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.
1998
Authors
Sondre Skatter Olav Albert Høibø Peder GjerdrumAbstract
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Authors
Sondre Skatter Olav Albert HøibøAbstract
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Authors
Bernt Olav Hoel Knut Asbjørn SolhaugAbstract
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Authors
Peter Botterveg Rodney Leek Eirik Romstad Arild VatnAbstract
It is generally accepted that changes in agricultural management during the last decades have had negative effects in the forms of increased erosion and nutrient losses. In our analysis farmers are assumed to maximize expected profits. Economic incentives or direct regulations of agronomic practices may be used to change the farmers' management into a direction that will reduce the losses of nutrients and erosion. In an interdisciplinary research project with economists and ecologists, the effect of different policy measureson erosion and nutrient losses has been analysed. Policy measures analysed were, among others, catch crop requirements and subsidies for spring ploughing instead of autumn ploughing. First, an economic decision making model was ran for farms for a period of 20 years. The model decides the agronomic practice for each year on the different fields for a set of model farms. With the newly developed erosion model, the European soil erosion model (EUROSEM), the effect of the different agricultural practices were analysednot only at the level of single model farms, but also at the landscape level by use of a terrain model. The paper discusses
Authors
Bjørn Arne Rukke Fred MidtgaardAbstract
Effects of isolation, habitat size and several microhabitat variables on presence/absence of the monophagous Bolitophagus reticulatus (L.) (Coleoptera, Tenebrionidae) were investigated in 58 forest fragments in an agricultural landscape (15 km2) in south-eastern Norway. All potential habitats of the beetle, dead Fomes fomentarius (L.) Kickx basidiocarps (n=587), were collected from trees (n=185) within the study area. The basidiocarps were dissected and the number of B. reticulatus specimens (larvae, pupae and adults) counted. The material was analysed at four distinguishable spatial scales: basidiocarp-, tree-, tree-group- and forest island level. Different patterns of beetle presence emerged at the different scales. Increasing habitat size and decreasing degree of isolation increased the probability of B. reticulatus presence at three (basidiocarp-, tree- and forest island level) and one (tree level) scales, respectively, whilst no such trends were found at the fourth level (tree-group level). Increasing insolation and thereby higher ambient temperatures, indicated by several microhabitat variables, improved the probability of beetle presence amongst the trees. The number of beetle specimens correlated positively with an increase in the habitat size at the tree level.
Authors
Fred Midtgaard Bjørn Arne Rukke Anne Sverdrup-ThygesonAbstract
1. Habitat use of Bolitophagus reticulatus (L.) (Coleoptera, Tenebrionidae), living in the basidiocarps of Fomes fomentarius (L.) Kickx, was investigated in three forest areas in south-eastern Norway: (1) a continuous, coniferous forest, (2) an agricultural area with mostly deciduous forest islands in a matrix of cultivated land and (3) a homogeneous, old deciduous forest stand. B. reticulatus was almost exclusively found inside dead basidiocarps. 2. The size of the basidiocarp was the most important variable for predicting the probability of B. reticulatus presence in the basidiocarps from all three study areas. 3. Drier basidiocarps had a higher probability of beetle presence than the wetter ones. Basidiocarps situated above the ground level had a higher probability of beetle presence than those close to or on the ground level. 4. The disappearance of beetles from previously inhabited basidiocarps seemed to be due to depletion of resources. 5. In the first study area, the presence of Cisidae was found to reduce the probability of B. reticulatus presence perhaps as a result of competition.
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No abstract has been registered