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Regeneration Aspects of the 50-Year-Old Douglas Fir Heredity Study by ROY R. SILEN Research Forester Pacific Northwest Forest and Range Experimer.t- Station Forest Service, U. S. Deportment of Agricuituro Corvallis, Oregot> Introduction
ft&
Possibly most of you were assigned a reference in
forestry school called "Growth of Douglas Fir Trees
of Known Seed Source," by lvlunger and Morris, U.S.
Deparhnent Technical Bulletin 537, published in 1936.
This gave 20-year results
of a Douglas fir seed
HANT JriTION
191
HING TON
progeny from known par­
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l'LAN1ATIQN
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? .'· sions of a reanalysis of
:.<"'' this 50- year - old study.
; '7 1!4 !"IY n:ajor findings defin­
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WIND RIVER
ents. There is simply no
substitute in forest re:/{ searc]1 for time, and I am
pleased to be able to give
you son1e of the conclu­
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1.0<>:>·f001 UYUIOlf
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1916 AVER G "12Y!YAl l;l'l
source study that involv­
ed over 25,000 tagged
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STlllAGUAMISH
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• .i..:_ · j 1tely mvolve forest genet­
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SANTIAM
ics and \vill be treated in
detail later in a major
publication. I will list them very hriefly here since
today's paper deals with the non-genetic aspects.
time detriment to a tree planted "offsite," (4) many
\vood characteristics are inherited reasonably strong­
ly and appear with the same relative strength at
wjdely different environinents, and (5) environment
generally has a larger effect on gro\vth than the source
of seed.
. 1'his p a1Jer concerns details of some nongenetic
findings from the Douglas fir heredity study-the re­
generation aspects. These involve long-tenn survival
records and co1n p arisons of seedling heights \Vith
heights at 50 years . 'fhc findings have direct applica­
tion to nursery cull ing practices, early thinnings, and
the effects of different environn1ents on the same
seedling lots. But before I go into the survival re­
cords covering 50 years, let us look briefly at a dia­
gram of the stu dy (fig. 1).
For the genetic a s pects of the study, the most
irnportant thing is the seed source . For nongcnetic
aspccfS, it is only irnport:int to knO\V that aJl the 120
parents gre\v in the Doug] as fir region of 'vestern
Oregon and \Vesterri \iVashington. The Stillaguamish
PLANTATIONS
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MIDDLE UOO·fOOl tlHUHM
VALLEY
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Among the genetic findings are {l) two trees on
the same acre will produce offspring families that
are greatly different in volume production at 50
years, (2) a superior family at one location will
likely be ordinary or inferior when planted else­
where under different environmental conditions, (3)
earliness or lateness of vegetative gro\vth is a life­
HOOD
lOWER 1.600· 00T£LfYATIOM
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F!gure !.-Location of parent trees and outpianting sites for
the 1912 f)ouglas fir heredity study. Figures show number
of parent trees :lnd percent of planted trees sttrviving ai50 years.
and \Vind River Valleys of Washington supplied 27
and 31 parents, respectively; the Santia1n \laJlcy in
Oregon, 33 parents; the broad Puget Sound­
Willamette Va lley t rough, 22 parents; and a single
Coast l{angcs collection \Vest of Corvallis, Ore., furn­
ished 7. 1-'he parent trees r;.1nged in elevation over
3,800 feet and in age from 15 to 600 years. Seedlings
\VCre gro\vn at theY\lincl River nursery and outp!anted
in 1915 on six plantations in old burns. Each of the
120 families of seedlings \Vas planted in a ro'\v
of 20> except for 12 fa1ni1ies \vhich \Vere represented
at each plantation lJy a ro\v of 100 seedlings. Sinee
I will use 9 of these 12 "long-row" families for il­
lustrati\;e pur1)oses, I call especial attention to then1.
Four of them \Yere fron1 the Io,ver end of the San­
tiam \1a1ley at the tO\\'n of Gates; the other five were
from 3,000- and 3,850- foot elevation at the upper
encl of the valley near Detroit. Thus, they represent
seed collection from a single typical Cascade Range
valley.
Of the six original plantations, four and one-half
are still intact-the Stillaguamish; \Vind River; Mt.
Hood, lower; Mt. Hood, upper; and Mt. Hebo (fig. 1).
