by Svetlana Savin | 30 January 2019
Published in Forest Science 54(5): 481-489
Fast-growing hybrid poplars have been proposed as a means of achieving restoration objectives on former agricultural land by providing shelter for slower-growing species. Intensive two-stage scenarios of mixed plantations are also possible using valuable hardwoods interplanted among hybrid poplars. The latter would be harvested at maturity (approximately 20 years) once their protective role has been accomplished, leaving more space for the full development of the second cohort. We implemented simulations of hybrid poplar growth in the SORTIE-ND model and used it to test scenarios with clones varying in growth and crown allometry, different hardwood species, and spatial arrangements, to maximize production of both groups. Important differences in growth and allometry were manifested among clones over time, which translated into important differences in available light between rows. Sustained growth for most hardwoods appeared optimal using wider spacings of 16 m, compared with 12 m, between poplar rows. To our knowledge, this is the first attempt to integrate fast-growing hybrids and intensive silviculture scenarios into spatially explicit models. These models are necessary support tools for the efforts now being invested in intensive silviculture in the face of diminishing forest resources, increasing wood and fiber demands, and climate change.
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.
