Monitoring of forest response to gradual environmental changes or abrupt disturbances provides insights into how forested ecosystems operate and allows for quantification of forest health. In this chapter, we provide an overview of Smartforests Canada, a national-scale research network consisting of regional investigators who support a wealth of existing and new monitoring sites. The objectives of Smartforests are threefold: (1) establish and coordinate a network of high-precision monitoring plots across a 4400 km gradient of environmental and forest conditions, (2) synthesize the collected multivariate observations to examine the effects of global changes on complex above- and belowground forest dynamics and resilience, and (3) analyze the collected data to guide the development of the next-generation forest growth models and inform policy-makers on best forest management and adaptation strategies. We present the methodological framework implemented in Smartforests to fulfill the aforementioned objectives. We then use an example from a temperate hardwood Smartforests site in Quebec to illustrate our approach for climate-smart forestry. We conclude by discussing how information from the Smartforests network can be integrated with existing data streams, from within Canada and abroad, guiding forest management and the development of climate change adaptation strategies.

Leaf photosynthetic characteristics could be determinant factors to identify the most productive clones of hybrid poplars (Populus spp.) and willows (Salix spp.). Photosynthetic acclimation of hybrid poplars and willows was studied under greenhouse conditions. Seven Populus and five Salix clones were grown for 3 months at three spacings [20 × 20, 35 × 35, and 60 × 60 cm] and two nitrogen (N) levels (20 and 200 ?g g-1). There were no significant spacing effects on leafless aboveground biomass per tree (AGBT) and height. Clonal acclimation to higher density was associated to increases in leaf area index (LAI) by 347% and specific leaf area (SLA) by 13% despite decreased leaf N content per unit leaf area (Narea) by 31%. There were no changes in net CO2 assimilation rate (A) and photosynthetic N-use efficiency in the ambient light condition (PNUEamb) within different spacings. The N addition alleviated competition effects by maximizing leaf area (LA) and SLA. Compared with less productive clones, more productive clones had 28% greater SLA, greater LA and AGBT per unit of increase in Narea over all treatments. The increased development of LA and SLA under high planting density is a key indicator of more productive clones. © 2017 Université Laval.

Les caractéristiques photosynthétiques des feuilles peuvent être déterminantes pour identifier les clones les plus productifs de peupliers (Populus spp.) et de saules (Salix spp.) hybrides. L’acclimatation photosynthétique de clones de peupliers et de saules hybrides a été étudiée en serre. Sept clones de Populus et cinq clones de Salix ont cru pendant trois mois selon trois espacements [20×20, 35 × 35 et 60 × 60 cm] et deux niveaux d’azote (20 et 200 ?g g?1). Il n’y avait pas d’effet significatif de l’espacement sur la biomasse aérienne sans feuilles par arbre (AGBT) et sur la hauteur. L’acclimatation des clones à des densités plus élevées était associée à une augmentation de 347% de l’indice de surface foliaire (LAI) et de 13% de la surface foliaire spécifique (SLA) malgré une diminution de 31% du contenu foliaire en azote par unité de surface foliaire (Narea). Il n’y a pas eu de changement du taux net d’assimilation de CO2 (A) et de l’efficacité d’utilisation photosynthétique de l’azote sous conditions de lumière ambiante (PNUEamb) et selon différents espacements. L’ajout d’azote a diminué les effets de la compétition en maximisant la surface foliaire (LA) et la SLA. Comparativement aux clones moins productifs, les clones plus productifs avaient des SLA 28% plus élevées, ainsi que des LA et AGBT plus élevées par unité d’augmentation de Narea dans tous les traitements. L’augmentation de LA et de SLA dans les plantations à forte densité est un indicateur clé de clones plus productifs. © 2017 Université Laval.

We developed allometric equations for small-diameter woody species growing on mixed forest marginal lands, which are potential sources of biomass for bioenergy. Eleven species of trees and shrubs were sampled from a site located in eastern Canada. Equations derived in this study generally performed better than equations from the literature. Also, fixed-area plots (FAP) and line-intersect sampling (LIS) methods using both random or systematic selection of sampling units were compared to determine which method required the lowest number of measurements to estimate stand biomass for the same precision.

The fixed-area plots method was successfully used to estimate relatively accurately oven-dry biomass per hectare. Results indicated that potentially harvestable woody biomass (oven dry basis) varied between 33-41 and 12–13 t ha?1 for the most and least productive marginal sites respectively. On the most productive site, LIS estimates (between 20 and 42 t ha?1) were usually lower than those obtained using different FAP sampling methods (i.e. systematic or random, small (50 m2) or large (100 m2) plots), but similar on the more open sites (between 10 and 14 t ha?1). Small FAP resulted in a plot without measurements in one case. Moreover, estimates based on small FAP were generally higher, even if not significantly different from larger plot estimates. We therefore suggest using FAP with 100 m2 plots to estimate small-diameter woody biomass on marginal lands with dense vegetation, while LIS, even if promising for open stands, needs further evaluation before recommendation.

