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.
2008
Sammendrag
Vegetation fire is the worldwide disturbance that affects the largest area and biggest biomes variety. Fire instantaneously generates large C fluxes to the atmosphere, as gas and soot particles. In the same time, part of ecosystem organic matter (OM) is converted into charred material that may contribute to the stable pool of soil organic carbon (SOC). The net effect of vegetation fire on C sequestration remains uncertain because the two major impacts operate at very different timescales and C budget is highly dependent on ecosystem and fire conditions. The aim of the present research was to assess fire-induced C fluxes to the atmosphere and as new litter and charcoal production during a prescribed fire in a subtropical oak shrub. Pre-fire biomass and post-fire charred and unburned biomass were determined for vegetation leaves and stems, litter and soil in 20 sub-plots installed in a 30-ha area prescribed for fire. Concentrations of C were determined, and fluxes among pools and to the atmosphere were derived from these measurements. In a first assessment, charred OM was visually identified in standing biomass and litter using its black and shiny aspect. In a second step, a strong chemical oxidation with K2Cr2O7/H2SO4 was used to isolate only a highly recalcitrant part of pyrogenic C. After the fire, standing dead biomass was only composed of stems with charred surface. The leaves transferred from vegetation to litter during the fire represented more than a half of post-fire litter. Percentage of initial C pool that was lost to the atmosphere as gas or particles was 55 % from vegetation stems, 80 % from vegetation leaves, and 70 % from litter. Soil C stocks were not significantly modified by fire, in agreement with moderate temperature elevation in the soil proper. Total C release to the atmosphere, including gas and particles, was 2.6 kg C m"2. Visually-identified charcoal represented 5% of remaining stem C (i.e. 60 g C m"2) and 21% of post-fire litter C (i.e. 80 g C m"2). The stem and litter charcoal contained 4±4 % and 16±5 % of highly recalcitrant C, respectively. We assessed that a typical scrubland fire may add between 10 and 140 g C m"2of chemically stable pyrogenic C to the soil. The conversion rate of ecosystem C to chemically stable pyrogenic C would be between 0.2 and 3.4 %.
Forfattere
Reidun PommerescheSammendrag
En variert og rik nyttedyrfauna er viktig i økologisk korn og andre kulturer som har problemer med flygende skadegjørere. Ulike nyttedyr utfyller hverandre ved å spise bladlus til ulike tider i sesongen. Noen spiser nesten bare bladlus, mens andre trenger mer variert kost.
Forfattere
Reidun PommerescheSammendrag
Alle edderkopper er rovdyr. Noen fanger byttet med nett, mens andre jakter langs bakken etter insekter og andre smådyr. Noen er aktive om dagen og andre om natta. Noen edderkopper flytter seg ved å «fly» hengende i en silketråd som de lager selv og som vinden tar med seg. Noen edderkopphunner spiser hannen etter parring. Les mer på Agropub...
Forfattere
Jeppe Kolding Lise Haug Sigurd StefanssonSammendrag
Growth, size at maturity, gonadosomatic index (GSI), egg size, and absolute fecundity of Nile tilapia (Oreochromis niloticus) were significantly affected by oxygen levels (1.5 +/- 1.0, 2.8 +/- 1.4, and 6.0 +/- 1.8 mg center dot L-1) in a controlled experiment designed to test the hypothesis (D. Pauly. 1984. J. Cons. Int. Explor. Mer, 41: 280-284) that O-2 is the controlling factor for the transition from juvenile to adult in fish, in general, in the context of phenotypic life history plasticity and "stunting" in tilapias. Size at maturity and the estimated asymptotic size decreased with decreasing O-2 concentration, as predicted by Pauly"s hypothesis. All fish matured at the same age (18 weeks old), which is in contrast to conventional definitions of stunting. This finding challenges the suggested plasticity in age at first maturity for tilapia. The results also challenge the hypothesis that stunting is a unique recruitment mechanism, as the smaller fish in the group with low oxygen concentration produced smaller and fewer eggs than the larger fish in the group with high oxygen concentration.
Forfattere
Rastislav Solár Miroslav Mamo Janka Dibdiakova Ladislav Reinprecht Milo Pánek Jozef HudecSammendrag
A series of comparable specimens of hornbeam wood were submitted to pre-treatments by white-rot fungi and by alkali, or alkali followed by oxidation agents. The pre-treatments caused weight loss of wood and modified its physical properties and chemical composition.All pre-treatments reduced axial permeability of the test specimens in wet state (w FSP). The pre-treatments of the test specimens by diluted sodium hydroxide, or sodium hydroxide followed by hydrogen peroxide, however increased rate of diffusion in direction parallel to grain. The pre-treatments also made the kinetics of wood/water interactions in its initial phase much higher, especially when the white-rot fungi were used.The chemical pre-treatments of hornbeam wood caused its extreme final swelling, and on the other hand, a careful drying to initial moisture content resulted in its deep collapse. An increased rate of wood/water interactions, higher uptake of water and higher diffusion coefficients of wood pre-treated by alkali may play a positive role in the pulping processes.
