Corinne Dunn HBESc Thesis Abstract

Throughout the Boreal Forest the bedrock of the Canadian Shield is seen on barren outcrops.  These areas are classified as alternating sequences of bare rock, lichen patches and treed islands.  On the rock barrens soils are typically shallow and the freeze-thaw and wet-dry cycles that characterize these systems result in a stressful environment for the plants and animals that inhabit these systems.  Despite the prominence of these systems on the landscape, particularly in Northwestern Ontario, we know very little about their structure and function.  This study examines soil properties and rates of net nitrogen mineralization and net nitrification of lichen patches and treed islands on three outcrops in Northwestern Ontario. The bedrock geology, slope and aspect of the three sites were similar among the studied sites. The plants and soils were characterized at each of the sites and soil samples were collected from lichen patches and treed islands.  Soil samples were analyzed in the laboratory for pH, carbon to nitrogen ratio, nitrogen concentrations, net nitrogen mineralization and net nitrification.  The lichen patches had thinner, more acidic soils with a lower carbon to nitrogen ratio when compared to the treed islands.  The results from the aerobic incubation showed that there was no difference in the rates of net nitrogen mineralization and net nitrification.  This could be due to immobilization from the microbial biomass.  Nitrogen is one of the limiting nutrients in plant growth as it controls net primary productivity, making it essential to further investigate nitrogen processes that occur on barren outcrops.