Reproduced with permi ssion from PACIFIC SEARCH, Vol. 10, No . B,
the Forest Service , u.s . Department of Agriculture, f or
official use .
June issue 1976 .
by
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SR:.::ELLY 1.1L.:i. C :~, AL LAii~
YALE UN IVEP-3/TY
THE CARE AND HANDLING
OF THE FOREST GENE POOL ROY R. S ILE N, WITH IVAN DOIG
What must be the world's most magnifi­
cent pool of fores t genes has timbered our
Pacific slo pes.
Why els.: do the tallest firs, pines, spruces,
hemlocks, redwoods, and la rches a ll rise
a lo ng the Pacific Coast of North America?
Docs their hugeness simply thrust up from
o ur dee p so ils a nd mild. rainy climate? From
a vant age poi nt of three decades in forest
research. I believe the key to this wea lth of
timber is more than a ma tter of soil and
moisture.
Taken together, the genes of our 22
commercial western conifers seem to me to
constitute our vital basic resource. And
unless we recognize the magnificent quality
of this gene pool. we may needlessly risk
pauperi1ing or destroyi ng it as man begins to
alter it along the lines of his customary
philosophy of genetic im provement.
Consider some evidence bea ring out the
rarity of this vast gene pool. In combination
with the rest of t he forest plant communit y,
o ur con ifers utilize what actually a re rather
ord inary soils a nd surprisingly droughty
climate to produce remarka ble growth. Our
climate, for insta nce, is mild. but can ha rd ly
be considered s uperior. It is characterized by
severe summer d ro ught - even in the
Do uglas fir region west of the Cascades there
can be from one to four mon.ths of moisture
deficiency between May and October of any
year- whereas the forest climates of the
eastern US. Europe. China. Japan. and New
Zealand generally have rain better dis­
tributed throughout the growing season. Our
soils. a lthough good , must undergo the
severe leaching of three to eight feet of rain
between fall and spring.
But if climate and soils in o ur region are
not superior. the growth rate of our conifers
clearly is. When appropriate strains of our
world-record species are planted in other
temperate fores t zones of the world , they
June 1976
usually outgrow native trees by wide
margins. When we try the best species from
other forest regions here. as we ha\'e for over
60 years. ou r own species outgrow them by
Pacific conifers are the best in
the world , in spite of ordinary
soils and regular drought.
wide m:1rgins. and few among them would
even come cl ose to meeting our timber needs
if our nati ve trees were unavailable.
How could th is bonanza of remarkable
growth rates and the presence of the world's
ta llest trees in each o f I 0 major genera have
uniquely ha ppened in western North
America? Across tens of million s of years.
three strokes o f fortune occurred :
- The climate of this region became cooler
and droughtier as the Cascades rose a nd the
ocean currents cooled. Earlier warm-c limate
species in our lowland s- palm, oak, acacia ,
cinnamon, pecan, ma gnolia - gave way
perha ps ten milli o n years ago to the more
va luable conifers of today.
- About a million yea rs ago there
appeared the Douglas fir. the remarkable
evolutionary success that has become our
most valuable tree. With its heavy armor of
bark t o ass ure its survival in the fire-prone
West. and durable wood that gave it long life
between major fi res. the Douglas fir came to
dominate the best sites of the West.
- The third stroke of fortune . a nd perhaps
the most crucial , was geographical. The
nort h-to-south orientation of the mountains
of North America furnished a high escape
route, virtllally all the way to the subtropics.
which appears to ha ve saved our migrating
forest complex intact from the ice ages. T his
was not the case on the Eurasian land mass,
where mountains and seas are oriented east
to west; there the oncoming ice must have
trapped many fast-growing, cold-sensitive
s pecies and strains against the crosswise
geographical barriers and eliminated them.
Besides this set of remarkable cir­
cumstances, there was the rare good fortune
that Western man did not arrive here early
enough to inflict upon the forest gene pool
t he drastic disruption that cha racterized
other temperate zones. Even when the course
of settlement ca me to the Pacific Northwest,
seve ral trends wove together to minimize
man's impact on the great gene pool. Until ·
early in this century, the nat ion's lumber
needs were met mostly by logging in the
La ke States and the South. Then between
1920 and World War II , the pe.· capita
demand .for wood slacked off; less wood
going into ho using and indust ry meant less
cutting in our forests. At about the same
time, the national forests, which in a unique
quirk of history had been set aside a few
decades earl ier, began to receive good pro­
tection. Federal ownership made up half the
fo rest land in Orego n and Washington; until
afte r World War II , relatively insignificant
cutting occurred on that protected acreage.
