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Assisted gene flow according to expected climate gradients is considered as a forest management strategy to mitigate impacts of environmental change on forest growth. However, the effects of seed translocation on wood properties and lumber quality remain unknown. This study evaluated the effect of provenance origin on lumber production and quality at rotation age in two white spruce provenance trials established in contrasting environments in eastern Canada. Based on 108 sample trees, which resulted in 943 pieces of lumber, average volume production per tree at the southernmost site was twice that of the production at the northern site. Provenance had a significant influence on growth and lumber strength in the first sawlog but had no effect on lumber stiffness and wood density. Although visual grade yields of No. 2 and better were high in both trials (over 86%), the machine stress rated (MSR) grade potential and percentage of lumber that met the bending stiffness design values of the visual grades were generally low (12%-26%). Hence, plantation-grown lumber should preferably be machine stress rated to ensure its fitness for structural applications in buildings. Management strategies aiming to efficiently sequester carbon should primarily maximize volume productivity in northern sites, as moving seed sources north still reduces provenance productivity, while breeding programs should aim to prevent decrease in lumber stiffness due to augmented productivity and shortened rotation cycles. Key words: assisted migration, lumber visual grade, provenance trial, MOE (stiffness), MOR (strength), wood density, tree breeding Le flux genetique assiste, selon les gradients climatiques prevus, est considere comme une strategie de gestion des forets visant a attenuer les impacts des changements environnementaux sur la croissance des forets. Toutefois, les effets de la translocation des graines sur les proprietes du bois et la qualite des sciages demeurent inconnus. La presente etude a evalue l'effet de l'origine de la provenance sur la production et la qualite du bois d'reuvre a un age de rotation dans deux essais de provenance d'epinettes blanches etablis dans des environnements contrastes dans l'Est du Canada. Fonde sur 108 arbres echantillons qui ont produit 943 pieces de bois d'reuvre, la production moyenne en volume par arbre sur le site le plus au sud etait le double de la production du site au nord. La provenance a eu une influence significative sur la croissance et la resistance du bois d'reuvre dans la premiere bille de sciage, mais n'a pas eu d'effet sur la rigidite des sciages et la densite du bois. Meme si les rendements en grades visuels No. 2 et meilleur etaient eleves dans les deux essais (plus de 86 %), le potentiel de classer les sciages dans les categories de bois MSR (bois evalues par contrainte mecanique) et le pourcentage de bois d'reuvre qui respectait les valeurs de conception de la rigidite en flexion des grades visuels etaient generalement faibles (12 % a 26 %). Par consequent, le bois d'reuvre qui a pousse en plantation devrait de preference etre classe par contrainte mecanique afin d'assurer sa conformite a des applications structurales dans des batiments. Les strategies de gestion visant a sequestrer efficacement le carbone devraient avant tout maximiser la productivite en volume dans les sites du nord, puisque le deplacement des sources de graines au nord reduit toujours la productivite de la provenance, alors que les programmes de selection devraient viser a prevenir la diminution de la rigidite du bois d'reuvre en raison de l'augmentation de la productivite et de la diminution des cycles de rotation. [Traduit par la Redaction] Mots-cles : migration assistee, qualite visuelle du bois d'reuvre, essai de provenance, MOE (rigidite), MOR (resistance), densite du bois, amelioration des arbres, Introduction Canada's forest economy has largely developed around the utilization of abundant, high-quality, but largely unmanaged softwood resource (Barbour and Kellogg 1990). However, the increasing pressure on fibre resources from [...]