As shown, they range from 1,100 to 4,600 feet. A
replication in time was added from seed stored 1
year and planted in 1916 at the same sites. Most
parent trees \vere represented, but only by families
of 10 trees. \Ve have today what is essentially a half­
sib study of 120 Douglas fir families, replicated
9 times. In 1964, it seems unbelievable that a study
plan, involving 25,252 tagged trees plus fair design
and adequate replication, could have been initiated
in 1912.
Survival
The first of the subjects to be covered is the sur·
viva! pattern during the 50 years from establishment
to the present. Survival after 2 years in the field
averaged 92 percent, with only one plantation drop­
ping below 88 percent. Considering 1915 problems,
one cannot help but wonder if we have really im­
proved our planting techniques in 50 years.
Within the 50-year period, fire destroyed the Mid­
dle J\Jt. Hood and a portion of the upper Mt. Hood
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plantations. Parts of two others were abandoned
because of· aniinal damage.
The total experiment has been reduced by about
25 percent in 50 years. This is probably a rather normal percentage of loss from fire and animals dur­
ing the past one-half of a century of normal forest haznrcls.
At age 20 years, the remaining plantations aver­
aged about 68 percent survival. As J'>fonger and
Morris stressed in their 1936 bulletin, most of the
mortality '\vas of a mechanical nongenetic nature.
Much of the mortality happened from snags falling
in the old burns, animal clipping, wind and snow
breakage. Deleting these causes, the remaining fac·
tors amounted to only about 5 percent. .The con·
clusion was that progeny from almost any Douglas
fir source \vill survive \Yell under most conditions in
the Douglas fir region.
The survival pattern at 50 years acids another facet
to the picture to alter Munger and Morris' conclusion
-the Characteristic survival percent. 1\bout 45 per­
cent of the original trees are presently alive at age
50. I-Io\vever, there are now great survival differences
\Ve find it includes those from the \Vind River and
Stil1agua111ish ''alleys over a range of elevations.
'rhese no\v average 52.-pcrcent survival-only 3 per­
cent a\vay fron1 average. The lo\ver tier of fan1ilies in
the 1915 plantation includes those from the Santiarn
Valley, the coast, and the Willanwlte-Pugct Sound
trough. They average 46 percent, again only 3 per­
cent away from the average. The middle tier, which
includes the nine long ro\v farnilies froin the Sanli H11
Valley, averages 49 percent, the same as the planta­
tion average. Corresponding seed sources in the 1916
portion, sho,vn 'vith corresponding stippling a n d
crosshatching in figure 1, have almost identical sur­
vival percentages of 51 and 46 percent.
Although the other three plantations vary a little
more, there is Do doubt about each having a char­
acteristic survival percent. Observe the characteris­
tic high survival of the lower Mt. Hood and the low
survival of the upper Mt. Hood on the same moun­
tain slope. The Hebo plantation is an even better
example. The 1916 planting was abandoned in 1918
because the survival dropped below 60 percent in con­
trast with 88 percent in the 1915 planting. Yet, today
the t\vO portions average 2.3 and 27 percent.· Even
\vith different h1itial stocking, the stocking after a
half century is the same. \V;1y?
Certainly, it is the long-term local climate at work.
liere \Vith good long-tin1e \vcather records, '\'e have
measure of this. The \Vind River and lower lv! t. Hood
plantations are the better l)rotected plantations. 1vft.
Ilebo and upper Mt. Hood have been exposed to
more natural calan1ities.
"
between plantations--the range being from 27 per­
cent at Mt. Hebo to 74 percent at lower Mt. Hood.
The truly striking thing is that there is so little vari­
ation \Vithin any plantation and SO much variation
bet\veen.
Look, for example, at various subdivisions of the
River
plantation \Vhich
average overall
49-percent survival. The portion planted in 1915 aver;
ages 49 percent; the 1916 planting averages 48.5 per·
cent. 1'hus, there is scarcely any variation/now from
2 different years of planting.
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SURVIVAL
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What about seed source? If we look at the upper
tier of families in the 1915 portion of the plantation,
at 50 years
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Figure 2.-Snrv.ival pattern of nine Douglas fir fanlilies fro1n
low- or high-elevation Santia1n Valley p rents.
