Gry Alfredsen
Research Professor
Abstract
The durability against decay organisms is an essential material property for wood in outdoor use. A jack of all trades method for above-ground wood durability testing has been sought for decades, but until now no method has found its way into European standardization. The method of choice shall be applicable for untreated and treated wood—ideally also for wood composites. It shall further be reproducible, objective, fast, easy, and inexpensive. Finally, it shall provide high predictive power. This study was aimed at a review of results and practical experience with the Bundle test method which could serve as a standard procedure for above-ground field tests of wood-based materials. The method allows for water-trapping, creates a moderate moisture-induced decay risk typical for UC 3 situations, and was found applicable for a wide range of wood materials. The method allows for rapid infestation and failure of non-durable reference species within five years in Central Europe. Based on results from Bundle tests with different modifications and performed at different locations, a guideline has been developed. The method is recommended as a suitable tool for determining the durability of various wood-based materials including modified and preservative-treated wood and can provide data for durability classification.
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Nicolas Valette Arnaud Legout Barry Goodell Gry Alfredsen Lucas Auer Eric Gelhaye Delphine DerrienAbstract
In forest ecosystems, fungi are the key actors in wood decay. They have the capability to degrade lignified substrates and the woody biomass of coniferous forests, with brown rot fungi being common colonizers. Brown rots are typically involved in the earliest phase of lignocellulose breakdown, which therefore influences colonization by other microorganisms. However, few studies have focused on the impact of introducing decayed wood into forest environments to gauge successional colonization by natural bacterial and fungal communities following partial decay. This study aimed to address this issue by investigating the bacterial and fungal colonization of Norway spruce (Picea abies) wood, after intermediate and advanced laboratory-based, pre-decay, by the brown rot fungus Gloeophyllum trabeum. Using Illumina metabarcoding, the in situ colonization of the wood blocks was monitored 70 days after the blocks were placed on the forest floor and covered with litter. We observed significant changes in the bacterial and fungal communities associated with the pre-decayed stage. Further, the wood substrate condition acted as a gatekeeper by reducing richness for both microbial communities and diversity of fungal communities. Our data also suggest that the growth of some fungal and bacterial species was driven by similar environmental conditions.
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Brown rot fungi are a marvel and an enigma of Nature. They are capable of depolymerizing holocellulose within wood cell walls without significantly ineralizing lignin. The exact details behind this feat remain unknown, but a staggered mechanism has been identified: 1) an initial step characterized by oxidative degradation of the wood cell wall biopolymers and hypothesized to involve transport of Fe3+ chelated by oxalate into the cell wall, and 2) a second degradation step dominated by hydrolytic enzymes, primarily endoglucanase activity. We subjected spruce wood (Picea abies) to Rhodonia placenta and isolated xylem tissue in the initial stage of degradation. Confocal Raman microscopy revealed oxalate accumulation in the secondary cell wall of a tracheid having fungal hyphae within the lumen. This observation is the first in situ verification of oxalate accumulation within the cell wall during the first step of brown rot degradation.
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Gry Alfredsen Lone Ross Mari Sand Austigard Johan Mattsson Anne Cathrine Flyen Nanna BjerregaardAbstract
This report is a documentation of the field data collection and sampling at Svalbard in 2022 within the project ArcticAlpineDecay. The sampling methods are described and for each object sampling was performed documentation is provided, incl. location, Askeladden ID, map coordinate, photo documentation and illustration of sampling. Compilation of the results from the project will be published in peer review journals and in a final report from the project.
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The genus Pinus represents more than a hundred different tree species, most of them forming stems that can be commercially utilised for both timber and wood pulp industry. Pines are native to most of the Northern Hemisphere, while introduced and often naturalized in the Southern Hemisphere. The sapwood of pines is considered ‘not durable’ but generally easy to impregnate. On the contrary, the coloured heartwood of pines is difficult to impregnate and considered ‘less to moderately durable’ against decay fungi, but due to varying content and composition of extractives, both moisture performance and inherent durability vary within and between species. This study reviewed the literature to quantify the extent of variability of pine wood and its potential causes. Literature data from durability tests performed under laboratory and field conditions made it possible to compile reference factors for 26 pine species. The inter-species variation of biological durability is more prominent in above-ground exposure (0.7–14.9 times higher compared to the non-durable pine sapwood) compared to soil contact scenarios (1.0–2.4). The latter might be explained by fungicidal and hydrophobic extractives of pines, which play a more dominant role in above-ground exposure compared to soil exposure with permanent wetting.
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Gry AlfredsenAbstract
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Given the right climatic and environmental conditions, a range of microorganisms can deteriorate wood. Decay by basidiomycete fungi accounts for significant volumes of wood in service that need to be replaced. In this study, a short-wave infrared hyperspectral camera was used to explore the possibilities of using spectral imaging technology for the fast and non-destructive detection of fungal decay. The study encompassed different degradation stages of Scots pine sapwood (Pinus sylvestris L.) specimens inoculated with monocultures of either a brown rot fungus (Rhodonia placenta Fr.) or a white rot fungus (Trametes versicolor L.). The research questions were if the hyperspectral camera can profile fungal wood decay and whether it also can differentiate between decay mechanisms of brown rot and white rot decay. The data analysis employed Partial Least Squares (PLS) regression with the mass loss percentage as the response variable. For all models, the mass loss could be predicted from the wavelength range 1460–1600 nm, confirming the reduction in cellulose. A single PLS component could describe the mass loss to a high degree (90%). The distinction between decay by brown or white rot fungi was made based on spectral peaks around 1680 and 2240 nm, related to lignin.
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Gry Alfredsen Lone Ross Atle Wehn Hegnes Mari Sand Austigard Johan Mattsson Nanna Bjerregaard Anatoly Sinitsyn Vibeke Vandrup Martens Anne Cathrine FlyenAbstract
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Gry Alfredsen Christian Brischke Richard Acquah Tolgay Akkurt Per Otto Flæte Eva Frühwald Hansson Geir Wæhler Gustavsen Hasan Hosseini Targo Kalamees Jaan Kers Villu Kukk Roja Modaresi Jonas Niklewski Anna Sandak Sandak Jakub Philip van NiekerkAbstract
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This study explores cell wall changes in Radiata pine (Pinus radiata) after modification with acetylation or furfurylation and subsequent prolonged subjection to the brown rot fungus R. placenta with the aim of better understanding the modus operandi of these two modifications. Both modifications have shown good durability in field tests, but in order to learn from their possible limitations, we used optimal environmental conditions for fungal growth, and extended the testing period compared to standard tests. Hyphae were found in acetylated wood after two weeks, and after 28 weeks of decay abundant amounts of encapsulated hyphae were present. In furfurylated wood, mass loss and a few hyphae were seen initially, but no further development was seen during weeks 18–42. The general degradation pattern was qualitatively the same for unmodified, acetylated and furfurylated wood: carbohydrates decreased relative to lignin. Acetyl groups were lost from acetylated wood during decay (earlier results), while the furan polymer did not seem to be altered by the fungus. Based on these findings it is hypothesized that modifications such as furfurylation that enhance moisture exclusion within the cell wall through impregnation polymerization offer better long term protection compared to modifications such as acetylation that depend on the replacement of hydroxyl groups with ether bound adducts that can be removed by fungi.
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Christian Brischke Gry Alfredsen Miha Humar Elena Conti Laurie Cookson Lukas Emmerich Per Otto Flæte Stefania Fortino Lesley Francis Ulrich Hundhausen Ilze Irbe Kordula Jacobs Morten Klamer Davor Krzisnik Bostjan Lesar Eckhard Melcher Linda Meyer-Veltrup Jeffrey J. Morrell Jack Norton Sabrina Palanti Gerald Presley Ladislav Reinprecht Tripti Singh Rod Stirling Martti Venäläinen Mats Westin Andrew H. H. Wong Ed SuttieAbstract
Durability-based designs with timber require reliable information about the wood properties and how they affect its performance under variable exposure conditions. This study aimed at utilizing a material resistance model (Part 2 of this publication) based on a dose–response approach for predicting the relative decay rates in above-ground situations. Laboratory and field test data were, for the first time, surveyed globally and used to determine material-specific resistance dose values, which were correlated to decay rates. In addition, laboratory indicators were used to adapt the material resistance model to in-ground exposure. The relationship between decay rates in- and above-ground, the predictive power of laboratory indicators to predict such decay rates, and a method for implementing both in a service life prediction tool, were established based on 195 hardwoods, 29 softwoods, 19 modified timbers, and 41 preservative-treated timbers.
Authors
Christian Brischke Gry Alfredsen Miha Humar Elena Conti Laurie Cookson Lukas Emmerich Per Otto Flæte Stefania Fortino Lesley Francis Ulrich Hundhausen Ilze Irbe Kordula Jacobs Morten Klamer Davor Krzisnik Bostjan Lesar Eckhard Melcher Linda Meyer-Veltrup Jeffrey J. Morrell Jack Norton Sabrina Palanti Gerald Presley Ladislav Reinprecht Tripti Singh Rod Stirling Martti Venäläinen Mats Westin Andrew H. H. Wong Ed SuttieAbstract
Service life planning with timber requires reliable models for quantifying the effects of exposure-related parameters and the material-inherent resistance of wood against biotic agents. The Meyer-Veltrup model was the first attempt to account for inherent protective properties and the wetting ability of wood to quantify resistance of wood in a quantitative manner. Based on test data on brown, white, and soft rot as well as moisture dynamics, the decay rates of different untreated wood species were predicted relative to the reference species of Norway spruce (Picea abies). The present study aimed to validate and optimize the resistance model for a wider range of wood species including very durable species, thermally and chemically modified wood, and preservative treated wood. The general model structure was shown to also be suitable for highly durable materials, but previously defined maximum thresholds had to be adjusted (i.e., maximum values of factors accounting for wetting ability and inherent protective properties) to 18 instead of 5 compared to Norway spruce. As expected, both the enlarged span in durability and the use of numerous and partly very divergent data sources (i.e., test methods, test locations, and types of data presentation) led to a decrease in the predictive power of the model compared to the original. In addition to the need to enlarge the database quantity and improve its quality, in particular for treated wood, it might be advantageous to use separate models for untreated and treated wood as long as the effect of additional impact variables (e.g., treatment quality) can be accounted for. Nevertheless, the adapted Meyer-Veltrup model will serve as an instrument to quantify material resistance for a wide range of wood-based materials as an input for comprehensive service life prediction software.
