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.
2013
Sammendrag
Acetylation appears suited to provide adequate protection against biological attack for materials derived from non-durable wood species. But still there are unanswered questions related to resistance against fungal decay. The paper summarises existing knowledge related to fungal deterioration of acetic anhydride modified wood and also highlights future research opportunities. In addition, statistical analyses based on previously published decay fungi studies were performed to quantify what factors contribute most to the performance (calculated as test sample/control). The results showed that weight per cent gain can explain approximately 50% of the performance for acetic anhydride treated wood. Others of the applied variables, like wood species or type of fungus, can reduce the variance in performance by additional 15%. Based on the surveyed literature the degree of cell wall bulking in combination with lowering of the equilibrium moisture content seems to be the primary mode of action.
Forfattere
Christian Brischke Christian Welzbacher Antje Gellerich Susanne Bollmus Miha Humar Katharina Plaschkies Wolfram Scheiding Gry Alfredsen Joris Van Acker Imke De WidtSammendrag
Det er ikke registrert sammendrag
Sammendrag
Even if it is well established that acetylation of wood by the use of acetic anhydride is able to impart a significant degree of decay resistance, more evidence is needed to understand the mechanisms by which acetylated wood is protected from fungal decay. The aim of this paper was to study if a standardised leaching procedure with water (EN 84) vs. no leaching affected the Postia placenta decay of acetylated samples. Three different acetylation levels (low, medium and high) were tested in addition to untreated Southern yellow pine as control. The samples were harvested at two different stages of fungal incubation; 4 and 28 weeks. We compared changes in mass loss, wood moisture content, fungal biomass measured indirectly as fungal DNA, plus a small gene expression screening including five different genes. Generally there were not any striking differences between the leached and the non-leached samples. For the acetylated samples a statistically significant difference in mass loss between leached and non-leached samples were found at low and medium acetylation level after 28 weeks. Wood moisture content differed significantly between leached and non-leached acetylated samples for low acetylation level after 4 weeks and for at low and medium levels after 28 weeks. The gene expression levels were generally significantly lower after 4 weeks compared to 28 weeks of incubation. After 28 weeks no significant difference was found between leached and non-leached acetylated samples for any of the measured genes.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Christian Brischke Linda Meyer Gry Alfredsen Mika Humar Lesley Francis Per Otto Flæte Pia Larsson-BrelidSammendrag
Besides its inherent resistance against degrading organisms, the durability of timber is infl uenced by design details and climatic conditions, making it diffi cult to treat wood durability as an absolute value. Durability classifi cation is, therefore, based on comparing performance indicators between the timber in question and a reference timber. These relative values are grouped and related to durability classes, which can refer to a high range of service-lives. The insuffi cient comparability of such durability records has turned out to be a key challenge for service-life prediction. This paper reviewed literature data, based on service-life measures, not masked by a durability classifi cation. It focused on natural durability of timber tested in the fi eld above-ground. Additionally, results from ongoing aboveground durability studies in Europe and Australia are presented and have been used for further analysis. In total, 163 durability recordings from 31 different test sites worldwide based on ten different test methods have been considered for calculation of resistance factors. The datasets were heterogeneous in quality and quantity; the resulting resistance factors suffered from high variation. In conclusion, an open platform for scientifi c exchange is needed to increase the amount of available service-life related data.
Forfattere
Imke De Widt Jan Van den Bulcke Christian Brischke Christian Welzbacher Antje Gellerich Susanne Bollmus Miha Humar Katharina Plaschkies Wolfram Scheiding Gry Alfredsen Joris Van AckerSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Rot fungi are a major problem in the construction sector, and method to study under which moisture and temperature coefficients they grow are therefore of significant interest. Measurements of heat production rate have been made on wood samples with the brown rot fungus Postia placenta at different moisture contents (MCs). The results clearly show the heat production rate (ameasure of respiration rate and fungal activity) is moisture-dependent. For most cases, less heat was produced when the MC was decreased, and more heat was produced when the MC was increased. It was also found that when the MC increased after a dry period, the increase in activity was significantly delayed. However, if the moisture state was then kept constant at a high level, the activity slowly increased, showing that the fungi need time to recover back to the original activity level after drying. Isothermal calorimetry is a measurement technique well suited for the study of the activity of wood-decaying fungi as a function of temperature and moisture content.
Forfattere
Jody Jellison Barry Goodell Gry Alfredsen Daniel Eastwood Geoffrey Daniel Simon Craig Kenneth GraceSammendrag
Det er ikke registrert sammendrag
Sammendrag
North European epiphytic lichens are often genetically impoverished compared with their North American counterparts. This has been hypothesized to impede sexual reproduction due to reduced chances of finding compatible mating type partners. We compared genetic variation and reproductive mode in two threatened Scandinavian lichens, Evernia divaricata and Usnea longissima, with more viable populations in North America to see (i) if these species also show genetical depletion in northern Europe and (ii) if the occurrence of sexual propagules (ascospores in apothecia) is more prevalent in genetically diverse populations. Genetic variation of the fungal component was assessed by sequencing two nuclear rDNA gene regions (ITS and IGS) in 1005 and 1477 thalli, collected from 92 and 160 localities of E. divaricata and U. longissima, respectively. Scandinavian populations of both species were almost devoid of genetic variation compared with much higher genetic diversity in North America.We found no support for the proposed relationship between genetic diversity and fertility. Fertile thalli were found in several genetically invariable populations. Fertility increased with population size and regional abundance in E. divaricata, but not in U. longissima. In Scandinavia, E. divaricata was more fertile than previously recorded, whereas all sampled populations of U. longissima were sterile and possibly clonal.