| 11. |
- Johansson, Marie, 1973-, et al.
(författare)
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Properties of materials from Birch – Variations and relationships : Part 2. Mechanical and physical properties
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Birch regarded as Sweden’s third largest tree species. The two birch species, Silver- and Downy birch represents about 12% of total Swedish timber volume. For forestry, birch an important tree species which today mainly used for the manufacture of pulp and paper.The aim of this project was to describe mechanical and physical properties of birch. The properties that have been studied are stiffness, bending strength, shrinkage, spiral gran angle, density and microfibril angle in the cell wall and vessel cells, from different parts of the birch stems grown at different rates. The mapped properties have been compared also with those of other tree species, mainly spruce. The long term aim is to increase the knowledge of the birch wood properties to provide better predict their impact on products as well as provide a basis for better utilization of Swedish birch raw material and hopefully using birch as future structural timber.Three birch stands with different growth was chosen: Two stands where the birch growth has been different in a mixed forests stand of spruce and pine, and a fast growing stand with improved birch seedlings. Samples were taken from four different heights in the trees. The main thing that has been analyzed is the bending strength, modulus of elasticity, shrinkage coefficients in different directions and spiral grain. The mechanical tests are carried out on tines that are 20 x 20 x 300 mm and the fiber angle measurements were carried out on discs. These results have supplemented by the results of analyzes conducted with lnnventias SilviScan instruments that are able to recognize variations of year ring wood properties. Some of these are density, and microfibril angle, which is also included in this report.The results show that the wood from normal growth and fast growth improved birch receive equivalent wood properties. The results also show that birch wood properties are slightly better than that in Norway spruce.The material in this project was limited to only three stands and 11 sampled trees and therefore it can´t provide complete answers to the birch trees different wood properties. Limitations include genetic origin, growth rate, earlier silvicultural treatment and number of sample trees.
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| 12. |
- Kliger, Robert, et al.
(författare)
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STUD: Improved Spruce Timber Utilizations : Prediction of Twist and Industrial Validation. Sub-task B9.1.
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- It has been shown that the number of straight battens after drying can be easily increased by avoiding converting logs with a somewhat large left-hand spiral grain measured under bark and by avoiding converting the central cylinder of logs with a diameter about 50 mm around the pith. It is assumed that more than 10% of the trees (Norway spruce) exceed a spiral grain angle of 3° measured under bark. Between 80% and 90% of the studs from these trees displayed an unacceptable amount of twist (3°). It should be of great interest for the sawmill industry to be able to reject logs with respect to their overly large spiral growth in order to improve the straightness of sawn lumber in service (at low moisture content).Other conclusion drawn from this study is that the spiral grain angle and the annual ring curvature of the stud can predict twist. If it is possible to measure effectively spiral grain angle on the logs or on the sawn timber prior to drying the twist-prone material would be possible to sort out and thus increase the value of the timber products. Simple models expressed in diagram form can produce enough information about twist to be a useful tool for improving the number of straight studs after drying.Over 90% of the studs sawn closer than 50 mm from the pith from five trees displayed unacceptable twist when dried to 12% moisture content. All the studs sawn from a tree (five logs) with a left-hand spiral grain of about 15° displayed very large twist after drying and they were all classified as rejects, independent of the grading criterion.
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| 13. |
- Malmqvist, Cecilia, 1965-, et al.