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Gry Alfredsen Christian Brischke Brendan N. Marais Robert F. A. Stein Katrin Zimmer Miha HumarAbstract
To evaluate the performance of new wood-based products, reference wood species with known performances are included in laboratory and field trials. However, different wood species vary in their durability performance, and there will also be a within-species variation. The primary aim of this paper was to compare the material resistance against decay fungi and moisture performance of three European reference wood species, i.e., Scots pine sapwood (Pinus sylvestris), Norway spruce (Picea abies), and European beech (Fagus sylvatica). Wood material was collected from 43 locations all over Europe and exposed to brown rot (Rhodonia placenta), white rot (Trametes versicolor) or soft rot fungi. In addition, five different moisture performance characteristics were analyzed. The main results were the two factors accounting for the wetting ability (kwa) and the inherent protective properties of wood (kinh), factors for conversion between Norway spruce vs. Scots pine sapwood or European beech for the three decay types and four moisture tests, and material resistance dose (DRd) per wood species. The data illustrate that the differences between the three European reference wood species were minor, both with regard to decay and moisture performance. The results also highlight the importance of defined boundaries for density and annual ring width when comparing materials within and between experiments. It was concluded that with the factors obtained, existing, and future test data, where only one or two of the mentioned reference species were used, can be transferred to models and prediction tools that use another of the reference species
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Gry Alfredsen Erik Larnøy Greeley Beck Johan Bjørnstad Lone Ross Callum Aidan Stephen Hill Andreas TreuAbstract
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Nanna Bjerregaard Pedersen Henning Matthiesen Robert A. Blanchette Gry Alfredsen Benjamin W. Held Andreas Westergaard‑Nielsen Jørgen HollesenAbstract
Climate change is expected to accelerate the microbial degradation of the many extraordinary well-preserved organic archaeological deposits found in the Arctic. This could potentially lead to a major loss of wooden artefacts that are still buried within the region. Here, we carry out the first large-scale investigation of wood degradation within archaeological deposits in the Arctic. This is done based on wooden samples from 11 archaeological sites that are located along a climatic gradient in Western Greenland. Our results show that Ascomycota fungi are causing extensive soft rot decay at all sites regardless of climate and local environment, but the group is diverse and many of the species were only found once. Cadophora species known to cause soft rot in polar environments were the most abundant Ascomycota found and their occurrence in native wood samples underlines that they are present locally. Basidiomycota fungi were also present at all sites. In the majority of samples, however, these aggressive and potentially very damaging wood degraders have caused limited decay so far, probably due to unfavorable growth conditions. The presence of these wood degrading fungi suggests that archaeological wooden artefacts may become further endangered if climate change leads to more favorable growth conditions.
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Wood in service is sequestering carbon, but it is principally prone to deterioration where different fungi metabolize wood, and carbon dioxide is released back to the atmosphere. A key prerequisite for fungal degradation of wood is the presence of moisture. Conversely, keeping wood dry is the most effective way to protect wood from wood degradation and for long-term binding of carbon. Wood is porous and hygroscopic; it can take up water in liquid and gaseous form, and water is released from wood through evaporation following a given water vapour pressure gradient. During the last decades, the perception of wood-water relationships changed significantly and so did the view on moisture-affected properties of wood. Among the latter is its susceptibility to fungal decay. This paper reviews findings related to wood-water relationships and their role for fungal wood decomposition. These are complex interrelationships not yet fully understood, and current knowledge gaps are therefore identified. Studies with chemically and thermally modified wood are included as examples of fungal wood substrates with altered moisture properties. Quantification and localization of capillary and cell wall water – especially in the over-hygroscopic range – is considered crucial for determining minimum moisture thresholds (MMThr) of wood-decay fungi. The limitations of the various methods and experimental set-ups to investigate wood-water relationships and their role for fungal decay are manifold. Hence, combining techniques from wood science, mycology, biotechnology and advanced analytics is expected to provide new insights and eventually a breakthrough in understanding the intricate balance between fungal decay and wood-water relations.
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Olav Aaseth Hegnar Barry Goodell Claus Felby Lars Johansson Nicolé Labbe Keonhee Kim Vincent Eijsink Gry Alfredsen Aniko VarnaiAbstract
The recalcitrance bottleneck of lignocellulosic materials presents a major challenge for biorefineries, including second-generation biofuel production. Because of their abundance in the northern hemisphere, softwoods, such as Norway spruce, are of major interest as a potential feedstock for biorefineries. In nature, softwoods are primarily degraded by basidiomycetous fungi causing brown rot. These fungi employ a non-enzymatic oxidative system to depolymerize wood cell wall components prior to depolymerization by a limited set of hydrolytic and oxidative enzymes. Here, it is shown that Norway spruce pretreated with two species of brown-rot fungi yielded more than 250% increase in glucose release when treated with a commercial enzyme cocktail and that there is a good correlation between mass loss and the degree of digestibility. A series of experiments was performed aimed at mimicking the brown-rot pretreatment, using a modified version of the Fenton reaction. A small increase in digestibility after pretreatment was shown where the aim was to generate reactive oxygen species within the wood cell wall matrix. Further experiments were performed to assess the possibility of performing pretreatment and saccharification in a single system, and the results indicated the need for a complete separation of oxidative pretreatment and saccharification. A more severe pretreatment was also completed, which interestingly did not yield a more digestible material. It was concluded that a biomimicking approach to pretreatment of softwoods using brown-rot fungal mechanisms is possible, but that there are additional factors of the system that need to be known and optimized before serious advances can be made to compete with already existing pretreatment methods.
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Carbon footprint over the life cycle is one of the most common environmental performance indicators. In recent years, several wood material producers have published environmental product declarations (EPDs) according to the EN 15804, which makes it possible to compare the carbon footprint of product alternatives. The objective of this study was to investigate the effect of service life aspects by comparing the carbon footprint of treated wood decking products with similar performance expectations. The results showed that the modified wood products had substantially larger carbon footprints during manufacturing than preservative-treated decking materials. Replacement of modified wood during service life creates a huge impact on life cycle carbon footprint, while maintenance with oil provided a large contribution for preservative-treated decking. Hence, service life and maintenance intervals are crucial for the performance ranking between products. The methodological issues to be aware of are: how the functional unit specifies the key performance requirements for the installed product, and whether full replacement is the best modeling option in cases where the decking installation is close to the end of the required service life.
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Ed Suttie Christian Brischke Eva Frühwald Hansson Stefania Fortino Jakub Sandak Magdalena Kutnik Gry Alfredsen Christophe Lucas Rod StirlingAbstract
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Inger Skrede Monica Hongrø Solbakken Jaqueline Hess Carl Gunnar Fossdal Olav Aaseth Hegnar Gry AlfredsenAbstract
The aim of this study was to investigate differential expression profiles of the brown rot fungus Rhodonia placenta (previously Postia placenta) harvested at several time points when grown on radiata pine (Pinus radiata) and radiata pine with three different levels of modification by furfuryl alcohol, an environmentally benign commercial wood protection system. The entire gene expression pattern of a decay fungus was followed in untreated and modified wood from initial to advanced stages of decay. The results support the current model of a two-step decay mechanism, with the expression of genes related to initial oxidative depolymerization, followed by an accumulation of transcripts of genes related to the hydrolysis of cell wall polysaccharides. When the wood decay process is finished, the fungus goes into starvation mode after five weeks when grown on unmodified radiata pine wood. The pattern of repression of oxidative processes and oxalic acid synthesis found in radiata pine at later stages of decay is not mirrored for the high-furfurylation treatment. The high treatment level provided a more unpredictable expression pattern throughout the incubation period. Furfurylation does not seem to directly influence the expression of core plant cell wall-hydrolyzing enzymes, as a delayed and prolonged, but similar, pattern was observed in the radiata pine and the modified experiments. This indicates that the fungus starts a common decay process in the modified wood but proceeds at a slower pace as access to the plant cell wall polysaccharides is restricted. This is further supported by the downregulation of hydrolytic enzymes for the high treatment level at the last harvest point (mass loss, 14%). Moreover, the mass loss does not increase during the last weeks. Collectively, this indicates a potential threshold for lower mass loss for the high-furfurylation treatment. IMPORTANCE Fungi are important decomposers of woody biomass in natural habitats. Investigation of the mechanisms employed by decay fungi in their attempt to degrade wood is important for both the basic scientific understanding of ecology and carbon cycling in nature and for applied uses of woody materials. For wooden building materials, long service life and carbon storage are essential, but decay fungi are responsible for massive losses of wood in service. Thus, the optimization of durable wood products for the future is of major importance. In this study, we have investigated the fungal genetic response to furfurylated wood, a commercial environmentally benign wood modification approach that improves the service life of wood in outdoor applications. Our results show that there is a delayed wood decay by the fungus as a response to furfurylated wood, and new knowledge about the mechanisms behind the delay is provided.
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Gry AlfredsenAbstract
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Acetylation of wood can provide protection against wood deteriorating fungi, but the exact degradation me- chanism remains unclear. The aim of this study was to determine the effect of acetylation of Pinus radiata wood (weight percent gain 13, 17 and 21%) on the expression of genes involved in decay by brown-rot fungus Rhodonia placenta. Gene expression analysis using qRT-PCR captured incipient to advanced decay stages. As expected the initiation of decay was delayed as a result the degree of acetylation. However, once decay was established, the rate of degradation in acetylated samples was similar to that of unmodi fied wood. This suggests a delay in decay rather than an absolute protection threshold at higher acetylation levels. In accordance with previous studies, the oxidative system of R. placenta was more active in wood with higher degrees of acetylation and expression of cellulose active enzymes was delayed for acetylated samples compared to untreated samples. The reason for the delay in the latter might be because of the slower diffusion rate in acetylated wood or that partially acetylated cellobiose may be less effective in triggering production of saccharification enzymes. Enzymes involved in hemicellulose and pectin degradation have previously not been focused on in studies of degradation of acetylated wood. Surprisingly, CE16 carbohydrate esterase, assumed to be involved in deace- tylation of carbohydrates, was expressed significantly more in untreated samples compared to highly acetylated samples. We hypothesise that this enzyme might be regulated through a negative feedback system, where acetic acid supresses the expression. The up-regulation of two expansin genes in acetylated samples suggests that their function, to loosen the cell wall, is needed more in acetylated wood due the physical bulking of the cell wall. In this study, we demonstrate that acetylation affects the expression of specific target genes not previously re- ported, resulting in delayed initiation of decay. Thus, targeting these degradation mechanisms can contribute to improving wood protection systems.
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Steven Tabor Lourdes Orjuela David Contreras Gry Alfredsen Jody Jellison Scott Renneckar Barry GoodellAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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Olav Aaseth Hegnar Dejan Petrovic Bastien Bissaro Gry Alfredsen Aniko Varnai Vincent EijsinkAbstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that perform oxidative cleavage of recalcitrant polysaccharides. We have purified and characterized a recombinant family AA9 LPMO, LPMO9B, from Gloeophyllum trabeum (GtLPMO9B) which is active on both cellulose and xyloglucan. Activity of the enzyme was tested in the presence of three different reductants: ascorbic acid, gallic acid, and 2,3-dihydroxybenzoic acid (2,3-DHBA). Under standard aerobic conditions typically used in LPMO experiments, the first two reductants could drive LPMO catalysis whereas 2,3-DHBA could not. In agreement with the recent discovery that H2O2 can drive LPMO catalysis, we show that gradual addition of H2O2 allowed LPMO activity at very low, substoichiometric (relative to products formed) reductant concentrations. Most importantly, we found that while 2,3-DHBA is not capable of driving the LPMO reaction under standard aerobic conditions, it can do so in the presence of externally added H2O2. At alkaline pH, 2,3-DHBA is able to drive the LPMO reaction without externally added H2O2, and this ability overlaps entirely the endogenous generation of H2O2 by GtLPMO9B-catalyzed oxidation of 2,3-DHBA. These findings support the notion that H2O2 is a cosubstrate of LPMOs and provide insight into how LPMO reactions depend on, and may be controlled by, the choice of pH and reductant.
