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.
2009
Forfattere
Vitalis Wafula Wekesa Gilberto Jose de Moraes Edwin Moisés Marcos Ortega Italo Delalibera Jr.Sammendrag
The fungal pathogen Neozygites floridana Weiser and Muma has been evaluated as a classical biologicalcandidate for introduction into Africa against the invasive tomato red spider mite Tetranychus evansiBaker and Pritchard. In this study, the effect of temperature on sporulation, germination and virulenceof three isolates of N. floridana collected from T. evansi in three climatically distinct regions of Braziland Argentina was determined. Six constant temperatures of 13 C, 17 C, 21 C, 25 C, 29 C and 33 Cwere tested for their effect on the ability of the three fungal isolates to sporulate, germinate and killthe mites. Six alternating-temperature regimes of 17-13 C, 21-13 C, 29-13 C, 33-13 C, 33-23 C,33-28 C under a 12 h photophase were also tested to estimate virulence of the three isolates againstT. evansi. The Vipos isolate discharged more conidia than isolates from Recife or Piracicaba at all temperaturesand sporulation was strongly temperature dependent. Optimal sporulation rates were observed at25 C while optimal germination rates were observed at 25 C and 29 C. At 29 C, the shortest mean survivaltime of T. evansi (3.16 days, 95% CI of 3.05-3.27) was observed for the isolate from Vipos, while thelongest LT50 (3.47 days, 95% CI 3.34-3.59) was observed for the isolate from Piracicaba. Mortality of mitesincreased as the differences between alternating day and night temperatures increased from 8 C (21-13 C), to 10 C (33-23 C), to 16 C (29-13 C), with smallest and highest temperature differences of4 C (17-13 C) and 20 C (33-13 C), both producing low mortalities. The overall results suggest thatthe Vipos isolate is better adapted to a wider range of temperatures than the other isolates tested.
Forfattere
Trygve S. Aamlid Mats Larsbo Nick JarvisSammendrag
Soil water repellency in golf putting greens may induce preferential "finger flow", leading to enhanced leaching of surface applied agrochemicals such as fungicides and nitrate. We examined the effects of root zone composition and the use of the non-ionic surfactant Revolution on soil water repellency, soil water content distributions, infiltration rates, turf quality, and fungicide and nitrate leaching from April 2007 to April 2008. The study was made on 4-year-old experimental green seeded with creeping bentgrass (Agrostis stolonifera L) ‘Penn A-4" at Landvik in southeast Norway. Eight lysimeters with two different root zone materials: (i) straight sand (1% gravel, 96% sand, 3% silt and clay, and 4 g kg-1 organic matter) (SS) and (ii) straight sand mixed with Sphagnum peat to an organic matter content of 25 g kg-1 (SP) were used in this study. Surfactant treatment reduced the spatial variability of water contents, increased infiltration rates and reduced water drop penetration times (WDPTs) by on average 99% in and just below the thatch layer. These effects were most evident for SS lysimeters. Surfactant treatment resulted on average in an 80% reduction of total fungicide leaching, presumably due to reduced preferential finger flow facilitated by decreased soil water repellency. Peat amendment reduced fungicide leaching by 90%, probably due to increased sorption of the fungicides to organic matter. Nitrate leaching was also smaller from surfactant-treated straight-sand root zones, but this effect was not significant.
Forfattere
Knut Anders Hovstad Silje Borvik Mikael OhlsonSammendrag
Questions: Is the red fox a potential vector for epizoochorous seed dispersal? Can seed attachment and retention be predicted from plant and seed traits? Location: Grasslands in southern Norway. Methods: Epizoochorous seed attachment on the red fox was studied by walking a dummy fox through the vegetation and comparing seeds found on the dummy with the estimated seed availability in the vegetation. Seed retention, i.e. the ability of different seeds to stay on the fox, was estimated in a separate experiment. Seed attachment and retention were related to plant and seed traits using statistical models that account for heteroscedasticity and zero-inflated data. Results: The majority of seeds attached to the fox originated from a few species, but also species without specific seed traits that are supposed to enhance epizoochory attached at least some seeds to the fox. The probability of seed attachment was positively related to plant height, bristle and hooked seed appendages, and negatively related to winged appendages, seed mass, and seed sphericity. Seed retention was positively related to theseed traits bristles, hooks and pappus. For several species, the results indicate a high potential for dispersal over long distances. Conclusions: In modern agricultural landscapes, large herbivores are often restricted in their mobility or are found at low densities, and other animal vectors may therefore be important for seed dispersal. In our study, a range of plant species were able to disperse by attaching seeds to, and having their seeds retained in, the fox fur some distance. We suggest that the red fox may be an important vector for epizoochorous seed dispersal in the agricultural landscape.
