Cone and Seed Weight Relationships in Douglas-Fir From Western and Central Oregon
Author(s): Frank C. Sorensen and Richard S. Miles
Source: Ecology, Vol. 59, No. 4 (Summer, 1978), pp. 641-644
Published by: Ecological Society of America
Stable URL: http://www.jstor.org/stable/1938763 .
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.'ii.J(4J. Jl)7X. pp. 641-M4
IIJ7X hy lht: Fc,1logical Society of America
CONE AND SEED WEIGHT RELATIONSHIPS IN
DOUGLAS-FIR FROM WESTERN AND CENTRAL OREGON 1
fRANK
C.
SORENSEN AND RICHARDS. MILES
USDA. Forest Sen•ice, Pacific Northwest Forest and Range Experiment Station.
Forestry Sciences Lahoratorv, 3200 Jejj{:rson Wav. Corvallis. Oregon 9733/ USA
Ahstroct. Cone sizes and weights and seed weights were determined for X9 trees in 9 stand s in
the Oregon Coast Ranges. Cascade Ranges. and central Oregon. From west to east this represented
a tra nsition from mes ic to xeric sites and from longer to shorter growing seasons. Differences among
regtons for all cone traits. and regressio n coefficients for change in cone and seed wetghts with
distance from the ocean. were s ignificant. Cone size and weight dec reased . seed weight increased .
and the regression coefficient of seed weight on cone weight. based on trees within regions. increased
with distance from the ocean. Geographic variation in cone and seed weight s was compared with
variation in the phenology of cone and seed development as reported in the literature. This comparison
indicated that where relative ly la rge seeds were important to regeneration success and the growing
season was short. Douglas-fir sh<Jwed at least 3 c hanges in the timing of development as compared
with milder sites. (I) The cone growth period was reduced more than the seed growth period . (2) The
overla p in time of the developmental cycles of cone and seed was im.:reased. (3) Cones a nd seeds
grew during a n inc reased portion of the growing season.
Kn· 11·ords: Adaptation:
\'ariation; trees.
Dou~;las-fir:
length o(grml'ing season; natura/selection :
Ore~;rJ11;
mcial
Seed size often increases with increasing dryness
(Bake r 1972) . presumabl y because of the need on dry
sites for vigorous earl y seedling deve lopment. In ma ny
coniferous species seed size is also found to increase
with increasing cone size (Willis a nd Hofmann 1915.
Eliason and Heit 1940. Plym Forshell 1953. Squillace
1957. Florescu et al. 1960, Dashkevitch 1961 , Veracion
1964 . Goggans a nd Posey 196H) . Cone size. in turn.
often increases with geogra phic changes that a re as­
sociated with a n increase in the length of the growing
season. for e xample. d ecreas ing latitud e (Lang le t
1938, Sziklai 1969) a nd decreasing e levation (Atay
1959. Hermann 1968).
In Oregon. on the average. elevation increases.
moi sture decreases. a nd length of the growing season
decreases from the Pacific Coast to the central part of
the state. This mean s that from west to east seed size
would be e xpec ted to increase because of increasing
dryness. but to dec rease because of decreasing grow­
ing season length and Jecreasing cone size. We report
here an analysis of seed size/cone size relationships in
Douglas-fir <Ps eudo t s u~a menziesii) along a transect
from the Coast Ranges to central Oregon.
(after 72 hat 80°C). and number of scales (in the part
of the cone bearing round seeds) were ueterntineu for
each cone. Seeds were ex tracted from the entire col­
lection from each tree. separateJ on an a ir column into
filled and em pty seeds, a nd the number of filled seeds
determined . Seed weight was calculated from 100-seeu
samples of filled seeds.
One-hunureu-seeJ weights. numbers of filled seeds
pe r cone. a nd weight of filled secus pe r gra m of cone
(dry weight) were ana lyzed using a nested classifica­
tion . Sources o f variation were reg ions . seed sources
within region s, and trees within seed sources. Cone
traits we re anal yzed similarl y . but inc lud ed cones
within trees as a n additional leve l of sa mpling.
