Historic, archived document

Do not assume content reflects current scientific knowledge, policies, or practices. \ of DOUGLAS-FIR

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U.S. Department of A . Forest Service grrculture This publication is one in a series on the genetics of important forest trees of North America being published by the Forest Serv­ ice, U.S. Department of Agriculture, in cooperation with the Society of American Foresters. Development of this series is in accord with the resolutions of the World Consultation on Forest Genetics and Tree Improvement at Stockholm in 1963 and the Second World Consultation on Forest Tree Breeding at Washington, D.C., in 1969. The Committee on Forest Tree Improvement of the Society of American Foresters undertook the preparation of manuscripts for North American species. CONTENTS

Page RESEARCH SUMMARY ------­ 111 INTRODUCTION ------__ _ 1 THE GENUS ------__ _ 2 Taxonomy ------­ 2 Cytology ------­ 2 Ancestral Distribution ------__ _ 2 THE SPECIES IN NATURE ______3 Present Distribution ------__ _ 3 Habitat ------­ 4 Growth ------­ 5 GENETICS ------5 Crossability ------__ _ 5 Genetic Markers ------­ 5 Reproductive Development ______6 Flowering ______8 Seed ------­ 9 Variation ------­ 10 Survival ------­ 10 Growth ------­ 10 Form ------13 Phenology ------__ _ 15 Resistances ------­ 15 Physiological Variation ------16 VVood ------­ 17 Age of Trait Expression ______17 GENETIC TECHNIQUES ------­ 18 Selection ------­ 18 Growth ------­ 18 Form ------19 Phenology _------­ 19 Resistances ------·--­ 19 Cone Production ------­ 19 Controlled Pollination ------­ 19 Testing ------­ 20 Asexual Reproduction ------­ 21 Grafting ------­ 21 Rooting ------­ 22 APPLIED PROGRAMS ------·­ 22 History ------­ 22 Seed Certification ------­ 23 Seed Production Areas ------­ 23 Seed Orchards ------­ 23 VVide Crossings ------­ 24 Clonal Progra-ms ------­ 24 Progressive Programs ------­ 24 STRATEGIES ------­ 26 Sources of Variation ------­ 26 Gains ------­ 26 Adaptation ------­ 27 ACKNOWLEDGMENTS ------­ 27 LITERATURE CITED ------­ 28

i

RESEARCH SUMMARY

Douglas-fir (Pseudotsuga menziesii [Mirb.] Details of the life cycle of Douglas-fir have Franco) dominates the most productive forest only recently become complete enough that the lands of Western North America. More genetics germinal line can be followed through pollen research is being done on this species than on and seed development. Pollen is captured by a any of its associates. Tree improvement, how­ sea-anemone-like growth of the developing seed. ever, has lagged because of technical problems The species is characterized by very large, for which solutions were only recently found. round, featureless pollen grains with a me­ Evolution of the genus is relatively recent, chanically strong intine layer permitting expan­ possibly originating from Larix which it closely sion longitudinally to the 500 micrometers resembles in morphology and floral mecha­ needed to grow across a liquidless micropylar nisms. The species existed north of its present canal. No physiological or physical barriers to range in recent geological times. Present distri­ pollination are known, but embryo collapse fol­ bution of the six species of Pseudotsuga around lowing fertilization is common. One embryo the north Pacific Rim places four species in per seed is normally produced, the competitive Asia and two in North America. Only P. men­ outcome of up to nine pollen grains per micro­ ziesii has a chromosome complement of N = 13 pylar canal, four to six archegonia, and up to instead of N == 12. Only crosses between P. four cells that can contribute their chromo­ menziesii and P. macrocarpa have succeeded. somes to the resulting embryo. Seedlings with P. menziesii's latitudinal distribution from 19° chlorophyll-deficient recessive marker genes and to 55 ° N. is the most extensive of commercial yewlike mutations are reported. Polyploidy has western conifers. Most of its traits display clinal been induced with colchicine. variation along its range, which resembles an The species grafts well initially, but about inverted V. A variety, glauca, is recognized as 35-percent rejection of grafts is normal. Early applying to more continental races of the in­ recognition of anatomical symptoms permits terior arm. Maximum development occurs along two kinds of evasion techniques so seed or­ its coastal arm west of the Cascade Range and chards may now be established virtually free the Coast Ranges. The species occurs on almost of incompatible grafts. A high percentage of any moist, well-drained forest habitat in its cuttings from year-old seedlings root, but suc­ range below midalpine zones, yet it withstands cess falls off to about 20 percent for 10- to droughts of several months. Its evolutionary 50-year-old trees. Cuttings of mature trees are niche as a fire species arises from its rapid usually rooted with great difficulty. growth, tallness, durable wood, thick bark, and Genetic variation is documented for many long life, the last two traits being of minor traits. Exact adaptation to local environments breeding interest. Its rapid growth period is is suggested from many studies showing growth, preceded by a decade of slow seedling growth. phenological, and terpene differences between The older growth, soft, fine-grained wood pro­ nearby populations despite pollen exchange. In­ duction, is preceded by a long period of pro­ herent growth differences appear to follow a ducing coarse-grained wood. westwide pattern of relative assurance of ade­ Douglas-fir is monoecious. It rarely flowers quate springtime moisture. The best inherent as early as 2 years and produces only small growth has evolved in the western and northern quantities of seed the first decade. Cone crops parts of Douglas-fir's range and the poorest in are usually cyclic, causing occasional severe the eastern and southern parts. Growth ratios local seed shortages. Nitrate fertilizers and gib­ between families within local populations can berellins have been successfully used to enhance exceed 2 :1, providing impetus for practical im­ crops. Naturally harvested cones average about provement of already adapted genotypes. 16 filled seed but can range up to 54 filled seed Growth traits require one or more decades for on some trees. Only about 7-percent average adequate expression. Heritabilities of growth selfing occurs despite the majority of pollen and form have been generally moderate and being received from the tree itself. Inbreeding heritabilities of phenology, resistances, and coefficient is estimated at 0.025, leading to wood traits generally strong. estimates of 1 to 1.5 percent inbreeding depres­ Practical programs include seed orchards, sion in seedling height. wide crossings, wind-pollinated seed, and clonal

iii emphasis. Practically all programs in the Doug­ generation programs for full-sib crosses are las-fir region use locally adapted parentage. established at several seedling orchards. Varia­ Programs in other temperate forest regions tions of the commonly used technologies have involve search for adapted races. Earlier seed developed especially for Douglas-fir. Special orchard problems are now largely alleviated. A strategies have also been developed to maxi­ graftless concept, based on tests of large num­ mize efficiencies, to utilize within-stand or racial bers of parents with wind-pollinated seed, is variation, and to minimize losses from mala­ widely used in the Douglas-fir region. Second- daptation.

iv GENETICS OF DOUGLAS-FIR

Roy R. Silen 1

INTRODUCTION

In the natural forest, Douglas-fir (Pseudot­ Pinaceae is interesting. The problems of graft­ suga menziesii [Mirb.] Franco) is a remark­ ing incompatibility, pollen contamination, dif­ ably successful species. It vies with coastal ficult rooting, and inadequate cone production redwood for height supremacy among the of Douglas-fir delayed large scale improvement world's conifer s. In the droughty, fire-prone programs until recent research found ways to natural environment of Western North Amer­ avoid them. ica, it has dominated the better sites, often Geneticists must be knowledgeable of the relegating its associates, most of which are the natural role of the genetic variability they dis­ best in their genus, to ecological niches too \vet, card as well as that small portion of variability dry, cold, hot, exposed, or shaded for Douglas­ they now select to fulfill immediate needs. Thus, fir. Douglas-fir's latitudinal range is the great­ their general understanding of the species in est of any commercial conifer of Western North nature is fully as important as a knowledge of America. The success of this species suggests an its genetics. ample, complex gene pool from which natural selection has produced populations competitive and adapted for each locality in its vast range. In the managed forest, Douglas-fir is pre­ ferred for its good growth and relative free­ dom from major pests (fig. 1). Its nearly pure continuous stands on the moist Pacific slopes from British Columbia to California-the so­ called Douglas-fir region-dominate the for­ estry of Western North America. In its drier interior range it is rapidly gaining in commer­ cial importance. Its use is expanding as an introduced tree for temperate zones of both hemispheres, where appropriate races typically outgrow the native conifers (Silen 1962a). Yet, it is sometimes difficult to regenerate after harvest on the best sites it once held. Wood of fast-growing young Douglas-fir trees is strong and durable but dense and coarse grained and less workable than the soft, fine-grained old growth for which people have found more uses than any other tree. Genetically, its haploid chromosome comple­ ment of 13 instead of the basic 12 of the Figure 1.-An old-growth Douglas-fir tree. This record 1 Principal plant geneticist, Forest Service, U.S. De­ tree found near Coos Bay, Oreg., was 13 feet in partment of Agriculture, Pacific Northwest Forest and diameter and 302 feet tall. It blew down in 1975 Range Experiment Station, Forestry Sciences Labora­ (photo courtesy Bureau of Land Management, Coos tory, Corvallis, Oreg. Bay District).

1 THE GENUS

TAXONOMY The genus includes two North American separation of coastal and interior types will species (Pseudotsuga menziesii and P. macro­ probably be long maintained for botanical con­ carpa) (Little 1953), and three to five (Peoples venience, and the status of possible varieties in Republic of China 1972) Asiatic species (P. Mexico is unsettled. japonica, P. 1vilsoniana, P. sinensis, P. forestii, and P. gausseni-the last three sometimes con­ CYTOLOGY sidered a single species). Nine additional species proposed for the Pseudotsuga of interior Support for classifying the genus into at North America (Flous 1935, Martinez 1963) least six species was provided when distinctive have had little support from other taxonomists karyotypes were shown for each species (Do­ (Little 1952, Tusko 1963). erksen and Ching 1972). Karyotypic investigations of the genus show The genus is distinguished by woody cones Douglas-fir with 2N==26 chromosomes (Sax and with persistent scales and protruding, trident­ Sax 1933) to be a striking exception in the like bracts; by spindle-shaped, pointed buds Pinaceae to the basic 2N==24 diploid chromo­ resembling those of beech; by firlike or yewlike some complement. Both its coastal and Rocky narrow leaves soft to the touch ; by larchlike Mour1tain races have similar karyotype (Liv­ winged seed; and by resin blisters on smooth ingston 1971, DeVescovi and Sziklai 1975). bark that becomes furrowed and marbled with Other members of the genus, including P. cork layers as it develops. The pollination mech­ macrocarpa, have 2N==24 complement (Christ­ anism and round pollen grains closely resemble iansen 1963, Doerksen and Ching 1972). The Larix (Christiansen 1972). Its intolerance to karyotype of Douglas-fir includes 2 chromo­ shade, fire-resistant marbled bark, wood anat­ somes strikingly dissimilar to the other 11 in omy, and the appearance of its seedlings, seeds, that they appear to have terminal centromeres. and cones are also strikingly similar to larch­ Such telocentric chromosomes have not been enough to suggest that the genus Larix has observed in other species of Pseudotsuga; this contributed most to its origin, if not its direct suggests that the two somehow originated from ancestry. a 12th metacentric chromosome. The telocentric Vegetative portions of adult trees of the two chromosomes provide a potentially sensitive but American species of Pseudotsuga are similar. still unsuccessful means for verifying putative Douglas-fir cones average 2 to 5 inches (5-13 hybrids with Douglas-fir. Existence of chromo­ em) in length. Botanical distinction of P. mac­ somal aberrations (Owens 1967) and a trisomic rocarpa is based on the 31/ 2 - to 61f:z-inch (9- to (2N+l) chimera (Ching and Doerksen 1971) 13-cm) cones, the largest in the genus. The has been shown for Douglas-fir. Polyploid germinants of P. macrocarpa are like·wise much seedlings of slow growth with thick cotyledons larger and have 10 to 15 cotyledons compared were produced with colchicine in our labora­ with the 4 to 11 cotyledons typical of P. ?nenzi­ tory, but they did not live beyond the first esii. Maps of the ranges of the two species year. sho·w no overlap, nor is there any evidence of gene exchange from studies of terpene compo­ ANCESTRAL DISTRIBUTION sition (Zavarin and Snajberk 1976). For P. 1nenziesii the variety glauca (Little Origin of Douglas-fir appears geologically re­ 1953), or alternatively, the subspecies gausseni cent. Even for the genus, the oldest known (Tusko 1963), of the interior West is recognized fossil remains date to the early Tertiary period botanically as distinct from P. menziesii, the only 50 million years ago. Morphological char­ typical coastal Douglas-fir. Little lists all other acteristics of the genus have changed little. interior Pseudotsuga described for North Cones, seeds, and needles of the modern Pseu­ America as synonyms of variety P. glauca. The dotsuga can hardly be distinguished from those clinical nature of both morphological and chemi­ of its ancestors. Thus, we lack a record of most cal traits over the range of Douglas-fir and the of the evolution of the genus Pseudotsuga as variability of types in a locality (Schober 1963) well as clues to its geographic center of origin. still raise doubts about the logic of varieties or All available evidence indicates that ancestral subspecies within the species. A taxonomic North American Pseudotsuga was represented

2 through much of the present range of Douglas­ of the accompanying flora was as distinct from fir, but the range then extended considerably that of floras containing P. sonomensis as is the farther north. P. sonomensis Dorf., predecessor modern forest in which P. macrocarpa lives of P. menziesii, however, seems to have been from the modern communities of which P. an insignificant component of Tertiary forests. menziesii is a member. This suggests that big­ Two lines of evidence indicate this: Megafossil cone Douglas-fir in Pliocene already had a remains of the genus are noticeably scarce in fairly restricted range. Tertiary floras, and pollen of the genus is not Fossil remnants of Asian members of the abundant in any pre-Pleistocene pollen as­ genus Pseudotsuga have been found in Pliocene semblage kno\vn so far (Wolfe 1969). deposits of Japan (Miki 1957). Of the three In contrast to its scarcity in the Tertiary fossil species distinguished, two, P. subrotunda period, Pseudotsuga is often abundantly repre­ and P. gondylocarpa, apparently became extinct sented in Quaternary megafossil and micro­ during Pleistocene. The third species, ancient fossil assemblages, especially in the second half P. faponica, appears to have been almost identi­ of the Pleistocene Epoch. This contrast would cal in appearance to modern Japanese Douglas­ indicate that dominance of Douglas-fir in the fir. present conifer forest of the North\vest was The fossil record of Pseudotsuga in Europe is attained during middle or late Pleistocene. It scant. Krause! (1926) has attributed fossil may very well have been the time when the wood in Miocene beds of Silesia and Styria as modern P. menziesii with a chromosome coinple­ belonging to the genus Pseudotsuga. Zalewska ment of N ==13 evolved. The cyclic climatic (1961) has described cones and leaves of Pseu­ changes during the Pleistocene and the ensu­ dotsuga from Miocene deposits in western ing migrations may have favored evolution of Poland. a new species. The fossil record furnishes little information Mid-Pliocene marks the first and only time on the relationship between Asiatic and Ameri­ that P. premacrocarpa, the predecessor of can members of the genus. Migration of coastal modern P. macroca.rpa, appears in the Tertiary and interior types of Douglas-fir since the last fossil record (Axelrod 1937). The character ice age is discussed by Tusko (1963).

