Abstract
Genetic variation of ten Norway spruce (Picea abies (L.) Karst.) clones regarding their decay resistance against brown rot fungi, as well as physical and chemical properties of clones were investigated. 31- year-old spruce clones: 26, 31, A10, A15, A7, B10, B15, B6, V7, V9 were selected across Latvia. The stem diameters of spruce clones varied between 13.0 and 20.9 cm. The wood density of clones ranged from 361 to 443 kg/m3. Klason lignin content, depending on the clone, was between 27.0%-28.9%. Cellular UV microspectrophotometry of the non-infected tracheids displayed the typical lignin distribution with highest absorbance values in the cell corners (abs280 nm 0.80) and compound middle lamellae (abs280 nm 0.48), while secondary wall showed lower lignin absorbance values (abs280 nm0.29 - 0.35). The deposition of phenolic extractives in ray parenchyma and epithelial cells of resin canals were emphasized by a significantly higher UV-absorbance (abs280 nm 0.68 to 0.78) when compared to the cell wall associated lignin. The content of acetone-soluble extractives of spruce clones varied between 1.1% - 1.8%. The x-value (natural durability) for all spruce clones after exposure to C. puteana and P. placentawas >0.90 (durability class 5, not durable). Most of clones after degradation by G. trabeum had x-value > 0.90 with exception of clones B15 and V9 that showed x-value ≤ 0.90 (durability class 4, slightly durable). Natural durability of spruce clones did not correlate with stem diameter, density, content of lignin and extractives.
Highlights
The end use of timber in exterior or interior constructions is determined by its natural durability i.e. inherent resistance to fungal degradation
Genetic variation of ten Norway spruce (Picea abies (L.) Karst.) clones regarding their decay resistance against brown rot fungi, as well as physical and chemical properties of clones were investigated. 31year-old spruce clones: 26, 31, A10, A15, A7, B10, B15, B6, V7, V9 were selected across Latvia
Natural durability of spruce clones did not correlate with stem diameter, density, content of lignin and extractives
Summary
The end use of timber in exterior or interior constructions is determined by its natural durability i.e. inherent resistance to fungal degradation. Brown rot fungi are generally considered the most important rot type for wood in service. They cause an extensive degradation of holocellulose in wood, whilst the lignin fraction is mainly demethylated and depolymerised [1,2,3,4]. It has been reported that the natural durability of wood is affected by the density and content of extractives. It was found [6] that oak heartwood with the narrowest growth rings and lower density was more susceptible to fungal decay than denser wood made of wider growth rings. The concentration of stilbenes improved decay resistance of Scots pine heartwood [10] while no detectable amounts of stilbenes were found in the heartwood of spruce [11]
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