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.
2008
Forfattere
Ragnhild Hafskjold Nærstad Arne Hermansen Tore BjorSammendrag
A series of field trials combining cultivars with different levels of resistance to Phythophtora infestans and different haulm killing methods was conducted in 1997, 1998 and 1999 to assess the contamination potential of the haulm. In addition, the frequency of tubers with late blight was assessed after harvest and storage, combining effects of pretreatment infection, infection by the haulm at harvest and the development of the disease during storage. Haulm killing was performed by diquat (200, 400, 600 g a.i. ha-1), half cutting of the haulm in combination with diquat (100, 200, 300 g a.i. ha-1) or full cutting of the haulm. In those treatments where haulm killing was performed purely chemically the haulm remnants¿ contamination potential tended to increase at reduced doses. Full mechanical destruction gave as low a contamination potential as application of the full dose of chemical haulm killer. However, there were no consistent differences between the haulm killing treatments in the frequency of blighted tubers after harvest and storage. This indicates that the input of chemical haulm killers may be reduced. There was a large difference between years in tuber blight after harvest and storage, which confirms that climatic factors are of major importance for tuber infection. The large difference found between the cultivars in the frequency of tuber blight indicates that tuber resistance should be an important part of integrated late blight disease management.
Forfattere
Vidar Selås Ronny Steen Sverre Kobro Terje Lislevand Ingvar StenbergSammendrag
In Norway, a positive relationship between spring numbers of lesser spotted woodpecker (Dendrocopos minor) and previous June temperatures has been interpreted as an effect of temperatures on woodpecker survival and reproduction during the breeding season. This article considers the possibility that woodpecker numbers are related to the abundance of the moth Argyresthia goedartella in the current year. Larvae and pupae of A. goedartella are important food for lesser spotted woodpeckers in early spring when few other surface-living invertebrates are available. The occurrence of this moth depends on the flowering of birch (Betula spp.) and alder (Alnus glutinosa), which in turn is influenced by June temperatures in the preceding year. Spring numbers of the lesser spotted woodpecker in two regions of Norway were compared with a trapping index of A. goedartella and weather variables assumed to influence the woodpeckers' breeding success and adult survival. The best multiple regression model included December temperatures and moth indices, supporting the hypothesis of a strong impact of A. goedartella on spring survival. Conservation strategies for the lesser spotted woodpecker should therefore focus not only on minimum areas of deciduous forests with decaying wood, but also on the availability of the moths' host trees, birch and alder.
Sammendrag
The coastal areas of SE Norway provide suitable conditions for studying soil development with time, because unweathered land surfaces have continuously been raised above sea level by glacio-isostatic uplift since the termination of the last ice age. We investigated Podzol development in a chronosequence of six soils on sandy beach deposits with ages ranging from 2,300 to 9,650 y at the W coast of the Oslofjord. The climate in this area is rather mild with a mean annual temperature of 6 degrees C and an annual precipitation of 975mm (Sandefjord). The youngest soil showed no evidence of pocizolization, while slight lightening of the A horizon of the second soil (3,800 years) indicated initial leaching of organic matter (OM). In the 4,300 y-old soil also Fe and humus accumulation in the B horizon were perceptible, but only the 6,600 y-old and older soils exhibited spodic horizons. Accumulation of OM in the A horizons reached a steady state in <2,300 y, while in the B horizons OM accumulated at increasing rates. pH dropped from 6.6 (H2O)/5-9 (KCI) in the recent beach sand to 4.5 (H2O)/3.8 (KCl) within approx. 4,500 y (pH(H2O))/2,500 y (pH(KCl)) and stayed constant thereafter, which was attributed to sesquioxide buffering. Base saturation showed an exponential decrease with time. Progressive weathering was reflected by increasing Fe-d and Al-d contents, and proceeding podzolization by increasing amounts of pyrophophate- and oxalate-soluble Fe and Al with soil age. These increases could be best described for most Fe and Al fractions by exponential models. Only the increasing amounts of Fe-p could be better described by a power function and those of Fe-o by a linear model.