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Gry AlfredsenAbstract
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Gry AlfredsenAbstract
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Graham Alan Ormondroyd Gry Alfredsen Raghavalu Thirumalai Durai Prabhakaran Simon F. Curling Bronia K. Stefanowski Morwenna J. Spear Lone RossAbstract
Microbiological degradation of wood by decay fungi can cause a rapid change in the structural properties of timber which can result in both strength and mass loss. Traditional techniques for the evaluation of decay (e.g. mass loss) lack the sensitivity to evaluate the effects of the very first stages of the decay process. This paper describes the effects of initial brown rot decay, defined by the amount of Poria placenta genomic DNA (gDNA) present in the samples, on the dynamic mechanical properties of the timber. It was found that there is a correlation between the mean storage modulus of the timber and the amount of P. placenta gDNA present, and therefore the level of decay. This shows that using dynamic mechanical analysis is a viable technique that can be used to study initial decay processes.
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Lise Dalsgaard Aaron Smith Ryan Bright Gunnhild Søgaard Gry Alfredsen Signe Kynding Borgen Johannes BreidenbachAbstract
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Yuka Kojima Aniko Varnai Takuya Ishida Naoki Sunagawa Dejan Petrovic Kiyohiko Igarashi Jody Jellison Barry Goodell Gry Alfredsen Bjørge Westereng Vincent Eijsink Makoto YoshidaAbstract
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B. Lesar Miha Humar Christian Brischke Linda Meyer-Veltrup Dennis Jones N. Thaler JM Abascal Gry Alfredsen B. Brunnhuber Eva Grodås M. Irle J. Kers M. Klamer K-C Mahnert Eckhard Melcher S. Palanti M Noël E. Suttie N. Pfabigan M. TouzaAbstract
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Aniko Varnai Olav Aaseth Hegnar Dejan Petrovic Barry Goodell Gry Alfredsen Vincentius Gerardus Henricus EijsinkAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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Linda Meyer-Veltrup Christian Brischke Gry Alfredsen Miha Humar Per Otto Flæte Tord Isaksson Pia Larsson Brelid Mats Westin Jöran JermerAbstract
Comprehensive approaches to predict performance of wood products are requested by international standards, and the first attempts have been made in the frame of European research projects. However, there is still an imminent need for a methodology to implement the durability and moisture performance of wood in an engineering design method and performance classification system. The aim of this study was therefore to establish an approach to predict service life of wood above ground taking into account the combined effect of wetting ability and durability data. A comprehensive data set was obtained from laboratory durability tests and still ongoing field trials in Norway, Germany and Sweden. In addition, four different wetting ability tests were performed with the same material. Based on a dose– response concept, decay rates for specimens exposed above ground were predicted implementing various indicating factors. A model was developed and optimised taking into account the resistance of wood against soft, white and brown rot as well as relevant types of water uptake and release. Decay rates from above-ground field tests at different test sites in Norway were predicted with the model. In a second step, the model was validated using data from laboratory and field tests performed in Germany and Sweden. The model was found to be fairly reliable, and it has the advantage to get implemented into existing engineering design guidelines. The approach at hand might furthermore be used for implementing wetting ability data into performance classification as requested by European standardisation bodies.
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Yuka Kojima Aniko Varnai Takuya Ishida Naoki Sunagawa Dejan Petrovic Kiyohiko Igarashi Jody Jellison Barry Goodell Gry Alfredsen Bjørge Westereng Vincentius Gerardus Henricus Eijsink Makoto YoshidaAbstract
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Yuka Kojima Aniko Varnai Takuya Ishida Naoki Sunagawa Dejan Petrovic Kiyohiko Igarashi Jody Jellison Barry Goodell Gry Alfredsen Bjørge Westereng Vincent Eijsink Makoto YoshidaAbstract
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Gry AlfredsenAbstract
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One way to protect timber in service against basidiomycete deterioration is by means of acetylation via reaction with acetic anhydride. The reason why acetylated wood (WAc) is resistant against decay fungi is still not exactly understood. The aim of this study was to contribute to this field of science, and Postia placenta colonisation after 4, 12, 20, 28 and 36 weeks was observed at Three acetylation levels of Pinus spp. sapwood. Mass loss (ML) and wood moisture content (MC) data reflected the acetylation levels. The initial equilibrium MC (EMC) proved to be a good indicator of subsequent ML. Genomic DNA quantification showed P. placenta colonisation in all samples, also in samples where no ML were detectable. The number of expressed gene transcripts was limited, but the findings supported the results of previous studies: WAc seems to have some resistance against oxidative mechanisms, which are part of the metabolism of P. placenta. This leads to a delay in decay initiation, a delay in Expression of genes involved in enzymatic depolymerisation, and a slower decay rate. The magnitudes of these effects are presented for each acetylation level. The data also imply that there is no absolute decay threshold at high acetylation levels, but instead a significant delay of decay initiation and a slower decay rate.
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Modified wood can provide protection against a range of wood deteriorating organisms. Several hypotheses have been put forward regarding the protection mechanisms against wood decaying fungi including fungal enzyme inefficiency due to non-recognition, lower micropore size, and insufficient wood moisture content. The aim of this study was to obtain new insight into the protection manner of furfuryl alcohol (FA) modified Scots pine sapwood (WFA), and to examine biochemical mechanisms and adaptive changes in gene expression utilised by Postia placenta during early colonisation of WFA. Samples were harvested after 2, 4, and 8 weeks of incubation. After 8 weeks, the mass loss (0.1%) and wood moisture content (21.0%) was lower inWFA, than in non-modified Scots pine sapwood samples (W), 26.1% and 46.1%, respectively. Microscopy revealed needle-shaped calcium oxalate crystals, at all harvesting points, most prominently present after 4 and 8 weeks, and only in the WFA samples. Among the findings based on gene profiles were indications of a possible shift toward increased expression, or at least no down regulation, of genes related to oxidative metabolism and concomitant reduction of several genes related to the breakdown of polysaccharides in WFA compared to W.
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R Stirling Gry Alfredsen Christian Brischke Imke De Windt Lesley Francis E Frühwald Hansson Miha Humar Jöran Jermer M. Klamer M Kutnik PE Laks I Le Bayon S Metsä-Kortelainen Linda Meyer-Veltrup P Morris J Norton T Singh Joris Van Acker Jan Van den Bulcke TM Venås Hannu Viitanen AHH WongAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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Signe Kynding Borgen Gry Alfredsen Johannes Breidenbach Lise Dalsgaard Gunnhild Søgaard Aaron SmithAbstract
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In order to encourage increased use of wood, different user groups need to be better informed regarding the variation in performance between different wood materials and the effect of different use classes. It is also important to provide good empirical data on the service life of wood products as input to for example life cycle assessment studies. In the current study the effect of temperature and moisture on the performance of different wood materials in laboratory decay trials was evaluated by different approaches and compared with field exposure data. The same materials were used throughout the different tests in order to reduce variation. The durability class allocation varied, as expected, between test fungi, climates, exposure times, and decay tests. This confirms that the durability classification of a material, and the ranking between materials, is not a fixed value that can be based on one single test. Interestingly, for the most durable materials and for Scots pine sapwood (low durability) the variation in durability classification seemed to be somewhat lower than for the materials with intermediate durability. A regression model approach was used in order to predict field performance from laboratory data. However, this approach was not successful and confirms that more sophisticated models are needed in order to make good predictions of service life.
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There is an increasing awareness of how the aesthetical performance of wood exposed outdoors changes over time and especially in the first few years after installation. Mould and blue stain fungi are biological agents that contribute to the weather grey colour on a wooden façade, and the blue stain fungi Aureobasidium pullulans is commonly identified as colonizer on coated and uncoated wood exposed outdoors. In this study 21 wood substrates (untreated, preservative treated and modified) were tested for their susceptibility to A. pullulans when incubated at three different temperatures (11, 16 and 22°C). Western red cedar and preservative treated wood had the lowest mould ratings at the end of the test period (84 days). Alder, ash, Norway spruce and Sitka spruce reached maximum rating already at day 28, and at day 84 also aspen, European larch, thermally modified pine, birch, acetylated pine and DMDHEU modified pine had reached maximum rating. Incubation temperature had a significant influence on the growth of A. pullulans throughout the test period for acetylated and DMDHEU modified samples – and generally the modified wood substrates were more sensitive to changes in temperature than the other tested substrates. Scots pine sapwood seemed to be less susceptible to A. pullulans in mono cultures, demonstrating low mould ratings throughout the test period. This contradicts to previous studies were Scots pine sapwood tended to have high susceptibility when using a mix of mould and blue stain fungi.
Authors
Yuka Kojima Aniko Varnai Takuya Ishida Naoki Sunagawa Kiyohiko Igarashi Masahiro Samejima Kiwamu Umezawa Jody Jellison Barry Goodell Gry Alfredsen Vincent Eijsink Makoto YoshidaAbstract
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M. Humar C. Brischke L. Meyer B. Lesar N. Thaler D. Jones S. Bardage C. Belloncle J. Van den Bulcke J. M. Abscal Gry Alfredsen D. Baisch B. Brunnhuber G. Cofta Eva Grodås E. Frühwald Hansson M. Irle H. Kallakas J. Kers M. Klamer P. Larsson Brelid A. B. Maider K.-C. Mahnert E. Melcher R. Moeller M. Nöel L. Nunes G. A. Ormondroyd S. Palanti N. Pfabigan A. Pilgard A. O. Rapp P. Schumaker E. Suttie T. Teppand M. Touza J. Van AckerAbstract
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Barry Goodell Jody Jellison Yuan Zhu Liangpeng Zhuang Vincent Eijsink Makoto Yoshida Gry Alfredsen Valdeir Arantes Sai Venkatesh Pingali Hugh Michael O’NeilAbstract
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Gry AlfredsenAbstract
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Christian Brischke Christian R. Welzbacher Antje Gellerich Susanne Bollmus Miha Humar Katharina Plaschkies Wolfram Scheiding Gry Alfredsen Joris Van Acker Imke De WindtAbstract
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Christian Brischke Linda Meyer Gry Alfredsen Per Otto Flæte Lesley Francis Mattias Hansson Pia Larsson-Brelid Jöran Jermer Christian Welzbacher Andreas Otto Rapp Karin Brandt Eckhard MelcherAbstract
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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.
Authors
Christian Brischke Christian Welzbacher Antje Gellerich Susanne Bollmus Miha Humar Katharina Plaschkies Wolfram Scheiding Gry Alfredsen Joris Van Acker Imke De WidtAbstract
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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.
