Despite new knowledge in recent years, our understanding of the phenology of wood formation for various species growing in different environments remains limited. To enhance our knowledge of the tree growth dynamics of boreal tree species, we investigated the average seasonal, monthly, daily, and diel patterns of tree growth and water status from 11 years of observations with the 15 min and 1.5 µm resolved stem radial size variation data of 12 balsam fir (Abies balsamea (L.) Mill.) trees growing in a cold and humid boreal environment. Growth only occurred above an air temperature threshold of 9–10 °C, and the maximal growth rate over the year (23–24 June) was synchronous with the maximal day length (20–21 June) and not with the maximal air temperature, which occurred on average about 2 weeks later (4–5 July). Tree growth was mostly restricted by air temperature and solar radiation under these cold and wet boreal conditions, but our results also highlight a turgor-driven growth mechanism. Diel dynamics reveal that tree growth is minimal during the day when the stem dehydrates, and higher past midnight when the stem is fully rehydrated. This pattern suggests that carbon assimilation through photosynthesis occurs primarily during the day, while energy production and carbon allocation to woody tissues occur primarily at night via cellular respiration. Overall, our results show that the temporal patterns of the growth and water status of balsam fir growing in cold and humid boreal environments are controlled by a set of environmental factors that influence various physiological processes and mechanisms, many of which still need to be documented.

In 2020, Quebec adopted a strategy to increase the quantity and quality of timber it produces. During a roundtable discussion held in the fall of 2021, experts in forestry and in related fields expressed their views on the new strategy and its implementation challenges. The main purpose of this article is to present the key observations from the roundtable. The observations addressed two themes: the general context in which the strategy was developed, and the context of its implementation on the ground. Although most of the panellists agreed on the relevance of such a strategy, particularly as regards to climate change mitigation and wealth creation, several questions remain. The challenge of harmonizing uses, regionalization, spatialization of management decisions, labour shortage, and uncertain ecosystem dynamics make it difficult to assess the strategy’s potential impact on the ground and its ability to achieve its targets.

En 2020, le Québec a adopté une stratégie nationale de production de bois (SNPB) afin d’augmenter la quantité et la qualité de la matière ligneuse produite. Au cours d’une table ronde tenue à l’automne 2021, des experts de la foresterie et de domaines connexes se sont prononcés sur cette nouvelle stratégie et sur les défis de mise en oeuvre qu’elle pose. L’objectif principal de cet article est de présenter les principaux constats émis au cours de cette table. Les constats ont été divisés en deux thématiques, soit le contexte général d’élaboration de cette stratégie et le contexte de sa mise en oeuvre en forêt. Bien que la plupart des panélistes s’entendent sur la pertinence de créer une telle stratégie, notamment en ce qui a trait à l’atténuation des changements climatiques et à la création de richesses, plusieurs interrogations persistent. Les défis d’harmonisation des usages, de régionalisation, de spatialisation des décisions d’aménagement, de manque de maind’oeuvre et de la dynamique incertaine des écosystèmes complexifient l’évaluation des retombées potentielles de la SNPB sur le terrain et sa capacité d’atteindre les cibles établies.

Sapwood characteristics, such as sapwood area as well as thermal and hydraulic conductivity, are linked to species-specific hydraulic function and resource allocation to water transport tissues (xylem). These characteristics are often unknown and thus a major source of uncertainty in sap flow data processing and transpiration estimates because bulk rather than species-specific values are usually applied. Here, we analyzed the sapwood characteristics of fifteen common tree species in eastern North America from different taxonomic (i.e., angiosperms and gymnosperms) and xylem porosity groups (i.e., tracheid-bearing, diffuse- or ring-porous species) and we assessed how uncertainties in sapwood characteristics involved in sap flow calculations are propagated in tree water use estimates. We quantified their sapwood area changes with stem diameter (allometric scaling) and thermal conductivity. We combined these measurements with species-specific values of wood density and hydraulic conductivity found in the literature and assessed the role of wood anatomy in orchestrating their covariation. Using an example sap flow dataset from tree species with different xylem porosity, we assessed the sensitivity of tree water use estimates to sapwood characteristics and their interactions. Angiosperms (ring- and diffuse-porous species), with specialized vessels for water transport, showed a steeper relationship (scaling) between tree stem diameter and sapwood area in comparison to gymnosperms (tracheid-bearing species). Gymnosperms (angiosperms) were characterized by lower (higher) wood density and higher (lower) sapwood moisture content, resulting in non-significant differences in sapwood thermal conductivity between taxonomic and xylem porosity groups. Clustering of species sapwood characteristics based on taxonomic or xylem porosity groups and constraining these parameters could facilitate more accurate sap flow calculations and tree water use estimates. When combined with an increasing number of sap flow observations, these findings should improve tree- and landscape-level transpiration estimates, leading to more robust partitioning of terrestrial water fluxes.

