Portrait préindustriel dans un contexte de grande variabilité naturelle: une étude de cas dans le centre du Québec (Canada)

Abstract

RÉSUMÉDéfinir un portrait préindustriel est une méthode reconnue comme base pour mettre en place une stratégie d'aménage-ment forestier durable. Toutefois, c' est une méthode spatialement et temporellement dépendante et dont l'application exige de la prudence en présence de grands feux. L' objectif de cette étude était de décrire le portrait préindustriel d'une forêt mélangée tempérée dans le centre du Québec à différentes échelles spatiales. L' étude s' est principalement basée sur les données d'archives d'une compagnie forestière. Il est apparu que la forêt mélangée préindustrielle de la Mauricie était principalement mature ou surannée (>100 ans) et dominée par le type de couvert « mélangé » avec feuillus intolérants. On y retrouvait une importante présence d' essences de début de succession après feu en forêt boréale, soit le bouleau blanc, l' épi-nette noire et le pin gris. Pour tenir compte de la variabilité rencontrée, les résultats de notre étude suggèrent que la sylviculture devrait être adaptée à différentes échelles spatiales. Les cibles concernant la proportion des types de couvert forestier et des stades de développements devraient être orientées vers les principales caractéristiques préindustrielles de cette forêt aux différentes échelles spatiales considérées.Mots-clés : préindustriel, perturbations naturelles, paysages, couvert forestier, stade de développement, échelle spatiale, Mauricie, forêt mélangée ABSTRACT Pre-industrial forest cover portrait is a recognized method for establishing the bases of sustainable forest management. However, it is a spatially and temporally dependant concept that should be used with caution in presence of big fires. The objective of the study was to portray the pre-industrial landscape in a mixedwood temperate forest in central Quebec at different spatial scales. The study was based on archival records from a forest company. The pre-industrial forest cover landscape of our study area was mainly composed of mature or old-growth (>100 years) stands and dominated by mixedwood forest stands with intolerant hardwoods. The main tree species were white birch, black spruce and jack pine, three species associated to forest succession after fire in the boreal forest. Considering the great variability caused by the fires and partial knowledge of this variability, for each spatial scale considered, we propose some management targets based on the main pre-industrial characteristics of this forest. To respect the pre-industrial variability, our study suggested that silviculture should be adapted at different landscape scales. Cover types and age class targets should be based on main preindustrial characteristics at each landscape scale analyzed.

Clear-cutting without additional regeneration treatments can trigger successional setbacks prolonging the expected time to compositional recovery in boreal forests

“…Effectively, all plots were on potential natural vegetation where successional trajectories always leads to stands dominated by late-successional shade-tolerant species (Grondin et al 2013;Robitaille et al 2015;Prach et al 2016). Moreover, the ecological regions covered by our study have always been dedicated to supply to pulp and paper industry in addition to the sawmill industry both of which target mature and old-growth forests dominated by late-successional shade-tolerant species (Barrette and Bélanger 2007;Alvarez et al 2011;Boucher et al 2021). Finally, there is evidences in our own study that pre-clearcut stand condition was dominated by late-successional shade-tolerant species.…”

“…Clearcuts in the ecological regions covered by our study have always been dedicated to supply to pulp and paper industry in addition to the sawmill industry both of which target all commercial trees (i.e. DBH ≥ 9.1 cm) in mature and old-growth forests dominated by late-successional shade-tolerant species (Barrette and Bélanger 2007;Alvarez et al 2011;Boucher et al 2021). Clearcutting without any particular modalities (82% of plots) and clearcutting with modalities to protect pre-established regeneration (17%) occurred during the complete period of the study while clearcutting with modalities to protect pre-established regeneration and soils (< 1%) occurred only in the last ten years.…”

Assessing the Potential Stem Growth and Quality of Yellow Birch Prior to Restoration: A Case Study in Eastern Canada

“…In contrast, past silvicultural practices mainly consisted of large clearcuts or diameter-limit cuts that create conditions more similar to those associated with severe natural disturbances [4][5][6]. Comparisons between pre-industrial forests and current forests have highlighted the effect of such harvesting practices on forest composition and stand structure [7][8][9][10][11][12][13]. In addition to the inversion of the distribution of stand ages in favor of younger stands, shade-intolerant species were favored over shade-tolerant species.…”