Hibbs, D.E., D.S. DeBell, and R.F. Tarrant. 1994. Whose
fat shadow nourisheth. Pages 248-251 in Hibbs, D.E., D.S.
DeBell, and R.F. Tarrant, eds. The Biology and
Management of Red Alder. Corvallis, OR: Oregon State
University Press. 256 p.
Whose Fat Shadow Nourisheth
DAVID E. HIBBS, DEAN S. DEBELL, & ROBERT F. TARRANT
Probably for the first time in the history of forestry,
considerable biological information for a tree spe­
cies has been developed in advance of its need in
forest resource management. The quantity and
quality of information on red alder, from basic bi­
ology to applied management issues, has increased
tremendously since publication of Utilization and
Management ofAlder (Briggs et al. 1978). The ex­
panded scope of red alder information provides a
much broader current understanding of the inter­
related processes that affect growth, development,
and management of red alder-a synthesis on a
level not possible in previous writings on red alder.
Some important advances have been possible only
because knowledge has reached, in some sense, a
critical mass. Research has reached large geo­
graphic scales and has established functional,
interdisciplinary connections betv.'een single disci­
pline research projects. In this chapter, we review
highlights of alder research since the 1970s and list
some research needs that appear most critical.
nodules has been studied extensively and funda­
mentals of the processes are known.
The Frankia of red alder can fix large amounts
of nitrogen over a wide range of growing condi­
tions. This fixation contributes more significantly
to the rapid growth of red alder than the presence
of mycorrhizal fungi, and fixation takes place even
in the presence of high levels of soil nitrogen. In
nature, colonization of red alder by Frankia appears
to take place readily and very early in seedling de­
velopment. It is not well known what kind of
tradeoffs are made throughout the life cycle of red
alder between fixing nitrogen, absorbing soil nitro­
gen (expanded root systems), and above-ground
growth.
The few ectomycorrhizal fungal species of red
alder are very host specific, yet seem to be present
wherever alder is found growing, always arriving
after Frankia. These mycorrhizae play a critical role
in phosphorus acquisition; red alder uses and cycles
large amounts of phosphorus.
Laboratory research on red alder and experience
Below-ground Biology
with other species has shown that Frankia strains
Red alder is a partner in an important three-way
and fungal species differ in growth characteristics,
symbiosis, a partnership whose interactions and
but these differences have not been systematically
ecosystem roles are becoming clear. Below ground,
investigated in red alder symbioses. Tailoring nurs­
alder roots grow in an intimate and essential
ery inoculations to specific field growing conditions
association with mycorrhizal fungi and the
may enhance alder survival and growth.
actinomycete Frankia. This three-way symbiosis
There has been considerable progress in under­
contributes to the rapid growth rates of red alder,
standing alder-soil interactions. Tools developed to
to its flexibility in site requirements, and to its large
predict alder growth from soil (and climatic)
influence on soil structure and fertility. As host,
characteristics need to be expanded through the
alder provides energy to both symbionts as well as
range of red alder and related to systems of soil
shelter to Frankia. The biology of the intimate
classification. At the same time, the impacts of
mycorrhizal association as well as the biology of the
alder on soil nitrogen, phosphorus, organic matter,
formation and function of the Frankia-containing
pH, and cation exchange capacity are increasingly
studied. In addition to its obviously beneficial
248
effects on soil nitrogen and organic matter, alder
by shrubs, not trees. This final step, however, has
appears to increase soil acidity and decrease
not been demonstrated.
amounts anellor availability of calcium, magnesium,
and phosphorus.
The Tree
Red alder has adopted a stress-avoidance strategy
in plant-water relations. Its roots explore a huge
soil volume early in life. While stomatal conduc­
tance under high soil and atmospheric moisture
conditions is much higher in red alder than in as­
sociated conifers, relatively small changes in plant
moisture potential or vapor pressure deficit restrict
stomatal conductance. At a plant water potential of
-0.8 MPa, stomatal conductance begins to be re­
When conifers become established before or si­
multaneously with alder, mixed species stands may
result. If alder density is not too great, these coni­
fer seedlings eventually grow through the alder. If
nitrogen limits conifer growth, the conifers can
benefit from the nitrogen fixed by the alder, even­
tually dominating and then replacing the alder.
