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.
1996
Authors
Paal KrokeneAbstract
Aggressive bark beetles kill healthy conifers through pheromone-mediated mass attacks. The exact mechanism by which trees are killed is still disputed, but phytopathogenic blue-stain fungi associated with the beetles are probably involved in most cases. This thesis compares the blue-stain flora of five bark beetle species that colonize Norway spruce of different resistance. The aggressive Ips typographus can kill healthy trees, while the other species are non-aggressive and colonize either severly stressed or dying trees (the facultatively parasitic Ips duplicatus, Polygraphus poligraphus and Pityogenes chalcographus), or dead trees (the saprophagic Hylurgops palliates). Ips typographus and I. duplicatus were both found to carry very high frequencies of the phytopathogenic fungus Ceratocystis polonica. This fungus has previously been found associated only with I. typographus, and has been shown to be pathogenic to Norway spruce in experimental mass inoculations. The other bark beetles carried no known pathogenic fungi. The phytopathogenicity of four of the isolated blue-stain fungi were evaluated through mass and low-density inoculation in young Norway spruce trees. Mass inoculations confirmed C. polonica\"s pathogenicity, while the other fungi, which are associated with non-aggressive beetles, were not pathogenic (Ophiostoma piceae, cfr. Ambrosiell sp., Dark sterile sp.A). Low-density inoculations revealed only small differences between the four fungi in phloem necrosis length. Necrosis length is used as a standard criterion of fungal pathogenicity, but it was not useful for assessing the pathogenicity of the fungi in the fungus-host tree system under study here. Ceratocystis polonica was found to penertrate deeper into the sapwood and induce deeper sapwood desiccation than the other fungi. The ability to invade sapwood is probably more important for fungal pathogenicity than the ability to colonize phloem, and may thus be a better criterion for assessing the pathogenicity of blue-stain fungi. General aspects of the association between bark beetles and blue-stain fungi are discussed.
Authors
Bjørn ØklandAbstract
A high trapping efficiency was found both for window traps and trunk-window traps, while the efficiency of extraction cylinders was low. Trunk-window traps are suitable for comparison of different substrates within the same forest environment, while comparative studies of different forest environments are more difficult, due to baiting effects. Window trap captures are more suitable for comparing different forest environments, but are related to ecological conditions over wide areas, and are almost unaffected by substrate conditions in the near surroundings of the traps
Abstract
There is a growing awareness to preserve the biodiversity in the forest ecosystems. A first step in biodiversity research is to find out what species really are found in the forest, using the scientific tool named taxonomy. Still there are species-rich groups of forest insects which have been poorly researched, and which include several unclearities concerning the species identities. One such group is the free-developing gall midges connected with litter, dead wood and fungi in the ground layer of the forest. This papers intends to improve the taxonomy of one genus in this group - Anaretella (Enderlein 1911), including the description of two new species and a key to the current species within the Holarctic region
Authors
Bjørn ØklandAbstract
The relationship between the mycetophilid fauna and a set of environmental variables was studied in spruce forests of southeastern Norway. At the stand level, the continuous presence of wood in all decay stages combined with a tree cover appeared to be a major factor for increasing the species richness of mycetophilids. However, the spatial representation of suitable stands in the landscape seems to be particularly important, since the % area of oldgrowth in the surrounding 100 km showed the strongest influence on both species richness and abundance within individual species. The present findings indicate that conservation of a species-rich mycetophilid fauna requires networks of stands within dispersal distances. A reserve network in southern Norway should give special priority to little disturbed forests in the more remote sub-montane areas, since they appear to be very species-rich, and since their strong populations may provide a long-term viability of many mycetophilid species.
Authors
Guro BrodalAbstract
No abstract has been registered
Authors
Guro BrodalAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Ingolf Nes Dzung Bao Diep Leiv Sigve Håvarstein May Bente Brurberg Vincent Eijsink Helge HoloAbstract
No abstract has been registered