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.
2013
Sammendrag
Old trees represent key features of old-growth forests and are important elements for maintaining biodiversity. Due to extensive human exploitation of Fennoscandian boreal forests during several centuries, old Norway spruce trees have become exceedingly rare. We analysed 91 spruce trees in Trillemarka Nature Reserve, southern Norway, to investigate (1) the maximum age of living trees, (2) growth rates of different-age trees and (3) growth trends in very old trees. Increment cores were taken from trees in selected old-growth stands located at 700–850 m a.s.l. Twelve spruce trees had an estimated total age of >400 years, the oldest one being 529 years and presumably the oldest known still living Norway spruce in northern Europe. A negative relationship between growth rate (basal area increment) and total age was observed, being most distinct for growth rates at 126–275 years and less marked for early stage growth (26–75 years). Thus, high age apparently was related more to low growth rates at adult and old stages of life rather than at the earlier stage. Among the trees >400 years, many of them did not show growth decrease with advancing age, indicating that ageing did not reduce growth. We conclude that the maximum age of stand-forming Fennoscandian Norway spruce trees would be in the range of 500–600 years.
Sammendrag
North European epiphytic lichens are often genetically impoverished compared with their North American counterparts. This has been hypothesized to impede sexual reproduction due to reduced chances of finding compatible mating type partners. We compared genetic variation and reproductive mode in two threatened Scandinavian lichens, Evernia divaricata and Usnea longissima, with more viable populations in North America to see (i) if these species also show genetical depletion in northern Europe and (ii) if the occurrence of sexual propagules (ascospores in apothecia) is more prevalent in genetically diverse populations. Genetic variation of the fungal component was assessed by sequencing two nuclear rDNA gene regions (ITS and IGS) in 1005 and 1477 thalli, collected from 92 and 160 localities of E. divaricata and U. longissima, respectively. Scandinavian populations of both species were almost devoid of genetic variation compared with much higher genetic diversity in North America.We found no support for the proposed relationship between genetic diversity and fertility. Fertile thalli were found in several genetically invariable populations. Fertility increased with population size and regional abundance in E. divaricata, but not in U. longissima. In Scandinavia, E. divaricata was more fertile than previously recorded, whereas all sampled populations of U. longissima were sterile and possibly clonal.
Forfattere
Jutta Kapfer Harry John Betteley Birks Vivian Astrup Felde Kari Klanderud Tone Constance Martinessen Louise C. Ross Fride Høistad Schei Risto Virtanen John Arvid GrytnesSammendrag
Background: Studies quantifying and comparing the variation and degree of compositional stability of vegetation and what determines this stability are needed to better understand the effects of the projected climate change. Aims: We quantified long-term vegetation changes in different habitats in northern Europe by exploring changes in species co-occurrences and their links to diversity and productivity gradients. Methods: We re-sampled vegetation in 16 arctic, mountain, and mire sites 20 to 90 years after first inventories. A site-specific change in species assemblages (stability) was quantified using species co-occurrences. We tested if the observed changes were significantly greater than would be expected by chance using a randomisation test. Relationships between patterns in vegetation stability and time between surveys, numbers of plots, or species diversity and proxies for productivity were tested using regression analysis. Results: At most sites, changes in species co-occurrences of vascular plants and bryophytes were greater than expected by chance. Observed changes were not found to be related to gradients in productivity or diversity. Conclusions: Changes in species co-occurrences are not strongly linked to diversity or productivity gradients in vegetation, suggesting that other gradients or site-specific factors (e.g. land-use, species interactions) might be more important in controlling recent compositional shifts in vegetation in northern Europe.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Foredrag – Beitegrunnlaget, elgforvaltningen og avskyningsstrategier
Olav Hjeljord, Hilde Karine Wam
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Arne SteffenremSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Arne SteffenremSammendrag
Det er ikke registrert sammendrag