-.
---·
_..._____
.
....
...
..._.
...
._,
.
-
. .
··--·
-·
. ..
..
.
.
....... � �
I
·-
ANUCNSV-TM-146
Energy from Biomass:
Building on a Generic Technology Base
Proceedings of the
Second Technical Review Meeting
April 23-25, 1984
OpPr.lll'Ci hv
THF lJt,JIVERSIT'! OF CHIC.�C.O for U.S. DFPARTMFNT OF FNFRl.Y
125
CULTURE OF RED ALDER (ALNUS RUBRA)
DeBell, M. A. Radwan,
D. S.
IN BIOMASS PLANTATIONS
C. A. Harrington,
and D. L. Reukema
USDA Forest Service, Pacific Northwest Forest and Range Experiment Station
Olympia, Washington.
ABSTRACT
Inherent biological traits .of red alder make it well-suited for culture in
biomass plantations, but silvicultural information and management experience
for the species are scant.
A research program at the USDA Forest Service
Forestry Sciences Laboratory, Olympia, Washington, has shown that the
species is responsive to spacing control, fertilization, and genetic
selection.
Although biomass production systems envisioned for most other
hardwood species involve close spacings,
regeneration,
very short rotations, and coppice
we recommend that red alder plantations be established at
relatively wide spacings
(1.8
rotations of 10 to 15 years,
x
1.8
m
or wider),
be managed
on
longer
and be regenerated after harvest by planting.
lliTRODUCTION
This paper describes recent research by the USDA Forest Service on
increasing the productivity of· red alder (Alnus rubra Bong.) in biomass
plantations in the Pacific Northwest. ·The research is part of the Short
Rotation Woody Crops Program of the U.S. Department of Energy and involves
cooperative studies with the University of Washington,
Corporation,
Crown Zellerbach
State of Washington Department of Natural Resources, and
Washington Irrigation and Development Company.
JUSTIFICATION AND GENERAL OBJECTIVES
Our research is focused on red alder because we believe alder's inherent
biological traits make it an ideal candidate for use in bioenergy
plantations in the Pacific Northwest.
Red alder exhibits rapid juvenile
growth and thus quick development of biomass.
Its early sexual maturity
provides opportunities for rapid genetic gains using selective breeding.
The ability of red alder to fix atmospheric nitrogen is extremely desirable
1
because it eliminates the need for application of synthetic nitrogen
fertilizers--the most energy-expensive of all management treatments (except
Of s veral hardwood species native to the Pacific Northwest,
irrigation).
re
alder is the most abundant and occurs naturally over the widest range of
soil and site conditions.
Pure stands of red alder now occupy about 1.2
million ha of forest land in Oregon and Washington.
In addition, millions
of hectares now occupied by conifers as well as most marginal farmland west
of the Cascade Range in these states appear suitable for growing alder and
are potentially available for producing bioenergy crops.
126
Alder production has received little attention to date in the
conifer-dominated forest economy of the Pacific Northwest. Much of the
information needed to manage the species effectively is lacking. We have
therefore developed an integrated program of studies to: ( 1 ) assess the
influence of cultural practices on tree growth and stand development, ( 2 )
examine genetic variability within the species, and ( 3 ) develop too ls for
predicting the relative productivity of land for short-rotation alder
plantations. Results from these investigations will be used to develop
guidelines for crop management, to design programs for tree ( genetic )
improvement, to select appropriate sites for plantation establishment, and
to estimate future yields from biomass plantations. SELECTED STUDIES AND RESULTS
The Forest Service research effort consists of approximately 20 studies. We
have selected some examples from our work in spacing, coppicing, nutrition,
genetic variation, and productivity assessment to illustrate the nature of
the research and the potew.tial for manipulating red alder in plantations. Spacing Knowledge of the effects of spacing or stand density on growth and
development of trees and stands is required to guide intensive management
activities for any species.
