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Reproduced from "GLOBAL FORESTRY AND THE WESTERN ROLE,"
1975
Permanent Association Committees Proceedings, Western Forestry
and Conservation Association, Portland, Oregon, by the FOREST
SERVICE, U.S. Department of Agriculture, for official use.
ADAPTATIONAL REQUIREMENTS OF PLANTING STOCK
ROBERT K. CAMPBELL
Pacific Northwest Forest & Range Experiment Station Corvallis, Oregon Most of you here would agree that the chief genetic
requirement of planting stock is seedlings that are
adapted to plantation sites. Because of this, foresters
commonly use seed in the zone from which it was
collected, following the dictum that "local" seed is
best. All seedlings from within the zone are considered
to be adapted, and allfrom without are non-adapted.
The zone classification is both simple and easy to
administer. However, we all recognize that it is also
artificial and sometimes too rigid. I will discuss a more
realistic concept of adaptation and show how adapta­
tional requirements can influence decisions made by
foresters before reforestation.
This will be done in four steps. First, I will use
some ohservations from the 60-year-old Douglas-fir
heredity study to show what happens to a plantation
that includes both "adapted" and "non-adapted"
provenances. Second, I will try to show how adapta­
tion is related to many facets of artificial regenera­
tion; i.e., spacing, initial plantation success, etc. Third,
we will look at some differences in adaptation among
Douglas-fir sources, especially sources from different
elevations in the Cascades. Finally, I will briefly
discuss the implications of these findings to planting
practices.
Evidence for adaptational differences among Doug­
las-fir sources was developed in our genetics work unit.
Most is unpublished, and some isfrom recent experi­
ments still in the first stages of analysis. Therefore,
the following should be considered as a preview and
as an illustration to show how information about
adaptation can be used practically, not as a final
report.
First, let us consider the 60-year-old Douglas-fir
heredity study. This experiment includes 120 families
of parent treesfrom 13 provenances in western Wash­
ington and Oregon. Families were planted in six
plantations which sample the same general region as
parent trees. At 30 years after planting, there was
little difference in mortality among plantations or.
Munger, Thornton T., and William G. Morris. 1936. Growth of
Douglas-fir trees of known seed source. USDA Tech. Bull. No.
537, 40 p.
2 Silen, R. R. 1964. Regeneration aspects of the 50-year-old Doug­
las-fir heredity study. Proc. 1964 Ann. Meet. West. Refor. Coard.
Comm., Portland, Ore., p. 35-39.
1
103
provenances1; but after 50 years, survival in planta­
tions varied from 27 to 74 percent.2 There were also
survival differences among provenances after 50 years.
Differences depended on the plantation and were
greatest at the most severe site. But the fact of most
interest to us today is that all provenances, and most
families, still have some survivors, eVen in the · most
severe plantation. Ofteri survivors are off-color or
badly broken, but usually the family with the poorest
survival will have one or more vigorous trees remain­
ing. On the other hand, the high-survival families
often have one or more poor trees.
We can speculate that this pattern is the result
of a large amount of within-population variability in
adaptation of Douglas-fir to specific sites. If so, we
might expect that a planting of an adapted seed source
will include only a few non-adapted seedlings: the
farther offsite the seed source, the higher the percent­
age of non-adapted seedlings. But, it is probably rare
that all seedlings from any source will be either
uniformly adapted or non-adapted to a site. Thus,
for purposes of regeneration, the suitability of a seed
source to a site is indicated by the proportion of
non-adapted trees it contains.
Now, consider what this concept of adaptation
means to the regeneration forester. Because adapta­
tion is not an all-or-nothing phenomenon, he cannot
consider adaptation as a discrete part of his plantiBg
problem - other things enter in, such as the degree
of risk he is willing to underwrite, the number of crop
trees desired, planting-spacing, initial planting suc­
cess, plans for thinnings, etc. For example, one forest­
er may reason that by using a source which is 50
percent non-adapted, he can risk the loss of half his
trees and still retain enough for a crop. Another may
conclude that the 50 percent remaining will be poorly
distributed because, as yet, adapted and non-adapted
trees cannot be distinguished at the planting stage.
