Some Aspects of Wetwood Formation in Fir

Bauch, J.; Höll, Wolfgang H.; Endeward, R.

doi:10.1515/hfsg.1975.29.6.198

Cited by 46 publications

(24 citation statements)

References 8 publications

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“…Wetwood formation in heartwood of fast-growing G. arborea probably cannot be attributed entirely to bacterial infection in the inner and outer heartwood area of the living trees, as has been suggested by some studies (Ward and Pong 1980), because many silvicultural practices (pruning, thinning, felling) are applied in plantations, and environmental conditions that contribute to wetwood formation are variable (Moya and Tomazello 2008). On the other hand, although wetwood was not observed in sapwood in the sampled trees, other researchers have reported that this infected tissue is not restricted to heartwood (Tiedemann et al 1977;Bauch et al 1975;Schink et al 1981).…”

Section: Identification Of Wetwoodmentioning

confidence: 80%

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

et al. 2009

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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]

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Section: Identification Of Wetwoodmentioning

confidence: 80%

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

et al. 2009

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“…The earliest studies mentioning this phenomenon date back to the beginning of the 20th century, with the work of Neger in 1908. Heartwood moisture content can reach levels as high as those in the sapwood, especially in fir trees (Bauch et al 1975;Ward and Kozlik 1975;Klein et al 1979;Schneider and Zhou 1989). The presence of wet heartwood has little or no impact on the mechanical properties of the wood (Wilcox 1968;Ward and Kozlik 1975;Klein et al 1979), but the drying process of trees with wet heartwood is known to be very long and accompanied by important shrinking (Wilcox and Pong 1971;Frühwald et al 1981;Sell and Kucera 1989;Shaw et al 1995;Chafe 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Because of the economic value of this species, it might be helpful to identify tree and site characteristics that are associated with wet heartwood to better define the affected areas. In spite of an intensive effort by scientists to identify the cause and the process of wetwood formation, little information has been obtained (Bauch et al 1975;Shaw et al 1995). A few studies hypothesized that branch breaks and root injuries might be the preferred access points of wetwood formation (Bauch et al 1975;Aufsess 1981;Lang 1981;Schütt 1981;Klein 1992).…”

Section: Introductionmentioning

confidence: 99%

“…In spite of an intensive effort by scientists to identify the cause and the process of wetwood formation, little information has been obtained (Bauch et al 1975;Shaw et al 1995). A few studies hypothesized that branch breaks and root injuries might be the preferred access points of wetwood formation (Bauch et al 1975;Aufsess 1981;Lang 1981;Schütt 1981;Klein 1992). However, others have suggested that sapwood could be the primary water source in the trees (Coutts and Rishbeth 1977).…”

Section: Introductionmentioning

confidence: 99%

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The relationship between site and tree characteristics and the presence of wet heartwood in black spruce in the boreal forest of Quebec, Canada

Krause¹,

Gagnon²

2006

Can. J. For. Res.

