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
Abstract
No abstract has been registered
Authors
O. Janne Kjønaas Richard Frederic WrightAbstract
Chronic deposition of inorganic nitrogen (N) compounds from the atmosphere to forested ecosystems can alter the status of a forest ecosystem from N-limited towards N-rich, which may cause, among other things, increased leaching of inorganic N below the rooting zone. To assess the time aspects of excess N leaching, a process-oriented dynamic model, MERLIN (Model of Ecosystem Retention and Loss of Inorganic Nitrogen), was tested on an N-manipulated catchment at Grdsjn, Sweden (NITREX project). Naturally generated mature Norway spruce dominates the catchment with Scots pine in drier areas. Since 1991, ammonium nitrate (NH4NO3) solution at a rate of about 35 kg N ha-1 yr-1 (250 mmol m-2 yr-1) has been sprinkled weekly, to simulate increased atmospheric N deposition. MERLIN describes C and N cycles, where rates of uptake and cycling between pools are governed by the C/N ratios of plant and soil pools. The model is calibrated through a hindcast period and then used to predict future trends. A major source of uncertainty in model calibration and prediction is the paucity of good historical information on the specific site and stand history over the hindcast period 1930 to 1990. The model is constrained poorly in an N-limited system. The final calibration, therefore, made use of the results from the 6-year N addition experiment. No independent data set was available to provide a test for the model calibration. The model suggests that most N deposition goes to the labile (LOM) and refractory (ROM) organic matter pools. Significant leaching is predicted to start as the C/N ratio in LOM is reduced from the 1990 value of 35 to 28. At ambient deposition levels, the system is capable of retaining virtually all incoming N over the next 50 years. Increased decomposition rates, however, could simulate nitrate leaching losses. The rate and capacity of N assimilation as well as the change in carbon dynamics are keys to ecosystem changes. Because the knowledge of these parameters is currently inadequate, the model has a limited ability to predict N leaching from currently N-limited coniferous forest ecosystems in Scandinavia. The model is a useful tool for bookkeeping of N pools and fluxes, and it is an important contribution to further development of qualitative understanding of forest N cycles.
Authors
Klaus MittenzweiAbstract
This paper discusses arguments to justify active income redistribution by governments based on the assumption that the redistribution of income is the only government objective. Other (legal) governmental objectives like providing public goods or correcting for externalities are neglected. There exist sound economic arguments to justify active income redistribution by governments (e.g. risk averse behavior, preferences for equality, and concerns for the poor). These arguments, however, do not seem to confirm that policies aimed to redistribute income only should be eligible for special interest groups. The choice of policy instruments should be based on the concept of transfer efficiency. This concept ranks policy instruments according to their costs of transferring a given amount of income between individuals in the economy. Economic theory is biased in the understanding of the role government plays in the decision making process. Neo-classical theory holds the view that governments act as if they represented the aggregated preferences of the individuals in the economy. Public choice theory assumes instead that governments are made up by individuals who pursue their own interests (but do not necessarily act egoistically). According to this theory, governments can be induced to implement policies that redistribute income as a result of lobbying and rent-seeking behavior. Norway is characterized by a relatively equal distribution of income compared to other countries. The more or less equal distribution of total household income of Norwegian farmers is to a greater extent a result of part-time farming than a result of domestic agricultural policies that aim to equalize (agricultural) income among farmers. This picture may change considerably when agricultural income per man-year is concerned but further research is needed to answer this question.
Authors
Svein Ole BorgenAbstract
No abstract has been registered
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No abstract has been registered
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No abstract has been registered
Authors
Tore SkrøppaAbstract
No abstract has been registered
Authors
Franck Brignolas François Lieutier Daniel Sauvard Erik Christiansen Alan A. BerrymanAbstract
Changes in phloem phenolic content of Norway spruce (Picea abies (L.) Karst.) clones were followed during the first 12 days of the reaction induced by phloem artificial inoculation with Ceratocystis polonica Siem., a bark beetle (Ips typographus L.) associated fungus. The aim was to confirm our previous results concerning the mechanisms of this reaction and the possible predictors of Norway spruce resistance to bark beetles and their associated fungi. The induced reaction was characterized by a slight decrease of tanning ability and an increase of ()-catechin concentration, which confirmed our previous observations. The relative resistance of the clones was first predicted using the predictors previously proposed. In addition, the first axis of the principal component analysis describing the phenolic content of all clones was used as a synthetic predictor (resistance axis). Related variables were also tested as predictors. Actual resistance of each clone was then measured, using mass inoculations of C. polonica, and was compared with the predictions. Four predictors were so validated: the resistance axis, tanning ability and isorhapontin concentration in uninoculated phloem, and ()-catechin concentration in the phloem 6 days after its inoculation. Phloem phenolic composition could thus be used to predict Norway spruce resistance to bark beetles and their associated fungi.
Authors
Tong ZhuAbstract
No abstract has been registered
Authors
Olavi Junttila Jorunn Elisabeth Olsen Jarle Halvard Nilsen Inger Martinussen Thomas Moritz Maria Eriksson Olle Olsson Göran SandbergAbstract
Photoperiodic effects on woody plants were reported already by Gardner and Allard in 1923 and comprehensive studies during the ’50s confirmed the role of photoperiod as an important environmental regulator of growth and growth cessation in many northern tree species (Nitsch, 1957; Wareing, 1956). In woody plants cessation of apical growth is a prerequisite for cold acclimation (Weiser, 1970) and photoperiod, as a factor controlling growth cessation, is therefore an important environmental signal for initiation of cold acclimation. In many cases a proper timing of acclimation and deacclimation, in respect to annual variation of temperature conditions, is more critical for winter survival than the maximum level of frost hardiness. Also in such coniferous species where cessation of apical growth is not controlled by photoperiod, short photoperiod is necessary for good cold acclimation, low temperature causes no or only a limited level of hardiness if combined with long day conditions (Schwarz, 1970; Aronsson, 1975; Christersson, 1978; Jonsson et al., 1981). Thus, photoperiod may have both an indirect, through induction of growth cessation, and a more direct influence on cold acclimation in woody plants.