Silvicultural Research and the Evolution ofForest Practices in the Douglas-Fir Region
Chapter 7: Genetics and Tree Improvement 1 Selection for traits useful to man has been practiced for
declined or succumbed to climatic and disease factors.
millennia in domestic animals and agricultural crops.
None of the introduced conifers equaled either the growth
Modem urbanized society would not be possible without
or survival of native species. The study strikingly illustrated
the increased agricultural production provided by such
how inferences from early short-term results can be widely
improvements. Yet, the application of similar techniques
different from long-term forest research findings. The slow
to forest trees is relatively recent.
failure of initially promising exotics is the best example.
The first areas of investigation (based on European
experience) were the possibility that exotic species might
Provenance Trials, Geographic Variation,
be superior to native species, and the probability that seed
and Seed Zones
collected in one portion of the range of a species might
One of the first major long-term studies undertaken in
not be suitable for other parts of the range. Later research
the Northwest was a comparison of geographical races of
focused on selection, testing, breeding, and seed production
Douglas-fir and its hereditary characteristics begun in 1912
in tree improvement programs begun in the 1950s and
and referred to as the Douglas-fir Heredity Study. The ini­
1960s.
tial impetus was provided by Raphael Zon as a result of his
knowledge of earlier European provenance investigations.
Exotic Species
Seed was collected from 120 parent trees of various ages
A number of exotic forest tree species had been introduced
to Europe in the 19111 century, with outstanding results in
and descriptions, at 13 widely scattered locations in westem
Oregon and Washington. Elevations ranged from l 00 to
some cases. Exotics were and are valuable supplements
3,850 feet (30 to 1170 meters). Seedlings were grown in the
to the relatively few native species available to European
Wind River nursery and then planted in six widely separ­
foresters. It was therefore natmal for the early foresters to
ated localities at elevations ranging from 1,000 to 4,600
ask whether exotics might have potential in this country.
feet (300 to 1400 meters). Survival and growth were
A worldwide search for fast-growing exotic trees
recorded over many years. Physical characteristics of the
appropriate for the Northwest began in 1912 at the Wind
parent tree (age, size, rot, competition) had little or no rela­
River Nursery and became known as the Wind River
tion to performance of progeny (Hofinann 1921, Morris
Arboretum. This work was begun and supervised for many
I 934,
years by T.T. Munger, and directed onsite in the early years
seed sources were found in survival, growth rate, and sen­
by J.V. Hofmann, E.L. Kolbe, Leo Isaac, R.W. Steele, and
sitivity to differences in local climate. Trees of several
Munger and Morris 1936). Major differences among
in recent decades by R.R. Silen. A number of progress
sources did not do well at sites differing markedly in cli­
reports were issued over this period, and a comprehensive
mate from their source, indicating the importance of using
and probably final report was published by Silen and Olson
seed adapted to local growing conditions. Some sources,
(1992). Results demonstrated the superiority of native
on the other hand, made good growth over a wide range of
species over exotics. Introduced broadleaved species failed.
elevations, showing inherently superior growth to other
Among conifers, there was a general similarity of growth
sources of similar climate and site. Collections from the
among species from a given forest region. Although some
Darrington and Granite Falls areas in Washington and
introduced conifers appeared promising in the early years,
Palmer in Oregon consistently out-performed others and
over the 70-year period of observation, they gradually
showed a wide climatic tolerance. A widespread freeze in
1
By J.B. St. Clair,
61
GENERAL TECHNICAL REPORT PNW-GTR-696
November 1955, however, damaged many of the larger
collections plus a site near the northern California coast.
trees from these and other provenances, illustrating the
Various problems reduced the number of study sites avail­
importance rare climatic events have to adaptation (Silen
able for analysis to I 0. Results for I 0 sites at age 20 and the
1963).