THE SPECIES IN NATURE PRESENT DISTRIBUTION

Douglas-fir has the most extensive latitudinal the species grows to elevations of 11,000 feet range of any North American commercial coni­ (3 355m). These trees are often in a zone above fer, from 19° to 55° N. latitude. On a map of the ponderosa pine zone and below the Engel­ Western North America, its range resembles mann spruce- subalpine fir zone, usually in mix­ an inverted V, the shorter arm extends south­ ture with coniferous associates. At the southern ward from its northern limits in British Colum­ limit of its range, Douglas-fir is confined to bia to the west along the Pacific slope into north slopes and shaded areas, but at high California and the longer arm extends south­ elevations or northerly latitudes it occupies east\vard along the Rockies into Mexico. On southerly aspects. Its eastern range terminates the Pacific slopes west of the Cascade Range or in Alberta, lVIontana, Wyoming, Colorado, and Coast Ranges, continuous stands of Douglas-fir N e\v Mexico. It occurs spottily southward occur from their northern limit on Vancouver through most of Mexico in high elevation for­ Island through western Washington, Oregon, ests. Douglas-fir grows to a markedly higher and northern California in what is called the elevation in the Rocky Mountains than at the Douglas-fir region. Elevations range up to 2,500 corresponding latitude on the coast. For ex­ feet (762.5 m) in the north and to 5.500 feet ample, at 45 ° N. latitude, it occurs up to about (1 677.5 m) in the south. Here, the species 4,000 feet (1 220 m) in the Coast Ranges and attains full development, with mature low and up to 8,000 feet (2 440 m) in the Rockies. middle elevation stands often exceeding 200 feet Whether this is a genetic adaptation or whether (61 m) in height. it reflects climatic difference is unclear. East of the Cascade and Sierra Ranges, and The detailed map of its natural range shown through the Rocky Mountains where the trees in figure 2 is from "Atlas of United States are usually under 100 feet (30.5 m) in height, Trees" (IJittle 1971). Corrections have been

3 made for British Columbia, California, Arizona, HABITAT New Mexico, and Mexico from advice of local authorities.2 Habitats of the species in Western North America are so extensive that it is more con­ venient to describe their limitations. Douglas­ fir is adapted to almost any moist, well-drained forest habitat below midalpine zones. Its lack of occurrence is usually explained by one of its relatively few limitations (Waring 1970) or by stand history. It gives way to more cold­ tolerant mountain hemlock (Tsuga heterophylla [Raf.] Sarg.), subalpine fir (Abies lasiocarpa [Hook.] Nutt.), Engelmann spruce (Picea en­ gelmannii Parry), western white pine (Pinus monticola Dougl.), and lodgepole pine (P. con­ torta Dougl.) at high elevations or northerly latitudes. It yields to more drought-tolerant ponderosa pine (P. pinderosa Laws.) and vari­ ous oaks on sites below about 25 inches ( 63 em) of annual rainfall and to western redcedar (Thuja plicata Donn), maples, alders, cotton­ wood, and other broadleafs on poorly drained sites. Sitka spruce (Picea sitchensis [Bong.] Carr.) and western hemlock predominate in the cool fog belt associated with tidal zones of the Pacific Ocean. Douglas-fir shows little tolerance for wet soils, and its anaerobic respiration system appears normally weak or inactive (Conkle 1974). As a seedling, it competes poorly with sod grasses or with overtopping broad­ leafs, such as red alder, which has replaced it on several million acres of the most fertile logged-over coastal sites. Natural occurrence of Douglas-fir is mainly Figure 2.-Natural range of Douglas-fir. determined by fire. Its thick, fire-resistant, corky bark, rapid growth, and long lifespan According to 1972 compilations of R. K. are the main adaptations that have assured Hermann, Oregon State University, Corvallis, seral supremacy in a region of dry summers over half a million acres of Douglas-fir forests with catastrophic natural forest fires. On the exist in 26 countries in Europe. There are Pacific slopes, essentially pure stands resulted plantations in France-250,000 acres (106 000 from crown fires that destroyed its associates, ha), in Great Britain-116,000 acres ( 47 000 almost all of which are thin barked, and left ha), and in Germany-110,000 acres ( 45 000 a seed source of pure Douglas-fir. Lesser fires ha). In the southern hemisphere, New Zealand resulted in a Douglas-fir overstory with a mixed has planted 65,500 acres (26 500 ha), Australia even-aged Douglas-fir and western hemlock 2,100 acres (850 ha), and Chile 5,000 acres understory. Here, the species does not usually (2 000 ha). reproduce a new stand in its own shade. Except in its youth when it is reasonably shade tolerant, Douglas-fir tolerance ranks between ponderosa pine and western hemlock (Isaac 1943). In its 2 R. Schmidt, British Columbia Forest Service; P. interior range, Douglas-fir ranks intermediate Haddock, University of British Columbia; W. Critch­ field, Pacific Southwest Forest and Range Experiment in tolerance among its associates; and lodge­ Station; R. Ryker, Intermountain Forest and Range pole pine is often the more successful fire Experiment Station; M. Haysworth, Rocky Mountain species. Without fire, even-aged stands are Forest and Range Experiment Station; and J. Frank­ gradually replaced over several centuries with lin, Pacific Northwest Forest and Range Experiment Statif n. more shade-tolerant western hemlocks, silver

4 fir (Abies amabilis [Dougl.] Forbes), or grand Beyond seedling stage, annual height growth fir (A. grandis [Dougl.] Lindl.), and western can surpass 6 feet (2m). An average of over redcedar, although individual Douglas-firs may 2 feet (61 em) can be sustained for the next live over 1,300 years (McArdle and others century on best sites, \vith periodic annual in­ 1961) to assure a high chance of species sur­ crement of about 200 cubic feet per acre (14 vival on a site. m 3 / ha). Best yields of Douglas-fir's native range, where summer droughts are common, GROWTH appear to be exceeded in countries such as New Zealand (Spurr 1961), where climates are Rotations of 50 to 100 years will use but a warmer at corresponding latitudes and summer small fraction of the species' potential lifespan rainfall is likely to be more adequate. For aver­ (1,325 years), reported height (385 ft or 126 age coastal sites, corresponding annual height m), diameter (15. 5 or 5.1 m) (Isaac and Dim­ and yield figures are 1.4 feet ( 43 em) and 140 ock 1965), or wood quality potential. The high cubic feet per acre (10 m 3 / ha) (McArdle and gro\vth rates, for \vhich the species is prized, others 1961). Young managed stands can pro­ come after a period of slow growth as seed­ duce about 30 percent more volume than un­ lings; 7 to 11 years are required for natural managed stands (Curtis and others 1973). Old­ regenerating stands to surpass breast height gro\vth coastal stands of 390,000 board feet (McArdle and others 1961). per acre (5 456 m 3 / ha) have been recorded Slo\V early growth in natural or nursery en­ (\Vorthington 1958), and volumes of over vironments probably reflects environmental 3 constraints. Seedlings can be gro\vn to 2 feet 100,000 board feet per acre (1 400 m / ha) (61 em) in height in 2 years under optimum are not unusual. Gro\vth drops markedly on nursery conditions. \Vhen constraints \vere poorer sites. Over the interior range of Douglas­ artificially removed, 8-foot-tall (2.4-m) seed­ fir, heights seldom exceed 160 feet ( 49 m) or lings were grown in 2 years (Copes and others volumes more than 60,000 board feet per acre 1969). (840 m 3 / ha) (Buell 1965).

GENETICS

CROSSABILITY

The North American Pseudotsuga macrocar­ tical use. The recessive gene for white cotyle­ pa was hybridized \Vith P. 1nenziesii (Ching dons, \vhich can be conveniently observed in 1959). Despite many trials, particularly by Orr­ dissected homozygous seed, \vas discovered in Ewing (British Columbia Forest Service) \vho t\vo unrelated trees (Sorensen 1971). Cuttings has all species of Pseudotsuga as fio\vering ar­ from these trees are no\v vegetatively propa­ boretum trees, no successful cross has been gated in several seed orchards to monitor the made bebveen the Douglas-fir and Asiatic Pseu­ proportion of stray-to-orchard tree pollen and dotsuga. Although differences in chromosome self-to-neighbor tree pollen. number is suspect in lack of success, this \vould The proportion of various marker types found not apply to crosses using P. 1nacrocarpa as in a study of 28 trees \vas estimated at 53-per­ pollen. Simpler causes may be involved. Sec­ cent yello\v foliage, 14-percent \Vhite cotyledons, tioned micropylar canals revealed that P. 'Wil­ 25-percent nonwhite cotyledonary lethals, 4­ soniana pollen expanded longitudinally only percent virescents, and 4-percent dwarfs. Most about 200 micrometers, a distance usually in­ have been found to segregate as single gene sufficient to contact the nucellar tissue. No bar­ recessive (Sorensen 1973). Piesch and Stettler riers to racial crosses of P. 1nenziesii are re­ (1971) reported additional mutant types that ported. they identified as mottled and curly, the segre­ gation ratios conformed to 9 :7 and 15 :1, and GENETIC MARKERS the expected ratios of pairs of genes sho\ved different degrees of epistasis. In addition, A number of genetic markers have been dis­ dwarfing genes have been reported from in­ covered, and one has been found to be of prac­ breeding of sl generation parents, but segrega­

5 tion ratios obtained subsequently suggest a Owens 1973) . Floral buds arise in April on low more complex inheritance (Orr-Ewing 1974). elevational trees from cells in axils of embry­ onic leaves (Owens and Smith 1964). The vege­ REPRODUCTIVE DEVELOPMENT tative shoot develops within the bud for about 6 weeks before the bud bursts, at 'vhich time Sufficient life cycle information to permit the embryonic buds are detected with a hand lens geneticist to follow the germinal line has only (Silen 1967a). Floral buds cannot be distin­ recently been published (Allen and Owens guished from vegetative buds visually or his­ 1972). tochemically until mid-May, about 10 weeks Floral bud structure and development follow­ after onset of growth (Owens 1969). However, ing initiation closely resemble Larix. Douglas­ male and female bud numbers are correlated fir normally produces male and female strobili well enough that a profusion of basal buds seen on the same twig (fig. 3). Females are subterm­ with a hand lens in April provides the earliest inal; males usually occur on the basal two-thirds practical indicator of a possible cone crop 17 of outer twigs and over the full length of in­ months later (Silen 1967a). terior twigs, although intermingling does rarely Floral buds continue to enlarge as they grad­ occur. ually differentiate from early July through No­ vember. Dissection permits certain identifica­ tion by September. By November, the larger size and non-waxy bud scales permit easy ex­ ternal distinction from the wax-covered vegeta­ tive buds. Overwintering seedcone buds contain visually recognizable trident bracts and scales with embryonic seed (Allen 1942a, Allen and Owens 1972). Floral buds burst in April, over a month ahead of vegetative flush, the females quickly becoming upright and the males pendant. Color variation from deep red to light green is a strongly inherited trait (Tusko 1963, Ching and others 1966, Copes 1972). Floral and vegetative bud burst is poorly correlated for individual trees (Griffith 1968, Sorensen and Campbell 1971). Female stobili have been found to be already receptive to pollen at bud burst and to continue so until they begin to turn down­ ward, a 20-day period. This surprisingly long receptive period provides opportunity for a tree to receive pollen from trees over a considerable elevational range in mountainous topography, which enhances Douglas-fir's potential adapta­ tion over a greater range of sites (Silen 1967c). Pollen dispersal follows a J -shaped distribu­ tion of frequency with distance from source. The majority of pollen from a tree falls within 400 feet (122m) (Wright 1952), but this is accompanied by a high level of background pollen over the Douglas-fir region in good pollen years (Silen 1962b). Enough pollen is shed even in short drying periods (Ebell and Schmidt 1964) that adequate seed set is accomplished Figure 3.- A Douglas-fir twig with megasporangiate despite prolonged rainy periods (Silen and and microsporangiate strobili at pollination stage. Krueger 1962). Pollination at low elevations occurs in mid­ The reproductive cycle of Douglas-fir for Vic­ April and advances upslope about 77 feet (23 toria: B.C., is diagrammed in figure 4 (from m) per day (Silen 1963). Anthesis and recep­

6 MEIOSIS AND POLlEN DEVELOPMENT

LEAF, BRACT AND MICROSPOROPHYLL INITIATION CONE BUDS BURST "FLOWERING" POLLINATION SEED CONES BECOME PENDANT

H FERTILIZATION POLLEN ENGULFED D POLLEN GROWTH LATERAL BUD PRIMORDIA BECOME DETERMINED

J c SEED CONES ENLARGE SHOOT ELONGATION LATERAL BUD PRIMORDIA ENLARG E BUD SCALE INITIATION

8 VEGETATIVE BUD BURST- FLUSHING K EMBRYO AND SEED DEVELOPMENT

L CONES MATURE AND OPEN

A ONSET OF VEGETATIVE BUD GROWTH LATERAL BUD INITIATION

SEED SHED

Figure 4.-The reproductive cycle of Douglas-fir extends over 17 months. LEtters A and L represent various stages and a brief description of these stages. -:J The approximate time each stage occupies in the reproductive cycle is represented by an arrow. (Reproduced from Owens (1973), with permission.) tivity normally occur together, events that are (Allen and Owens 1972). No abnormality is sensitive to cumulative temperatures ( Silen and apparent in pollen growth, fertilization, and Keane 1969, Campbell1974). early embryo development from self pollination, Although one-fourth to three-fourths of the but most such embryos collapse within a few pollen catch is a tree's own pollen, only about weeks, probably because of increased homozy­ 7-percent self-pollinated seedlings occur in an gosity of deleterious recessive genes (Orr­ average seed lot, which leads to an average Ewing 1956, 1957a). inbreeding depression of 1.5-2.0 percent in 1st­ Because of numerous pollen grains per mi­ year seedlings (Orr-Ewing 1954, Sorensen cropylar canal-four-to-six archegonia-and at 1973). About one-third of the trees produce least three patterns of embryo development less than 2-percent selfed seed and rarely do from the free-nucleate stage embryos, the op­ more than 20-percent filled seed originate from portunity for both gamete selection and genetic self pollen (Sorensen 1973, Sorensen and Miles diversity in the development of a single seed is 1974). About a third of the conelets ultimately apparent. This poses potential complexities for abort (Griffith 1968). About 16 percent (range breeding. 0-49 percent based on a 12-tree sample) of the normal-size seed halt embryo development and Flowering appear as flattened seed. Douglas-fir ordinarily retains its juvenile, Bracts are arranged to capture and carry nonflowering condition from 5 to 12 years (Al­ pollen efficiently to stigmatic areas. Pollen len 1942b) ; however, flowering in the second grains falling on the stigmatic surface are year has been observed (Oregon State Univer­ curled inward into the micropylar canal by a sity 1974). Flowering before age 15 is light and sea-anemone-like movement caused by differ­ markedly favors female production, a factor of ential growth of the stigmatic area (Barner some consequence in planning for adequate and Christiansen 1962, Allen and Owens 1972). early pollination in seedling seed orchards. At­ The large round pollen grain (90-100 microm­ tempts at stimulating precocious flowering by eters) has a thick, smooth exine layer that doubling the yearly growth cycle (Ching and breaks on imbibition to expose a mechanically Lavender 1970) or applying fertilizer (Allen strong plastic intine layer. Before producing a 1963) have not been successful, but applications pollen tube, the grain swells to about 500 mi­ of hormones have been successful (Pharis crometers longitudinally, but only a small 1974). The inheritance of flowering tendencies amount in cross section to bridge the space in appears strong as evidenced by consistently the micropylar canal between the stigmatic end poor or good early production from progeny and the nucellar cap. A rigid pollen grain is when both types of parents were systematically essential because the micropylar canal is dry crossed at the Dennie Ahl Seed Orchard. Flow­ rather than liquid-filled as in Pinus. Up to nine ering of 5-year-old seedlings among crosses in pollen grains (average 1.8, basis 343 wind­ a 6 X 6 diallel mating at our laboratory pro.. pollinated seed) may elongate within a micro­ vided a family heritability estimate of 0.68. pylar canal. Cone crop differences arise from a combina­ Male gametophytes develop through the nor­ tion of many causes. The most important causes mal sequence of cell divisions, mostly prior to are variation in numbers of primordial floral pollen release, to produce a five-cell structure buds or their subsequent losses, induced latency (Allen and Owens 1972) . Male gametes are re­ of immature buds, overwinter killing of devel­ leased after the swelled grain contacts the nu­ oped buds, freezing of conelets, and insect at­ cellus. Only then is a pollen tube formed which tacks on seeds and cones. Average number of dissolves its way through the nucellar tissue to buds initiated per shoot is quite consistent from one of four-to-six archegonia. Several embryos tree to tree (Griffith 1968), from year to year may develop per seed after fertilization in June, (Owens 1969), and between elevations ( Silen but mature seed with double or triple embryos 1967c). Climatic events of the previous year are uncommon. Unusual features for Douglas­ appear to affect number of floral buds that de­ fir are the brief opportunity for intermingling velop (Lowry 1966, van Vredenburch and La­ or possibly even pairing of homologous chromo­ Bastide 1969, Silen 1973a, Eis 1973). Effects somes during syngamy and the absence of of 1 year's heavy production can carry over to cleavage polyembryony which permits from any depress the next crop (Owens 1969) and reduce one of up-to-four cells of the free nucleate state growth of shoots (Puritch 1972) and roots to contribute genes to the resulting embryo (Rook and Sweet 1971). Conversely, removal of

