by Svetlana Savin | 30 January 2019
Published in Forest Science 54(3): 255-259
To better understand the variability in mechanical properties caused by genetic differences in hybrid poplars, modulus of elasticity and modulus of rupture in static bending were examined at two 10-year-old clonal trials located at Windsor and St-Ours, southern Québec, Canada. The materials consisted of three hybrids, Populus deltoides X Populus nigra, Populus trichocarpa X P. deltoides, Populus maximowiczii X Populus balsamifera, and native P. deltoides. Significant differences were observed in mechanical properties among hybrids and P. deltoides. The effects of growth on the mechanical properties were inconsistent and varied considerably by site and by hybrid. Results indicated no uniform trends relating growth rate to either higher or lower modulus of elasticity/modulus of rupture. It appears that selection for strength properties may not uniformly lead to decreased growth production, especially for P. trichocarpa X P. deltoides and P. maximowiczii X P. balsamifera.
by André Boily | 30 January 2019
Published in Tree Seed Working Group – News Bulletin – Canadian forest genetics association. 48(December) : 3-10. https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/tree-seed/tree-seed-centre/tswgnewsbulletin48.pdf
For 40 years, the Research Division (Direction de la recherche forestière – DRF) of the Quebec Ministry of Natural Resources and Wildlife (ministère des Ressources naturelles et de la Faune – MRNF) has managed an avant-garde research and development program in the fields of genetic tree improvement for commercial species and the production of forest seedlings and seeds, while integrating new in vitro techniques for the
multiplication of coniferous species.
by equipewp | 30 January 2019
Published in For. Ecol. Manage. 291: 289-299. The introduction of the fungal pathogen Cryphonectria parasitica (Murr.) Barr. decimated American chestnut (Castanea dentata (Marsh.) Borkh.) throughout its native range in North America. A blight-resistant backcross hybrid form of American chestnut has been developed, and these backcross trees are likely to be incorporated into restoration programs in the near future. (…)
by Marie-Claude Boileau | 30 January 2019
Published in The Forestry Chronicle 84(6): 886-899
A tree classification system was developed in the 1980s as part of a guide for tree-marking in the rehabilitation of uneven-aged northern hardwood stands in Québec. It differentiates trees that are at high and low risk of mortality, trees with sawlog potential and cull trees. The risk class was assessed based on the presence of major crown and bole defects. The main objective of the present study was to evaluate this system with respect to its capacity to predict the probability of tree mortality. The variables used to classify the trees were observed in 88 experimental plots (0.5 ha) established between 1983 and 1999. Tree-level mortality probabilities were modelled for sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.) and yellow birch (Betula alleghaniensis Britt.) to test the significance of the classification variables. The presence of decay, fungus or canker, wounds, uprooting, the death of at least 30% of the crown or of the roots, and the product class had significant (p < 0.05) effects on mortality probabilities for at least one of the 3 species studied. In the main, the results supported the tree classification system. However, this system could be modified to differentiate not only trees with a high or low mortality risk, but also to identify some very high-risk trees.
by Claire Morin | 30 January 2019
Published in Journal of Plant Nutrition and Soil Science 171: 858-871
Experimental application of eight acidifying, neutral, or alkalizer compounds (range: –16 to 16 kmol ha–1 of acid-neutralizing capacity [ANC]) was realized in two northern hardwood stands having significantly different soil base saturation (BS) (a “poor” and a “rich” site) to assess responses of soil physico-chemical properties, and nutrition, growth, and health of sugar maple (Acer saccharum Marsh.) trees in the short (3 y) and longer term (10 y). The treatments influenced the main indicators of acidity in the forest floor (soil exchangeable-Ca saturation [SCa], BS, exchangeable-acidity saturation [SH+Al], and the SCa/SH+Al ratio) at both sites, their values increasing (decreasing for SH+Al) along the ANC treatment gradient in both the short and longer term, except for pH. Base saturation of the upper 15 cm of the mineral B horizons of soils was influenced at the two sites 10 y after treatment application. Although ANC treatments affected nutrient concentrations of tree foliage in the short term, their effect was no longer detectable after 10 y at the two sites. Growth, however, was strongly related to ANC treatments after 10 y, but only at the poor site. From 1990 to 2000, the basal-area growth rate of trees at the poor site was (mean ± SE) –0.62 ± 0.28 cm2 y–2 tree–1 for the most negative ANC treatment to +0.90 ± 0.20 cm2 y–2 tree–1 for the most positive ANC treatment. A climatic-stress episode occurring in 1995/96 appeared to accentuate the growth decline of trees subjected to the most negative ANC treatment at the poor site. The experimental results support the hypothesis that atmospheric acid deposition load can cause forest soil base-cation depletion, acidification, and predispose sugar maple to health and growth decline in the longer term in base-cation-poor soils, and that the phenomenon may be reversible by adding alkalizers.
