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.