This second forester may opt to plant a source with
a smaller proportion of non-adapted seedlings, or to
plant at closer spacing. A third forester may plan
thinnings, or may anticipate poor initial survival
after planting. The influence of genetic adaptation
of planting stock on plantation growth and survival
is modified by all these factors.
Consider the forester planning for 109 crop trees,
scattered evenly over an acre. For security and opti­
mum growth potential, he needs at least one adapted
tree in each 20- x 20-foot square. Table La. shows
the proportion of 20- x 20-foot squares containing at
least one adapted tree under alternative plant spac­
ings and degrees of adaptation, providing he has no
initial mortality caused by poor planting or nursery
techniques. If the non-adapted seedlings do not ex­
ceed 50 percent of his seedling population, his goal
can be attained by using one of several planting spac­
ings. If planting mortality from nongenetic causes is
20 percent, fewer combinations of spacing and adap­
tation are satisfactory (Table Lb.). On the assump­
tion that thinnings will not always remove non­
adapted seedlings, results of thinning and initial
planting mortality are probably similar.
104
Table 1, a and b. - Proportions of 20- x 20-foot
squares (goal, 109 crop trees per acre) contain­
ing at least one adapted seedling when initial
planting mortality is: a) 0%, b) 20%
Planting
spacing (feet)
a)
b)
6 x6
8x8
10x10
12x 12
14x14
6x6
BxB
lOxW
UxU
MxM
Proportions of non-adapted
seedlings in planting stock
.2
100
100
100
99
96
.4
100
100
97
92
85
.6
100
96
87
76
65
.8
92
75
59
54
37
100
100
W
ITT
100
00
96
ITT
IB
97
78
ITT
51
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•
If the forester plans for 150 evenly scattered crop
trees, good adaptation becomes even more important.
The proportions of 17- x 17-foot squares with at least
one adapted tree are given in Tables 2a and 2b for
several initial planting spacings. In summary, good
adaptation becomes more important as the number
of crop trees increases, as the initial mortality in­
creases, as planting-spacing is larger, or as thinnings
are removed.
Table 2, a. and b. - Proportions of 17- x 17-foot
squares (goal, 150 crop trees, per acre) contain­
ing at least one adapted seedling when initial
planting mortality is: a) 0%, b) 20%
Planting
spacing (feet)
b)
Proportions of non-adapted
seedlings in planting stock
6x6
8' 8
10 x 10
12x12
14x14
.2
100
100
99
96
91
.4
100
98
93
84
74
.6
98
90
77
64
47
.8
83
64
47
36
28
6x6
8x8
WxW
12x12
14x14
100
99
00
93
85
100
96
•
77
66
96
84
m
56
45
76
M
30
23
When seed is transferred, the proportion of non­
adapted seedlings depends on the differences in mean
and within-population variability of an adapted
source compared to an introduced source. This is il­
lustrated in Figure 1, where frequently diagrams are
presented for an adaptive index X in three hypothet­
ical populations
X can be any adaptive trait, such
as bud-burst, frost susceptibility, or, better yet, some
suitable combination of traits. Later on, I will use
seedling height as my index, so we will consider the
curves in Figure 1 as showing variability in heights
among seedlings. The curve A represents the adapted
population, estimated by the genetic variability
among parent trees in a stand at a specific location.
If parents are 400 years old, there is probably little
doubt they are adapted to their site. If 50 years .or
less, there may be some quibbling; for example,
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parents may not have sampled the potential long­
term variability in climate. If curve A represents
variability among the parents, curve S represents
variability within a seedling population from the
adapted parent stand. It has larger within-population
variability than the parent stand. Hamrick' has
found this in California white fir - he believes it re­
sultsfrom pollination by non-adapted fathers. Curve
M represents an offsite seedling population that
differs from the adapted population in mean and
variability of the adaptive index. The proportion of
non-adapted seedlings is the cross-hatched part of
curve M expressed as a percentage of the total area
under the curve. From Figure 1 it is clear that propor­
tions of non-adapted seedlings will be greatly in­
fluenced by the average difference between popula­
tions.