One-hunureu-seeu weight. cone weight. and filleu­
seeu weight per gram of cone weight we re regresseJ
on dista nce from the ocean. and I00-seeu weight and
seed weight per gra m cone weight were regressed on
cone dry weight. Because variation amo ng locations
within regions was not significant. the regress ions
were based on regional means or o n tree means within
regio ns . Within-region regre ss ion lines were compared
using analysis of covariance afte r testing for homo­
ge neity of variance (Sneuecor and Cochran 1967).
M ETHODS
R ESULTS
Ten undamaged cones we re take n at random from
uppe r-c rown cone collections from te n 50- to 100-year­
olu trees at 3 locations within eac h of the following
regions: (I) Coast Ra nges. (:2) CascaJe Ranges (upper
elevation and east slopes). and (3) central Orego n
(Table 1) . Cone le ngth anJ max imum width (measured
with calipe rs to the nearest millimetre) . dry weight
Diffe re nces bet ween reg ion s a nd bet ween tre e s
within reg ions were highl y sig nificant for a ll co ne tra its
(Table 2. top). Differe nces between locations within
region s were nonsignificant or. in the case of cone
scale numbe r. barely so a nd contributed o nl y a minor
component to the variation . The uniformit y within re­
gions v is-a-vis betwee n regions suggests. a t first
glance. no nc linal differences between regions. Ho w­
ever, because the sample poi nts within regions were
close togethe r and the regions large, the re sult s also
I NTRODUCTION
' Manusnipt rc<.:eivcd 7 June 1977 : accept ed 15 Decem­
ber 1977.
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FRANK C. SORENSEN AND RICHARDS. MILES
642
Ecology. Vol. 59. No. 4
T"'BII I. Topographic data for the seed sources and climatic and growth data for the 3 regions. Climatic data are averaged
from representative weather stations in each region (Johnsgard 1963). Cone development periods. which refer to time from
pollen shed to seed shed . are estimated from unpublished records of authors and from anonymous ( 1952). Ching and Ching
( 1962). and Wheeler ( 1967)
Localities
Elevation
(m)
Potential evaporation (mm)
MaySeptember
MaySeptember
Co ne
development
period
(wk)
250
190
20-2 1
180
225
17- 18
125
300
12-14
Precipitation (mm)
Distance
from ocean
(km)
Annual
Coast Ranges
Tidewater
Oleman Creek
Marys Peak
.i' (region)
215
215
19
41
50
37
365
265
]()50
Cascade Range
Tombstone Pass
Santiam Pass
Metolius River
.r (region)
1525
1400
915
1280
154
179
195
176
1200
Central Oregon
Gri zzly Mountain
Wildcat Mountain
Baldy Mountain
.\'(region)
1555
1430
1735
1573
250
283
421
318
140
would be consistent with a clinal pattern of variation .
Neit her regions nor locat ions within regions differed
significantl y for seed weight traits.
Cone size. by all criteria. decreased as distance from
the ocean increased. while 100-seed weight increased
and weight of filled seeds per gram cone dry weight
fluctuated irregularly. Regression coefficients testing
th e response of cone weight and seed weight to dis­
tance from th e ocean were both significant (p < .05).
and estimated with each 100-km increase in distance
from the ocean at latitude 45°N an increase in I00-seed
weight of .05g and a decrease in cone weight of . 97g.
The regression coefficient of seed weight on cone
weight using region means was not significant. Regres­
sion coefficients based o n trees within regions were
positive. being steepest for central O regon and flattest
for the Coast Ranges. The coefficients differed signif­
icant ly among themselves (p < .05) (Fig. 1) .
Cones from the 3 regions did not differ in number
of sou nd seeds per cone nor in weight of filled seeds
produced per gram dry weight of cone . When the latter
trait was regressed against cone weight using region
means and values for trees within region. the calcu­
lated h-values were not significant, but in all cases the
weight of seeds per gram of cone weight decreased
with increasing cone weight.
