Growth and crown morphological responses of boreal conifer seedlings and saplings with contrasting shade tolerance to a gradient of light and height

Abstract

The effects of gradients in light levels and tree height on growth and crown attributes of six conifer species were studied in eastern and western Canada. Three conifers were studied in British Columbia (Abies lasiocarpa (Hook.) Nutt., Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm., and Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), and three in Quebec (Abies balsamea (L.) Mill., Picea glauca, and Pinus banksiana Lamb.). For several growth and morphological parameters, conifers reacted strongly to both an increase in light and tree height. Significant or nearly significant interactions between light classes and height were found for height and diameter growth of most species as well as for many crown attributes for both Abies and Picea. These interactions usually indicated that growth or morphological changes occurred with increasing height from a certain light level. Within a single genus, both eastern and western tree species showed the same overall acclimation to light and height. As generally reported, Pinus species showed less variation in growth and morphological responses to light than Abies and Picea species. Résumé: Les effets de gradients d'intensité lumineuse et de hauteur des arbres sur la croissance et les attributs du houppier de six espèces de conifères ont été étudiés dans l'est et l'ouest du Canada. Trois espèces de conifères ont été étudiées en Colombie-Britannique (Abies lasiocarpa (Hook.) Nutt., Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm. et Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) et trois autres au Québec (Abies balsamea (L.) Mill., Picea glauca et Pinus banksiana Lamb.). Pour plusieurs paramètres liés à la croissance et à la morphologie, les conifères réagissent fortement à la fois à une augmentation de la lumière et de la hauteur des arbres. Des interactions significatives ou presque significatives entre les classes de lumière et de hauteur ont été trouvées pour la croissance en hauteur et en diamètre de la plupart des espèces ainsi que pour de nombreux attributs du houppier dans le cas d'Abies et de Picea. Ces interactions signifient habituellement que les changements dans la croissance ou la morphologie apparaissent avec une augmentation de la hauteur à partir d'un certain niveau de lumière. À l'intérieur d'un genre, les espèces de l'Ouest et de l'Est montrent la même acclimatation globale à la lumière et à la hauteur. Tel que rapporté généralement, les espèces de Pinus montrent moins de variation dans leurs réponses à la lumière, dans le cas de la croissance et de la morphologie, que les espèces d'Abies et de Picea.[Traduit par la Rédaction] Claveau et al. 468

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

“…Grassi, R. Giannini affected by light level [8]. Within the range of irradiance of our study, no significant relationships were found between RHG, ADR or LCR and sapling height (P > 0.05 in all cases).…”

“…Therefore, understanding how these traits vary in relation to interacting factors is important in order to promote and assure effectively natural regeneration [1]. Several studies have shown that the effect of light on crown, shoot and needle morphology differs among tree species, with shade-tolerant species typically showing greater morphological changes along a light gradient than do the more shade-intolerant species [4,7,8,12,33]. At the whole plant level, interspecific differences reflect alternative choices between height growth for future gain and investment for survival at present height [32].…”

“…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.…”

Use of a spatially explicit individual-tree model (SORTIE/BC) to explore the implications of patchiness in structurally complex forests

“…Understory light availability is a good proxy for predicting juvenile tree growth in complex structured northern latitude forests (e.g., Klinka et al, 1992;Chen, 1997;Wright et al, 1998;Coates and Burton, 1999;Drever and Lertzman, 2001;Claveau et al, 2002). SORTIE/BC can predict light levels after any type of partial cutting, and it can be easily parameterized for different forest ecosystems (Canham et al, 1994(Canham et al, , 1999Beaudet et al, 2002).…”

Managing understory light conditions in boreal mixedwoods through variation in the intensity and spatial pattern of harvest: A modelling approach

“…The 30% uniform partial cut created slightly more shaded conditions (Figs. 5 and 6), less favourable to increased growth among pre-established shade-tolerant conifers (Parent and Messier, 1995;Claveau et al, 2002). More shaded conditions might even compromise regeneration survival for some species (e.g., below 8% for white spruce: Lieffers and Stadt, 1994), especially among larger saplings (Kneeshaw et al, 2006).…”