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.
2012
Sammendrag
Springs are characterized by consistent thermal and hydrologic conditions, which enable use of spring-inhabiting organisms as sensitive indicators of biogeochemical changes in their catchments. We hypothesized that bryophytes would show a stronger response than vascular plants to changes in spring water quality because submerged bryophytes do not take up compounds from the soil. We analyzed species responses to interannual changes in spring water quality (discharge, water temperature, electrical conductivity, and pH) in 57 forest springs over 4 consecutive years. We calculated interannual turnover in species composition for bryophytes and vascular plants with the Bray–Curtis dissimilarity index. We applied regression analysis to test interannual changes in species composition of the taxonomic groups over time, and we used 2-sided t-tests to compare year-to-year changes in species composition between bryophytes and vascular plants. We used boosted regression tree (BRT) models to quantify the relative importance of different physicochemical variables and Pearson linear correlation to quantify short-term changes in vegetation relative to changes in spring-water pH. For both groups, interannual changes in species composition were significantly positively related to time scale. Bryophytes did not show a significantly stronger response than vascular plants to interannual changes in the environment. Alterations in pH and conductivity explained most of the observed interannual changes in species composition of both groups, whereas changes in water temperature and discharge were less important. However, responses of single species to environmental change may be delayed, resulting in inertia at the community and ecosystem scales. Hence, longer time periods need to be considered for a better understanding of response times of the vegetation of European forest springs to changes in spring water quality.
Forfattere
Julie Nåvik HvalSammendrag
De senere årene har det skjedd store endringer i det globale, men også det nasjonale, matmarkedet. Samtidig som strukturen i dagligvarehandelen er endret og konsentrasjonen økt, er også forbrukernes preferanser endret. Velstandsutviklingen har bidratt til større krav til variasjon og matmangfold, kvalitet, tilgjengelighet, trygg mat og andre verdier som miljø‐ og samfunnsmessig ansvar. Spesielt ser vi at det har vokst frem en økt etterspørsel etter matspesialiteter og mat med såkalt tilleggsverdi. Dette har gitt norske matprodusenter nye muligheter for økt verdiskaping og lønnsomhet. Samtidig har konkurransen på de nasjonale og internasjonale matmarkedene økt og utviklingen i Norge har gått i retning av større og færre jordbruksbedrifter og økende nettoimport av mat. Det krever at norske matprodusenter i økende grad må tenke strategisk for å møte den økende konkurransen og utfordringene fremover, også når det gjelder småskala matproduksjon. I henhold til Matkjedeutvalgets mandat, har notatet hatt til formål å si noe om fremveksten av nye og mindre leverandører, her tolket som utviklingen innenfor småskala matproduksjon og matspesialiteter. Det finnes ingen klar felles definisjon av hva som omfattes av begrep som nisjemat, lokalmat og småskala matproduksjon. LMD har laget en definisjon på matspesialiteter, mens SIFO har laget en rapport om ulike tolkninger av begrepet lokal mat. Dette er nærmere forklart i en egen boks i innledningskapittelet. Notatet er basert på allerede tilgjengelig materiale, og inneholder ingen egne analyser. På grunn av lite tilgjengelig kvantitativt materiale om småskala matprodusenter og matspesialiteter, er notatet mer kvalitativt og beskrivende. Spesielt ser det på nye måter å organisere seg på, og hvor tett dette er knyttet opp mot markedsføring og salg. I tillegg blir myndighetenes initiativ trukket frem. Til slutt følger en del om erfaringer som Innovasjon Norge har gjort seg i Spania, Frankrike og Italia. Prosjektet har hatt en ramme på 50 timer.
Forfattere
Peder Gjerdrum Birger EikenesSammendrag
Density is one of the most basic quality traits, influential for wood processing and most applications. The aim of this paper has been to present a mathematical model for dry density variation along spruce stems. 85 mature spruce trees were sampled from afforestation plantations at the west coast region of Norway. 20 mm wide cubes of clear wood were extracted from the pith outwards in north and south directions at 10 equidistant heights along the trunk. Green and dry weight and volume were recorded. In this way, the 85 stems yielded 523 disks and a total of 6019 valid observation sets. A mathematically expressed model for density variation is presented. Overall R2 = 0.64, of which between stem variation s = 35 kg/m3 accounts for two thirds. The model standard error is 32 kg/m3; however, the model fails to identify the most extreme density values. The most important results are the quantitative, mathematical form of the model, and the identification of a general density minimum at a certain distance from the pith.
