Measurement of surface growth stress in Eucalyptus nitens Maiden by splitting a log along its axis

Abstract

When a log is sawn along the length, an outward bending or deflection of two half rounds arises from the release of growth stresses in the log. The relationship between this outward bending and the peripheral longitudinal growth strain in logs from a 10-year-old Eucalyptus nitens plantation was investigated. In total, 63 trees were felled and two logs (one bottom and an upper log) were cut from each felled tree. A strong association was observed between the measured longitudinal growth strain and the outward bending produced by splitting the log along its axis. A mathematical model was developed that enables calculation of the relationship between the surface axial growth stress and the opening of the split log. This involves calculation of the lateral deflection of a tapered cantilever beam of semi-circular cross-section under a known bending moment. The relationship between the opening of the slit log and the surface axial stress showed good agreement with the measured data on 126 logs. The model equation is effective in predicting the growth stress from the magnitude of the log distortion. This log sawing or splitting method is quick and reliable for assessing the surface growth stresses in small diameter trees. It could have potential in breeding programs for identifying families or clones for low-growth stresses of superior eucalypts for sawn timber production.

Early genetic evaluation of morphology and some wood properties of Tectona grandis L. clones

“…Longitudinal growth strain was measured on the second log using the procedure described by CHAUHAN and ENTWISTLE (2010). The log was cut longitudinally along the centre-line, from end to end (Figure 1c) using a band saw.…”

“…Weight and volume were determined for this sample using the water displacement method specified by standard ASTM D-2395-02 (ASTM, 2003a). Longitudinal growth strain was measured on the second log using the procedure described by CHAUHAN and ENTWISTLE (2010). The log was cut longitudinally along the centre-line, from end to end (Figure 1c) using a band saw.…”

Heritability of growth strain in Eucalyptus bosistoana: a Bayesian approach with left-censored data§

“…Growth strain was measured using a modified version of the Chauhan and Entwistle (2010) and Entwistle et al (2014) log-splitting methods. The newly developed "rapid splitting test" substantially reduces measurement time, enabling larger numbers of samples to be processed.…”

“…The newly developed "rapid splitting test" substantially reduces measurement time, enabling larger numbers of samples to be processed. The modified method involves stripping the bark and measuring the under-bark largeend diameter of a clear section of the stem, giving an overestimate of the average diameter used by Chauhan and Entwistle (2010). The sample is then cut lengthwise, with the slit length determined by the length of clear wood and diameter of the sample.…”

“…The University of Canterbury has developed and implemented a rapid growth strain-testing procedure, based on the work by Chauhan and Entwistle (2010) and Entwistle et al (2014). In order to minimise the time taken to measure the growth strain on each tree, the rapid-testing procedure does not account for negative values, where the wood in the centre of the stem is under tension rather than compression, assigning instead a zero that results in left-censored data sets.…”