Compression wood in Scots pine and Norway spruce
Compression wood in Scots pine and Norway spruce
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发表时间：
2003-12
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通讯作者：
M. Warensjö
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作者：
M. Warensjö
本文总结和讨论了五项研究的结果：压缩木材的分布与外部干和原木几何形状的关系以及压缩木材分布对锯材变形的影响。此外，还讨论了树木的矫直过程。为了研究压缩木在树干和原木中的分布，将63棵代表不同年龄和曲率类别的挪威云杉和苏格兰松切成621个圆盘。为了研究压缩木材对锯材变形的影响，将146根苏格兰松和挪威云杉原木加工成钉和板条。横切前，评估股骨柄和原木的外部几何结构。使用3D-logscanner评估日志。在绿色条件下、在18%含水量下和在12%含水量下，测量螺柱和板条上的变形，例如弓形、弹簧和扭曲。利用透射光和图像分析法对圆盘、立柱和板条的薄横截面中的压缩木材含量进行了分析。分析表明，大多数的所有光盘和横截面包含压缩木材。在所有的研究中，髓心偏心率显着相关的光盘的压缩木材含量。对于6年生的苏格兰松树，压缩木材含量显着相关的大小，但不出圆度的基础扫描。对于22年生的苏格兰松树，压缩木含量与弓高或基部扫描尺寸均不相关。对于60年生挪威云杉，木材压缩量与原木端部压缩量、髓心偏心率和弓高显著相关。对于锯材，压缩木含量和压缩木位置与弯曲度和弹性显著相关，而与扭曲度不相关。扭转显着相关性，以粮食角测得的弦向面的螺柱和螺旋纹角下测量的树皮表面上的日志。结果表明，偏心生长和压缩木的形成在树干直度的形成中起主要作用。此外，随着时间的推移，具有基部扫掠的幼树将更直。因此，原木的平直度不是衡量树干中压缩木材含量的可靠指标。通过将描述外部几何形状的数据与从原木端部获得的关于压缩木材含量和髓心偏心率的信息相结合，可以检测易于包含压缩木材的原木。结果还表明，压缩木在锯材中的分布影响着弯曲和弹簧的方向和大小。
This thesis gives a summary and discussion of results from five studies concerned with: the distribution of compression wood in relation to external stem and log geometry and the impact of the compression wood distribution on deformations of sawn timber. Moreover the straightening process of trees is discussed. In order to study the distribution of compression wood in stems and logs, 63 trees of Norway spruce and Scots pine representing different age and curvature categories were sliced into 621 discs. In order to study the impact of compression wood on deformations of sawn timber, 146 logs of Scots pine and Norway spruce were processed into studs and battens. Before crosscutting, the external geometry of stems and logs were assessed. A 3D-logscanner was used for the assessment of logs. Deformations such as bow, spring and twist were measured on studs and battens at green condition, at 18% moisture content and at 12% moisture content. Compression wood content in thin cross sections of discs, studs and battens were analysed using transmitted light and image analysis. The analyses showed that a majority of all discs and cross sections contained compression wood. In all studies, the pith eccentricity was significantly correlated to the discs´ compression wood content. For the 6-year-old Scots pine trees, the compression wood content was significantly correlated to the size of basal sweep but not to out-of-roundness. For the 22-year-old Scots pine trees, the compression wood content was not correlated to either bow height or size of basal sweep. For the 60-year-old Norway spruce trees, the compression wood content was significantly correlated to compression wood content in log ends, pith eccentricity and bow height. For sawn timber, the compression wood content and its position was significantly correlated to bow and spring but not twist. Twist was significantly correlated to grain angle measured on tangential faces of studs and spiral grain angle measured under bark on the surface of logs. Results indicate that eccentric growth and compression wood formation play major roles in the development of stem straightness. Moreover, young trees with basal sweep will be straighter over time. Consequently, the straightness of a log is not a reliable measure of the compression wood content within the stem. By combining data describing external geometry with information regarding compression wood content and pith eccentricity obtained from log ends it is possible to detect logs that are prone to contain compression wood. The results also indicate that the distribution of compression wood in sawn timber influences the direction and size of bow and spring.