8 a crop of female buds enhances cone production shedding takes place over several months as the next year (Silen and Copes 1972). Number cone scales open successively wider after each of floral buds that develop may be greatly in­ wetting (Allen and Owens 1972). An average fluenced by lifting, girdling, shading, debud­ of one viable seed per cone remains unshed as ding, defoliating, and fertilizing trees from a late as March. Unlike pines, cones develop with­ few weeks to 15 months before buds begin to out pollination to produce normal size but differentiate (Ebell 1971; Silen 1967 c, 1973b; empty seed. Even as late as mid-July before Stoate and others 1962 ; Pharis 1974, 1976). gametophytes collapse, the unpollinated seed Most of these treatments appear to increase or appears full, leading to possible overestimates decrease the proport ion of immature buds that of seed yields from early cone crop surveys. become latent rather than to initiate new bud Distribution of nutrients and photosynthate primordia. Such treatments are often most ef­ during cone development has been extensively fective when applied at onset of spring growth. studied (Ching and Ching 1962). Cones har­ The physiology involved with varying pro­ vested and dried more than 20 days before ma­ portions of floral buds to vegetat ive buds is st ill turity produce seed of substantially reduced obscure. The relatively less polar gibberellins, ger mination, a major cause of light seed and particularly combinations of GA4, GA7, and weak seedlings (Olson and Silen 1975). Arti­ GA9, have enhanced fl oral bud number, espe­ fic ial ripening of seed in cool, moist storage is, cially in combination with auxin. Four-year-old however, possible up to 30 days before maturity seedling-s as well as mature grafts have re­ (Silen 1958). Seed removed from green cones sponded to treatment, with evidence of differ­ up to a month before seedfall will germinate ential male and female effects (Pharis 1974, (Ching and Ching 1962). Normal seedlings up Ross and Phar is 1976). The switching between to 10.4 inches (26 em) tall have been grown floral and vegetative stage is usually complete, from such immature seed before winter in our except for r are poliferated cones that show var­ laboratory as a potential way of gaining a sea­ ious combinations of female. male. and verreta­ son's gro\vth. tive sectors. E ven here the line between sectors Wind-pollinated seed of most parent trees is sharp, sometimes resulting in a single scale ger minated at time of seedfall show no dor­ with po1len and seed on oppo~ite sides. Switch­ mancy. Dry, stored seed of some parents con­ ing between sets of developmental genes has tinue to be nondormant, but the germination been surrrrested as an underlying mechanism rate of others dr ops off rapidly. (Silen 1973a). Seed cr ops ar e irregular (Garman 1951) ; SucceRsful enhancement of cone crops is pres­ nonetheless, seed is produced on some trees in 'Jntly limited to the practices of providin.Q" most localities each year. Some trees produce sunny, somewhat drou_g·hty locations for seed cones nearly every year, others remain barren orchards, r emoving comneting vegetation, and f or long intervals. Cones are produced on sunlit anplving nitrate fertilizers in early spring branches, more are found on southerly quad­ (Steinbrenner and others 1960, Sloate and r ants of the crown (Winjum and Jobnson others 1962, Allen 1963). Drought ~tre~s, rrird­ 1962). Good crops are seldom spaced more than linrr (Ehell 1967, 1971), and tree lifting (Silen 3 year s apart in low elevation, dry, sunny areas 1973b) have also increased cone production and like the Willamette Valley: however, severe are used for special genetjc nurpo~es. Gibber el­ seed shortages occur from less freauent good lins and auxins are already used to enhance crops over large portions of Douglas-fir's range. flowering and permit ear lier eros~ pollinations, As many as 10 years may pass without a rrood but technologies for large-scale use are still t o cone crop in some high elevation stands. This be deve1oped. A typical resnonse of all such irregularity of crops can seriously len_gthen tree practices has heen t o multiply t he number of improvement programs and ha~ contributed to cones produced. Greatest increases usually occur disgenic use of the more plentiful low elevation with large crops or on prolifi c t rees. Small ef­ seed at higher elevations. fects or no effects are usually experienced with Yields vary greatly by cron, age of tree, and small crops or on poor flowernig trees ( Silen cone size (Garman 1951, Kozak and others and Copes 1972). 1963). Yao (1971) reportPd that seed weight decreases with latitude. Willis and Hofmann Seed (1915) observed that younger trees produce larger cones havin.g larger, heavier seed than Seed rinens from late Aug-ust at low eleva­ older trees, with similar yields of about one­ tions to late October at high elevations. Natural half pound per bushel in a good crop year. A v­

9 erage yields were 16 seeds per cone and 1,000 Study planted in 1913 and still maintained by cones per bushel. From our own observations the Forestry Sciences Laboratory, Corvallis, of 697 trees in the Oregon and Washington Cas­ Oreg., have several of the 13 races obviously cades, we recorded an average of 17.3 seeds per failing. The study sources and plantations are cone from collections covering three seasons, localized to western Oregon and Washington. with a maximum of 52.5 for the best yielding Initial survival of trees on all five sites was tree. Filled-seed yields of 309 trees harvested over 90 percent. Survival of trees by age 17 was at Vernonia, Oreg., in the bumper crop of 1966 still generally over 80 percent (Munger and averaged 25.6 seeds; filled seed on individual Morris 1936) ; it now varies from 24 to 64 per­ trees ranged from 7.2 to 53.7. Corresponding cent. On the highest and most severe site at seed yields were experienced in Ne'v Zealand 4,600 feet (1,400 m), severe decimation of some (Sweet and Bollman 1972), but lower yields low elevation races was apparent in the first were reported in Europe (Otto and Kleinschmit decade. By age 60 only three high elevation 1975). Artificial pollination can more than dou­ races survived in sufficient numbers to make a ble average yields, although occasional trees stand, the most local race was clearly superior produce few filled seed. in both growth and survival. On three other exposed sites ranging from 1,100 to 2,000 feet VARIATION (330-610 m) in elevation, decimation of non­ adapted races began after age 30. All three Survival have several races now seriously understocked as well as growing poorly. On a sheltered site Survival through a rotation becomes a major at 2,600 feet ( 800 m), however, all but two consideration when Douglas-fir ecotypes are races have full stocking, the decimation of the moved to an environment where they are un­ two occurred mainly in the last decade. Thus, adapted. Incentive for faster growth is strong relative exposure of the site is a major element to use ecotypes with genes that have developed in time needed to uncover unadapted races. in more mesic and temperate sites than the local Large differences in survival have also devel­ source. Losses have been dramatic where seed oped between families within races in every movements have obviously exceeded the genetic plantation. The decimating agents are often amplitude of the ecotype. Killing of coastal mystifying and are different at each site. Be­ sources by deep cold in eastern Europe ( Scho­ fore dying, trees often display a gradual decline ber 196.3) or in the Eastern United States in vigor. Much mortality or damage also dates (Baldwin and Murphy 1956, Wright and others from climatic extremes such as freezes, heavy 1971) are classic examules. In Europe, and late­ snow loads, ice storms, winter exposure above ly in New Zealand (Wilcox 1974) , the common snow, hurricanes, and probably drought. Sur­ outcome has been a slow decimation by diseases rounding natural stands were usually damaged native to the Douglas-fir range, or by frost. less and recovered better than the races tested. Within the species range, similar but less Natural selection, continued over this 60-year dramatic examples have been numerous. Coastal timespan, appears to favor genotypes similar Douglas-fir planted in the interior of its range to those occurring in natural stands. Thus, seed is eventually killed by unseasonal low tempera­ movement can involve risks of unacceptable tures. Conversely, plantings of interior sources mortality that appear over a longer period than west of the Cascades (Silen and Woike 1959, spanned by the career of the geneticist. Risks Silen 196.2c, Haddock and others 1967) have are lessened by shorter rotations, by seed move­ gradually failed over several decades, primarily ment involving only modest environmental from endemic needle diseases of little conse­ changes, or by choice of sheltered sites. Too quence to local trees. intensive selection even within the local stand Within the Douglas-fir region, similar sur­ may be subject to the same risks. vival problems have been associated with seed movement but have developed over a longer Growth time span than most genetic studies. Several large commercial plantations established in Genetic variation of a magnitude expected western Oregon and Washington before 1920 for so wide-ranging and long-lived a species as appeared thrifty for decades but now exhibit Douglas-fir has been documented for a number obvious survival problems. Practically all are of phenological, growth, form, and resistance from coastal but nonlocal seed. All five experi­ traits (table 1). As with other western conifers ment·!lJ plantations of the Douglas-fir Heredity (Hamrick and Libby 1972), most traits display

10 clonal variation but a few vary ecotypically. A TABLE 1.-Traits exhibiting genetic variation westwide, clinal pattern of inherent growth of in Douglas-fir Douglas-fir over its range has long been obvi­ ous, as has a generalized inverse relationship behveen growth and cold-hardiness or drought Estimated resistance. genetic Literature citation Collectively, the documentation of genetic Trait control~ or source 2 variation in Douglas-fir suggests that selection Total height W-M Campbell 1964 (0.10); from among these and many other traits has Campbell1972 (0.10-0.30); been stabilized by several thousand years of N amkoong and others similar climate into populations having a sensi­ 1972 (0.24-0.50); Klein­ tive adaptation to local environments. A major schmit and others 1974 Stem diameter M Campbell1964 (0.20) feature of recent literature on genetic variation Stem straightness M Orr-Ewing 1967; Wilcox is that populations, sometimes only a few miles 1974 apart, maintain measurable genetic differences Dry weight w Campbell and Rediske in growth and phenology despite pollen ex­ 1966 (0.09) change. Branching \V-M Campbell 1961, 1963 (0.05-0.30) Geographic Variation.-A west\vide pattern Stockiness M-S Silen (see text "Form") of inherent growth rates similar to the one re­ (0.26) ported earlier for ponderosa pine (Squillace \Vood specific gravity M-S Nicholas 1963 (0.17-0.52) and Silen 1962) is also apparent for Douglas­ "\Vood trachied length M Nicholas 1963 (0.11-0.27) McKimmy 1966 (0.00-0.66) fir. Three features of the annual precipitation Percent summerwood M Nicholas 1963; pattern in the range of Doug-las-fir appear im­ McKimmy 1966; portant in its development. One feature is the "\Vilcox 1968, 1974 decrease in precipitation and humidity behind Percent heartwood w Wilcox 1968, 197 4 \Vood permeability w Miller and Graham 1963; successively higher north-south mountain Bramhall 1955 ranges from the Coast Ranges through the \Vood extractives Hancock and Swan 1965 Rocky Mountains. A second feature is a charac­ Terpene composition MS Zavarin and Snajberk teristic summer drought that begins in spring­ 1973; von Rudloff 1972 Spiral grain MS Campbell 1964 across the South\vest United States and ad­ Frost resistance M Bellmann and Schonbach vances slo\vly north·ward over most of the 1964; Schonbach and species range by early July. Thus, long severe Bellmann 1967; Campbell moisture deficiencies can occur any summer in and Sorensen 1973 any part of the range. For example, even as far Disease resistance M Larsen 1946; Meyer 1954; Brandt 1960; Schober north and in as maritime a climate as Van­ 1963; von Stephan 1973; couver, B.C., \vhere annual precipitation ranges Wilcox 1974 fom 66 to 107 inches (1.7-2.7 m), a 74-day Insect resistance M Mitchell and Nagel 1969 rainless period occurred in the 1951 gTo\ving Animal resistance MS Radwan 1969; Dimock and others 1976 season. In such droughty years survival de­ Rooting Black 1973 pends primarily on moisture within the soil Cotyledon number M Sziklai 1963, 1965; and the tree at the onset of gro\vth. A third Sorensen 1966 feature is that relief from summer drought by Graft incompatibility s Copes 1973 (0.81) Cone production s Allen 1963 (see text rains from thunderstorms is usually of minor "Seed") importance in the high rainfall north\vest por­ Top injury Anderson and Wilson 1970 tion of Douglas-fir's range, but these rains con­ Survival M-S Bialobok and Mejnarto­ stitute a major part of the lo\v annual precipi­ wicz, 1970; (see text tation in the drier southern and eastern por­ "Survival") Fertilizer response w Rediske and others 1968 tions. Floral color s Ching and others 1966; Selection response to this precipitation pat­ Copes 1972 tern has been that highest inherent rates of Seed W-M Allen 1960, 1962 growth characterize races along the Pacific Foliar nutrients van den Driessche 1973 slopes of Washington, Oregon, British Colum­ ~Figures cited by authors are mainly broad sense bia, and California \vhere annual moisture is heritability or upper limit estimates: (W) weak (h2 less generally more plentiful and yearly recharge than 0.1), (M) moderate (h2 = 0.1-0.3), (MS) moder­ of the soil is dependable. Races from interior ately strong (h2 = 0.3 to 0.5), (S) strong (h2 above British Columbia and \Vestern Idaho are gen­ 0.5). erally of intermediate growth. Slo\vest growing 2 Heritability estimates are shown in parentheses.