5 fastest growing sites at age 25 showed that tree growth
While researchers were learning from the early
did not differ greatly among provinces, except that trees
Douglas-fir provenance trial, foresters were also gaining
from the southern Oregon provenance were much smaller
experience from operational plantations established in the
first half of the 20th century, Stock of unknown seed origin
(Ching and Hinz 1978, White and Ching 1985). The prove­
was often used in early plantations. Many plantations failed
provenances did not appear to grow best. White and Ching
or grew poorly, which was attributed to the use of seed
(1985), however, questioned the experimental precision of
sources not adapted to the conditions of the planting site.
the study. Furthermore, the study sites presented in the 1985
Isaac (1949) reviewed several examples of poor growth and
publication represented a limited range of environments,
survival of Douglas-fir plantations of lmown seed sources
and not enough detail is presented in the 1978 publication
in which seed sources from lower elevations had poor
to determine the effect of moving seeds from low-elevation
growth and survival at higher elevations. Experiences with
sources to the more challenging, high-elevation sites.
plantation failures as well as the results from the early
nance x site interaction was nonsignificant; trees from local
Provenance trials are expensive and long term by their
Douglas-fir provenance trial led to the first delineation of
nature. Because of practical and economic limitations on
seed collection zones (Kummel and others 1944) and seed
the size of tests, only a limited munber of seed sources can
collection guidelines (Isaac 1949). A system to certify the
be evaluated. Thus, provenance trial results have tended to
stand origin of forest tree seed was established by the mid
be largely descriptive of geographic variation, rather than
1960s, and in 1966, seed zone maps for Washington and
predictive. In the 1970s, Robert Campbell pioneered the
Oregon were published (slightly revised in 1973).
development and use of predictive models of geographic
Revised tree seed zone maps and guidelines were pub­
variation to provide seed transfer guidelines and evaluate
lished in 1996 for western Oregon (Randall 1996) and in
seed and breeding zones. In 1974, he published two papers
2002 for Washington (Randall and Berrang 2002). The
(Campbell l974a, 1974b) that predicted the seedling adap­
earlier seed zone maps were based on climatic, vegetative,
tive traits (bud burst or survival) in response to moving
and topographic information, and a single map was used for
provenances between locations, from information on t4e
all species. Research over the past three decades, however,
environment of the seed source and the environment of
showed that tree species differ greatly in their distribution
the plantation site. Environments were characterized by
and patterns of genetic variation. Thus, the revised maps
surrogates such as elevation, latitude, or distance to the
are specific for each species, and are less restrictive, partic­
ocean. Later, he developed a methodology to estimate trans­
ularly for latitudinal transfers within elevation bands.
fer risks as a function of the differences between sites and
Dissatisfaction with the sampling design of the early
provenance trial and concern that seed movement guide­
the genetic variation within sites (Campbell 1979, 1986).
Short-term nursery tests facilitated the development of pre­
lines were too restrictive led to the establishment of a sec­
dictive models by allowing the evaluation of many seed
ond provenance trial of Douglas-fir in 1959 (Ching and
sou ces from a large range. of environments. Over the next
Bever 1960). Seed was collected from 16 provenances
couple of decades, Campbell and Frank Sorensen used this
across a wide latitudinal range from southern Oregon to
methodology to explore geographic variation and provide
northern Vancouver Island. Seedlings from all 16 prove­
seed transfer guidelines for a number of conifer species
nances were planted at 16 sites in the same area of the seed
in the Northwest (for example, Campbell 1986, 1991;
62
Silvicultural Research and the Evolution ofForest Practices in the Douglas-Fir Region
Campbell and Sorenson 1978; Campbell and Sugano 1987,
the first chairman. Over the next several decades, extensive
1989, 1993; Sorensen 1992, 1994).
research was carried out on the genetics of Douglas-fir and
Tree Improvement Programs in
involved the PNW Research Station, universities in Oregon,
Douglas-Fir
Washington, and British Columbia, the British Columbia
Tree breeding work in the United States began with the
Forest Service, the Industrial Forestry Association, and
establishment of the Institute of Forest Genetics in 1925 in
major industrial landowners (Silen 1978).
