45 km transect eastward from the
central Oregon coast.2 The other study showed considerable variation in
height, diameter and several other traits at plantation age 8 years among
10 red alder sources from Alaska, British Columbia, Washington,
Oregon and Idaho.3 Two studies of variation among open-pollinated
families of red alder are underway, and initial results of plantation ages
ranging from 3 to 5 years indicate that families vary in growth traits4,5
and in tolerances to soil waterlogging.6 Preliminary research on natural
genetic variation of several Oregon and Washington populations of red
alder have shown that source and family within source selection could
lead to gains in growth rate of 10-40%.4,5
The role of dry weight partitioning in determining the yield of red
alder has not been investigated. Many of the gains in yield of agricultural
plants during the past 20-40 years have been achieved by addressing
specific partitioning traits.7 Yields of modern wheat, soybean, corn and
peanut varieties are 40-100% higher than those of earlier origin.s The
higher yields are largely due to increasing the yield potential of crops by
selecting and breeding for genotypes that are better adapted to fertile
environments, high planting densities, and those that maximize the parti­
tioning of photoassimilate into desired products.8,g
This study was undertaken to assess variation in some of the plant
characteristics that might influence total or 'usable' biomass production
per unit area. We measured height, stem and crown diameters, and leaf,
branch and stem dry weights of 36 red alder open-pollinated families
near the end of the third growing season. The results were used to (1)
evaluate family differences by parent elevation and drainage source and
(2) evaluate differences among low elevation families on leaf, crown,
growth production indices, and their inherent ability to partition carbon
into various aboveground plant components.
Dry weight partitioning among 36 red alder/amities
13
MATERIALS AND METHODS
Establishment of test plantation
The materials used in the study were selected from an open-pollinated
genetic test plantation established in the winter of 1983 with 1-0
seedlings. The test contained 120 open-pollinated families from 60 seed
sources (two families per source) collected from four river drainages
(Santiam, Nisqually, Hoh and Nooksack) in western Washington and
Oregon. Santiam was the most southerly drainage and Nooksack was the
most northerly. The two central drainage systems were the Hoh directly
on the coast and the Nisqually inland (about 100-110 kIn) and slightly
south of the Hoh.
The design was an interlocking block design with five replications,
three interlocked blocks per replication, and two non-contiguous
seedlings per family in each interlocked block. Distance between
seedlings was 0·95 m, giving a density of 11 080 trees per hectare. The
site is located on the Western Washington Research and Extension
Center Farm of the Washington State University near Puyallup,
Washington. It is on a level alluvial terrace along the Puyallup River. The
soil is a Pilchuck (Typic Xeropsamment, mixed mesic) fine sandy loam,
with a pH of 5'8, and is excessively drained and underlain in places by
lenses of coarse gravel. Rainfall averages 100 cm/year, with 24 cm
falling between 1 May and 30 September. The frostfree growing season
is about 170 days, with a mean growing-season temperature of 16°C.
Plantation management involved selective herbicide treatments
during the establishment year and irrigation with overhead sprinklers
during July and August of 1983 and 1984, adding approximately 12 cm
of water per year.
Thirty-six red alder families were systematically selected from this
larger genetic test plantation to sample for biomass and dry weight parti­
tioning traits.s In selecting the 36 families, sampling was designed to
encompass a wide range of performances for each drainage and replica­
tion within elevation within a drainage. Selection was based on
performance data at the end of the first field season. Six families were
sampled from the most southerly and northerly drainage systems, and 12
families were selected from each of the two central drainage systems.
The central drainage systems were sampled more intensively because
they were nearest the plantation site and were most likely sites for future
selection of red alder for short rotation culture in western Washington.
D. D. Hook et al.
14
Sampling coincided with a systematic thinning of the plantation in
September 1984 of the second field growing season. For each family, two
trees were harvested from each of the three interlocked blocks (i.e.
Blocks 1, 2 and 3) for a total of six trees per family. However, trees were
obtained from Block 4 when families had a missing tree in Blocks 1, 2 or
3, or when existing trees were atypical (excessively large or small as com­
pared to the population average) because of obvious border or micro­
site effects.
Prior to harvest, each tree was rated for crown class in relation to its
four nearest neighbors (i.e. 1 dominant; 2 codominant; 3 inter­
mediate; 4 suppressed), and diameter (cm) was measured at 4-6 cm
above the soil surface. The trees were cut at the point of diameter
measurement and the following data were obtained: crown width in two
cardinal directions (free standing), total height, weight of leaves,
branches and bole. After obtaining fresh weights, samples of the various
components were dried at 105°C until a constant weight was attained to
determine moisture content. Leaf area was determined with aLI-COR
LI-3100 leaf area meter (LI-COR Lincoln, NE 68504) on approximately
50 fresh leaves, selected randomly from throughout the crown of each
tree.
