Reproduced with permi ssion from PACIFIC SEARCH, Vol. 10, No . B, the Forest Service , u.s . Department of Agriculture, f or official use . June issue 1976 . by f, j I '':9!(5 SR:.::ELLY 1.1L.:i. C :~, AL LAii~ YALE UN IVEP-3/TY THE CARE AND HANDLING OF THE FOREST GENE POOL ROY R. S ILE N, WITH IVAN DOIG What must be the world's most magnifi­ cent pool of fores t genes has timbered our Pacific slo pes. Why els.: do the tallest firs, pines, spruces, hemlocks, redwoods, and la rches a ll rise a lo ng the Pacific Coast of North America? Docs their hugeness simply thrust up from o ur dee p so ils a nd mild. rainy climate? From a vant age poi nt of three decades in forest research. I believe the key to this wea lth of timber is more than a ma tter of soil and moisture. Taken together, the genes of our 22 commercial western conifers seem to me to constitute our vital basic resource. And unless we recognize the magnificent quality of this gene pool. we may needlessly risk pauperi1ing or destroyi ng it as man begins to alter it along the lines of his customary philosophy of genetic im provement. Consider some evidence bea ring out the rarity of this vast gene pool. In combination with the rest of t he forest plant communit y, o ur con ifers utilize what actually a re rather ord inary soils a nd surprisingly droughty climate to produce remarka ble growth. Our climate, for insta nce, is mild. but can ha rd ly be considered s uperior. It is characterized by severe summer d ro ught - even in the Do uglas fir region west of the Cascades there can be from one to four mon.ths of moisture deficiency between May and October of any year- whereas the forest climates of the eastern US. Europe. China. Japan. and New Zealand generally have rain better dis­ tributed throughout the growing season. Our soils. a lthough good , must undergo the severe leaching of three to eight feet of rain between fall and spring. But if climate and soils in o ur region are not superior. the growth rate of our conifers clearly is. When appropriate strains of our world-record species are planted in other temperate fores t zones of the world , they June 1976 usually outgrow native trees by wide margins. When we try the best species from other forest regions here. as we ha\'e for over 60 years. ou r own species outgrow them by Pacific conifers are the best in the world , in spite of ordinary soils and regular drought. wide m:1rgins. and few among them would even come cl ose to meeting our timber needs if our nati ve trees were unavailable. How could th is bonanza of remarkable growth rates and the presence of the world's ta llest trees in each o f I 0 major genera have uniquely ha ppened in western North America? Across tens of million s of years. three strokes o f fortune occurred : - The climate of this region became cooler and droughtier as the Cascades rose a nd the ocean currents cooled. Earlier warm-c limate species in our lowland s- palm, oak, acacia , cinnamon, pecan, ma gnolia - gave way perha ps ten milli o n years ago to the more va luable conifers of today. - About a million yea rs ago there appeared the Douglas fir. the remarkable evolutionary success that has become our most valuable tree. With its heavy armor of bark t o ass ure its survival in the fire-prone West. and durable wood that gave it long life between major fi res. the Douglas fir came to dominate the best sites of the West. - The third stroke of fortune . a nd perhaps the most crucial , was geographical. The nort h-to-south orientation of the mountains of North America furnished a high escape route, virtllally all the way to the subtropics. which appears to ha ve saved our migrating forest complex intact from the ice ages. T his was not the case on the Eurasian land mass, where mountains and seas are oriented east to west; there the oncoming ice must have trapped many fast-growing, cold-sensitive s pecies and strains against the crosswise geographical barriers and eliminated them. Besides this set of remarkable cir­ cumstances, there was the rare good fortune that Western man did not arrive here early enough to inflict upon the forest gene pool t he drastic disruption that cha racterized other temperate zones. Even when the course of settlement ca me to the Pacific Northwest, seve ral trends wove together to minimize man's impact on the great gene pool. Until · early in this century, the nat ion's lumber needs were met mostly by logging in the La ke States and the South. Then between 1920 and World War II , the pe.