DISCUSSION
Changes in seed and cone weights followed th e ex­
pected trends. Seed weight increased from west to east
with increasing dryness of the si te and cone weight
inc re ased with increasing moisture and increasing
lengt h of growing season. Within a region (i.e .. within
areas of similar moisture conditions and growing sea­
son length) the expected positive relationship between
seed weight and cone weight was observed. However.
between regions the seed we ight/cone weight relation­
ship was not positive . When regeneration and growing
TAHI.L 2. Components of variam:e expressed as percentages of total variation and significa nce for cone and seed traits.
Signifkance levels: N S = nonsignificant: '· = s ignificant at 5% level: ' ' = sign ificant at I% level. Seed weight s were only
available for individual trees. not for cones in trees. C. V . = coefficient of varia tion
Cones
Component
Regions
Sources in regions
Trees in sources
Cones in trees
c. v . ('/r )
Coast Ranges
Cascade Ranges
Ce ntra l O regon
Scales
(number)
Length
Width
Wt
2!l. 9<7o
0.0% NS
30.8%**
40.3%
11.7
30.4%*'
2.3% NS
38.5%**
28.8%
7 .9
27. 0%'*
3.6% NS
39.4%**
30.0%
2 1.2
6.92 e m
6.47cm
5.47cm
Mean
3.53 em
3 .5 1 e m
3.00 em
values for regions
8.02 g
47 .2
6.42 g
41.9
36.2
5.30 g
Seed wt
( 100 filled
seed)
Fi lled seeds/
cone
8.9'fr.
8. 1%
83 .(JC/6
Filled seed
wt/g cone
WI
~.7% NS
45 .6%* *
3.6%*
24.1 %**
26.8%
9.6%
6. 1%
84 .3'7<
II. I
14.1
53 .5
55 .5
1. 16 g
1. 22 g
1.30 g
17. 5
26.2 mg
36. 1 mg
29 .5 mg
NS
NS
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1 9. ~
12.2
NS
NS
NS
7 .7%
89.6%
NS
Summer 1':17H
CONE AND SEED WEIGHTS IN DOUGLAS-FIR
1.5
1.4
E
;:::u
"'
l5
I
<.:J
w
:;:.
§u
(/)
0
g
1.1
CONE DRY WEIGHT (Grams)
FIG. I.
Regress ions of 100-seed weight on cone dry
weight based on region means (solid line. solid squares) and
on individual trees within the 3 regions separately (dashed
lines).
conJitions rcquireJ it. the species was able to proJuce
relativel y large seeJs in relativel y small cones anJ in
a relativel y short growing season. Information in th e
literature on reproJuctive growth anJ phenology of
Douglas-fir inJicates that this has been accomplisheJ
primarily by aJjusting the timing of seeJ anJ cone Je­
velopment within the growing season. anJ probably to
a lesser extent by Jifferences in rates anJ Jurations of
seeJ growth.
Growth rat es of Dougl as-fir embryos have been re­
corJeJ at IXO anJ 915 min the Oregon Coast Ranges
(Wheeler 1967). Temperature-Jevelopment rate rela­
tionships were remarkably similar at the 2 elevations.
as were the average temperatures Juring embryo
growth (Wheeler 1%7. p. 61) . Average temperatures
(J o hnsga rJ 1963) for representative stations in the 3
regions we sam pleJ Juring the ex pecteJ perioJs of
embryo growth (June anJ Jul y in the Coast Ranges .
July anJ August in the CascaJ es and central Oregon)
were 15.9. 16.1. anJ 16.2°C. respectively . If the tem­
perature-growth relationship observed by Wheeler
( 1%7) is ge neral. then the occurrence of seeJs of sim­
ilar size would imply that the seed growth perioJs
were also of similar length . The fact that seed weight
JiJ increase by = 10% from west to eas t inJicates that
seeJ growth rate s or growing season le ngths ma y have
varied somewhat between localities . Nevertheless. the
observations suggest consiJerable uniformit y in rate
a nJ Juration of seeJ dev elopme nt.