Forfattere
Vegard Gundersen Lars Helge FrivoldSammendrag
We reviewed 53 studies of forest landscape preferences carried out as quantitative surveys in Finland, Sweden and Norway and published between 1972 and 2006. Most of them were related to boreal coniferous forests in which even-aged forestry had been the rule. There was a great diversity in survey designs, ranging from nation-wide or regional surveys where target populations and sampling frames were clearly defined, to studies where neither a target population nor a sampling frame could be identified. The latter type of surveys, however, often had a high validity, with measurements made either in the forest or indoors by use of colour slides or advanced digital imaging. A common feature was that people¿s preferences for a forest stand increased with increasing tree size and advancing stage of stand development. Some surveys indicated that the public tended to give high scores to irregular stands with a mixture of trees of different sizes, but on the other hand, a feeling of accessibility and provision of a view was also very important. Large clear-cuts and obvious traces from forest operations were little appreciated. Trained foresters were more positive to clear-cuts than the general population. Few studies included virgin stands, and those that did mostly found low scores for unmanaged forests. Preferences appeared to be fairly stable over time. Elderly or handicapped people, and children and young adolescents, were strongly underrepresented in the surveys.
Sammendrag
Studies regarding the environmental impact of engineered nanoparticles (ENPs) are hampered by the lack of tools to localize and quantify ENPs in water, sediments, soils, and organisms. Neutron activation of mineral ENPs offers the possibility of labeling ENPs in a way that avoids surface modification and permits both localization and quantification within a matrix or an organism. Time-course experiments in vivo also may be conducted with small organisms to study metabolism and exposure, two aspects currently lacking in ecotoxicological knowledge about ENPs. The present report explains some of the prerequisites and advantages of neutron activation as a tool for studying ENPs in environmental samples and ecologically relevant organisms, and it demonstrates the suitability of neutron activation for Ag, Co/Co3O4, and CeO2 nanoparticles. In a preliminary experiment with the earthworm Eisenia fetida, the dietary uptake and excretion of a Co nanopowder (average particle size, 4 nm; surface area, 59 m(2)/g) were studied. Cobalt ENPs were taken up to a high extent during 7 d of exposure (concentration ratios of 0.16-0.20 relative to the ENP concentration in horse manure) and were largely retained within the worms for a period of eight weeks, with less than 20% of absorbed ENPs being excreted. Following dissection of the worms, Co-60 was detected in spermatogenic cells, cocoons, and blood using scintillation counting and autoradiography. The experimental opportunities that neutron activation of ENPs offer are discussed.
Sammendrag
Three unsprayed coffee farms (farm 1, 2 and 3) were studied for the natural occurrence of the insect pathogenic fungus Beauveria bassiana in Hypothenemus hampei populations throughout the rainy season of 2004 (July-November) and 2005 (July-December). B. bassiana infections were found during most sampling dates in both years, on all three farms. The B. bassiana infection levels were higher in 2005 than in 2004 with mean prevalence of 12.1 % and 2.7%, respectively. No consistent significant differences in infection level between farms were found in any of the years. B. bassiana infection levels fluctuated widely throughout the season, and peaked at 13.5% on farm 3 in 2004 and at 44.0% on farm 1 in 2005. The H. hampei population was significantly higher in 2004 than in 2005, with 6.9% of the berries infested in 2004 and only 0.7% in 2005. In both years, the H. hampei infestation level was significantly higher on farm 2. No consistent significant differences in H. hampei infestation levels were found between sampling dates on any of the farms. H. hampei infestation levels fluctuated throughout both seasons, and peaked at 15.3% on farm 2 in 2004 and 2.2% on farm 2 in 2005. No consistent density dependent correlation between H. hampei infestation level and B. bassiana infection level was found. Correlations between climatic conditions and R bassiana or H. hampei were not found. (C) 2007 Elsevier Inc. All rights reserved.
