Siberian larch (Larix sibirica Ledeb.) has been cultivated in Northern Europe, i.e. outside its natural range of distribution since 1738 (Redgo and Mälkönen 2001). Currently there are plenty of planted larch stands in Finland and Sweden and even in Iceland. This introduced species has proved to be well adapting and promising with regard to production of good quality timber. Most of these stands are still young and thus, sawn larch timber is imported from Russia for building purposes.
The natural durability of larch heartwood is a well-known feature from the past history and a great number of studies. The naturally durable heartwood of larch is one economically viable option to substitute chemically impregnated timber.
Natural durability of heartwood depends on its extractive composition. Studies have illustrated the role of phenolic taxifolin in providing the decay resistance of larch heartwood while the most abundant extractives, water soluble arabinogalactans have no effect (Venäläinen et al. 2006). There is wide variation in decay resistance between individual trees similar with many other growth and quality traits. The variation rises partly from the genetic differences (Venäläinen et al. 2001) and partly from the effect of the growth environment. There is also a common speculation that trees growing in their natural distribution area wouldbe better regarding quality characteristics, including decay resistance, than trees introduced and cultivated outside the range.
The aim of this study was to compare the durability of Siberian larch timber imported from natural stands from Siberia and timber harvested from cultivated stands in Finland. The comparison was carried out as a long-term ground contact test according to standard EN 252.
Keywords: Phenol-formaldehyde resin, dimensional stability, birch wood
Authors
Martti Venäläinen
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