Fertilization of hybrid poplar (HP) plantations with papermill by-products is a promising solution to improve soil fertility and nutrient availability, increase plantation productivity, and provide added value to these materials that would otherwise be incinerated or sent to the landfill. We assessed the growth and foliar nutrition of a HP clone (Populus × canadensis × Populus maximowiczii) at six plantation sites aged 3–5 years in southern Quebec, Canada. Sites received a fertilization treatment consisting of a mixture of papermill biosolids (120 to 140 t·ha-1, depending on site) and lime mud (10 to 15 t·ha-1) before being planted, or no fertilization (control). Tree growth was significantly improved by fertilization, with fertilized trees showing a mean annual height increment of 1.3 m (all-site mean; SD = 0.2), compared with 0.5 m (SD = 0.4) for unfertilized trees. Foliar calcium and magnesium increased following fertilization and levels met optimal thresholds at all sites, whereas nitrogen, phosphorous, and potassium concentrations also increased, but nutritional deficiencies remained for these elements at several sites. Our results confirm the benefits of fertilizing hybrid poplars with papermill by-products, but they also indicate that adjustments in application rates or type of by-products could be made to fully satisfy nutritional requirements and thus optimize tree growth. © 2021 Authors Palma Ponce, Miquel, Lafleur, Brais, and Bélanger, and The Crown.

The use of wood ash as a soil amendment in afforestation and reforestation efforts is increasing. While most studies suggest benefits or neutral results on tree growth and survival, a few studies indicate adverse effects. Hybrid larch, jack pine and white spruce were studied at three northwestern Quebec plantation sites after they received wood ash at two application rates. Soil chemical properties, foliar nutrients and seedling growth and mortality were monitored over a period of eight years. The response of soil to ash application was mostly observed in the forest floor and was more pronounced in year 3 than year 8, likely due to the acidifying nature of the boreal soils studied. Jack pine growth increased linearly with wood ash application rates, white spruce growth showed an inconsistent and delayed positive response under the higher application rate, and hybrid larch growth and survival were either increased or decreased under the lower application rate depending of site but decreased at all sites under the higher application rate. The divergence in growth response between tree species underlines a trade-off between species with rapid acquisition of resources (e.g., pine, larch) to species that use more conservative strategies and store nutrients in their tissues for longer periods (e.g., spruce). In the case of hybrid larch, it accumulated larger amounts of Mn in its needles under the higher application rate and thus, the high bioavailability of Mn appears to have been detrimental to its survival and growth. Its higher sensitivity to Mn addition from ash is likely due to its highly acquisitive (nutrients) nature compared to other coniferous species as well as the initial levels of available Mn levels in the soil. The contrasted growth responses reported here under similar growing conditions highlight the importance of identifying suitable species, sites and application rates to maximize the benefits of wood ash amendments for future tree plantations in the boreal forest.

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.

Wood ash amendment to forest soils contributes to the sustainability of the growing bioenergy industry, not only through decreased wood ash waste disposal in landfills but also by increasing soil/site productivity and tree growth. However, tree growth studies to date have reported variable responses to wood ash, highlighting the need to identify proper application rates under various soil/site conditions to maximize their benefits. We explored the influence of tree species, wood ash nutrient application rates, time since application, stand development stage, and initial (i.e., before wood ash application) soil pH and N on short-term tree growth response to wood ash amendment across eight unique study sites spanning five Canadian Provinces. Jack pine (Pinus banksiana Lamb) had the most positive response to wood ash amendment compared to white (Picea glauca Moench), hybrid (Picea engelmannii x glauca Parry), and black spruce (Picea mariana Miller), where increasing nutrient application rates increased height growth response. In comparison, black spruce had the most negative response to wood ash amendment, where increasing nutrient application rates slightly decreased height growth response. Site as a random effect explained additional variation, highlighting the importance of other unidentified site characteristics. By examining trends in short-term growth response across multiple studies with variable site characteristics, we found growth response differed by tree species and nutrient application rates, and that jack pine is a promising candidate for wood ash amendment. These results contribute to our knowledge of optimal wood ash amendment practices and environmentally sustainable bioenergy production. © 2019 The Authors. GCB Bioenergy published by John Wiley & Sons Ltd

