Collaborative Research (ETBC): Climate Warming and Northern Peatland Decomposition, Accumulation and Carbon Sequestration Examined Through Molecular and Paleohydrological Analysis

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The widespread occurrence of northern peatlands (above 50°N) is a distinctive and important attribute of the subarctic system that has global ramifications. The net sequestration of atmospheric carbon in northern peatlands (274-489 Pg C) has played a significant role in the global carbon cycle during the Holocene and will continue to be an important factor in the carbon cycle of the Anthropocene. A clearer understanding of how climate affects peat accumulation and decomposition rates, and ultimately net carbon sequestration, is critical for predicting how current and future warming will impact northern peatlands and the global carbon cycle. We propose a novel approach to gain a mechanistic understanding of the role of climate warming on rates of peat decomposition and net accumulation in a network of cores collected from the West Siberian Lowland (Russia), under a previous NSF-supported project, and the James Bay Lowland (Canada), under a separate NSF-supported project. Net rates of peat accumulation and carbon sequestration will be calculated from radiocarbon-dated cores. Hydrological changes, represented by changes in water table depth, will be directly calculated for the core sites using testate amoebae analysis. Detailed chemical characterizations of peat samples will be used to develop molecular indicators of peat decomposition. These molecular indicators and diagenesis models will then be applied to quantify rates and extent of peat decomposition and the relative importance of production and decomposition in determining carbon sequestration rates. Instrumental climate data and published paleoclimate research will be used to examine linkages among climate, hydrology, decomposition and accumulation and the mechanisms controlling the balance between peat production and decomposition. In view of current and anticipated warming of the subarctic over the next century, the proposed studies will focus on the Holocene Thermal Maximum (~8,000-4,000 Cal yr BP), the Medieval Warm Period (~1,100 to 700 Cal yr BP) and the comparative impacts of Modern Warming. Climate warming is having a disproportionately large affect on the hydrology, biota and biogeochemical cycles of the subarctic system. Northern peatlands have been major players in soil and atmospheric carbon cycling during the Holocene, and this study will provide a clearer picture of how climate shapes these processes. Novel approaches and potentially transformative concepts will be developed to provide a quantitative understanding of the mechanisms controlling carbon sequestration and release in northern peatlands. The research will provide a data base of over 20,000 detailed assays on past and present peatland biogeochemical conditions from ~40 core sites and ~100 surface sites in Siberia and central Canada. This project will provide training, experience and support for a postdoctoral associate in Benner?s laboratory at USC and a graduate student in MacDonald?s laboratory at UCLA. They will present their data at scientific meetings and prepare articles for publication in peer-reviewed journals. Benner and MacDonald teach undergraduate and graduate classes that cover various aspects of the global carbon cycle and climate change, and data collected from this project will be used as specific examples in these classes. This approach of bringing information from active research programs into the classroom has proven to be very effective for increasing student awareness and interest in science. An undergraduate student will be recruited to participate in this project (Benner?s laboratory) as part of the Magellan Scholars program at USC to provide research experiences for undergraduates. Results will be posted on research websites and data contributed to appropriate national and international data bases for widespread use.