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Western redcedar has high economic value and has been traditionally used for cultural purposes by Indigenous communities. Second-growth redcedar is potentially growing faster due to lower planting densities, fertilization, and tree breeding. Little quantitative information is available about the impact of management practices on wood quality, particularly heartwood extractives. This study evaluated the effects of growth rate and site on heartwood extractives at two locations aged 70–90 years in British Columbia, Canada. A three-parameter sigmoid model was fit to the data using nonlinear mixed effects to analyze the relationship between heartwood extractives relative to cambial age, growth rate, and sampling site. The southern site had significantly higher cumulative extractive concentrations, while all extractive concentrations increased faster. This study shows that smaller trees will reach their peak concentrations earlier than larger trees. Results show that faster growth through active management of western redcedar may lead to increased and more uniformly distributed content of heartwood extractives. [ABSTRACT FROM AUTHOR] more...

Late-rotation fertilization of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) 5 to 10 years before harvesting is a common management practice in British Columbia and the US Pacific Northwest. Despite widespread operational application, knowledge on the impact of late-rotation fertilization on forests, especially fibre properties, is lacking. In this study, we evaluate the growth response and fibre properties following nitrogen fertilization in a productive second-growth coastal Douglas-fir site at age 57 years. Destructive sampling of dominant and co-dominant trees in fertilized and control plots 5 years after fertilization indicated significant gain in stem volume (30%-40%) that was uniformly distributed along the stem. There were no discernible effects on wood quality at the log level in terms of resonance acoustic velocity. However, fibre properties within breast height tree rings indicated significant reductions of ring wood density (by 8%), earlywood density (17%), latewood percentage (10%), and modulus of elasticity (8%). Tracheid dimensions declined in earlywood (reduction of wall thickness by 15%), latewood (radial diameter by 8%), and fibre length (by 6%). Results indicate that late-rotation nitrogen fertilization of Douglas-fir may lead to a significant growth response with only minimal reduction of fibre properties. It is possible that the negative impact on fibre properties could become more significant for repeated applications or higher rates of nitrogen fertilization. Key words: Douglas-fir, nitrogen fertilization, late-rotation, growth, fibre properties. La fertilisation du douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) en fin de rotation, 5-10 ans avant la coupe, est une pratique d'amenagement courante en Colombie-Britannique et dans le Pacific Northwest, aux Etats-Unis. Bien qu'elle soit largement appliquee sur une base operationnelle, l'impact de la fertilisation en fin de rotation sur les forets, plus particulierement sur les proprietes des fibres, est mal connu. Dans cette etude, nous avons evalue la reaction en croissance et les proprietes des fibres apres une fertilisation azotee dans une station cotiere productive de douglas de Menzies de seconde venue age de 57 ans. Un echantillonnage destructif d'arbres dominants et codominants dans des places echantillons fertilisees et temoins indiquait qu'il y avait un gain en volume important (30-40 %) uniformement reparti le long de la tige 5 ans apres la fertilisation. On ne pouvait discerner d'effets sur la qualite du bois dans les billes en termes de vitesse sonique par resonance. Cependant, les proprietes des fibres dans les cernes annuels a hauteur de poitrine montraient qu'il y avait une reduction significative de la densite du bois dans les cernes annuels (8 %), de la densite du bois initial (17 %), du pourcentage de bois final (10 %) et du module d'elasticite (8 %). Les dimensions des tracheides ont diminue dans le bois initial (reduction de 15 % de l'epaisseur de la paroi), dans le bois final (reduction de 8% du diametre radial) ainsi que la longueur des fibres (diminution de 6 %). Les resultats indiquent que la fertilisation azotee du douglas de Menzies en fin de rotation peut produire une reponse en croissance significative en causant seulement une reduction minime des proprietes des fibres. L'impact negatif sur les proprietes des fibres pourrait devenir plus serieux si les applications etaient repetees ou le taux de fertilisation azotee etait plus eleve. [Traduit par la Redaction] Mots-cles: douglas de Menzies, fertilisation azotee, fin de rotation, croissance, proprietes des fibres., Introduction Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is an important tree species of North American forests (Burns and Honkala 1990). Historically a significant component of natural stands, Douglas-fir is currently a [...] more...