Climate change (CC) necessitates reforestation/afforestation programs to mitigate its impacts and maximize carbon sequestration. But comprehending how tree growth, a proxy for fitness and resilience, responds to CC is critical to maximize these programs' effectiveness. Variability in tree response to CC across populations can notably be influenced by the standing genetic variation encompassing both neutral and adaptive genetic diversity. Here, a framework is proposed to assess tree growth potential at the population scale while accounting for standing genetic variation. We applied this framework to black spruce (BS, Picea mariana [Mill] B.S.P.), with the objectives to (1) determine the key climate variables having impacted BS growth response from 1974 to 2019, (2) examine the relative roles of local adaptation and the phylogeographic structure in this response, and (3) project BS growth under two Shared Socioeconomic Pathways while taking standing genetic variation into account. We modeled growth using a machine learning algorithm trained with dendroecological and genetic data obtained from over 2600 trees (62 populations divided in three genetic clusters) in four 48‐year‐old common gardens, and simulated growth until year 2100 at the common garden locations. Our study revealed that high summer and autumn temperatures negatively impacted BS growth. As a consequence of warming, this species is projected to experience a decline in growth by the end of the century, suggesting maladaptation to anticipated CC and a potential threat to its carbon sequestration capacity. This being said, we observed a clear difference in response to CC within and among genetic clusters, with the western cluster being more impacted than the central and eastern clusters. Our results show that intraspecific genetic variation, notably associated with the phylogeographic structure, must be considered when estimating the response of widespread species to CC. [ABSTRACT FROM AUTHOR]

Methods using genomic information to forecast potential population maladaptation to climate change or new environments are becoming increasingly common, yet the lack of model validation poses serious hurdles toward their incorporation into management and policy. Here, we compare the validation of maladaptation estimates derived from two methods—Gradient Forests (GFoffset) and the risk of non‐adaptedness (RONA)—using exome capture pool‐seq data from 35 to 39 populations across three conifer taxa: two Douglas‐fir varieties and jack pine. We evaluate sensitivity of these algorithms to the source of input loci (markers selected from genotype–environment associations [GEA] or those selected at random). We validate these methods against 2‐ and 52‐year growth and mortality measured in independent transplant experiments. Overall, we find that both methods often better predict transplant performance than climatic or geographic distances. We also find that GFoffset and RONA models are surprisingly not improved using GEA candidates. Even with promising validation results, variation in model projections to future climates makes it difficult to identify the most maladapted populations using either method. Our work advances understanding of the sensitivity and applicability of these approaches, and we discuss recommendations for their future use. [ABSTRACT FROM AUTHOR]

Climate change is affecting Canada's boreal zone, which includes most of the country's managed forests. The impacts of climate change in this zone are expected to be pervasive and will require adaptation of Canada's forest management system. This paper reviews potential climate change adaptation actions and strategies for the forest management system, considering current and projected climate change impacts and their related vulnerabilities. These impacts and vulnerabilities include regional increases in disturbance rates, regional changes in forest productivity, increased variability in timber supply, decreased socioeconomic resilience, and increased severity of safety and health issues for forest communities. Potential climate change adaptation actions of the forest management system are categorized as those that reduce nonclimatic stressors, those that reduce sensitivity to climate change, or those that maintain or enhance adaptive capacity in the biophysical and human subsystems of the forest management system. Efficient adaptation of the forest management system will revolve around the inclusion of risk management in planning processes, the selection of robust, diversified, and no-regret adaptation actions, and the adoption of an adaptive management framework. Monitoring is highlighted as a no-regret action that is central to the implementation of adaptive forest management. Key words: adaptation, adaptive capacity, boreal forest, climate change, resilience, vulnerability. Le changement climatique affecte la zone boreale du Canada dans laquelle on retrouve la plupart des forets amenagees du pays. Les impacts du changement climatique dans cette zone devraient etre assez importants pour que l'on y voie la necessite d'adapter les systemes d'amenagement forestier au Canada. Ce document examine les mesures et strategies potentielles d'adaptation a mettre en place pour les systemes d'amenagement forestier, compte tenu des impacts actuels et futurs des changements climatiques et de