by Audrey Verreault | 30 January 2019
Published in Ecoscience 16(2): 183-196
This study aims to evaluate the relative contribution to biodiversity of 4 dominant types of virgin black spruce (Picea mariana) forests found in a typical regional landscape of the black spruce–moss bioclimatic domain of central Québec: mature black spruce forests with a regular structure, old black spruce forests with a regular structure, old black spruce–fir (Abies balsamea) mixed forests with 2 stories, and mixed forests with irregular structure. A total of 16 stands covering these 4 forest types were sampled to characterize forest composition and structure as well as epixylic communities. Multivariate analyses of variance were performed to evaluate to what extent the epixylic community structure differed among the 4 forest types. Results show that the old two-story and irregular forest types sustain higher species richness of epixylics per unit area; therefore, these types may be key habitats for old-growth dependent species of bryophytes and lichens. The close association of epixylics with these forest types was mainly due to better moisture conditions and the presence of greater amounts of coarse woody debris in advanced decaying stages. We also demonstrated that forest compositional and structural attributes are good indicators of epixylic diversity. Finally, we suggest that maintaining old irregular black spruce–fir mixed forests should be the primary aim of conservation strategies for old-growth forests.
by Audrey Verreault | 30 January 2019
Publisher in Forest Ecology and Management 228(2006): 115-123
The objectives of this study were to predict the survival probability of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton) affected by dieback and to evaluate the critical threshold beyond which mortality caused by dieback is inevitable. Mortality and dieback growth rate of all the trees in 133 sample plots located in the Appalachian region of southeastern Québec were measured annually from 1984 to 1993. These measurements were associated with the evaluation of the intensity of dieback. Results indicated that the mortality of sugar maple and yellow birch was related to the progression of dieback. Inversely, in the majority of cases, mortality occurred only when dieback increased in intensity and affected trees with different rates of missing foliage.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 36(2006): 2364-2376
Conifer-regeneration failure is often observed on sites invaded by ericaceous shrubs. In northeastern Québec, Canada, these sites are frequently characterized by dense Kalmia angustifolia L. – Rhododendron groenlandicum (Oeder) K.A. Kron & Judd cover. Such failures are potential consequences of nutrient limitation, allelopathy, or low soil temperatures. Conversion of productive forests into heaths poses a threat to the maintenance of forest productivity and biodiversity. We evaluated scarification, spot fertilization, and increased seedling foliar N concentration as treatments to promote planted black spruce (Picea mariana (Mill.) BSP) seedling survival and growth. We measured seedling, vegetation, and soil responses to the treatments for 5 years following planting. Scarification had positive impacts on seedling growth: the differences between scarified and unscarified plots increased over time, and double-pass scarification proved slightly more effective than a single-pass treatment. Responses to scarification were enhanced when seedlings were fertilized. A slow-release fertilizer with micronutrients proved slightly more effective than the 26N-12P-6K formulation; the latter also induced higher mortality than the former or no fertilizer. Gains due to increased N concentrations based on nursery practices were significant but short-lived. Our results demonstrate how silviculture and nursery practices can be used for resetting the secondary succession where ecosystem retrogression is observed following K. angustifolia – R. groenlandicum invasion.
by Audrey Verreault | 30 January 2019
Published in Abstracts of the conference on Natural disturbance-based silviculture: Managing for complexity. IUFRO 1.05 Uneven-aged Silvicuture Research Group. Rouyn-Noranda, QC. p. 241-244
by Marie-Claude Boileau | 30 January 2019
Published in Northern Journal of Applied Forestry 29(4): 173-181
Motor-manual brushcutting is commonly used throughout North America for regeneration release. Companies pay for this silvicultural treatment according to a piece-rate wage system that does not consider stand and site characteristics, though both have been shown to affect worker productivity. This study aimed to establish a formal regression model relating stand and site conditions to brushcutter productivity for regeneration release operations.
Time studies were conducted in 0.12 ha observation areas, with the participation of 91 brushcutters representing 22 silvicultural contractors (32 sites). The best fitted regression model (theoretical model) to predict effective time consumption (ETC) (R2 = 0.61, RMSE = 4.3 hours per hectare, n = 91) contained three independent variables: (1) percent cover (%) of three brush species (raspberry, ferns, fireweed), (2) density of young trees higher than 1 m (number per hectare) and (3) density of obstacles hindering worker progression in the field (woody residue, stumps left after harvest, boulders and terrain roughness). As workers indicated that hindering obstacles significantly affected their productivity, principal component analysis was used to discriminate between obstacle types. Two components representing woody residue and stumps bypassed by the worker were significant predictors of ETC (R2 = 0.14, RMSE = 6.4 hours per hectare, n = 91). The findings could be useful for piece-rates adjustment. Further research is needed to better understand how obstacles impact worker productivity.
