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.
2012
Forfattere
Kjell Andreassen Bernt-Håvard ØyenSammendrag
Thirteen Nordic stand growth models have been validated by use of a test data set from long-term research plots in Norway. The evaluated data was from time-series of even-aged, pure stands of Norway spruce, Scots pine and birch (silver birch and downy birch). In selected models from Finland, Norway and Sweden measures of site productivity, mean tree size and various stand characteristics are represented. Different models display both strengths and weaknesses in their predicting ability. Several measures of precision and bias have been calculated and the models are ranked due to their performance. We observed site quality, stand density and average tree size as the three main components in the models. Basal area increment model for spruce from Sweden had the lowest standard deviation with 23%. The mean R2 between residuals and stand characteristics from this model was also low (1.3%), which indicates that independent variables are well included. For Scots pine and birch, Finnish volume increment models showed the best fit to the Norwegian test data, with a R2 between residuals and stand characteristics of 2.8 and 6.7%, respectively. Several of the models from Sweden and Finland predicted the growth as well as stand models frequently in use in Norway. The results indicated that similar forest conditions and traditional even-aged forest management practice in the Nordic countries could be seen as a suitable basis for developing a joint family of growth models. By careful recalibration of existing models, a reasonable accuracy could be achieved and the prediction bias could be reduced.
Forfattere
Anders T Bråten Daniel Flø Sigmund Hågvar Oddvar Hanssen Christian Einar Mong Kjetil AakraSammendrag
Det er ikke registrert sammendrag
Forfattere
S.B.K. Bengtsson R. Vasaitis T. Kirisits Halvor Solheim I. StenlidSammendrag
The ascomycete fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) is responsible for ash dieback currently expanding over large parts of Europe. Our objective was to investigate the genetic structure of H. pseudoalbidus and to examine its relationship to the species H. albidus, known as a saprotroph. The study comprised 181 isolates of H. pseudoalbidus collected within the diseased area, 17 H. albidus isolates from six apothecia, collected outside the diseased area in Norway, and nine apothecia of H. pseudoalbidus collected in Sweden. By analysis of microsatellite markers developed for this study, combined with AP-PCR using the M13 primer, we demonstrated sexual heterothally in H. pseudoalbidus, detected high gene flow and low geographic structure of the H. pseudoalbidus population and found indications of a founder effect. Also, substantial genetic differences were detected between the two species of fungi; only four of seven microsatellite markers developed for H. pseudoalbidus were amplified for H. albidus, and no alleles were shared among the species. Furthermore, AP-PCR banding patterns were distinctly different for the two species. We conclude that even though the two fungi have a similar habitat and are morphologically virtually identical, they do not share a recent common ancestor.
Sammendrag
The objective of this paper is to examine a method for estimation of land cover statistics for local environments from available area frame surveys of larger, surrounding areas. The method is a simple version of the small-area estimation methodology. The starting point is a national area frame survey of land cover. This survey is post-stratified using a coarse land cover map based on topographic maps and segmentation of satellite images. The approach is to describe the land cover composition of each stratum and subsequently use the results to calculate land cover statistics for a smaller area where the relative distribution of the strata is known. The method was applied to a mountain environment in Gausdal in Eastern Norway and the result was compared to reference data from a complete in situ land cover map of the study area. The overall correlation (Pearson’s rho) between the observed and the estimated land cover figures was r = 0.95. The method does not produce a map of the target area and the estimation error was large for a few of the land cover classes. The overall conclusion is, however, that the method is applicable when the objective is to produce land cover statistics and the interest is the general composition of land cover classes – not the precise estimate of each class. The method will be applied in outfield pasture management in Norway, where it offers a cost-efficient way to screen the management units and identify local areas with a land cover composition suitable for grazing. The limited resources available for in situ land cover mapping can then be allocated efficiently to in-depth studies of the areas with the highest grazing potential. It is also expected that the method can be used to compile land cover statistics for other purposes as well, provided that the motivation is to describe the overall land cover composition and not to provide exact estimates for the individual land cover classes.
Forfattere
Mette Algreen Arno Rein Charlotte N. Legind Carl Amundsen Ulrich Gosewinkel Karlson Stefan TrappSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Gage Koehler Robert Wilson John V. Goodpaster Anita Sønsteby Xianyin Lai Frank A. Witzmann Jin-Sam You Jens Rohloff Stephen K, Randall Muath Alsheikh-YousefSammendrag
© 2012. This is the authors' accepted and refereed manuscript to the article. The final authenticated version is available online at: http://dx.doi.org/10.1104/pp.112.198267
Forfattere
Arne Sæbø Robert Popek Barbara Nawrot Hans Martin Hanslin Helena Gawronska Stanislaw W GawronskiSammendrag
Det er ikke registrert sammendrag
Sammendrag
Logging exceeded growth and timber trees were sparse in Norwegian forests in the early 1900s. Still, the forest canopy was lush green and characterised by large tree-crowns. This situation was referred to as the “Green lie” and was advocated by foresters throughout Scandinavia as an argument in favour of forestry practices based on clear-felling. Here we examine effects of past selective loggings on forest structure and composition in a spruce forest landscape using dendroecology and historical records. Our results show that forests that were selectively logged up to the early 1900s could be structurally heterogeneous with multi-layered canopies, varying degree of openness and continuous presence of old trees across different spatial scales. Because the past forests were not clear-felled, a diverse forest structure in terms of tree species composition and age and diameter distribution was maintained over time, which could enable forest-dwelling species to persist during the early phase following the loggings in the past. This is in sharp contrast to the situation in most modern managed forest landscapes in Scandinavia. A better understanding of the link between loggings in the past- and present-day forest structure and diversity will contribute to rewarding discussions on forestry methods for the future.
Forfattere
Belachew Asalf Tadesse Nina Trandem Arne Stensvand Vitalis Wekesa Gilberto J de Moraes Ingeborg KlingenSammendrag
Det er ikke registrert sammendrag