Such information is scant for managed red alder
stands. Our oldest spacing trial is located in northwest Oregon at 300-350 m
elevation on a site formerly occupied by Douglas-fir ( Pseudotsuga menziesii
(Mirb. ) Franco ) . Spacing treatments of 0.6 x 1. 2 m, 1. 2 x 1 . 2 m,
1. 2 x 1. 8 m, ,1. 8 x 1.8 m, and 2. 7 x 2. 7 m were replicated twice on plots
0 . 04-ha or larger. The plots were planted in winter 1974-75 with
container-grown seedlings.
Data regarding stand st!ucture and yield 9 years after planting are
presented in Table 1. Number of trees planted varied from about 130 0 trees
per hectare in the 2. 7- x 2. 7-m spacing to nearly 12, 0 0 0 trees per hectare
in the 0.6- x 1. 2-m spacing. At age 9, mortality ranged from less than 10%
in the two widest spacings to 54% in the 0. 6- x 1. 2-m spacing.
Diameter was significantly affected by spacing; mean diameter for the widest
spacing was 68% larger than for the closest spacing. Height averaged 12. 4 m
and was not significantly influenced by spacing. Total above-ground dry yields were similar for the four closest spacings at
62 to 67 t/ ha, and are equivalent to mean annual dry yields of 6.9 to 7.5
t/ ha. Total yield at the widest spacing was 53 t/ ha, about 17% less than
the average of yields in the four closer sǘcings. Differences among
spacings in per hectare characteristics diminished substantially between
years 7 and 9. 127
Table 1.
Stand Characteristics of Red Alder Plan'tings at Age 9
Planted spacing (m)
Stand characteristic
0.6
X
1.2
.Trees per hectare
Planted
11, 9 18
5, 444
Surviving
Average diameter (em)
7.1
Mean height (m)
11.6
Total live, above-ground,
65
dry yield (t/ha)
NA
=
1.2
X
1.2
6, 586
4, 870
7.6
11.5
67
'
1.2
X
1.8
4, 272
3, 047
8.9
12.3
63
1.8
X
1.8
2, 989
2, 722
9.4
13.2
62
2.7
X
2.7
NA
1, 272
11.9 .
12.5
53 not available
Trends in quadratic mean diameter indicate that the difference between the
widest spacing and the four closest spacings is becoming greater (Fig. l);
and the closest spacings are maintaining their relative ranking. Height
measurements show that trees attained breast-height during the second
growing season, but diameter at breast height was not measured until year
4. At that time, mean diameters varied among spacings by 0.76 em. Differences increased to about 2 em by age 5, to nearly 4 em by age 7, and to nearly 5 em by age 9. Diameter growth at all spacings appears to be continuing at a relatively constant rate. Patterns of above-ground dry matter production are shown in Figure 2.
Fivefold differences among spacings at year 4 (3.5 to 17.2 t/ha) diminished
substantially by age 7 (27.5 to 37.7 t/ha), and were even less by age 9
(53.4 to 67.3 t/ha). Periodic annual increment from age 4 to 7 years
averaged 8.3 t/ha, ranging from 6.8 t in the closest spacing to 9.8 t in the
1.8- x 1.8-m spacing. Periodic annual increment for the past 2 years (age 7
to 9) has averaged 13.8 t/ha, and variation among spacings has diminished
(13.0 to .14.9 t/ha). Moreover, current annual production has not peaked;
thus the stands are still in a highly productive stage.
Findings to date indicated that diameter growth of individual alder trees
was very sensitive to spacing, but current dry matter production per hectare
at age 8 or 9 was rather similar across a wide range of spacings. Current
production has accelerated greatly in all s·pacings during the last 3 to 4
years, thus suggesting rotations of 6 years or longer would be necessary to
capture the species' growth potential.
Finally, the mean annual yields of 7
to 8 t/ha and current production rates of 13 to 15 t/ha in this trial were
obtained without fertilization, pre-planting herbicide applications, or any
post-planting weed control. With such treatments and somewhat longer
rotations of 10 to 15 years, yields would likely be much higher.
128
0
E
12
10
%" )' ( $
-··% +'
"
*+ ,Jv t-l$1 f:l &
e;f
#
r:.
