Current issue: 58(5)
Articles containing the keyword 'puuaine'
Category : Article
Ring width at breast height is presented as a function of stem radius at breast height, the ratio between the diameter of a tree and the basal area median diameter, site index, and density of stand. By means of a conversion model ring width at stump height can be estimated as a function of ring width at breast height.
According to previous studies substantially better wood quality can be expected if mean width near the pith at stump height decreases from 3 to 2 mm. According to the present study only on the poorest sites suitable for Scots pine (Pinus sylvestris L.) planting (poor Vaccinium type) the ring width is less than 3 mm at stump height even in the thickest trees. On more fertile sites a substantial increase in the recommended planting density is required, if the mean ring width is aimed to be less than 3 mm. On the best sites it is impossible to reach mean ring width of less than 2 mm, when the density is less than 4,000 stems/ha. Only the thinnest trees on the poorest sites can have a mean ring width less than 2mm.
The PDF includes an abstract in English.
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Varmola,
E-mail:
mv@mm.unknown
Properties of fibres in pulpwood, especially length, width and the thickness of walls in tracheids, are essential for strength properties of pulp and paper. Length and width of tracheids increase from pith to surface in radial direction. Young and small-sized stems have also smaller fibres. Small-sized Pinus sylvestris L. test trees had tracheids that were shorter both in stems and knot wood than those in normal sized trees. However, cell walls in test trees were as thick as in normal sized trees. It seems that especially the L/T -ratio (length/thickness) in small stems is worse than in normal sized pulp wood.
The PDF includes an abstract in English.
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Laurila,
E-mail:
rl@mm.unknown
In laboratory studies the heartwood content seems to be the only natural property of a wood of different tree species influencing the decay resistance. Moistening and drying by diffusion happen quite slowly. Scots pine (Pinus sylvestris L.) sapwood takes moisture by capillary action quicker than pine heartwood and Norway spruce (Picea abies (L.) H. Karst.) wood. Swelling and shrinkage are also greatest in pine sapwood. Impregnation of pine sapwood can give it better hydrophobic and dimensional stability than that of pine heartwood.
The PDF includes an abstract in English.
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Kärenlampi,
E-mail:
pk@mm.unknown
The basic density of the wood of the rowan tree (Sorbus aucuparia L.) is almost the same along the stem but that of the bark is increasing along the stem. The moisture content of the wood and of the bark is increasing along the stem. Its strength in the bending and in the compression is high. The volume shrinkage is high.
The PDF includes an abstract in Finnish
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Maasalo,
E-mail:
km@mm.unknown
The purpose of the study was to determine the effects of the origin of seeds and the location of cultivation of Scots pine (Pinus sylvestris L.) on certain properties particularly important to the pulp industry. The research material consisted of six parallel trials of the same 12 provenances. Increment cores were taken of a total of 1,267 sample trees, 19 years old. The location of the trial site generally affected the properties to a larger extent than the origin of the seed. The effect of the variation of wood density and fibre yield on the cultivation values of the provenances was only a few percentages on average, however, at most the effect was nearly 10%. Eastern Finnish provenances adapted well to western Finnish conditions.
The PDF includes an abstract in Finnish and French.
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Velling,
E-mail:
pv@mm.unknown
- Nepveu, E-mail: gn@mm.unknown
The aim of this literature review was to compare Finnish Norway spruce (Picea abies (L.) H. Karst.) sawn goods to Central European spruce sawn goods which contain fir in some amount. However, it was found that no statistically valid comparisons have been made. Therefore, conclusions have been based mainly on the relationship between various properties and growth rate. According to this analysis, most properties of Finnish spruce are better, although small in practice.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
Variation in tracheid morphology were examined for the bole wood of lodgepole pine (Pinus contorta Douglas ex Loudon) grown in Southern and Central Finland. Tracheid lengths were examined in a fast-grown and in slow-grown trees from three stands. Tracheid length increased with increasing height to 4–8 metres and decreased after that, and increased also with increasing age from the pith. The variation between stems was high. The shortest tracheids were about 1.11 mm near the piths and the longest about 4.10 mm near the bark.
Tracheid diameter and cell wall thickness were measured for the total number of 16 stems from Southern and Central Finland. Tracheid diameter increased with increasing distance from pith and the largest tracheids were at a height of 4–8 metres. Cell wall thickness varied independently of height in the stem. Summerwood cell wall thickness was twice that of springwood. There was a difference of 0.6 μm in springwood and 1.0 μm in summerwood double cell wall thickness between the two stands. Cell wall percentage was 29±4.7 in springwood and 69±7.3 in summerwood.