Abstract
Local climate conditions have a major influence on the biological decomposition of wood. To examine the influence of different temperature regimes on wood decay caused by the brown rot fungus Postia placenta in wood with differing natural durability, sapwood (sW) and heartwood (hW) of Scots pine, inoculated mini-blocks were incubated for up to 10 weeks at temperatures conducive or above optimal to wood decay. We profiled mass loss (ML) and wood composition, and accompanying changes in wood colonization and transcript level regulation of fungal candidate genes. The suppressive effect of suboptimal temperature on wood decay caused by P. placenta appeared more pronounced in Scots pine hW with increased durability than in sW with low decay resistance. The differences between sW and hW were particularly pronounced for cultures incubated at 30°C: unlike sW, hW showed no ML, poor substrate colonization and marker gene transcript level profiles indicating a starvation situation. As brown rot fungi show considerable species-specific variation in temperature optima and ability to mineralize components that contribute to wood durability, interactions between these factors will continue to shape the fungal communities associated to wood in service.
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Authors
Christian Brischke Linda Meyer Gry Alfredsen Mika Humar Lesley Francis Per Otto Flæte Pia Larsson-BrelidAbstract
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.
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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 AckerAbstract
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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.
Authors
Jody Jellison Barry Goodell Gry Alfredsen Daniel Eastwood Geoffrey Daniel Simon Craig Kenneth GraceAbstract
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From the range of information published, acetylation appears well suited to provide adequate protection against biological attack for materials derived from typically non-durable wood species. Acetylated wood is now commercially available both in Europe and in the USA. But still there are a lot of unanswered questions related to fungal decay mechanisms in acetylated wood.The paper summarize existing knowledge and highlight future research opportunities related to fungal deterioration of acetic anhydride modified wood. In addition statistical analyses based on previously published data were performed to quantify what factors contribute most to the performance (calculated as test sample/control).The results showed that WPG can explain approximately 50 % of the performance, measured as test sample/control (T/C), for acetic anhydride treated wood. Other of the applied variables, like wood species or type of fungus can reduce the variance in T/C by additional 15 %.
Authors
Christian Brischke Christian Welzbacher Antje Gellerich Susanne Bollmus Katharina Plaschkies Wolfram Scheiding Gry Alfredsen Joris Van Acker Imke De WindtAbstract
Die Dauerhaftigkeit von Holz gegenber Basidiomyceten wird in Europa nach CEN/TS 15083-1 (2005) bestimmt. Die bisherigen Erfahrungen mit diesem Standard sind sehr heterogen, und Ergebnisse frherer Ringversuche teilweise nicht oder nur unvollstndig verffentlicht. Insbesondere die Notwendigkeit einer natrlichen Vorbewitterung der Prfkrper, u.a. mit dem Ziel einer Detoxifizierung des Materials, wird kontrovers diskutiert. Fnf europische Forschungseinrichtungen haben sich deshalb zu einem neuen Ringversuch zusammengeschlossen, in dem die Dauerhaftigkeit gegen holzzerstrende Pilze von fnf Holzarten mit und ohne Auswaschbeanspruchung bzw. 6-monatiger natrlicher Vorbewitterung gegen Coniophora puteana und Trametes versicolor geprft wurden. Es ergaben sich Unterschiede in der Dauerhaftigkeitsklassifizierung zwischen den Prfinstituten (bis zu vier Klassen) sowie in Abhngigkeit von der Vorbeanspruchung und den statistischen Auswertungsgren. Die natrliche Vorbewitterung der Prfkrper hatte teilweise eine Angleichung der Dauerhaftigkeitsklassifizierung zwischen den Prfinstituten zur Folge. In allen Fllen wurde eine Homogenisierung der Dauerhaftigkeitseinschtzung durch Vorbewitterung jedoch nicht erreicht. Generelle Aussagen zum Einfluss der Vorbeanspruchung auf die Klassifizierung der Dauerhaftigkeiten lieen sich somit nicht ableiten, weshalb diese weder zwingend zu empfehlen noch abzulehnen ist.
Abstract
Fungal decay considerably affects the macroscopic mechanical properties of wood as a result of modifications and degradations in its microscopic structure. While effects on mechanical properties related to the stem direction are fairly well understood, effects on radial and tangential directions (transverse properties) are less well investigated. In the present study, changes of longitudinal elastic moduli and stiffness data in all anatomical directions of Scots pine (Pinus sylvestris) sapwood which was degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks have been investigated. Transverse properties were found to be much more deteriorated than the longitudinal ones. This is because of the degradation of the polymer matrix between the cellulose microfibrils, which has a strong effect on transverse stiffness. Longitudinal stiffness, on the other hand, is mainly governed by cellulose microfibrils, which are more stable agains fungal decay. G. trabeum (more active in earlywood) strongly weakens radial stiffness, whereas T. versicolor (more active in latewood) strongly reduces tangential stiffness. The data in terms of radial and tangential stiffnesses, as well as the corresponding anisotropy ratios, seem to be suitable as durability indicators of wood and even allow conclusions to be made on the degradation mechanisms of fungi.
Abstract
During the last decade wood modification has become a recognized method for delivery of enhanced timber. Hence, a range of studies have been performed to evaluate the decay resistance of modified wood. High resistance of modified wood against fungal decay is assumed to be due to changes in the wood properties rather than a toxic effect on fungal physiology. This is an advantage due to the concern from the European Union, national movements and society in general about the environmental impact of wood protection is increasing. In this paper we aimed to quantitatively summarise the performance of the different types of modified wood. However, this turned out only to be possible for acetylation. This was due to the format of the published data, variation in treatment processes and wood species used for the other treatments. For acetylated wood statistical analyses based on previously published data were performed to quantify what factors contribute most to the performance (calculated as test sample/control). The results showed that WPG can explain approximately 50 % of the performance, measured as test sample/control (T/C), for acetic anhydride treated wood. Other of the applied variables, like wood species or type of fungus can reduce the variance in T/C by additional 15 %. In addition, the paper highlight future research opportunities related to fungal deterioration of modified wood.
Abstract
Wood for outdoor decking has a high market share in the Nordic and Baltic countries among private house owners. Important issues for the consumer are maintenance intervals and aesthetic appearance as well as decay resistance. Knowledge and consumer information about these aspects are required to ensure that wood can compete with alternative decking materials. In this paper an accelerated testing of decking, “stapelbädds metoden”, was evaluated after ten years of exposure at Ås, Norway. The test method covers different hazard situations within use class 3. Different preservatives and wood modification treatments were used in addition to untreated Scots pine (sapwood and heartwood) and larch (heartwood). The samples were treated with two different surface treatments. In addition there was one set without any surface treatment. Fungal discoloration and decay was evaluated. This provided new information about performance both on and above ground for a range of different combinations of preservative/modified systems and surface treatments of wood in decking for outdoor use. Generally, there were no significant differences in performance between the surface treatments, both with regard to surface discolouring fungi and decay fungi. For all surface treatments, the samples with rating 3 (heavy attack) in bottom layer in one or several stacks was: Tanalith M, Tanalith M (c), Gori Pres 10, Scanimp, styren, furfurylation, thermal modification, Ultrawood, larch heartwood, pine heartwood and pine sapwood. For all surface treatments, the samples with mean rating ≤ 2 (evident attack) in top and middle layer in one or several stacks was: ACQ 1900, Wolmanit CX 8, Tanalith E7, Gori SC 100, Royal, Royal with pigment, Scanimp, styrene and larch heartwood
Authors
Christian Brischke Linda Meyer Gry Alfredsen Miha Humar Lesley Francis Per Otto Flæte Pia Larsson-BrelidAbstract
The material-inherent resistance of wood is one of the most important qualities influencing the durability of timber. Hence, it has also a major effect on the service life to be expected from a timber construction. In addition, design details and the respective climatic conditions determine durability and make it impossible to treat wood durability as an absolute value. Moreover, the reference magnitude varies between locations because of climatic differences. Durability classification is therefore based on comparing a certain performance indicator between the timber in question and a reference timber. Finally, the relative values (= resistance factors) are grouped and related to durability classes, which can refer to a high range of service lives for a certain location. The insufficient comparability of such durability records turned out to be a key problem for the service life prediction of timber structures, even when the climatic conditions are clearly defined. This study aimed therefore on an inventory of literature data, directly based on service life measures, not masked by a durability classification schedule. It focused on natural durability of timber tested in the field under above-ground conditions. In total 395 durability recordings from 31 different test sites worldwide and based on ten different test methods have been considered for the calculation of resistance factors: 190 for hardwoods and 205 for softwoods. Nevertheless, the considered datasets were heterogeneous in quality and quantity; the resulting resistance factors suffered from high variation. In many cases information was presented too condensed and incompletely, which is inescapable for instance in journal articles. To increase the amount of available, comparable, and directly service-life related data a reliable platform is needed. A proposal for a corresponding data base is provided in part 2 of this paper.
Abstract
A proposal for a web-based platform for scientific exchange of test data in the field of wood durability and wood protection has been made. The overall aim of the durability data base is to improve the usability of existing test data and to create an added value for durability research and service life prediction. The database allows for test results from standardized and non-standardized laboratory and field tests. Natural durable timber, preservative and water-repellent treated timber, chemically and thermally modified timber as well as composites have been considered. Finally all types of decay organisms and other degrading agents are regarded.
Abstract
Various oils can be used to lower the equilibrium moisture content and increase the service life of Scots pine wood products. The aim of this study was to investigate effects of the lateral wood zone on the brown rot resistance of untreated and linseed oil-impregnated Scots pine wood in a laboratory test (EN 113). Significant differences were found in the mean mass losses of treated and untreated specimens taken from three lateral heartwood zones, but not between specimens taken from sapwood. The treatment had no significant effect on sapwood, although it seems to have some positive effect on the durability of heartwood, apparently due to interactive effects with the high extractives contents of heartwood.
Abstract
The extractives responsible for the natural durability of western redcedar (WRC) are not well understood. Recent work by the Norwegian Institute of Wood Technology and the Norwegian Forest and Landscape Institute has evaluated the natural durability of Norwegian wood species and reference species, including Norwegian-grown WRC and North American-grown WRC, in a series of decay tests. The availability of retained samples from these tests presented an excellent opportunity to compare the extractives contents of North American and Norwegian grown-WRC, and to correlate field test decay data and extractives content. The North American-grown WRC contained much greater concentrations of extractives than the Norwegian-grown WRC evaluated in this test. However, despite these differences, performance in the EN 252 stake test in Sørkedalen was only marginally better for North American-grown WRC. Both sets of samples were comparatively low in an as yet uncharacterized compound previously associated with decay resistance. However, there were not enough data to thoroughly examine the correlations between extractives and durability data in this material.