la vulnerabilite qui leur sont associes. Ces impacts et ces vulnerabilites comprennent les augmentations regionales des taux de perturbation, les changements regionaux dans la productivite des forets, la variabilite accrue de l'approvisionnement en bois, la diminution de la resilience socio-economique et l'augmentation de la gravite des problemes de securite et de sante pour les communautes forestieres. Les actions potentielles d'adaptation du systeme d'amenagement forestier sont categorisees selon qu'elles reduisent les facteurs de stress non climatiques, qu'elles reduisent la sensibilite au changement climatique ou qu'elles maintiennent ou ameliorent la capacite d'adaptation des sous-systemes biophysique et humain du systeme d'amenagement forestier. Une adaptation efficace du systeme d'amenagement forestier s'articulera autour de l'inclusion de la gestion des risques dans les processus de planification, de la selection d'actions d'adaptation robustes, diversifiees et sans regret, et de l'adoption d'un cadre de gestion adaptative. Le suivi (monitoring) est mis en evidence comme une action sans regret qui est au creur de la mise en reuvre de la gestion adaptative des forets. Mots-cles: adaptation, capacite d'adaptation, foret boreale, changement climatique, resilience, vulnerabilite., 1. Introduction The mean global temperature has increased by almost 1 °C since 1900 (Hansen et al. 2006), owing in large part to human influences, and is expected to continue [...]

The present study documents the changes in carbon and nitrogen metabolites occurring in apical buds and previous year stems of white spruce seedlings (Picea glauca [Moench] Voss) with contrasting growth phenotypes (tall vs. small) after transfer to short day (SD; 8 h) photoperiod to induce bud formation. Concentrations of total nonstructural carbohydrates markedly increased in the developing buds within the days after transfer to SD, mainly as a result of increased concentrations of monosaccharides such as glucose, fructose, and pinitol. At the same time, starch levels declined, with the resulting carbohydrates presumably used to meet early carbon requirements of the SD-induced apical bud. Concentrations of glutamine, glutamic acid and proline also decreased immediately after transfer to SD in both organs. Later stages of SD-induced bud formation were characterized by an increase in starch, sucrose, and glutamine concentrations in previous year stems, concomitant with an increase in the steady-state levels of UDP-glucose pyrophosphorylase and glutamine synthetase protein. In contrast, arginine levels increased after 2 weeks of SD exposure, indicating a transition in arginine metabolism at the time of initiation of shoot stem primordia and bud elongation. Higher accumulation of total nonstructural carbohydrates and total amino acids in previous year stems of small trees could indicate lower sink strength of apical bud during its development, which could in turn impact subsequent tree growth. Key words: amino acids, bud set, carbohydrates, growth, Picea glauca, soluble proteins. La presente etude presente les changements se produisant au niveau des metabolites carbones et azotes dans le bourgeon terminal et la tige de l'annee precedente d'epinettes blanches (Picea glauca [Moench] Voss) ayant des phenotypes de croissance contrastes (petits versus grands arbres), apres avoir ete transferees en conditions de jours courts (JC ; 8 heures) de maniere a induire la formation des bourgeons. Les concentrations en hydrates de carbone non structuraux augmentent de maniere marquee dans les bourgeons en developpement immediatement apres le transfert en JC, principalement en raison de l'augmentation des concentrations en monosaccharides tels que le glucose, le fructose et le pinitol. Au meme moment, les niveaux d' amidon diminuent en faveur de l' augmentation des sucres solubles indispensables a la demande en carbone reliee a formation des bourgeons terminaux induite en JC. Les concentrations en glutamine, acide glutamique et proline diminuent egalement immediatement apres le transfert des epinettes en JC dans les deux organes. Les stades plus avances de la formation des bourgeons terminaux induite en JC sont caracterises par une augmentation des concentrations en amidon, en saccharose et en glutamine dans les tiges de l'annee precedente, en concomitance avec une augmentation des niveaux d'UDPglucose pyrophosphorylase et de glutamine synthase. En revanche, les concentrations en arginine augmentent apres 2 semaines d'exposition aux JC, suggerant qu'une transition au niveau du metabolisme de l'arginine se produit au moment de l'elongation des bourgeons et de la formation des primordia des tiges dans le bourgeon. L'accumulation superieure d'hydrates de carbone non structuraux et d'acides amines dans les tiges de l'annee precedente des petits arbres indique une force moindre exercee par le puits (bourgeon terminal) pendant son developpement sur l'organe source (tige), avec au final des repercussions sur la croissance subsequente de l'arbre. Mots-cles : acides amines, croissance, formation du bourgeon, hydrates de carbone, Picea glauca, proteines solubles., Introduction The annual growth cycle of woody plants is characterized by alternating periods of active growth and dormancy. The duration of the growing season of trees is defined by the [...]

