Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
1992
Sammendrag
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Sammendrag
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Forfattere
Erik NæssetSammendrag
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Ann Merete Furuberg GjedtjernetSammendrag
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Forfattere
Reidar SkaarSammendrag
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Forfattere
Stein MagnesenSammendrag
The presence of genetic differences attributable to differences in geographic origin has been demonstrated in many temperate zone tree species. The variation between provenances is usually thought of as a result of natural selection. Most strongly affected by selection are characters of great importance to the trees, such as fast growth and resistance to frost. A provenance may be regarded as a climatic type adapted to the climatic conditions at the place of origin. Trees of local provenance will normally be capable of surviving without damage, but introduction of non-local provenances may lead to complete failure. Different climatic types will behave differently according to the climate of the region into which they are introduced. Experiments and field observations have shown that species and provenances transferred to an environment to which they are not adapted, will suffer physiological damage. This in turn leads to inferior growth and weakened trees. Subsequently, injuries and loss of vigour make the trees highly susceptible to pathogens and attacks by insects. Use of poorly adapted provenances may cause, not only reduced vitality and vigour in the trees, but complete destruction of whole stands. The unfortunate choice of provenance may not become apparent till trees are 20-30 years old. There can be mentioned many cases in which promising plantations have become failures at a later stage. In western Norway climatic damage and attacks of the pine needle cast fungus nearly devastated coast plantations of non-coastal Scots pine during the years 1921-23. In the same region climatic damage and disease caused destruction in stands of white spruce and lodgepole pine of interior provenance. In a field trial with Scots pine in eastern Norway nearly all trees of continental European provenance died after 29 growth seasons. In eastern Norway and the Trndelag counties dead and dying trees were observed in planted stands of Norway spruce at age 30-50 years. Investigations showed that the trees in the plantations had a growth-rhythm different from that of the local Norway spruce. An unfortunate growth-rhythm which was out of phase with the climate at the sites, was the most plausible explanation for the damage and mortality found in the plantations. Among forest injuries related to provenance climatic damage is most prominent, and in a northern country like Norway most climatic injuries are attributable to frost. Frost injuries cause reduced height growth and poor wood quality. The extent to which any particular provenance is liable to suffer damage by frost depends on the degree to which its annual growth rhythm synchronizes with the cycle of the seasons. Autumn frost affects forest trees with late and incomplete growth termination. Generally, northern provenances, high altitude provenances and continental provenances stop growing and pass into the hardy winter stage at an earlier date than southern provenances, low altitude provenances and coastal provenances respectively. The variation in resistance to autumn frost is more or less clinal, depending on the tree species. Winter frost damage frequently occurs in late winter when there is a large temperature difference between day and night. However, causal relation is often complicated. Low temperature is decisive, but other factors may be disposing or contributing. A long, mild, wet, dark autumn or a summer extremely deficient in warmth will cause insufficient maturation of tissue, and shoots will not acquire their normal frost hardiness. The predisposed shoots may then be injured by frost during the following winter. For the same reason provenances with late growth cessation and improperly matured shoots will be most liable to injury caused by winter frost. Accordingly, provenance variation in winter frost resistance will be much the same as that in autumn frost resistance. A mild winter period lowers the resistance, and later frost may cause damage. Winter frost stability resistance is the ability to maintain frost hardiness after a period of mild weather. Research indicates that this type of resistance is also under genetic control, i.e. provenance variation does exist. However, winter frost stability resistance does not correspond completely to the seasonal growth rhythm of trees. Spring frost damage is related to the time of flushing, and early flushing populations are most susceptible to frost. In general, southern provenances, low altitude provenances and coastal provenances tend to flush late, but clinal variation in spring frost resistance is hard to establish owing to substantial local variation in most tree species. Differences between species are frequently more significant than those between provenances. Southern provenances commence shoot elongation late in spring. Nevertheless, spring frost has been known to damage southern provenances more severely than those of northerly origin. It seems that populations which mature late in autumn also become more susceptible to spring frosts. On several occasions a significant relationship has been established between spring frost damage and injuries caused by autumn and winter frost. Research indicates that frost damage may also disturb the annual growth rhythm of trees. Drought damage occurs during dry periods in summer or in winter when the frozen ground prevents the trees from replacing their water loss. Constant winds will also cause drought damage. With reference to drought resistance, there are considerable differences between tree species, but provenance variation, e.g. in cuticular transpiration, does not seem to be of great consequence. For Scots pine and lodgepole pine grown in coastal areas, however, there are considerable differences between provenances in their ability to withstand desiccation by wind. Coastal provenances consistently show greater resistance to this type of damage than those of interior origin. For Norway spruce provenance is of great importance regarding stem cracks caused by late summer drought. Trees of continental European provenances are most frequently affected.Diseases caused by pathogenic fungi may seriously damage, or even kill forest trees. From field observations it would appear that many tree species are less resistant to pathogens when grown outside their natural range. Climatic conditions to which the trees are not adapted, may lead to physiological disorders which greatly reduce the capacity of the trees to withstand threats from the major pathogens. As fungi frequently enter through wounds and other injuries, frost is of great importance as a predisposing factor. This has the effect of making frosthardy provenances less prone to infection. On the whole, trees weakened by climatic injuries are apparently more susceptible to pathogens than others. As a result of experiments and field observations it would appear that in some cases resistance to disease is not related to climatic injuries. Attacks by insects may constitute a threat to the growth and vitality of forest trees. However, very little information is available regarding provenance variation in susceptibility to insect attacks. So far investigations suggest that provenance is not of great importance. On the other hand, the physiological condition of the trees will affect the ability of insects to feed and multiply. As weakened trees apparently succumb more easily to invasion pressure than others, it is of great importance to keep the forest healthy and vigorous by using well adapted provenances. Investigations indicate that air pollution may have the effect of making poorly adapted provenances even more susceptible to climatic damage. It is quite obvious that the use of well adapted provenances is a prerequisite for obtaining a healthy and vigorous forest. The occurrence of unexplainable forest injuries may be due to an unfortunate choice of provenance. It is important therefore to check the provenance of injured trees.
Forfattere
Arnstein Orlund Jarle BerganSammendrag
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Bjørn ØklandSammendrag
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Tor J. JohansenSammendrag
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Forfattere
Tore FrognerSammendrag
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