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REGENERATING OREGON'S FORESTS





Cleary, Brian D., Robert D. Greaves, and Richard R. 


Hermann. 1978. Regenerating Oregon's Forests, A Guide For 


the Regeneration Forester. Oregon State University School 


of Forestry.  Corvallis, Oregon





(Note:  This document addresses seed selection for 


reforestation and the development of seed zones in Oregon. 


The purpose for including this paper in a series of studies 


having to do with gene conservation for salmonids, is to 


show how gene conservation measures have been used in 


industrial forestry in Oregon.  Actually, gene conservation 


policy in forestry predates gene conservation for salmonids 


in Oregon.  In 1938, Oregon scientists developed a 


management theory called the Home Stream Theory for Salmon 


Management (Willis Rich 1938).  This work recommended that 


since salmon return to their home steams to spawn, 


conservation of salmon should be based on protection of 


both the locally adapted salmon population and the stream 


habitats that sustain them.  However, the theory was not 


generally applied, and hatchery programs moved salmon among 


watersheds as if salmon were a homogenous species.  In 


1978, Reg Reisenbichler and John McIntyre, published their 


work on hatchery and wild steelhead showing that hatchery 


fish were different than wild fish in fitness that affected 


survival. As research biologists began to define the value 


of local adaptation in salmon, forestry had already 


developed a policy on using locally adapted trees for 


reforestation. This document shows the reasoning behind 


this forest regeneration policy. This document addresses 


trees, but the principles are the same for salmon 


conservation.   All passages and words in italics in the 


text are from the document and all passages reprinted below 


are quotes form the original document.)





SEED SOURCES SELECTION AND GENETICS


The properties and outward appearance of a tree (its 


phenotype) are the combined result of the interaction 


between the tree's genetic potential (its genotype) and the 


tree's environment.  Each tree has a slightly different 


genotype and, therefore, a slightly different potential for 


development in a specific environment.


Naturally-established trees are adapted to their 


environment; their genotypes have favorable survival and 


growth characteristics for that environment.  The best 


adapted individual plants leave the most viable offspring, 


thus, the best adapted characteristics are perpetuated.


Adaptation influences a tree's ability to reproduce, but 


does not necessarily coincide with the forester's desire 


for improved yield or increased quality.  Trees in a warm 


and dry climate, for instance, are adapted for drought 


resistance.  Foresters may desire to improve yield or 


quality in such areas through genetic selection, but 


without the general adaptation to drought, any improvement 


in yield or quality is impossible.  Attempts to improve any 


tree characteristics by genetic selection must be done 


without sacrificing general adaptation.  Furthermore, the 


"superiority" of any specific type or race of trees within 


a species must always be in reference to a given set of 


environmental conditions.  No type or race is superior in


all environments, or for all reforestation goals.


To achieve the full benefits of genetic selection, or 


"improved seed" you must manage the tree's environment 


intensively.  Genetic improvement is not a shortcut to less 


intensive management.  Overstocking, or intensive 


vegetative competition, for example, will negate any 


increased genetic potential by creating adverse 


environmental conditions.  If intensive management (for 


example, brush control or thinnings) is not planned, it is 


better to stick to local seed sources.


Matching Seed Source With Site


The seed source with the greatest general adaptation to a 


site is from the immediate vicinity of the area to be 


reforested.  The problem in seed source selection is how to 


define "immediate vicinity".  The immediate vicinity 


depends on the geographic area.


The coastal strip from the crest of the Coast Range 


Mountains west has a fairly uniform climate in a north-to-


south direction, but there are different, localized 


climates.  Seed sources from a considerable distance to 


either the north or south of the planting area sometimes 


are considered "local," but it is still risky to use seed 


collected beyond the local area.  In southern, or eastern 


Oregon where the climate and topography are more variable, 


local seed source usually implies the same aspect, same 


drainage, and same elevation.


Nursery and growth room studies of seeds collected in the 


southern Cascade Mountains of Oregon had different seedling 


growth characteristics, depending on the altitude and 


topography (north versus south aspect) of the seed source. 


This suggested the existence of "aspect races" in Douglas 


fir.  In general the more environmental conditions vary 


with distance, aspect, and elevation, the more restricted 


is the meaning of "local sources."


Without actual experience there is no way to predict what 


distance from the planting site can be considered local 


without losing general adaptation.  Based on experience and 


meteorological observations, a seed özone map has been 


constructed for Oregon. In general, seed within one zone


can be moved to other localities within that zone at the 


same elevation without any major loss of adaptation. 


Restriction on north to south seed movement within a region 


should be based on a local assessment of the probability of 


drought or cold damage.  In some locations, there is little 


evidence of elevational differentiation, while at other 


locations adhering to 500 foot elevation sub-zones may be 


more important.  Since the pattern of climatic variation in 


most cases is continuous, zone borders should be viewed as 


arbitrary, administratively convenient borders.  In some 


areas, however, distribution of a species is not 


continuous. East of the Cascade Mountains, boundaries such 


as intervening stretches of desert should be considered 


real restrictions for seed movement.


