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
The growth and development of frost tolerance (LT50) of four cultivars of timothy and four of perennial ryegrass was followed from autumn to spring at Holt (69º N) and Særheim (58º N). The plants were grown in pots placed close together in the field to simulate sward conditions. Most cultivars achieved a higher level of frost hardiness at Særheim than at Holt. The exception is `Engmo" timothy that achieved similar frost tolerance at both locations, and `Riikka" perennial ryegrass that reached higher frost tolerance at Holt. At Holt, all cultivars of both species showed their maximum frost tolerance in January. At Særheim, all ryegrass cultivars showed their highest frost tolerance in January, whereas all timothy cultivars showed their maximum in March. Substantial dehardening occurred from January onwards at Holt, and from March onwards at Særheim. Partial ice encasement in the pots at Holt can probably explain, to a large degree, the rapid loss of frost tolerance from January to March. There was a much larger loss of tillers during winter at Holt compared to Særheim, and in perennial ryegrass compared to timothy. The data will be used in the development of a simulation model for grass overwintering. A major challenge in the modelling seem to be the interaction between ice encasement and frost hardiness: on one hand, frost hardiness and ice encasement tolerance are often positively correlated; on the other hand, ice encasement can severely reduce frost hardiness.
Forfattere
Per Ove Lindemark Lars Tørres HavstadSammendrag
Ulike strategier for høst- og vårgjødsling i frøeng av "Grindstad" timotei (Phleum pratense L.) i gjenleggsåret og første engår ble prøvd ut i til sammen fem feltforsøk på Sørøstlandet i perioden 2003-2005. I hvert felt var det med ugjødsla ruter og ruter som var gjødslet med 30 kg N ha-1 om høsten i gjenleggsåret, enten like etter tresking av dekkveksten (bygg eller vårhvete) eller om lag en måned etter tresking. De tre ulike høstgjødslingsledda ble om våren i første engår kombinert med fire ulike N-strategier ved vekststart + begynnende strekningsvekst i midten av mai (75+0, 0+75, 50 +25 og 25 +50 kg N ha-1). Gjødsla ble tilført i form av kalksalpeter om høsten og fullgjødsel om våren. I et felt hvor skuddtettheten om høsten var lav (112 skudd m-2 ) ble de høyeste frøavlingene, uansett vårgjødslingsstrategi, oppnådd på ruter som var gjødslet med 30 kg N ha-1 like etter høsting av dekkveksten. I de fire andre forsøkene, hvor skuddtettheten ved tresking av dekkveksten var høyere (over 300 skudd m-2), var det ikke nødvendig å høstgjødsle for å oppnå høye frøavlinger i første engår. I alle fem felta ble de høyeste frøavlingene oppnådd på ruter hvor den totale gjødselmengden på 75 kg N ha-1 om våren i første engår var delt mellom en hovedgjødsling (50 kg N ha-1) ved vekststart og en senere delgjødsling (25 kg N ha-1) ved begynnende strekningsvekst. Det anbefales å gjødsle tynne timoteigjenlegg (
Sammendrag
The role of light in control of cyathia abscission and bract discolouration in poinsettia (Euphorbia pulcherrima) is unclear. The aim of this work was to study the involvement of photosynthetic photon flux (PPF) and extended photoperiod from 10 to 13, 16 or 24 hours with supplemental lighting at the end of the culture period on development of bract discoloration at marketing stage of the plants, and the postharvest performance of cyathia abscission in interior climate of two poinsettia cultivars, `Lilo" and `Millenium". The plants were grown at different photoperiods with supplemental PPF of 73 and 146 µmol m-2 s-1 at plant level. The extended supplemental light treatments were given for one, two or three weeks at the final cultivation period before marketing stage. Extended photoperiod from 10 up to 24 h had no influence on discolouration of the bracts as black and greenish areas of the bract in `Millenium". In contrast, `Lilo" developed serious bract discoloration at photoperiods longer than 13 h. The most serious symptom appeared at 24 h and three weeks of exposure time. Extended photoperiods with supplemental lighting enhanced cyathia abscission at the end of the culture time and during the postharvest test in interior climate. `Millenium" had a better ability to retain cyathia than `Lilo". It is concluded that poinsettia plants should be grown in a photoperiod not longer than 13 h in order to maintain a low rate of cyathia abscission at the end of the production period and during the first 2-3 weeks in interior climate.