Planting white spruce (Picea glauca (Moench) Voss) under established aspen (Populus tremuloides Michx.) stands has substantial potential for regenerating mixedwood ecosystems in the western Canadian boreal forest. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. Under future climatic regimes with more frequent and severe drought episodes, underplanting may be a cost-effective strategy for lowering the risk of mortality in mixedwood regeneration. We examine the growth of white spruce during the first 18 years after being planted beneath a 39-year-old stand of trembling aspen. Treatments included thinning from over 6000 stemsx[ha.sup.-1] to 3000, 2000, and 1000 stemsx[ha.sup.-1] and fertilization. Initial stimulation of understory vegetation by fertilization had no measureable effect on spruce heights or diameters at year 18. Aspen thinning treatments did not have a significant effect on spruce height growth rates after spruce crowns had emerged above the understory shrub layer due to rapid aspen basal area increases after thinning. Small, but significant, increases for spruce height and diameter were present in the 1000 and 2000 stemsx[ha.sup.-1] aspen thinnings. A much wider range of aspen stand conditions may be suitable for planting spruce to create mixedwood ecosystems than has been previously considered. Key words: white spruce, aspen, boreal mixedwood, underplanting, thinning. La plantation d'epinette blanche (Picea glauca (Moench) Voss) sous un couvert de peuplier faux-tremble (Populus tremuloides Michx.) a un potentiel interessant pour regenerer les ecosystemes mixtes de la foret boreale de l'Ouest canadien. La presence d'un couvert dominant de peuplier est utile pour attenuer les problemes de gel et de blessures hivernales et pour reprimer la vegetation de sous-etage qui peut concurrencer l'epinette blanche. Sous les futurs regimes climatiques caracterises par des episodes de secheresse plus frequents et plus severes, la plantation sous couvert peut constituer une strategie rentable pour diminuer les risques de mortalite de la regeneration dans les peuplements mixtes. Nous etudions la croissance de plants d'epinette blanche au cours des 18 premieres annees apres leur plantation sous un peuplement de peuplier faux-tremble age de 39 ans. Les traitements incluent des eclaircies faisant passer la densite du peuplement de 6000 tigesx[ha.sup.-1] a 3000, 2000 et 1000 tigesx[ha.sup.-1], ainsi que la fertilisation. La stimulation initiale de la vegetation de sous-etage par la fertilisation n'a pas eu d'effet mesurable sur la hauteur ou le diametre de l'epinette blanche apres 18 ans. Les traitements d'eclaircie du peuplier n'ont pas eu d'effet significatif sur le taux de croissance en hauteur de l'epinette apres que leur cime ait depasse la strate arbustive du sous-etage parce que la surface terriere du peuplier a augmente rapidement apres les eclaircies. Une augmentation faible, mais significative, de la hauteur et du diametre des epinettes a ete observee dans les eclaircies du peuplier qui ont laisse 1000 et 2000 tigesx[ha.sup.-1]. Une gamme de conditions de peupleraie beaucoup plus large que ce qui a ete precedemment envisage pourrait convenir a la plantation d'epinette dans le but de creer des ecosystemes mixtes. [Traduit par la Redaction] Mots-cles : epinette blanche, peuplier faux-tremble, peuplements boreaux mixtes, plantation sous couvert, eclaircie., Introduction The underplanting of mature (40- to 60-year-old) trembling aspen (Populus tremuloides Michx.) stands with white spruce (Picea glauca (Moench) Voss) has been recommended as a feasible mixedwood management silviculture [...] more...

