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
May-Guri Saethre Trond HofsvangSammendrag
Timed catches of Cydia pomonella (L.) males in sex pheromone traps were used to investigate the influence of twilight and climatic parameters on the flight activity of the moths at different latitudes. Traps were operated from 15 May until 31 July at several locations between 59ºN and 60ºN in south-eastern Norway, and at Sogndal (61ºN) in western Norway, during 1997-2000. Time and duration of twilights were calculated from May-August for each trap-location, and compared with the activity of C. pomonella. Flight response appeared to be determined by the daily photoperiod, corresponding to time of sunset at the different latitudes involved in the study. This response began about two hours before sunset, and declined around 23:00 and 24:00 hours in the evening, in western and eastern Norway, respectively. Main flight activity in both eastern and western Norway was recorded when temperatures were in the range 10-20 ºC, the relative humidity was above 50 %, and at wind speeds below three m/s at the time of capture. In Norway, light conditions are suitable for C. pomonella flight activity all night long during the entire lifetime of the adult moths. It is concluded that temperature is the limiting factor for flight at high latitudes.
Forfattere
Arvid Steen Turid Strøm Sissel Hansen Bal Ram Singh Aksel Bernhoft Espen GovasmarkSammendrag
Herbage selenium (Se) concentration is generally low in Norway. It is unknown, if feeding practises on Norwegian organic farms fulfil the dietary need of Se and vitamin E to sheep and dairy cattle. Therefore, we analysed Se in soil and herbage, and Se and vitamin E in animal blood in the indoor feeding season at 14 organic dairy and 14 organic sheep farms. The herbage Se concentration was low. Approximately 50 and 35 % of all samples in the first and second cut, respectively, had Se concentrations below the detection limit of 0.01 mg/kg dry matter (DM). The median (10th, 90th percentile) Se concentrations were
Forfattere
F. Suliman H.K. French L.E. Haugen B. Kløve P. JenssenSammendrag
Horizontal subsurface "ow constructed wetlands have proven their ef"ciency in treating wastewater and removing the pollutants of concern. Treatment ef"ciency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed "lter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed "lters using saturated horizontal "ow at three scales (small and medium lab scales and full-scale system) using the same "lter media is reported. Light-weight aggregate ("lter media termed Filtralite-PTM) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA "lters are evaluated from small-scale experiments. KeywordsHeterogeneity; hydraulic parameters; horizontal subsurface "ow constructed wetlands.
Forfattere
Astrid JohansenSammendrag
Artikkel med råd om stell og gjennomføring av beitedrift i mjølkeproduksjonen.
Forfattere
Ricardo Holgado Stig Andersson Christer Magnusson Janet RoweSammendrag
A survey of cereals, carried out in 1995-2005 in Norway, revealed that Heterodera spp. are common throughout the country. Nematodes belonging to the H. avenae complex were recorded from the county of Agder in southern Norway (58.08o N) to the county of Nordland in the north (65.5o N), and this so far is the most northern location reported for Heterodera in cereals. Studies in Norway have recently recorded H. filipjevi and also additional and possibly new species. H. filipjevi is of economic importance in Scandinavia. It was first recorded in the beginning of the 1970s and then referred to as the "Gotland strain of H. avenae". Biotests carried out in Sweden demonstrated the occurrence of two pathotypes, "East" and "West", named according to their geographical distribution. In Norway H. filipjevi, was first recorded causing damage to winter rye, Compared to H. avenae, H. filipjevi has the ability of hatching easily and at low temperatures, this ability of rapid hatch suggests that field population densities could easily be underestimated if based on cyst extractions only. Hence, accurate assessments of pre-plant densities of H. filipjevi require quantification of infective juveniles in soil. Nematode management practices must be based on the knowledge of the population dynamics and the threshold levels needed to cause economic damage. Tests of 63 cereal cultivars on the Norwegian market revealed 13 oat and six barley cultivars to be resistant to H. filipjevi "West" It is important that resistant cultivars of barley are recommended when nematode populations are high, as resistant barley is more tolerant than resistant oats. However even in rotations with resistant barley the farmer should be prepared to accept some yield losses in the first year of management. One important challenge in the management of H. filipjevi is the common occurrence of mixed populations. H. avenae "sensu stricto" and/or its slightly diverging form "Våxtorp" is often found together with H. filipjevi. From our experience the dynamics of mixed populations needs a stronger emphasis in management systems for cereal cyst nematodes. Our knowledge of the occurrence and distribution of cereal cyst nematode species and pathotypes in Norway has increased, and the screening of cultivars for resistance against various populations particularly H. filipjevi, H. avenae "sensu stricto" and the "Våxtorp"-type has been intensified. Hence, today farmers can be provided with control strategies which are easily implemented. With this management system, farmers in the county of Vestfold have increased cereal yields. After 3-4 years of implementation farmers have reported yield increases averaging 1000 kg ha. Compared to the earlier situation (when control was not practiced), a full implementation of the current management program in the county of Vestfold has been estimated to give an annual economic gain in the order of "800 000.