The zone map will help you choose the correct seed variety 


for your area.  Select your local seed zone as a first 


choice.  Seed from adjacent zones is acceptable only if the 


environment of that zone is similar to your local zone.


Seed zone maps can be improved only if good records of seed


sources and subsequent performance of plantings (both 


seedling survival and growth rate) are kept.  Performance 


should be monitored on permanently-marked sample trees. 


There is no better means of improving our knowledge of what 


constitutes "local" seed source in a given area.


Seed buyers should purchase only certified seed to help 


insure that identification and labeling of seed origin is 


correct.   In the Northwest, tree seed certification is 


done by the Oregon-Washington Interagency Forest Tree Seed 


Certification Program...


Non-local Sources


Using non-local seed sources for reforestation is risky 


throughout the rotation.  Non-local seed may result in one 


of the following: total initial failure of seedlings to 


survive; good initial establishment, but plantation failure 


later in the rotation because of disease, or infrequent 


climatic extremes (for example, early or late season 


frosts); production of a less valuable crop because of 


lower quantity or inferior quality.  Thus regeneration 


foresters must be extremely cautious in judging the success 


of a nonlocal source.


 Genotypes must be adapted to environmental extremes on a 


given site to be successful.  The most selective forces in 


the environment, such as unusually droughty years, or early 


severe frosts, occur periodically, often at long intervals, 


during the life of a stand.  Such infrequent events often 


determine the success or failure of a non-local source.


For example, in a small provenance experiment near 


Corvallis, Oregon, a seed source from the west side of the 


Olympic Mountains (Forks) produced the fastest growing 


trees during initial establishment compared to other seed 


sources, including a local source.  After 10 years, 


however, a severe drought killed a significant portion of 


the trees from nonlocal sources.


Off-Site Plantations


An off site plantation is a stand of trees incapable of 


fully utilizing the growth capacity of the site.  


Generally, off site plantations have been created by the 


use of seed or planting stock of unknown origin; the use of 


known, but unsuitable seed sources; planting ponderosa pine 


as a nurse crop on sever sites; and planting introduce 


species.


Off site plantations usually show poor vigor and are 


particularly susceptible to snow breakage, frost injury, 


and attack by insects and diseases.  Another serious 


problem of off site plantations is the introduction of 


genetically undesirable material through pollination of 


native trees by off site trees and establishment of natural 


reproduction from off site parents.  Do not collect cones 


for seed from these off site plantations unless you know 


the origin of the parent tree.


Planned Seed Production


Production Areas


You can establish seed production areas, relatively 


permanent seed sources of know origin that are easily 


accessible, instead of collecting seed from wild


populations.


There are two levels of selection, phenotypic and 


genotypic. Phenotypic selection (often called plus tree 


selection) is based solely on the appearance of the tree.  


The assumption is that progeny growing under similar 


conditions will perform in a manner similar to their 


parents.  Genotypic selection is based on actual 


performance of progeny; less emphasis is put on appearance 


of parent trees.


Whichever method is used, the real value of a parent tree 


for seed production can be determined only by the 


performance of its progeny under specified conditions.  In 


many species, there is little correlation between the 


appearance of parent trees and performance of their 


progeny. In such cases, large expenditures on establishing 


seed production areas, or seed orchards, are hard to 


justify until the parent trees have yielded desirable 


progeny for particular situations.


Seed Orchards


You may wish to establish a seed orchard especially during 


the first generation, by planting the best individual trees 


from a wide variety of stands.  Some genetic selection 


(that is, testing of progeny) should be a prerequisite 


before including a tree in a seed orchard.  Test the 


progeny in more than one area


Managing The Gene Pool


Planting has largely replaced natural reseeding and has 


quickly altered the gene pool.  A locally adapted, well-


buffered, multi-species gene pool should not be 


thoughtlessly discarded.  Existing strains are adapted to 


the site and are probably growing at the rate that long-


term extremes of the environment permit.  A tree 


imporvemental philosophy that will insure preservation of a 


large gene pool is needed.  Ample amounts of the natural 


gene pool should be preserved by natural seeding and 


natural selection in many localities.  We need a different 


kind of breeding in our forest species, in which the 


geneticist begins by assuming that the local strain already 


has been bred for most of the adaptation and buffering that 


is wanted, and he need change a strain only to the extent 


necessary to incorporate genes for safe enhancement of 


growth.  Such a philosophy may sacrifice quick, short-term 


gains by not breeding for a pure genetic product, but will 


maximize long run gains by avoiding costly environmental 


and pest losses.