(författare)
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Differences in bud burst timing and bud freezing tolerance among interior and coastal seed sources of Douglas fir
- 2017
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Ingår i: Trees. - : Springer. - 0931-1890 .- 1432-2285. ; 31:6, s. 1987-1998
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Tidskriftsartikel (refereegranskat)abstract
- The need for species that will grow well through ongoing climate change has increased the interest in Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] in Sweden. One of the most common problems seen in plantations of Douglas fir seedlings is damage caused by late spring frost, known to be highly correlated with the timing of bud burst. The objective of this study was to investigate spring-related bud development under Nordic conditions of seven Douglas fir provenances and to compare data with a local provenance of Norway spruce (Picea abies (L.) Karst). Results from a field trial and a greenhouse-based study were compared. The interior Douglas fir provenances exhibited an earlier bud burst than coastal provenances, both in the greenhouse and in the field trial. When comparing differences within the groups of interior and coastal Douglas fir provenances, no differences could be found. The local Norway spruce, only grown in the greenhouse, showed an intermediate bud development profile similar to the interior Douglas fir provenance Three Valley. We therefore suggest that Three Valley could be planted at the same locations as the investigated local provenance of Norway spruce in mid-Sweden. To avoid spring frost damage the Douglas fir seedlings need to be frozen stored and planted late in spring. Planting under shelterwood can also help protect the seedlings from spring frost damages. As similar results for bud development patterns of Douglas fir and Norway spruce provenances were obtained from the greenhouse and field trials, greenhouse tests could facilitate selection of provenances.
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| 14. |
- Malmqvist, Cecilia, 1965-
(författare)
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Planting and survivability of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in Sweden : Questions of seedling storability, site preparation, bud burst timing and freezing tolerance
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The non-native Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) has been grown to a limited extent in the southern part of Sweden since the early 1900s. A more extensive use has probably been curtailed by its known susceptibility to damage by frost, pine weevil and other pests. Limited access to vital seedlings of suitable provenances has also restricted its more widespread growth. The need for valuable species that will grow well through ongoing climate change has increased the interest for Douglas fir in Sweden.This thesis addresses a number of important questions relating to the planting of Douglas fir in Sweden: seedling storability, freezing tolerance, timing of bud burst, frost damage and seedling response to site preparation. Seven Douglas fir provenances originating from British Columbia, Canada were used in the experiments and where applicable, compared with a local provenance of Norway spruce (Picea abies (L.) Karst.). The early bud burst of interior Douglas fir provenances, observed both in greenhouse tests and in the field, results in a high risk of damage by late spring frost. This type of damage does not seem, however, to be fatal and does not obviously retard the early growth of seedlings. The difference in growth between coastal and interior provenances was insignificant, but survival was greater for interior than for coastal provenances. All the provenances of Douglas fir studied showed a later development of freezing tolerance of shoots and roots in the autumn than Norway spruce, with the coastal provenances developing such tolerance even later than interior provenances. This could be a contributory cause for the severe damage by winter desiccation observed on seedlings of coastal origin. A thorough site preparation proved to be an effective way to increase survival and root growth. Interior provenances of Douglas fir became ready for storage earlier in autumn than coastal provenances. When freezing tolerance of shoots had increased sufficiently, Douglas fir seedlings could safely be kept in frozen storage using the same procedures used for Norway spruce. The results emphasise the need to gain further knowledge about how the remaining obstacles to establishment of Douglas fir could be reduced with different silviculture methods.
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| 15. |
- Nilsson, Börje, et al.
(författare)
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A method for under bark detection of the wood grain angle radial dependence
- 2007
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Ingår i: Wood Material Science and Engineering. - : Taylor & Francis. - 1748-0272. ; 2:3,4, s. 118-129
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Tidskriftsartikel (refereegranskat)abstract
- Twist in wood, being closely related to spiral grain, may cause serious problems in building structures, furniture, and joinery. It is therefore of great interest to sort out, at an early stage in the manufacturing process, trees, logs and boards that have an access of spiral grain. The spiral grain pattern is described by a helical deviation of the fibre direction in relation to the longitudinal direction of a living tree or a log and seems to be an indicator for other defects such as compression wood. Remote microwave sensing of spiral grain has received a large interest during the latest two decades. Its development has been impeded by the large variation with moisture content of the microwave properties of wood and by the complexity in modelling the electromagnetic field in a log with spiral grain. A review is presented of a direct method with no requirement of information on moisture content for boards. This procedure has recently been generalized to cylindrical logs and trees having a constant slope of the grain. A further generalization is presented here to allow for the normal spiral grain pattern with radially changing slope of grain in wood under bark. Based on this theory, a measurement procedure is proposed for the detection of wood grain angle with radial dependence, requiring no information on moisture content in the sapwood, also applicable for completely or partially frozen wood. A suitable application would be an instrument to use in the forest for measurements on living trees or logs.
