Variabilité de la résistance à la dégradation du bois de mélèze par les champignons

Abstract

Abstract• Decay resistance of larch (Larix sp.) to fungi was evaluated on heartwood samples belonging to 3 species (L. decidua, L. kaempferi and their hybrid), 3 races of European larch (polonica, sudetica and alpine), 13 wood lots (populations) and 313 trees.• Larch wood appeared, on average, as moderately durable although a high variability was observed. At the sample level as well as at the mean individual tree level, durability ranged from class 1 to 5 according to EN 350-1 standard. At the population level, larch wood varied from 'durable' to 'slightly durable'. Genetics played a major role in decay resistance at the species, provenance and tree levels. Environmental factors such as the position of heartwood samples and the age of trees were also identified as a source of variability.• The most durable wood was not necessarily from old native alpine stands of European larch: some young larches from faster growing lowland origins also produced durable wood.• Genetic improvement of larch wood durability appeared therefore likely by the selection of the best populations for decay resistance as well as from the selection of individuals. Mots-clés :durabilité naturelle / champignon / Larix / génétique / effet environnemental Résumé -Variabilité de la résistance à la dégradation du bois de mélèze par les champignons.• La résistance à la dégradation du bois de duramen du mélèze (Larix sp.) est évaluée à partir d'un échantillon d'éprouvettes extraites de 313 arbres appartenant à 3 espèces (L. decidua, L. kaempferi et leur hybride), 3 races de mélèze européen (polonica, sudetica et alpine) et 13 lots différents.• Le bois de mélèze apparaît, en moyenne, comme 'modérément durable', mais une grande variabilité due à plusieurs facteurs a été observée. Au niveau arbres et échantillons, la durabilité naturelle s'étend de la classe 1 à 5 suivant la norme EN 350-1. Suivant les origines, le bois de mélèze peut être classé comme 'durable' à 'faiblement durable'. Les facteurs génétiques jouent un rôle significatif sur la résistance à la dégradation du bois aux niveaux espèce, provenance et arbre. Des facteurs environnementaux tels que la position des échantillons au sein du duramen et l'âge des arbres ont également été mis en évidence.• Le bois à plus forte durabilité ne provient pas exclusivement des vieux peuplements naturels de mé-lèze alpin : certaines origines de mélèze cultivées à basse altitude et constituées d'arbres plus jeunes et à croissance rapide peuvent aussi produire du bois durable.• L'amélioration génétique de la durabilité naturelle du mélèze apparaît donc comme envisageable au travers de la sélection des meilleures populations et des meilleurs individus.

Perspectives for genetic improvement in heartwood size and extractive content in relation to natural durability and aesthetics in interspecific hybrid larch (Larix × eurolepis)

“…Many recent results support this assumption; several authors have indeed observed significant differences in extractive content and in particular in total phenolic compounds in wood of conifers between decay-resistant and susceptible trees Harju et al 2003 in Scots pine; Windeisen et al 2002 in hybrid larch; Venäläinen et al 2006 in Siberian larch). In addition, the higher decay resistance of outer heartwood compared to inner heartwood within a tree (Curnel et al 2008) can also be directly related to its higher extractives content Gierlinger and Wimmer 2004). In a coherent way, highly negative phenotypic correlations between mass loss in durability test and extractives content have been found for Scots pine (Venäläinen et al 2004) and especially for larch: by Gierlinger et al (2004b) for Larix decidua (r = -0.63 to -0.84) and for L. kaempferi (r = -0.87 to -0.88), by Windeisen et al 2002 for the hybrid L. 9 eurolepis (r = -0.77 to -0.80) and by Venäläinen et al (2006) for See description of traits codes in Table 1 Eur J Forest Res L. sibirica (r = -0.68).…”

“…Indeed, larch heartwood is classified as 'moderately durable' according to European standard NF EN 350-2. A large variability has been shown between species, populations and trees within populations with wood samples ranging from 'non-durable' to 'very durable' (Gambetta et al 2004, Curnel et al 2008). In addition, a strong link was found between total extractives, in particular total phenol content, and natural wood durability (Windeisen et al 2002;Gierlinger et al 2004b;Venäläinen et al 2004).…”

Influence of Norway Spruce and European Larch Heartwood Ring-Width on Extractive Content and Durability

“…Besides wood quality, it seems obvious that the longevity of these constructions also relies on a high ancestral level of building expertise. Furthermore, the apparent natural durability and longevity qualities of larch wood do not seem to be expressed in the same way outside its distribution within the Alps (Curnel et al, 2008). Consequently, larch from the warmer, more fertile regions of the lowlandssometimes performs considerably worse than larch from the Alps.…”

“…Consequently, larch from the warmer, more fertile regions of the lowlandssometimes performs considerably worse than larch from the Alps. However, some of the authors reported, that durable larch wood can be found even in the lowland plantations in Eastern Europe (Curnel et al, 2008).…”

Ageing and Deterioration of Materials in the Environment – Application of Multivariate Data Analysis

“…Wood is a remarkably naturally durable material. This natural durability in terms of decay resistance against fungi, varies in a wide range between species and even within species [78][79][80] and can also be predicted by infrared spectroscopy [78,81,82]. The natural durability of wood mainly depends on the extractives composition [79,83] but also on the extractives content [79] and is in general higher in hardwoods than in softwoods.…”