Paleoecological studies across northwestern Canada

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Northwestern Canada has experienced the greatest warming in Canada during the past 50 years and numerous dendroclimatological studies also suggest that the 20th century may have been the warmest period during the past 3 centuries or more. Climate modeling experiments suggest temperatures will continue to increase in this region during the current century. Such increases in temperature are likely to have dramatic impacts on northern ecosystems, including altering the composition and position of some biomes, altering the response of biotic communities to climate or possibly changing the frequency and intensity of disturbance events. This research will have three main objectives: 1. Determining the controls on tree growth at northern treeline. To investigate this automatic point dendrometers will be used to measure tree growth at very high temporal resolution (every 15 mins.) during the growing season in the eastern Mackenzie Delta region. Onsite climate data will also be collected using a portable weather station. The climate data will be used to develop a mechanistic model of tree growth which will greatly improve our understanding of climate-growth relations. 2. Investigating the utility of alternative proxy indicators from tree ring growth records for studies of past climate. Given divergence between tree growth and climate, alternative data sources need to be investigated to develop accurate reconstructions of past climate and to put recent climate change in a long term context. We will expand on our initial work developing annually resolved records of stable carbon and oxygen isotopes from tree rings. We hope to develop a millennial length isotope record from northwestern Canada so that comparisons can be made between recent warming and the so-called Medieval Warm Period. 3. Determining the natural frequency of forest fires and the impact of fire on succession and development in boreal type forests of northwestern Canada. Using high-resolution lake sediment records and tree establishment and fire scar records we will reconstruct fire frequency during the Holocene. These types of records will help us better constrain the natural fire frequency in the northwest of Canada.