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
Det er ikke registrert sammendrag
Forfattere
Arne Grønlund Ove Klakegg Rune SolbergSammendrag
Det er ikke registrert sammendrag
1991
Forfattere
Mekjell MelandSammendrag
Det er ikke registrert sammendrag
Forfattere
Mekjell MelandSammendrag
Det er ikke registrert sammendrag
Forfattere
Erik NæssetSammendrag
Formålet med dette arbeidet er å undersøke nøyaktigheten av fotoregistrering av volum i bestand. 97 bestand i hogstklasse IV-V i Grue og Kongsvinger kommuner er totalklavet eller taksert ved en intensiv systematisk prøveflatetakst. Totalt volum med bark er beregnet ut fra de markmålte dataene. 5 trenede stereo-operatører har registrert bestandsmiddelhøyde, kronedekning og treslagsfordeling i hvert bestand i pankromatiske (svart-hvite) flybilder i målestokk 1:15000. Det er benyttet Wild B8 for alle registreringene. Bildene er tatt 0-4 år etter totalklaving. Markmålt volum er korrigert til fotograferingstidspunktet. Fotovolum er beregnet ved hjelp av volumfunksjoner utviklet av Tomter (1988). For hele materialet er standardavviket til differansene mellom foto- og markmålt volum på 24-28 % (5,1-5,9 m3/daa), og det er en systematisk feil på inntil -22 %. Den tilfeldige feilen som er funnet i dette arbeidet, er noe større enn det som er påvist i tidligere norske og svenske undersøkelser. Det er undersøkt om treslagsspesifikke gran- og furufunksjoner gir bedre tilpasning i treslagsrene bestand enn en funksjon utviklet for barskog. Den tilfeldige feilen blir tilnærmet den samme i alle funksjonene, men det er en signifikant systematisk forskjell mellom barskogfunksjonen og granfunksjonen, og mellom barskogfunksjonen og furufunksjonen.Store personavhengige systematiske feil og feil ved fototolking av treslagsfordeling i flybilder, gir likevel grunn til å anbefale at barskogfunksjonen benyttes i alle typer barskogbestand ved fototakst. Bestandene er inndelt etter hogstklasse, tetthetsklasse og bonitet. Det er funnet en signifikant forskjell i systematiske feil mellom hogstklasser for 2 av observatørene. For 4 av observatørene er det funnet en signifikant forskjell i systematiske feil mellom tetthetsklasser. Mellom bonitetsklasser er forskjellen i systematisk feil signifikant for 1 av observatørene. De systematiske feilene er mest negative i virkesrike strata. Materialet er inndelt i volumklasser på to forskjellige måter. Ved å inndele materialet etter markmålt volum, er det funnet en signifikant forskjell i den systematiske feilen mellom de ulike volumklassene for 4 av observatørene. Dette skyldes først og fremst volumfunksjonens tendens til feilprediksjon når en sorterer observasjonene etter markmålte verdier. Ved å inndele materialet etter fotomålt volum, er det påvist en signifikant forskjell mellom volumklasser for bare 1 observatør. Bestandsvise fototakster bør korrigeres mot prøveflatetakster p.g.a. systematiske feil. Hogstklasse, tetthet og bonitet synes å være egnede stratifiseringskriterier.
