Multi-proxy, medium-resolution Holocene and high-resolution late Holocene records from a southern Ontario ombrotrophic peatland examined factors affecting carbon accumulation. These records include radiometric dating, calculation of long-term apparent rate of carbon accumulation (LORCA), determination of peat humification, and analysis of plant macro-remains, charcoal and nitrogen concentration. Coupled with existing paleo-climate reconstructions, these data were integrated to determine how factors, such as climate, autogenic succession and fire, influenced carbon accumulation. Mean LORCA were similar to other northern and temperate peatlands. LORCA was high during the marsh phase and decreased following a transition to fen. Neoglacial cooling and the fen to bog transition did not lead to significant differences in LORCA. The last millennium did not exhibit much variation in LORCA; however, there is evidence for warming associated with the Medieval Climate Anomaly. Recent disturbances did impact LORCA; however, fire did not play a role in peatland dynamics in the pre-industrial Holocene.

Multi-proxy, medium-resolution Holocene and high-resolution late Holocene records from a southern Ontario ombrotrophic peatland examined factors affecting carbon accumulation. These records include radiometric dating, calculation of long-term apparent rate of carbon accumulation (LORCA), determination of peat humification, and analysis of plant macro-remains, charcoal and nitrogen concentration. Coupled with existing paleo-climate reconstructions, these data were integrated to determine how factors, such as climate, autogenic succession and fire, influenced carbon accumulation. Mean LORCA were similar to other northern and temperate peatlands. LORCA was high during the marsh phase and decreased following a transition to fen. Neoglacial cooling and the fen to bog transition did not lead to significant differences in LORCA. The last millennium did not exhibit much variation in LORCA; however, there is evidence for warming associated with the Medieval Climate Anomaly. Recent disturbances did impact LORCA; however, fire did not play a role in peatland dynamics in the pre-industrial Holocene.

This thesis assessed object-based image analysis techniques using multi-source remote sensing data in order to automatically delineate canopy gaps and individual tree crowns (ITCs). Image segmentation is much more complex when conducted on data covering deciduous, un-even aged forests like those in Central Ontario. To delineate canopy gaps high spatial resolution multispectral ADS40 aerial imagery and a LiDAR CHM were assessed both separately and jointly. To delineate ITCs two commonly used segmentation approaches were assessed – region growing and watershed segmentation. Ground based measurements and manually delineated data were used as reference to evaluate results. Using multi-source data to delineate canopy gaps produced an average overall accuracy of 99.35%, whereas using the imagery and CHM individually resulted in average overall accuracies of 81.41% and 82.45%, respectively. For the delineation of ITCs, the watershed and region growing segmentations resulted in average overall accuracies of 67.5% and 65.5%, respectively.

Mercury (Hg) is a contaminant of global concern due to its long-range atmospheric transport and high toxicity. The focus of this research is on the role of the forest canopy in the accumulation, and delivery of Hg to the soil Hg pool. Particular focus is on the role of atmospheric speciation of Hg on deposition. An urban-rural gradient was examined from Mississauga to Dorset, Ontario, to determine the role of locally emitted Hg: RGM, and PM on deposition. [GEM] was measured to be similar at both sites, and [PM] and [RGM] were greater in the urban location. Seasonal accumulation of Hg on foliar surfaces was dominated by GEM, and similar at the urban (8.74 ng cm-2) and rural (9.80 ng cm-2) locations. Increased [PM] and [RGM] at the urban location resulted in a transient upper canopy Hg pool, and throughfall enrichment at the urban site.

Northern peatlands play a significant role in the global carbon (C) cycle by functioning as sources of atmospheric methane (CH4). Peatlands are becoming polluted as a result of nitrogen (N) deposition, which is likely to impact CH4 dynamics. This thesis presents research at the Mer Bleue bog (Ottawa, Canada) in the longest known simulated atmospheric nutrient deposition experiment. After 8 years of simulated N (and other nutrient) deposition, activities of microbial communities involved in CH4 cycling have been analyzed in the laboratory and CH4 fluxes measured using chamber techniques in the field. High rates (>10 times ambient deposition) of simulated N deposition decreased CH4 production, and enhanced CH4 oxidation in vitro. However, in situ CH4¬ emissions were greater in the high N plots. I hypothesize that CH4 production is therefore driven by short-lived root exudates in the field, consistent with increased shrub biomass that occurs concomitantly with high N deposition.