Forfattere
Kåre A. Lye Mary Namaganda Halvor B. GjærumSammendrag
Mt. Elgon is one of the largest volcanoes in the world, about 50 km across and with a 5-6 km wide crater. It is situated on the border between Kenya and Uganda between 1o and 2o north. From the Ugandan side of Mt. Elgon are reported 98 species of rust fungi (Urediniomycetes) from 13 genera. Out of a total of 153 collections, 79 are gathered by the authors. Based on this material nine species were described as new to science by the senior aothor (H.B.G.)
Forfattere
Anne Kari Bergjord Arne Oddvar SkjelvågSammendrag
God overvintring er avgjørendel for å lykkes med dyrking av høsthvete (Triticum aestivum L.). For å kunne utføre risikoberegninger for høsthvete-dyrking i et klima i endring, og på nye lokaliteter, er en avhengig av redskaper som overvintringsmodeller som kan kvantifisere forhold mellom klimatiske faktorer og plantenes evne til å overleve vinteren. Som en del av forskningsprogrammet WINSUR, der effekter av klimaforandringer blir studert, ble det utført feltforsøk med høsthvete i to vintre på tre ulike steder. To ulike sorter med høsthvete, Bjørke og Portal, ble benyttet i forsøkene. Alle plantene stod i Sjørdal fra såing og fram til midten av november for at de skulle få like herdingsforhold. I november ble de distribuert til tre ulike steder; Stjørdal, Selbu og Oppdal. Planter ble hentet inn fra felt en gang i måneden fra november til april for test av frosttoleranse og studier av fenologisk utvikling. Jordtemperatur og snøforhold påvirket plantenes nivå av frosttoleranse gjennom høst og vinter. Fenologisk utvikling ble studert både like etter inntak av planter fra felt, og etter at plantene hadde fått vokse i tre uker ved 18 C, enten ved kort (7.5 t) eller lang (18 t) dag. Lang dag ble gitt i form av fullt lys (120 mikromol/m2/s) i 18 timer den første vinteren, og lang dags-plantene mottok dermed 2.4 ganger så mye lysenergi som kort dags-plantene. Lang dags-plantene gikk over fra vegetativ til generativ utvikling mye tidligere enn kort dags-plantene. Vinteren etter, da alle planter fikk fullt lys i kun 7.5 timer, og lang dags-plantene bare fikk dagforlengingslys (4 mikromol/m2/s) etter dette, var det ingen signifikant forskjell i utviklingshastighet mellom planter fra kort og lang dag. Plantene som ble studert like etter inntak fra felt viste ingen utvikling i fenologisk utvikling i perioden november til mars. Men utviklingen gikk raskt når snøen smeltet og temperaturen begynte å stige i mars/april. Resultatene fra disse forsøkene vil, sammen med andre resultat fra feltforsøkene, bli brukt i den videre utviklingen av en overvintringsmodell for høsthvete.