Forfattere
Bernhard Speiser L Tamm T Amsler J Lambion C Bertrand Arne Hermansen Theo Ruissen Palle Haaland J Zarb J Santos P Shotton S Wilcockson P Juntharathep R Ghorbani C LeifertSammendrag
Late blight of potatoes, caused by Phytopthora infestans, is particularly difficult to prevent or control in organic agriculture. In this study, the host resistance of selected varieties to foliar and tuber blight and their yield under organic growing conditions were assessed in trials carried out in four countries (Switzerland, France, England and Norway) in 2001 and 2002. The objective was to identify new, more resistant varieties, which might replace some of the more susceptible varieties which are currently grown in organic agriculture. In each country, five test varieties were compared with two reference varieties, identical for all sites, and two local popular varieties. In addtion, the effect of copper fungicides was assessed for all varieties in England. Several new potato varieties (Appell, Derby, Innovator and Naturelle in Switzerland; Derby, Eden, Escort and Naturella in France; Sarpo Axona, Eve Balfour, Lady Balfour, Sarpo Mira and Sarpo Tomina in England; N89-1756 and N92-1538 in Norway) proved far less susceptible to foliar and tuber blight than most of the varieties currently grown. However, market requirements could restrict their introduction into practice. The copper fungicide treatment reduced foliar blight severity in all varieties tested in England and in both years, by 27 % on average, and increased yield by 20 % on average, but did not affect tuber blight. In organic farming, a shift towards the use of blight resistant varieties should be strongly encouraged, although this is unlikely to eliminate the need to use copper fungicides.
Forfattere
Christian UhligSammendrag
Soil erosion control mats generally prevent erosion and enhance soil physical conditions for plant growth. However, commonly used mat materials as coconut fiber and synthetic fabrics are naturally poor in plant nutrients and thus do not improve soil chemical properties. The main aim of this paper is to propose alternative materials for the production of erosion control mats, which mutually improves soil physical and chemical properties. Theoretically, the perfect material for soil erosion control mats combines all essential physical properties, e.g. physical stability, together with beneficial biological and chemical properties, like adequate bio-degradability and plant nutrient release. Furthermore, mat material, which promote soil organic matter (SOM) enrichment and thus soil development, would be favourable. From the economically and practically point of view, mat material should be cheap, available and workable. According to a literature review and practical experiences organic material derived from Epilobium angustifolium (fireweed) fulfil several of the above listed requirements. Furthermore, fireweed widely appears in early successional phases within several boreal and temperate vegetation types, and can consequently be considered a natural component for revegetation and soil development of these ecosystems. So far no allelopathic effects of its plant residues have been reported. Additionally benefits by using fireweed for the production of soil erosion control mats may derive from its ability to effectively disperse vegetative and generatively. Root cuttings as small as 2.5 x 1.5 mm were capable of producing adventitious buds and single plants might yield as many as 80,000 seeds per year with a germination rate of up to 100 % (Jobidon 1986 and literature within). Thus, the use of entire fireweed plants, including roots and matured seeds for the production of soil erosion control mats may indirectly support revegetation efforts of disturbed sites. According to Broderick (1990) and Mitich (1999) fireweed may prove to be a good species for artificial revegetation and land rehabilitation projects.
Sammendrag
The effects of photoperiod (10, 12, 16, 20 or 24 h), day-temperature (12, 15, 18, 24 or 30°C), the number of short days (14, 21 or 28 days), plant age (4, 8 or 12 weeks) and their interactions on flower and inflorescence initiation were investigated in strawberry cv. Korona. No flowers emerged in plants exposed to photoperiods of 16, 20 or 24 h or to a short day treatment for 14 days. All plants exposed to short days at daily photoperiods of 10 or 12 h for 21 days or longer, emerged flowers at temperatures between 12 and 18°C. A further increase in temperature led to a drastic decrease in the total number of flowers per plant. A short day treatment (10 or 12 h photoperiod) of 28 days resulted in highest numbers of inflorescences and flowers per plant, while a short day treatment of 21 days resulted in the highest numbers of flowers per inflorescence. Complete flower induction was observed in only 4-week-old runner plants. The number of inflorescences and the number of flowers per inflorescence increased with plant age. However, the start of flowering was delayed with increasing plant age. Results clearly demonstrate interactions between photoperiod, temperature, duration of short day treatment and plant age on flowering. This knowledge may be used to produce flower-induced plants in a greenhouse or to develop a model for predicting flower behaviour in the field.
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.
