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 Bohumil KuceraAbstract
A new theory is presented on the cause of the prevalent directions of the spiral grain patterns found in conifers. The hypothesis is based upon the assumption that spiral grain has a function, i.e. that it represents a growth strategy to ensure survival of the trees. The mechanical function of the tree trunk is placed in focus, that is the ability of the trees to withstand external mechanical loads, mainly from wind. Spiral grain is an optimized growth feature when the trees are exposed to combined bending and torsion. Torsion occurs when the crown is asymmetric in the plane perpendicular to the wind direction. Systematic crown asymmetry, with heavier crowns on the south side, was confirmed by measuring the crown projections on 253 sparsely grown pines; 76.7% of the trees had longer branches on the south than on the north side, and the average length difference was 40.8 cm. By studying wind maps it was seen that most of the coniferous forests have prevailing westerly winds, which, when combined with the crown asymmetry, leads to a prevailing torque. Right-handed spiral grain in the outermost layers of mature trees is proposed to be a strategy to withstand this torque, i.e. to avoid stem breakage
Abstract
The seasonal variations in volume of the milk in Norwegian goat dairyfarming, complicate production of brand goat cheeses. In the specialised goat dairy farming system most kids are culled shortly after birth without utilising the meat. In this paper the farm economics of an alternative system with altered period of kidding (currently in theperiod from January to March) combined with production of meat and cashmere fibre, is examined. May kidding combined with raising the kids for 8 or 20 months yielded the m ost promising economical return. Raising the kids one year is also profitable when kidding takes place in February while December kidding seems to perform best with thepresent system of culling the kids right after birth. Cashmere fibre production seems to be profitable on Norwegian dairy goat farms and fibre and meat could become an optio n in countries seeking to improve incomes on dairy goat farms. Compared to the present system the changes also would be favourable from an animal welfare point of view.
Authors
Albert Tietema Bridget A. Emmett Per Gundersen O. Janne Kjønaas Chris J. KoopmansAbstract
As part of four European ecosystem manipulation experiments in coniferous forests, field-scale 15N tracer experiments have been carried out. The experiments involved a year-long addition of 15NH4 and/or 15NO3- to throughfall at experimental plots with different N inputs. The fate of this applied 15N in the important ecosystems pools (trees, ground vegetation, forest floor and mineral soil), as well as in drainage was measured. About 10-30% of added 15N was taken up by the trees and 10-15% was retained in the mineral soil. Both retention efficiencies were found to be constant with N input. The part of 15N retained in the organic layer was relatively high (20-45% of applied) at low N inputs (0-30 kg N ha-1 yr-1) but low (10-20%) at high N inputs (30-80 kg N ha-1 yr-1). An inverse relationship between N input and the loss of 15N in drainage was found: drainage losses increased as a function of N input. These results suggest that increased N inputs exceed the capacity of the microbial population to retain throughfall-N in the organic layer, with the result that N leaching increases.
Abstract
The genus Bryomyia comprises altogether eight species in the Palearctic region, including one new species Bryomyia amurensis Mamaev et Økland described in the present article. A revised key to the species of Bryomyia in the Holarctic region is presented.
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.