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Wet heartwood in black spruce (Picea mariana (Mill.) BSP) causes considerable problems during the drying process. Forest companies try to avoid harvesting stands with wet heartwood, but no relationship has been yet established between the incidence of wet heartwood and tree or site characteristics. To characterize areas containing a significant proportion of black spruce affected by wet heartwood, a total of 635 black spruce trees were sampled in eighteen 400 m 2 study plots under management in the central boreal forest of Quebec. A total of 18 study sites were analysed and classified as wet, intermediate, or dry, based on the proportion of individuals with wet heartwood. Thirteen of the study sites were classified as wet, two as intermediate, and three as dry. The average age calculated for trees on wet sites was significantly (p = 0.0001) higher than that of the other two classes, whereas growth rate was significantly lower on wet sites. No difference was noted in the average height or diameter of the individuals from all three classes. The wet sites contained organic soil, whereas Podzols characterized two of the three dry study sites. An additional sampling of black spruce (n = 509) revealed a significant relationship between the groundwater level and heartwood moisture content classification (i.e., dry, intermediate, or wet). Trees in the dry heartwood class grew on sites with the lowest groundwater levels (p = 0.002) compared with trees in the wet or intermediate classes.Résumé : Le bois de coeur humide présent dans l'épinette noire (Picea marinana (Mill.) BSP) entraîne de sérieux problèmes durant le processus de séchage. Les compagnies forestières essaient d'éviter la récolte de ces peuplements avec du bois de coeur humide, mais aucune relation n'a encore été établie avec les caractéristiques des arbres et du site. Afin de caractériser certains secteurs affectés par une proportion importante d'épinette noire avec du bois de coeur humide, un nombre de 635 carottes d'épinette noire ont été échantillonnées dans 18 quadrats d'étude de 400 m 2 situés en forêt aménagée dans la partie centrale de la forêt boréale du Québec. Un total de 18 sites d'étude ont été analysés et classés humide, intermédiaire et sec en se basant sur la proportion des individus avec du bois de coeur humide. Treize quadrats ont été classés humide, two quadrats classés intermédiaire et trois quadrats classés sec. L'âge moyen des arbres échantillonnés dans les sites classés humide était significativement (p = 0,0001) plus élevé que dans les deux autres classes tandis que le taux de croissance était significativement plus faible. Aucune différence n'a été notée pour la hauteur moyenne ou le diamètre moyen des individus des trois classes. Les sites classés humide contenaient du sol organique tandis que deux des trois sites classés sec étaient caractérisés par la présence d'un podzol. Un échantillonnage supplémentaire de carottes d'épinette noire (n = 509) le long de transects a révélé qu'il y avait une relation significative entre le niveau de...

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“…lumber is mainly associated with the occurrence of wet pockets (wet wood) that is characterized by its unusually high moisture content (MC). Higher extractive contents [1] and a larger number of aspirated and encrusted pit membranes on tracheid cell walls are observed in wet wood compared to normal wood. [2] Various drying models reported in the literature propose different mechanisms for moisture movement in wood.…”

mentioning

confidence: 99%

A Simulation of Wet Pocket Lumber Drying

Cai

Oliveira

2008

Drying Technology

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In general, wood containing wet pockets is difficult to dry and to ensure uniformity of moisture content at the end of the drying process. Large variations of final moisture content and severe case hardening are common problems associated with the drying of wet wood. In order to devise optimal strategies for drying wood containing wet pockets, it is necessary to understand its complex moisture movement mechanisms and therefore predict drying times and final moisture content. Sub-alpine fir dimension lumber was used in this research because of its inherent issues related to wet pockets.A two-dimensional mathematical drying model for wood containing wet pockets was developed. An effective diffusion coefficient (D eff ) was utilized in the model and heat and mass transfer equations were solved using a control volume approach. The difficulties involved in the simulation of the drying process of wet pocket lumber are due to the differences in moisture content and physical properties between wet and normal wood. Thus, an adjustable D eff based on the moisture content (for both below and above fiber saturation point) was used during the simulation.Four drying runs involving green unsorted sub-alpine fir lumber were carried out in a 3-ft laboratory kiln and in an 8-ft pilot kiln. The results of the simulations were in agreement with the results obtained through the drying experiments. INTRODUCTIONThe difficulty in drying sub-alpine fir (Abies lasiocarpa (Hook) Nutt.) lumber is mainly associated with the occurrence of wet pockets (wet wood) that is characterized by its unusually high moisture content (MC). Higher extractive contents [1] and a larger number of aspirated and encrusted pit membranes on tracheid cell walls are observed in wet wood compared to normal wood. [2] Various drying models reported in the literature propose different mechanisms for moisture movement in wood. Empirical models, such as curve fitting, can be practical and relatively simple. A semi-empirical model proposed by Bramhall [3] can be used to estimate final moisture content and drying times by changing schedule set points. However, this type of model does not predict drying behavior when process conditions (temperature, air velocity, and relative humidity) are outside of the range for which the experiments were carried out.

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Some Aspects of Wetwood Formation in Fir

Cited by 46 publications

References 8 publications

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

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

The relationship between site and tree characteristics and the presence of wet heartwood in black spruce in the boreal forest of Quebec, Canada

A Simulation of Wet Pocket Lumber Drying

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