Understory community dynamics 12 years after commercial thinning and gap creation in naturally regenerated and planted stands

Turquin, Raphaël ORCID: https://orcid.org/0009-0009-6090-5083, Aubin, Isabelle, Cardou, Françoise, Schneider, Robert, Barrette, Martin et Sirois, Luc (2025). Understory community dynamics 12 years after commercial thinning and gap creation in naturally regenerated and planted stands. Forest Ecology and Management, 593 (122815).

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Résumé

New commercial thinning methods, combined with small gap creation, were introduced to better achieve ecosystem-based management objectives and reduce structural differences between unmanaged and planted stands. However, some aspects of the understory response to these silvicultural treatments remains unknown. Here we evaluate the effect of commercial thinning (from below, crop-tree release) and gap creation on the understory communities in naturally regenerated balsam fir (Abies balsamea) stands and white spruce (Picea glauca) plantations in eastern Canada. Understory communities were surveyed before thinning and gap creation, and then again 1, 2, and 12 years after treatment. The split-split-plot experimental design included four levels of thinning (none, thinning from below, and thinning by the release of 50 or 100 crop trees per hectare) combined with three gap sizes (none, 100 m², and 500 m²). Among the plots, we compared three understory characteristics: taxonomic composition and diversity, trait assemblage and diversity, and vertical structure. We found differences in trait assemblage and vertical structure between the naturally regenerated stands and plantations 12 years after treatment. Our results show that thinning has negligible effect on understory communities, whereas gaps influence understory structure and composition, and differences remained 12 years after treatment. Large gaps (500 m²) produced the most conspicuous change in the understory communities. Relative to small gaps (100 m²), large gaps favoured shade-intolerant, ruderal species (e.g., Hieracium spp., Carex spp., Rubus idaeus, Chamaenerion angustifolium), and the development of dense shrub and forb layers. The effect of large gaps was greater in planted stands than in naturally regenerated ones. Commercial thinning did not significantly affect understory communities. Gaps should be used sparingly, especially in plantations with site preparation, to avoid the development of a recalcitrant vegetation layer.

Type de document :	Article
Validation par les pairs :	Oui
Mots-clés :	Éclaircissage par libération des arbres de culture ; Création de trouée ; Sous-bois ; Composition et diversité taxonomiques ; Assemblage et diversité des traits ; Structure verticale / Thinning by crop-tree release ; Gap creation ; Understory ; Taxonomic composition and diversity ; Trait assemblage and diversity ; Vertical structure.
Départements et unités départementales :	Département de biologie, chimie et géographie
Date de dépôt :	20 févr. 2026 16:18
Dernière modification :	20 févr. 2026 16:18
URI :	https://semaphore.uqar.ca/id/eprint/3470