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
Authors
Peder GjerdrumAbstract
Moisture content, volatile in nature, is an important trait for any timber customer. Commercial board samples were observed to yield formulas for EMC reduction by kiln temperature, for hysteresis by board length, and for MC sorption dynamics by temperature. Industrial kiln practice lowers the EMC to approximately 95% of tabulated values. In this work, hysteresis was verified, and the most significant impact in natural ambient is that moisture migration to the board center appears to catch up with surface adsorption, reducing the influence of temperature and surface resistance. A concluding procedure for estimating MC dynamics for timber boards on stickers is outlined.
Authors
Peder Gjerdrum Olav Albert HøibøAbstract
A huge effort has been put into modelling wood quality the last few decades. Predicting knot size has been the centre of interest, either for timber quality, for tree growth models, or related purposes. The main objective of this paper is to analyse the stochastic features connected to knot distribution inside the three-dimensional volume of a tree\"s trunk. Four large Alpine spruce trees were sampled; age 150 years, DBH 30 to 70 cm, total volume 14.5 m3. To open a possibly large part of the stems, they were cross-cut to 31 logs and sawn to 193 unedged boards. On each unique board surface all perceptible knots were observed and localised in polar coordinates; origin in the stem base, along the pith and in the north direction. A total of 6200 knot intersections were observed in the 283 m2 sawn surfaces; however, most knots were observed several times in consecutive sawn surfaces. In order to obtain stationary variable, knot size was transformed by dividing by the square root of radial distance, and radial distance was transformed by dividing by log radius at the given location. Relative size, knot quality and spatial distribution were largely random and not correlated to each other in a tree. Thus, knots demonstrate a double nature, one part obeying the physiological laws, and another part stochastic.
Authors
Anne Kari Bergjord Helge Bonesmo Arne Oddvar SkjelvågAbstract
En canadisk model som simulerer utvikling av frost-toleranse i høsthvete under kontinental-klimatiske forhold ble videreutviklet for bruk i områder med et mer kystbasert klima. Forsøk med to sorter av høsthvete ble gjennomført i Midt-Norge gjennom to vintersesonger. Alle plantene ble herdet ved samme lokalitet, men etter herding, i midten av november, ble de distribuert til tre forskjellige lokaliteter med ulike vinter klima. Planter ble tatt inn fra felt til ulike tider gjennom høsten og vinteren og testet for frost-toleranse, uttrykt som LT50 (den temperaturen der 50 % av plantene ble drept). Resultater fra forsøkene ble brukt til å parameterisere og validere den nye modellen, kalt FROSTOL, som simulerer daglig utvikling av LT50 fra såing og utover gjennom vinteren. Frost-toleransen øker ved herding og reduseres ved avherding og stress, der stress forårsakes enten av lave temperaturer, eller av forhold med mer eller mindre telefri jord som er dekket med snø. Alle funksjonene i modellen styres av jordtemperatur i 2 cm dybde. En av funksjonene påvirkes i tillegg av snødybde, og to funksjoner av plantenes vernaliserings-status. De i alt fem koeffisientene tilhørende fire ulike funksjoner gav god korrelasjon mellom registrerte og simulerte LT50-verdier. En kryssvalidering av modellen indikerte at parameternes følsomhet i forhold til variasjoner i vintervær var tilfredsstillende liten.
Abstract
A Canadian model that simulates the course of frost tolerance in winter wheat under continental climatic conditions was adopted and further developed for use in an oceanic climate. Experiments with two cultivars were conducted during two winters in Central Norway. All plants were hardened at the same location. After hardening, in mid November, they were distributed to three locations with contrasting winter climates. Plants were sampled several times during autumn and winter and tested for frost tolerance, expressed as LT50 (the temperature at which 50% of the plants were killed). Results from the experiment were used in parameterization and cross validation of the new model, called FROSTOL, which simulates LT50 on a daily basis from sowing onwards. Frost tolerance increases by hardening and decreases by dehardening and stress, the latter caused by either low temperatures, or by conditions where the soil is largely unfrozen and simultaneously covered with snow. The functional relationships of the model are all driven by soil temperature at 2 cut depth. One of them is in addition affected by snow cover depth, and two of them are conditioned by stage of vernalization. Altogether five coefficients allotted to four of the functional relationships produced a good agreement (R-2 = 0.84) between measured and modelled values of LT50. A cross validation of the model indicated that the parameters were satisfactorily insensitive to variation in winter weather. (c) 2007 Elsevier B.V. All rights reserved.
