Current issue: 58(5)
Articles containing the keyword 'growth rings'
Category : Article
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.
-
Kärkkäinen,
E-mail:
mk@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.
-
Kärkkäinen,
E-mail:
mk@mm.unknown
- Dumell, E-mail: od@mm.unknown
Eighty Betula nana samples were collected from three swamp sites. In the butt portion of the dwarf shrub the average number of growth rings was 12 and the average diameter of the sprouts 6 mm. The basic density of wood was 457 kg/m3 and that of bark 544 kg/m3. The proportion of bark was 32–38% of weight or volume. The vessel elements and fibres were short and their diameter small. The proportion of vessels was 15%, that of fibres 70% and that of rays 15%.
The PDF includes a summary in Finnish.
-
Bhat,
E-mail:
kb@mm.unknown
- Kärkkäinen, E-mail: mk@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.
-
Ollinmaa,
E-mail:
po@mm.unknown
A picture of growth rings of a tree can be obtained on paper by placing it over a disc of a trunk or stump and rubbing it with a pencil. The ‘shadows’, while not yielding the complex data obtainable from the actual wood, do show the proportion of the growth rings composed of spring wood and the denser summer wood. It is possible to collect large amount of data by using an unexperienced staff cheaply and quickly, and the samples may be mailed at little expense. The method may be used to study the previous cuttings of a stand from stumps. The shadowing of tree rings is possible to do even from rather decayed stumps.
The article includes a Finnish abstract.
-
Rogers,
E-mail:
mr@mm.unknown
