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THE SOCIETY
A PUBLICATION OF
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MEIUCAN FORESTERS
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Ill
rosa Pine
Racial Variation in Ponde
By
A. E. SQUILLACE
ROY R. SILEH
2-1962
Forest Science-Monograph
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Copyright, 1962 by the Society of American Foresters Printed in tire Unitetl States of AmericrJ
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CONTENTS
2
Review of Literature
The Studies
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The Northern Idaho Study -The Oregon-Washington Study
-----------
3
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4
7
Analyses
Results
3
7
·
--- --
7
Height Growth Differences
--
Genetic Component of Variance
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-
--
10
Relation of Height Growth to Geographic and
Climatic Factors of Seed Source Loc•lities
11
Geography -
11
- -
Precipitation
-----
Temperature
Survival -
--
--
-
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-
-
-----
--
-
-- --
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----------
-­
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Differences in Diameter and Volume Growth
- - --- -- -----
11
13
15
15
Animal Damage--------------------------------­
17
Frost Injury
18
Need!es
19
---------- ------- ------------------- ---------- - --
Stem Form
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Growth Periodicity --Reliability of Early Growth Measurements
Discussion
Summary
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Literature Cited
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19
20
21
22
25
26
Acknowledgments
The authors gratefully acknowledge cooperatioa of
Professor George H. Barnes, Oregon State University,
and Professor Stanley P. Gessel, University of Washing­
ton, in providing recent data from two plots established and
maintained by their institutions for the Oregon-Washing­
ton test.
The authors are also deeply indebted to many
research foresters, too numerous to list individually, who
have participated in the measurement and analysis of the
ponderosa pine provenance studies over the years.
·· · . - ·
Racial Variation in Ponderosa Pine BY
A. E. SQUILLACE
ROY R. SILEN
MucH of the speculation and some
f the
known information about the effect of seed
source and inh ritance iri forest trees have
come from provenance studies. Until more
precise studies develop, these often furnish
the best estimates we have of the genetic va­
riability existing within a species. Many of
them were established long before statistical
designs were developed. Even so, they can
often be subjected to statistical analysis.
.
. . ·
Two such studies, now 30 and 45 years
old, i:onducted with ponderosa pine (Pinus
ponderosa Laws.) in the Northwest, have
advanced to the stage where results can be
presented with a greater degree of confi­
dence than heretofore. In these experiments
seeds were collected from widely separated
localities within the natural range of pon­
derosa pine and planted in. various areas
within the Northwest. One of these, in­
volving a single plantation in northern
Idaho (hereafter called "Northern Idaho"
study), was begun in 1911 by the Priest
River Forest Experiment Station (now a
part of the Intermountain Forest and
Range Experiment Station). The other,
involving five plantations in Oregon and
western Washington (hereafter called
"Oregon-Washington" study), was begun
in 1926 by the Pacific Northwest Forest
and Range Experiment Station. The pres­
ent report verifies statistically the existence
of racial growth differences and correlates
growth of trees from various sources with
geographic and with climatic factors of
their native habitats.
The correlations with geography and
climate were investigated to help determine
if it is possible to predict performance of
seed from a given source in a particular l
cality. With topographic and climatic vari­
ation as great as it is throughout the range
of_ ponderosa pine, provenance testing of all
possible seed sources in all localities is prac­
tically impossible. If inherent differences in
growth and other traits can be related to
such geographic factors as latitude, longi­
tude, and altitude, or to specific climatic
factors such as rainfall and temperature, the
need for testing would be greatly decreased.
Limited investigation of these relations was
possible and yielded useful information
about patterns of inherent differences in
growth, as well as in survival, form, frost
hardiness, resistance to damaging agents,
and other traits in ponderosa pine.
Senior authorship was decided by toss of a
coin. At the time of writing, A. E. Squillace
was Forest Geneticist, lntermountain Forest
and Range Experiment Station, Forest Service,
U. S. Department of Agriculture, stationed at
Spokane, Wash. He is currently with the
Southeastern Forest Experiment Station, at
Olustee, Fla. Roy R. Silen occupies a similar
position with the Pacific Northwest Forest and
Range Experiment Station, and is stationed at
Corvallis, Ore. Manuscript received Jan. 19,
1 962.
1
Review of Literature
Most of the many studies of racial or eco­
typic variation conducted in the past have shown heritable differences occurring in ya­
rious parts of the range of the species con­
. cerned. Similarly, trees derived from lo­
calities nearest to or closely resembling the
planting site generally performed best. In
some of the studies performance on the
planting site was correlated with such fac­
tors as altitude, latitude, and longitude of
the native habitat, while a few dealt with
specific climatic factors. Recent articles by
Echols ( 1958), Squillace and Bingham
(1958a), and Vaartaja (1959) summar­
ized much of the past literature on racial
variation dealing with both coniferous and
hardwood species. Fischer's ( 1949) an­
alysis of Engler's 1899 provenance studies
discusses the characteristic patterns of vari­
ation that are experienced in such older
studies as these.
Several trials of ponderosa pine seed
sources were begun in the early part of the
20th century.Roeser (1926), briefly sum­
marizing early results of a test conducted
near Pikes Peak, Colorado, stated that
"...
- proximity to the point of sowing was
a more desirable basis of selection than lati­
tudinal or altitudinal distribution, although
altitude is decidedly important." Seed from localities in California and Oregon failed in the nursery "'1Jile seed from local and other 1 Also reporting on the
sources survived.
Pikes Peak test, Bates (1927a) noted the
preference of animals, presumably deer, for
a Black Hills, South Dakota source over
others.Bates (1927b) and Higgins (1927)
reported results of a plantation in Nebraska
from widely differing seed sources; local
seed appeared to be best. In addition to
differences in survival, they noted differ­
ences in susceptibility to tip moth.
Schreiner ( 1937) has reported that on
the Fort Valley Experimental Forest north
of Flagstaff, Arizona, ponderosa pine seeds
1Personal communication from Jacob Roeser,
Jr., in the files of Intermountain Forest and
Range Experimc;::nt Station.
2
from California and the Northwest pro­
duced rapidly growing but less hardy seed­
2 He also gave general
lings than local seed.
notes on heritable differences in ponderosa
pine. in a rather extensive trial in Califor­
nia, detailed results of which have not yet
been published.
Moore ( 1944) reported differences in
grOwth and survival among ponderosa pine
from different sources planted in New Zea­
land.
Lorenz (1949) summarized early results
of a ponderosa pine seed source study in
Illinois. Although it was too early to inter­
pret differences in survival, he noted differ­
ences in needle color and texture and tree
form.
A study of altitudinal races in California
by Mirov et al. (1952) showed a curvi­
linear relation of growth with altitude of
seed source; trees from altitudes of 1,500
to 3,500 feet above sea level grew best.
These results were confirmed in a later re­
port by Callaham and Metcalf (1959).
Earlier results of the Northern Idaho
and Oregon-Washington studies, the sub­
ject of this report, have been extensively
reported. Kempff (1928) and Weidman
( 1939) summarized early results in north­
ern Idaho. Starker ( 1940) and Munger
(1941 and 1947) did the same for the
Oregon-Washington plantings. Generally
speaking, early results of both showed large
differences in survival, growth, and mor­
phological characteristics of foliage among
trees from various sources. The existence
of racial differences on the basis of survival
and morp ological characteristics of foliage
was considered proved. However, some
doubt remained about the inheritance of
growth rate, especially in view of great
differences among planting sites and appar­
ent planting site-seed source interactions
in the Oregon-Washington trials. No at­
2A personal communication from G. A.
Pearson, in the files at Intermountain Forest
and Range Experiment Station, stated that all
seedlings in the study originating from regions
other than the northern Rocky Mountains died
within S or 6 years after planting.
"II
"
I
I
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tempts were made to relate growth rate to
specific geographic or climatic variables of the source localities. Daubenmire (1950)
studied the time of beginning and ending of
cambial growth in the Northern Idaho
plantation and concluded that there were
no differences among the trees from the
various sources.
'I
The Studies The Northern /doho Study
This study includes a single plantation of
ponderosa pines grown from seeds collected
at various localities over the range of this
species (Fig. 1 and Table 1). A total of
22 seed sources was originally represented,
OREGON - WASHINGTON TEST
1926-1956
1111.*
,I
/1
PLANTATIONS WIND RIVER MCllONALD PACI( OESCHllTES WHITMAN j
'f
•
•
SEED SOU/ICES
J. ELDOllADO
I. llOGtJE RIVER
.1 ttflLLAMETTE
°" BITrERROOT
$. S TEILACOOM
& DESCHUTES
7. LASSEN
a. CARSON
'- COCONINO
10. HAllNir
NORTHERN IOAHO TEST
1911-19 6
!
/:,l,lJ PLANTATION
PRIEST RIVER
ifiJ4
A
"
"
f'.-.
SEED SOURCES
I. S/$1(/'fOU
Z, SHASTA
.l BOISE
.f. PAYETTE
$.WHITMAN
& UMATILLA
7. COLVILLE
• KAN!KSU
LOLO
IO. l l T TERNX>T
.. 4000FEET
6.
FEU
- 7200FEET"
IL C«OlllNO
II.SANTEFE
I.I HELENA
/If.CU STER
15.. HAllllE'f
11. llOOSEVELT
1% SAN /SABEL
IA ASHLEY
F1GURE 1 .
Localities of seeJ origin tmJ j>Lmting sitN in the Northern Idaho anJ Oregon-lVash­
ington studies. SeeJ was co1/e.
- cteJ at points intlicQteJ by stems o-f tree Jiagrams, anJ pk/nteJ at
loca#01'f shown by f>lantation area symbols, Heights and widths of tree tri<lngle.s indicate
4fJerage differences in heights on.J basal, 11ru, respectit:Jely, of trees from differmt sources when
planteJ in a c(Jmmon locality. Differences in age onJ site between the two tests were reconciled
here by maRing the tree sizes praportional too common fJllerage height and Jianzeter. Interac­
tions of seed source f#ld-plonting site, which were large.in some instances (Figure 2), are masked
here.
