by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 38: 317-330
This paper presents the 5 year results of different cutting intensities (removal of 0%, 40%, 50%, 60%, and 100% of the basal area) applied in two mixed yellow birch (Betula alleghaniensis Britt.) – conifer stands of eastern Québec, Canada. Two sites 90 km apart were used: Armagh and Duchesnay. Each site had four replicates of the treatments in a randomized block design. The effect on light availability was similar in the two sites: the 0%, 40%, 50%, 60%, and 100% cuts transmitting a mean of 5%, 21%, 26%, 30%, and 94% of full light, respectively, during the first summer. Soil temperature increased only in the 100% cut (4-5 °C, maximum daily temperature). Soil disturbance during harvest was higher at Duchesnay than at Armagh, which clearly improved seedbed receptivity, particularly to yellow birch. After 5 years, treated areas contained 21 000 to 48 300 seedlings/ha at Duchesnay compared with 5500 – 10 500 seedlings/ha at Armagh. Significant losses of coniferous advance growth were observed at both sites, but a subsequent seedling recruitment occurred only at Duchesnay. Red spruce (Picea rubens Sarg.) showed superior establishment in the 60% cut (4400 seedlings/ha) than under other cutting intensities (1600-2100 seedlings/ha), whereas balsam fir (Abies balsamea (L.) Mill.) responded well to all partial cutting treatments. At both sites, pin cherry (Prunus pensylvanica L.f.) was the main competing species in the 100% cut, whereas densities of the preestablished mountain maple (Acer spicatum Lamb.) and striped maple (Acer pensylvanicum L.) either remained the same or increased in the partial cuts.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 38: 31-39
The shelterwood system can be used to establish regeneration and to improve the growing conditions of seedlings and, thereby, increase their probability of survival after final harvest. To determine the cutting intensity that best promotes the development of red spruce (Picea rubens Sarg.) regeneration, an experiment, including four repetitions of five treatments (control; low, moderate, and heavy partial cuttings; and clear-cutting), was established in a lowland stand in Québec, Canada, dominated by red spruce and balsam fir (Abies balsamea (L.) Mill.). Regeneration development responses to treatments varied according to cutting intensity, species, and position relative to the skidding trails in the residual stands. Ten years after treatment, red spruce seedlings were well established but were smaller than those of balsam fir and deciduous species. Red spruce seedling height was generally greater in partial-cut skidding trails, as was light availability. However, in clearcuts, the size of red spruce seedlings established in skidding trails seemed to be negatively affected by the considerable quantity of woody debris strewn over them. Among the partial-cut treatments, tree regeneration leaf biomass was the highest where 60% of the initial basal area was removed. Thus, this treatment is an attractive alternative to clear-cutting in such lowland stands where watering-up is anticipated after final harvest.
by André Boily | 30 January 2019
Published in Annals of Forest Science 65: 1-12 https://link.springer.com/article/10.1051/forest:2007088
This study proposes a generalized linear mixed model to predict individual tree mortality in northern hardwood stands under uneven-aged management. The model is based on a complementary log-log (CLL) link function, and was calibrated using permanent-plot data. Tree vigor, stem product, diameter at breast height and stand basal area were tested as explanatory variables. A plot and an interval random effect were specified to account for spatial correlations. When compared with the traditional logit link function, the CLL facilitates the inclusion of the time factor. In this case study, there was an important variability of mortality predictions between the plots and the intervals for a given plot. The interval random effect is thought to be associated with catastrophic mortality. Since both tree vigor and stem product proved to be significant mortality predictors, we recommend that these variables be evaluated to increase the accuracy of mortality models.
by Claire Morin | 30 January 2019
Published in Canadian Journal of Botany 85(12): 1227-1232
Natural hybridization has long been recognized as a means for gene flow between species and has important evolutionary consequences. Although hybridization is generally considered to be symmetrical, with both hybridizing species being equally likely to be the male or female parent, several studies have demonstrated the presence of asymmetrical hybridization and introgression from one species to the other. We investigated the direction of natural hybridization between two sympatric forest tree species in North America (Populus deltoides Bartr. ex Marsh. and Populus balsamifera L.) using species-specific single nucleotide polymorphism (SNP) markers in both the nuclear and chloroplast genomes. All natural hybrid individuals, identified from morphological traits, had nuclear alleles corresponding to both parental species, while the chloroplast genotypes showed similarity to P. deltoides, indicating asymmetrical hybridization with P. deltoides as the maternal and P. balsamifera as the patternal donor species. This observed asymmetrical hybridization may be attributable to cytonuclear interactions.
by André Boily | 30 January 2019
Published in Tree Seed Working Group – News Bulletin Canadian Tree Improvement Association. 46(December): 8-9. https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/tree-seed/tree-seed-centre/tswgnewsbulletin46.pdf
The main concern for tree breeders and reforestation managers is to provide seedlings of good genetic and morphological quality, that are well adapted to a variety of growing conditions, so their genetic potential can be realized. To achieve this goal, the Ministère des Ressources naturelles et de la Faune du Québec (MRNF) has established seed transfer rules across the province, that take into account the genetic quality of the material.