!���
tl
i i I # r;
!:c
,i: .diii * = !
..., .,
'"
tO
••
†'
:r.
/_.
r•
E I
]
f:i
..
.
•
,q
;e
E
-·--
\
0
..
>
" .
.
•
2
••
·
••
ü
•
Age (ynl
s
11
e
.
=
=
=
·-
..M.
·
�--�--�----�h
2
{.j
:.þ. ;:,
t:!!
iJ ·,j:
•.
11
Figure 1. Quadratic Mean Diameter
as Related to Plantation Age and Spacing:
A= 0. 6 X 1.2 m; B = 1.2 X 1.2 m;
C = 1.2 X 1.8 m; D. = 1.8 X 1.8 m;
E= 2. 7 X 2. 7 m
r
.:;ÿ
s-'1
ý· ..=
=
2
o
;.·:·:-:
p·,;.
.J
'
••
o.a.1.2
t.2a1.1
u.au
Planted Spacing
t.h u
(m)
-. . .
X·"-':
r�
r:
L
=
=
.
J.f•J.7
Figure 2. Total Above-Ground Dry
Matter Production as Related to
Spacing and Time Since Planting
A new spacing trial--with larger plots, more replication, and a wider range
in spacings.-.is now entering its third growing season. This trial will
provide data for a more complete evaluation of .effects of both initial
spacing and subsequent thinning. In-addition, a comprehensive productivity
study involving spacing, fertilization, weed control, and irrigation
treatments will be established next spring with seedlings of 20 to 30
half-sib (wind-pollinated) families.
Coppicing
Most proponents of the bf oenergy plantation concept advocate regeneration by
coppicing or sprouting of stumps after harvest. We therefore conducted
several studies to assess factors involved in sprouting of red alder
stumps. Information has been collected on effects of tree age, stump
height, season of harvest, and repeated harvest on sprouting success.
A study to examine effects of tree age was established in 1982 in 24 natural
'
stands. Stands ranged in age from 1 to 32 years and were located in both
Oregon and Washington. One hundred trees in each measurement plot plus
trees in a surrounding buffer area were cut in February, and sprout
production was assessed for two growing seasons. Sprouting success (percent
of stumps with sprouts after 2 years) was negatively correlated wit h tree
age. Ninety percent or more of the stumps in 1- to 3-year-old stands had
sp routs; but less than 75 percent of the stumps in stands older than age 6
had sprouts. Stumps in four of five plots in stands 15 years of age or
older did not produce a single sprout that lived to the end of the second
growing season.
if ú·û'---..-----------"""'
,..-,
,....
..,..
,..__
_.
,..· ,...
_
,ey...,
""""'
""'"""
'""
"'
-..
....W.
. _
...--...,....
_
"
••-----,.
.. t1'-rl""''"'""'"
'z+""'
....
""''"'"C_.O
. .iiQ
il.ll
t...:illo.fl
d\%
lilillwdl
ff"""""".-Bi't
S ...
__
T""
___
129
Another experiment assessed the influence of stump height and season of
harvest on sprouting of 4-year-old saplings. Results are shown in Table 2.
S prouting success was rather poor for stumps cut lower than 30 em and cut
during the growing season (May, July, September); 50% or less of the stumps
had live sprouts after 2 years. Sprouting was best if trees were cut in
January; presumably, coppice regeneration would be reasonably successful if
stumps were cut during the dormant season from November to March.
Table 2. Percent of Red Alder Stumps With Sprouts After Two Growing Seasons by Stump Height and Month of Harvest Month of harvest Stump height
Centimeters 0
10
30
50
70
September
-
-
- -
15
10
40
70
90
-
January
-
- -
-
-
- -Percent15
50
70
90
95
July May
15
40
50
65
80
-
-
-
-
0
5
35
80
85
A third study provided information on effects of repeated harvest on
sprouting of red alder trees cut at age 2 and every 2 years thereafter. All
harvests were made during winter and stumps were cut at 15 em. Essentially
all (99. 6%) stumps sprouted following the first harvest. Sprouting success,
however, declined with each successǖve harvest. Percentages of original
stumps with live sprouts were 93, 76, 43, and 31% at the time of the second,
third, fourth, and fifth harvests, respectively.
