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Study on the production potential for high-quality spruce wood in the forests of the Jura Arc

Updated: Dec 9, 2023





WHFF Project: 2016.05

Authors: Sylvain Jacot, forest engineer HES (field surveys) , Fabien Langenegger, Laboratoire de dendrochronologie de Neuchâtel (dendrochronological analyses) and Prof. Dr. Ernst Zürcher.

Coordination: François Godi


The short video about the project on YouTube can be watched at the following link (only available in French): https://youtu.be/JgZX6WGBZYk


The most important facts in brief

  • The production potential of high-quality spruce wood for use as tonewood in the forests of the Jura Arc was investigated.

  • The production potential of high-quality spruce wood in the Jura Arc exceeds the expected quantities with a production potential of about 5,500 m3/year of quality class A, of which more than 600 m3/year can be utilized as sound wood.

  • The forest stands of the Jura heights already offer potential for high-quality wood, especially resonance wood, at an altitude between 800m and 1400m.

  • The dendrochronological, physical and mechanical analyses of the samples taken confirm the exceptional quality of the spruces of the Jura arc

  • Simple visual and technical criteria to distinguish high quality lumber from resonance wood have been developed.


Project description

After the southern side of the Alps, the Jura Arc is the most densely forested region in Switzerland. Almost half of the Jura Arc (48%) is covered with forest.

High-quality spruce wood and especially clay wood are assortments with the potential to offer significant added value to the members of an organized value chain from producer to end user. This study is important for the valorization of wood from the Jura Arc, since 3% of the spruce logs used are A-quality and 1% are resonance wood, while the latter assortments in the form of logs already exceed the turnover of a much larger quantity of A-quality wood.

To contribute to a better utilization of high-grade spruce wood and to promote quality-oriented forest management, the project had the following objectives:

  • Determine the production potential of high-quality spruce wood.

  • To establish the relationship between site and silvicultural characteristics and the properties and qualities of the wood,

  • to establish simple visual and technical criteria to distinguish between high quality sawn timber and

  • resonance wood.

To determine the production potential of category A spruce lumber, visual methods were used to evaluate logs from cuts harvested at elevations greater than 1000 m, with slopes less than 15°, tree heights greater than 25 m, and karst or marl geology.

For the analysis, the "most beautiful spruce" was selected in each logging and analyzed based on the following criteria: Branch freedom for at least 5 m, straightness of the stem, and a minimum diameter of 50 cm. If the quality was the same, the tree with the largest diameter was selected.

The influence of growth conditions such as altitude, exposure, temperature level, slope, soil surface, etc. on wood characteristics was analyzed to show possible correlations. These analyses aim to complement the very general rules formulated by practitioners with a scientific basis.



Conclusions

The forest areas of the Jura heights offer their potential for high-quality wood, especially resonance wood, already at an altitude between 800m and 1400m. However, the influence of altitude on density is only weakly evident in the tested materials.

The most common local slopes characterizing the location of the selected trees are between 10 and 40%. This puts into perspective the rule that high quality wood (especially resonant wood) would grow especially on locally flat topographies.

In addition, the study shows that high quality wood is supplied by relatively large trees. Other parameters do not appear to have a significant effect on classification as resonance wood.


The project's method for visually identifying category A trees and criteria for classifying logs as resonance wood, high-grade wood, and joinery wood can help distinguish high-grade lumber from resonance wood.



Download the full report here:

2016.05
.pdf
Download PDF • 10.91MB

You can find more information about the project on ARAMIS.




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