Meanwhile, the concept of sustained yield
of timber was gradua lly accepted, first on the
publ ic lands and then more a nd more on
private land s. as owners began to find that
there were no new timberlands to buy and
that nurturing the existing forest to produce
future timber crops made economic good
sense.
Along with these major trends went a
customary reliance on natural seeding
whenever timber was cut. Most of our
cutover land was being reforested by wind­
borne seed which came from the edge of the
uncut stand or from single cull trees left
stand ing amid clearcuts. This method t oo
helped to carry on the gene pool mostly
intact. Natural seeding accomplished
somet hing else only now being scientifically
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docum rnkd: the vital preserva tion of the
ge ne pool in every locality. Rece nt research
~ h o ws that genetic make up can be di fferen t
in natu ral stands o nly a few miles apart - a
co mplex selection respon se amo ng mul­
ti llld inous traits, spec ies by species and niche
by niche. to fit the varied e nvironmental
cha nges in ou r broken to pography.
l a ken toget her. these trends prolonged
much of the region's natural forests until
after Wo rld War II. T o find any cultivated
plant wtt h \ irtua lly any intact gene pool is
not t he r ule. for the impacts of man on the
plan t resources of the wo rld are severe a nd in
many cases tragic. Yet a bout three decades
ago o ur phenomenal gene pool was
miraculo usly intact. sa ved by the series of
unique human a nd geological events; a nd
Until the end of World War II ,
natural seeding kept our
timber gene pool mostly
intact.
. reliance on natura l seeding meanwhile
assured tha t degrada ti on of the conifer genes
would be slow , if it happened at all.
Much has cha nged since then. T he two
most signi fican t tendencies are those fro m
na tural regenera tion of fo rests to planting.
a nd toward increased investmen t in genetic
improvement of ti mber species. Both have
s tro ng economic justifications, and both
ha ve the potential of a ltering our basic
reso urce , t he gene pool.
P la nti ng al ters it in a somewhat random
but slow process. Genetic improvement
al ters it delibera tely and rapidly. We should
direct our co ncern fo r this a lterat ion in our
gene pool reso urce as so berly as if we were
talk ing about protecting the very soi l it se lf.
J ust as the factors preserving the gene pool
have been complex. so are those tre nding
towa rd its a lt era tion. One came about wit h
the renewed demand for wood in the
building boom whic h fo llowed World Wa r
II. As the cutting to meet thi s demand
advanced southward from the earlier loggi ng
areas of Puget So und a nd the Co lumbia
Increased demand for wood
has made nature's
reg eneration period
econom ically unacceptable.
Planting has replaced natural
reseeding, quickly altering the
gene pool.
River, and into higher e levatio ns which
previo usly had not been touched, the
perce ntage of land that would not regenerate
ea sily by natural means increased. The
rea so n was a comb ination of browsing· by
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anima ls. extreme competition fr om brush,
T he change from natural seeding to
and too-se vere ex posure. Where rege nera­ pla nting. then, has represented the first
tion fai led over a n exte nsive area. a ny large-scale alteration of the 'o rthwest's
re placement growt h would be a somewhat unique gene pool. Now we co me to the final
differe nt gene pool.
trend - the introducti o n of genetic improve­
An even large r a lteration was deve lo ping ment to forest trees.
unnot iced o n our best timber si tes. This was
A fe w decades back. fo resters began trying
the replacement of coni fers by broad leafs in to copy from Europe a nd t he ea stern US a
the man-made successio n. Althoug h the practical progra m intended to produce
ea rly forestry researche rs of this a rea were ge netically superior tree stock for reforesta­
genera lly correct in assuming a cutover patch tion. About 600 acres in western North
would regrow in a natural successio n starting America became devoted to what we call
wit h annua l plants, then perennial plants, seed o rcha rds. There cuttings ta ken from
then broad leaf brush, then conifer trees, this expe nsively selected trees in the forest were
did not always occur. Instead, brush species grafted o nto seed lings planted orchard-like
quickly d ominated ma ny sites a nd have o n far m land. As the gra fts grew, they wou ld
persisted for most of a century. On about interpollinate a nd the seed would he used in
30% of the acreage - usually the best 30% for .refo restation . The program ha d worked
growth- the
succession
through
the satisfactorily in the pines of the eastern U.S .
broadleaf brush stage le ngt hened to re pre­ But for the species of main interest here , the
sent a lasti ng change. Three million ac res , or Douglas fir, there began to be problems.
