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.
2006
Sammendrag
Presentasjon av en analyse av hydrologien i to nedbørsfelter i Estland og Norge. Analysen aer basert på flashiness indeks. Det er store forskjeller i flashiness indeks mellom Norske og Estiske felt. Analysen kan være et bidrag i forklaringen av forskjeller i næringsstofftap og erosjon. Samtidig kan det gi et bidrag i utformingen av prøvetakingsrutiner.
Sammendrag
An analysis of runoff measurements can reveal a great deal about the hydrological character of a catchment. There are different ways to carry out such a hydrological characterization. In this paper, characterisation of the hydrological behaviour of catchments is carried out by describing the flashiness of the runoff. Flashiness in this case is meant to express the variation in runoff over short periods. A modified flashiness index has been calculated for small agricultural catchments in Estonia and Norway respectively, based on hourly recorded discharges and a comparison has been made with results obtained from a flashiness index, which is based on average daily discharge values. The comparison revealed large differences between the two index values for the Norwegian catchments, indicating large variations in discharge values over short periods or a "flashy" nature in runoff. Only small differences were found for the Estonian catchments. Large differences were found when comparing the Norwegian and Estonian catchments. Although the flashiness index does not a-priori give information about the flow processes, it might be helpful in explaining differences in nutrient and soil losses between catchments.
Forfattere
Hege Hvattum Divon Carmit Ziv Olga Davydov Oded Yarden Robert Fluhr Hege DivonSammendrag
Fusarium oxysporum is a soil-borne pathogen that infects plants through the roots and uses the vascular system for host ingress. Specialized for this route of infection, F. oxysporum is able to adapt to the scarce nutrient environment in the xylem vessels. Here we report the cloning of the F. oxysporum global nitrogen regulator, Fnr1, and show that it is one of the determinants for fungal fitness during in planta growth. The Fnr1 gene has a single conserved GATA-type zinc finger domain and is 96% and 48% identical to AREA-GF from Gibberella fujikuroi, and NIT2 from Neurospora crassa, respectively. Fnr1 cDNA, expressed under a constitutive promoter, was able to complement functionally an N. crassa nit-2(RIP) mutant, restoring the ability of the mutant to utilize nitrate. Fnr1 disruption mutants showed high tolerance to chlorate and reduced ability to utilize several secondary nitrogen sources such as amino acids, hypoxanthine and uric acid, whereas growth on favourable nitrogen sources was not affected. Fnr1 disruption also abolished in vitro expression of nutrition genes, normally induced during the early phase of infection. In an infection assay on tomato seedlings, infection rate of disruption mutants was significantly delayed in comparison with the parental strain. Our results indicate that FNR1 mediates adaptation to nitrogen-poor conditions in planta through the regulation of secondary nitrogen acquisition, and as such acts as a determinant for fungal fitness during infection.
Forfattere
Christian UhligSammendrag
Reindeer husbandry has lead to consecutive landscape changes in Finnmark, Northern Norway, during the last 30 years. Vegetational changes, particularly the degradation of fruticose lichen winter pastures, are well documented. Impacts on other landscape components such as soils are less known. The aim of this paper is I) to document changes in soil properties due to reindeer grazing and II) to specify potential implications for future landscape changes and management. In general, reported pattern for impacts of reindeer grazing on lichen pastures are rather similar, but opposite to those found for the post-fire succession of many lichen dominated boreal and arctic ecosystems, which floristically are characterized by the succession of cryptogams. Based on this assumption four degradation/ succession stages (DS) ranging from an average fruticose lichen (FL) carpet exceeding 4 cm in depth (DS I) to the total disappearance of FL and dominance of crustose lichens and bare mineral soil (DS IV) were characterised. Results showed a significant decrease in humus mass per area from approximately 4800 g/m2 (DS I) to 4100 g/m2 (DS II) and 3600 g/m2 (DS III). Furthermore, total calculated amounts of the essential plant nutrients N, P, Ca, Mg, and K stored in the upper organic horizon at DS III were about 30 to 45 % lower than those of DS I. Findings clearly indicate that degradation of fruticose lichen carpets by reindeers also negatively influence on soil organic matter quantity and quality. At Finnmarksvidda the organic layer can be considered the key factor for soil fertility, and thus landscape stability. The sustainable management of soil resources may therefore be of vital importance to avoid further degradation of reindeer pastures on Finnmarksvidda.