Research has demonstrated a variety of possible
outcomes to mixed-species stand development, but
we have only a rudimentary understanding of how
density, proportion, spatial pattern, site character­
istics, and species choice determine the outcome
of any particular stand.
duced; stomata are closed at -1.5 MPa. So far, all
studies of alder physiology have utilized seedlings
Plantation Management
or tree branches; now, research on whole, large
A large body of knowledge is necessary to the suc­
trees is needed.
cessful establishment of vigorous plantations of any
A variety of studies have provided a basic genetic
species. For red alder, the plantation establishment
characterization of red alder. Regional and
process has moved in the last 10 years from being
elevational trends in characteristics have been
unheard of to routinely done. Several thousand
documented and initial calculations of heritabili­
acres of alder plantations are established every year
ties of simple growth traits ma de. The most
in western Oregon and Washington, an amazing
important research needs are assessment of the
technological accomplishment.
risks involved in seed transfer and of the benefits
of a breeding program.
Alder seed is collected annually, the collections
being based on both basic genetic considerations
Growth studies have demonstrated the different
of seed movement and physiological understand­
seasonal growth patterns of height, diameter, and
ings of seed maturation. Seed can be stored for at
biomass, and described the roles of weather and
least 10 years. Several nursery techniques for pro­
soils in regulating these patterns. Tree age, stand
ducing high-quality seedlings have been developed;
density, and genetics have also been shown to play
all involve the common factors of seed stratifica­
role in regulating growth and allocation of dry
tion, low bed density, and inoculation with Frankia.
Standards to describe the "target" seedling have
a
matter.
Natural Stands
Alder stands generally begin at such high densities
been developed and tested. Bed sowing technology,
container technology, and predicting germination
in beds all need improvement.
that understories are nearly excluded. As stands
Identification of good plantation sites for red al­
grow, structural and species complexity increases
der has been improved through studies that have
as a succession of understory species takes place,
helped clarify the mesic-site, pioneer ecological
eventually resulting in a forest with a high, open
tree canopy, a tall shrub layer, and a simple herb
niche of alder as well to predict tree survival and
layer. Unless large conifer logs are present on the
growth after planting. Before-planting treatments
that reduce the competitive ability of associated
ground, colonization by any tree seedlings is rare
plants are generally beneficial and, in some cases,
in many parts of alder's range. The details of this
essential. Planting is done in the spring after frost
process vary with site conditions, but the direction
danger is passed and before the summer drought.
of this succession suggests that the next stage af­
In southern Washington, this planting window falls
ter alder in these areas is likely to be dominated
between mid-March and mid-April. First-year
height growth can be 1 to 2 meters.
Conclusion
249
A region-wide analysis of dynamics of natural
and managed red alder stands has produced a den­
sity management guide that provides the key to
Health and Protection
The rapid deterioration of alder logs is well known,
but living alder trees are surprisingly decay-resis­
stand management decisions. The strength of this
tant to stem injury and natural branch pruning.
new guide is the breadth of the data base used in
Alder supports a variety of insects, some of which
its construction. With it, a land manager can make
can reach epidemic proportions. The observed epi­
the critical decisions that regulate the processes of
demics have lasted only a few years. Red alder
mortality and growth. The guide now needs vali­
suffers damage from the large herbivores in its
dation through long-term research.
range, but the impact is usually localized, patchy,
Fertilizing alder with phosphorus may be ben­
and restricted to young trees. There has been no
eficial, especially on wet soils. Like research on
systematic evaluation of the extent of any of these
alder physiology, most of the nutritional research
kinds of losses, so we have no knowledge of the real
has been with seedlings or small saplings and so
importance of these agents to alder survival,
needs to be expanded to older, larger trees. One in­
growth, or wood quality.
triguing hypothesis is that the growth slow-down
and senescence in natural stands of alder over forty
Interactions with Other Resources
years old may be due, in part, to inadequate nutri­
Basic investigations have shown the habitat and
tion; fertilizing with phosphorus might improve
food source associations betvveen alder and some
wildlife species; few critical dependencies have been
growth.
