Light quantity and quality on the forest floor of pioneer and climax stages in a birch–beech–sugar maple stand

Abstract

The quantity and quality of solar radiation (300 to 1100 nm) beneath forest canopies were compared on sunny (sunflecks excluded) and cloudy days between the pioneer and climax stages of a birch–beech–sugar maple stand, and among the main species within these two stages of succession. The climax stage (mature canopies) transmits less energy between 300 and 1100 nm and casts smaller red to far red ratios than the pioneer stage (5-year-old canopies) on both sunny and cloudy days. Moreover, the canopies of the main species within each of these two stages of succession do not transmit the same quantity and quality of solar radiation. All these differences are greater on cloudy than sunny days. Leaf transmittance varies among species but this alone does not explain the differences in canopy transmission among these same species. The results are discussed in relation to the ecological significance for the plants growing under birch–beech–sugar maple stands.