Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2011
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
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.
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
The main task of the C1-Dep-22(SI) action was to compare national throughfall collectors with a harmonized collector which was designed according to the requirements of the WMO. The action spread onthe took place in very different climate zones and vegetation, and included a very different types of national collectors with different sampling procedures. The number of harmonized throughfall collectors was 30 for all participants. The spatial arrangement in the plot, sampling times, sampling and cleaning procedures, bulking of the subsamples and chemical analysis procedures were in all cases the national procedures. The time when the precipitation was in the form of snow was excluded from the sampling periods. The associated beneficiaries reported the amounts of the precipitation per collector and the results from chemical analysis per pooled sample. The measured quantities were compared for different types of forest or main tree species. The deviations between collectors were lower in the plots with the broadleaf trees than in the plots with conifers as the main tree species. The median deviations for conifers and for broadleaves trees is not significantly different from zero. Except in a few cases, a good agreement in the amount of precipitation was found between the national and harmonized collectors for both throughfall and bulk precipitation. In a few incidents this was not the case but we assume that where this was not the case, this was due to happened in extreme weather conditions e. g. heavy storms. Also good agreement was also found within for the chemical composition of the solutions, gathered with different types of collectors. Again, there were some deviations limited to on single occasions. It was found that the harmonized collectors were attractive to birds and thus a bird ring is a must in this (white) -coloured version of the collector. Chemical analysis (chemical composition) together with the collected amount of the solution depends on give the total deposition values. It was made a close up to the deposition values of ammonium-nitrogen, nitrate-nitrogen and sulphate-sulphur were compared in detail. For ammonium-nitrogen no bigger difference was found for the one-year deposition values except in one case what which turned out to be almost certainly a consequence of birds activity. Differences in all other cases were no more than 0.3 g m-2 yr-1. For nitrate-nitrogen smaller deviations were found but in none of the case was the difference was in total annual deposition higher than 0.3 g m-2 yr-1. For sulphate-sulphur good agreement was found for all associated beneficiaries except two. One of the Possible reasons could be in the difference of in the ability in collecting dry deposition and/or the total area which contributes to the capturing area for dry deposition. Despite their heterogeneity and some unlack of adaptation for representative sampling at the plot scale, the national devices for throughfall collection gave comparable results infor throughfall deposition to the harmonized, optimal collectors. In conclusion national throughfall collection devices can be maintained to ensure the continuity of the time series in deposition monitoring. And to improve the harmonized collector even more, problems with the possible blockages of the tube at the bottom of the funnel because of debris should be solved.
Authors
Nina Hovden Sæther Anna Caroline RehnbergAbstract
No abstract has been registered
Authors
Nina Hovden Sæther Anna Caroline RehnbergAbstract
No abstract has been registered
Authors
Ylva-li Blanck Juan Gowda Linda-Maria Mårtensson Jakob Sandberg Ann-Mari FranssonAbstract
The aim of this study was to ascertain whether there is a relationship between plant species richness and plant-available N, P and water in an environment subject to little anthropogenic disturbance. To accomplish this we studied the vegetation in matorral shrub-lands in northern Patagonia, Argentina. Due to the variation in slope, precipitation and aspect between the sites water status was determined using the 12C/13C fraction, δ13C, to investigate whether this was a confounding factor. The numbers of herb, shrub, liana and tree species were determined at 20 sites along an estimated precipitation gradient. Leaf P and N content and the δ13C of Berberis buxifolia were determined, as well as the soil P and N content at the different sites. A negative correlation was found between species richness and Berberis buxifolia foliar P concentration (52% of the species richness variation was accounted for), and a positive correlation was found between plant species richness and Berberis buxifolia foliar N: P ratios (54% of the species richness variation was accounted for). The relationship between species richness and foliar P was seen when all layers of vegetation were included (trees, lianas, shrubs and herbs). Foliar N showed no correlation with species richness, while soil extractable NH4 showed a weak positive correlation with the number of shrub layer species (lianas, shrubs and trees). The species richness of the shrub layer increased with decreasing values of δ13C. Low soil P availability thus affects local species richness in the matorral shrub-lands of Patagonia in Argentina although the growth of vegetation in the area has been shown to be limited by N. We suggest that low P levels increase plant species richness because low soil P concentration is associated with a high P partitioning and high potential for niche separation.
Authors
Karl Hilding Thunes Fred Midtgaard Lawrence R. Kirkendall Oscar Leveron Vicente EspinoAbstract
Next to expansion of agricultural land and natural disasters, forest fires, illegal logging and bark beetles constitute the largest threat to the pine forests of Central America. Every year, 80-100.000 ha disappears due to the combined activity of the three factors. Natural disasters such as hurricanes and droughts, as well as poor forest management and wildfires lead to a stressed forest which in turn is advantageous for the increase in bark beetle population levels. Epidemic population levels of attacking beetles are able to kill large quantities of forests within weeks. Moreover, dead wood material acts as fuel for wildfires that have escaped control. We propose a monitoring and control regime which aims holistically and directly to the root causes of wildfires, bark beetle outbreaks and subsequent illegal logging in the pine forests of Central America. Monitoring activities focus on community participation and communication, while control of bark beetles is a combination of both long-term sustainable forest management procedures as well as direct and non-destructive control measures of the beetles to reduce their population levels to an endemic level.
Authors
Peder GjerdrumAbstract
Grain angle was observed on 178 discs equally spaced along each of 24 mostly quite large spruce stems, and a general model estimated for grain angle variation along the radial distance from pith. Due to the three-dimensional approach and the large-size stems, new variability was identified, as compared to traditional two-dimensional approach applied on moderate-sized stem discs. The model standard error was 2.3º; half of this variation can be attributed to combined stem and disc effects, and half to purely random variation. Standard error for the model estimated for individual discs was 1.6 º. Observed against the stem centroid, pith angle varies randomly with average close to zero and standard deviation 2.2º. The results should be applicable for wood quality modelling and for commercial sawn timber production.
Authors
Halvor Solheim Martti VuorinenAbstract
During a survey conducted in August 2009 in northern Norway, symptoms typical for red band needle blight (1) were observed in four young Scots pine (Pinus sylvestris) stands. The stands, less than 15 years old, were located in humid sites near rivers in Bardu and Målselv municipalities, Troms County. Many of the oldest needles (2- to 3- years-old) in the lower part of young trees were partially or completely brown, but still attached, and red bands could be observed. Aggregations of conidial stromata were often seen in the red bands. Conidia were hyaline, smooth, thin walled, and filiform, 1.9 to 2.6 μm wide and 12 to 36 μm long....