The PDF includes a summary in English.
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Saranpää,
E-mail:
ps@mm.unknown
Basic density and absorbed energy in impact bending were measured for 500 Norway spruce (Picea abies (L.) H. Karst.) samples from Northern and Southern Finland. Statistical analysis showed that the relationship between impact strength and basic density was significant and regression analysis showed that it was linear.
Furthermore, with constant density, the impact strength was higher in Northern than in Southern Finland. This was due to growth ring width: i.e. when density was kept constant the impact strength increased with decreasing growth ring width. In addition, when the growth ring width was kept constant, the basic density of wood was higher in Southern Finland than in Northern Finland.
The PDF includes a summary in English.
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Saranpää,
E-mail:
ps@mm.unknown
In order to evaluate the strength properties of boards made from small and large Norway spruce (Picea abies) butt logs, 15 small (top end diameter 13 cm) and 15 large (top end diameter 25 cm) logs were sampled from a sawmill in Finland. From each log two test pieces were made in order to measure the bending and compression strength, dry density and average ring width.
The boards from small logs were stronger and their density higher. When the differences between groups were analysed it was found that the strength was determined by the density and ring width. When the density was kept constant, the increase in ring width had a decreasing effect on the strength properties. Because there was a negative correlation between ring width and density, ring width alone had a great effect on the strength properties.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Hakala, E-mail: hh@mm.unknown
A population consisting of 450 Norway spruce (Picea abies (L.) H. Karst.) samples was gathered from northern and southern Finnish wood. The static bending strength was affected greatly by the density of the wood. However, keeping the density constant, the bending strength was higher in northern than in southern Finnish wood. The reason was the effect of the growth ring width.
The basic density was affected by the growth rate. Keeping the growth ring width constant, the basic density was over 5 kg/m3 lower in northern than in southern Finnish wood. This result supports the earlier findings on the effect of latitude.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
- Dumell, E-mail: od@mm.unknown
The objective of the investigation was to determine the differences between timber grown on a peatland before and after draining, in respect of compressive strength parallel to the grain, static bending strength and density. In addition, the characteristics of boundary zone between the wood formed before, and after the draining with wider growth rings was studied. 41 Scots pine (Pinus sylvestris L.) and 22 Norway spruce (Picea abies (L.) H. Karst.) trees were studied.
The compressive strength of pine usually decreased from the butt end upwards, but no trend was observed in spruce wood. In coniferous trees, wide-ringed wood formed subsequent to draining was slightly lighter than the close-ringed wood produced prior the draining. The density of pine as well as spruce increases as the width of the growth rings decrease up to a certain limit. The strength of the different kinds of wood seems to decrease from the butt end upwards.
In both species, the compressive strength parallel to the grain and the bending strength are lowest in such wood that contains exclusively wide-ringed wood formed subsequent to draining. Also, compressive and bending strength increase with decreasing width of the growth rings. The longitudinal shrinkage of compression wood in spruce was several times that of normal wood, and the bending strength was lower than that of normal wood particularly in spruce. The compressive strength parallel to the grain in dry condition was, however, higher than in normal wood both in pine and spruce.
The PDF includes a summary in English.
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Ollinmaa,
E-mail:
po@mm.unknown
According to the available literature, the appearance of Parana pine (Araucaria angustifolia (Bertol.) Kuntze) wood resembles that of Scots pine (Pinus sylvestris L.). The anatomy is quite different, however. There are no resin canals and fusiform rays with resin canals in Parana pine. They are abundant in Scots pine, however. The basic density of Parana pine is higher. In both species the density increases from the pith outwards, the maximum being reached at the age of 100 years. Compression wood is more common in Parana pine than in Scots pine, and this makes the longitudinal shrinkage of Parana pine greater than that of Scots pine. Otherwise the shrinkage properties do not differ. The mechanical strength is of the same magnitude with the exception of hardness, where Parana pine is superior.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
In this study the width and height of 1,588 uniseriate and 454 fusiform rays were measured from tangential sections of four Scots pine (Pinus sylvestris L.) trunks. The samples represented various height levels and distances from the pith. The average width of the uniseriate rays was 19.7 μm and that of the fusiform rays, 51.9 μm. The average height of the uniseriate rays was 215.7 μm and that of the fusiform rays 406.2 μm. Due to this difference in height, it may be possible to develop an automatic system for distinguishing between uniseriate end fusiform rays on the basis of their height.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
The material consists of four Scots pine (Pinus sylvestris L.) stems from which 757 samples were taken from various heights and distances from the pith. According to the results, the number of rays and their sizes are greater at the stump level than higher up in the stem. The size increases, and the number decreases on moving from the pith outwards. However, there are differences between stems as regards the variation model. The ratio between the number of fusiform rays and that of uniseriate rays seems to be lower than anticipated earlier, about 1:40–1:50. The average proportion of ray volume varied from 5.6% to 7.3%.
