Progressive Tree Improvement Program In Coastal Douglas-fir Roy R. Silen and Joseph G. Wheat
ABSTRACT-Since it began in 1966, the "progressive"
system of tree improvement has been applied on 18 million
acres of the Douglas-fir (Pseudotsuga menziesii [Mirb.]
Franco) region. It departs markedly from earlier practice,
needing no grafted seed orchard. Its flexibility, low cost,
minimal needs for skilled personnel, and large genetic base
attracted landowners who were reluctant to invest in grafted
orchards, which were then beset with many problems. The
early adoption of a second phase, involving crossing of all
parent trees and establishment of seedling seed orchards,
has accelerated the region toward widespread use of
second-generation seed about 15 years earlier than origi­
nally anticipated.
Other than an initial research note (Sileo 1966),
there has been no formal documentation and little pub­
licity covering the most widely used tree improvement
program in the coastal Douglas-fir region. The pro­
gram was proposed by the senior author in 1966 and
was accepted that year by the Industrial Forestry As­
sociation. Under the Association's sponsorship, most
of the private forest owners in Oregon and Washington
were gradually included. The U.S. Forest Service, the
Bureau of Land Management, and the state of Oregon
have incorporated its basic features into their pro­
grams. Today it is applied over nearly 18 million acres.
This paper documents its features and development.
A Typical Program
The name "progressive" arises from incremental
genetic gains with each succeeding seed crop as infor­
mation about parent trees improves. Commercial seed
is initially collected directly from parent trees instead
of from a grafted orchard. Main basis of genetic gain is
from family selection based on a wind-pollinated prog­
eny test of all parent trees. Seed from a best parental
fraction, usually the top one-fourth, is used for plant­
ing through the first 15 years. As test results improve,
so does the choice of parents. A tandem part of the
program quickly starts a second generation, in which
progeny resulting from crossing the parents are used
for a seedling seed orchard; the aim is to furnish seed
with a second increment of improvement after 15
years. The wind-pollinated progeny test for evaluating
the first-generation parents is also used to estimate
performance of crosses for their combined contribu­
tion to the second-generation seed. For the third gen­
eration, the best individuals of best faQlilies of the
wind-pollinated progenies are to be crossed to estab­
lish an orchard and field test.
The three phases of a typical program can be
78/JoURNAL OF FORESTRY/February 1979
illustrated by an actual example. The first installation
was near Vernonia, Oregon, in 1966 on 100,000 acres
of the Crown Zellerbach Corporation; trees were 30
years old. In this example, Phase I describes activities
associated with the parent trees and their seed. Phases
II and III, subsequently described, refer in turn to
succeeding generations. The landowner has the option
of stopping in Phase I with an anticipated genetic gain
in the 10-percent range. Alternatively, he can go into
subsequent phases, each anticipated to provide addi­
tional gains of about 10 percent. The steps by year
were:
Phase 1-Seed from Parents
Year
1966 Breeding activities
Selection of 300 parent
trees, collection of
wind-pollinated seed
for progeny test
Spring 1%9 Outplanting of progeny of all parents on 9
test sites (300 families
x 12 seedlings per
family on each site)
Winter 1971, Measurement of prog1976, 1981, eny at 9 test sites
1986
Seed production
activities
Collection of commer­
cial seed from same
300 parents
First
commercial
planting of seedlings
from selected parents
Three genotypic up­
gradings of seed col­
lected from parent
trees on the basis of
test results
Phase IT-Seed from Progeny Orchards (Note that activities overlapped in time with Phase I) Spring 1971 Single-pair mating of None
original 300 parents
(150+ crosses)
Establishment of sec­
Spring 1974 None ond generation full-sib
seed orchard from
1971 matings
Winter 1977- Progressive roguing of None
79 poorest ~ of individu­
als in each family of second-generation or­
chard Winter 1980 Roguing poorest
None
(planned)
~ of orchard families
Fail 1988 Final roguing to
Initial collection of
(planned)
best 3 !.6 of families commercial seed from
second-generation or­
chard
Phase III-Seed Orchards from Progeny Crosses
Phase III would establish a seedling orchard from crosses
among progeny of the wind-pollinated test, with roguing
planned over a 15-year period as in second-generation or­
chards.
crossing of None
Spring 1989 Field
(planned)
best performing trees
in progeny test for
third-generation
or­
chard
Spring 1990 Establishing field
Establishment of third­
(planned)
test of above crosses generation full-sib or­
chard
1990-2025
Measurements and
As testing progresses,
(planned)
roguing as in second phase third-generation
generation
seed into use
In more recent examples, the time frame has been
compressed by using year-old, container-grown seed­
lings for progeny evaluations and starting the single­
pair matings earlier. If these alternatives had been
used at Vernonia, the field crossing for the third­
generation seed orchard might have been possible by
I982 instead of I989.
