| Summary: | This data set contains volumetric soil moisture and temperature data in moist acidic tussock tundra near Toolik Field Station. This data was collected in support of a project that aimed to understand the sources of carbon dioxide emitted from Arctic tundra year-round. The data helps our team understand how carbon dioxide may be produced and move within the soil. Arctic soils contain very large amounts of organic carbon most of which is frozen in permafrost and has not participated in the global carbon cycle for thousands of years. Perturbations to carbon storage in permafrost soils have the potential to significantly increase the amount of carbon in the atmosphere and contribute to global climate change. Recent work indicates that many Arctic ecosystems are losing carbon due to small, but sustained emissions during the winter. A major question is what types of carbon pools fuel this flux today and in the future as permafrost thaws. In this project, our team built and deployed new technology to characterize the sources of carbon emissions from Arctic tundra year-round, with a special focus on winter emissions. Specifically, we developed a sampling system that continuously collects carbon dioxide over a period of 1-4 weeks. The system is passive (no power requirements, ambient pressure and temperature), rugged (suitable for well-aerated, waterlogged, and frozen soils), light-weight (<0.5 kg/sample), and isotopically-clean (i.e. the recovered carbon dioxide is suitable for radiocarbon analysis and the sampler itself does not emit carbon). The samples are shipped to the W. M. Keck Carbon Cycle Accelerator Mass Spectrometer facility at the University of California, Irvine, where they are analyzed for their radiocarbon content. Their isotopic information allows us to elucidate which soil carbon pools are being consumed by microorganism during the winter, and to quantify what proportion of the carbon originates from microorganisms decomposing organic matter (as opposed to from the roots of plants that are fixing carbon from the atmosphere) during the summer.
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