Tracking changes in organic matter reservoirs in boreal forest landscapes

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The movement of organic matter (OM) from the terrestrial to aquatic environment and its cycling within inland waters is a significant component of the global carbon cycle. Factors regulating the reactivity of soil and dissolved OM across these environments has traditionally been studied in isolation and remains poorly understood- preventing a predictive understanding of the role these reservoirs play in feedbacks regulating climate. The formation and fate of OM depends largely upon activity of microorganisms operating on short-time scales- yet these activities have decadal and centennial ramifications. Therefore, our understanding of these OM reservoirs requires the coupling of aquatic and terrestrial biogeochemical concepts and improving our ability to link geochemical tools to microbial activities to address these concepts. The potential role for boreal OM in climate feedbacks is significant given the boreal region holds >30% of the global soil carbon and is expected to experience some of the greatest warming over the next century. This research program will focus on key biogeochemical mechanisms potentially controlling OM reservoirs in boreal forest landscapes. Studies will be conducted to assess; (1) The role of OM source, composition and stoichiometry on the loss of dissolved OM via stream microbial biofilm respiration, (2) Turnover of microbial inputs to soil OM pools, (3) The factors regulating the interpretation of the stable carbon isotopes of microbial biomarkers- a critical tool for assessing microbial substrate use in natural OM samples, and (4) How each of these may be regulated by climate warming. This research will be conducted along an established climate gradient of study sites where other governmental and university researchers are conducting complementary research. This will facilitate the proposed research and also promote interactions between students and provincial and Canadian government researchers directly involved in environmental management and policy. The studies proposed will, therefore, serve as an exceptional means for training undergraduate and graduate students to become highly skilled, independent researchers who can ask and answer relevant earth science questions.