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.
1996
Forfattere
Marit Slåttelid Skeie May Bente Brurberg P.H. Middelhoven Gunnar Fimland Jon Nissen-Meyer Ingolf F. Nes Vincent G. H. EijsinkSammendrag
Det er ikke registrert sammendrag
Forfattere
Tonje ØklandSammendrag
Vegetational and environmental monitoring of boreal spruce forest was initiated in 1988, as a part of the programme “Contrywide Monitoring of Forest Health” at the Norwegian Institute of Land Inventory (NIJOS). As a basis for monitoring, relationships between trees, understory vegetation and environmental conditions (vertical relationships) were analysed for each of ten reference areas. The reference areas were selected to span regional gradients, in climatic conditions and deposition of airborne pollutants, in old-growth, so-called “bilberry-dominated”, “small-fern” and “low-herb”, also paludified, spruce forests south of the Polar Circle. Fifty 1-m2 meso sample plots, randomly chosen within ten 50-m2 macro sample plots in each reference area, were subjected to vegetation analysis, using frequency in subplots as species abundance measure. Environmental (including soil chemical) and tree parameters were recorded for meso as well as macro sample plots. The main vegetational gradients were found by parallel use of DCA and LNMDS ordination methods and subjected to environmental interpretation, mainly by means of non-parametric correlation analyses. DCA and LNMDS in most cases revealed the same main gradients in vegetation, but outliers were more frequent in LNMDS ordinations, due to higher vulnerability of this method to plots with deviating number of species. A complex-gradient in nutrient conditions, with pH and the concentration of nitrogen as the most constantly contributing variables, but with considerable between-area variation with respect to important cations, was evident in nine reference areas. Soil moisture varied along the second vegetational gradient in most areas. In the three most humid reference areas, the Ca concentration was related to variation in soil moisture and gradients from below to between trees, while unrelated or inversely related to the same vegetational gradient as pH. Species abundances were plotted on plot positions in DCA ordinations in order to summarize the species´ responses to environmental variation in each area. Variation in vegetation in the total data set (500 meso sample plots) was partitioned onto two sets of explantory variables (environmental and climatic/geographical) by use of CCA, in order to find the relative importance of environmental and climatic/geographical variation. The fraction of variation exclusively explained by environmental variables was about 17%, while only 5% of the variation was explained exclusively by climatic variables. The variation shared by both sets of variables was about 8%. The main vegetational gradients and environmental/climatic/geographical complex-gradients in the total data set were found by DCA and subsequent interpretation of axes. The main complex-gradients found by separate analyses of data from each reference area, were reflected along the DCA axes in total ordinations, but differences between areas with respect to positions along both environmental and climatic/geographical gradients were also evident. Meso plot occurrences of selected species were plotted in a DCA ordination of the total data set, with variation exclusively due to climatic/geographical variables removed, in order to express regional similarities and differences in the species´ responses to the environment. The different patterns of species´ distributions in the DCA ordination were discussed in the light of their use as indicators of specified environmental conditions.
Forfattere
Torild Wickstrøm W. Lund R. ByeSammendrag
It is shown, by using ICP-AES, that some Ni, Co, Fe and Cr is transported, probably as an aerosol, with the hydrides to the atom cell during a hydride generation process. The amount of matrix elements introduced to the atom cell depends on the concentrations of the sodium tetrahydroborate and the acid used for the hydride generation. For solutions containing 5000 mg l(-1) of Ni and Co, the signals obtained are equivalent to those obtained from 1-5 mg I-1 metal solutions nebulized in the ordinary way. A glass filter Frit placed between the gas-liquid separator and the torch reduces the transport of metal to the plasma by 50-80%. When HGAAS is used, a decrease in sensitivity is observed for As in samples containing high concentrations of Ni and Co. This may be owing to the presence of Ni and Co in the quartz tube atomizer.
Forfattere
Arnstein Orlund Øystein AustaråSammendrag
During 1987-90 heavy infestations of Sitka spruce (Picea sitchensis) plantations by the green spruce aphid Elatobium abietinum were reported from the coastal areas of Møre and Romsdal county, Norway. Annual growth ring width analyses in 1992 showed that minimum growth ring width occurred 6 years after the first infestation. For trees with breast height diameters more than or equal to 20 cm, the loss in diameter increment amounted to an average of 40.5% for 1988-95 compared to control trees (loss equals 3.2 years of normal growth). Growth loss was less pronounced for smaller diameter classes, and the smallest trees even exhibited an increase in increment during the first years of infestation. Possible reasons for different growth patterns are discussed.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Wenche E. DramstadSammendrag
This paper questions whether bumblebees really forage as close to their nests as has commonly been assumed in the bumblebee literature. Three experiments are described that involved marking and reobservation bumblebees. None of these experiments showed any tendency for bumblebees to concentrate their foraging close to (e.g., within 50 m from) the nest. Rather, the results suggested that bumblebees may prefer to forage at some distance from their nest. Further, a closer review of the bumblebee literature showed that similar findings were quite common. Some possible explanations to the observed behavior patterns are given as outlines for further research.
