by Svetlana Savin | 30 January 2019
Published in Silvæ Genetica 57: 282-291
A strategy for the genetic improvement of Larix decidua P. Mill., L. kaempferi (Lamb.) Carrière and their hybrid (L. x marschlinsii Coaz) in Québec, Canada, was set up to provide short and long-term genetic gains, as well as basic populations for some fundamental experiments. A reciprocal recurrent selection with forward selection strategy (RRS-FS) will be applied by using a pollen mix breeding with a partial population parternity analysis (PMX/WPPA). The genetic mechanisms responsible for heterosis among trees remain poorly understood. This complicates the implementation of multi-species genetic improvement programmes seeking to achieve the full benefits of interspecific hybridization. Various strategies to exploit heterosis are outlined. To expand our knowledge and guide our future choices, basic research has been integrated directly into breeding and testing activities, as well as through experiments integrated within activities leading to recommendations about the top-ranked families to be used in reforestation (cuttings). These experiments can also serve as the basis for future studies seeking a better understanding of heterosis through molecular genetics.
by Claire Morin | 30 January 2019
Published in International Journal of Forestry Research 2009: 1-13
This study reports on the contemporary structure, composition, and dynamics of the pristine northern boreal forest in Québec, Canada, associated with air temperature, precipitation, and soil texture, using 147 permanent sample plots located at the limit of continuous forest in Québec. The results show that tree species composition of stands is associated with stand age, soil texture, air temperature, and precipitation regime. After establishment of the pioneer cohort, the postsuccessional stand dynamics differed among temperature and precipitation regimes, probably because of their influence on tree growth. Our results support the hypothesis that shifts in forest composition related to stand dynamics and the subsequent senescing phase associated with the old growth stage generally occur sooner and proceed faster on more fertile sites due to quicker growth and the subsequent earlier mortality of pioneer species. This study suggests that climate warming should accelerate the successional dynamics of these ecosystems through its positive influence on tree growth.
by Claire Morin | 30 January 2019
Published in Landscape Ecology 24: 171-184
Forestry practices associated with the industrial era (since ~1900) have altered the natural disturbance regimes and greatly impacted the world’s forests. We quantified twentieth century logging patterns and regional scale consequences in three sub-boreal forest landscapes of Eastern Canada (117,000, 49,400 and 92,300 ha), comparing forestry maps depicting age and forest cover types for early industrial (1930) and present-day (2000) conditions. Results were similar for the three landscapes, indicating large-scale forest change during the twentieth century. In 1930, previous logging activities had been concentrated in the lowlands and along the main hydrographical network, as compared to a more even distribution over the landscapes in 2000, reflecting a decreasing influence of the environmental constraints on forest harvesting. In 1930, old-aged forests (>100 years) accounted for more than 75% of the unlogged areas of the three landscapes, as compared to less than 15% for the present-day conditions.
Logging practices have thus inverted the stand age distribution of the landscapes that are currently dominated by young and regenerating stands. The 1930 forest cover types showed a clear relationship with elevation, with conifers located in the lowlands and mixed and deciduous stands restricted to the upper slopes. Between 1930 and 2000, 58–64% of the conifer areas transformed to mixed and deciduous forests, such that no clear altitudinal relationships remained in 2000. We conclude that twentieth century logging practices have strongly altered the preindustrial vegetation patterns in our study area, to the point that ecosystem-based management strategies should be developed to restore conifer dominance, altitudinal gradients, as well as the irregular structure inspired from old forest stands.
by André Boily | 30 January 2019
Abstract of the paper presented to the 15th International Congress of the International Soil Conservation Organization: “Soil and Water Conservation, Climate Change and Environmental Sensitivity”. May 18-23, 2008. Budapest, Hongrie. 6 p. In Canada’s boreal forest, black spruce seedling growth is sometimes kept in check by the invasion of the ericaceous shrub, Kalmia angustifolia. A series of experiments were devised to elucidate the mechanisms by which Kalmia gains a competitive advantage over spruce. Soil incubations and bioassays revealed that humus formed under Kalmia produced very little mineal N. Kalmia was able to uptake soil N from this humus whereas black spruce seedlings could not. Kalmia foliage produced 5x more tannins than spruce needles, and the addition of purified Kalmia tannins to soil resulted in lower mineral N accumulation with no sign of this being provoked by microbial immobilization. Tannin-protein precipitates formed with Kalmia tannins contained more N than those produced with spruce tannins. These protein-tannin complexes were more easily metabolized by mycorrhizae associated with Kalmia than those associated with spruce. Kalmia tannins were shown to inhibit important soil enzymes (acid phosphatase, amidase and b-glucosidase), and these effects were concentration-dependent. Soil enzyme inhibition was higher when Kalmia leaves were added to forest humus, and a field study demonstrated a negative relationship between % Kalmia ground cover and soil enzyme activity. Silvicultural trials showed that fertilization had a positive effect on black spruce growth, but still better growth and improved soil properties were obtained by the complete eradication of Kalmia. Scarification is a promising management option to restore fertility on Kalmia-dominated cutovers.
by Claire Morin | 30 January 2019
Published in Scandinavian Journal of Forest Research 23: 137-147. https://doi.org/10.1080/02827580801968486
This study examined the impact of increased irrigation efficiency on the hardening and frost tolerance of 2-year-old containerized white spruce seedlings in the context of groundwater protection, irrigation management and the maintenance of seedling quality in northern climates. The seedlings were grown under three different irrigation regimes (IR = 30%, 40% and 55% v/v; cm3 H2O/cm3 substrate) and were hardened under conditions of natural photoperiod and temperature. After being subjected to artificial frost tests on four sampling dates during autumn, the seedlings were compared for bud development and frost tolerance. IR had no influence on frost tolerance as determined by measurements of physiological (electrolyte leakage, root water loss) and morphological (shoot damage, root initiation) variables. At the end of the second growing season, there was no significant difference between IRs in seedling height, root collar diameter, shoot dry mass and root dry mass. The results indicate that the amount of water applied to large-dimension 2-year-old white spruce seedlings during the growing season can be significantly decreased without prematurely impeding their growth or hindering their acquisition of frost tolerance.
