Increasing dissolved organic carbon (DOC) concentrations have been observed in peatland drainage waters. The objective of the thesis is to determine the influence of water content and temperature on the processes thought to control DOC concentrations in streams during the fall (a major export period) using peat microcosms, a one year field study and analysis of long-term data (1980--2001). Different processes appear to have varying influences at the microcosm, peatland and catchment scale. Water content was important at the microcosm scale as DOC production and the amount of humification increased with peat water-saturation. Drought caused a decrease in DOC and was associated with an increase in ionic strength, sulphate and base cation concentrations. At the peatland scale high DOC concentrations were associated with high temperatures, possibly due to increased inputs from vegetation during the summer. DOC concentrations in upland drainage streams increased after storms, but decreased during high flow events in wetland outflows. No single predictor of fall DOC concentration was found at the catchment scale, despite multiple correlations with climate, hydrology and chemical parameters. This thesis suggests that stream DOC concentration is affected by various processes that are affected by temperature and hydrology but the relative importance of each process differ among catchments resulting in asynchronous pattern of DOC in stream outflows.;Keywords: DOC, climate, hydrology, temperature, sulphate, microbial activity
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