3
TABLE 1. Location, altitude, and summary of weather records of the localities of seed
origin in the Northern Idaho study; mean total height of tallest one-th;,.d of rhe trees and
survival 40 years after planting.1
Average precipitation
Locality
of eced
origin2
Latitude
Longitude
Altitude
Annual
}
42°05'
41°30'
43°30'
44<>30•
"4 o g•
4 3
46°00'
48°40'
48°20'
4'7°10'
123° 4-0'
122°20'
115°00'
116°00'
118°25'
117°30'
119°00'
116°50'
114°50'
2,000
4,000
5,500
5,000
5,000
3,500
2,700
2,600
3,000
4,000
5,000
7,200
35°10' 111°50' 7,100
35°40' 105°30' $,000
46° 30' 111°50' 4,500
45.030' 104°00' 3,200
43°40' 103°30' 5,000
40°30' 105°40' s,ooo
38°00' 105°00' 8,000
40°40' 109°40' 7,500
46°00'
114°20'
}
April
••d
M•y
July
lcH
Jan,
"F
Inches Inell.es
Feet
Siskiyou
Shasta
Boise
Payette
Whitman
Umatilla
Colville
Kanikau
Lolo
Bitterroot
4,000 ft.
5,000 ft.
7,200 ft.
Coconino
Santa Fe
He_Iena
Custer
Harney
Roosevelt
San Isabel
Ashley
Mean temperature
Sept.
th,.
Sept.
June
thru as% of
June annual Annual
SI.48
38.47
22.79
25.4S
20.51
21.24
14.26
29.19
15.91
Sl.12
38.05
21.67
24.31
19.20
19.63
12.74
27.39
14.44
99.3
98.9
9S.l
95.5
93.6
92.4
89.3
93.8
90,8
16.53
14.58
88.2
22.45 15.99
24.12 IS.29
12.44 10.34
9.93
13.12
17.19 12.70
18.00 13.38
16.86 12.15
13.65 11.26
71.2
63.4
83. l
75.7
73.9
74.3
72.I
82.5
49.9
47.0
38.9
39.8
38.4
43.4
41.7
43.7
4S.7
51.6
47.7
43.4
42.4
42.0
47.0
46.4
47.6
49.6
44.S
42.5
38.1
43.4
42.9
41.7
43.7
42.5
42.5
42.9
41.4
48.2
46.2
41.6
44.6
43.9
46.4
48.7
44.7
43.4
45.4
44.4
}
28.9
32.4
47.1
44.7
40.6
40.9
43.S
40.8
42.8
39.8
38.3
32.J
50.4
54.5
43.2
36.8
39.S
4S.2
Progenies
Mean
total
height
Survi-
Feet
Percenl
S2.4
47.2
41.6
4 6 .6
50.8
49.4
49.2
55.7
IO
0
29
13
24
,48
56
46
42
49.2
48.9
47.4
34.9
3o.6
43.7
42.0
33.6
34.4
35.5
29.6
29
44
13
23
9
34
18
19
20
24
21
vol
1 Weather data are from the latest Weather Bureau records obtained for atationa nearest to and most reprcsentative of the individual localitiet of aced origin. Where the point• of _ origin differed appreciably in altitude
from that of the weather atation1 approximate correction• were made (aa done by Weidman 1939). Neverthe
lesa the poasibility of error exists because of the hazard• associated with eJ:trapolation in mountainou• country,
1 All locatitiea of seed origin are designated by the national forests containing them. The three localitiea on
the Bitterroot National Forest are further designated by altitude.
but two of them were of questionable ori­
gin and were dropped from the study in
earlier years. Although details of seed col­
lection are lacking, it is believed that seeds
of each source were collected from a num..
her of trees rather than from single trees.
The trees were planted at the Priest
River Experiment Station (now Experi­
mental Forest) in northern Idaho in the
years 1911-1917. The climate here is
rather typical of the western white pine
(P. monticola Dougi.) habitat, with mod­
erate precipitation, much of it accumulating
as snow in the winter; summers are hot
and dry with the possibility of frost occur­
ring in any month (Table 2). The trees
were planted as 2- and 3-year-old trans­
4
plants in unreplicated plots, four of the plots
being 25 by 50 feet in size, and the remain­
der 50 by 50 feet. Spacing of trees was
5 by 5 feet. All plots were examined for
mortality and trees were measured for:
height and diameter from time to time.
The last examination, upon which the pres­
ent study is based, was made in the early
spring of 1956. Thus, the trees at that
time varied in age from 42 to 46 years.
However, the growth data were adjusted
to represent 40 years' growth on the plots
(irrespective of the I-year difference in age
of planting stock).
Tho 0'"90n-Wcuh/ngfon Stucly
Started in I 926, this study includes plant­
ings of ponderosa pine from I0 seed sources
i
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TABLE. 2. Location, altitude, and summary of weather records of the planting sites.
Average prcc:ipitation
Planting
site
Latitude
Longitudc
Altitudc
Feel
Sept.
Annual
lmAes
thns
June
Mean temperature
Sept.
thru June
as% of
Annual
annual
Inches
April
and
May
July
len
Jan.
'F
NORTHERN IDAHO STUDY
-- ·--- --·-- -
--
Priest ·River Ezpt.
Forest
----
48°20'
116°50'
2,380
29.19
27.39
93.8
43.7
47.6
40.8
OREGON-WASHINGTON STUDY
McDonald Forest,
o.s.u.
I
Pack Demonstration
F'orest, U. of W.
Wind River Expt.
Forest
Dcschutce National
f'orcst
Whitman National
F rcst
_
-
-
-
44"35'
123°20'
950
40.06
39.31
98.1
52.4
53.3
26.9
46"45'
122°20'
1,lSO
45.64
44.07
96.6
5o.4
51.6
25.9
45°50'
121°SS'
1,300
86.84
85.39
98.3
47.8
49.9
32.I
43°55'
121°20'
3,800
16.65
15.6+
93.9
+6.7
+7.3
34.6
44°35'
t 18°35'
4,400
18.65
17.46
93.6
+1.1
++.7
40.9
on five sites, but, like the Northern Idaho experiment, it has no replication at planting sites. Originally there were 11 sources, but trees from the Dixie National Forest in Utah failed early. The 10 seed collection points, as in the Northern Idaho study, were widely spread to sample the periphery of the species range (Fig. l and Table 3). The Eldorado seed source was represented by seed from a single parent tree, but all oth­
ers were from inany trees in one locali_ty. The five existing plantations furnish excel­
lent opportunities to study differences in
adaptation to particular sites among trees of
different sources. The plantings in 1928
originally included a sixth site, near Wash­
ington State College at Pullman, but. it is
not included here because the plot was de­
stroyed in 1946.
Of the five plantations now remaining,
two are east of the Cascade Mountains.
One is at 4,200 feet elevation on the .Des­
chutes National Forest near Bend, Oregon;
the other is on the Whitman National For­
est at 4,400 feet, near Austin, Oregon.
Both of these plantations are surrounded by
stands of ponderosa pine, and have conti
nental climates like that descn"bed for the
Northern Idaho study. Both are main-
tained by the U.S. Forest Service. Three plantations are west of the Cas­
cade Mountains on Douglas-fir (Pseudo­
tsuga menziesii (Mirb.} Franco) sites, but
native ponderosa pine is found within a few
miles of each site. Through most of the
year climates are mild and humid, but little
rain falls in July and August. The planta­
tion on the Wind River Experimental For­
est near Carson, Washington, is at 1,300
feet elevation and is maintained by the U.S.
Forest Service. Another, near Corvallis,
Oregon, on the McDonald Forest at 950
feet, is maintained by Oregon State Uni­
versity. The Pack Forest plantation, near
LaGrande, Washington, at 1,150 feet is
maintained by the University of Washing­
ton.
The Oregon-Washington study included
more trees per source at each plantation
(75-1,225) than did the earlier Northern
Idaho one. Hence more site variability was
encompassed by the plantings because of
the larger area covered. Planting was at
6- by 6-foot spacing. Seeds from the Wil­
lamette and Steilacoom sources were col­
lected one year later than those from other
sources; outplanting in 1929 was likewise
one year later. This age difference, how­
5
..
TABLE 3. Location, altitude, and summary of weather records of the localities of reed origin in the Oregon-Washington study, and mean total height of tallest one-third of trees at 30 years from reed.1
Average precipitation
Latitu de
Locality of
seed origin1
Longitu de
Sept.
thru
June
Altitude
Annual
Feet
lnt:Ms
lnclles
Mean progeny height by planting sites
Mean temperature
Sept. thru
June
at% of Anannual
nual
April
•nd
M•y
July
leH
Jan.
M<Donald
Pack
Wind
River
Fo
Desch....
Whitman
Means
Feel·
Steilacoom
47°00'
122°20'
100
38.27
36.65
95.8
50.4
52.1
25.0
54.7
25.3
24.8
8.8
21.2
27.0
Willamette
44°30'
123°00'
300
39.06
38.35
98.2
52.4
53.3
26.9
39.9
25.7
30.6
12.4
29.2
27.6
Eldorado
38°40'
120°3S'
3,000
41.23
41.19
99.9
53.2
53.6
33.8
62.8
29.9
27.4
7.0
27.5
30.9
Bitterroot
46°00'
114°20'
4,600
16.53
14.58
88.2
43.0
47.2
41.1
39.9
28.5
30.0
13.2
26.8
27.7
Rogue River
42°50'
122°05'
4,300
38.63
37.95
98.2
42.5
46.2
31.6
38.3
28.7
31.9
12.1
27.6
27.7
Deschutet
44°00'
121°10'
3,600
16.65
IS.65
94.0
46.7
47.3
34.6
37.1
30.5
28.0
9.6
27.3
26.5
LaHen
40°25'
121°10'
5,500
23.04
22.78
98.9
45.4
46.6
36.0
26.2
18.5
22.0
9.4
24.4
20.1
Canon
36°25'
105°25'
8,000
15.73
10.64
67.6
39.2
42.8
40.8
29.7
16.0
23.4
4.3
23.7
19.4 Coconino
3S020'
111°40'
7,000
22.45
IS.99
71.2
42.9
44.0
38.3
29.1
20.7
24.2
7.8
13.0
19.0 Harney
43°55'
103°40'
5,700
17.19
12.70
73.9
41.S
43.7
37.2
Means
15.2
17.2
21.0
5.9
18.2
15.5
37.2
24.1
26.3
9.0
23.9
24.1
1Weather data arc from Weather Bureau records obtained for stations most repreeentative of the individul localitiea of seed origin. 2All but the Steilacoom and Willamette localities are national foreets. The Steilacoom locality ie near Tacoma, WashingonJ the Willamette, near Corvallis, Oregon. -------·
·----··-
-···--
·--
'.. -
---4'-
'
---
· --------
---·
... - --- -- -
-
,,
ever, has been ignored in the analysis. As
will be shown later, trees produced from
seeds of both sources are above average i11
height; hence, the _estimates for them are
conservative. Measurements after the 1955
growing season represent the heights and
diameters of trees 30 years from seed in all
but· these two sources.
