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.
2005
Forfattere
Vegard Gundersen Lars Helge Frivold Irja Löfström Bruno Bilde Jørgensen Jan Falck Bernt-Håvard ØyenSammendrag
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Sammendrag
Considerable knowledge exists about the effect of aluminium (Al) on root vitality, but whether elevated levels of Al affect soil microorganisms is largely unknown. We thus compared soils from Al-treated and control plots of a field experiment with respect to microbial and chemical parameters, as well as root growth and vitality. Soil from a field experiment established in a 50 year old Norway spruce (Picea abies L.) stand where low concentrations of aluminum (0.5 mM AlCl3) had been added weekly or bi-weekly during the growth season for seven years was compared to a control treatment with respect to microbial and chemical parameters, as well as root growth and vitality. Analysis of soil solutions collected using zero tension lysimeters and porous suction cups showed that Al treatment lead to increased concentrations of Al, Ca and Mg and lower pH and [Ca+Mg]/[Al] molar ratio. Corresponding soil analyses showed that soil pH remained unaffected (pH 3.8), that Al increased, while extractable Ca and Mg decreased due to the Al treatment. Root ingrowth into cores placed in the upper 20 cm of the soil during 28 months was not affected by Al additions, neither was the mortality of these roots. The biomass of some taxonomical groups of soil microorganisms in the humus layer, analyzed using specific membrane components (phospholipid fatty acids; PLFAs), was clearly affected by the imposed Al treatment, but less so in the underlying mineral soil. Microbial community structure in the humus layer was also clearly modified by the Al treatment, whereas differences in the mineral horizon were less clear. Shifts in PLFA trans/cis ratios indicative of short term physiological stress were not observed. Yet, aluminium stress was indicated both by changes in community structure and in ratios of single PLFAs for treated/untreated plots. Thus, soil microorganisms were more sensitive indicators of subtle chemical changes in soil than chemical composition and vitality of roots.
Sammendrag
Rhizoctonia solani was frequently isolated in the Italian Alps from ursery-grown European beech (Fagus sylvatica) seedlings displaying symptoms of cotyledon rot. Koch?s postulates were verified and mode of infection of the associated isolates was investigated with light and scanning electron microscopy. Population structure of the pathogen was investigated by scoring the anastomosis reaction type in pairings between different isolates from the same seedbed. One pathogen genotype showed a large distribution area within the seedbed, this implying that the inoculum had been building up in the seedbed over a longer time period. Hyphal anastomosis tests and sequence analysis of the internal transcribed spacer (ITS) region of ribosomal DNA indicated that the pathogen belongs to AG 2-1 of R. solani. ITS sequence analysis indicates that the isolates from beech are closely related to R. solani isolates causing a disease on tulip. The striking similarities between the two diseases are discussed.
Sammendrag
*Strawberry Fragaria × ananassa (cv. Korona) was inoculated with Botrytis cinerea by dipping berries in a conidial suspension. *Colonization by the pathogen was monitored using real-time PCR, ELISA and ergosterol assays, the first showing the highest sensitivity. The expression of pathogen B-tubulin and six polygalacturonases (Bcpg1-6) and three host defence genes (polygalacturonase-inhibiting protein (FaPGIP) and two class II chitinases) were monitored using real-time RT-PCR. *The maximum transcript levels of the host defence genes occurred at 16 h postinoculation (hpi) at the presumed initial penetration stage. The unique transcript profile of Bcpg2 over the 96-h incubation time and its high transcript levels relative to those of the other Bcpgs at 8-24 hpi suggest that the gene has a specific role in the penetration stage. *Bcpg1 was expressed constitutively at a relatively high level in actively growing mycelia throughout the experimental period. Comparison of the transcript profiles indicated that Bcpg1 and Bcpg3-6 were coordinately regulated.
Forfattere
Bent Christen Braskerud K.S. Tonderski B. Wedding Rune Bakke A.-G.B. Blankenberg B. Ulen J. KoskiahoSammendrag
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Sammendrag
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Forfattere
Mathias Forsberg Mikael Frisk Mikael Rönnqvist Mikael RönnqvistSammendrag
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Sammendrag
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Sammendrag
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Forfattere
Ivar Gjerde Magne Sætersdahl Jørund Rolstad Ken Olaf Storaunet Hans Blom Vegard Gundersen Einar HeegaardSammendrag
We investigated the relationship between site productivity and diversity of vascular plants, bryophytes, lichens, and polypore fungi in forests based on species richness data in 0.25 ha forest plots (grain size), selected from six 150-200 ha study areas (focus), and spanning over a latitudinal distance of 1350 km (extent) in Norway. We (1) searched for prevailing productivity-diversity relationships (PDRs), (2) compared PDRs among taxonomic groups and species found in different micro-habitats, and (3) investigated the effect of increasing plot (grain) size on PDRs. Using vegetation types as a surrogate for site productivity, we found a general pattern of increasing species richness with site productivity. On average total species richness doubled with a ten-fold increase in productivity. Lichens PDRs stood out as less pronounced and more variable than for other species groups investigated. PDRs of species associated with downed logs tended to level off at high-productive sites, a pattern interpreted as an effect of disturbance. Increasing the grain size >10-fold did not change the proportional difference in species richness between sites with high and low productivity.