Hybridization frequently occurs among poplars, both naturally and artificially, hindering identification. Over 32 million clonal poplars, predominantly hybrids, have been planted throughout the Canadian prairies over the past century, making confirmation of genomic identity important. We developed a genotyping assay that rapidly diagnoses four compatible Populus species (Populus balsamifera L. and Populus deltoides Bartr. ex Marsh.: indigenous, Populus laurifolia Ledeb. and Populus nigra L.: exotics) and their hybrids found throughout this ecozone. First, we sequenced 23 genes from representative provenances of the four Populus species to discover single nucleotide polymorphisms (SNPs). Second, we developed and validated a medium-throughput genotyping assay of 26 diagnostic SNPs within these genes. We used this assay to genotype 198 trees from natural populations as well as 30 clones (pure species and hybrids), including those broadly distributed by Agriculture and Agri-Food Canada's Agroforestry Development Centre since 1910. This suite of SNPs has the resolving power to correctly identify pure species and hybrids of Populus. We confirmed the identity of clones of well-documented origin, complex hybrids with exotic components, and paternity of open-pollinated progenies from breeding programs. This diagnostic tool should prove useful for efficient molecular fingerprinting of breeding material and for further studies of interspecific gene flow on the Canadian prairies. L'hybridation est frequente chez les peupliers et rend parfois difficile leur identification. Au cours du dernier siecle, plus de 32 millions de peupliers, principalement hybrides, ont ete distribues dans l'ecozone des Prairies canadiennes rendant la confirmation de leur identite genomique necessaire. Nous avons developpe une puce de genotypage permettant de diagnostiquer rapidement quatre especes compatibles du genre Populus (Populus balsamifera L. et Populus deltoides Bartr. ex Marsh.: indigenes, Populus laurifolia Ledeb. et Populus nigra L.: exotiques) et leurs hybrides retrouves dans cette ecozone. Nous avons d'abord sequence 23 regions genetiques d'individus provenant des aires de distribution naturelle pour decouvrir des SNPs (single nucleotide polymorphisms) specifiques des especes. Ensuite, nous avons valide un ensemble de 26 SNPs diagnostiques en genotypant 198 arbres provenant de populations naturelles, ainsi que 30 clones distribues par le Centre de Developpement de l'Agroforesterie d'Agriculture et Agroalimentaire Canada depuis 1910. L'ensemble de SNP developpes possede la resolution necessaire pour identifier correctement les quatre especes pures etudiees et leurs hybrides. Il nous a permis de confirmer l'identite de clones d'origine connue, d'hybrides complexes a composantes exotiques, et la paternite de descendances issues de pollinisation libre. Cet outil diagnostique devrait s'averer utile pour obtenir rapidement des empreintes moleculaires de materiel utilise dans des programmes de selection et pour des etudes de flux genique dans les Prairies canadiennes. [Traduit par la Redaction], Introduction Poplars are a significant component of the prairie ecosystem and have a panoply of human uses (reviewed in Tuskan et al. 2006). The low reproductive barriers and overlapping phenologies [...]