Influence of extractives on durability of Cupressus lusitanica heartwood
A Mohareb, P Sirmah, L Desharnais, S Dumarçay, M Pétrissans, P Gérardin
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 high amounts of benzaldehyde and numerous of terpenic compounds such as cedrol, agathadiol, epimanool, bornyl acetate, -cedrene and -cedrene. Effect of extractives on cypress natural durability has been investigated on wood blocks extracted or unextracted and then exposed to pure culture of Poria placenta in a laboratory test. Mass losses revealed severe degradation for the extracted specimens compared to a significant decay inhibition in the cypress control unextracted blocks.Efficacy of heartwood extractives on the growth of Poria placenta was evaluated. The results showed a strong inhibition of the fungal development. Heat treatment was investigated to improve cypress durability due to the conflicting literature reports describing the wood as resistant to non resistant to decay. Evaporation of the volatile extractives during the first stage of heat treatment caused a decrease of durability, while with a longer heating time, an increase of conferred durability was observed.
This study suggests that extractives content, which may be modified during drying processes or wood weathering, could be the origin of the conflicting data described in the literatures on cypress durability.