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Wood discoloration was investigated in 721 paper birch (Betula papyrifera Marsh.) trees from 146 sites across the managed forest of Quebec, Canada. Discoloration was present at breast height in 85% of trees, but its impact was limited in terms of tree basal area and volume, with proportions of 6.4% and 3.6%, respectively. These two measures were strongly correlated. Discoloration changed wood appearance but had no effect on microfibril angle and modulus of elasticity. Discolored wood was nevertheless denser, probably due to the accumulation of colored extractives. Predictive models were also developed and applied to 415 711 paper birch trees from 51689 inventory plots across the province to study regional variation. Higher proportions of discolored basal area were obtained in the southwestern areas of the province where the climate is warmer and drier. In these areas, paper birch trees are larger and, likely, support bigger branches which can cause larger columns of discoloration when broken. Lower proportions were found in eastern regions where snowfall is more abundant. Smaller, more flexible branches in trees growing in these areas could explain this result. This study confirms the feasibility of large-scale mapping of wood discoloration in standing trees based on forest inventory and climate data. Key words: paper birch, wood discoloration, wood properties, regional variation, climate. La coloration du bois a ete etudiee chez 721 tiges de bouleau blanc (Betula papyrifera Marsh.) provenant de 146 sites repartis a travers la foret amenagee du Quebec, au Canada. La coloration etait presente chez 85 % des arbres mais son impact etait faible : elle occupait seulement 6,4 % de la surface terriere et 3,6 % du volume des tiges. Ces deux variables etaient etroitement correlees. La coloration a modifie l'apparence du bois mais n'a eu aucun effet sur l'angle des microfibrilles ni sur le module d'elasticite. Le bois colore est neanmoins plus dense, vraisemblablement a cause de l'accumulation de matieres extractibles colorees. Des modeles de prediction ont egalement ete elabores et appliques a 415 711 tiges de bouleau blanc provenant de 51689 parcelles d'inventaire reparties a travers la province pour etudier la variation regionale. De plus grandes proportions de surface terriere de bois colore ont ete obtenues dans les regions du sud-ouest de la province oU le climat est plus chaud et plus sec. Dans ces regions, les tiges de bouleau blanc sont plus grosses et supportent probablement de plus grosses branches qui peuvent causer de plus grandes colonnes de coloration lorsqu'elles cassent. De plus faibles proportions de coloration ont ete trouvees dans les regions de l'est oU les chutes de neige sont plus abondantes. Le fait que les arbres croissant dans ces regions aient des branches plus petites et plus flexibles pourrait expliquer ce resultat. Cette etude confirme que la cartographie de la coloration a grande echelle dans les arbres sur pied est realisable a partir de donnees d'inventaire forestier et du climat. [Traduit par la Redaction] Mots-cles: bouleau blanc, coloration du bois, proprietes du bois, variation regionale, climat., Introduction Paper birch (Betula papyrifera Marsh.) is one of the most abundant hardwood species in Canada with a natural range from eastern to western coast (Safford et al. 1990). In [...]

The identification of low-vigor trees with potential for sawlog production is a key objective of tree marking guidelines used for partial cuts in northern hardwoods. The aim of this study was to measure the impact of various vigor-related defects on the monetary value of hardwoods. To achieve this, we sampled 64 sugar maple (Acer saccharum Marshall) and 32 yellow birch (Betula alleghaniensis Britton) trees from two locations in southern Quebec, Canada. We identified over 420 defects, which were grouped into 8 categories. The trees were then harvested and processed into lumber, and the value per unit volume of each stem was calculated from the value of the product assortment (lumber, chips, and sawdust). We found that visible evidence of fungal infections (sporocarps and (or) stroma) and cracks had the largest negative influence on value in both species. A model that included these defects was almost as good at predicting value as one that included a specifically designed quality classification. A more accurate assessment of value could be achieved using wood decay assessment tools and (or) by considering site- specific variables. Results from this study showed that visual identification of fungal infections and cracks could be used to enhance tree marking guidelines for hardwoods. This would meet both the silvicultural objective of selection cuts, by removing low- vigor trees, and the wood supply objective, by improving stem quality assessment prior to harvest. Key words: hardwoods, tree marking, defects, tree vigor, tree quality. L'identification des arbres moribonds qui ont un potentiel pour la production de billes de sciage est un objectif cle des directives de martelage lors de coupes partielles dans les peuplements de feuillus nordiques. Cette etude avait pour but de mesurer l'impact de divers defauts relies a la vigueur sur la valeur monetaire des feuillus. A cette fin, nous avons echantillonne 64 erables a sucre (Acer saccharum Marshall) et 32 bouleaux jaunes (Betula alleghaniensis Britton) a deux endroits dans le sud du Quebec, au Canada. Nous avons identifie plus de 420 defauts que nous avons regroupes en huit categories. Ces arbres ont ensuite ete recoltes et transformes en sciage et la valeur par unite de volume de chaque tige a ete calculee a partir de la valeur de l'assortiment de produits (sciages, copeaux et sciures). Nous avons constate que les signes visibles d'infection fongique (sporocarpes ou stroma) et les fentes avaient la plus grande influence negative sur la valeur des deux especes. Un modele qui incluait ces defauts etait presque aussi bon pour predire la valeur qu'un modele base sur un systeme de classes de qualite specifiquement concu. On pouvait obtenir une evaluation plus precise de la qualite en utilisant des outils pour evaluer la carie du bois ou en tenant compte de variables propres au site. Les resultats de cette etude montrent que l'identiication visuelle des infections fongiques et des fentes peut etre utilisee pour ameliorer les directives de martelage chez les feuillus. Cela devrait satisfaire tant les objectifs sylvicoles des coupes de jardinage, en eliminant les arbres moribonds, que les objectifs d'approvisionnement en bois, en ameliorant l'evaluation de la qualite des tiges avant la recolte. [Traduit par la Redaction] Mots-cles : feuillus, martelage, defauts, vigueur des arbres, qualite des arbres., Introduction The natural disturbance regime of North American temperate deciduous forests is characterized by mortality of individual trees, or group of trees, with very rare occurrence of severe, large-scale disturbances [...]

