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Emissions of Forest Floor and Mineral Soil Carbon, Nitrogen and Mercury Pools and Relationships with Fire Severity for the Pagami Creek Fire in the Boreal Forest of Northern Minnesota
Forest fires cause large emissions of carbon (C), nitrogen (N) and mercury (Hg) to the atmosphere and thus have important implications for global warming (e.g. via CO2 and N2O emissions), anthropogenic fertilization of natural ecosystems (e.g. via N deposition), and bioaccumulation of harmful metals in aquatic and terrestrial systems (e.g. via Hg deposition). Research indicates that fires are becoming more severe over much of North America thus increasing element emissions during fire. However, there has been little research relating forest floor and mineral soil losses of C, N and Hg to on-the-ground indices of fire severity that enable scaling up those losses for larger scale accounting of fire-level emissions. We investigated the relationships between forest floor and mineral soil elemental pools across a range of soil-level fire severities following the 2011 Pagami Creek wildfire in northern Minnesota, USA. We were able to statistically differentiate losses of forest floor C, N and Hg among a five class soil-level fire severity classification system. Regression relationships using soil fire severity class were able to predict remaining forest floor C, N and Hg pools with 82%-96% confidence. We correlated NASA Airborne Visible and Infrared Imaging Spectrometer-Classic imagery to ground-based plot scale estimates of soil fire severity to upscale emissions of C, N, and Hg to the fire-level. We estimate that 468,000 Mg C, 11,000 Mg of N and over 122 g of Hg were emitted from the forest floor during the burning of the 28,310 ha upland area of the Pagami Creek fire.
WF16128 Accepted 17 February 2017
© CSIRO 2017