Abstract
Fungal degradation alters the microstructure of wood and its physical and chemical properties are also changed. While these changes are well investigated as a function of mass loss, mass density loss and changes in equilibrium moisture content are not well elucidated. The physical and chemical alterations are crucial when linking microstructural characteristics with macroscopic mechanical properties. In the present article, a consistent set of physical, chemical and mechanical characteristics is presented, which were measured on the same sample before and after fungal degradation. In the first part of this two-part contribution, elucidating microstructure/stiffness-relationships of degraded wood, changes in physical and chemical data are presented, which were collected from specimens of Scots pine (Pinus sylvestris) sapwood degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks degradation time. A comparison of mass loss with corresponding mass density loss demonstrated that mass loss entails two effects: firstly, a decrease in sample size (more pronounced for G. trabeum), and secondly, a decrease of mass density within the sample (more pronounced for T. versicolor). These two concurrent effects are interrelated with sample size and shape. Hemicelluloses and cellulose are degraded by G. trabeum, while T. versicolor was additionally able to degrade lignin. In particular because of the breakdown of hemicelluloses and paracrystalline parts of cellulose, the equilibrium moisture content of degraded samples is lower than that in the initial state
Abstract
Genomic sequencing gives us a tool to systematically and rapidly discover novel genes, how their products function in the cell, and explore their interactions. When the DNA sequences are known, primers can be designed to detect transcripts of genes with gene products related to basic cellular processes and hyphal growth. The characteristic gene products induced in different fungi by different wood protection systems during decay can be identified. This knowledge will give us a better understanding of the fungal degradation of wood and we can optimize wood protection systems. Hence, no single technique will give us the answer to all questions about the decay of wood we need to gather small pieces of the puzzle using different approaches. The aim of the present study was to investigate the effects of acetylation level on the growth of Postia placenta with regard to amount of total DNA and gene expression targeting six different genes. This paper presents preliminary results after 36 weeks of incubation. We found no mass loss in the acetylated samples treated to a high treatment level after 36 weeks of incubation in a modified monoculture soil-block test. The presence of P. placenta DNA and the absence of mass loss could indicate on an inability of the mycelia to establish a wood exploitation phase. The results also showed that P. placenta increased the expression of AlO (involved in production of H2O2), cytochrome P450 (related to breakdown of toxic compounds), and QRD (involved in generating biodegradative hydroxyl radicals via redox cycling) along the incubation time, growing on acetylated wood treated to a high treatment level.
Abstract
The paper focuses on the use of thermogravimetric analysis (TGA) as a fast method for estimating the change of lignocellulosic materials during fungal degradation in laboratory trials. Traditionally, evaluations of durability tests are based on mass loss. However, to gain more knowledge of the reasons for differences in durability and strength between wooden materials, information on the chemical changes is needed. Pinus sylvestris sapwood was incubated with the brown rot fungus Gloeophyllum trabeum and the white rot fungus Trametes versicolor. The TGA approach used was found to be reproducible between laboratories. The TGA method did not prove useful for wood deteriorated by white rot, but the TGA showed to be a convenient tool for fast estimation of lignocellulosic components both in sound wood and wood decayed by brown rot.
Abstract
Brown-rot fungi such as Postia placenta are common inhabitants of forest ecosystems and brown rot fungi are also largely responsible for the destructive decay of wooden structures. The aim of this study was to compare two commonly used strains of Postia placenta MAD-698-R and FPRL 280. Scots pine sapwood samples were exposed for two and eight weeks to both fungal strains. The following was investigated: mass loss, fungal gDNA content and gene expression.A significant difference was found in mass loss after eight weeks between the P. placenta strains MAD-698-R and FPRL 280. MAD-698-R gave higher mass loss than FPRL 280. However, MAD-698-R seems to have a slightly slower growth rate than FPRL 280, reflected in lower gDNA content after two weeks.After eight weeks of exposure the gDNA content dropped and no significant difference was found between MAD-698-R and FPRL 280. We observed differences in mass loss, colonization-rate and gene expression between the two Postia strains. Results suggest significant differences in the regulation of key lignocellulose degrading enzymes between MAD-698-R and FPRL 280.
Abstract
Scots pine (Pinus sylvestris L.) is an important softwood species in Northern Europe and is frequently used as material for various wood protection systems. In Europe, EN 113 is the standard basidiomycete laboratory durability test method, using mass loss as evaluation criteria. In this paper quantitative real-time PCR (qPCR) and thermogravimetric analysis (TGA) was used to characterize colonization by basidiomycetes in Scots pine sapwood, but also to learn more about the EN 113 test. Two different wood sample sizes were tested. For Gloeophyllum trabeum the largest sample size gave the highest mass loss, while for the smallest samples Trametes versicolor gave the highest mass loss. As expected, fungal DNA content and mass loss in Scots pine sapwood samples decayed by G. trabeum became higher with increasing incubation time of 16 weeks. More unexpectedly, the T. versicolor DNA content in Scots pine sapwood samples was highest at the start of the incubation period and declined during the incubation period, while mass loss increased during the 28 week incubation period. The fungal colonization in the side and middle of EN 113 samples was tested. Highest DNA contents of G. trabeum were measured in the sides during 16 weeks of incubation. The T. versicolor DNA content was higher or similar in the side compared to the middle of the samples until week 20. For weeks 20 and 22 the DNA content was higher in the middle than in the sides, while for the remaining incubation period (weeks 24, 26 and 28) it was quite similar. TGA was shown to be a useful and fast method for chemical characterization of brown rot decayed wood, but cannot be used for white rot decayed wood. For T. versicolor moisture and fungal DNA explained most of the variation in mass loss, while for G. trabeum moisture explained most of the variation in mass loss.
Abstract
Wood exhibits a highly anisotropic mechanical behavior due to its heterogeneous microscopic structure and composition. Its microstructure is organized in a strictly hierarchical manner from a length scale of some nanometers, where the elementary constituents cellulose, hemicelluloses, lignin, and extractives are found, up to a length scale of some millimeters, where growth rings composed of earlywood and latewood are observed. To resolve the microscale origin of the mechanical response of the macro-homogeneous but micro-heterogeneous material wood, micromechanical modeling techniques were applied. They allow for prediction of clear wood stiffness (Hofstetter et al. 2005,2007, Bader et al. 2010a,b) from microstructural characteristics. Fungal decay causes changes in the wood microstructure, expressed by decomposition or degradation of its components (Côté 1965, Schwarze 2007). Consequently, macroscopic mechanical properties are decreasing (see e.g. Wilcox 1978). Thus, in the same manner as for clear wood, consideration of alterations of wood in a micromechanical model allows predicting changes in the macroscopic mechanical properties. This contribution covers results from an extensive experimental program, where changes in chemophysical properties and corresponding changes in the mechanical behavior were investigated. For this purpose, pine (Pinus sylvestris) sapwood samples were measured in the reference condition, as well as degraded by brown rot (G. loeophyllum trabeum) or white rot (Trametes. versicolor). Stiffness properties of the unaffected and the degraded material were not only measured in uniaxial tension tests in the longitudinal direction, but also in the three principal material directions by means of ultrasonic testing. The experiments revealed transversal stiffness properties to be much more sensitive to degradation than longitudinal stiffness properties. This is due to the degradation of the polymer matrix between the cellulose fibers, which has a strong effect on the transversal stiffness. On the contrary, longitudinal stiffness is mainly governed by cellulose, which is more stable with respect to degradation by fungi. Consequently, transversal stiffness properties or ratios of normal stiffness tensor components may constitute suitable durability indicators. Subsequently, simple micromechanical models, as well as a multiscale micromechanical model for wood stiffness, were applied for verification of hypotheses on degradation mechanisms and model validation.
Abstract
In 2005 an extensive test program including field tests was set up in order to obtain more data on the durability and long term performance of modified wood and semi-durable wood species. One of the main challenges for modified wood is to predict accurate service life time in UC3 (Use use class 3, above ground) and UC4 (use class 4, in soil or fresh water contact). So far, data from in-service conditions are rare, while several studies have evaluated the durability in lab or field test exposure. However, there is still a lack of studies comparing replicate modified wood products in both field and lab exposure. This study evaluates the efficacy of modified wood in AWPA E10, three different types of soil in lab (ENV 807), three test fields in-ground (EN 252) and two close to ground (horizontal double layer test) set-ups at two test sites. The test material includes furfurylated, acetylated and thermally modified wood in addition to reference treated and control samples. In laboratory, both furfurylated, acetylated and thermally modified pine (212ºC) performed well. The modified wood samples performed at the same level, or better, than the reference CC and CCA preservatives in retentions for UC4 applications. In the horizontal double layer test, five years is still too short time to be able to draw firm conclusions. However, in the most accelerated HDL set-up, all controls have failed or are moderately to severely decayed whereas most preservative treated, furfurylated and acetylated wood are sound or only slightly decayed. After 5 years of testing CCA-preserved wood performs better in-ground in field tests than in lab tests, whereas modified wood generally performs slightly poorer. Just like in the lab tests, however, acetylated wood performs equal to CCA-preserved wood in UC4. Furfurylated wood performs equal to or better than UC3 level preservative treated wood. Thermally modified wood actually performs much poorer than all preservative treated wood references. Finally, natural durability classification of the same treatment in different lab and field tests was surprisingly similar.
Authors
Gry AlfredsenAbstract
Modified wood can provide protection against a range of wood deteriorating organisms. Several hypotheses have been put forward for the mode of action against wood decaying fungi, including inhibition of action of specific enzymes, but they still need further testing. This paper summarizes results from a project focusing on molecular studies of fungal colonization in modified wood. The focus has been on furfurylated wood, but also thermally modified and acetylated wood has been studied. Among the main finding was that wood modifications have an effect on the exploitation face of both brown and white rot colonization, but not on the exploration face. As already reported in a range of papers wood modification effects the wood moisture content, and this was confirmed within this project. New information was gathered about the effect on gene expression. Even before any mass loss was detected, differences in gene expression were measured. [...]
Abstract
Brown rot is the most common and destructive type of fungal decay for wood in service. These fungi depolymerize preferentially the structural carbohydrates, cellulose and hemicellulose in the cell wall leaving oxidized lignin behind. Modified wood can provide protection against a variety of wood deteriorating organisms, including decay fungi. However, there is still little known about the mode of function of the different wood modifications concerning the decay resistance. The biochemical mechanisms and gene products induced in brown rot during growth in modified wood are poorly understood. In this paper the data collected from mass loss studies and qPCR and qRT-PCR were used for profiling growth dynamics and gene expression of the brown rot fungus Postia placenta in different wood substrates through different stages of decay. Pinus sylvestris (L.) sapwood was used for the following treatments and modifications: chromated copper arsenate CCA (0.67%), furfurylation (WPG 37), thermal modification (D212) and acetylation (WPG 23). Untreated Pinus sylvestris (L.) sapwood was used as control. Samples were taken at different time intervals from 2 to 26 weeks. The highest mass loss and the highest fungal DNA content were found in the control samples while acetylated wood had the lowest mass loss and fungal DNA content. These results reflect a close relation of mass loss and fungal DNA content, both reflecting the amount of Postia placenta decaying the samples. Generally, expression of the investigated genes was highest in CCA treated wood. In the beginning of the incubation of all treated wood samples, the genes coding for oxidative metabolic activity had higher expression levels than the untreated control. In the end of the incubation most of these genes were less expressed than in the untreated control. The genes used for carbohydrate metabolism and the alcohol oxidase showed a significant decrease after 14 weeks of incubation. At the same time an increase in gene expression of an enzyme putative involved in lignin decomposition was detected.
