FAIR-CT97-3606 Stresses in beech

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FAIR Area 1.3 - Forestry-Wood Chain : Solid Wood Products : Wood (Lignocellulose)

	Contract No:	FAIR-CT97-3606
	Date Prepared:	June 2000
	Source:	Second Annual Progress Report

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Second Annual Progress Report Abstract

Objectives

The aim of this project is to improve the utilisation of beech wood which can be significantly devalued due to the natural occurrence of two kinds of stresses: Residual (internal) growth stresses in standing trees and drying stresses in products derived from them.

To achieve this goal, the project has the following objectives:

• To assess the occurrence and the technical and economic impact of stresses in Beech at a European level through enquiries and expert-interviews. Similarly, to identify existing methods of handling stress-related problems at a silviculture and industrial level,
• To develop a better understanding of the development of internal growth stresses during the formation of wood, by considering possible cause-effect relationships with stand and individual tree growth characteristics.
• Based on 2, to develop predictive (in the short term) methodology and preventive (in the long term) silvicultural strategies aiming to minimise the occurrence of residual growth stresses in high value standing beech trees.
• To minimise or even to eliminate the negative impact of stresses during the various steps of processing by developing adequate processing/treatment methodology at laboratory and industrial scale.
• Based on the above, to compile an overall evaluation of the impact of stresses on the utilisation of high value beech timber and suggest solutions to minimise this impact both at silvicultural and processing, industrial level.
• To communicate the results and conclusions to the relevant forestry and industrial sectors and seek their feedback and comments.

Activities

A comprehensive questionnaire concerning the relevance of stresses in beech has been distributed and answered by forest industry and wood industry experts from all participating countries. On the basis of the results of this questionnaire, a preliminary hypothesis could be developed and a detailed empirical design was implemented. A total of ten different beech wood stands have been selected by the project partners in France, Denmark, Austria, Switzerland and Germany. In every country two stands were selected: One stand represents the classical silvicultural treatment of a high forest. These stands have been selected and harvested in first year of the project. The second set of stands has been chosen to represent typical silvicultural practice in each participating country. Hence, in this way the various silvicultural practices are reflected in the sample material. These stands had been harvested during the second year of the project. Because of the heavy storms in December 1999, the second stand in Denmark was no longer available. To compensate for this, a third stand which reflected a similar silvicultural treatment as it had been planned for Denmark, has been harvested in Germany during the second face. The German partner also took over all the remaining duties of Denmark for the third project year.

Within every stand 50 trees were selected as sample trees. A comprehensive set of parameters which are believed to influence growth stresses in beech have been measured on the stand level as well as on the tree level, among these are tree shape, crown enlargement, stem quality, neighbouring trees etc. In addition other characteristics of all stands were notified. Stress measurements had been made on all of those trees.

From these 50 trees per stand, ten trees were selected for industrial and laboratory evaluation. So at the end of year two the project, a total of 60 trees has been harvested and samples for industrial measurements have been taken and transferred to the labs where the respective analysis and evaluation were carried out. Also logs from all these sample trees have been transported to the participating industries: saw milling, rotary veneer and sliced veneer. The logs are processed and converted into the respective products. Output characteristics as well as quality of the projects have been measured and evaluated following both scientific and industry standards. Parallel to this work in the participating industries, the part of the laboratory analysis has been carried out in the participating labs. Imported wood properties related or influenced by stresses are measured for instance ring-width, density, rigidity, locked in strains, shrinkage, tension wood etc. The data are all collected in a common data-bank and have been transferred and exchanged between the partners. First statistical analysis has been carried out, or complex analysis and statistical evaluation are part of the future work in year three of the project.

Progress

A questionnaire was addressed to forest enterprises and wood processing enterprises all over Europe inquiring about the relevance of stresses in beech. Almost 1200 questionnaires have been sent out to enterprise in Germany, France, Austria, Switzerland and Denmark. Almost 510 enterprises responded to the questionnaire.

As already done within the first project year, in the second year of the project 250 trees have again been selected out of five stands in Austria, Switzerland, France, while this was done twice in Germany. Full trees descriptions as well as stress measurements have been carried out. Out of this 250 trees bottom logs of 50 trees have been selected for the industrial and the laboratory evaluation. From 5 trees a second log was also taken, so that a total of 60 logs have been processed. 20 logs have been used to produce sliced veneer in a German factory, from 20 logs rotary cut veneer was produced in France and 20 logs were used to produce sawn products in Switzerland. Samples for laboratory evaluation have been cut from all 60 logs. At present the samples are drying to avoid deformation. Discs for year ring measurements have been taken to be analysed in Freiburg. The various laboratory analysis of these samples are still running in the participating laboratories. Over all a total of 500 trees have been measured in field tests. 120 logs, formed out of 100 sample trees have been processed in industrial tests. Sample sticks were formed from 120 logs and laboratory testing of these samples is still running.

Achievements

Corresponding to the working plan:

• after two years of the project, task 1 is finished as planed. The report about this task 1 is available.
• all other milestones of the year 1 and 2 of the project are fulfilled.
• the sampling (task 2) of the material is also finished and the processing is mostly done.
• the laboratory testing is still running, the data from these measurements will be available as planned this autumn.
• first data and experiences about the different ways of processing the stress containing beech wood is still under analysis as is the testing of the wood product quality.

Future activities

The overall industrial and laboratory evaluation will be continued after the processing in industry and the laboratory measurements are executed. At the workshop meeting in Zurich (in September 2000) the first results of the evaluation of laboratory and processing data were discussed and further evaluations planned.