11 races characterize the interior basin and east In maritime western Europe, races from Van­ slope of the Rocky Mountains, where spring­ couver Island and western Washington are pre­ time soil moisture may be seriously deficient ferred; but in southern Europe, races from and cyclic droughts can extend over several Oregon and California appear better suited years. Arizona and New Mexico sources range (Schober 1963). In New Zealand (Wilcox 1974) from slow to moderately fast growing under better performance is displayed by coastal fog­ the influence of more plentiful summer rains. belt races of California and southern Oregon. An index of the westwide seasonal moisture Such experience suggests importance of day distribution pattern, September-through-June length as well as climatic adaptation. precipitation as a percent of annual precipita­ Improvement strategies using racial varia­ tion, has been correlated 'vith racial growth tion for faster growth rates generally seek the differences in both ponderosa pine (Squillace genes developed in a milder and more mesic and Silen 1962) and Douglas-fir (Sorensen part of the range than the intended planting 1967). site. Such strategies must generally balance bet­ Such a generalized clinal pattern of inherent ter growth against poorer hardiness. rate of growth is seen in table 2 in which av­ Local Variation.-The pronounced genetic erage height as a percent of study plot mean of differences in growth and other traits of geo­ races in each geographic region is pooled from graphic races apparently grade clinally so that four rangewide studies conducted in Western differences between local populations only a few North America and western Europe. Mature kilometers apart are detectable. natural stands over the West also display a Several studies along a transect near 45 ° N. similar relationship in comparative heights, latitude in western Oregon show that sharp which lends credence to the pattern. changes in local climate are accompanied by Results reported from tests conducted in correspondingly sharp changes in inherent rates other climates or latitudes can be broadly in­ of growth or phenological expression. From terpreted from the pattern (Hermann and seed collections grown in different years at Cor­ Ching 1975). In Eastern United States, where vallis, Irgens-Moller (1957, 1967) and Sorensen frost-sensitive coastal races are killed in win­ (1967), for example, report a 2-week-later av­ ter, races from New Mexico and Arizona grow erage bud burst and a 13- to 17-percent superi­ best (Wright and others 1971), presumably re­ ority in height for low elevation seedlings from sponding to an adaptation for a summertime the coast hills seed over those from a seed of rainfall pattern as well as cold winters. In the similar elevation on the west side of the Wil­ continental climate of eastern and northern lamette Valley separated by only 11 and 15 Europe, races from southwestern Britis"'fl. Co­ miles (18 and 24 km). The latter presumably lumbia, western Washington, and northern was adapted to less spring rainfall and earlier Oregon are best (Jahn 1955, Rohmeder 1956). onset of seasonal drought. Sorensen (personal

TABLE 2.-Comparative height growth of Douglas-fir and ponderosa pine from different geographic regions tested in the Douglas-fir region of the United States and in ~oestern Europe1

Dougla~-fir Ponderosa pine Western United Region Western Western States 6 and of Oregon 2 Washington 3 Denmark 4 Germany 5 New Zealand origin (14 years) (20 years) (21 years) (44 years) (25-43 years) West of Cascade Mountains 7 176 (2) 141 ( 3) 127 (3) 136 (2) 118 ( 5) West of Sierra Mountains 114 (1) 81 (1) 111 (1) 109 ( 3) 137 (3) Interior British Columbia 95 (1) 95 ( 1) 97 (6) Northern Rocky Mountains 79 (3) 102 ( 3) 95 (2) 95 (3) 107 (13) Southern Rocky Mountains 95 (2) 102 (1) 93 (3) 80 (7) East slope Rocky Mountains 48 ( 1) 67 (1) 76 (1) 70 (1) 70 (2) Intermountain 41 (1) 20 (1) 77 (2) 74 (5) 76 (6) 1 Height growth of provenance trees as a percent of average height of plantation trees. 2 Data from plantation at Corvallis, Oregon. 3 Data from plantation at Wind River Experimental Forest, Wash. 4 Lundberg (1957). 5 Schober (1959). u Squillace and Silen (1962) reporting on three studies. 7 Numbers in parentheses are numbers of regional average provenances.

12 correspondence 197 4), using seed collections at by 5 days per 400-foot (122-m) rise in source 7 -mile intervals along the Willamette Valley elevation, the same elevational delay rate re­ and Coast Ranges portion of the transect, found ported by Silen ( 1963) for pollen shedding in significant differences in bud burst and other western Or egon and Washington. Campbell also phenological traits between some adjacent sta­ found an average delay of 4 days per degree of tions. A consistent pattern has been displayed latitude as predicted by "Hopkins law" to sug­ between other stations along the transect. Even gest that phenological adaptation of the 44 on the floor of the Willamette Valley along the races to the local climate was very exacting. transect, west- and east-side populations are His mor e recent growth data 3 sampling 193 clearly different. In a study by our laboratory locations within a single Cascade Range drain­ of 50 wind-pollinated families tested on eight age show that different genetic populations low elevation sites in western Oregon and wer e pr esent to conform closely with each Washington, families from the more mesic change of landform (Campbell 1976). Specula­ east-side Williamette Valley floor averaged 12.1 tions about the way such population differences percent greater average height at 5 years than can be maintained despite pollen exchange usu­ families from the drier west side. ally involve effective selection for each genera­ A similar experience is reported from Europe tion from among the large seedling populations (Schober 1963) with seed from the transition (Silen 1967b, F ryer and Ledig 1972, Rehfeldt zone between coastal and interior British Co­ 1974b). lumbia. Races from the grasslands east of the Within-stand variation.-Variation among coastal mountains are susceptible to Rhabdo­ family means of parents within a locality or cline and are slow growing compared with stand can approach the same order as racial nearby types to the east and west in higher differences (Rehfeldt 1974a). Table 3 provides moisture regimes (see also Kleinschmit and examples from my studies of local growth vari­ others 1974). ation of families at various ages. Typically, the On a single ridge in southern Oregon, Her­ range in average height of families from a sin­ mann and Lavender (1968) found genetic dif­ gle locality is one-thir d to one-half the general ferences among seedling traits of north and average. Coefficients of variation in average south slope populations in nursery and growth family height are lar ge for seedlings but drop chamber studies. Sweet (1965), studying clin­ to the 3- to 6-percent range in older seedlings ally varying seedling traits of 22 coastal sources and mature trees, most of which reflects the from California, Oregon, and Washington, ob­ smaller ratio of living crown to bole length in served predictable differences between races older stands. Variation in family volume per that differed more than 1,000 feet (305 m) in hectare is larger, with the coefficient of varia­ elevation at the same latitude, or somewhat tion remaining in the 8-percent range at age more than a degree of latitude at the same ele­ 50 for the half-sib families cited. Other data vation. Von Rudloff (1972) in British Columbia from the Douglas-fir Her edity Study (table 4) and Zavarin and Snajberk ( 1975) in California, suggest that top performing families in each studying ratio of terpene fractions in leaf oils race, in addition to producing a larger average or resin blisters, found populations that differed tree, survive about 11 percent better than measurably between short sampling intervals, average. particularly in situations where accompanying climatic changes were abrupt in moutainous Form topography. Rehfeldt (1974b), studyjng seed­ ling populations originating at 2,950, 3,700, and Though Douglas-fir stands appear superfi­ 4,260 feet (900, 1 125, and 1 300 m) from two cially straight stemmed and of good form, a sur­ valleys in northern Idaho 10.5 miles ( 17 km) prising amount of sweep sinuosity, roughness, apart, found differences in various phenological excessive limbiness, and undesirable crown and growth traits among most of the six popu­ form is normal. In stands marked commercially lations. for piling, where only slight deviations from Using racial seed collections of coastal Doug­ straightness are permissible, selection seldom las-fir at 44 weather stations, Campbell (1974) exceeds 20 percent of the trees. generalized that the predicted date of seedling Potential for improvement in bole straight­ bud burst in a common environment was later ness, stockiness, and crown and limb character­ ist ics appears certain. Inheritance of poor or ' Campbell, Robert K. Genecolog-y of Douglas-fir in an good form was clearly demonstrated by Orr­ Oregon Cascades watershed. Unpublished data on file, F orestry Sciences Laboratory, Corvallis, Oreg. E wing ( 1967). Moderately strong inheritance 13 TABLE 3.-Examples of variation in height and volume among wind-pollinated families of Douglas-fir originating from a single stand or locality

Mean family Range of Coefficient Number of height or family of Age Source Elevation parents volumes means variation Test details Years Feet --Centimeters-­Percent HEIGHT 2 Vernonia, Oreg. 300 300 33 17-47 15 4 repljcations of 50 seedlings/replication 5 Corvallis, Oreg. 250 31 118 107- 140 4 8 sites, 3 replications/site (West Willamette Valley) 5 Lacomb, Oreg. 900 19 133 119-145 4 8 sites, 3 replications/site (East Willamette Valley) 5 Shelton, Wash. 400 33 113 104-130 5 8 sites, 3 replications/site 5 McLeary, Wash. 400 17 120 114-150 6 8 sites, 3 replications/ site 50 Gates, Oreg. 1,000 17 116.6 112-118 3 100 per parent on 5 sites 50 Santiam, Oreg. 3,400 12 116.7 113-118 3 100 per parent on 5 sites VOLUME Cubic feet 50 Gates, Oreg. 1,000 17 10.2 8-11 8 100 per parent on 5 sites 50 Santiam, Oreg. 3,400 12 8.1 7-9 8 100 per parent on 5 sites

TABLE 4.- A comparison of individual tree volumes at 50 years of age for the average family, best family, and best 14, of the families at five plantations in the Do/uglas-fir Heredity Study 1

Plantation: Wind River Hebo Mount Hood Mount Baker Mount Hood Elevation (feet): 1,100 2,000 2,600 2,000 4,600 Number of parents in source: 9 7 11 8 12 Cubic feet Average family 12.5 17.8 5.3 37.9 2.8 Best family 2 15.9 22.7 7.4 62.8 4.8 (27) (28) (40) (66) (71) Best 14 of families 2 14.7 20.9 6.7 57.4 4.3 (18) (17) (26) (51) (53) 1 Data are presented for the seed source most nearly local to the plantation site. 2 Numbers in parentheses are the percent gain over the average tree. of straightness is suggested by the same order bility on 100 trees suggest substantial inheri­ of family ranking at 5 years in each of the five tance for several crown characteristics, such as plantations of the Douglas-fir Heredity Study limb size, crown width, and ratio of width to (see also Wilcox 1974). height of top 10 whorls. Inheritance of stockiness also appears fairly Bole imperfection from cold damage varies strong but may be difficult to predict. From a 3 greatly by family. Cambial freezing, such as X 6 factorial rnating of randomly chosen par­ occurred during the record 1955 severe early ents, individual tree heritability was estimated freeze in the Northwest, caused major wounds at 0.27 for 8-year-old seedlings based on ratio and stem rotting. In every race in the Douglas­ of height to diameter at one-fourth the height. fir Heredity Study, certain families were much Most of the variance is additive. Phenotypic more damaged or resistant than average. Simi­ selection of parent trees was ineffective in up­ larly, family differences in ice or snow breakage grading the portion of desired stocky, tall fami­ lies. Nursery rankings of families for stocki­ that caused offset stems were repeatedly experi­ ness were poorly related with stocky families at enced in the study. Both types of wounds be­ 8 years. No data exist on whether as many come more damaging with time as the stem, stocky trees as slender trees can be grown per weakened by rot in the wound, often breaks unit area. again years later below the live crown and the Campbell's (1961) measurements of repeata­ tree dies.

14 Phenology Terminal buds are usually last to burst on a tree. Relative delay between lateral and termi­ Only growth has received more genetic study nal buds was progressively longer for seedlings than phenological traits. Long-term phenologi­ of southerly races in a west coast transect study cal records have been made at many weather (Svveet 1965). stations.4 (Griffith 1968). Phenology is inti­ For races gro\vn in a common environment, mately associated with adaptation and survival, bud set is earliest in the interior provenances. but it appears less well related to tree height For coastal sources, northern provenances growth (Munger and Morris 1936, Griffith (Kleinschmidt and others 1974) and high ele­ 1968). vations (Bialobok and Mejnartovvicz 1970) Bud burst is an easily studied, sharply de­ cease growth earliest. Inherent variation in bud lineated phenological event of high heritability set provides an evasion mechanism against fall (Silen 1962c). Its variable occurrence from 30 frosts (Campbell and Sorensen 1973, Griffin to 45 days after onset of cambial growth and 197 4) and early onset of summer drought. 11 to 34 days after flowering (Griffith 1968), The inherent seasonal rhythm of phenological however, reduces its interpretive value as an events persists when plants are moved to new indicator. Unlike the less variable onset of cam­ environments. Adjustment to the new environ­ bial growth (Griffith 1968), bud burst varies ment is believed to occur primarily at one end yearly in response to summations of heat above of the growth period. Offsite plants thus poorly growth thresholds (Campbell 1974). Its control utilize the growing season and may be delayed appears to be mediated by gibberellins (Laven­ in meeting physiological requirements for dor­ der and others 1973) . mancy and growth (Campbell 1974). Many observations of bud burst inheritance come from early studies of races. For 13 races Resistances grown at five locations, a common order of bud burst was always observed even though bud Pests.-In its natural range, Douglas-fir is burst occurred 2 months later at the highest relatively free from serious pests, although it is site than at the lovvest (Munger and Morris attacked by numerous biotic agents. Of these, 1936, Haddock and others 1967). The same only resistance to bro\vsing by deer and clip­ burst order was noted in observations 30 years ping by hare have been pursued with a sus­ apart (Morris and others 1957). Bud burst oc­ tained research effort (Dimock and others curred earliest for races from broad valley ori­ 1976). A useful level of variation in resistance gins, follo\ved elevationally by those on open was found among nine parents. Inheritance of slopes. Races from the floors of narrow valleys their resistance in crosses was primarily addi­ characterized by cold air drainages, however, tive. Laboratory studies of factors related to burst relatively late, an important feature since animal resistance are promising (see "Physi­ they also display good inherent growth rates. ological Variation"). When grown in a common environment, races Outside the range of Douglas-fir, selection bordering the cool Pacific Ocean are generally for resistances to the needle diseases Rhabdo­ late, whereas those from high elevations or cline pseudotsuga and Phaeocryptopus gaeu­ interior portions of Douglas-fir's range burst mannii, both of little consequence to natural early and are prone to frost damage (Irgens­ stands, has been a key to successful introduc­ Moller 1968) and Rhabdocline attack (Liese tion. In northern Europe, for example, races 1936, Haddock and others 1967). With such from areas in western Washington character­ exceptions, bud burst is earliest for southerly ized by high humidities often show high resist­ coastal races, with each degree of latitude con­ ance to Rhabdocline attack. Those from the tributing a delay of about 1.8 days in inherent more arid interior are usually susceptible bud burst (Sweet 1965). Racial bud burst tends (Schober 1963). Present epidemics of Pha.eo­ to be progressively earlier with distance from cryptopus in N e\v Zealand stands have exposed the Pacific Ocean, the greatest change occurring much within-stand variability to indicate po­ within the first 30 miles (50 km) (Campbell tential resistance (Wilcox 197 4). Resistance to 1974). root rots has not been demonstrated. Resistance to a number of other pests has 'Morris, W. G. 1952. Average day of year on which been suggested or demonstrated in published given phenological development occurred in given spe­ reports (table 1). These include midges, Con­ cies at points in Oregon and Washington. 7 p. Unpub­ lished report on file at Pacific Northwest Forest and ta.rinia sp. (Mitchell and Nagel 1969), the twig Range Experiment Station, Portland, Oreg. weevil, Cylindrocopturus furnissi (V. Allen,