the practical problems of producing improved seed. This
Placerville, California (which emphasized work on pines),
As seed orchards became common in the early 1960s,
and the work of E.J. Schreiner, A.B. Stout, and R.H. McKee
a serious problem developed-many seed orchard trees
with poplars in the Northeast, begun in 1924. However,
died because of graft incompatibility. The result was a grad­
active tree-improvement work in Douglas-fir-beyond
ual disenchantment with Douglas-fir tree improvement. In
early efforts to· determine appropriate seed sources--did not
1966, Roy Silen proposed an alternative strategy to get
get underway until the 1950s.
around the problem of graft incompatibility. Silen advo­
In 1949, Leo Isaac made a strong case for an active
tree-improvement program for Douglas-fir in his book
Better Douglas-jir Forests From Better Seed (Isaac 1949).
cated progeny testing of a large number of wind-pollinated
families from less intensively selected roadside trees, fol­
lowed by the establishment of seedling seed orchards using
Two meetings were held in 1953 to review existing work
full-sib crosses of the parents in the field (Silen 1966, Silen
in forest genetics and consider proposals to develop formal
and Wanek 1986, Silen and Wheat 1979). As information
programs in basic biology and forest tree improvement.
on the parents became available from progeny tests, the
Participation included public agencies, the universities, the
seedling seed orchards were incrementally rogued (culled)
Industrial Forestry Association, and a number of the major
to provide greater genetic gains. Another feature of the pro­
industrial firms. This was a period when the major land­
gram was small breeding zones to ensure that all planting
owners were shifting from natural regeneration to planting,
stock would be locally adapted. This approach came to be
and they had a keen interest in securing well-adapted seed
called the "progressive" tree improvement program. Under
and in possible improvements through applied genetics.
the leadership of Roy Silen and Joe Wheat (of the Industrial
Consequently, there was wide support in both public and
Forestry Association), many local forest landowners, public
industrial organizations for tree improvement programs.
and private, adopted the progressive approach as they came
In 1954, the Industrial Forestry Association initiated
a program of Douglas-fir tree improvement. John Duffield
together to cooperate in tree improvement activities across
their interlocking ownerships. The Douglas-Fir Heredity
was hired to oversee the program. Superior parents were
Study was often used by Silen to show the potential of tree
selected in wild stands, and the first clonal seed orchards
improvement by pointing out the large differences among
were established by grafting. Also in 1954, a formal
family row plots.
research project in forest genetics and tree improvement
was founded at the Pacific Northwest (PNW) Research
Grafted seed orchards, however, offer advantages over
seedling seed orchards. Grafting mature branches from
Station, directed by Roy Silen. In February 1955, a meet­
select trees onto rootstock provides seed production at
ing, chaired by Leo Isaac, discussed the need for an organi­
younger ages and with greater certainty of the genetic worth
zation of research workers in tree improvement, to be called
of the parents. Don Copes of the PNW Research Station
the Northwest Forest Genetics Association (later renamed
addressed problems in Douglas-fir seed orchards, in par­
the Western Forest Genetics Association). This association
ticular the problem of graft incompatibility. Copes devel­
was formally established in June of 1955, with Duffield as
oped a system to test for graft incompatibility and began a
63
GENERAL TECHNICAL REPORT PNW-GTR-696
Figure 26-Research to overcome graft incompatibility made
Figu re 27-Controlled pollination of Douglas-fir in a seed
high-genetic-gain seed orchards possible. Most Douglas-fir seed
orchard. Tree breeding for wood production has become an impor­
now comes from seed orch rds, such as the Oregon Department of
tant component of modem forest management.
Forestry's J.E. Schroeder Seed Orchard, near St. Paul, Oregon.
breeding program to produce graft-compatible rootstock
history. Second-generation programs were initiated by
(Copes 1999, Silen and Copes 1972). As a result, the prob­
Weyerhaeuser and the British Columbia Ministry of Forests
lem of graft incompatibility has mostly been solved, and
in the 1980s and by the Northwest Tree Improvement
most seed orchards today are clonal seed orchards from
Cooperative in the 1990s. Research at the PNW Research
grafted parents (figs. 26, 27).