Much variability other than seed source
and planting site difference has entered the
experiment over the 30 years since sowing.
Spacing among the five plantations now
varies widely because of differential mor­
tality from grazing, snow, freezing, and
drought. On one plantation (Pack Forest)
trees were planted to replace those that
died. Brush and tree competition has va­
ried greatly among plantations.
Analyses
/I
One does not expect to find that experi­
ments started before 1926 were designed
for statistical analysis, nor were they. How­
ever, valid statistical methods may be ap­
plied to both studies. In the Oregon­
Washington study, the differences in
growth rates among the seed source means
for all plantations may be tested by analysis
of variance. Differences in growth rat
among seed so rces in the single site in the
Northern Idaho study could not, of course,
be analyzed similarly because there was no
replication at the planting site. The same
was true of differences between sources at
any single plantation in the Oregon-Wash­
ington experiment.
These shortcomings were largely over­
come by using gross correlation and mul­
tiple correlation methods in both cases. Re­
lations of height growth with geographic
and climatic factors of seed source localities
may be investigated by assuming that site
and di:fferen-ees in spacing were variables
contributing randomly to statistical error_:_
along with other unmeasured factors. The
pattern of inherent differences in growth
by seed source for all plantations was strong
and consistent enough to override these
sources of environmental variability.
After considerable thought, we chose
average height growth of the. tallest one-
third of the trees as the most satisfactory
measure of growth potential. In both stud­
ies rankings were compared by using aver..
ages by seed source for heights of (1) all
trees, (2) dominants and codominants, and
(3) tallest one-third. For the Whitman
site, the averages for the tallest one-quarter
and tallest one-tenth were also tabulated.
Usually these tabulations made little differ­
ence in the ranking of progenies.
Use of the tallest one-third had the ad­
vantage of eliminating personal bias that
might enter into choice of dominants and
codominants. Use of average height of all
trees had the disadvantage that differential
shade tolerance may be a confounding fac­
tor. Sources that have many small sup­
pressed trees barely alive (often a matter of
personal judgment) would thus be penal­
ized. Sources that have had much mortality
-and .hence have many gaps in spacing­
would be unduly favored over those for
which original spacing was intact. Use of
the tallest one-third reduces the effect of
such di:ffCrences in spacing, and it eliminates
many trees accidentally damaged by cli­
matic or biotic factors wholly unrelated to
inherent differences in growth rate. When
ihe sample is small, the average could be
significantly affected by such trees. Use of
the tallest one-quarter or tallest one-tenth
was not considered since the averages for
some sources would be based on too few
trees. Munger (1947) had also concluded
the tallest one-third of the trees to be a bet­
ter expression of growth potential for the
Oregon-Washington study than the aver­
age of all trees.
Results
Height Growth Differences
The analysis provided statistical verification
for observations reported earlier by W eid­
man (1939) and Munger (1947), that
trees from the different sources, when
grown in a common environment, exhib­
ited inherent differences in height growth.
Present data on height growth are sum­
marized in Table 1 for the Northern Idaho
7
study and in Table 3 for the Oregon­
Washington study.
Thus far, trees from localities near the
planting sites have usually (but not invari­
.ably) grown the tallest. Those from the
.northern and western portion of the species
range, where all the plantations were l<>­
-cated, generally grew the tallest (Figs. 1
.and 2.) In the Northern Idaho study,
trees from the western and north..central
portions of the species range averaged 48.9
feet in total height (tallest one-third in each
source) while those from the remammg
areas (including Helena) averaged 35.5
feet 40 years after planting. Results of the
Oregon-Washington plots were similar:
trees of western and north-central sources
averaged 26.8 feet, and those from the east
and southeast portion of the species range,
18.0 feet at 30 years. A statistical expres­
sion of this, the correlation of height growth
with distance from planting site, was nega­
tive and highly significant in both tests but
has no simple biological interpretation.
COMPARATIVE HEIGHTS of TREES of DIFFERENT SEED SOURCES in THREE TESTS
TEST
1--
• R •
- -
• S
-
REGIO N
--t
OREGON-WASHINGTON
I 30 years J
-·-•_c_._,_,_,
_,_
OF
·-· T E
·
·
o · · T · · ·'--
ORI GIN
-l-'--·
·
· T'--'-"
S L o · ·'--
l!,eiQht
....... WINO RIVEH·l-fOOFEET
MC OONALO - 950 FEET
PACK- 1 00 FEET
WHITMAN- 4400FEET
PROGENY
AVERAGE
NORTHERN IDAHO
( 4Syeor1)
PH/£51" RIVER·2400FEET
NEW ZEALAND
l 215 years I
KAINGAROA STATE FOREST
1600FEET
Height growth of ponderosa pine in the Northern Idaho and Oregon-Washington
studies. The seeJ sources are JMJd into .Pacific, lntermoontain, and ettJt slope groups, the
sources being arranged from north to south toitkin each group. Instances in which seed sources
closely corres1>0nJ between tests, such as the Bitte"oot, Coconino, ®J Harney, are fl()/eJ Dy
fine dotted Unes. The New Zealand lest ;, added for comparisons discu11ed later.
FIGURE 2.
8
t
!
I
ir
----------·
,.. , ,
In the Oregon-Washington experiment
a statistical test of differences in average
height among sources on all sites was pos­
sible; a moderately strong effect of inherit­
ance was apparent. Results of the analysis
of variance test, shown below, leave little
possibility of this effect being due to chance.
Degrees of
Mun Sfuares
·freedom
131.56 highly
9
significant
1,013.98 highly
4
Planting sites
significant
Error (seed source
34.30
36
X planting site)
Source of
t1ariation
Seed source
I
I
!
!
..
Total
49
Thus, in spite of great differences be­
tween planting sites, trees of each source
tended to perform consistently well or con­
sistently poorly on all planting sites. Al­
though it was not possible to test seed
source X site interaction, there likely was
a real effect. For example, trees of the El­
dorado and Steilacoom sources grew ex­
tremely well on the moist McDonald site,
but did very poorly on the drier De hutes
and Whitman sites. Close inspection of
Figure 2 reveals other examples of the same
kind. However, four of the ten sources
were consistently. better than average, and
three consistently poorer. Even among the
three sources ·that varied most in relative
performance, two were decidedly better
than average on most plantations. In gen­
eral, consistency prevails.
Mention should be made of the impor­
tant question of local versus introduced seed
Sources, not because the two studies answer
the question, but tO for,estall any inferences
from this test beyond the scope of the data.
In a general sense, the data show a
strong relationship of decreasing height
growth with distance of seed source from
the experimental site. Specifically there was
no case in which the nearest seed source
was top performer, even though it _ w_as
usually among the better ones. Probably no
seed sources were local in the sense that the
seed used came from the immediate vicinity
of the planting sites. This circumstance,
coupled with the lack of replication at any
experimental site, leaves the question still
largely unanswered.
The extremely large differences in mean
total height on the different planting sites
of the Oregon-Washington study are puz­
zling. Growth was rather uniform among
three of them-Pack, Wind River, and
Whitman-in spite of large differences in
annual rainfall and elevation. It seems
especially odd that growth on the Pack and
Wind River sites, which have heavy rain­
fall and warm temperatures, was little bet­
ter than that on the Whitman site, which
has little rainfall and cooler temperatures.
Any of a number of factors may explain the strong environmental effects.
Trees from similar localities planted in
both the Northern Idaho and Oregon­
Washington plots grew at rather similar
rates (discounting complete failures). This
can be seen in Figure 2, which is arranged
to compare growth of trees from similar
sources.
A report by Moore (1944 ) 8 provided an
opportunity for further comparisons. In
Moore's experiment, trees from some of the
same general localities as included in the
Northern Idaho and Oregon-Washington
plots were planted at the Kaingaroa State
Forest in New Zealand in 1929. Relative
growth rates of trees from the same general
localities in all three tests are compared in
Table 4. Similarities are striking. Trees
from sources in the same geographic region
seldom vary as much as I 0 percent. Even
the apparently aberrant Lassen trees in the
Oregon-\Vashington and New Zealand
experiments performed poorly whereas the
Eldorado trees grew well in both test areas.
A rough approximation of planting site
effects is afforded by the average annual
growth rates shown at the bottom of Table
4. Growth was best at the New Zealand
site, while growth at the Northern Idaho
site was somewhat better than at most of
BMoore's 1944 report gave data on perform... ance of trees through their 17th year ( 1944) from seed. Total height data through 1952 (25 years from seed) were furnished the au· thors by the New Zealand Forest Service. 9
the sites used in the Oregon-Washington
study. It should be acknowledged here that
large proportions of the fast growing trees
from California in the New Zealand test
Were described as being "malformed." At
any rate, the results leave little doubt about
the existence of heritable differences in
growth rate among ponderosa pines from
different regions.
Although strong emphasis is placed here
in testing the generic effects on growth, one
should not overlook the fact that the larg­
est differences found are due to environ­
ment. Obviously such environmental dif­
ferences as those between the Deschutes
and McDonald sites, where the best source
at Deschutes did not equal the poorest at
McDonald, override generic effects. The
more important question in these studies is
the proportion of the growth variation
within plantations that is generic in nature.
Even here the environmental component
appears relatively larger than the generic
component from the best estimates that can
be made from these tests.
Genetic Component of Variance
The proportion of genetic variance can be
roughly estimated from the Oregon-Wash­
ington data. Applying simple population
generic formulae this is computed to be
0.
364 using the figures from the analysis of
variance previously presented. The inter­
•Computed ·from the following formulae:
mean square for progenies = a2+Ka2a, and
a"a,
h" h
in w 1c
a2a+a2
a2 = error mean square, a2a = genetic vari­
ance, and K = number of planting sites.
·
genetic component
·
=
TABLE 4. Comparison of relati'lle height growth of trees of different sources tested in
three independent tnals.
