by Marie-Claude Boileau | 10 April 2020
Published in Plant Ecology 219(4): 381-390. https://doi.org/10.1007/s11258-018-0802-x
We carried out a study to determine if bark type could reflect the growth potential of yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) at the northern limit of their range in Québec, Canada (47°N, 75°W). We measured a large sample of 266 trees that ranged in size from 95 to 712 mm in diameter at breast height, on two independent study sites. Our results suggest that trees with smooth bark type had mean 5-year diameter increment 8 and 11 mm higher than trees with rough bark type, depending upon the study site. Differences in growth of 8 and 11 mm represented 85% of the overall rough bark type increment in the first site and 78% of the overall rough bark type increment in the second site. The rapid identification of a tree’s growth potential using bark type could be of great use to practitioners because it avoids the need to bore trees to collect increment cores, which injures trees and may serve as an entry point for disease. Moreover, the proposed method helps protect or release the smallest trees with high growth potential and remove trees with low growth potential. While the proposed method is valuable to practitioners operating in uneven-aged forests, its applicability still needs to be tested in even-aged forests.
by Audrey Verreault | 10 April 2020
Published in Botany 96(7): 437-448. https://doi.org/10.1139/cjb-2017-0182
Today, scattered disjunct stands of two temperate species, yellow birch and white pine, are present north of their continuous distributional range in southern Quebec (Canada) at topographical locations that offer protection from severe fires. This study tested whether these species had populations more numerous and widespread millennia ago when the climate was presumably warmer. Specifically, this research involved the analyses of pollen, plant macrofossils, and charcoal fragments of two sites within the western part of Quebec’s balsam fir – paper birch bioclimatic domain: a forest humus deposit from a yellow birch stand (local scale), and a peatland (regional scale). Fossil data suggest that white pine was more abundant regionally between 7500 and 5000 cal. BP, before coming rare under subsequent cooler conditions. Likewise, yellow birch was more abundant regionally between 7700 and 1500 cal BP. Its subsequent decline and the local disappearance of white pine by 200 cal. BP may both be explained by the severe fires that occurred in recent centuries, as well as the rarity of suitable habitats for these species. The sustained presence of temperate species in mixed boreal forests is the result of the combined action of climate, natural disturbances and habitat characteristics.
by Audrey Verreault | 10 April 2020
Published in WIREs Energy Environment 7(5): e298. doi 10.1002/wene.298
Driven by the policy imperatives of mitigating greenhouse gas (GHG) emissions and improving energy security, an increasing proportion of global energy demand is being met by nonfossil energy sources. The socioeconomic and environmental benefits of replacing fossil fuels with bioenergy are complex; however, debate continues about issues such as best practices for biomass removal, stable supply chains, and GHG mitigation. With the greatest biomass per capita in the world, Canada could play an increasing role in the future of global bioenergy and the emerging bioeconomy. This paper reviews the utilization of feedstock salvaged after natural disturbances (fire and insect outbreaks) to supply wood-based bioenergy, by addressing the following multidisciplinary questions: (1) How much salvaged feedstock is available, and what are the uncertainties around these estimates? (2) How can sustainable practices to support increased removal of biomass be implemented? (3) What are the constraints on development of an integrated supply chain and cost-effective mobilization of the biomass? (4) Is the quality of biomass from salvaged trees suitable for conversion to bioenergy? (5) What is the potential for climate change mitigation? In average, salvaged feedstock from fire and insects could theoretically provide about 100 × 106 oven Dry ton (ODT) biomass per year, with high variability over time and space. Existing policies and guidelines for harvesting of woody biomass in Canadian jurisdictions could support sustainable biomass removal. However, uncertainties remain as to the development of competitive and profitable supply chains, because of the large distances between the locations of this feedstock and available processing sites. Another uncertainty lies in the time needed for a benefit in climate change mitigation to occur. A flexible supply chain, integrated with other sources of biomass residues, is needed to develop a cost-efficient bioenergy sector.
by Marie-Claude Boileau | 10 April 2020
Published in Heredity 121(2): 142-154. https://doi.org/10.1038/s41437-018-0061-6
Insect herbivory may drive evolution by selecting for trees with heritable resistance against defoliation. The spruce budworm (Choristoneura fumiferana, SBW) is a highly damaging forest insect pest that can affect population structure of white spruce (Picea glauca) in North America. Resistance against SBW was recently described in white spruce and was linked to three constitutive resistance biomarkers: the phenolic compounds piceol and pungenol, and expression of a beta-glucosidase encoding gene (Pgβglu-1). We investigated the phenotypic variability and heritability of these resistance biomarkers and of picein, the precursor of piceol, in the foliage of 874 trees belonging to 33 full-sib families and 71 clonal lines under evaluation in seven field locations in Eastern Canada. We aimed to (i) determine their genetic control, (ii) estimate the genetic and phenotypic correlations among defense biomarkers, and (iii) determine whether their constitutive levels are associated with detrimental trade-offs on growth. Quantitative genetics analyses indicated that all four traits are moderately to highly heritable. The full-sib and clonal analyses showed that additive and non-additive genetic effects play major and minor roles, respectively. Positive genetic and phenotypic correlations between resistance biomarkers and primary growth indicated that there is no trade-off between total height and height increment and resistance traits, contradicting the GDBH (Growth Differentiation Balance Hypothesis). Our findings about the predominant additive genetic basis of the resistance biomarkers show that adaptive evolution of white spruce natural populations to resist to SBW is possible and that potentially important gains could also be expected from artificial selection.
by Claire Morin | 10 April 2020
Published in Environmental Reviews 26(2): 113-120. https://doi.org/10.1139/er-2017-0066
Exotic species invasions are among the most significant global-scale problems caused by human activities. They can seriously threaten the conservation of biological diversity and of natural resources. Exotic European earthworms have been colonizing forest ecosystems in northeastern United States and southern Canada since the European settlement. By comparison, Asian earthworms began colonizing forests in the northeastern United States more recently. Since Asian species have biological traits compatible with a greater potential for colonization and disturbance than some European species, apprehension is growing about their dispersal into new territories. Here we review the extent of the current northern range of Asian earthworms in northeastern North America, the factors facilitating or limiting their propagation and colonization, and the potential effects of their invasion on forest ecosystems. Data compilation shows that Asian earthworms are present in all northeastern American states. So far, only one mention has been reported in Canada. Data confirm that their distribution has now reached the Canadian border, particularly along the Michigan–Ontario, New York–Ontario, Maine–New Brunswick, and Vermont–Québec frontiers. Studies report that the presence of Asian earthworms is strongly associated with human activities such as horticulture, vermicomposting, and the use of worms as fish bait. Some climatic (temperature, soil moisture) and edaphic (soil pH) factors may also influence their distribution. Controlling their dispersal at the source is essential to limiting their spread, as there is currently no effective way to eradicate established earthworm populations without unacceptable nontarget effects. Proposed management options in the United States include the prohibition of fish bait disposal and better management of the international trade of horticultural goods, commercial nurseries, and vermicomposting industries. We conclude that although regulations and awareness may delay their expansion, Asian earthworms are likely to spread further north into Canada. They are expected to cause important changes to biodiversity and dynamics of the newly invaded forest ecosystems.
