Vol. 33, No. I, 1987, pp. 224-229
Copyright 198 7, by the Society of American Foresters
Forest Sci.,
Variation in Growth of Red Alder Families in Relation to
Shallow Water Table Levels
Donal D. Hook, Marshall D. Murray, DeanS. DeBell, and Boyd C. Wilson
ABSTRACT.
Growth of 24 Alnus rubra Bong. families was studied on wet microsites within a
5-year-old progeny trial in western Washington to evaluate variation in response to waterlogged
soil. Depth to water table varied from 0 to 30 em and was determined by depth of rusting on
steel rods placed in the soil near each tree. By plotting the data and use of correlation matrices
and regression analyses, tree height was found to be related to water table level. Eighteen families
had a linear and 6 families a curvilinear relationship between height and water table level.
Analysis of covariance, with water table as the covariate, showed that family slope coefficients
were heterogeneous, hence families varied in height response to water table level. Several families
showed no change in height across the water table level range (30 to 0 em), but the most sensitive
families showed more than a 50% decrease in height across this range. The results suggest that
growth of red alder on wet sites may be enhanced by selection and propagation of progeny
tolerant of waterlogging. FoR. Sci. 33( 1):224-229.
ADDITIONAL
KEY
woRDS.
Alnus rubra, waterlogged soils, genetic variation, reduced soils, sat­
urated soils, waterlogging tolerance.
RED ALDER (Alnus rubra Bong.) can tolerate poorly drained soil conditions and some
flooding during the growing season; it prevails on soils of restricted internal drainage, along
streams, and in swampy or marshy areas. On such sites the species grows faster than its
coniferous associates and is generally regarded as the commercial tree species best adapted
to wet sites in the Pacific Northwest. Although the most productive red alder stands are
usually found on deep, well-drained loams and sandy loams, such sites are also very
productive for Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and other conifer species
that are more valuable than alder. Thus, the wetter or inherently less productive sites
probably offer the greatest potential for commercial stands of red alder.
Productivity of alder stands on wet sites might be enhanced by breeding programs
designed to exploit whatever natural variation that exists in growth under waterlogged soil
conditions. Previous studies suggest that there is considerable variation (DeBell and Wilson
1978) and plasticity (Stettler 1978) in a number of its genetic traits. Genetic variation
within the species with regard to growth and survival under waterlogged soil conditions
has not been explored.
This paper reports on variation in size among 24 open-pollinated families of a 5-year­
old red alder plantation in relation to shallow water table levels at one site.
METHODS
PARENT STANDS, PROGENY TEST LAYOUT, AND GROWTH MEASUREMENTS
The trial contained a total of 33 open-pollinated families from 7 collection sites located
within a 40-km radius of the outplanting site (Table l ) at McCleary Experimental Forest
The authors are, respectively, Professor, Department of Forestry, Clemson University, Clemson,
SC 29634; Forester and Principal Silviculturist, USDA Forest Service, Pacific Northwest Research
Station, Olympia, W A 98502; and Geneticist, Washington State Department of Natural Resources,
Olympia, WA 98502. The paper was prepared when the senior author was on sabbatical leave as a
Visiting Scientist with the USDA Forest Service, Pacific Northwest Research Station, Olympia, WA.
The authors appreciate the assistance of Gary Clendenen and F. Thomas Lloyd in analyzing the data
and technical personnel of the Forest Service and Washington State Department of Natural Resources
for measuring and maintaining the plots. This research was supported in part by funding from the
U.S. Department of Energy, Short Rotation Woody Crops Program under Interagency Agreement DI­
AOl5-8lOR 20914.
224 I FOREST SCIENCE
TABLE 1.
Collection
site
McCleary
Description of physical and biological characteristics of parent stands and mother trees.
EstiElevation Estimated mated
above
annual
site
mean
index
precipi­
sea level
tation
(50 yr)
m
em
m
90
152
23
Range for mother trees
Soil series and parent material
Mixture of Dabob, very gravelly
Physiographic position
Identifica­
tion
numbers
Age of
trees
Height of
trees
yr
m
Alluvial flat
61-72
67-88
24-30
Moist side slope and swale
73-84
39
28
Side slope
37-48
40
26
Low ridge
25-36
57--60
29-31
Aood plain of creek
85-96
61--63
21-24
1-12
15-22
12-20
loam and Siffon, gravelly silt loam­
wet variant alluvium derived from
basalt
Porter
168
140
31
Garrard clay loam derived from silt­
stone
Rock Candy
274
140
26
Boistford clay loam derived from
Eocene basalt
Schafer Park
99
190
28
Hoquiam gravelly silt loam derived
from mixed sediments and basalt
Stillwater
76
203
20
Shelton, gravelly sandy loam derived
from glacial till mixed with local
basalt
f
(')
=
-
\0
00
--.J
'-.
