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| Titel |
Long-term behaviour of timber structures in torrent control |
| VerfasserIn |
Christian Rickli, Frank Graf |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089052
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| Publikation (Nr.) |
 EGU/EGU2014-3239.pdf |
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| Zusammenfassung |
| Timber is widely used for protection measures in torrent control. However, life
span of woody constructions such as timber check dams is limited due to fungal
decay. However, only sparse scientific information is available on the long-term
behaviour of timber structures and the colonisation with decay fungi. Related to this, in
practice a controversial discussion has been going on if either Norway Spruce (Picea
abies) or Silver Fir (Abies alba) is more enduring and if bark removal increases
resistance against fungal decay. In order to going into this matter a series of 15 timber
check dams built in 1996 has been monitored. The constructions were alternatively
realised with Norway Spruce and Silver Fir, half of them each with remaining and
removed bark, respectively. The scientific investigations included the documentation of
colonisation with rot fungi and the identification of decayed zones with a simple
practical approach as well as based on drilling resistance. Colonisation by decay fungi
started three years after construction (e.g. Gloeophyllum sepiarium), detecting two
years later first parts with reduced wood resistance. Sixteen years after construction
decay was found on all check dams but two. Wood quality was markedly better
in watered sections compared to the occasionally dry lateral abutment sections.
Taking the whole check dams into consideration, slightly more decay was detected in
Norway Spruce compared to logs in Silver Fir and both the practical approach
and the drilling resistance measurement yielded in more defects on logs without
bark. However, due to limited number of replications and fungal data, it was not
possible to statistically verify these results. Statistical analysis was restricted to the
drilling resistance data and fruit-bodies of decay fungi of the uppermost log of each
check dam. Based on this limited analysis significant differences in the effect on the
drilling resistance were found for watered sections and lateral abutments, brown
and white rot as well as fir with and without bark. Taking further into account that
brown rot reduces wood strength faster than white rot, it may be speculated that
spruce logs without bark and fir logs with bark are more resistant against fungal
decay compared to logs of spruce with and fir without bark, respectively. However,
this has to be treated with caution as only the uppermost logs were considered,
the observation period was only 15 years and the relative abundance of the most
important decay fungi considerably varied between as well as within the check
dams.
Consequently, for statistically sound and well-funded recommendations further
investigations over a longer period are indispensable. |
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