Anna Banaszweska

This research was designed to address recent concern that natural regeneration of Quercus rubra (Red Oak) may be declining in eastern North America. It examined the role of understory canopy light, measured as Photosynthetically Active Radiation (PAR), to ascertain its role in supporting natural regeneration of Quercus rubra within an urban park naturalization area, located in Kew Gardens, Toronto. PAR was recorded at three instances, which included April, May and June of 2009 by taking measurements in the forest understory (2m above ground) and near the ground (20 cm above ground). Ordinary kriging was used to generate prediction surface maps for PAR light levels; these were complemented with spatial delineations of optimal light level probability thresholds. Overall, light availability was demonstrated to be a major limiting resource for natural regeneration of this tree species. Specifically, results show that at the beginning of the growing season, PAR levels were found to be favourable for regeneration, but that this circumstance changed rapidly with progression of the growing season. An abundance of seedlings were found in the southeast corner of the middle enclosure where optimal light levels were present throughout the data collection period (April to June). Low PAR levels, found especially in May and June, are believed to be seriously curtailing germination and seedling establishment in most of Kew Gardens' naturalization areas. These findings have the potential to directly impact understory management strategy; PAR prediction surfaces could be used to select areas for understory thinning and removal of aggressive shade-tolerant colonizing vegetation.