Forfattere
Clemens Reimann Arnold Arnoldussen Rognvald Boyd Tor Erik Finne Øystein Nordgulen Tore Volden Peter EnglmaierSammendrag
Forty terrestrial moss (Hylocomium splendens) samples were collected along a 120-km-long south–north transect running through Norway\"s largest city Oslo. Concentrations of 29 chemical elements (Ag, Al, Au, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, Pt, S, Sb, Sr, Th, Ti, and Zn) and values for loss on ignition (475 °C) are reported. Silver (Ag), Al, Au, Bi, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Pt, Sb, Th, Ti, and Zn all show a characteristic Oslo peak when element concentrations are plotted against location of the sample site along the transect. Gold (Au) and Pt show the greatest relative enrichment of all elements in the city (ca. 10× “background”). Titanium (Ti), which is related to local minerogenic dust rather than anthropogenic emissions, shows a significant peak in Oslo. Loss on ignition, a measure of the amount of organic material in a sample, shows a negative peak in Oslo and at sites close to a known dust source. Input of fine dust thus appears to dominate many of the observed element concentrations in moss. The concentrations of Na are clearly influenced by the input of marine aerosols and show decreasing concentrations from south (near Oslo Fjord) to north (inland). The major plant nutrients Ca, K, Mg, P and S, as well as Hg, are the few elements displaying no spatial dependency along the transect. Element concentrations reach background variation levels at a distance of 20–40 km from the city centre.
Sammendrag
Winter conditions with seasonally frozen soils may have profound effects on soil structure and erodibility, and consequently for runoff and erosion. Such effects on aggregate stability are poorly documented for Nordic winter conditions. The purpose of this study was to quantify the effect of variable freeze-thaw cycles and soil moisture conditions on aggregate stability of three soils (silt, structured clay loam-clay A and levelled silty clay loam-clay B), which are representative of two erosion prone areas in southeastern Norway. A second purpose was to compare aggregate stabilities measured by the Norwegian standard procedure (rainfall simulator) and the more widely used wet-sieving procedure. Surface soil was sampled in autumn. Field moist soil was sieved into the fraction 1-4 mm and packed into cylinders. The water content of the soil was adjusted, corresponding to matric potentials of -0.75, -2 and -10 kPa. The soil cores were insulated and covered, and subjected to 0, 1, 3 or 6 freeze -thaw cycles: freezing at -15 °C for 24 h and thawing at 9 °C for 48 h. Aggregate stability was measured in a rainfall simulator (all soils) and a wet-sieving apparatus (silt and clay B). The rainfall stability of silt was found to be significantly lower than of clay A and clay B. Clay A and clay B had similar rainfall stabilities, even though it was expected that the artificially levelled clay B would have lower stability. Freezing and thawing decreased the rainfall stability of all soils, but the effect was more severe on the silt soil. There was no evident effect of water content on the stability, probably due to experimental limitations. The same effects were observed for wet-sieved soil, but the wet-sieving resulted in less aggregate breakdown than the rainfall simulator. Rainfall impact seemed to be more detrimental than wet-sieving on more unstable soil, that is, on silt soil and soil subjected to many freeze-thaw cycles. Such conditions are expected to occur frequently during field conditions in unstable winters.
