Net effect of competing vegetation on selected environmental conditions and performance of four spruce seedling stock sizes after eight years in Qu�bec (Canada)

Abstract

A study was established in 1993 to determine the response of four black spruce (Picea mariana) and white spruce (P. glauca) stock sizes on two sites located in Qubec (Canada), each representing a different type of competing vegetation. At each site, a split-split-plot design with 15 to 17 replicates was used, in which the presence of competition (weedy and bare plots), seedling initial size, and spruce species were assigned respectively to the whole plot, the subplot, and the sub-subplot. Larger initial seedling size provided a greater competitive ability for light and had higher growth rates than the standard stock size for both species. Growth gains from combining plantation of large stock with vegetation control were multiplicative. Non-crop vegetation significantly lowered the seasonal profile of 10-cm depth soil temperature on both sites. This study shows that early release treatment is required on sites dominated by raspberry-hardwood competition complex and planting large spruce stock on such harsh competition sites will help reduce the need for repeated vegetation control. large seedling / competition / vegetation control / soil temperature / release treatment Rsum -Effet net de la vgtation de comptition sur certaines conditions environnementales et sur la performance de quatre dimensions de plants d'pinette aprs huit ans. Une tude a t tablie en 1993 afin de dterminer la performance de quatre dimensions de semis d'pinette noire (Picea mariana) et d'pinette blanche (P. glauca) mis en terre sur deux sites situs au Qubec (Canada), chacun reprsentant un type de comptition. chaque site d'tude, un dispositif en tiroirs subdiviss avec 15 et 17 rptitions a t utilis, avec la prsence de comptition, la dimension initiale des semis et l'espce, assignes la parcelle principale, la sous-parcelle et la sous sous-parcelle, respectivement. Les plants de fortes dimensions (PFD) ont reu plus de lumire et ils affichaient une meilleure croissance que le plant de dimension standard. Les gains de croissance dcoulant de la combinaison d'une plantation de PFD avec contrle de la comptition ont t multiplicatifs. La vgtation de comptition a significativement abaiss le profil saisonnier de la temprature du sol mesure 10 cm de profondeur. Cette tude dmontre qu'un dgagement htif est ncessaire sur les stations caractrises par une forte comptition de framboisiers et de feuillus intolrants. De plus, sur ces mmes stations, un reboisement avec des PFD devrait limiter le besoin de rpter les dgagements mcaniques. plant de fortes dimensions / comptition / gestion de la vgtation / temprature du sol / dgagement mcanique