Departures
The program was developed because the only other
system at the time was failing for Douglas-fir (Silen
and Copes I972). Six innovations, designed specifi­
cally for conditions of the Douglas-fir region, were
included.·
I. A very localized breeding unit (generally under
150,000 acres). Unique features of the mountainous
Douglas-fir region include unusually high growth rates
of its species, despite a droughty summer climate and
substantial mile-by-mile site variation. Such a combi­
nation places a major constraint on tree improvement.
Douglas-fir, the omnipresent species, forms tall, uni­
form stands from sea level nearly to timberline. Asso­
ciated species, however, show that such uniformity is
accomplished by unusual genetic diversity. For exam­
ple, Douglas-frr competes at sea level with Sitka
spruce and at high elevation with mountain hemlock;
but neither of these wide-ranging species could be in­
terchanged. Douglas-fir from sea level or high eleva­
tions also cannot be interchanged. In fact, there is evi­
dence now that genetic adaptation to local conditions
in Douglas-fir is so precise (Campbell 1979) that each
local population probably is genetically different in
some respects from all others. Hence, to take advan­
tage of the balance of adaptive traits naturally evolved
in the local population, genetic improvement in growth
had best be limited at first to small breeding zones.
These zones were initially defined as ecologically simi­
lar units under I50,000 acres in size and with a change
in elevation of less than I ,000 feet.
ll. A much larger parent tree base (usually three
trees per 1,000 acres) than usual. The quantity of seed
needed for sustained commercial planting required a
large parental population. A large base also lessens the
possibility that any strain of a native pest can over­
come a large fraction of our plantations. Of equal im­
portance, it minimizes inbreeding and allows con­
tinued selection in subsequent generations without re­
duction to a few vulnerable genotypes.
Ill. Reliance on family selection for growth, as
evaluated primarily by genetic testing rather than
phenotypic selection. For some traits less affected by
site variation, like resistance, straightness, or form,
ample gains are expected from phenotypic selection.
Selection for growth, however, placed major reliance
on family performance in field tests rather than on
phenotypic selection.
There has been no discouragement to any
phenotypic selection level the owner wished. Several
landowners have used very intensive methods. Most
have preferred moderate intensities and confined
selection to the network of roads sampling their own­
ership.
Extreme microsite differences, mountainous topog­
raphy, differences in within-stand tree age, competi­
tive and browsing differences at early ages, and ten­
dency for individuals to be uniquely adapted make use
of comparison-tree or other selection methods very
difficult in the Northwest. This difficulty is illustrated
by the outcome of recent progeny-test data from two
landowners' selections for volume production. Each
used IOO groups of IO trees whose only qualification
was production of \4 bushel of cones. Out of each IO
trees, one was randomly chosen. In addition, the best
and second-best of the remaining trees were chosen.
Average diameters of the 8- and 10-year progeny in
inches for the three groups were:
Landowner I:
8-year
progeny
Landowner II:
10-year
progeny
Best
Second best
Random
0.823±0.007
0.826±0.006
0.826±0.006
1.405±0.012
1.398±0.010
1.402±0.010
Although greater benefits of selection may appear
when the progeny attain parent age, at present each
group is yielding about equal numbers of superior fami­
lies.
IV. Use of wind-pollinated seed for testing (rather
than seed offull-sib families). Use of wind-pollinated
seed for progeny testing was still questionable in I966.
The equivalency with an average of many outcrosses
was, however, soon demonstrated. We have several
studies in which height growth of wind-pollinated fami­
lies was highly correlated with the average height of a
number of outcrosses made with the same set of parent
trees. Many screening programs of parent trees
throughout the world now employ wind-pollinated
seed.