Sammendrag
The European plum cultivar ‘Jubileum" blossoms abundantly most years and too many flowers can be set if not properly thinned. For two seasons started in 2007 mature ‘Jubileum/St. Julien A were treated with ethephon when full bloom opened at concentration of 250, 375 and 500 ppm and at 10-12 mm fruitlets stage at concentration of 125, 250 and 375 ppm. The experimental design was completely randomised with 6 replications of single trees. The trees were sprayed to run-off with a hand sprayer when temperature was above 15 ºC. All thinning treatments reduced the fruit set significantly. The fruit set decreased with increasing ethephon concentration, and the highest rates at bloom and fruitlet overthinned. Less dosage of ethephon was required at fruitlet time in order to obtain the same fruit set. The yield did confirm the fruit set response and the yield reductions were significant. All thinning treatments gave higher percentage of fruits larger than 38 mm fruit size compared to the unthinned control. Fruit quality characterized by blue surface cover and the content of soluble solids was in general high and increased significantly by reduced fruit. Fruit firmness, however, slightly declined in the ethephon thinned trees. Other fruit quality parameter like percentage acid content did not show a clear response to the thinning. Return bloom was little improved on thinned trees the following year. The crop load per tree was reduced to about the half of the previous year control trees included. In conclusion, ethephon application at a rate of 375 ppm applied at full bloom or 250 ppm at 10 mm fruit diameter thinned ‘Jubileum" plums to a target of about 10 -15 % fruit set.
Forfattere
Trygve S. Aamlid Tatsiana Espevig Trond Olav Pettersen Siv Lene Gangenes Skar Agnar KvalbeinSammendrag
Soil water repellency (SWR) is a common phenomenon on sand-based golf greens. Soils are considered severely water repellent if water droplets remain on the surface of undisturbed, air-dried soil samples for more than 600 seconds before penetrating. The objective of this research was to evaluate the potential of a surfactant to overcome SWR and restore turfgrass quality on a green with severe drought symptoms. The surfactant Aqueduct® was applied at a rate of 25 L ha-1 at weekly intervals from 4 June through 25 June 2008, either alone or after aeration with solid tines to 5 cm depth before each application. The experiment was irrigated uniformly corresponding to 1.65 times pan evaporation values from 4 June till 12 June, after which irrigation was not necessary due to natural rainfall. Conspicuous and statistically significant improvements in turfgrass quality occurred 10-12 days after the first application of surfactant, and the difference from untreated control plots continued to increase for about two and a half months after the completion of treatments. The improvement was accompanied by a significant increase in the SWC of the 0-20 cm soil layer and a deeper root system. The difference in WDPT between treated and untreated plots was significant at 1 cm, but not at 2, 3, 5 or 10 cm soil depths which were always far more water repellent than the thatch layer. Repeated aeration had no significant effect on turfgrass quality, and there was no significant interaction between surfactant and aeration treatments.
Forfattere
Anne-Grete Roer HjelkremSammendrag
Computer models are built to simulate real world systems. It is well known that models are related with uncertainty, still uncertainties are rarely quantified. The Bayesian statistical approach is used to calibrate a complex deterministic dynamic model of snow depth. Challenges emerging when applying the method will be explored. The Bayesian approach regards parameters as random and allows integration of prior knowledge. It will be demonstrated how prior information and new data affect the calibration process, parameters and model outputs, with focus on uncertainty. Point estimates and uncertainties are calculated and visualized for both parameters and model outputs. Generally, uncertainty decreased when new data were incorporated. Uniformly distributed priors gave the best fit for this model according to root mean square error, while the more informative beta distributed priors gave more physically meaningful parameter estimates. Markov chains of samples from the posterior distribution of the parameters were obtained by the random walk Metropolis algorithm. Crucial points when using these methods are reaching and determining convergence of the chains. In order to reach convergence faster, informative priors, Sivia"s likelihood, reflection and updating the proposal distribution with parts of the data gave successful results. To determine convergence objectively and correctly, the use of multiple chains and the Gelman Rubin method was found useful. Several decisions must be made when implementing Bayesian calibration and the choices that were found to be most effective will be highlighted and visualized.
Forfattere
Inger Martinussen Vladimir Volodin S. Volodina I. Poletaeva D. Bacharov R. Belyaeva Marja Uusitalo Alpo Heinonen Bertalan Galambosi Z. Galambosi Mette Thomsen Gunnlaug Røthe Erling Fjelldal Paul Eric AspholmSammendrag
At present the development of a modern life-stile in the Barents region has become not only a medical, but a social and economic problem as well. To prevent organism from unfavorable factors of the North and life-stile diseases much attention is paid now to the application of adaptogenic plants. "Herbs in the Barents region - a natural resource that improves health and creates business" is a title of the joint project of Norwegian, Finnish and Russian scientists on the adaptogenic plants. The project main goal is to create job opportunities in the Barents region based on the natural resources of adaptogenic herbs. This shall be done by the development of cultivation techniques for the adaptogenic pants Rhodiola rosea, Rhaponticum carthamolides and Serratula coronata. The industry will develop new herb products that will improve health conditions in the region. In order to promote adaptogenic products made from local plant raw material we have investigated the effect of the climate and geographical location on the level of active substances. Gene banks of plant species studied are established in all countries-participants. Experiments conducted in phytotrone showed that all three plant species like long days (northern conditions) and the levels of adaptogen"s substances are highest at the low and intermediate temperatures. Cultivation techniques are developed. To ensure the best quality of the raw material the methods of harvesting, drying and storing of plants are optimized. New methods for extraction from fresh raw material of R. rosea are developed. Fields at growers are established. The project was financing by Interreg IIIA, Norwegian Barents Secretary and agricultural offices of the counties Troms and Finnmark.