These studies and other observations indicated that alder does not sprout as
readily or as consistently as Populus, Salix, and some other hardwood genera
and species. Sprouting of stumps cut during the growing season or in stands
older than 6 years was too inconsistent to recommend coppice as a
regeneration system for such conditions. Moreover, repeated coppicing of
alder plants by dormant season harvests at 2-year intervals resulted in high
mortality (> 50%) after three such harvests. Because of these coppicing
traits .and other biological.and economic factors, we believe future research
and management efforts in alder should be concentrated primarily on
conventional management and regeneration systems rather than on coppice
systems. In addition, somewhat longer rotations of planted trees (similar
to pulpwood rotations in the South) would permit use of conventional
harvesting equipment and would also substantially increase the area suitable
and available for alder production.
Red alder could be grown as a
short-term, alternating crop on lands dedicated primarily to conifer
management.
130
Nutrition and Fertilization
Although nitrogen (N) requirements of alder are probably met through
N2 -fixation, maximum growth and development also require adequate supplies
of other essential elements. Amounts of certain elements may be limiting in
some soils, and thus red alder on such sites may respond to appropriate
nutrient amendments. We conducted several studies concerning nutrient
status in natural stands and tested application of fertilizer to seedlings
and saplings.
Three studies of nutrient levels in soil, foliage, or leaf litter in natural
(1)
red alder stands have been completed. Principal findings were:
exchangeable calcium (Ca) and magnesium (Mg) decreased substantially with
increases in N content and concomitant decreases in pH of soils beneath
alder stands, (2 ) foliar concentrations of several nutrients (especially
phosphorus) decreased with stand age, and (3) phosphorus (P) content of leaf
litter decreased with stand age. Such relationships suggest that growth of
this N 2-fixing species might be limited by native levels of P, Ca, or
other mineral nutrients in the soil and thus might be increased by
application of non-nitrogenous fertilizers.
These suggestions are supported by results from fertilizer tests conducted
in the lathhouse at the Forestry Sciences Laboratory using potted seedlings
and three different forest soils. In all three soils, seedling growth was
increased substantially by application of P fertilizer. In one soil, good
responses were also obtained from applications of Ca, Mg, potassium (K), and
sulfur (S)-applied alone or in combination with P.
In the other two soils,
growth of alder was mostly reduced when these nutrients were applied alone
or in mixture with P, presumably because native soil P was low and additions
of most other fertilizers aggravated the P deficiency.
A field fertilizer test was established in a 4-year-old plantation growing on a fourth and different soil. Treatments were: ( 1) no fertilizer, (2)
200 kg P/ha and 125 kg Ca/ha, applied as triple superphosphate (TSP), and (3) TSP plus 100 kg K/ha and 4Z kg S/ha, applied as K2 S04 . Measurements
after 1 year indicated tbat h eight and diameter growth of alders receiving
TSP was already somewhat greater than that of unfertilized trees; growth of
trees receiving both TSP and K2S04, however, was slightly less than
growth of the unfertilized trees. Such an early expression of treatment
differences was surprising; based on work in established stands with other
species, we anticipated that at least 2 years would be needed before
response to TSP would be observed in these 4-year-old plantings. Although
thƶ observation of reduced growth when TSP was combined with other nutrient
amendments paralleled the findings in our lathhouse studies, similar effects
did not persist beyond the first year in a fertilizer trial with a conifer
species.
The early results from the field trial coupled with the lathhouse tests and
nutritional studies in natural stands suggest that growth of red alder can
be enhanced substantially with non-nitrogenous fertilizers (especially P).
The next logical step is the establishment of a series of trials on the
major soils suitable for production of alder in the Pacific Northwest.