· capita demand .for wood slacked off; less wood going into ho using and indust ry meant less cutting in our forests. At about the same time, the national forests, which in a unique quirk of history had been set aside a few decades earl ier, began to receive good pro­ tection. Federal ownership made up half the fo rest land in Orego n and Washington; until afte r World War II , relatively insignificant cutting occurred on that protected acreage. Meanwhile, the concept of sustained yield of timber was gradua lly accepted, first on the publ ic lands and then more a nd more on private land s. as owners began to find that there were no new timberlands to buy and that nurturing the existing forest to produce future timber crops made economic good sense. Along with these major trends went a customary reliance on natural seeding whenever timber was cut. Most of our cutover land was being reforested by wind­ borne seed which came from the edge of the uncut stand or from single cull trees left stand ing amid clearcuts. This method t oo helped to carry on the gene pool mostly intact. Natural seeding accomplished somet hing else only now being scientifically 7 docum rnkd: the vital preserva tion of the ge ne pool in every locality. Rece nt research ~ h o ws that genetic make up can be di fferen t in natu ral stands o nly a few miles apart - a co mplex selection respon se amo ng mul­ ti llld inous traits, spec ies by species and niche by niche. to fit the varied e nvironmental cha nges in ou r broken to pography. l a ken toget her. these trends prolonged much of the region's natural forests until after Wo rld War II. T o find any cultivated plant wtt h \ irtua lly any intact gene pool is not t he r ule. for the impacts of man on the plan t resources of the wo rld are severe a nd in many cases tragic. Yet a bout three decades ago o ur phenomenal gene pool was miraculo usly intact. sa ved by the series of unique human a nd geological events; a nd Until the end of World War II , natural seeding kept our timber gene pool mostly intact. . reliance on natura l seeding meanwhile assured tha t degrada ti on of the conifer genes would be slow , if it happened at all. Much has cha nged since then. T he two most signi fican t tendencies are those fro m na tural regenera tion of fo rests to planting. a nd toward increased investmen t in genetic improvement of ti mber species. Both have s tro ng economic justifications, and both ha ve the potential of a ltering our basic reso urce , t he gene pool. P la nti ng al ters it in a somewhat random but slow process. Genetic improvement al ters it delibera tely and rapidly. We should direct our co ncern fo r this a lterat ion in our gene pool reso urce as so berly as if we were talk ing about protecting the very soi l it se lf. J ust as the factors preserving the gene pool have been complex. so are those tre nding towa rd its a lt era tion. One came about wit h the renewed demand for wood in the building boom whic h fo llowed World Wa r II. As the cutting to meet thi s demand advanced southward from the earlier loggi ng areas of Puget So und a nd the Co lumbia Increased demand for wood has made nature's reg eneration period econom ically unacceptable. Planting has replaced natural reseeding, quickly altering the gene pool. River, and into higher e levatio ns which previo usly had not been touched, the perce ntage of land that would not regenerate ea sily by natural means increased. The rea so n was a comb ination of browsing· by 8 anima ls. extreme competition fr om brush, T he change from natural seeding to and too-se vere ex posure. Where rege nera­ pla nting. then, has represented the first tion fai led over a n exte nsive area. a ny large-scale alteration of the 'o rthwest's re placement growt h would be a somewhat unique gene pool. Now we co me to the final differe nt gene pool. trend - the introducti o n of genetic improve­ An even large r a lteration was deve lo ping ment to forest trees. unnot iced o n our best timber si tes. This was A fe w decades back. fo resters began trying the replacement of coni fers by broad leafs in to copy from Europe a nd t he ea stern US a the man-made successio n. Althoug h the practical progra m intended to produce ea rly forestry researche rs of this a rea were ge netically superior tree stock for reforesta­ genera lly correct in assuming a cutover patch tion. About 600 acres in western North would regrow in a natural successio n starting America became devoted to what we call wit h annua l plants, then perennial plants, seed o rcha rds. There cuttings ta ken from then broad leaf brush, then conifer trees, this expe nsively selected trees in the forest were did not always occur. Instead, brush species grafted o nto seed lings planted orchard-like quickly d ominated ma ny sites a nd have o n far m land. As the gra fts grew, they wou ld persisted for most of a century. On about interpollinate a nd the seed would he used in 30% of the acreage - usually the best 30% for .refo restation . The program ha d worked growth- the succession through the satisfactorily in the pines