Impacts of environmental change on Wisconsin seepage lake chemistry
This research aims to assess the susceptibility and resilience of lake chemistry to environmental change on the Chequamegon-Nicolet National Forest in northern Wisconsin. Many lakes in this region are sensitive to acid deposition due to the low buffering capacity of the surrounding watersheds. Emission controls implemented in the 1970s and 1980s have been effective at reducing acid deposition to the area and should result in the chemical recovery of affected lakes. However, little or no data exist on the current chemical status of many seepage lakes in northern Wisconsin. This project aims to characterize current and past lake conditions by examining historical data and undertaking additional sampling within the Chequamegon-Nicolet National Forest to determine how lake chemistry is responding to decreases in acid deposition, as well as to other stressors such as climate change. The results of this characterization will inform mechanistic experiments to look at drivers of changes in lake chemistry. This work is a collaboration between the University of Wisconsin (Emily Stanley) and the United States Forest Service (Steve Sebestyen and Randy Kolka).
Controls on winter nutrient export from forested catchments
Winter nutrient export from forested catchments is extremely variable from year-to-year and across the landscape of south-central Ontario. Understanding the controls on this variability is critical, as what happens during the winter sets up the timing and nature of the spring snowmelt, the major period of export for water and nutrients from seasonally snow-covered forests. Furthermore, winter processes are especially vulnerable to changes in climate, particularly to shifts in precipitation from snow to rain as temperatures rise. The objective of my doctoral research was to assess climatic and topographic controls on variability in stream nutrient export from a series of forested, calibrated catchments in south-central Ontario. The impacts of climate on the timing and magnitude of winter stream nutrient export, with particular focus on the impact of winter rain-on-snow events was investigated through a) analysis of long-term hydrological, chemical and meteorological records and b) high frequency chemical and isotopic measurements of stream and snow samples over two winters. The relationship between topography and variability in stream chemistry amongst catchments was investigated through a) a series of field and laboratory incubations to measure rates and discern controls on biogeochemical processes and b) analysis of high resolution spatial data to assess relationships between topographic metrics and seasonal stream chemistry. This work was done at Trent University in Peterborough, Ontario under the supervision of Catherine Eimers and Shaun Watmough.