Northern peatlands play a significant role in the global carbon (C) cycle by functioning as sources of atmospheric methane (CH4). Peatlands are becoming polluted as a result of nitrogen (N) deposition, which is likely to impact CH4 dynamics. This thesis presents research at the Mer Bleue bog (Ottawa, Canada) in the longest known simulated atmospheric nutrient deposition experiment. After 8 years of simulated N (and other nutrient) deposition, activities of microbial communities involved in CH4 cycling have been analyzed in the laboratory and CH4 fluxes measured using chamber techniques in the field. High rates (>10 times ambient deposition) of simulated N deposition decreased CH4 production, and enhanced CH4 oxidation in vitro. However, in situ CH4¬ emissions were greater in the high N plots. I hypothesize that CH4 production is therefore driven by short-lived root exudates in the field, consistent with increased shrub biomass that occurs concomitantly with high N deposition.

Mercury (Hg) is a contaminant of global concern due to its long-range atmospheric transport and high toxicity. The focus of this research is on the role of the forest canopy in the accumulation, and delivery of Hg to the soil Hg pool. Particular focus is on the role of atmospheric speciation of Hg on deposition. An urban-rural gradient was examined from Mississauga to Dorset, Ontario, to determine the role of locally emitted Hg: RGM, and PM on deposition. [GEM] was measured to be similar at both sites, and [PM] and [RGM] were greater in the urban location. Seasonal accumulation of Hg on foliar surfaces was dominated by GEM, and similar at the urban (8.74 ng cm-2) and rural (9.80 ng cm-2) locations. Increased [PM] and [RGM] at the urban location resulted in a transient upper canopy Hg pool, and throughfall enrichment at the urban site.

Sea ice is essential to the survival of many human settlements in Arctic Canada in that it provides a means for basic sustenance, travel and largely defines the seasons. Northern communities base their livelihoods on these traditionally well established cryogenic cycles. In this work, seasonal sea ice is analyzed off the coast of Cape Dorset, Nunavut. Significant trends are established for earlier sea ice break-up and later freeze up dates for the period 1982 to 2007. The timing of sea ice formation and retreat is significantly changing in the Cape Dorset region, with the ice free season increasing ~40 days since 1982. Relationships are established statistically between the shifting ice free season and temperature, weather types (air masses), precipitation, and wind. The results of this study illustrate the changing nature of sea ice formation and retreat in Cape Dorset and the importance of completing localized studies in the Arctic.

The impacts of extreme temperatures on human health and morbidity have been well documented in many studies. In literature, changes in the trends of extreme temperatures have been studied using percentiles, indicators and climate modeling. The aim of this study is to determine if the trend exhibited in the literature of statistically significant increases in extreme minimum temperatures, is also exhibited in the Greater Toronto Area during the 1971 to 2000 timeframe. A methodological approach using counts is the basis for the analysis. Statistical significance is determined through the use of Spearman’s Rank, Kendal-Tau and T-tests. A total of five stations are analysed, three being urban and two representing the surrounding suburban areas. The results indicate that statistically significant decline in extreme minimum temperature counts have occurred. In agreement with the literature, statistically significant increases in extreme maximum temperature counts can not be determined.

Sea ice is essential to the survival of many human settlements in Arctic Canada in that it provides a means for basic sustenance, travel and largely defines the seasons. Northern communities base their livelihoods on these traditionally well established cryogenic cycles. In this work, seasonal sea ice is analyzed off the coast of Cape Dorset, Nunavut. Significant trends are established for earlier sea ice break-up and later freeze up dates for the period 1982 to 2007. The timing of sea ice formation and retreat is significantly changing in the Cape Dorset region, with the ice free season increasing ~40 days since 1982. Relationships are established statistically between the shifting ice free season and temperature, weather types (air masses), precipitation, and wind. The results of this study illustrate the changing nature of sea ice formation and retreat in Cape Dorset and the importance of completing localized studies in the Arctic.