131
Genetic Variation
Studies of genetic variation in red alder are being conducted by both the
Forest Service and University of Washington
T his presentation focuses
primarily on the Forest Service studies--a 15-year-old provenance trial and
a 5-year-old open-pollinated family inheritance test.
•
.
The provenance trial was established in 1969 at the Cascade Head
Experimental Forest, Siuslaw National Forest, near Lincoln City, Oregon,
and consists of 10 seedling sources collected throughout the range of red
alder. Locations included Juneau, Alaska, Sandpoint, Idaho, and eight
well-spaced locations in Oregon, Washington, and southern British Columbia.
Cumulative heights to age 15 for the test provenances are shown in Figure 3.
Sources that were tallest at age 3 and 4 (e. g. , Concrete and Sequim,
Washington) have continued their superiority. Diameter rankings are similar
and have also remained rather constant since diameter was first measured at
age 8.
50
·15
40
Q)
01
Ill 'tl
Q)
•10
30
iO
U-
:o;
.EQ)
-Ill
""
01
·a;
:I:
..
E
20
•5
10
Figure 3.
Cumulative Height of Red Alder Provenances
Mean annual production for the two best provenances (Concrete and Sequim)
was 7. 8 and 6.3 oven-dry t/ha, respectively. Estimated periodic annual
production (age 12-15) exceeded 10 t/ha for four of the sources.
Differences among sources in biomass production were much greater than those
for height and diameter. For example, the best and poorest growing
provenances from Oregon and Washington differed at age 15 by 11% in height
and.by 38% in diameter. Comparable differences for estimated total dry
weight per hectare at age 15 and periodic annual production (age 12-15)
amounted to more than 100%.
The inheritance test consists of 33
seven stands located within a 40-km
outplanting site.
Five years after
and farnil:r means ranged from 6.3 to
open-pollinated (half-sib) families from
radius oi the McCleary, Washington,
planting, a ve rage tree height was 7.0 m,
8.0 m; average diameter was 7.1 em, and
.
.
132
family means range from 6.0 to 8.0 ern. Heights and diameters were not
related to location of parent stands, but significant growth differences did
occu:r among families within stands.
Estimates of family heritability ( 7
years from seed, 5 years since outplanting) are 0.28 for height and 0.51 for
diameter. Based on this work, we suggest that dry weight of biomass
produced in shdrt-rotation red alder plantations can be increased by at
least 20% using rather modest tree improvement programs.
The University of Washington field trials to assess natural genetic variation in Oregon and Washington populations were outplanted 1 year ago. This work has demonstrated significant differences in growth traits among families; most of the variation is related to latitude and elevation. Tentative conclusions from the genetics work to date are: (1) substantial
genetic gains can be made by selecting superior populations, (2 )
reproductive material can be moved over rather long distances and
established successfully on mild coastal sites, and (3) within a limited
geographic area, selection of families within stands may also lead to
further genetic gains. Future work will consist of continuing the
previously-mentioned studies; in addition, we plan to examine differences in
family responses to cultural treatmen.ts in the comprehensive product! vity
study. Differences in the accumulation and distribution of biomass and
nutrients among selected families will be assessed in the University of
Washington field trials.. Such information will help explain differences in early growth among families, will provide data on genetic variation in nutrition and efficiency of nutrient use, and will add to the general knowledge about opportunities and limitations for manipulating short-rotation crops of alder. Productivity Assessment
One of the most important decisions a manager of biomass plantations must
make is the selection of sites on which to plant and manage various
species. Mistakes will be costly not only in biologic and economic
performance of specifiƷ plantations but also in public perceptions of the
bioenergy farm concept. A portion of our research was therefore devoted to
developing a guide to evaluating site quality for red alder.
Forty, well-stocked, even-aged, natural stands of red alder were selected to
sample as wide a range as possible of site conditions. In each stand, a
0.1-ha plot was established and site index was estimated. Information was
then recorded on local topography, soil, and vegetation. Soil samples were
collected and analyzed for physical and chemical properties. Climatological
data were obtained from pub_lished isohyetal maps. These data were summarized
and analyzed to develop a guide for evaluating red alder site quality.