=
=
=
=
Dry weight partitioning
The variables were leaf area ratio (LAR), specific leaf area (SLA), and
leaf weight ratio (LW R) as per Hunt 10 and the harvest indices:
.
Branch harvest mdex
.
Stem harvest mdex
=
=
.
Woody harvest mdex
BW
W2
-
SW
W2
-
=
WW
W2
--
where BW branch dry weight, 1984 (g), SW stem dry weight, 1984
(g), W W stem and branch dry weight, 1984 (g), and W2 aboveground
dry weight, 1984 (g).
=
=
=
=
Statistical analyses
Because seedlings were sampled unevenly among the four blocks and the
trees to be thinned were selected randomly by position, the data were
DIY weight partitioning among 36 red alder families
15
treated as random samples from the entire plantation. Consequently, the
data were subjected to a one-way analysis of variance (ANaVA) to test
for family differences, elevation, drainage and to estimate variance com­
ponents for heritability calculations. Although the crown class variables
were ordinal values, they were analyzed as interval variables in the
ANaVA and correlation analyses.
Elevation influences were efaluated by separating the 36 families into
six arbitrary elevation classes (0-50, 51-110, 111-200, 201-300,
301-600 and 601-1037 m) with approximately equal number of
families per class (Table 1). Drainage influence was evaluated by the four
parent drainage systems, and the number of families varied by drainage
system according to our initial sample plan. Family variation was tested
among all 36 families and among the 24 families that originated at or
below 300 m.
TABLE 1
Mean Dry Total Weight of Red Alder Families by Elevation Class and Drainage System
Class
(a) Elevation
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
(b) Drainage
Santiam
Nisqually
Hoh
Nooksack
Range
(m)
Approx.
latitude
0-50
Number of
families
7
51-100
111-200
301-600
1·29a
6
1·22ac
47"N
48°N
49°N
41·2
50'1
49'9
43·0
61·2
0'6Ib
68'9
6
0'66a
72'7
12
l-32b
53'0
6
45°N
1·14ac
Coefficient
of variation
(%)
0'86bc
6
601-1037
1·47a"
6
5
201-300
Mean dlY weight
(kg)
12
6
HOb
1·15b
49·1
46·1
"Values in columns with similar letters were not statistically different at the 0·05 level.
All of the dry matter partitioning variables (LAR, LWR, etc.) were
transformed to natural logarithms and analyzed for deviations from
normality. No differences were found between transformed and non­
transformed data, so only non-transformed data are reported herein.
Duncan's Multiple Range Test was used to compare family means when
significant family effects were found in the ANaVA.
16
D. D. Hooket al.
Family heritability estimates were calculated to assess the relative
genetic control of measured traits. Heritability of the 24 low elevation
families was estimated as follows:
h2f-
lit
lit + (Ve/6)
The family variance component (Vf) was obtained from the one-way
analysis of variance. Ve was estimated as the error means square in the
same analysis.
RESULTS AND DISCUSSION
All families
Elevation
Elevation had a significant influence on average aboveground dry
weights (Table 1 and F ig. 1). Most families from elevations greater than
300 m had only a fraction of the dry weight of families below 300 m and
their coefficients of variation were larger than those from lower eleva­
tions. Families from elevations greater than 300 m tended to occupy
intermediate and suppressed positions in the plantation canopy and the
degree of suppression was most pronounced in families from the
Santiam drainage as the elevation increased above 300 m (note Families
4, 5 and 6 in F ig. 1). All growth traits varied by family, drainage, and
elevation when all families were included in the analysis (Table 2, (a)).
Thus, the elevation relationships found by our sampling scheme were
similar to the results that AgerS found for the entire genetic population.
In this regard, red alder seems to be similar to other tree species of the
Pacific Northwest region. AgerS, in reviewing geographic variation
patterns of tree species for the region, found elevation to be consistently
important. Campbell I I showed that parent elevation strongly influenced
the performance of Douglas-fir (Pseudotsuga menziesii Mirb. Franco) in
Oregon.
Leaf area ratio and leaf weight ratio were smaller and woody harvest
index was higher for families from higher elevations. These responses
are probably the result of the higher elevation families being more
suppressed within the plantation canopy. Suppression within the canopy
reduces relative leaf area without a concomitant proportional reduction
in relative woody dry weight because much of the latter was produced
prior to suppression. Consequently, suppressed trees tend to give a mis­
leading low leaf area ratio and high woody to total dry weight ratio.