V. Planting of progeny tests immediately to test
each parent. Advantages of early test establishment
are obvious in maximizing gain per unit of time. As
tests on so large a scale were rare in the mid-I960s,
guidance was sought from geneticists throughout the
world. We were advised to apportion tests involving
more than I00 parents into sets of 50 parents or less to
be tested separately. Eight to twelve test sites were
recommended to properly sample a breeding zone, the
number also influenced by the difficulty of finding uni­
form sites more extensive than IO acres in mountain­
ous forestlands. A typical test of 300 parents would
require I20 seedlings to test each parent. Use of 10
sites with three replications, each containing four ran­
domly distributed seedlings of the same family, is the
most common pattern. Parents are ranked initially ac­
cording to performance over all sites. The accuracy of
the ranking at any one site is of less concern than
February 1979/JouRNAL oF FoRESTRvn9
adequate sampling for performance over the breeding
unit. Subsequently, those that perform well for certain
elevations or aspects, as determined from regression
analysis, are used for special planting situations.
VI. Immediate procurement of seed from phenotyp­
ically selected parents in the forest to meet needs of
commercial planting (rather than seed from commer­
cial collections or later from grafted orchards). The
need for commercial seed can be met from the outset
from parent trees in the forest. Selection of the top
one-fourth progresses from phenotypic to genotypic as
the test proceeds.
With equal selection intensity, the remaining distinc­
tion between parent trees in the forest and grafts in a
seed orchard is the genetic disadvantage of knowing
the contribution of only one parent. Knowing only one
parent appears to have the potential effect of cutting
usable additive variation in half. In early days of tree
improvement, this disadvantage loomed so large as to
cut out such wind-pollinated programs from further
consideration. By 1966, with a failing Douglas-ftr seed
orchard program, we were practically forced to give
such programs another look. Once we did, we found at
least seven attractions or simpliftcations of using
wind-pollinated seed directly from forest trees:
I. Seed of best wind-pollinated families col­
lected directly from the trees can provide genetic
gains in the 10-percent range.
2. Such programs are quickest and least ex­
pensive to initiate and complete.
3. Such programs provide largest base popula­
tion per unit of cost.
4. Seed is immediately available in commercial
quantity and roughly comparable in quality to
seed from orchards.
5. No seed-orchard specialists are initially re­
quired.
6. Because capital outlays occur primarily by
year 3, forestry staffs are quickly freed to con­
centrate on activities of the next generation of
tree improvement.
7. Early crossing of all parents by single-pair
matings provides seedlings for early establish­
ment of second-generation seed orchards, thus
avoiding a 15-year delay in production of
second-generation seed. (Single-pair matings be­
came part of the program in 1971. The rationale
for early crossing of parent trees is discussed
later.)
Most of these attractions are obvious, or have be­
come widely accepted, but perhaps point four needs
clarification. Advantage of genetic contribution from
both parents is not immediate in orchard seed. The
first orchard crops often receive their pollen mainly
from trees surrounding the orchard, whereas all seed
from forest parents are pollinated from locally adapted
trees. Also, the early mix of seed from grafted or­
chards is mostly from a few productive and phenologi­
cally synchronous clones. The mix from forest trees
contains reasonably uniform amounts of seed from
Table 1. Cooperative tree improvement programs, Industrial Forestry Association and Pacific Northwest Forest and
Range Experiment Station.