15 personal communication, 1975), the gall insect, others 1974; Zavitkovski and Ferrell 1968, Chermes cooleyi (Wheat 1965) , and the limb 1970). Seedlings from dry sites also have more gall, Bacterium pseudotsugae. rapid root growth than those from wetter sites Cold.-The relative cold hardiness of interior (Heiner and Lavender 1972). Data indicate races has long been used in choice of seed that populations on adjacent north and south sources for introductions into continental cli­ slopes display significant local differences in mates of Europe (Schober 1963, Bellman and drought avoidance (Ferrell and Woodard 1966). Schonbach 1964) and the United States (Bald­ There are fewer drought hardiness data, but win and Murphy 1956, Wright and others they indicate inherent differences between 1971). Unfortunately, cold hardiness appears populations in this characteristic as well loosely correlated with reduced growth rate. (Pharis and Ferrell 1966). For coastal races, inherent resistance to fall frosts was shown to be related to both early Physiological Variation bud set, an evasion mechanism, and to a phy­ Genetic variation has been revealed in many siological sensitivity related to latitude. In studies of physiological traits of Douglas-fir provenance collections grown at Corvallis, such as photoperiod, thermoperiod, photosyn­ Oreg., races from the mild climates of Puget thetic rate, or with chemical determinations of Sound, the Willamette Valley, and the Oregon monoterpenes, isoenzymes, and DNA ( deoxy­ coast were most sensitive (Campbell and Soren­ ribonucleic acid) content. sen 1973) . The same two factors explained most The species light requirement is satisfied by of the sensitivity to damage in another study a short light break during the night (Irgens­ of 10 California races (Griffin 197 4). Moller 1962). A considerable period of short Within the amplitude of a single race, indi­ days is required to force dormancy. Despite vidual families display wide differences in cold long days, Douglas-fir also normally goes dor­ sensitivity. For example, in a study of 309 mant during the summer dry period. Sensitivity wind-pollinated families from Vernonia, Oreg., to photoperiod is greater with interior sources grown at Corvallis, a severe spring frost com­ (Irgens-Moller 1958, 1962). A thermoperiod of pletely defoliated 94 percent of the year-old 75°F (24°C) soil temperature combined with seedlings. The 10 least defoliated families an 18-hour photoperiod maximizes dry weight averaged 28 percent uninjured plants, and in increment for the species, but interior sources one family 49 percent were uninjured. Like­ are less affected by lower than optimum tem­ wise, in the record November 15, 1955, cold, the peratures and have lower shoot-root ratios (Lav­ 13 races and 120 families of the Douglas-fir ender and Overton 1972). Interior races respond Heredity Study, then 42 years old, sustained an differently in photosynthetic rates and satura­ interesting family and racial damage pattern. tion points than do coastal races (Campbell and Heavy killing of trees in all crown classes oc­ Rediske 1966, Krueger and Ferrel 1965), par­ curred at only two of the five plantations (Hebo, ticularly to seedling preconditioning (Soren­ Oreg., and Verlot, Wash., both at 2,000 feet sen and Ferrell 1973). Cell nuclear volumes and ( 600 m)) still having active cambial growth. In DNA content are strongly correlated with in­ both, all races sustained some killing; but low creasing latitude and appear higher for coastal elevation races were most damaged. Every race sources than for interior sources (El-Lakany also had some families with no damage inter­ and Sziklai 1971, 1973); this finding was of spersed with families with up to 38 percent use in determining origin of plantations (Ber­ dead trees. The pattern was related to propor­ ney 1972). tions of trees whose cambiums were still active Distinctions between adjacent populations in late November, a phenological characteristic have been most successful with studies of ole­ of the family. oresins (von Rudloff 1972; Zavarin and Snaj­ Drought.-Douglas-fir seedlings have been berk 1973, 1975; Snajberk and others 1974). shown to have both drought avoidance and Differences between genotypes are easily dem­ drought hardiness differences related to seed onstrated for at least 10 enzymes. Application origin. Seedlings from seed from the Rocky of isoenzyme investigations to studies of racial Mountains and from dry sites in the Cascade variation (Muhs 1974), individual genotypic Range consistently have lower transpiration differences, grafting incompatibility, mutations, rates and show more sensitive stomatal control and flowering are in progress in several labora­ than seedlings from wet sites of the Cascade tories in Western North America. and Coast Ranges (Ferrell and Woodard 1966; Attempts to relate animal damage resistance Pharis and Ferrell 1966; Unterschuetz and to chemical content of foliage by genotype have

16 led to investigations of tissue digestability, forms of cold inujry, two forms of drought essential oils, and several chemical constitu­ resistance, animal browsing, photoperiod, ther­ tents. Resistance is related to lower dry matter moperiod, transpiration, respiration, and photo­ content and cellular digestabilities, essential synthetic rate. Young trees have been used to oils with greater inhibitory action on rumen, display differences in form and resistances to more monoterpenes in vapor from foliage, and at least two needle diseases and two insects, as lower levels of chlorogenic acid, the last being well as to needle shedding after cutting. Obser­ the most promising screening chemical for ani­ vations of mature trees are required to evaluate mal-damage-resistance types (Radwan 1969). resistance to some wood pathogens, mortality Chlorogenic acid content is a highly heritable from long term-climatic extremes, certain gene­ trait showing primarily additive variation environment interactions, and differences in (Radwan 1975, Radwan and Ellis 1975). mature volume growth per acre. The 1912 Douglas-fir Heredity Study (Mun­ Wood ger and Morris 1936, USDA Forest Service 1963), based on seed from 120 wind-pollinated Prospect of breeding for specific wood traits parents from 13 localities in western Oregon is promising. Study of wind-pollinated Douglas­ and Washington, illustrates various time re­ fir families at age 46 has indicated family herit­ quirements. Bud bursting order has remained abilities range from 0.17 to 0.52 for specific essentially unchanged since young trees were gravity (McKimmy 1966) and 0.11 to 0.27 per­ evaluated (Morris and others 1957). Frost sus­ cent for tracheid length (Nicholas 1963). Meas­ ceptibilities were accurately recorded on young urements of juvenile wood were of low relia­ trees. Early expressions of differences in bility for estimating traits in mature wood in straightness and taper changed slowly with this study, but good correlations with mature stand development. Likewise, wood sampled wood were reported by Reck and Sziklai ( 1973) . earlier than 25 years showed little relationship Ranking of average specific gravity and fiber to mature wood traits (McKimmy 1966). Rank­ length was essentially the same for five wind­ ing of races in growth reported at age 17 pollinated families on three widely separated (Munger and Morris 1936) practically all coastal plantations of the Douglas-fir Heredity changed by age 50 ( Silen 1966a). Even corre­ Study, indicating considerable stability for lation of early height growth of individual trees these wood traits (McKimmy 1966). A more ·with mature heights was very low (2 years recent study of Douglas-fir at age 9 years based with 50 years, r == 0.005; 11 years with 50 on 54 full-sib families in a hierarchical mating years, r == 0.112; and 22 years with 50 years, design provided an individual tree heritability r == 0.47 (Silen 1965)). Gene-environment in­ for specific gravity of 0.61. No interactions were teractions, of minor consequence at 17 years, found between the two test sites, and a highly were large at age 50 for both families and for significant parent offspring correlation of 0.51 races. An especially clear case is illustrated in was calculated.5 Bramhall (1955) reports racial figure 5. Survival differences between races, differences in permeability of wood to preser­ minor at 17 years, were about 2 :1 at 50 years, vations. the greatest differences occurring on most se­ vere sites. Survival differences, appreciably AGE OF TRAIT EXPRESSION favoring adapted races, developed within a decade on the most severe site but only recently Meaningful expression of genetic variation have become noticeable on the most sheltered can occur early for some traits but requires site. Unfortunately, the relative severity of the many decades for several that are commercially five sites would have been difficult to predict important. Traits of germinants involve single­ in the study since severity of the site is only gene mutants for at least five chlorophyll de­ weakly related to site quality or to elevation ficiencies and three needle irregularities (see (Silen 1966a). "Genetic Markers"). Seedlings 1 to 5 years of Similar trends through time began to appear age have shown genetic variations in seven in a 1958 regional study of 16 reciprocally phenological traits, four growth traits, three planted races (Rowe and Ching 1973). Like­ wise, comparison of 2-year heights versus 10­ 5 Campbell, Robert K., Robert Echols, and Roy Stone­ year heights on 26 full-sib families from par­ cypher. Heritabilities of volume and specific gravity entage of the Dennie Ahl Seed Orchard pro­ and expected gain from early selection in Douglas-fir. Unpublished data on file, Forestry Sciences Laboratory, vides generally low relationships (r == 0.01 to Corvallis, Oreg. 0.46) 0

17 0 +40 V9LUME PER TREE SURVIVAL

c: -G) (.) ... ~ +20 z + -Q) c: -Q) w ...... -...., ~ 0 Q.= ll. Q.= 0 ~ .J:. ~ 01 ~ 0 0 .21 -40 ...J ::t: ...J ::t: + 500 1,000 1,500 500 1,000 1,500

ELEVATION I meters!

Figure 5.-Gene-environment interactions at age 50 of a high elevation source and a low elevation source collected in 1912 from the Santiam Valley, Oregon Cascades, grcwn at five sites in western Oregon and Washington. Vol­ ume per tree and percent survival are shown as percent deviation from their common means. The low elevation source (Gates, 1,000 feet or 300 meters, represented by four parents-O) shows superiority in both traits at low elevations, whereas the high elevation source (Santiam, 3,500 feet or 1 070 meters, represented by five parents­ +) shows superiority at high elevations. Note that switching of both traits occurs at the middle elevation planta­ tion. Plantings in 1915 were represented by 100 progeny per parent per site.

GENETIC TECHNIQUES

Initially dependent on technologies developed field performance of their progeny, using wind­ for pines, Douglas-fir tree improvement now pollinated seed (see "Testing"). In most pheno­ incorporates many additional technologies spe­ typic selection programs most trees in a stand cifically adapted for the species. are ocularly eliminated in choosing a few straight, well-formed candidates. Stands are

SELECTION 6 The largest known comparison of selected versus random parent trees was done by Crown Zellerbach Growth Corporation and State of Oregon, each in a 300-parent program. Each marked 100 groups of 10 parent trees in 30- to 40-year stands, from which a random, a best, and The mountainous topography of the West a second-best were selected for volume growth. Progeny provides mainly natural stands of variable age mean diameters of 100 families in each group were: rather than plantations for selection. Great Best in 10 Best in 5 Random difficulties have been experienced in statistically (mm) (mm) (mm) setting aside enough environmental variability or stand developmental effects to make confi­ Crown Zellerbach Corporation 6 (at 10 years) 35.7 -+- 0.30 35.5 -+- 0.25 35.6-+- 0.26 dent selections for inherent growth rates. Con­ State of Oregon sequently, most selections are now tested for (at 8 years) 20.9-+- 0.20 21.0-+- 0.15 21.0-+- 0.14 18 sometimes strip cruised for this purpose. Can­ logical researches now underway are better didate trees are usually compared with neigh­ correlated to specific tree traits. boring trees on some basis that attempts to account for differences in age and growing Resistances space. Sometimes such comparisons are further refined for differences in developmental history With few serious pests in the mesic parts of as evidenced by limb growth and age of neigh­ Douglas-fir's natural range, present selection boring trees (Krueger 1960). guides simply concentrate on healthy undam­ A refinement in systematically setting aside aged trees. Frost and cold resistance as ex­ the environmental component in phenotypic pressed in progeny families are, however, cru­ field selection, developed at Weyerhaeuser Com­ cial selection traits where the species is intro­ pany by R. K. Campbell, recorded coordinate duced and are of growing importance in selec­ location and diameter of each tree in a stand tions for its interior native range. Seed mixes and computed growing space in a computer of parentage whose progeny display frost re­ program that selected trees for their efficient sistance is an obvious practical genetic appli­ use ofspace in terms of volume growth. Develop­ cation for planting frost-prone areas. Any par­ mental history was then evaluated to further entage displaying resistance to browsing by improve the selected group of parents. deer and hare may have similar application in areas of heavy animal pressure. Form CONE PRODUCTION Selecting only straight and unbroken trees­ traits that are universally desired and have a Early selection guides recommended trees useful degree of inheritance-as candidates is "\vith evidence of cone bearing. Although a heavy practical for the species. Although selections for seed crop reduces a tree's growth, a negative most seed orchards have prized trees of slender relationship bet"\veen inherent heavy cone bear­ form, there is evidence that volume-per-acre ing and gro·wth rate has not been established. improvement may be enhanced by tall but Besides seed production, cone and seed damage stocky types. Snow breakage, a concern west and germination rates are possible traits for of the Cascade Range where heavy, wet snows selection as factors causing parental contribu­ are common, as well as ice breakage, is also less tion to vary in seed orchard seed. among stocky tree types. Although inheritance of stockiness appears at least moderate, the un­ CONTROLLED POLLINATION reliability of phenotypic selection, the lo"\v reli­ ability of a nursery to predict the trait in older Early publications (Orr-Ewing 1956, Ching trees (see "Form" under "Variation"), and the 1960) still provide useful guidelines. New prod­ correlation with larger limb size limit present ucts and technologies, however, have simplified selection opportunities. procedures. Horizontal branching was emphasized in The expanding seed cone buds are isolated early selection guides as desirable for reducing in bags in early March after pollen cone buds knot size (Isaac 1955). Few limbs per whorl are removed. Most easily missed are a ring of or better limb spacing at the whorl has been tiny buds at the base of the shoot. Bags with suggested as a selection criterion to prevent an observation window are expensive. Pollina­ structural weakness in wood. Both traits have tion programs now generally use low cost, cool, been used only sporadically. kraft "\Vindo"\vless bags (Wilson 1969) that can be left in place from March to September for Phenology both isolation and protection against insects. They are often too deteriorated from needle Despite almost certain relationships of phe­ abrasion by September, ho"\vever, to assure nology with such traits as frost, drought, insect holding shed seed. resistance, and possibly wood and growth, little Pollen collection, extraction, and handling use has been made to date of selection for differ little from that developed for pines phenological differences of parent trees. Un­ (Duffield 1954), although Douglas-fir's large doubtedly, phenological differences will become pollen grain is more convenient for handling. of much use as seed orchardists seek better Pollen must be air dried to below a 10-percent control of pollen and insects, as progeny fami­ moisture content for preservation in cold stor­ lies are evaluated, and as the extensive pheno­ age or in freeze drying (Livingston and Ching