nearly 5000 square miles. of the Coast a nd
Studies demonst rated that very high leve ls
no rthern Cascade Ranges today are oc­ of "outside" pollen were co ntamina ting the
cupied by a lders, maples, a nd lesser brushy seed o rchards. Also, o rchards were expen­
broad leaf species instead of the fast-growing sive because of the specialists needed and the
coniferous fo rests worth fi ve to ten times as price of cultivated land. The most dra ma tic
much.
pro blem, however, was gra ft inco mpatib ility
Si multa neously, as log prices rose, it in the Douglas fir. A rejection of tissue was
became uneconomical in logging to leave cull occurring between t he seedling understock
trees as the natural seed sou rce. By 1960, a nd the graft , much like the problem in
virtua lly eve ry conife r of a c hosen stand was human heart t ransplants.
Altho ugh mostly reso lved by now, these
being felled for its merchantable wood. This
meant that o n priva te timberlands, where disturbing problems, plus t he fact that the
large clearcutt ings were the rule, planting Douglas fir was found to be discouragingly
had to be genera lly substituted fo r na tural s low and cyclic in its production of seed ,
began to suggest there s ho uld be a search fo r
reseeding.
O n public fo rest la nd s, a lthough clearcuts so me approach besides the seed orcha rd s. A
were smaller, a similar cha nge from natural genetic program I had ea rlier proposed for
reseeding to planting was being encouraged the region's C hristma s tree growers had
by the "regeneration period" concept. This is proven successful. Stripped to its basics, the
the assumed time after cutting until a new notion had been t ha t good ge netic ga ins
sta nd is naturally regenerated . Economists cou ld come about by planting wind­
could show that eve n a 5-year regeneration pollinated seed fr o m trees growing na tura lly
period without gro wth was financia lly in­ in the forest, if o ne kept track of the ir
tolerable. Remova l of every con ifer tree progeny value and used seed of o nly·the best
became a contract specification fo r c utting o ne-quarter o r less of pa rents for reforesta­
o n public la nds as we ll as the custom o n the tion. This "non-seed o rchard" approach
began to find adherents. By 197 1, what has
la rge private timber tracts.
Thus, where re latively little planting was come to be ca lled the "progressive program"
done for reforesta tio n befo re Wo rld War II , was in use on two million acres; it now
pla nting is now the primary regeneration encompasses muc h of the fo rest land in
method. But to replace the na tura l gene pool western Oregon and Wash ington.
Even tho ugh so simple a program was
while using pla nted stock is difficult to do.
There is no way in t he seed collection never envisioned as the dominant beginning
methods, whether by climbing trees or rob­ genet ics program, it has proved to have
bing the caches of cone-cutting sq uirrels , to practical adva ntages. No seed o rc hard
investment is needed. no new expertise by
avoid a d ifferent selection of seed than would
drift down from the natura l stand itself.
forestry staffs. It has permitted rapid ad­
Nursery progra ms assure a differe nt se lec­ vance into more sophisticated progra ms
tion too. A high percentage of nursery seed
invo lving cross-pollinations. More impor­
tant, the program was economical enough so
become plants in the forest, whereas a
natural stand may start with a millio n seed
that about 20,000 pa rent t rees will be
per acre and only a few hundred will survive.
tested - a nd hence has been more effective
than programs used in other forest regions in
Difficulties of scheduling the seed collection,
nursery, a nd cutting o perations assure that
terms of preserving the ge ne pool of each
much no n-loca l seed is represented in
locality.
plantmg.
But so extensive have become the two
Pacific Search
... !>igni fica nt t rend !>
from the natura l
regeneration of fore sts to pla nting. a nd
toward inc reased in vest me nt in ge netic im­
pro\'e mcnt o f the t imber spec ies that we
must a sk w h.: n: they may be ta king us. Right
now . ~o m .: im o.:stmcnt in tree impro vement
programs of o ne kind or another has been
made in ~eve n o ut o f eve ry ten acres of
co mmercia l fo rest la nd in the Pacific
1\onhwc!>t. The histo ry of man's effects on
o ther ge ne pools is a warni ng to us that once
begun. any alteration tends to become more
and mo re ex tensive.
If we look broadly a t the pa th of a ll genetic
improvement. we fi nd really o nly o ne
phil oso phy or mode l. There are strong
parallels in it to mining. O ne prospects the
gene pool for the richest sources of the
desired genes. refines them into as pure a
s tate as possible. then spreads the product a s
broadly a s the competitive market permits .