Forfattere
Halvor SolheimSammendrag
During an outbreak in the 1970\"s, millions of Norway spruce trees were killed by the spruce bark beetle Ips typographus. At that time, little was known about the associated fungi and their role in the tree-killing process. Studies were started to elucidate ecological aspects of fungi associated with I. typographus, with special emphasis on the fungal invasion process.I. typographus has no mycangium and caries a variety of fungal spores, externally in pits on the pronota and elytra and internally within the digestive tract. Spores are also transmitted by phoretic mites. Most species belong to Ophiostomataceae and confusions within some important species have been put right. The fungal flora aseetle, but with some variations. Four species proved to be common in Norway, but Ophiostoma polonicum was more frequent in epidemic areas man in endemic areas . The frequency of this species is thus suspected to increase during epidemics. Studies during epidemic conditions revealed that the fungi invaded the sapwood of infested Norway spruce trees in an obvious succession, with O. polonicum in the leading edge of fungal penetration until heartwood was reached. The species found to be most commonly transmitted by I. typographus were shown to be first in the succession.The temperature is important for the rate of fungal invasion and the development of visible blue-stain, which occurred close to the leading edge of fungal penetration. The fungal colonization of sapwood leads to a gradual decrease in the moisture content, followed by desiccation symptoms in the foliage of infested trees. The tree trunks soon reached a moisture level not favourable for decaying Hymenomycetes, except near the base of the trees.The primary invader O. polonicum appeared to be pathogenic to Norway spruce trees when mass inoculated, while the secondary invaders were not at the given load of infection doses. However, the inoculation doses are of importance for the success of inoculated fungi. Judging from the large reaction zones in the phloem made by same secondary invaders, they may play an important role in the tree killing process in areas with low frequencies of O. polonicum. O. polonicum can kill other species of spruce used in European forestry and Douglas fir, so the fact that conifers other than Norway spruce rather rarely are attacked by I. typographus seems not to depend on the absence of a pathogenic fungus to overwhelm the trees.The fungi associated with I. typographus are sensitive to the lesion resin produced by Norway spruce trees in response to the fungal invasion. The potential of O. polonicum to be a primary invader seems to be linked to its rapid growth rate and ability to grow for a prolonged period under oxygen-deficient conditions. In conclusion, it seems that the interrelationship between Norway spruce, I. typographus and associated fungi is similar to other interrelationships. One of the associated fungi, O. polonicum, appeared lo play a key role in overwhelming infested trees due its abilily to grow for a prolonged period in wood with low oxygen pressure.
Forfattere
Ivar SamsetSammendrag
Rundt Islands nord- og vestkyster ligger det betydelige mengder drivtømmer. Det er mest furu og lerk, men også en del gran, edelgran, bjørk og osp. Det er tildels store tømmerdimensjoner, men også en del som er istykkerslått av isgang og bølgeslag mot strendene. Drivtømmeret på Jan Mayen ligner det vi fant på Island. Det er sannsynlig at tømmeret stammer fra Sibirs nordkyst. Det er revet løs av flom, isgang og storm, bl.a. fra områdene ved elvene, Ob, Jenisei og Lena. Derfra tar de nordøstlige overflatestrømmene tømmeret med til det når hovedstrømmer fra Beringstredet. Isen bringer tømmeret over Polhavet til havområdene mellom Spitsbergen og Grønland. Derfra bringer overflatestrømmene og nordveststormene det videre til Jan Mayens og Islands kyster. Bøndene foredler tømmeret i små sagbruk på gårdene. Lengst i nord er gårdene fraflyttet, slik at tømmerressursene samler seg opp.
