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
Methods for measuring prevalence of Neozygites floridana in a Tetranychus urticae population collected from strawberries were developed and compared. T. urticae were extracted from leaves using a soapy water solution (0.5 ml washing detergent : 8 l water) and then placed into 80% alcohol for use in methods 1 and 2. Method 1: N. floridana-sporulating T. urticae cadavers were observed and quantified under a compound microscope (40-80X). Method 2: Adult females were mounted in lactophenol cotton blue and observed for the presence or absence of N. floridana hyphal bodies under a microscope (200-400X). Method 3: Live T. urticae females were incubated at 25ºC and 75% RH and observed for mortality and N. floridana infection under a compound microscope (6.4-40X). Method 1 was the most time-efficient method and it also allows processing of samples as time permits. Method 2 quantified significantly higher fungal prevalence than method 1 and 3, but method 2 is not considered to be reliable because hyphal bodies are difficult to detect. No significant differences were found between methods 1 and 3.
Sammendrag
Freezing and thawing influence the transport potential and pathways for contaminants by altering the soil physical properties. Firstly, soil frost delays or impedes infiltration of rain and meltwater, reducing the transport rate of dissolved contaminants. But at the same time, particle bound contaminants may be mobilised because the reduced infiltration capacity increases surface runoff and erosion risk. Secondly, freezing water expands and imposes mechanical stresses on the soil, which may cause aggregate breakdown and facilitate particle detachment and transport. The influence of repeated freezing and thawing on aggregate stability of different soils is poorly documented for Nordic winter conditions. The purpose of this study (Kværnø and Øygarden, subm.) 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 artificially levelled silty clay loam (Clay B). These soils are representative of two erosion prone areas in South-eastern Norway. Field moist surface 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 hours, and thawing at 9"C for 48 hours. Aggregate stability was measured in a rainfall simulator (representing rainfall) and a wet-sieving apparatus (representing surface runoff). The aggregate stability of Silt was found to be significantly lower than of Clay A and Clay B. Clay A and Clay B had similar aggregate stabilities, even if it was expected that the artificially levelled Clay B would have lower stability. Freezing and thawing decreased the aggregate stability for all three soils, but the effect was more severe on the silt soil. There was no evident effect of water content on the aggregate stability, probably due to experimental limitations. The wet-sieving apparatus resulted in less aggregate breakdown than the rainfall simulator. Rainfall impact seemed to be more detrimental than wet-sieving the more unstable the soil was, that is, after many freeze-thaw cycles, and on silt soil. The results indicate that freezing and thawing is an important factor influencing the erosion risk of the studied soils. In the future, climate change is expected to give more unstable winters with more freezing and thawing events. Combined with more precipitation as rainfall during the winter period both runoff and erosion will probably increase, possibly resulting in heavier loads of particulate bound contaminants to surface waters. The results are also helpful for improving predictions of contaminant fate and transport, as most of the existing hydrological and soil erosion prediction models do not satisfactorily describe soil processes occurring under Nordic winter conditions. This study focused on arable soils with conventional agricultural management, where plant nutrients and pesticides pose a threat to water quality. It would be useful to conduct similar experiments on soils where other organic and inorganic contaminants are of concern, e.g. on soils where sewage sludge and compost have been applied, and soils in road cuttings and on contruction sites. References Kværnø, S.H. & Øygarden, L. submitted: The influence of freeze-thaw cycles and soil moisture on aggregate stability of three soils in Norway.
Sammendrag
Grønnsakdyrking foregår ofte på intensivt dyrkede arealer med tilførsel av store mengder næringsstoffer, noe som gjerne fører til store overskudd i næringsbalansen. Tap av næringsstoffer fra slike arealer er som regel større enn fra øvrige jordbruksarealer. Risiko for avrenning av fosfor er særlig stor på grunn av generell sterk fosforgjødsling og ved at slike åkerkulturer er mer utsatt for jorderosjon, særlig etter høsting i forbindelse med sterke nedbørsepisoder.