Over a period of 2 yr, the effects of dehydrated septic tank sludge application on the chemical properties of a severely disturbed forest clayey soil were assessed and compared with application of native forest floor (i.e., from neighboring forest). Six treatments [fresh and mature sludges × two depths (15 and 25 cm), forest floor, and a control] were replicated three times according to a complete random design. Total organic C and N concentrations of amendments and their chemical structure, based on13 C nuclear magnetic resonance (NMR) spectroscopy, were determined. Mineral soil C and N concentrations and C mineralization rates were monitored as well as nutrient supply rates using Plant Root Simulator™ probes. White spruce [Picea glauca (Moench) Voss] seedling foliar nutrition and growth were also monitored. NMR spectroscopy revealed differences among amendments, with the forest floor spectra displaying lower O-alkyl C and higher alkyl C and carbonyl C proportions relative to sludge. Neither soil C concentrations nor mineralization were significantly improved in the mineral soil under any treatment, even at application rates exceeding 700 t sludge ha?1 (dry mass). The sludges supplied more NO3 and P, and less NH4 and K to the mineral soil than the forest floor and control. Increased nutrient availability under sludge and forest floor generally resulted in improved foliar nutrition and growth of white spruce seedlings. Despite differences in organic matter quality and mineral N form supplied by sludge and forest floor, sludge application is a valid restoration approach. © 2018, Agricultural Institute of Canada. All rights reserved.

Tree plantations are commonly used to restore abandoned agricultural fields with varying degrees of success. Agricultural soils differ from forest soils in nutrient availability and microbial communities. The objective of this study was to test the effect of adding small amounts of forest soil on the survival, growth and rates of mycorrhizal fungal colonization of trees planted in an abandoned agricultural field over the crucial first three growing seasons. Seedlings of two arbuscular mycorrhizal (AM) and two ectomycorrhizal (EM) tree species were planted in an abandoned agricultural field. Soil inocula were taken from four forest stands, each dominated by one of the planted species. Half of the soil samples were sterilized before inoculation to distinguish microbial from nutrient effects. The effect of the quantity of soil inoculum added was tested using 300 and 1500 ml of forest soil. Tree mortality was low and did not vary between treatments. The growth of EM tree species responded, positively or negatively, to forest soil inoculation. A negative feedback was detected on the growth of red oak seedlings inoculated with red oak soil. Seedlings inoculated with EM sterilized soils were smaller than control seedlings, presumably due to lower nutrient availability of EM forest soils compared to agricultural field soil. The majority of the effects, either positive or negative, were observed the first year. After three seasons of growth, only yellow birch seedlings that had received 1500 ml of non-sterilized red oak soil still benefited from soil inoculation. More research is needed in nutrient-limited soils to determine whether inoculation would have greater or longer term benefits on tree survival and growth. © 2016

Aboveground biomass yields of short rotation cultures (SRC) of willow can vary substantially depending on site quality. Among others, aboveground biomass yields depend on climatic conditions, soil properties, age of the SRC, and number of harvesting cycles. In this study, we investigated the effects of coppicing on growth variables (i.e., largest basal stem, height, and aboveground biomass) at ten SRC of Salix miyabeana SX67 established on various soils in southern Quebec. More than 1100 shrubs with stool ages varying between 1 and 15 years were measured. Strain analysis was carried out to calculate past annual aboveground productivities, and maximum annual yield potential was quantified at each site. Annual growth rates were highly variable and depended on site and coppicing history. To achieve optimal stool development and aboveground yields, two to three growing seasons following coppicing were necessary for sandy and clayey sites, respectively. The delays for reaching maximum yields were shortened when soil cation exchange capacity was dramatically low and were prolonged when soil was physically restricting stool development. This lag influenced the total yield of the first rotation and also modulated the magnitude of the increase of aboveground biomass that is generally observed in the second rotation. To increase yields in southern Quebec, our results suggest that it is preferable to extend the length of the first rotation instead of coppicing at the end of the first growing season after establishment.

Wood ash fertilization has yet to be investigated in Canadian boreal forests. Ash often improves soil acid–base status, but without N addition it seldom increases tree growth on poor mineral soils. We report results of a large scale experiment conducted in a boreal jack pine (Pinus banksiana Lamb) stand growing on sandy acidic soil in Northeastern Canada. The experiment was completely random with four replications (1 ha each) of five treatments (0, 1, 2, 4 and 8 dry Mg ha?1) of loose fly ash with and without urea (280 kg N ha?1). Soils were sampled in the 0, 2, and 8 Mg ha?1 treatment up to eight years after application. Foliar nutrition and stand growth were assessed in all treatments one and two years and five years after treatment, respectively.