Northern Idaho
General
locality of
seed origin
Spcci.fic
locality of
seed origin
Oregon-Washington
Relative
growth1
Specific
locality of
seed origin
Percent
Percent
California
W. Sierras
E. Sierras
Siskiyou•
W. Oregon
E. Oregon
Shasta
Siskiyou
(Failed)
126
New Me.1:ico
UmatiJla
Whitman
Bitterroot
Harney
Roosevelt
San Isabel
Santa Fe
122
112
118
81
83
86
74
Arizona
Coconino
84
W. Montana
South Dakota
Colorado
Mean annual growth-tint
4 General Iocalitics1
Mean annual growth--tecond
4 General 1ocalities1
Average mean annual growth11
Relative
growth1
New Zealand
Specific
locality of
seed origin
Eldorado
Lassen
138
90
Willamette
Rogue River
Deachutee:
123
124
118
Bitterroot
Harney
124
69
Canon
Coconino
86
85
.Relative
growth1
Percent
Sierra
Eldorado
Lanen
Klamath
141
ll7
74
120
r
Pike
69
Santa Fe
Lincoln
74
88
1.14
0.89
1.85
.79
0.96
.60
0.74"
1.16
J.50
1 .Relative growth i1 expreesed a1 percent of average mean annual grow_th as shown at bottom of table.
2Height growth in feet-per year. - Based on the following ages from seed: northern IdahoJ 43 yean; Oregon­
WashingtonJ 30- ycarsJ and New ZealandJ 25 yean.
• Averagc_of both groups of general localities.
'Based on all five planting sites. Comparable figures for each 1ite follow: McDonaldJ l.09; Pack, 0.74; Co­
lumbia, 0.85; Deschutes, 0.27; and Whitman, 0.76.
10
I
I
'
.....
pretation is that 36 percent of the total vari­
ati.on in average height of trees of different
sources within a plan_tation was due to in­
herent differences. The other 64 percent
was due to environmental differences and
interactions of genetic and planting site
effects.
By way of caution, the figures presented
here apply to the particular experiment dis­
cussed and may not apply where environ­
mental control is better or poorer. Also,
since the material was gathered from over
most of the species range, the genetic vari­
ability is expected to be greater than would
be encountered in a single area. Since one­
third of the variability was estimated to be
genetic, we were encouraged to investigate
further the relationships of inherent differ­
ences in height growth to geographic and
climatic factors.
Relation of Height Growth to GeogrfJpllic oncl
Climatic factor• of Seed Source Localities
Gross or simple correlations of mean total
height by sources (tallest one-third of all
trees) with various geographic and climatic
factors of the seed source localities are
shown in Table 5. High or low correla­
tions, as well as negative and positive corre­
lations, fell into a remarkably similar pat­
tern in both tests.
Geography.
:· ;,;. .
Note first that growth varied
inversely with altitude and directly with
longitude and latitude. Some of the rela
tion.ships found are strong. However, from
the standpoint of the causes of the apparent
inherent variation they are in a sense mean­
ingless. Each undoubtedly ties back to some
meaningful climatic difference (as in tem­
perature, precipitation, and day length) be­
tween seed source localities.
For these reasons, we tried to concen­
trate the remainder of the analyses on cli­
matic variables. We hoped to gain some in­
sight into what may have caused the inher­
ent variation in growth.
Precipitation.
Taking the precipitation fac­
tor first, we note that the range of ponder­
osa pine in western United States is charac­
terized by heaviest annual precipitation west
of the Cascade and Sierra Nevada ranges.
It decreases sharply to the east, and is pro­
gressively less behind each major north­
south range as one proceeds eastward
through the Rocky Mountains. Precipita­
tion is usually heavier as one proceeds from
south to north. The broad valleys usually
receive less precipitation than surrounding
mountains. Precipitation from westerly Pa­
cific storms usually ceases during July and
August, bringing a period of drought over
much of the West. This drought occurs
even earlier in the Southwest where spring
droughts are common. However, in July
and August an average of 3 to 5 inches of
rainfall from local thunderstorms occurs
east of the Rocky Mountains and in Ari­
zona and New Mexico. Progressively less
precipitation occurs from this source as one
proceeds toward the Pacific Northwest.
Summertime rainfall is nearly absent west
of the Cascade-Sierra Nevada divide. Be­
cause of this yearly pattern of precipitation,
the ratio of July-August rainfall (or its
complement - September - through - June
precipitation) to total annual precipitation
appears to be a fair index of moisture dis­
tribution. (In Tables I and 3, see precipi­
tation from September through June as a
percent of annual.)
Growth of trees of different sources was
rather strongly correlated with moisture
distnbution, as measured by the amount of
precipitation occurring from September
through June expressed as a percent of an­
nual precipitation (Table 5). Trees from
localities receiving most of their precipita­
tion in fall, winter, and spring usually grew
faster ·than those from localities receiving
relatively less precipitation during those sea­
sons. Other measures of precipitation were
positively but less strongly associated with
differences in growth, with the exception
of springtime precipitation (April through
June), which was unrelated to growth in
both studies.
Note that the Colville, Lolo, Bitterroot,
and Deschutes trees were from localities
that receive much less annual precipitation
11
'
..,
TABLE 5. Correlation coefficients relating gruwth of trees of different sources at planting rites with geographic and .climatic factors
of seed source lacalities.
Mean precipitation
Altitu de
Planting
aite
Latitu de
Longitude
Annual
April
thru
June
Jan.
thru
June
Mean· temperature•
Sept. thru
June
Precipitation
eJiec:u%of
annual
tivene111
Sept.
thru
June
AprilMay
Annual
Number
of seed
1ource1
NORTHERN IDAHO STUDY
Prie1t River
-o.1 s••
+o.1s••
+o.1s••
+0.24
-0.02
McDonald
- .66*
Pack
+ .19
+ .7 1•
+ .12
+ .73 '
+ .73•
- .60
+ .41
- .01
Wind River
+ .49
+ .53
- .47
+ .45
+ .41
+ .50
- .50
+ .24
- .45
+ .29
- .24
Whitman
+ .59
+ .39
+ .58
+ .64'
- .26
Descbutel
+ .44
+ .36
+ .64'
+ .10 •
+ .58 + .36
+ .33
- .OJ
+ .41
+ .45
Oregon-Waeh.
pooled
-0.49 **
+0.28
+o.4s••
-0.01
+0.46 **
+o.s o ••
+o.Bt••
+0.40
+0.16
+o.35
+0.22
+o.5o •
19
+ .30
+ .75 •
OREGON-WASHINGTON STUDY
+o. s4
••
+
.61
+ .69'
+ .54
+ .36
+
+ .82••
10
.55
+ .62
10
+ .32
+ .45
10
10
10 +
+ .63
.63'
+ .10•
+ .27
+ .26
+ .29
+ .40
+ .37
+ .52
+o.54**
+0.40**
+0.47 ••
+o. ss••
10
•Significant a t 5 percent level; ••significant a t 1 percent level. 11\. measure of *1ie inte,ratcd e.tr cte of evaporation and precipitation determined by the method proposed by Thornthwaite (1931). 4
'·-
--·----·
--
--- --
-
-- ---
--
----
----------·--·-·-·---------·--"""
than others to the west and somewhat
smaller amounts than many of those to the
east and south; and yet they were relative­
ly fast growing. In fact, the Lolo trees,
coming from a locality that receives only
15. 91 inches of annual precipitation, grew
the fastest of all trees in the Northern
Idaho experiment. The native habitats of
"the four progenies mentioned above, how­
ever, have low summer-high winter moig.o.
ture patterns like those to the west but are
very unlike those to the east and southeast.
This same situation w_as true, though t() a
lesser extent, considering only September­
through-June precipitation. Just why mois­
ture distribution was more strongly related
to growth than other measures of precipi­
tation is puzzling. However it agrees with
Pearson's (1951) stress on the importance
of seasonal distribution of precipitation in
the distribution and si1vicultural character­
istics of ponderosa pine.
'':·
;·:;.. ·
·\··
Temperature. Height growth of the dif­
ferent provenances was also related to sea­
sonal average temperature at the localities
of origin. Several relationships were ex"
plored, including those between present
average height and temperatures at various
times within the growing season.
These analyses (see Table 5) indicated
that growth· differences were related to
both average annual temperature and
April-May temperature of the seed source
localities. Trees from the warmer areas
usually grew faster than those from cooler
areas. Also, the relationship with Apn1­
May temperature was stronger than with
average annual temperature. It is posSI"ble
that Apru-May temperatures at the source
localities reflect conditions relating to nat­
ural selection for growth rate better than
do average annual temperatures. This hy­
pothesis will be discussed further. In any
event the result agrees witli a report by
workers in Canada (Anonymous 1958)
that in a white spruce (Picea gl.auca
(Moench) Voss) provenance test, growth
decreased 10 percent for each 2 °F lower­
ing of the May-August monthly average
temperature of the source locality.
Slow growing provenances from the
southern portion of the species range were
thought at lirst to be exceptions to this
relationship because warmer temperatures
were assumed to prevail. On inspection,
however, spring and summertime temper­
atures of those southern source localities
used in these studies were found to average
4 or 5 degrees cooler than northern locali­
ties; the reverse occurs in winter (Fig. 3).
Hence growth of both southern and north­
ern sources was related to April-May tem­
peratures. Average annual temperatures
corresponded closely, but elevations of the
northern sources averaged 4,500 feet low­
er. Whether this alternating temperature
pattern is generally true for corresponding
elevational zones at northern and southern
parts of the range, or is simply an accidont
of sampling is not clear. Chapline and
Cooperrider ( 1941) observed that seasonal
temperature extremes are usually greater in
the northern than in the southern latitudes
of the United States.
Growth may also be correlated with an­
other climatic variable, namely frost-free
period. However, Weidman's data (1939)
on average frostlf:ss season shown for some
of the localities revealed no such correla­
tion. Similar trials with results from the
Oregon-Washington test also revealed no
correlation between growth and frost-free
periods at the seed source locality.
Attempts to relate growth with soil char­
acteristics or with the occurrence of pro­
longed cyclic droughts at the parent locali­
ties could not be made because reliable in­
dices of these factors could not be found.
In a multiple correlation analysis the two
strongest climatic variables found in the
simple correlations (September-through­
June precipitation as percent of annual,
and Apru-May temperature), accounted
for a highly signilicant 76 percent of the
variation in progeny growth on the North­
ern Idaho plot. In the Oregon-Washing­
ton test an average of 33 percent (from
pooled multiple correlation coefficient) of
the progeny growth variation, also highly
significant, could be accounted for by the
two variables.
13
with any of the factors studied. The resid­
uals or deviations of actual values from the
regression were then plotted against other
variables shown in Table 5. No significant
correlations could be found.
The same multiple correlation analysis
gave the following partial correlation co­
efficients:
Sept.-June
precipitation
(percent)
Apr.-May
temperature
Northern
/Jaho
Ore.-Wask.
(all sites
pooled)
+0.82**
+0.21
+o.ss•
+0.26
Thus, it is apparent that many of the in­
dependent variables studied were highly in­
tercorrelated. For example, longitude was
highly correlated with moisture distribution
(September-through-June precipitation per­
cent) and also with annual precipitation.
