by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 40: 357-369
We present the 6 year effects of different cutting patterns (patch-selection cutting with 20, 30, and 40 m diameter gaps, 1 ha patch clear-cut, and uncut control) and spot scarification, on seedbed coverage and regeneration dynamics in yellow birch (Betula alleghaniensis Britton) – conifer stands in eastern Québec, Canada. After 3 years, yellow birch had established better in cutting patterns with gaps than in the patch clear-cut and in the control, while its density was 7 times higher in scarified than in nonscarified subplots. After 6 years, scarified openings and the borders of openings had 3-5 times more seedlings >30 cm in height than nonscarified openings and the understory between the gaps. The loss of advance growth in openings was the main result for conifer species, although recruitment of new balsam fir (Abies balsamea (L.) Mill.) seedlings was accelerated by scarification. Despite the abundance of red spruce (Picea rubens Sarg.) seed-trees on the site, our treatment combinations failed to promote its natural regeneration. Varying gap size did not change the total density of competing vegetation but modified the composition of this shrub layer. Our 6 year results suggest that maintaining conifer species, and the mixed composition of the stands, is uncertain over the long term.
by André Boily | 30 January 2019
Forestry research note – Special issue.
More than 30 years of tree improvement work in Québec has resulted in the establishment of a large collection of material, comprising several native and introduced species. Among them, six are currently used for reforestation-three native species: black spruce (Picea mariana (Mill.) B.S.P.), white spruce (P. glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.), as well as a few introduced larch species (Larix spp.), poplars (Populus spp.) and Norway spruce (Picea abies (L.) Karst.). (…)
by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 259: 1571-1579
The vigorous vegetative reproduction of intolerant deciduous competition limits the efficacy of mechanical release operations in young softwood plantations. Applying bioherbicides such as the fungus Chondrostereum purpureum (Pers. ex Fr.) Pouzar could improve the effectiveness of release by reducing stump sprouting while gaining public acceptance. A field experiment was conducted in Québec (Canada) in two white spruce (Picea glauca [Moench] Voss) plantations invaded by intolerant hardwoods.
This study compared four-year response of traditional mechanical release and mechanical release with an application of C. purpureum under the commercial formulation Myco-TechTM. The general objective of the project was to measure the silvicultural efficacy and worker productivity related to applying C. purpureum to control intolerant hardwoods in young white spruce plantations.
The potential of C. purpureum was somewhat expressed four years after treatment by reducing paper birch (Betula papyrifera Marsh.) competition. However, because of the slight effect of the treatment on pin cherry (Prunus pensylvanica L.f.), red maple (Acer rubrum L.) and trembling aspen (Populus tremuloïdes Michx.), the addition of the biological treatment did not significantly improve light availability and morphological parameters (height, diameter) of white spruce seedlings. A 2.6-fold reduction in worker productivity compared to traditional mechanical release was caused by the additional operations and weight of the equipment used for the application of the Myco-TechTM paste. The conditions that facilitate the operational application and effectiveness of C. purpureum applied in the form of the Myco-TechTM paste do not seem to be present in young conifer plantations with a high density of intolerant hardwood competition.
by Audrey Verreault | 30 January 2019
Published in Plant Ecology 208(2): 213-221
In a declining sugar maple (SM) stand, we tested the hypothesis that an increasing relative abundance of American beech (AB) and yellow birch (YB) would improve litter quality by providing a higher proportion of litterfall richer in base cations and lower in acidity. From 1989 to 2006, SM leaf fall diminished from 59% (1,718 kg ha-1 year-1) to 36% (915 kg ha-1 year-1) of the total leaf fall biomass. Overall, the increase in AB and YB litterfall compensated for the SM decrease, resulting in constant annual leaf litterfall fluxes (2,803 kg ha-1 year-1) over the period studied. However, because the leaf litter for AB and YB had Ca and Mg concentrations 2-3 times higher than did SM, Ca and Mg concentrations and fluxes in leaf litterfall significantly increased between 1989 and 2006. Leaf litterfall of AB and YB also has a higher base/acid ratio than SM. Consequently, changes in forest composition following SM decline led to a clear improvement in litterfall quality in terms of base cations content and fluxes and acid-base properties.
by Claire Morin | 30 January 2019
Published in Forests 4: 1141-1157 https://doi.org/10.3390/f4041141
The objective of this study was to compare organic carbon (C) accumulation in plantations (PL) and natural succession (NS) established on fallow lands along a 50-year chronosequence in the eastern mixed forest subzone of Quebec (Canada). Above- and below-ground woody biomass were estimated from vegetation measurement surveys, and litter and soil (0–50 cm depth) C from samplings. At the year of abandonment, total C content of both PL and NS sites averaged 100 ± 13 Mg C ha−1. Over 50 years, total C content doubled on NS sites and tripled on PL sites (217.9 ± 28.7 vs. 285.7 ± 31.0 Mg ha−1) with respect to fallow land. On NS sites, the new C stocks accumulated entirely in the vegetation. On PL sites, C accumulated mostly in the vegetation and to a lesser extent in the litter, whereas it decreased by a third in the soil. As a result, the net C accumulation rate was 1.7 ± 0.7 Mg ha−1 yr−1 greater on PL sites than on NS sites over 50 years. By the 23rd year, PL sites became greater net C sinks than NS sites in the fallow lands of the study area, even with the loss of soil C.