Even under low ash loading, forest floor exchangeable base cations, pH, and base saturation increased within a year of application. Ash application also resulted in a swift decrease in forest floor organic C and an increase in N potential net mineralization rate. The initial dominant pattern of upper mineral soil properties in relation to ash loading was a curvilinear relationship with the highest values observed in the 2 Mg ha?1treatment. Eight years after ash application, significant linear relationships were found between ash loading and base cations and base saturation in the forest floor and mineral soil (0–10 cm, 10–20 cm). Contrary to N fertilization, ash had no effect on jack pine foliar nutrition and on its five-year growth. However, a decrease of 30% in relative growth rate was observed between the control and the 8 Mg ha?1ash treatment for large (?10 cm DBH) black spruces (Picea mariana (Mill.) BSP). Black spruce is the dominant commercial species of Canadian eastern boreal forests and thus, additional studies are needed to validate the deleterious effect of ash on spruce growth and to elucidate the mechanisms involved.

Abstract

In order to receive forest certification and to respond to societal desires,many forest companies are attempting to demonstrate that their forest activities are «sustainable». The main objective of this paper is to qualitatively evaluate the ways in which forestry-related provincial regulations in the three provinces (Alberta, Ontario and Quebec) that contain most of the Canadian boreal forest help forest companies achieve certification with respect to ecological criteria. In the process of continually evolving towards sustainable forest management,we evaluate how these provincial regulations governing forest operations can be helpful in maintaining three criteria: biodiversity, the aquatic environment and soils. This study shows that the regulations evaluated have varied in their approach and thus have different strengths that must be underlined: (1) Ontario’s approach is the strongest in terms of biodiversity, (2) Alberta and Ontario provide measures to abandon roads after harvesting, (3) Quebec provides the greatest specific measures for protecting waterways and aquatic species, (4) Alberta shows the greatest consideration for maintaining the most soil properties and functions. Better links between different regulations are necessary in all jurisdictions. The continual improvement of Canadian forest rules is often slow and advances at a different pace depending on regulators but it should be supported in all provinces.

Résumé

Afin d’obtenir une certification forestière et de répondre aux besoins de la société, les compagnies doivent démontrer que leurs activités forestières sont «durables». L’objectif principal de cet article est d’évaluer de quelles façons les normes forestières provinciales des ministères des ressources naturelles aident les compagnies forestières à obtenir une certification environnementale.Nous avons évalué de façon qualitative les lois encadrant les opérations forestières en forêt boréale, la zone forestière dominante au Canada. Nous mettons l’emphase sur trois provinces (Alberta, Ontario et Québec) qui couvrent la plus grande proportion de la zone boréale au pays. Dans une démarche d’amélioration continue, nous évaluons comment ces normes peuvent aider à maintenir trois critères : la biodiversité, le milieu aquatique et les sols. Cette étude montre que ces règlements présentent des différences dans leurs approches et des forces qui doivent être soulignées : (1) l’approche de l’Ontario est la plus forte en termes de biodiversité, (2) l’Alberta et l’Ontario proposent des mesures pour abandonner les routes suite aux activités de récolte, (3) le Québec offre les meilleures mesures spécifiques pour un nombre de milieux humides et d’espèces aquatiques, (4) l’Alberta présente la meilleure réflexion sur le maintien du plus grand nombre de propriétés et fonctions des sols. De meilleurs liens entre les différentes lois sont nécessaires bien qu’il faille appuyer l’amélioration continue des règlements forestiers au Canada.

The relationships between site quality indices (SQI) (estimated height at age 50) of black spruce and Jack pine and site characteristics were investigated over a large territory in the boreal forest of Quebec. The relationships with degree-days (DD) and parent material, which are considered as permanent site factors, were significant for both species. Linear regressions with these two parameters as independent variables explained about 40% of the variability in site quality indices for black spruce and Jack pine. The addition of soil chemistry and biological data to this model indicated a significant contribution of exchangeable Mg concentrations or Al:CEC molar ratios in the forest floor and lichen cover to the prediction of site quality indices. Inclusion of these variables increased the model R² up to 60% for both species. Whether these variables reflect permanent site conditions or conditions related to the history of the sites is unknown. © 2004 Elsevier B.V. All rights reserved.