by Svetlana Savin | 30 January 2019
Published in Canadian Journal of Forest Research 41: 568-582
Regeneration of northern white-cedar (Thuja occidentalis L.) is often deficient after harvesting in mixedwood stands growing on mesic sites even where browsing pressure is low. We compared the effectiveness of silviculture treatments on early regeneration of white-cedar after single-tree selection cutting (25% of basal area removed), shelterwood seed cut (50% of basal area removed), and group selection cutting (gaps of 625 m2) in three yellow birch (Betula alleghaniensis Britt.) – softwood uneven-aged stands in Quebec, Canada. Three years after harvesting, the combination of factors that maximized abundance of white-cedar seedlings was single-tree selection cutting with artificial seeding on exposed mineral seedbeds (68.8% of plots with the presence of white-cedar). Early growth of planted white-cedar seedlings (40 cm tall) and biomass production were proportional to light availability, i.e., best under group selection cutting (mean height increment = 14.8 cm/year, mean root collar diameter increment = 3.0 mm/year). Browsing pressure has regional impacts depending on herbivore occupancy of the area. Our study was conducted near the northern limit of white-tailed deer (Odocoileus virginianus (Zimmerman, 1780)), and deer were locally absent, while snowshoe hare (Lepus americanus Erxleben, 1777) did not have a consistent effect on seedling abundance and early survival, limiting height growth only during the first year following planting.
by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 217: 275-293
Single-tree selection cutting is sometimes believed to be similar to the natural gap disturbance regime of hardwood forests, but few studies have specifically compared the compositional and structural characteristics of old-growth hardwood stands, undergoing natural gap dynamics and hardwood stands previously subjected to partial cuts. This study characterized and compared the composition (saplings and trees) and structure (gaps, foliage distribution, tree diameter and density, snags and coarse woody debris) of old-growth stands (OG), 12-year-old selection cuts (SC), and 28–33-year-old diameter-limit cuts (DLC) in sugar maple (Acer saccharum)-dominated northern hardwood stands.
Results showed marked structural differences between OG and harvested stands, with stronger differences between DLC and OG than between SC and OG. The synchronized formation of numerous canopy openings in harvested stands induced a massive post-harvest recruitment of advance regeneration in both SC and DLC that created a dense foliage layer in the understory. Large living trees (dbh > 39.1 cm) and defective trees were less numerous in SC than OG, which can have a detrimental impact on species dependent on these structural elements, and on the future availability and characteristics of coarse woody debris. Relatively few compositional differences were noticed among stand types, although a greater proportion of mid-tolerant species was found in the post-harvest recruitment cohorts of harvested stands compared to OG, and a lower proportion of beech (Fagus grandifolia Ehrh.) saplings was observed in DLC compared to OG and SC.
We argue that even if selection cutting is closer to the natural disturbance regime of hardwood forests than diameter-limit cutting, and therefore representing progress toward the development and implementation of a natural-disturbance-based management, a recurring application of selection cutting might lead to a homogenization of forest structure and composition, a reduction of key structural features and a reduction in biological diversity at both the stand and landscape scales. Some management recommendations are proposed.
by Audrey Verreault | 30 January 2019
Proceedings of the Twenty-Ninth Meeting of the Canadian Tree Improvement Association. July 26-29, 2004. Kelowna, Colombie-Britannique. Part 1. p. 43-44.
by Audrey Verreault | 30 January 2019
Published in Tree Seed Working Group – News Bulletin 33(May) 22p.
Seed orchards are an important element in the reforestation program in Québec. Most of these seed orchards are managed in order to produce a maximum of seeds as quickly as possible. The presence of insect pests in these orchards, which provoke damage to cones and seeds, cannot be tolerated since they cause substantial loss, especially during the good years of crop production. These pests can considerably slow down the seed production in white spruce, black spruce and larch seed orchards, while for other tree species, the losses caused by insects are more sporadic. (…)