Test established
Programs 1
Species2
Vernonia
Molalla
Burnt Woods
Umpqua
Dallas
Forks
Snow Peak
Tillamook
Gold Beach
OF
OF
OF
OF
OF
OF
OF
WH
OF
Coquille
Mapleton
Cowlitz
OF
OF
OF
Cowlitz
Snoqualmie
Snoqualmie
Skagit
Roseburg
NF
OF
NF
OF
OF
Medford
OF
Oakridge
Totals
OF
Cooperators
OS, LF, CZ, IP
CZ, PP, OS,LF
OS, SF
BL, IP, OS
WI, BC, HF, IP
A, CZ, MR
TS, WI, CT, OS
FS,OS,PP,BL
FS, A, BL, CT,
GP, SL, C
BL, M, IP, CC
FS, CT, 01
FS, BN, MP, CT,
BC,M
FS, BN, MP
FS, BN, SA
FS, BN, SA
FS, SP, GP
FS, BL, RL, CT,
LF, SS, CD, OS
FS, BL, MD, BC,
JC, LF, OS, CM
FS,PT
1Abbreviations:
Program
size
M acres
326
103
69
582
141
72
172
130
Breeding
units
Year
started
Parent
trees
Sites
Seedlings
Area
Acres
306
19
8
20
11
Number
91,800
40,716
15,456
218,752
48,840
27,520
46,560
47,520
928
570
450
33
13
0
121,368
57,680
0
219
102
0
1976
1976
1976
1976
1976
1,770
360
540
460
980
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
18
1978
5,330
0
0
0
914
124
20
2
1978
1978
4,164
495
0
0
6,205
74
0
0
173
0
0
1,578
1
2
1
5
2
1
2
1
1967
1968
1968
1969
1971
1971
1971
1974
900
375
161
1,709
441
215
388
270
299
214
345
3
2
2
1975
1975
1976
596
125
183
132
346
5
1
2
2
2
1,332
20,506
12
9
8
40
716,212
94
36
467
112
64
107
71
A =Agnew Timber Products; BC = Boise Cascade Corp.; BL = Bureau of Land Management; BN = Burlington Northern; C = Crook Estate; CC = Coos County; CD = C&D Lumber Company; CM = Cotton and Miller; CT = Champion Timberlands; CZ =Crown Zellerbach Corp.; Dl =Davidson Industries; FS =U.S. Forest Service; GP =Georgia-Pacific Corp.; HF =Hampton Tree Farms; IP = International Paper Co.; JC =Josephine Co.; LF =Longview Fibre Co.; M = Menasha; MD = Medford Corporation; MP = Murray Pacific; MR = Merrill & Ring; OS = Oregon State Forestry Dept.; PP = Publishers' Paper Co.; PT =Pope and Talbot; R = ITT-Rayonier; RL = Roseburg Lumber; SF= Starker Forests; SL = Simonson Lumber; SP = Scott Paper; SR = St. Regis; SS = Sun Studs, Inc.; TS = Timber Service; WI = Willamette Industries. 2DF = Douglas-fir, WH = western hemlock, NF = noble fir. SO/JouRNAL OF FoRESTRY/February 1979
Figure 1. Interior view of the special containerized
greenhouses erected by the Industrial Forestry Associa­
tion to grow progeny for testing of parent trees. Over
each parent. The advantage of the contribution of both
parents to seed in Douglas-fir orchards does not occur
much before 11 to 15 years. By this time, both pro­
grams should begin phasing into use of second­
generation seed. Thus, both kinds of seed have advan­
tages and both have shortcomings.
A Regional Program
Of the nearly 18 million acres in the program, about
two-thirds are on large blocks of single ownerships,
primarily U.S. Forest Service lands. About 6.2 million
acres, however, are represented by intermingled own­
erships covered by cooperative programs. Early
events shaped a pattern that was to become an or­
ganized regional activity.
The first was the establishment of cooperatives (ta­
ble 1 ).. In 1966 the Crown Zellerbach program for
northwest Oregon was viewed with high interest by
neighboring landowners. Before the excellent 1968
seed year, the state of Oregon and Longview Fibre
Company had decided to participate in similar pro­
grams. At the urging of the authors of this paper, a
single plan for three ownerships was accepted. In
northwest Oregon each organization owned about
100,000 acres of intermingled forestlands. By pooling
plans, each contributed 300 parent trees to form a
900-parent base population. A fourth cooperator, In­
ternational Paper Company with 30,000 acres, joined
too late to contribute parent trees. Each of the four
developed three sites for a test of the 900 parents.
1,500 parental lots have been grown yearly since /972 and
distributed to 173 outplanting sites.
Under no circumstances could any of the owners
have then carried such a comprehensive program
alone. Yet costs were comparable since each owner
was selecting the same number of trees and testing
with the same number of progeny as before. The main
difference with a 900-parent base was the assurance
that not only would the landowner use the best of
known parentage on his own lands, but also share in
the best on his neighbors' land. Thus, at its inception
the tree improvement cooperative became a hallmark
of the progressive program. In the decade which fol­
lowed, 16 additional cooperatives were formed, each
independent yet integrally meshed by common land
ownerships and by uniform technical guidance from
the two authors.
A second early development was a regional center
to grow progeny for testing. The first test seedlings
were produced in nurseries. With the need to grow
more than 5,000 parent-tree seed lots collected from
the 1971 crop, the Industrial Forestry Association
constructed greenhouses at NisquaUy, Washington,
with annual capacity to grow 1,500 progeny lots in
containers (fig. 1).
