Shape and distribution of knots in a sample of picea abies logs

Abstract

In an attempt to develop a better understanding of the effect of knottiness on the yield of logs for sawn timber products, the present study examines the position and geometrical characteristics of 429 knots found in seven Norway spruce (Picea abies (L.) Karst) middle logs from southern Finland. The raw data used in this study were in the form of coordinates of points located on the knot surface recorded in a cylindrical (R, L, T) reference frame. The data were smoothed using a non linear three-dimensional model. A curvature analysis of the knot pith was used to differentiate the curved and straight portions of the knots. This analysis made possible calculation of knot angles, symmetry, ovality and volume. The major finding of this study is the uneven distribution of knots around the log circumference. Nearly 50% of the total knot volume was concentrated in one-third of the log facing the south-east. Knots were also more prominent in higher portions of the logs studied. These observations support the argument that the uneven distribution of knots offers potential for improving the grade yield of timber sawn from trees harvested in high-latitude countries.

Variation in knot size of Pinus sylvestris in two initial spacing trials

“…These methods are time consuming (Oja 1997), but provide a means of directly observing quality traits within stems (such as knots) while also recognising the dynamic development of trees. Data obtained through application of such methods have been used to study geometric knot structure and past branch dynamics (Dietrich 1973, Kershaw et al 1990, Maguire and Hann 1990, Björklund 1997, Lemieux et al 1997. However, the impact of site and silviculture on knot structure is not directly analysed in these studies.…”

Modelling knot morphology as a function of external tree and branch attributes

“…One advantage of our models is the flexibility of the equations, which allow a representation of many possible knot shapes using only five parameters. Previously published knot models were generally based on polynomial equations or on segmented linear equations (Lemieux et al 1997a), but such models do not allow for the interpretation of the parameters. Trincado and Burkart (2008) developed a system of equations for loblolly pine based on nonlinear functions, but these models were developed for young trees in fast-growing plantations, which exhibit very little knot curvature.…”

“…Previous studies by Samson (1993) and Lemieux et al (1997a) reported some ovality in knot cross sections in black spruce, with the vertical diameter approximately 10% to 15% greater than the horizontal diameter. However, because external branch diameter was only recorded in the vertical direction, we chose to model the knot profile along the same axis.…”

Tracking rameal traces in sessile oak trunks with X-ray computer tomography: biological bases, preliminary results and perspectives

“…Trunk dissections were mainly carried out in the radial-longitudinal plane (Grah 1961;Dietrich 1973;Vestol et al 1999;Benjamin et al 2009;Kershaw et al 2009). Lemieux et al (1997aLemieux et al ( , 1997bLemieux et al ( , 2001 adopted the methodology of peeling and automatic knot reconstruction. Several studies focused on the effect of pruning on wood quality.…”