Forestry Commission logo

Commissioned Reports - Quality


Date: 2006
Title: Non-destructive evaluation of Scots pine (Pinus sylvestris L.) to determine timber quality following conversion to continuous cover forestry systems
Authors: David Auty
Full Report: PDF


Date: 2005
Title: Wood Quality Modelling (213021, 213022)
Authors: Report commissioned from BRE
Full Report: Awaiting electronic version

Summary
This project aimed to:

  1. Assess the methodology and silvicultural strategies aimed at minimising the occurrence and the severity of compression wood in high value softwood stands by characterising and validating the quality of the timber originating from different sites in terms of log assessment (visual and by 3D scanning at the sawmill).
  2. Assess quantitatively the impact of compression wood on micro-structural, physical and mechanical properties on well defined smallsamples.
  3. Minimise the negative impact of compression wood during the various steps of processing by developing adequate processing/ treatment methodology at industrial scale (drying schedules, product finishing).
  4. Develop new methods for identifying the presence of compression wood in saw logs and “green” sawn timber.

Based on the above, to compile an overall evaluation of the impact of compression wood on the utilisation of softwood timber and suggest solutions to minimise this impact both at silvicultural and processing, industrial level. To incorporate the effect of compression wood into existing wood-quality models developed in the STUD project.


Date: 2005
Title: The implications of transformation to continuous cover forestry systems for conifer timber quality and log supply in the UK
Authors: Elspeth Macdonald and Barry Gardiner
Full Report: PDF


Date: 2004
Title: EU Compression Wood (QLK5-CT-2001-00177) (213023)
Authors: Report commissioned from BRE
Full Report: PDF

Summary
This is the final report for the following project, entitled: "Wood characteristics - The influence of compression wood on timber quality". The project aim is to achieve a greater understanding of the influence of compression wood on timber quality.


Date: 2004
Title: The influence of compression wood on timber quality (218309)
Authors: Report commissioned from BRE
Full Report: PDF
Interim Report: PDF

Summary
The project aim is to achieve a greater understanding of the influence of compression wood on timber quality.

Work on determining compression wood properties and in evaluating in-line 3D log sorting for compression wood has gone very well – yielding useful results. Compression wood was found to have little effect on the stiffness of the full scale battens studied and therefore should not be a significant variable in the model to predict machine grade output (Indicating Property). In small clear samples (300mm x 20 x 20) a trend for decreasing stiffness with increasing amounts of compression wood was observed. Compression wood was found to occur in straight, round logs – often leading to serious distortion because the compression wood was consistently along the edge or side of a batten.  Log ovality was not found to be a good indicator of the likelihood of compression wood being present in battens.

Modelling work for machine grading stiffness (low mean IP) showed good results for 100 x 47mm size battens, but was less successful for 150 x 47mm battens. The most successful combined site model for 100 x 47mm battens explained 56% of the variance, however it was found that for differing sites and sizes of timber (ie different parts of the tree) there were differing significant variables both positive and negative. Modelling work did not have a high level of success in predicting distortion in bow and spring because it is simply not possible to determine with any certainty the extent and nature of compression wood below the surface, without cross cutting into sections. Because of the generally lower level of compression wood and bow and spring in the FR1,2,3 and 4 sets of timber and the fact that that detailed STUD data already existed, the models were re-worked using compression wood variables alone.

The rate of prediction is described as successful by the modeller; however they account for only 40% of the variance. Based on longitudinal shrinkage of small scale samples of normal wood and compression wood it was possible to calculate the maximum bow and spring of full scale battens. Investigations into the potential of image analysis, laser tracheid effect  and X rays to identify compression wood in battens have been carried out, but these methods are not capable of resolving below the surface details.

Preliminary recommendations for dealing with compression wood have been formulated. In general it is recommended that compression wood rich material should be ear-marked for applications where it will not be allowed to dry out unrestrained, or where it is well-restrained in service e.g. timber frame. Generally, compression wood in large sizes of timber such as joists will have a more serious effect than on shorter, smaller sections such as timber frame studding and one solution might be to cut down 200mm joists into 100mm studding on indications of high compression wood content. This will, however, require an advanced scanner to be placed in-line. It is important to realise that the opportunity for close inspection of battens probably only currently occurs during grading and that if re-sizing is performed the material will have to be graded once more.  The particular need to effectively deal with compression wood in laminated re-engineered timber products has been highlighted.


Date: 2002
Title: The Effect of Windblow on Timber Quality in Sitka spruce
Authors: Shaun Mochan
Full Report: PDF


Date: 2000
Title: The influence of the site factor wind exposure on wood quality
Authors: Franka Bruchert
Full Report: PDF