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.
2005
Forfattere
Ingerd Skow Hofgaard Åshild Ergon Birgitte Henriksen Hilde Kolstad Helge Skinnes Yalew Tarkegne Anne-Marte TronsmoSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
J. Jacobs Halvor Solheim Brenda D. Wingfield Michael J. WingfieldSammendrag
The genus Leptographium was described in 1927 and currently includes 48 species, with L. lundbergii as the type species. In recent years, the taxonomic status of L. lundbergii has not been uniformly agreed upon and it has been the topic of considerable debate. The problem was compounded by the absence of a type specimen, and the species was epitypified at a later stage. Unfortunately, the whereabouts of the epitype is now unknown. In 1983, Wingfield & Marasas described L. truncatum, which is morphologically similar to L. lundbergii. Based on DNA comparisons and similarities in their morphology, this fungus was reduced to synonymy with L. lundbergii. The loss of the type specimen as well as variation in the morphology of strains identified as L. lundbergii prompted us to re-examine the taxonomic status of this species. A number of strains from various geographic areas were studied. These include a strain of L. lundbergii deposited at CBS by Melin in 1929 (CBS 352.29) as well as the ex-type strain of L. truncatum. The strains were compared based on morphology and comparison of multiple gene sequences. Three genes or genic regions, ITS2 and part of the 28S gene, partial â-tubulin and partial elongation factor 1-α were compared. Strains currently identified as L. lundbergii, represented a complex of species. Strains initially described as L. truncatum clustered separately from other L. lundbergii strains, could be distinguished morphologically and should be treated as a distinct taxon. L. lundbergii is provided with a new and expanded description based on a neotype designated for it. A third group was also identified as separate from the main L. lundbergii clade and had a distinct Hyalorhinocladiella-type anamorph, described here as H. pinicola sp.nov.
Forfattere
Bjørn ØklandSammendrag
Ips typographus is considered the most destructive of the bark beetles in the coniferous forests of the Palaearctic region. At low population densities this species breeds in fresh windfalls or dying trees of Norway spruce. At high densities, in contrast, the beetles may show tree-killing outbreaks at regional scales. Spatio-temporal analyses based on pheromone trap data indicated that large windfall events may be a major instigator and synchronizer of beetle outbreaks in areas subjected to regionalized weather systems. The general dominance of lag 1 density dependence of the time series indicated that the beetle populations are constrained by intraspecific competition for breeding substrates. The time series sequence before the large windfelling of 1987 was however declining without significant density dependence. We suggest this to be a transition period, reflecting a drop in carrying capacity due to depletion of susceptible trees during the preceding outbreak period (1970s) and a drop in beetle number to below the density required to kill trees. A variety of organisms exhibit episodes of explosive population growth, triggered by disturbance events. A new general model is constructed to capture the coupling of disturbance events with resource accumulation / depletion. The model is refined and parameterized using the dynamics of the Ips typographus in Scandinavia as a model system. The waiting times between outbreaks of simulated time series were generally longer and more variable than the outbreak lengths, which agree well with the historical records in the last 250 years. Spectral analysis and logspline density plots of waiting times suggest that the transition from aperiodic to periodic population dynamics should be regarded as a continuum.
Sammendrag
Overvåkingsprogrammet for skogskader (OPS) har siden starten registrert skader på de undersøkte trærne. Målet med skaderegistreringene har vært og vil fortsatt være å forklare variasjoner i trærnes kronetetthet og kronefarge. Men fra og med 2005 ønsker ICP Forests en standardisert rapportering av skader på trær fra alle land som deltar i det europeiske overvåkingsprogrammet. En slik harmonisering av registreringer vil over tid kunne gi et bilde av utbredelse, forekomst og skadelige virkninger av insekter, sopp, værforhold eller andre årsaker som påvirker skogen i Europa. Uten denne informasjonen vil det være svært vanskelig å tolke kronetetthets- og kronefargeresultatene. Data fra skogskaderegistreringene vil også kunne bli brukt i andre internasjonale skogpolitiske sammenhenger, som blant annet spørsmålet om bærekraftig skogbruk. For å imøtekomme kravene i den nye internasjonale instruksen har Skogforsk og NIJOS i samarbeid plukket ut viktige sopper, insekter, vilt/beitedyr, værforhold og andre årsaker som kan påvirke trærne i norsk skog. De viktigste er presentert i dette heftet. Tekstene og bildene skal være en hjelp til gjenkjenning av skadene som kan observeres i trekronene.
Forfattere
Karin Jacobs Brenda D. Wingfield Halvor Solheim Michael J. WingfieldSammendrag
Det er ikke registrert sammendrag
Forfattere
Halvor SolheimSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Jolanda Roux Halvor Solheim Michael J. WingfieldSammendrag
Det er ikke registrert sammendrag