Visual identification, physical properties, ash composition, and water diffusion of wetwood inGmelina arborea

Abstract

Wetwood is commonly reported in temperate species but not so in tropical species. In an old Gmelina arborea Roxb. plantation, wetwood was identified by a darker colour compared with the rest of heartwood; by a higher moisture content (average 182%); and a lower specific gravity (0.34, compared with 0.38 for sapwood and heartwood). Tangential shrinkage was 3.7%, which was significantly higher than that of heartwood and sapwood. Radial shrinkage was not significantly different between wetwood and sapwood, but it was significantly greater (2.6%) in wetwood than in heartwood (1.8%). Wetwood had a significantly higher pH than normal wood, but ash composition was similar to that of normal wood, with the exception of the amounts of iron and potassium. Wetwood and sapwood were less decay resistant than heartwood. Wetwood required less time than heartwood to reach equilibrium moisture content, but more time than sapwood. The tangential and longitudinal diffusion coefficients of wetwood were significantly higher than those of heartwood and lower than those of sapwood. In the radial direction sapwood showed a faster drying rate than wetwood but there was no significant difference between wetwood and heartwood.Résumé : Le coeur mouillé est souvent rapporté chez les espèces tempérées mais il n'est pas commun chez les espèces tropicales. Dans une vieille plantation de Gmelina arborea Roxb., le coeur mouillé a été identifié par sa couleur plus foncée que le reste du bois de coeur, sa teneur en humidité plus élevée (moyenne de 182 %) et sa densité plus faible (0,34 comparativement à 0,38 pour le bois d'aubier et le bois de coeur). Le retrait tangentiel dans le coeur mouillé était de 3,7 %, ce qui était significativement plus élevé que celui du bois de coeur et du bois d'aubier. Le retrait radial dans le coeur mouillé et le bois d'aubier n'était pas significativement différent mais il était significativement plus important (2,6 %) que dans le bois de coeur (1,8 %). Le coeur mouillé avait un pH significativement plus élevé que le bois normal mais la composition de la cendre était similaire à l'exception des quantités de fer (Fe) et de potassium (K). Le coeur mouillé et le bois d'aubier étaient moins résistants à la carie que le bois de coeur. Le temps requis pour atteindre le degré d'humidité d'équilibre était plus court dans le coeur mouillé que dans le bois de coeur mais pas plus long que pour le bois d'aubier. Les coefficients de diffusion longitudinale et tangentielle du coeur mouillé étaient significativement plus élevés que ceux du bois de coeur mais plus faibles que ceux du bois d'aubier. Dans le sens radial, le taux de séchage du bois d'aubier était plus rapide que celui du coeur mouillé mais il n'y avait pas de différence significative entre le coeur mouillé et le bois de coeur.[Traduit par la Rédaction]

Methane emissions from the trunks of living trees on upland soils

“…Although wet heartwoods in living trees tend to be formed in wet environments, they are also widely formed in living trees growing on upland soils (Lihra et al ., ; Xu et al ., ; Krause & Gagnon, , ; Moya et al ., ). Previous studies have focused on the role of wetland trees as conduits for soilborne CH 4 emissions (Rusch & Rennenberg, ; Terazawa et al ., ; Gauci et al ., ; Rice et al ., ; Pangala et al ., , ).…”

“…). Wet heartwood is commonly reported in temperate tree species, particularly in the basal part of a tree trunk (Moya et al ., ). Diameter ratio of heartwood vs trunk in P. davidiana was 69% at the 35–65 cm height, decreasing to 55% at the 435–465 cm height (Table S3).…”

Methane Production Explained Largely by Water Content in the Heartwood of Living Trees in Upland Forests

“…No consistent relationship was found between the presence of wet heartwood and the occurrence of decay in Populus trichocarpa (Moya et al, 2009). Accordingly, wet heartwood may be identified by its water content, rather than its state of decay and/or color.…”

“…However, wet heartwood has also been widely found in upland forests, but it tended to be formed in the tree species growing in periodically wet belowground environments (Krause & Gagnon, ; Lihra et al, ). No consistent relationship was found between the presence of wet heartwood and the occurrence of decay in Populus trichocarpa (Moya et al, ). Accordingly, wet heartwood may be identified by its water content, rather than its state of decay and/or color.…”

“…For instance, previous studies have reported that wet heartwood is widespread in living trees in wetland forests (Bushong, ; Ward et al, ; Zeikus & Ward, ). Different extents of patchy and/or continuous wet heartwood have been commonly reported in temperate tree species, particularly in the basal part of tree stems (Moya et al, ). However, wet heartwood has also been widely found in upland forests, but it tended to be formed in the tree species growing in periodically wet belowground environments (Krause & Gagnon, ; Lihra et al, ).…”