Fig. 1.
C:::J I£of
..
Q
..
..
•
400
6
] R
20
a
Ull
5 43630 151718 3
600
800
1000-
1200
1400
1600
1800
•
..
•
..
0
••
•
•
•
..
..
..
.....
..
•
..
•
..
Elevation
11
1
Family Number
13 141612 3433 2 422 102 711 7 2 2 8 352332 9 29 8 31252 6 19212 0
•
..
..
•
o
o
100
200
300
a..
u
500 jjj
....
400
600
700 .2
....
It:
E
BOO'""-'
900 ....... 1000
1100
largest based on stem dry weight.
Average component dry weight per tree and parent elevation for 36 red alder families. Families were ordered from smallest to
.2. c
....
o
c:-
:i:
0>
"ii
....... 0>
'""-'
.. StIlm
2000l 1SS!1 Sronch
2200
---..)
-
.
i:i:
'"
;;S
:::,.
:;:,
e
.
:
"<:::I
:;:,
::::;.
o<i'
tJ
1-68
0-47
0-38-0-55
0-74-0-86
Stem harvest index(gig)
0-21
0-79
10-2(m2/g)
Woody harvest index(gig)
x
Leaf weight ratio(gig)
Leaf area ratio
0-32 0-12-0-15
0-53-4-74
Branch harvest index(gig)
0-28
0-13
3-06
1-01-2-14
0-24-1-83
1-00-3-67
2-28-4-66 2-52-4-89
Range
0-17-0-36
0-17-0-25
0-27-0-41
Specific leaf area x 10-1 (m2/g)
Dry weight partitioning Total leaf area (m2)
2-14
Crown diameter (m)
Relative crown class
1-11
4-07 3-77
Mean
Total dry weight(kg)
Diameter(cm)
Height(m)
Growth
(a) All families
Trait
TABLE 2
5
14
20
21
21
12
59
27
44
56
24
21
Coefficient
of
variation
Heritabilitya
0-00
0-00
0-01
0-00
0-01
0-00
0-00
0-00
0-00
0-00
0-00
0-00
Family
0-03
0-23
0-06
0-03
0-00
0-20
0-00
0-00
0-00
0-00
0-00
0-00
Drainage
0-00 0-95
0-08 0-00 0-00 0-79 0-00 0-00 0-00 0-00 0-00
0-00
Elevation Probability of significant difference
Selected Growth and Dry Weight Partitioning Traits for 36 Red Alder Families
.....
??-
0
?;('D
......
00
10-2(m2jg)
0-12-0-15
0-18-0-25
0-37-0-53
0-74-0-82
0-27-0-41
0-63
0-68
5
14
0-52
0-63
0-69
0-39
0-08
0-28
0-39
0-00
0-02
0-23
19
17
11
20
47
22
40
46
19
15
0-00
0-00
0-01
0-00
0-00
0-04
0-37
0-13
0-66
0-04
0-82
0-18
0-20 0-27
0-77
0-01
0-00
0-15
0-18
0-01
0-07
0-07
0-13
7
hi
=
(Ve/6
VI
VI + where Vf is the family variance from the one-way ANOVA and V e is the within family variance from the one-way ANOVA_ For low elevation families:
aHeritabilities are not included for 'all families' because elevation influences were not taken out by the one-way ANOVA.
0-46
0-78
Stem harvest index(gjg)
Woody harvest index(gjg)
0-22
0-32
0-23-0-36
0-13
0-29
B ranch harvest index(gjg)
Leaf weight ratio (gjg)
x
Specific leaf area x 10-1 (m2jg)
Leaf area ratio
1-50-2-13
2-29-4-74
3-67
1-81
Dry weight partitioning
0-94-1-83
1-00-2-67
1-87
C rown diameter(m)
Total leaf area (m2)
Relative crown class
1-30
3-95-4-68
3-77-4-80
4-03
4-35
Total dry weight(kg)
Diameter(cm)
Height(m)
Growth
(b) Low elevation families(300 m or less)
i}
\0
>-
2-
....,
s::,..
s::,
a
:::
s::,
:::
g:
.
:::t
'2 ciQ-
t:I
20
D. D. Hook et al.
Drainage system
Families from the Santiam drainage had much smaller aboveground dry
weights than those from the other three drainages and larger coefficients
of variation about the family mean (Table 1). Not all dry weight partition­
ing traits varied with drainage as did growth traits (Table 2).
