Canada has the third largest area of forest in the world, covering 402 million ha. The country thus plays an important role in timber production and in the global carbon cycle. Until now, 93% of the harvested area in Canadian boreal forests has been cut by clearcutting, due to economic considerations: cheaper operational cost and greater harvested volume of timber. However, the impacts of clearcutting in the simplification of stand structure, biodiversity and sustainability of boreal forest have been critized and society has expressed its concern.
Canadian boreal forest in the North Shore Region (Quebec). Credit: Miguel Montoro Girona -Université de Québec à Chicoutimi
Forest ecosystem management proposes partial cuttings as an alternative in order to integrate the ecological, economic and social objectives in the silvicultural planning so as to achieve the sustainability of boreal forestry. Partial cuttings integrate ecological and economic factors such as stand growth, tree quality, product yields, species composition, and tree value of residual stands. They also increase the habitat for wildlife by maintaining the overstore residual cover. Consequently, the use of partial cuttings is increasing in the context of the forestry practices in boreal forest management. However, research is necessary to adapt the treatments to the species and stand conditions that will optimize the growth response in the tree residual stands.
Example of one experimental silvicultural treatment (Mini-strip shelterwood) in black spruce stands. Credit: Miguel Montoro Girona -Université de Québec à Chicoutimi
New studies from the Canadian boreal forest for the first time investigates new silvicultural treatments in the context of ecosystem management (published in Forests and PLOS-One). The results demonstrate that the experimental shelterwood and seed-tree methods are effective treatments to promote the growth of residual trees. This research identified forest structure, edge effect and growth before cutting are key parameters for optimizing the radial growth performance. Consequently, the authors recommend the inclusion of these variables in the silvicultural planning and forest management:
Spatial patterns of the experimental silvicultural treatments. Credit: Miguel Montoro Girona -Université de Québec à Chicoutimi
“Based on our results, age structure and density are two elementary criteria in stand selection before cutting to maximize the growth yield of the treatments; the experimental shelterwood treatments were more efficient in younger and denser stands. An edge effect on growth response has been demonstrated for the first time in black spruce even-aged stands; this suggests caution in the interpretation of traditional growth studies, in which spatial distribution or position classes of the trees were typically not taken into consideration. The growth before cutting was one of the most influential variables in the growth response, and it helped to understand that dominant trees manifest a better growth response. However, previously suppressed trees experienced the greatest growth ratio before and after cutting, especially in edge position and younger stands.”
Core samples used in the dendroecological study and measurements with WinDendro. Credit: Miguel Montoro Girona -Université de Québec à Chicoutimi
These innovative approaches evidenced the different growth patterns of trees that could reduce the variance unexplained by the classical models. Within the stand, heterogeneous growth has to be accurately assessed and ecologically interpreted to correctly evaluate the effects of partial cuttings on the trees. Consequently, quantifying the response in tree growth following partial cutting treatments is essential for the planning of the long-term timber supply within the context of sustainability of forests to conciliate ecosystem management with wood production. Thus, these studied treatments could be considered as a silvicultural alternative for the implementation of sustainable forest management in the boreal forest although more research is necessary to study the effects of experimental treatments on mortality, regeneration and resilience.
Fieldwork measurements. Credit: Miguel Montoro Girona -Université de Québec à Chicoutimi
The original papers:
Radial Growth Response of Black Spruce Stands Ten Years after Experimental Shelterwoods and Seed-Tree Cuttings in Boreal Forest,” published Oct. 15 in the journal Forests. http://www.mdpi.com/1999-4907/7/10/240
Understanding tree growth responses after partial cuttings: A new approach. PLoS ONE 12(2): e0172653. https://doi.org/10.1371/journal.pone.0172653
This study was supported by the Fonds de Recherche du Québec – Nature et Technologies (FQRNT), the Programme de mise en valeur des ressources forestières (MFFPQ), the Canadian Wood Fibre Centre of the Canadian Forest Service (Natural Resources Canada), and the Forest Complexity Modelling program of the Center for Forest Research.
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