Abstract
Carbon from complex and structural plant molecules has long been considered more efficiently retained in soils than that of soluble molecules. This dominant paradigm is now being challenged by data emerging from recent isotopic-labeling and compoundspecific isotopic studies. We recently demonstrated that large proportions of plantresidue lignin decompose within a year of incorporation to soils, and that soilextracted lignin has a turnover time of about 20 years (Rasse et al, 2006). In contrast, turnover time of soil-extracted polysaccharides can reach 40 years (Gleixner et al., 2002). Long-term incubation studies have shown that C from labeled glucose is better conserved in certain soil types than C from more complex molecules such as cellulose (e.g. Vinten et al, 2002). These studies suggest that the initial decomposability of plant molecules has limited impact on the long-term fate of their constitutive C in soils. Here we will present a new model where soluble molecules have a competitive advantage over structural molecules for the long-term preservation of their constitutive C in soils. Implementation of compound-specific data in quantitative soil models will also be discussed.
Authors
Guro BrodalAbstract
Ut fra økonomiske hensyn og politiske føringer dyrkes korn i store sammenhengende jordbruksområder med liten grad av vekstskifte, og etterhvert med til dels lite jordarbeiding av hensyn til miljø og vannkvalitet. En slik dyrkningsstrategi kan medføre høyere risiko for utvikling av mykotoksiner (soppgifter) i kornet i tillegg til å øke behovet for bruk av kjemiske plantevernmidler mot ugras og kornsjukdommer.
Abstract
Ut fra økonomiske hensyn og politiske føringer dyrkes korn i store sammenhengende jordbruksområder med liten grad av vekstskifte, og etterhvert med til dels lite jordarbeiding av hensyn til miljø og vannkvalitet. En slik dyrkningsstrategi kan medføre høyere risiko for utvikling av mykotoksiner (soppgifter) i kornet i tillegg til å øke behovet for bruk av kjemiske plantevernmidler mot ugras og kornsjukdommer.
Authors
Hans Ragnar Norli Agnethe ChristiansenAbstract
Cereals often give interfering peaks originating from fatty acids and their alkyl esters. The amount of interferences can be so high, that in addition to mask the target pesticides, the retention times increases and makes identification difficult. Standard QuEChERS cleanup with 25 mg/ml of PSA/ml of acetonitrile extract, or increasing the amount of PSA up to 300 mg/ml is not enough to remove the fatty acids. By adding calcium chloride to the extract, the polarity was changed in such a way that the polar pesticides were recovered in acceptable rates and fatty acids were not coextracted. By also include a freeze out step more unpolar fatty acid alkyl esters and plant sterols was removed.
Authors
Stein Rune Karlsen Anne Tolvanen Eero Kubin Jarmo Poikolainen Kjell Arild Høgda Bernt Johansen Fiona S. Danks Paul Eric Aspholm Frans Emil Wielgolaski Olga MakarovaAbstract
Northern Fennoscandia is an ecologically heterogeneous region in the arctic/alpine-boreal transition area. Phenology data on birch from 13 stations and 16-day MODIS-NDVI composite satellite data with 250 m resolution for the period 2000 to 2006 were used to map the growing season. A new combined pixel-specific NDVI threshold and decision rule-based mapping method was developed to determine the onset and end of the growing season. A moderately high correlation was found between NDVI data and birch phenology data. The earliest onset of the growing season is found in the narrow strip of lowland between the mountains and the sea along the coast of northern Norway. The onset follows a clear gradient from lowland to mountain corresponding to the decreasing temperature gradient. In autumn, the yellowing of the vegetation shows a more heterogeneous pattern. The length of the growing season is between 100 and 130 days in 55% of the study area.
Authors
Marie-France Dignac C Rumpel Daniel Rasse M Mendez-Millan H Bahri S Derenne G Bardoux A MariottiAbstract
How the chemical composition of plant biomolecules controls their dynamics in soils at the long-term scale remains largely unknown. Stabilisation mechanisms in soils might depend upon the chemical nature of organic matter. These mechanisms either involve soil mineral constituents or are related to chemical recalcitrance of specific molecules such as lignins. Physical and physico-chemical protection mechanisms may act differently on above- and belowground tissues of plants, leading to contrasting contributions of these tissues to soil organic matter (SOM). Cutins and suberins are specific for above and the belowground tissues of higher plants, respectively. Their molecular constituents can be used as biomarkers of the inputs of these plant tissues to soils. In this study, the molecular turnover of specifically plant-derived constituents in soils were estimated using compound specific isotopic tracer techniques applied to agricultural lands converted from C3 plant to C4 plant cropping. We assessed the specific residence times of lignins, cutins and suberins in soils, in order to compare the contributions of above- and belowground tissues to SOM. Lignin turnover in soil was faster than that of total organic carbon. Contrasting dynamics in soils were observed among lignin monomers as well as among cutin/suberin markers, which might be related to their chemical nature, their position into the polymeric structure and/or to the plant tissue in which they are present. This study, combining compound specific isotope measurements with a long term field trial helped understanding soil carbon turnover on a molecular level.