Forfattere
Ingjerd Solfjeld Øystein JohnsenSammendrag
We have examined shoot and root growth and the concentration of carbohydrates in seedlings of a northern (67 degrees N) and a southern (61 degrees N) ecotype of Betula pendula Roth. cultivated at root-zone temperatures of 2, 6, 12 and 17 degrees C. Three hydroponic experiments were conducted in controlled environments. We used three different pretreatments before seedlings were subjected to the experimental temperature treatments. Actively growing seedlings that were acclimated to the hydroponic solution for 3 weeks at a root temperature of 17 degrees C, continued to grow at all the experimental temperatures, with an expected increase in growth from 2 to 17 degrees C. However, if we started with ecodormant cold stored plants or used seedlings grown actively in perlite, no growth was observed at 2 degrees C and only minor growth was found at 6 degrees C. The highest root temperature always produced the best growth. The concentration of nonstructural carbohydrates was higher in seedlings grown at 2 degrees C than at 17 degrees C, and this is probably due to extensive incorporation of carbohydrates into cell walls and other structural elements at 17 degrees C. We found no evidence for differences between the two ecotypes in root growth, in timing of bud burst, but shoot growth terminated in the northern ecotype in the first experiment because the natural photoperiod was below the critical value. Our study highlights the importance of post-transplantation stress (planting check) related to root growth, and that root threshold temperatures may change according to the way plants are pretreated. Abstract: We have examined shoot and root growth and the concentration of carbohydrates in seedlings of a northern (67 degrees N) and a southern (61 degrees N) ecotype of Betula pendula Roth. cultivated at root-zone temperatures of 2, 6, 12 and 17 degrees C. Three hydroponic experiments were conducted in controlled environments. We used three different pretreatments before seedlings were subjected to the experimental temperature treatments. Actively growing seedlings that were acclimated to the hydroponic solution for 3 weeks at a root temperature of 17 degrees C, continued to grow at all the experimental temperatures, with an expected increase in growth from 2 to 17 degrees C. However, if we started with ecodormant cold stored plants or used seedlings grown actively in perlite, no growth was observed at 2 degrees C and only minor growth was found at 6 degrees C. The highest root temperature always produced the best growth. The concentration of nonstructural carbohydrates was higher in seedlings grown at 2 degrees C than at 17 degrees C, and this is probably due to extensive incorporation of carbohydrates into cell walls and other structural elements at 17 degrees C. We found no evidence for differences between the two ecotypes in root growth, in timing of bud burst, but shoot growth terminated in the northern ecotype in the first experiment because the natural photoperiod was below the critical value. Our study highlights the importance of post-transplantation stress (planting check) related to root growth, and that root threshold temperatures may change according to the way plants are pretreated.
Forfattere
Ingjerd Solfjeld Øystein JohnsenSammendrag
We have examined shoot and root growth and the concentration of carbohydrates in seedlings of a northern (67oN) and a southern (61oN) ecotype of Betula pendula Roth. cultivated at root-zone temperatures of 2, 6, 12 and 17oC. Three hydroponic experiments were conducted in controlled environments. We used three different pretreatments before seedlings were subjected to the experimental temperature treatments. Actively growing seedlings that were acclimated to the hydroponic solution for 3 weeks at a root temperature of 17oC, continued to grow at all the experimental temperatures, with an expected increase in growth from 2 to 17oC. However, if we started with ecodormant cold stored plants or used seedlings grown actively in perlite, no growth was observed at 2oC and only minor growth was found at 6oC. The highest root temperature always produced the best growth. The concentration of nonstructural carbohydrates was higher in seedlings grown at 2oC than at 17oC, and this is probably due to extensive incorporation of carbohydrates into cell walls and otherstructural elements at 17oC. We found no evidence for differences between the two ecotypes in root growth, in timing of bud burst, but shoot growth terminated in the northern ecotype in the first experiment because the natural photoperiod was below the critical value. Our study highlights the importance of post-transplantation stress (planting check) related to root growth, and that root threshold temperatures may change according to the way plants are pretreated.
Forfattere
Trude Wicklund S. Dimitrijevic Eldrid Lein Molteberg V.E. Segtnan Svein KnutsenSammendrag
Akryamid dannes gjennom varmebehandlinger som steking, baking og fritering. I poteter regnes de reduserende sukkerartene glukose fruktose å være de de viktigste forløperne. I posteren rettes søkelyset mot innholdet av fruktose, glukose og asparagin og sammenhengen med innhold av akrylamid etter ovns-steking. Resultatene tyder på at innholdet av reduserende sukker og asparagin alene ikke er nok til forutsi sannelsen av akrylamid.
Sammendrag
Neozygites floridana is a fungus in the order Entomophthorales that infects and kills the two-spotted spider mite, Tetranychus urticae. In a study conducted in Norwegian strawberry fields, N. floridana infected and killed T. urticae in all 12 fields studied. Infections up to 90% were registered, and the highest infection levels were observed late in the season. The infection levels throughout a season varied considerably. To evaluate factors that might be important for conservational biological control, the effect of pesticides used in strawberries on the N. floridana infection level were also studied. The pesticides tested were three fungicides; Euparen (tolylfluanid), Teldor (fenhexamid), Switch (cyprodinil +fludioxonil) and one acaricide: Mesurol (mercaptodimethur). The experiment indicates that Euparen and Switch do not affect the N. floridana killing capacity, but both Teldor and Mesurol do. Methods for the production and storage of N. floridana infected T. urticae cadavers for inoculative/ inundative biological control in strawberries were established in our laboratory and are presented briefly in this paper. Similar methods might be adapted for the inoculative/ inundative biological control of T. urticae in for example greenhouse crops.