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
Sammendrag
Organochlorine pollutants in the major fish species (pike Esox lucius, perch Perca fluviatilis, and roach Rutilus rutilus) of Lake Arungen, Norway, were investigated after an extensive removal of large pike in 2004. The organochlorine pollutants detected in fish liver samples in 2005 were dichlorodiphenyltrichloroethane (DDTs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and heptachlor epoxide (HCE). DDTs were the dominant among all analyzed OCs. Sigma PCB and HCB, detected in fish from two clearly distinct trophic levels (prey and predators), give an indication of biontagnification. All OC concentrations in female pike were significantly lower compared to males, which might be due to the removal of high concentrations of pollutants in roe during spawning. (c) 2009 Elsevier Ltd. All rights reserved.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
In the Nordic strawberry industry only single-cropping cultivars are used. Several everbearing cultivars have been tried, but neither yield nor quality has been satisfactory. In 2005, new everbearing cultivars were collected and an experiment was established in a polyethylene tunnel. Yield and runnering capacity were recorded in two seasons. The cultivars were the English 'Flamenco' and 'Everest', the Dutch 'Elan' and the Norwegian 'Rita', 'Rondo', 'Ridder' and 'Rosa'. Plug plants were planted in double rows on low ridges mulched with plastic at a plant density equivalent to 50,000 plants per ha. A block design with 20 plants per plot and four replicates was used. The field was harvested two to three times a week during the whole season from June until the beginning of October in both years. Berry size was recorded at all harvests while taste and general performance were evaluated using a scale 1-9. In the first year, the everbearing cultivars had significantly higher yield than the single-cropping cultivars due to more inflorescences, but this was levelled out the second year. While the cropping season of the single-cropping cultivars is only about four weeks, the everbearing cultivars were picked from late June until beginning of October, in both years. The highest yields were obtained by 'Everest' (729 and 844 g) followed by 'Rita' and 'Ridder'. The cultivars 'Elan' and 'Rondo' scored highest both in taste and general performance. 'Everest' also performed well, but flavour was not acceptable.
Forfattere
Anita Sønsteby Ola M. HeideSammendrag
Octoploid strawberry (Fragaria × ananassa Duch.) cultivars can be classified into mono-flowering (single-cropping or June-bearing) and perpetual-flowering (everbearing) types according to their horticultural performance. Whereas floral induction in mono-flowering cultivars is well-documented, the literature on the control of flowering of perpetual-flowering cultivars is rather inconsistent. Photoperiod and temperature control of flowering in several perpetual-flowering strawberry cultivars of widely varying pedigree were therefore studied in controlled environments. Flower bud initiation in all cultivars was significantly advanced by long day (LD) conditions at temperatures of 15°C and 21°C; while, at 27°C, flowering took place under LD conditions only. When vegetative plants growing in short day (SD) at 27°C were transferred to LD conditions at the same temperature, they consistently initiated flower buds and started flowering after about 4 weeks. At such a high temperature, flowering could thus be turned on and off by switching between SD and LD conditions. At 9°C, flowering was substantially delayed, and, at this temperature, flowering was unaffected by photoperiod. Runner formation was generally promoted by high temperature and SD conditions, but the photoperiodic effect varied between experiments. We conclude that everbearing strawberry cultivars, in general, whether of the older European type or the modern Californian type, are qualitative (obligatory) LD plants at high temperature (27°C), and quantitative LD plants at intermediate temperatures. Only at temperatures below 10°C these cultivars are day-neutral.
Forfattere
Anita Sønsteby Ola M. HeideSammendrag
The effect of night temperature on short day (SD) floral induction in three June-bearing strawberry cultivars of different geographic origin was studied and compared with yield performance in the cool Nordic environment. At the optimum day temperature of 18°C, the SD flowering response of the cultivars ?Florence? and ?Korona? increased significantly with increasing night temperature from 9 to 18°C, while an optimum was reached at 15°C in ?Frida?, a cultivar selected under coolenvironment conditions in Norway. Also, while saturated flowering response was obtained with three weeks of SD treatment at all temperatures in ?Frida?, several plants of ?Florence? and ?Korona? failed to initiate flowers at 9°C night temperature even with five weeks of SD. The effect of extended SD period was particularly pronounced in ?Florence?. The slow SD floral induction response of ?Florence? was associated with a two-week delay of anthesis in subsequent long day (LD) conditions at 21°C. Performance studies of the same cultivars during two years under field conditions also demonstrated that the yield potential of ?Florence? was not realized under the climatic conditions prevailing at these locations. The yields varied significantly among the cultivars, ?Frida? having the highest yields, followed by ?Korona? and ?Florence? far below. It is concluded that, in the Nordic environment, autumn (September) night temperatures are obviously sub-optimal for yield performance of some June-bearing strawberry cultivars, and that this effect is mediated by autumn temperature effects on flower initiation responses. In the biennial-fruiting raspberry cultivar ?Glen Ample?, flowering and dormancy induction are controlled by the interaction of low temperature and short photoperiods. As neither process takes place at temperatures above 15°C regardless of the photoperiodic conditions, low temperature is of crucial regulatory importance. Environmental control of annual-fruiting cultivars is also briefly discussed.
