Dear,
I observed a darker zone in ring shape in some of my 6-year-old Eucalyptus wood samples grown in Brazil for pulp and paper industry. Then, I observed an intense shrinkage at the lateral of the specimen. We can visualize the pores in the normal zone, but in the (supposed to be ) collapsed zone, it is not possible to see any pore. Could you try to explain which factors could play a role on the development of this kind of drying defect appearing in ring? Please, find enclosed a picture with two samples presenting the same problem. Thanks in advance! Paulo Hein (DCF-UFLA, Brazil)
Hi,
that's probably tension wood. Collapses and high shrinkage appears in tension wood.
Does the dark ring is continuous around the section ?
Dear Paulo,
I don’t have a huge experiences with Eucalyptus wood, unfortunately in Poland it is too cold for this specimen, but I think that the observed darker zone in annual ring with an intense shrinkage is a reaction wood (in angiosperms called tension wood). The narrow falciform zone with tension wood is typical in fast growing wood (trees) e.g. European poplar. This is reaction on growth conditions: wind, gravity. The anatomy and physical and mechanical properties of tension wood are different than normal wood e.g. large thickness of wood cells and bigger shrinkage.
Best regards
Paweł Kozakiewicz
Hello, I also do not have experience of Eucalyptus, but it does look like tension wood seen in many trees.
Thanks for your replies. I agree with you, these samples present tension wood and collapse. However, the question remains: which factors possibly played a role on the development of this phenomenon appearing in ring?
Initial moisture content
Drying temperature
and the rate of your temperature increase (schedule)
Hello,
Possibly this is an area of lower or higher concentration of dry matter (this can be confirmed by a test of specific mass this part) and possibly due to the high rate of drying has occurred an shrinkage in the ring which is not accompanied by the rest of wood (other rings) causing collapse. One could try a slower drying and parceled.
Regards.
We recently published a paper with some images of what sounds similar collapse prone wood. We have been trying to develop an NIR=based method for detecting regions of non-recoverable collapse in eucalypts associated with tension wood.
Previous work by Washusen et al suggesting that open grown trees will have less tension wood, as it seems to be attributable to a slenderness issue. fast growth and high stocking results in more slender trees prone to wind sway, triggering tension wood. Open grown trees tend to be able to put on more diameter as opposed to tension wood. I am sure there is more to it, and having a method for detecting TW across a radius should assist in exploring cause and effect more precisely.
I am currently working on a data set that examines thinning treatments in E.globulus on the non-recoverable collapse indicator we defined in the recent paper in Eur. j Wood Prod.
http://link.springer.com/article/10.1007/s00107-014-0813-9#page-1
You might also find the report by Washusen 2013 helpful. It is not published in the peer-reviewed literature
http://www.fwpa.com.au/rd-and-e/processing/174-processing-methods-for-production-of-solid-wood-products-from-plantation-grown-eucalyptus-species-of-importance-to-australia.html
Hello,
I think that's tension wood. In evergreen hardwoods such as Eucalyptus, tension wood can be seen through the growth rings.
Although I am not very familiar with Eucalyptus, answering your question: the collapse might be caused by tension wood (therefore the question, is this phenomenom seen through the whole ring or only partly?) since tension wood is more vurnerable for collapse. If so, due to drying stresses this collapse occured.
o Differential shrinkage: the shell dries faster than the core, thus the shell has tension and the core compression. When the shell dries permanently stretched the core will be prevented from normal shrinkage. Thereby, the core has tension and the shell has compression.
The ring might be located between the strechted surface/shell and the tensioned core. This sounds the most logic to me.
Hi.
It seems to be resin pockets that appears as a result of stress or responses of the tree to injury to the stem.
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