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! It is not prudent for foresters to asstime that. the
sa1ne characteristic stocking from place to place
will be a feature of their plantations 50 years from
no,v. If so, there is little point jn planning for thin­
ning in those destined for characteristic lo\v stock­
ing. Perhaps something in the 50-year record, still
undiscovered, \vill provide an indicator of such sites.
The most reasonable suggestion is that any sign of
greater than average natural mortality should con­
stitute a '\Vaming signal to foresters to relax thinning
schedules.
The question as to whether seedlings from some
sources ultimately survive better than others has an
interesting answer. It depends entirely on \vhere they
are planted. Figure 2 shows this quite clearly.
I mentioned earlier that the nine families from
parents at low and high elevation in the Santiam
Valley were ·particularly fine for illustrating various
conclusions common to the \vhole study. I-Iere \Ve see
them graphed, showing height-over-survival per­
centage at 50 years. If we start at the lower left
corner with results from the Mt. Hood 4,600-foot
plantation, we see that the high-elevation group of
five families has generally better survival than the
lo\v-elevation group of four families. fhe reverse is
true at both Mt. Hebo (2,COO feet) and Wind River
{1,100 feet). There the high-elevation families show
poorer survival, as well as growth, than do the low­
elevation families. In the intermediate lower Mt.
Hood plantation (2,600 feet), the two groups are not
significantly different. Thus, seedlings from the same
lot survive well or poorly, depending on where
_planted.
most cases, 50 years old. I-Icight n1cas1:1ren1cnts are
expensive; therefore, in 191.5 the crc\v took heights
of only 5 trees in each family except the 100-trce
families, in which case they recorded 10 heights. Al­
though we have about 600 heights per plantation
measured in 1915 fron1 \vhich to deteTmine the corre­
lation bet,veen seedling and n1aturc heights, the. con1­
parisons '!Ve can make today <lcpcncl on ho,v- many
of these particular trees have survived.
The first atten1pl \vas simply a straightfor\vard
Torrelation between 593 seedling heights taken on the
lower Mt. Hood plantation at 2 years of age com­
pared with heights at 22 years. The result was a cor­
relation coefficient of 0.0005-no correlation at all_ A
small seedling or a tall one had an equal chance to
become a tall tree at age 22. A -corriputation inade
as recently as last \vcek on the 12 ro\vs represented
by 100-tree families, gave a small but significant
negative relationship-small seedlings had a- greater
chance than large seedlings to produce large trees
at 50 years within those particular families.
Our data permitted us to check the results of com­
paring the outcome of the top 10 percent and bottom
10 percent of the seedlings on the basis of average
1-year nursery heights in 1913. On two of the four
plantations, the top 10 percent performed slightly,
but not significantly, better at 22 years. On the other
two plantations, the top 10 percent performed slightly,
but not significantly, poorer. But such a criterion is
not very realistic, since nursery culling ls not -done
on any average height but on the individual seed­
lings.
In summarizing survival patterns, \Ve must expect
important catastrophic losses such as fires. Little
difference between races in survival appears before
.'20 years. By 50 years, plantations take on a charac­
teristic survival percentage, irrespective of seed
source. 'Vithin the limits of this characteristic sur­
vival percentage, progeny from better adapted seed
sources survive best.
One could point up a host of genetic differences in
Figure 2. One example is the better growth of trees
from low-elevation sources planted at low eleva­
tions and ·vice versa; also, individual families both
follow and reverse this trend. The strong positive cor­
relation between· good growth and good survival
raises important questions about the capacity of some
families to respond to thinning. I-lo\vever, these are
genetic features of the study to be covered in other
. reports.
Height Correlations
The last subject for consideration is the relation­
shi11 of seedling heights to inature heights and its
irnplication in nursery culling and progeny testing.
Hov.. much genetic improvement can \Ve expect by
nursery culling? Can a superior tree be recognized
in a nursery?· The answer to both appears to be
negative.
·
Let's list first the kind of basic data at hand. We
have 1913 records of average I-year heights for 90
of the families. \Ve also have heights of individual
trees when they were 2, 3, 4, 5, 10, 15, 20, and, in
*
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at l ye-or
(INC!lES)
Figure 3.-Scedling-1nalure height rel:ttionship for nine Doug1ns fir fatnilics. Positive or negative relaHonship depend<:
upon where plant('<l.