However. cone Jevelopment perioJs anJ vegetative
phenology have been observeJ to Jiffer greatly. both
in length (Table I) and with respect to each other. At
low ele vations in western Oregon. Douglas-fir pollen
flight is about miJ-April. cones reac h max imum Jry
643
weight in early August. and seed shed starts in early
September (Ching and Ching 1962): at upper eleva­
tions in the Cascades. pollen shed does not occur until
mid-May to early June anJ seeJ fall starts in mid-Sep­
tember to early October (personal ohsen•afions). At
low elevations. vegetative buJ flush occurs 6-7 weeks
after floral bud flush (Sorensen and Campbell 1971).
at high elevation the separation is 3-4 weeks (personal
ohsen•afion.l). At low elevation . cambial growth is still
strong at the time of seeJ sheJ. at high elevation it is
over by the time of seeJ fall (Emmingham 1977) .
Taken together . these observations indicate that
where relatively large seeds a re advantageous and the
growing season relatively short. Douglas-fir has been
able to adapt primarily because the length and the tim­
ing of vegetative. cone . and seed growth perioJs could
vary inJependentl y. We propose specifically that un­
Jer the conditions of increasing dryne ss and shortness
of growing season. (I) the cone growth period has de­
creased more than the seeJ growth period. (2) the
overlap in time of growth of cone and seeJ has in­
creased. anJ (3) the proportion of the growing season
used for cone anJ seed growth has increased.
As a result of the first response. variation in the
length of growing season. even of the cone growth
period. need not be accompanieJ by comparable vari­
ation in inJiviJual seed weight. As a result of the sec­
ond anJ thirJ responses. seeJs and cones Jevelop in
common environmental conJitions for a larger portion
of the growing season on sites with short seasons than
on sites with long seasons. Consequently. seed size
should be more closely relateJ to the cone size whe:·e
the growing season is short.
The thirJ response also suggests that if th e growing
season is short. the time available for late summer
seeJ and cone maturation may be much shortened.
For example. collecting Douglas-Fir cones 2 weeks
before natural cone opening may give cones anJ seeJs
which are much more immature on sites with short
seasons than on sites with long seasons .
ACKNOWLEDGME N TS
We are grateful for the he lpful comments and id eas of re­
v iewers a nd referees . particularly R. D. Burdon and F. T.
Ledig .
LITERATURE
Cn
ELJ
Anonymous . 1952. Average day of year o n which given phe­
nological development o ccurred in g iven species at points
in Oregon a nd Washington. Officia l Report . Pacitic North­
west Forest and Range Experime nt Station. Portland.
Oregon . USA .
Atay . I. 1959. Researc h o n the seeds nf black pine (Pinus
nig ru var. pallu:>iww) . lnstanbul Univ c rsit esi O rman Fak­
ultesi Derg. 9A:4X- 96. (Turkish with Engli s h su mmary .)
Baker. H. G. 1972. Seed weight in re latinn to e nvironm e ntal
conditions in California. Ecology 53:9':17-1010.
C hing. T . M .. and K . K . Ching. 1962. Physical and phys­
iological c hanges in maturing Douglas-fir cones and seed.
Forest Science 8 :2 1- 3 1.
Dashkevich. M . D. 196 1. Influence of cone size in common
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All use subject to JSTOR Terms and Conditions
644
FRANK C. SORENSEN AND RI C HARDS. MILES
pine on seed germination and quality and on growth of
seedlings in progenies. Lesnoj Zhurna l (Archangel'sk)
4:159-161. (In Russian).
Eliason. E. J .. a nd C. E. He it. 1940. The s ize of Scotch pine
cones as related to seed size a nd yie ld. Jo urnal of Forestry
38:65-66.
Emmingham. W. H. 1977. Comparison of selected Douglas­
fir seed sources for cambial and leader growth patterns in
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pressu.l". Alabama Agricultural Experiment Station Circu­
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