N
N
VI
Wedekind
549
140
27
Mahaffey gravelly clay loam, allu­
vium derived from basalt
Depression and drainage at
high elevation
near McCleary, Washington. The experiment was planted in March 1979 in a randomized
incomplete block design with five blocks. Number of families varied from 24 to 33 per
block (all families used in this experiment were planted in all 5 blocks, and the sample
trees within a family came from 3 or more blocks). Each family was planted as a row plot
consisting of 6 trees in each block. Spacing between trees was 2 x 2 m and the planting
stock was 1-1. Survival was assessed after the first growing season. Mortality was 5% and
appeared to occur randomly throughout the plantation. Dead seedlings were replaced with
"surplus" seedlings that had been planted in the outside row of each block. Height and
dbh of all trees were measured after the fifth growing season.
The plantation is located on an alluvial fiat that did not appear to have any waterlogging
problems prior to harvest of the original stand of red alder and mixed conifers. Since
harvest, however, waterlogged soil conditions occurred in all blocks during the rainy winter
seasons and sometimes persisted into the growing seasons. Soil maps of the alluvial fiat
indicates that the higher and drier areas are a Dabob, very gravelly loam series, and the
lower waterlogged areas are a Siffon, gravelly silt loam-wet variant series. The prevalence
of waterlogging since harvesting may have resulted from reduced transpiration losses.
Regardless of the cause of waterlogging, the microsites were distributed across blocks and
within families in such a random pattern that we were able to evaluate and compare the
growth of 24 families over a range of 0 to 30-cm water table depths.
WATER TABLE LEVEL ESTIMATES
The length of rusting on an iron rod driven into waterlogged soils proved to be a reliable
indicator of the depth to the average water table level over a 16-wk period in coastal South
Carolina (McKee 1978). This technique is based on the fact that an iron rod will rust in
the aerated zone of the soil but will not rust in the saturated (nonaerated) or reduced zone.
In our study, we used iron rods (mild steel about 89 em long and 3.6 mm diameter) and
cleaned the rod surface to remove oil, wax, and dirt before installation. Rods were pushed
into the soil within 15 em of each tree stem to a depth of 7 5 em, or until a barrier was
encountered. In the wettest portions of the site, rods were placed on two sides of each tree.
Rods were installed on November 17-18, 1983. One rod was removed from the soil near
each tree on February 6, 1984, and measured to determine: (A) depth rod penetrated into
the soil, and (B) length of unrusted portion of the rod. Depth to water table was estimated
by subtracting B from A. The second rod in each set was removed on May 24, 1984, and
measured in the same manner.
We restricted our analyses to trees on microsites having water tables within 30 em of
the soil surface because: (1) at some locations rods could not be pushed into the soil more
than 30 em, (2) in other areas rods were pushed in deeper and the entire length of rod in
the soil rusted, hence depth to the water table could not be determined, and (3) our primary
interest was to evaluate response to shallow water table levels. In addition, families with
less than 13 observations of water table levels within 30 em of the soil surface were excluded
from our analysis. After all rejections, we used data from 24 families consisting of 13 to
25 trees each in our investigation. Six collection sites were represented by the 24 families.
In the wetter portion of the plantation, water table levels were similar during November­
February and the November-May measurement periods. Therefore, only the measurements
from the November-February period were used in the analyses.
ANALYSES
Relationships between tree growth and depth to the water table were examined using a
four-step process: ( l ) plotting of growth variables vs. depth to water table to examine
general patterns of the relationships, (2) developing a correlation matrix consisting of growth
variables (height, diameter, diameter squared multiplied by height), depth to water table,
and the natural logarithms of growth and water table variables; (3) selecting the most
appropriate functions for describing the general relationship between growth and water
table for each family and developing a regression equation therefrom (the selection of
functions or variables was based on the plottings and correlations); and (4) testing the
·slopes of linear regressions of all 24 families by the assumption of homogeneity as a null
hypothesis in an analysis of covariance where water table level was the covariate.