of the eastern U.S . broadleaf brush stage le ngt hened to re pre­ But for the species of main interest here , the sent a lasti ng change. Three million ac res , or Douglas fir, there began to be problems. nearly 5000 square miles. of the Coast a nd Studies demonst rated that very high leve ls no rthern Cascade Ranges today are oc­ of "outside" pollen were co ntamina ting the cupied by a lders, maples, a nd lesser brushy seed o rchards. Also, o rchards were expen­ broad leaf species instead of the fast-growing sive because of the specialists needed and the coniferous fo rests worth fi ve to ten times as price of cultivated land. The most dra ma tic much. pro blem, however, was gra ft inco mpatib ility Si multa neously, as log prices rose, it in the Douglas fir. A rejection of tissue was became uneconomical in logging to leave cull occurring between t he seedling understock trees as the natural seed sou rce. By 1960, a nd the graft , much like the problem in virtua lly eve ry conife r of a c hosen stand was human heart t ransplants. Altho ugh mostly reso lved by now, these being felled for its merchantable wood. This meant that o n priva te timberlands, where disturbing problems, plus t he fact that the large clearcutt ings were the rule, planting Douglas fir was found to be discouragingly had to be genera lly substituted fo r na tural s low and cyclic in its production of seed , began to suggest there s ho uld be a search fo r reseeding. O n public fo rest la nd s, a lthough clearcuts so me approach besides the seed orcha rd s. A were smaller, a similar cha nge from natural genetic program I had ea rlier proposed for reseeding to planting was being encouraged the region's C hristma s tree growers had by the "regeneration period" concept. This is proven successful. Stripped to its basics, the the assumed time after cutting until a new notion had been t ha t good ge netic ga ins sta nd is naturally regenerated . Economists cou ld come about by planting wind­ could show that eve n a 5-year regeneration pollinated seed fr o m trees growing na tura lly period without gro wth was financia lly in­ in the forest, if o ne kept track of the ir tolerable. Remova l of every con ifer tree progeny value and used seed of o nly·the best became a contract specification fo r c utting o ne-quarter o r less of pa rents for reforesta­ o n public la nds as we ll as the custom o n the tion. This "non-seed o rchard" approach began to find adherents. By 197 1, what has la rge private timber tracts. Thus, where re latively little planting was come to be ca lled the "progressive program" done for reforesta tio n befo re Wo rld War II , was in use on two million acres; it now pla nting is now the primary regeneration encompasses muc h of the fo rest land in method. But to replace the na tura l gene pool western Oregon and Wash ington. Even tho ugh so simple a program was while using pla nted stock is difficult to do. There is no way in t he seed collection never envisioned as the dominant beginning methods, whether by climbing trees or rob­ genet ics program, it has proved to have bing the caches of cone-cutting sq uirrels , to practical adva ntages. No seed o rc hard investment is needed. no new expertise by avoid a d ifferent selection of seed than would drift down from the natura l stand itself. forestry staffs. It has permitted rapid ad­ Nursery progra ms assure a differe nt se lec­ vance into more sophisticated progra ms tion too. A high percentage of nursery seed invo lving cross-pollinations. More impor­ tant, the program was economical enough so become plants in the forest, whereas a natural stand may start with a millio n seed that about 20,000 pa rent t rees will be per acre and only a few hundred will survive. tested - a nd hence has been more effective than programs used in other forest regions in Difficulties of scheduling the seed collection, nursery, a nd cutting o perations assure that terms of preserving the ge ne pool of each much no n-loca l seed is represented in locality. plantmg. But so extensive have become the two Pacific Search ... !>igni fica nt t rend !> from the natura l regeneration of fore sts to pla nting. a nd toward inc reased in vest me nt in ge netic im­ pro\'e mcnt o f the t imber spec ies that we must a sk w h.: n: they may be ta king us. Right now . ~o m .: im o.:stmcnt in tree impro vement programs of o ne kind or another has been made in ~eve n o ut o f eve ry ten acres of co mmercia l fo rest la nd in the Pacific 1\onhwc!