| 1. |
- Eklund, Leif, et al.
(författare)
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Enhanced growth and ethylene increases spiral grain formationin Picea abies and Abies balsamea trees
- 2003
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Ingår i: Trees. - : Springer. - 0931-1890 .- 1432-2285. ; 17:1, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- Spiral grain angle in Norway spruce (Piceaabies) trees and balsam fir (Abies balsamea) seedlingswas investigated in relation to growth rate, endogenousand applied ethylene. Trees from stands of Norwayspruce, which were irrigated and fertilised in order to enhancegrowth, and trees having different growth rates innon-treated stands were studied. Stem growth rate at thestand level (m3 ha–1 year–1) was measured annually, orby means of microscopy on stem sections as the numberand size of tracheids produced. Enhanced growth increasedethylene evolution and maintained a high levelof left-handed spiral grain angle in comparison to slower-growing trees. An increased number of earlywoodtracheids in fast growing trees was correlated to a moreleft-handed spiral grain angle. Ethrel, applied to stems ofbalsam fir seedlings, increased the internal ethylene levelsin parallel with increased left-handed spiral grain angle.The results indicate that ethylene regulates the extentof spiral grain angle.
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| 2. |
- Eklund, Leif, et al.
(författare)
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Spiral grain from an environmental, genetic and economical point of view
- 2000
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Ingår i: The Tree.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Characteristic of wood is that its behavior is strongly orthotropic due to the internal structure of the material and dependent on moisture and temperature. In addition, the material is characterized by a strong variation of the properties in the radial direction. Another important property that affects the behavior of wood is spiral grain, causing the direction of the fibers to deviate from the longitudinal direction of the tree. It is hardly possible to assess spiral grain in the woods, no rejection of severe spiraled trees are done before the log arrives into the sawmill. If a method for on site rejection is available, and the severest spiraled trees, 2-10%, could be avoided in the shipment to the sawmill substantial money could be saved in the forest industry. The causes of spiral grain have been thoroughly discussed through the years and the debate about the environmental and genetic impact on the phenomenon is still not settled. We present evidence for a direct effect of wind on the degree of spiral grain. We also present evidence for a putative thinning effect on spiral grain that is probably connected to wind. Additionally we also present evidence for a strong genetic impact on the formation of spiral grain in conifer trees. In another study mechanical properties such as shape stability has been investigated for the same trees. In some of the logs it may therefore be possible to quantify the relation between spiral grain and distortion in sawn timber.
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| 3. |
- Eklund, Leif, et al.
(författare)
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The influence of wind on spiral grain formation in conifer trees
- 2000
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Ingår i: Trees. - : Springer. - 0931-1890 .- 1432-2285. ; 14, s. 324-328
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Tidskriftsartikel (refereegranskat)abstract
- The correlation between spiral grain formationand crown asymmetry was investigated in 18 Scots pine(Pinus sylvestris L.) and 17 Norway spruce [Picea abies(L.) Karst.] trees selected from clones of each speciesgrowing in the south of Sweden. The angle between thelongitudinal direction of the tracheids in the outermostyear ring compared to the longitudinal direction of thestem was measured by scribing lines which followed thedirection of the tracheids. The crown asymmetry wasmeasured by taking photographs of the trees followed bya simple picture analysis of the tree. Wind data for thegrowing seasons of 1997 and 1998 were obtained fromthe Swedish Meteorological and Hydrological Institute.The results showed a significant correlation between theangle of the tracheids compared to the stem longitudinaldirection going from a left-handed angle if the trees hada crown projected to the north towards a right-handedangle the more the crown projects to the south.
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| 4. |
- Gjerdrum, Peder, et al.
(författare)
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Spiral grain in Norway spruce : constant change in grain angle in Scandinavian sawlogs
- 2002
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Ingår i: Forestry (London). - : Oxford University Press. - 0015-752X .- 1464-3626. ; 75:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- Any evident grain deviation will reduce strength and increase warp in sawn timber. To describe the magnitude and variance of grain angle in Norway spruce, specimens from 1046 Norwegian sawlogs and 380 logs from Sweden and Finland were examined. For individual specimens, grain angle outside the innermost zone closest to the pith might be expressed by a simple linear function of radial distance from the pith. The intercept and inclination of this function are close to bivariate normally distributed with mean values (SD) of 2.7° mm−1 (1.9) and −0.039° mm−1 (0.037), respectively. Inclination is less negative for wider annual rings (r = 0.3), and intercept and inclination are negatively correlated (r = −0.4). The constant rate of change indicates inherited property rather than influence of any dynamic, external stimulus. No predictor for grain angle pattern was found. The linear model leads to simplifications both when observing the grain angle in the forestry, and in calculations of strength properties and distortion in the timber industry.