Sammendrag
Alpha-cypermethrin, a synthetic pyrethroid, is used as an insecticide in agricultural settings and is increasingly replacing organophosphates and carbamates because of lower application rates and lower toxicity to mammals. Because very little is known about the acute and chronic toxicity of this compound for soil-living organisms, the present study investigated acute and sublethal toxicity of alpha-cypermethrin for four terrestrial invertebrate species in an agricultural soil from Norway. Bioassays with the earthworm Eisenia fetida, the potworm Enchytraeus crypticus, the springtail Folsomia candida, and the land snail Helix aspersa were performed according to slightly modified versions of Organization for Economic Cooperation and Development (Paris, France) or International Organization for Standardization (Geneva, Switzerland) guidelines and resulted in median lethal concentrations of greater than >1,000 to 31.4 mg/kg and sublethal no-observed-effect concentrations of 2.51 to 82 mg/kg. A high acute to chronic ratio was found, especially in the earthworms. Interspecies differences in sensitivity may be explained by differences in exposure and differences in metabolization rate. When based on measured pore-water concentrations, terrestrial species overall appear to be approximately one order of magnitude less sensitive than aquatic species. Effect assessments conducted according to European guideline for risk assessment of pesticides reveal that assessments based on acute toxicity tests are not always conservative enough to determine environmentally safe concentrations in soil. Mandatory incorporation of sublethal toxicity data will ensure that in regions with temperate climate, the effects of pesticides on populations of soil-living organisms are unlikely.
Forfattere
Kåre Arnstein Lye Halvor B. GjærumSammendrag
Det er ikke registrert sammendrag
Sammendrag
A possible cost-effective real-time patch spraying implementation against seed-propagated broad-leaved weeds in cereals is a camera mounted in front of the tractor taking images at feasible distances in the direction of travel, on-board image analysis software and entire boom switched on and off. To assess this implementation, manual weed counts (0.25 m(2) quadrats) in a 1.5 m x 2 m grid, were used to simulate camera outputs. Each quadrat was classified into 'spray' and 'not spray' decisions based on a threshold model, and the resulting map defined the 'ground truth'. Subsequently, 'on/off' spraying at larger control areas where sizes were given by the boom width and image distance, and spraying decision controlled by weed status at the single quadrat simulating the camera's view, were simulated. These coarser maps were compared with 'ground truth', to estimate mapping error (area above threshold not sprayed), spraying error (area below threshold sprayed), total error (sum of mapping and spraying error) and the herbicide reduction. Three levels of the threshold model were tested. Results were used to fit models that predict errors from boom width and image distance. Size of control area did not on average affect the magnitude of the simulated herbicide reductions, but the bigger the control area the higher the risk that the simulated herbicide reduction deviate from the reduction in 'ground truth'. Mean simulated herbicide reductions were 42-59%, depending on threshold level. Only minor differences due to threshold level were seen for mean mapping and spraying errors at given spraying resolutions. Using original threshold level and image distance 2 m, predicted total errors for boom widths 2 m, 6 m, 20 m and 40 m would be 6%, 10%, 16% and 17%, respectively. Results indicate that control area should not exceed about 10 m 2 if acceptable total error is maximum 10%.
Sammendrag
Lack of automatic weed detection tools has hampered the adoption of site-specific weed control in cereals. An initial object-oriented algorithm for the automatic detection of broad-leaved weeds in cereals developed by SINTEF ICT (Oslo, Norway) was evaluated. The algorithm ("WeedFinder") estimates total density and cover of broad-leaved weed seedlings in cereal fields from near-ground red-green-blue images. The ability of "WeedFinder" to predict 'spray'/'no spray' decisions according to a previously suggested spray decision model for spring cereals was tested with images from two wheat fields sown with the normal row spacing of the region, 0.125 m. Applying the decision model as a simple look-up table, "WeedFinder" gave correct spray decisions in 65-85% of the test images. With discriminant analysis, corresponding mean rates were 84-90%. Future versions of "WeedFinder" must be more accurate and accommodate weed species recognition.