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
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
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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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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.
Authors
Halvor TorgersenAbstract
Excavator based harvesters for mechanisation in steep terrain, on tracks or wheels?
Authors
Carl Gunnar Fossdal Nina Elisabeth Nagy Praveen Sharma Anders LönneborgAbstract
Here we describe the detection, developmental accumulation and cellular location of the putative plant defensin SPI1 (spruce pathogen induced 1), in the gymnosperm Norway spruce [Picea abies (L.) Karst.], using specific antibodies. Contrary to what has been found in angiosperms, it was not detected in the embryo or other parts of the seed, but accumulated during root development. The protein was detected by immunolocalization along the cell membrane of cells forming the root cortex. Furthermore, a significant accumulation of the SPI1 protein was detected in roots during the first day of infection with the fungal pathogen Heterobasidium annosum, but not in response to the pathogens Pythium dimorphum or Ceratocystis polonica