Sammendrag
Growth and flowering of the annual-fruiting raspberry (Rubus idaeus L.) cultivar 'Polka' were studied under controlled environment conditions in order to facilitate out-of-season production. Vegetatively-propagated plants originating from adventitious root buds were used. Height growth and the rate of leaf formation increased with increasing temperature, up to a broad optimum in the mid-20 degrees C range. While elongation was consistently enhanced by long-day (LD) conditions, photoperiod had no effect on the rate of leaf formation. LD stimulation of growth thus resulted from increased internode length only. In agreement with earlier reports, it was found that, in contrast to biennial-fruiting cultivars, such annual-fruiting cultivars do not need low temperatures for flower initiation, nor do they appear to have a juvenile phase during which they are un-responsive to flower-inducing conditions. 'Polka' plants responded to inductive conditions as early as the 5-leaf stage, and flowered freely across the entire range of growth temperatures, even at 30 degrees C. Flowering was advanced and the number of flowers increased with increasing temperature, up to an optimum at 27 degrees C. Flowering was also consistently advanced and occurred at lower nodes under LD than under short-day (SD) conditions across the whole range of temperatures. Night interruption for 3 h in the middle of the night was also effective, demonstrating that this is a true photoperiodic response and not merely an effect of increased light integral in LD. It was also confirmed that a distinct vernalisation-type advancement of flowering took place when small, non-dormant plants were exposed to additional chilling at 6 degrees C for several weeks. At low temperatures, a large proportion of the lateral buds were dormant, so that, at 12 degrees C, the plants actually flowered only at their tips. Dissections also revealed that the dormant buds had initiated flowers; but, because of their dormant state, they needed several weeks of chilling before they could flower (biennial-fruiting behaviour). Both types of buds were initiated by the same environmental conditions. Practical applications of the findings are suggested.
Forfattere
Arve Heistad Razak Seidu Andreas Svarstad Flø Adam Paruch Jon Fredrik Hanssen Thor-Axel StenströmSammendrag
Tie long-term use of a filter-based, on-site wastewater treatment system increases nutrient discharge to receiving waters and may reduce its hygienic barrier efficiency. The main purpose of this research was to assess the hygienic barrier efficiency and the associated health risks of an on-site system that had exceeded its 5-yr design capacity with respect to phosphorus (P) removal. The system was investigated for bacteria and virus removal and assessed with respect to potential health risks in relation to reuse of effluent for irrigation. The system consists of a septic tank, a pressure-dosed vertical flow biofilter, and an up-flow filter unit with lightweight clay aggregates. The total P concentration in the effluent had increased gradually from initially <0.1 mg P L-1 during the first 2 yr of operation to 1.8 mg P L-1 after 5.3 yr. Escherichia coli was used as an indicator organism for fecal bacteria removal, whereas bacteriophages phi X174 and Salmonella typhimurium phage 28B (S.t. 28B) were used to model enteric virus removal. An overall decrease in E. coli removal occurred from a complete (approximately 5.6 log(10)) reduction during the first 3 yr of operation to 2.6 log(10) reduction. The removal amounts of the bacteriophages phi X174 and S.t. 28B were 3.9 and 3.7 log(10), respectively. Based on removal of S.t. 28B, the risks of rotavirus infection and disease for the investigated scenarios were above the acceptable level of 10(-4) and 10(-3), respectively, as defined by the World Health Organization.
Forfattere
Knut Anders Hovstad Silje Borvik Mikael OhlsonSammendrag
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.
Forfattere
Knut Anders Hovstad Mikael OhlsonSammendrag
Plant litter is an important determinant of seed germination and seedling establishment. Positive effects of litter have received considerable attention, but few studies have explicitly tested whether seedlings are more facilitated by conspecific litter compared to heterospecific litter. In order to contrast conspecific and heterospecific facilitative effects on seedling establishment, we used Anthriscus sylvestris, Angelica sylvestris, Pimpinella saxifraga and different combinations of their seeds and litter seedbeds as a model system. Although litter had a significant species-specific effect on seedling emergence, we found no evidence of strictly conspecific facilitation. Anthriscus sylvestris displayed a positive response to all types of litter. In contrast, there was a clear negative effect of conspecific litter in Pimpinella saxifraga. Activated carbon did not modify the negative effect, indicating that chemical compounds were not the cause. Our study suggests a high level of idiosyncrasy in response to litter at the species level.
Forfattere
Ole Martin Bollandsås Ingvild Rekstad Erik Næsset Ingvald RøsbergSammendrag
The objectives of this study were (1) to develop models for estimation of total above-ground biomass, tree crown biomass and stem biomass of mountain birch (Betula pubescens spp. czerepanovii), and (2) to test the stability of the relationships between biomass and biophysical tree properties across geographical regions and tree size ranges. The models were developed using a mixed modelling approach accounting for the hierarchical structure of the data that originated from sample plots. Diameter at breast height, tree height, and the ratio between height and diameter were candidate explanatory variables, but only diameter was statistically significant (p0.05). The model fit values (pseudo-R 2) were 0.91, 0.60 and 0.85 for the three respective models. A substantial part of the model random errors could be attributed to between-plot variations. The conclusion related to objective (1) was that the models are well suited for biomass prediction of mountain birch in the mountain areas of southern Norway. Furthermore, models reported in previous research that had been calibrated on data from other regions were applied on the current data set. The results indicate that models calibrated for small trees produced predictions diverging from the observed values of the current data set. The differences between predicted and observed values also seem to vary along a site productivity gradient. Still, even though the differences between predicted and observed values using the different models varied quite a lot, the relationships were relatively stable within certain limits. The conclusion related to objective (2) was that biomass models can be applied outside the region for which they were developed, which in many cases is necessary because local models do not exist. However, the properties of the model development data related to tree size range and site productivity should be similar to those of the area for which predictions are being made.