Most localities in the western part of the
range of ponderosa pine have high annual
rainfall and dry summers while those in the
east and southeast have low annual rainfall
and wet summers. Similarly altitude and
to some extent latitude were correlated with
Apn1•May temperature. Most localities in
the southeast had cooler April-May temper­
atures than those in the northeast, mainly
Thus, in the Northern Idaho experiment,
it is apparent that September-through-June
precipitation percent was the inore strongly
related factor. In the Oregon-Washington
study either factor was about as effective as
the other.
We tried to determine whether any of
the remaining variation in mean growth,
beyond that accounted for by the two
strongest climatic factors, was correlated
--- Average
of
Colville, Kaniksu, Helena, and Custer
(Meon latitude,
... .'
47• 15';
mean altitude,
mean ahnual temperature,
42.7• F. )
-----Average of Coconino, Sante Fe,
\5250
Roosevelt
and
localities.
feet;
S a n Isobel
localities. (Mean latitude, 37• 20\ mean altitude,
7775 feet; mean amual temperature, 42.9• F. J
"'
•
I
"" a:
::>
a:
Q.
,.
"" .... 30
....
,.
... "' ..
a:
>
<I ..
40
>
...J :r
""
60
50
""
z
0
70
20
10
0
Jan.
Feb.
Mar
Apr:
May
J une
July
Aug.
Sept,
Oct.
Nov.
Dec.
. .
M.ONTH
FIGURE 3 .
Comparison of se(Jl(JnO/. uaridtion in atJ#rage monthly temperatures of
four seeJ source locatities in the northern portion of the r1111ge of ponderosa pine
'Versus four in the southern 'P<Jrtion.
14
·
.. ·
.,
'
because they were usually at high elevation.
In spite of the high intercorrelations among
independent variables, there is fair evide.nce
that seasonal moisture distribution and
April-May temperatures are fairly well cor­
related with growth differences.
Surrival
-----
---- - ____,
Present differences in survival largely re­
flect early mortality and are, of course, con­
founded to some extent by natural mor­
tality associated with stand density and
growth rates. Kempff ( 1928) and Mun­
ger ( I 94 7) summarized early records. In
our study some attention was directed to­
ward possible differences in survival due to
seed source.
We attempted a statistical analysis of sur­
vival data for four areas in the Oregon­
W ashington study. Data for the Pack area
could not be used because replanting was
done to replace mortality. Records on the
remaining test areas (McDonald, Wind
River, Deschutes, and Whitman) were
suitable for an analysis of variance (Table
6). This revealed differences in survival
by seed source (significant at the 5-percent
level) ; the genetic component of variance
for this trait was estimated to be 39 percent.
Survival proved to be positively related
(r = 0.79) to present mean heights, which
in turn probably reflect differences in
Vigor of trees at the early age when greatest
mortality occurred. A consequence of this
tendency for poorer survival among slow
growing provenances is a more conserva­
tive estimate of racial differences in height
growth. The top one-third component
would represent fewer of the original trees
planted in slow-growing, poor-surviving
groups, and hence, would favor them in
comparison with groups having high sur­
vival.
Smaller variances would also be
expected in low surviving provenances
(Fischer 1949).
Dillerenees in Diameter oncl Volume Growth
Stem diameters differ among races in
much the same pattern as heights. These
differences do not vary as would be ex­
pected from spacing caused by differential
mortality. The pattern of survival (Table
6) has been such that the slower growing
races have generally sustained the greatest
mortality and now have the most growing
space. However, they have shown no
strong tendency to produce larger average
diameters as a result of their present great­
er spacing.
Tallest races generally have the largest
average diameters and shortest races the
smallest diameters. In the Northern Idaho
TABLE 6. Survival of trees in the Oregon-Washington study by planting sites, 1946.
Locality of
seed origin
McDonald
Pack1
Planting sites
Wind River
Deschutes
Whitman
Percent
Steilacoom
Willamette
Eldorado
Bitterroot
Rogue River
Deschutes
Lassen
Carson
Cocon ino
Harney
Means
62.0
24.5
63.1
72.1
36.4
32.4
25. 9
89.4
86.2
1 6.0
37.0
3.4
17.0
94-.0
94-.7
99.1
8 1 .2
.8
90.0
100.0
25. 5
87.0
88.6
1 00.0
76.0
92.6
85.3
88.6
93.6
67.8
68.0
1 3.8
2 1 .0
39.3
20.9
1 8.1
37.2
36.0
20.3
6.9
51.I
3.2
8 1 .2
2 1 .2
2.427.0
.8
20.9
6.0
26.7
7.7
1.0 .2 1 .6
9.4-
1 High values reflect replanting done to replace early losses at Pack. This was not done at
other sites.
15
TABLE 7. Diameters at breast height (inches) of trees 30 years from seed in the Orego,._
TVashington study by plantation sites.1
Locality of
seed origin
Steilacoom
Willamette
Eldorado
Bitterroot
Rogue Rh·er
Deschutes
Lanen
Carson
Coconino
Harney
Planting sites
McDonald
11.2
6.6
14.0
7.4
7.7
7.4
4.8
7.0
s. ;
3.7
7.ll
Means
Pack
Wind River
.
Deschutes
Whitman
Mean•
6.2
5.2
6.4
5.2
5.4
5.2
3.9
3.0
4.5
3.3
6.0
5.8
6.7
6.2
6.3
5.1
5.0
5.6
5.4
4.6
2.3
3.5
1.6
4.8
2.9
2.6
2.9
0.6
1.8
1.0
8.9
7.4
9.4
7.6
9.6
6.8
8.7
6.1
3.7
1.6
6.92
5.70
7.62
6.24
6.38
5.42
5.06
4.46
4.18
2.84
4.83
5.67
2.40
6.98
5.48
.. . ..
.
1TaIIest one·third of all trees.
TABLE 8. Average volume in cubic feet per tree for different sources in the OregonWashington stud y.1
Locality of
seed origin
Steilacoom
Willamette
Eldorado
Bitterroot
Rogue River
Deschutes
Lassen
Carson
Coconino
Harney
Planting sites
McDonald
13.8
3.8
24.5
4.8
4.9
4.4
1.4
3.2
2.0
o.s
Means
6.29
Pack
Deschutes
Whitman
Mean•
2.2
1.6
2.7
1.8
2.0
2.0
0.7
0.6
1.0
0.5
2.0
2.4
2.9
2.6
2.8
1.7
1.3
1.6
1.6
I.I
0.1
0.4
0.1
0.7
0.3
0.2
0.2
0.1
0.1
0.1
3.5
4.5
5.2
3.4
5.2
3.0
4.0
1.7
0.7
0.1
4.24
2.54
7.07
2.66
l.06
2.25
1.52
1.44
1.10
0.45
1.51
2.01
0.22
3.14
2.63
Wind River
1Ta1Jest one-third of all trees.
study the average height growth among the
nineteen sources accoU.nts for 73 percent of
the variation in diameter growth ( r :....
0.85). For the Oregon-Washington study
(Table 7) the correspondence is about the
same. The pooled correlation coefficient
(r = 0.83) indicates that 69 percent of
the variation in average diameter follows
.differences in height growth of the ten
sources on the five plantations.
Results from an analysis of variance on
diameters of races in the Oregon-Wash­
ington study (Table 7) were very similar
to results from the same analysis for height
growth. Seed source differences were high­
ly significant (F ratio = 4.34, significant
at I -percent level with 9 and 36 degrees of
16
freedom). An estimate of the genetic
component of variance for diameter growth
indicated that 40 percent of the variation
in diameter growth within a plantation was
attributed to seed source differences, which
corresponds closely to the estimate made
for height growth, namely, 36 percent.
Volume of the average tree in the Ore­
gon-Washington study emphasizes seed
source differences even more. Such differ­
ences (Table 8) are about 50 to 1 between
the Eldorado and Harney sources on both
the McDonald and Whitman plantations,
but differences greater than 2.5 to 1 are
found between some sources on the other
plantations.
I
r--··----
· · '•'
"
•
-
- ---- _____..
I
I
The extreme difference in variation be­
tween the McDonald and Deschutes plant­
ations makes the data unsuitable for an an­
alysis of variance because variances are not
homogeneous. After transformation, how­
ever (in this case the logarithms of the vol­
umes were analyzed), the effect of seed
source is once more highly significant and
the genetic component of variance was
found to be 44 percent.
The observation that diameter and vol­
ume follow the same pattern as height dif­
ferences of the races adds an interesting
facet to the question of spacing and incre­
ment. The expected tendency for the
shorter races to produce larger diameters
and thus produce about the same volume
per acre is not strongly evident. Tallest
races tend to have greatest diameters and
volumes as well. The outcome of variable
spacing within each race from unequal mor­
tality is even more pertinent since distribu­
tion of the same volume on fewer stems
would be expected as stocking decreased.
However, on every plantation those races
that average the tallest and largest trees
generally have the reverse-least mortal­
ity and heaviest stocking. This observation
suggests a need for caution in the design
and interpretation of spacing studies, since .
inherent. growth rates apparently set limits
on the ability of the tree to use extra space.
Animal Dama9e
.
,,; .
Rabbits, deer, and porcupines have shown
different preferences for plants of different
sources in the Oregon-Washington study.
The first thorough record" was made by
P. M. Covington in 1933 on the Pack
area; he examined all trees and compiled
the percent cutting of terminal buds and
stripping of branches, which apparently had
been done by rabbits. In 19 51, Sowder
and Dahms recorded all fresh damage by
porcupines at the Whitman site. Browsing
11n the l 928 examination report for the
Whitman site appears th.is note by Kolbe and
Furst: "Grazing is most severe in the Coco­
nino, Rogue, and Eldorado. Deschutes and
·Harney had the least grazing damage."
by deer on the Deschutes area was sampled
1956 by Sowder and Silen. Finally, a
record of all trees found damaged by por­
cupines over the period of the study was
made on the Whitman and \Vind River
sites in 1959.
