Effect of extractives on conferred and natural durability of Cupressus lusitanica heartwood

Abstract

Abstract• Identification of extractives present in Cupressus lusitanica heartwood has been conducted using GC-MS analyses. The chromatogram of toluene/ethanol extracts indicated the presence of large amounts of benzaldehyde and numerous terpenic compounds such as cedrol, agathadiol, epimanool, bornyl acetate, α-cedrene and β-cedrene.• The effect of these extractives on the natural durability of cypress wood was investigated on heart wood blocks exposed to pure culture of Poria placenta before or after solvent extraction. Weight losses revealed severe fungal degradations on the extracted blocks compared to unextracted ones.• Efficiency of heartwood extractives as inhibitors of the growth of Poria placenta on malt/agar test confirms their contribution to cypress natural durability.• Cypress blocks were treated at 240 • C for different times to reach different levels of thermodegradation to evaluate effect of heat treatment on fungal durability. Results indicate that evaporation of volatile extractives during the first few minutes of heat treatment contribute to decreased wood durability, while longer treatment times lead to the expected improvement of durability.• This study suggests that the content of extractives, which may be modified during wood drying or weathering processes, could be the origin of the conflicting data described in the literature concerning cypress natural durability. Mots-clés :Cupressus lusitanica / durabilité / extractibles / traitement thermique / pourriture Résumé -Effet des extractibles sur la durabilité naturelle du duramen de cyprès.• Les extractibles présents dans le duramen de Cupressus lusitanica ont été analysés par GC-MS. Le chromatogramme des extraits obtenus à l'aide d'un mélange toluène/éthanol met en évidence des quantités importantes de benzaldéhyde et de nombreux composés terpéniques comme le cédrol, l'agathadiol, l'épimanool, l'acétate de bornyl, l'α-cédrène et le β-cédrène.• L'effet des extractibles sur la durabilité naturelle du cyprès a été évalué à l'aide d'essais réalisés sur des blocs préalablement extraits ou non puis exposés à Poria placenta. Les pertes de masse mettent en évidence une dégradation importante des échantillons extraits comparativement aux témoins non extraits.• L'efficacité des extractibles comme inhibiteur de croissance de Poria placenta a été évaluée. Les résultats indiquent une forte inhibition du développement fongique.• Des blocs de cyprès ont été traités à 240 • C pendant des temps variables pour atteindre différents niveaux de thermo-dégradation. L'évaporation des extractibles volatils durant la première phase du traitement thermique conduit à une diminution de la durabilité du bois aux agents de pourriture, alors que des traitements plus longs conduisent à l'augmentation de durabilité attendue.• Cette étude suggère que la teneur en extractibles, susceptible de varier suite au séchage ou aux intempéries, peut être à l'origine des observations contradictoires rapportées dans la littérature concernant la durabilité naturelle du cyprès.

Genetic variation of natural durability traits in Eucalyptus cladocalyx (sugar gum)

“…Toxic polyphenolic extractives act as chemical barriers (e.g. Mohareb et al 2010) and tyloses act as physical barriers limiting access to the transpiration system (Beckman 2000). The amount of extractives has been shown to be correlated with decay resistance in both softwoods (e.g.…”

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

“…Pinus patula is a common wood species in the Kenyan forest plantations and has a significant share among the most important industrial softwood species used for timber production in this country (Venkatasamy 2006;Mburu et al 2007;Mohareb et al 2010). Because of the poor durability of this wood species and analogous to numerous studies carried out in the last ten years on heat treatment to improve decay durability of low natural durability wood species (Mburu et al 2007;Welzbacher and Rapp 2007;Calonego et al 2010;Mohareb et al 2010;Yilgör and Nami Kartal 2010), it appears of interest to evaluate the effect of heat treatment on Pinus patula durability.…”

“…Because of the poor durability of this wood species and analogous to numerous studies carried out in the last ten years on heat treatment to improve decay durability of low natural durability wood species (Mburu et al 2007;Welzbacher and Rapp 2007;Calonego et al 2010;Mohareb et al 2010;Yilgör and Nami Kartal 2010), it appears of interest to evaluate the effect of heat treatment on Pinus patula durability. The aim of this study is to investigate the improvement of Pinus patula durability generated by a heat treatment for development of its uses in Kenya and increasing its service life.…”

Chemical Composition and Resistance to Decay of Thermally Modified Wood from Casuarina glauca and Eucalyptus camaldulensis Grown in Egypt

“…In general, the temperature and duration for heat treatment vary from 180 to 280ºC for 15 min to 24h depending on the heat treatment process, wood species, sample size, moisture content of the sample, the desired mechanical properties, resistance to biological attack and dimensional stability of the final product (Hakkou et al, 2005 andMouras et al, 2002). In this context, the literatures pointed out that temperature has a greater influence than time on many properties including the biological resistance against fungal decay (Brito et al, 2008 andMohareb et al, 2010). In addition, the change in properties is mainly caused by thermic degradation of hemicelluloses.…”