Station influenced breeding zone size, seed orchard layout,
From 1967 to 1985, cooperative tree improvement pro­
mating designs, and field-testing procedures (Johnson
grams using the progressive tree improvement approach
1998). As a result, the second-generation breeding plan for
were jointly guided by the PNW Research Station and the
the Northwest Tree Improvement Cooperative is very dif­
Industrial Forestry Association. After the retirement of Roy
ferent from the first-generation strategy (Johnson 1998).
Silen and Joe Wheat, the leadership of the cooperative
As reforestation relied less on natural regeneration and
programs was passed in 1985 to an umbrella organization
tree improvement programs began to advance, forest gen­
called the Northwest Tree Improvement Cooperative direct­
eticists and forest managers recognized a responsibility to
ed by Jess Daniels, hired as a contractor. In April 2000, the
conserve the rich genetic heritage within our native forests
organization moved to Oregon State University and Keith
(Ledig 1986, Namkoong 1984, Silen and Doig 1976).
Jayawickrama was hired as director.
Efforts to evaluate and ensure the conservation of forest
By the 1980s, 125 Douglas-fir breeding programs in­
genetic resources were begun in the 1990s in western
volving over 30,000 parents tested in nearly I ,000 test plan­
Oregon and Washington (Wheeler and others 1995) and in
tations were in existence in western Oregon, Washington,
British Columbia (Yanchuk and Lester 1996). Conservation
and British Columbia (Johnson 2000b, Lipow and others
of genetic resources may be achieved by perpetuating
2003). Most of these programs are part of the Northwest
native stands and processes at their original location, called
Tree Improvement Cooperative, but several organizations
in situ conservation, or by collecting and preserving the
have separate programs with their own approaches and
genetic material at some other location, called ex situ
64
Silvicultural Research and the Evolution of Forest Practices in the Douglas-Fir Region
conservation. Yanchuk and Lester (1996) and Lipow and
realized gains in stand productivity under operational con­
others (2004) considered population sizes of conifer species
ditions with gains predicted from mixed-family genetic
in in situ protected areas such as wilderness areas, national
tests (St. Clair and others 2004).
parks, and other reserves, and determined that genetic
diversity is well represented.
Tree improvement populations may be considered a
form of ex situ conservation. Yanchuk (2001) and Johnson
Tree Improvement Programs in Other
Species
Although Douglas-fir has received the most attention,
and others (2001) reviewed the role of applied tree breeding
a substantial amount of similar work has been done in
programs in genetic conservation, including discussions of
western hemlock under the Northwest Tree Improvement
numbers of parents needed. They concluded that breeding
Cooperative and the British Columbia Ministry of Forests
populations are appropriately structured and populations are
(Daniels 1995). The USDA Forest Service and Bureau of
sufficiently large to ensure conservation of genetic diver­
Land Management have long had special breeding pro­
sity. The large num,ber of first-generation Douglas-fir selec­
grams for western white pine and sugar pine, aimed at pro­
tions in the Northwest represents an important ex situ
ducing blister-rust-resistant planting stock (Johnson 2000a).
genetic resource (Lipow and others, 2003).
The British Columbia Ministry of Forests has breeding pro­
Today most Douglas-fir seed used in planting programs
grams for western white pine, western redcedar, Alaskan
is produced in seed orchards from selected parents. This has
yellow-cedar, and Sitka spruce. Public agencies have tree
clearly increased productivity in early stand development.
improvement programs for ponderosa pine on the east side
There is uncertainty as to the magnitude of the increase in
of the Cascades.
stand productivity over a rotation, because of the limited
The University of Washington (Reinhard Stettler) and
period of observation of operationally planted stands. Also,
Washington State Univ,rsity (Paul Heilman) were active
most genetic tests use mixed-family plantings, which
in developing hybrid poplars (usually crosses of the native
involve uncertainties in genotype interactions and do not
black cottonwood with various other Populus species), and
lend themselves to expansion to a stand basis (St. Clair
in recent years a number of industrial owners have under­
1993). Genetic gain trials are being established to compare
taken extensive poplar planting programs.
65