Impacts of Paleoclimatic Change and Disturbance on Past Ecosystem Dynamics and Peatland Carbon Accumulation

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Effective management of Canada's forest, lake and wetland resources requires long-term environmental monitoring. However, the impacts of climate change and disturbance extend over longer timescales than can be detected using real-time, direct observations. In addition, limited temporal perspectives can lead to ineffective management approaches with unanticipated consequences as new climate and disturbance regimes arise. Sedimentary archives from lakes and wetlands extend the temporal record by providing information on the effects of environmental change over decades, centuries and millennia. Understanding longer-term impacts is essential for setting realistic resource management goals that incorporate knowledge of natural ranges of variability, how ecosystems function under changing environmental conditions, and potential responses to ongoing and future change. The main objective of this research program is to determine the roles that climate and disturbance play in the long-term development and dynamics of ecosystems, with emphasis on forests, lakes and wetlands in Pacific Canada. Our approach relies on analyses of lake sediments and wetland deposits, which provide a long-term perspective that is not possible through direct observation of the modern environment. We use the sedimentological, chemical and biological composition of these sedimentary archives to track past ecosystem changes, identify past disturbance events such as forest fires, and determine ecosystem responses to changes in climate and disturbance regimes. Over the next five years, our research will concentrate on two focal points. We will determine the role of past changes in climate and fire regimes on forest composition, structure and function through analysis of fossil pollen and charcoal preserved in lake sediments. This will allow us to quantify natural changes in fire frequency and severity, to clarify the consequences of climate change for forests, and to identify potential analogues for predicting future responses as forests and fire regimes re-organize as climate changes. We will also investigate the impacts of past changes in climate on wetlands and their thick deposits of peat, which are important sinks and sources of carbon dioxide and methane. Peatlands play an important role in the global carbon cycle and have the potential to both mitigate and enhance global climate change through greenhouse gas storage and release. Our research will focus on improving our understanding of how peatlands form and the influence of past climate change on their long-term carbon accumulation. This will help strengthen predictions of peatland carbon storage and release under different climate change scenarios. Determining how forests and peatlands responded to past changes in climate and disturbance is vital for understanding the consequences of environmental change for Canada's natural resources and for guiding national forest and wetland management policies.