Abstract
Some of the most common Norwegian wood species were tested in a Double layer test in South East Norway. After eight years of exposure the highest decay rating (≥3) was found in Scots pine sapwood, Norway spruce, alder, birch and aspen. Two wood types had decay rate ≤1: Scots pine heartwood and cedar. Wood moisture was logged and compared with precipitation during a two month period the second year of exposure. Scots pine sapwood had higher wood moisture content than Norway spruce, and a good correlation was found between precipitation and wood moisture content. When comparing similar materials exposed at three different geographical locations in Southern Norway, the samples exposed in Bergen had higher decay rating than samples exposed at Ås and Oslo.
Abstract
Moisture is often recognised as a key factor regarding the long time performance of wooden products, and one of the main challenges for timber products is to predict accurate service life in use class 3 (not covered above ground) and use class 4 (in soil or fresh water contact). A range of durability classification studies have been performed both in field and laboratory. But for several wood species information regarding the durability in use class 3 is lacking. Also, there is still a lack of studies comparing replicate wood products in different field exposure situations. This study evaluates the natural durability of different North European wood species in two different climates and in two different use classes. The wood species were compared with imported species and two preservative treatments. The overall picture shows a higher decay rating for wood species tested in ground contact compared with the results from the above ground “Double layer tests”. Moreover, the woods tested in Western Norway are more decayed than those tested in Eastern Norway. These findings can be explained by higher decay risk in use class 4 than in use class 3, and higher decay risk in a humid climate (Western Norway) than in a dry climate (Eastern Norway). The results indicate similar ranking of the durability of the wood species regardless of the environment they have been exposed to. The results from a linear regression show that MOE-loss of the mini-stakes after three years describes 70 % of the variation in decay rating of the “Double layer” stakes after six years exposure in Western Norway. This result strongly indicates that MOE-loss can be a prospective tool for rapid field testing of natural durability of wood.
Abstract
This report presents presentations and summaries of posters presented during the conference "7th meeting of the Nordic-Baltic Network in Wood Materials & Engineering". The conference was held Oct. 27 to 28, 2011 in Oslo, and gathered around 70 participants from 9 countries. Norwegian Forest and Landscape institute hosted the event.
Abstract
Molecular methods are emerging also as useful tools for wood protection studies. The aim of the present study was to evaluate quantitative real-time polymerase chain reaction (qPCR) as a tool for investigating details of the colonization pattern of basidiomycete decay fungi in wood samples after 6 years of soil exposure. Samples of Pinus sylvestris L. (heartwood without treatment), furfurylated P. sylvestris sapwood and Cu-HDO treated P. sylvestris sapwood was in focus. The qPCR method based on basidiomycete DNA content in the wood had the highest sensitivity, while the ergosterol assay was more sensitive than the chitin assay. Visual rating was compared with laboratory analyses and was found to be correlating well with qPCR. This study demonstrates that qPCR in combination with microscopy provides relevant data about basidiomycete colonization in wooden material.
Abstract
Logging residues, branches and treetops after logging, were considered in the past as unsalable portions of the felled trees and remained on the landing. Currently, logging residues are harvested, stored in piles for variable time periods prior to being utilized as a bioenergy source. However, it is still unclear to what extent the colonization by decay fungi during outdoor storage impairs the fuel quality. Our objective was to find out whether the storage method influenced the amount of basidiomycetous fungi, the main wood degraders in logging residues....
Abstract
To understand the defence mechanisms utilized by decay fungi when exposed to different wood protection systems the study of gene expression can give us some answers. When the DNA sequences are known, primers can be designed to detect transcripts of genes with gene products related to basic cellular processes and hyphal growth. The characteristic gene products induced in different fungi by different wood protection systems can be identified. Studies on the expression of fungal genes will give us a better understanding of the fungal degradation of wood and we can optimize wood protection systems. Hence, no single technique will give us the answer to all questions about the decay of wood we need to gather small pieces of the puzzle using different approaches. The aim of the present study was to investigate the effects of acetylation level on the growth of Postia placenta with regard to amount of total DNA and gene expression targeting 7 different genes. This paper presents preliminary results after 4 weeks of incubation. The results presented in this paper are parts of a larger project which reaches over a period of 36 weeks with sampling times after 12, 20, 28 and 36 weeks. We found no mass loss in the acetylated samples after 4 weeks of incubation in a modified soil-block test. The presence of P. placenta DNA and the absence of mass loss could indicate on an inability of the mycelia to establish a wood exploitation phase. Two genes related to carbohydrate metabolism were expressed in a higher amount in P. placenta during growth on untreated wood than during growth on acetylated wood. However, for a third gene, also related to carbohydrate metabolism, the relationship was the opposite. Two genes related to oxidative metabolism were expressed in a higher amount in P. placenta during growth on acetylated wood than during growth on untreated wood and another two genes related to oxidative metabolism showed inconsistent results.
Authors
Per Otto Flæte Gry Alfredsen Kristian Bysheim Øyvind Eriksen Anders Qvale Nyrud Birger VenneslandAbstract
Roundwood timber is raw material for numerous products. Wood based products are generally recognised as favourable regarding energy consumption and greenhouse gas (GHG) emissions. Several studies have shown that the net CO2 emissions can be reduced by using biofuels harvested from forests to substitute fossil fuels, and by using wood for building materials. Energy use and GHG emissions associated with producing roundwood can be influenced by a broad range of factors, such as silvicultural practice, topography, applied technology, forestland ownership, industrial structure, etc. This emphasizes the importance of using representative data for energy use and GHG emissions when calculating environmental impacts. The aim of this study was to investigate the embodied energy and life cycle GHG emissions of industrial softwood sawlogs in Norway, covering the production chain from tree seed to log yard. Analyses were based on activity data for the Norwegian forest sector for the year 2007. The results showed that the embodied energy and GHG emissions were low compared with the energy and CO2-equivalents stored in the roundwood (about 2%). The findings from this study can be used to inform future decisions on processes in forestry that should be focused on when planning actions to reduce energy consumption and GHG emissions. Additionally, as roundwood timber is raw material for numerous products the results can be useful when preparing documentation of environmental impacts, such as environmental product declarations, which are increasingly demanded by the market.
Abstract
Measurements of heat production rate have been made on wood samples with the brown rot fungus Postia placenta at different moisture contents. The results clearly indicate that the heat production rate (a measure of respiration rate and activity) is moisture dependent. When the moisture content is decreased, less heat is produced, and when the moisture content is increased, more heat is produced. Isothermal calorimetry seems to be a measurement technique well suited to the study of rot fungal activity as a function of temperature and moisture content.
Abstract
One of the main challenges for new wood protection systems is to predict in a fast and accurate way service life in use class 3 (above ground) and use class 4 (in soil or fresh water contact). New environmentally benign wood protection systems are expected to have different modes of action against wood deteriorating fungi compared to the traditional preservatives, change in water sorption being one of them. Therefore it is of importance to evaluate new treated wood products in a broad range of exposure situations, also exploring the variation within use class 3 and 4. Due to the restrictions in the use of chromium containing wood preservatives, a range of studies have been published the last decade evaluating the performance of new products after laboratory or field test exposure. However, there is still a lack of studies comparing the same material in different field exposure situations. This study evaluates the efficacy of 13 novel wood protecting systems in three different above ground tests (horizontal double layer, block test and mini stakes) and two different in-ground tests (EN 252 and mini stakes). Scots pine (Pinus sylvestris L.) sapwood from the same wood source was used for all treatments. For each wood protecting system the wood specimens for all five tests were treated together in the same batch. The results after five years of field exposure are presented. In the three above ground tests no or only initial signs of decay were detected after five years (not reaching a mean rating of 1). The decay rate in soil contact was faster than above ground, but after five years only untreated wood (controls) failed in both tests. No significant difference in performance was found between the two tests in soil contact. The use of median decay rate values gave an earlier indication of performance than the use of mean decay rate values.
Abstract
Modified wood can provide protection against a range of wood deteriorating organisms. But we still lack information about why the modified wood is protected from microbial attack. Several hypotheses have been put forward for the mode of action against wood decaying fungi, including inhibition of action of specific enzymes, but they still need further testing. In this study gene expression of the brown rot fungus Postia placenta FPRL 280 has been monitored after 2, 4 and 8 weeks of colonization in furfurylated Scots pine (Pinus sylvestris L.) and in untreated control samples. Preliminary results are given. The main finding was that genes related to oxidative metabolic activity generally was higher in furfurylated wood compared to untreated Scots pine. Carbohydrate metabolism related expression varied. For one endo-glucanase and two β-glucosidases the expression was lower in furfurylated wood compared to untreated control, while for one glucoamylase and one glucan 1,3b glucosidase the expression was higher in furfurylated wood. The four cytochrome P450 tested, involved in breakdown of toxic compounds, gave inconsistent results between furfurylated and untreated control samples. Phenylalanine ammonia lyase and cytosolic oxaloacetase gave higher expression in control than in furfurylated samples.
Abstract
Traditional wood preservatives based on biocides are effective against wood-deteriorating organisms because of their toxicity. By contrast, modified woods are non-toxic by definition. To investigate the efficiency of various wood modifications, quantitative real-time polymerase chain reaction (qPCR) was used to profile the DNA amounts of the white-rot fungus Trametes versicolor (L.) [Lloyd strain CTB 863 A] during an 8-week-long growth period in treated Pinus sylvestris (L.) sapwood. The studied wood was modified by acetylation, furfurylation, and thermal treatment. The traditional wood preservatives bis-(N-cyclohexyldiazeniumdioxy)-copper (Cu-HDO) and chromated copper arsenate (CCA) were used as references, whereas untreated P. sylvestris (L.) sapwood served as a control. The maximum levels of fungal DNA in native wood occurred at the end of the experiment. For all wood treatments, the maximum fungal DNA level was recorded after an incubation period of 2 weeks, followed by a decline until the end of the trial. For the preservative-treated woods, Cu-HDO showed the lowest level of fungal DNA throughout the experiment, indicating that exploratory hyphal growth is limited owing to the phytotoxicity of the treatment. The other treatments did not inhibit the exploratory hyphal growth phase. We conclude that qPCR studies of hyphal growth patterns within wood should provide a powerful tool for evaluating and further optimizing new wood protection systems.
Abstract
A range of studies the last decade has shown that modified wood can provide excellent protection against a range of wood deteriorating organisms, including decay fungi. However, we still lack information about why the modified wood is protected from microbial attack. An understanding of the mechanisms utilized by decay fungi when exposed to modified wood is important for further optimisation of new modified wood products. Several hypotheses have been put forward, but they still need testing. The aim of this study was to summarize our earlier studies using molecular methods as a tool for better understanding of the mode of action of decay fungi in furfurylated wood. The studies include laboratory and field evaluations of decay colonisation patterns and gene expression....