226 / FOREST SCIENCE
TABLE 2. Regression relationships between 5-year tree height and depth to water
table and the family means for height and water table level for red alder families.
Regression Parameters
Family
number
Intercept
a
Slope
coefficient
Coefficient of
determination
b
y2
p
for slope
Number of
observation
Mean
family
height*
Mean
water table
level**
(m)
(em)
12.4
Linear responses (tree height vs. water table level)
tO
6.96
0.03
0.06
0.25
24
7.3
62
6.68
0.06
0.07
0.28
18
7.5
13.7
6
5.78
0.07
0.14
0.06
25
6.7
12.7
12
6.24
0.07
0.35
0.00
23
7.2
13.7
85
5. 12
0.09
0.3 1
0.02
17
6.3
12.5
72
5.43
0.09
0.19
0.14
13
5.9
5.5
42
5.54
0.10
0.32
0.01
18
6.6
10.7
71
5.95
0.10
0.31
6.8
8.0
5.62
0.11
0.33
O.Dl
O.Dl
23
9
21
6.5
7.7
90
5.26
0.11
0.64
0.00
24
6.8
13.7
70
4.59
0.12
0.31
0.02
17
5.9
10.6
66
4.70
0.13
0.65
0.00
17
6.5
14.1
65
4.38
0.13
0.58
0.00
19
5.7
10.1
81
4.17
0.14
0.54
0.00
14
5.7
10.9
26
4.67
0. 14
0.75
0.00
17
6.0
9.3
67
4.71
0.17
0.82
0.00
15
6.8
12.8
63
3.85
0.17
0.76
0.00
16
5.5
9.9
8
4.28
0.18
0.83
0.00
18
6.0
9.4
Curvilinear responses*** (tree height vs. natural log of water table level)
3
5.04
0.92
0.36
0.01
20
7.3
7
4.96
0.94
0.40
0.00
18
6.6
7.8
11
4.26
0.98
0.62
0.00
18
6.1
10.3
4
4.44
1.01
0.54
0.00
18
6.9
15.5
28
3.94
1.25
0.40
0.00
19
7.0
13.8
4.30
1.41
0.66
0.00
18
6.5
7.0
* Critical range for pairs of means by Tukey HSD
=
1.9 m. ** Critical range for pairs of means by Tukey HSD
=
10.8 em. 13.5
*** Families were placed in the curvilinear category if basic data indicated such a response and if
the regression of the natural log of the water table level improved the r2 more than 0.05 over that of
a linear regression.
The family heights and water table levels were analyzed for difference by analysis of
variance using a completely randomized design.
RESULTS
The plottings and correlation matrix showed that for 19 of 24 families, height was more
strongly correlated to changes in depth to water table than were the other growth variables.
Consequently, height was chosen as the dependent variable to use in comparisons among
all families. Plottings of height and depth to water table and regressions showed a linear
relationship for 18 families and a curvilinear relationship for the remaining 6 families. The
latter relationship was best described with a linear regression equation using height and
the natural logarithm of depth to water table.
The null hypothesis that slope coefficients were homogeneous among the family regres­
sions of height vs. water table level was rejected by the results of the analysis of covariance
(P 0.000). Thus, families were shown to differ significantly in their height response to a
range of shallow water table levels. Slope coefficients (Table 2) varied from essentially flat
=
MARCH 1987 I 227
9
.....
E
-
s:.
c:n 6
•
s:.
Family 4
Family 10
Family 63
CD
•
...
1-
3
0
10
Water table level
FIGURE 1.
20
30
(em)
Regression relationships between fifth-year height (y) and depth to water table (x) for three
representative families of red alder (Y=a+ bx for linear andY=a+ bIn x for curvilinear).
for nonsensitive families (6, 10, 62, and 72) to steep for very sensitive families (8, 26, 63,
and 67). The 18 families with linear responses had a nearly continuous distribution in
slope coefficients from 0.03 to 0.18 (Table 2).
Plottings of representative family responses in Figure 1 show that Family 10 had no
significant change in height across the water table range of 30 to 0 em deep, but Family
63 showed a decline in height of about 5 m across the same water table range. In contrast,
Family 4 showed a decline in height of only 0.9 m from 30 to 10 em depth but a 2.4 m
decline from 10 to 1 em depth.
