by Marie-Claude Boileau | 30 January 2019
Published in Forest Ecology and Management 291: 404-416
We evaluated the effectiveness of the regular shelterwood system in mitigating water table rise and regenerating a new cohort while favoring red spruce (Picea rubens Sarg.) in an 80-year-old, red spruce – balsam fir (Abies balsamea (L.) Mill.) lowland site. We used an experimental design established in 1994, with four completely randomized blocks and five treatments (uncut control, low, moderate, and heavy shelterwood cuttings, and clearcutting). In 2006, final overstory removal was carried out in the three shelterwoods and we monitored the first five growing seasons after treatment. Results showed that final cut did not lead to significant watering-up during the 2006–2010 period compared to levels measured in 1999, but water table levels did not fully recover from shelterwood cutting or clearcutting compared to precut levels measured in 1994. Under conditions of abundant seed supply, poor drainage, and low herbaceous and noncommercial woody competition, clearcutting (0.25 ha patches) provided the best red spruce cohort in terms of regeneration density, stocking, and growth. Balsam fir and red maple (Acer rubrum L.) regeneration was abundant in both silvicultural systems. Regeneration density and stocking of red spruce, balsam fir, and all commercial broadleaf species were generally lower inside logging trails than between trails, likely due to disturbance by machinery. For poorly-drained lowland sites, findings indicate patch clearcutting may be more effective in regenerating red spruce than the regular shelterwood system.
by Marie-Claude Boileau | 30 January 2019
Published in Canadian Journal of Forest Research 39: 596-605
The use of large clearcuts with protection of advance regeneration is inappropriate for regeneration of balsam fir (Abies balsamea (L.) Mill.) under severe browsing from white-tailed deer (Odocoileus virginianus (Zimmermann)). However, little is known about the effects of tree-retention methods along with scarification on the establishment of balsam fir in a context of severe herbivory. Consequently, we hypothesized that seed-tree-group cutting in conjunction with soil scarification creates favourable conditions for balsam fir regeneration. In 1998 and 1999 we set up three circular forest groups of different sizes (40, 60 and 80 m in diameter) surrounded by three different intensities of scarification (no treatment, single pass, double pass) in two balsam fir stands on Anticosti Island, Québec, Canada. Moreover, we used a network of fenced and unfenced regeneration plots to evaluate the impact of white-tailed deer browsing. The results showed that up to 7 years after harvest, seed-tree-group cutting did not improve the establishment of conifer species. Scarification had a negative impact on the abundance of conifer species, whereas white birch (Betula papyrifera Marshall) density was significantly higher in areas scarified twice than in unscarified areas. Overall, the development of palatable tree species appears unlikely at deer densities >20 individuals/km2.
by Marie-Claude Boileau | 30 January 2019
Published in Scandinavian Journal of Forest Research 24(1): 67-75
The objectives of this study were (1) to compare six methods for predicting parameters of the Weibull probability density function (PDF) for diameter at breast height (dbh) distribution in the unthinned white spruce plantations in eastern Canada with respect to their applicability, and (2) to evaluate their predictive abilities in terms of error index (EI) and Kolmogorov-Smirnov (K-S) statistic. The reasons for undertaking this study were (1) there are no available models for the dbh distributions of the studied species and (2) to determine the best method for projecting dbh distributions of white spruce plantations. A total of 113 sample plots which consisted of the commonly measured stand-level variables [stand age (A), site index at 25-year base age (SI), average height of dominant and co-dominant trees (Hd), and stand density (SD)] and associated diameter frequency distributions were used in this study. Of all the six prediction methods, the moment-based and percentile-based parameter recovery approach (PRM and PCT), maximum likelihood estimation regression (MLER), cumulative distribution function regression (CDFR) and parameter prediction method (PPM) were able to be applied for adequately modeling the diameter frequency distributions for the data sets used in this study. The moment-percentile estimation hybrid method (HYBM) performed the poorest. PCT was most highly recommended as it had the consistently lowest EI and K-S statistic values for both fit and validation data sets. Therefore, the dbh distributions for white spruce plantations could be predicted at a point over time using the established methods here, especially the PCT method, from the stand variables (A, SI, Hd, SD).
by Audrey Verreault | 30 January 2019
Published in Global biogeochemical cycles 24(4). doi: 10.1029/2009GB003757
The predictions from most forest ecosystem models originate from deterministic simulations. However, few evaluation exercises for model outputs are performed by either model developers or users. This issue has important consequences for decision makers using these models to develop natural resource management policies, as they cannot evaluate the extent to which predictions stemming from the simulation of alternative management scenarios may result in significant environmental or economic differences. Various numerical methods, such as sensitivity/uncertainty analyses, or bootstrap methods, may be used to evaluate models and the errors associated with their outputs. However, the application of each of these methods carries unique challenges which decision makers do not necessarily understand; guidance is required when interpreting the output generated from each model. This paper proposes a decision flow chart in the form of an analytical framework to help decision makers apply, in an orderly fashion, different steps involved in examining the model outputs. The analytical framework is discussed with regard to the definition of problems and objectives and includes the following topics: model selection, identification of alternatives, modelling tasks and selecting alternatives for developing policy or implementing management scenarios. Its application is illustrated using an on-going exercise in developing silvicultural guidelines for a forest management enterprise in Ontario, Canada.
by Audrey Verreault | 30 January 2019
Published in Combined proceedings. International Plant Propagators’ Society 57: 26-33
Mass cutting propagation of forest species is widely used in many different countries for reproducing elite material from the best controlled crosses. The production of coniferous plants from cuttings has continued to increase since 1989, when the Cutting Propagation Centre at the Pépinière forestière de Saint-Modeste (Saint-Modeste Forest Nursery) was established. White spruce (Picea glauca [Moench] Voss), black spruce (P. mariana [Mill.] B.S.P.), Norway spruce (P. abies [L.] Korst.) and hybrid larch (Larix x marschlinsii Coaz.) are now propagated at the centre using two unique and complementary systems (Bouturathèques and double-walled enclosures) developed by the Ministère des Ressources naturelles et de la Faune du Québec (MRNFQ). A collaboration between the researchers at the Direction de la recherche forestière (Forest Research Directorate) and practitioners at the Direction générale des pépinières et des stations piscicoles (Nurseries and Fish Farms Directorate), has led to refined cultural scenarios to meet the demands of each species (stock plant culture, rooting of cuttings and transplanting geared toward the production of large-sized plants). The integration of somatic embryogenesis, development of new production scenarios, and characterization of controlled crosses are presently receiving particular attention. In 2007, the provincial objective is to produce, via cutting propagation, 5.15 million of the 150 million conifer seedlings destined for reforestation in Québec.