Woody harvest index was highest, leaf area ratio was lowest, and
specific leaf area was highest (thinner leaves) for the Santiam families as
compared to the two most northerly drainages (Hoh and Nooksack). The
Santiam families had the highest relative crown class i.e. they were more
suppressed within the plantation canopy than families from the Hoh and
Nooksack drainages.
Low elevation families (at or below 300 m)
Families from elevations higher than 300 m tended to peliorm poorer, to
have higher coefficients of variations about family means than those
from low elevations, and to give somewhat false indications of genetic
variation of some traits (Table 1 and F ig. 1). Thus, the 300 m elevation
was chosen as a criterion to segregate families that did not perform well
at the low elevation plantation site. By separating the high elevation
sources, it allowed us to focus on the genetic variation of the low eleva­
tion families, those that are apt to have the greatest practical use in
bioenergy plantations west of the Cascades in Washington and Oregon.
Growth and size
The only growth or size trait to vary by drainage or family for the low
elevation families was the ordinal value, relative crown clas (Table 2,
(b)). Families from the Santiam were more suppressed than families from
the Hoh and Nooksack drainages and families from the Nisqually were
more suppressed than those from the Hoh drainage. In contrast, specific
leaf area and leaf area ratio varied by drainage and the dry weight parti­
tioning traits varied among the low elevation families (Table 2, (b)). The
specific leaf area of families from the Nisqually and Santiam drainages
were larger (thinner leaves) than from families of the Hoh and Nooksack
drainages.
Family means for specific leaf area varied by as much as 11% around
the population mean. Specific leaf area was negatively correlated with
stem dry weight and volume index (DH) and positively with leaf area
ratio and relative crown class (Table 3). These correlations suggest that
in addition to drainage influences, specific leaf area of red alder seems to
be associated with leafiness, degree of suppression within the canopy,
and two growth traits.
0-14
0-56
0-79
D
0-91
0-01
0-60
0-66
DH
0-47
0-25
-0-35
-0-86
-0-55
-0-31
-0-27
0-22
0-32
0-18
0-15
0-27
0-00
-0-06
LAR
-0-21
0-01
0-07
HIw
-0-11
0-85
0-66
-0-58
-0-23
-0-53
HIs
-0-06
0-65
0-49
H
0-49
-0-26
-0-27
-0-63
-0-67
-0-62
-0-08
-0-45
-0-48
RCC
0-54
-0-75
-0-42
_
-0-24
0-67
-0-39
-0-23
-0-42
-0-39
0-19
-0-02
-0-05
SLA
0-23
-0-35
0-33
0-90
0-94
0-80
0-00
0-62
0-55
SDW
0-27
0-89
-0-68
-0-14
0-04
-0-12
0-79
0-91
0-89
0-28
0-76
0-85
TDW
0-81
0-13
0-58
-0-35
0-43
-0-46
-0-47
0-50
0-58
0-65
0-46
0-71
0-74
TLA
0-73
0-99
-0-30
0-92
-0-70
-0-26
0-18
-0-04
0-82
0-93
0-90
-0-08
0-84
0-75
W DW
total aboveground dry weight; TLA, total leaf area; W DW, woody dry weight_ b Coefficients must exceed 0-40 to be significant at the 0-05 level. index = (BDW+ SDW )/TDW; LAR, leaf area ratio; R C C , relative crown class; SDW, stem dry weight; SLA, specific leaf area; TDW, cm aboveground level; DH, diameter squared times height; H, total height; HIs, stem harvest index = (SDW/TDW); HIw, woody harvest aTrait abbreviations: BDW, branch dry weight; CD, crown diameter; CD/H, crown diameter divided by total height; D, diameter at 5-6 W DW
TLA
TDW
SLA
SDW
RCC
LAR
HIw
HIs
H
DH
D
CD/H
0-72
0-49
0-71 b
BDW
CD
CD/H
CD
BDwa
TABLE 3
Correlation Matrix of Selected Traits for 24 Low Elevation Red Alder Families
.
.
N
.....
:;:,
-
C)
3!
:;:,
0:::
"'=l
:;:,
oti-
tl
D. D. Hook et al.
22
The Nisqually drainage had a significantly higher leaf area ratio than
the coastal Hoh drainage. W hy this occurred is not readily apparent; the
Hoh drainage is directly on the Washington coast and the Nisqually is
inland about 100-110 km and slightly south of the Hoh latitude.s Subtle
differences between the coastal and inland environment may have con­
tributed to such differences or it may have been due to random variation.