Forfattere
Bjørnar Sæther Torger GjefsenSammendrag
Det er ikke registrert sammendrag
Sammendrag
The objective of the present study was to examine the effect of grazing on different pasture types and hay feeding on dairy goat milk fatty acid (FA) composition in early and late grazing season. Eighty goats were grouped according to genotype and lactation, and randomly divided into two groups (Early and Late) with approximately 8 weeks difference in mating and kidding dates. Goats within each of the two groups were further allocated to four forage treatment groups: R, forest rangeland pasture; C, cultivated pasture; HH, high quality hay; HL, low quality hay. The goats in Early were subjected to forage treatments in early grazing season, while the goats in Late received the forage treatments 8 weeks later. The most abundant FAs were C16:0 and C18:1c9 followed by C14:0 and C18:0. The milk proportion of the short and medium chained fatty acids (C6:0-C14:0) and C16:0 was higher (P < 0.0001) in Late than in Early grazing season, whilst the proportion of long chained FAs (C18:0, C18:1c9, C18:1t11, C18:2c9, 12, C18:2c9t11 and C18:3c9, 12, 15) were lower (P < 0.001). Goats grazing R yielded less milk (1.5 vs. 2.0 kg/d, P < 0.001) but with higher milk fat content (46 vs. 37 g/kg, P < 0.001) than C. The milk from goats on R had lower (P < 0.01) proportion of medium chained FAs (C10:0-C14:0) and C18:2c9, t11 but higher (P < 0.05) proportion of C18:0, C18:2c9,12 and C20:0 than C. Grazing compared to hay gave milk with lower proportion of medium chained FAs (C12:0-C14:0) and C16:0 but higher proportion of the long chained FAs C18:0, C18:1t11, C18:3c9, 12, C18:2c9, t11, C18:3c9, 12, 15, C20:0 than hay feeding. Higher supply of energy may explain higher proportion of de novo synthesised low and medium chained FA and lower proportion of long chained FA on C than on R, whilst higher supply of FA from mobilized fat may explain higher milk proportion of long chain FA in Early than in late season. Moreover, goats on pasture had likely higher supply of FA from dietary fat, which explain higher milk proportion of the long chained FA than on hay.
Forfattere
Kyrre Linné Kausrud Bjørn Økland Olav Skarpaas Jean-Claude Grégoire Nadir Erbilgin Nils Christian StensethSammendrag
In recent decades we have seen rapid and co-occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major forest pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi-annual landscape-wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co-occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed-species and age-heterogeneous forests with good site-matching tend to be less susceptible to large-scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating forestry practices should be adopted as soon as possible considering the time lags involved.
Forfattere
Kjersti Holt HanssenSammendrag
Selective cutting and other continuous cover forestry systems may be used in spruce forests where for instance environmental or recreational considerations are more important than forest production. However, in order for this system to be sustainable, successful regeneration must be achieved. The supply of both light and below-ground resources may influence the growth and development of seedlings. If a diverse tree species composition is desirable, knowledge of the gap sizes necessary to sustain seedling survival and growth of different species is important. We studied the growth of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) seedlings in the understory, using two Norway spruce sites with selective cutting and group fellings in SE Norway. 4-week old seedlings (henceforth: mini seedlings) were planted in plots with and without trenching in gaps of four different sizes, ranging from 20 to 500 m2. In addition, commercial seedlings of the two species were planted pairwise across the sites. After three years the mini seedlings were dug up and measured, while the survival and growth of the commercial seedlings were followed for eight years. Differences in seedling survival and growth characteristics due to gap size and (for mini seedlings) trenching were analysed using GLM. Mortality was high, especially for pine seedlings. This was due to grazing as well as competition for light and nutrients. Growth of both species was positively correlated with increasing gap size. This applied for height, diameter, shoot volume and needle biomass as well as total dry weight for both spruce and pine seedlings. However, trenching had a significant positive effect on growth too, also in the smallest gaps.