Characteristics of annual rings are reliable indicators of growth and wood quality in trees. The main objective of our study was to model the variation in annual ring attributes due to intensive silviculture and inherent regional differences in climate and site across a wide geographic range of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Ring specific gravity and ring width of Douglas-fir were examined at five long-term Levels-Of-Growing-Stock (LOGS) installations, three in the US and two in Canada, covering a latitudinal gradient between 43°N and 50°N. At each location, increment cores were collected from replicated plots with three levels of stocking: control (unthinned), lightly thinned (70% basal area retention), and heavily thinned (30% basal area retention). X-ray densitometry analysis provided ring specific gravity and width profiles for 5676 rings from 134 trees. The reduction of stand density through repeated entries resulted in decreased ring specific gravity and increased ring width. A four-parameter mixed-effects logistic model was used to predict ring specific gravity using cambial age, stand density (as number of stems per hectare), and two climatic variables: average temperature from March to May and total precipitation from April to August. A three-parameter mixed-effects logistic model was used to predict ring width using cambial age, stand density (as stand density index), and total climatic moisture deficit of June and July. Both models indicated significant site differences that were included in the models through indicator variables. Ring specific gravity increased slightly with increasing average temperature from March to May and decreasing total precipitation from April to August. Predictions of ring specific gravity of Douglas-fir appear to be more sensitive to changes in temperature compared with changes in precipitation. Key words: Douglas-fir, specific gravity, annual ring width, thinning, wood quality. Resume: Les caracteristiques des cernes annuels sont des indices fiables de la croissance et de la qualite du bois chez les arbres. Le principal objectif de notre etude consistait a modeliser la variation des attributs des cernes annuels attribuable a la sylviculture intensive et aux differences regionales inherentes au climat et aux stations sur une vaste etendue geographique occupee par le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco). La densite et la largeur des cernes du douglas de Menzies ont ete etudiees dans cinq endroits, trois aux etats-Unis et deux au Canada, etablis pour observer l'effet a long terme de la densite des tiges sur pied et couvrant un gradient latitudinal allant de 43° N a 50° N. a chaque endroit, des carottes ont ete prelevees dans des placettes repliquees correspondant a trois niveaux de densite relative: temoin (pas d'eclaircie), eclaircie legere (retention de 70 % de la surface terriere) et eclaircie forte (retention de 30 % de la surface terriere). L'analyse par densitometrie aux rayons X a permis d'obtenir les profils de largeur et de densite de 5676 cernes provenant de 134 arbres. La reduction de la densite relative des peuplements par des interventions repetees a cause une diminution de la densite des cernes et une augmentation de la largeur des cernes. Un modele logistique a effets mixtes a quatre parametres a ete utilise pour predire la densite des cernes annuels a partir de l'age cambial, de la densite du peuplement (nombre de tiges a l'hectare) et de deux variables climatiques: la temperature moyenne du mois de mars au mois de mai et la precipitation totale du mois d'avril au mois d'aout. Un modele logistique a effets mixtes a trois parametres a ete utilise pour predire la largeur des cernes annuels a partir de l'age cambial, de la densite du peuplement (indice de densite du peuplement) et du deficit hydrique total du au climat en juin et juillet. Les deux modeles indiquaient qu'il y avait d'importantes differences entre les stations. Ces differences etaient incluses dans les modeles grace a des variables indicatrices. La densite des cernes augmentait legerement avec l'augmentation de la temperature moyenne du mois de mars au mois de mai et la diminution de la precipitation totale du mois d'avril au mois d'aout. Les predictions de la densite des cernes annuels du douglas de Menzies semblent plus sensibles aux variations de temperature qu'aux variations dans les precipitations. [Traduit par la Redaction] Motscles: douglas de Menzies, densite, largeur des cernes annuels, eclaircie, qualite du bois., Introduction Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is one of the most valuable tree species grown in western North America. Its commercial importance lies in its use in structural applications because [...] more...

Abstract: The effectiveness of competition indices for predicting light transmittance and white spruce (Picea glauca (Moench) Voss) growth were examined across trembling aspen (Populus tremuloides Michx.) density gradients using sites [...] more...

Changing climates are altering the structural and functional components of forest ecosystems at an unprecedented rate. Simultaneously, we are seeing a diversification of public expectations on the broader sustainable use of forest resources beyond timber production. As a result, the science and art of silviculture needs to adapt to these changing realities. In this piece, we argue that silviculturists are gradually shifting from the application of empirically derived silvicultural scenarios to new sets of approaches, methods and practices, a process that calls for broadening our conception of silviculture as a scientific discipline. We propose a holistic view of silviculture revolving around three key themes: observe, anticipate and adapt. In observe, we present how recent advances in remote sensing now enable silviculturists to observe forest structural, compositional and functional attributes in near-real-time, which in turn facilitates the deployment of efficient, targeted silvicultural measures in practice that are adapted to rapidly changing constraints. In anticipate, we highlight the importance of developing state-of-the-art models designed to take into account the effects of changing environmental conditions on forest growth and dynamics. In adapt, we discuss the need to provide spatially explicit guidance for the implementation of adaptive silvicultural actions that are efficient, cost-effective and socially acceptable. We conclude by presenting key steps towards the development of new tools and practical knowledge that will ensure meeting societal demands in rapidly changing environmental conditions. We classify these actions into three main categories: re-examining existing silvicultural trials to identify key stand attributes associated with the resistance and resilience of forests to multiple stressors, developing technological workflows and infrastructures to allow for continuous forest inventory updating frameworks, and implementing bold, innovative silvicultural trials in consultation with the relevant communities where a range of adaptive silvicultural strategies are tested. In this holistic perspective, silviculture can be defined as the science of observing forest condition and anticipating its development to apply tending and regeneration treatments adapted to a multiplicity of desired outcomes in rapidly changing realities. [ABSTRACT FROM AUTHOR] more...

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