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.
2002
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Abstract
Patrolling with livestock guard dogs in mountain rangelands in Norway was evaluated as a method to prevent predation in areas with widely dispersed sheep. In contrast to the traditional use of guard dogs, patrol dogs are closer socially bonded to people and follow a range inspector around. Range inspection was performed in 5 h bouts during three nights per week. The method was tested during three summer seasons in a total of eight sheep flocks grazing in three different mountain ranges. In total, three inspectors and four dogs were involved. Significant reductions in the number of sheep lost were achieved in one of the study areas. Lack of significance in the other areas were mainly due to the size of the area and qualities of the dogs: the range to be patrolled by one man/dog unit should not exceeed 10-12 km2, and the dogs should be experienced guard dogs, which are properly socialized for this method.
Authors
Erik Næsset Tonje ØklandAbstract
No abstract has been registered
Abstract
We investigated the effects of heavy metals (Cd, Cu, and Zn) on the enzyme activity of soil denitrifying community, and tolerance to the same heavy metals as indicated by denitrification rates. We focused on the rates of nitrate reduction to N2O and the N20 reductase activity, because the ratio between these two process rates is an indicator of the community's intrinsic capacity to release N20 to the atmosphere. A sandy loam was given a single and double dose of a heavy metal mixture (single dose = 0.32, 80, 120 mg kg 1 dry soil of Cd, Cu, and Zn, respectively). Ground straw was added together with the metals to enhance microbial growth, and the soil was incubated aerobically at 15 °C for 2 months. Kinetics of production and reduction of N20 by the denitrifying community of this soil was investigated by anaerobic incubation of soil slurries or extracted bacterial cells, using glutamate as a C source. Time courses of the N20 production and reduction curves (with and without acetylene) were used to estimate kinetic parameters to characterize the community. Heavy metal tolerance was tested by exposing extracted cells to heavy metals during such anaerobic incubations. The immediate effect (after 1 day) of heavy metals was a general reduction of the denitrification rate but also to decrease the N20 reduction more than N20 production rate. N20 production was partly recovered 8 days after heavy metal introduction, and completely restored (equal to the control soil) after 2 months. In contrast, the N20 reductase activity was still not completely restored after 2 months. Exposure of extracted cells to the different heavy metals showed that soil exposure of heavy metals had induced an increased Cd-, Cu-, and Zn-tolerance of N20 reductase activity. Simulation of the NO production and reduction curves during the anaerobic incubation allowed an estimation of the apparent specific growth rate by fitting the simulated to the measured curves. Estimated growth rates were significantly lowered as the community heavy metal tolerance developed (heavy metal exposed soil after 2 months versus control soil), possibly reflecting a metabolic burden of the metal resistance mechanisms.
Abstract
Norwegian fluid milk consumption has declined steadily over the last twenty years, despite the dairy industry spending increasing amounts of money on advertising. Using a two-stage model, we investigate whether advertising has increased the demand for milk. No effect of advertising on the demand for non-alcoholic beverages is found in the first stage. In the second stage, an almost ideal demand system including advertising expenditures on competing beverages is estimated. The effects of generic advertising within the beverage group are positive and significant for whole milk and negative and significant for lower fat milk. The own-advertising elasticity for the combined fluid milk group is 0.0008. This highly inelastic elasticity suggests that increased advertising will not be profitable for the producers. Several cross-advertising effects are statistically significant, emphasizing the usefulness of a demand system approach.
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Authors
Per K. Egeberg Alfred A. Christy Morten EikenesAbstract
The objectives of this work are; 1) to determine the diffuison coefficients of NOM by diffusivimetry. 2) to compare the results with diffusion coefficients determined by two other methods (fluorescence correlation spectroscopy (FCS) and dynamic adsorption experiments (DAM). 3) to compare molecular weights derived from the diffusion coefficients to molecular weights determined by three different ultra filtration experiments and High Perfomance Size Exclusion Chromatography (HPSEC). The diffusion coefficients determined in this work (stirred diffusion cell) are about 70% higher than determined by DAM, and agree well with diffusion coefficients determined by FCS. Molecular weights determined by HPSEC are of the same magnitude as molecular weights derived from diffusion coefficients. Molecular weights determined by ultra filtration vary considerably depending on the choice of membrane types. Membranes made of cellulose acetate generate results similar to results derived from diffusion coefficients. Membranes made of regenerated cellulose and polyether sulfone appear to retain too much NOM, resulting in artificially high molecular weights.
Authors
Anna Martha Elgersma Shivcharn DhillionAbstract
No abstract has been registered
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No abstract has been registered