Several . of our ·recent experiments with coastal
Douglas-firfrom western Washington and Oregon in­
dicate large average differences between seedling pop­
ulations in traits such as bud-burst and bud-set dates,
cdry weights, and height. More than half of these
differences can be related to source - latitude, dis­
tance from the ocean, and elevation. Despite the fair­
ly close.association of a provenance's performance to
its origin, there still is stand-to-stand variation. That
is, closely adjacent populations in terms of the above ·
geographical factors may still perform differently due
to adaptation to microenvironments. We recently
completed an experiment to examine this subregional
genetic variation. It provided information that was
used in this report to esti ate proportions of non­
adapted seedlings in adjacent tree neighborhoods.
Collections for.this experiment all came from the
H. J. Andrews Experimental Forest, approximately
50 miles east of Eugene, Oregon, in t.he Cascade
Range. The forest is a roughly triangular watershed,
8 miles east-west by 5 miles north-south, with eleva­
tions rangingfrom 1,500 to 5,000 feet. Seeds were col­
lected in a 400-year-old stand from 193 trees,
sampling most of the watershed. Seed was sown in
Corvallis nursery beds to measure phenological and
growth traits of 3-year-old seedlings from the 193 fa­
milies. Traits were then analyzed to determine the
genetic sources of variation. Depending on the trait,
from 10 to 42 percent of variation in family means
could be explained simply by location of parent trees
within the watershed. Much of the between-location
differences was related to elevation, but differences
between populations at the same elevation were also
significant. For example, seedling heights for sources
from 1,500 feet and 5,000 feet were 71 and 48 centime­
ters, respectively, a range of 23 centimeters, or, rough­
ly 6.6 centimeters per 1,000 feet of elevation. The dif­
ference between two sources 5 miles apart, at
identical elevations of 3,000 feet in eastern and west­
ern parts of the watershed, was 6 centimeters
26
percent of the range for sources in the watershed.
Although other traits might be better measures of
3
Hamrick, J. L. Variaticiii arid selection in western montane species.
11. Variation within and between populations of white fir on an
elevatiorial tran ct Theor. &_ Appl.: Genet. _ jln press)
adaptation, I have chosen seedling height as an index
of adaptation. By so doing, it is possible to estimate
within-population genetic variation in adaptability.
From this we can get an estimate of the proportion
of non-adapted seedlings by comparing local and in­
troduced sources with given differences in mean
height. These estimates were calculated for datafrom
the Andrews experiment and the resulting propor­
tions of non-adapted seedlings for a range of height
differences are labeled line. S in Figure 2.
Proportions of non-adapted seedlings are a func­
tion of within-population variation as well as of dif­
ferences between populations. This is seen by com­
paring lines C and S in Figure 2. Remember that
line S is calculated from data established by our ex­
periment. Line C is a hypothetical situation. It por­
trays results of moving sources that have only one­
quarter the within-population variation found in the
actual experiment. This could be the situation if clon­
al mixes rather than seedling populations were used
in planting, for example.
As noted before, in the Andrews experiment, we
found a strong relationship between elevation and
seedling height. This can be used to illustrate results
we might obtain by moving seed upward along slopes
in the watershed. The uppermost line in Figure 3 rep­
resents a 1,500-foot source from the western edge of
the watershed moved upward along a northwest-fac­
ing slope. Movements are in increments of 500 feet
to a top height of 4,000 feet, the crown of the ridge
in the western end of the watershed. The other two
lines represent 2,500-foot sources in the eastern part
of the watershed moved upward by increments of 500
feet to a top height of 5,000 feet. There appear to
be substantial differences in proportions of non­
adapted seedlings, depending on source elevation and
aspect of slope.
