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.
2012
Abstract
Various oils can be used to lower the equilibrium moisture content and increase the service life of Scots pine wood products. The aim of this study was to investigate effects of the lateral wood zone on the brown rot resistance of untreated and linseed oil-impregnated Scots pine wood in a laboratory test (EN 113). Significant differences were found in the mean mass losses of treated and untreated specimens taken from three lateral heartwood zones, but not between specimens taken from sapwood. The treatment had no significant effect on sapwood, although it seems to have some positive effect on the durability of heartwood, apparently due to interactive effects with the high extractives contents of heartwood.
Authors
Jozef Martinka Karol Balog Tomás Chrebet Emília Hroncová Janka DibdiakovaAbstract
The presented article deals with the assessment of combined impact of temperature and flow of oxidising atmosphere, its oxygen concentration and heat flux on the ignition time of isotactic polypropylene (PP). The ignition time was determined in a specially adapted hot air Setchkin furnace at temperatures (450 and 600 °C), density of heat flux (12.4 and 26.4 kW m−2), flows of oxidation mixture (6 and 8 L min−1) and volume oxygen concentrations (3, 9, 15, 21, 27, 33, 39, 45 and 50 %). Obtained data allows us to assume that the temperature influence on PP induction period of ignition increases with decreasing flow rate of oxidising atmosphere. At the flow of oxidising mixture equal to 6 L min−1 and temperature of 600 °C, oxygen concentration had only a negligible impact on the the induction period of ignition in the analysed period. From the presented results, the induction period of ignition depends on the temperature and also on the flow rate of oxidising mixture and oxygen concentration in it. In addition, heat flux has a significant influence on the induction period. However, the quantification of the heat flux influence was not possible with the applied experimental device.
Authors
Håvard Kauserud Einar Heegaard Ulf Büntgen Rune Halvorsen Simon Egli Beatrice Senn-Irlet Irmgard Krisai-Greilhuber Wolfgang Dämon Tim Sparks Jenni Nordén Klaus Høiland Paul Kirk Mikhail A. Semenov Lynne Boddy Nils Christian StensethAbstract
In terrestrial ecosystems, fungi are the major agents of decomposition processes and nutrient cycling and of plant nutrient uptake. Hence, they have a vital impact on ecosystem processes and the terrestrial carbon cycle. Changes in productivity and phenology of fungal fruit bodies can give clues to changes in fungal activity, but understanding these changes in relation to a changing climate is a pending challenge among ecologists. Here we report on phenological changes in fungal fruiting in Europe over the past four decades. Analyses of 746,297 dated and geo-referenced mushroom records of 486 autumnal fruiting species from Austria, Norway, Switzerland, and the United Kingdom revealed a widening of the annual fruiting season in all countries during the period 1970–2007. The mean annual day of fruiting has become later in all countries. However, the interspecific variation in phenological responses was high. Most species moved toward a later ending of their annual fruiting period, a trend that was particularly strong in the United Kingdom, which may reflect regional variation in climate change and its effects. Fruiting of both saprotrophic and mycorrhizal fungi now continues later in the year, but mycorrhizal fungi generally have a more compressed season than saprotrophs. This difference is probably due to the fruiting of mycorrhizal fungi partly depending on cues from the host plant. Extension of the European fungal fruiting season parallels an extended vegetation season in Europe. Changes in fruiting phenology imply changes in mycelia activity, with implications for ecosystem function.
Abstract
Stand and disturbance dynamics are key processes that need to be assessed along with climate-species interactions if we are to better understand the impacts of climate change on species. In this study we investigated the biotic interactions (competition) between species, the influence of disturbance type, and changes in resource availability (moisture and light) on the response of six tree species to climate change in the northwest region of central British Columbia, Canada. Two ecological models were parameterized, linked together and coupled to climate change scenarios to explore the interactions between: (1) the response of species in the regeneration phase and (2) the role of disturbance, resource availability and competition on determining stand composition and productivity. Climate change was found to reduce soil moisture availability which resulted in a decline in regeneration potential for all species on dry sites and negative to neutral responses on sites with higher water availability. Following fire, stand dynamics and composition were modeled to undergo significant changes under the 2080s climate compared to current climate conditions on dry and mesic sites. Changes in stand dynamics under climate change were marginal following bark beetle disturbances. While significant changes to stand dynamics were found on dry sites, the presented results suggest that the sites with the highest moisture availability maintain the same general stand dynamics and composition following disturbances under climate change. This study highlights the need to consider species response to climate change in interaction with existing stand conditions, disturbance type, competition, resource availability, not just temperature and precipitation.
Authors
Peder GjerdrumAbstract
Scaling accuracy is of utmost importance to obtain optimal sawn timber yield in primary breakdown. In this article, sawmill observations, review of available publications and supplementary tests are combined to analyse the accuracy of conifer roundwood scaling. The influence of important log parameters are considered for various scaling technology: one- and twodirectional (1Dir and 2Dir) shadow scanners and three-dimensional (3Dim) reflected beam scanners. Standard error for each of the terms, ovality, bark and scanner technology, is discussed. The overall accuracy for diameter under bark can be calculated by adding the variances for each independent term. Results show that for unbarked logs, 2Dir shadow scanner remains the most accurate technology. For barked logs, 3Dim reflected laser beam scanner combines the highest accuracy and the ability of providing a wide range of important log parameters. For a case study sawmill, annual roundwood consumption are reduced by 2.0% by transferring from scaling unbarked logs in a two-dimensional shadow scanner to 3Dim scanning of barked logs, while keeping the volume yield of the sawn timber.
Authors
Bernt-Håvard Øyen Petter Nilsen Fredrik Bøhler Kjell AndreassenAbstract
Models for predicting diameter increment in multi-storey spruce stands following mountain forest selective cutting (MFS) were developed. They were based on increment cores, tree ring analyses and stump registrations. The presented models rely upon time series data from 1600 trees in thirty-one Norway spruce stands in south-eastern and central parts of Norway. The selective cuttings were heavy; on average two thirds of the standing volume were cut. The increment following the interventions was highly variable, resulting in large random variability in the models with R2 varying between 0.18–0.31 for individual tree diameter growth and 0.40–0.50 for mean tree stand diameter growth. Dummy variables referring to three first 5-year periods after cutting were found to increase the precision and significantly reduce the random error. Selected models were validated using a test material from central Norway and also compared with the mostly applied Norwegian diameter increment models. Despite a large random variation in all models, the model performances appeared logical and the general fit to the data was acceptable. Based on tests, two diameter increment models are recommended for future yield prognoses in MFS. The models should also be of interest for wider use in other parts of the Nordic and Baltic boreal zone.
Authors
Kjell Andreassen Bernt-Håvard ØyenAbstract
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.
Authors
Anders T Bråten Daniel Flø Sigmund Hågvar Oddvar Hanssen Christian Einar Mong Kjetil AakraAbstract
No abstract has been registered
Authors
S.B.K. Bengtsson R. Vasaitis T. Kirisits Halvor Solheim I. StenlidAbstract
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.
Abstract
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.