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.
2008
Authors
H. Dupré de Boulois Erik J. Joner C. Leyval I. Jakobsen B.D. Chen P. Roos Y. Thiry G. Rufyikiri B. Delvaux S. DeclerckAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Yijie WuAbstract
Luftforurensninger og klimaendringer påvirker kjemien i kronedrypp og jordvann i boreale skoger. Løst organisk materiale (DOM), inklusiv løst organisk karbon (DOC) og løst organisk nitrogen (DON), spiller en nøkkelrolle, og det er derfor nødvendig å forstå hvordan DOM blir påvirket, ikke bare av luftforurensninger og klimatiske faktorer, men også av andre faktorer. Denne avhandling undersøker faktorer som påvirker DOC og DON i norske skogøkosystem, med bruk av data fra de norske ICP Forests Level II-flater og andre studier...
Abstract
Quota regulations that prevent output expansion of farms and reallocation of output between farms can cause lower growth in output and productivity. The aim of this study was to explain the output growth rate of Norwegian dairy farms since 1976, and to decompose it into output, input, socioeconomic and technical change components. Instead of using the standard distance function approach for multi-output technologies, we use a growth rate formulation, which automatically removes the farm-specific effects. This formulation also helps to impose non-negativity constraints on marginal products of inputs (input elasticities), which are often violated for many observations, especially when flexible functional forms are used. The farm-level panel data cover three periods: before the quota scheme was introduced (1976-1982); the period with the most output-restricting quota scheme (1983-1996); and the period with a more flexible quota scheme (from 1997 onwards). Results show that the milk quota regulations had a significant constraining effect on output growth, in particular on milk output in the period 1983-1996. Furthermore, the output mix has shifted towards meat production for the average farm. What emerges from this study is that output growth and technical change are negatively influenced by policy aims where productive performance has not been the primary objective, and that there is scope for increased farm growth if the quota regime is liberalised.
Abstract
Runoff time series are known to contain long term structures on interannual to decadal time scales. Investigating spatial patterns of long term structures is a way to elucidate the relationship between external forcings and watershed properties. This would be a valuable contribution to an improved water resources management. Singular System Analysis (SSA) is a powerful technique to identify and extract significant long term components from time series. However, many observations from natural systems are prone to missing data that hamper many analysis techniques, including the SSA in its original formulation...
Abstract
Wood is a unique building material, but is by nature designed to deteriorate. A detailed understanding of the factors and interactions involved are important when working with service life prediction of wooden components in buildings. Wood may experience exponential fungal degradation caused by variation in the climatic factors within a small limited area and by minor imperfection in the wooden component. In this paper we put forward a new term: critical in-situ conditions (CIC). This is meant to bring the attention to the importance of looking into details in the construction design, the specific climatic factors and interactions involved. Gaining realistic and useful data for prediction of service life is only possible by controlling and understanding the factors that are target specific for a wooden component or even only a part of it. Performing measurements in a right way and in the proper part of the wooden component are vital for getting useful data for further processing. The objective in this paper is to exemplify the CIC in inservice situations and to describe the factors and interactions that control the service life. Case studies were performed on a building at Bryggen in Bergen, on a hunting cabin on Svalbard, on several wooden windows in the southern part of Norway and on an external wall of a residence house in Ås.
Abstract
Tree-killing bark beetles conquer healthy trees by means of pheromone mediated mass-attacks. The initial attackers select trees through a process of random landing and processing of tactile and short-range chemical stimuli. Inside acceptable hosts they produce aggregation pheromones that attract additional attackers. In a recent field experiment we induced defense responses in 60-year-old Norway spruce trees and monitored colonization by the spruce bark beetle Ips typographus. Induced stem sections had significantly less beetle colonization than control sections, with shorter parental galleries and fewer eggs deposited. In addition, fewer beetles were attracted to beetles tunnelling in induced bark. This reduced ability to attract conspecifics suggests that induced host defenses interfere with beetle pheromone production or emission. The mechanisms responsible for this are unknown, but may involve emission of volatile terpenes such as (E)-b-farnesene and linalool, which have been shown to increase up to 100-fold in induced Norway spruce trees. These compounds have been reported to attract natural enemies of herbivores or repel herbivores directly in other conifer-insect interactions.
Abstract
Seed production in Norway spruce (Picea abies) seed orchards may be severely reduced by insects attacking cones and seeds. Insects in several orders and genera are responsible for the damage, and at present there are no effective and environmentally acceptable control options. Studies in Sweden have shown promising results with spraying Bt (Bacillus thuringiensis var. kurstaki x aizawai) against species of Lepidoptera, but for other pests other control methods must be developed....
Authors
Christian Guido BrucknerAbstract
No abstract has been registered
Authors
Christian Guido Bruckner Peter, G. KrothAbstract
No abstract has been registered