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.
2001
Abstract
No abstract has been registered
Abstract
Two zone sites, i.e. two circular areas with 50 km radius, were established in southern Norway. The zone sites were centred in Tofte (the location of a major pulp mill) and in Drammen (the site of a major timber yard). From June to October 2000, 66 forest blocks were visited, 65 of which were situated within the zone site areas. Samples were collected from 40 forest blocks, especially from wood attacked by wood boring insects. At 34 forest blocks, trees of Scots pine, Pinus sylvestris, or Norway spruce Picea abies were provided as trap-logs for Monochamus spp. This material will be sampled in the survey of 2001. Some samples were also taken from a wood chip pile and from imported wood material. The total number of wood samples analysed for nematodes were 275. Out of these, 214 samples were collected from forest trees, stumps, timber and logging wastes of P. sylvestris and P. abies. Three samples contained nematodes belonging to the genus Bursaphelenchus, but the Pine Wood Nematode (PWN), B. xylophilus, was not detected. Similarly, this nematode was not detected in the 10 samples of wood chips, or in the 25 samples of imported lumber or in the 26 samples of imported solid wood packing material. In order reach the minimal number of 3000 samples within reasonable time, the number of samples for the next survey season of 2001 needs to be increased drastically. To achieve this, the sampling will continue within the existing zone sites, and be extended into new zone sites to be established in 2001.
Authors
Oddvar SkreAbstract
Småplanter av tre bjørkepopulasjonar (Betula pubescens) blei dyrka i veksttorv ved to ulike gjødselnivå, tilsvarande 1 og 10 g N m-2 yr-1 ved 50 og 450 m høgd i det sørlege Noreg. Det var ei sterk opphoping av karbohydrat i røter frå det høgaste feltet, samanlikna med det lågaste. Normal og alternativ (cyanid-resistent) respirasjon blei målt i stengel- og rotsegment og på avskorne bladskiver frå dei tre bjørkepopulasjonane. Den totale og alternative mørkerespirasjonen minka med aukande temperatur i bladskiver og stengelsegment. I rotsegment frå dei same plantene auka derimot totalrespirasjonen med temperaturen. Ved lågt gjødselnivå var det ein viss reduksjon av respirasjonen i skot ved høg temperatur, og det meste av denne var cyanid-resistent, i.e. ikkje kopla til veksten. Den økologiske tydinga av dette er at ved låg temperatur kan auka alternativ respirasjon i blad og stengel føra til redusert vekst. Ved høg temperatur derimot, tyder auka totalrespirasjon i røter på auka absorbsjon av nitrogen i røter, som igjen fører til auka fotosyntesekapasitet, som kan kompensera for karbohydratmangel ved sterk vekst. Den alternative respirasjonen ved lågt næringsnivå og temperatur kan vera ein mekanisme for å unngå vekst ved ugunstige forhold.
Authors
Steen Koekebakker Gudbrand LienAbstract
Empirical evidence suggests that agricultural futures price movements have fat-tailed distributions and exhibit sudden and un xpected price jumps. There is also evidence that the volatility of futures prices contains a term structure depending on both calendar-time and time to maturity. This paper extends Bates (1991) jump-diffusion option pricing model by including both seas nal and maturity effects in volatility. An in-sample fit to market option prices on wheat futures show that our model outperforms previous models considered in the literature. A numerical example illustrates the economic significance of our results for option valuation.
Authors
Steen Koekebakker Gudbrand LienAbstract
No abstract has been registered
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No abstract has been registered
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Farmers in northern Norway have experienced frequent winter damages of grassland, especially on flat areas and peat soils. The use of open ditches and surface grading has become the common method to drain such fields and for reclaiming new land with such characteristics. We designate this as surface grading in this paper. An investment analysis is carried out to explore the profitability of this method. This analysis indicates that the method is profitable from the farmers’ point of view. However, the conclusions are sensitive to changes in crop yields and the value of the yields. The cost of a winter damage and thus an unplanned reseeding is high for young leys, but is small for leys approaching the optimal replacement age.
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No abstract has been registered
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No abstract has been registered
Abstract
Epiphytic lichen vegetation on birch stems was studied in the border areas between Norway and Russia. The area is heavily influenced by sulphur dioxide pollution emitted from Russian nickel smelters.Hypogymnia physodes and Melanelia olivacea were the two most abundant lichen species on birch stems in the investigated area. However, the coverage of H. physodes and M. olivacea was clearly reduced in parts of the investigated area. The lichen vegetation increased with increasing distance from the pollution source, i.e. from a lichen desert to normal background levels. A different pattern of occurrence of the two lichen species was observed.