Forfattere
Arve Aarhus Arve AarhusSammendrag
Målet med rapporten er å kunne:Beskrivelse av bestandsforholdene for hjort med kjønns- og alderssammensetning og bestandsestimat før jakt 2009.Beskrive ulike scenarioer om hvordan bestanden vil endre seg ved ulike avskytingsmønster framover i tid.Komme med anbefalinger for framtidig forvaltning av hjort i Bremanger.Rapporten viser sammenstillinger over ulike typer materiale fra Bremanger kommune. For modellering av bestand, og som grunnlag for utarbeiding av scenarioer, har vi brukt en deterministisk bestandsmodell og definert et utgangspunkt for antall dyr i bestanden fordelt på ulike aldersklasser og kjønn.Bremanger kommune hadde sannsynligvis en på en stor økning i bestanden i løpet av 1990-tallet og fram til om lag 1998. Da fulgte en del åra med en mer eller mindre utflating av uttaket og sannsynligvis også i bestandsstørrelsen. Ut fra avskytningen og overvåkningsdata ser det ut til at bestandens igjen har økt noe de siste par åra. Overvåkningsdataene (Sett hjort) tyder på en økning i andelen bukk i bestanden de senere åra. Hvis man sammenholder denne utviklingen (økt andel bukk) med at den faktiske avskytningen, som har en overvekt av hanndyr i uttaket, så tyder dette også på en økning i bestandsstørrelsen. Både sett hjort og innmarkstellingene tyder på en variasjon i rekruttering til bestanden mellom åra, men usikkerheten i disse talla er foreløpig relativt stor.Ut fra de forutsetningene vi har satt i bestandsmodellen sammenholdt med avskytningstall og overvåkningsdata har Bremanger kommune en sannsynlig (jakt) bestand før jakt i 2008 på 3000 ± 300 dyr. Denne bestanden kan gi et bærekraftig uttak i 2008 på 630-735 ± 60 hjort avhengig av hvilke mål man har for bestandsutviklingen framover.Rapporten inneholder i tillegg noen anbefalinger for Bremanger kommunes hjorteforvaltning for åra som kommer.
Forfattere
Arne Stensvand David M. Gadoury Håvard Eikemo Andrew Dobson M. Catherine Heidenreich Robert C. SeemSammendrag
Field trials at Ås, Norway and Geneva, NY, USA revealed a substantial impact of initial levels of powdery mildew (Podosphaera macularis) upon disease development in strawberry (Fragaria × ananassa). Five-row plots of 50 to 100 mildew-free plants (planting distance 0.45 × 1.2 m) were established each year within large grain fields with a minimum distance of 90 m between plots and were left untreated with fungicides. Beginning each season, plants at the center of each plot were inoculated with 0, 1, 10, or 100 mildew-infected leaflets. Uninoculated plots developed only trace levels of powdery mildew, despite nearby diseased plots and wild strawberries in both Norway and NY trials over 3 years. More rapid and severe disease development was observed in the inoculated plots; e.g., mildew was observed on 31, 36, 311, and 912 leaflets in the 0, 1, 10, and 100 plots, respectively, in Norway in year 1 of the trial, and reached only 6 leaves per plot in the 0 plot in year 2. Spatiotemporal analyses were subsequently performed, but the practical impact of the trials was to demonstrate long-lasting benefits of clean, mildew-free planting stock in commercial strawberry production, even in areas where the pathogen is endemic and the environment is very conducive to disease.
Sammendrag
Colletotrichum acutatum is the causal agent of bitter rot in fruit crops (cherry, plum, apple, pear) and black spot in strawberry (Fragaria × ananassa). C. acutatum has also been isolated from a number of other cultivated and non-cultivated plant species; to date the fungus has been found on more than 25 different host species in Norway. The wide host range of C. acutatum necessitates research on the possibility of cross infection between alternative hosts and the potential of isolates of different origin to cause disease in strawberry. Planting healthy strawberry transplants adjacent to infected sweet cherry (Prunus avium) trees resulted in latent C. acutatum infections in the strawberry plants, indicating that cross infections between host species readily occur under field conditions. Molecular analyses (AFLP) have shown that isolates collected in Norway could be separated into three major phylogenetic groups in which isolates collected from either Prunus spp., Malus domestica or Fragaria × ananassa predominated. Two isolates from each of these groups were selected for experiments in vitro and in the field. Preliminary results indicate that isolates from all these groups are able to cause disease in strawberry, but that there may be differences in aggressiveness. In a field trial carried out in 2009 all six isolates caused symptoms in strawberry fruits when spore suspensions were applied three times during fruit development. The isolates from the Prunus group resulted in black spot on 42 and 53% of the strawberry fruits at harvest, while the corresponding numbers were 22 and 54% for the isolates from the Malus group, and 90 and 98% for the isolates from the Fragaria group.