Major fraction of global soil organic carbon is stored in permafrost soils, and thawing and rapid losses of organic carbon in the form of CO2, associated with warming of polar regions, raises a serious concern for the stability of carbon in permafrost soils. In this study, we examined the forms of organic carbon associated with permafrost soils of Canadian high-Arctic (Axel Heiberg, Nunavut) using X-ray Absorption and NMR spectroscopic techniques, and high-resolution FT-ICR ESI-mass-spectrometry. In addition, we evaluated the forms of other organic matter bound biogenic elements, S, P, and Cl to assess organic carbon dynamics.  We compared the chemistries of these elements in Arctic soils with soils collected from temperate coniferous and deciduous forests.Our studies indicate that the organic carbon is rich in lipids, and poor in aromatic and carboxylic carbon in the high Arctic soils when compared to soils of other climates. The O/C ratios of the extractable organic carbon also indicate that it is O-poor. This is in direct contrast to the organic matter found in soils of tropical and temperate climates, which is rich in lignins, tannins, and other condensed aromatics. The abundance of such a lipid-rich organic carbon in high Arctic soils may be attributed to the moss, algae and fungal (or lichen) mats, whereas lignin and other aromatic-rich vascular plants are the common sources of organic carbon in other climatic regions.  Such a contrasting composition of organic carbon in Arctic soils when compared to others suggests that these soils respond differently to temperature changes. We will also present how these different molecular probes can be used to evaluate the bulk and mineral bound organic carbon to assess the organic carbon dynamics in soils.

Contrasting organic carbon dynamics in temperate and permafrost soils

247th National Meeting (2014)

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