Sammendrag
I dag betrakter vi ofte gammelskogsområdene som verdifulle fordi de er viktige biotoper for et stort antall skogslevende arter. I tråd med den klassiske "naturverntanken" anses skogen som mer verdifull jo mer uberørt den er. Undersøkelser i Trøndelag viser imidlertid en allsidig utnytting av utmarksressursene i slike boreale gammelskogsområder. Den historiske bruken har også satt direkte spor etter seg i form av kulturspor på trærne. Slike spor forteller blant annet om stølsdrift, ferdsel og tradisjonell tømmerhogst. Undersøkelsen avslører også at man har brukt ild på en regulert måte for å forbedre beiteforholdene og bekrefter at gammelskogen ofte ikke er så uberørt som vi tror. Kunnskap om hvordan man finner og tolker kulturspor er liten fordi kunnskap om gamle driftsformer og sporenes funksjon ofte er borte. Spor etter tidligere bruk er idag heller ikke alltid direkte synlige i terrenget, men kan likevel ha stor betydning for det biologiske mangfoldet. Undersøkelser har for eksempel vist at forekomst av arter i høy grad betinges av den historiske bruken av landskapet og ikke bare av dagens biotopkvalitet. Forekomsten av kulturspor i gammelskogen bør derfor få konskevenser for hvordan vernede barskogsområder forvaltes og skjøttes for framtida. Det er uten tvil behov for "klassisk naturvern" som ivaretar arter og vegetasjonstyper som betinges av "uberørthet". Hvis vi skal stoppe tap av biologisk mangfold må vi være oppmerksomme på at en del av det biologiske mangfoldet sannsynligvis er betinget av tidligere bruk. Regelmessig brenning skaper for eksempel en branndynamikk som kan være viktig for det biologiske mangfoldet. Stølsdrift med utstrakt bruk av skogarealene til beite og slått resulterte i et åpnere skogbilde og gir plass for andre arter enn "tett urskog". Kunnskap om skogens historie bør derfor brukes som et viktig grunnlag for utforming av skjøtselsplaner for vernede skogsområder.
Sammendrag
Lignin is a major plant litter compound. Due to its aromatic structure it is not easily decomposable by the soil microbial biomass and has for a long-time been considered to accumulate in soil. A recent study, however, indicated that lignin has a faster turnover than the bulk soil organic matter, suggesting that there is no long-term storage of the pristine lignin molecule in soil. Using a modelling approach we were able to show that more than 90 % of lignin deposited on the soil surface is transformed into non-lignin products. The aim of this study was to elucidate the forms of lignin derived carbon during a longterm laboratory incubation of 13C labelled lignin in soil. The conceptual approach included the extraction of lignin from a 13C labelled maize plant and its incubation under ideal conditions for 11 months. Our results show that the non-lignin products are mostly CO2, with few incorporation of lignin-derived carbon into the soil microbial biomass. We were able to detect a priming effect of soil organic matter induced by lignin addition. Analysis of the mineralisation kinetics suggested that the 13C labelled isolated lignin consisted of two compartments with different decomposition rates. One of the two compartments might be related to the presence of cellulose within the isolated lignin, which has been detected using 13C CPMAS NMR spectroscopy. Molecular analysis of lignin using chemolytical methods showed that lignin becomes more accessible to chemical attack in the course of incubation. Higher yields of lignin monomers were obtained after 4 month using cupric oxide oxidation as well as thioacidolysis. These results indicate that lignin degradation in soil can hardly be separated from cellulose decomposition
Forfattere
Daniel Rasse Marie-France Dignac Bahri Haithem Cornelia Rumpel Mariotti Andre Claire ChenuSammendrag
Lignin har lenge vært antatt å være en viktig kilde for karbon i jord på grunn av sin lite nedbrytbare polyfenol-struktur i forhold til andre grupper organisk materiale. Studier av omsetning av lignin har imidlertid vist motstridende resultater og de fleste tyder på at en stor del av lignin fra planterester brytes ned i løpet av ett år etter innblanding i jord. Vi har her foreslått en to-pool modell hvor lignin i ferskt plantemateriale (Lp) enten kan opptre delvis beskyttet i jord mot videre nedbryting (Ls) eller blir omdannet til ikke-lignin produkter. Data til kalibrering av modellen ble skaffet ved hjelp av isotopanalyse av lignin spesifikk 13C fra en serie med 0-9 års ensidig maisdyrking etter hvete på en lettleire i Frankrike. Lignin ble kvantifisert ved CuO-oksidasjon som VSC-lignin, det vil si som summen av fenoltypene vanillil (V), syringyl (S) og coumaryl (C). Kalibreringene indikerte at Lp har en omsetningshastighet raskere enn ett år og at 92 % ble mineralisert til CO2 eller omdannet til andre ikke lignin-produkter, mens bare 8 % tilhørte Ls-fraksjonen. Estimert omsetningshastighet av Ls-fraksjonen var 0,05 år-1. Modellen tydet også på at om lag halvparten av Lp ikke var målt fordi det var blitt fjerne gjennom siktingen av prøven (5 mm). Som konklusjon, modellen tydet på at kjemisk bertandighet ikke er tilstrekkelig alene til å forklare omsetningen av VSC-lignin i jord, og at den mest relevante mekanismen funksjonelt synes å være overgang av VSC-ligning molekyler og fragmenter fra nedbrutt plantevev til jord-beskyttede fraksjoner.