The preference patterns of animals that
browse the foliage (rabbits and deer) are
strikingly similar. Figure 4 lists the races
in descending order of preference accord­
ing to percent damaged. This percentage
varied considerably between the 1933 ex­
amination of damage (presumably rabbits)
at Pack and the 1956 record of deer dam­
age at Bend. However, on both lists the
positions of the Coconino and Eldorado
races were in the highly damaged group,
the Steilacoom and Lassen races fell into
. intermediate positi0ns, and Deschutes, Car­
son, and Bitterroot races were lightly
browsed. The relationship of the two sets
of data is below statistical significance (r =
0.29) because .of the reversals in position
of the Willamette and Harney races. The
I 00 percent sample of the Pack plantation
in 1933 was based on large numbers of
small trees, all easily browsed ; hence it is
the more reliable set of data. At Deschutes,
the Willamette race was generally so tall
that only lowest branches of the crown
were within reach of deer. The Harney
plot has so few small survivors that the sam­
ple is questionable. Without these two races
the relation is highly significant (r =
0.81 ) .
Porcupine damage follows a different
and clearer pattern. Two observations are
compared in Figure 4. Porcupine damage
was not noted at the Wind River site be­
fore 1957, whereas damage has . been re­
peated over the years at the Whitman site.
Thus it was interesting to compare the
pattern of damage developed at Wind Riv­
er with that at Whitman. Note that the
Rogue, Willamette, Carson, Deschutes,
and Lassen sources fall in the same relative
position in each list. The relationship of
percentage damaged in the two lists is high­
ly significant (r = 0.81).
Considering that at each site the com­
pared observations were years apart and in­
in
17
I
------- ----- -- ------ -----
volved animals' habitats as different as
those of the Douglas-fir and ponderosa pine
types, the similarities are all the more strik...
ing. These data strongly suggest genetic
differences between races as well -as a taste
preference by animals, such as Bates sug­
gested earlier (Bates l 927a, Leopold
1936).
Frost Injury
Frost injury has been reported in many
observations to v ry greatly among trees
according to seed origin. Kempff ( 1928)
presented data on the amount of severe or
fatal frost injury resulting from an extreme
sudden drop in temperature in December
1924 on the Northern Idaho plot. This
freeze killed all the Shasta and many of the
Siskiyou trees. Kempff's data were used
RAB B I TS
DEER
PACK
1933
DESCHUTES
1956
20
Eldorado
91
Coconino
to correlate the extent of damage with cli­
matic variables of the seed source localities.
A logical factor is seasonal temperature va­
riation, presuming that races are adapted to
the extent of variation in their native locali­
ties. The difference between mean July
and mean January temperature was used
as a measure of this variation (Tables 1
and 3). These values were used in a sim­
ple correlation analysis with the "percent
of severe or fatal frost injury" given in
Kempff's Table 4. The result was a high­
ly significant correlation coefficient (r =
-0.70). Sources that suffered most sever­
ly from the frost were usually from locali­
ties having least seasonal variation in
temperature.
The extremely damaging frost in No­
vember 1955 (Duffield 1956) once again
PORCUPINES WHITMAN
1928-59
67
57
"
Coconino
'i:
II
Willomelfe
a.
9
Steilacoom
5
Lassen
•
0
Deschures
Horney,
Corson
Billerroaf Rogue
56
Eldorado
46
Harney
21
Lassen
Steilacoom
Rogue
J
c"""
Billerroat
H
0
Deschutes
Willamette
'"''"''
Hor!t!!v
!Willamette!
34
33
Bitterroot
Coconino
S1eitocoorn
23
17
17.7
18
I
I
I
'
\Rogue!
I Carsanl
I Deschutes\
I Lassen!
16
!Willamette!
40
34
!Carson.I
Eldorado
20
17
II
8
Bitterroot
•
Horney
a.om
Evidence of differences in preference by tmimals for certain ;eed sources is shown by
percentages of trees damaged in the Oregon-Washington Jtudy. On the left, the same sources
(boJreJ) were prefe"ed or reiected premtlUIDly by rabbits at Pack plantation as by deer at
Deschutes 23 year; later. On the right, -porcupine recently showed same orJer of peference at
Wind Rir1er for five seed sources (boxed) as 4J tke Whitman site O!ler a 32-year period. (Per­
cent scales are adjusted to egual length to facilitate comparisom.)
F1cuRE 4.
I
I
Eldorado
42
41
27
WINO RIVER
1957-59
I
l.1
•
------ · - - · · - ------ ·-----
- · ···
-----·
- - - --····---
J
emphasized inh_erent differences in resist­
ance to frost. Some frost damage occurred
on all sites in the Oregon-Washington
study, but it was greatest on the low eleva­
tion sites. Over the five plantations in this
test, severest damage consistently occurred
to the Eldorado and Ste11acoom trees;
needles were generally damaged, and much
mortality has appeared since the 1956 re­
measurement in the low elevation planta­
tions. The Willamette, Deschutes, Lassen,
and Coconino sources also showed needle
damage, but little permanent injury. The
Rogue, Bitterroot, Carson, and Harney
sources showed little or no effect.
Needler
Weidman ( 1939) studied several charac­
teristics other than growth and survival.
His observation that trees from the north­
eastern portion of the species range were
typically two-needled rather than three­
needled is completely confirmed by the
Harney trees in all five Oregon-Washing­
ton plantations. He also presented strong
evidence of heritable differences in needle
length, the general appearance of the foli­
age, and internal structure of needles,
showing they followed a geographic pat­
tern as well. Westem and northern sources
had long needles with little hypodermal
thickening. Trees originating from the
eastern and southern parts of the range pos­
sessed short needles with heavy hypodermal
thickening; intermediate sources usually
graded between. Recent measurements
made by R. Z. Callaham (reported in a
personal communication) on trees of the
Oregon-Washington study confirm these
results with only one exception. The Co-.
conino and Carson sources had varying
numbers of hypodermal layers rather than
having a consistently heavy hypodermal
thickening.
Further analysis of Weidman's data on
needle length and an analysis of the relation
of needle length to growth potential proved
very interesting. His data included average
length of needles for native trees at each of
the parent localities as well as for trees at
the Northern Idaho plantation. First, the
--
correlation between these two variables was
computed and found to be 0.64, highly sig­
nificant. This statistically verified Weid­
man's conclusion on the inheritance of
needle length as mentioned above, and pro­
vided a measure of the strength of the rela­
tion. Then, using available data from both
the Northern Idaho and Oregon-Washing­
ton tests, various correlations of mean tree
heights by sources with needle length were
computed (Table 9).
Data on needle length were available
for only two plantations of the Oregon­
Washington study-Deschutes and \Vind
River. All data used in the above correla­
tions were current, except for those on
needle length in the Northern Idaho study ;
these _were taken from Weidman.
The correlations in Table 9 suggest the
possibility of using needle length measure­
ments as one criterion in selecting individ..
ual trees or races of trees for growth po­
tential.
Stem form
Weidman showed differences in stem taper
among trees of different sources in the
Northern Idaho study. Large differences
were still apparent in 1 956 (Table 10).
The Helena and Harney trees are not as
slender, relatively, as they were earlier; but
the Siskiyou trees have become more slen­
der. The poor taper reported earlier for the
Siskiyou trees may have been due to severe
TABLE 9. The correlation between aver­
age height of trees in various plantations
and fJ'1Jerage needle length of trees in the
same source in various plantations.
Heights at:
Needle
lengths at:
Northern
Idaho
Northern
Idaho
Deschutes
Wind River
Alt plantations
All plantations
Northern
Idaho
Parent
locations
Deschutes
Wind Rh•er
Deschutes
Wind River
Correlation
coefficients
0.8 1 **
0.59**
0.54 N.S.
0.72*
0.79**
0.89**
*Significant :i.t 5 percent level ; **significant at
percent level.
19
frost injury in 1924 to trees of this source.
Contrasts between stocky and slender
races in the Oregon-Washington study are
even more striking, and are quite consistent
from site to site. Analysis of variance of
the estimated heights of 6-inch diameter
trees on all sites in the Oregon-Washing­
ton study (Table 11 ) shows a significant
difference in stem form by races; the ge­
netic component of variance was estimated
to be 2 7 percent. The Willamette and
Steilacoom races show the greatest changes
in ranking because of their high site inter­
action. If their contribution to the varia­
tion is removed, the genetic component of
the remaining races is increased to 5 I per­
cent with a highly significant pattern to­
ward slender races (Rogue, Deschutes, and
Bitterroot) and stocky races (Lassen and
Carson) .
Growth Periodicity
Racial differences in starting of cambial
and shoot growth have been sporadically
investigated in both studies. Daubenmire
( 1 95 0) studied the dates of beginning and
end of cambial activity of 14 of the sources
in the Northern Idaho study. Date of ces­
sation of cambial activity varied consider..
ably from tree to tree within individual
sources. However, in analyzing the data
(approximated from bar diagrams) given
in his report
"7 we found that mean differ-
TABLE 10. Atparent past and present
differences in stem toper among trees of
different sources, Northern Idaho study.
Steilacoom
WiJiamette
Eldorado
Bitterroot
Rogue River
Deschutes
Lanen
Canon
Coconino
Harney
Means
l inchrs d.b.h.
in 19391
Siskiyou
Sha1ta
HQise
Pavette
Whitman
Umatilla
Colville
Kaniksu
Lolo
Bitterroot
4.000 feet
S,000 feet
7,200 feet
Coconino
Santa Fe
Helena
Custer
Hamey
Roosevelt
San Isabel
Ashley
7 inches d.b.h.
in 19S6•
12.S
46
13.5
13.S
1 3.0
14.0
14.0
14.0
15.5
43
42
40
47
4!
45
so
l l.O
1 5.0
14.0
12.0
12.0
16.0
15.!
14.0
13.0
13.0
12.0
4
••
41
36
31
46
4<i
37
36
39
34
1 Read from free-hand hroit"ht/diameter curves given
by Weidman (1939, Fig. 4) .
'Read from free.hand height/diameter curves drawn
from present data.
ences in date of growth inception were
highlv significant. The Coconino (Ari­
zona) trees were noteworthy for having
started cambial growth 2 weeks later than
trees from localities near the planting site.
.,
Estimated total heighu in feet of trees 6 inches d.b.h.1
by planting sites at 30 rean
McDonald
Pack
Wind River
Deschutes
Whitman
Meant
46.0
37.3
38.S
35.6
36.2
32.0
29.0
26.l
29.2
24.0
25.1
28.0
28.7
34.0
32.0
32.0
25.S
24.S
24.S
· 28.4
24.0
32.0
25.0
28.0
30.6
31.8
23.S
23.1
2!.6
24.1
! l.6
18.6
16.0
16.l
1 8.0
16.4
!l.9
ll.O
1 5.S
!S.O
1 5.2
23.2
20.0
24.0
21.7
25.0
18.1
20.2
17.S
20.0
25.2
27.8
2!.6
27.6
27.7
27.4
22.4
21.8
22.S
22.3
33.4
28.3
26.8
16.l
20.S
25.0
1Read from free·hand height/diameter curves drawn from 19S6 data,
20
'
Estimated height. of trttt (feet)
Locality of
teed origin
TABLE 11. Differences in a stem taper of different sources in the Orego,,,.Washington
study.
