Stabilité mécanique et caractéristiques racinaires de plants de fortes dimensions de Picea mariana produits en récipients ou à racines nues

Abstract

In Québec (Canada), large planting stock are used for reforestation of high-competition sites, sometimes in combination with soil scarification. Large conifer seedlings are typically produced in containers >300 cm 3 , or as bare-root stock. Nursery practices are expected to influence seedling mechanical stability. We measured large containerized and bare-root black spruce (Picea mariana) seedling stability (resistance to winching), and characterized their root architecture, during their seventh growing season since planting in scarified or non-scarified plots devoid of any competing vegetation. We detected no significant stock type or scarification effect on seedling height, diameter, height/diameter ratio, stability, total number of roots and adventive roots. Occurrences of root deformations, as well as vertical and horizontal root distributions, were not influenced significantly by the treatments. The height/diameter ratio was the sole significant predictor of the resistance to winching. Our results indicate that the use of either large containerized or large bare-root stock has limited silvicultural consequences. In this context, the choice of large stock type should be based on other factors, such as handling constraints.Key words: black spruce, reforestation, stock type, scarification, root system