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 Québec (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 Résumé -Effet net de la végétation de compétition sur certaines conditions environnementales et sur la performance de quatre dimensions de plants d'épinette après huit ans. Une étude a été établie en 1993 afin de déterminer la performance de quatre dimensions de semis d'épinette noire (Picea mariana) et d'épinette blanche (P. glauca) mis en terre sur deux sites situés au Québec (Canada), chacun représentant un type de compétition. À chaque site d'étude, un dispositif en tiroirs subdivisés avec 15 et 17 répétitions a été utilisé, avec la présence de compétition, la dimension initiale des semis et l'espèce, assignées à la parcelle principale, la sous-parcelle et la sous sous-parcelle, respectivement. Les plants de fortes dimensions (PFD) ont reçu plus de lumière et ils affichaient une meilleure croissance que le plant de dimension standard. Les gains de croissance découlant de la combinaison d'une plantation de PFD avec contrôle de la compétition ont été multiplicatifs. La végétation de compétition a significativement abaissé le profil saisonnier de la température du sol mesurée à 10 cm de profondeur. Cette étude démontre qu'un dégagement hâtif est nécessaire sur les stations caractérisées par une forte compétition de framboisiers et de feuillus intolérants. De plus, sur ces mêmes stations, un reboisement avec des PFD devrait limiter le besoin de répéter les dégagements mécaniques. plant de fortes dimensions / compétition / gestion de la végétation / température du sol / dégagement mécanique

Role of planting stock size and fertilizing in initial growth performance of rowan (Sorbus aucuparia L.) reforestation in a mountain frost hollow

“…Nonetheless, due to serious stem deformations, the prospects of common-sized transplants seem much worse than the prospects of saplings. In this regard we agree with Jobidon (2000) and Jobidon et al (2003) who suggested that early survival of plantation should not be used as a criterion for assessing the severity of weed competition.…”

“…Nonetheless, some implications can be derived from comparison of saplings, semisaplings or large seedlings with common-sized transplants or seedlings, although the studies were conducted mostly on conifers. Schmidt-Vogt and Grüth (1969), Jobidon et al (2003) and Thiffault (2004) reported a greater growth potential and competitive ability of larger planting stock as compared to common stock sizes. According to Van den Driessche (1992), seedlings selected as large in the nursery had significantly greater height than seedlings selected as small throughout the referred period (1984)(1985)(1986)(1987)(1988)(1989)(1990) and absolute size differences increased.…”

Influence of light and competition on crown and shoot morphological parameters of Norway spruce and silver fir saplings

“…However, the relationships between light and growth or morphological parameters are far to be fully understood. Other than to be species-specific, for a certain species these relationships may vary among climatic regions [34] and may be greatly affected by the interaction with other factors 270 G. Grassi, R. Giannini such nutrient availability, sapling size and competition [8,10,16,25,[31][32][33]. This complexity becomes especially relevant in uneven-aged managed forests, where the high structural fragmentation of the canopy and the clustering pattern of natural regeneration [15] lead to a high spatial variability of light in the understory and of competition between saplings.…”

Morning, noon, or afternoon: does timing of direct radiation influence the growth of Picea abies seedlings in mountain forests?

“…In a field experiment in subalpine forests of south central British Columbia, Coates [16] found that, throughout the snow free period, soil temperatures at 10 cm depth were about 5 °C higher in soils where competing vegetation was removed than in soils beneath undisturbed vegetation. Smaller, but still notable differences due to vegetation cover were found in an experiment in Quebec [28]. Alexander [1] and Brang [9] both recorded higher soil surface temperatures on soils with a humus layer than on mineral soils.…”

“…Soil temperature within this layer limits root growth [4,16], which starts at a temperature of 8 and 12°C [42] and increases up to about 20 °C [41,42]. Site factors affecting near-surface soil temperatures are air temperature, direct sunlight, vegetation cover [3,16,28], snow cover [3], and soil properties such as water content [38].…”