There has been little research on pruning. De­
noted. The frequent association between red alder
cay studies, however, indicate that decay is
and riparian zones makes it difficult to separate as­
compartmentalized in red alder very quickly so
sociations just \,'I'ith alder from other riparian
there is little concern for decay problems follow­
effects. Studies in mixed conifer-alder stands have
ing pruning. Although early work (Berntsen 1961)
shown higher wildlife diversity than monocultures
indicated that pruning stimulated epicormic
of either species. Studies to date have focused on
branches in a 21-year-old stand, we believe that
birds and small mammals, so studies with other
pruning in younger plantations warrants investiga­
species groups are needed. Studies of the functional
tion.
interactions between all wildlife species and habi­
Growth and Yield
Several growth and yield tools have been used to
tat components are needed to separate the often
confounded effects of factors like plant species,
stand age, topography, and slope position.
predict the growth of alder stands. An analysis of
Relatively little is known about water quality and
these tools using a region-wide data base has shown
fisheries. Taste and odor of domestic water have
that only the Empirical Yield Tables (Chambers
been affected by heavy annual alder litter fall. The
1973) can be recommended for general use and,
contribution of alder to ground-water nitrates that
then, only for unmanaged stands. This last point
enter into streams is being studied, but alder's role
highlights the primary need in growth and yield
in general stream nutrient dynamics is unknown.
research: studies in managed stands. We know that
Winter light is greater on streams with a decidu­
height growth, both of newly planted seedlings and
ous canopy than on those under a coniferous
following thinning, changes with management
canopy. The rapid decay of alder trunks is gener­
practices, but we cannot predict the magnitude of
ally thought to make it a poor source of large
these changes or how they relate to site index or
woody debris for enhancing stream structure and
relative density. We also know that form changes
fish habitat. The brief and qualitative nature of
with spacing control, but have no volume equations
these comments makes it clear that there are many
developed from managed stands. Because of these
research needs in alder-stream system interactions.
unknowns, we do not have good predictions of
growth or yield from managed stands.
250
The Biology and Management ofRed Alder
Wood Quality and Economics
Acknowledgment
Two lumber recovery studies have shown the dra­
This is publication 2922 of the Forest Research
matic rise in average value per board foot, and thus
in log value, with increases in log diameter, a re­
Laboratory, Oregon State University.
flection of the rapid increase in percentage of
Literature Cited
high-value lumber with diameter. Results of these
Berntsen, C. M. 1961. Pruning and epicormic branching in
alder studies are particularly apparent when alder
and Douglas-fir are compared. Douglas-fir has a
Briggs, D. G., D. S. DeBell, and W. A. Atkinson, camps. 1978.
gradually increasing response curve of average
value per board foot as log diameter increases. Red
alder has a steeper curve, indicating that manage­
ment practices like pruning (to reduce knot
density) and thinning (to increase log diameter)
will probably be good investments. These studies
red alder. J. For. 59(9):675-676.
Utilization and management of alder. USDA For. Serv.,
Gen. Tech. Rep. PNW-70.
Chambers, C. J. 1974. Empirical yield tables for predomi­
nantly alder stands in western Washington. Washington
State Dept. of Natural Resources, DNR Rep. 31. Olympia,
WA.
have not examined the link between growing con­
ditions and the quality of wood recovered from logs.
No lumber quality recovery studies or economic
analyses of managed stands have been made be­
cause there are no mature managed stands. The
need is clearly great, and some preliminary conclu­
sions might be drawn from analysis of existing
young plantations and reconstruction analysis in
the few old spacing trials.
Conclusions
Forty years of research with red alder has resulted
in a substantial body of information about the bi­
ology and management of the species. Remarkably,
this background knowledge was created in advance
of widespread management-a unique occurrence
in the history of forestry. Several thousand acres
of red alder are now established annually in the Pa­
cific Northwest. While this new practice is expected
to be expanded, the finite wild alder resource is rap­
idly being harvested. Without a continued flow of
information from research to speed plantation pro­
duction, the alder resource and its dependent
industry essentially will be lost.
Revolutionary new forest management practices
are being demanded. Maintaining the health of soil­
plant-water ecosystems has the highest priority.
Sustaining biological and structural diversity is
widely understood and expected. How best to man­
age riparian vegetation is yet to be decided, and
forest products must be produced in the best man­
ner under new approaches to forest management.
We will continue to learn about and use, to the
world's benefit, "the alder, whose fat shadow
nourisheth."
Conclusion
251
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