Stems of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.) trees often contain a column of discoloured wood known as red heartwood, which reduces lumber value. To quantify the regional-scale variation in red heartwood, 192 trees of each species were sampled in 12 locations across the temperate forest zone of southern Quebec, Canada. Large regional variation in the radial proportion of red heartwood (RHP) at breast height (1.3 m) was observed in both species. Statistical modeling showed that such variation was mainly attributable to factors related to tree development. Cambial age had a strong positive effect on RHP in both species, suggesting that the occurrence of red heartwood ultimately might be unavoidable. There was also a positive effect of ring area increment at the limit of the discoloured zone. In the case of sugar maple, there was an added effect of the trend in ring area increments observed in the same zone, with a negative trend being generally indicative of a larger RHP. Further variability in this species was also associated with the annual minimum temperature of the sampling locations. The models developed for each species explained around 60% of the variance in RHP and could be used to improve forest management and wood procurement decisions. Resume: Les tiges d'erable a sucre (Acer saccharum Marsh.) et de bouleau jaune (Betula alleghaniensis Britt.) contiennent frequemment une colonne de bois brun-rougeatre, appelee coloration de coeur, qui reduit la valeur des produits du bois. Afin d'en quantifier la variation a l'echelle regionale, 192 arbres de chaque espece ont ete echantillonnes dans 12 localisations couvrant l'ensemble de la foret temperee du sud du Quebec, Canada. Une variation regionale elevee de la proportion radiale de la zone coloree (PRC) a hauteur de poitrine (1,3 m) a ete observee chez les deux especes. La modelisation statistique a revele que cette variation etait principalement attribuable a des facteurs lies au developpement des arbres. L'age cambial avait un effet positif sur la PRC des deux especes, ce qui indique que l'occurrence de la coloration de coeur serait ultimement inevitable. Un effet positif de la superficie des anneaux de croissance a la limite de la zone coloree a aussi ete observe. Dans le cas de l'erable a sucre, il y avait un effet additionnel de la tendance des accroissements en superficies des anneaux dans la meme zone, les tendances negatives etant generalement indicatrices d'une PRC plus elevee. Une partie de la variabilite chez cette espece etait aussi associee a la temperature minimale annuelle d'une localisation. Les modeles developpes pour chaque espece expliquent pres de 60 % de la variance et pourront etre utilises pour ameliorer les decisions liees a l'amenagement forestier et aux approvisionnements en bois., Introduction Sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.) are dominant components of the North American temperate deciduous forests. Both tree species are commercially important, especially as [...]

Long-term success of forest management requires knowledge of standing tree characteristics and, an estimation of their evolution over time. In this study, hardwood stem quality was assessed using a specifically designed, non-destructive quality classification system that comprises four categorical output classes based on stem size and occurrence of external defects. We used data from national forest inventory sample plots distributed across Quebec (Canada) to predict hardwood stem quality and its evolution over time. We used ordinal logistic regression to model multiple stem quality classes. Hardwood stem quality was strongly related to stem harvest priority class and bioclimatic subdomain. Stem quality generally improved with d.b.h. and stand basal area. Changes in hardwood stem quality were strongly related to initial stem quality, with most trees retaining their initial quality over time. Stem quality evolution was also positively related to diameter growth. Overall, both initial and future stem quality were estimated with acceptable precision and minimal bias. Our results suggest that the equations could predict hardwood stem quality distribution and evolution among groups of forest stands. [ABSTRACT FROM AUTHOR]