Homogeneous light in shade-house experiment overestimates carbon gains in Norway maple seedlings

Alain Paquette^1*, Bastien Fontaine², Christian Messier¹ and Jacques Brisson^1.2

¹Centre for Forest Research, Université du Québec à Montréal, P. O. Box 8888, Centre-Ville Station, Montréal QC Canada H3C 3P8.

²Institut de recherche en biologie végétale, Université de Montréal, 4101 Sherbrooke Est, Montréal QC Canada H1X 2B2.

*Corresponding author. E-mail: alain.paquette@gmail.com. Tel: (514) 987-3000. Ext. 5048. Fax: (514) 987-4647.

Accepted 1 June, 2010

 Abstract

We set up a shade-house experiment with Norway maple growing at two light intensities typical of a disturbed and undisturbed forest canopy from either a homogeneous or a dynamic regime that mimics sunflecks. We show that although horticultural-grade shade-cloths can be finely tuned to provide daily averages of any light intensity, they do not appropriately mimic natural forest understories which are characterized by dynamic light environments composed of intense but short direct light events interspaced with prolonged period of low diffuse light. The results suggest that replicating the dynamic light environment of forests could be very important in experiments aimed at identifying the traits responsible for invasiveness in exotic species in forest understories, such as Norway maple in North America.

Key words: Norway maple (Acer platanoides), shade-house, tree seedling growth, photosynthetic response, forest understory, sunfleck, invasive tree species, pot experiment.