Locality of
seed origin
... . .
· · ..
. ,. .
A clear-cut instance of difference in begin­
ning of leader growth is reported in the
Oregon-Washington study. On May 8,
1958, elongation was occurring in all the
10 sources of the Deschutes plantation ex­
cept the Coconino progeny, in which all
trees were completely dormant.
Although neither observation has been
repeated, racial differences in the date of
starting growth seem fairly certain since
the observations are in harmony with thC
findings for many other species besides pon­
derosa pine. Weidman (1939) stated that
native ponderosa pine growing in the Co­
conino locality, as reported by Pearson
(1931), began leader elongation between
May 15 and May 25, while trees indige­
nous to northern Idaho began leader elon­
gation between April 12 and May 25, or
average about 3 weeks earlier. In a white
spruce provenance test in Canada, the pe­
riod of shoot elongation was related to the
climate of the place of origin (Anonymous
1958). In Douglas-fir the racial variation
in the bud bursting date is considered
proved (Morris et al. 1957).
Reliohility of Early Growth Meo•urement1
. '
Weidman (1939 ) pointed out the danger
of relying too much upon early growth rec­
ords, mentioning specifically the perform­
ance of the Coconino source. This source
(Northern Idaho study) was about average
in height at time of outplanting and grew
rapidly during the next few years to attain
top rank. Then it slowed down and be­
came about eleventh in rank in its sixteenth
year from seed; it is now fifteenth. Simi­
lar gross changes in rank were experienced
in the Oregon-Washington study. How­
ever, such changes were the exception
rather than the rule.
For the Northern Idaho data, a test of
the correlation between mean total height
by sources at the end of their third year
after outplanting and present mean total
heights showed a small nonsignificant cor­
relation. The same was true using height
increment during the third year and pres­
ent mean total heights. Close examination
of the early records, however, indicated
that the Northern Idaho study does not
fairly evaluate early growth performance
because: (1) trees of different sources were
not all of the same age when outplanted;
(2) they were planted at different times
over the period of years between 1911 and
1917; (3) early measurements were made
on only small numbers of the trees planted
(up to but often fewer than 20 trees per
source); and ( 4) seedlings were not all
grown in the same nursery-some of the
stock was grown in nurseries of different
regions. Height measurements made in
1927 (when most of the trees had com­
pleted their twelfth growing season) agree
considerably more closely with mean
heights in 1956 (correlation coefficient
+ 0.69, highly significant). Some of the
relative changes in mean heights by sources
were due to differential frost injury in
1924 mentioned earlier. Changes since
1935 have been small and relatively un­
important.
In the Oregon-Washington study, rec­
ords were unusually complete the first 10
years after planting, and experimental con­
trol was fairly sensitive. Agreement be­
tween average heights in the nursery at 2
years and average heights in the plantations
at 30 years was very high. The pooled cor­
relation coefficient representing an average
for all planting sites was highly significant
(r = 0.85). The relation dropped sharp­
ly after planting at each site, but then began
to rise at about 5 or 6 years (Table 12).
By the time the trees were 11 years old the
relation was again strong.
Results of the Oregon-Washington study
agree closely with data from the 1929 study
in New Zealand of ponderosa pine from 13
sources (Moore 1944; see footnote 3).
Data available included mean total heights
at ages of 1, 2, 5, and 25 years from seed.
It is important to note here that the seed­
lings were transplanted in the nursery at
the end of their first year from seed and
were outplanted at the end of their second
year from seed. Correlation coefficients
21
-
Discussion
were computed as follows:
Mean height at 25 years versus: Mean height at I year (r = 0.8 1 , highly significant) Mean height at 2 years (r = 0. 1 1 , nonsignificant) Mean height at S years (r = 0.84, highly significant) Admittedly, in provenance trials where
seed is often moved great distances, the tests
must be carried through at least a large por­
tion of rotation age before final evaluations
can be made. However, the authors feel
that inability to predict later growth in the
Northern Idaho study, or the occasional
divergent performance in the Oregon­
Washington study, should not discourage
use of early measurements in other genetics
studies. In individual tree selection, for ex­
ample, where large numbers of local selec­
tions are progeny-tested, there is consider­
ably less danger of inadaptability. A pre­
liminary screening, based on careful meas­
urements of growth prior to transplanting
in the nursery may be very worthwhile.
Adjusting for or minimizing the effects of
seed weight and time of germination, as
Squillace and Bingham ( ! 958b) did,
would likely further improve the evalua­
tion.
The results show rather definite relations
of growth rate to certain geographic and
. climatic factors, confirming the existence
of ..racial differences in growth rate in
ponderosa pine. Heretofore, lack of repli­
cation in the design of both tests has neces­
sarily caused some lack of confidence in the
results. Additional proof of the existence of
heritable growth differences occurring
throughout the range of ponderosa pine,
then, is probably the most significant contri­
bution of this study. However, going fur­
ther than this, the results also shed some
light on the possible clinal pattern of inher­
ent differences in growth rate with respect
to geographic and climatic factors. This
leads to speculation on the effects of cli­
matic factors in the evolution of the inher­
ent variation.
A rather strong east-to-west gradient or
cline in growth differences was found.
This gradient, although somewhat related
to the total amount of moisture falling in
fall, winter, and spring, was most closely
related to seasonal distribution of moisture.
Trees in localities receiving large amounts
of fall, winter, and spring precipitation or
in localities receiving relatively large pro­
portions of their total rainfall during these
TABLE 12. Coefficients of correlation between average heights at age 301 and at
younger ages for 10 sources in the Oregon-Washington study.
Plan ting
site
2•
McDonald
Pack
Wind River
Deschutes
Whitman
Pooled
3a
Age from eed at time of measurement (years)
4
0.40
0.81**
.53
.51
.92**
0.85**
0.75**
.83**
.67*
.5 5
.68*
0.48**
5
6
11
20
0.8 5**
0.83**
.67*
.79**
0.91**
.56
.90**
0.88**
.61
.75*
.75*
.90**
.8 7**
0.69**
0.86**
0.86**
.51
.75*
.54
.61
0.65**
.73**
.91**
.89**
*Significant at 5 percent level; **significant at 1 percent level.
1Average heighta of tallest one third were used for the 30-year values, Values for earlier years were average
heights of all trees, leading to somewhat lower correlation coefficient! than if average heights for all trees at
30 years were used,
• The pooled correlation coeBicient is based "on average height of progenies at Jive sites at 30 years related to
seedling heights at 2 years measured at Wind River Nursery in 1928 by Westveld, Since all trees were in the
nursery at 2 years of age there are no data for individual planting sites_.
• Based on 8 instead of 10 seed sources. The Willamette and Steilacoom progenies were outplanted in the spring
of 1929.
22
.,--
-
--
·
-
-
--
-
. -.
.. ·"
_months, are inherently more rapid growing.
Although the relationship lacks a straight­
forward biological explanation, it is surpris­
ingly consistent.
· --
-- -
- -- · --'
II
I
. : ·.;;
A moderate latitudinal dine in growth
was found. Although this dine may be due
to adaptation for different lengths of day,
the results closely follow a pattern related
to temperature. In the portion of ponder­
osa pine territory east of the Cascade and
Sierra Nevada ranges, trees from the north
generally grow faster than those from the
south. However, the natural habitat of pon­
derosa pine in the outh is usually _at consid­
erably higher altitudes than in the north
(Pearson 1931). Thus, although the aver­
age annual temperatures in the north and
south may be. rather similar, the spring and
summer temperatures may be warmer in the
north. Thus, the apparent latitudinal dine
in growth in the eastern part of the range
of ponderosa pine may he more closely re"
lated to the variation in spring and summer
mean temperatures.
West of the Cascade and Sierra Nevada
ranges, no such north-south gradient is ap­
parent. Here, however, the situation is
different: the species is found at both high
and low elevations in the north and south.
In the west, within altitudinal zones, spring­
summer temperatures may be warmer in
the south than in the north. Therefore, it is
possible that trees from low altitude sources
in the south may he inherently more rapid
growing than those in the north. Of course,
when trees from the south are planted in
the north, climatic extremes may prevent
their survival (for example, the Shasta trees
of the Northern Idaho study) . Trees from
the south grow rapidly in the north if they
survive (for example, those of the Siskiyou
and Eldorado sources). If planted in a
mild climate, they are likely to do very well
(as for example, the Eldorado trees plant­
ed at McDonald) .
A moderate altitudinal gradient in
growth was also found. Trees from high
altitudes usuallr grew more slowly than
those from low altitudes. This trend was
apparent1y due to cooler temperatures exist..
ing at high altitudes hut also partly to the
fact that many of the high altitude sources
were characterized by unfavorable moisture
patterns.
In view of the apparent clinal nature of
the inherent growth differences found, one
might question Weidman's (1939) delin­
eation of racial boundaries. However, the
climatic gradients discussed are by no means
uniform. For example, such topographic
features as the Cascade and Rocky Moun­
tain ranges greatly disrupt the east-west
precipitation patterns, even though the gen...
era! trends hold. Hence, it is not suggested
that the growth trends are uniform. Rath­
er, tliey likely would tend to follow the
disruption in climatic patterns.
The apparent superiority in growth rate
of trees in the Eldorado locality over those
in the Lassen may he due to a disruption
of the climatic pattern by mountain masses.
Both localities are "western." The Eld°'"'
rado is west of the Sierra summit, and the
Lassen slightly east of it. In addition, the
Trinity Mountains, with peaks more than
8,000 feet high, lie west of the Lassen area.
The Lassen locality, lying in the climatic
shadow of two major ranges, is unique
among the "western" _ localities in having a
thoroughly continental climate. Other devi­
ations from the climatic patterns, such as
thQse exhibited by the Payette, Helena, and
Ashley source localities, might be ration­
alized in the same way.
Weidman's boundaries delineated chiefly
on the basis of precipitation types, often fol­
low major topographic features. Whether
ponderosa pines growing in the different
regions should be Called "geographic races"
is largely an academic question of termi­
nology beyond the scope of this report.8
The important point is that much of the in­
herent growth variation seems to be associ­
ated with variations in specific climatic fac­
tors, which are characteristically continuous
8For a discussion of this question as it per­
tains to inherent variation in Scotch pine (P.
syf'lJestrls L.), see recent publications by Wright
and Baldwin ( 1 957) and Langlet ( 1 959).
