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.
2008
Sammendrag
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.
Forfattere
Peder Gjerdrum Olav Albert HøibøSammendrag
A huge effort has been put into modelling wood quality the last few decades. Predicting knot size has been the centre of interest, either for timber quality, for tree growth models, or related purposes. The main objective of this paper is to analyse the stochastic features connected to knot distribution inside the three-dimensional volume of a tree\"s trunk. Four large Alpine spruce trees were sampled; age 150 years, DBH 30 to 70 cm, total volume 14.5 m3. To open a possibly large part of the stems, they were cross-cut to 31 logs and sawn to 193 unedged boards. On each unique board surface all perceptible knots were observed and localised in polar coordinates; origin in the stem base, along the pith and in the north direction. A total of 6200 knot intersections were observed in the 283 m2 sawn surfaces; however, most knots were observed several times in consecutive sawn surfaces. In order to obtain stationary variable, knot size was transformed by dividing by the square root of radial distance, and radial distance was transformed by dividing by log radius at the given location. Relative size, knot quality and spatial distribution were largely random and not correlated to each other in a tree. Thus, knots demonstrate a double nature, one part obeying the physiological laws, and another part stochastic.
Forfattere
Peder Gjerdrum Mauro BernabeiSammendrag
The grain direction along an arbitrary radius is known to change at a constant rate during the life-span of a tree. A wide variety of professions involve in analysing and understanding GA, included searching new technology for automated detection and significance for wood application. The objective of the study presented in this paper has been to identify a joint, three-dimensional model for grain angle in stems of Norway spruce. Five possibly large spruce trees, DBH at least 40 cm and height ca. 30 m, were sampled near Ås, Norway. 10 cm thick transverse discs were extracted at intervals of ca 5 m along the stem, split through the pith along the north-south diameter with a blunt knife, and grain angle and cambial age observed at regular intervals of 15 mm along the north radius. Pith observation was set to zero; left-handed (clock-wise) angles were denoted as positive, and vice versa. A The grain direction along an arbitrary radius is known to change at a constant rate during the life-span of a tree. A wide variety of professions involve in analysing and understanding GA, included searching new technology for automated detection and significance for wood application...
Sammendrag
The variations on the ratio of filling (RoF) were investigated on Norwegian grown Scots pine (Pinus sylvestris). The samples were taken from 10 different stands in south-east Norway, and treated with furfuryl alcohol and a copper-containing wood preservative. Both within tree variations, between tree variations and variations between stands were investigated for significant differences. Factors like horizontal and vertical positioning of the stem, annual ring width, density, tree height, tree age and latitude were tested. Samples of 20 x 20 x 60 mm were impregnated with a mild treatment scheme to avoid full penetration, which made it possible to distinguish the RoF. A significant variation was found between copper impregnated a furfuryl treated samples, favouring the copper impregnated samples. Within tree variations show a positive significance of the first log compared to the other logs, and a higher RoF in younger sapwood. The latitude of the stand gave a strong correlation, favouring southern stands.
Sammendrag
An easier penetrability and a more even uptake of wood protection agents is aimed for the two most common wood species in Europe, namely Norway spruce (Picea abies) and Scots pine heartwood (Pinus sylvestris), particularly when there is a great difference in absorption behavior of sapwood and heartwood. Microwave conditioning can improve permeability, reduce density and heat conductivity and change dimensional stability of wood. It could also improve the permeability of refractory wood species. This study deals with the evaluation of different parameters of a microwave treatment and their influence on the penetrability of water during dipping and impregnation of Scots pine heartwood and Norway spruce. Microwave irradiation lead to an increased water uptake after a submersion test, and after vacuum and pressure impregnation of the tested samples. This effect was more pronounced for Scots pine heartwood samples than for spruce wood samples. A short process with high microwave energy is recommended in order to reduce the development of large cracks but to increase the sorption behavior due to small checks in wood.
Forfattere
Peder GjerdrumSammendrag
Pine (Pinus sylvestris) heartwood and pine sapwood can, in several respects, be considered two different timber products. Sapwood demonstrates open structures that easily adsorb moisture and is vulnerable to bio-chemical disintegration, but also more easily painted, glued or impregnated. Heartwood, on the other hand, is less disposed to moisture fluctuations, hence, more dimensionally stable, and durable. Heartwood content is closely related to cambial age and to the progress of annual ring width. It is also the nature of pine is to grow timber of quite varying quality along the stem. Resins are more abundant near the base, and the knottiness is shifting, following certain patterns from the base upwards. Several of those traits can be identified prior to breakdown, applying specific wood technology knowledge, recent research and standard log scanner equipment. Even with this potential for producing more homogeneous board quality by including heartwood in the breakdown decision basis, one should not forget the practical implications for the sawmill. The cost of keeping separate heartwood quality classes and the risk of mistakes might easily exceed the price gain.
Forfattere
Silja Korhonen-Sande Erlend NybakkSammendrag
No abstract has been registered
Sammendrag
Runoff time series are known to contain long term structures on interannual to decadal time scales. Investigating spatial patterns of long term structures is a way to elucidate the relationship between external forcings and watershed properties. This would be a valuable contribution to an improved water resources management. Singular System Analysis (SSA) is a powerful technique to identify and extract significant long term components from time series. However, many observations from natural systems are prone to missing data that hamper many analysis techniques, including the SSA in its original formulation...
Forfattere
Per Otto FlæteSammendrag
The use of traditional preservative treated wood has been highly restricted in recent years, and there is a need to find environmental benign alternatives. Utilisation of naturally durable wood is commonly proposed as an alternative for wood used in above ground applications. Traditionally, heartwood of Scots pine (Pinus sylvestris L.) has been used in constructions prone to biological degradation. However, when utilising the heartwood for solid wood products, one has to consider that the stemwood of Scots pine also comprises non-durable sapwood, and that the heartwood varies with respect to decay resistance. The purpose of this thesis was to study techniques for improved utilisation of natural durability, with special focus on Scots pine heartwood. A study was conducted aiming to describe the variation of heartwood diameter in mature Scots pine...
Sammendrag
Many time series analysis methods depend on equally spaced observations with no data point missing. If this condition is met, powerful techniques are available that identify temporal structures such as trends or periodic phenomena or nonlinear dynamics. Unfortunately, most of observations of natural systems, in particular over longer periods of time such as decades, are prone to sampling errors leading to missing points in the observations. Singular System Analysis (SSA) is a powerful tool to extract the dynamics contained in time series at arbitrary temporal scales...