Forfattere
Knut SolbraaSammendrag
This is the first of five annual reports from the research program Forest ecology and multiple use, in which the universities in Trondheim, Bergen, Oslo and s, the Norwegian Institute for Nature Research and the Norwegian Forest Research Institute participate. To date, 12 projects have been started, covering bird species, invertebrates, cryptogames, methods of forest regeneration, timber production and quality in uneven-aged stands, timber extraction methods, and public use of forests, as well as economic consequences of various silvicultural methods and usages of forest land. The programme period is five years, with an estimated total input of resources between 30 and 40 million NOK. In accordance with the conditions set by the government departments of Environment and Agriculture, the highest priority is given to research dealing with conservation of animal and plant species threatened by modern forestry. The content of this report is summarized in the following eight points. 1. Despite a 75% reduction in input of resources compared to an initial evaluation of the needs, it was possible to establish an integrated research programme, covering important gaps in knowledge of ecologically better forestry practices in Norway. At least the projects dealing with invertebrates and cryptogames should be continued after the period in order to work out lists of threatened species, describe their living area requirements, and examine their distribution in Norway. 2. In Norway today, there are likely neither large areas of virgin forest nor areas of coniferous forest which have been in climax stage throughout several tree generations. This may limit the number of strongly specialized species. 3. Probably only a small number of higher animal and plant species are threatened by forestry in Norway. A large number of invertebrates and cryptogames may be vulnerable, however. Most of these are directly or indirectly dependent on a continuous supply of dying or dead trees, high air humidity and protection against heavy wind and sun radiation. Therefore, they may survive only in old and dense forest stands, often on high-productivity sites. 4. By pointing out threatened species or groups of species and describing their living area requirements, the programme may provide a basis for a better choice between alternative treatments in silviculture and also secure a great diversity of less specialized species. 5. Many of the species in question should be maintainable during commercial forestry. In order to secure the genetic variation and spread of specialized species, smaller areas should be preserved, as a supplement to the larger state-owned areas. 6. Norwegian forestry is now at the end of a 40 to 50-year period of partly exaggerated perfectionism and intensive utilization of the timber production potential. This is now shifting to more extensive silvicultural methods and a widespread interest in multiple use. 7. Descriptions of alternatives to clear-cutting and planting and cost-benefit analyses given by the programme may also contribute to ecologically better forestry in Norway. Evaluation of non-commercial benefits, such as the preservation of species, is necessary for a complete cost-benefit analysis. 8. Forest planning on both district and property levels is an important tool in multiple use which makes claims both to the field work and to the plan utilization in practical forestry.
Forfattere
Anders Göransson Toril Drabløs EldhusetSammendrag
The effects of aluminium concentrations between 0.2 and 30 mM at pH 3.8 0.2 on small plants of Norway spruce [(Picea abies (L.) Karst], Scots pine (Pinus sylvestris L.), and Scots pine infected with the ectomycorrhizal fungus Suillus bovinus (L. ex Fr.) O. Kuntze were investigated. The plants were grown at maximum relative growth rate (RG % day1) with free access but very low external concentrations of nutrients. Steady-state conditions with respect to relative growth rate (RG) and internal nutrient concentrations were achieved before addition of aluminium, which was added as AlCl3 and/or Al(NO3)3. There were reductions in rg at aluminium concentrations of 0.3 mM in spruce, 6 mM in pine and 10 mM in ectomycorrhizal pine, i. e. at aluminium concentrations considerably higher than those normally occurring in the top layer of the mineral soil where most fine roots are found. Nutrient uptake rate per unit root growth rate was calculated for different nutrient elements. The uptake rate of calcium and magnesium was reduced at aluminium concentrations of 0.2 mM (spruce), 1 mM (pine) and 3 mM (ectomycorrhizal pine), without influencing Rg. The results question the validity of the hypothesis of aluminium toxicity to forest tree species at low external concentrations.
Forfattere
Per Holm Nygaard Gunnar AbrahamsenSammendrag
A study on the effects of eight years application of artificial acid rain on the vegetation and soil in an old Scots pine forest is described. Artificial rain of pH 2.5 and 3.0 caused severe damage to mosses, especially Pleurozium schreberi and Dicranum polysetum. The presence of Melampyrum pratense decreased drastically in plots treated with rain of pH 2.5 and 3.0. In Vaccinium myrtillus reduced leaf production was found in plots treated with rain of pH 2.5. A considerable decrease in base saturation had taken place in plots treated with pH 2.5 and pH 3.0 rain. Exchangeable calcium and magnesium in particular had been reduced, and the content of mangnesium in tissue of Vaccinium myrtillus appeared also to be reduced in plots treated with water of pH 2.5. The study demonstrates the need for better methods in evaluating vegetation responses in field studies. The use of visual cover recording should be supplemented by frequency analysis and harvesting methods to get better estimates of changes in vegetation structure.