Forfattere
Shala Werner Michael Albers Terry Cryderman Danko Dimenic Robert Heyd Boris Hrasovic Sverre Kobro Stig Larsson Roger Mech Pekka Niemela Matti Rousi Kenneth Raffa Kyoko Scanlon Shane WeberSammendrag
The introduced basswood thrips, Thrips calcaratus, undergoes outbreaks on and damages American basswood, Tilia americana, in North America, but is less common on and does not cause significant damage to little-leaf linden, Tilia cordata, in its native European range. A possible explanation is that altered host relationships in North America allow increased exploitation of T. americana. Three experiments were conducted to compare host associations of T. calcaratus between T. americana and T. cordata. In a laboratory choice bioassay, T. calcaratus occupied foliage of both tree species with equal frequency. A field assay conducted in North America revealed an identical trend on planted T. americana and T. cordata seedlings planted in a paired design. In a separate field experiment bud break phenology, peak T. calcaratus emergence, and foliar development showed similar temporal patterns in 10 T. cordata and T. americana sites distributed across the insect"s native range of Europe and introduced range of North America. These results suggest that physiological and phenological differences between native and newly acquired Tilia hosts are not likely responsible for the increased impact of T. calcaratus in its introduced range. Rather, temporal escape from natural enemies seems to be the more likely explanation. This is evidenced by the stronger synchrony of the North American predator, Leptothrips mali, with the native basswood thrips, Neohydatothrips tiliae, than with T. calcaratus. Understanding the basis for increased success of T. calcaratus in its introduced range may provide insight into managing this insect in basswood forests in the Great Lakes region.
Forfattere
Sverre Kobro Trond RafossSammendrag
The presence of multiple phenological forms has previously made adults of Hoplothrips species difficult to identify. We present a set of diagnostic metric characters by which the 8 species recorded from Norway can be recognised.Some biological interpretations are also given.
Forfattere
Liv OstremSammendrag
I nytteplanter så vel som i prydplanter vert det stadig arbeidd med å få fram nye sortar med nye eigenskapar. I dette arbeidet er genetisk variasjon eit nøkkelord. Variasjonen kan finnast i viltveksande plantemateriale og i gamle sortar, eller skapast ved å kryssa saman materiale med ulike karakterar, ved å framkalla mutasjonar o.s.v. Genetisk variasjon vert heile tida skapt ved danning av kjønnsceller (meiose) og ved kombinasjon av desse til nye individ (befruktning). I naturen blir dei individa som passar best til veksttilhøva valde ut, medan kultursortane blir til ved at ein tek vare på dei plantene som passar best til det menneska treng. Ein mindre kjend variant når det gjeld genetisk variasjon er å utnytta potensialet som ligg i kjønnscellene før befruktning. Kan androgenese vera eit reelt alternativ?
Forfattere
Liv OstremSammendrag
Resultat frå 2. engåret på fem felt i Rogaland / Agder viser svært god overvintring i Hykor medan Felopa varierer mykje meir. Tidleg skyting krev at spesielt Hykor må haustast tidleg.
Forfattere
Liv OstremSammendrag
Belgvekstar i blanding med gras er med og aukar den totale fôrkvaliteten, og som nitrogenfangar kan belgvekstane redusera gjødselkostnadene. Det er belgvekstar i dei aller fleste frøblandingane. Raudkløver har vore ein sjølvsagt del av høyblandingar saman med timotei og er elles med i mange blandingar for surfôr og surfôr/beite. I blandingane for kombinert slått og beite, er både raud- og kvitkløversortar med. Det er kome mange gode norske sortar, spesielt i raudkløver, dei siste åra, og ulike såvarefirma vil truleg frøavla og selja ulike sortar.
Forfattere
Liv OstremSammendrag
Fleirårig raigras er eit bladrikt strågras som gir størst avling i første engår. Arten bør helst nyttast i blanding med andre artar for å betra den totale fôrkvaliteten, men kan også nyttast i reine raigrasblandingar der dyra får tilgang til strukturfôr på andre måtar. Arten er generelt lite vinterherdig, men med god smak og kvalitet og stor avling er arten svært godt eigna til drift der ein treng fleire eller mange gongers slått og beiting. Hybridraigras og raisvingel har til dels same eigenskapane. Det er mange tilgjengelege sortar, også nokre nye frå Graminor.
Forfattere
Liv OstremSammendrag
Det finst i dag mange frøblandingar til ulike føremål og vekstområde. Artane og sortane i blandingane finst også som reinfrø om ein vil prøva sortane åleine eller laga sine eigne blandingar. I dei siste åra er det også kome nye sortar på marknaden som det er viktig å kjenna eigenskapane til.