Date of Award


Degree Type


Degree Name

Master of Science




Dr. Irena Creed


This study determined controls on snow free season soil CO2 efflux in a sugar maple forest in central Ontario. Soil CO2 efflux data were collected with soil temperature, moisture, nutrient pools and sorption capacity. Soil CO2 efflux ranged from 0.2 to 30 pmol/m2/s. Temperature and moisture explained 49% of the variance (p<0.0001), with carbon pools and sorption capacity explaining an additional 31% (p<0.0001). The forest floor carbon pool was negatively correlated with soil CO2 efflux, indicating it is a net carbon sink to the atmosphere. In contrast, a positive correlation was found between soil CO2 efflux and the carbon-rich Ah horizon, indicating Ah carbon is actively respired, and the carbon-poor Ae horizon with high sorption capacity, indicating Ae serves as a trap for dissolved carbon flowing downslope that is subsequently respired. This finding has implications for managing forests for carbon offsets, because the majority of carbon is respired from older soils underneath the forest floor.



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