23
rather than discontinuous. Further, because
of variation in climatic patterns and topo­
graphic features occurring locally within re­
gions, secondary clinal variations may often
be present within the regions. One exam­
ple is the elevational dine found by Mirov
et al. ( 1 952) in California. A recent re­
port by Callaham and Liddicoet ( 1 96 1 )
sheds more light on this subject.
It is of more than mere academic interest
to speculate as to how the inherent growth
variation may have evolved. In the south­
eastern portion of its range, ponderosa pine
is found mainly at high elevations where
spring-summer temperatures are relatively
cool and where precipitation from Septem­
ber through June is rather low. Heavy
summer rains here apparently are not con­
ducive to height growth (Pearson 1 9 5 1 ) .
Spring growth begins late, usually after
springtime rains have ceased. In most years
seedlings do not begin to germinate untJ1
July or August, while in the north and
west germination occurs in spring (Pear­
son 1 95 1 ) . Droughts of a long-time cyclic
nature are more common in this region
than in the northern part of the species
range (Chapline and Cooperrider 1 9 4 1 ) .
These rather critical conditions probably
favor traits such as drought resistance more
than rapid growth rate in producing the
best adapted type. In the northeastern part
of the range, extremes in seasonal temper­
atures prevail ; fall and winter precipitation
is very low; and prolonged droughts occur.
Hence, the situation in respect to natural
selection here is the same as in the south­
eastern part.
In the north-central region, although
the spread between winter and summer
temperatures is large, spring-summer tem­
peratures are relatively high and adequate
precipitation occurs during fall, winter, a,nd
spring. Natural selection here probably
favored rapid growth more strongly than
in the eastern and southeastern parts of the
range. The warm climates of the west
coast, where soil moisture is plentiful for
spring growth, present a maximum oppor­
tunity to select for growth rate, and appar­
ently have caused the evolution of the very
rapid growing, though least frost-resistant,
trees. Physiological studies like those briefly
reported by Callaham ( l 960b) will help
test these hypotheses.
..
... ...'
It is quite apparent that at least some
part of the geographic patterns, if not the
climatic pattern, of inherent differences in
-growth rate found for ponderosa pine -are
repeated for Douglas-fir.
Data provid­
ed the authors by P. G. Haddock in a per­
sonal communication cover two proven­
ance tests of Douglas-fir begun in 1948.
One of the replications is at Wind River.
Already trees from the southern and east­
ern part of the species' range are displaying
markedly slower growth than those from
the western part of the range. The pat­
tern is apparent also from the extensive
provenance studies in Denmark (Lundberg
1957) involving many seed sources from
British Columbia, Oregon, Washington,
Idaho, Montana, and northern California.
Both north-to-south and west-to-east gradi­
ents in height growth corresponding to
those found for ponderosa pine are readily
apparent in the data. Thus the trends re­
ported here are supported by trends in an­
other species having a closely corresponding
geographical range.
An original question foremost in both
studies: "Can benefits be gained from
choice of seed from non-local sources? n
still cannot be answered directly. Is the
"local seed source rule" as discussed by Cal­
laham ( 1 960a) a good general policy?
Inherent growth rates, as separated from
other features of adaptability, are clearly
different among the races studied. Substan­
tial increases in growth rate over local
planting stock seem possible over much of
the ponderosa pine range. These studies
have attempted to identify the particular
climatic factors that seem to be linked with
faster inherent growth rate. Learning
whether these factors apply on a local level,
or only to the species-wide seed collections
studied, will require more intensive studies.
The fact that the tallest progeny group on
each plantation of these studies was "nonlo­
.
.
. '
--· ...
•
24
·
-�-----
cal" was likely a reflection of inherent
growth differences. But lack of replication
on test sites, coupled with a lack of truly lo­
cal sources in the study prevent conclusive
·
.
comparisons of the performance of non...
local versus local sources within a specific
are_a.
- -- - - -
---'
. ,.
..
Moreover, growth rate cannot be di­
vorced from other features of adaptability.
Numerous other traits contribute to sur­
vival value such as frost, browsing, and
snow resistance mentioned in this study.
Where clinal or ecotypic adaptation to the
environment has occurred, the rates of
growth exhibited by local trees probably
represent a feature associated with its long­
term survival in its native habitat. Hence
some risks of poor adaptability accompany
all movements of planting stock. Possible
gains in growth must be weighed against
possible risks of poor adaptability. As yet,
neither . gains - nor risks are understood very
well. The only certainly adapted stock is
the local stock. But as understanding
grows, moderate risks will probably be ac­
cepted for moderate gains as they are in
agriculture.
For purposes of future genetic studies in
ponderosa pine, these investigations point
toward possibilities of breeding toward spe­
cific growth rates, stem taper, survival, and
resistance to frost and animal damage.
Summary
. ;. , ;;.
Data from two ponderosa pine provenance
studies conducted in northern . Idaho ( 45
years old) and in Oregon and Washington
( 30 years old) were analyzed in detail.
The results verify apparent differences in
growth rate found earlier and correlate
these differences with various geographic
and climatic factors of the seed source lo­
calities. The two studies sampled nearly
the entire range of the species. In the
Northern Idaho study, trees of 20 sources
were planted at one locality while in the
Oregon-Washington study trees of ten
sources were planted in five localities. A
major fault of the design of both tests was
-----·-·---- ..----·­ -
- ---
-
a lack of replication at planting sites. Haw­
ver, by relating growth differences to geo­
graphic and climatic factors of the seed
source localities, effects of the faulty design
were alleviated.
Results proved that inherent differences
in rate of height growth exist among trees
in various regions of the range of ponder­
osa pine. Approximately 36 percent of the
vari3tion in total height among trees with­
in a plantation was found to be due to seed
source. Growth rates seemed to increase as
clines going from east to west, and from
south to north in the eastern portion of the
range of the spedes. Evidence of an alti­
tudinal cline, with increasing growth rate
going from high to low altitude was also
shown. No strong latitudinal effect was
apparent in the west.
Among several climatic variables of the
seed source localities, height growth of
progenies was most strongly correlated
With the following: moisture distribution
(expressed by September-through-June pre­
cipitation as a percent of annual) (r =
0. 54 to 0.81) and mean April-May tem­
peratures (r = 0.37 to 0.82). Growth
was also correlated with absolute Septem­
ber-through-June precipitation (r = 0.36
to 0.73), but to a lesser extent than the
relative measure. The fastest growing
trees were mostly from localities having
high proportions or absolute amounts of
September-through-June precipitation and
high April-May temperatures. The strong
longitudinal dine was largely associated
with moisture distribution, while the alti­
tudinal and latitudinal dines were largely
associated with April-May temperatures.
It was speculated that the characteristic
of inherent slow _growth in the eastern and
southeastern parts 0£ the species' range
largely resulted from an adaptation to rela­
tively cool spring-summer temperatures and
high summer rainfall with relatively little
precipitation in the fall, winter, and spring.
Under these conditions seedlings germinate
late, and trees are also late in starting spring
growth. In the northeast habitats, low fall
and winter precipitation at low a1titudes
25
and cool spring temperatures at high alti­
tudes restrict growth. The possibility is not
ruled out that the slow growth may be
linked to increased resistance to prolonged
drought. In the optimum conditions of the
extreme west and northwest, natural selec­
tion possibly favors growth rate to a: great­
er degree than in the more critical climates
of the east.
Some rapidly growing trees may fail
completely in extreme environments. Liin­
ited data showed that the spread between
July and January mean temperatures may
he- a fair indicator of frost resistance-trees
from localities having greatest tetnperature
extremes were found to be more resistant
than those from habitats having less vari­
ation in temperature.
Inherent differences among the seed
sources were also shown for diameter
growth, volume growth, stem taper, sur­
vival, browsing preference by wild animals,
onset of cambial growth, and needle length.
A moderately strong correlation (r =
0.64) was shown between average needle
length of trees on the plantations and aver­
age needle length of trees growing in their
corresponding native habitats. Similarly,
rather strong relations (r = 0.54 to 0.89)
between needle length and height growth
rate were shown. A study of the reliability
of early measurements led to the conclu­
siOn that, with careful experimental or sta­
tistical contrM- of environmental factors,
early evaluations may be useful in progeny
testing of local selections.
4.NONYMous. 1 9 5 8 . Forest tree breeding at
the Pctawawa Forest Experin1ent Station.
•
Canada Dept. Northern Affairs and Nat.
Resources. (Presented at the Tenth Inter­
national Congress of Genetics) 5 pp.
C. G. J927a.
J. For. 2 5 : 6 1 0.
Varietal differences.
----- .
1 927b. A vision of the future
Nebraska Forest. J. For. 2 5 : 1 030-1 040.
CAt.J.AHAM,
1959. Attitudinal races of
R. Z. 1 960a. Selecting the prop­
er seed source of ponderosa pine. Proc. Soc.
Am. For. 1959: 26-27.
----- . 1 960b. Geographic variation in
Proc.
METCALF. Pinus ponderosa confirmed. J. For. 5 7 : 500-502. ----,- and A. R. L1nn1coET. 1 9 6 1 . Altitudinal variation a t 20 years in ponder­
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1 94 1 . Climate and grazing. CJin1ate and
Man.
In
i
Yearbook, U. S. Dept. Agric.,
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DAUBENMIRE) R. F.
1950. A comparison of
season of ca1nbial growth in different geo-­
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1 1 2 : 1 8 2-188.
DUFFIELD, J. W. 1956. Damage to western
Washington forests from NoYember 1 9 5 5
cold wave. U. S. Dept. Agric., Forest Serv.,
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Sta. Research Note 1 29. 5 pp.
Ecuo1.s, R. M. 1 9 5 8 . Variation in tracheid
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of Scotch pine. Yale Univ., Sch. For. Bull.
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FISCHER, F.
1 949.
Ergebnisse van Anbau­
versuchen mit verschicdenen Fichtenher­
klinften (Picea abies (L.) Karst) (Results of
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proveniences) .
Mitteil.
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Biol. Abstracts 24: 341 5 3 . 1 9 5 0 ) .
HIGGINS, J . 1927. Facts and figures regard­
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2 5 : 1 023-1030.
KEMPFF, G. 1928. Nonindigcnous western
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Northwest Sci. 2: 54-58 .
LANGLET, 01.oF. 1959. A cline or not a cline
-a question of Scots pine. Silvae Genetica
8 : 1 3-22.
LEOPOLD, A.
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-----, and
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i
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·i
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26
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-
27