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| 5. |
- Hannrup, Björn, et al.
(författare)
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Genetic parameters for spiral grain in Scots pine and Norway spruce
- 2003
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Ingår i: Silvae Genetica. - 0037-5349. ; 52:5-6, s. 215-220
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Tidskriftsartikel (refereegranskat)abstract
- Genetic parameters were estimated for grain angle, growth and exterior quality traits in two 18-year-old Scots pine (Pinus sylvestris L.) progeny trials and for grain angle and growth traits in two 12-year-old clonal trials of Norway spruce (Picea abies L. Karst.). Mean grain angles ranged 1.4 to 2.0 degrees and 2.1 to 2.6 degrees in the Scots pine and Norway spruce trials, respectively. Heritabilities for grain angle were high in Scots pine (h2>0.40) and moderate in Norway spruce (H2>0.30). The genetic standard deviations were around or slightly below one degree. In general, grain angle was genetically and phenotypically uncorrelated with the growth and exterior quality traits. All traits showed low amount of genotype by environment interaction and there was no tendency of grain angle being a more stable traits than the other traits studied. A newly developed measurement device for grain angle where the grain angle is revealed by a wedge that is pushed through the bark into the wood and follows the inclination of the tracheids was tested and found suitable for measurements in genetic tests.
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| 6. |
- 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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| 7. |
- Säll, Harald
(författare)
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Spiral Grain in Norway Spruce
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wood is a major construction material that is used in many contexts, and for different purposes. Serious problems may arise, however, when moisture related deformations as twist occur in wood used in different types of building structures, joinery and furniture. Twist can be explained to a great degree by the helical deviation of the grain angle in relation to the longitudinal direction of the log or the sawn board. Wood fibres form a spiral within the tree, and this is a natural occurrence that is named spiral grain. The wood fibres close to the pith in Norway spruce form a left-handed spiral. In most trees the grain angle turns over to be right-handed with time. Sawn timber that exhibits large grain angles lead to problems of shape stability and stiffness in finished constructions. In this thesis the spiral grain in Norway spruce (Picea abies (L.) Karst.) was stated as well as the effect on sawn timber.The material was based on sample trees from Sweden and Finland. Samples were taken in twenty-two stands at different heights in tree. From six stands studs were sawn and dried for measuring twist and other deformations. The spiral grain was measured with the method scribe test on 390 log discs taken at the top-end of the logs. Account was given concerning changes in grain angle from pith to bark, regarding both increasing annual ring numbers and distance from pith. The development of grain angle over tree age was utilized to study whether annual growth, size of tree, height in tree as well as silvicultural treatments affected spiral grain. Moreover, the relation between grain angle and distance to pith (in mm) was used to forecast twist in sawn timber.The left-handed grain angle was at its greatest between the fourth and eighth annual rings. Thereafter for most trees the grain angle turned from left-handed to right-handed in a linear fashion, in a manner that was unique for each individual tree. The pattern of spiral grain differed significantly between different stands, regarding change of inclination with increasing age or distance from pith. The culmination of the grain angle close to the pith occurred at somewhat higher age higher up in the trunk. The grain angle decreased faster in top logs than it did in the butt logs. The largest trees within a stand had a grain angle that turned to right in a slower way than smaller ones. The thinning strength and type of thinning regime also affected the character of spiral grain in the remaining trees in a stand. There was an indication that strong thinnings, where fast growing trees are retained, may lead to more individuals in a stand that exhibit high grain angles under bark.With knowledge of the size and direction of the grain angle under bark, and the diameter of the log, calculations can be made that show how twisted the sawn timber will be after drying. This can be used for deciding whether an individual log can profitably be sawn and processed further or not. The grain angle under bark can be used to remove trees showing the greatest degree of spiral grain already in the first thinning. Silvicultural methods aiming at even and dense Norway spruce stands, which normally is practised in Scandinavia, will probably result in timber with relatively low risk concerning large grain angle and subsequent risk for twist in sawn wood.
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