Everything except the pure product goes into
the waste hea p. (Admittedly. ma ny genetic
programs do carry alo ng sufficient genetic
di versity in their product to prevent loss o f
vigor or to p rotect aga inst pests or environ­
ment. The esse ntial point remains that the
ge net ic g oal is to have a s refined a product as
conditi o ns will permit.)
Renecting o n the "mining" philoso phy.
one ca n sec th at o nly certa in parts of it have
large con eque nccs for the gene pool.
Prospecting and purifying are in themse lves
relatively innocuous. It is the replaceme nt of
the origina l gene pool with a mo re
"profitable" one which wreaks the great
consequence.
The hist o ry of plant improve me nt is that
we us ually ha\'e bee n thorough in replacing
the original ge ne pool wi th an "improved"
strain . For example, by the time of Co lum­
bus. corn had been so altered by se lect ion
Replacing the original gene
pool with an "improved" strain
can turn out-a lifetime later­
to be a mistake.
done b y the Ind ians that the origina l wild
corn plant was extinct. and co rn's future was
en tirely dependent upon man : it could no t
persist in the wild . The h istory o f improve­
ment in wheat simila rly ha s been the refining
of the ge ne poo l int o o ne st ra in a fter anot her,
no ne of which could exist with o ut man: each.
in turn . was wiped ou t by a pest. Fo rtuna tely.
a new imprO\'Cd s train was always in the
wings. a risi ng fro m some resistance g leaned
out o f the s hrinking origina l ge ne pool.
Today the origina l gene pool of wheat is
reduced to a few small acreages in the "fertile
crescent" of t he Med iterra nea n area .
To follow this "mining" model is by far the
most likely path for our fo rest gene pool.
Ex plo itat ion a nd quick gains have always
preva iled in o ur resource ma nage ment.
Picture the la ndowner's cho ice of alter­
June 1976
natives in refores tation if some forest
geneticist s ho uld produce a refined strain
that promises to give a SO% gain in produc­
t ion. Will that landowner have any long­
range concern for hi present forest gene
pool'? Can he co mpete if he rc!>ists using the
new strain?
Yet the alread y c xi~ ting s train . genetically
tuned to its own local la nd fo rm a nd
ecosystem a nd pro bably g rowi ng at the rate
that lo ng-term ex t re me ~ o f the e nvironment
will permit , may well be supe rior in most
ways. And much is a t stake wheneve r we
thoughtless ly disca rd a local adapted. well­
buffered . multi- s pec i e~ gene pool. In forest ry
the crop is long-lived. and it may take the
length of human lifetime just for any
mis ta kes in t he altered gene bala nce to show
up.
Histo rically, however. we ca n sec that with
both economics a n d estab l is h e d
phil osophies so well served by simply mining
o ur gene pool. it would tak e a miracle to keep
intact thi s unique forest resource . What
would this miracle invo lve? A different
genetic philosophy.
It wo uld mean . first , the patient accept­
ance by the forest landowner that this most
magnificent gene pool is no t yet understood ,
a nd th at ample a mounts should be preserved
by nat ural seeding with na tural selecti on in
e\ c ry locality until it is understood for its
tota l worth. adaptation. buffering. and other
qualities.
Secondl y. it would ca ll for acceptance of a
diffe rent kind of breed ing in o ur forest
s p ecie~ . in which the geneticist begins by
a ssum ing that the local strain a lready has
bee n bred fo r most of the adaptation a nd
buffering that is wa nted. and he need change
that s train o nly to the ex tent necessa r y to
incor porate genes fo r safe enhancement of
gro wth .
In 1he s hort run. this might sacrifice quick
ga ins by not breeding for a purer genetic
product , but in the long run it might max­
im i7c gains by avoid ing costly environmental
'lnd pest losses. T he d etails of s uch a
phil osoph y remain to be worked o ut. but it is
highly important that geneticists g ive it a try.
It is more a cha nge in goals tha n in tech­
niques.
O nce we full y rea lize that o ur forest genes
a re a more valuab le and critica l source of
wealth than the soi l itse lf, perhaps the
·orthwcst gene pool will aga in be saved
intact by one mo re unique historic event - a
caut ionary approach by man .
DR. SILEN is Principal Plant Geneticist.
USDA Forest Se rvice, Pacific NW Forest
a nd R a nge Experiment S tation. Forestry
Sciences Laboratory. Corvallis, Oregon.
This article is adapted by Ivan Doig o f the
Pac((ic Search staff from a lecture give n by
Dr. Silen to the Ho nors Colloquium , Orego n
State University , November 19. 1975.
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