Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
1998
Authors
Geir-Harald Strand Tonje Økland Rune Halvorsen ØklandAbstract
Change in crown density for Norway spruce (Picea abies (L.) Karst.) from 1988 to 1993 in three independent forest monitoring projects in southern Norway were compared. An increase in crown density was found in countrywide systematic random sample, while measurements taken in old-growth forests reported a decline. These contradictory results may be due to (1) high sensitivity of high-elevation forests to various kinds of environmental impact; (2) differences in stand-age and management practice; and (3) different densitivity to long distance airborne pollutants. The systematic random sample encompassed stand of several age classes from two counties, while the two other studies were restricted to old-growth forest in two smaller areas. A possible explanation of the differences is thus that the three studies refer to different populations as a result of different sampling strategies.
Authors
Ingvald Røsberg Jon Anders Frank Arne StuanesAbstract
Det er ikke registrert sammendrag
Authors
Bjørn Arne Rukke Fred MidtgaardAbstract
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Abstract
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Authors
Sveinung Nersten Bo Eide Arild VeidahlEditors
Bjørn LangerudAbstract
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Authors
Bo Eide Arild VeidahlEditors
Bjørn LangerudAbstract
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Authors
Knut SolbraaEditors
Bjørn LangerudAbstract
Total avdøing av furu i høytliggende skog og områder eksponert for so mmerfrost helt ned til 300 m.o.h. forklares i hovedsak av angrep fra furuas knopp- og greintørkesopp (G. abietina). Denne skaden skyldes p rimært frost om sommeren og tidlig om høsten, og soppen angriper gjen nom skadde deler av barken. Elgbeiting kan også åpne for soppangrep, og holder plantene nede på en høyde som er lik en vanlig snøhøyde på 60-70 cm. Contortafuru fra 55-60 grader N viste høy resistens mot sop pen, men ble beitet like hardt som vår furu i forsøkene. På syv forsø ksområder ser det ut til at bare syv prosent av totalt 7 600 furuplan ter har muligheter til å utvikle seg til trær med dagens elgtetthet. Snøskytte spilte en uvesentlig rolle i disse forsøkene. Total mortality after planting of P. sylvestris in high-level forests and in areas exposed to summer frosts down to 300 meters a.s.l. is m ainly explained with attacks from Gremmeniella abietina. Primarily th is damage is caused by low temperatures in summer and early autumn, a nd the fungus is supposed to attack through damaged tissues in the ba rk and bark phloem . Moose browsing may also open up for fungal attac ks, and keeps the plants down at heights which are identically with a common snow depth of 60-70 centimeters. P. contorta from 55-60 degre es N was fairly resistant to the fungus, but was browsed as hard as P . sylvestris within the experiments. On seven experimental areas, onl y around 7% of totally 7 600 P. sylvestr is- and P. contorta-plants s eem to have the potential to develop to trees with the moose density of today. P. infestans attacked only a few plants in these experiment s.
Abstract
Change in crown density for Norway spruce (Picea abies) from 1988 to 1993 in three independent forest monitoring projects in southern Norway were compared. An increase in crown density was found in a countywide systematic random sample, whie measurements taken in old-growth forests reported a decline. These contradictory results may be due to: (1) high sensitivity of high-elevation forests to various kinds of environmental impact; (2) differences in stand age and management practice; and (3) different sensitivity to long distance airborne pollutants. The systematic random sample encompassed stans of several age classes from two counties, while the two other studies were restricted to old-growth forest in two smaller are as. A possibe explanation of the differences is thus that the three studies refer to differet popuations as a resut of different sampling strategies.
Authors
Peter Botterveg Rodney Leek Eirik Romstad Arild VatnAbstract
It is generally accepted that changes in agricultural management during the last decades have had negative effects in the forms of increased erosion and nutrient losses. In our analysis farmers are assumed to maximize expected profits. Economic incentives or direct regulations of agronomic practices may be used to change the farmers' management into a direction that will reduce the losses of nutrients and erosion. In an interdisciplinary research project with economists and ecologists, the effect of different policy measureson erosion and nutrient losses has been analysed. Policy measures analysed were, among others, catch crop requirements and subsidies for spring ploughing instead of autumn ploughing. First, an economic decision making model was ran for farms for a period of 20 years. The model decides the agronomic practice for each year on the different fields for a set of model farms. With the newly developed erosion model, the European soil erosion model (EUROSEM), the effect of the different agricultural practices were analysednot only at the level of single model farms, but also at the landscape level by use of a terrain model. The paper discusses
Authors
Bjørn Arne Rukke Fred MidtgaardAbstract
Effects of isolation, habitat size and several microhabitat variables on presence/absence of the monophagous Bolitophagus reticulatus (L.) (Coleoptera, Tenebrionidae) were investigated in 58 forest fragments in an agricultural landscape (15 km2) in south-eastern Norway. All potential habitats of the beetle, dead Fomes fomentarius (L.) Kickx basidiocarps (n=587), were collected from trees (n=185) within the study area. The basidiocarps were dissected and the number of B. reticulatus specimens (larvae, pupae and adults) counted. The material was analysed at four distinguishable spatial scales: basidiocarp-, tree-, tree-group- and forest island level. Different patterns of beetle presence emerged at the different scales. Increasing habitat size and decreasing degree of isolation increased the probability of B. reticulatus presence at three (basidiocarp-, tree- and forest island level) and one (tree level) scales, respectively, whilst no such trends were found at the fourth level (tree-group level). Increasing insolation and thereby higher ambient temperatures, indicated by several microhabitat variables, improved the probability of beetle presence amongst the trees. The number of beetle specimens correlated positively with an increase in the habitat size at the tree level.