Sammendrag
Trender og utfordringer ved P-gjødsling til grønnsaker er drøftet og resultater av eldre og nyere norske forsøk med P-gjødsling til grønnsaksarter er presentert. Grønnsaker er en vekstgruppe med varierende rotvekstmønster, noe som gir ulik evne til å utnytte tilført fosfor. Fordi grønnsaker er høyverdivekster, betyr verdien av små avlingstap ofte langt mer enn marginale P-gjødselkostnader. Dette gjør at norske gjødslingsanbefalinger hittil har vært formulert for å være ’på den sikre siden’. En sammenlikning med anbefalingene i en rekke europeiske land, viser at de norske P-normene til grønnsaker er omtrent dobbelt så høye som i flere av disse landene. God tilgang på fosfor er viktig for rask etablering av et godt rotsystem. I Norge er det gjerne seinere og kjøligere vår, og somrene er som regel kortere. Dette er en sannsynlig årsak til at det ofte kan være større effekt av å gi mye fosfor til grønnsaker i Norge. Høy P-gjødsling kan derfor forsvares i noen tilfeller på bakgrunn av kort vekstsesong og lav jordtemperatur, som reduserer mulighetene for effektivt P-opptak og utnyttelsen av fosforreservene i jorda. Dette gjelder først og fremst ved dyrking av tidligkulturer. Sterk P-gjødsling kombinert med den lave høsteindeksen hos mange grønnsaker, fører imidlertid til opphoping av lett-tilgjengelig fosfor i jorda. Dette er funnet å være tilfellet i mange distrikt med intensiv grønnsaksdyrking, og det utgjør en stor risiko for tap av fosfor ved avrenning til vassdrag. Det er derfor et prioritert miljømål å redusere jordas P-status til et mer akseptabelt nivå. På bakgrunn av disse vurderingene, sammen med resultatene fra forsøkene, er det foreslått nye anbefalte P-gjødselmengder til ulike hodekål, løk og gulrot, både ved et middels (optimalt) innhold av plantetilgjengelig fosfor i jorda (PAL 5-7), og ved høyere P-innhold i jorda. I forhold til tidligere, er det innført to nye klasser av P-status til å dekke situasjonene med svært høyt innhold (PAL 20-24) og ekstremt høyt innhold (PAL >24), som nå er vanlige i grønnsaksdistrikt. For disse klassene anbefales det bruk av P-gjødselmengder som er i nærheten av P-mengdene som fjernes med produktene. Det blir ikke anbefalt å sløyfe P-gjødsling fullstendig. De nye P-gjødselnormene ved middels P-innhold i jorda, er nå ca. 40 % lavere enn tidligere.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
In order to detect the efficiency of the nitrogen (N2) fixation in clover-grass leys in northern climate conditions, we studied how soil compaction affects growth and N2 -fixation of white clover (Trifolium repens L.) under contrasting growth conditions. A pot experiment was carried out under controlled climatic conditions in the phytotron at Holt (Tromsø). Sandy soil was compacted to two levels, 60% and 85% of the standard degree of compactness (SDC). Four seedlings of white clover plants or timothy (Phleum pratense L.) were carefully planted in each pot. Timothy was used as reference plant. The plants were placed at 15 ºC for twelve weeks and subjected to 18 or 24 h daylight. The 15N isotope dilution method was used to assess N2 -fixation. Results suggest that 24 h daylight increased white clover biomass production as compared to 18 h daylight and favoured leaf and stolon production significantly more at 85% of SDC than at 60% of SDC. However, for white clover plants grown at 18 h day length higher compactness reduced the root development. On average, white clover derived 44-58% of its total N from N2 -fixation grown at 60% of SDC and 46-47% at 85% of SDC, regardless of light conditions. The N2 -fixation was somewhat higher at 24 h day length only under the low soil compaction level.