19 1987), but drying to a moisture content below sides of the conelet are poured full. Scarce 3.5 percent is harmful (Rediske 1977). Mois­ pollen may be diluted up to five times its volume ture-sensitive colored paper strips are helpful with dead pollen and still provide a good set in monitoring desired moisture levels. Pollen of filled seed. Success of such dilution is pos­ may be ripened ahead of normal shedding. sible because the micropylar canal can accom­ Hsin and Daniels (1977) reported on a variety modate up to nine pollen grains, only one of of methods using potted 6- to 10-year-old grafts which need be successful. that advanced shedding up to 50.6 days. All Supplemental pollen has been successfully treatments reduced pollen viability, but forcing applied to seed orchard trees with a mist blower in a greenhouse or in polyethylene bags after (Karlsson 1977). A vacuum cleaner with a rake dormacy gave acceptable pollen about 2 weeks attachment was used to obtain large quantities ahead of normal shedding. of pollen. Seed yields were increased 21 percent. In ordinary pollen testing in water or on agar, no pollen tube forms. Shedding of exine TESTING on imbibition followed by grain elongation of 200 to 500 micrometers is used, instead, as an Field testing for growth performance is often indicator of pollen vigor.' Such elongation re­ made difficult by mountainous topography. With quires 24 to 48 hours in ordinary testing meth­ thousands of parent trees now under field tests, ods (Ho and Sziklai 1972). Adenosine triphos­ technology has rapidly developed. A typical phate determinations have been developed by commercial testing procedure begins with grow­ Ching and Ching (1972, 1976) as a quick test ing test seedlings, usually 100 to 250 per parent, with reported high reproducibility. Another in special nursery beds for 2 years, or in con­ quick test in our laboratory uses a 0.15-percent tainer nurseries for 1 year. Seedlings are H~O~ solution. Viable pollen grains fully elon­ shipped from these facilities to the test sites, gate 1 to 2 hours, then burst. The test is rea­ individually labeled, and segregated into repli­ sonably reliable in evaluating seed set of cates. Douglas-fir.s A typical improvement program testing 300 Maximum set of seed averaging about 37 or more parents will use 6 to 12 sites of 5 to 15 seeds per cone is obtained when good pollen is acres (2-6 ha) in size, sampling the range of liberally applied to fully expanded conelets. sites in the forest ownership (fig. 6). The Seed set of over 20 seeds per cone, however, is needed uniform within-plot conditions in typi­ obtained from pollen applied at any time over cal rugged topography of the region often limits the 14-day period from bursting until the cone­ choice to small sites. Scarification or herbicides lets begin to turn horizontally. Some seed set is are ordinarily required to control plant compe­ obtained from pollen applied before buds have tition, and fences to keep out deer and elk. burst or as the cones bend down·ward. Trapping, baiting, and individual screening, When rigorous isolation is needed, pollen is however, have also been needed to control hare applied with a syringe, either dry or in water or mountain beaver. Randomized block designs suspension (Allen and Sziklai 1962). As in corn in rectangular plots are most commonly used, breeding, for most large-scale practical pro­ although wheellike designs on flat ground have grams where evaluations are based on average been used. Single tree plots are used more fre­ growth of a large family, the bag is carefully quently than row plots. In instances of more removed for a brief time while pollen is poured than 60 parents in a test, sets of 30 to 60 par­ over each conelet. Our laboratory has deter­ ents are tested separately, with or without mined that seed set is enhanced if bracts on all common or standard parentage. Spacing is 7 Christiansen (1969) found that some dead pollens usually about 10 feet (3 m). No evidence of a elongate. This must be a rare occurrence as no seed Eet spacing-genotype interaction was observed in has yet been obtained with any pollen lot judged to be studies by Campbell and Wilson (1973). One dead by pollen germination tests in our laboratory. early Oregon program testing 900 parents used s Fresh, 1-year-old, 2-year-old, and killed pollen were three spacings-8-, 12-, and 15-ft (2.4-, 3.7-, first compared for percent elongated pollen using 14­ percent sucrose-agar and 0.15-percent H:!O:! against ger­ and 4.6-m). Growth is measured either at regu­ minated pollen counts seen in hand-sectioned micropylar lar time intervals or before a good seed year canals. Later they were compared with percent filled to provide means of updating the ranking of seed per cone. Very poor or very good pollen lots were parents selected for seed collections or cross­ identified to the same accuracy with either agar or H:!O:! ings. Information on animal injury and frost tests. Weak lots were highly variable in seed set in all tests, probably because micropylar canals hold several damage is usually recorded for possible use in grains. resistance breeding. With over 125 such test

20 produce naturally by asexual means, although two instances of viable seed produced from unpollinated cones are reported (Orr-Ewing 1957b, Allen 1942c). Douglas-fir is easily grafted, but it ranks among the most troublesome species for graft incompatibility, a major factor influencing tree improvement strategies. It roots readily from cuttings or air layers of juvenile trees, but no instances of stump sprouting, suckering, or natural air layering are recorded. It is rooted with greater difficulty after ortets reach 10 years of age (Black 1973), an obstacle to con­ sideration of clonal forests of superior mature trees. Reproduction from single cell and genetic combinations using protoplast fusions are, as yet, unsuccessful (Winton and others 1974), but whole plants have been produced from pieces of cotyledons (Cheng 1975).

Grafting

Information on grafting has been developed to meet seed orchard needs (Orr-Ewing and Prideaux 1959). Over 90-percent initial success is usually attained from careful field grafting in springtime without bag protection, using cleft, veneer, and sometimes other common graft types (Copes 1969). Grafting can be done Figure 6.-A typical progeny test site. Establi~hed in at any season in the greenhouse or by enclosing 1970, this is one of eight similar plantations testing the grafts in protective bags to prevent desicca­ 170 parent trees for a 70,000-acre (29 000 ha) co­ tion or overheating of grafts. Scions are usually operative tree improvement program in western Oregon. The wind-pollinated progeny are 6 years old collected during \vinter dormancy and can be (photo courtesy Starker Forests, Corvallis, Oreg.). stored in polyethylene bags at 32° F (0° C) for at least 4 months if desiccation and molding are controlled. Major factors influencing successful sites established in the Douglas-fir region, all grafting are condition of scions, time of graft­ informational phases depend heavily on com­ ing, length of graft union, and weather condi­ puters. tions immediately before and after grafting Most commercial testing has been designed (Copes 1967b, 1970). Scions collected from the for minimizing costs. In such minimal-cost major branch tips in the top whorls of mature tests, a progeny family must display generally trees are more prone to grow upright than are superior performance over all sites, or a site­ branch tips or scions collected from a lower related trend~ to be statistically detectable position in the tree. Scions of the latter type for selection. The concept of segregating often show plagiotropic growth for many years. parentage from the tests that trend toward Use of vigorously growing rootstocks, however, better performance on good or poor sites, high greatly reduces the period of plagiotropic or low elevations, or north or south slopes, pro­ growth. vides opportunities to enhance the selection of Graft rejection, or grafting incompatibility, families adapted for specific sites. is a major problem. An average of 35 percent of all grafts are ultimately rejected by under­ ASEXUAL REPRODUCTION stock tissue (Copes 1969). Percentage of rejec­ tion for clones has ranged from 5 to 95 percent. Information on asexual reproduction is com­ The incompatibility problem was serious enough paratively ·well developed for Douglas-fir be­ to slow major new investment in Douglas-fir cause of its early dependence on grafted seed tree improvement for several years (Silen and orchards. The species does not ordinarily re­ Copes 1972). Solutions ·were found, based on

21 early recognition of symptoms and evasion Knowledge developed mainly within the last (Copes 1967a). By 13 months after the graft­ decade has more than doubled rooting success ing, a characteristic incompatibility symptom from cuttings from 10- to 50-year-old trees in the xylem is seen microscopically in incom­ (Brix and Barker 1969, 1971; Black 1973; patible unions. In one evasion technique, two Cornu 1973; Copes 1977). It appears that cut­ grafts of a clone are made lJer rootstock and tings must have satisfied auxin, chilling, and one graft is sacrificed and inspected after thin day length requirements for best success; but sectioning and tissue staining. A different scion auxin can partially substitute for lack of chill­ clone is substituted on the rootstock if the char­ ing (Roberts and Fuchigami 1973; Bhella and acteristic incompatibility symptom appears in Roberts 1974, 1975). Rooting of mature tree the sacrificed union. This technique results in cuttings is still erratic. Best success has been variable seed orchard spacing. For uniform achieved with a buried inarch technique in spacing, another technique with the same in­ ·which adult cuttings are grafted to lo·wer stems compatibility symptom is used to detect and of young seedlings (Wheat 1964, Brix and select understocks compatible with each scion Barker 1971). clone. Enough grafts of each scion clone are Best results are reported with collections made to insure at least one compatible stock­ made in the December-to-March period (Rob­ scion combination for every clone. The young erts and Fuchigami 1973). Use of IBA (0.5 compatible rootstocks can then be easily propa­ percent best according to Cornu (1973)) ap­ gated by rooted cuttings in quantities sufficient pears to maximize rooting as well as to enhance for orchard understock requirements of each shoot grovvth (Ross 1975). Intermittent mist specific scion clone. Present research is aimed and bottom heat are considered advantageous, at producing highly compatible understocks but soil moisture control is essential to reduce through breeding and use of rooted cuttings. fungal attack. Fibrousness of roots is influ­ Breeding work is based on the finding that enced by the rooting media, with a 2 :1 peat­ inheritance of graft compatibility is fairly high sand mixture recommended by Copes (1977) and primarily additive (Copes 1973, 1974). Thousands of highly compatible rootstocks are when mist and bottom heat are used. Number routinely produced yearly. of cuttings obtained from young seedlings is greatly enhanced by shearing (Ross 1975). Rooting Under all conditions, results can vary greatly among clones. Douglas-fir roots less readily than ·western Techniques of growing plantlets through hemlocks, spruces, or firs. Erratic and low root­ tissue culture techniques have recently defined ability of cuttings from mature trees led to plant growth regulator for each developmental an early reputation as a difficult species to root. state (Cheng and others 1977). Adventitious The finding that seedling cuttings rooted readily root development following formation of shoots has led to increased use of rooting for asexual required 0.05-0.25 micrometer NAA (naphtha­ reproduction. Decreasing rootability with age leneacetic acid). Shoot formation required only is seen in a compilation of experience at Cor­ vallis, Oreg. Success from rooting cuttings in basal medium. Adventitious bud formation re­ sweatboxes without mist or bottom heat has quired 5 micrometers BAP (N6 -benzylamino­ averaged about 90 percent for 1-year seedlings, purine) plus 0.5-5.0 micrometers NAA, or 5 60 percent for 4-year seedlings, 20 percent for micrometers BAP and 0.25-5.0 micrometers 8-year seedlings, and less than 10 percent for each of IBA (indole-3-butyric acid) and IAA rnature trees. (indole-3-acetic acid).

APPLIED PROGRAMS

HISTORY

A variety of practical tree improvement pro­ 1950's, many abandoned them out of discour­ grams has evolved to accommodate the serious agement or reduced tree improvement financing technical problems with the species. Although during the mid-1960's. This discouragement most large landowners established seed produc­ arose from problems associated with mountain­ tion areas or seed orchards during the late ous topography, small seed zones, animal dam­

22 age, brush competition, planting failures, high cient programs, or because too high a propor­ establishment costs, and need for skilled staffs tion of seed originated from relatively few and special seed orchard sites. Additionally, the parents. unanswered technical questions of heavy pollen contamination, uncertainty of selection, diffi­ SEED ORCHARDS cult rooting, and the slow, erratic or unequal seed production of clones cooled early optimism. As the only available tree improvement con­ The species proved to be among the worst of the cept initially, the grafted, general-combining­ major species in expressing latent mortality ability seed orchard program was widely from grafting incompatibility. adopted in the Douglas-fir region. By 1965, 20 By the mid-1960's, planting, which earlier Douglas-fir orchards totaling over 200 acres (80 had been practiced on only a modest scale, was ha) had been started. About 20 more orchards greatly expanded. Better data on potential gene­ and over 700 acres (280 ha) have since been tic gains began to restore confidence. Proposed added (fig. 7), but 10 of the original 20 earlier use of wide crossing of races and a concept that ones are no longer maintained. Genetic gain avoided need for grafted seed orchards engen­ 'vas based on utilizing the additive component dered hope. By 1970 most of the early seed of genetic variance from intensive phenotypic orchard problems were being solved with eva­ selection. Plus-tree selections ranged from 15 sion techniques (Silen and Copes 1972). Fueled to 100 per seed zone, with 10 to 80 ramets of by favorable changes, an exponential expansion each parent grafted to understock seedlings. in program acreage that spread to most of the Most orchard spacing is now about 40 trees per Douglas-fir region was underway by 1970 and acre. Only recently have any seed orchard pro­ is still rapidly expanding over other parts of grams begun systematic and comprehensive the West. field testing of progeny to assess performance The systematic search for suitable races of of individual parents. Western North American species, occasioned by the seed collection of the International Union of Forest Research Organizations (IUFRO) and other European seed collections and by seed collections appropriate for trial in the southern hemisphere, has also led to expanding improve­ ment programs of Douglas-fir as an exotic.

SEED CERTIFICATION

Need to assure landowners of the source of Douglas-fir region better natural seed collec­ tions led to the establishment of a system of certification in Oregon and Washington in 1962. Overall guidance of the program is by the Figure 7.-An 8-year-old Douglas-fir seed orchard, at North,vest Forest Seed Certifiers, Inc., com­ Colton, Oreg. (photo courtesy of Bureau of Land posed of major seed-using landowners and com­ Management, Salem, Oreg.). mercial seedsmen. British Columbia instituted a program in 1971 (Piesch and Phelps). Actual Discovery of evasion techniques has provided field certification is done by Washington Crop major breakthroughs for solutions to most early Improvement Association, Oregon State Uni­ seed orchard problems. Graft incompatibility versity Extension Service, and British Colum­ research has provided a method of producing bia Forest Service. an orchard virtually free of the problem (see "Grafting"). Widely compatible rootstocks are SEED PRODUCTION AREAS now being bred (Copes 1973, 1974). The perplexing problem of heavy contamina­ Some early programs used seed production tion from outside pollen has also been solved by areas that had been rogued of pole-size stands another evasion technique. Spraying the or­ to leave widely spaced, good dominants to pro­ chards with cold water prior to bud burst delays duce wind-pollinated seed. Most seed produc­ floral buds from bursting until the peak period tion areas have been phased out in favor of of local pollen shed has passed ( Silen and Keane more genetically efficient and financially effi­ 1969). The contamination problem itself dissi­