The third event was the coordination of program
guidance. For a typical program, the two present auTHE AUTHORs-Roy R. Silen is principal plant geneticist,
USDA Forest Service, Pacific Northwest Forest and Range
Experiment Station, Forestry Sciences Laboratory, Corvallis,
Oregon. Joseph G. Wheat is director, Tree Improvement Labo­
ratory, Industrial Forestry Association, Olympia, Washington.
February 1979/JoURNAL
oF
FoRESTRY/81
thors jointly propose a basic plan that spells out the
cooperators' acreages, breeding units, division of par­
ent tree numbers, and test sites. The exact design of
the test usually is an activity of the Pacific Northwest
Forest and Range Experiment Station; advances in
methodology are incorporated into each succeeding
program. The Industrial Forestry Association
provides coordination and guidance, and grows the
test seedlings. Scientists of the Pacific Northwest Sta­
tion's genetics project have assured that best research
information is applied. A considerable portion of the
project's research arises out of field problems encoun­
tered by cooperators.
The fourth development has been an informal re­
gional organization. As individual cooperatives began
to meet regularly, we saved travel and time by setting
aside certain weeks early in the year for-general meet­
ings. Problems of each cooperative are aired before all
members, and newcomers receive advice and help.
Unsolved problems are directed toward researchers
who also attend. Outdoor meetings are held in early
summer with visits to progeny outplanting sites or seed
orchards. The result of these meetings has beena high
level of uniform regional practice in planning, test
seedling production, testing, measurement, and data
processing. Despite its scope, complexity, and con­
tinuity, the organization has no formal name.
A fifth development, the second-generation seed or­
chard, is discussed immediately below.
The Second-Phase Program
By 1971, the Vernonia Cooperative had reached a
maintenance stage. The cooperators asked, "What
next?" The outcome ofthis question was a simple plan
that will produce next-generation improved seed 15
years earlier than originally programmed.
A bumper cone crop was anticipated for 1971,
though the financial climate was bleak. Only the most
austere mating design for crossing of parents could
have any hope of acceptance. The plan proposed by
the senior author was to employ single-pair matings
(Libby 1968, 1969}--e.g., parent AxB, Cx D, Ex F,
etc., giving half as many crosses as the base
parentage-and then plant the progeny as a seedling
seed orchard. When the existing progeny test reaches
15 years, data cari presumably be used with confi­
dence. The seed orchard will then be rogued of all
crosses except those representing parents in the top
three-sixteenths of field performance, made up of
crosses representing the best one-fourth of females
and males crossed with the best one-half of the other
sex. These winning families will be allowed to interpol­
linate for production of next generation seed. The
novel feature was that the crosses were made in 1971
82/JoURNAL OF
FORESTRY/February 1979
at random, before we had any information on parental
rankings, so that both the test and the orchard could
simultaneously mature.
The members of the Vernonia Cooperative pro­
duced 499 crosses in 1971, the seedlings of which have
been established in two seed orchards in the
Willamette Valley (table 1). The initial planting, now 7
years old, is already producing some seed. Second­
generation seed production is expected to phase into
the program before 1988. Molalla, Burnt Woods, and
Umpqua cooperatives have since started second­
generation orchards on the same sites following the
same plan. The crosses can be rogued accurately on
the basis of field performance of progeny tests, but
within-family roguing may not be as exact because this
orchard is located outside the breeding zone.
Two unusual developments have occurred. One is
use of consulting forestry firms to make the pollina­
tions. Presently several such firms constitute an un­
usual regional asset, providing economical and readily
available climbing and crossing skills.
The other development has been an expanded role
for the state of Oregon in providing a second­
generation seed orchard service for cooperatives.
Large landowners, like Crown Zellerbach, Interna­
tional Paper Company, and the Bureau of Land Man­
agement, are setting up their own orchards. The state
of Oregon participates directly in eight cooperatives.
In order to provide the state's needs for second­
generation seed, a 400-acre seed orchard site was pro­
cured in the Willamette Valley near St. Paul (fig. 2).