Forfattere
Rastislav Solár Frantiek Kaík Ladislav Reinprecht Marta Laurová Jarmila Geffertová Janka DibdiakovaSammendrag
A series of comparable specimens of hornbeam wood were submitted to fungal and chemical pretreatments. Two strains of erosive white-rot fungi (P. chrysosporium and T. versicolor) and a lignin-selective fungus C. subvermispora were used. Chemical pretreatments were carried out with diluted sodium hydroxide, or sodium hydroxide and then by hydrogen peroxide, or per-acetic acid. Both biotic and abiotic pre-treatments modified the chemical composition of wood and were accompanied by its weight loss. The applied fungi apparently delignified the specimens, however at the expense of cellulose, especially when the erosive strains of fungi were used. The chemical pretreatments caused deep deacetylation, and milder delignification of wood and did not cause an apparent loss of cellulose. Biotic pretreatments of hornbeam wood, despite their marked delignification effect, led to unexpected increase in the contents of residual lignin in the resulting kraft pulps. On the other hand, pulping of the chemically pre-treated chips yielded pulps with low contents of residual lignin and much higher brightness.
Sammendrag
Clonal plants of Leuzea charthamoides and Rhodiola rosea, and plants from a seed population of Serratula coronata, were grown in a phytotrone under controlled conditions at 9"C, 15"C, 21"C day/9"C night and 21"C. All these treatments had 24 hours of light (long day). In addition there was one treatment at 21"C with only 12 hours light (short day). Each treatment had 28, 36 and 40 individuals of Rhodiola, Leuzea and Serratula respectively. Plants were harvested after 4 months and plant height and number of leaves were recorded. Leaves of Serratula and roots of Leuzea and Rhodiola were dried and analyzed for adaptogenic compounds. Number of shoots and dry weight of roots of Rhodiola increased from 9"C to 15"C. Differentiated day and night temperature with a temperature sum of 15"C further increased the growth. The highest temperature, 21"C, produced the lowest number of shoots and the lowest dry weight of roots. The results indicate that the concentration of most of the analyzed adaptogenic compounds was not effected by temperature, while the levels of total rosavins were highest at 9"C. The temperature effect of plant height and dry weight of roots of Leuzea was comparable to the results of Rhodiola, but with a slightly better growth at 21"C. On the contrary, Serratula seems to prefer warmer temperatures and produced most leaves at 21"C. At 21"C, all three species preferred long days (24 h light) compared to short days (12 h light). The results of this experiment indicate that it might be an advantage to grow Rhodiola and Leuzea at low average temperatures, while Serratula should be grown at slightly warmer places, however, it must be remembered that the experiment is limited to certain clones of each species.
Sammendrag
Clonal plants of Leuzea charthamoides and Rhodiola rosea and plants from one seedpopulation of Serratula coronata were grown at 5 different temperature treatments in a phytotrone. The treatments were 9, 15, 21 day/9 night and 21 degrees. All these treatments had 24 hours of light. In addition there was one treatment at 21 degrees with only 12 hours day. At 21 degrees the growth was reduced by short days for all species. Rhodiola grow best at low temperatures (9 degrees) and results indicate that it prefers differentiated day/night temperatures. On the contrary Serratula grows best at 21 degrees, and had a very slow growth at 9 degrees. The analysis of the level of adaptogens is not available yet.
Forfattere
Ragnhild Hafskjold Nærstad Arne Hermansen Tore BjorSammendrag
A series of field trials combining cultivars with different levels of resistance to Phythophtora infestans and different haulm killing methods was conducted in 1997, 1998 and 1999 to assess the contamination potential of the haulm. In addition, the frequency of tubers with late blight was assessed after harvest and storage, combining effects of pretreatment infection, infection by the haulm at harvest and the development of the disease during storage. Haulm killing was performed by diquat (200, 400, 600 g a.i. ha-1), half cutting of the haulm in combination with diquat (100, 200, 300 g a.i. ha-1) or full cutting of the haulm. In those treatments where haulm killing was performed purely chemically the haulm remnants¿ contamination potential tended to increase at reduced doses. Full mechanical destruction gave as low a contamination potential as application of the full dose of chemical haulm killer. However, there were no consistent differences between the haulm killing treatments in the frequency of blighted tubers after harvest and storage. This indicates that the input of chemical haulm killers may be reduced. There was a large difference between years in tuber blight after harvest and storage, which confirms that climatic factors are of major importance for tuber infection. The large difference found between the cultivars in the frequency of tuber blight indicates that tuber resistance should be an important part of integrated late blight disease management.
Forfattere
Kathrine Høybakk Anita Tøsse T. Nilsen Silje Engdal Bent Håvard Hellum Jens Rohloff Mette Thomsen Odd Georg NilsenSammendrag
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