The kind of cheek we could make was to go back
to the records of the five seedling heights taken for
each family at all plantations in 1915. The smallest
ai1d largest tree in five, or botton.1 and top 20 percent,
then could be co1npared \Vith the same trees no\v.
This con1parison on the \Vind River plantation.
the one that showed up strongest in the previous
correlation sho,ved no_ significant difference. Such an
accu1nulation of nonsignificant seedling-mature cor­
relations was discon certing for a geneticist: \Ve began
to ask why there should be so little relationship.
One of the first causes found was the dependence
on where the seedlings were planted. Let us look
again at the nine families from the Santiam Valley.
In Figure 3, we have seedling height graphed against
50-year height at the four plantations. The low-eleva­
vation families generally had larger seedlings than
the high-elevation families. On the low-elevation
plantation, this resulted in a positive relationship
between seedling height and 50-year height. A nega­
tive relationship resulted at the high-elevation planta­
tion 'vhere the high-elevation seedlings \vere small
but now have better height growth. One could get
any relationship he wished by picking the place of
testing.
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Discussion
But seedling-mature relationships depend on other
things as well. The early day foresters also left us
records of age, cro\vn length, and nun1ber of seed per
pound for each parent tree. We find now that part
of the differences in the original height of the seed­
lings can be accounted for by their vigor tis expressed
- in these traits. For exainp1e, seed size on this study
accounts for about 31 percent of the seedling size
differences; percent crO\vn length, about 19 per­
cent; and parent tree age, about 11 percent. The
younger, 1nore vigorous parents, like those from the
low elevation of the Santiam Valley, produced larger
seedlings than the corresponding high-elevation par­
ents there. These seed-vigor differences disappear
after a few years. After that genetic differences come
into prominence.
I•'actors such as soil differences bet\veen planting
spots, injury from sno\v or \Vind, and animal_ browsing
REPRINTED
all cause differences in a trcc,s height .at 50 years.
No one rationalJy could expect any seedling trait to
presage such accidental factors. The tree)s microsite
the initial seed vigor, and accidental factors taken
together explain why the relationship is so poor be­
tween seedling height and mature height.
From these correlations, I feel we can say that
any straightforward nursery culling on size would be
heavily biased against seedlings from old-growth
trees. These would likely be smaller simply because
of seed vigor and not less desirable genetically. Grad­
ing the seed by size before sowing would seem a
reasonable way of overcoming this possibility. Then
any further culling of the smallest seedlings from a
bed would more likely be removing the self pollin­
ated and stunted from among comparable seedlings
From these results, it appears that further grading
for strictly economic reasons, like ease .of handling,
would not make much genetic difference, at least t o
age 50. I n any event, there seems little likelihood
that any worth\vhile tree improvement in Douglas
fir could be expected from picking, say, the top 10
per cent of the seedlings on the basis of size,
For progeny testing, seedling results seem of little
value. \Ve \vil1 simply have to evaluate at a later age.
How late I still cannot say. One sure conclusion is that
a progeny test a t any other pl ace than the place the
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trees are to be gro\vn is uninterpretable at present.
This iS because the perforinance of a race or an
individual family changes in each plantation, for
gro\vth> and 1nany other traits.
It seems odd that with 50 years' results at hand
I should encl on a note of caution about these con­
clusions. \\Te have seen ho,v the interpretation of
results at 50 years is ahnost diametrically opposed to
interpretation of results at age 20. Soinc of this change
has resulted fro1n important changes witl1 time i n
the plantations then1selves. Soine has come from the
human sonrce. Our experience, our technfr1ues, and
our concepts have changed in 30 years about as much
as the plantations then1;:;elves. 1 his could happen
again by the time the study reaches age 80. Cer­
tainly, neither the plantations nor our concepts of
forestry are going to remain the san1e another 30
years.
FROM The Proceedin95 of the 1964 Annual Meeting of Weslern Reforeslalion Coordinating Comminee A Permanent Committee of WESTERN FORESTRY AND CONSERVATION
ASSOCIATION Am(:rican Ban!< Building, Portland, Oregon 97205 Presented November 30 and
December 1, 1964 at Spokane, \Vashingfon