by Audrey Verreault | 29 July 2020
Published in Pulp and Paper Research Institute of Canada 107(16): 1-32
This report presents data from 125 black spruce stands located in the Boreal forest of Canada from Newfoundland to western Ontario. A description of the vegetation is presented by strata and in total.
Two major vegetation regions were found: the Atlantic located to the east, and the Continental, located to the west of the 65th meridian. Site fertility was lower in the Atlantic region than in the Continental region. The diversity of the vascular species increased from east to west, with a maximum found to the north of the Great Lakes. The highest number of species was found on the most fertile of the mesic to hydric sites. The herb stratum contributed most to the total number of observed species. For the sake of comparison the stands were also described according to currently used site types.
To explore the possibility of using the dominance of vegetation as a continuous variable in relation to site fertility, certain species and species groups were selected for intensive study. By grouping appropriate species, a closer correlation with site index was obtained than by considering the species individually. For site index prediction, the multiple regression equations for these groups were developed which would minimize prediction errors, and would consist of variables which would be easy to identify and be suitable for air photo interpretation or direct ground measurement. Both multiple regression equations and currently used site types appear to be applicable throughout the study area. However, site index prediction was better with regression equations than with site types. This is due, in part, to the wide range of fertility found within a given site type.
by Marie-Claude Boileau | 29 July 2020
Published in Canadian Journal of Forest Research 6(3): 357-367
Dry matter production data were obtained for jack pine (Pinus banksiana Lamb.) stands growing at three density levels on two sites. Regression equations relating tree weight to diameter and height were calculated for stem wood, stem bark, branches, needles, cones, and total aboveground biomass, as well as for periodic net annual increment of these components. Different sets of equations were needed to evaluate biomass on each site, but density levels within sites could be grouped. Total net periodic annual weight increment was linearly related to foliage weight and basal area, but a levelling-off at higher densities was evident when basal area was replaced by stand density index or bole area equivalent as the measure of density.
by Audrey Verreault | 29 July 2020
Published in Annals of the Entomological Society of America 78: 14-19
ln laboratory studies larval development and total mortality of Agromyza frontella on hop medic, Medicago lupulina, were similar to previously reported values on alfalfa, M. sativa. However, pupal development was longer and both pupal weight and total fecundity were somewhat lower than for alfalfa-reared individuals. Nevertheless hop medic is a suitable alternate host and, given its widespread occurrence throughout northeastern North America, could play a role in the dynamics of established and expanding populations of A. frontella, particularly when alfalfa is unavailable.
by Audrey Verreault | 28 July 2020
Published in Canadian Journal of Forest Research 17: 840-845
Containerized jack pine (Pinus banksiana Lamb.) seedlings were grown in a peat moss – vermiculite substrate and inoculated at sowing with pure cultures of three ectomycorrhizal fungi. After 18 weeks of growth in the greenhouse, seedlings inoculated with Laccaria bicolor had 97% of their short roots mycorrhizal, while those inoculated with Hebeloma cylindrosporum had 36% of their rootlets mycorrhizal. No mycorrhizae were obtained with Rhizopogon sp. After both 12 and 18 weeks of growth with the fertilization schedule used, seedlings colonized with L. bicolor and H. cylindrosporum were significantly smaller than those inoculated with Rhizopogon sp. or control seedlings. After 18 weeks of growth, the available nitrogen (N) content of the substrate was considerably greater with L. bicolor inoculated seedlings than with control seedlings, whereas the available phosphorus (P) content of the substrate was the same for these two treatments. Also, after 18 weeks, seedlings mycorrhizal with L. bicolor had a greater concentration (%) of N and P in their tissues than control seedlings; however, they contained fewer milligrams of N and P than control seedlings. From our results on substrate fertility of mycorrhizal seedlings, we state that it is possible to induce mycorrhiza formation of jack pine seedlings with L. bicolor when substrate fertility in available N and P is less than or equal to 39 and 60 ppm, respectively, and that it is possible to maintain L. bicolor mycorrhizae when N and P fertility is less than or equal to 24 and 28 ppm, respectively. From analysis of tissue nutrient content in mycorrhizal seedlings, it appears that the appropriate N and P concentrations to maintain mycorrhiza formation of jack pine seedlings with L. bicolor are less than or equal to 1.6 and 0.2%, respectively.
by Marie-Claude Boileau | 28 July 2020
Published in Canadian Journal of Forest Research 18: 723-727
Balsam fir trees established from advanced regeneration following a clear-cut in 1970 were pruned in June 1985 to live crown ratios of 0.6, 0.4, and 0.2 compared with control trees, which had live crown ratios of 0.8. After two growing seasons, we investigated the homeostatic adjustment of these trees to the loss of their foliage. The height growth, basal area growth, sapwood cross-sectional area, heartwood area, and sapwood saturated permeability of the trees that were pruned to a 0.6 live crown ratio were not significantly different from those of the controls. On the other hand, height growth increment following pruning was reduced 16.7 cm (23%) and 19.5 cm (27%) for the trees pruned to 0.4 and 0.2 live crown ratios, respectively. Furthermore, basal area growth following pruning was reduced 3.2 cm2 (30%) and 6.5 cm2 (61%), respectively. While trees in both the 0.4 and 0.2 live crown ratio pruning treatments did adjust their breast height sapwood area in response to the removal of foliage, the nature of this adjustment differed between the two treatments. For the trees with the 0.4 live crown ratio, sapwood area was reduced because of a reduction in basal area growth but the area of heartwood remained unchanged. For the trees with the 0.2 live crown ratio, the changes in sapwood area were due both to a reduction in basal area growth and an expansion of the heartwood. The saturated permeability of sapwood was not significantly affected by pruning. The adaptive implications of balsam fir’s response to the loss of foliage are discussed in terms of the optimizing the allocation of a limited amount of available carbon.
