Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2014
Authors
Per Gundersen Shimon Ozeri Ginzburg Lars Vesterdal Teresa Gómez de la Bárcena Bjarni D. Sigurdsson Helena M Stefánsdóttir Edda S Oddsdottir Nicholas Clarke O. Janne Kjønaas Tryggve Persson Göran Ågren Bengt Olsson Mats Fröberg Erik Karltun Riitta Hyvönen Olsson Cecilia Akselsson Per Bengtsson Salim Belyazid Håkan Wallander Andis Lazdins Zane Libiete Dagnija LazdinaAbstract
No abstract has been registered
Authors
Rainer Hentschel Sabine Rosner Zachary E. Kayler Kjell Andreassen Isabella Børja Svein Solberg Ole Einar Tveito Eckart Priesack Arthur GesslerAbstract
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Authors
Igor A. Yakovlev YeonKyeong Lee Björn Rotter Jorunn Elisabeth Olsen Tore Skrøppa Øystein Johnsen Carl Gunnar FossdalAbstract
Embryogenesis is the initial stage of plant life, when the basics of body plan and the post-embryonic development are laid down. Epigenetic memory formed in the Norway spruce embryos permanently affect the timing of bud burst and bud set in progenies, vitally important adaptive traits in this long-lived forest species. The epigenetic memory marks are established in response to the temperature conditions prevailing during zygotic and somatic embryogenesis; the epitype is fixed by the time the embryo is fully developed and is mitotically propagated throughout the tree’s life span. Somatic embryogenesis closely mimics the natural zygotic embryo formation and results in epigenetically different plants in a predictable temperature-dependent manner with respect to altered phenology. Using Illumina-based Massive Analysis of cDNA Ends, the transcriptome changes were monitored in somatic embryos during morphogenesis stage under two different temperatures (18 vs. 30 °C). We found distinct differences in transcriptomes between the genetically identical embryogenic tissues grown under the two epitype-inducing temperatures suggesting temperature-dependent canalizing of gene expression during embryo formation, putatively based on chromatin modifications. From 448 transcripts of genes coding for proteins involved in epigenetic machinery, we found 35 of these to be differentially expressed at high level under the epitype-inducing conditions. Therefore, temperature conditions during embryogenesis significantly alter transcriptional profiles including numerous orthologs of transcriptional regulators, epigenetic-related genes, and large sets of unknown and uncharacterized transcripts.
2013
Abstract
Retention of selected trees in clear-felling areas has become an important conservation measure in managed forests. Trees with large size or high age are usually preferred as retention trees. In this paper we investigated whether a single large or several small trees should be left in clear-felling areas to serve as life boats and future habitat for epiphytic species. The focal species were 25 Lobarion epiphytic lichens hosted by aspen (Populus tremula). We analyzed the relationships between: (1) proportion of trees colonized and tree size, (2) number of lichen thalli (lichen bodies) and aspen area, and (3) number of lichen species and aspen area, for 38 forest sites. Mixed effect models and rarefaction analyzes showed that large and small host trees had the same proportion of trees colonized, the same number of thalli, and the same species richness for the same area of aspen bark. This indicates that larger aspens do not have qualities, beyond size, that make them more suitable for Lobarion lichens than smaller sized aspen trees. None of the species, not even the red-listed, showed any tendencies of being dependent on larger aspens, and our results therefore did not support a strategy of retaining only large and old trees for conservation of epiphytic Lobarion lichens. Additionally, young aspens have a longer expected persistence than old aspens. However, old retention trees might be important for other species groups. We therefore recommend a conservational strategy of retaining a mixed selection of small/young and large/old aspens.
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Authors
Ryan Bright Rasmus Astrup Anders Hammer Strømman Clara Antón Fernández Maria Malene Kvalevåg Francesco CherubiniAbstract
No abstract has been registered
Abstract
National Forest Inventories (NFIs) provide estimates of forest parameters for national and regional scales. Many key variables of interest, such as biomass and timber volume, cannot be measured directly in the field. Instead, models are used to predict those variables from measurements of other field variables. Therefore, the uncertainty or variability of NFI estimates results not only from selecting a sample of the population but also from uncertainties in the models used to predict the variables of interest. The aim of this study was to quantify the model-related variability of Norway spruce (Picea abies [L.] Karst) biomass stock and change estimates for the Norwegian NFI. The model-related variability of the estimates stems from uncertainty in parameter estimates of biomass models as well as residual variability and was quantified using a Monte Carlo simulation technique. Uncertainties in model parameter estimates, which are often not available for published biomass models, had considerable influence on the model-related variability of biomass stock and change estimates. The assumption that the residual variability is larger than documented for the models and the correlation of within-plot model residuals influenced the model-related variability of biomass stock change estimates much more than estimates of the biomass stock. The larger influence on the stock change resulted from the large influence of harvests on the stock change, although harvests were observed rarely on the NFI sample plots in the 5-year period that was considered. In addition, the temporal correlation between model residuals due to changes in the allometry had considerable influence on the model-related variability of the biomass stock change estimate. The allometry may, however, be assumed to be rather stable over a 5-year period. Because the effects of model-related variability of the biomass stock and change estimates were much smaller than those of the sampling-related variability, efforts to increase the precision of estimates should focus on reducing the sampling variability. If the model-related variability is to be decreased, the focus should be on the tree fractions of living branches as well as stump and roots.
Authors
Tor Myking Erling Johan Solberg Gunnar Austrheim James David Mervyn Speed Fredrik Bøhler Rasmus Astrup Rune EriksenAbstract
Sallow (Salix caprea L.) and rowan (Sorbus aucuparia L.) constitute small proportions of the deciduous tree volume in Scandinavia, but are highly preferred winter forage for moose and red deer, which occur at historically high densities. Thus, a possible decline of these tree species has been indicated. Against this background, we have reviewed the life histories of relevance for browsing, as well as the basic biology and genetics of sallow and rowan. The species show similarities with respect to short lifespan, small size and sympodial growth pattern, which are risk factors in a browsing context. They also have high juvenile growth rate, important for growing quickly out of reach of browsers. Sallow depends strongly on disturbance for establishment and is more demanding with respect to soil and light conditions than rowan, possibly important for the substantially lower abundance of sallow on the Norwegian Forest Inventory plots. Similarly, the relative recruitment of small size classes of sallow is less than for rowan. Although recruitment is reported to be hampered in wintering areas with high moose or red deer densities, the inventory data, however, dating only back to 1994, do not suggest a general decrease in any of the species. Sallow and rowan saplings show low mortality in moose and deer dominated areas and the species can be characterised as rather resilient to browsing. Of more concern is that browsing can constrain the development of mature rowan and sallow trees locally, with possible consequences for associated epiphytic biodiversity.