23 pates with time. Pollen production in orchards Seedling seed orchards established from full­ more than a decade old becomes so abundant sib families are a major element of several that it reduces the contribution of outside pollen programs to provide second-generation seed. to a minor component. Even so, some early Orchards established on farmland use the same flowering clones may be poorly pollinated or practices and have the same problems of dif­ late flowering ones may be pollinated mainly by ferential cone production and pollen manage­ outside sources. ment as the grafted orchards. Some have been Lack of cone production was a persistent established with seedlings in large pots to ac­ problem for early orchards located in high rain­ celerate early cone production and breeding and fall portions of the Douglas-fir range. Sunny to permit flexible management. localities in the Williamette Valley-Puget Sound trough and on the Sannich Peninsula of Van­ WIDE CROSSINGS couver Island have been sought for newer orchards. In such locations the problem of slow Programs aimed at genetic gains from hetero­ and erratic early cone production usually sis or at better growth from genes found in changes to overproduction for the intended seed more mesic and mild portions of the range have zone after about a decade. During the bumper been started in Germany (Schonbach and Bell­ crop year of 1971, the three oldest Douglas-fir mann 1967); British Columbia (Orr-Ewing and orchards, started over a decade earlier, pro­ others 1972); Colorado, Idaho, and Oregon duced 20 to 30 pounds (9-13.5 kg) of seed per (Rowe and Ching 1973). The programs require acre. In two of these, seed needs for the breed­ a search to find best performers by race and ing zone were exceeded. by local percentage. The British Columbia ex­ The problem of unequal seed production of perience since 1963 has narrowed the range­ clones in Douglas-fir is serious. For example, wide search to Oregon and Washington parents records of the first two good seed crops at the because of poor growth of crosses resulting Dennie Ahl Seed Orchard show that, of 35 from interior or low latitude parentage. Adap­ clones, about eight-tenths of each seed crop was tation risks of such programs may be reduced produced by the same 9 clones (V. Allen, per­ by including wide-cross planting stock mixed sonal communication). Much of the orchard with native stock. If the progeny do not per­ pollen is also from a few clones. form to expectation, seedlings of local parent­ Seed orchard concepts have undergone many age will make the final crop (Orr-Ewing and changes. Phasing grafted orchards into long­ others 1972). ~hese programs are in the testing term breeding programs has taken several pat­ stages. terns. Sophisticated breeding designs have been incorporated. For example, one of the earliest large seed orchard programs was on Vancouver CLONAL PROGRAMS Island. A cooperative effort of all landowners has led to crossing of over 400 parents in a Since Douglas-fir roots in satisfactory per­ mating scheme of small partial diallels for centages as seedlings, clonal forestry becomes genetic evaluations and future seed orchards. possible. A program to use clones of best paren­ Early orchards with few clones have usually tal combinations of adapted races is being de­ incorporated new selections for a larger genetic veloped in West Germany by the Escherode base. In one program, five additional field selec­ Tree Breeding Station. Similar concepts are tions are being crossed as males onto each or­ being explored in New Zealand by the geneti­ chard clone. Seed from the crosses serve three cists at the Rotorua Station. A substantial purposes: testing genetic worth of clones for American research effort is in progress to pro­ possible orchard roguing, selecting seed within duce plants from cotyledons (Cheng 1975) and families from which a next generation of selec­ from single cell culture (Winton and others tions can be made, and establishing a seedling 1974). seed orchard for production of seed for the next generation. Many Northwest seed orchard PROGRESSIVE PROGRAMS owners have combined progressive programs (see "Progressive Programs") with their or­ Initially designed for small Douglas-fir own­ chard programs to obtain early seed before erships, versions of progressive programs have their orchards begin to produce, to reduce in­ spread to over 15 million acres ( 6 million ha) breeding, and to correct deficiencies in the centered in the Douglas-fir region. These pro­ gene'jc base of their programs. grams (Silen 1966b) feature a large genetic

24 base, dependence on family selectio:a from tests second decade. For example, in a span of 2 to 4 using wind-pollinated seed, immediate use of years, a landowner begins fulfilling seed needs seed from parent trees for commercial planting, from phenotypically selected parents, estab­ rapid phasing from phenotypic to genotypic lishes a field test of parents, crosses them, and selection, and early crossing of parent trees in establishes a seedling seed orchard for the next the forest for second-generation seed orchard generation of seed. Assurance of a seed supply stock. Advanced versions of the program con­ from known parents has been the most immedi­ sist of three distinct phases. ate benefit. The first phase usually begins during a good The program involves nearly 10,000 parent seed year. Breeding zones, usually under trees. Sixteen cooperatives of private, State, 250,000 acres (100 000 ha) are delimited. and Federal landowners in Oregon and Wash­ Enough parent trees are selected, usually three ington have been formed to share parentage, to parent trees per 1,000 acres ( 400 ha), to satisfy test programs, to cross parents, and to establish seed needs of the landowner. A wide range of seedling seed orchards. Such cooperatives range selection intensity has been used. The pro­ from 70,000 to 560,000 acres (28 000 to 242 000 gram, however, depends primarily on gains ha). The cooperatives receive overall guidance from family selection based on testing of from the Forest Service, U.S. Department of progeny. Wind-pollinated seed are collected Agriculture, and Industrial Forestry Associa­ from every parent for a genetic test. All seed tion geneticists. Special greenhouse facilities from the best one-fourth of the parents are have been established by private, State, and collected for commercial planting. The follow­ Federal landowners for growing containerized ing year, 6 to 12 field progeny tests of the seedlings for the progeny tests (fig. 8). parents are installed (see "Testing"). The second phase, aimed at providing seed from years 15 to 30 of the program, consists of establishing second-generation seed orchards by year 5 of the program. Usual crossing design has been a single-pair mating of all parents to provide half as many crosses as number of parents. Full-sib progeny are planted in or­ chards at close spacing. No field tests of these crosses are considered essential since the paren­ tal ranking for general combining ability is established by the wind-pollinated test. Final intent is to remove 15 or 16 planted trees when the best one-fourth of the families and best one-fourth of the progenies are kno\vn, allowing panmixia among the final seed orchards at an Figure 8.-A regional facility developed for the pro­ irregular spacing averaging 36 feet (10 m). gressive program to grow progeny-test seedlings in Costs of phases one and two in 1975 were $3.50 containers for tree improvement cooperatives. Seed­ lings are produced from about 1,500 parents yearly per forested acre of ownership. for test sites which already surpass 125 in number in The third phase is initiated between years Oregon and Washington (photo, courtesy of Indus­ 15 and 20 of the progressive program. This calls trial Forestry Association). for selection of the best individual trees of the best wind-pollinated families for second genera­ A small progressive program vvas started tion crossing. Seed from these crosses would be in 1964 to improve Christmas trees. It was field tested as well as used in a seedling seed based on wind-nollinated seed of 100 randomly orchard for the follovving generation. selected parent trees tested on eight plantations from Roseburg, Oreg., to Shelton, Wash. By Many variations of the program now exist. They aim to eliminate steps such as a grafted 1974 the trees were harvested and sold. Of the seed orchard, a multiple cross-mating design, 100 parents, the best 10 provided an average and an initial field test of ful-sib crosses. Re­ value gain of 18 percent, the top parent pro­ duced genetic effciency from control over only duced a 28-percent value gain. The top 11 par­ one parent in the first decade is a trade-off for ents have been crossed in a 6 X 11 mating to the low cost and rapid pace with which a land­ initiate a second generation program. owner can advance with a very large genetic base in a long-range breeding program by the 25 STRATEGIES

Strategies depend on objectives. A minor be much more efficient. Adequate local varia­ crop with a short rotation, such as Christmas tion permits good initial gains. The basic aim trees, can have a relatively unsophisticated, is to enhance growth without changing adapta­ economically defined objective. For a major tion, particularly to keep the buffering qualities long-term crop, like timber, the entire local or of the adapted population. regional natural gene pool can become perma­ In the more xeric or cooler parts of Douglas­ nently altered. Tree improvement objectives and fir's range where greater hardiness is accom­ strategies for a major species like Douglas-fir panied by slower inherent growth, improve­ are complicated by adaptational considerations ment strategy combines testing of local par­ (Silen and Doig 1976). Tree improvement entage while incorporating genes for faster strategies depend on whether or not the pro­ growth from races in milder or more mesic gram begins with an adapted population. locations. The strategy is further intended to capitalize on occurrence of hybrid vigor from SOURCES OF VARIATION new gene combinations of previously separated populations (see "Wide Crossings"). Beginning improvement strategies are under­ In all strategies, customs have changed dra­ standably different where Douglas-fir is intro­ matically from use of small numbers of selected duced, as contrasted to programs in its native parents per seed zone to use of very large num­ range. Where it is an introduced tree, emphasis bers of parents to provide for adequate selec­ is on sampling enough races from appropriate tion differential after the tests and to buffer climatic zones in the Douglas-fir range to find losses from poor adaptation. An ownership fastest growing adapted strains 01· in simply testing more than 1,000 parents is no longer using seed from earlier importations (Hey­ rare. Screening of such large numbers became broek 1974). Hardiness and resistance to di­ economically feasible with wind-pollinated sease are critical. In the Eastern United States, tests. Europe, and New Zealand, the exact location The long period required for testing growth, of the best source is being sought from screen­ survival, and ·wood quality in the species has ings of hundreds of collections of races from prompted new strategies. Since short rotations Douglas-fir's native range (Kriek 1974, Klein­ enhanced predictability of juvenile-mature cor­ schmit and others 1974). An important strategy relations, gro\ving of short rotation products for western Europe involves use of late burst­ (pulp, Christmas trees, for example), and pe­ ing, rapid growing, low elevation races from riodic application of fertilizers to speed growth narrow valleys of the Cascades, ·which are na­ are used as evasion strategies. Another strategy turally selected for frost resistance to avoid involves use of early traits that may be corre­ freezing air draining from large mountainous lated with later good growth, such as photosyn­ basins. Once good races are found, utilization of thetic efficiency (Campbell and Rediske 1966) the large range of phenology exhibited in every or stockiness (Silen and Rowe 1971). The strat­ race to find particularly adapted individuals is egy is to rogue all but tall-stocky or high-pho­ a further logical step (Sweet 1965, Bialobok tosynthetic families and to carry along large and Mejnartowicz 1970). numbers of such families in field tests and later In contrast, in the most mesic, mild, and roguing for long-term adaptation. Neither fastest growing part of its native range, the strategy has become operational. so-called Douglas-fir r egion, initial emphasis on improvement is usually confined to individuals GAINS from adapted populations ·within localities smal­ ler than 250,000 acres (100 000 ha). The ra­ Strategies aimed at maximizing gain per tionale is that potential gains from adapted year are incorporated into several programs. pest-resistant local parents are adequate and One company is growing large numbers of risk free, whereas seed movement involves \Vind- and cross-pollinated seedlings in large demonstrated risks. Moreover, the high ex­ pots under a semicontrolled environment to re­ penses of testing nonlocal races can prudently duce the breeding and t esting cycle to about 5 be delayed. In a few years when tree improve­ years. me?t programs will have r educed selected popu­ A widespread practice is to eliminate about lation~! to only a few percent of numbers now 15 years dead time between first- and second­ being tested in each locality, such testing will generation seed. Crosses involving all selections 26 are made soon after field testing of parents is Again, evasion techniques may become useful underway. The full-sib progeny are immedi­ strategies. Changing local populations only to ately planted so they will reach seed-producing the extent needed to achieve gains in commer­ age about the same time that the field tests can cial traits may continue the buffered balanc.e confidently evaluate best parentage, in both between trees and endemic pests. The time pe­ cases thought to be about 15 years. All but the riod when many selective events occur may be best fortuitous crosses will be rogued by this avoided if large seedlings are planted. Early time to leave a full-sib seed orchard. harvesting may avoid others. Enhancing mois­ Clones provide several opportunities to ture and fertility with silvicultural practices shorten programs. Replicated tests of relative may permit the landowner to control still growth by individual trees are possible, and the others. But a major part of any strategy may growing of forest mixes of best clones is a simply be to judiciously confine genetically im­ powerful potential technique. proved Douglas-fir to the less severe sites. On severe sites where Douglas-fir has difficulty ADAPTATION even to survive, the purportedly superior tree from a genetics program should not be expected Of all the Douglas-fir strategy questions the to survive for long, let alone produce superior most serious concern long-term adaptation. No grO\Vth. geneticist will ever be able to use as expensive and effective methods, involving virtually infi­ A.griculture experts long ago learned that nite time and numbers of trees, as were em­ only part of most land areas were economic for ployed in natural selection for adaptation to the intensive culture. In the natural state, almost local environment and climate. The trends of any square mile of the forested West was a data on long-term adaptation suggest that with mosaic of sites in which various species and decreasing site severity, a concept still poorly species mixtures found ecological niches which defined, the geneticist has increasing oppor­ they successfully dominated by specializations. tunity to successfully increase growth. But even To bring in an artificial population of a differ­ then he seems to be taking advantage only of ent species like Douglas-fir to generally replace an increasing time scale between climatic or them would seemingly require a more complex biologic events that have struck the past genetic balance found in the local gene pool. The geneti­ breeding program than was ever envisioned. cist strikes a different balance to achieve gains. Geneticaly improved and locally adapted Hence, he must properly appraise any maladap­ Douglas-fir, confined to favorable sites, should tation in his product and exercise control over contribute significantly to the economy of tem­ ho\v and where it is used. perate zone forests of the world.

ACKNOWLEDGMENTS

Many scientists in the Western United States The first draft of the section on ancestral his­ having information on Douglas-fir genetics and tory was authored by Dr. R. K. Hermann; that related fields have personally contributed infor­ on drought resistance was authored by Dr. W. mation, both published and unpublished, to this K. Ferrell. Both are at Oregon State University. paper. Twenty-eight scientists were sent por­ The extensive help given by Dr. Alan Orr­ tions of the first draft to verify its contents. Ewing, Dr. Kim Ching, Dr. Robert K. Camp­ Many were solicited for unpublished informa­ bell, and Dr. Jochen Kleinschmit on the final tion known by the author, which is given recog­ draft contributed to a markedly improved pa­ nition as a dated personal contribution (p.c.). per.

