Shelf Life, The No.1 Question
By 250 News
UNBC Researcher Kathy Lewis says her study of standing Mountain Pine Beetle killed trees indicates the worst damage happens within two years after death, then the wood stabilizes
How long will the fibre last? That is the number one mountain pine beetle attack question facing the region on an economic basis. Researchers looked at the quality of the wood, related to the time of death and the moisture content.
There is no clear answer. It looks like the shelf life is longer than expected as the majority of damage happens within two years of the trees death.
Kelly Lewis from UNBC says her study ( available on the CFS mountain pine beetle initiative website ) looked at tree stands throughout the Prince George region and measured
- Moisture
- density,
- penetration of blue stain
- depth of checks (cracks)
- depth of fungi
- Wood borer damage.
Their report shows the rate of fall was relatively low five years after the tree had died. “the rate of fall down of mountain pine beetle trees was less than one quarter of a percent in the stands we studied” says Lewis.
She also found:
· Most changes will happen within first 1-2 years following death.
· Response is difference depending on height of tree.
The mid section of the tree (1.5 meters) has the most checks but she raised a concern about the impact logging these trees and storing them in a horizontal position will have on the quality of the logs. “If the trees are only being stored for a couple of days, fine, but any length of time and those checks allow more concern for the entry of moisture and increased cracking.”
The second study was determining shelf life for the pulp industry. Barbara Dalpke of Paprican Research says her research indicated there was no influence of “time since death” on fibre length, and fibre properties, but there was a small influence on coarseness and there was a drop in wood moisture. However she says the study used a small sample, and further work needs to be done.
Next steps will see the Canadian Forest Service collect data to build some predictive models so no matter what the intended application for the wood, a prediction for shelf life can be made. Studies are also showing that larger trees are checking more, so companies wanting to get more lumber out of a larger tree may not get what they want.
There is now a suggestion that rather than look at time since death, the moisture content of the tree is a more likely indicator of shelf life as the reduction in moisture means more checks as the tree dries out, and that moisture content will vary because of things like location or amount of intense sunlight.
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