Abstract
The durability of wood in exterior use is limited by to climatic factors and wood deteriorating organisms. The natural durability of the Nordic wood species is generally regarded as low, and for e.g. decking and use in soil contact wood protection is needed. Within the last years, new non-biocidal treatments, like wood modification systems, have been developed to improve the biological resistance of wood. For information about the decay resistance of untreated and modified wood, natural outside exposure is necessary. European standard EN 252 is the main field test method for use class 4. In use class 3 the need of new or improved test setups has been put forward. Traditionally evaluation of field trials has mainly been based on visual evaluation and pick-test. However, to get in depth knowledge about: 1) different field trial methods and 2) fungal colonization of new wood protection systems, additional assessment methods can be used. Hence, comparative studies are needed.....
Abstract
No abstract has been registered
Abstract
There is a need to establish new objective and sensitive methods for early detection and quantification of decay fungi in wood materials. Molecular methods have proven to be a useful tool within wood protection issues, however, this field is still poorly explored and so far relatively few have used these methods within the field of wood deterioration. Among the techniques used in the indirect quantification of fungi in decayed wood and building material are chitin and ergosterol assays. DNA-based methods are rarely used for identification in connection with quantification. Access to knowledge about fungal colonisation paterns in different wood substrates would allow further improvement of new products. The aim of this study was to investigate the colonisation pattern of decay fungi in wood samples after six years in soil exposure, in an EN252 test.....
Abstract
One of the main challenges for modified wood and modified wood based WPCs (Wood Plastic Composites) is to predict accurate service life time in UC3 (Use class 3, above ground) and UC4 (in soil or fresh water contact). So far, data from in-service conditions are rare, while several studies have evaluated the durability in lab or field test exposure. However, there is still a lack of studies comparing replicate modified wood products in both field and lab exposure. This study evaluates the efficacy of modified wood and modified wood based WPCs in AWPA E10, three different types of soil in lab (ENV 807), three test fields in-ground (EN 252) and two test sites close to ground (horizontal double layer test)......
Abstract
Information given in EN 350-2 on natural durability of different wood species against wood destroying fungi is mainly based on heartwood tested in ground contact. The objective of this study was to test and compare durability of many different wood species in a field test in ground contact. The material consisted of Norwegian wood species able to give sufficient sawn wood dimensions (commercial and less utilised species, indigenous and introduced species) and imported species (Larch from Russia; Oak, Douglas fir and Western Red Cedar from North America; Merbau and Teak from Asia). Additionally, modified wood (thermally modified and tall oil treated) and preservative treated wood (CCA- and Cu-preservative) were included in the test. The wood types, 31 in total, were tested according to EN 252 and EN 350-1 at NTIs test site in Sørkedalen, Norway. Results after five years exposure show that most of the Norwegian grown wood species have low durability. This study also provides information on durability of four species not included in EN 350-2: Juniperus communis, Salix caprea, Sorbus aucuparia and Populus tremula.
Abstract
A range of studies the last decade have shown that modified wood can provide excellent protection against a range of wood deteriorating organisms, including decay fungi. However, we still lack information about why the modified wood is protected from microbial attack. Several hypotheses have been put forward e.g. inhibition of action of specific enzymes, but they still need testing. An understanding of the mechanisms utilized by decay fungi when exposed to modified wood is important for further optimisation of new modified wood products. In this study gene expression of the brown rot fungus Postia placenta has been monitored after 2, 4 and 8 weeks of colonization in furfurylated Scots pine and control samples. Preliminary results are given. The main finding was that genes related to oxidative metabolic activity was higher in furfurylated wood compared to untreated Scots pine, and that carbohydrate metabolism related expression was lower in furfurylated wood compared to untreated control.
Abstract
Mechanical strength properties are the most important feature of wood in constructions. In decaying wood strength loss can precede mass loss. Hence, both in laboratory and outdoor applications non-destructive measurement methods for early decay detection are in demand. The aim of this study was to evaluate the applicability of ultrasonic pulse propagation as a tool for decay detection in different laboratory setups. A dynamic MOE (MOEdyn) strength test device based on measurement of ultrasonic pulse propagation was used for non-destructive strength evaluation in different exposure situations for Scots pine sapwood. Two different test setups were used. In the first test MOEdyn was measured above fibre saturation. A range of different wood protection treatments were tested according to the terrestrial microcosms (TMC) test, a modified ENV 807. Three different soil types were used: forest soil dominated by white rot, Simlångsdalen test field soil dominated by brown rot and compost soil characterised by a mixture of bacteria and soft rot. Before strength testing the samples were water saturated and MOEdyn was measured above the fibre saturation point at time intervals (0, 8, 16, 24, 32 and 40 weeks) using ultrasound. Comparisons of strength loss were performed between treatments in the different soil types, and strength loss was also compared with mass loss. In the second test MOEdyn were measured below fibre saturation. Ultrasound measurements were performed on 0.5 m pine logs sampled from five trees from the same stand in central Southern Norway. Logs from two of the trees had varying amounts of discoloration due to an incipient attack by the white rot fungus Phlebiopsis gigantea during storage. Amount of visible discoloration had effect on MOEdyn values from measurements on log ends. Transversal measurement of MOEdyn was not successful. In a subsequent water uptake test, logs with discoloration absorbed substantially more water than the rest of the sample. The conclusion of this study was that the use of ultrasonic MOE is applicable as an evaluation tool in early decay detection.
Abstract
The area of wood protection is in a period of change. New wood protection systems have been developed while their mode of action remains insufficiently understood. The development of molecular methods provides potential tools to investigate the interaction between modified wood and decay fungi. One small step to tackle some of the unsolved questions about the mode of action of modified wood is taken in this study. A specific and quantitative real-time PCR (QRT-PCR) assay was now established for identifying and quantifying early stages of fungal colonisation in modified wood and for profiling growth dynamics of the white-rot fungus Trametes versicolor through different stages of decay. QRT-PCR of colonisation of three different wood modification systems (acetylation, furfurylation, thermal modification), two reference treatments (Cu-HDO, CCA) and Scots pine sapwood as control was performed. Incubation time was 2, 4, 6, 8 and 10 weeks...
Abstract
The inhibitory effect of methanol bark extracts from six deciduous and three coniferous European tree species were bioassayed against eight fungi from the different damage categories, brown rot, white rot, canker and blue-stain. This is the first report providing data on the antifungal activity of several Europaen tree species against fungi within these damage categories. Generally the decay fungi were more inhibited by the bark extracts than the blue-stain fungi, while the lowest inhibition was found among the cancer fungi. The main pattern found between the fungal groups in relation to the bark extracts in this study is believed to be caused by the route of ingress. Acer platanoides bark extract proved to be the most effcient bark extract tested, significantly reducing the growth rate of all tested fungi. Betula pubescens bark extract generally gave the weakest reduction in growth rate. In this study, the conifer bark extracts were in general more active against the canker and blue stain ascomycete fungi than the deciduous trees extracts.
Abstract
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Picea abies and Pinus sylvestris. In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The main objective of this paper is to evaluate natural durability of Norwegian wood species for above ground applications comparing two non-standard above ground tests with the European standard tests for soil contact (EN 252) and lab performance against basidiomycetes (EN 113). The European standard tests EN 113 and EN 252 gave quite similar results, and they also corresponded well with the natural durability classification in EN 350-2. The two non-standard above ground tests differed to some extend from EN 113, EN 252 and EN 350-2. The results indicate that natural durability classification for one single wood species can change depending on use class. However, the field trials need a longer period of time before a final classification can be performed. Four species not included in EN 350-2 were classified in this study: Juniperus communis (1), Salix caprea (5), Sorbus aucuparia (5) and Populus tremula (5).
Abstract
In this study, the effect of two boric acid concentrations (1% and 2%) and four derivates of tall oil with varying chemical composition were tested separately and in combination. The tall oil derivates were chosen in a way that they consist of different amounts of free fatty, resin acids and neutral compounds. Decay tests using two brown rot fungi (Postia placenta and Coniophora puteana) were performed on both unleached and leached test samples. Boric acid showed a low weight loss in test samples when exposed to fungal decay before leaching, but no effect after leaching...
Abstract
Wood for outdoor decking has a high marked share in the Nordic and Baltic countries among private house owners. Important issues for the consumer are maintenance intervals and aesthetic appearance as well as decay resistance. Knowledge and consumer information about these aspects are required to ensure that wood can compete with alternative decking materials. In this paper an accelerated testing of decking, “stapelbäddsmetoden”, was evaluated after six years of exposure at Ås, Norway, and compared with earlier reported results after three years. Twelve different preservatives and wood modification treatments were used in addition to untreated Scots pine (sapwood and heartwood) and larch (heartwood). The samples were treated with two different surface treatments. In addition there was one set without any surface treatment. In this method for accelerated testing, discolouration and decay was evaluated. This provided new information about performance both on and above ground for a range of different combinations of preservative/modified systems and surface treatments of wood in decking for outdoor use. For example, no clear differences were found between the surface treatments and no surface treatment. The wood modifications with styrene and furfurylalcohol performed just as good, or better, than the copper containing treatments.
Abstract
In Norway, exterior wood structures have traditionally, nearly exclusively been made of untreated Norway spruce (Picea abies (L.) Karst) and pressure treated Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other wood species, like various Norwegian hardwoods or imported species, have been used in exterior above ground applications, often not surface treated. For several wood species, especially hardwoods, information regarding the durability in use class 3 is limited. Most information given in EN 350 part 2 is based on testing of the heartwood in ground contact. The test procedures for above ground test prescribed in European standards, both laboratory and field tests, have some weaknesses regarding natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian and some imported wood species for above ground applications, and to study various methods for assessing decay in wood. The project material and methods used in the project, and the results from double layer tests after one year of exposure has earlier been described, Flæte et al. (2006). This paper presents the results of the weight and MOE loss in small samples after about 3 years exposure above ground.
Abstract
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Picea abies and Pinus sylvestris. In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The main objective of this paper is to evaluate natural durability of Norwegian wood species for above ground applications comparing two non-standard above ground tests with the European standard tests for soil contact (EN 252) and lab performance against basidiomycetes (EN 113). The European standard tests EN 113 and EN 252 gave quite similar results, and they also corresponded well with the natural durability classification in EN 350-2. The two non-standard above ground tests differed to some extend from EN 113, EN 252 and EN 350-2. The results indicate that natural durability classification for one single wood species can change depending on use class. However, the field trials need a longer period of time before a final classification can be performed. Four species not included in EN 350-2 were classified in this study: Juniperus communis (1), Salix caprea (5), Sorbus aucuparia (5) and Populus tremula (5).
