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.
1997
Authors
Erik Christiansen Alf BakkeAbstract
Availability of defenceless or weakly defended breeding material, e.g. trees felled or damaged by major wind storms, is a necessary requirement for an outbreak of the spruce bark beetle. Water stress is also hypothesised to be an important predisposing factor, although this idea is mostly based on circumstantial observation of a coincidence between dry weather and beetle outbreaks. Whereas a causal relationship may well exist for certain scolytid beetles, experimental evidence is often scarce and in some cases contradictory. We examine information pertaining to population dynamics of the spruce bark beetle Ips typographus in Norway. This includesexperiments to assess effect of drought stress on host tree susceptibility to the beetle’s pathogenic fungal associate, Ceratocystis polonica, andresults from a population monitoring program which has been in operation since 1980. Because drought often coincides with hot weather, one can confuse a direct effect on beetle propagation by hot weather with an indirect effect on insect dynamics through predisposition of the host trees. We conclude that apart from extremely rare cases of severe droughts lasting for a long period of time, direct effects of spring weather on beetle propagation are more likely to affect I. typographus dynamics than are indirect physiological effects working through the host trees.
Authors
Tor MykingAbstract
No abstract has been registered
Authors
Jorunn Elisabeth Olsen Olavi Junttila Jarle Nilsen M. E. Eriksson Inger Martinussen Olaf Olsson Göran Sandberg Thomas MoritzAbstract
Resultatene i arbeidet indikerer at den fotoperiodiske responsen hos tre kan være regulert av mengde PHYA genuttrykk, og at mengden av fytokrom A påvirker metabolismen av GAs (gibberelliner) og IAA (auxin).
Authors
Toril Drabløs Eldhuset Per Holm NygaardAbstract
No abstract has been registered
Authors
Tor MykingAbstract
No abstract has been registered
Authors
Atle Hindar Petter Nilsen A. Skiple R. HøgbergetAbstract
No abstract has been registered
Abstract
We compared diversity of birds in 35 study plots of equal size (58 ha) and productivity in western Norway, ranging from pure native pine Pinus sylvestris forests (n = 7), through different mosaics of native pine forests and spruce Picea spp. plantations (n = 21), to pure spruce plantations (n = 7). Diversity was evaluated by means of species richness, diversity indices, relative abundance curves and rarefaction. The diversity indices appeared to be less suitable for our purpose. Species richness was higher in pine forest than in spruce forest. However, a peak in species richness was found in mosaic forest. For pooled samples (408 ha), 11 bird species recorded in pine forest were not found in spruce forest, seven species were found in spruce forest but not in pine forest, and seven species were confined to the medium mosaics of pine and spruce forest (on average 56% pine and 44% spruce). We argue that, when mixing two habitat types A and B, the ratio of these habitats that maximize avian diversity depends on the ratio of species confined to habitat A and B, as well as the number of species favoured by the mixture of A and B. Existing spruce plantations (13% of the area) in native pine forests of western Norway have reduced the diversity of birds locally, but increased the diversity of birds on the landscape and regional scale.
Authors
Inger Aandahl Raastad Gunnar OgnerAbstract
No abstract has been registered
Authors
Rune Halvorsen Økland Eiliv Steinnes Tonje ØklandAbstract
No abstract has been registered
Authors
Ann Merete Furuberg GjedtjernetAbstract
No abstract has been registered