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| 16. |
- Phiri, Darius, et al.
(författare)
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Biomass equations for selected drought-tolerant eucalypts in South Africa
- 2015
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Ingår i: Southern Forests, a journal of forest science. - : National Inquiry Services Center (NISC). - 2070-2620 .- 2070-2639. ; 77:4, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- In the water-scarce environment of South Africa, drought-tolerant eucalypt species have the potential to contribute to the timber and biomass resource. Biomass functions are a necessary prerequisite to predict yield and carbon sequestration. In this study preliminary biomass models for Eucalyptus cladocalyx, E. gomphocephala and E. grandis x E. camaldulensis from the dry West Coast of South Africa were developed. The study was based on 33 trees, which were destructively sampled for biomass components (branchwood, stems, bark and foliage). Simultaneous regression equations based on seemingly unrelated regression were fitted to estimate biomass while ensuring additivity. Models were of the classical allometric form, ln(Y) = a+x(1)ln(dbh)+x(2)ln(h), of which the best models explained between 70% and 98% of the variation of the predicted biomass quantities. A general model for the pooled data of all species showed a good fit as well as robust model behaviour. The average biomass proportions of the stemwood, bark, branches and foliage were 60%, 6%, 29% and 5%, respectively.
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| 17. |
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Silviculture Influence on Spiral Grain in Norway Spruce
- 1999
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Proceedings (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- In the present investigation a significant variation of spiral grain with annual ring number as well as with height in stem was observed. It was also observed that the spiral grain may be significantly different in stands with different site conditions and silvicultural treatment. It will however require further research to gain knowledge about to what extent differences in spiral grain in different stands are due to site conditions and to what extent they are due to silvicultural treatment. In addition to site conditions and silvicultural treatment the development of spiral grain may be affected by the genetics of the trees.
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| 18. |
- Säll, Harald, et al.
(författare)
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Bending strength and stiffness of aspen sawn timber
- 2007
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Ingår i: Quality Control for Wood and Wood Products. - : COST, Warsaw. ; , s. 6-
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Konferensbidrag (refereegranskat)abstract
- In order to investigate the possibility of using sawn timber of European aspen (Populus tremula L.) as a structural material, 150 pieces of the dimension 45 x 120 mm2 were selected from a sawmill in the south of Sweden. The material was visually strength graded using the Nordic standard INSTA 142 and the British standard BS 4978-1996, respectively. The timber pieces were also subjected to flat-wise bending in a Cook-Bolinder Ò strength grading machine. Finally all specimens were tested in edge-wise bending according to the European testing standard EN 408. Global and local moduli of elasticity as well as bending strength were determined. The results indicate that the visual grading rules, intended for use on Norway spruce and Scots pine, seem to work fairly well on European aspen. However, grading in a flat-wise bending machine like the Cook-Bolinder seems to give a lower correlation between stiffness and strength for aspen timber than generally found for coniferous. Further, the correlation between density and bending strength was found to be very low for the aspen timber tested. It was also noticed that the aspen timber has a slightly higher bending strength and modulus of elasticity than is the case for normal qualities of Norway spruce. The study indicates that sawn timber of European aspen grown in southern Sweden can be visually graded and used as structural material.
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| 19. |
- Säll, Harald, et al.
(författare)
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Bending strength and stiffness of aspen sawn timber
- 2007
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Ingår i: COST Action E53 The First Conference: Quality Control for Wood and Wood Products.. - : Warsaw University of Life Sciences.
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Konferensbidrag (refereegranskat)
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| 20. |
- Säll, Harald, et al.
(författare)
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Masurbjörk
- 2008
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Bok (populärvet., debatt m.m.)abstract
- Detta häfte är en introduktion till dig som är intresserad av att ekonomiskt utveckla ditt skogsbruk genom odling och användning av masurbjörk, Skandinaviens värdefullaste trädslag. Vi vill här kort ge dig grundfakta så att du kan förstå den ekonomiska möjlighet som odling av klonade masurbjörk för med sig, också i ditt skogsbruk.
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