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.
2005
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Morten EikenesAbstract
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Øystein Johnsen Carl Gunnar Fossdal Nina Elisabeth Nagy Jørgen A.B. Mølmann OG Dæhlen Tore SkrøppaAbstract
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The spruce bark beetle is the most serious pest of mature spruce trees in Eurasia. At low population densities it breeds in weakened or newly dead trees, but at high densities it becomes a tree killer. The exact factors triggering outbreaks are not fully understood, but climatic variables are important candidates. Populations in SE Norway have been monitored since 1979. Various time series methods are used to explore the role of climate in outbreaks of the spruce bark beetle in space and time, and to estimate the distribution of bivoltism under different scenarios of climate change. Large windfall events appear to be a major synchronizer of beetle outbreaks in areas subjected to regionalized weather systems, and the northern border of bivoltism may be moved towards north as a function of increasing temperature. Preliminary models of the population dynamics emphasize the frequency of large windfall events and phenological changes due to temperature increase. Final aims are to estimate the regional risks of forest damage under different scenarios of climate change, and to describe practices that may reduce the impact for forest managers.
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Päivi Rinne Carl Gunnar Fossdal Sissel Torre Heather Danforth Aksel Granhus Gunnhild Søgaard John Einset Harald Kvaalen Øystein Johnsen Chris Van der SchootAbstract
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Paivi L.H. Rinne Carl Gunnar Fossdal Sissel Torre Heather Danforth Aksel Granhus Gunnhild Søgaard John Einset Harald Kvaalen Øystein Johnsen Christiaan van der SchootAbstract
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This study was conducted to explore organic and conventional dairy farmers' perceptions of risk and risk management, and to examine relationships between farm and farmer characteristics, risk perceptions, and strategies. The data originate from a survey of conventional (n=363) and organic (n=162) dairy farmers in Norway. Organic farmers had the least risk averse perceptions. Institutional and production risks were perceived as primary sources of risk, with farm support payments at the top. Compared to their conventional colleagues, organic farmers gave more weight to institutional factors related to their production systems. Conventional farmers were more concerned about costs of purchased inputs and animal welfare policy. Organic and conventional farmers' management responses were more similar than their risk perceptions. Financial measures such as liquidity and costs of production, disease prevention, and insurance were perceived as important ways to handle risk. Even though perceptions were highly farmer-specific, a number of socio-economic variables were found to be related to risk and risk management. The primary role of institutional risks implies that policy makers should be cautious about changing policy capriciously and they should consider the scope for strategic policy initiatives that give farmers some greater confidence about the longer term. Further, researchers should pay more attention to institutional risks. (c) 2004 Elsevier B.V. All rights reserved.
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Fungi cause serious problems in wood utilization, and environmentally benign wood protection is required as an alternative to traditional chemicals. Chitosan has shown promising antimicrobial properties against several microorganisms. In this study, we present the characterization of and antifungal properties of a commercial chitosan formulation developed for impregnation of wood.A broad range of chemical and mycological methods were used to evaluate the uptake, fixation, and antifungal properties of chitosan for wood preservation. The results show that the higher the uptake of chitosan the lower the relative recovery of chitosan in wood after leaching, and the higher the molecular weight of chitosan the higher the recovery.Chitosan with high molecular weight proved to be more efficient against decay fungi than chitosan with low molecular weight. The fungi tested on chitosan-amended nutrient agar medium were totally inhibited at 1% (w/v) concentration.In decay studies using small wood blocks, 4.8% (w/v) chitosan concentration gave the best protection against brown rot fungi.
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This paper describes the use of quantitative real-time PCR for monitoring colonization of birch wood (Betula pubescens) by the white-rot fungus Trametes versicolor in an EN113 decay experiment. The wood samples were harvested after 4, 8, 12, 16 and 20 weeks of incubation.The mass loss was in the range of 440%. Chitin and ergosterol assays were conducted for comparison. Second-order polynomial fits of the mass loss of decayed wood versus chitin, ergosterol and DNA gave correlations (r2) of 0.87, 0.61 and 0.84, respectively. Compared to the other two assays employed, real-time PCR data correlated best with the relative mass loss of decayed samples 48 weeks after inoculation, while the saturation and decline of DNA-based estimates for fungal colonization 1620 weeks after inoculation indicated that the DNA assay is not suited for quantification purposes in the late stages of decay.The impact of conversion factors, extraction efficiency, inhibitory compounds and background levels in relation to the three detection assays used is discussed.