As development began, it became efficient to simply
enlarge the acreage for each cooperative in order to
supply seed for the other, usually smaller, landowners
on a formal cost-sharing arrangement. Thus, orchards
for part or all of the landowners in the Vernonia,
Molalla, Burnt Woods, and Umpqua cooperatives
have been developed on this site. Each cooperative
breeding unit has agreed that ownerships too small to
be members will be provided seed surplus to the mem­
bers' seed needs at cost.
This second phase of the progressive program, like
the first phase, is designed toward the minimal effort
that will produce a satisfactory product. Like the ac­
cepted shortcomings of wind-pollinated seed in the
first phase, the crosses that will furnish the seed for the
second generation will not necessarily be those that
would be made with more complete data on parentage
performance in 1985. The best of present random mat­
ings will simply provide the best available seed for a
decade until seed from better matings is produced.
Even now landowners are beginning to supplement the
basic plan with additional cross pollinations to assure
progressive improvement.
Looking Ahead
The first grafted seed orchards of Douglas-fir were
installed in 1957. By 1960 there were 16 in the region,
totaling 145 acres. Thus, there was a decade of dis­
couraging experience with the more common method
oftree improvement by 1966. Had plus-tree selection
and grafted seed orchards been as inexpensive and
convenient to apply as with most pine species, there
would have been little reason for posing an alternative.
Application of grafted orchards to Douglas-fir was
neither, and the progressive approach was a welcome
alternative. Several major landowners were deeply
committed to grafted orchards before 1966, and have
continued these programs. Most of these have also
added progressive programs to expand base popula­
tions. For the uncommitted landowners, however,
there had been reluctance to take on the heavy capital
expense, and the known problems of dying grafts, pol­
len contamination, slow and unequal seed production,
and costly specialized personnel.
It was only after 1966, when there was an alterna­
tive, that most landowners committed themselves to
tree improvement. The pivotal consideration for land­
owners was that they could carry such a program
through the first phase with existing forestry staffs on
low budgets and a limited commitment.
Now, a decade later, the region can look back on an
exciting experience. Many foresters and workers who
were abruptly given the tasks of choosing hundreds of
parent trees, establishing nurseries, and measuring
complex test plantations felt this was their first inten­
sive forestry experience. Few had previously faced the
challenge of bringing every planted test-seedling
through alive. By early 1979, almost-% million tagged
Figure 2. The second-generation seed orchard site main­
tained by the state of Oregon in the Willamette Valley.
Oldest full-sib progeny are 6 years from seed. Orchards
seedlings from 5,957 parent-trees were being tested on
173 sites, with this number certain to double when the
region has another bumper seed crop. The huge ge­
netic base and small breeding zones are gradually
being recognized as safeguards against possible loss of
adaptiveness. The establishment phase is now almost
completed as the last major ownerships west of the
Cascade Range are forming into cooperatives, and
with programs under way for two other major species:
western hemlock and noble fir.
It is now clear that initial concerns over whether to
use grafted seed orchards or the ''progressive'' system
were unjustified. This is because second-generation
programs have turned out to be very similar, regard­
less of initial programs. In all programs, the best par­
ents or progeny in the testing are crossed and tested,
and the progeny used in another seed orchard. In all
programs, the sooner the crossing can be properly
done, the sooner the initial program can be phased out
in favor of seed populations from crosses of known
performance. On a large scale, the progressive pro­
gram is reaching this time goal more quickly than most
foresters expected. •
Literature Cited
CAMPBELL, R. K. 1979. Genecology of Douglas-fir in an Oregon Cascades
watershed. Ecology (in process).
LIBBY. W. J. 1968. Mating designs for second-generation selection in forest
trees (abstr.). P. II in Proc. West. For. Genet. Assoc. Meet., Corvallis,
Ore.
LIBBY, W. J. 1969. Seedling versus vegetative orchards. Pap. to FAO-N.C.
State For. Tree Improv. Train. Cent., Sch. of For. Resour., N.C. State
Univ ., Raleigh, p. 306-316.
StLEN, R. R. 1966. A simple, progressive tree improvement program for
Douglas-fir. USDA For. Serv. Res. Note PNW-45, 13 p.
SILEN, R. R., and D. L. COPES. 1972 Douglas-fir seed orchard-a progress
report. J. For. 70:145-147.
for partial or complete fulfillment of seed needs of three
cooperatives are established.
February 1979/JouRNAL oF FoRESTRY/83