27 LITERATURE CITED

Allen, G. S. fir seedlings. Arbor. Kronickie, Rocz. 15:197­ 1942a. Douglas-fir (Pseudotsuga taxifolia (Lamb.) 219. Nadbitka. Britt). A summary of its life history. B. C. Black, Darvil K. For. Serv. Res. Note No. 9, 27 p. 1973. Influences of shoot or1gm and certain pre­ Allen, G. S. and post-severance treatments on the rooting 1960. A method of distinguishing coastal from in­ and growth characteristics of Douglas-fir terior Douglas-fir seed. B. C. Lumberman 44 (Pseudotsuga menziesii (Mirb.) Franco) stem (8) :26-30. cuttings. Ph.D. thesis, Oreg. State Univ., Cor­ Allen, G. S. vallis. 143 p. 1962. Factors affecting the viability and germi­ Bramhall, G. nation behavior of coniferous seed. 4. For. 1955. Permeability of Douglas-fir heartwood from Chron. 38 ( 4) :485-496. various areas of growth in British Columbia. Allen, G. S., and 0. Sziklai. B. C. Lumberman 50(4) :98, 100, 102. 1962. Pollination of Douglas-fir with water sus­ Brandt, R. W. pensions of pollen. For. Sci. 8 (1) :64-65. 1960. The Rhabdocline needle cast of Douglas-fir. Allen, George S. State Univ., Coll. For., Tech. Pub. No. 84, 66 p. 1942b. Douglas-fir seed from young trees. J. For. New York. 40(9) :722-723. Brix, H., and H. Barker. Allen, George S. 1969. Rooting of Douglas-fir and western hemlock 1942c. Parthenocarpy, parthenogenesis and self­ cuttings. Can. Dep. }'or. Bimon. Res. Notes sterility of Douglas-fir. J. For. 40 (8) :642-644. 25(3):22. Allen, George S., and John N. Owens. Brix, H., and H. Barker. 1972. The life history of Douglas-fir. Inf. Can., 1971. Trials in rooting of Douglas-fir cuttings by 139 p. Can. For. Serv., Ottawa. a paired-cutting technique. Can. J. For. Res. Allen, Virgil. 1 (2) :121-125. 1963. Dennie Ahl Seed Orchard. Olympic N atl. Buell, Jesse. For., USDA For. Serv., 17 p. Olympia, Wash. 1965. Rocky Mountain Douglas-fir (Pseudotsuga Anderson, Harry W., and Boyd C. Wilson. menziesii var. glauca (Beissn.) Franco). In 1970. Top injury in young Douglas-fir plantation Silvics of forest trees of the United States. on the Olympic Peninsula. State Wash., Dep. U.S. Dep. Agric., Agric. Handb. 271, p. 554­ Nat. Resour., DNR Note 2, 6 p. 556. Axelrod, D. I. Campbell, Robert K. 1937. A pliocene flora from the Mount Eden beds, 1961. Phenotypic variation and some estimates of southern California. Contrib. Paleontol. 3:125­ repeatability in branching characteristics of 183. Douglas-fir. Silvae Genet. 10(4) :109-118. Baldwin, H. I., and Daniel Murphy. Campbell, Robert K. 1956. Rocky Mountain Douglas-fir succeeds in 1963. Phenotypic correlation among branch and New Hampshire. N.H. For. and Recreation upper crown stem attributes m Douglas-fir. Comm., Carolina A. Fox. Res. and Demonstr. For. Sci. 9(4) :444-451. For ., Hillsboro. Fox For. Notes 67, 2 p. Campbell, Robert K. Barner, H., and H. Christiansen. 1964. Recommended traits to be improved in a 1962. The formation of pollen, the pollination breeding program for Douglas-fir. Weyerhaeu­ mechanism and the determination of the most ser For. Res. Cent., Res. Note 57, 19 p. Cen­ favorable time for controlled pollination in tralia, Wash. Pseudotsuga menziesii. Silvae Genet. 11 (4): Campbell, Robert K. 89-102. 1972. Genetic variability in juvenile height-growth Hellmann, Erich, and Hans Schonbach. of Douglas-fir. Silvae Genet. 21 (3-4): 126-129. 1964. Chances of breeding coastal Douglas-fir for Campbell, Robert K. frost resistance. (In German) Arch. fur 197 4. Use of phenology for examining provenance Forstwes. 13 (3) :307-331. transfers in reforestation of Douglas-fir. J. Berney, Jean Louis Ami. Appl. Ecol. 11 (3) :1069-1080. 1972. Studies on probable origin of some Euro­ Campbell, Robert K. pean Douglas-fir (Pseudotsuga menziesii 1976. Adaptational requirements of planting stock. (Mirb.) F r anco) plantations. M.S. thesis, West. For. Conserv. Assoc. Perm. Comm. Proc., Univ. B. C., Vancouver. 99 p. 66th West. For. Conf., 1975, p. 103-107. Bhella, H. S., and A. N. Roberts. Campbell, Robert K., and John H. Rediske. 197 4. The influence of photoperiod and rooting 1966. Genetic variability of photosynthetic effi­ temperature on rooting of Douglas-fir (Pseu­ ciency and dry matter accumulation in seed­ dotsuga menziesii (Mirb.) Franco). Am. Soc. ling Douglas-fir. Silvae Genet. 15(3) :65-72. Hort. Sci. 99:551-555. Campbell, Robert K., and Frank C. Sorensen. Bhella, H. S., and A. N. Roberts. 1973. Cold-acclimation in seedling Douglas-fir re­ 1975. Bud and cambial activity in Douglas-fir as lated to phenology and provenance. Ecology related to stem cutting rootability. For. Sci. 54 ( 5) : 1148-1151. 21(3) :269-274. Campbell, Robert K., and Boyd C. Wilson. Bialobok, Stefan, and Leon Mejnartowicz. 1973. Spacing-genotype interaction in Douglas-fir. 1970. Provenance differentiation among Douglas- Silvae Genet. 22 (1-2):15-20. 28 Cheng, Tsai. Northwest For. and Range Exp. Stn., Port­ 1975. Adventitious bud formation in culture of land, Oreg. Douglas-fir. Plant Sci. Lett. 5:97-102. Copes, Donald. Cheng, Tsai Y., K. T. Cheah, P. M. Hasegawa, E. G. 1969. Effect of graft type on 6-month scion sur­ Kirby, and T. Yasuda. vival of field grown Douglas-fir grafts. USDA 1977. Development of tissue culture techniques for For. Serv. Res. Note PNW-104, 5 p. Pac. mass propagation of Douglas-fir. (Abstr.) Northwest For. and Range Exp. Stn., Port­ Proc. West. For. Genet. Assoc. Colo. State land, Oreg. Univ., p. 3-4. Copes, Donald L. Ching, Kim K. 1970. Effect of date of grafting on survival in 1959. Hybridization between Douglas-fir and big­ Douglas-fir. USDA For. Serv. Res. Note PNW­ cone Douglas-fir. For. Sci. 5(3) :246-254. 135, 4 p. Pac. Northwest For. and Range Exp. Ching, Kim K. Stn., Portland, Oreg. 1960. Controlled pollination of Douglas-fir-a pic­ Copes, Donald L. torial manual on technique. For. Lands Res. 1972. Inheritance of megastrobili color in Douglas­ Cent., Oreg. State Univ. Res. Note 40, 11 p. fir (Pseudotsuga m enziesii (Mirb.) Franco). Ching, Kim K., Harvey Aft, and Terry Highley. Can. J. Bot. 50(10) :2045-2048. 1966. Color variation in strobili of Douglas-fir. In Copes, Donald L. Proc. West. For. Genet. Assoc. 1965:37-43. 1973. Inheritance of graft compatibility in Doug­ Ching. Kim K., and Allan Doerksen. las-fir. Bot. Gaz. 134(1) :49-52. 1971. A natural chimeria of Douglas-fir. Silvae Copes, Donald L. Genet.20(5/ 6):209-210. 1974. Genetics of graft rejection m Douglas-fir. Ching, Kim K., and Denis P. Lavender. Can. J. For. Res. 4(2) :186-192. 1970. Effects of certain controlled environments Copes, Donald, Frank Sorensen, and Roy Silen. upon incidence of prococious flo wering in 1969. Douglas-fir seedling grows 8 feet tall in two Douglas-fir (Pseudotsuga m enziesii (Mirb.) seasons. J. For. 67(3) :174-175. Franco) seedlings. (Abstr.) F ir st North Am. Cornu, D. For. Bioi. Workshop, Mich. State Univ., East 1973. Essais preliminaires sur la selection de Lansing. cones Bouturables de Douglas (Pseudotsuga Ching, T. M., and K. K. Ching. m enziesii (Mir b. ) Franco). Ann. Sci. For. 30: 1962. Physical and physiological changes in ma­ 157-173. turing Douglas-fir cones and seed. For. Sci. Curtis, Robert 0., Donald L. Reukema, Roy R Silen, 8 ( 1 ) : 21-31. Roger Fight, and Robert M. Romancier. Ching, T. M., and K. K. Ching. 1973. Intensive management of coastal Douglas­ 1972. Content of adenosine phosphates and adeny­ fir. Pacific Logging Congr. Loggers Handb. late energy charge in germinating ponderosa Vol. 33, 6 p. pine seeds. Plant Physiol 50 :536-540. De-Vescovi, M. A., and 0. Sziklai. Ching, Te May, and Kim K. Ching. 1975. Comparative karyotype analysis of Douglas­ 1976. Rapid viability tests and aging study of fir . Silvae Genet. 24(3) :68-72. some coniferous pollen. Can. J . For. Res. 6 ( 4): Dimock, Edwa rd J. II, Roy R. Silen, and Virgil E. Allen. 516-522. 1976. Genetic resistance in Douglas-fir to damage Christiansen, H. by snowshoe hare and black-tailed deer. For. 1963. On the chromosomes of Pseudotsuga macro­ Sci. 22(2) :106-121. carpa and Pseudotsuga m enziesii. Silvae Genet. Doer ksen, A. H., and K . K. Ching. 12(4) :124-127. 1972. Karyotypes in the genus Pseudotsuga. For. Christiansen, H. Sci. 18(1) :66-69. 1969. On the pollen grain and the fertilization Duffield, John. mechanism of Pseudotsuga m enziesii. Silvae 1954. Studies of extraction, testing and storage of Genet. 18 ( 4) :97-104. pine pollen. Z. fur Forstgenetic 3 :39-45. Christiansen, H. Ebell, L. F. 1972. On the development of pollen and the ferti­ 1971. Gridling: its effect on carbohydrate status lization mechanism of La'rix and Pseudotsuga and on reproductive bud and cone development menziesii. Silvae Genet. 21(5) :166-174. of Douglas-fir. Can. J. Bot. 49(3) :453-466. Conkle, M. T. 1974. Enzyme polymorphism in forest trees. In Ebell, L .F., and R. L. Schmidt. Proc. Third North Am. For. Bioi. Workshop, 1964. Metrological factors affecting conifer pollen Colo. State Univ., p. 95-105. dispersal on Vancouver Island. Dep. For. Can. Copes, D. L. Publ. No. 1036, 28 p. 1977. Influence of rooting media on root structure Ebell, Lorne F. and rooting percentage of Douglas-fir cuttings. 1967. Cone production induced by drought of Silvae Genet. 26(2-3) :102-106, illus. potted Douglas-fir. Can. Dep. For. Bimon. Res. Copes, Donald. Notes 23(4) :26- 27. 1967a. Graft incompatibility symptom develop­ Eis, S. ment in Douglas-fir and orchard screening 1973. Cone production of Douglas-fir and grand method. (Abstr.), Proc. West. For. Genet. fir and its climatic requirements. Can. J. For. Assoc., p. 4. Res. 3(1) :61-70. Copes, Donald. E l-Lakany, M. H., and Oscar Sziklai. 1967b. Influence of cambial contact length on graft 1971. Intraspecific variation in nuclear character­ survival and leader elongation in Douglas-fir. istics of Douglas-fir. Adv. Front. Plant Sci. USDA For. Serv. Res. Note PNW-69, 8 p. Pac. 28 :363- 378. 29 El-Lakany, M. H., and Oscar Sziklai. West. For. Genet. Assoc. Colo. State Univ., 1973. Further investigations on intraspecific vari­ p. 9. ation in DNA content of Douglas-fir (Pseudot­ Irgens-Moller, H. suga menziesii (Mirb.) Franco). Egypt. J. 1962. Genotypic variation in photoperiodic re­ Cytol. 2 ( 2) : 345-354. sponse of Douglas-fir seedlings. For. Sci. 8 ( 4) : Ferrell, William K., and E. Stephen Woodard. 360-362. 1966. Effects of seed origin in drought resistance Irgens-Moller, H. of Douglas-fir. Ecology 47(3) :499-503. 1967. Patterns of height growth initiation and Flous, F. cessation in Douglas-fir. Silvae Genet. 16 (2): 1935. Revision of the genus Pseudotsuga. (In 56-58. French). Trav. du Lab. For. de Toulouse, Irgens-Moller, H. Tome 2, Vol. 4, Artie. 2. 1968. Geographical variation in growth patterns Fryer, J. H., and F. T. Ledig. of Douglas-fir. Silvae Genet. 17(2/ 3) :106-110. 1972. Microevolution of the photosynthetic tem­ Irgens-Moller, Helge. perature optimum in relation to the elevational 1957. Ecotypic response to temperatures and pho­ complex gradient. Can. J. Bot. 50 (6):1231­ toperiod in Douglas-fir. For. Sci. 3(1) :79-83. 1235. Irgens-Moller, Helge. Garman, E. H. 1958. Genotypic variation in time of cessation of 1951. Seed production by conifers in the coas-~al height growth in Douglas-fir. For. Sci. 4(4): region of British Columbia related to dissemi­ 325-330. nation and regeneration. B. C. For. Serv., Isaac, Leo A. Tech. Publ. T35, 47 p. Victoria. 1943. Reproductive habits of Douglas-fir. 107 p. Griffin, Anthony Roderick. Charles Lathrop Pack For. Found., Washing­ 1974. Geographic variation in juvenile growth ton, D.C. characteristics of Douglas-fir (Pseudotsuga Isaac, Leo A. menziesii (Mirb.) Franco) from the coastal 1955. Tentative guides for the selection of plus­ range of California. Ph.D. thesis. Oreg. State trees and superior stands in Douglas-fir. Univ., Corvallis. 153 p. USDA For. Serv. Pac. Northwest For. and Griffith, Braham G. Range Exp. Stn. Res. Note 112, 9 p. Portland, 1968. Phenology, growth, and flower and cone Oreg. production of 154 Douglas-fir trees on the Uni­ Isaac, Leo A., and Edward J. Dimock II. versity Research Forest as influenced by cli­ 1965. Douglas-fir (Pseudotsuga menziesii (Mirb.) mate and fertilizer, 1957-1967. Univ. B. C., Franco) var. m enziesii. In Silvics of forest Fac. For. Bull. No. 6, 70 p. Vancouver. trees of the United States. U.S. Dep. Agric., Haddock, Philip G., John Walters, and Antal Kozak. Agric. Handb. 271, p. 547-553. 1967. Growth of coastal and interior provenances J ahn, Giesla. of Douglas-fir (Pseudotsuga menziesii (Mirb.) 1955. Comparison of German and American Doug­ Franco) at Vancouver and Haney in British las-fir provenance trials. (In German.) Allge­ Columbia. Univ. B. C., Fac. For. Res. Pap. 79, meine Forst- und J agdzeitung 126 ( 4): 68-76. 32 p. Vancouver. Karlsson, Ingemar. Hamrick, J. L., and W. J. Libby. 1977. Supplemental pollination in Douglas-fir. 1972. Variation and selection in western U.S. (Abstr.) Proc. West. For. Genet. Assoc. Colo. montane species. Silvae Genet. 21 (1/ 2) :29-34. State Univ., p. 8. Hancock, W. V., and E. P. Swan. Kleinschmit, von J., J. Racz, H. Weisgerber, W. Dietze, 1965. The petroleum ether soluble extractives of H. Dieterich, and R. Dimpflmeier. British Columbia coastal and interior-type 1974. Ergebnisse aus dem internationalen Doug­ Douglas-fir. Phytochemistry 4:791-798. lasien-Her Kunftsversuch von 1970 in der Heiner, T. D., and D. P. Lavender. Bundes republik Deutschland. (In German.) 1972. Early growth and drought avoidance in Silvae Genet. 23(6) :167-176. Douglas-fir seedlings. Oreg. State Univ., For. Kozak, A., 0. Sziklai, B. G. Griffith, and J. H. G. Smith. Res. Lab. Res. Pap. No. 14, 7 p. 1963. Variation in cone and seed yield from young, Hermann, Richard K., and Kim K. Ching. open-grown Douglas-fir on the U. B. C. Re­ 1975. Bibliography of Douglas-fir provenances search Forest. Univ. B. C. Fac. For. Res. Pap. studies 1907-1974. Oreg. State Univ. For. Res. 57, 7 p. Pap. 25, 30 p. Krausel, R. Hermann, Richard K., and Denis P. Lavender. 1926. Fossile Coniferenhoelzer in: Engler-Prantl. 1968. Early growth of Douglas-fir from various Die N atuerlichen Pflanzenfamilien. 2d ed. Vol. altitudes and aspects in southern Oregon. Sil­ 13, 447 p. Wilhelm Engelmann, Leipzig. vae Genet. 17(4) :143-151. Heybroek, H. M. Kriek, W. 1974. The development of forest tree breeding in 1974. Douglas-fir IUFRO provenances in the the Netherlands. Stichting Bosbouwproefsta­ Netherlands, 1966/ 1967 series. Ned. Bosbouw­ tion "DeDorschKamp", Wageningen, Overdruk proefstn. Tijdschr. 46(1) :1-14. nr. 17. Krueger, Kenneth W. Ho, Rong Hui, and Oscar Sziklai. 1960. 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~ U.S. GOVERNMENT PRINTING OFFICE: 1979 0-272-756

34

Reference Abstract

Silen, Roy R.

1978. Genetics of Douglas-fir. USDA For. Serv. Res. Pap. vV0- 35, 34 p. Summarizes the natural distribution, habitat, taxonomy, life history, ge­ netic variation, genetic techniques, programs, and strategies for Douglas-fir.

KEYWORDS: Natural variation, taxonomy, genetic programs, reproduction.