The site evaluation guide uses 14 soil-site properties (Table 3) . The
properties are divided into three groups or factors: (1) geographic and
topographic position (including climatic characteristics), (2) soil moisture
and aeration during the growing season, and (3) soil physical condition and
fertility. Evaluation of potential site quality of an area requires
determination of several characteristics of the actual location or position
'
.
133
of the site and of various soil properties. Predicted site index is
calculated by summing the site points for each property. The range in
points assigned to each property is shown in Table 3 and is indicative of
the relative importance of the property in this guide
The exact number of
points assigned will vary with characteristics of the property at each site;
these characteristics are described in detail in the guide.
•
The site evaluation tables for red alder were designed to predict a maximum
value of 40 (site index in meter s at 50 years). Factor 1 (Geographic
Location and Topographic Position) at its maximum level can account for 20
site points or half of the maximum total number of points. The properties
·
and quickly in the field or
evaluated in Factor 1 can be determined eaaily
by using readily available information sources such as topographic maps or
weather records. This factor might therefore be used by itself for a quick,
preliminary screening of potential planting sites
•
..
When used properly, this method .. of site evaluation is fairly precise and
accurate. The model was constructed with data from 25 of the 40 plots. The
remaining 15 plots were used for independent verification. A chi-square
test of accuracy indicated that true site index should be within + 2 m of
the predicted value 95% of the time. Future work will include validation
tests with data collected independently by other workers.
Table 3. Soil-Site Properties Included in Red Alder Site Evaluation Guide and RaǗe of Points Assignable to Each Property Factor III:
Factor I:
Factor II:
Geography /Topography
Soil Moisture/Aeration
perty
Points
,
Soil Fertility/
Physical Condition
Property
Points
Property
Points
Elevation
0 to 8
Internal
drainage
0 to 4
Parent
material
1 to 4
Physiographic
position
0 to 5
Texture
0 to 3
Soil pH
0 to 2
Aspect and
slope
l · to 4
Soil depth
0 to 2
Organic
matter
1 to 2
I
Precipitation 0 to 3
(growing-season)
Rock and
-2 to 1
gravel content
Special
-3 to 0
hazards (frost,
Depth to
water table
wind)
0 to 2
Bulk
density
- 2 to 0
134
CONCLUSIONS
Our research has shown that red alder not only has some ideal inherent
biological traits (rapid early growth, nitrogen fixation, wide adaptability)
but also · that it can be very responsive to management. Research on spacing
has indicated that individual tree size can be greatly increased by wide
spacing with little reduction in yield, provided that rotations are 10
years or longer. Inadequate amounts of nutrients other than nitrogen are
likely to limit production on some sites, and responses to fertilizer
(especially phosphorus) have been substantial in our initial tests. Genetic
variation among populations and within local stands suggests good
opportunities for growth gains via tree improvement programs. Although red
alder sprouts poorly, we do not consider this a major disadvantage. In
fact, several factors point to the desirability of managing red alder by
more conventional systems than by coppice systems. In addition to poor
sprout production, these factors include: (1) gǕowth patterns--accelerated
growth after year 6 and substantially increased tree sizes with wider
spacings, (2) the opportunity to introduce improved genetic stock if stands
are replanted after harvest, and (3) the possibility of using presently
available harvesting equipment--use of existing equipment and larger-sized
trees could result in lower harvesting and handling costs. Moreover, the
ability to use more conventional equipment could g reatly increase the land
area suitable and available for alder production in the Pacific Northwest;
i.e., red alder could be grown as a short-term crop alternating with
Douglas-fir on lands now dedicated exclusively to conifer production. In
short, many factors suggest that more conventional (albeit short rotation)
management systems are more appropriate for red alder in the Pacific
Northwest than are the coppice systems usually· advocated for bioenergy
plantations of other hardwood species in other regions.
About this file: This file was created by scanning the printed publication.
Misscans identified by the software have been identified; however, mistakes may
remain.