Decomposition of Permafrost Carbon with Increasing Incubation Temperature on the Qinghai-Xizang (Tibetan) Plateau

Wednesday, 17 December 2014
Cuicui Mu1 and Tingjun Zhang1,2, (1)LZU Lanzhou University, Lanzhou, China, (2)University of Colorado, Boulder, CO, United States
Little is currently known about the decomposition of deep-permafrost organic carbon on the Qinghai-Xizang (Tibetan) Plateau (QXP) with increasing temperature. We studied the effect of temperature on CO2 emissions from soil, from the active layer to deep permafrost (400 cm), during a 140-day incubation at temperatures of −5.0 °C to +5.0 °C. We found that permafrost carbon emissions on the QXP increase with soil temperature. Temperature has greater impact on soil organic carbon (SOC) decomposition in permafrost soils than in thawed soils. A temperature increase of 4.5° results in an average increase in carbon release of 482.8% (±60%) at temperature below 0 °C (−5.0 to −0.5 °C), and 102.0% (±37.5%) at temperatures above 0 °C (0.5 to 5.0 °C). Permafrost carbon has greater vulnerability at subzero temperatures than at temperature above 0 °C. Moreover, the increase in permafrost carbon release in mineral soils was larger than that in organic soils at temperatures form −5.0 to −0.5 °C. The released CO2 mostly came from soils at depths of 10−20 cm and deep permafrost soils at depths of 245−255 cm and 285−295 cm, based on the stable carbon isotope analysis of δ13SOC and δ13CO2.