Influence du gauchissement de semis d'épinette noire (Picea mariana (Mill.) B.S.P.) produits en serre sur leur performance en plantation

Abstract

Spiralization is a developmental deformation in winter greenhouse produced black spruce seedlings characterized by a drooping stem or portion of stem. During lignification, the seedling redresses but maintains part of its deformation. The objective of this study is to evaluate the long-term effect of spiralization on the growth, survival and morphology of black spruce seedlings in order to determine to what degree the rejection of spiralized seedlings is justified. Field evaluation was undertaken on 2304 black spruce seedlings planted on three sites with different soil conditions in Abitibi, Québec. The seedlings were divided in the greenhouse into six stem deformation classes of varying intensities, including a control, and laid out on a randomized complete block design. From 1986, the year of plantation, to 1990, spiralization had little effect on height and diameter growth. However, severely deformed seedlings planted on a heavy-textured site suffered sufficiently high mortality rates to justify their rejection. Moreover, these seedlings developed a higher proportion of double leaders. The study suggests that systematic rejection of all classes of deformed seedlings, especially those in the less severe classes, is probably not justified. Key words: Spiralization, stem deformation, seedlings, planting, black spruce, greenhouse, early growth, mortality.