Based on relationships shown in Figure 3 and
Tables 1 and 2, a seed movement upward, or down­
ward, by 1,000 feet might be permissible, provided
initial planting mortality is small and pl;1nting spac­
ing is 10 x 10 feet or closer. However, recall that
curves in Figure 3 represent transfers along a single
slope. Transfers in both elevation and distance com­
plicate the picture. Remember that a height dif­
ference of 6 centimeters was found between east and
west sources at identical 3,000-foot elevations. If we
refer to Figure 2, we can estimate that 43 percent
of seedlings from one source would be non-adapted
if moved to the origin of the other. If we compound
the problem by moving seed from 3,000 feet on the
eastern side of the watershed to 2,000 feet on the
west, we could expect 65 percent non-adapted seed­
lings.
·
Also, it should be kept in mind that I used height
of seedlings measured in a single environment as an
index of adaptation. Another of our recent experi­
ments shows that we must measure several traits in
several environments to get a good index. Thus, as
we refine our estimates, the proportions of non-adapt­
ed seedlings in relation to seed movement will proba­
bly be higher than I have shown here. This means
105
P
that any recommended movements in eleVatio -are
likely to become smaller rather than larger; or plan­
tation spacing will have to be reduced to decrease
risks.
In an actual plantation, what would happen to the
seedlings I have called non-adapted? We know they
are not likely to die immediately, unless transfers are
very far or to extremely severe sites. The Douglas-fir
heredity study indicates that early survival of moved
provenances within western Washington and Oregon
is rarely a problem (see footnote 1). This is verified
by Kim Ching's younger, more extensive-provenance
trial.' We suspect that slight movements from mild
to harsher sites may even produce a stand with higher
growth potential than the original, but with atten­
dant greater risk of damage by climatic fluctuations
and disease. On the other hand, movements from
harsh to milder environments are likely to promote
slower growth. In this case, climatic fluctuations
should be less disastrous. Relative susceptibility to
disease is an open question. In most cases in the Pa­
cific Northwest, damage by climate may not be im­
mediately apparent. The Scandinavian ·experience
with Scots pine'' shows that offsite provenances may
accumulate seemingly minor cambial and bark inju­
ries for many years before being destroyed, finally,
by a secondary disease. Differences in mortality
among provenances in the Douglas-fir heredity study
did not show up until after 30 years (see footnote
FREQUENCY \
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0
These are only a small part of our recent gains in
knowledge about adaptation in Douglas-fir - only
that part having to do with elevation in a very small
section of the Cascades. We now also have enough
information to recommend strongly against extensive
transfers east and west - high elevation transfers are
particularly sensitive. Also, north-south transfers at
low elevations appear to be more risky in the Coast
Ranges than in the Cascades.
I have emphasized just four points. First, that trees
within populations vary in adaptability to sites. This
means that adapted versus non-adapted sources can
be thought of in terms of proportions of nol)-adapted
seedlings. Second, that this fact should and would
influence our regeneration decisions if we had the cor­
x
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rect information abo.ut differences between seed
sources. Third, that we now have the techniques for
getting this kind of information. Finally, I hinted
that although we can estimate proportions of non­
adapted seedlings, we. cannot yet provide disaster
probabilities "r quantitative estimates of growth
losses caused by poor adaptation. This factor needs
research, either inspired, or long term. But, until that
time, I would advise considerable caution in planting
seed out of its local zone:
4
5
Rowe, K. E., and K. K. Ching. 1973. Provenance study of Douglas­
fir in the Pacific Northwest Region. IL Field performance at age
nine. Silvae Genet. 22:115-119.
Dietrichson, J. 1968.-Provenance and resistance to Scleroderis la­
gerbergii Gremmen (Crumenula abietina Lager_b.)7 The interna­
tional Scots pine provenance ·experiment of .1H38. at Ma.trand.
Meddr. Norske SkogforsVes 21:398-410. '
·
106
Figure 1.
Three hypothetical populations: A
an adapted population, s
a seedling popula­
an offsite seed­
tion from adapted parents, M
ling population moved to environment of A.
Cross-hatched area estimates . proportion of
non-adapted seedlings in population M.
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