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
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
Bjørn Arne Rukke Fred MidtgaardAbstract
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Authors
Jan MulderAbstract
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Authors
Sjur Spildo PrestegardAbstract
In this note it is first shown that public intervention in agriculture may be desirable in the case of market failure. Then the focus is on objectives concerning income distribution, price and income stability. The note then focuses on the proposition that some of the conflicting views on agricultural policy between economists, politicians and countries, arise from a difference in the fundamental view on agricultural policy. Is agricultural policy basically seen as an income policy or social policy, or as an intervention to correct market failures in agriculture? I suggest that this difference in viewing agricultural policy, also influence views on which policy instruments to use. Economists (and politicians) who look upon agricultural policy as mainly an income policy or social policy, often speak in favour of decoupling support, i.e. that support not should be linked to production. This argument has a strong basis in economic theory. However, if the objectives of agricultural policy are regarded as mainly policy interventions to correct market failures, decoupling of support can not be seen as effective. If the objective is to maintain a public good such as the agricultural landscape, the support must be given to landscape maintenance (and this requires some agricultural activity). This implies that «a greening of policies» which intends to decouple support totally from agricultural production, will not be an effective policy. But «a greening of policy» by reducing tariffs and price support in favour of for example different forms of acreage support or support per head of animals, will be more efficient and less trade distorting. It is argued that this has to be taken into account in the forthcoming negotiations within the WTO on further agricultural liberalisation. To give purely income support, is the same as stating that the main reason for keeping an agriculture in that country, is to give farmers an income. In this note it is argued that it should be seen the other way round. To give farmers a decent income and standard of living can not be regarded as an agricultural objective in itself, it must be seen as a necessary condition for maintaining a national agriculture and thereby obtain other objectives (i.e. correcting market failures). If a society has as its main agricultural objective to secure the income of farmers compared to other groups in society, it can be argued that this could be done better through the regular tax and social system than as an integrated part of agricultural policy.
Authors
Aksel GranhusAbstract
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Authors
Tore SkrøppaAbstract
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Authors
Tore SkrøppaAbstract
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Authors
Andries W. Boxman Kai Blanck Tor Erik Brandrud B. A. Emmett Per Gundersen Rene F. Hogervorst O. Janne Kjønaas Hans Persson Volkmar TimmermannAbstract
Enhancement of the atmospheric N deposition is a serious threat for the structure and function of ecosystems. Here we evaluate the ecological effects of excess N with respect to changes in vegetation and soil biota in a series of experiments along a N gradient across Europe. The aim of this project (NITREX: N saturation EXperiments) is to assess the risk of N saturation and the reversibility of N saturation. At the experimental sites with a low-to-moderate input, N was added (n = 3), while at sites with a high input, N was removed by means of a transparent roof (n = 4). The experiments started between 1989 and 1991. Across the N gradient a positive correlation was found between the N concentration in deposition or soil solution with the N concentration in the needles and in general a negative correlation with the base cations K and Mg. In the N-addition plots there was a tendency towards a decreasing nutrient status of the needles, whereas at one site N-removal led to an improvement. Addition of N hardly affected fine-root biomass production, whereas signs of growth increase were recorded when the input was reduced. Tree growth was accelerated upon input reduction at two of three sites. Manipulation of N input did not alter the decomposition rate, although significant differences between sites were noted. Manipulation of the N input hardly affected the biomass of fungi and bacteria, but a negative relation between the N-addition and part of the soil fauna may be present among sites.