The curves in Figure 1 tend to converge at the 20-25 em water table depth. This may
represent a critical point in the relationship between height and water table level for red
alder at this age; i.e., height is reduced at shallower water table but is changed little by
water tables at greater depths.
Mean height and water table level varied significantly among families (P = 0.001 for
height and 0.05 2 for water table level), but in each case only two families were significantly
different: families 62 and 63 for height and families 4 and 72 for water table level (Table
2). Thus, important family differences would have been missed if height had been analyzed
independently from water table level.
DISCUSSION
Use of the "rusty rod" technique-a simple, inexpensive method-is a sensitive indicator
of water table level (McKee 1978). In addition, our study showed that the index developed
by this technique was strongly related to tree growth. Previous tests of the method have
been limited to the South Atlantic coastal plain, and measurements obtained were examined
in relation to water table only; no relationships to tree growth were assessed (McKee 1978).
Other investigators may find the rusty rod technique useful for evaluating site conditions
or for developing an index with which to assess effects of waterlogging on tree growth or
to examine variation among or within species with respect to tolerance of soil waterlogging.
In general, our study confirms previous qualitative reports that growth of red alder is
reduced on sites with soil waterlogging problems (Minore and Smith 1971, Dolan et al.
1984). Some families were shown to deviate from this general pattern; i.e., height was not
reduced by a shallow water table. The most sensitive families on the other hand, showed
more than 50% reductions in height as water table level rose from 30 em below to the soil
228 / FOREST SCIENCE
surface (Figure l ). Families with curvilinear responses appear to have shallower threshold
points than other sensitive families; i.e., their growth was not reduced markedly until the
water table was in the 10- to 0-cm zone (Figure 1).
Differences in sensitivity to water table level did not seem to be strongly related to the
relative wetness of the parent (collection) site. The parent sites, however, were not equally
sampled in our data so efforts to exploit genetic variation should continue to evaluate site
effects as well as individual trees or families within populations.
The large variation in height response to shallow water table levels among families
suggests that red alder may exhibit variation in waterlogging adaptive traits. Based on
adaptive responses to soil waterlogging of other tree species (Hook 1984), differences in
root morphology and distribution in the upper 20 em of the soil, variation in oxygen
diffusion within roots among families, and metabolic adaptations all seem probable in red
alder. Also, the effects of soil waterlogging on nitrogen fixation in red alder roots need to
be investigated further. Field experiments by Dolan et al. ( 1984) showed that nodulation
on red alder roots was greatly reduced by soil waterlogged conditions, but family variation
was not investigated.
We have discovered genetic differences in response to soil waterlogging among red alder
families and genetic selection programs aimed at enhancing growth on wet sites should be
effective. Optimal selection methods cannot be determined on the basis of available data.
LITERATURE CITED
DEBELL, D. S., and B. C. WILSON.
1978.
Natural variation in red alder. P. 193-208 in Utilization
and management of alder, USDA For. Serv. Gen. Tech. Rep. PNW-70.
DoLAN, L. S., P. SCHROEDER, M. GILLHAM, K. CLARK, and E. SMITH-0MAR. 1984. The cultural
treatment of selected species for woody biomass production in the Pacific Northwest. Final Rep.
Aug. 1978-Sept. 1984. DOE Grant #DE-FG-79-78BP35773. Seattle City Light Department.
Home, D. D.
1984.
Adaptations to flooding with fresh water. P. 265-294 in Flooding and plant
growth, T. T. Kozlowski ( ed.). Academic Press, New York.
McKEE, W. H., JR. 1978. Rust on iron rods indicate depth of soil water tables. P. 286-291 in Soil
moisture-site productivity symp. proc., W. E. Balmer (ed.). USDA For. Serv. Southeast. Area,
State & Priv. For., Myrtle Beach, SC.
MrNORE, D., and C. E. SMITH. 1971. Occurrence and growth of four Northwestern tree species over
shallow water tables. USDA For. Serv. Res. Note PNW-160. 9 p.
STETILER, R. F.
1978. Biological aspects of red alder pertinent to potential breeding programs. P.
209-222 in Utilization and management of alder, USDA For. Serv. Gen. Tech. Rep. PNW-70.
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MARCH 1987 I 229