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DIVISION S-10—WETLAND SOILS

Carbon Pools and Accumulation Rates in an Age-Series of Soils in Drained Thaw-Lake Basins, Arctic Alaska

^a Dep. of Soil Sci., 1525 Observatory Dr., Univ. of Wisconsin, Madison, WI 537060-1299
^b Dep. of Geography, P.O. Box 210131, Univ. of Cincinnati, Cincinnati, OH 45221-0131

^* Corresponding author (bockheim{at}wisc.edu).

We examined soils in 20 drained thaw-lake basins (DTLBs) near Barrow representing four age classes: young [0–50 years before present (BP)], medium (50–300 BP), old (300–2000 BP), and ancient (2000–5500 BP). In addition, we examined an erosional remnant that is about 8000 yr in age with deep organic deposits. There are significant age-related differences in thickness of the organic layer, which for DTLBs represents surface organic accumulation since lake drainage. The lower portion of the organic layer progresses in decomposition stage from fibric in young basins to sapric in ancient basins and the erosional remnant. Whereas extractable organic matter (humic- and fulvic-acid fractions) in the organic layer decreases, the nonextractable portion (humin) increases with basin age. There are significant age-related differences (p = 0.027) in soil organic carbon (SOC) of the organic layer; however, there were no significant differences in C pools for other depths or within the upper 100 cm. Profile SOC pools in DTLBs average 48 kg m^–3, which is less than elsewhere on the Arctic Coastal Plain (62 kg m^–3). From a depth of 100 to approximately 160 cm, SOC pools average 3.2 kg C m^–2 dm^–1, confirming that there are large amounts of SOC below the traditional reporting depth of 100 cm. The spatial variability of SOC pools increases with relative basin age class and is likely because of increased variability in hydrology related to enrichment of ground ice in the upper permafrost. The long-term net accumulation (during the last 5500 yr) of SOC is 13 g m^–2 yr^–1.

Abbreviations: BP, years before present • DTLB, drained thaw-lake basin • SOC, soil organic carbon • PER, Peterson Erosional Remnant