>t. The histo ry of man's effects on o ther ge ne pools is a warni ng to us that once begun. any alteration tends to become more and mo re ex tensive. If we look broadly a t the pa th of a ll genetic improvement. we fi nd really o nly o ne phil oso phy or mode l. There are strong parallels in it to mining. O ne prospects the gene pool for the richest sources of the desired genes. refines them into as pure a s tate as possible. then spreads the product a s broadly a s the competitive market permits . Everything except the pure product goes into the waste hea p. (Admittedly. ma ny genetic programs do carry alo ng sufficient genetic di versity in their product to prevent loss o f vigor or to p rotect aga inst pests or environ­ ment. The esse ntial point remains that the ge net ic g oal is to have a s refined a product as conditi o ns will permit.) Renecting o n the "mining" philoso phy. one ca n sec th at o nly certa in parts of it have large con eque nccs for the gene pool. Prospecting and purifying are in themse lves relatively innocuous. It is the replaceme nt of the origina l gene pool with a mo re "profitable" one which wreaks the great consequence. The hist o ry of plant improve me nt is that we us ually ha\'e bee n thorough in replacing the original ge ne pool wi th an "improved" strain . For example, by the time of Co lum­ bus. corn had been so altered by se lect ion Replacing the original gene pool with an "improved" strain can turn out-a lifetime later­ to be a mistake. done b y the Ind ians that the origina l wild corn plant was extinct. and co rn's future was en tirely dependent upon man : it could no t persist in the wild . The h istory o f improve­ ment in wheat simila rly ha s been the refining of the ge ne poo l int o o ne st ra in a fter anot her, no ne of which could exist with o ut man: each. in turn . was wiped ou t by a pest. Fo rtuna tely. a new imprO\'Cd s train was always in the wings. a risi ng fro m some resistance g leaned out o f the s hrinking origina l ge ne pool. Today the origina l gene pool of wheat is reduced to a few small acreages in the "fertile crescent" of t he Med iterra nea n area . To follow this "mining" model is by far the most likely path for our fo rest gene pool. Ex plo itat ion a nd quick gains have always preva iled in o ur resource ma nage ment. Picture the la ndowner's cho ice of alter­ June 1976 natives in refores tation if some forest geneticist s ho uld produce a refined strain that promises to give a SO% gain in produc­ t ion. Will that landowner have any long­ range concern for hi present forest gene pool'? Can he co mpete if he rc!>ists using the new strain? Yet the alread y c xi~ ting s train . genetically tuned to its own local la nd fo rm a nd ecosystem a nd pro bably g rowi ng at the rate that lo ng-term ex t re me ~ o f the e nvironment will permit , may well be supe rior in most ways. And much is a t stake wheneve r we thoughtless ly disca rd a local adapted. well­ buffered . multi- s pec i e~ gene pool. In forest ry the crop is long-lived. and it may take the length of human lifetime just for any mis ta kes in t he altered gene bala nce to show up. Histo rically, however. we ca n sec that with both economics a n d estab l is h e d phil osophies so well served by simply mining o ur gene pool. it would tak e a miracle to keep intact thi s unique forest resource . What would this miracle invo lve? A different genetic philosophy. It wo uld mean . first , the patient accept­ ance by the forest landowner that this most magnificent gene pool is no t yet understood , a nd th at ample a mounts should be preserved by nat ural seeding with na tural selecti on in e\ c ry locality until it is understood for its tota l worth. adaptation. buffering. and other qualities. Secondl y. it would ca ll for acceptance of a diffe rent kind of breed ing in o ur forest s p ecie~ . in which the geneticist begins by a ssum ing that the local strain a lready has bee n bred fo r most of the adaptation a nd buffering that is wa nted. and he need change that s train o nly to the ex tent necessa r y to incor porate genes fo r safe enhancement of gro wth . In 1he s hort run. this might sacrifice quick ga ins by not breeding for a purer genetic product , but in the long run it might max­ im i7c gains by avoid ing costly environmental 'lnd pest losses. T he d etails of s uch a phil osoph y remain to be worked o ut. but it is highly important that geneticists g ive it a try. It is more a cha nge in goals tha n in tech­ niques. O nce we full y rea lize that o ur forest genes a re a more valuab le and critica l source of wealth than the soi l itse lf, perhaps the ·orthwcst gene pool will aga in be saved intact by one mo re unique historic event - a caut ionary approach by man . DR. SILEN is Principal Plant Geneticist. USDA Forest Se rvice, Pacific NW Forest a nd R a nge Experiment S tation. Forestry Sciences Laboratory. Corvallis, Oregon. This article is adapted by Ivan Doig o f the Pac((ic Search staff from a lecture give n by Dr. Silen to the Ho nors Colloquium , Orego n State University , November 19. 1975. 9