Balsam poplar seeds are short-lived and require moist seedbeds soon after they are released to germinate. In addition to sexual reproduction, balsam poplar stands can regenerate clonally by root suckering. The origin of stands will in turn affect their genetic structure and root system architecture, which are poorly understood for upland forest stands. Three stands were hydraulically excavated in Quebec (moist) and Alberta (dry) to determine the origin of trees and to characterize root systems with respect to presence of parental roots and root grafts connections. Clones were identified using single-nucleotide polymorphism (SNPs), and all stems, roots and root grafts were aged using dendrochronology techniques. All 82 excavated trees were of sucker origin, and four of the six stands contained a single clone. Parental root connections were found between 22% and 25% of excavated trees, and 53% and 48% of trees were linked with a root graft between the same or different clones, in Alberta and Quebec, respectively. Mean distance between trees connected by parental root was significantly lower than the distance between unconnected trees (0.47 ± 0.25 m vs. 3.14 ± 0.15 m and 1.55 ± 0.27 m vs. 4.25 ± 0.13 m) in Alberta and in Quebec, respectively. The excavations also revealed many dead stumps with live roots, maintained through root connections with live trees. This research highlights that balsam poplar growing in upland stands is a clonal species that can maintain relatively high genotypic diversity, with frequent root connections between trees at maturity. Maintaining an extensive root system through root connections increases the chances of a clone surviving when the above ground tree is dead and may also enhance the resilience of balsam poplar stands after disturbance.

Morphological characteristics of poplar and willow clones were determined in order to identify main characteristics leading to superior growth under increased plant competition with low or high nitrogen (N) availability. Seven hybrid poplar (Populus spp. including one hybrid aspen) and five willow (Salix spp.) clones were grown under greenhouse conditions for 13 weeks at three spacings (20 × 20, 35 × 35, and 60 × 60 cm) and two N levels (20 and 200 mg kg?1). The decrease in spacing from 60 to 20 cm reduced leaf area by 50% but clones had similar aboveground biomass per tree under all spacings, with increasing their height per unit leaf area. More productive clones had greater leaf area (+102%), leaf area per unit plant biomass (+12%) and lower root-to-shoot ratios (?27%) compared to less productive clones. There were positive relationships between leaf area and above-ground biomass per tree for both more and less productive clones. Compared to low N level and 60 cm spacing, trees growing in high N level and 20 cm spacing reached similar root collar diameter, crown width, and leaf area values and even greater height, suggesting that an addition of N could help mitigate negative effects of tree competition.

Il y a un intérêt pour les plantations d'espèces à croissance rapide de peupliers hybrides et de saules au Canada. Cet intérêt s'explique à la fois par le taux de croissance rapide et le potentiel élevé de rendement de ce type de système de production. Cependant, leur établissement et leur entretien requièrent des investissements considérables. Les efforts de recherche sur les comparaisons de productivité de différents clones ou espèces, les croisements, la physiologie, la nutrition, la sylviculture, la gestion des ravageurs, les méthodes de récolte, les aspects socio-économiques et la transformation industrielle contribuent à maximiser la production de fibre et à minimiser les coûts de production. L'objectif de cet article est de décrire brièvement des travaux de recherche en cours ou récemment complétés sur les plantations d'espèces à croissance rapide de peupliers hybrides et de saules et de discuter de leur utilité et de leurs impacts à des fins d'applications pratiques.

Trees from three hybrid poplar clones (one Populus balsamifera
P. simonii clone and two P. deltoides
P.
petrowskyana clones), were grown for 3 years in an agricultural field and fertilized at planting with 27 combinations of nitrogen (N), phosphorus (P) and potassium (K) fertilizers. Fertilizers used were granular ammonium nitrate (34.5 0 0) at three levels (0, 8 and 16 g/tree), triple-super-phosphate (0 45 0) at three levels (0, 12.5 and 25 g/tree), and potassium sulfate (0 0 50) at three levels (0, 8 and 16 g /tree). Growth responses to N fertilization were negative during the first growing season: N fertilization reduced growth, net assimilation rate (A), stomatal conductance (Gs), and increased the abundance of 13C in the leaves. These results might be related to the soil pH at the site which ranged from 7.7 to 8.1, and to the dry conditions that prevailed during the first growing season. Leaf N concentrations were unaffected by the fertilization level. Conversely, N fertilization decreased leaf P concentrations, which were in turn positively correlated with growth and negatively correlated with carbon isotopic composition (d13C). There were clonal differences in d13C that varied between the first and second growing seasons in relation to the relative growth rates of the clones. Growth responses to fertilization at planting were nil or slightly positive during the second and third growing seasons. These results indicated that ammonium nitrate was unsuitable for fertilizing these hybrid poplar clones at planting, and that further study is required to test fertilization at planting with nitrate-N versus ammonium-N sources under these field conditions. <b>&#169; 2006 Elsevier B.V. All rights reserved</b>.

Balsam poplar (Populus balsamifera L.) can easily be grown when planted as dormant, unrooted cuttings. The first part of this research project consisted of a greenhouse study to identify the best combination of pre-planting treatments to maximize rooting of hardwood cuttings for large-scale greenhouse propagation. Eighty-four treatment combinations were tested on 10 cm-long cuttings, including seven soaking lengths of time (0, 1, 2, 3, 4, 5 and 14 days), three dips (none, powder and liquid rooting hormone), two collection dates (fall and spring), and two cutting selections (average trees and a superior clone).

Secondly, we tested the performance of unrooted cuttings on typical forestry sites lacking natural regeneration, using 30 cm-long cuttings and full-length whips (>60 cm). Three pre-planting treatment combinations were used (soaking for 1 or 3 days, or 3 days with a dip in rooting hormone). Other factors tested were two collection dates (fall and spring), two cutting selections (average trees and a superior clone), two storage methods (stored as full whips or cut to size), and two cutting locations (basal or top 30 cm of stools). © 2004 Elsevier B.V. All rights reserved.