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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

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Abstract

Abstract Strict control of morphogenesis is essential in production of potted poinsettia. Commonly, this is obtained by the use of plant growth retardants (PGRs), often in combination with early morning temperature drops. Due to negative effects on human health and the environment, the use of PGRs is becoming restricted. Also, energy-saving growth regimes and periods of high temperatures limit effective use of temperature drops. In the present study the use of a high proportion of blue (B) light provided by light emitting diodes [LEDs, 20% blue (B), 80% red (R)] was compared with traditional high pressure sodium (HPS) lamps (5% B) providing similar phytochrome photostationary state to produce compact poinsettia plants. Both in the greenhouse and growth chamber, all cultivars were 20–34% shorter for LED compared to HPS grown plants. Also, leaf and bract area as well as chlorophyll content and total dry matter accumulation were lower under LED. The LED did not delay bract color formation, visible cyathia and flowering compared to HPS, and no difference in post production performance (cyathia/bract abscission or necrosis) between the two light treatments was found. The effect of end of day-red (EOD-R) lighting combination with LED and HPS supplemental lamps during the photoperiod in the greenhouse was also investigated. Reduced stem extension (13%) was observed under HPS only and for one of the two cultivars tested, whereas under the LED regime, there was no effect of EOD-R lighting.

Abstract

Winter damage caused by frost is frequently observed on common ash (Fraxinus excelsior) in Norway. In spring 2007, extensive winter damage most likely camouflaged ash dieback caused by Chalara fraxinea. In 2008, ash dieback caused by C. fraxinea had spread to large areas in the southern part of Norway. The disease was widespread in forests and nurseries, but also on roadside trees, and in gardens and parks. In 2009, the disease had spread to new areas; about 30 km into Rogaland county in southwestern Norway and also further into some valleys in southeastern Norway.

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Abstract

This paper presents a bioeconomic analysis of a red deer population within a Norwegian institutional context. This population is managed by a well-defined manager, typically consisting of many landowners operating in a cooperative manner, with the goal of maximizing the present-value hunting related income while taking browsing and grazing damages into account. The red deer population is structured in five categories of animals (calves, female and male yearlings, adult females and adult males). It is shown that differences in the per-animal meat values and survival rates (‘biological discounted’ values) are instrumental in determining the optimal harvest composition. Fertility plays no direct role. It is argued that this is a general result working in stage-structured models with harvest values. In the numerical illustration it is shown that the optimal harvest pattern stays quite stable under various parameter changes. It is revealed which parameters and harvest restrictions that is most important. We also show that the current harvest pattern involves too much yearling harvest compared with the economically efficient level.