Abstract
No abstract has been registered
Authors
Kristoffer Segerholm Roger Rowell Pia Larsson-Brelid Magnus Wålinder Mats Westin Gry AlfredsenAbstract
No abstract has been registered
Abstract
The area of wood protection is in a period of change. New tools are needed to understand the mode of action, and to further improve the new wood protection systems. A set of useful tools are found among the molecular methods. This paper presents an overview of some of the tools available, and the methods are exemplified by papers within the frame of wood protection issues. However, there is still a great unexplored potential within the field of wood protection by the use of various molecular methods. The majority of the work using molecular methods has been performed on species identification issues and within species variation. This paper lists some new promising molecular methods for wood protection issues and a presentation of a new project. The new project will help to gain some new knowledge about how the fungal decay processes are affected by different wood modification systems.
Abstract
The aim of this study was to compare two methods for non-destructive strength testing of wood by the use of dynamic modulus of elasticity (MOEdyn). The two methods are based on resonant vibration excitation and ultrasonic pulse excitation. Sound Pinus sylvestris L. sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated at two moisture levels. There was a significant correlation between the measurements given by the two MOEdyn test devices. An analysis of variance showed significant differences between the different treatments and between different moisture levels. Potential use of the non-destructive MOEdyn methods in durability testing is discussed.
Abstract
This study evaluates the decay and termite resistance of Scots pine (Pinus sylvestris L.) treated with 4-methoxytrityl tetrafluoroborate (MTFB).Decay resistance tests of unleached samples showed that 2%, 1.5% and 1% concentrations of MTFB (15.4kg/m3, 11.1kg/m3, and 7.4kg/m3, retention levels, respectively) gave less than 2% decay of Postia placenta and concentrations of 2% and 1.5% less than 2% decay of Coniophora puteana.Wood specimens treated with 4-methoxytrityl tetrafluoroborate solutions were not protected against the brown rot fungi after a 14-day severe leaching process, suggesting excessive leaching of the chemical from wood. Treatment with 2% concentration protected against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens in comparison with lower concentration levels.These results suggest that 4-methoxytrityl tetrafluoroborate might be promising to protect wood being used outdoors against termite attack. However, 4-methoxytrityl tetrafluoroborate did not protect wood against fungal decay. Field tests are needed to observe the performance of 4-methoxytrityl tetrafluoroborate treated wood in ground contact.
Abstract
There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing.As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasin values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples.MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control.In this study a correction value (\"k\") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected.Wood treatments influence the \"k\" value, and a \"k\" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a \"k\" value is calculated for MOEdyn ultrasound above fibre saturation.
Abstract
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The test procedures prescribed in the European standards, both laboratory and field tests, have some weaknesses regarding to natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian wood species for above ground applications, and to study various methods for assessing decay in wood. This paper presents the material and methods used in the project, and report the results from double layer tests after one year of exposure. No decay was detected, but almost all wood species were considerably discoloured. Thuja (Norw.), Thuja (Am.), Intsia and Tectona had the least amount of discolouration. The Norwegian softwood species had generally less discolouration than the Norwegian hardwood species. CCA and Cu preservative impregnated and FA modified Pinus sylvestris sapwood had more cracks than most of the untreated wood species. Moreover, some of the Picea abies qualities and Pinus sylvestris sapwood samples had substantial amounts of cracks.
Abstract
No abstract has been registered
Authors
Gry AlfredsenAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Fungi cause serious problems in wood utilization, and environmentally benign wood protection is required as an alternative to traditional chemicals. Chitosan has shown promising antimicrobial properties against several microorganisms. In this study, we present the characterization of and antifungal properties of a commercial chitosan formulation developed for impregnation of wood.A broad range of chemical and mycological methods were used to evaluate the uptake, fixation, and antifungal properties of chitosan for wood preservation. The results show that the higher the uptake of chitosan the lower the relative recovery of chitosan in wood after leaching, and the higher the molecular weight of chitosan the higher the recovery.Chitosan with high molecular weight proved to be more efficient against decay fungi than chitosan with low molecular weight. The fungi tested on chitosan-amended nutrient agar medium were totally inhibited at 1% (w/v) concentration.In decay studies using small wood blocks, 4.8% (w/v) chitosan concentration gave the best protection against brown rot fungi.
Abstract
This paper describes the use of quantitative real-time PCR for monitoring colonization of birch wood (Betula pubescens) by the white-rot fungus Trametes versicolor in an EN113 decay experiment. The wood samples were harvested after 4, 8, 12, 16 and 20 weeks of incubation.The mass loss was in the range of 440%. Chitin and ergosterol assays were conducted for comparison. Second-order polynomial fits of the mass loss of decayed wood versus chitin, ergosterol and DNA gave correlations (r2) of 0.87, 0.61 and 0.84, respectively. Compared to the other two assays employed, real-time PCR data correlated best with the relative mass loss of decayed samples 48 weeks after inoculation, while the saturation and decline of DNA-based estimates for fungal colonization 1620 weeks after inoculation indicated that the DNA assay is not suited for quantification purposes in the late stages of decay.The impact of conversion factors, extraction efficiency, inhibitory compounds and background levels in relation to the three detection assays used is discussed.
Abstract
In this study modified wood samples were tested according to the extended standardised test procedures of ENV 807 (3 types of soils). A Round Robin test was carried out at two laboratories: Swedish National Testing and Research Institute and Norwegian Forest Research Institute.The different soil types used were conifer forest soil (pH 4.6), soil from the Simlngsdalen test field (pH 5.2) and garden compost soil (pH 7.4). The wood modifications used were furfurylation (Visorwood), acetylation and heat treatment (Thermowood). Other materials tested were linseed oil impregnated pine, reference preservative (CC and CCA) treated pine and Robinia psuedoaccacia heartwood.A dynamic MOE (MOEdyn) test device based on measurement of ultrasonic pulse propagation was used for non-destructive decay strength evaluation during the incubation period. The MOE values were correlated to measured decay mass loss of the test specimens after different periods of exposure to the soils. Type of fungal attack was also evaluated using light microscopy.Results from preliminary studies indicate that ultrasound seems to be an excellent tool for evaluation of early brown rot decay. It also seems to be feasible for detecting white rot. However it does not seem to be very accurate in evaluating early stages of soft rot decay.
Abstract
During a period of 2 years and 3 months (1 January 2001 - 20 March 2003) Mycoteam had 3161 consultations in buildings in southern Norway, 1428 revealing damage from decay fungi. One consultation often revealed several occurrences of fungi, and the total number of occurrences of decay fungi was 3434. Thirty-five different species/genera/groups of decay fungi were recorded. During this period brown rot was more frequent (77.4 %) than soft rot (19.2 %) and white rot (3.4 %). Coniophora puteana (16.3 %) and Serpula lacrymans (16 %) were the most frequently identified species. Different species of the genus Antrodia were recorded in 18.4 % of the occurrences, while the group Corticiaceae accounted for 5.7 % and soft rot for 15.8 %. Investigations of damaged structural parts of buildings showed that decay fungi were most common in walls (18.3 %). Floor damage accounted for 13.4 % of the damaged structures and roofs for 8.8 %. Nearly all species and groups of the investigated fungi were most common indoors. Gloeophyllum sepiarium on the other hand was most common outdoors, and Dacrymyces stillatus was exclusively found outdoors. The Norwegian data were compared with published time series data from Denmark (1946-66, 1966-71, 1974-75, 1982) and Finland (1978-84, 1985-88). S. lacrymans and C. puteana were the most frequent species in these datasets too. Antrodia spp. were also common in the Finnish reports, but barely recorded (as identified species) in Denmark. In both the Danish and the Finnish data, damage to floors is the most frequently recorded structural damage in buildings.
Abstract
Wood samples treated with ammonium copper quat (ACQ 1900 and ACQ 2200), chromated copper arsenate (CCA), Tanalith E 3491 and Wolmanit CX-8 have been studied in accelerated weathering experiments. The weathering experiment was performed by cycles of 2 h UV-light irradiation followed by water spray for 18 min. The changes on the surface of the weathered samples were characterized by roughness and color measurements on the samples with 0, 200, 400 and 600 h of total weathering.The objective of this study was to investigate the changes created by weathering on impregnated wood with several different wood preservatives. This study was performed on the accelerated weathering test cycle, using UVirradiation and water spray in order to simulate natural weathering. Surface roughness and color measurement was used to investigate the changes after several intervals (0200400600 h) in artificial weathering of treated and untreated wood.
Abstract
Artikkelen drøfter saltinnhold i ulike bygningsdeler i Bryggen i Bergen, saltets opphav og betydning i forhold til bevaring av trevirket. Ulike nedbrytningsorganismer i saltholdig tømmer er også vurdert.
Abstract
Chitosan, a derivate of the natural amino polysaccharide chitin, has proven effective as a potential environmentally benign antimicrobial component. Few studies have focused on chitosan applied to wood against wood inhabiting and decaying fungi.In these screening studies several mycological experiments were performed to screen chitosan as a potential wood protecting agent. Growth studies on chitosan-amended media showed total inhibition of Poria placenta, Coriolus versicolor and Aspergillus niger using 1% w/v concentration.Chitosan with high average molecular weight (MW) was more efficient against mould and staining fungi than chitosan with low MW. Agar plate leaching tests showed only a small leaching effect using a 5% concentration on A. niger and P. placenta. Decay testing with P. placenta demonstrated efficacy using 5% and 2.5% concentrations in unleached samples. Leaching decreased the efficacy of chitosan and further investigations are needed to improve the fixation in wood.
Abstract
Tall oil is a by-product in pulping of resinous wood by the sulphate process. Tall oil contains a complex mixture of wood extractives. Some of these extractives act as natural protection against wood decaying fungi while other serve as nutrition for the fungi. This report describes a screening of the efficacy of four refined tall oils with different chemical composition on wood decaying fungi.Testing was performed as filter paper assay and mini-block assay. In the filter paper assay growth rates of the white rot fungus Coriolus versicolor and the brown rot fungus Poria placenta were inhibited by the tall oils. None of the oils caused total inhibition of the fungi but there was a clear pattern towards increased efficacy with increased portion of resin acids in the oils.Impregnated mini-blocks with approximately 200 kg/m3 retention of tall oil after leaching showed an evident effect against Coniophora puteana and Poria placenta compared to untreated control samples. However, using the criteria from EN 113 requiring less than 3% mass loss, tall oil failed.The results indicate that decay resistance of tall oil impregnated Scots pine sapwood to the retention level used in this study is comparable with the decay resistance of Scots pine heartwood. It was expected that the efficacy of the tall oils was related to chemical composition of the oils. This was confirmed for the filter paper assay where the efficacy increased with increasing amount of resin acids. However, this pattern was not found for the mini-block assay.The protective effect of the tall oils in wood seems therefore to be more related to their hydrophobic properties than to their fungicidal properties.
Abstract
No abstract has been registered
Division of Forest and Forest Resources
WoodLCC
In Enhanced Life-Cycle-Costing in wood construction by novel methods for service life planning (WoodLCC), researches will enable robust and precise Life-Cycle-Costing (LCC) based on input from novel models for detailed service life performance specification for wooden components and buildings.
Division of Forest and Forest Resources
Deterioration and decay of wooden cultural heritage in Arctic and Alpine environments (ArcticAlpineDecay)
