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.
2012
Sammendrag
No abstract has been registered
Forfattere
Kyrre Linné Kausrud Bjørn Økland Olav Skarpaas Jean-Claude Grégoire Nadir Erbilgin Nils Christian StensethSammendrag
In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major forest pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating forestry practices should be adopted as soon as possible considering the time lags involved.
Sammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Forfattere
DJ Sargent T Passey N Surbanovski E. Lopez Girona P Kuchta Jahn Davik R. Harrison A Passey AB Whitehouse DW SimpsonSammendrag
No abstract has been registered
Forfattere
Christian Schiebe Almuth Hammerbacher Göran Birgersson Johanna Witzell Peter E. Brodelius Jonathan Gershenzon Bill S. Hansson Paal Krokene Fredrik SchlyterSammendrag
Secondary attraction to aggregation pheromones plays a central role in the host colonization behavior of the European spruce bark beetle Ips typographus. However, it is largely unknown how the beetles pioneering an attack locate suitable host trees, and eventually accept or reject them. To find possible biomarkers for host choice by I. typographus, we analyzed the chemistry of 58 Norway spruce (Picea abies) trees that were subsequently either (1) successfully attacked and killed, (2) unsuccessfully attacked, or (3) left unattacked. The trees were sampled before the main beetle flight in a natural Norway spruce-dominated forest. No pheromones were used to attract beetles to the experimental trees. To test the trees’ defense potential, each tree was treated in a local area with the defense hormone methyl jasmonate (MeJ), and treated and untreated bark were analyzed for 66 different compounds, including terpenes, phenolics and alkaloids. The chemistry of MeJ-treated bark correlated strongly with the success of I. typographus attack, revealing major chemical differences between killed trees and unsuccessfully attacked trees. Surviving trees produced significantly higher amounts of most of the 39 analyzed mono-, sesqui-, and diterpenes and of 4 of 20 phenolics. Alkaloids showed no clear pattern. Differences in untreated bark were less pronounced, where only 1,8-cineole and (−)-limonene were significantly higher in unsuccessfully attacked trees. Our results show that the potential of individual P. abies trees for inducing defense compounds upon I. typographus attack may partly determine tree resistance to this bark beetle by inhibiting its mass attack.
Forfattere
Roman Gebauer Daniel Volařík Josef Urban Isabella Børja Nina Elisabeth Nagy Toril Eldhuset Paal KrokeneSammendrag
Conifer needles are extraordinarily variable and much of this diversity is linked to the water transport capacity of the xylem and to xylem conduit properties. However, we still know little about how anatomical characteristics influence the hydraulic efficiency of needle xylem in different parts of the crown. In this study we evaluated needle function and anatomy in Norway spruce families exposed to different light conditions. We measured tracheid and needle characteristics of sun-exposed and shaded current-year needles in two experimental plots: a control plot and a thinned plot with 50% reduction in stand density. Sun-exposed needles had a larger tracheid lumen area than shaded needles, and this was caused by a larger maximum tracheid lumen diameter, while the minimum lumen diameter was less plastic. Sun-exposed needles had also higher theoretical hydraulic conductivity than shaded needles. Thinning leads to increased radiation to the lower branches, and presumably exposes the upper branches to stronger water stress than before thinning. Thinning affected several needle parameters both in sun-exposed and shaded needles; tracheid lumens were more circular and minimum tracheid lumen diameter was larger in the thinned plot, whereas maximum tracheid lumen diameter was less plastic on both plots. This study demonstrates that needle xylem structure in Norway spruce is clearly influenced by the light gradient within the tree crown.
Forfattere
Carl Gunnar Fossdal Nina Elisabeth Nagy Ari Hietala Harald Kvaalen Rune Slimestad Steve Woodward Halvor SolheimSammendrag
No abstract has been registered
Sammendrag
No abstract has been registered
Sammendrag
A survey of the prevalence of skin blemish diseases in potatoes after the growing seasons of 2008 and 2009 was carried out on 247 potato lots representing different cultivars and production regions in Norway. The results showed the presence of silver scurf (Helminthosporium solani) in all lots. Skin spot (Polyscytalum pustulans) and black scurf (Rhizoctonia solani) were found in 80% of the lots, and black dot (Colletotrichum coccodes) and common scab caused by Streptomyces spp. were present in 50–70%. Also, powdery scab (Spongospora subterranea) occurred in 65–80% of the lots, and root-lesion nematodes (Pratylenchus spp.) were detected in 60% of the sub-samples that exhibited symptoms of common scab.