The PDF includes a summary in English.
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Kärkkäinen,
E-mail:
mk@mm.unknown
Category : Article
The objective of the investigation was to determine the differences between faultless timber grown on a peatland before and after draining, in respect of compressive strength to the grain, volume weight, and shrinkage. In addition, the influence of the boundary zone between the close-ringed wood formed before draining and the wide-ringed wood produced after draining on strength of the timber was studied. The material consisted of 15 sample trees of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), white birch (Betula pubescens Ehrh.) and silver birch (B. Pendula Roth).
The volume weight of wood of the tree species in ascending order is; spruce, pine, white birch, silver birch. The volume weight of Scots pine seems to decrease from the butt end upwards, while no trend was revealed for spruce. In the coniferous trees, the wide-ringed wood formed subsequent to draining was slightly lighter than the close-ringed wood produced prior draining. No distinct trend was seen in the birch species. The volume weight of pine and spruce increased with decreasing width of the growth rings up to a certain limit, after which the conditions inverted.
The compressive strength of the different kinds of wood seems to increase from the butt end upwards, but after height of two meters it begins to decrease considerably. In birch, this point of inversion is in somewhat greater height. In spruce timber, the compressive strength parallel to the grain is lowest for wood which contains exclusively wide-ringed wood formed after draining. The boundary zone between the woods formed before and after draining is very distinguishable, but has no remarkable influence on the compressive strength parallel to the grain. Shrinkage of close-ringed wood is higher in all three principal directions than that of wide-ringed wood. This can be explained by the variations in volume weight and fibrillar orientation of the tracheid walls.
The PDF includes a summary in English.
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Ollinmaa,
E-mail:
po@mm.unknown
The article reviews the change in how the most sufficient wood material was chosen for different uses. The craftsmen used different characteristics to determine the quality of wood, for instance, tree species, location in the stem, whether it was sapwood or heartwood etc. Scientifically, the quality of the wood has been described by, for instance, specific gravity, bending strength and compressive strength. Durability would, however, be better attribute than strength to describe the quality of wood, because circumstances, like humidity and temperature can change where the wood is used. The article discusses further the development of durability indexes.
The PDF includes a summary in German.
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Lassila,
E-mail:
il@mm.unknown
The growth of a tree is influenced by inherited properties and external circumstances, including climate, soil, the position of the tree in the stand, and the position of the wood in the stem. The tree species have optimum climate and optimum conditions. The aim of this study was to determine if the summerwood content of the wood of Scots pine (Pinus sylvestris L.) is dependent on the rate of growth of the tree. Comparing the position of the sample trees in the stand, it seems that the position of the tree and the size of its crown influences strongly the quality of the wood. In a dense stand the summerwood content was higher in the trees that had small crowns. Thinning of the stand decreased the difference in summerwood content of the trees.
The PDF includes a summary in English.
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Jalava,
E-mail:
mj@mm.unknown
Earlier research has presented contradictory results of the influence of forest site type on the weight of wood. In this study, dominant trees of Scots pine (Pinus sylvestris L.) was chosen as sample trees on four forest site types: Calluna, Vaccinium, Myrtillus and Oxalis site types. The trees were felled in autumn, when the water content of the wood is low. Weight of the test samples was measured weigh before and after drying. Undried wood, both sapwood and heartwood, is heavier in Myrtillus type than in Vaccinium type. The weight of the air-dried heartwood did not differ between the two forest site types. Air-dried- sapwood was heaviest in Myrtillus site type. Air-dried heartwood was heaviest in Vaccinium site type, and lightest in Oxalis type. Owen-dried sapwood was heaviest in Calluna site type, where the tree growth is slow, but weight differences were small in owen-dried heartwood. It can be claimed that forest type affects wood quality.
The PDF includes a summary in English.
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Lassila,
E-mail:
il@mm.unknown
The article includes a detailed review on the technical properties of wood. The weight, water content, strength and conductivity of the wood, and the factors affecting them are discussed. The mechanical and technical properties of wood are influenced, for instance, by tree species, age and part of the tree, geographical situation, site and growth conditions of the stand, anatomical structure of the wood, and temperature. The author summarizes the topics where further research should be addressed. For instance, the forest site types developed in Finland could be utilized in studies of the mechanic technical properties of wood.
The PDF includes a summary in English.
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Lassila,
E-mail:
il@mm.unknown