Sammendrag
Blomster er både dekorative og viktig i hverdagslivet vårt. Euphorbia pulcherrima Willd. Ex Klotzsch, julestjerne (poinsettia på engelsk) er en av de blomstene som har stor symbolverdi og som dyrkes i mange land i verden (Ecke III et al. 2004). Julestjernen har blitt vår mest populære juleblomst. Det produseres faktisk mellom 5 og 6 millioner julestjerner årlig i Norge (Hagen 2004). Julestjernen framviser store variasjoner i forskjellige deler av verden, fra å være høye og busklignende til kompakte potteblomster med mange grener. Mange patogener og skadegjørere kan angripe julestjerne, blant annet virus. Poinsettia mosaic virus (PnMV) og poinsettia latent virus (PnLV) er to virus som ofte infiserer julestjerne. PnMV forårsaker symptomer på bladene slik at kvaliteten blir redusert i følsomme sorter. Vi ønsker å lage PnMV-resistent julestjerne for å kunne få til en julestjerne av ennå høyere kvalitet. I tillegg ønsker vi å bruke samspillet mellom PnMV og julestjerneplanta som et modellsystem for å bygge opp kompetansen på genmodifisering av planter.
Forfattere
Astrid Oberson Erik JonerSammendrag
Microbial uptake and immobilization of P, and its subsequent release and redistribution, play central roles in the biogeochemical cycling of P in soil. Soil microorganisms constitute a pool of mostly labile organic P compounds that are rapidly hydrolysed once the cells are disrupted. The size of this pool mainly depends on soil type, land use and the related content of soil organic matter and can, therefore, in agricultural soils be affected through organic matter management. The quantities of microbial P extractable after fumigation-extraction reported for mineral topsoils across different ecosystems and litter layers encompass a range from 1 to around 200 mg P kg-1, or between 0.5 and 26% of the total P content in the corresponding soils. Because fumigation does not release all microbial P, the total amount of microbial P can be up to several times higher. Current estimates are precise enough to detect changes in the microbial P pool as a result of changes in land use, agricultural practices or environmental factors. Refined methods are still needed to quantify P fluxes through the soil microbial biomass and to describe mechanisms and ecological interactions between microorganisms and their substrates at the physiological, biochemical and molecular level. In soils with small P contents, microbial activity does not suffer from P limitation to the same extent as plants, as soil microorganisms have highly efficient mechanisms to acquire P. Progress has been made in our understanding and quantification of organic P mineralization, and the factors determining microbial immobilization and re-mineralization sequences are better understood. Studies of P turnover using radioisotopes have revealed a highly dynamic nature of the microbial P pool even in the absence of changes in microbial P. Here, we will review recent advances in radiotracer studies of P turnover and emphasize the importance of trophic interactions, microenvironments and aspects of specific microbial life-cycles that have a major impact on turnover rates and subsequent release of microbial P in soil.
Forfattere
Marcel van Oijen Mats Høglind Hans Martin Hanslin Nick CaldwellSammendrag
Previously, the literature on the growth of timothy (Phleum pratense L.) in Scandinavia was reviewed and a simple process-based model was developed to explain and predict the response of this species to different environments and management regimes. The model could not be tested in detail, because only biomass data were available at the time. However, recent experimental work has generated a large (n = 633) and uniquely detailed dataset on the growth and underlying physiology of timothy and its response to cutting at different growth stages. The present study aimed to use this dataset to test the model, and to use the model to identify the key physiological and morphological mechanisms that determine the regrowth rate of timothy after cutting. Model testing consisted of comparing simulations and measurements for eight variables: biomass, leaf area index (LAI), tiller and leaf density, rates of leaf appearance and elongation, carbohydrate concentration, and specific leaf area. Although the new data referred to a different cultivar, a different site, and different years from those used in the original model parameterization, the model was still able to account for nearly half the variation in the dataset [r2 = 0.468, normalized root mean squared error (RMSE) = 0.631]. This suggested that the key assumptions of the model (i.e., dependence of growth and allocation on the source-sink balance of the plants and a dose link between tillering and leaf area dynamics were plausible. However, the original model was not able to account for the observation that cutting at early heading tended to be followed by a longer lag phase than cutting at anthesis. We identified six mechanisms, not previously incorporated in the model, that improved its behavior: (1, 2) dependence of tillering and leaf appearance rate on carbohydrate concentration, (3, 4) dependence of leaf appearance and leaf elongation rate on plant phenological stage, (5) sprouting of new tillers from decapitated generative tillers, and (6) proportionality of the number of elongating leaves with tiller size. Incorporation of these mechanisms, followed by reparameterization using a Metropolis-Hastings Monte Carlo method, improved performance statistics (r2 = 0.521, normalized RMSE = 0.415) and explained the long duratjon of slow growth after early cutting. These mechanisms may thus be keys to understanding timothy regrowth.