Dry weight partitioning
Family means for leaf area ratio varied around the population mean by
as much as 20% (Table 2, (b)). Leaf area ratio was negatively correlated
with woody harvest index (r
0'86, Table 3) and it also had the highest
family heritability value of any trait (h 2 0'69, Table 2, (b)). Therefore,
leaf area ratio seems to be a very important trait to consider in improving
the biomass yields of red alder. Leaf weight ratio also varied among
families. It measured about the same attributes as leaf area ratio but did
not seem to be as sensitive a measure of family differences as leaf area
ratio (Table 2, (b)).
Of the three harvest indices measured, i.e. branch, stem and woody
harvest indices, the latter is most closely related to usable biomass.
Woody harvest index varied significantly among low elevation families
but family means varied by a maximum of 5% around the population
mean. Its heritability value in this small sample was fairly large
(h2 0'63); thus, it seems that small gains in woody biomass might be
achieved by considering this trait in improvement efforts.
Although branch and stem harvest indices may seem less important
than the woody harvest index, a close scrutiny of their implications indi­
cates that considerable attention should also be paid to these traits. For
instance, branch harvest index averaged 0'32 for the low elevation popu­
lation but families varied around this mean by as much as 19% and its
heritability was fairly high (h2 0'52). Consider family 27 in F ig. 1;
although it has an above average woody harvest index, the branch com­
ponent made up 41% of the aboveground biomass. It obviously is not the
best choice for maximum total energy output because of its high branch
component. Although its biomass yield appears to be high, it would be
more cumbersome to harvest, store and process. Therefore, selection
should favor families with high woody harvest indices in which the stem
makes up the largest possible component of the biomass. Families with
such indices would. appear to require less energy to harvest and process.
Families 26 and 34 in F ig. 1 meet this criterion. Family 34 has the highest
stem harvest index and the fifth largest woody harvest index and family
26 has the fourth largest stem harvest index and second largest woody
harvest index. In contrast, the family with the largest trees, family 20, had
=
-
=
=
=
D,y weight partitioning among 36 red alder famities
23
the sixth largest stern harvest index and the eleventh largest woody
harvest index.
The mean stern harvest index of 0·46 for red alder (Table 2, (b)) was
slightly lower than the 0'51 reported for 16-year-old Scots pine (Pinus
sylvestris) by Tigerstedt and Vellingl2 and slightly higher than the 0·39
dry stern wood reported for slash pine (Pinus elliottii Engelm.) by van
Buijtenen.13 Stern harvest index of Scots pine was positively correlated
with several growth traits and negatively correlated with relative crown
width and relative branch diameter. Velling and Tigerstedtl4 suggested
that since past phenotype selection in Scots pine had favored tall, slender
trees with fine branching habits, harvest index had probably been
increased unintentionally. However, the lack of correlation of woody and
stern harvest indices with height, diameter and volume index (DH)
indicates that selecting and breeding for large and fast growing trees of
red alder will not automatically lead to increasing the harvest indices
(Table 3). However, if attention were paid to crown diameter/height
ratios, total leaf area ratios, traits that were positively correlated with
larger woody and stern harvest indices, harvest indices of red alder might
be significantly increased.
Factors other than growth and partitioning traits should be considered
in seeking to increase unit area yield. Deployment strategies of ideotypes
and potential stocking densities have proven to be important in improv­
ing the yield of agronomic crops7,8 and some tree species.13,15,16 Our data
suggested that red alder production may be influenced by similar charac­
teristics; consider families 20 and 25 (F ig. 1). Family 20 had the largest
total woody dry weight, the largest crown diameter, largest total leaf area
and a relative crown class of 1'0 (dominant) of the 24 low elevation
families (data not shown). Family 25 had the ninth largest total dry
weight, fifth largest stern harvest index, below average crown diameter
and total leaf area and a relative crown class of 1'3 (data not shown).
Both families occupied dominant or strong co dominant positions in the
canopy. Such differences may reflect ideotypes and, if so, each family
would need to be deployed at different densities to achieve maximum
harvestable biomass per unit area. Further examination of relationships
between dry weight partitioning and harvestable biomass yields per unit
area in red alder planted at different spacings is needed.
ACKNOW LEDGEMENT
This research was collected while the senior author was on sabbatical
leave as a visiting Scientist at the Pacific Northwest Experiment Station,
24
D. D. Hooket al.
Olympia, Washington. The research was partially supported by the US
Department of Energy, Woody Biomass Program, Agreement No.
DE-Al05-810R20914.
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