Sammendrag
The diversity in different groups of obligate saproxylic beetles was related to ecological variables at three levels of spatial scale in mature spruce-dominated forest. The variables were connected to: decaying woodwood-inhabiting fungilevel of disturbancelandscape ecologyvegetational structure. Several strong relationships were found at medium (1 km2) and large scales (4 km2), while only weak relationships were found at a small scale (0.16 ha; 1ha=104m2). This may be explained by the local variations in habitat parameters and the high mobilities of many beetle species. Factors connected to decaying wood and wood-inhabiting fungi were clearly the most important factors at all scale levels. In particular, the variables diversity of dead tree parts, number of dead trees of large diameter and number of polypore fungi species increased the species richness of many groups and increased the abundance of many species. Eight species were not recorded below a certain density of decaying wood per 1 or 4 km2. Former extensive cutting was a negative factor at large scale, probably because of decreasing recolonization with increasing distance to source habitats. Thinning reduced the diversity of species associated with birch. The development of guidelines favouring the diversity of saproxylic beetles are discussed below
Forfattere
Stein MagnesenSammendrag
I denne rapporten behandles resultater fra et proveniensforsøk med kjempeedelgran anlagt i Marnardal i Vest-Agder i 1981. Forsøksmaterialet omfatter 16 provenienser anskaffet gjennom internasjonalt samarbeid (IUFRO). Proveniensforsøk med dette materialet er anlagt i en rekke land i Vest- og Nord-Europa. Overleving på feltet ved totalalder 16 år utgjorde 86%, og den alt overveiende del av avgangen skjedde i løpet av de første årene etter planting. For de enkelte provenienser varierte overlevingsprosenten fra 73 til 97, og det ble påvist sikre proveniensforskjeller. En oppdeling av materialet i regionale grupper viste at innlandsprovenienser fra det nordlige Idaho hadde signifikant bedre overleving enn andre grupper. Skader etter vinterfrost, i form av brunfargete nåler, ble observert i forsøksfeltet i 1985. Skadene var ikke særlig alvorlige, men en fjerdedel av trærne på feltet var rammet. For de enkelte provenienser varierte skadeomfanget fra 4% opp til 50% og proveniensforskjellene var signifikante. Kystprovenienser fra lav høyde over havet var mest skadd, og frostskadene avtok med opprinnelsesstedets økende høyde over havet. For høydevekst er det påvist signifikante forskjeller mellom provenienser. Høydeveksten øker i store trekk med opprinnelsesstedets nordlige beliggenhet, og synker med økende lengdegrad, eller kortere avstand til kysten. Sammen reduserer breddegrad og lengdegrad variasjonen i høydevekst med 51%. Proveniensenes rekkefølge med hensyn til middelhøyde stabiliserte seg først etter 8-10 år. Innlandsprovenienser fra Idaho forbedret sin posisjon på bekostning av mange kystprovenienser, og ved 16 års alder har Idaho-proveniensene signifikant større middelhøyde enn alle andre regionale grupper. Mellom disse gruppene er det ingen sikre forskjeller og det er stor variasjon innen grupper. I andre land er det kystprovenienser fra det nordlige Washington og Vancouver Island som viser best vekst. Resultatene fra det norske forsøket skiller seg således ut fra de øvrige resultatene. Dette viser at kystprovenienser av kjempeedelgran har størst vekstpotensiale, men taper i konkurransen mot mer frostherdige innlandsprovenienser under ugunstige klimaforhold. Provenienser fra Cascadefjellene i det sentrale Oregon har vist svak vekst overalt, også under norske forhold. Redusert vekst i denne regionen skyldes sannsynligvis innblanding av koloradoedelgran. Sammenhengen mellom høydevekst og geografiske parametere er generelt liten. Når det i det norske forsøket er funnet at breddegrad og lengdegrad reduserer variasjonen i høydevekst med mer enn halvparten, skyldes dette god vekst hos nordlige innlandsprovenienser samt hos enkelte av de nordligste kystproveniensene. Det er således de nordligste proveniensene av kjempeedelgran, og i særdeleshet innlandsprovenienser fra det nordlige Idaho, som passer best for norske forhold.
Forfattere
Knut SolbraaSammendrag
Det er ikke registrert sammendrag
Forfattere
Nina JohansenSammendrag
Studies on the population dynamic of Mamestra brassicae (L.) (Lepidoptera: Noctuidae) were conducted during 1988-1992 in order to improve forecasting and control. The influence of temperature on development, fecundity and survival were investigated in climatic chambers, and lower developmental thresholds and thermal requirements were established for the preoviposition period and the immature stages. Pheromone traps were tested in cabbage fields at 5 locations in south-eastern Norway during 1989-1991. The trap catches were low at all locations and years, and the traps could therefore not be recommended for practical monitoring. A degree-day model for prediction of favourable times for assessment of infestation level and insecticide application was developed, validated and implemented. Mortality in the immature stages, and larval dispersal, was investigated in the laboratory and in the field. Highest mortality was found in first instar larvae and in hibernating pupae. The mortality in first instar larvae was probably caused by failure to locate and establish feeding sites and predation, whereas the winter loss probably was caused by unfavourable weather conditions. Life tables for five generations of a natural population of M. brassicae on white cabbage in Ås during 1988-1992 was constructed and analysed. Generation survival was very low, and the key factor was mortality in small larvae. The stage specific mortality appeared to be mainly density-independent. Parasitoids and pathogens were of little importance in controlling the M. brassicae population, although they were more or less persistently present throughout the experimental period. Trichogramma semblidis (Aurivillius) (Trichogrammatidae) was reared from eggs, and Microplitis mediator (Haliday) and Aleiodes (Aleiodes) sp., both Braconidae, were reared from larvae. Erynia virescens (Entomophtorales) was identified in medium and large larvae. Implications of the results in this study for integrated pest management is discussed, and management tactics are proposed.